DRYER

Abstract

The present application relates to a dryer comprising: a case forming the exterior thereof; a drum which is provided inside the case and which accommodates an object to be dried; and a driving part which is provided so as to drive the drum and which includes a motor having a stator and a rotor, wherein the case includes a rear case forming the exterior of the rear part of the dryer, the rotor is supported to be coaxially rotatable with a rotational axis of the drum with respect to the rear case on the outer side of the rear case, and the stator is fixed to the rear case on the outer side of the rear case.

Claims

1. A dryer, comprising: a case forming to support an appearance of the dryer; a drum provided within the case to receive a drying object therein; and a drive unit configured to drive the drum and including a motor having a stator and a rotor, wherein the case includes a rear case forming to support a rear appearance of the dryer, wherein the rotor is supported on an outside of the rear case in a manner of being coaxially rotatable to the rear case on a rotation axis of the drum, and wherein the stator is fixed to the rear case on the outside of the rear case.

2. The dryer of claim 1, wherein the drive unit comprises a power transfer unit transferring a rotation force of the rotor to the drum and wherein the power transfer unit is provided between the rotor and the drum.

3. The dryer of claim 2, wherein the motor comprises an outer rotor type motor having the rotor provided to be rotatable on a radial outside of the stator.

4. The dryer of claim 2, wherein the stator having a hollow part provided to a radial inside is fixed to an outside of the rear case.

5. The dryer of claim 4, comprising a connector provided between the stator and the rear case to fix the stator to the rear case and form a front-rear space between the stator and the rear case.

6. The dryer of claim 5, wherein a portion of the connector is inserted in the hollow part of the stator.

7. The dryer of claim 5, wherein the connector has a hollow part provided to a radial inside.

8. The dryer of claim 7, wherein the power transfer unit includes a decelerator transforming high-RPM low-torque of the rotor into low-RPM high-torque of the drum and wherein at least one portion of the decelerator is located by being inserted in the hollow part of the connector.

9. The dryer of claim 2, the power transfer unit comprising: a drum shaft connected to a rear side of the drum; a rotor shaft connected to the rotor; and a decelerator provided between the drum shaft and the rotor shaft.

10. The dryer of claim 9, wherein a shaft perforated hole perforated by the drum shaft is formed in the rear case.

11. The dryer of claim 10, the decelerator comprising: a housing; and a transforming device provided within the housing to transform high-RPM low-torque of the rotor into low-RPM high-torque of the drum.

12. The dryer of claim 11, wherein the housing of the decelerator is fixed to an outside of the rear case.

13. The dryer of claim 12, the housing of the decelerator, comprising: a drum shaft perforated hole projected in prescribed length in front direction to be perforated by the drum shaft and having a bearing installed inside to support the drum shaft rotatably; and a rotor shaft perforated hole projected in prescribed length in rear direction to be perforated by the rotor shaft and having a bearing installed inside to support the rotor shaft rotatably.

14. The dryer of claim 13, wherein the drum shaft perforated hole is located by being inserted in the shaft perforated hole of the rear case and wherein the rotor shaft perforated hole is located in a hollow part formed in a radial inside of the stator.

15. The dryer of claim 1, wherein a shaft perforated hole perforated by a drum shaft connected to the drum to transfer power of the rotor to the drum is formed in the rear case and wherein an installation area for installation of the drive unit is formed on a radial outside centering on the shaft perforated hole in the rear case.

16. The dryer of claim 15, wherein an air supply area for supplying air into the drum is formed in the rear case and wherein the air supply area is formed on a radial outside of the installation area centering on the installation area.

17. The dryer of claim 16, wherein an air intake area for sucking air from the drum is formed in the rear case and wherein the air intake area is formed on a radial outside of the air supply area.

18. The dryer of claim 17, comprising a flow path duct coupled to the rear case on an outside of the rear case so as to form an air flow space with the rear case in between by covering the air intake area and the air supply area.

19. The dryer of claim 15, wherein a donut-shaped air intake area confronting the air supply area of the rear case is formed in a rear wall of the drum.

20. The dryer of claim 19, comprising a gasket provided between the rear case and the rear wall of the drum to enable air supplied from the air supply area of the rear case to flow into the air intake area of the drum.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0202] FIG. 1 is a cross-sectional diagram of a dryer according to one embodiment of the present disclosure.

[0203] FIG. 2 is a diagram showing a rear view of a dryer according to one embodiment of the present disclosure.

[0204] FIG. 3 is an enlarged diagram of a drive unit of a dryer according to one embodiment of the present disclosure.

[0205] FIG. 4 is an exploded diagram showing components of a drum, rear case and drive unit of a dryer according to one embodiment of the present disclosure.

[0206] FIG. 5 is a diagram showing a front view of a drum according to one embodiment of the present disclosure.

[0207] FIG. 6 is a diagram showing a rear view of a drum according to one embodiment of the present disclosure.

[0208] FIG. 7 is a diagram showing an air inflow structure in a drive unit of a dryer according to one embodiment of the present disclosure.

[0209] FIG. 8 is a diagram showing an external view of a rear case of a dryer according to one embodiment of the present disclosure.

[0210] FIG. 9 is a diagram showing an internal view of a rear case of a dryer according to one embodiment of the present disclosure.

[0211] FIG. 10 is a graph showing the necessity and deceleration rate of a decelerator in a dryer according to an embodiment of the present disclosure.

[0212] FIG. 11 is an exploded diagram of components of a decelerator of a dryer according to one embodiment of the present disclosure.

[0213] FIG. 12 is a diagram showing the components engaged for a first-stage shift of a decelerator.

[0214] FIG. 13 is a diagram showing the components engaged for a second-stage shift of a decelerator.

[0215] FIG. 14 is a graph of comparison of speed standard deviation depending on a position of a cross section of a drum between a dryer according to one embodiment of the present disclosure and a related art dryer.

DETAILED DESCRIPTION

[0216] Reference will now be made in detail to the preferred embodiments of the present disclosure, examples of which are illustrated in the accompanying drawings.

[0217] First of all, major components of a dryer will be described with reference to FIG. 1 and FIG. 2. In the present specification, for clarity of description, a direction of a door 140 of a dryer shown in FIG. 1 may be defined as a front direction and a direction of a drive unit 200 may be defined as a rear direction.

[0218] A dryer 10 includes a case 100, 120, 130 and 150 and a drum 20 provided within the case. Drying objects may be placed within the drum 20. In case of a laundry dryer, laundry may be put in the drum 20 and then dried.

[0219] The case may include a top case 100 forming a top surface of the dryer, a front case 120 forming a front surface a rear case 130 forming a rear surface and a lateral case 150 forming a lateral surface. In addition, the case may include a dryer base 155 forming a bottom part of the dryer. The cabinet forms an inner surface, and various components including the drum 20 are received in the inner space.

[0220] The top case 100, the front case 120, the rear case 130, the lateral case 150 and the base 155 are structurally coupled together. Hence, each of the cases and the base forms a support structure supportive of an outer shape of the dryer as well as an exterior in a prescribed direction of the dryer.

[0221] A door 140 is provided to the front case. After the door 140 has been open, laundry may be put into the drum.

[0222] The drum 20 may be rotatably provided with reference to a horizontal axis parallel to a ground surface.

[0223] The drum 20 is formed in a cylindrical shape, and a front side of the drum 20 is open to put laundry in the drum.

[0224] A plurality of lifters 30 may be provided on an inner wall of the drum 20. The lifter 30 may be provided in a manner of extending in front-rear direction. The lifter 30 may be configured to be rotated together with the drum as an integral part. As the drum 20 is rotated, the lifter 30 lifts laundry. If the drum is further rotated, the laundry leaves the lifter 30 and then falls down by gravity. Owing to the rotation of the drum 20, the shaking of the laundry may be further smoothened and activated within the drum 20 by the lifter 30. Therefore, the laundry may be evenly exposed to hot air.

[0225] According to the present embodiment, a drive unit 200 configured to drive the drum 20 is located in rear of the drum 20. The drive unit 200 includes a motor 260 including a rotor 270 and a stator 280. A rotation axis of the rotor 270 and a rotation axis of the drum may be formed coaxially. Namely, the drum 20 and the rotor 270 are rotated with the same center of rotation. Hence, the dryer according to the present embodiment may be referred to as a Direct Drive (DD) dryer.

[0226] To transfer the power of the rotor 270 to the drum 20, a drum shaft 210 is provided to the drum 20. The drum shaft 210 is connected to the center of a rear wall 22 of the drum 20. Hence, as the drum shaft 210 is rotated, the drum 20 is rotated with the drum shaft 210 as an integral part.

[0227] To support a front side of the drum 20, a front supporter 160 may be provided. The front supporter 160 may be coupled to a rear side of the front case 120 or formed as a portion of the front case 120.

[0228] In the belt type dryer of the related art, an opening is formed in the rear side of a drum as well as in the front side of the drum and the drum substantially includes a cylindrical sidewall having open front and rear sides only. And, a rear supporter is provided to the rear opening of the drum. Namely, the drum is supported by the rear supporter while the rear opening of the drum is closed. As the rear supporter is a fixed component, the sidewall of the drum is rotated only by a belt.

[0229] Yet, according to the present embodiment, the drum 20 includes the rear wall 22 as well as the sidewall 21 of the cylindrical type, and the sidewall 21 and the rear wall 22 are rotated as an integral part. Therefore, the drum rear support structure of the present embodiment is different from the belt type dryer of the related art.

[0230] Regarding the drum of the present embodiment, unlike the drum of the related art dryer, the sidewall 21 and the rear wall 22 of the drum 20 are rotated as an integral part. The drum of the present embodiment may be similar to a drum of a washer. Yet, since the drum of the present embodiment is not provided for washing, through-holes for air or water entrance are not formed on the sidewall of the drum. Instead, a plurality of perforated holes or a perforated portion for allowing air communication but excluding entrance of laundry may be formed in the rear wall 22. This will be described later.

[0231] The rear side of the drum 20 may be rotatably supported by the drum shaft 210. Particularly, as the drum shaft 210 is rotatably supported to the rear case 130, the rear side of the drum may be eventually regarded as rotatably supported to the rear case 130. The rear case 130 is configured to form a support structure of the whole dryer. Hence, the rear side of the drum 20 may be supported rotatably and solidly through the rear case 130 that is the support structure of the dryer.

[0232] As shown in FIG. 3, the drum shaft 210 is extended in the rear direction from the center of the rear wall 22 of the drum 20. And, the drive unit 200 and the power transfer unit 210, 220 and 230 are provided in rear of the drum rear wall 22. The power transfer unit 210, 220 and 230 includes the drum shaft 210, and the drive unit 200 includes the motor 260 and the power transfer unit 210, 220 and 230.

[0233] The power transfer unit 210, 220 and 230 is provided between the drum 20 and a rotor 270 of the motor 260, thereby transferring a drive force of the rotor to the drum. Hence, the drive unit 200 including the power transfer unit 210, 220 and 230 may be located in rear of the rear side of the drum 200.

[0234] The motor 260 may include a stator 280 and the rotor 270 rotatably provided outside in a radial direction of the stator 280. Thus, the motor 260 may be referred to as an outer rotor type motor. Such an outer motor type motor is popularly used for a Direct Drive (DD) washer. Yet, as described above, since the related art dryer has difficulty in implementing a DD dryer, it is difficult to apply an outer rotor type motor to the related art dryer.

[0235] According to the present embodiment, the stator 280 is preferably provided to an outside of the rear case 130. Particularly, the stator 280 is preferably provided as fixed to the outside of the rear case 130. The rear case 130 is configured to form an appearance of the dryer on the rear side of the dryer 10 and also form an inner space of the dryer. Hence, the rear case 130 is configured to be fixed. Thus, as the stator 280 is fixed to the outside of the rear case 130, it can be fixed solidly.

[0236] As the motor 260 is provided to the outside of the rear case 130, a space between an inner side of the rear case 130 and the drum rear wall 22 may be provided enough to avoid a rotation interference of the drum. In addition, as the motor 260 is provided outside the rear case 130, the manufacturing is considerably facilitated.

[0237] The stator 280 may be provided so as to be spaced apart from a rear surface of the rear case 130. Namely, it is preferable that the stator 280 is not coupled to contact with the rear case 130 in direct. A connector 250 is provided between the rear case 130 and the stator 280. The stator 280 may be coupled to the rear case 130 through the connector 250.

[0238] A decelerator 230 may be provided to an inside of the connector 250, and more particularly, to a hollow part 250a located at a radial inside of the connector. Namely, the decelerator 230 may be inserted in the connector 250. Hence, it is able to minimize that a front-rear space of the drive unit 200 or the power transfer unit 210, 220 and 230 is increased by the decelerator 230.

[0239] The decelerator 230 may be located between the rotor 270 and the drum 20. The decelerator 230 may be configured to transform and transfer the drive force of the rotor 270 to the drum 20. Particularly, the decelerator 240 may be configured to transform high RPM and low torque of the rotor 270 into low RPM and high torque of the drum 20.

[0240] The drum shaft 210 coupled to the drum 20 is located in front of the decelerator 230, and a rotor shaft 220 coupled to the rotor 270 is located in rear of the decelerator 230. The rotor shaft 220 is rotated with the rotor as an integral part, and the drum shaft 210 is rotated with the drum 20 as an integral part. Hence, the decelerator 230 may configure the power transfer unit that transforms and transfers the power of the rotor shaft to the drum shaft. To secure efficiency and facilitation of such power transfer, it is preferable that the drum shaft 210 and the rotor shaft 220 are formed coaxially.

[0241] The decelerator 230 may be installed in the rear case 130. The decelerator 230 may be installed in a manner of directly contacting with the rear surface of the rear case 130. The connector 250 is provided to a radial outside of the decelerator 230, and the stator 280 may be installed in the rear case 130 through the connector 250.

[0242] The rotor 270 rotates on the radial outside of the stator 280, and is substantially configured in a manner of being further extended in a front direction from the radial outside of the stator toward the rear case. Hence, securing a front-rear spaced distance between the rear case 130 and the stator 280 through the connector 250 may be necessary to secure a rotation space of the rotor 270.

[0243] In addition, the decelerator 230 is located in a manner of being inserted in the connector 250. Therefore, a front-rear with of the drive unit 200 by the decelerator 230 and the motor 260 may be formed to be very compact, whereby the external width extension of the rear case 130 can be minimized.

[0244] In some implementations, the drive unit 200 including the power transfer unit 210, 220 and 230 may be regarded as supported by the rear case that forms the exterior of the rear side of the dryer and the support structure of the dryer.

[0245] According to the present embodiment, since the motor 260 and the decelerator 230 are located in rear of the rear case 130, such components may be externally exposed and need protection. To this end, as shown in FIG. 4, a drive unit cover 180 may be provided to cover the drive unit in rear of the dryer 10.

[0246] Among the components configuring the drive unit 200, the largest component in a radial direction may be the rotor 270. Hence, except the rotor 270, all the components configuring the drive unit 200 are located within a radial inside of the rotor 270. Hence, it is necessary for the drive unit cover 180 to fully cover the rotor 270 only. Namely, the drive unit cover 180 may be formed in a circular dish having an outer diameter slightly greater than that of the rotor 270.

[0247] The drive unit cover 180 may be coupled to the rear case 130 in the rear direction of the rear case. Alternatively, the drive unit cover 180 may be coupled to a flow path duct 170 described later. The drive unit cover 180 and the flow path duct 170 are just located in rear of the rear case 130 but may not be the components that configure the support structure of the dryer. Therefore, although the drive unit cover 180 and the flow path duct 170 are removed, the support structure of the dryer may not change. Yet, according to the present embodiment, in a manner that the drive unit 200 and the air flow path are partially extended to a rear outside of the rear case 130 instead of an inside of the case 10, the drive unit cover 180 and the flow path duct 170 may be provided.

[0248] According to the present embodiment, a rear air inflow structure for providing air to the drum 20 from an outside of the rear case 130 may be provided. Particularly, as the flow path duct 170 is installed in the rear case 130, air may be supplied into the drum 20 through the flow path duct 170.

[0249] The flow path duct 170 is mounted on the rear surface of the rear case 130, thereby forming a space 171 inside to enable air to flow therein. The flow path duct 170 may be formed on a radial outside of the drive unit 200. Namely, the flow path duct 170 may be configured to enclose the drive unit 200.

[0250] Therefore, the air flow space 171 in the flow path duct 170, the motor 260 and the decelerator 230 may be structurally divided or separated outside the rear case 130. Thus, air flow may be performed smoothly, and hot or humid air may be prevented from entering the motor 260 or the decelerator 230.

[0251] An air communication structure among the flow path duct 170, the rear case 130 and the drum 20 will be described in detail later.

[0252] The motor 260 is located on a rear outside of the rear case 130. And, the motor 260 is enclosed by the flow path duct 170 on the rear outside of the rear case 130. Hence, a wire or signal line extended from an inside of the case 100 has difficulty in being connected to the motor 260.

[0253] According to the present embodiment, a wire or signal line passing through the rear case 130 may be extended to a radial inside from a radial outside of the flow path duct 170 and then connected to the motor 260. In this case, the wire or signal line may be exposed externally. To prevent such exposure, a wire cover 190 may be provided.

[0254] The connection and position relation among the drum rear wall 22, the rear case 130 and the drive unit 200 will be described in detail with reference to FIG. 3 and FIG. 4 as follows. FIG. 3 is an enlarged cross-sectional diagram of the rear part of the dryer shown in FIG. 1, and FIG. 4 is an exploded perspective diagram of the drum, rear case and drive unit.

[0255] The rear case 130 is located in rear of the drum rear wall 22. As the drum rear wall 22 is rotatably configured, it is located in a manner of being spaced apart from the rear case 130.

[0256] The motor 260 is provided to an outside of the rear case 130. The stator 280 of the motor is located in a manner of being spaced apart from the rear surface of the rear case toward a rear direction by the connector 250 and fixed to the rear case 130.

[0257] To transfer a drive force of the rotor 270 of the motor to the drum 20, the power transfer unit 210, 220 and 230 are provided. The power transfer unit 210, 220 and 230 includes the drum shaft 210, the decelerator 230 and the rotor shaft 220.

[0258] To transfer a drive force of the rotor 270, the rotor 270 is coupled to the rotor shaft 220. The rotor shaft 220 forms the same axis with a rotation axis of a rotor and rotates with the rotor as an integral part. Hence, to secure the coupling rigidity and the power transfer reliability, a coupler 296 may be provided. The coupler 296 may be referred to as a rotor coupler 296.

[0259] The rotor coupler 296 may be coupled to an inner surface of the rotor through a plurality of bolts. The rotor shaft 220 may pass through the rotor coupler 296 and be coupled to the rotor 270 by a stud 294. To rigidify the coupling by the stud, a washer 295 may be inserted between the stud 294 and the rotor 270.

[0260] Regarding the stud 294, a female screw may be formed at the center of the rotor shaft 220 so as to be coupled with the stud.

[0261] In addition, the rotor shaft 220 may be coupled to the rotor coupler 296 by serration. A serration may be formed on an outer circumference of the rotor shaft 220 and a serration may be formed on the rotor coupler through which the rotor shaft passes. Hence, a drive force of the rotor may be solidly transferred to the rotor shaft 220.

[0262] A drive force of the rotor shaft 220 is transformed through the decelerator 230 and then transferred to the drum shaft 210. The drum shaft 210 may have the coupling structure identical or similar to that of the rotor shaft 220 and be coupled to the drum rear wall 22.

[0263] Namely, a stud 291, a washer 292 and a drum coupler 293 may be provided. Shapes and structures of them may be identical or similar to those of the stud 294, washer 295 and rotor coupler 296 for the coupling of the rotor shaft 220.

[0264] The stud 291 may pass through a stud perforated hole 29a from an inside of the drum to an outside (i.e., from a front side to a rear side) and be then coupled to the drum shaft 210. On the other hand, the stud 294 may pass through a stud perforated hole from an inside of the rotor to an outside of the rotor (i.e., from a rear side to a front side) and be then coupled to the rotor shaft 220.

[0265] The rotor shaft 220 rotates with the rotor 270 as an integral part, and the drum shaft 210 rotates with the drum 20 as an integral part. Hence, the decelerator 230 may be referred to as a device for performing power transform between the rotor shaft 220 and the drum shaft 210.

[0266] The decelerator 230 includes a transforming device 240 provided within the housing. The transforming device may include various gears. The rotor shaft 220 and the drum shaft 210 may be extended into the housing 231 and then connected to the transforming device. The rotor shaft 220 and the drum shaft 210 may be parts of the decelerator 230 or partial configuration of the transforming device.

[0267] A drum shaft perforated hole 232 is provided to a front side of the housing 231 so that the drum shaft 210 can pass through the drum shaft perforated hole 232. The drum shaft perforated hole 232 may be configured in a manner of being extended in the front direction. Namely, it may be configured to form a prescribed front straight-line distance. The drum shaft perforated hole 232 may pass through a shaft perforated hole 130a formed in the rear case 130.

[0268] The shaft perforated hole 130a is formed to enable the drum shaft 210 to be extended from the rear wall 22 of the drum 20 to the decelerator 230 in a manner of passing through the rear case q130. Here, it is not preferable that the drum shaft 210 is rotatably supported through the shaft perforated hole 130a. Namely, since the rear case 130 is formed using a plate such as a thin steel sheet, if a bearing support structure is formed in a perforated hole formed in a plate, it is not easy and preferable.

[0269] Therefore, it is preferable that the shaft perforated hole 130a is formed to have a diameter so that the drum shaft perforated hole 232 of the decelerator housing 231 as well as the drum shaft 210 can pass through the shaft perforated hole 130a.

[0270] The decelerator housing 231 may be fixed and coupled to the rear side of the rear case 130. The drum shaft perforated hole 232 of the decelerator housing 231 may be further extended in the front direction by passing through the shaft perforated hole 130a.

[0271] A bearing 234 may be provided within the drum shaft perforated hole 232. The drum shaft 210 may be inserted into the bearing 234. Therefore, the drum shaft 210 may be rotatably supported to the housing through the bearing 234. As the housing 231 is fixed to the rear case 130, the drum shaft 210 may be rotatably provided to the rear case 130 through the housing.

[0272] In addition, the decelerator housing 231 may be fixed and coupled to the connector 250. The decelerator housing 231 may be coupled in a manner of being fixed to an inside of the connector 250 by stamping. The connector 250 may be fixed to the rear case in the rear direction of the rear case in a manner of enclosing the decelerator housing 231.

[0273] Therefore, the decelerator 230 may be solidly fixed to the rear case 30 through the connector 250. This is because a radius of a part (e.g., a coupling part through a bolt or stud) for coupling the connector 250 to the rear case 130 is greater than that of the decelerator housing 231.

[0274] As described above, the motor 260 may include an outer rotor type motor. Therefore, the rotor 260 rotates on a radial outside of the stator 280. Based on such a structure, a hollow part 280a may be formed in a radial inside of the stator 280.

[0275] A portion of the connector 250 may be inserted in the hollow part 280a. Through this, the front-rear length increase of the drive unit 200 may be prevented and the stator 280 may be solidly coupled to the connector 250.

[0276] By the decelerator 230, a front-rear length for the connection of a rotation axis (i.e., a rotation axis including a drum shaft, a middle shaft described later, and a rotor shaft) between the rotor 270 and the drum 20 may be increased. Therefore, it is important to secure a rotatable support point of the rotation axis. However, it is not preferable that an overall length of a rotation axis is increased for the support point securing.

[0277] A portion of the rear side of the decelerator housing 231 is preferably inserted in the hollow part 280a of the stator 280.

[0278] A rotor shaft perforated hole 233, through which the rotor shaft 220 passes, is formed in the rear side of the decelerator housing. The rotor shaft perforated hole 233 may be formed in a manner of extending in a rear direction. Namely, it may be provided to form a prescribed rear straight-line distance. The rotor shaft perforated hole 233 is preferably inserted in the hollow part 280a of the stator 280.

[0279] A bearing 236 may be provided within the rotor shaft perforated hole 233. The rotor shaft 220 may be inserted in the bearing 236. Hence, the rotor shaft 220 may be rotatably supported to the housing 231 through the bearing 236. As the housing 231 is fixed to the rear case 130, and more particularly, may be fixed through the connector, the rotor shaft 220 may be regarded as provided rotatably to the rear case 130 as well.

[0280] As described above, the bearing support point of the drum shaft 210 is substantially located in a space between the drum rear wall 22 and the front side of the rear case 130. In addition, the bearing support point of the rotor shaft 220 is substantially located within the stator 280, i.e., the hollow part 280a. Therefore, the bearing support point of the overall rotation axis can be secured smoothly, thereby preventing an overall length of the rotation axis from being increased.

[0281] In addition, since the bearings 234 and 236 can be installed in the decelerator housing 231 in advance, the manufacturing is further facilitated.

[0282] The decelerator 230 may include a middle shaft 241. The transforming device 240 of the decelerator may include the middle shaft 241. The middle shaft 241 is the shaft 241 for connecting the rotor shaft 220 and the drum shaft 210 coaxially and is configured to be rotated independently from the drum shaft 210 or the rotor shaft 220.

[0283] The middle shaft 241 is inserted in the center of each of the rotor shaft 220 and the drum shaft 210, whereby those shafts are configured coaxially. A bearing is 235 provided to an outside of the middle shaft 241 and an inside of the drum shaft 210. Through the bearing 235, the middle shaft and the drum shaft may be rotated independently. A bearing 237 is provided to an outside of the middle shaft 241 and an inside of the rotor shaft 220. Through the bearing 237, the middle shaft and the rotor shaft may be rotated independently.

[0284] By the aforementioned structures of the drum 20, the rear case 130, the power transfer unit and the drive unit, the assembly may be further facilitated.

[0285] First of all, the decelerator 230 and the connector 250 are coupled together. The connector 250 is coupled to the rear case 130. After the stator 280 has been coupled to the connector 250, the connector 250 may be coupled to the rear case 130. Thereafter, the stator is coupled to the connector 250. As the rotor shaft 220 is semi-coupled by being inserted in the center of the rotor 260. Likewise, the drum shaft 210 may be semi-coupled by being inserted in the center of the drum rear wall 22.

[0286] Inside the drum, through the stud 291, the drum rear wall and the drum shaft 210 are coupled together. On the outer rear side of the rotor 270, through the stud 294, the rotor 270 and the rotor shaft 220 are coupled together.

[0287] Through such a sequence, the coupling of the drum 20, the rear case 130, the power transfer unit 210, 220 and 230 and the motor 260 may be facilitated. Thereafter, the flow path duct 170 may be coupled to the rear case 130 in the rear direction of the rear case, and the drive unit cover 180 may be coupled to the flow path duct 270 so as to protect the drive unit 200. Wires or signal lines exposed after having been connected to the motor 260 may be protected by the wire cover 190. One end of the wire cover 190 may be coupled to the rear case 130 on the radial outside of the flow path duct, and the other end may be coupled to the flow path duct or the rear case 130 on the radial inside of the flow path 170. Alternatively, after the wire cover 190 has been coupled, the drive unit cover 180 may be coupled.

[0288] In the following, with reference to FIG. 5 and FIG. 6, the drum 20 applicable to the present embodiment will be described in detail.

[0289] FIG. 5 is a perspective diagram of a front side of a drum, and FIG. 6 is a front diagram of a rear side of the drum.

[0290] The drum 20 may include the sidewall 21 and the rea wall 22 in a manner that a front side is open. The drum may be configured in a cylindrical shape of which rear side is blocked by the rear wall 22. Here, the ‘blocked’ means that entrance of laundry is impossible and that air communication is possible.

[0291] An installation area 23 is formed at a central portion of the rear wall 22. The installation area 23 may include an area in which the drum shaft 210 is installed and indicate an area that confronts the decelerator 230. An air intake area 24 may be formed on a radial outside of the installation area 23. A rear wall rim area 25 is formed on a radial outside of the air intake area 24 and may be connected to the sidewall 21.

[0292] Assuming that the rear wall 22 has a circular shape, the installation area 23 may be formed to exclude the air communication for the installation of the drum shaft at the central portion, and the air intake area 24 may be formed on a radial outside of the installation area 23 to enable air to pass therethrough.

[0293] To enable air to communicate, a plurality of holes 26 are formed in the air intake area 24. Particularly, the air intake area 24 of a mesh type is formed. If the air intake area 24 becomes wider, air may be supplied with the drum more evenly, whereby drying efficiency can be raised. A diameter of the hole 26 is very small. This is to prevent laundry from entering the hole 26 and being damaged. Therefore, the number of the holes 26 will be very high to enable air to be supplied into the drum smoothly.

[0294] However, the rigidity of the rea wall 22 may become vulnerable by the holes 26. To reinforce the rigidity of the rear wall 22 from the air intake area 24, a plurality of radial bridges 27 and a circumferential bridge 28 may be included. The radial bridges 27 may be provided to divide the air intake area 24 along a circumferential direction, and the circumferential bridge 28 may be provided to divide the air intake area 24 into a radial inside and a radial outside.

[0295] The radial bridge 27 may be extended from the installation are 23 to the rear wall rim area 25 via the air intake area 24. The radial bridge 27 may be connected to the circumferential bridge 28.

[0296] It is preferable that the holes 26 are not formed in the radial bridges 27 and the circumferential bridge 28. Therefore, as a support structure supportive of the air intake area 24 of the mesh type attributed to a plurality of the holes 26, the radial bridges 27 and the circumferential bridge 28 may be formed. Preferably, to reinforce self-rigidity, the radial bridges 27 and the circumferential bridge 28 may be formed convex in front or rear direction.

[0297] Preferably, the holes 26 are not formed in the rear wall rim area 25 as well. As the rear wall rim area 25 is connected to the sidewall 21, it is necessary to prevent the rigidity of the rear wall rim area 25 from being weakened. Moreover, in case that air flows in the rear wall rim area 25, the air may be supplied to laundry closely attached to an inner wall of the drum or a place in which laundry does not exist. Therefore, to raise the drying efficiency, it is preferable that air supply is focused not on the rear wall rim area 25 but on the air intake area 24.

[0298] A stud hole 29a may be formed at the center of the installation area 29 of the central portion of the drum rear wall 22. A washer seat part 29c may be formed on a radial outside that encloses the stud hole 29. A plurality of bolt fastening parts 29b may be formed in a radial outside of the washer seat part 29. Here, a stud, bolt or screw in the present embodiment may be named for convenience according to a relative size of a fastening means. Therefore, the fastening means may be non-limited by the specific names.

[0299] The installation area 29 may be the area that is fastened with the drum shaft 210. To fasten the drum shaft 210 to the drum 20 rigidly and secure reliability of power transfer, a coupler is provided. This may be referred to as a drum coupler 293 (see FIG. 3).

[0300] It is not preferable that hot air substantially flows into the drum through the central portion of the drum rear wall. Therefore, it is preferable that the installation area 29 is more extended to a further radial outside of the drum coupler.

[0301] FIG. 6 shows that a gasket 40 and 50 is projected on the drum rear wall 22. The gasket 40 and 50 may be provided for air sealing between the drum rear wall 22 and the rear case 130. Namely, air flowing in from an outside of the rear case 130 flows into the drum through the air intake area 24 by the sealing provided by the gasket between the drum rear wall 22 and the rear case 130.

[0302] The position, structure and function of the gasket 40 and 50 are described in detail with reference to FIG. 7. FIG. 7 is a cross-sectional diagram of the drum, drive unit and flow path duct in a gasket part.

[0303] The gasket 40 and 50 may include an inner gasket 40 of a radial inside and an outer gasket 50 of a radial outside. The inner gasket 40 partitions the installation area 29 and the air intake area 24 of the drum. Therefore, it is able to prevent hot air from leaking in an installation area direction (toward a radial inside) of the drum from an outside of the drum. The outer gasket 50 partitions the air intake area 24 and the rear wall rim area 25 of the drum. Therefore, it is able to prevent hot air from leaking into the rear wall rim area 25 of the drum from an outside of the drum.

[0304] The inner gasket 40 includes a fixing part 41 and an extension part 42, and a fastening part 43 may be formed in the fixing part 41. The inner gasket 40 may be mounted on an inner surface of the rear case through the fixing part 41 and the fastening part 43, and the extension part 42 may be formed in a manner of being extended from the fixing part 41 in a direction of the drum rear wall 22. The extension part 42 is configured to contact with the drum rear wall, whereby sealing can be performed. The extension part 42 may be slantly extended toward an inside from a radial outside. Namely, the extension part 42 may be located on a radial inside of the fixing part 41.

[0305] Likewise, the outer gasket 50 includes a fixing part 51 and an extension part 52, and a fastening part 53 may be formed in the fixing part 51. The outer gasket 50 may be mounted on an inner surface of the rear case through the fixing part 51 and the fastening part 53, and the extension part 52 may be formed in a manner of being extended from the fixing part 51 in a direction of the drum rear wall 22. The extension part 52 is configured to contact with the drum rear wall, whereby sealing can be performed. The extension part 52 may be slantly extended toward an outside from a radial inside. Namely, the extension part 52 may be located on a radial outside of the fixing part 51.

[0306] The extension part 42/52 of the inner/outer gasket 40/50 may be slantly extended from the fixing part 41/51 toward the drum rear wall. Through this, air sealing may be performed while the frictional force between the rotating drum and the end of the extension part 42/52.

[0307] Of course, unlike the above description, the gasket 40 and 50 may be installed not in the rear case 130 but in the drum 20. Yet, it will be preferable that the gasket is installed not in the rotatably-configured drum 20 but in the fixed rear case 130. Through this, as the sealing point may be formed not in the upstream of an air flow path but in the downstream thereof, it becomes more advantageous in aspect of sealing as well as manufacturing facilitation.

[0308] Meanwhile, as shown in FIG. 7, the power transfer unit may be placed in a hermetically sealed space. For example, the motor including the stator 280 and the rotor 260 and the decelerator may be located within a space enclosed by the rear case 130, the flow path duct 170 and the drive unit cover 180.

[0309] As the drum is driven, heat is generated from the decelerator and the motor, and more particularly, from the stator. If such a heat problem is resolved, it is very advantageous in securing performance. Therefore, it is preferable that a component for heat radiation or cooling is added.

[0310] Instead of adding such a component as a separate cooling fan, cooling performance may be secured using natural convection or convection through rotation of a rotor.

[0311] A plurality of openings 260a may be formed in the rotor 260. As the rotor rotates, air may flow into the rotor from an outside of the rotor. The inflow air may flow toward the stator 280.

[0312] Meanwhile, the air flowing into the rotor 260 preferably includes external air. To this end, an opening 180a may be provided to the drive unit cover 180. A plurality of the openings 180a may be provided.

[0313] The air flowing in through the opening 180a of the drive unit cover 180 cools down the stator within the rotor through the opening 260a of the rotor. Here, if the air having cooled down the rotor is discharged externally, effective air circulation or flow can be generated. Therefore, a discharge part 180b for discharging air externally is preferably formed in the drive unit cover 180.

[0314] By such a structure, as shown in FIG. 7, an air flow is generated, whereby effective cooling can be performed.

[0315] Here, it is preferable that the opening 260a of the rotor and the opening 180a of the drive unit cover 180 are located to confront each other. Through this, air flow resistance can be minimized. Meanwhile, in case that air flows in from an outside, it is not preferable that an inflow pressure becomes excessively high. Therefore, the number and total size of the openings 180a may be preferably greater than those of the rotor, respectively.

[0316] In addition, to perform the inflow and discharge of air smoothly, a position of an inflow part of air is preferably different from that of a discharge part of air. Namely, the position of the discharge part is located at a radial outside of the position of the inflow part.

[0317] Accordingly, by forming the openings for the air inflow and discharge in the drive unit cover 180 with ease, effective cooling of the motor and decelerator can be performed.

[0318] With reference to FIG. 8 and FIG. 9, an air flow path of a dryer according to one embodiment of the present disclosure is described in detail.

[0319] An outlet 131 for discharging air from a dryer inside externally may be formed in the rear case 130. An inlet 135 for the air discharged through the outlet 131 to flow into the dryer may be formed in the rear case 130. The outlet 131 is a single outlet but a plurality of the inlets 135 may be formed.

[0320] The inlet may be formed in an air supply area 134 of the rear case 130, and the air supply area 134 may be formed on a radial outside of an installation area 136. The air supply area 134 may be configured to enclose the installation area 136.

[0321] The outlet 131 may be formed in the air intake area of the rear case 130. The air intake area may be provided to a radial outside of the air supply area 134. As the outlet 131 may be configured as a single outlet, the outlet may be regarded as the air intake area.

[0322] The air having flown into the flow path duct 170 via the outlet 135 flows into the dryer through the inlet 135. Particularly, a flow path passing through the inlet 135 may enter the drum in a manner of passing through a space between the drum rear wall 22 sealed by the gasket 40 and 50 and a front side of the rear case.

[0323] To reduce resistance of a flow of air that flows in via the inlet 135, it is preferable that a size of the inlet 135 is greater than that of a hole 26 through which air flows into the drum. As shown in the drawing, the number of the holes 26 of the drum projected onto the single inlet 135 may be equal to or greater than 10.

[0324] The area in which the holes 26 of the drum are formed is formed continuously along a circumferential direction except a radial rib 27. On the other hand, the inlet 135 and the inlet 135 may be configured in a manner of being spaced apart from each other along the circumferential direction. A size of a portion of the air inflow area 134, in which the inlet 135 is formed, may be similar to that of a portion in which the inlet is not formed.

[0325] Moreover, it is preferable that a radial direction width of the inlet 135 is preferably smaller than a radial width of the air intake area 24 of the drum. Namely, it is preferable that a size for sucking air from the drum is greater than a size for supplying air to the drum from the rear case. Through this, air inflow may be performed more smoothly and air can be evenly flow into the drum.

[0326] The flow path duct 170 may be configured to cover both of the air intake area 131 and the air supply area 134 of the rear case except the installation area of the rear case. Therefore, the air having flown into the flow path duct 170 via the air intake are 131 may diverge into both sides of the installation area and then flow along an installation area circumference, thereby being discharged from the flow path duct through the inlet 134.

[0327] The air discharged through the inlet 134 flows into the drum through a plurality of holes 29 formed in the air intake area 24 formed in the drum rear wall 22. The air having flown into the drum is discharged to a drum front side, passes through a heat pump 300 and a fan 179, and is then discharged out of the dryer rear case 130 through the outlet 131 of the rear case.

[0328] In some implementations, the heat pump 300 may be substituted with a heating part (not shown). Namely, a configuration for condensing moisture in air may be omitted. So to speak, air outside the dryer is made to flow into the dryer and then heated,

[0329] Through such a structure, air can be dried in a manner of circulating in the dryer according to the present embodiment. A fan 179 for generating circulation flow of air, a heat pump 300 as an exemplary configuration for heating and condensing air, a flow path duct 170 forming a flow path of air, a connecting duct 179 forming the flow path of the air and the like may be included.

[0330] Meanwhile, a fan mount part 132 projected in rear direction may be provided to the rear case 130. The outlet 131 may be formed in the fan mount part 132. A wire draw-out hole 133 may be formed in a top portion of the rear case 130.

[0331] The flow path duct 170 may include an inner coupling part 172 and an outer coupling part 171. The inner coupling part 172 may be coupled to the rear case between the mount area of the rear case and the air supply area. The outer coupling part 171 may be coupled to the rear case in a manner of enclosing both of the air supply area and the air intake area of the rear case. An extension part 173 is formed between the outer coupling part 171 and the inner coupling part 172 so as to form an air flow space 171.

[0332] The extension part 173 may be configured in a manner of being convex in rear of the rear case 130. Hence, a wire extended to a rear case outside through the wire draw-out hole 133 needs to be connected to the motor located at a radial inside of the inner coupling part 172 of the flow path duct 170 by crossing the extension part 173. Hence, a wire cover 133 for protecting the crossing wire crosses the extension part 173 as well. The front-rear width of the dryer may be increased by the wire cover 133. Therefore, a seat part 173 recessed in front direction is preferably formed at a prescribed portion of the extension part 173 so that the wire cover is seated on the seat part 173.

[0333] A wire coupling area or a wire cover coupling area 137 may be formed between the air supply area 134 and the installation area 136 of the rear case 130. The wire coupling area 137 may include an area formed in a manner that a prescribed portion of the installation area 136 is extended to a radial outside. Hence, a radial width of the inlet 135 formed in the radial outside of the wire coupling area may be decreased by the wire coupling area 137.

[0334] A wire coupling area may be formed in the flow path duct to correspond to the wire coupling area of the rear case. Through the wire coupling area, one end of the wire cover 190 may be fixed and coupled thereto.

[0335] As described above, the decelerator 230 is preferably included in the dryer according to one embodiment of the present disclosure. In the following, why the decelerator is required for one embodiment of the present disclosure and what is an optimal deceleration ratio will be described with reference to FIG. 10.

[0336] To facilitate the torque and RPM control of a motor, an outer rotor type motor having a permanent magnet provided to a rotor is popularly used for a Direct Drive type device. In order to apply such an outer rotor type motor to the present embodiment, it is necessary to consider efficiency of a motor. FIG. 10 shows efficiency of a motor according to a current phase angle in case of using a motor of 269-W power consumption.

[0337] As shown in the drawing, it is observed that efficiency of an outer rotor type motor is high in a high-speed drive range, e.g., 600˜750 RPM range. Yet, in a low sped drive at about 50 RPM that is a general drive RPM of a dryer drum, efficiency is noticeably decreased or a drum is not rotated due to the insufficient torque. Namely, there may occur a case that it is impossible to drive a drum. Thus, there may be a demand for a decelerator capable of driving a drum at about 50 RPM while driving a motor at the RPM having optimal efficiency. Therefore, according to the present embodiment, a decelerator having a deceleration ratio of 15:1 may be provided. Although an optimal deceleration ratio may be changed due to the difference of a motor and the difference of a drum drive RPM, it may be similar to 15:1 approximately.

[0338] Generally, a decelerator that uses a planet gear is manufactured for the purpose of deceleration of a servo motor and the like and fastened to a front side of a motor. Hence, due the outer diameter limit of a decelerator by a motor, a safety rate is generally secured in a manner of increasing a thickness of a planet gear (e.g., an axial length of a gear).

[0339] However, a decelerator of a dryer according to one embodiment of the present disclosure may require a compact design for a height (i.e., an axial length) of the decelerator rather than an outer diameter thereof. Namely, since a motor of the present embodiment is a motor of an outer rotor type, an outer diameter of a decelerator may be set to approach an outer diameter of a rotor as close as possible.

[0340] To implement a high deceleration ratio (e.g., 15:1), a decelerator of a 2-stage planet gear type may be applicable. A decelerator of a 1-stage planet gear type is normally used at a deceleration ratio of about 9:1. If a deceleration ratio of about 15:1 is implemented in a decelerator of a 1-stage planetary type, the number of planet gears becomes two according to the geometrical feature of implementing the deceleration mechanism. Therefore, stability becomes very low. According to the present embodiment, to implement a high deceleration ratio and secure stability, it is able to apply a decelerator of a 2-stage planet gear type that eventually performs 2-stage deceleration by performing deceleration through four planet gears in 1-stage deceleration.

[0341] Meanwhile, in case of using a 2-stage gear, as thickness (i.e., axial length of decelerator) due to gears is increased, the demand for the compact and light-weight design is considerably rising. According to the present embodiment, a decelerator capable of 2-stage changing high-RPM low-torque into low RPM high-torque between a rotor and a drum can be provided. And, a decelerator capable of implementing compactness and lightweight in consideration of power transform features in a dryer can be provided.

[0342] In 1-stage power transform, a thickness of a gear may be decreased in consideration of a feature that a torque of an input shaft (e.g., a rotor shaft in the present embodiment) is low. And, it is able to form a gear not through steel series materials but through engineering plastics such as Poly Oxy Methylene (POM) series materials. Therefore, by decreasing thickness and weight of a gear in proportion to strength of a gear, the compact and lightweight design will be possible.

[0343] Yet, in 2-stage power transform, since a torque of an output shaft (e.g., a drum shaft in the present embodiment) is raised through 1-stage power transform, higher gear strength may be required. Therefore, in the 2-stage power transform, it will be preferable that a height of a gear is relatively increased and that a gear of steel materials is formed.

[0344] In this respect, it may be difficult to implement a compact decelerator due to a thickness of a gear for power transform, and particularly, in 2-stage power transform,

[0345] One embodiment of the present disclosure pays attention to gear strength improvement through an outer diameter increase of a gear instead of a thickness increase of a gear.

[0346] By increasing a total outer diameter of a planet gear using the same deceleration ratio and the same-rated configurations, gear strength can be improved. Namely, if an outer diameter is increased in a gear having the same number of gear teeth, a size of a support part of the gear tooth is increased. So to speak, it is able to increase a size of a support part of a gear tooth in a manner of increasing a size of the gear tooth instead of increasing a thickness of a gear.

[0347] Such gear strength securing is identically applicable to 2-stage power transform as well as 1-stage power transform. Hence, it is able to implement a decelerator that is very compact in front-rear direction in all of 1-stage gears and 2-stage gears having the same outer diameter. Particularly, since a decelerator of the present embodiment transforms power of an outer rotor type motor, an outer diameter increase of the decelerator can be allowed sufficiently. Specifically, it is possible to increase an outer diameter of a decelerator to correspond to an inner diameter of the hollow part 250a of the connector that fixes the stator to the rear case.

[0348] In the following, a decelerator and deceleration principle according to one embodiment of the present disclosure will be described in detail with reference to FIGS. 11 to 13. FIG. 11 is an exploded perspective diagram of a decelerator, FIG. 12 shows a connection structure of decelerator components for 1-stage transform of power, and FIG. 13 shows a connection structure of decelerator components for 2-stage transform of power.

[0349] A decelerator 230 includes a housing 231, and the housing may include a front housing 231a and a rear housing 231b. Various components for a transforming device may be received in the housing 231. A fastening part 231c may be provided to the housing 231. The rear housing 231b may substantially receive the components for the transforming device therein, the front housing 231a may perform a cover function of covering the rear housing, and vice versa.

[0350] When the rear housing 231b substantially receives the components for the transforming device, the fastening part 231c may be provided to the rear housing 231b. The rear housing 231b is inserted in the hollow part 250a of the connector and then coupled and fixed to the connector 250 through the fastening part 231c.

[0351] A perforated hole 233 of a rotor shaft 220 is formed in a central portion of the rear housing 231b, and a bearing 236 is provided within the perforated hole 233, whereby the rotor shaft 220 is rotatably supported.

[0352] A perforated hole 232 of a drum shaft 210 is formed in a central portion of the front housing 231a, and a bearing 234 is provided within the perforated hole 232, whereby the drum shaft 210 is rotatably supported.

[0353] An input RPM in 1-stage power transform may be regarded as a high RPM. Hence, the bearing 236 supporting the rotor shaft 220 preferably includes a ball bearing. In addition, two ball bearings are preferably provided along the rotor shaft 220. An output RPM in 2-stage power transform may be regarded as a low RPM. Hence, a bearing supporting the drum shaft 210 preferably uses an oilless bearing. This is to secure reliability and save manufacturing costs.

[0354] Power of the rotor 260 is directly transferred to the rotor shaft 220. The rotor shaft 220 is solidly coupled to the rotor 260 through the rotor coupler 296, the washer 295 and the stud 194. One side of the rotor shaft 220 is coupled to the rotor, and the other side may configure a first sun ear 221. Hence, the rotor shaft 220 and the first sun gear 221 may be regarded as a single part or component, and may be the component formed of a single material.

[0355] The same first planet gear 223 is located on a radial outside of the first sun gear 221, and the first sun gear and the first planet gear are engaged. If the first planet gear is provided to leave the same space in between along a circumferential direction of the first sun gear, four first planet gears may be provided for example.

[0356] The first planet gear 223 is provided rotatably centering on a roller shaft 222, and the roller shaft 222 may be fixed to a first carrier 243. For the front-rear position fixing of the first planet gear and the fixing of the roller shaft, a first carrier supporter 224 may be provided. Hence, the first planet gear 223 may be rotatably provided to the first carrier 243. As the first planet gear 223 revolves around the first sun gear 221, the first carrier 243 rotates.

[0357] All the first planet gears 223 may be engaged in a manner of being inscribed in a ring gear 244.

[0358] When a deceleration ratio in each step is set to ‘a’, if the ring gear 244 is provided to be fixed within the decelerator housing 231, ‘a’ has the value resulting from adding 1 to a value obtained from dividing the number of gear teeth of the ring gear 244 by the number of teeth of the sun gear.

[0359] If a motor power of N RPM and T torque is inputted to the rotor shaft 220, the first sun gear 221 has the same N RPM and the same T torque.

[0360] As the rotor shaft 220 rotates, the first planet gear 223 and the first carrier 243 rotate. In doing so, the first carrier 243 has a deceleration ratio ‘a’, N/a RPM, and T*a torque. Hence, the power of the rotor shaft 220 is 1-stage transformed through the first carrier 243.

[0361] The first planet gear 223 is rotatably provided to one side (e.g., a rotor shaft side) of the first carrier 243. And, a second sun gear 242 may be provided to the other side (e.g., a drum shaft side) of the second carrier 243. The second carrier 243 and the second sun gear 242 may be configured as an integral part. Thus, the second carrier 243 and the second sun gear 242 rotate as an integral part. Therefore, the second sun gear 242 has a deceleration ratio ‘a’, N/a RPM, and T*a torque.

[0362] As the second sun gear rotates, the second planet gear 213 and the second carrier 211 rotate. The second planet gear 213 may be rotatably provided to the second carrier 211 through a roller shaft 212. For the front-rear position fixing of the second planet gear 213 and the fixing of the roller shaft 212, a second carrier supporter 214 may be provided.

[0363] As the second planet gear 213 revolves around the second sun gear 242, the second carrier 211 rotates.

[0364] In this case, the second carrier 211 has a deceleration ratio ‘a’, N/a/a RPM, and T*a*a torque.

[0365] The second carrier 211 may be coupled to the drum shaft 210. Preferably, the second carrier 211 and the drum shaft 210 may be provided as a single part or component. Hence, the drum shaft 210 has N/a/a RPM and T*a*a torque.

[0366] As described above, a deceleration ratio of a decelerator in the present embodiment is 15:1. Hence, if each of a first-stage deceleration ratio and a second-stage deceleration ratio has the same value ‘a’, the value of ‘a’ may have the square root of 15, i.e., 3.871.

[0367] Here, it is very effective to have a final deceleration ratio of the square root of ‘a’ by setting the second stage deceleration ratio to ‘a’ with the first stage deceleration ratio ‘a’. This is because a ring gear used for the first stage deceleration and the second stage deceleration may be implemented as a single ring gear. Namely, a rear side of a fixed single ring gear may be engaged with the first planet gears and a front side of the single ring gear may be engaged with the second planet gears. Therefore, implementation of a decelerator can be very facilitated.

[0368] In addition, there is an effect that radius sizes of planet gears and carriers can be set equally. Hence, it is able to implement a decelerator having a cylindrical shape and the same front-rear diameter. Of course, a fastening part structure for the fixed coupling of a decelerator is out of the question.

[0369] The drum shaft 210 may be solidly fixed to the drum rear wall through a drum shaft coupler 293, a washer 292 and a stud 291.

[0370] Eventually, according to the present embodiment, there decelerator 230 is provided between the drum rear wall and the rotor inner wall, thereby transforming high-RPM and low-torque of the rotor into low-RPM and high-torque of the drum.

[0371] Meanwhile, the rotor shaft 220 and the drum shaft 210 are spaced apart from each other in front-rear direction. The rotor shaft 220 and the drum shaft 210 are configured to form a co-axis, and the co-axis needs to be maintained solidly.

[0372] To this end, a middle shaft 241 may be provided. One side of the middle shaft may form a co-axis by being connected to the rotor shaft 220, and the other side may form the co-axis by being connected to the drum shaft 210.

[0373] The middle shaft 241 may configure an integral part with the first carrier 243 and the second sun gear 242. Namely, they may include a single component or part. Hence, the middle shaft 241 and the first carrier 243 may rotate as an integral part. This means that a rotation speed of the first carrier is different from a rotation speed of each of the rotor shaft and the drum shaft.

[0374] Therefore, a structure for supporting that the middle shift 241, the drum shaft 210 and the rotor shaft 220 may rotate at different rotation speeds, respectively or rotate independently is necessary. Of course, such a support structure may include a structure for forming and maintaining a co-axis.

[0375] The middle shaft 241 is positioned in a manner of being inserted in the center of the drum shaft 210 and the center of the rotor shaft 220. The middle shaft may be inserted in a hollow formed at prescribed portions of the drum and rotor shafts. A bearing 235 is provided between the drum shaft and the middle shaft. Likewise, a bearing 237 may be provided between the rotor shaft and the middle shaft.

[0376] A thrust generated between the rotor 260 and the drum rear wall 22 may be supported the aforementioned bearings 236 and 234. For example, it may be supported in a manner that a short sill formed on a lateral side of the oilless bearing 234 comes in contact with a circumference of the drum shaft and a lateral side of the ball bearing 236 comes in contact with an annular ring (no reference number in FIG. 10) coupled to the shafts. Therefore, a frictional force due to the thrust in the drive unit or the power transfer unit can be minimized.

[0377] Meanwhile, a decelerator different from the above-described planet gear decelerator of one embodiment of the present disclosure may be applicable to a dryer according to one embodiment of the present disclosure. For example, a cyclo-decelerator is applicable.

[0378] A cyclo-decelerator is a decelerator that uses a decelerating device having a cyclo-tooth shape. The cyclo-decelerator is a decelerator of which gear tooth shape forms a continuous curve of a cyclo-tooth shape to enable rolling contact. As an input shaft and an output shaft may form a co-axis, it is applicable to the present embodiment.

[0379] In a dryer according to one embodiment of the present disclosure, uniform drying can be performed. As shown in FIG. 14, it can be observed that an air flow speed is uniform irrespective of a front-rear position of a drum in a dryer according to one embodiment of the present disclosure.

[0380] The speed standard deviation means a deviation of an air flow speed in a whole cross section at a drum cross section position. If a speed standard deviation is small, it means that a speed difference in a whole area of a specific cross section is insignificant.

[0381] Therefore, according to the present embodiment, it can be observed that a speed standard deviation at seven cross section positions between front and rear sides of a drum is about 0.7 or below, and more particularly, about 0.6 or below except the rear side of the drum. Since air inflow is performed in a predetermined area of the drum rear side only, such a result is predictable.

[0382] On the contrary, in a related art dryer having a structure that air flows in through a drum rear side, it is observed that a speed standard deviation increases significantly depending on a drum cross section position. Particularly, it can be observed that the speed standard deviation is greater than that of the present disclosure at all positions. In addition, it can be observed that the speed standard deviation is significantly high near the rear side of the drum. This paradoxically shows that the speed standard deviation is significantly low at the rear side of the drum in one embodiment of the present disclosure.

[0383] It can be assumed that the speed standard deviation characteristics of a dryer according to one embodiment of the present disclosure are attributed to the annular air supply area of the rear case and the annular air intake area of the rear wall of the drum. That is, since the position of air entering the drum is the same regardless of whether the drum is rotated or a rotation speed of the drum, it can be assumed that such characteristics are provided. In addition, it can be assumed that the area where air enters the drum and the area where air is supplied to the drum are increased in comparison to conventional dryers.

[0384] In particular, according to the present embodiment, air can flow into a drum throughout 360 degrees inside. Therefore, a larger volume of air can be supplied into the drum, and air can be supplied evenly. In addition, in a dryer according to the present embodiment, drying efficiency can be increased and uniform drying can be performed.