DIVIDED GEAR WHEEL FOR AN AUTOMATIC POWER TRANSMISSION SYSTEM

Abstract

The present application relates to a divided gear wheel 100, 200, for an automatic power transmission system 1, to an automatic power transmission system and a method to operate said automatic power transmission system. The automatic power transmission system comprises at least one divided gear wheel that comprises an inner part 130, 230, being engageable with a shaft and an outer part 110, 210, comprising teeth, adapted for torque transmission to another gear wheel. The inner part and the outer part have a common rotational axis, and the inner part is at least partially arranged within the outer part. Further, the inner part is coupled to the outer part by means of two elastic elements, so that the inner part is arranged angularly deflectable with respect to the outer part around the common rotational axis. The inner part and the outer part are adapted to rotate with the same angular speed if the elastic elements are fully loaded.

Claims

1. A divided gear wheel (100, 200), for an automatic power transmission system (1), wherein the divided gear wheel (100, 200) comprises an inner part (130, 230), being engageable with a shaft (10, 20) and an outer part (110, 210), comprising teeth (115, 215), adapted for torque transmission to another gear wheel, wherein the inner part (130, 230) and the outer part (110, 210) have a common rotational axis, and wherein the inner part (130, 230) is at least partially arranged within the outer part (110, 210), the inner part (130, 230) being coupled to the outer part (110, 210) by means of two elastic elements (154, 156, 254, 256), so that the inner part (130, 230) is arranged angularly deflectable with respect to the outer part (130, 230) around the common rotational axis, wherein the inner part (130, 230) and the outer part (110, 210) are adapted to rotate with the same angular speed if the elastic elements (154, 156, 254, 256) are fully loaded, wherein the first elastic element (154, 254) is partially arranged within the second elastic element (156, 256) and protrudes out of the second elastic element (156, 256) on a front face, wherein a spring rate of the first elastic element (154, 254) is lower than a spring rate of the second elastic element (156, 256) and wherein the inner part (130, 230) comprises engagement means (131, 231) that are adapted to engage with an engaging part (30, 60) of an automatic power transmission system (1), wherein upon engagement, the inner part (130, 230) is torque proof engaged with a shaft.

2. An automatic power transmission system (1), in particular for an automotive vehicle, comprising: an input shaft (10), supporting input gear wheels (100); an output shaft (20), supporting output gear wheels (200), wherein each of the input gear wheels (100) engages with a corresponding output gear wheel (200), thereby defining a gear ratio, wherein at least one of the input gear wheels (100) and/or at least one of the output gear wheels (200), of a gear ratio, is a divided gear wheel according to claim 1; and at least one engaging part (300, 60), that is assigned to the input shaft (10) or the output shaft (20) and to at least a divided gear wheel, wherein the engaging part (30, 600) is arranged axially movable along the assigned shaft (10, 20) to change a gear ratio, wherein the engaging part (30, 600) is adapted to engage with the inner part (130, 230) of the divided gear wheel, thereby torque proof fixing the inner part (130, 230) with the shaft.

3. The automatic power transmission system (1) according to claim 2, wherein the engaging part (30, 60) is arranged concentrically to the assigned shaft (10, 20), and wherein the axial movement of the engaging part (30, 60) along the assigned shaft (10, 20) is guided by a helical means (80, 90), so that the engaging part is rotated relative to the assigned shaft upon axial movement.

4. The automatic power transmission system (1) according to any of claims 2 to 3, wherein the helical means (80, 90) is integrally formed with the assigned shaft (10, 20).

5. The automatic power transmission system (1) according to any of claims 2 to 4, wherein the helical means (80, 90) comprises a helix angle , that follows the equation $.Math..Math.=\frac{\tan \left(\right).Math.U_a}{R},$ wherein defines a difference in angular velocity at the beginning of a gear ratio changing action between the assigned shaft and a gear wheel to be engaged, wherein U.sub.a is a desired velocity of the axial movement, and wherein R is the effective radius of the helical means.

6. The automatic power transmission system (1) according to any of claims 2 to 5, wherein the helical means (80) comprises at least one helical groove (82, 84) and wherein the engaging part (30) comprises at least one helical arm (32, 34), being guided in the helical groove (82, 84), and a corresponding engagement means (36, 38) arranged at the helical arm (32, 34) and being adapted to engage with an engagement means (231) provided on an inner circumferential surface of the inner part (230) of the divided gear wheel (200).

7. The automatic power transmission system (1) according to any of claims 2 to 6, wherein the helical means (80, 90) comprises at least one helical tooth (92) on an outer circumferential surface and wherein the engaging part (60) comprises a bushing portion (61) having at least one corresponding helical tooth (62) provided on an inner circumferential surface, and a corresponding engagement means (66) arranged at the bushing portion and being adapted to engage with the engagement means (131, 231) of the inner part (130, 230) of the divided gear wheel (100, 200), wherein the engagement means (131, 231) are preferably provided on an outer circumferential surface and/or a front face of the of the inner part (130, 230) of the divided gear wheel (100, 200).

8. The automatic power transmission system (1) according to any of claims 2 to 7, wherein at least one gear ratio of the automatic power transmission system (1) is defined by two divided gear wheels (100, 200), according to claim 1.

9. The automatic power transmission system (1) according to any of claims 2 to 8, wherein at least one additional gear wheel is supported by the input shaft (10) and/or the output shaft (20), and wherein the additional gear wheel preferably engages with a gear wheel of a planetary gear.

10. The automatic power transmission system (1) according to any of claims 2 to 9, further comprising a sequential shift actuator, adapted to axially move the at least one engaging part (300, 60), to change a gear ratio.

11. The automatic power transmission system (1) according to any of claims 2 to 10, further comprising a control unit that is adapted to command a gear ratio changing action.

12. A method for operating an automatic power transmission system (1) according to any of claims 2 to 11, the method comprising the following steps: rotating the input shaft and transferring power to the output shaft by means of a first gear ratio; commanding a gear ratio changing action from a first gear ratio to a second gear ratio; axially moving at least one engaging part (30, 600) and thereby disengaging the inner part (130, 230) of the divided gear wheel (100, 200) of the first gear ratio from the torque proof fixing with the shaft and engaging the inner part (130, 230) of the divided gear wheel (100, 200) of the second gear ratio, thereby torque proof fixing said inner part (130, 230) with the shaft, wherein the inner part (130, 230) of the divided gear wheel (100, 200) of the second gear ratio is angularly deflected with respect to the outer part (130, 230) and loads the elastic element (154, 156, 254, 256); rotating the input shaft and transferring power to the output shaft by means of the second gear ratio.

13. The method according to claim 12, wherein during axial moving the at least one engaging part (30, 60) the engaging part (30, 600) is guided by a helical means and rotated relative to the assigned shaft to compensate for a difference in angular velocity at the beginning of the commanded gear ratio changing action between the assigned shaft and the gear wheel to be engaged of the second gear ratio.

14. An automotive vehicle comprising a divided gear wheel (100, 200) according to claim 1 or an automatic power transmission system (1) according to any one of claims 2 to 11.

Description

BRIEF DESCRIPTION OF THE FIGURES

[0059] In the following, preferred embodiments of the present invention are described with respect to the accompanying figures.

[0060] FIG. 1 is a schematic illustration of an output shaft, supporting two output gear wheels;

[0061] FIG. 2 is a schematic perspective view of an automatic power transmission system according to a first embodiment;

[0062] FIG. 3 is a schematic side view of an engaging part;

[0063] FIG. 4 is a schematic cut view of an input gear wheel and an output gear wheel, defining a gear ratio;

[0064] FIGS. 5A to C give a schematic illustration of a gear ratio changing action sequence;

[0065] FIG. 6A to C give a further schematic illustration of the gear ratio changing action sequence illustrated in FIG. 5;

[0066] FIG. 7 is a schematic cut view of an automatic power transmission system according to a second embodiment;

[0067] FIG. 8A is a schematic top view of an automatic power transmission system according to the second embodiment;

[0068] FIG. 8B is a schematic cut view of an input gear wheel and an output gear wheel, defining a gear ratio;

[0069] FIGS. 8C and 8D are schematic detailed views of an engaging part, being engaged/disengaged with an inner part of a divided gear wheel;

[0070] FIG. 9 is a schematic cut view of a further engaging part;

[0071] FIG. 10 is a schematic perspective view of an automatic power transmission system,

[0072] FIGS. 11A and 11B are a schematic illustrations of an automatic power transmission system;

[0073] FIGS. 12A to 12E give a schematic illustration of a gear ratio changing action sequence presenting a gradient torque transfer, and

[0074] FIG. 13 gives a schematic illustration of individual components of a divided gear wheel.

DETAILED DESCRIPTION

[0075] As will become apparent from the following, the present application allows to provide a sequential automatic power transmission system that delivers power continuously without power losses from friction between clutch disks, due to the absence of clutch disengagement (or engagement) in every gear ratio changing action.

[0076] FIG. 1 is a schematic illustration of an output shaft 20, supporting two output gear wheels 200a, 200b. The output shaft 20 is provided with helical means 80 that are provided in form of a helical groove. The helical means serve to guide an engaging part 30. The engaging party 30 is depicted in greater detail in FIG. 3. The output gear wheels 200a, 200b may be divided gear wheels, as depicted in FIG. 4. The helical means 80 has a helix angle that follows the equation

[00003]$.Math..Math.=\frac{U_v}{R}.Math..Math.\underset{.fwdarw.}{U_v=\tan \left(\right).Math.U_a}.Math..Math..Math..Math.=\frac{\tan \left(\right).Math.U_a}{R}$

wherein defines a difference in angular velocity at the beginning of a gear ratio changing action between the assigned shaft and a divided gear wheel to be engaged, wherein U.sub.a is a desired velocity of the axial movement, and wherein R is the effective radius of the helical means. U.sub.v is the vertical velocity of the engaging part. The given parameters are depicted in FIG. 1.

[0077] FIG. 2 is a perspective view of an automatic power transmission system according to the first embodiment. The automatic power transmission system 1 that is depicted in FIG. 2 comprises an input shaft 10 and an output shaft 20. The input shaft 10 supports the input gear wheels 100a, 100b. The output shaft 20 supports the output gear wheels 200a, 200b. It is apparent that the automatic power transmission system can comprise multiple input and output gear wheels and is not limited to the two pairs of input/output gear wheels, depicted in FIG. 2.

[0078] Input gear wheels 100a, 100b are fixed gear wheels, i.e. they rotate with the same speed as the input shaft to. Further, input gear wheels 100a, 100b can be divided gear wheels, wherein an inner part of the respective divided gear wheel is torque proof fixed to the input shaft 10 (see e.g. FIG. 4). Output gear wheels 200a, 200b are free gear wheels and are provided as divided gear wheels. Accordingly, if the engaging part 30 is not engaged with the respective output gear wheel 200a, 200b, the output gear wheel 200a, 200b can freely rotate on the output shaft 20. This means that the output shaft 20 and the respective output gear wheels 200a, 200b may have different angular velocities. The engaging part 30 is guided by the helical means 80, which defines two helical grooves 82, 84. The helical grooves 82, 84 receive respective helical arms 32, 34 of the engaging part 30. Further, the engaging part 30 comprises a bushing portion 33 having an actuator coupling in form of a groove or a notch, that is adapted to couple with an actuator that moves the engaging part 30 axially along the output shaft 20 as will be described in greater detail with respect to FIGS. 5A to 6C.

[0079] FIG. 3 is a detailed side view of an engaging part 30. The engaging part 30 comprises a bushing portion 33 that is guided on the output shaft 20. Helical arms 32, 34 extend from the bushing portion 33 and are provided at a distal end with corresponding engagement means 36, 38 that are adapted to engage with engagement means 231 of inner parts 230 of output gear wheels 200. The bushing portion 33 may further be provided with an actuator coupling 35 in form of a groove.

[0080] FIG. 4 is a schematic cut view of an input gear wheel 100a, that is in an engagement with an output gear wheel 200a, defining a first gear ratio. The input gear wheel 100a is provided as a fixed divided gear wheel, wherein the output gear wheel 200a is provided as a free, divided gear wheel. Accordingly, the inner part 130 of the first gear wheel 100a is permanently torque prove fixed to the input shaft 10. An outer part 110 is coupled to the inner part 130 by means of spring elements 154, 156. The spring elements are received in spring compartments, formed by the inner and outer part 110, 130. A bearing 140 allows the outer part 110 to be deflected angularly around the inner part 130. The spring elements 154, 156 are supported by elastic element supports 112 and 132, that are preferably integrally formed with the inner part 110 or the outer part 130, respectively.

[0081] The first spring element 154 may be arranged concentrically within a second spring element 156, wherein the first spring element 154 has a smaller spring rate than the second spring element 156. The outer part 110 is provided with a gearing comprising teeth 115, to transfer torque to the output gear wheel 200a. The output gear wheel 200a is also a divided gear wheel, comprising an inner part 230 and an outer part 210. The outer part 210 is provided with a gearing, comprising teeth 215. Further, the inner part 230 is coupled to the outer part 210 by means of spring elements, 254, 256. The spring elements are supported by respective elastic element supports 232, 212 which are preferably integrally formed with the inner part 230 or the outer part 210, respectively. Spring element 254 may be a first spring element that is concentrically arranged within a second spring element 256 and that has a smaller spring rate as the second spring element 256. Further, the outer part 210 is supported by a bearing 240 that allows for deflecting the inner part 230 relative to the outer part 210. The inner part 230 further comprises engagement means 231, in form of grooves provided on an inner circumferential surface of the inner part 230, facing the output shaft 20. The corresponding engagement means 36, 38 of the engagement means 30 can be inserted into said engagement means 231 and achieve a temporary torque proof connection between the output shaft 20 and the inner part 230 of the output gear wheel 200a. The permanent torque proof connection between the input shaft 10 and the inner part 130 of the input gear wheel 100a is achieved by corresponding engagement means 131, such as a spline shaft or the like.

[0082] A schematic sequence of a gear ratio changing action is illustrated in FIGS. 5 and 6. In particular, FIG. 5 illustrates how an engaging part, being assigned to multiple divided gear wheels, works. FIG. 6 illustrates the function of the divided gear wheels. FIGS. 5 and 6 show schematically a power transmission system, comprising an input shaft 10, an output shaft 20 and two input gear wheels 100a, 100b and two output gear wheels 200a, 200b. The power transmission system may comprise further gear wheels that are presently not depicted. The pair of gear wheels 100a, 200a defines a first gear ratio and the pair of gear wheels 100b, 200b defines a second gear ratio. Further, the power transmission system comprises an engaging part 30. As illustrated, input gear wheels 100a, 100b are fixed gear wheels that can be conventional gear wheels or divided gear wheels. The output gear wheels 200a, 200b are free gear wheels that are provided as divided gear wheels. Accordingly, the first output gear wheel 200a comprises an inner part 230a that is coupled to an outer part 21a by means of two elastic elements 250a. The second output gear wheel 200b comprises an inner part 230b that is coupled to an outer part 210b by means of two elastic elements 250b.

[0083] FIGS. 5A and 6A depict the power transmission system being operated at the first gear ratio, i.e. the first output gear wheel 200a is engaged with the output shaft 20 by means of the engaging part 30. The second output gear wheel 200b is disengaged and rotates freely. FIGS. 5B and 6B depict the power transmission system upon a gear ratio changing action from the first gear ratio to the second gear ratio and FIGS. 5C and 6C depict the power transmission system being operated at the second gear ratio, i.e. the second output gear wheel 200b is engaged with the output shaft 20 by means of the engaging part 30. The first output gear wheel 200a is disengaged and rotates freely.

[0084] To arrive at the state shown in FIGS. 5A and 6A, i.e. operating the power transmission system at the first gear ratio, the power transmission system may be transferred from neutral to the first gear ratio with help of a clutch (not shown). Accordingly, the first pair of gear wheels 100a, 200a starts moving and the engine's power is transferred from the input shaft 10 to the output shaft 20 via the first pair of gear wheels 100a, 200a, defining the first gear ratio.

[0085] The second pair of gear wheels, i.e. gear wheels 100b, 200b are also engaged with each other. However, as gear wheel 200b is a free gear wheel and is not engaged with the output shaft (cf. FIGS. 5A and 6A), gear wheel 200b can rotate freely with respect to the output shaft freely. Accordingly, the second pair of gear wheels 100b, 200b does not transfer torque to the output shaft 20 (or vice versa). The same applies to further pairs of gear wheels (not shown) that define additional gear ratios.

[0086] When engine reaches a desired speed level, e.g. as it tends to leave a desired operation point, or when the driver commands a gear ratio changing action (e.g. from the first gear ratio to the second gear ratio), a control unit may command the respective gear ratio changing action. Accordingly, an actuator (not shown) may push (or pull) the engaging part 30 linearly. Due to the axial movement of the engaging part 30, the engaging part 30 will engage the following divided gear wheel 200b. As the actuator moves the engaging part axially, the engaging part will be forced to accelerate in rotational and axial direction due to the helical guiding. Thus, the engaging part 30 will rotate with the output shaft 30 and in addition with an angular velocity . The dimensions and in particular the helix angle of the helical means and the desired velocity of the axial movement of the engaging part U.sub.a may be chosen so that the angular velocity of the engaging part 30 matches the angular velocity of the following divided gear wheel 200b, upon engaging. Accordingly, when the engaging part 30 reaches the divided gear wheel 200b, they will have the same angular velocity and as a result a smooth engagement can be achieved.

[0087] As shown in FIGS. 5B and 6B, when the engaging part 30 begins entering/engaging the inner part 230b of divided gear wheel 200b the two elastic elements 250b, in its interior begins to be compressed due to the deflection of the inner part 230b. In this point of time, engaging part 30 is still partially engaged with the first output gear wheel 200a. This is, as the length of the corresponding engagement means 36, 38 that engage with the engagement means 231 of the inner parts 230a, 230b of the divided gear wheels 200a, 200b may be equal to the distance from center to center between two consecutive divided gear wheels 200a, 200b.

[0088] The two elastic elements 250b, may comprise a first spring element that is partially arranged within a second spring element and protrudes out of the second spring element on a front face. The spring rate of the first spring element may be smaller than the spring rate of the second spring element. Thus, initially, the first spring element is compressed. Subsequently, if the inner part 230b reaches the second, stiffer spring element the second spring element starts to be compressed. Accordingly, power can be transferred via the spring elements and the inner part 230b to the output shaft 20. The two elastic elements of the previous gear ratio, such as the two elastic elements 250a, of the first output gear wheel 200a, begin to decompress simultaneously up till the engaging part 30 fully engages the desired gear ratio.

[0089] As further shown in FIGS. 5B and 6B, when the engaging part 30 is engaged with both output gear wheels 200a, 200b of the first and second gear ratio, the flow of power is transferred from both gear ratios. Consequently, when the engaging part 30 is engaged only with one output gear wheel 200a, 200b of either the first or the second gear ratio, the flow of power is transferred exclusively by the pair of gear wheels, defining the respective gear ratio, as illustrated in FIGS. 5C and 6C. As the engagement progresses, a greater amount of power will be transferred by the second gear ratio with equivalent decrease of transferred power by the first gear ratio. The reverse action will take place when a smaller gear ratio is desired, e.g. if the gear ratio changing action is from the second to the first gear ratio.

[0090] In the following an example gear ratio changing action is describer, using random numbers of angular velocity of the respective gear wheels. The first input gear wheel 100a may rotate with an angular velocity of 1000 rpm and the first output gear wheel 200a with an angular velocity of 900 rpm (both inner and outer parts 210a, 230a). The second input gear wheel 100b may also rotate with an angular velocity of 1000 rpm, as first and second input gear wheels are fixed gear wheels, as shown in FIGS. 5A and 6A. The second output gear wheel may rotate freely with an angular velocity of 1000 rpm (both inner and outer parts 210b, 230b). Therefor the first gear ratio will be 0.9 and the second gear ratio will be 1.

[0091] The engaging part 30 rotates with the same angular velocity as the output shaft 20, i.e. with goo rpm. Thus, the difference in angular velocity between the engaging part 30 and the second output gear wheel 200b is about 100 rpm

[0092] When a command is given to change the gear ratio, the engaging part 30 begins to move axially with the help of an actuator and is at the same time rotationally accelerated (due to the helical guiding). As a result, when the engaging part 30 reaches the inner part 230b of the second output gear wheel 200b it has an angular velocity, equal to the sum of the rotational speed of the shaft (900 rpm) and the rotational speed due to the helical guiding (e.g. 100 rpm).

[0093] Upon engaging the engaging part 30 with the inner part 230b of the divided gear wheel 200b, the engaging part 30 begins to decelerate, continuing the engagement between the two parts up till it is fully engaged. The outer part 210b of the divided gear wheel 200b still rotates with 1000 rpm and the inner part 230b also decelerates due to the engagement, i.e. it rotates with about 900 rpm. Accordingly, the two elastic elements 250b and in particular, a first spring element is compressed as the engaging part 30 engages the inner part 230b of the divided gear wheel 200b. When the second spring element of the two elastic elements 250b begins to bare load, the two elastic elements 25a (such as the second spring element) of the previous gear ratio (i.e. the first gear ratio) begins to decompress. When the decompression of the previous two elastic elements 250a is completed and the compression of the following two elastic elements 250b is also completed the power is only transferred via the pair of gear wheels 100b, 200b, forming the second gear ratio, as shown in FIGS. 5C and 6C.

[0094] When the engagement of the engaging part 30 and the second output gear wheel 200b completed, the second output gear wheel 200b rotates with an angular velocity of 900 rpm, and so does the second input gear wheel 100b, resulting in an engine velocity of 900 rpm.

[0095] In particular, as the engaging part 30 starts to engage/disengage with any of gear wheels 200a, 200b, the two elastic elements 250a, 250b are compressed, or decompressed, respectively. As soon as the two elastic elements 250b begins to compress, the other two elastic elements 25a begins to decompress. The total needed torque is the sum of torques in the output gear wheels 200a, 200b, when the engaging part 30 is partially engaged in both (scenario of FIGS. 5B and 6B). As a consequence, as the two elastic elements 250b compress, managing greater torque, and the two elastic elements 25a decompress, managing lesser torque up till the torque is fully borne by the second output gear wheel 200b. As a result, when the engagement of the engaging part 30 with the second output gear wheel 200b is completed, the flow of power is as follows: input shaft 10second input gear wheel 100bsecond output gear wheel 200boutput shaft 20. As power can be transferred during the gear ratio changing action, a continuous power transfer is established.

[0096] FIG. 7 is a cut view of an automatic power transmission system according to a second embodiment. The power transmission system 1 shown in FIG. 7 comprises an input shaft 10 and an output shaft 20. The input shaft 10 supports input gear wheels 100a and 100b and the output shaft 20 supports output gear wheels 200a and 200b. As the skilled person will notice, the power transmission system 1 can provide further input and/or output gear wheels that are supported on the input or output shaft, respectively. However, these gear wheels are not shown.

[0097] The input gear wheels 100a, 100b and the output gear wheels 200a, 200b are provided as divided gear wheels, each having an inner part 130a, 130b, 230a, 230b and an outer part 110a, 110b, 210a, 210b. The pair of gear wheels 100a, 200a defines a first gear ratio and the pair of gear wheels 100b, 200b defines a second gear ratio.

[0098] The input gear wheel 100a is a fixed gear wheel, wherein the inner part 130a is permanently torque proof attached to the input shaft 10. So is the output gear wheel 200b. Accordingly, the inner part 230b is permanently torque proof attached to the output shaft 20. As will become apparent from FIG. 7, each gear ratio is defined by a pair of gear wheels, wherein one of the pair of gear wheels is a fixed gear wheel and the respective other one is a free gear wheel. Accordingly, the output gear wheel 200a is a free gear wheel, comprising an inner part 230a that can freely rotate on the output shaft 20, if it is not engaged with an engaging part 60a, as will be described later. Similarly, the input gear wheel 100b is a free gear wheel, comprising an inner part 130b that can freely rotate on the input shaft 10, if not engaged with a respective engaging part 60b. To provide a freely rotating gear wheel, bearings 142b and 242a are provided between the input shaft 10 and the inner part 130b, respectively between the output shaft 20 and the inner part 230a.

[0099] The gear wheels 100a, 100b, 200a, 200b are provided with respective gearings, comprising teeth 115a, 215a, 215b. Further, the divided gear wheels 100a, 100b, 200a, 200b each comprise respective inner parts 130a, 130b, 230a, 230b, that are coupled to respective outer parts 110a, 110b, 210a, 210b by means of sets of two elastic elements 150a, 150b, 250a, 250b. This coupling allows for an angular deflection of the inner parts 130a, 130b, 230a, 230b relative to the outer parts 110a, 110b, 210a, 210b. If the sets of two elastic elements 150, 250 are fully loaded, torque is transferred from the respective inner parts 130a, 130b, 230a, 230b to the outer parts 110a, 110b, 210a, 210b with a ratio of 1:1.

[0100] As shown, the automatic power transmission system 1, as depicted in FIG. 7, differs from the automatic power transmission system 1, as e.g. depicted in FIG. 2, in particular in that the engaging part(s) is designed differently. This different engaging parts 60a, 60b allows to provide an automatic transmission system, having reduced length dimensions. This is, as each free divided gear wheel 100b, 200a is assigned to a separate engaging part 60a, 60b. Accordingly, the free gears of adjacent gear ratios can be provided alternatingly on the input and output shaft 10, 20.

[0101] The engaging parts 60a, 60b are helically guided by respective helical means 90a, 90b that are provided as separate parts and that are attached torque proved to the respective input and output shafts 10, 20. The helical means 90a, 90b are provided with helical teeth 92a, 92b. This helical teeth guide the engaging part 60a, 60b helically, i.e. in an axial and rotational direction as described above.

[0102] Further, each free divided gear wheel comprises at its inner part 230a, 130b engagement means 231a, 131b that are adapted to engage with engagement means 66 of the engaging part 60a, 60b.

[0103] FIG. 8A shows a schematic top view of the automatic power transmission system 1 of FIG. 7. The automatic power transmission system comprises an input shaft 10 and an output shaft 20 as well as input gear wheels 100a, 100b and output gear wheels 200a, 200b. The free gear wheels 100b, 200a can be temporarily torque proof attached to the respective input shaft 10 or output shaft 20 by means of engaging parts 60a, 60b. In the configuration shown in FIG. 8A, the output gear wheel 200a is engaged with the engaging part 6a thereby being able to transfer torque to the output shaft 20. The engaging part 60b is disengaged and thus, the input gear wheel 100b cannot transfer torque to the input shaft 10.

[0104] FIG. 8B is a schematic cut view of the first input gear wheel 100a and the first output gear wheel 200a, that are in engagement with each other. The design of the input and output gear wheels 100a and 200a corresponds to the design of the gear wheels, discussed with respect to FIG. 4. In particular, the input gear wheel 100a corresponds to the input gear wheel 100a. The output gear wheel 200a differs from the output gear wheel 200a depicted in FIG. 4 in respect to the inner part 230a/230a. In particular, the inner part 230a is supported by a bearing 242a on the output shaft 20. No engagement means are provided on the inner circumferential surface of the inner part 230a.

[0105] Those engagement means 231a are provided on a front face of the inner part 230a as shown in FIG. 7.

[0106] FIGS. 8C and 8D show detailed views of the engagement parts 60a, 60b. As shown in FIG. 8C, the engaging part 60b is disengaged and the engagement means 131b of input gear wheel 100b are not engaged with the engaging part 60b. FIG. 8D shows an engaged engaging part 60a. Accordingly, the engagement means of output gear wheel 200a are covered by the engaging part 6a and the helical means 9a can be seen in the top view of FIG. 8D.

[0107] FIG. 9 shows a cut view of an engaging part 60. The engaging part 60 comprises a bushing portion 63 that has on its inner circumferential surface corresponding helical teeth 62 that are in engagement with the helical teeth 92 of helical means 90, as shown e.g. in the previous figures. Thus, helical guiding of the engaging part 60 can be achieved. Further, corresponding engagement means 66 are provided, which are adapted to engage with engagement means of respective inner parts of the divided gear wheels 100, 200. On an outer circumferential surface of the bushing portion 63, an actuator coupling 65 is provided in form of a groove that allows an actuator to move the engaging part axially.

[0108] Figure to shows an example of an automatic power transmission system, comprising six gear ratios, defined by respective pairs of input gear wheels 100a, 100b, 100c, 100d, 100e, 100f and output gear wheels 200a, 200b, 200c, 200d, 200e, 200f. The input gear wheels are supported by the input shaft 10 and the output gear wheels are supported by the output shaft 20.

[0109] FIGS. 11A and 11B show schematic illustrations of an automatic power transmission system wherein according to FIG. 11A a first gear ratio is operated and according to FIG. 11B, a second gear ratio is operated. The first gear ratio is defined by the pair of gear wheels 100a, 200a and the second gear ratio is defined by the pair of gear wheels 100b, 200b.

[0110] The flow of power is illustrated as bold dashed line. According to FIG. 11A, the power is transferred via the input shaft 10 and the engaging part 6a to the input gear wheel 100a and then via the output gear wheel 200a to the output shaft 20. According to FIG. 11B, the power is transferred via the input shaft 10 and the input gear wheel 100b to the output gear wheel 200b. Then, the power is transferred via the engaging part 60b to the output shaft 20.

[0111] Further, the automatic power transmission system 1 may comprise an additional set of gear wheels provided upstream the first gear ratio, to reduce the engines revolutions.

[0112] This set of gear wheels may comprise a primary input gear wheel 410, provided on a primary input shaft 41. The primary input gear wheel 410 may be coupled to a primary complementary input gear wheel 412, which is provided on the input shaft 10. The flow of power may then be transferred from the primary input shaft 41 via the set of gear wheels 410, 412 to the input shaft 10.

[0113] Additionally, or alternatively, the automatic power transmission system 1 may comprise a set of gear wheels provided downstream the last gear ratio of the automatic power transmission system, i.e. at the end of the output shaft 20. This set of gear wheels may comprise a subsequent output gear wheel 422, provided on the output shaft 20. The subsequent output gear wheel 422 may be coupled to a subsequent complementary output gear wheel 420, which is provided on a subsequent output shaft 42. The flow of power may then be transferred from the output shaft 20 via the set of gear wheels 422, 420 to the subsequent output shaft 42. As shown, the divided gear wheels that are free gear wheels are provided alternately on the input shaft 10 and the output shaft 20. Each free gear wheel is assigned with a respective engaging part 60a to 60j. To operate the depicted automatic power transmission system, only one engaging part of the set of engaging parts 60a to 60j is engaged with the respective divided gear wheel, at a time where no power ratio changing action is performed, i.e. when a gear ratio is operated. During power transfer changing actions, two engaging parts may at least partly be engaged with the respective gear wheels, as described above with respect to FIGS. 5A to 6C. To change the gear ratio, the power transmission system requires to change gear ratios sequentially. That means that to change a gear ratio from the first to e.g. the fifth gear ratio, all gear ratios that are sandwiched between the first and fifth gear ratio must be operated for a short period of time. Thus, no direct gear ratio change from the first to the fifth gear ratio is possible.

[0114] The above described automatic power transmission system, comprising divided gear wheels allows for a continuous power transfer during gear ratio changing actions and for reduced power losses.

[0115] FIGS. 12A to 12E show schematic illustrations of the gradient torque transfer between gear ratio n to gear ratio n+1. In the demonstration the engaging part is guided by straight guiding means instead of helical (helix angle equal to zero). Therefore upon axial movement the engaging part rotates with the same angular velocity as the assigned shaft. This set of figures depicts two divided gear wheels of two consecutive gear ratios n, n+1 with both the divided gear wheels being engageable by an engaging part, and the depiction is a schematic equivalent to the previously explained configuration presented in FIG. 6A to 6C. Each engageable divided gear wheel meshes with a corresponding fixed (to the assigned shaft) gear wheel (presented as a tangent circle on top of the divided gear wheels) forming a gear ratio. The fixed gear wheels can either be divided gear wheels or gear wheels as previously mentioned.

[0116] As can be seen in FIG. 12A, the two elastic elements of gear ratio n are fully compressed and the two elastic elements of gear ratio n+1 are fully decompressed. Therefore gear ratio n is selected and the corresponding free divided gear wheel is engaged. The divided gear wheel of gear ratio n+1 is not engaged and therefore free to rotate and as a consequence 100% of the torque is transferred to output shaft by gear ratio n. The term selected is used when the stiffer elastic elements of a gear ratio, are compressed and the term engaged is used when the engaging part interacts with the inner part of the divided gear wheels. As a consequence a divided gear wheel can be engaged but the gear ratio not selected (i.e. the stiffer elastic elements are not compressed, but the softer elastic elements are). In contrast a gear ratio cannot be selected without the divided gear wheel of that gear ratio not being engaged.

[0117] In FIG. 12B a gear changing action is commanded by the CPU and corresponding engaging parts or part are moved.

[0118] As a result gear ratio n continues to be selected and engaged and gear ratio n+1 is engaged but not selected since only the softer elastic element of the two elastic elements starts to compress and provides the time for a complete engagement of the inner part of the divided gear wheel of gear ratio n+1.

[0119] When the engagement is completed only about 0.1% of the torque is transferred to output shaft by gear ratio n+1 (since the stiffer elastic element is not compressed at all) with an equal decrease in the transferred torque by gear ratio n. As can be seen the set of elastic elements of gear ratio n+1 is visually compressed due to the compression of the softer elastic element.

[0120] In FIG. 12C both gear ratios n and n+1 are selected and engaged.

[0121] As a consequence, the stiffer elastic elements of both gear ratios are compressed with the stiffer elastic element of gear ratio n+1 beginning to transfer torque to output shaft, with a corresponding decrease in the transferred torque (to the output shaft) by gear ratio n. For example 80% of the occurring torque is being transferred by gear ratio n and 20% by gear ratio n+1.

[0122] As can be seen in FIG. 12D, as time passes more torque is being transferred by gear ratio n+1 and less torque is being transferred by gear ratio n. As a result the two elastic elements of gear ratio n+1 are more compressed and the two elastic elements of gear ratio n are less compressed. At the presented stage equal amounts of torque are being transferred by each gear ratio.

[0123] Finally in FIG. 12E, gear ratio n+1 transfers 100% of the torque and gear ratio n is not selected nor engaged with its divided gear wheel rotating freely. The two elastic elements of gear ratio n are decompressed and the two elastic elements of gear ratio n+1 are compressed. At this stage the gear changing action is completed and gear ratio n+1 is selected. Since gear ratio n+1 transfers the 99.9% of the torque, the CPU can command the disengagement of gear ratio n.

[0124] In FIG. 13 an alternative configuration of the two elastic elements inside a divided gear wheel is presented, with an exploded view of a divided gear wheel.

[0125] In this alternative the divided gear wheel 200a presented in FIGS. 7 to 8D comprises one spring element as a first elastic element and one rubber element as a second elastic element. More particularly the first softer elastic element 254a comprises a spring element and the second stiffer elastic element 256a comprises a rubber element.

[0126] The arrangement of the two elastic elements is the same as before with the first elastic element being partially arranged within the second elastic element and protruding out of the second elastic element on a front face. As it is obvious the rubber element comprises a corresponding cavity on its core in order to house the spring element. In addition the previously presented bearings have been omitted.

LIST OF REFERENCE SIGNS

[0127] 1 automatic power transmission system [0128] 10 input shaft [0129] 20 output shaft [0130] 30 engaging part [0131] 33 bushing portion [0132] 32 helical arm [0133] 34 helical arm [0134] 35 actuator coupling [0135] 36 corresponding engagement means [0136] 38 corresponding engagement means [0137] 41 primary input shaft [0138] 42 subsequent output shaft [0139] 60 engaging part [0140] 62 corresponding helical teeth [0141] 63 bushing portion [0142] 65 actuator coupling [0143] 66 corresponding engagement means [0144] 80 helical means [0145] 82 helical groove [0146] 84 helical groove [0147] 90 helical means [0148] 92 helical teeth [0149] 100 input gear wheel [0150] 110 outer part [0151] 112 elastic element support [0152] 115 teeth [0153] 130 inner part [0154] 131 engagement means [0155] 132 elastic element support [0156] 140 bearing [0157] 142 bearing [0158] 150 elastic element [0159] 154 elastic element (spring element) [0160] 156 elastic element (spring element) [0161] 200 output gear wheel [0162] 210 outer part [0163] 212 elastic element support [0164] 215 teeth [0165] 230 inner part [0166] 231 engagement means [0167] 232 elastic element support [0168] 240 bearing [0169] 242 bearing [0170] 250 elastic element [0171] 254 elastic element (spring element) [0172] 256 elastic element (spring element) [0173] 410 primary input gear wheel [0174] 412 primary complementary input gear wheel [0175] 420 subsequent complementary output gear wheel [0176] 422 subsequent output gear wheel