Scroll compressor having offset portion provided on discharge port to reduce backflow

Abstract

A scroll compressor includes fixed and movable scrolls defining a compression chamber, and a crankshaft. The movable scroll at least partially covers a discharge port formed in the fixed scroll to change a communication area that is a portion of a total area of the discharge port that contributes to communication with the compression chamber. First to third rotation angle positions become larger in order. As the crankshaft rotates from the first to second rotation angle position the communication area increases at a first rate. In the first rotation angle position the compression chamber and the discharge port start communicating with each other. The second rotation angle position is a preliminary discharge interval angle. As the crankshaft rotates from the second to third rotation angle position the communication area increases at a second rate. The second rate of increase is greater than the first rate of increase.

Claims

1. A scroll compressor comprising: a fixed scroll including a fixed scroll wrap; a movable scroll revolvable with respect to the fixed scroll, the movable scroll including a movable scroll wrap; and a crankshaft rotatable to cause the movable scroll to revolve, the fixed scroll and the movable scroll defining a compression chamber configured to compress a fluid, a discharge port formed in the fixed scroll, the discharge port being configured to discharge the fluid from the compression chamber, the movable scroll wrap at least partially covering the discharge port such that a communication area changes as the movable scroll revolves, the communication area being an area of a portion of a total area of the discharge port that contributes to communication with the compression chamber, the communication area increasing at a first rate of increase as the crankshaft rotates from a first rotation angle position to a second rotation angle position, the first rotation angle position corresponding to a disposition in which the compression chamber and the discharge port start communicating with each other, and the second rotation angle position being a preliminary discharge interval angle greater than the first rotation angle position, the communication area increasing at a second rate of increase as the crankshaft rotates from the second rotation angle position to a third rotation angle position, the third rotation angle position being greater than the second rotation angle position, and the second rate of increase being greater than the first rate of increase, and a profile of the discharge port including a section configured to coincide with a profile of an outer edge of the movable scroll wrap when the crankshaft is at a prescribed rotation angle position disposed between the first rotation angle position and the third rotation angle position, and an offset portion that is offset to an outer side of the discharge port with respect to the section such that the movable scroll wrap does not cover the offset portion when the crankshaft is at the prescribed rotation angle position.

2. The scroll compressor according to claim 1, wherein the preliminary discharge interval angle is 20° to 60°.

3. The scroll compressor according to claim 2, wherein the communication area in the second rotation angle position is 7% to 15% of the total area of the discharge port.

4. The scroll compressor according to claim 2, wherein the second rate of increase is two or more times the first rate of increase.

5. The scroll compressor according to claim 2, wherein the third rotation angle position is greater than the second rotation angle position by 90° or more.

6. The scroll compressor according to claim 2, wherein the preliminary discharge interval angle is 35° to 60°.

7. The scroll compressor according to claim 1, wherein the communication area in the second rotation angle position is 7% to 15% of the total area of the discharge port.

8. The scroll compressor according to claim 7, wherein the second rate of increase is two or more times the first rate of increase.

9. The scroll compressor according to claim 7, wherein the third rotation angle position is or more greater than the second rotation angle position by 90° or more.

10. The scroll compressor according to claim 1, wherein the second rate of increase is two or more times the first rate of increase.

11. The scroll compressor according to claim 10, wherein the second rate of increase is three or more times the first rate of increase.

12. The scroll compressor according to claim 10, wherein the third rotation angle position is greater than the second rotation angle position by 90° or more.

13. The scroll compressor according to claim 1, wherein the third rotation angle position is greater than the second rotation angle position by 90° or more.

14. The scroll compressor according to claim 1, wherein the preliminary discharge interval angle is 35° to 60°.

15. The scroll compressor according to claim 1, wherein the offset portion is disposed at an intermediate position along the section such that the section is divided in two by the offset portion.

16. The scroll compressor according to claim 1, wherein the fixed scroll includes a fixed scroll end plate and the movable scroll includes a movable scroll end plate, the discharge port is formed in the fixed scroll end plate, a recessed portion is formed in the movable scroll end plate, and a positional relationship between a profile of the recessed portion and the profile of the discharge port is point symmetrical.

17. The scroll compressor according to claim 16, wherein an offset portion is provided on the profile of the recessed portion.

Description

BRIEF DESCRIPTION OF DRAWINGS

(1) FIG. 1 is a sectional view of a scroll compressor 10 pertaining to a first embodiment of the invention.

(2) FIG. 2 is a schematic exploded view of a central portion of a compression element 50 pertaining to the first embodiment of the invention.

(3) FIG. 3 is a top view of a wrap 52b of a movable scroll 52.

(4) FIG. 4 is a schematic plan view of the central portion of the compression element 50 pertaining to the first embodiment of the invention.

(5) FIG. 5 is a schematic plan view of the central portion of the compression element 50 pertaining to the first embodiment of the invention.

(6) FIG. 6 is a graph showing a change in a communication area S resulting from the rotation of a crankshaft 30.

(7) FIG. 7 is a schematic plan view of the central portion of the compression element 50 pertaining to a comparative example.

(8) FIG. 8 is a schematic plan view of the central portion of the compression element 50 pertaining to an example modification of the first embodiment of the invention.

(9) FIG. 9 is a schematic exploded view of the central portion of the compression element 50 pertaining to a second embodiment of the invention.

(10) FIG. 10 is a schematic plan view of the central portion of the compression element 50 pertaining to the second embodiment of the invention.

DETAILED DESCRIPTION OF EMBODIMENT(S)

First Embodiment

(1) Overall Configuration

(11) FIG. 1 is a sectional view of a scroll compressor 10 pertaining to a first embodiment of the invention. The scroll compressor 10 compresses fluid low-pressure refrigerant it has sucked in into high-pressure refrigerant and discharges the high-pressure refrigerant. The scroll compressor 10 has a casing 11, a motor 20, a crankshaft 30, a compression element 50, and a high-pressure space forming member 60.

(2) Detailed Configuration

(12) (2-1) Casing 11

(13) The casing 11 houses constituent elements of the scroll compressor 10. The casing 11 has a middle body portion 11a and also an upper portion 11b and a lower portion 11c that are secured to the middle body portion 11a, and forms an inside space. The casing 11 has a strength able to withstand the pressure of the high-pressure refrigerant existing in the inside space. In the casing 11 are provided a suction pipe 15 for sucking in the low-pressure refrigerant that is a fluid and a discharge pipe 16 for discharging the high-pressure refrigerant that is a fluid.

(14) (2-2) Motor 20

(15) The motor 20 generates power needed for the compression operation. The motor 20 has a stator 21, which is directly or indirectly secured to the casing 11, and a rotor 22 that can rotate. The motor is driven by electrical power supplied by a conductor wire not shown in the drawings.

(16) (2-3) Crankshaft 30

(17) The crankshaft 30 is for transmitting to the compression element 50 the power generated by the motor 20. The crankshaft 30 is pivotally supported by bearings secured to a first bearing securing member 70 and a second bearing securing member 79 and can rotate together with the rotor 22. The crankshaft 30 has a main shaft portion 31 and an eccentric portion 32. The main shaft portion 31 is secured to the rotor 22.

(18) (2-4) Compression Element 50

(19) The compression element 50 compresses the low-pressure refrigerant into the high-pressure refrigerant. The compression element 50 has a fixed scroll 51 and a movable scroll 52. Moreover, compression chambers 53, in which the compression operation is performed, are formed in the compression element 50.

(20) (2-4-1) Fixed Scroll 51

(21) The fixed scroll 51 is directly or indirectly secured to the casing 11. The fixed scroll 51 has a flat plate-shaped end plate 51a and a wrap 51b that is erected on the end plate 51a. The wrap 51b is spiral and has the shape of an involute curve, for example. A discharge port 55 is formed in the center of the end plate 51a.

(22) (2-4-2) Movable Scroll 52

(23) The movable scroll 52 is attached to the eccentric portion 32 of the crankshaft 30 and can revolve while sliding against the fixed scroll 51 because of the rotation of the crankshaft 30. The movable scroll 52 has a flat plate-shaped end plate 52a and a wrap 52b that is erected on the end plate 52a. The wrap 52b is spiral and has the shape of an involute curve, for example.

(24) (2-4-3) Compression Chambers 53

(25) The compression chambers 53 are spaces surrounded by the fixed scroll 51 and the movable scroll 52. The wrap 51b of the fixed scroll 51 and the wrap 52b of the movable scroll 52 contact each other at plural places, so plural compression chambers 53 are simultaneously formed. The compression chambers 53 decrease in capacity while moving from the outer peripheral portion of the compression element 50 to the central portion in accompaniment with the revolution of the movable scroll 52.

(26) (2-5) High-Pressure Space Forming Member 60

(27) The high-pressure space forming member 60 divides the inside space of the casing 11 into a low-pressure space 61 and a high-pressure space 62. The high-pressure space forming member 60 is provided in the neighborhood of the discharge port 55 of the fixed scroll 51. The high-pressure space 62 extends over a range including the outer side of the discharge port 55, the lower side of the first bearing securing member 70, the periphery of the motor 20, and the periphery of the second bearing securing member 79.

(3) Basic Operation

(28) The motor 20 is driven by electrical power and causes the rotor 22 to rotate. The rotation of the rotor 22 is transmitted to the crankshaft 30, whereby the eccentric portion 32 causes the movable scroll 52 to revolve. The low-pressure refrigerant is sucked from the suction pipe 15 into the low-pressure space 61 and from there goes into the compression chambers 53 positioned in the outer peripheral portion of the compression element 50. The compression chambers 53 move to the central portion while decreasing in capacity and compress the refrigerant in the process. When the compression chambers 53 reach the central portion, the high-pressure refrigerant produced by the compression exits at the discharge port 55 to the outside of the compression element 50, from there flows into the high-pressure space 62, and finally is discharged through the discharge pipe 16 to the outside of the casing 11.

(4) Detailed Structure

(29) (4-1) Shape of Discharge Port 55

(30) FIG. 2 is a schematic exploded view of the central portion of the compression element 50. In FIG. 2 are shown the lower side of the end plate 51a of the fixed scroll 51 and the upper side of the wrap 52b of the movable scroll 52 that slides against the end plate 51a. The discharge port 55 is provided in the end plate 51a of the fixed scroll 51. The discharge port 55 runs through the end plate 51a. A later-described offset portion 55x is provided in the profile of the discharge port 55.

(31) FIG. 3 is a top view of the wrap 52b of the movable scroll 52. The spiral shape of the wrap 52b lies along a center curve 52x. The center curve 52x is an involute curve, for example. An inner edge 52i positioned on the center side of the wrap 52b and an outer edge 52o positioned on the outer side are spaced apart from each other across the center curve 52x, and the dimension of the spacing is in principle a fixed value corresponding to the width of the wrap 52b.

(32) FIG. 4 is a schematic plan view of the central portion of the compression element 50. The wrap 51b of the fixed scroll 51 has the same spiral shape as the wrap 52b of the movable scroll 52. The position of the wrap 51b of the fixed scroll 51 is fixed with respect to the discharge port 55. The wrap 52b of the movable scroll 52 relatively moves with respect to the position of the discharge port 55. The plural compression chambers 53 defined by the wrap 51b and the wrap 52b have two types, A-chambers 53a and B-chambers 53b. The A-chambers 53a are compression chambers defined by an inner edge 51i of the wrap 51b of the fixed scroll 51 and the outer edge 52o of the wrap 52b of the movable scroll 52. The B-chambers 53b are compression chambers defined by an outer edge 51o of the wrap 51b of the fixed scroll 51 and the inner edge 52i of the wrap 52b of the movable scroll 52.

(33) The wrap 52b partially covers the discharge port 55 and thereby decides a communication area S that is the area of a portion of the total area of the discharge port 55 that contributes to communication with the A-chamber 53a. The wrap 52b increases/decreases the communication area S by revolving counter-clockwise.

(34) FIG. 4 shows the position of the wrap 52b of the movable scroll 52 at a certain time in one period of revolution. The profile of the discharge port 55 comprises a first section 55a, a second section 55b, and a third section 55c. The first section 55a coincides with the inner edge 51i of the wrap 51b of the fixed scroll 51. The second section 55b coincides with the outer edge 52o of the wrap 52b of the movable scroll 52. The third section 55c moves between the inner edge 51i of the wrap 51b and the outer edge 52o of the wrap 52b. In the second section 55b is formed a small offset portion 55x that is offset to the outer side of the discharge port 55 from the profile of the wrap 52b. That is, the second section 55b comprises two sections that are divided, and the offset portion 55x is sandwiched by those two sections.

(35) The offset portion 55x contributes to increasing the communication area S. In FIG. 4, the communication area S coincides with the area of the offset portion 55x.

(36) FIG. 5 shows the position of the wrap 52b of the movable scroll 52 at a time a little past the time of FIG. 4. The wrap 52b moves by revolving movement from the position shown in FIG. 4. In FIG. 5, the communication area S exceeds the area of the offset portion 55x.

(37) (4-2) Change in Communication Area S

(38) FIG. 6 is a graph schematically showing a change in the communication area S resulting from the rotation of the crankshaft 30. In the graph is also shown a change in the communication area S of the discharge port 55 of the compression element 50 pertaining to a comparative example shown in FIG. 7. In the comparative example of FIG. 7, in contrast to the configuration pertaining to the invention, the offset portion 55x is not formed in the second section 55b of the profile of the discharge port 55.

(39) The horizontal axis of the graph in FIG. 6 is a rotation angle position θ of the crankshaft 30. A first rotation angle position θ1 corresponds to a disposition in which the A-chamber 53a of the compression element 50 pertaining to the invention and the discharge port 55 start communicating with each other. A second rotation angle position θ2 is a preliminary discharge interval angle Δθ greater than the first rotation angle position θ1. A third rotation angle position θ3 is greater than the second rotation angle position θ2 from the second rotation angle position.

(40) In the configuration pertaining to the comparative example, before the rotation angle position θ reaches the second rotation angle position θ2, the communication area S is zero, and after the rotation angle position θ has reached the second rotation angle position θ2, the communication area S suddenly increases at a large second rate of increase G2. This increase continues at least until the third rotation angle position θ3.

(41) In contrast, in the configuration pertaining to the invention, preceding the increase at the large second rate of increase G2, the communication area S increases at a small first rate of increase G1 as the rotation angle position θ moves from the first rotation angle position θ1 to the second rotation angle position θ2.

(42) (4-3) Operation of Compression Element 50

(43) In the operation of the compression element 50 pertaining to the invention, the fluid refrigerant is discharged through the opening of the offset portion 55x in the time period from the first rotation angle position θ1 to the second rotation angle position θ2. In this time period, the communication area S increases at the small first rate of increase G1, and discharge with a low flow rate called “preliminary discharge” is performed.

(44) The preliminary discharge is performed over the preliminary discharge interval angle Δθ that is the difference between the second rotation angle position θ2 and the first rotation angle position θ1. The preliminary discharge interval angle Δθ is designed so as to be 20° to 60°. After the preliminary discharge has ended, discharge with a high flow rate called “main discharge” is performed in the time period from the second rotation angle position θ2 to the third rotation angle position θ3.

(45) In the preliminary discharge, the communication area S increases from zero to SP.

(46) In the main discharge, the communication area S increases from SP to at least SF.

(5) Characteristics

(47) (5-1)

(48) For a predetermined amount of time after the A-chamber 53a of the plural compression chambers 53 and the discharge port 55 start communicating with each other, that is, as the crankshaft 30 rotates from the first rotation angle position θ1 to the second rotation angle position θ2, the communication area S gently increases. At this time, some of the fluid refrigerant inside the A-chamber 53a is discharged at a low flow rate, whereby the pressure of the fluid refrigerant inside the A-chamber 53a becomes lower. Consequently, backflow of the fluid refrigerant to the A-chamber 53a as the crankshaft 30 thereafter rotates from the second rotation angle position θ2 to the third rotation angle position θ3 can be inhibited.

(49) (5-2)

(50) The preliminary discharge interval angle Δθ having a predetermined size of 20° to 60° is ensured. Consequently, backflow of the fluid can be more reliably inhibited.

(51) (5-3)

(52) The communication area S may also be set so as to become 7% to 15% of the total area of the discharge port 55 as the crankshaft 30 rotates from the first rotation angle position θ1 to the second rotation angle position θ2. In this case, the preliminary discharge with a low flow rate can be reliably realized.

(53) (5-4)

(54) The second rate of increase G2 in the main discharge with the high flow rate may also be two or more times the first rate of increase G1 in the preliminary discharge with the low flow rate. In this case, the flow rates in the two discharge stages change significantly, so backflow reduction becomes reliable.

(55) (5-5)

(56) The second rate of increase G2 in the main discharge with the high flow rate may also be three or more times the first rate of increase G1 in the preliminary discharge with the low flow rate. In this case, the flow rates in the two discharge stages change more significantly, so backflow reduction becomes more reliable.

(57) (5-6)

(58) The third rotation angle position θ3 may be determined so as to be 90° or more greater than the second rotation angle position θ2. In this case, the size of the range of the rotation angle at which the main discharge can be executed can be maintained.

(59) (5-7)

(60) The preliminary discharge interval angle Δθ may be determined so as to be 35° to 60°. In this case, the value of the preliminary discharge interval angle Δθ at which the fluid refrigerant is preliminary discharged at a low flow rate is greater, so backflow of the fluid refrigerant is more reliably inhibited or reduced.

(61) (5-8)

(62) The offset portion 55x slightly increases the communication area S. At this time, some of the fluid inside the A-chamber 53a of the compression chambers 53 is discharged through the offset portion 55x at a low flow rate, whereby the pressure of the fluid inside the A-chamber 53a becomes lower. Consequently, backflow of the fluid to the A-chamber 53a can be inhibited by simple means.

(6) Example Modifications

(63) FIG. 8 is a schematic view of the central portion of the compression element 50 pertaining to an example modification of the above embodiment of the invention. In the example modification of FIG. 8, the shape of the offset portion 55x differs from the configuration of FIG. 4.

(64) According to this configuration, the profile of the discharge port 55 does not have a section where the radius of curvature of small, so it is easy to process the discharge port 55 in the manufacturing process of the scroll compressor 10.

Second Embodiment

(1) Configuration

(65) FIG. 9 is a schematic exploded view of the central portion of the compression element 50 of the scroll compressor 10 pertaining to a second embodiment of the invention. The second embodiment differs from the first embodiment in the structure of the end plate 52a of the movable scroll 52, but configurations other than this are the same as those of the first embodiment.

(66) In FIG. 9 are shown the lower side of the wrap 51b of the fixed scroll 51 and the upper side of the end plate 52a of the movable scroll 52 that slides against the wrap 51b. A recessed portion 57 is provided in the end plate 52a of the movable scroll 52. The profile of the recessed portion 57 is congruent with the profile of the discharge port 55.

(67) The recessed portion 57 has a depth of 2 mm, for example, and does not run through the end plate 52a. An offset portion 57x is provided in the recessed portion 57.

(68) FIG. 10 is a schematic plan view of the central portion of the compression element 50. The positional relationship between the profile of the discharge port 55 and the profile of the recessed portion 57 is point-symmetrical in the same way as the positional relationship between the wrap 51b of the fixed scroll 51 and the wrap 52b of the movable scroll 52. The recessed portion 57 communicates with the discharge port 55 in the central region of the compression element 50.

(2) Characteristics

(69) The offset portion 55x of the discharge port 55 contributes to increasing the communication area relating to the communication between the discharge port 55 and the A-chamber 53a. In the same way, the offset portion 57x of the recessed portion 57 contributes to increasing the communication area relating to the communication between the discharge port 55 and the B-chamber 53b.

(70) For a predetermined amount of time after the B-chamber 53b of the plural compression chambers 53 and the discharge port 55 start communicating with each other, the communication area relating to the communication between the discharge port 55 and the B-chamber 53b gently increases. At this time, some of the fluid refrigerant inside the B-chamber 53b is discharged at a low flow rate, whereby the pressure of the fluid refrigerant inside the B-chamber 53b becomes lower. Consequently, backflow of the fluid refrigerant to the B-chamber 53b thereafter can be inhibited.

(3) Example Modifications

(71) The example modifications of the first embodiment may also be applied to the second embodiment.