Variable displacement mechanism for scroll type compressor

Abstract

In a scroll type compressor having a movable scroll member and a fixed scroll member, the movable scroll member and the fixed scroll member defines compression chambers therebetween. The compression chambers reduce in volume in accordance with orbital motion of the movable scroll member relative to the fixed scroll member. Thus gas is compressed. A variable displacement mechanism for the scroll type compressor has a by-pass passage, a pivotal plate and an actuator. The by-pass passage serves to interconnect the compression chamber in a process of volume-reducing and a suction pressure region. The pivotal plate has a communication hole that partially constitutes the by-pass passage and is selectively pivoted between a first pivotal position for opening the by-pass passage by the communication hole and a second pivotal position for closing the by-pass passage. The actuator serves to pivot the pivotal plate.

Description

BACKGROUND OF THE INVENTION

[0001] The present invention relates to a scroll type compressor for use in a vehicle air conditioner and more particularly to a variable displacement mechanism for varying the displacement of the scroll type compressor.

[0002] A variable displacement mechanism of such type is, for example, disclosed in Unexamined Japanese Patent Publication No. 2001-32787. A compression chamber communicates with a suction pressure region through a by-pass passage in the process of volume-reducing. A spool valve opens and closes the by-pass passage to optionally vary the displacement of the scroll type compressor.

[0003] In the spool valve, a spool is slidably accommodated in a cylinder. The spool has an outer diameter that is substantially equal to the inner diameter of the cylinder and includes a rod for partially constituting the by-pass passage.

[0004] An unwanted feature is that the spool valve of the variable displacement mechanism is configured to open and close a port that opens at the inner circumferential surface of the cylinder (the inner surface of the cylinder) by a valve portion (a column) of the spool so that it is difficult to arrange a seal member at the valve portion. Therefore, the valve portion of the spool contacts the inner circumferential surface of the cylinder so as to prevent refrigerant gas from leaking from the spool valve.

[0005] A small clearance between the valve portion of the spool and the inner circumferential surface of the cylinder effectively suppresses the leakage of the refrigerant gas from the by-pass passage. However, as the clearance between the valve portion of the spool and the inner circumferential surface of the cylinder is small, sliding resistance increases between the spool and the cylinder. Consequently, problems such as deterioration in response to displacement variation and enlargement of an actuator for actuating the spool are arisen.

[0006] Accordingly, in a prior art, in view of suppressing the rise of cost for manufacturing the highly accurate clearance, the clearance between the valve portion of the spool and the inner circumferential surface of the cylinder is relatively large. Then, for example, even if the scroll type compressor is tried to operate at the maximum displacement by closing the by-pass passage, the leakage from the spool valve (the by-pass passage) becomes an obstacle to achieving a desired maximum displacement. Namely, deterioration in performance of the scroll type compressor has arisen. Therefore, there is a need for a variable displacement mechanism that reliably seals a by-pass passage for a scroll type compressor.

SUMMARY OF THE INVENTION

[0007] In accordance with the present invention, in a scroll type compressor having a movable scroll member and a fixed scroll member, the movable scroll member and the fixed scroll member defines compression chambers therebetween. The compression chambers reduce in volume as they move in accordance with orbital motion of the movable scroll member relative to the fixed scroll member. Thus gas is compressed. A variable displacement mechanism for the scroll type compressor has a by-pass passage, a pivotal plate and an actuator. The by-pass passage serves to interconnect the compression chamber in a process of volume-reducing and a suction pressure region. The pivotal plate has a communication hole that partially constitutes the by-pass passage and is selectively pivoted between a first pivotal position for opening the by-pass passage by the communication hole and a second pivotal position for closing the by-pass passage. The actuator serves to pivot the pivotal plate.

[0008] Other aspects and advantages of the invention will become apparent from the following description, taken in conjunction with the accompanying drawings, illustrating by way of example the principles of the invention.

BRIEF DESCRIPTION OF THE DRAWINGS

[0009] The features of the present invention that are believed to be novel are set forth with particularity in the appended claims. The invention together with objects and advantages thereof, may best be understood by reference to the following description of the presently preferred embodiments together with the accompanying drawings in which:

[0010] FIG. 1 is a longitudinal cross-sectional view of a hybrid compressor according to a preferred embodiment of the present invention;

[0011] FIG. 2 is a cross-sectional view that is taken along the line I-I in FIG. 1;

[0012] FIG. 3 is a cross-sectional view that is taken along the line II-II in FIG. 1;

[0013] FIG. 4 is a cross-sectional view that corresponds to FIG. 3 in a state where a pivotal plate is switched to a second pivotal position; and

[0014] FIG. 5 is a cross-sectional view that is taken along the line I-I in FIG. 1 according to an alternative embodiment of the present invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0015] A preferred embodiment of the present invention will now be described with reference to FIGS. 1 through 4. The preferred embodiment applies the present invention to a hybrid compressor C that is a scroll type. The left side and the right side of FIG. 1 respectively correspond to the front side and the rear side of the compressor C.

[0016] The hybrid compressor C will schematically be described at the beginning.

[0017] FIG. 1 illustrates a longitudinal cross-sectional view of the compressor C according to the preferred embodiment of the present invention. The compressor C partially constitutes a refrigeration cycle of a vehicle air conditioner. The compressor C accommodates a compression mechanism 12 and an electric motor 21 in a housing 11. A power transmission mechanism 22 is arranged on an outer wall of the housing 11. The compression mechanism 12 is a scroll type and is configured to optionally vary displacement of the compressor C. The power transmission mechanism 22 receives power from an (internal combustion) engine E for traveling a vehicle.

[0018] The compressor C is selectively driven by one of power from the engine E through the power transmission mechanism 22 and power from the electric motor 21. Thus, with the electric motor 21, air-conditioning (cooling) is optionally enabled during stop of the engine E. Accordingly, the vehicle air conditioner of the preferred embodiment is particularly appropriate for an idle-stop vehicle or a hybrid vehicle.

[0019] The compressor C will now be described in detail.

[0020] Still referring to FIG. 1, the housing 11 includes a casing 11a and a cover 11b. The casing 11a is cylindrical in shape and has a bottom at one end. The cover 11b is fixedly connected to the rear end of the casing 11a. The casing 11a of the housing 11 has a through hole 34 at the center of the bottom of the housing 11, and the through hole 34 extends through the bottom of the housing 11. A pulley shaft 13 is inserted through the through hole 34 and is rotatably supported by the is housing 11 through a bearing 35 in the through hole 34.

[0021] A shaft support member 31 is fixed near the opening end of the casing 11a in the housing 11. A through hole 31a extends through the center of the shaft support member 31. A compressor shaft 19 is coaxially arranged with the pulley shaft 13 in the housing 11. The rear end of the compressor shaft 19 is inserted into the through hole 31a of the shaft support member 31 and is rotatably supported by the shaft support member 31 through a bearing 32 in the through hole 31a. The front end of the compressor shaft 19 is fitted to the rear end of the pulley shaft 13 through a bearing 33 so as to rotate relative to the pulley shaft 13.

[0022] The power transmission mechanism 22 includes a pulley 17 and an electromagnetic clutch 18. The pulley 17 is rotatably supported by the housing 11 and transmits power from the engine E to the pulley shaft 13. The electromagnetic clutch 18, when in an ON-state (energized), permits power transmission between the pulley 17 and the pulley shaft 13 and, when in an OFF-state (de-energized), disrupts the power transmission therebetween.

[0023] A speed increasing mechanism 23 including a planetary gear mechanism is provided between the pulley shaft 13 and the compressor shaft. 19 in the housing 11 for increasing the rotational speed of the pulley shaft 13 and for transmitting the rotation of the pulley shaft 13 to the compressor shaft 19. This speed increasing mechanism 23 has a known structure including a sun gear 45, an internal gear 46, a holder 47 and a plurality of planetary gears 48. With the speed increasing mechanism 23, for example, even if the rotational speed of the pulley shaft13 is relatively low due to an idling state of the engine, the compressor shaft 19 is rotated at a relatively high speed so as to ensure a large amount of refrigerant gas discharged from the compression mechanism 12 per unit time, that is, to exert a relatively high cooling performance.

[0024] A stator 15 is provided on the inner circumferential-surface of the casing 11a of the housing 11 and is located on the front side of housing 11. A rotor 14 is fixedly connected to the compressor shaft 19 in the housing 11 so as to be arranged inside the stator 15. The electric motor 21 includes the stator 15 and the rotor 14. The electric motor 21 integrally rotates the rotor 14 and the compressor shaft 19 by supplying electric current to the stator 15.

[0025] A fixed scroll member 41 is fixedly accommodated at the opening end of the casing 11a in the housing 11. The fixed scroll member 41 includes a base plate 61 which has a disc-shape, an outer wall 62 which has a cylindrical shape and a spiral wall 63. The outer wall 62 extends from the outer periphery of the base plate 61. The spiral wall 63 extends from the base plate 61 inside the outer wall 62. The fixed scroll member 41 is fixedly connected to the rear surface of the shaft support member 31 at the distal end surface of the outer wall 62.

[0026] A crankshaft 43 is provided at the rear end of the compressor shaft 19 and is located at a position that is offset from an axis L of the compressor shaft 19. A bushing 51 is fixedly fitted around the crankshaft 43. A movable scroll member 42 is supported by the bushing 51 through a bearing 52 for rotation relative to the fixed scroll member 41 so as to face the fixed scroll member 41. The movable scroll member 42 includes a base plate 65 which has a disc-shape and a spiral wall 66 that extends from the base plate 65 toward the fixed scroll member 41.

[0027] The fixed scroll member 41 and the movable scroll member 42 engage each other by the spiral walls 63, 66 of the fixed and movable scroll members 41, 42, while the distal ends of the spiral walls 63, 66 respectively contact the base plates 65, 61 of the movable and fixed scroll members 42, 41. Accordingly, the base plate 61 of the fixed scroll member 41, the spiral wall 63 of the fixed scroll member 41, the base plate 65 of the movable scroll member 42 and the spiral wall 66 of the movable scroll member 42 define compression chambers 67.

[0028] A self-rotation blocking mechanism 68 is interposed between the base plate 65 of the movable scroll member 42 and the shaft support member 31 facing the base plate 65. The self-rotation blocking mechanism 68 includes a plurality of cylindrical recesses 68a and a plurality of pins 68b. The cylindrical recesses 68a are provided at the back surface (the front surface) of the base plate 65 of the movable scroll member 42. The pins 68b are arranged at radially outer portions 64 of the shaft support member 31 and are loosely fitted in the respective cylindrical recesses 68a.

[0029] A suction chamber 69 is defined between the outer wall 62 of the fixed scroll member 41 and the outermost portion of the spiral wall 66. An accommodating recess 61b is partially formed at a back surface 61a of the base plate 61 of the fixed scroll member 41 in the range from the adjacent center portion to the adjacent outer periphery. A discharge hole 61c is formed through the center of the base plate 61 of the fixed scroll member 41, and the compression chamber 67 near the center of the base plate 61 communicates with the inner space of the accommodating recess 61b through the discharge hole 61c. A discharge valve 55 constituted of a reed valve is arranged in the accommodating recess 61b of the fixed scroll member 41 for opening and closing the discharge hole 61c. The opening degree of the discharge valve 55 is regulated by a retainer 56, which is fixedly arranged in the accommodating recess 61b of the fixed scroll member 41.

[0030] As the compressor shaft 19 is rotated by the engine E or by the electric motor 21, the movable scroll member 42 orbits around the axis L of the fixed scroll member 41 through the crankshaft 43 in the compression mechanism 12. Then, the self-rotation blocking mechanism 68 blocks the self-rotation of the movable scroll member 42 and only permits the orbital motion of the movable scroll member 42. As the movable scroll member 42 orbits relative to the fixed scroll member 41, the compression chambers 67 are gradually reduced in volume and are moved from the outer side of the spiral walls 63, 66 of the scroll members 41, 42 toward the center side of the spiral walls 63, 66 of the scroll members 41, 42. Thereby, relatively low pressure refrigerant gas introduced from the suction chamber 69 to the compression chambers 67 is compressed. The compressed refrigerant gas is discharged from the compression chamber 67 near the center of the spiral walls 63, 66 to the inner space of the accommodating recess 61b through the discharge hole 61c by pushing away the discharge valve 55.

[0031] An accommodating chamber 36 is defined in the housing 11 between the base plate 61 of the fixed scroll member 41 and the cover 11 b. A pivotal plate 37 which has a donut-shape is accommodated in the accommodating chamber 36. The pivotal plate 37 is laid on the back surface 61a of the base plate 61 of the fixed scroll member 41. The opening of the accommodating recess 61b of the fixed scroll member 41 is shut by laying the pivotal plate 37 on the back surface ]o 61a of the base plate 61. Accordingly, the accommodating chamber 36 is partitioned by the pivotal plate 37 into a discharge chamber 70 and an introducing chamber 38. The inner space of the accommodating recess 61b provides the discharge chamber 70. The space between the pivotal plate 37 and the cover 11b provides the introducing chamber 38 is. Namely, the pivotal plate 37 also serves as a partition wall for partitioning the accommodating chamber 36 into the introducing chamber 38 and the discharge chamber 70.

[0032] A support portion 54 which has a cylindrical shape extends from the middle portion of the cover 11b in the accommodating chamber 36. A distal end surface of the support portion 54 is elongated to contact the back surface 61a of the base plate 61 of the fixed scroll member 41. A boss 37a is provided at the rear surface and the middle portion of the pivotal plate 37. The pivotal plate 37 is rotatably supported by the support portion 54 through the boss 37a.

[0033] As shown in FIGS. 1, 3 and 4, an electromagnetic actuator 60 is arranged in the cover 11b of the housing 11. The actuator 60 is configured to reciprocate a rod 60b by energizing and de-energizing a solenoid 60a based upon an external command. A pin 37d is connected to the pivotal plate 37, and the rod 60d of the actuator 60 is operatively connected to the pin 37d. Accordingly, the pivotal plate 37 is pivotally switched between a first pivotal position (a state shown in FIG. 3) and a second pivotal position (a state shown in FIG. 4) by actuating the actuator 60. The first pivotal position is performed by an ON-state of the actuator 60 (energizing the solenoid 60a). The second pivotal position is performed by an OFF-state of the actuator 60 (de-energizing the solenoid 60a).

[0034] As shown in FIG. 1, a seal member 57 is arranged on the outer circumferential surface of the proximal portion of the support portion 54. This seal member 57 serves to seal a contact portion between the support portion 54 and the pivotal plate 37 (the boss 37a) with cylindrical contact region. A seal member 59 is arranged on the back surface 61a of the base plate 61 in the fixed scroll member 41 so as to surround the accommodating recess 61b. This seal member 59 serves to seal a contact portion between the back surface 61a of the base plate 61 and the pivotal plate 37 with annular contact region. Namely, these seal members 57, 59 and lubricating oil contained in the refrigerant gas intervene in layer between the support portion 54 and the pivotal plate 37 (the boss 37a) and between the back surface 61a of the base plate 61 and the pivotal plate 37. As a result, the introducing chamber 38 is separated from the discharge chamber 70.

[0035] An inlet 50 is formed in the outer circumferential wall of the casing 11a of the housing 11 so as to correspond with the accommodating space for the electric motor 21. An external conduit for connecting with an evaporator of an external refrigerant circuit (not shown) is connected to the inlet 50. A suction passage 39 is formed at the outer circumferential portion of the shaft support member 31 and the fixed scroll member 41 in the housing 11 for interconnecting the accommodating region of the electric motor 21 and the introducing chamber 38.

[0036] A suction hole 61d is formed at the radially outer portion of the base plate 61 of the fixed scroll member 41. The suction hole 61d opens to the suction chamber 69 at the front end and opens at the back surface 61a at the rear end. A suction port 37b is formed at the radially outer portion of the pivotal plate 37 for interconnecting the introducing chamber 38 and the suction hole 61d at any pivotal positions of the pivotal plate 37. Accordingly, the relatively low pressure refrigerant gas from the external refrigerant circuit is introduced into the suction chamber 69 through the inlet 50, the suction passage 39, the introducing chamber 38, the suction port 37b and the suction hole 61d.

[0037] The middle portion of the cover 11b of the housing 11b forms a discharge passage 58. The front end of the discharge passage 58 extends through the center of the support portion 54 and the center of the pivotal plate 37 (the boss 37a) and then communicates with the discharge chamber 70, while an external conduit, which connects a condenser of the external refrigerant circuit (not shown), is connected to the rear end of the discharge passage 58. Accordingly, the relatively high pressure refrigerant gas in the discharge chamber 70 is discharged to the external refrigerant circuit through the discharge passage 58.

[0038] As shown in FIGS. 1 through 4, the base plate 61 of the fixed scroll member 41 includes a plurality of by-pass holes 61e. One end of each by-pass hole 61e opens to the compression chamber 67 that is volume-reducing, while the other end opens at the back surface 61a. A plurality of the by-pass holes 61e is arranged in such a manner that each of the by-pass holes 61e alternatively communicates with the compression chamber 67 that is volume-reducing during times when the compression chamber 67 at an initial position that is the maximum volume reduces in volume to a predetermined value (for example, 20% of the maximum volume). A plurality of communication holes 37c extends through the pivotal plate 37 in the direction of the axis L so as to correspond with the by-pass holes 61e of the base plate 61.

[0039] In the preferred embodiment, the by-pass holes 61e of the base plate 61 and the communication holes 37c of the pivotal plate 37 form by-pass passages (hereinafter the by-pass passages 37c, 61e) for interconnecting the compression chamber 67 that is volume-reducing and the introducing chamber or a suction pressure region 38. The pivotal plate 37 is pivotally switched between an open position for opening the by-pass passages 37c, 61e by the communication holes 37c and a close position for closing the by-pass passages 37c, 61e by means of ON/OFF control of the actuator 60.

[0040] Namely, as shown in FIG. 4, each communication hole 37c of the pivotal plate 37 is offset from the corresponding by-pass hole 61e of the base plate 61 when the pivotal plate 37 is located at the second pivotal position (the closing position) by turning off the actuator 60. As a result, the by-pass holes 61e are closed by the plate surface of the pivotal plate 37. Accordingly, the compression chamber 67 that is volume-reducing does not communicate with the introducing chamber 38 and completely compresses the refrigerant gas so that the amount of refrigerant gas discharged from the compression mechanism 12 per unit rotation, that is, the displacement of the compression mechanism 12, becomes maximum.

[0041] The compression mechanism 12 performs the maximum displacement, for example, when the engine E is selected to drive the compression mechanism 12. Accordingly, even if the rotational speed of the pulley shaft 13 is slow due to an idling state of the engine E, the compression mechanism 12 ensures a large amount of discharged refrigerant gas per unit time, that is, the compression mechanism 12 exercises relatively high cooling performance.

[0042] As shown in FIG. 3, when the pivotal plate 37 is located at the first pivotal position (the opening position) by turning on the actuator 60, each communication hole 37c communicates with the corresponding by-pass hole 61e. Accordingly, the compression chamber 67 that is volume-reducing constantly communicates with the introducing chamber 38 through one of the by-pass holes 61e and one of the communication holes 37c during times when the volume of the compression chamber 67 that is volume-reducing is reduced to a predetermined value. As a result, the compression chamber 67 does not completely compress the refrigerant gas so that the displacement of the compression mechanism 12 reduces in comparison to the maximum displacement.

[0043] The compression mechanism 12 reduces in displacement, for example, when the electric motor 21 is selected to drive the compression mechanism 12. As the displacement of the compression mechanism 12 reduces, torque required for driving the compression mechanism 12 also reduces. Accordingly, the compressor C becomes compact by reducing the size of the electric motor 21.

[0044] According to the preferred embodiment, the following advantageous effects are obtained.

[0045] (1) The opening and closing of the by-pass passages 37c, 61e, that is, the variation of the displacement of the compressor C, is performed by pivotally switching the pivotal plate 37. Accordingly, adherence between the pivotal plate 37 and the fixed scroll member 41, on which the pivotal plate 37 slides, seals the by-pass passages 37c, 61e around the pivotal plate 37. The plate-like member such as the pivotal plate 37 easily enhances adherence with relatively large area against a facing member on which the plate-like member slides in comparison to, for example, the cylindrical member (the valve portion of the spool) disclosed in the Unexamined Japanese Patent Publication No. 2001-32787. Additionally, a layer of lubricating oil is interposed between the pivotal plate 37 and the base plate 61 of the fixed scroll member 41. Accordingly, the by-pass passages 37c, 61e around the pivotal plate 37 are reliably sealed. As a result, the deterioration of the performance of the compressor C due to the leakage of the refrigerant gas from the by-pass passages 37c, 61e is suppressed.

[0046] (2) The by-pass passage 37c, 61e is configured to constantly interconnect the compression chamber 67 that is volume-reducing and the introducing chamber 38 until the volume of the compression chamber 67 that is volume-reducing is reduced to a predetermined value when the pivotal plate 37 is switched to the opening position. Namely, the compression chamber 67 does not completely compress until the volume of the compression chamber 67 is reduced to a predetermined value after the commencement of reducing volume. Accordingly, for example, in comparison to a variable displacement mechanism that interconnects a compression chamber that is volume-reducing and a suction pressure region after the compression chamber compresses until the volume of the compression chamber is reduced to a predetermined value, power loss of the compressor C due to re-compression of the refrigerant gas, that is, useless compression work, is suppressed.

[0047] Particularly, in the preferred embodiment, a plurality of the by-pass passages 37c, 61e is provided to achieve the above described constant communication. Namely, the fixed scroll member 41 provides a plurality of the by-pass holes 61e. A plurality of the by-pass holes 61e is distributed around the axis L and along the orthogonal direction relative to the axis L. For example, when a plurality of the by-pass holes 61e is opened or closed by the spool valve as disclosed in the Unexamined Japanese Patent Publication No. 2001-32787, a plurality of the spool valves needs to be provided due to the distribution of the by-pass holes 61e. However, the plate-like pivotal plate 37 of the preferred embodiment easily forms a plurality of the communication holes 37c distributed around the axis L and along the orthogonal direction relative to the axis L so as to correspond with the distributed by-pass holes 61e. As a result, the above described constant communication may easily be achieved without any complicated structure.

[0048] (3) The pivotal plate 37 is slidably laid on the back surface 61a of the base plate 61 of the fixed scroll member 41. The above arrangement of the pivotal plate 37 prevents the enlarged compressor C in the direction of the axis L due to the provision of the variable displacement mechanism. In other words, the employment of the plate-like member such as the pivotal plate 37 for opening and closing the by-pass passages 37c, 61e enables universally compact design for laying the plate-like member on the back surface 61a of the base plate 61 of the fixed scroll member 41.

[0049] Particularly, the compressor C is a hybrid type that is alternatively driven by the power from the engine E through the power transmission mechanism 22 arranged in the housing 11 or by the power from the electric motor 21 accommodated in the housing 11. Accordingly, the compressor C tends to become large due to the power transmission mechanism 22 and the electric motor 21. When a compact variable displacement mechanism is utilized for the compressor C, increasing size of the compressor C is efficiently suppressed.

[0050] (4) The pivotal plate 37 also serves as a partition wall for partitioning the discharge chamber 70. Accordingly, an exclusive partition wall is not required for partitioning the discharge chamber 70 so that the compressor C is simplified and becomes compact.

[0051] (5) The pivotal plate 37 also serves as a partition wall for partitioning the introducing chamber 38 and the discharge chamber 70. Accordingly, an exclusive partition wall is not required for partitioning the introducing chamber 38 and the discharge chamber 70 but the compressor C is simplified and becomes compact. Furthermore, a portion of the pivotal plate 37 (the side of the back surface) is exposed to the atmosphere in the introducing chamber 38 so that the pivotal plate 37 is easily handled by forming the by-pass passages 37c, 61e in relatively short.

[0052] (6) The pivotal plate 37 has a donut-shape, and the discharge passage 58 passes through the center through hole of the pivotal plate 37. As a through hole is formed at the center of the pivotal plate 37 that is not utilized for opening and closing the by-pass passages 37c, 61e, the discharge passage 58 is defined to include the through hole. Thus, the radially inner compression chamber 67 and the discharge passage 58 are interconnected at a minimum distance. Accordingly, gas smoothly flows from the radially inner compression chamber 67 to the discharge passage 58 so that the compressor C is prevented from deteriorating efficiency of the compressor C due to pressure loss based upon conduit resistance between the compression chamber 67 and the discharge passage 58.

[0053] The present invention is not limited to the embodiments described above but may be modified into the following alternative embodiments.

[0054] The pivotal plate 37 is configured to be pivotally switched between two positions (the first pivotal position and the second pivotal position) in the preferred embodiment. In other words, the displacement of the compressor C is configured to vary between the maximum and the minimum. In alternative embodiments to those of the above preferred embodiment, the number of pivotal positions is not limited. The pivotal plate 37 is configured to be pivotally switched among three or more pivotal positions and is configured to selectively vary the displacement of the compressor C at an intermediate displacement between the maximum and the minimum.

[0055] The by-pass passages 37c, 61e are configured to constantly interconnect the compression chamber 67 that is volume-reducing and the introducing chamber 38 until the volume of the compression chamber 67 that is volume-reducing is reduced to a predetermined value when the pivotal plate 37 is switched to the opening position. In alternative embodiments to those of the above preferred embodiment, the by-pass passages 37c, 61e are not limited to the above structure. Referring to FIGS. 1 and 5, the by-pass passages 37c and 61e are not formed at the radially outer side of the base plate 61 of the fixed scroll member 41 and the pivotal plate 37, respectively but are only formed at the radially inner side of the base plate 61 of the fixed scroll member 41 and the pivotal plate 37, respectively, in comparison to the above described preferred embodiment. In this state, the by-pass passages 37c, 61e are configured to interconnect the compression chamber 67 that is volume-reducing and the suction pressure region after the compression chamber 67 has compressed to reduce in volume to a predetermined value, that is, after the volume of the compression chamber 67 that is volume-reducing has reduced to a predetermined value. This simplifies the structure of the by-pass passage.

[0056] Therefore, the present examples and embodiments are to be considered as illustrative and not restrictive, and the invention is not to be limited to the details given herein but may be modified within the scope of the appended claims.

Claims

1. A variable displacement mechanism in a scroll type compressor having a movable scroll member and a fixed scroll member, the movable scroll member and the fixed scroll member defining compression chambers therebetween, the compression chambers reducing in volume in accordance with orbital motion of the movable scroll member relative to the fixed scroll member, whereby gas is compressed, a suction pressure region being defined in the scroll type compressor, the variable displacement mechanism comprising:

a by-pass passage provided for interconnecting the compression chamber in a process of volume-reducing and the suction pressure region;

a pivotal plate having a communication hole that partially constitutes the by-pass passage, the pivotal plate being pivotally switched between a first pivotal position for opening the by-pass passage by the communication hole and a second pivotal position for closing the by-pass passage; and

an actuator for pivoting the pivotal plate.

2. The variable displacement mechanism according to claim 1, wherein the by-pass passage is configured to regularly interconnect the compression chamber in the process of volume-reducing and the suction pressure region until volume of the compression chamber in the process of volume-reducing is reduced to a predetermined value in a state where the pivotal plate is switched to the first pivotal position.

3. The variable displacement mechanism according to claim 1, wherein the by-pass passage is plurally formed.

4. The variable displacement mechanism according to claim 3, wherein the scroll type compressor includes a rotary shaft that has a central axis, the by-pass passages being distributed around the central axis and along an orthogonal direction relative to the central axis.

5. The variable displacement mechanism according to claim 1, wherein the by-pass passage is configured to interconnect the compression chamber in the process of volume-reducing and the suction pressure region after the volume of the compression chamber in the process of volume-reducing has been reduced to a predetermined value in a state where the pivotal plate is switched to the first pivotal position.

6. The variable displacement mechanism according to claim 1, wherein the fixed scroll member includes a base plate and a spiral wall that extends from the base plate, the pivotal plate being slidably laid on a back surface of the base plate.

7. The variable displacement mechanism according to claim 6, wherein the back surface of the base plate of the fixed scroll member includes an accommodating recess, a discharge hole opening to the accommodating recess for communicating with the compression chamber near a center of the spiral wall, a discharge chamber being defined in such a manner that the accommodating recess is closed by laying the pivotal plate on the back surface of the base plate.

8. The variable displacement mechanism according to claim 7, wherein the suction pressure region is defined on a side that is opposite to a side of the base plate relative to the pivotal plate, the pivotal plate serving as a partition wall for partitioning the suction pressure region and the discharge chamber.

9. The variable displacement mechanism according to claim 7, wherein the pivotal plate has a donut-shape, a through hole being formed at the center of the pivotal plate, a discharge passage extending through the through hole for discharging the gas in the discharge chamber.

10. The variable displacement mechanism according to claim 9, wherein adherence between the pivotal plate and the fixed scroll member seals the by-pass passage.

11. The variable displacement mechanism according to claim 10, wherein a layer of lubricating oil is interposed between the pivotal plate and the base plate of the fixed scroll member.

12. The variable displacement compressor according to claim 1, wherein the scroll type compressor is used for a vehicle air conditioner, the scroll type compressor being a hybrid type that is selectively driven by power from an engine for traveling a vehicle and by power from an internal electric motor.