Heat insulating structure in piston type compressor

Abstract

A heat insulating structure in a piston type compressor includes a heat insulating member. The piston type compressor includes a cylinder block and a cover housing connected to the cylinder block, a piston is accommodated in a cylinder bore defined in the cylinder block to define a compression chamber. A suction pressure region and a discharge pressure region are defined in the cover housing. The piston is reciprocated in the cylinder bore in accordance with rotation of a rotary shaft so that refrigerant gas is drawn from the suction pressure region to the compression chamber and discharged from the compression chamber to the discharge pressure region. The heat insulating member has a predetermined shape and is located in the cylinder block. The heat insulating member has an inner peripheral surface that defines the cylinder bore.

Description

BACKGROUND OF THE INVENTION

The present invention relates to a heat insulating structure in a piston type compressor, in which a piston is reciprocated in accordance with the rotation of a rotary shaft to draw refrigerant gas from a suction pressure region to a compression chamber as well as to discharge the refrigerant gas from the compression chamber to a discharge pressure chamber.

In a piston type compressor (cf. Unexamined Japanese Patent Application Publication No. 2001-515174), refrigerant gas is introduced into a compression chamber. The temperature of the introduced refrigerant gas in the compression chamber affects the performance of the compressor. As the temperature is higher, the density of the refrigerant gas in the compression chamber is lower, so that the performance of the compressor deteriorates. On the other hand, as the temperature is lower, the density of the refrigerant gas in the compression chamber is higher, so that the performance of the compressor improves.

By compressing the refrigerant gas, its temperature rises. Thus, heat is transmitted from the compressed refrigerant gas to a wall that defines the compression chamber, and the temperature of the wall rises. After compressing and discharging the refrigerant gas, the refrigerant gas is newly introduced into the compression chamber. The newly introduced refrigerant gas receives the heat from the wall, and its temperature rises. Therefore, if the temperature of the wall substantially rises or the wall has high heat conductivity, the temperature of the refrigerant gas in the compression chamber substantially rises before compression, and the performance of the compression deteriorates.

The present invention is directed to boosting the heat insulating characteristics of the compression chamber in a piston type compressor.

SUMMARY OF THE INVENTION

According to the present invention, a heat insulating structure in a piston type compressor includes a heat insulating member. The piston type compressor includes a cylinder block and a cover housing connected to the cylinder block, a piston is accommodated in a cylinder bore defined in the cylinder block to define a compression chamber. A suction pressure region and a discharge pressure region are defined in the cover housing. The piston is reciprocated in the cylinder bore in accordance with rotation of a rotary shaft so that refrigerant gas is drawn from the suction pressure region to the compression chamber and discharged from the compression chamber to the discharge pressure region. The heat insulating member has a predetermined shape and is located in the cylinder block. The heat insulating member has an inner peripheral surface that defines the cylinder bore.

BRIEF DESCRIPTION OF THE DRAWINGS

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:

FIG. 1 is a longitudinal cross-sectional view of a compressor according to a first preferred embodiment;

FIG. 2 is a cross-sectional view of the compressor taken along the line I-I in FIG. 1;

FIG. 3 is a cross-sectional view of the compressor taken along the line II-II in FIG. 1;

FIG. 4 is a partially enlarged cross-sectional view of the compressor when a piston is located at its top dead center according to the first preferred embodiment;

FIG. 5 is a partially enlarged cross-sectional view of the compressor when the piston is located at its bottom dead center according to the first preferred embodiment;

FIG. 6 is a partially enlarged cross-sectional view of a compressor according to a second preferred embodiment;

FIG. 7 is a partially enlarged cross-sectional view of a compressor according to a third preferred embodiment;

FIG. 8 is a partially enlarged cross-sectional view of a compressor according to a fourth preferred embodiment;

FIG. 9A is a partially enlarged cross-sectional view of a compressor according to a fifth preferred embodiment;

FIG. 9B is a cross-sectional view of the compressor taken along the line III-III in FIG. 9A;

FIG. 10A is a partially enlarged cross-sectional view of a compressor according to a sixth preferred embodiment;

FIG. 10B is a cross-sectional view of the compressor taken along the line IV-IV in FIG. 10A;

FIG. 11 is a partially enlarged cross-sectional view of a compressor according to a seventh preferred embodiment; and

FIG. 12 is a partially enlarged cross-sectional view of a compressor according to an eighth preferred embodiment.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

A first preferred embodiment will be described with reference to FIGS. 1 through 5, in which the present invention is applied to a piston type variable displacement compressor.

As shown in FIG. 1, the housing of a piston type variable displacement compressor 10 includes a cylinder block 11 of aluminum, a front housing 12 of aluminum and a rear housing or cover housing 13 of aluminum. The front housing 12 is joined to the front end of the cylinder block 11, and the rear housing 13 is joined to the rear end of the cylinder block 11 through a valve plate 14 and gasket type valve forming plates 15, 16. The cylinder block 11, the front housing 12 and the rear housing 13 are combined by a screw 53. As shown in FIGS. 4 and 5, the valve forming plate 15 includes a metallic plate 152 and rubber layers 153, 154 that are respectively provided on the surfaces of the metallic plate 152. In a similar manner, the valve forming plate 16 includes a metallic plate 162 and rubber layers 163, 164 that are respectively provided on the surfaces of the metallic plate 162.

The front housing 12 and the cylinder block 11 define a pressure control chamber 121 and rotatably support a rotary shaft 18 through radial bearings 19, 20, respectively. The rotary shaft 18 extends in the pressure control chamber 121 and protrudes to the outside therefrom. The rotary shaft 18 receives driving power from a vehicle engine 17 as an external drive source through a pulley (not shown) and a belt (not shown).

A lug plate 21 is mounted on the rotary shaft 18, and a swash plate 22 is supported on the rotary shaft 18 so as to slide in and incline with respect to the axial direction of the rotary shaft 18. A connection member 23 is mounted on the swash plate 22, and a guide pin 24 is mounted on the connection member 23. A guide hole 211 is formed in the lug plate 21. The head portion of the guide pin 24 is slidably inserted into the guide hole 211. The cooperation of the guide hole 211 and the guide pin 24 allows the swash plate 22 to incline with respect to the axial direction of the rotary shaft 18 and to rotate together with the rotary shaft 18. The inclination of the swash plate 22 is guided by the slide guide relation between the guide hole 211 and the guide pin 24 and the slide support of the rotary shaft 18.

As the middle part of the swash plate 22 moves toward the lug plate 21, an inclination angle of the swash plate 22 is increased. The swash plate 22 comes into contact with the lug plate 21 to restrict the maximum inclination angle. At the position of the swash plate 22 indicated by the solid line in FIG. 1, the inclination angle of the swash plate 22 is the maximum. As the middle part of the swash plate 22 moves toward the cylinder block 11, the inclination angle of the swash plate 22 is decreased. At the position of the swash plate 22 indicated by the two-dot chain line in FIG. 1, the inclination angle of the swash plate 22 is the minimum.

As shown in FIGS. 1, 2 and 4, a plurality of holes 111 are formed through the cylinder block 11 for forming compression chambers. A cylindrical-shaped heat insulating member 30 of synthetic resin is press-fitted into each of the hole 111. The inner peripheral surface of the cylinder block 21 that defines the hole 111 is covered by the heat insulating member 30.

A piston 25 of aluminum is accommodated in each of the heat insulating members 30. Only one piston 25 is shown in FIG. 2. The piston 25 includes a cylindrical-shaped head portion 252 and a neck portion 253 as shown in FIG. 1. The head portion 252 is inserted into the heat insulating member 30, and the neck portion 253 is engaged with the swash plate 22 through a pair of shoes 26. The rotational movement of the swash plate 22 is converted into the reciprocating movement of the piston 25, and the piston 25 is reciprocated in the heat insulating member 25. The inside of the heat insulating member 30 is a cylinder bore 43 for reciprocating the piston 25 therein, and the heat insulating member 30 has an inner peripheral surface 431 that defines the cylinder bore 43 as shown in FIGS. 2 and 3. A compression chamber 112 is defined by the piston 25, the heat insulating member 30 and the valve forming plate 15 in the inside of the heat insulating member 30 (the cylinder bore 43) as shown in FIG. 1. FIG. 5 shows a state where the piston 25 is located at its bottom dead center.

As shown in FIGS. 1 and 3, the rear housing 13 and the valve plate 14 define a suction chamber or suction pressure region 27 and a discharge chamber or discharge pressure region 28 that are separated by an annular partition wall 29. The suction chamber 27 is located on the radially outer side of the rear housing 13 and surrounds the discharge chamber 28 around an axial line 181 of the rotary shaft 18. The compression chamber 112 is separated from the suction chamber 27 and the discharge chamber 28 by the valve plate 14. The valve forming plates 15, 16 and a retainer 31 are combined with the valve plate 14 by a screw 32.

As shown in FIGS. 4 and 5, a suction port 141 is formed in the valve plate 14 and the valve forming plate 16, and a discharge port 142 is formed in the valve plate 14 and the valve forming plate 15. A suction valve 151 is formed in the valve forming plate 15, and a discharge valve 161 is formed in the valve forming plate 16. Gaseous refrigerant in the suction chamber 27 pushes away the suction valve 151 and is drawn into the compression chamber 112 through the suction port 141 by the movement of the piston 25 from the right to the left as seen in FIG. 1.

A regulating recess 301 is formed on the end face of the heat insulating member 30 near the valve forming plate 15, and a metallic member 302 is mounted on the bottom of the regulating recess 301. The suction valve 151 comes into contact with the metallic member 302 at the bottom of the regulating member 301 to regulate its opening degree. The drawn gaseous refrigerant in the compression chamber 112 pushes away the discharge valve 161 and is discharged into the discharge chamber 28 through the discharge port 142 by the movement of the piston 25 from the left to the right as seen in FIG. 1. The discharge valve 161 comes into contact with the retainer 31 to regulate its opening degree.

As shown in FIG. 1, an inlet 33 for introducing the gaseous refrigerant into the suction chamber 27 and an outlet 34 for discharging the gaseous refrigerant from the discharge chamber 28 are formed in the rear housing 13. The inlet 33 and the outlet 34 is interconnected by an external refrigerant circuit 35 on which a heat exchanger 36 for obtaining heat from the refrigerant, a fixed throttle 37, a heat exchanger 38 for transmitting heat from the surrounding air to the refrigerant and an accumulator 39 are arranged. The accumulator 39 feeds the only gaseous refrigerant to the compressor 10. The refrigerant in the discharge chamber 28 flows into the suction chamber 27 via the outlet 34, the heat exchanger 36, the fixed throttle 37, the heat exchanger 38, the accumulator 39 and the inlet 33.

The discharge chamber 28 and the pressure control chamber 121 are interconnected by a supply passage 40 formed in the cylinder block 11. The pressure control chamber 121 and the suction chamber 27 are interconnected by a bleed passage 41 formed in the cylinder block 11 and the rear housing 13. The refrigerant in the pressure control chamber 121 flows out to the suction chamber 27 through the bleed passage 41.

An electromagnetic displacement control valve 42 is arranged on the supply passage 40. When the displacement control valve 42 is de-energized, the displacement control valve 42 is closed so that the refrigerant does not flow from the discharge chamber 28 to the pressure control chamber 121 through the supply passage 40. Since the refrigerant in the pressure control chamber 121 flows out to the suction chamber 27 through the bleed passage 41, the pressure in the pressure control chamber 121 falls. Therefore, the inclination angle of the swash plate 22 is increased, and the displacement is increased. When the displacement control valve 42 is energized, the displacement control valve 42 is opened so that the refrigerant flows from the discharge chamber 28 to the pressure control chamber 121 through the supply passage 40. Therefore, the pressure in the pressure control chamber 121 rises, the inclination angle of the swash plate 22 is decreased and the displacement is decreased. In the first preferred embodiment, carbon dioxide is used as the refrigerant.

According to the first preferred embodiment, the following advantageous effects are obtained.

(1-1) In accordance with the movement of the piston 25 from the right to the left as seen in FIG. 1, the refrigerant gas in the suction chamber 27 is drawn into the compression chamber 112 through the suction port 141. In accordance wit the movement of the piston 25 from the left to the right as seen in FIG. 1, the refrigerant gas in the compression chamber 112 is compressed and discharged into the discharge chamber 28 through the discharge port 142. As the refrigerant gas in the compression chamber 112 is compressed, the temperature thereof rises. However, synthetic resin or the material for the heat insulating member 30 has heat conductivity lower than aluminum or the material for the cylinder block 11. Thus, the heat insulating member 30 having the inner peripheral surface 431 that defines the cylinder bore 43 is hard to be heated by the refrigerant gas in the compression chamber 112, and the temperature of the heat insulating member 30 substantially does not rise. Therefore, a small amount of heat is transmitted from the heat insulating member 30 to the refrigerant gas that is newly drawn into the compression chamber 112 after compressing and discharging the previously drawn refrigerant gas. Namely, the temperature of the refrigerant gas in the compression chamber 112 is substantially prevented from being increased by the heat insulating member 30. The heat insulating member 30 enhances the heat insulating characteristics of the compression chamber 112 and contributes to the improvement in the performance of the piston type variable displacement compressor 10.

(1-2) The heat insulating member 30 having a predetermined shape or the cylindrical shape is made thicker to enhance the heat insulation effectiveness.

(1-3) The heat insulation member 30 is made of synthetic resin that has low heat conductivity. The heat insulating member 30 reduces the heat transmission from the cylinder block 11 of aluminum, which has high heat conductivity, to the refrigerant gas in the compression chamber 112. Thus, the heat insulating member 30 contributes to the improvement in the performance of the compressor.

(1-4) If the piston type variable displacement compressor 10 becomes unusable, the heat insulating member 30 is removed from the hole 111 and is recyclable.

(1-5) Carbon dioxide is used as refrigerant under the pressure higher than when chlorofluorocarbon is used. Thus, small flow rate is required. When the flow rate is small, it is important to prevent the refrigerant gas in the compression chamber 112 from being heated. The piston type variable displacement compressor 10 using carbon dioxide as the refrigerant is suitable for the application of the present invention.

In the present invention, the following preferred embodiments are practiced as shown in FIGS. 6 through 12. In these preferred embodiments, similar elements are referred to by the same reference numerals as the first is preferred embodiment.

In a second preferred embodiment as shown in FIG. 6, a heat insulating member 44 includes a cylindrical portion 441 and a flange 442 that is located at the end of the cylindrical portion 441 near the valve plate 14 and is integrated with the cylindrical portion 441. The cylindrical portion 441 is inserted into the hole 111, and the flange 442 is sandwiched between the cylinder block 11 and the valve plate 14. Since the flange 442 is sandwiched between the cylinder block 11 and the valve plate 14, the cylindrical portion 441 is held in the hole 111 without following the reciprocating movement of the piston 25.

In a third preferred embodiment as shown in FIG. 7, the cylinder block 11 is formed with a protrusion 114 on its inner peripheral surface that defines the hole 111. A cylindrical-shaped heat insulating member 45 is inserted into the hole 111 and sandwiched between the protrusion 114 and the valve plate 14. Thus, the heat insulating member 45 is held in the hole 111 without following the reciprocating movement of the piston 25.

In a fourth preferred embodiment as shown in FIG. 8, a valve forming plate 15A is made of metal, and a seal ring 46 is interposed between the cylinder block 11 and the valve forming plate 15A near the outer periphery of the cylinder block 11 so as to surround the axial line 181 of the rotary shaft 18 and all of the is heat insulating members 44. The flange 442 of the heat insulating member 44 serves to seal the compression chamber 112, so that the refrigerant gas is prevented from leaking along the surface of the valve forming plate 15A from the compression chamber 112 to a hole 115 that is formed in the cylinder block 11 for inserting the rotary shaft 18 therein. The seal ring 46 prevents the refrigerant gas from leaking along the surface of the valve forming plate 15A from the compression chamber 112 to the outside of the compressor.

In a fifth preferred embodiment as shown in FIGS. 9A and 9B, a heat insulating member 47 includes a cylindrical portion 471 and an end wall 472. The cylindrical portion 471 is inserted into the hole 111, and the end wall 472 is in contact with the valve forming plate 15A of metal and faces the top end surface of the piston 25. The heat insulating member 47 is sandwiched between the protrusion 114 and the valve plate 14. Thus, the heat insulating member 47 is held in the hole 111 without following the reciprocating movement of the piston 25. The end wall 472 has formed therein a suction hole 473 facing the suction port 141 and a discharge hole 474 facing the discharge port 142. The refrigerant gas in the suction chamber 27 is drawn into the compression chamber 112 through the suction port 112 and the suction hole 473 while the refrigerant gas in the compression chamber 112 is discharged into the discharge chamber 28 through the discharge hole 474 and the discharge port 142. The end wall 472 further improves the heat insulating characteristics of the compression chamber 112.

In a sixth preferred embodiment as shown in FIGS. 10A and 10B, a cylinder block 11 A includes an annular base block 48 of aluminum and an annular block 49 of synthetic resin. The base block 48 includes a radially outer portion 481, a radially inner portion 482 and an end wall 483, and the annular block 49 is interposed between the radially outer portion 481 and the radially inner portion 482 to surround the axial line 181 of the rotary shaft 18. A plurality of the cylinder bores 43 are formed in the annular block 49. Namely, the annular block 49 or a heat insulating member of synthetic resin has the inner peripheral surface 431 that defines the cylinder bore 43. The end wall 483 has formed therein a through hole 484 corresponding to each of the cylinder bore 43. The piston 25 is inserted into the cylinder bore 43 through the through hole 484. The above structure, in which a plurality of the cylinder bores 43 are formed in the annular block 49 of heat insulating material or synthetic resin, is more productive than a structure in which a plurality of cylinder bores are respectively formed in a plurality of heat insulating members.

In a seventh preferred embodiment as shown in FIG. 11, the peripheral surface of the head portion 252 of the piston 25 is covered with a coating layer 50 made of the same material as the heat insulating member 45. The structure, in which the heat insulating member 45 and the coating layer 50 are made of material having the same coefficient of linear expansion, facilitates control of the clearance between the inner peripheral surface 431 of the heat insulating member 45 and the surface of the coating layer 50 in thermal expansion.

In an eighth preferred embodiment as shown in FIG. 12, a disc-shaped heat insulating member 51 is bound to a top end surface 251 of the piston 25 to cover the top end surface 251. The heat insulating member 51 further improves the heat insulating characteristics of the compression chamber 112.

According to the present invention, the following alternative embodiments are practicable.

(1) In the seventh preferred embodiment, the coating layer 50 is made of the same material as the heat insulating member 45. However, the coating layer is made of material that has abrasive resistance higher than the heat insulating member or sliding characteristics better than the heat insulating member, so that the lifetime of the compressor improves. Furthermore, the coating layer is provided in the other preferred embodiments.

(2) Hard rubber or ceramics is used as material for the heat insulating member having the inner peripheral surface that defines the cylinder bore.

(3) The cylindrical-shaped heat insulating member includes two parts, or a radially inner part and a radially outer part that are made of different synthetic resins. Synthetic resin having high abrasive resistance (e.g. polytetrafluoroethylene) is used as the synthetic resin for the radially inner part.

(4) The present invention is applicable to a piston type compressor in which the discharge chamber is defined on the outer peripheral side of the rear housing 13 so as to surround the suction chamber around the axial line 181 of the rotary shaft 18.

(5) The present invention is applicable to a piton type fixed displacement compressor.

(6) The present invention is applicable to a compressor in which refrigerant other than carbon dioxide is used.

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 heat insulating structure in a piston type compressor including a cylinder block and a cover housing connected to the cylinder block, a piston being accommodated in a cylinder bore defined in the cylinder block to define a compression chamber, a suction pressure region and a discharge pressure region being defined in the cover housing, the piston being reciprocated in the cylinder bore in accordance with rotation of a rotary shaft so that refrigerant gas is drawn from the suction pressure region to the compression chamber and discharged from the compression chamber to the discharge pressure region, comprising:

a heat insulating member having a predetermined shape and located in the cylinder block, the heat insulating member having an inner peripheral surface that defines the cylinder bore.

2. The heat insulating structure according to claim 1, wherein a hole is formed in the cylinder block for forming the compression chamber, the heat insulating member having a cylindrical shape and being inserted into the hole.

3. The heat insulating structure according to claim 2, wherein a valve plate is interposed between the cylinder block and the cover housing to separate the compression chamber from the suction pressure region and the discharge pressure region, the heat insulating member including a flange at its end near the valve plate, the flange being sandwiched between the cylinder block and the valve plate.

4. The heat insulating structure according to claim 2, wherein a valve forming plate of metal is interposed between the valve plate and the cylinder block, a seal ring being interposed between the valve forming plate and the cylinder block so as to surround an axial line of the rotary shaft and the heat insulating member.

5. The heat insulating structure according to claim 2, wherein a valve plate is interposed between the cylinder block and the cover housing to separate the compression chamber from the suction pressure region and the discharge pressure region, a protrusion being formed on an inner peripheral surface of the cylinder block that defines the hole, the heat insulating member being sandwiched between the protrusion and the valve plate.

6. The heat insulating structure according to claim 2, wherein the heat insulating member includes an end wall that faces a top end surface of the piston.

7. The heat insulating structure according to claim 1, wherein the heat insulating member is an annular block included in the cylinder block, the annular block surrounds an axial line of the rotary shaft, the annular block having the cylinder bore.

8. The heat insulating structure according to claim 1, wherein the heat insulating member is made of synthetic resin.

9. The heat insulating structure according to claim 1, wherein the heat insulating member is made of one of hard rubber and ceramics.

10. The heat insulating structure according to claim 1, wherein a top end surface of the piston is covered with another heat insulating member.

11. The heat insulating structure according to claim 1, wherein the piston includes a head portion having a peripheral surface, the peripheral surface of the head portion is covered with a coating layer made of the same material as the heat insulating member.

12. The heat insulating structure according to claim 1, wherein the refrigerant gas is carbon dioxide.