PISTON COMPRESSOR

Abstract

A piston compressor includes first and second cylinder blocks having an inlet port and a swash plate chamber, a drive shaft having first and second guide holes, and a swash plate having first and second supply ports. The swash plate chamber communicates with the inlet port and also with the first and second guide holes via the first and second supply ports, respectively. A distance from the inlet port to the first supply port when the first supply port is moved closest to the inlet port is greater than a distance from the inlet port to the second supply port when the second supply port is moved closest to the inlet port, and the smallest flow passage area in the first supply port and the first guide hole is greater than the smallest flow passage area in the second supply port and the second guide hole.

Description

BACKGROUND OF THE INVENTION

The present invention relates to a piston compressor.

Japanese Utility Model Application Publication No. 63-174579 discloses a piston compressor which includes a pair of front and rear cylinder blocks. The front cylinder block has at the center thereof a front shaft hole and a plurality of front cylinder bores formed around the front shaft hole. Similarly, the rear cylinder block has at the center thereof a rear shaft hole and a plurality of rear cylinder bores formed around the rear shaft hole. The front cylinder block and the rear cylinder block are joined together so that the front shaft hole and the front cylinder bores are aligned with the rear shaft hole and the rear cylinder bores, respectively. The front cylinder bores and the rear cylinder bores cooperate to form a plurality of pairs of the front and rear cylinder bores. The front cylinder block and the rear cylinder block have therebetween a swash plate chamber.

The piston compressor further includes a pair of front and rear housings. The front housing is joined to the front cylinder block via a front valve unit including a plurality of reed type front discharge valves and a plurality of reed type front suction valves. The front housing has a front discharge chamber which is communicable with the front cylinder bores via the respective reed type discharge valves and a front suction chamber which is communicable with the front cylinder bores via the respective reed type front suction valves. Similarly, the rear housing is joined to the rear cylinder block via a rear valve unit including a plurality of reed type rear discharge valves and a plurality of reed type rear suction valves. The rear housing has a rear discharge chamber which is communicable with the rear cylinder bores via the respective reed type rear discharge valves and a suction chamber which is communicable with the rear cylinder bores via the respective reed type rear suction valves.

A drive shaft is rotatably supported at the shaft holes by the front housing, the front cylinder block and the rear cylinder block. A swash plate is mounted on the drive shaft for rotation therewith synchronously. The swash plate has a boss portion held between the front cylinder block and the rear cylinder block via thrust bearings and a cam portion formed integrally with the boss portion. A plurality of double-headed pistons are received in the respective pairs of front and rear cylinder bores. When the drive shaft is rotated, the cam portion of the swash plate causes the pistons to reciprocate in their corresponding pairs of front and rear cylinder bores. Each piston has on the opposite sides thereof in the pair of front and rear cylinder bores a front compression chamber and a rear compression chamber. The front cylinder block has therein an inlet port extending radially to interconnect the swash plate chamber and the external refrigerant circuit of the piston compressor. The front cylinder block and the rear cylinder block have therethrough a plurality of suction passages which extend in parallel with the axis of the drive shaft and interconnect the front suction chamber and the rear suction chamber via the swash plate chamber.

According to the piston compressor, the suction passage having a longer pathway from the inlet port is formed with a larger flow passage area. Thus, flow rates of refrigerant gas flowing through the suction passages are substantially equalized and substantially the same amount of refrigerant gas is drawn into each compression chamber. Therefore, the intake efficiency of the compressor is improved and noise development of the compressor is reduced.

Some compressors dispense with reed type suction valves and instead use a rotary valve which is rotatable synchronously with the drive shaft of the compressor for drawing refrigerant gas selectively to the respective compression chambers in order to forestall a pressure loss caused by the reed type suction valves. Specifically, a compressor is known wherein refrigerant gas in the swash plate chamber is drawn into the respective compression chambers not through the suction passages but through passages formed in the boss portion of the swash plate and also passages formed in the drive shaft. More specifically, the boss portion of the swash plate of this compressor has therethrough a front supply port and a rear supply port which extend radially and are opened to the swash plate chamber. The supply ports are spaced from each other in rotation direction of the swash plate. The drive shaft has therein an axial hole extending in axial direction of the drive shaft, a front guide hole which communicates with the front supply port and the axial hole, a rear guide hole which communicates with the rear supply port and the axial hole, a front suction guide hole which communicates with the axial hole, and a rear suction guide hole which communicates with the axial hole. The front cylinder block has therein a plurality of front admission ports which are communicable with the front suction guide hole and the respective front compression chambers. The rear cylinder block has therein a plurality of rear admission ports which are communicable with the rear suction guide hole and the respective rear compression chambers.

In such a compressor, refrigerant gas in the swash plate chamber is drawn into the front and rear compression chambers through the front and rear supply ports, the front and rear guide holes, the axial hole, the front and rear suction guide holes, and the front and rear admission ports. Thus, the front supply port, the front guide hole, the axial hole, the front suction guide hole and the front admission ports cooperate to form a front suction flow passage for drawing refrigerant gas in the swash plate chamber into each front compression chamber then on the suction stroke of the double-headed piston for the front compression chamber. The rear supply port, the rear guide hole, the axial hole, the rear suction guide hole and the rear admission ports cooperate to form a rear suction flow passage for drawing refrigerant gas in the swash plate chamber into each rear compression chamber then on the suction stroke of the double-headed piston for the rear compression chamber.

It is also required in this type of compressor that intake of refrigerant gas into the compression chambers should be even as in the case of the compressor described in the aforementioned publication. In the above compressor wherein the supply ports are rotated in the swash plate chamber, however, the length of passage for refrigerant gas to flow from the inlet port to the supply ports is variable, so that the same technical solution as in the case of the compressor described in the aforementioned publication cannot be employed.

If the inlet port is formed at a position of the front or rear cylinder block corresponding to the center of the cam portion of the swash plate as viewed in axial direction of the drive shaft, refrigerant gas drawn through the inlet port into the swash plate chamber tends to be diffused by the rotation of the swash plate. Thus, intake efficiency of refrigerant gas flowing into the respective front and rear compression chambers through the front and rear supply ports is reduced. In order to prevent the reduction of the intake efficiency, the inlet port is formed in one of the front and rear cylinder blocks at a position which is spaced away from, or forward or rearward of, the center of the cam portion as viewed in the axial direction. An inlet port thus formed in one of the front and rear cylinder blocks is preferable from the viewpoint of prevention of refrigerant gas leakage and simple structure of the compressor, as well as the prevention of reduction of the intake efficiency.

If the inlet port is spaced away from the center of the cam portion forward or rearward as viewed in the axial direction of the drive shaft, however, the inlet port is located close to one of the front and rear supply ports and remote from the other. In such a case, there occurs difference in intake between the front and rear compression chambers. In this case, there is a fear that the temperature of refrigerant gas discharged from the compression chambers which are lower in intake efficiency is excessively raised and, therefore, the gasket of either one of the front and rear valve units deteriorates early, accordingly. Such deterioration of the gasket may badly affect the durability of the compressor. In addition, there occurs difference in reaction force between the front and rear compression chambers, thereby causing vibration which badly affects quiet operation of the compressor.

The present invention is directed to a piston compressor which offers high durability and quiet operation while maintaining a high intake efficiency.

SUMMARY OF THE INVENTION

In accordance with an aspect of the present invention, a piston compressor includes a first cylinder block, a second cylinder block, a drive shaft, a swash plate and a plurality of double-headed pistons. The first cylinder block has a first shaft hole, a plurality of first cylinder bores and a plurality of first admission ports. The first cylinder bores are formed around the first shaft hole and communicate with the first shaft hole via the respective first admission ports. The second cylinder block has a second shaft hole, a plurality of second cylinder bores and a plurality of second admission ports. The second cylinder bores are formed around the second shaft hole and communicate with the second shaft hole via the respective second admission ports. The first cylinder block and the second cylinder block are joined together. The first cylinder block and the second cylinder block form a swash plate chamber between the first cylinder bores and the second cylinder bores. One of the first cylinder block and the second cylinder block has therein an inlet port connected to the swash plate chamber for allowing refrigerant gas to be drawn thereinto. The drive shaft is rotatably supported at the first shaft hole and the second shaft hole by the first cylinder block and the second cylinder block, respectively. The drive shaft has therein an axial hole, a first suction guide hole, a second suction guide hole, a first guide hole and a second guide hole. The axial hole extends in axial direction of the drive shaft. The first suction guide hole communicates with the first guide hole via the axial hole and is communicable with the first admission ports of the first cylinder block. The second suction guide hole communicates with the second guide hole via the axial hole and is communicable with the second admission ports of the second cylinder block. The swash plate is mounted on the drive shaft in the swash plate chamber for rotating therewith integrally. The swash plate has a boss portion fitted on the drive shaft and a cam portion formed integrally with the boss portion. The boss portion has therein a first supply port and a second supply port. The first supply port communicates with the first guide hole of the drive shaft and the swash plate chamber. The second supply port communicates with the second guide hole of the drive shaft and the swash plate chamber. The first supply port and the second supply port are spaced from each other in rotation direction of the swash plate. The plurality of double-headed pistons are received in the respective first and second cylinder bores and engaged with the cam portion. The rotation of the cam portion of the swash plate with the drive shaft causes the double-headed pistons to reciprocate in the respective first and second cylinder bores. Opposite heads of the double-headed pistons and the first and second cylinder bores respectively define first compression chambers and second compression chambers. The first compression chamber and the second compression chamber are communicable with the first admission port and the second admission port, respectively. The first supply port, the first guide hole, the axial hole, the first suction guide hole and the first admission ports cooperate to form a first suction flow passage for allowing the refrigerant gas in the swash plate chamber to be drawn into each first compression chamber on a suction stroke of the double-headed piston for the first compression chamber. The second supply port, the second guide hole, the axial hole, the second suction guide hole and the second admission ports cooperate to form a second suction flow passage for allowing the refrigerant gas in the swash plate chamber to be drawn into each second compression chamber on a suction stroke of the double-headed piston for the second compression chamber. A distance from the inlet port to the first supply port when the first supply port is moved closest to the inlet port is greater than a distance from the inlet port to the second supply port when the second supply port is moved closest to the inlet port. The smallest flow passage area in the first supply port and the first guide hole is greater than the smallest flow passage area in the second supply port and the second guide hole.

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

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 sectional view showing a piston compressor according to a first embodiment of the present invention;

FIG. 2 is a fragmentary longitudinal sectional view showing the piston compressor of FIG. 1;

FIG. 3 is a fragmentary longitudinal sectional view showing a piston compressor according to a second embodiment of the present invention;

FIG. 4 is a fragmentary longitudinal sectional view showing a piston compressor according to a third embodiment of the present invention;

FIG. 5 is a fragmentary longitudinal sectional view showing a piston compressor according to a fourth embodiment of the present invention;

FIG. 6 is a fragmentary longitudinal sectional view showing a piston compressor according to a fifth embodiment of the present invention;

FIG. 7 is a fragmentary plan view showing front and rear cylinder bores of the piston compressor of FIG. 6;

FIG. 8 is a fragmentary plan view showing front and rear cylinder bores of a piston compressor according to a sixth embodiment of the present invention;

FIG. 9 is an elevation view showing a swash plate of a piston compressor according to a seventh embodiment of the present invention, wherein part of the swash plate is shown in cross section; and

FIG. 10 is an elevation view showing a swash plate of a piston compressor according to an eighth embodiment of the present invention, wherein part of the swash plate is shown in cross section.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

The following will describe the piston compressors according to the first through eighth embodiments of the present invention with reference to the accompanying drawings.

Referring to FIG. 1, the piston compressor of the first embodiment is a fixed displacement type swash plate compressor. The compressor includes a front cylinder block 1 and a rear cylinder block 3. The front cylinder block 1 has therethrough a front shaft hole 1A and a plurality of front cylinder bores 1B formed around the front shaft hole 1A. Similarly, the rear cylinder block 3 has therethrough a rear shaft hole 3A and a plurality of rear cylinder bores 3B formed around the rear shaft hole 3A. The front cylinder block 1 and the rear cylinder block 3 are joined together so that the front shaft hole 1A and the front cylinder bores 1B are aligned with their corresponding rear shaft hole 3A and rear cylinder bores 3B, respectively. The front cylinder bores 1B and the rear cylinder bores 3B cooperate to form a plurality of pairs of the front and rear cylinder bores 1B and 3B. The front cylinder block 1 and the rear cylinder block 3 have therebetween an O ring 2. The front cylinder block 1 and the rear cylinder block 3 also have a swash plate chamber 25 between the first cylinder bores 3B and the second cylinder bores 1B. It is noted that the left-hand side and the right-hand side of FIG. 1 correspond to the front and rear of the compressor, respectively.

The compressor further includes a front housing 7 and a rear housing 11. The front housing 7 is joined to the front cylinder block 1 via a front valve unit 5. The front valve unit 5 includes a valve plate 51 having therethrough a plurality of discharge ports 51B, a plurality of reed type discharge valves 52A which are operable to open and close the discharge ports 51B, and a plurality of retainers 53A which restrict the opening of the discharge valves 52A. The valve plate 51 is formed on the side thereof adjacent to the front cylinder block 1 with a gasket (not shown). The gasket is formed by coating rubber material. The front housing 7 has therein a discharge chamber 7A which is communicable with the front cylinder bores 1B via the respective discharge valves 52A. The front housing 7 and the front cylinder block 1 have therebetween an O ring 4.

In a similar manner, the rear housing 11 is joined to the rear cylinder block 3 via a rear valve unit 9. The rear valve unit 9 includes a valve plate 91 having therethrough a plurality of discharge ports 91B, a plurality of reed type discharge valves 92A which are operable to open and close the discharge ports 91B, and a plurality of retainers 93A which restrict the opening of the discharge valves 92A. The valve plate 91 is formed on the side thereof adjacent to the rear cylinder block 3 with a gasket (not shown). The gasket is formed by coating rubber material. The rear housing 11 has therein a discharge chamber 11A which is communicable with the rear cylinder bores 3B via the respective discharge valves 92A. The rear housing 11 and the rear cylinder block 3 have therebetween an O ring 6. The housings 7, 11 and the cylinder blocks 1, 3 are fastened together by a plurality of bolts 8 (only one being shown). The discharge chambers 7A, 11A communicate with a single discharge chamber (not shown).

The front housing 7 has therethrough a front shaft hole 7B. A drive shaft 13 is rotatably supported at the shaft holes 1A, 3A and 7B by the cylinder blocks 1, 3 and the front housing 7, respectively. A swash plate 27 is mounted on the drive shaft 13 in the swash plate chamber 25 for rotating therewith integrally. The swash plate 27 has a boss portion 27A held between the front cylinder block 1 and the rear cylinder block 3 via thrust bearings 31A, 31B and a cam portion 27B formed integrally with the boss portion 27A. The boss portion 27A is fitted on the drive shaft 13. A plurality of double-headed pistons 17 are received in the respective pairs of the front and rear cylinder bores 1B and 3B and engaged with the cam portion 27B via a plurality of pairs of front and rear shoes 18A and 18B, respectively. When the drive shaft 13 is rotated, the cam portion 27B of the swash plate 27 causes the pistons 17 to reciprocate in their corresponding pairs of front and rear cylinder bores 1B and 3B via the plurality of pairs of front and rear shoes 18A and 18B, respectively.

The opposite heads of each piston 17 define in the pair of the front and rear cylinder bores 1B and 3B a front compression chamber 19A and a rear compression chamber 19B. The front cylinder block 1 has therein an inlet port 1C extending radially and connected to the swash plate chamber 25 for allowing refrigerant gas in the external refrigerant circuit of the compressor to be drawn into the swash plate chamber 25.

Referring to FIG. 2, the boss portion 27A of the swash plate 27 has therethrough a front supply port 27C and a rear supply port 27D which extend radially in opposite directions and communicate with the swash plate chamber 25. That is, the front supply port 27C and the rear supply port 27D are spaced angularly from each other in the rotation direction of the swash plate 27 at an angle of about 180 degrees. The distance from the inlet port 1C to the rear supply port 27D when the rear supply port 270 is moved closest to the inlet port 1C is greater than the distance from the inlet port 1C to the front supply port 27C when the front supply port 27C is moved closest to the inlet port 1C, and the flow passage area of the rear supply port 27D as viewed in cross section is larger than that of the front supply port 27C as viewed in cross section. In other words, the distance from the inlet port 1C to the front supply port 27C when the front supply port 27C is moved closest to the inlet port 1C is shorter than the distance from the inlet port 1C to the rear supply port 27D when the rear supply port 27D is moved closest to the inlet port 1C, and the flow passage area of the front supply port 27C as viewed in cross section is smaller than that of the rear supply port 27D as viewed in cross section. The difference in flow passage area between the rear supply port 27D and the front supply port 27C is determined so as to minimize the difference between the intake flows to each front compression chamber 19A and to its corresponding rear compression chamber 19B.

The drive shaft 13 has therein an axial hole 13A extending in axial direction of the drive shaft 13, a front guide hole 13B which communicates with the front supply port 27C and the axial hole 13A, a rear guide hole 13C which communicates with the rear supply port 27D and the axial hole 13A, a front suction guide hole 13D which communicates with the axial hole 13A, and a rear suction guide hole 13E which communicates with the axial hole 13A. The front guide hole 13B has the same diameter as the front supply port 27C and the rear guide hole 13C has the same diameter as the rear supply port 27D. That is, the distance from the inlet port 1C to the rear guide hole 13C when the rear guide hole 13C is moved closest to the inlet port 1C is greater than the distance from the inlet port 1C to the front guide hole 13B when the front guide hole 13B is moved closest to the inlet port 1C, and the flow passage area of the rear guide hole 13C as viewed in cross section is greater than that of the front guide hole 13B as viewed in cross section. In other words, the distance from the inlet port 1C to the front guide hole 13B when the front guide hole 13B is moved closest to the inlet port 1C is shorter than the distance from the inlet port 1C to the rear guide hole 13C when the rear guide hole 13C is moved closest to the inlet port 1C, and the flow passage area of the front guide hole 13B as viewed in cross section is smaller than that of the rear guide hole 13C as viewed in cross section. The front suction guide hole 13D and the rear suction guide hole 13E have substantially the same flow passage area. Thus, the part of the drive shaft 13 which is located in the front shaft hole 1A and the rear shaft hole 3A forms a rotary valve, which improves the intake efficiency and simplifies the structure of the compressor.

The front cylinder block 1 has therein a plurality of front admission ports 21 which extend radially from the front shaft hole 1A and are communicable with the respective front compression chambers 19A. The front suction guide hole 13D of the drive shaft 13 is communicable with each front admission port 21 by the rotation of the drive shaft 13. The rear cylinder block 3 has therein a plurality of rear admission port 23 which extend radially from the rear shaft hole 3A and are communicable with the respective rear compression chambers 19B. The rear suction guide hole 13E of the drive shaft 13 is communicable with each rear admission port 23 by the rotation of the drive shaft 13. The front admission port 21 and the rear admission port 23 have substantially the same flow passage area.

Thus, the front supply port 27C, the front guide hole 13B, the axial hole 13A, the front suction guide hole 13D and the front admission ports 21 cooperate to form a front suction flow passage for allowing refrigerant gas in the swash plate chamber 25 to be drawn into each front compression chamber 19A then on the suction stroke of the piston 17 moving rearward. The rear supply port 27D, the rear guide hole 13C, the axial hole 13A, the rear suction guide hole 13E and the rear admission ports 23 cooperate to form a rear suction flow passage for allowing refrigerant gas in the swash plate chamber 25 to be drawn into each rear compression chamber 19B then on the suction stroke of the piston 17 moving forward. In the compressor of the first embodiment, the flow passage areas of the rear supply port 27D and the rear guide hole 13C are larger than those of the front supply port 27C and the front guide hole 13B, respectively.

When the compressor of FIG. 1 is used for a vehicle air conditioner, its single discharge chamber (not shown) is connected to a condenser (not shown) in the external refrigerant circuit having therein other components such as an expansion valve and an evaporator (each of which is not shown) via a conduit (not shown). The evaporator is connected to the inlet port 1C via a conduit (not shown). The drive shaft 13 is driven by an engine (not shown) through a belt trained between the engine and a pulley or an electromagnetic clutch mounted on the drive shaft 13.

When the drive shaft 13 is driven to rotate by the engine, the swash plate 27 is integrally rotated with the drive shaft 13 thereby to cause each piston 17 to reciprocate in its corresponding pair of front and rear cylinder bores 1B and 3B for a stroke length that is determined by the inclination of the swash plate 27. In conjunction with the reciprocating movement of the pistons 17, fluid communication is made between the front suction guide hole 13D and the front admission port 21 and also between the rear suction guide hole 13E and the rear admission port 23. Thus, the swash plate chamber 25 communicates with the front compression chamber 19A via the front suction flow passage and also with the rear compression chamber 19B via the rear suction flow passage. Refrigerant gas compressed in the front and rear compression chambers 19A, 19B is discharged into the front and rear discharge chambers 7A, 11A, respectively. Refrigerant gas discharged to the front and rear discharge chambers 7A, 11A is then delivered to the condenser via the single discharge chamber and the conduit and returns to the inlet port 1C of the compressor via the expansion valve and the evaporator. Thus, air conditioning cycle is completed.

In the compressor, the inlet port 1C, which is formed in the front cylinder block 1, is positioned axially forward of the center of the cam portion 27B of the swash plate 27, as shown in FIG. 2, so that refrigerant gas is less susceptible to diffusion caused by the rotation of the swash plate 27, with the result that a high intake efficiency is maintained. The arrangement of the inlet port 1C helps to prevent refrigerant gas from leaking and to simplify the structure of the compressor.

In the compressor of the present embodiment wherein the flow passage area of the rear supply port 27D is greater than that of the front supply port 27C, the difference between the intake flow to the front compression chambers 19A and the intake flow to the rear compression chambers 19B is minimized. Accordingly, the difference in temperature between the refrigerant gas discharged from the front compression chamber 19A and from the rear compression chamber 19B is minimized, so that early deterioration of either one of the gaskets of the valve units 5 and 9 and/or of the O-rings 4 and 6 is prevented. The difference in reaction force between the front and rear compression chambers 19A and 19B is also minimized, therefore, generation of vibration due to such difference is prevented successfully.

Consequently, the compressor of the present embodiment offers high durability and quiet operation while maintaining a high intake efficiency.

The piston compressor according to the second embodiment of the present invention will be described with reference to FIG. 3. The compressor of the second embodiment is substantially the same as the compressor of the first embodiment in that the flow passage area of the rear supply port 27D of the boss portion 27A of the swash plate 27 is greater than that of the front supply port 27C. The second embodiment differs from the first embodiment in that the front guide hole 13F corresponding to the front guide hole 13B of the first embodiment has the same flow passage area as the rear guide hole 13C. The rest of the structure of the second embodiment is substantially the same as that of the first embodiment.

In the compressor of the second embodiment wherein the flow passage area of the rear supply port 27D is greater than that of the front supply port 27C, the flow resistance of refrigerant gas flowing through the rear supply port 27D, which is more remote from the inlet port 1C than the front supply port 27C, is smaller than the flow resistance of refrigerant gas flowing through the front supply port 27C.

Therefore, the compressor of the second embodiment offers substantially the same advantageous effects as that of the first embodiment.

The piston compressor according to the third embodiment of the present invention will be described with reference to FIG. 4. The compressor of the third embodiment is substantially the same as the compressor of the first embodiment in that the flow passage area of the rear guide hole 13C, which is more remote from the inlet port 1C than the front guide hole 13B, is greater than that of the front guide hole 13B. The third embodiment differs from the first embodiment in that the front supply port 27E corresponding to the front supply port 27C of the first embodiment has the same flow passage area as the rear supply port 27D. The rest of the structure of the third embodiment is substantially the same as that of the first embodiment.

In the compressor of the third embodiment wherein the flow passage area of the rear guide hole 13C is greater than that of the front guide hole 13B, the flow resistance of refrigerant gas flowing through the rear guide hole 13C, which is more remote from the inlet port 10 than the front guide hole 13B, is smaller than the flow resistance of refrigerant gas flowing through the front guide hole 13B.

Therefore, the compressor of the third embodiment offers substantially the same advantageous effects as that of the first embodiment.

The piston compressor according to the fourth embodiment of the present invention will be described with reference to FIG. 5. In the fourth embodiment, the flow passage area of the rear suction guide hole 13E, which is more remote from the inlet port 1C than the front suction guide hole 13G corresponding to the front suction guide hole 13D of the first embodiment, is greater than that of the front suction guide hole 13G. That is, when the drive shaft 13 rotates, the shortest flow path from the inlet port 1C to the rear suction guide hole 13E through the first supply port 27D is longer than the shortest flow path from the inlet port 1C to the front suction guide hole 13G through the second supply port 27C and the flow passage area of the rear suction guide hole 13E is greater than that of the front suction guide hole 13G. The rest of the structure of the fourth embodiment is substantially the same as that of the first embodiment.

In the compressor of the fourth embodiment wherein the flow passage area of the rear suction guide hole 13E is greater than that of the front suction guide hole 13G, the flow resistance of refrigerant gas flowing through the rear suction guide hole 13E, which is more remote from the inlet port 1C than the front suction guide hole 13G, is smaller than the flow resistance of refrigerant gas flowing through the front suction guide hole 13G.

Therefore, the compressor of the fourth embodiment offers substantially the same advantageous effects as that of the first embodiment.

The piston compressor according to the fifth embodiment of the present invention will be described with reference to FIGS. 6 and 7. In the fifth embodiment, the flow passage area of each rear admission port 23, which is more remote from the inlet port 1C than the front admission port 24 corresponding to the front admission port 21 of the first embodiment, is greater than that of the front admission port 24. Each front admission port 24 is in the form of a round hole as viewed in cross section as shown in FIG. 7 and each rear admission port 23 is also in the form of a round hole. The rest of the structure of the fifth embodiment is substantially the same as that of the first embodiment.

In the compressor of the fifth embodiment wherein the flow passage area of the rear admission port 23 is greater than that of the front admission port 24, the flow resistance of refrigerant gas flowing through the rear admission port 23, which is more remote from the inlet port 1C than the front admission port 24, is smaller than the flow resistance of refrigerant gas flowing through the front admission port 24. The rear admission port 23 and the front admission port 24 provided by a round hole can reduce the flow resistance of refrigerant gas flowing through these admission ports 23 and 24 as compared to a case where the rear admission port 23 and the front admission port 24 are provided by a hole having other shape than round shape.

Therefore, the compressor of the fifth embodiment offers substantially the same advantageous effects as that of the first embodiment.

In addition, there is not only the difference between the flow passage area of the rear supply port 27D and the rear guide hole 13C and the flow passage area of the front supply port 27C and the front guide hole 13B, but also the difference between the flow passage area of each rear admission port 23 and the corresponding front admission port 24. Thus, the advantageous effects of the present invention are remarkably accomplished.

The piston compressor according to the sixth embodiment of the present invention will be described with reference to FIG. 8. In the sixth embodiment, each rear admission port 23 which is more remote from the inlet port 1C than the corresponding front admission port 26 is formed by a round hole as viewed in cross section as shown in FIG. 8. The front admission port 26 is formed by an elongated hole as viewed in cross section as shown in FIG. 8. As viewed axially of the drive shaft 13, the rear admission port 23 is formed with a diameter that is substantially the same as the length of the front admission port 26. The rest of the structure of the sixth embodiment is substantially the same as that of the first embodiment.

In the compressor, the suction stroke of the piston 17 is performed at the same timing in the front and rear compression chambers 19A and 19B, which helps to restrict the generation of vibration.

The piston compressor according to the seventh embodiment of the present invention will be described with reference to FIG. 9. In the seventh embodiment, the rear supply port 28 corresponding to the rear supply port 27D of the first embodiment is formed with a projection 28A and a recess 28B. Specifically, the projection 28A is formed on the outer surface of the boss portion 27A which is formed by the trailing side of the opening of the first supply port 28 with respect to the rotation direction R of the swash plate 27. The recess 28B is formed on the outer surface of the boss portion 27A which is formed by the opposite leading side of the opening of the first supply port 28 with respect to the rotation direction R of the swash plate 27. The rest of the structure of the seventh embodiment is substantially the same as that of the first embodiment.

In the compressor of the seventh embodiment, during the rotation of the swash plate 27, refrigerant gas 32 can flow easily into the rear supply port 28 that is more remote from the inlet port 1C than the front supply port 27C.

Therefore, the compressor of the seventh embodiment offers substantially the same advantageous effects as that of the first embodiment.

The piston compressor according to the eighth embodiment of the present invention will be described with reference to FIG. 10. In the eighth embodiment, the rear supply port 30 corresponding to the rear supply port 27D of the first embodiment is inclined from the radial direction of the boss portion 27A so as to guide the refrigerant gas 32 into the axial hole 13A by the rotation of the swash plate 27. The rest of the structure of the eighth embodiment is substantially the same as that of the first embodiment.

In the compressor of the eighth embodiment, likewise the seventh embodiment, during the rotation of the swash plate 27, refrigerant gas 32 can flow easily into the rear supply port 30 that is more remote from the inlet port 1C than the front supply port 27C.

Thus, the compressor of the eighth embodiment offers substantially the same advantageous effects as that of the first embodiment.

The present invention has been described in the context of the above-described first through eighth embodiments, but it is not limited to those embodiments. It is obvious that the invention may be practiced in various manners as exemplified below.

Although the inlet port 1C in the above-described embodiments is formed in the front cylinder block 1, the inlet port may be formed in the rear cylinder block. In this case, the above-described distant relations are reversed.

Claims

1. A piston compressor comprising:

a first cylinder block having a first shaft hole, a plurality of first cylinder bores and a plurality of first admission ports, wherein the first cylinder bores are formed around the first shaft hole and communicate with the first shaft hole via the respective first admission ports;

a second cylinder block having a second shaft hole, a plurality of second cylinder bores and a plurality of second admission ports, wherein the second cylinder bores are formed around the second shaft hole and communicate with the second shaft hole via the respective second admission ports, wherein the first cylinder block and the second cylinder block are joined together, wherein the first cylinder block and the second cylinder block form a swash plate chamber between the first cylinder bores and the second cylinder bores, wherein one of the first cylinder block and the second cylinder block has therein an inlet port connected to the swash plate chamber for allowing refrigerant gas to be drawn thereinto;

a drive shaft rotatably supported at the first shaft hole and the second shaft hole by the first cylinder block and the second cylinder block, respectively, the drive shaft having therein an axial hole, a first suction guide hole, a second suction guide hole, a first guide hole and a second guide hole, wherein the axial hole extends in axial direction of the drive shaft, wherein the first suction guide hole communicates with the first guide hole via the axial hole and is communicable with the first admission ports of the first cylinder block, wherein the second suction guide hole communicates with the second guide hole via the axial hole and is communicable with the second admission ports of the second cylinder block;

a swash plate mounted on the drive shaft in the swash plate chamber for rotating therewith integrally, wherein the swash plate has a boss portion fitted on the drive shaft and a cam portion formed integrally with the boss portion, wherein the boss portion has therein a first supply port and a second supply port, wherein the first supply port communicates with the first guide hole of the drive shaft and the swash plate chamber, wherein the second supply port communicates with the second guide hole of the drive shaft and the swash plate chamber, wherein the first supply port and the second supply port are spaced from each other in rotation direction of the swash plate; and

a plurality of double-headed pistons received in the respective first and second cylinder bores and engaged with the cam portion, wherein the rotation of the cam portion with the drive shaft causes the double-headed pistons to reciprocate in the respective first and second cylinder bores, wherein opposite heads of the double-headed pistons and the first and second cylinder bores respectively define first compression chambers and second compression chambers, wherein the first compression chamber and the second compression chamber are communicable with the first admission port and the second admission port, respectively;

wherein the first supply port, the first guide hole, the axial hole, the first suction guide hole and the first admission ports cooperate to form a first suction flow passage for allowing the refrigerant gas in the swash plate chamber to be drawn into each first compression chamber on a suction stroke of the double-headed piston for the first compression chamber,

wherein the second supply port, the second guide hole, the axial hole, the second suction guide hole and the second admission ports cooperate to form a second suction flow passage for allowing the refrigerant gas in the swash plate chamber to be drawn into each second compression chamber on a suction stroke of the double-headed piston for the second compression chamber, and

wherein a distance from the inlet port to the first supply port when the first supply port is moved closest to the inlet port is greater than a distance from the inlet port to the second supply port when the second supply port is moved closest to the inlet port, wherein the smallest flow passage area in the first supply port and the first guide hole is greater than the smallest flow passage area in the second supply port and the second guide hole.

2. The piston compressor according to claim 1, wherein the respective flow passage areas of the first supply port and the first guide hole are greater than the flow passage areas of the second supply port and the second guide hole.

3. The piston compressor according to claim 1, wherein the flow passage area of the first guide hole is equal to the flow passage area of the second guide hole.

4. The piston compressor according to claim 1, wherein the flow passage area of the first supply port is equal to the flow passage area of the second supply port.

5. The piston compressor according to claim 1, wherein when the drive shaft rotates, the shortest flow path from the inlet port to the first suction guide hole through the first supply port is longer than the shortest flow path from the inlet port to the second suction guide hole through the second supply port, and wherein flow passage area of the first suction guide hole is greater than flow passage area of the second suction guide hole.

6. The piston compressor according to claim 1, wherein when the drive shaft rotates, flow path from the inlet port to each first admission port through the first supply port is longer than flow path from the inlet port to the corresponding second admission port through the second supply port, and wherein flow passage area of the first admission port is greater than flow passage area of the second admission port.

7. The piston compressor according to claim 1, wherein each of the first and second admission ports is in the form of a round hole as viewed in cross section.

8. The piston compressor according to claim 1, wherein when the drive shaft rotates, flow path from the inlet port to each first admission port through the first supply port is longer than flow path from the inlet port to the corresponding second admission port through the second supply port, and wherein the first admission port is in the form of a round hole as viewed in cross section and the second admission port is in the form of an elongated hole as viewed in cross section.

9. The piston compressor according to claim 1, wherein a projection is formed on the outer surface of the boss portion which is formed by a trailing side of the opening of the first supply port with respect to the rotation direction of the swash plate.

10. The piston compressor according to claim 1, wherein the first supply port is inclined from radial direction of the boss portion so as to guide the refrigerant gas into the axial hole by the rotation of the swash plate.