Reciprocating Fluid Machine

Abstract

A reciprocating fluid machine includes a cylinder block (18) arranged inside a casing shell (16) and having cylinder bores (38), a cylinder head (54) fastened to the casing shell (16), a valve plate (50) interposed between the cylinder block (18) and the cylinder head (54) each with a gasket (46, 48, 52) therebetween, and a fastening device for fastening the valve plate (50) to the cylinder block (18). The fastening device includes outer tapped holes (42) formed in the cylinder block (18), and outer fastening bolts (68) extending from the cylinder head side through the valve plate (50) and the gaskets (46, 48, 52) and screwed into the respective outer tapped holes (42). The outer fastening bolts (68) have axes located outward of a bore distribution circle on which the axes of the cylinder bores (38) are located, as viewed in the radial direction of the cylinder block (54), and have bolt heads (69) located inside the cylinder head (54).

Description

TECHNICAL FIELD

The present invention relates to reciprocating fluid machines, and more particularly, to a reciprocating fluid machine suited for discharging a high-pressure working fluid.

BACKGROUND ART

In recent years, development of refrigeration systems is focused on the use of refrigerants with small global warming potentials in consideration of global environments. As such refrigerants, natural CO₂ (carbon dioxide) gas, for example, has been known.

When CO₂ as a refrigerant passes through a high-pressure section of a refrigeration system, that is, a refrigerant circuit, the CO₂ refrigerant turns into a supercritical state. The pressure of supercritical CO₂ is approximately seven to ten times higher than that of a fluorocarbon refrigerant flowing through the high-pressure section.

Accordingly, where CO₂ is used as the refrigerant, a compressor for circulating the CO₂ refrigerant through the refrigerant circuit is required to discharge the high-pressure CO₂ refrigerant. To meet the requirement, the compressor needs to have a discharge chamber with high sealing performance. Patent Documents 1 and 2 identified below, for example, disclose techniques of sealing the discharge chamber of a compressor.

Patent Document 1: Unexamined Japanese Patent Publication No. 2001-99058

Patent Document 2: Unexamined Japanese Patent Publication No. 2002-5014

The compressor disclosed in Patent Document 1 includes a casing, a cylinder block arranged inside the casing, and a cylinder head adjoining the cylinder block. The cylinder block and the cylinder head are fastened together by a plurality of bolts.

More specifically, a valve plate is sandwiched between the cylinder block and the cylinder head, with one gasket interposed between the valve plate and the cylinder block and another gasket interposed between the valve plate and the cylinder head. Thus, the bolts are inserted from inside the casing through the cylinder block, the gasket, the valve plate and the gasket and screwed into the cylinder head. Further, the bolts have their heads sunk into the cylinder block, and the bolt heads are positioned between respective adjacent ones of cylinder bores in the cylinder block, as viewed in the circumferential direction of the cylinder block.

The presence of the bolts makes it difficult to detach the cylinder head from the cylinder block when, for example, the top clearance of pistons in the cylinder bores is to be adjusted. Specifically, the heads of the bolts are located inside the casing, and therefore, prior to removal of the bolts, parts such as the pistons and the drive shaft need to be detached from the cylinder block. Consequently, the use of the bolts leads to lowering in the disassembling efficiency and productivity of the compressor.

On the other hand, the compressor disclosed in Patent Document 2 includes a center bolt for fixing discharge valves and valve retainers to the valve plate. The center bolt is also used to fasten the valve plate and the cylinder block together.

A center bolt may alternatively be used for fastening the cylinder block and the cylinder head. In this case, the center bolt is inserted from outside of the cylinder head through the cylinder head, the valve plate and the gasket and screwed into the cylinder block.

This center bolt has its head located on the outside of the cylinder head, and therefore, it is easy to remove the center bolt. However, since the center bolt is positioned substantially at the center of the cylinder head, tightness between the gasket and the valve plate is not uniform over the entire area of the valve plate, making it difficult to satisfactorily seal the cylinder bores. As a result, the compression efficiency of the compressor lowers, and especially in cases where the CO₂ refrigerant is used, the compression efficiency remarkably lowers.

DISCLOSURE OF THE INVENTION

An object of the present invention is to provide a reciprocating fluid machine which ensures high productivity and high disassembling efficiency and yet is capable of preventing lowering in compression efficiency.

To achieve the object, the present invention provides a reciprocating fluid machine comprising: a housing; a cylinder block having at least part thereof contained in the housing and including a plurality of cylinder bores therein, the cylinder bores having axes located on a bore distribution circle concentric with an axis of the cylinder block; a cylinder head fastened to the housing and including a suction chamber and a discharge chamber for a working fluid, the suction and discharge chambers opening toward the cylinder block; a compression unit including a valve mechanism having pistons received in the respective cylinder bores and capable of reciprocating motion therein and a valve plate interposed between the cylinder block and the cylinder head each with a gasket therebetween, the reciprocating motion of the pistons and operation of the valve mechanism causing the compression unit to successively carry out suction of the working fluid from the suction chamber into the cylinder bores, compression of the sucked working fluid in the cylinder bores, and discharge of the compressed working fluid from the cylinder bores to the discharge chamber; and a fastening device for fastening the valve plate to the cylinder block. The fastening device includes: a plurality of outer tapped holes formed in the cylinder block and extending parallel with the cylinder bores, the outer tapped holes having axes located outward of the bore distribution circle as viewed in a radial direction of the cylinder block; and a plurality of outer fastening bolts extending from a side near the cylinder head through the valve plate and the gaskets and screwed into the respective outer tapped holes, the outer fastening bolts having bolt heads located inside the cylinder head.

In the above reciprocating fluid machine, the valve plate is fastened to the cylinder block by the multiple outer fastening bolts, and the bolt heads of the outer fastening bolts are located inside the cylinder head. In cases where the top clearance of the pistons of the compression unit needs to be adjusted, it is necessary that the valve plate should be detached from the cylinder block. Since the bolt heads of the outer fastening bolts are located inside the cylinder head and not inside the housing, it is possible to access the bolt heads of the outer fastening bolts from outside of the housing. Accordingly, the outer fastening bolts, namely, the valve plate can be detached without the need to remove internal parts, such as the drive shaft and the pistons of the compression unit, from within the housing, thus making it easy to adjust the top clearance of the pistons. As a result, the time required to manufacture the fluid machine is shortened, improving the production efficiency of the fluid machine.

Further, the axes of the outer tapped holes are located outward of the bore distribution circle. Accordingly, the outer fastening bolts screwed into the outer tapped holes tightly press the gasket at the outer peripheral portion of the valve plate against the cylinder block, thereby significantly improving the sealing performance of the junction between the cylinder block and the valve plate, namely, the sealing of the cylinder bores.

Specifically, the bolt heads of the outer fastening bolts are located in the suction chamber defined in the cylinder head, and the suction chamber has an annular form surrounding the discharge chamber.

The fastening device may further include: a center tapped hole formed in the cylinder block coaxially with the cylinder block; and a center fastening bolt extending from the cylinder head side through the valve plate and the gaskets and screwed into the center tapped hole, the center fastening bolt having a bolt head located inside the cylinder head. In this case, the bolt head of the center fastening bolt is located in the discharge chamber defined in the cylinder head, and the discharge chamber is located at the center of the cylinder head.

The center fastening bolt tightly presses the gasket at the central portion of the valve plate against the cylinder block, whereby the sealing performance of the junction between the cylinder block and the valve plate is further enhanced.

Preferably, the valve mechanism includes discharge valves for controlling discharge of the compressed working fluid, and the center fastening bolt serves also as a fixing bolt for fixing the discharge valves to the valve plate.

Further, the fastening device may additionally include: a plurality of inner tapped holes formed in the cylinder block and having axes located inward of the bore distribution circle as viewed in the radial direction of the cylinder block; and a plurality of inner fastening bolts extending from the cylinder head side through the valve plate and the gaskets and screwed into the respective inner tapped holes, the inner fastening bolts having bolt heads located inside the cylinder head. In this case, the bolt heads of the inner fastening bolts are located in the discharge chamber, and the discharge chamber is located at the center of the cylinder head.

The inner fastening bolts firmly press the gasket at the central portion of the valve plate against the cylinder block, thereby further improving the sealing performance of the junction between the cylinder block and the valve plate.

The outer fastening bolts may each comprise a stud bolt buried in the cylinder block, and the fastening device may further include nuts screwed onto the respective stud bolts and pressing the valve plate against the cylinder block.

Connecting bolts may be screwed from outside of the cylinder head into the respective stud bolts, and in this case, the cylinder block and the cylinder head can be fastened together by the connecting bolts.

Preferably, the fluid machine is a compressor used for compressing CO₂ refrigerant flowing through a refrigeration circuit. In this case, the compressor discharges high-pressure CO₂ refrigerant from the cylinder bores into the discharge chamber, but since the sealing performance of the junction between the cylinder block and the valve plate is high, the CO₂ refrigerant does not leak to outside from the junction between the cylinder block and the valve plate. Also, the use of CO₂ refrigerant greatly contributes toward reducing the environment load.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a longitudinal sectional view of a compressor, as a reciprocating fluid machine, according to a first embodiment of the invention.

FIG. 2 is a sectional view taken along line II-II in FIG. 1.

FIG. 3 is a front view showing a block-side gasket and a shell-side gasket, both appearing in FIG. 1.

FIG. 4 is a front view showing a head-side gasket in FIG. 1.

FIG. 5 is a longitudinal sectional view of a compressor, as a reciprocating fluid machine, according to a second embodiment of the invention.

FIG. 6 is a front view showing a shell-side gasket in FIG. 5.

FIG. 7 is a front view showing a block-side gasket in FIG. 5.

FIG. 8 is a front view showing a head-side gasket in FIG. 5.

FIG. 9 is a longitudinal sectional view of a compressor, as a reciprocating fluid machine, according to a third embodiment of the invention.

FIG. 10 is a sectional view taken along line X-X in FIG. 9.

FIG. 11 shows a stud bolt and a nut for fastening a valve plate to a cylinder block.

BEST MODE OF CARRYING OUT THE INVENTION

FIG. 1 schematically shows an air-conditioning system for a motor vehicle, or more specifically, part of a refrigeration circuit 2 of the system.

The refrigeration circuit 2 includes a circulation path for a refrigerant, and CO₂ gas is used as the refrigerant. A compressor 4 of a first embodiment as a reciprocating fluid machine, a gas cooler 6, an expansion valve 8 and an evaporator 10 are inserted in order in the circulation path. The compressor 4 compresses the refrigerant and then discharges the compressed, high-pressure refrigerant to the gas cooler 6, thereby causing the refrigerant to circulate through the refrigeration circuit 2.

As is clear from FIG. 1, the compressor 4 is of a swash plate type, and this type of compressor is capable of varying its displacement.

The compressor 4 has a housing including a front casing 12. The front casing 12 is in the form of a stepped cylinder and has a boss 14 and a casing shell 16. The boss 14 is located at one end of the front casing 12 and has a diameter smaller than that of the casing shell 16.

A cylinder block 18 is fitted into the casing shell 16 and has a substantially cylindrical shape. The cylinder block 18 defines a crank chamber 20 inside the casing shell 16 and has one end face facing the crank chamber 20 and the other end face exposed from the casing shell 16.

The cylinder block 18 has, for example, seven cylinder bores 36. The cylinder bores 36 extend through the cylinder block 18 in parallel with the axis of the block 18. As is clear from FIG. 2, the cylinder bores 36 have their axes located on a bore distribution circle concentric with the axis of a drive shaft 24 and are arranged at equal intervals in the circumferential direction of the cylinder block 18.

A compression unit is arranged inside the front casing 12. The following explains the compression unit.

The compression unit includes the drive shaft 24, which is arranged coaxially with the cylinder block 18. The drive shaft 24 extends through the crank chamber 20 and is rotatably supported by both of the front casing 12 and the cylinder block 18 through bearings 26 and 28, respectively. A swash plate 30 is mounted on the drive shaft 24 through a tilt mechanism 32 and accommodated in the crank chamber 20. The tilt mechanism 32 includes a rotor 34 rotated together with the drive shaft 24 and causes the swash plate 30 to rotate together with the drive shaft 24 through the rotor 34 while at the same time permits the swash plate 30 to tilt relative to the drive shaft 24.

The drive shaft 24 has one end portion 25 projecting from the casing shell 16 into the boss 14, and a mechanical seal 74 is arranged between the end portion 25 and the casing shell 16. The mechanical seal 74 seals the crank chamber 20 in a gastight fashion.

An electromagnetic clutch 76 is coupled to the end portion 25 of the drive shaft 24 and includes a pulley 78. The pulley 78 is rotatably supported on the outer peripheral surface of the boss 14 through a bearing 80. The pulley 78 is connected to a driving source, such as an engine or a motor, and is rotated in one direction by motive power supplied from the driving source. Further, the pulley 78 has a solenoid 82 received therein, and the solenoid 82 is fixed to the casing shell 16.

When the solenoid 82 is energized, the electromagnetic clutch 76 transmits rotation of the pulley 78 to the drive shaft 24. On the other hand, when the solenoid 82 is de-energized, the electromagnetic clutch 76 stops transmitting rotation of the pulley 78 to the drive shaft 24.

The casing shell 16 has a plurality of mounts 84 formed integrally on an outer peripheral surface thereof. The mounts 84 each have a bolt insertion hole therein and are used to install the compressor 4 in an engine compartment.

A piston 38 is received in each cylinder bore 36 and includes a tail 39 projecting into the crank chamber 20. The tail 39 is in the form of the letter U and opens in the radial direction of the cylinder bock 18 toward the drive shaft 24 as well as in the circumferential direction of the cylinder block 18. Also, each tail 39 has a spherical seat therein for slidably supporting a pair of shoes 44. The shoes 44 are semispherical in shape and hold the outer peripheral edge of the swash plate 30 therebetween. Thus, while the swash plate 30 is rotating, the outer peripheral edge thereof and the shoes 44 are kept in sliding contact with each other.

The cylinder block 18 has a center tapped hole 40 formed in the other end face thereof. The center tapped hole 40 is located on the axis of the cylinder block 18 and extends parallel with the cylinder bores 36.

Further, seven outer tapped holes 42 are formed in the other end face of the cylinder block 18. The outer tapped holes 42 have their axes located outward of the aforementioned bore distribution circle, as viewed in the radial direction of the cylinder block 18, and are arranged at equal intervals in the circumferential direction of the cylinder block 18. More specifically, the axes of the outer tapped holes 42 are located on a hole distribution circle having a larger diameter than the bore distribution circle, and the outer tapped holes 42 are individually positioned between adjacent ones of the cylinder bores 36 as viewed in the circumferential direction of the cylinder block 18.

As is clear from FIG. 1, the other end face of the cylinder block 18 is flush with the counterpart of the casing shell 16, and a cylinder head 54 adjoins the other end faces with a valve plate 50 therebetween.

A block-side gasket 46 is interposed between the other end face of the cylinder block 18 and the valve plate 50, and a shell-side gasket 48 is interposed between the other end face of the casing shell 16 and the valve plate 50. Further, a head-side gasket 52 is sandwiched between the valve plate 50 and the cylinder head 54. The gaskets 46, 48 and 52 respectively serve as a seal between the cylinder block 18 and the valve plate 50, a seal between the casing shell 16 and the valve plate 50, and a seal between the valve plate 50 and the cylinder head 54.

Ten tapped holes 17, for example, are formed in the other end face of the casing shell 16. The tapped holes 17 extend in the axial direction of the casing shell 16 and are arranged at equal intervals in the circumferential direction of the casing shell 16. The valve plate 50 and the cylinder head 54 have ten through holes 53 and 55, respectively, formed through their outer peripheral portions and aligned with the respective tapped holes 17. Connecting bolts 56 are inserted from outside of the cylinder head 54 into the respective through holes 53 and 55 and are screwed into the respective tapped holes 17. The connecting bolts 56 separably fix the cylinder head 54 to the casing shell 16 with the valve plate 50 and the gaskets 48 and 52 therebetween.

Further, the valve plate 50 has through holes 51 aligned with the respective outer tapped holes 42 of the cylinder block 18. Outer fastening bolts 68 are inserted into the respective through holes 51 and screwed into the respective tapped holes 42. Namely, the outer fastening bolts 68 fasten the valve plate 50 to the cylinder block 18 together with the gaskets 46 and 52.

The cylinder head 54 has a suction chamber 58 and a discharge chamber 60 defined therein, and the suction and discharge chambers 58 and 60 individually open in the end face of the cylinder head 54 adjacent to the valve plate 50. Namely, the suction and discharge chambers 58 and 60 open toward the cylinder block 54. As is clear from FIG. 1, the discharge chamber 60 is located at the center of the cylinder head 54, and the suction chamber 58 is an annular chamber surrounding the discharge chamber 60. The outer fastening bolts 68 have their bolt heads 69 located in the suction chamber 58.

A suction port and a discharge port (neither of which is shown) communicating with the suction and discharge chambers 58 and 60, respectively, are formed in the outer peripheral wall of the cylinder head 54. The suction and discharge ports are connected to the aforementioned refrigerant circulation path.

A pressure regulation passage (not shown) for connecting the discharge chamber 60 and the crank chamber 20 is formed through the cylinder block 18 and the valve plate 50. Also, an orifice passage connecting the suction chamber 58 and the crank chamber 20 at all times is formed through the cylinder block 18 and the valve plate 50. In FIG. 1, only a fixed orifice 62 formed in the valve plate 50 is shown as part of the orifice passage.

The cylinder head 54 further includes a solenoid control valve (not shown) accommodated therein. In this embodiment, the solenoid control valve has a valve element for opening and closing the pressure regulation passage, a solenoid, and a pressure-sensitive actuator applied with the pressure in the suction chamber 58. The solenoid and the pressure-sensitive actuator cooperate with each other to actuate the valve element, thereby adjusting the opening of the pressure regulation passage and, as a consequence, controlling the pressure in the crank chamber 20.

The solenoid control valve may be of the type including no pressure-sensitive actuator. In this case, the valve element is actuated by the solenoid of the solenoid control valve, whereby the opening of the pressure regulation passage, that is, the pressure in the crank chamber 20 is controlled.

The valve plate 50 is an element constituting a valve mechanism. The valve mechanism includes suction and discharge holes 58a and 60a associated with each of the cylinder bores 36 and formed through the valve plate 50. The suction holes 58a communicate with the suction chamber 58, and the discharge holes 60a communicate with the discharge chamber 60. Each suction hole 58a can be opened and closed by a suction valve (not shown). The suction valve comprises a reed valve and is interposed between the other end face of the cylinder block 18 and the valve plate 50. On the other hand, the discharge holes 60a can be opened and closed by a discharge valve unit 66. The discharge valve unit 66 includes reed valves 61 (see FIG. 2) arranged on the surface of the valve plate 50 facing the discharge chamber 60, and valve retainers 63. The reed valves 61 and the valve retainers 63 are fixed by a center fastening bolt 64 to the cylinder block 18 with the valve plate 50 therebetween. Specifically, the center fastening bolt 64 extends through the valve plate 50 and the gaskets 46 and 52 and is screwed into the aforementioned center tapped hole 40 of the cylinder block 18. The bolt head of the center fastening bolt 64 is located in the discharge chamber 60.

As is clear from FIG. 2, the reed valves 61 and the valve retainers 63 have a star-like shape corresponding to the arrangement of the discharge holes 60a. The suction valves also have a star-like shape corresponding to the arrangement of the suction holes 58a.

FIG. 3 shows in detail the block-side gasket 46 and the shell-side gasket 48, both mentioned above.

The block-side gasket 46 has a circular shape coinciding with the other end face of the cylinder block 18 and has a hole 40H at its center through which the center fastening bolt 64 is passed. Also, a plurality of holes 42H are formed in the outer peripheral portion of the block-side gasket 46 to allow the respective outer fastening bolts 68 to be passed therethrough.

The shell-side gasket 48 functions also as an adjusting member for adjusting the top clearance of the pistons 38, as described later. Accordingly, the shell-side gasket 48 is prepared separately from the block-side gasket 46. The shell-side gasket 48 has a plurality of holes 17H through which the respective connecting bolts 56 are passed. As is clear from FIG. 3, the shell-side gasket 48 has an outward form coinciding with the contour of the casing shell 16.

FIG. 4 shows the head-side gasket 52.

The head-side gasket 52 has an outward form coinciding with the contour of the cylinder head 54, and has an aperture 52a formed at its center and permitting the discharge valve unit 66 to be arranged, a plurality of holes 42h through which the respective outer fastening bolts 68 are passed, and a plurality of holes 55h through which the respective connecting bolts 56 are passed.

In the first embodiment described above, the valve plate 50 is not only fastened to the cylinder block 18 by the center fastening bolt 64 with the gasket 46 therebetween but also is clamped between the cylinder block 18 and the cylinder head 54 by the connecting bolts 56 and the outer fastening bolts 68 together with the gaskets 46, 48 and 52.

When the solenoid of the electromagnetic clutch 76 is energized, that is, when the clutch 76 is in operation, the electromagnetic clutch 76 transmits the motive power from the driving source to the drive shaft 24, so that the drive shaft 24 rotates in one direction. The rotation of the drive shaft 24 is converted through the swash plate 30 to reciprocating motion of the individual pistons 38. As each piston 38 reciprocates, the refrigerant undergoes a series of processes including a suction process in which the refrigerant is sucked from the suction chamber 58 into the pressure chamber of the cylinder bore 36 through the suction valve, a compression process in which the sucked refrigerant is compressed in the pressure chamber, and a discharge process in which the compressed refrigerant is discharged through the discharge valve 61 to the discharge chamber 60.

The amount of the refrigerant discharged, or the displacement, is determined by the tilt angle of the swash plate 30, namely, the length of the reciprocating stroke of the piston 38. The tilt angle of the swash plate 30 is adjusted by controlling the pressure in the crank chamber 20 by means of the aforementioned solenoid control valve.

Generally, the compressor 4 is assembled in the manner described below.

First, the cylinder block 18 is fixed on a workbench (not shown) by making use of the outer fastening bolts 68. The outer fastening bolts 68 are passed through the workbench and screwed into the respective outer tapped holes 42 of the cylinder block 18.

Then, with internal parts such as the swash plate 30, the tilt mechanism 32, the pistons 38 and the shoes 44 fitted onto the drive shaft 24, the drive shaft 24 is rotatably supported on the cylinder block 18 through the bearing 28 while at the same time the pistons 38 are inserted into the respective cylinder bores 36 of the cylinder block 18. Subsequently, the front casing 12 is fitted over the cylinder block 18. Thus, the drive shaft 24 is rotatably supported by the front casing 12 through the bearing 26 with the internal parts located inside the front casing 12, and the end portion of the drive shaft projects from the front casing 12.

At this stage, a dimension by which the top clearance of the pistons 38 needs to be adjusted is measured, and a shell-side gasket 48 with a thickness corresponding to the measured dimension is selected.

Subsequently, with the internal parts contained in the front housing 12, the outer fastening bolts 68 are removed from the cylinder block 18, so that the cylinder block 18 is separated from the workbench. The block-side gasket 46 and the shell-side gasket 48 selected in the aforementioned manner are then placed between the cylinder block 18 and the valve plate 50, and the valve plate 50 is fastened to the front casing 12 and the cylinder block 18 by the outer fastening bolts 68 with the block-side gasket 46 and the shell-side gasket 48 therebetween. At this time, the discharge valve unit 66 is fixed, together with the valve plate 50, to the cylinder block 18 by the center fastening bolt 64.

Then, the cylinder head 54 containing the aforementioned solenoid control valve is abutted against the valve plate 50 with the head-side gasket 52 therebetween and is fastened to the front housing 12 by the connecting bolts 56.

Finally, the electromagnetic clutch 76 is coupled to the end portion 25 of the drive shaft 24 projecting into the boss 14 of the front housing 12, thus completing the assembling of the compressor 4.

The present invention is not limited to the compressor of the first embodiment explained above and may be modified in various ways. The following describes compressors according to second and third embodiments. In the following description of the second and third embodiments, identical reference numerals are used to denote elements and parts having the same functions as those of the first embodiment, and description of such elements and parts is omitted.

FIGS. 5 through 8 illustrate the compressor according to the second embodiment.

As is clear from FIG. 5, a cylinder block 18A forms part of a front housing 12A. Specifically, the cylinder block 18A is in the form of a stepped cylinder and has a flange 19 interposed between a casing shell 16A and the cylinder head 54. In this arrangement, a shell-side gasket 48A is sandwiched between the flange 19 of the cylinder block 18A and the other end face of the casing shell 16A. The shell-side gasket 48A is shown in detail in FIG. 6.

The flange 19 has through holes 19a for passing the connecting bolts 56 therethrough, and thus, the connecting bolts 56 are screwed into the casing shell 16A through the cylinder block 18A.

In the second embodiment, a valve plate 50A is in the form of a circle with an outer diameter equal to the inner diameter of the flange 19. The cylinder head 54 has a circular recess 54a for receiving the valve plate 50A. Thus, as is clear from FIG. 5, the connecting bolts 56 do not penetrate through the valve plate 50A but extend outward of the valve plate 50A.

The discharge valve unit 66 is fixed to the valve plate 50A by a bolt 73a and a nut 73b.

In the second embodiment, a block-side gasket 46A between the cylinder block 18A and the valve plate 50A is also held between the cylinder block 18A and the cylinder head 54. The block-side gasket 46A also functions as the adjusting member for adjusting the top clearance of the pistons 38. A head-side gasket 52A is interposed between the valve plate 50A and the cylinder head 54.

FIG. 7 shows the block-side gasket 46A in detail. As clearly shown in FIG. 7, the block-side gasket 46A has a plurality of holes 17H′ for passing the respective connecting bolts 56 therethrough.

FIG. 8 illustrates the head-side gasket 52A in detail. As is clear from FIG. 8, the head-side gasket 52A does not have the holes 55h for the connecting bolts 56, as distinct from the head-side gasket 52 shown in FIG. 4.

Also in the second embodiment, the valve plate 50A is held between the cylinder block 18A and the cylinder head 54 by means of the connecting bolts 56 and the outer fastening bolts 68 together with the block-side gasket 46A and the head-side gasket 52A.

On assembly of the compressor 4A shown in FIG. 5, the outer fastening bolts 68 extend from the cylinder head side through the valve plate 50A and are screwed into the respective outer tapped holes 42 in the cylinder block 18A.

FIGS. 9 and 10 illustrate the compressor according to the third embodiment.

In the compressor 4B of FIG. 9, a cylinder block 18B additionally includes seven inner tapped holes 70. The inner tapped holes 70 have their axes located on a hole distribution circle having a diameter smaller than that of the hole distribution circle on which the outer tapped holes 42 are distributed, and are arranged at equal intervals in the circumferential direction of the cylinder block 18B. Needless to say, the inner tapped holes 70 also are individually arranged between adjacent ones of the cylinder bores 38 as viewed in the circumferential direction of the cylinder block 18B.

A block-side gasket 46B is interposed between the cylinder block 18B and a valve plate 50B, and the valve plate 50B and the block-side gasket 46B each have holes coinciding with the respective inner tapped holes 70. Thus, inner fastening bolts 71 are inserted through these holes and screwed into the respective inner tapped holes 70. The inner fastening bolts 71 fasten the valve plate 50B to the cylinder block 18B together with the block-side gasket 46B and have bolt heads 72 located in the discharge chamber 60.

The arrangement of the inner fastening bolts 71 and of the outer fastening bolts 68 is clearly shown in FIG. 10.

In the compressors of the first to third embodiments, the bolt heads 69 of the outer fastening bolts 68 are not exposed to the crank chamber 20 but are located in the suction chamber 58. Namely, the outer fastening bolts 68 are screwed into the respective outer tapped holes 42 of the cylinder block 18 (18A, 18B) from the same side as the cylinder head 54.

With the compressor of the present invention, therefore, the top clearance of the pistons can be adjusted with ease, unlike the compressor disclosed in the aforementioned Patent Document 1. Specifically, to adjust the top clearance, the gasket needs to be replaced, that is, the valve plate needs to be detached. In the case of the compressor disclosed in Patent Document 1, the internal parts such as the pistons and the drive shaft need to be removed from the front housing 12 before the valve plate is detached (the bolts are removed), as mentioned above. Then, after a suitable gasket 48 (48A) for adjusting the top clearance is selected, the internal parts need to be again fitted in the front housing 12. Consequently, in the case of the compressor of Patent Document 1, not only the manufacturing time required per compressor increases but also complicated management is needed during the disassembling and reassembling of the compressor, in order to avoid damage to the internal parts.

In the compressor of the present invention, by contrast, the outer fastening bolts 68 can be unscrewed on the same side as the cylinder head 54, thus making it possible to detach the valve plate 50 (50A, 50B), that is, to adjust the top clearance without the need to remove the internal parts from the cylinder block 18 (18A, 18B). Consequently, the compressor 4 (4A, 4B) can be easily assembled, whereby the production efficiency is significantly improved and also damage to the internal parts can be avoided.

Further, since the outer fastening bolts 68 are located in the outer peripheral portion of the valve plate 50 (50A, 50B), the block-side gasket 46 (46A, 46B) is tightly pressed against the other end face of the cylinder block 18 (18A, 18B) by the outer fastening bolts 68 so that the block-side gasket may be in close contact with the surface around the cylinder bores 36. The sealing performance of the junction between the cylinder block 18 and the valve plate 50 (50A, 50B) therefore greatly improves, and even in cases where CO₂ gas is used as the refrigerant, the compression efficiency of the compressor does not lower.

In the first embodiment, the center fastening bolt 64 also fastens the valve plate 50 to the cylinder block 18. Accordingly, the central portion of the valve plate 50 also is brought into close contact with the other end face of the cylinder block 18 through the block-side gasket 46, thus further improving the sealing performance of the junction between the cylinder block 18 and the valve plate 50.

Moreover, where the inner fastening bolts 71 are additionally used as in the third embodiment, the sealing performance of the junction between the cylinder block 18 and the valve plate 50 can be remarkably improved.

The present invention is not limited to the first to third embodiments described above and may be modified in various ways without departing from the scope of the invention.

For example, the outer fastening bolts 68 and the inner fastening bolts 71 may each be replaced by a stud bolt 100 shown in FIG. 11. The stud bolt 100 is buried in the cylinder block 18, and the valve plate 50 is fastened to the cylinder block 18 by a nut 102 screwed onto the stud bolt 100.

Further, a connecting bolt 104 may be screwed from outside of the cylinder head 54 into the stud bolt 100, as indicated by the dot-dot-dash line in FIG. 11. In this case, the cylinder head 54 and the cylinder block 18 can be fastened by the connecting bolts 104.

The reciprocating fluid machine to which the present invention is applied may alternatively be a fixed-displacement compressor or expander.

Claims

1. A reciprocating fluid machine comprising: a housing;a cylinder block having at least part thereof contained in the housing and including a plurality of cylinder bores therein, the cylinder bores having axes located on a bore distribution circle concentric with an axis of the cylinder block;a cylinder head fastened to the housing and including a suction chamber and a discharge chamber for a working fluid, the suction and discharge chambers opening toward the cylinder block;a compression unit including a valve mechanism having pistons received in the respective cylinder bores and capable of reciprocating motion therein and a valve plate interposed between the cylinder block and the cylinder head each with a gasket therebetween, the reciprocating motion of the pistons and operation of the valve mechanism causing the compression unit to successively carry out suction of the working fluid from the suction chamber into the cylinder bores, compression of the sucked working fluid in the cylinder bores, and discharge of the compressed working fluid from the cylinder bores to the discharge chamber; anda fastening device for fastening the valve plate to the cylinder block,the fastening device including a plurality of outer tapped holes formed in the cylinder block and extending parallel with the cylinder bores, the outer tapped holes having axes located outward of the bore distribution circle as viewed in a radial direction of the cylinder block, anda plurality of outer fastening bolts extending from a side near the cylinder head through the valve plate and the gaskets and screwed into the respective outer tapped holes, the outer fastening bolts having bolt heads located inside the cylinder head.

2. The reciprocating fluid machine according to claim 1, wherein the bolt heads of the outer fastening bolts are located in the suction chamber, and the suction chamber has an annular form surrounding the discharge chamber.

3. The reciprocating fluid machine according to claim 1, wherein the fastening device further includes: a center tapped hole formed in the cylinder block coaxially with the cylinder block; anda center fastening bolt extending from the side near the cylinder head through the valve plate and the gaskets and screwed into the center tapped hole, the center fastening bolt having a bolt head located inside the cylinder head.

4. The reciprocating fluid machine according to claim 3, wherein the bolt head of the center fastening bolt is located in the discharge chamber, and the discharge chamber is located at center of the cylinder head.

5. The reciprocating fluid machine according to claim 4, wherein the valve mechanism includes discharge valves for controlling discharge of the compressed working fluid, and the center fastening bolt serves also as a fixing bolt for fixing the discharge valves to the valve plate.

6. The reciprocating fluid machine according to claim 1, wherein the fastening device further includes: a plurality of inner tapped holes formed in the cylinder block and having axes located inward of the bore distribution circle as viewed in the radial direction of the cylinder block, anda plurality of inner fastening bolts extending from the side near the cylinder head through the valve plate and the gaskets and screwed into the respective inner tapped holes, the inner fastening bolts having bolt heads located inside the cylinder head.

7. The reciprocating fluid machine according to claim 6, wherein the bolt heads of the inner fastening bolts are located in the discharge chamber, and the discharge chamber is located at center of the cylinder head.

8. The reciprocating fluid machine according to claim 1, wherein the outer fastening bolts each comprise a stud bolt buried in the cylinder block, and the fastening device further includes nuts screwed onto the respective stud bolts and pressing the valve plate against the cylinder block.

9. The reciprocating fluid machine according to claim 1, wherein the fluid machine is a compressor used for compressing CO2 refrigerant flowing through a refrigeration circuit.