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Reciprocating fluid machine

Reciprocating fluid machine description/claims

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

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.

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.

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.

• Provisional Patent
• Utility Patent

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