JP2002031059A - Reciprocating refrigerant compressor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a reciprocating refrigerant compressor capable of preventing dispersion of the total adiabatic compressing efficiency and the volume efficiency without increasing the manufacturing cost to a significant extent. SOLUTION: The reciprocating refrigerant compressor equipped with a cylinder block 1 having a cylinder bore 6 and a piston 7 reciprocating linearly inside the cylinder bore 6 works with a refrigerant as working fluid which is carbon dioxide, wherein the clearance between the inside surface of the cylinder bore 6 and the outside surface 72c of the piston 7 is made between 10 and 20 μm.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

TECHNICAL FIELD The present invention relates to a reciprocating refrigerant compressor, of a preferred reciprocating refrigerant compressor, especially CO ₂ as a refrigerant compressor of a vehicle air conditioner used as a refrigerant.

[0002]

2. Description of the Related Art A reciprocating refrigerant compressor includes a cylinder block having a cylinder bore, a shaft rotatably supported at the center of the cylinder block, a swash plate that rotates integrally with the rotation of the shaft, and a swash plate. A piston that reciprocates linearly in the cylinder bore as the plate rotates.

[0003] A compression chamber is formed in the cylinder bore.

A rear head is fixed to one end face of the cylinder block via a valve plate. A suction chamber is formed in the rear head.

[0005] The compression chamber and the suction chamber communicate with each other through a suction port formed in a valve plate, and the suction port is opened and closed by a suction valve.

When the piston moves from the top dead center position to the bottom dead center position, the suction valve opens and refrigerant gas in the suction chamber flows into the compression chamber.

When the piston moves from the bottom dead center position to the top dead center position, the suction valve closes and the piston compresses the refrigerant gas in the compression chamber.

[0008]

By the way, the refrigerant is CO
_{In the case of 2} , since the difference between the high pressure and the low pressure is remarkably large (up to about 15 MPa) as compared with the case where the refrigerant is Freon, when the refrigerant gas in the compression chamber is compressed by the piston as described above, Leakage easily occurs through the gap between the surface and the inner peripheral surface of the cylinder bore, and the volumetric efficiency and the total adiabatic compression efficiency vary greatly. In order to suppress the leakage of the refrigerant gas, the clearance between the outer peripheral surface of the piston and the inner peripheral surface of the cylinder bore may be reduced.

However, for this purpose, the dimensional accuracy of the piston and the cylinder bore must be increased, which causes a problem that the manufacturing cost is increased.

SUMMARY OF THE INVENTION The present invention has been made in view of such circumstances, and an object thereof is to reciprocate a refrigerant compressor capable of preventing variations in volumetric efficiency and total adiabatic compression efficiency without significantly increasing manufacturing costs. It is to provide.

[0011]

According to a first aspect of the present invention, there is provided a reciprocating refrigerant compressor including a cylinder block having a cylinder bore, and a piston reciprocating linearly in the cylinder bore. In a reciprocating refrigerant compressor in which the refrigerant as the working fluid is carbon dioxide, the clearance between the inner peripheral surface of the cylinder bore and the outer peripheral surface of the piston (the difference between the inner diameter of the cylinder bore and the diameter of the piston) is 10 to 20 μm. There is a feature.

Since the clearance is 20 μm or less,
When the refrigerant gas is compressed by the piston, the refrigerant gas in the compression chamber hardly leaks through a gap between the inner peripheral surface of the cylinder bore and the outer peripheral surface of the piston. Therefore, the volume efficiency and the total adiabatic compression efficiency do not vary greatly. Since the clearance is 10 μm or more, the clearance is 10 μm
Higher dimensional accuracy is not required for the inner peripheral surface of the cylinder bore and the outer peripheral surface of the piston as compared with the case where the diameter is smaller.

[0013]

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 is a longitudinal sectional view of a variable displacement swash plate type compressor according to an embodiment of the present invention, and FIG. 2 is a partially enlarged view of FIG.

This variable capacity swash plate type compressor is used as one component of a refrigeration cycle using CO ₂ (carbon dioxide) as a refrigerant. A rear head 3 is disposed on one end surface of a cylinder block 1 of the compressor via a valve plate 2, and a front head 4 is disposed on the other end surface. The front head 4, the cylinder block 1, the valve plate 2, and the rear head 3 are integrally connected in the axial direction with a through bolt 31 and a nut 32.

The front head 4 has a crank chamber 8 for accommodating a thrust flange 40, a swash plate 10, and the like.

The thrust flange 40 is fixed to the shaft 5 and rotates integrally with the shaft 5. The thrust flange 40 is rotatably supported on the inner wall surface 4a of the front head 4 via a thrust bearing 33. Swash plate 10
Is mounted so as to be slidable with respect to the shaft 5 and tiltable with respect to an imaginary plane perpendicular to the shaft 5.

The swash plate 10 is connected to a thrust flange 40 via a link mechanism 41, and rotates integrally with the rotation of the thrust flange 40. Both sliding surfaces 10 of the swash plate 10
Hemispherical shoes 60, 61 are arranged on the swash plate 10 so as to sandwich the swash plate 10, and can relatively rotate on the sliding surfaces 10 a, 10 b of the swash plate 10 as the shaft 5 rotates.

The cylinder block 1 has a shaft 5
A plurality of cylinder bores 6 are formed at predetermined intervals along a circumference centered at. A piston 7 is slidably housed in the cylinder bore 6.

The piston 7 has a cylindrical portion 72 and a concave portion 7.
1 and 70, and a bridge portion 73 connecting the concave portions 71 and 70. The cylindrical portion 72 slides in the cylinder bore 6. The concave portion 71 is formed at one end of the cylindrical portion 72 and holds the shoe 61 so as to roll. Concave surface 70
Is arranged to face the concave surface portion 71 and holds the shoe 60 so that it can roll.

The clearance between the inner peripheral surface of the cylinder bore 6 and the outer peripheral surface 72c of the cylindrical portion 72 (difference between the inner diameter of the cylinder bore 6 and the diameter of the cylindrical portion 72 of the piston 7) is 10 to 20 μm.
m. Since the clearance is 10 μm or more, the surface accuracy of the inner peripheral surface of the cylinder bore 6 and the outer peripheral surface 72c of the piston 7 is not higher than when the clearance is smaller than 10 μm.

The rear head 3 has a suction chamber 13 and a discharge chamber 12 formed therein. The suction chamber 13 is located around the discharge chamber 12. The suction chamber 13 contains a low-pressure refrigerant gas to be supplied to the compression chamber 22. The discharge chamber 12 contains the high-pressure refrigerant gas discharged from the compression chamber 22.

The valve plate 2 has a discharge port 16 for communicating the compression chamber 22 and the discharge chamber 12, and a compression chamber 22.
A suction port 15 for communicating the air with the suction chamber 13 is provided at predetermined intervals along the circumferential direction. The discharge port 16 is opened and closed by a discharge valve 17.
Is a valve retainer 18 on the end face of the valve plate 2 on the rear head side.
Together with bolts 19. The suction port 15 is opened and closed by a suction valve 21, and the suction valve 21 is disposed on a front end surface of the valve plate 2.

One end of the shaft 5 is rotatably supported by the front head 4 via a radial bearing 26, and the other end of the shaft 5 is a radial bearing 25 and a thrust bearing 24.
And is rotatably supported by the cylinder block 1 via the.

A communication path (not shown) is provided between the suction chamber 13 and the crank chamber 8, and an orifice (not shown) is provided in the middle of the communication path. The discharge chamber 12
A communication passage (not shown) is provided between the motor and the crank chamber 8, and a pressure adjusting valve (not shown) is provided in the middle of the communication passage, and the pressure in the crank chamber 8 is adjusted by the pressure adjusting valve. The communication passage is opened and closed.

The link mechanism 41 includes a bracket 10c provided on the front sliding surface 10a of the swash plate 10, a linear guide groove 10d formed in the bracket 10c, and a rod 43 fixed to the thrust flange 40. It consists of. The longitudinal axis of the guide groove 10d is inclined at a predetermined angle with respect to the sliding surface 10a. Spherical tip 43a of rod 43
Are fitted in the guide groove 10d so as to be relatively slidable.

A helical spring 47 is mounted between the thrust flange 40 and the swash plate 10, and the swash plate 10 is urged rearward by the urging force of the helical spring 47. A winding spring 48 is mounted between the swash plate 10 and the thrust bearing 24, and the swash plate 10 is urged toward the front side by the urging force of the winding spring 48.

Next, the operation of the variable displacement type swash plate type compressor will be described.

When the rotational power of a vehicle-mounted engine (not shown) is transmitted to the shaft 5, the rotational force of the shaft 5 is transmitted to the swash plate 10 via the thrust flange 40 and the link mechanism 41, and the swash plate 10 rotates.

The rotation of the swash plate 10 causes the shoes 60 and 61 to relatively rotate on the sliding surfaces 10a and 10b of the swash plate 10, and the rotational force from the swash plate 10 is converted into a linear reciprocating motion of the piston 7. When the piston 7 reciprocates in the cylinder bore 6, the volume of the compression chamber 22 in the cylinder bore 6 changes, and the suction, compression, and discharge of the refrigerant gas are sequentially performed by the change in volume, and the suction gas corresponds to the inclination angle of the swash plate 10. A volume of high-pressure refrigerant gas is discharged. At the time of suction, the suction valve 21 is opened, low-pressure refrigerant is sucked from the suction chamber 13 into the compression chamber 22 in the cylinder bore 6, and at the time of discharge, the discharge valve 17 is opened, and high-pressure refrigerant gas flows from the compression chamber 22 to the discharge chamber 12. Discharged. Discharge chamber 1
The high-pressure refrigerant gas in 2 is discharged from a discharge port 3a to a cooler (not shown).

FIG. 3 is a diagram showing the relationship between the clearance between the piston and the cylinder bore and the volumetric efficiency, and FIG.
It is a figure showing the relation between the clearance between cylinder bores and the total adiabatic compression efficiency.

Since the clearance is 10 to 20 μm, when the refrigerant gas is compressed by the piston 7, the refrigerant gas in the compression chamber 22 is removed from the inner peripheral surface of the cylinder bore 6 and the piston 7 as compared with the case where the clearance is larger than 20 μm.
Hardly leaks into the crank chamber 8 through a gap with the outer peripheral surface 72c. Therefore, as shown in FIGS.
Total adiabatic compression efficiency does not vary greatly. In particular, the case where the clearance is 11 to 18 μm is stable.

When the heat load decreases and the pressure regulating valve opens to increase the pressure in the crank chamber 8, the inclination angle of the swash plate 10 decreases, so that the stroke of the piston 7 decreases and the discharge capacity decreases. . On the other hand, when the heat load increases and the pressure regulating valve closes and the pressure in the crank chamber 8 decreases, the inclination angle of the swash plate 10 increases, so that the stroke amount of the piston 7 increases and the displacement increases. .

According to this embodiment, since it is not necessary to increase the surface accuracy between the inner peripheral surface of the cylinder bore 6 and the outer peripheral surface 72c of the piston 7, the manufacturing cost does not increase significantly. In addition, the volume efficiency and the total adiabatic compression efficiency do not vary greatly. Therefore, it is possible to prevent variations in volumetric efficiency and total adiabatic compression efficiency without significantly increasing manufacturing costs.

In the above-described embodiment, the variable displacement type swash plate type compressor has been described as an example of the reciprocating type refrigerant compressor. The present invention can also be applied to.

[0036]

As described above, according to the reciprocating refrigerant compressor of the first aspect of the present invention, it is possible to prevent variations in volume efficiency and total adiabatic compression efficiency without significantly increasing manufacturing costs.

[Brief description of the drawings]

FIG. 1 is a longitudinal sectional view of a variable displacement swash plate type compressor according to an embodiment of the present invention.

FIG. 2 is a partially enlarged view of FIG. 1;

FIG. 3 is a diagram showing a relationship between a clearance between a piston and a cylinder bore and a volumetric efficiency.

FIG. 4 is a diagram showing the relationship between the clearance between the piston and the cylinder bore and the total adiabatic compression efficiency.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Cylinder block 6 Cylinder bore 7 Piston 72c Outer peripheral surface

Claims (1)

[Claims] A reciprocating refrigerant compressor comprising: a cylinder block having a cylinder bore; and a piston reciprocating linearly in the cylinder bore, wherein a refrigerant as a working fluid is carbon dioxide. A reciprocating refrigerant compressor, wherein a clearance between the outer peripheral surface of the piston and the outer peripheral surface is 10 to 20 μm.