JP2002303370A - Piston - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a piston capable of lowering edge force and improving durability of a compressor. SOLUTION: This piston 7 is equipped with a cylinder part 50 slidably moving in a cylinder bore 6, a first supporting part 51 formed on a bottom surface 50d of the cylinder part 50 and supporting one of shoes 80, a second supporting part 52 confronting the first supporting part 51 along the piston central axis O direction and supporting the other shoe 81, and a bridge part 53 for connecting the supporting parts 51 and 52. A weight 56 is provided in the cylinder part 50 so that the center of the gravity of the piston approaches the piston central axis O.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a piston,
In particular, the present invention relates to a piston of a type that clamps a swash plate via a shoe.

[0002]

2. Description of the Related Art A swash plate compressor includes a cylinder block having a plurality of cylinder bores, a shaft supported at the center of the cylinder block, a swash plate which rotates integrally with the rotation of the shaft, and a swash plate. The vehicle includes a pair of shoes that are relatively rotatably arranged on both sides, and a piston that engages with the swash plate via the shoes and linearly reciprocates in the cylinder bore as the swash plate rotates.

[0003] A compression chamber is formed in the cylinder bore. The swash plate is inclined with respect to a virtual plane orthogonal to the shaft.

FIG. 8 is a view for explaining a piston of a conventional swash plate type compressor. FIG. 8A is a bottom end view of the piston, and FIG. 8B is a longitudinal sectional view.

The piston 607 has a cylindrical portion 650,
The first portion formed on the bottom surface 650d of the cylindrical portion 650
, A second support portion 652 opposed to the first support portion 651 in the direction of the piston center axis O, and a bridge portion 653 connecting the two support portions 651 and 652.

[0006] The cylindrical portion 650 slides inside the cylinder bore.

[0007] The first support 651 supports one shoe, and the second support 652 supports the other shoe.

When the shaft rotates, the swash plate rotates integrally with the shaft. Due to the rotation of the swash plate, the shoe relatively rotates on the sliding surface of the swash plate, and the rotational force from the swash plate is applied to the piston
, And the refrigerant gas in the compression chamber is compressed.

[0009]

However, since the swash plate is inclined with respect to an imaginary plane orthogonal to the shaft as described above, when the swash plate receives a compression reaction force of the refrigerant gas, the edge of the piston 607 is moved. Load (edge force) R1, R
2, the outer peripheral surface of the cylindrical portion 650 is severely worn, and the durability of the compressor tends to be reduced.

In particular, the bridge 6 shown in FIG.
In the piston 607 having 53, the center of gravity of the piston is as shown in FIG.
Since the center of gravity of the piston and the center axis O of the piston are separated from each other at the position A in (b), the edge forces R1 and R2 of the piston 607 were large and easily worn.

The present invention has been made in view of such circumstances, and an object of the present invention is to provide a piston capable of reducing edge force and improving the durability of a compressor.

[0012]

According to a first aspect of the present invention, there is provided a piston according to the present invention, which is formed on a cylindrical portion which slides in a cylinder bore, and is formed on a bottom surface of the cylindrical portion. A first supporting portion for supporting the first
A piston having a second support portion that faces the support portion of the piston in the axial direction of the piston and supports the other shoe, and a bridge portion that connects the two support portions. It is characterized in that a center-of-gravity adjustment unit that approaches the axis is provided.

[0013] As described above, since the center of gravity adjusting portion that brings the center of gravity of the piston closer to the center axis of the piston is provided in the cylindrical portion, the center of gravity of the piston is not so far away from the center axis of the piston, and the rotation generated by the inertia force of the piston. The moment is small and the edge force of the piston is small.

According to a second aspect of the present invention, in the piston according to the first aspect, the cylindrical portion is hollow.
The center-of-gravity adjusting portion is a weight provided on the inner peripheral surface of the cylindrical portion, and the weight is located at approximately 180 ° in the piston circumferential direction with respect to the bridge portion.

As described above, the center-of-gravity adjusting portion is a weight provided on the inner peripheral surface of the cylindrical portion, and this weight is located at approximately 180 ° with respect to the bridge portion in the circumferential direction of the piston. It is easy to adjust the amount of weight by shaving or adding another weight to the weight. Therefore, the position of the center of gravity of the piston can be easily changed as compared with the configuration in which the weight is provided on the bottom surface of the cylindrical portion.

According to a third aspect of the present invention, in the piston according to the first aspect, the cylindrical portion is hollow;
The center-of-gravity adjusting portion is a weight provided on the bottom surface of the cylindrical portion, and the weight is located at approximately 180 ° with respect to the bridge portion in the circumferential direction of the piston.

As described above, the center-of-gravity adjusting portion is the weight provided on the bottom surface of the cylindrical portion, and the weight is located at approximately 180 ° in the circumferential direction of the piston with respect to the bridge portion. Assuming that the weight formed and the weight formed on the inner peripheral surface of the cylindrical portion and the weight formed on the top surface of the cylindrical portion have the same weight, the weight formed on the bottom portion of the cylindrical portion is a cylinder. The piston is located farther from the center of gravity of the conventional piston than the weight formed on the inner peripheral surface of the portion.

According to a fourth aspect of the present invention, in the piston according to the first aspect, the center-of-gravity adjusting portion is a weight, and the weight is provided on a top surface of the piston. About 18 in the circumferential direction of the piston
It is characterized by being located at 0 °.

As described above, the center-of-gravity adjusting portion is the weight, and the weight is provided on the top surface of the piston, and the weight is located at approximately 180 ° with respect to the bridge portion in the circumferential direction of the piston. When the point is reached, the weight is inserted into the discharge port and is accommodated in the discharge port. As a result, the refrigerant gas in the discharge port is eliminated by the weight, and the refrigerant gas is also discharged to the discharge chamber.

According to a fifth aspect of the present invention, there is provided a piston having a cylindrical portion which slides in a cylinder bore.
A weight as a center-of-gravity adjustment unit that brings the center of gravity of the piston closer to the center axis of the piston is provided on the top surface of the piston, and when the piston is at the top dead center, the weight enters a discharge port that sends out a working fluid in the cylinder bore. It is characterized by the following.

As described above, the weight serving as a center of gravity adjustment unit for bringing the center of gravity of the piston closer to the center axis of the piston is provided on the top surface of the piston, and the discharge port discharges the working fluid in the cylinder bore when the piston is at the top dead center. Since the piston enters the inside, the center of gravity of the piston is not so far away from the center axis of the piston, the rotational moment generated by the inertia of the piston is small, and the edge force of the piston is small.

According to a sixth aspect of the present invention, in the piston according to any one of the first to fifth aspects, the center-of-gravity adjusting portion is formed integrally with the cylindrical portion.

Since the center-of-gravity adjusting portion is formed integrally with the cylindrical portion as described above, it is not necessary to add a weight to the piston when assembling the piston.

According to a seventh aspect of the present invention, in the piston according to any one of the first to fifth aspects, the center-of-gravity adjusting portion is a weight attached to an inner peripheral surface of the cylindrical portion. Features.

As described above, the center-of-gravity adjusting portion is a weight attached to the inner peripheral surface of the cylindrical portion. Therefore, by appropriately selecting and using previously prepared weights having different weights, the positions of the centers of gravity of the pistons are different. Multiple pistons can be manufactured.
Therefore, as compared with the configuration in which the weight is integrally formed with the cylindrical portion, the die for the cylindrical portion of the piston can be shared, and the manufacturing cost of the piston can be reduced.

According to an eighth aspect of the present invention, in the piston according to any one of the first to seventh aspects, the bridge portion is provided with a bridge-side lightened portion for bringing the center of gravity of the piston closer to the center axis of the piston. It is characterized by being.

As described above, since the bridge portion is provided with the bridge-side lightening portion for bringing the center of gravity of the piston closer to the center axis of the piston, the center of gravity of the piston can be reliably brought closer to the center axis of the piston.

According to a ninth aspect of the present invention, a piston slides in a cylinder bore, a first support formed on a bottom surface of the cylinder and supporting one shoe, and a first support. A piston having a second support portion opposed to the support portion in the direction of the piston center axis and supporting the other shoe, and a bridge portion connecting the two support portions, wherein the bridge center is provided with the center of gravity of the piston. , A bridge-side lightening portion which is provided close to.

As described above, the cylindrical portion is provided with the center-of-gravity adjusting portion for bringing the center of gravity of the piston closer to the center axis of the piston. The moment is small and the edge force of the piston is small.

[0030]

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

FIG. 2 is a longitudinal sectional view of a variable displacement swash plate type compressor having a piston according to a first embodiment of the present invention.
Is a diagram for explaining the piston, FIG.
Is a bottom side end view of the piston, FIG. (B) is a side view, FIG. (C) is a bottom side end view of the piston body, and FIG.
FIG. 3 is a vertical sectional view of a piston body.

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 by through bolts 31.

In the front head 4, there is formed a crank chamber 8 for accommodating the thrust flange 40, the 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 by the front head 4 via a thrust bearing 33. Swash plate 10 is shaft 5
And the hinge ball 2 of the shaft 5
It is attached so as to be tiltable with respect to a virtual plane perpendicular to the shaft 5 around the center 7.

The swash plate 10 is connected to a thrust flange 40 via a link mechanism 41, and rotates together with the rotation of the thrust flange 40. Both sliding surfaces 10 of the swash plate 10
Hemispherical shoes 80 and 81 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 and 10 b of the swash plate 10 as the shaft 5 rotates.

A plurality of cylinder bores 6 are formed in the cylinder block 1 along the circumferential direction.
Accommodate the pistons 7 respectively.

The piston 7 includes a cylindrical portion 50 and a first support portion 51 formed on a bottom surface 50d of the cylindrical portion 50.
And a second support portion 52 facing the first support portion 51 in the direction of the piston center axis O, and a bridge portion 53 connecting the two support portions 51, 52.

The inside of the cylindrical portion 50 is hollow. Four holes 54 are formed in the bottom surface 50a of the cylindrical portion 50 along the circumferential direction of the piston, and ribs 55 are formed between these holes 54. A weight (center-of-gravity adjusting portion) 56 is attached to the inner peripheral surface 50b of the cylindrical portion 50 by welding. The weight 56 is located at approximately 180 ° with respect to the bridge 53 in the circumferential direction of the piston. The weight 56 extends along the direction of the piston center axis O. The weight 56 is a lead-based or iron-based material. The weight 56 brings the position of the center of gravity of the piston closer to the center axis O of the piston. The cylindrical portion 50 is a portion that slides in the cylinder bore 6.

The piston 7 has a bottomed cylindrical portion (piston main body) 57 and portions other than the cylindrical portion 50 (first portion).
(A part composed of the support part 51, the second support part 52, and the bridge part 53) 58).

The first support portion 51 supports one shoe 80 of a pair of hemispherical shoes 80, 81, and the second support portion 52 supports the other shoe 81.

The piston 7 is connected to the cylinder block 1
First, all the pistons 7 are attached to the swash plate 10.
Then, the swash plate 10 and the piston 7 are arranged above the cylinder block 1, and finally, the piston 7 is inserted into each cylinder bore 6.

At this time, since the center axis O of the piston is not so inclined with respect to the center axis of the cylinder bore 6, the piston 7
Is smoothly inserted into each cylinder bore 6. For this reason, the piston 7 is assembled to the cylinder block 1 without using a jig for preventing the center axis O of the piston 7 from being inclined with respect to the center axis of each cylinder bore 6.

The rear head 3 has a suction port 3a, a suction chamber 13 and a discharge chamber 12. 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. Discharge chamber 1
A high-pressure refrigerant gas discharged from the compression chamber 22 is accommodated in 2.

The valve plate 2 has a discharge port 16 for communicating the compression chamber 22 with the suction chamber 13, and a compression chamber 22.
And a suction port 15 for communicating the suction chamber 13 with the suction chamber 13 are provided at predetermined intervals along the circumferential direction. 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.
The discharge port 16 is opened and closed by a discharge valve 17, and the discharge valve 1
7 is a valve retainer 1 on the end face of the valve plate 2 on the rear head side.
8 together with bolts 19.

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 connected to a radial bearing 25 and a thrust bearing 24.
And is rotatably supported by the cylinder block 1 via the. A communication passage 35 is provided between the suction chamber 13 and the crank chamber 8. A communication passage 36 is provided between the discharge chamber 12 and the crank chamber 8, and a pressure regulating valve 32 is provided in the middle of the communication passage 36, and the communication passage 36 is opened and closed by the pressure regulating valve 32. , The pressure of the crank chamber 8 is adjusted.

A winding spring 48 is mounted between the thrust flange 40 and the swash plate 10, and the hinge ball 27 is biased rearward by the biasing force of the winding spring 48. Swash plate 10
A stopper 47 for preventing the hinge ball 27 from moving to the rear side is mounted between the thrust bearing 24 and the thrust bearing 24.

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

When the rotational power of the 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. Due to the rotation of the swash plate 10, the shoes 80 and 81 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 the linear reciprocating motion of the piston 7.

The cylindrical portion 50 of the piston 7 is
When reciprocating in the cylinder, the volume of the compression chamber 22 in the cylinder bore 6 changes.
The compression and the discharge are sequentially performed, and a high-pressure refrigerant gas having a capacity corresponding to the inclination angle of the swash plate 10 is discharged.

At the time of suction, the suction valve 21 opens, and low-pressure refrigerant gas 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 opens, and the high-pressure refrigerant gas flows from the compression chamber 22 to the discharge chamber 12. Is discharged. The high-pressure refrigerant gas in the discharge chamber 12 is discharged from the discharge port to the condenser (not shown).

In the suction stroke, as the piston 7 moves toward the bottom dead center, the refrigerant gas in the suction chamber 13
5 flows into the compression chamber 22.

In the compression stroke, the volume in the compression chamber 22 decreases as the piston 7 moves to the top dead center, and the pressure in the compression chamber 22 increases. As described above, since the swash plate 10 is inclined with respect to an imaginary plane orthogonal to the shaft 5, when the swash plate 10 receives the compression reaction force of the refrigerant gas, the piston 7
(Edge force) R1, R2 (FIG. 1)
(See (b)). However, since the weight 56 is provided in the cylindrical portion 50, the center of gravity of the piston is
, The rotational moment generated by the inertia of the piston is small, and the edge forces R1 and R2 of the piston 7 are small.

In the discharge stroke, the volume of the compression chamber 22 becomes minimum and the pressure in the compression chamber 22 becomes maximum. When a certain pressure difference occurs between the compression chamber 22 and the discharge chamber 12, the discharge valve 17 bends toward the discharge chamber 12, and the discharge port 16 is opened.

When the heat load is reduced and the pressure regulating valve 32 is opened to increase the pressure in the crank chamber 8, the inclination angle of the swash plate 10 is reduced, so that the stroke of the piston 7 is reduced and the discharge capacity is reduced. I do. On the other hand, when the heat load increases and the pressure in the crank chamber 8 decreases by closing the pressure regulating valve 32, the inclination angle of the swash plate 10 increases, so that the stroke amount of the piston 7 increases and the discharge capacity increases. I do.

According to this embodiment, since the edge forces R1 and R2 of the piston 7 are reduced, the wear of the cylindrical portion 50 of the piston 7 is suppressed, and the durability of the compressor is improved.

Further, since the piston 7 is mounted on the cylinder block 1 without using a jig, the mounting of the compressor is facilitated, and the manufacturing cost of the compressor can be reduced.

Further, when the outer peripheral surface of the cylindrical portion 50 is polished while rotating the piston 7, the piston 7 is less likely to oscillate in the radial direction, and high processing accuracy is obtained.

The weight 56 is formed on the inner peripheral surface 50 b of the cylindrical portion 50.
Since the weight 56 is located at approximately 180 ° with respect to the bridge 53 in the circumferential direction of the piston, a part of the weight 56 can be cut or another weight can be added to the weight 56. Therefore, it is easy to adjust the amount of the weight 56. Therefore, the position of the center of gravity of the piston can be easily changed as compared with the configuration in which the weight 56 is provided on the bottom surface 50a of the cylindrical portion 50.

Further, since the weight 56 is a weight attached to the cylindrical portion 50, a plurality of pistons having different positions of the centers of gravity of the pistons can be manufactured by appropriately selecting and using weights having different weights prepared in advance. Can be. Therefore,
Compared to a configuration in which the weight 56 is integrally formed with the cylindrical portion 50, the die for the cylindrical portion 50 of the piston 7 can be shared, and the manufacturing cost of the piston 7 can be reduced.

FIG. 3 is a view for explaining a piston according to a second embodiment of the present invention. FIG. 3 (a) is a bottom end view of the piston body, and FIG. 3 (b) is a longitudinal sectional view. .
The structure of this piston other than the piston main body is the same as that of the first embodiment, and a description thereof will be omitted.

In the first embodiment shown in FIG. 1, the case in which the piston 7 is provided with a separate weight 56 is described.
In the embodiment, the piston 107 has a weight 156 (center of gravity adjustment unit).
Was integrally molded.

According to the second embodiment, since the weight 156 is formed integrally with the cylindrical portion 50, the piston 107
When assembling, there is no need to weld a separate weight to the piston body. Therefore, the step of fixing the weight 156 can be eliminated, and the number of steps for assembling the piston 107 can be reduced.

FIG. 4 is a view for explaining a piston according to a third embodiment of the present invention. FIG. 4A is a bottom end view of the piston body, and FIG. 4B is a longitudinal sectional view. .
The structure of this piston other than the piston main body is the same as that of the first embodiment, and a description thereof will be omitted.

In the first and second embodiments, the cylindrical portion 50 is used.
In the third embodiment, thin ribs 257 are provided on the bottom surface 50a of the cylindrical portion 50 of the piston 207, and the thick ribs (functioning as weights) are provided in the third embodiment. (Center of gravity adjustment unit) 256 is provided.

The thick rib 256 is located at approximately 180 ° with respect to the bridge 53 in the circumferential direction of the piston. The thick rib 256 is located farthest from the position A (see FIG. 8B) of the center of gravity of the piston 607 of the conventional example as compared with the first and second embodiments.

The thin rib 257 is located at substantially the same position as the bridge 53 in the circumferential direction of the piston.

According to the third embodiment, assuming that the thick rib 256, the weight 56, and the weight 156 have the same weight, the thick rib 256 is different from the first and second embodiments as described above. In comparison, since the piston 607 of the conventional example is farthest from the center of gravity A of the piston 607, a high piston center of gravity adjustment effect (effect of bringing the center of gravity of the piston closer to the piston center axis O) can be obtained.

FIG. 5 is a view for explaining a piston according to a fourth embodiment of the present invention. FIG. 5A is a top end view of a piston body, and FIG. 5B is a longitudinal sectional view. .
The structure of this piston other than the piston main body is the same as that of the first embodiment, and a description thereof will be omitted.

In the first and second embodiments described above, the cylindrical portion 50
The case where the weights 56 and 156 are provided on the inner peripheral surface 50b has been described. However, in the fourth embodiment, the weight (centroid adjustment portion) 356 is retrofitted to the top surface 50c of the cylindrical portion 50 of the piston 307.

The weight 356 is located at approximately 180 ° with respect to the bridge 53 in the circumferential direction of the piston.

In the discharge stroke, when the piston 307 reaches the top dead center, the weight 356 is inserted into the discharge port 16. As a result, the refrigerant gas in the discharge port 16
The refrigerant gas is discharged by the discharge chamber 56 and discharged into the discharge chamber 12.

According to the fourth embodiment, the dead volume of the compression chamber 22 is reduced.

Further, since the weight 356 is a weight to be attached to the cylindrical portion 50, a plurality of pistons having different positions of the center of gravity of the piston can be manufactured by appropriately selecting and using previously prepared weights having different weights. Can be. Therefore, as compared with the configuration in which the weight 356 is integrally formed with the cylindrical portion 50,
The mold for the cylindrical portion 50 of the piston 307 can be shared, and the manufacturing cost of the piston 307 can be reduced.

FIG. 6 is a view for explaining a piston according to a fifth embodiment of the present invention. FIG. 6 (a) is a top end view of the piston body, and FIG. 6 (b) is a longitudinal sectional view. .
The structure of this piston other than the piston main body is the same as that of the first embodiment, and a description thereof will be omitted.

In the fourth embodiment of FIG. 5, a case is described in which the piston 307 is provided with a separate weight 356, but in the fifth embodiment, the piston 407 has a weight (centroid adjustment unit).
456 were integrally molded.

According to the fifth embodiment, the same effects as in the fourth embodiment can be obtained, and the number of steps for assembling the piston 407 can be reduced by eliminating the step of fixing the weight 356.

FIG. 7 is a view for explaining a piston according to a sixth embodiment of the present invention. FIG. 7 (a) is a bottom end view of the piston, FIG. 7 (b) is a longitudinal sectional view, and FIG. (C)
Is a diagram for explaining the position of the lightening portion, and FIG. 4D is a partially enlarged perspective view of the bridge portion. The structure of this piston other than the piston is the same as that of the first embodiment, and a description thereof will be omitted.

In the first embodiment, the cylindrical portion 50 of the piston 7
In the sixth embodiment, a lightening portion (bridge-side lightening portion) 556 is formed in the bridge portion 53 of the piston 507 in the sixth embodiment.

Since the hollow portion 556 is formed in the bridge portion 53, the center of gravity of the piston is not so far away from the center axis O of the piston, the rotational moment generated by the inertia of the piston is small, and the edge force of the piston 507 is reduced. small.

According to the sixth embodiment, since the edge force of the piston 7 is reduced, the wear of the cylindrical portion 50 of the piston 7 is suppressed, and the durability of the compressor is improved.

In the above-described sixth embodiment, the case where only the hollow portion 556 is provided on the piston 507 as means for bringing the center of gravity of the piston closer to the center axis O of the piston has been described, but the scope of the present invention is not limited to this. Instead, the lightening portion 556 is provided in the bridge portion 53, and the weights 56, 156, 356, 456 or the thick ribs 256 are provided in the cylindrical portion 50, and the lightening portion 556 and the weights 56, 156, 356, 456 are provided.
Alternatively, it is also possible to adjust the center of gravity of the piston by combining with the thick rib 256. In this case, the center of gravity of the piston approaches the center axis O of the piston.

[0082]

According to the present invention, as described above,
According to the piston of the described invention, since the edge force of the piston is reduced, the wear of the cylindrical portion of the piston is suppressed, and the durability of the compressor is improved.

According to the piston of the second aspect of the present invention,
Since the weight of the weight can be easily changed, the position of the center of gravity of the piston can be easily adjusted.

According to the piston of the third aspect of the present invention,
As compared with the first aspect of the invention, a higher piston center-of-gravity adjusting effect can be obtained.

According to the piston of the fourth or fifth aspect, the dead volume of the compression chamber is reduced.

According to the piston of the invention described in claim 6,
The step of fixing the weight is eliminated, and the number of man-hours for assembling the piston can be reduced.

According to the piston of the invention described in claim 7,
Manufacturing costs can be reduced.

According to the piston of the eighth aspect,
The center of gravity of the piston can be reliably brought close to the center axis of the piston.

[Brief description of the drawings]

FIG. 1 is a view for explaining a piston.

FIG. 2 is a longitudinal sectional view of a variable displacement swash plate type compressor having a piston according to the first embodiment of the present invention.

FIG. 3 is a view for explaining a piston according to a second embodiment of the present invention.

FIG. 4 is a view for explaining a piston according to a third embodiment of the present invention.

FIG. 5 is a view for explaining a piston according to a fourth embodiment of the present invention.

FIG. 6 is a view for explaining a piston according to a fifth embodiment of the present invention.

FIG. 7 is a view for explaining a piston according to a sixth embodiment of the present invention.

FIG. 8 is a view for explaining a piston of a conventional swash plate type compressor.

[Explanation of symbols]

 6 Cylinder bore 50,650 Cylindrical part 50a Bottom part 50b Inner peripheral surface 50c Top surface 50d, 650d Bottom surface 51,651 First support part 52,652 Second support part 53,653 Bridge part 56,156,356,456 Weight (center of gravity adjustment) 80 One shoe 81 The other shoe 256 Thick rib (center of gravity adjustment) 556 Lightening (bridge-side lightening) O Piston center axis

 ────────────────────────────────────────────────── ─── Continuing on the front page (72) Inventor Hiromichi Tanabe 39, Higashihara, Chiyo, Odai-gun, Osato-gun, Saitama Prefecture F-term (reference) 3H076 AA06 BB26 CC20 CC29 CC31 3J044 AA02 CA01 CA20 DA09

Claims (9)

[Claims] 1. A cylindrical portion that slides in a cylinder bore, a first support portion formed on a bottom surface of the cylindrical portion and supporting one shoe, and a first support portion and a piston central axis direction. A piston including a second support portion facing the other shoe and supporting the other shoe, and a bridge portion connecting the two support portions, wherein the cylindrical portion is provided with a center-of-gravity adjusting portion for bringing the center of gravity of the piston closer to the center axis of the piston. A piston characterized in that: 2. The cylindrical portion is hollow, and the center-of-gravity adjusting portion is a weight provided on an inner peripheral surface of the cylindrical portion. The weight is substantially 180 ° in a piston circumferential direction with respect to the bridge portion. The piston of claim 1, wherein the piston is in a position. 3. The cylindrical portion is hollow, the center-of-gravity adjusting portion is a weight provided on the bottom surface of the cylindrical portion, and the weight is located at approximately 180 ° in the circumferential direction of the piston with respect to the bridge portion. The piston according to claim 1, wherein the piston is provided. 4. The center of gravity adjusting portion is a weight, the weight is provided on a top surface of the piston, and the weight is substantially 180 ° in a circumferential direction of the piston with respect to the bridge portion.
The piston according to claim 1, wherein 5. A piston having a cylindrical portion that slides in a cylinder bore, wherein a weight serving as a center-of-gravity adjusting portion that brings the center of gravity of the piston closer to the center axis of the piston is provided on a top surface of the piston, and the piston has a top dead center. A piston for a reciprocating refrigerant compressor, wherein the weight sometimes enters a discharge port for sending out a working fluid in the cylinder bore. 6. The piston according to claim 1, wherein the center-of-gravity adjusting portion is formed integrally with the cylindrical portion. 7. The piston according to claim 1, wherein the center-of-gravity adjusting portion is a weight attached to an inner peripheral surface of the cylindrical portion. 8. The piston according to claim 1, wherein the bridge portion is provided with a bridge-side hollow portion for bringing the center of gravity of the piston closer to the center axis of the piston. 9. A cylindrical portion that slides in a cylinder bore, a first support portion formed on a bottom surface of the cylindrical portion and supporting one of the shoes, and a first support portion and a piston central axis direction. In a piston having a second support portion facing the other shoe and supporting the other shoe, and a bridge portion connecting the two support portions, the bridge portion has a bridge-side hollow portion for bringing the center of gravity of the piston closer to the center axis of the piston. A piston, which is provided.