JP2002349440A - Reciprocating refrigerant compressor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a reciprocating refrigerant compressor which can prevent surely and over a long period a delay of opening of a suction valve when a suction stroke is started. SOLUTION: This reciprocating refrigerant compressor comprises: a cylinder block 1 having a cylinder bore 6; a piston 7 movably received in the cylinder bore 6; a compression chamber 14 formed in the cylinder bore 6, a rear head 3 formed with a suction chamber 13 temporarily accumulating refrigerant gas sucked to the compression chamber 14 to be connected to one end face of the cylinder block 1; a valve plate 2 arranged between the compression chamber 14 and the suction chamber 13 to be formed with a suction port 60 for guiding the refrigerant gas in the suction chamber 13 to the compression chamber 14; and a suction valve 70 opening/closing the suction port 60. An elastic thin piece 80 pulling the suction valve 70 into the compression chamber 14, when the piston 7 is transferred from a delivery stroke to a suction stroke, is also provided in a top surface 7c of the piston 7.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a reciprocating refrigerant compressor, and more particularly, to a reciprocating refrigerant compressor having a suction valve disposed between a cylinder block and a valve plate.

[0002]

2. Description of the Related Art A conventional reciprocating refrigerant compressor includes a cylinder block having a cylinder bore, a piston reciprocating linearly in the cylinder bore, a compression chamber formed in the cylinder bore, and a refrigerant drawn into the compression chamber. A cylinder head in which a suction chamber for temporarily storing gas is formed, a valve plate in which a suction port for guiding refrigerant gas in the suction chamber to the compression chamber is formed, and a suction valve for opening and closing the suction port. There is something.

[0003] The cylinder head is fixed to one end face of the cylinder block.

FIG. 8 is a cross-sectional view showing a part of a conventional reciprocating refrigerant compressor. FIG. 8 (a) is a cross-sectional view showing a state immediately before the end of a discharge stroke, and FIG. 8 (b) is a suction stroke. FIG. 6 is a cross-sectional view showing a state immediately after the start of FIG.

[0005] A valve plate 302 is disposed between the cylinder head 303 and the cylinder block 301, and a suction valve seat 311 having a suction valve 370 is disposed between the valve plate 302 and the cylinder block 301. A suction port 360 and a discharge port 361 are formed in the valve plate 302.

As the piston 307 moves from the top dead center to the bottom dead center, the volume of the compression chamber 314 gradually increases, the pressure in the compression chamber 314 decreases, and becomes lower than the pressure in the suction chamber 313. As a result, the refrigerant gas in the suction chamber 313 pushes the suction valve 370 open, flows into the compression chamber 314 through the suction port 360, and the refrigerant gas suction stroke starts. This suction stroke continues until the piston 307 reaches the bottom dead center.

As the piston 307 moves from the bottom dead center to the top dead center, the volume of the compression chamber 314 gradually decreases, and the refrigerant gas inside is compressed, so that the pressure in the compression chamber 314 increases. At this time, the suction valve 370 is in close contact with the valve plate 302, and the suction port 360 is closed. This compression stroke continues until the piston 307 reaches the vicinity of the top dead center.

When the piston 307 approaches the vicinity of the top dead center, the pressure in the compression chamber 314 becomes higher than the pressure in the discharge chamber 312. As a result, the refrigerant gas in the compression chamber 314 pushes open the discharge valve 352 and flows out into the discharge chamber 312 through the discharge port 361. The refrigerant gas discharge process continues until the piston 307 reaches the top dead center.

When the piston 307 reciprocates, suction, compression and discharge are repeated.

On the other hand, lubricating oil is mixed with the refrigerant.
As a result, the lubricating oil circulates in the refrigeration circuit together with the refrigerant, is supplied to each sliding portion of the reciprocating refrigerant compressor, and each sliding portion is lubricated.

[0011]

As described above, since lubricating oil is mixed with the refrigerant, the valve plate 302
The lubricating oil also adheres to the surface of the valve, and the viscosity of the lubricating oil causes the suction valve 370 to adhere to the valve plate 302. Therefore, when the piston 307 moves from the top dead center position to the bottom dead center side, the suction valve 370 does not open immediately, delaying the start of suction, causing problems such as a reduction in compression efficiency and generation of suction pulsation. .

As a conventional technique for preventing a delay in the operation of a valve in a compressor, a compressor in which the surface roughness of a surface facing a port of a valve is relatively roughened so as to weaken the adhesion between the valve and a valve plate (for example, a conventional compressor). Japanese Unexamined Patent Publication (Kokai) No. 7-174071), or a concave groove which is in contact with the band arm portion of the suction reed valve and which is connected to the suction port and which is narrower than the band arm is provided. A compressor having reduced adhesion between an arm and a valve plate (for example, Utility Model Registration No. 258708)
No. 5) has been proposed.

However, in the above-described compressor in which the valve surface is roughened, the fine irregularities on the valve surface are crushed and the valve surface becomes flat while the operation of the compressor is continued. Will stick to

In the above-described compressor in which the valve plate is provided with a concave groove, when the concave groove is enlarged, the sticking force of the suction valve to the valve plate is weakened, but the sealing force of the suction valve to the suction port is also weakened. On the contrary, if the concave groove is made smaller, the sealing force of the suction valve with respect to the suction port is increased, but the sticking force of the suction valve with respect to the valve plate is also increased.

The present invention has been made in view of such circumstances, and an object thereof is to provide a reciprocating refrigerant compressor that can reliably and reliably prevent a delay in opening of a suction valve at the start of a suction stroke for a long period of time. It is to provide.

[0016]

According to a first aspect of the present invention, there is provided a reciprocating refrigerant compressor comprising: a cylinder block having a cylinder bore; a piston movably accommodated in the cylinder bore; A compression chamber formed in the cylinder bore, a suction chamber for temporarily storing a refrigerant gas sucked into the compression chamber, and a cylinder head coupled to one end side of the cylinder block; A reciprocating valve disposed between the suction chamber and the suction chamber, the valve plate having a suction port for guiding refrigerant gas in the suction chamber to the compression chamber, and a suction valve for opening and closing the suction port. In the refrigerant compressor, a valve-opening assisting portion that pulls the suction valve toward the compression chamber when the piston shifts from top dead center to bottom dead center is provided on the top surface of the piston. And wherein the digit.

Since the valve opening assisting portion is provided on the top surface of the piston as described above, the suction valve is attracted into the compression chamber when the piston moves from the top dead center to the bottom dead center by the valve opening assisting portion. The suction valve opens without delaying the movement of the piston to the bottom dead center.

According to a second aspect of the present invention, there is provided a reciprocating type refrigerant compressor according to the first aspect, wherein the piston of the reciprocating type refrigerating compressor has a top dead center on a surface of the valve opening assisting portion facing the suction valve. A part of the suction valve is pushed into the suction port when the pressure reaches the suction port.

As described above, when the piston reaches the top dead center, the valve plate side end face of the valve opening assisting part pushes a part of the suction valve into the suction port. A gap called a pressure release passage is generated between the port and the port, and refrigerant gas remaining in the compression chamber and the discharge port escapes to the suction chamber through the pressure release passage. For this reason, a decrease in volumetric efficiency caused by the refrigerant gas remaining in the compression chamber and the discharge port re-expanding is prevented.

According to a third aspect of the present invention, there is provided a reciprocating refrigerant compressor according to the first or second aspect.
The valve opening assisting portion has a size that is opposed to the suction port and that fits within a projection plane of the suction port.

As described above, since the valve-opening assisting portion is opposed to the suction port and is large enough to be accommodated in the suction port, when the valve-opening assisting portion comes into contact with the suction valve, the above-described pressure relief passage is reliably formed. Is done.

According to a fourth aspect of the present invention, there is provided the reciprocating type refrigerant compressor according to the first, second or third aspect, wherein the valve opening assisting portion has a lower hardness than the material of the suction valve. It is characterized by being formed of a material.

As described above, since the valve opening assisting portion is formed of a material having a lower hardness than the material of the suction valve and is fixed to the top surface of the piston, damage to the suction valve can be prevented.

According to a fifth aspect of the present invention, there is provided a reciprocating type refrigerant compressor according to any one of the first to fourth aspects, wherein a surface of the valve opening assisting portion facing the suction valve is provided. The piston is a convex surface, and a distance from a vertex of the convex surface to a top surface of the piston is slightly longer than a distance from the valve plate to a top surface of the piston.

As described above, the valve plate-side end surface of the valve-opening assisting portion is convex, and the distance from the top of the convex surface to the top surface of the piston is slightly longer than the distance from the valve plate to the top surface of the piston. The valve opening assisting part presses the suction valve at the top of the convex surface. For this reason, the above-described pressure release passage is reliably formed.

[0026]

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

FIG. 1 shows a partial cross section of a variable displacement swash plate type compressor according to a first embodiment of the present invention, and FIG.
Is a sectional view showing a state immediately before the end of the discharge stroke, and FIG.
2 is a cross-sectional view when a suction stroke is started, FIG. 2 is a longitudinal sectional view of the variable displacement type swash plate type compressor, and FIG. 3 is an exploded perspective view of main components of the variable displacement type swash plate type compressor of FIG. 4 is FIG.
FIG. 5 is a view of a suction valve and a cylinder block viewed from line AA of FIG. 5, FIG. 5 is a plan view of a suction valve seat of the variable displacement swash plate type compressor of FIG. 2, and FIG. It is a top view of the valve plate of FIG.

A rear head (cylinder head) 3 is provided on one end surface of a cylinder block 1 of the variable displacement type swash plate type compressor (reciprocating refrigerant compressor) via a valve plate 2 and a front head 4 is provided on the other end surface. Fixed.

The cylinder block 1 has a shaft 5
A plurality of cylinder bores 6 are disposed at predetermined intervals in the circumferential direction around the center. A piston 7 is slidably housed in the cylinder bore 6. A compression chamber 14 (see FIG. 1B) is formed inside the cylinder bore 6, and the volume of the compression chamber 14 changes as the piston 7 moves.

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 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 about the hinge ball 9 of the shaft 5.

The swash plate 10 is connected to a thrust flange 40 via a link mechanism 41 described later, and rotates together with the rotation of the thrust flange 40. The swash plate 10 can be inclined with respect to a virtual plane perpendicular to the shaft 5. Swash plate 10
Is connected to the concave portions 7a, 7b of the piston 7 via shoes 50, 51 (see FIG. 2). As the shaft 5 rotates, the shoes 50 and 51 slide on the sliding surfaces 10 a and 1 of the swash plate 10.
0b is relatively rotated.

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.

The rear head 3 has a suction chamber (low pressure chamber) 13 and a discharge chamber 1 located around the suction chamber 13.
2 are formed (see FIG. 2).

As shown in FIG. 6, the valve plate 2 has a plurality of discharge ports 61 for communicating the cylinder bore 6 with the discharge chamber 12, and a plurality of suction ports 60 for communicating the cylinder bore 6 with the suction chamber 13. Are provided at predetermined intervals in the circumferential direction. Further, the valve plate 2 forms holes 66 and 62 for inserting the bolts 19 and 31, a hole 65 for inserting the positioning pin 23 for assembling the valve plate 2, and a part of a plurality of communication passages 44 described later. A hole 63 is formed.

A suction valve seat 11 is overlaid on the valve plate 2. As shown in FIG. 5, the suction valve seat 11 integrally forms a plurality of suction valves 70 and a gasket 79 surrounding them by making cuts in a circular sealing material having elasticity. The suction valve 70 is formed with a hole 71 for preventing the discharge port 61 from being closed by the suction valve 70. Also, the suction valve seat 11
Are formed with holes 76, 72, 75, 73 corresponding to the holes 66, 62, 65, 63 of the valve plate 2.

The suction port 60 is opened and closed by a suction valve 70, and the discharge port 61 is opened and closed by a discharge valve 152 of a discharge valve seat 15 described later.

The discharge valve seat 15 has a disk-shaped fixing portion 151.
And a plurality of discharge valves 1 formed integrally with the fixed portion 151
52 (see FIG. 3). The fixing portion 151 has a hole 151 a for not blocking the suction port 60, a hole 151 b constituting a part of a communication path 44 described later, a hole 151 c for positioning, and a hole 1 for inserting the bolt 19.
51d are formed. The discharge valve 152 has a fixed part 151.
Are arranged at predetermined intervals on the outer peripheral edge of the fixing member 151 and extend in the radial direction of the fixing portion 151.

A gasket 17 is arranged between the cylinder block 1 and the suction valve seat 11. As shown in FIG. 3, the gasket 17 has a hole 17a connected to the cylinder bore 6, a hole 17b forming a part of a communication path 44 described later, a hole 17c for positioning, and a hole 17d for inserting the bolt 19. Have.

A gasket retainer 18 is disposed between the discharge valve seat 15 and the rear head 3 (see FIG. 3). The gasket retainer 18 connects the first gasket part 181 at the center, the second gasket part 182 surrounding the first gasket part 181, and the first gasket part 181 and the second gasket part 182. And a retainer 183 for limiting the lift amount of the discharge valve 152. First gasket part 18
1 has a hole 181a for not blocking the suction port 60, and a hole 18
1b, a hole 181c for positioning and a hole 181d for inserting the bolt 19 are formed.

Suction valve 70, discharge valve 152, suction port 6
0, the number of discharge ports 61 and the number of compression chambers 14 are each equal to the number of cylinder bores 6 (seven in this embodiment).

The suction port 60 and the discharge port 61 are shown in FIG.
Are located inside the opening edge 6a of the cylinder bore 6, respectively. The suction port 60 is connected to the discharge port 61.
(Inside of the valve plate 2 in the radial direction). The suction port 60 is substantially rhombic. As described above, in the present embodiment, the opening shape of the suction port 60 is set to a shape other than the circle or the ellipse. As a result, the suction valve 70 is driven by an external force such as the pressure of the refrigerant gas (in the present embodiment, an elastic thin piece 80 described later).
A gap is formed between the suction valve 70 and the opening edge of the suction port 60 when deformed by being pressed against the suction port 60 by the pressing force of the suction port 60. This gap is
And a pressure release passage for allowing the refrigerant gas in the discharge port 61 to escape to the suction chamber 13.

The cylinder block 1 is provided with a communication passage 44 for communicating the suction chamber 13 with the crank chamber 8.
A valve 45 for opening and closing the communication passage 44 is provided in the middle of 4. Further, a pressure regulating valve 32 is provided in the middle of a communication passage 46 that communicates the discharge chamber 12 and the crank chamber 8,
The pressure in the crank chamber 8 is adjusted.

As shown in FIG. 1, a stopper recess 35 for restricting the bending of the suction valve 70 at the time of suction is formed at a position of the opening edge 6a of the cylinder bore 6 on the valve plate side facing the tip of the suction valve 70. ing. The lift amount of the suction valve 70 (the opening degree of the suction valve 70) is limited by the stopper recess 35.

The top surface 7c of the piston 7 is provided with an elastic thin piece 80 (valve opening assist part). This elastic flake 8
0 is a size that is opposite to the suction port 60 and can be accommodated in the suction port 60. The top surface (valve plate side end surface) 80a of the elastic thin piece 80 comes into contact with the suction valve 70 when the piston 7 reaches the top dead center, and pushes a part of the suction valve 70 into the suction port 60. It is. Therefore, the thickness of the elastic thin piece 80 is slightly larger than the distance from the top surface 7c of the piston 7 to the end surface of the suction valve 70 on the cylinder block side when the piston 7 is located at the top dead center. In addition, the elastic lamella 80 is
It is formed of a material having a lower hardness than the material of No. 0. Specifically, polyamide imide resin, furan resin, vinyl ester resin, etc. are suitable as the material of the elastic flake 80,
In order to adjust the hardness, it is preferable to include air bubbles in these resins.

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

Now, as shown in FIG.
When the spring reaches the top dead center from the bottom dead center, the elastic thin piece 80 comes into contact with the surface of the suction valve 70. Then, the elastic thin piece 80 sticks to the suction valve 70 due to an adhesion phenomenon caused by the viscous force of the lubricating oil existing between the elastic thin piece 80 and the suction valve 70.
In this state, as shown in FIG. 1B, when the piston 7 shifts from the discharge stroke to the suction stroke, the elastic thin piece 80 forcibly pulls the suction valve 70 toward the compression chamber 14. Suction valve 7
Since 0 is pulled by the elastic thin piece 80 and the suction port 60 is opened, the timing of suction is not delayed.

In the suction stroke, the refrigerant gas in the suction chamber 13 flows into the compression chamber 14 through the suction port 60 as the piston 7 moves toward the bottom dead center.

When the piston 7 reaches the bottom dead center, the suction stroke ends, the piston 7 moves to the top dead center side, and the compression stroke starts.

In the compression stroke, the volume of the compression chamber 14 gradually decreases as the piston 7 moves to the top dead center,
The pressure in the compression chamber 14 increases. At this time, the suction valve 70 is seated on the suction port 60.

In the discharge stroke, the volume of the compression chamber 14 becomes minimum and the pressure in the compression chamber 14 becomes maximum. When a certain pressure difference occurs between the compression chamber 14 and the discharge chamber 12, the discharge valve 152
Is bent toward the discharge chamber 12, and the discharge port 61 is opened.
At this time, the suction valve 70 blocks the suction port 60.

When the piston 7 reaches the top dead center, FIG.
The suction stroke is started by the action of the elastic thin piece 80 at the same time as the piston 7 moves to the bottom dead center side as described above, and thereafter a series of operations are repeated.

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

According to this embodiment, the suction valve 70 can be forcibly pulled into the compression chamber 14 when the piston 7 shifts from the discharge stroke to the suction stroke by the elastic lamella 80. The delay can be reliably prevented, and the function of pulling the suction valve 70 does not decrease even after long-term use, so that reliability can be maintained.

FIG. 7 shows a partial cross section of a variable displacement swash plate type compressor according to a second embodiment of the present invention.
Is a sectional view showing a state immediately before the end of the discharge stroke, and FIG.
FIG. 4 is a sectional view when a suction stroke is started.

Since this embodiment has substantially the same configuration as the first embodiment, the same parts as those in the first embodiment are denoted by the same reference numerals as those in the first embodiment, and the description thereof will be omitted.
Only the parts that are different in configuration from the first embodiment will be described.

The elastic plate (valve opening assisting portion) 81 of the second embodiment has a convex surface 81a on the valve plate side end surface.
The distance D1 from the apex of the convex surface 81a to the top surface 7c of the piston 7 is slightly longer than the distance D2 from the cylinder-side end surface of the valve plate 2 to the top surface 7c of the piston 7.

According to the second embodiment, the elastic thin piece 8
Since the one convex surface 81a surely presses the suction valve 70, the above-described pressure release passage is reliably formed, and the elastic thin piece 8
Since 1 is securely attached to the suction valve 70, the compression efficiency can be reliably improved.

In the first and second embodiments, the elastic thin pieces 80 and 81 are used as the valve-opening assisting parts, and the elastic thin pieces 80 and 81 are attached to the suction valve 70 by lubricating oil. For example, using a permanent magnet as a valve auxiliary part,
The suction valve formed of a magnetic material such as an iron-based material may be forcibly opened when the piston moves from the discharge stroke to the suction stroke by the magnetic force of the permanent magnet.

In the first and second embodiments, the elastic thin pieces 80 and 81 are used as the valve-opening assisting members. However, the valve-opening assisting members need not necessarily have elasticity.

Further, in the first and second embodiments, the suction valve 70 is pushed into the suction port 60 by the elastic thin pieces 80 and 81, but this is not always necessary.

Although the elastic flakes 80 and 81 are brought into contact with the suction valve 70, the valve opening auxiliary part does not necessarily need to be brought into contact with the suction valve 70. For example, in the case where the valve opening assist unit is attached to the suction valve using the viscosity of the lubricating oil or the like, the valve opening assist unit may contact the lubricating oil attached to the surface of the suction valve.

Further, in the above embodiment, the variable displacement type swash plate type compressor was described as an example of the reciprocating type refrigerant compressor.
The present invention can also be applied to a reciprocating refrigerant compressor such as a fixed displacement swash plate compressor and a swinging plate compressor.

[0063]

As described above, according to the reciprocating refrigerant compressor of the first aspect of the present invention, the suction valve is forced into the compression chamber when the piston shifts from the discharge stroke to the suction stroke by the valve opening assist portion. Therefore, the delay in the start of inhalation can be reliably and long-term prevented.

According to the reciprocating refrigerant compressor of the second aspect of the present invention, the suction valve is deformed to form a gap called a pressure release passage between the suction valve and the suction port, so that the pressure in the compression chamber and the discharge port is reduced. Since the remaining refrigerant gas escapes to the suction chamber through the pressure release passage, the volume efficiency is further improved.

According to the reciprocating refrigerant compressor of the third aspect of the present invention, since the valve opening assisting portion is sized to be opposed to the suction port and to fit in the suction port, the valve opening assisting portion is connected to the suction valve. Upon contact, the above-described pressure release passage is formed reliably.

According to the fourth aspect of the present invention, the valve-opening assisting portion is formed of a material having a lower hardness than the material of the suction valve and is fixed to the top surface of the piston. Damage to the suction valve can be prevented.

According to the reciprocating refrigerant compressor of the fifth aspect of the present invention, since the valve opening assisting part presses the suction valve at the apex of the convex surface, the pressure relief passage can be reliably formed.

[Brief description of the drawings]

FIG. 1 is a sectional view of a part of a variable displacement swash plate type compressor according to a first embodiment of the present invention, and FIG. 1 (a) is a sectional view showing a state immediately before the end of a discharge stroke; FIG. 4B is a cross-sectional view when the suction stroke starts.

FIG. 2 is a vertical sectional view of the variable displacement type swash plate type compressor.

FIG. 3 is an exploded perspective view of main components of the variable displacement swash plate type compressor of FIG. 2;

FIG. 4 is a view of a suction valve and a cylinder block as viewed from a line AA in FIG. 3;

FIG. 5 is a plan view of a suction valve seat of the variable displacement swash plate type compressor of FIG. 2;

FIG. 6 is a plan view of a valve plate of the variable displacement swash plate type compressor shown in FIG. 2;

FIG. 7 is a cross-sectional view of a part of a variable displacement swash plate type compressor according to a second embodiment of the present invention, and FIG. 7 (a) is a cross-sectional view showing a state immediately before the end of a discharge stroke; FIG. 4B is a cross-sectional view when the suction stroke starts.

FIG. 8 is a cross-sectional view of a part of a conventional variable displacement swash plate type compressor, in which FIG. 8 (a) is a cross-sectional view showing a state immediately before the end of a discharge stroke, and FIG. FIG. 4 is a cross-sectional view when the operation is started.

[Explanation of symbols]

Reference Signs List 1 cylinder block 2 valve plate 3 rear head (cylinder head) 6 cylinder bore 7 piston 7c top surface 13 suction chamber 14 compression chamber 60 suction port 70 suction valve 80 elastic flake 80a top surface (side surface of valve plate) 81 elastic flake 81a convex surface D1 convex surface 81c From the top of the top surface 7c of the piston 7
Distance D2 from valve plate 2 to top surface 7c of piston 7
Distance to

Claims (5)

[Claims] 1. A cylinder block having a cylinder bore, a piston movably accommodated in the cylinder bore, a compression chamber formed in the cylinder bore, and a refrigerant gas temporarily sucked into the compression chamber. A suction head formed with a cylinder head coupled to one end surface of the cylinder block; and a suction head disposed between the compression chamber and the suction chamber for guiding refrigerant gas in the suction chamber to the compression chamber. In a reciprocating refrigerant compressor including a valve plate having a port formed therein and a suction valve for opening and closing the suction port, when the piston moves from top dead center to bottom dead center, the suction valve is compressed. A reciprocating refrigerant compressor, wherein a valve-opening assisting portion is provided on a top surface of the piston to be drawn to a chamber side. 2. A surface of the valve-opening assisting portion facing the suction valve has a shape in which a part of the suction valve is pushed into the suction port when the piston reaches a top dead center. The reciprocating refrigerant compressor according to claim 1, wherein 3. The reciprocating refrigerant compressor according to claim 1, wherein the valve opening assisting portion has a size opposed to the suction port and within a projection plane of the suction port. . 4. The reciprocating refrigerant compressor according to claim 1, wherein the valve opening assist portion is formed of a material having a lower hardness than a material of the suction valve. 5. A surface of the valve-opening assisting portion facing the suction valve is a convex surface, and a distance from an apex of the convex surface to a top surface of the piston is longer than a distance from the valve plate to a top surface of the piston. The reciprocating refrigerant compressor according to any one of claims 1 to 4, wherein the compressor is slightly longer.