JPS6338554B2 - - Google Patents

Description

Detailed Description of the Invention Technical Field The present invention relates to a reciprocating compressor that sucks in and compresses gas by reciprocating a piston within a cylinder, and particularly relates to a technology for alleviating overcompression during compression. It is related to.

Prior art Gas is sucked in from the suction port by retracting the piston within the cylinder, and the retracted piston is advanced to the forward end position (top dead center), compressing the inhaled gas and expelling it. Reciprocating compressors that discharge from an outlet have been provided in the past. Examples include a swash plate type compressor, a crank type compressor, and a swinging swash plate type compressor. In such a compressor, it is desirable to discharge all of the compressed gas in order to increase the volumetric efficiency and improve the performance of the compressor. For this reason, in general, the gap (top clearance) between the top surface of the piston and the cylinder end wall at the forward end position of the piston is made as small as possible so that almost all of the inhaled gas is discharged from the discharge port. .

By the way, in the above-mentioned compressor which compresses gas as the piston advances and discharges the compressed gas from the discharge port, the pressure of the gas in the cylinder is greater than the pressure of the discharged gas (pressure in the discharge chamber). This results in overcompression, which also increases. This overcompression occurs due to, for example, the viscous resistance or inertia of the gas, and it is impossible for the compressor to completely prevent this. However, this overcompression not only impedes the movement of the piston and increases power loss, but also becomes one cause of increasing the noise associated with its operation.

Therefore, we investigated this type of overcompression in more detail and found that this overcompression occurs when the piston reaches near the forward end position, especially from the discharge port in a direction perpendicular to the reciprocating direction of the piston. It was found that there was an extreme pressure increase in isolated areas. In other words, in the vicinity of the discharge port, the gas to be compressed is discharged from the discharge port, and the rate of change in volume of the gas as the piston moves forward is reduced by the volume of the discharge port, so overcompression is prevented. It will be alleviated. On the other hand, in the area away from the discharge port, the top clearance is set to be extremely small as mentioned above.
As the piston approaches the forward end position, the flow resistance due to the viscosity of the gas increases, impeding the flow of gas toward the discharge port, and the further away from the discharge port there is no place for the gas to escape, causing an extreme pressure rise. This is considered to be an indication.

Purpose of the Invention The present invention has been made based on the above knowledge, and its purpose is to alleviate overcompression in a reciprocating compressor in which the top clearance is extremely small. It is in.

Structure of the Invention In order to achieve this object, the reciprocating compressor according to the present invention has a gap between the top surface of the piston and the end wall of the cylinder at a position away from the discharge port in a direction perpendicular to the moving direction of the piston. It is constructed by providing an overcompression alleviating portion larger than that of the portion around the discharge port. Here, the overcompression alleviation section is one in which almost the entire top surface of the piston and the end wall of the cylinder are parallel to each other, and the top surface of the piston is partially depressed, or the top surface of the piston is completely flat. In some cases, the surface of the piston is not parallel to the cylinder end wall, and the gap between the piston top surface and the cylinder end wall is larger in the area around the discharge port and in the area farther from the discharge port.

Effects of the Invention By doing this, even if the piston is advanced to the vicinity of the forward end position and the flow of gas toward the discharge port is obstructed, the gas volume will change as the piston moves forward thereafter. Since the ratio of the overcompression reduction portion is reduced by the provision of the overcompression reduction portion, the extreme pressure increase in the portion remote from the discharge port is reduced. Moreover, since the overcompression alleviation section is provided in a portion away from the discharge port where pressure is particularly likely to increase, the pressure distribution acting on the top surface of the piston is made uniform.

Furthermore, if an overcompression relief part is provided, the volume of the space left in the cylinder when the piston reaches the forward end position will be increased, and the gas remaining in the large volume space will be regenerated when the piston retreats. At first glance, it seems that the volumetric efficiency decreases due to expansion, but in reality, if you reduce the top clearance in the area away from the discharge port, the gas in that area will not be discharged, but will simply be compressed to a smaller size. The pressure will only increase, and when the piston retreats, this small compressed gas will re-expand. Therefore, the overcompression mitigation section was installed to avoid the wasteful compression work described above. This does not necessarily mean that the volumetric efficiency decreases.

By relieving overcompression in this way, the pressure acting on the top surface of the piston becomes smaller and more uniform, so the movement of the piston becomes smoother and its power loss is reduced. Compressor operating noise is reduced. Further, since an extremely large load is not applied to the piston drive mechanism near the forward end of the piston, the durability and reliability of the compressor are improved.

Embodiments Hereinafter, embodiments of the present invention will be described in detail based on the drawings.

FIG. 1 is a front sectional view showing the configuration of a swash plate type refrigerant gas compressor used in an automobile cabin cooling system or the like. In the figure, 10 is the front block, 12
is a rear block, and two mutually symmetrical blocks are combined to form one cylinder block 14. A plurality of cylinder bores 16 are formed in the cylinder block 14 at equal angular intervals on one circumference, and a double-headed piston 18 is slidably fitted into each cylinder bore 16. A swash plate chamber 20 is formed at the abutting portion of the front block 10 and rear block 12, and a swash plate 24 fixed to the rotating shaft 22 at a constant angle is disposed within the swash plate chamber 20. A rotating shaft 22 is rotatably supported within a central hole 26 of the cylinder block 14. The outer circumference of the swash plate 24 is 2
The piston 18 is engaged with the piston 18 through the individual spheres 28 and shoes 29, and as the swash plate 24 is rotated together with the rotating shaft 22, the piston 18 is reciprocated within the cylinder bore 16.
At this time, the axial load applied from the piston 18 to the swash plate 24 is received by a pair of thrust bearings 30 provided at both ends of the boss portion of the swash plate 24.

A suction valve seat 32, a valve plate 34 and a gasket 36 are provided on the end face of the front block 10.
A front housing 38 is fixed in between. A suction port 40 and a discharge port 42 are formed in the valve plate 34 in correspondence with each cylinder bore 16, and a suction valve 44 and a discharge valve 46 are provided in correspondence therewith. Both the suction valve 44 and the discharge valve 46 are reed valves, but the opening amount of the discharge valve 46 is regulated by a regulating plate 48 formed integrally with the gasket 36. Each suction port 40 is provided at a position where refrigerant gas can be sucked in from a common suction chamber 50 formed on the outer periphery of the front housing 38, while each discharge port 42 is located on the center side of the front housing 38. It is formed at a position where refrigerant gas can be discharged to a common discharge chamber 52 formed in the. A center hole 54 is formed in the center of the front housing 38, and one end of the rotating shaft 22 extends into the center hole 54. The airtightness between the front housing 38 and the rotating shaft 22 is maintained by a shaft sealing device. 56.

I have explained the front side in detail above,
It is almost the same on the rear side, rear block 12
A suction valve seat 32 and a valve plate 3 are installed on the end face of the
4 and a gasket 36 therebetween, refrigerant gas is sucked into the cylinder bore 16 from a suction chamber 60 in the rear housing 58 through a suction port 40 equipped with a suction valve 44, and then into the cylinder bore 16 through a suction valve 44. The liquid is discharged into the discharge chamber 62 through the discharge port 42 having the discharge port 46 .

The front side discharge chamber 52 and the rear side discharge chamber 62 are communicated with a common discharge port via a discharge passage (not shown), and the front side discharge chamber 52 is connected to a common discharge port through a discharge passage (not shown).
0 and the rear side suction chamber 60 have a plurality of suction passages 64.
It is communicated with the swash plate chamber 20 by the swash plate chamber 20, and further communicated with a suction port (not shown). The suction passage 64 is connected to the front block 10 and the rear block 1.
2. It also serves as an insertion hole for a bolt 66 for tightening the front housing 38 and rear housing 58.

Both top surfaces 68 of the piston 18 are formed perpendicularly to the axis of the piston 18, and these top surfaces 68 and the inner surface 69 of the suction valve seat 32, which forms the cylinder end wall together with the valve plate 34, are formed as a whole. They are parallel to each other. When the piston 18 is advanced to one forward end position as the swash plate 24 rotates, the gap between the top surface 68 and the inner surface 69, that is, the top clearance 70, is extremely small, and the suction refrigerant gas Almost the entire amount is discharged from the discharge port 42. Note that FIG. 1 shows a state in which the piston 18 has been advanced to the forward end position on the front side.

As is clear from FIG. 2, four bottomed circular holes 72, 73, 74, and
5 is bored, and the top surface 68 is partially recessed. Each of the bottomed circular holes 72 to 75 is connected to the piston 1 from a position corresponding to the discharge port 42 on the top surface 68.
The circular hole 72 with a bottom is provided at a position substantially corresponding to the suction port 40. Further, the bottomed circular hole 73 is located at a position corresponding to the discharge port 42 and the bottomed circular hole 73 is located at a position corresponding to the discharge port 42.
The bottomed circular holes 74 and 75 are located on the outer periphery of the top surface 68 and are spaced equidistantly apart from the straight line connecting the center of the suction port 40 and the center of the discharge port 42 on opposite sides. located at each location. As a result, the top clearance 70 is limited only to the portion where these bottomed circular holes 72 to 75 are provided.
It is larger than other parts.

In the compressor configured as described above, when rotational torque is applied to the rotating shaft 22 and the swash plate 24 is rotated, the piston 18 starts reciprocating within the cylinder bore 16. For example, when the piston 18 is driven toward the front side, the piston 18 on the front side of the cylinder bore 16
is moved forward, and the refrigerant gas is discharged from the discharge port 42 into the discharge chamber 52 while being compressed. Further, on the rear side of the cylinder bore 16, the piston 18 is moved backward, and the refrigerant gas in the suction chamber 60 is sucked into the cylinder bore 16 from the suction port 40.

When the piston 18 is advanced and reaches near its forward end position, the gap between the top surface 68 and the inner surface 69, in other words, the discharge port 4, starts from the point where the top clearance 70 is set to be extremely small.
The thickness of the flow path for the refrigerant gas flowing toward the refrigerant gas 2 becomes extremely thin. Therefore, the flow resistance becomes large based on the viscosity of the refrigerant gas and the lubricating oil contained therein, and the flow of the refrigerant gas toward the discharge port 42 side is inhibited. Further, the portion near the inner surface 69 and away from the discharge port 42 was originally the piston 18.
The refrigerant gas is out of the flow path of the refrigerant gas as the piston 18 moves forward, and remains there regardless of the forward movement of the piston 18, making it difficult for it to flow immediately due to inertia.

From the above, even if the piston 18 is further advanced at high speed, only the refrigerant gas in the vicinity is discharged from the discharge port 42, and the refrigerant gas located away from the discharge port 42 is compressed as it is. It will be done. Here, the piston 1 of this embodiment
8, there are four bottomed circular holes 72 to 75 in the part where the flow of refrigerant gas is obstructed, that is, in the part away from the position corresponding to the discharge port 42.
are provided, the bottomed circular holes 72 to 7
The volume of the refrigerant gas increases by the volume of 5,
The rate of change in volume of the refrigerant gas as the piston 18 moves forward becomes smaller. Therefore, the compression ratio of the refrigerant gas is also reduced, and overcompression is alleviated. That is, the bottomed circular holes 72 to 7
5 constitutes an overcompression alleviating section.

Incidentally, the pressure distribution acting on the top surface 68 when the piston 18 is advanced to the forward end position is expressed as
The pressure distribution on line A-B in the same figure is shown in Figure a.
Shown in Figure b. Further, a conventional case in which the top surface 68 of the piston 18 is a flat plane completely parallel to the inner surface 69 is shown in FIGS. 4a and 4b. As is clear from these figures, in the conventional case where the top surface 68 was a completely flat surface, the pressure increased rapidly as the distance from the discharge port 42 increased, but in the case of this embodiment, the pressure increases rapidly as the distance from the discharge port 42 increases. No such increase in pressure was observed in
The pressure acting on the top surface 68 of the piston 18 is approximately uniform.

Thereafter, when the piston 18 is moved backward, refrigerant gas is sucked through the suction port 40. At this time, the refrigerant gas remaining in the top clearance 70 between the top surface 68 and the inner surface 69 of the piston 18 expands again as the piston 18 retreats.
Since the amount of this re-expanded refrigerant gas is almost the same as when the bottomed circular holes 72 to 75 are not provided, the volumetric efficiency is reduced by providing the bottomed circular holes 72 to 75 to reduce overcompression. There's nothing to do. Moreover, since the bottomed circular holes 72 to 75 are all provided at positions corresponding to the suction port 40 or in the vicinity thereof, a decrease in volumetric efficiency due to the provision of the bottomed circular holes 72 to 75 is more effectively prevented. Ru. This is because during suction, the pressure becomes higher near the suction port 40 where the refrigerant gas is sucked, so that re-expansion of the residual refrigerant gas is suppressed by the sucked refrigerant gas.

Then, the piston 18 is at the backward end position (bottom dead center)
When it is retracted to this point, it is moved forward again and the compression work described above is performed. In addition, the piston 18
The strokes on the front side and the rear side of the cylinder are shifted by half a cycle, and the strokes within the plurality of cylinder bores 16 provided in the cylinder block 14 are shifted from each other by a phase corresponding to the angular spacing between the cylinder bores. As a result, the compressor as a whole continuously performs the work of compressing the refrigerant gas.

As described above, in the compressor of this embodiment, overcompression is alleviated without substantially impairing its volumetric efficiency, and the pressure acting on the top surface 68 of the piston 18 is reduced and made uniform.
The movement of the piston 18 becomes extremely smooth. As a result, the power loss of the piston 18 is reduced, and the operating noise of the compressor is reduced.
This improves the durability of the compressor.

In the above-described embodiment, the overcompression relief portion is formed by providing four bottomed circular holes 72 to 75 in the top surface 68 of the piston 18. It is also possible to form the overcompression relaxation section from one or more of the above-mentioned 75, or even from five or more circular holes with bottoms, and the shape and position also depend on the purpose and usage conditions of the compressor. , discharge port 42 and income port 40
It may be set by taking into consideration the position of .

For example, in the above embodiment, if only one bottomed circular hole 72 is provided on the top surface 68 of the piston 18, when overcompression occurs, the top surface 68
The distribution of pressure acting on the line is as shown in FIG. 5a, and the pressure distribution on line A-B is as shown in FIG. 5b. Therefore, compared to the conventional case shown in FIGS. 4a and 4b, in which no overcompression alleviation portion is provided on the top surface 68, overcompression is alleviated, particularly in a portion away from the discharge port 42. .

Moreover, FIGS. 6a and 6b show the pressure distribution when overcompression occurs when three bottomed circular holes 72, 74 and 75 are provided in the top surface 68. In this case, overcompression is more effectively alleviated than in the case shown in FIG. 5 above.

Furthermore, the overcompression alleviation part does not necessarily have to be formed from a circular hole with a bottom as described above; for example, as in the case of the piston 76 shown in an exaggerated manner in FIG. It is also possible to form an overcompression relief portion by forming a curved surface that is not parallel to 69.
That is, based on the overcompression pressure distribution shown in FIG. 4a, the top surface 78 is formed such that the gap between the top surface 78 and the inner surface 69 becomes larger in areas where the pressure is higher. In this case, overcompression can be made more uniform than in each of the embodiments described above.

Although several embodiments of the present invention have been described above based on the drawings, the present invention can be implemented in other embodiments as well.

For example, in each of the above-described embodiments, an overcompression relief portion is formed on the top surface of the piston, but it is also possible to form an overcompression relief portion such as a recess on the cylinder end wall or cylinder bore.

Furthermore, it goes without saying that the present invention can be applied not only to the swash plate type compressor as shown in FIG. 1, but also to other reciprocating type compressors such as a crank type compressor and a swinging swash plate type compressor.

In addition, the present invention can be implemented with various changes and improvements based on the knowledge of those skilled in the art without departing from the spirit thereof.

[Brief explanation of the drawing]

FIG. 1 is a front sectional view of a swash plate type refrigerant gas compressor which is an embodiment of the present invention. FIG. 2 is a plan view showing the top surface of the piston of the compressor. Figure 3a
is a diagram showing the pressure distribution at the time of overcompression that acts on the top surface of the piston;
It is a figure showing pressure distribution on a line. Figures 4a and 4b are diagrams showing the distribution of pressure acting on the top surface of the piston during overcompression in a conventional compressor that does not have an overcompression relief section.
FIG. 3 is a diagram corresponding to figures a and b; 5a, b and 6a, b are diagrams showing the pressure distribution during overcompression acting on the top surface of the piston in other embodiments of the present invention, respectively, and FIGS. 3a, b
FIG. FIG. 7 is a diagram showing the main parts of still another embodiment of the present invention, and is a sectional view of the vicinity of the top surface of the piston. 14... Cylinder block, 16... Cylinder bore, 18, 76... Piston, 24... Swash plate, 40...
Suction port, 42...Discharge port, 68, 78...Top surface, {3
2... Suction valve seat, 34... Valve plate} (cylinder end wall), 70... Top clearance, 72,
73, 74, 75...Bottomed circular hole.

Claims (1)

[Claims] 1. Gas is sucked in from the suction port by retracting the piston within the cylinder, and the retracted piston leaves only a small gap between its top surface and the end wall of the cylinder. In a reciprocating compressor that discharges almost the entire amount of gas sucked in from a discharge port by being advanced to a forward end position of the piston, the piston is located at a position away from the discharge port in a direction perpendicular to the direction of movement of the piston. 1. A reciprocating compressor, characterized in that an overcompression alleviating section is provided in which a gap between the top surface of the cylinder and the cylinder end wall is larger than that of a portion around the discharge port. 2. The top surface of the piston and the cylinder end wall are substantially entirely parallel surfaces, and the top surface of the piston is partially recessed to form the overcompression alleviating portion. A reciprocating compressor according to scope 1. 3. By making the piston top surface entirely non-parallel to the cylinder end wall, the gap between the piston top surface and the cylinder end wall is made larger in a portion farther from the discharge port around the discharge port. 2. The reciprocating compressor according to claim 1, wherein said overcompression alleviating section is formed.