Reciprocating compressor

Abstract

A reciprocating compressor is provided. The compressor includes a casing, a linear reciprocating motor provided inside the casing to generate a linear driving force, a cylinder fixed with respect to the casing, and a piston which reciprocates within the cylinder based on movement of the linear motor. An oil pump provided in the compressor includes an oil piston which reciprocates in response to the reciprocating motion of the piston to provide oil to the cylinder and piston.

Description

[0001] This application claims priority to Korean Application No. 10-2005-0122720, filed in Korea on Dec. 13, 2005, the entirety of which is incorporated herein by reference.

BACKGROUND

[0002] 1. Field

[0003] The field relates to a compressor, and more particularly, to a reciprocating compressor.

[0004] 2. Background

[0005] In general, a compressor converts mechanical energy into compressive energy. Compressor may typically be categorized into a reciprocating type, a scroll type, a centrifugal type and a vane type. Reciprocating compressors may be further categorized into a horizontal type compressor, and a vertical type compressor.

[0006] Due to the need to provide for lubrication of various components, combined with the placement and orientation of the various components of the horizontal and vertical type reciprocating compressors, additional space is required in the casing to accommodate the oil. Further, in a horizontal type reciprocating compressor, assembly is complicated due to the number of components of the oil pump, and oil is not smoothly and continuously provided when oil viscosity is high. Likewise, the vertical orientation of the components of a vertical type reciprocating compressor makes it difficult to pump oil to the various components, thus decreases reliabilities of the compressor.

BRIEF DESCRIPTION OF THE DRAWINGS

[0007] The embodiments will be described in detail with reference to the following drawings in which like reference numerals refer to like elements wherein:

[0008] FIG. 1 is a cross-sectional view of an exemplary horizontal type reciprocating compressor;

[0009] FIG. 2 is a disassembled perspective view of an oil pumping unit in accordance with embodiments as broadly described herein;

[0010] FIG. 3 illustrates an oil suction process in accordance with embodiments as broadly described herein;

[0011] FIG. 4 illustrates an oil supply process in accordance with embodiments as broadly described herein;

[0012] FIG. 5 is a cross-sectional view of another exemplary horizontal type reciprocating compressor incorporating an oil pumping assembly as embodied and broadly described herein;

[0013] FIG. 6 is a cross-sectional view of another exemplary horizontal type reciprocating compressor incorporating an oil pumping assembly as embodied and broadly described herein; and

[0014] FIGS. 7-9 are exemplary installations of a compressor incorporating an oil pumping assembly as embodied and broadly described herein.

DETAILED DESCRIPTION

[0015] A reciprocating compressor having an oil pump in accordance with embodiments as broadly described herein is shown in FIG. 1. Although a reciprocating compressor, and particularly a horizontal type reciprocating compressor, is presented for ease of discussion, it is well understood that an oil pumping assembly as embodied and broadly described herein may be applied to other types of compressors and/or other applications which require fluid pumping as described herein.

[0016] Descriptions of reciprocating compressors and operation thereof can be found, for example, in U.S. Pat. Nos. 6,875,000, 6,875,001 and 6,863,506, which are subject to an obligation of assignment to the same entity, and the entirety of which is incorporated herein by reference.

[0017] The exemplary reciprocating compressor includes a casing 100, a reciprocating motor 200 provided in the casing 100 and having a linearly-reciprocating mover 230, a compression unit 300 for compressing a fluid, such as, for example a refrigerant as a piston 320 coupled to the mover 230 reciprocate together, and a pumping unit 400 installed near the piston 320 of the compression unit 300 for pumping fluid, such as, for example, oil, contained in the casing 100.

[0018] The reciprocating motor 200 includes an outer stator 210 fixed to the casing 100 and having a winding coil 211 thereon, an inner stator 220 provided at an inner side of the outer stator 210 with a predetermined gap therebetween, and a mover 230 having a magnet 231 positioned in the gap between the outer stator 210 and the inner stator 220.

[0019] The mover 230 is fixedly coupled to an outer circumferential surface of a movable frame 232, the moveable frame 232 having a substantially cylindrical shape so as to support a plurality of magnets 231 arranged between the outer stator 210 and the inner stator 220. The movable frame 232 has two opened sides, with a rear side of the two opened sides having a portion which extends towards the center so as to be coupled to a piston 320 of the compression unit 300 by a bolt or other suitable fastener. A passage (not shown) for transferring a refrigerant from inside the movable frame 232 outwardly when the mover 230 reciprocates can be formed in the movable frame 232. Since the oil pumping assembly 400 operates under an air pressure generated by the movable frame 232, the passage may be formed large enough to generate an adequate air pressure.

[0020] The outer stator 210 is supported by first and second fixed frames 240 and 250, respectively, coupled to both ends of the mover 230, and is fixedly coupled to the casing 100. The inner stator 220 may be press fit to an outer circumferential surface of the front, or first fixed frame 240.

[0021] The first fixed frame 240 may have a disc shape having an outer diameter similar to that of the outer stator 220. A cylindrical fixing protrusion 241 may protrude back from a center of the first fixed frame 240. The inner stator 220 is inserted into an outer circumferential surface of the first fixed frame 240, and a cylinder 310 of the compression unit 300 is inserted into an inner circumferential surface of the first fixed frame 240.

[0022] An oil passage 242 for guiding oil inside the casing 100 may be formed at the first fixed frame 240, penetrating the fixing protrusion 241 from a lower side to an upper side. The oil passage 242 guides oil between the cylinder 310 and the piston 320, and then back into the casing 100. A valve seat portion 243 may be connected to the oil passage 242. The valve seat portion 243 may have a circular-arc shape, with an oil inlet 243a and an oil outlet 243b for supporting an oil valve 420 extending from an inner circumferential surface of the fixing protrusion 241 of the first fixed frame 240.

[0023] An oil pocket 244 in communication with the oil passage 242 may be formed between an inner circumferential surface of the fixing protrusion 241 and an outer circumferential surface of the cylinder 310 (including a front surface of the cylinder 310). The oil pocket 244 is connected to an oil passing hole 312 of the cylinder 310 so that oil can be supplied between an inner circumferential surface of the cylinder 310 and an outer circumferential surface of the piston 320.

[0024] The compression unit 300 includes a cylinder 310 which is inserted into and fixed to the fixing protrusion 241 of the first fixed frame 240, the piston 320 which is coupled to the mover 230 of the reciprocating motor 200 so as to reciprocate in a compression space 311 of the cylinder 310, a plurality of resonance springs 330 and 340 which elastically support the piston 320, thereby causing resonance in the piston 320, a suction valve 350 provided at an end surface of the piston 320 so as to open and close a suction channel 321 of the piston 320 thereby restricting suction of refrigerant gas, a discharge valve 360 provided at a discharge side of the cylinder 310 so as to open and close the compression space 311 thereby restricting discharge of the refrigerant gas, a valve spring 370 which elastically supports the discharge valve 360, and a discharge cover 380 which covers a discharge side of the cylinder 310 so as to receive the discharge valve 360 and the valve spring 370. The discharge cover 380 is inserted into a cover insertion hole 110 provided at one side of the casing 100.

[0025] The oil pocket 244 has a certain volume defined by an outer circumferential surface of the cylinder 310 and an inner circumferential surface of the fixing protrusion 241 of the first fixed frame 240. The cylinder 310 is inserted into and fixed to the fixing protrusion 241 so that the oil pumping assembly 400 can be installed at the oil pocket 244.

[0026] The piston 320 is provided with a connection portion 322 which connects to the movable frame 232. The connection portion 322 is formed as a flange which extends from a rear end of a body portion 321. A suction channel 321a is formed within the shaft of the piston 320. Another passage (not shown) for passing a refrigerant inside the movable frame 232 outwardly when the piston 320 is reciprocated can be formed at the connection portion 322. Since the oil pumping assembly 400 operates under an air pressure generated by the movable frame 232, the passage may be formed large enough to generate an adequate air pressure.

[0027] The first and second resonance springs 330 and 340 may be compression coil springs. One end of the first, or front resonance spring 330 is fixed to a front side of a connection portion 332 which is coupled to the connection portion 322 of the piston 320, and another end of the first resonance spring 330 is fixed to the second fixed frame 250 that supports a rear side of the outer stator 210. One end of the second, or rear resonance spring 340 is fixed to a rear side of the connection portion 332, and another end of the second resonance spring 340 is fixed to an inner circumferential surface of the casing 100.

[0028] A fixed portion 351 (see FIG. 3) is formed as a cut-out at a middle portion of the suction valve 350 so as to be fixed to an end surface of the piston 320. An opening/closing portion 352 (see FIG. 3) for opening and closing the suction channel 321a of the piston 320 by being either bent or straightened based on a position of the fixed portion 351 is formed as a cut-out at an outer side of the fixed portion 351.

[0029] The discharge valve 360 may be formed of an appropriate material, such as, for example a plastic material. A compression surface of the discharge valve 360 is detachably coupled to an end surface of the cylinder 310, thus allowing the valve 360 to be opened and closed. The outer surface of the compression surface may have a substantially semi-spherical shape.

[0030] The valve spring 370 may be, for example, a cylindrical or a conical compression coil spring. One end of the valve spring 370 is fixed to the outer surface of the compression surface of the discharge valve 360, and another end thereof is fixed to an inner surface of the discharge cover 380. When the valve spring 370 has a conical shape, a relatively wider end of the valve spring 370 may be fixed to the discharge cover 380 to provide stability.

[0031] The discharge cover 380 can form a single discharge space as shown, for example, in FIG. 1. In alternative embodiments, the discharge cover 380 may form a plurality of discharge spaces (not shown). The discharge cover 380 is installed so that a discharge space portion 381 of the discharge cover 380 can be exposed outwardly through the cover insertion hole 110 of the casing 100. A coupling flange portion 382 of the discharge cover 380 hermetically coupled to an outer surface of the first fixed frame 240 may be formed at an outer circumferential surface of an opened side of the discharge space portion 381.

[0032] The oil pumping assembly 400 may include an oil piston 410 slidably inserted into the oil pocket 244 and arranged between an outer circumferential surface of the cylinder 310 and an inner circumferential surface of the first fixed frame 240 along a motion direction of the piston 320, an oil valve 420 for opening and closing the oil pocket 244 connected to the oil passage 242 when the oil piston 410 is reciprocated, a valve seat 430 for supporting a rear side of the oil valve 420, first and second piston springs 440 and 450 installed along a motion direction of the oil piston 410 so as to elastically support reciprocation of the oil piston 410, and a spring supporting plate 460 pressed-fit between an outer circumferential surface of the cylinder 310 and an inner circumferential surface of the first fixed frame 240 so as to support the second piston spring 450.

[0033] The oil piston 410 may have a substantially cylindrical shape with a certain thickness so that an inner circumferential surface thereof can slidably contact an outer circumferential surface of the cylinder 310, and an outer circumferential surface thereof can slidably contact an inner circumferential surface of the fixing protrusion 241 of the first fixed frame 240. In certain embodiments, the length the oil piston 410 is selected so as to allow the oil passing hole 312 of the cylinder 310 to be open to the oil pocket 244, and not blocked by the oil piston 410, during an oil suction stroke to allow for a smooth supply of oil. The oil piston 410 may be formed of a plastic material, taking into consideration friction with the cylinder 310 or the first fixed frame 240.

[0034] The oil valve 420 may be formed in a ring shape so as to be supported by the valve seat portion 243 of the first fixed frame 240. One side of the oil valve 420 is provided with a suction valve portion 421, and another side thereof is provided with a discharge valve portion 422 which opens and closes in a direction opposite that of the suction valve portion 421.

[0035] The valve seat 430, which supports a rear side of the oil valve 420, may also be formed in a ring shape. A suction hole 431 for opening the suction valve portion 421 of the oil valve 420 is formed at a lower end of the valve seat 430, and a discharge hole 432 for opening the discharge valve portion 422 of the oil valve 420 is formed at an upper end of the valve seat 430.

[0036] The first and second piston springs 440 and 450 are installed at opposite sides of the oil piston 410, along a motion direction of the oil piston 410. The first piston spring 440 is supported by the valve seat 430, and the second piston spring 450 is supported by the spring supporting plate 460 and press fit or welded between an outer circumferential surface of the cylinder 310 and an inner circumferential surface of the first fixed frame 240.

[0037] A plurality of air passing holes 461 may be formed at the spring supporting plate 460. The air passing holes 461 receive an inner pressure developed in the mover 230 when the piston 320 is reciprocated, and this received pressure causes the oil piston 410 to smoothly reciprocate by outwardly applying an inner pressure of the oil pocket 244 when the oil piston 410 is retreated.

[0038] The oil pumping assembly 400 can be installed between an inner circumferential surface of the first fixed frame 240 and an outer circumferential surface of the cylinder 310. In alternative embodiments, the cylinder 310 may have a double structure. For example, the cylinder may include a first cylinder which receives the piston, and a second cylinder inserted into an inner circumferential surface of the first fixed frame. The first cylinder and the second cylinder may be coupled to each other with a gap formed therebetween so as to form an oil pocket in which the oil pumping assembly may be installed.

[0039] The compressor as shown in FIG. 1 also includes an oil guiding pipe 260, a suction pipe SP, and a discharge pipe DP.

[0040] Operation of the exemplary reciprocating compressor having an oil pumping assembly as embodied and broadly described herein will now be explained.

[0041] When power is supplied to the winding coil 211 fixed to the outer stator 210 of the reciprocating motor 200, a flux is generated between the outer stator 210 and the inner stator 220. This causes the mover 230 positioned between the outer stator 210 and the inner stator 220 to be continuously reciprocated due to the resonance springs 330 and 340. As the piston 320 is coupled to the mover 230, the mover 230 is reciprocated in the cylinder 310, and a volume of the compression space 311 formed between the cylinder 310 and the piston 320 is changed. Accordingly, refrigerant gas is sucked into the compression space 311, compressed, and then discharged.

[0042] A semi-hermetic space is formed in the mover 230, and thus a refrigerant filled in the mover 230 is repeatedly contracted and expanded when the mover 230 reciprocates together with the piston 320. As shown in FIG. 3, when the mover 230 moves backward, a pressure inside the mover 230 is lowered, causing the first piston spring 440 arranged at a front side of the oil piston 410 to be restored to a rest position and the oil piston 410 to move backward along with the mover 230 and the piston 320. A volume of the oil pocket 244 formed a front side of the oil piston 410 is increased, thus generating a suction force. The suction force causes the suction valve portion 421 of the oil valve 420 to open, thereby sucking oil from the casing 100 in through the oil passage 242. The oil is dispersed between the cylinder 310 and the piston 320 through the oil passing hole 312 of the cylinder 310 to provide for lubrication between the cylinder 310 and the piston 320.

[0043] As shown in FIG. 4, when the mover 230 moves forward, pressure inside the mover 230 is increased and oil is moved to the oil pocket 244 through the air passing holes 461 in the spring supporting plate 460. When the oil piston 410 moves forward along with the mover 230 due to the pressure, a pressure in the oil pocket 244 is increased, thus closing the suction valve portion 421 of the oil valve 420 and opening the discharge valve portion 422. Through the opened discharge valve portion 422, the oil in the oil pocket 244 is returned to the casing 100 through the oil passage 242. In this first embodiment, the oil in the casing 100 is pumped in response to a pressure difference generated in the mover 230 when the mover 230 and the piston 320 are reciprocated.

[0044] In a second embodiment shown in FIG. 5, the second piston spring 450 extends a longer distance, between a rear side of the oil piston 410 and the connection portion 322 of the piston 320. An oil pumping operation associated with this second embodiment is similar to that of the first embodiment. As a reciprocation force of the mover 230 and the piston 320 causes the oil piston 410 to reciprocate, a pumping force of the oil piston 410 is increased and a stability of the oil piston 410 is enhanced due to the longer extension of the second piston spring 450 and its attachment to the connection portion 322 of the piston 320.

[0045] In alternative embodiments, the oil piston 410 may be connected to the piston 320 by a cylindrical body or a rigid body, such as, for example, a plurality of bars, rather than by the second piston spring 450. This would further increase the pumping force and the stability of the oil piston 410. However in certain embodiments a damping device may also be required.

[0046] A reciprocating compressor having an oil pumping assembly in accordance with a third embodiment will now be explained. As shown in FIG. 6, front and rear sides of the oil piston 410 are supported by the first and second piston springs 440 and 450. A ring-shaped collision plate 470 is interposed between the second piston spring 450 and the spring supporting plate 460, and a collision member 323 protrudes from the connection portion 322 of the piston 320. The collision member 323 applies an impact force to the second piston spring 450 via the collision plate 470.

[0047] More specifically, when the piston 320 moves forward, the collision member 323 repeatedly collides with the collision plate 470 as it passes through one of the holes 461 in the spring supporting plate 460, thereby applying an impact force to the second piston spring 450 via the collision plate 470. This impact causes the second piston spring 450 to be repeatedly contracted and expanded, with corresponding movement of the first piston spring 440, thus causing the oil piston 410 to be reciprocated.

[0048] The oil pumping assembly 400 reciprocates together with the mover 230 and the piston 320, thereby further increasing a pumping force and a reliability for the oil pumping operation.

[0049] Furthermore, since the oil pumping assembly 400 is installed inside the compression unit 300, a size of the compressor may be reduced and an entire structure of the compressor may be simplified.

[0050] Although an exemplary horizontal-type reciprocating compressor is presented herein, for ease of discussion, it is well understood that this can be equally applied to a vertical-type reciprocating compressor, or other type of compressor, or another application in which this type of fluid pumping is required and/or advantageous.

[0051] More specifically, the oil pumping assembly for a compressor as embodied and broadly described herein has numerous applications in which compression of fluids is required, and in different types of compressors. Such applications may include, for example, air conditioning and refrigeration applications. One such exemplary application is shown in FIG. 7, in which a compressor 710 having an oil pumping assembly as embodied and broadly described herein is installed in a refrigerator/freezer 700. Installation and functionality of a compressor in a refrigerator is discussed in detail in U.S. Pat. Nos. 7,082,776, 6,955,064, 7,114,345, 7,055,338 and 6,772,601, the entirety of which are incorporated herein by reference.

[0052] Another such exemplary application is shown in FIG. 8, in which a compressor 810 having an oil pumping assembly as embodied and broadly described herein is installed in an outdoor unit of an air conditioner 800. Installation and functionality of a compressor in a refrigerator is discussed in detail in U.S. Pat. Nos. 7,121,106, 6,868,681, 5,775,120, 6,374,492, 6,962,058, 6,951,628 and 5,947,373, the entirety of which are incorporated herein by reference.

[0053] Another such exemplary application is shown in FIG. 9, in which a compressor 910 having an oil pumping assembly as embodied and broadly described herein is installed in a single, integrated air conditioning unit 900. Installation and functionality of a compressor in a refrigerator is discussed in detail in U.S. Pat. Nos. 7,032,404, 6,412,298, 7,036,331, 6,588,228, 6,182,460 and 5,775,123, the entirety of which are incorporated herein by reference.

[0054] Likewise, the oil pumping assembly as embodied and broadly described herein is not limited to installation in compressors. Rather, the oil pumping assembly as embodied and broadly described herein may be applied in any situation in which this type of fluid pumping is required and/or advantageous.

[0055] An object is to provide a reciprocating compressor capable of reducing a production cost by reducing a number of components, and capable of enhancing a reliability with an oil supply device.

[0056] To achieve these and other advantages and in accordance with the purpose of the embodiments as broadly described herein, there is provided a reciprocating compressor, including a frame for supporting a stator of a reciprocating compressor having a linearly-reciprocated mover, and having an oil passage, a cylinder fixedly coupled to the frame, a piston sidably inserted into the cylinder and reciprocating with the mover, and an oil pump installed between the frame and the cylinder so as to be connected to the oil passage of the frame and reciprocating with the piston, for generating a pumping force.

[0057] Any reference in this specification to "one embodiment," "an exemplary," "example embodiment," "certain embodiment," "alternative embodiment," and the like means that a particular feature, structure, or characteristic described in connection with the embodiment is included in at least one embodiment as broadly described herein. The appearances of such phrases in various places in the specification are not necessarily all referring to the same embodiment. Further, when a particular feature, structure, or characteristic is described in connection with any embodiment, it is submitted that it is within the purview of one skilled in the art to affect such feature, structure, or characteristic in connection with other ones of the embodiments.

[0058] Although embodiments have been described with reference to a number of illustrative embodiments thereof, it should be understood that numerous other modifications and embodiments can be devised by those skilled in the art that will fall within the spirit and scope of the principles of this disclosure. More particularly, numerous variations and modifications are possible in the component parts and/or arrangements of the subject combination arrangement within the scope of the disclosure, the drawings and the appended claims. In addition to variations and modifications in the component parts and/or arrangements, alternative uses will also be apparent to those skilled in the art.

Claims

1. A reciprocating compressor, comprising: a casing; a frame fixed within the casing and configured to support a stator coupled to a linearly-reciprocated mover; a cylinder fixed to the frame; a first piston coupled to the mover and configured to reciprocate within the cylinder as the mover reciprocates; and a pump installed between the frame and the cylinder so as to be in communication with a passage formed in the frame, wherein the pump is configured to reciprocate with the piston so as to generate a pumping force.

2. The reciprocating compressor of claim 1, wherein the pump is installed surrounding an outer circumferential surface of the cylinder.

3. The reciprocating compressor of claim 1, wherein the pump comprises: a second piston configured to reciprocate within a pocket defined by the cylinder and the frame, in a motion direction of the first piston; a valve configured to open and close the passage formed in the frame when the second piston is reciprocated; and one or more piston springs installed along a motion direction of the second piston and configured to elastically support a reciprocation of the second piston.

4. The reciprocating compressor of claim 3, wherein the second piston has a substantially cylindrical shape such that an inner circumferential surface of the second piston contacts an outer circumferential surface of the cylinder, and an outer circumferential surface of the oil piston contacts an inner circumferential surface of the frame.

5. The reciprocating compressor of claim 3, wherein the valve is substantially ring shaped, and wherein the valve comprises a suction valve portion at one side thereof and a discharge valve portion at another side thereof.

6. The reciprocating compressor of claim 5, wherein the valve is supported by a piston spring.

7. The reciprocating compressor of claim 3, wherein the piston spring is a compression coil spring.

8. The reciprocating compressor of claim 3, wherein the pump comprises an oil pump and the second piston comprises an oil piston, and wherein the oil pump is configured to pump oil through the passage so as to provide for lubrication between the first piston and the cylinder.

9. The reciprocating compressor of claim 1, wherein the pump is configured to reciprocate in response to air pressure developed in the mover.

10. The reciprocating compressor of claim 9, wherein the pump comprises: a second piston configured to reciprocate within a pocket formed between the cylinder and the frame, in a motion direction of the first piston; a valve configured to open and close the passage; a plurality of piston springs positioned on opposite sides of the second piston and orientated a motion direction of the second piston; and a spring supporting plate positioned between the cylinder and the frame and having a plurality of air passing holes formed therein, wherein the spring supporting plate is configured to support one of the plurality of piston springs, and to apply an air pressure difference due to a reciprocation of the first piston to the second piston.

11. The reciprocating compressor of claim 1, wherein the pump is coupled to the first piston so as to reciprocate as the first piston reciprocates.

12. The reciprocating compressor of claim 11, wherein the pump comprises: a second piston configured to reciprocate within a pocket formed between the cylinder and the frame, in a motion direction of the first piston; a valve configured to open and close the passage formed in the frame; and a plurality of piston springs installed on opposite sides of the second piston and oriented in a motion direction of the second piston, wherein one of the plurality of piston springs has a first end connected to the second piston and a second end connected to the first piston.

13. The reciprocating compressor of claim 11, wherein the pump comprises: a second piston and configured to reciprocate within a pocket formed between the cylinder and the frame, in a motion direction of the first piston; a valve configured to open and close the passage formed in the frame; a plurality of piston springs installed on opposite sides of the second piston and oriented in a motion direction of the second piston; a spring supporting plate positioned between the cylinder and the frame and having at least one opening formed therein, wherein the spring supporting plate is configured to support one of the plurality of piston springs; and a connection member configured to be slidably inserted into the at least one opening formed in the spring supporting plate, wherein the connection member is coupled to the second piston and the first piston.

14. The reciprocating compressor of claim 1, wherein the pump performs a reciprocation in response to an impact force which occurs when a part of the first piston periodically collides with a part of the pump.

15. The reciprocating compressor of claim 14, wherein the pump comprises: a second piston configured to reciprocate within a pocket formed between the cylinder and the frame, in a motion direction of the first piston; a valve configured to open and close the passage; a plurality of piston springs installed at opposite sides of the second piston and oriented in a motion direction of the second piston; a spring supporting plate positioned between the cylinder and the frame and having at least one opening formed therein, wherein the spring supporting plate is configured to support one of the plurality of piston springs; and a collision member protruding from the first piston and configured to be sidably inserted into the at least one opening in the spring supporting plate so as to periodically collide with the second piston.

16. The reciprocating compressor of claim 15, further comprising a collision plate positioned between one of the plurality of piston springs and the spring supporting plate, wherein the collision plate is configured to apply an impact force to the piston spring when the collision member collides with the collision plate.

17. The reciprocating compressor of claim 15, wherein the collision member is a compression coil spring.

18. The reciprocating compressor of claim 15, wherein the collision member extends from the first piston or from the second piston as a protrusion.