Rotary compressor

Abstract

To provide an oil-free rotary compressor that reduces frictional resistance of piston rotational sliding within a cylinder while dispensing with lubricating oil.SOLUTION: A rotary compressor (1) comprises: a piston (8) eccentrically rotating along an inner circumferential wall of a cylinder hole (7a) of a cylinder member (7) accommodated in a case (2); a rotary shaft (10) integrally coupled with a crankshaft (9) that causes the piston (8) to eccentrically rotate; and a driving device (6) that drives the rotary shaft (10). The piston (8) has a double structure of a cylindrical inner piston (32) eccentrically rotated by the crankshaft (9) and a cylindrical outer piston (33) rotatably fitted around an outer periphery of the inner piston (32), the inner piston (32) and the outer piston (33) being formed of a member with a self-lubricating coating or of a self-lubricating material.SELECTED DRAWING: Figure 4

Description

[Technical Field]

[0001] The present invention relates to a rotary compressor, and more particularly to an oil-free rotary compressor that can reduce the frictional resistance of the piston rotation and sliding within a cylinder without using lubricating oil. [Background technology]

[0002] Conventionally, rotary compressors have been widely used, each of which includes a compression mechanism that compresses refrigerant gas and has a cylinder, a piston that rotates eccentrically within the cylinder, a crankshaft that rotates the piston, and a vane that slides against the outer circumferential surface of the piston, a drive device that drives the crankshaft, and a reservoir that stores lubricating oil that lubricates the compression mechanism.

[0003] For example, the rotary compressor described in Patent Document 1 has a piston that rotates eccentrically inside a cylinder and has a double structure of an outer roller and an inner roller, and a vane whose tip is in sliding contact with the outer surface of the outer roller, and lubricating oil is supplied between the outer roller and the inner roller by a V-groove formed on the outer surface of the inner roller.

[0004] The rotary compressor described in Patent Document 2 has a piston that rotates eccentrically inside a cylinder and has a double structure of an outer roller and an inner roller, and a vane whose tip is slidably engaged in a recess formed on the outer surface of the outer roller, and the roller and vane are provided with oil holes. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Patent Publication No. 2-207188 [Patent Document 2] Japanese Patent Application Publication No. 8-151988 Summary of the Invention [Problem to be solved by the invention]

[0006] In the rotary compressors of Patent Documents 1 and 2, the sliding speed changes from moment to moment due to changes in the viscosity of the lubricating oil caused by temperature changes and changes in the oil film thickness caused by the changes in viscosity of the lubricating oil, resulting in unstable sliding motion, making it difficult to reduce the frictional resistance of the rotating sliding of the piston inside the cylinder and the wear of the piston and vanes.

[0007] Furthermore, when rotary compressors are used in refrigeration and air conditioning equipment, heat pump units, etc., the refrigerant gas is mixed with lubricating oil and circulated through the compression mechanism. However, when the refrigerant gas mixed with the lubricating oil is discharged from the compression mechanism to the heat exchanger, an oil film of the lubricating oil adheres to the inside of the tubes of the heat exchanger, resulting in a decrease in heat exchange efficiency.

[0008] An object of the present invention is to provide an oil-free rotary compressor that can reduce the frictional resistance of the piston rotation and sliding within the cylinder without using lubricating oil. [Means for solving the problem]

[0009] The rotary compressor of claim 1 comprises a cylinder member having a cylinder bore housed in a case, a piston that rotates eccentrically along the inner circumferential wall of the cylinder bore, a crankshaft that rotates the piston eccentrically, a rotating shaft that is integrally connected to the crankshaft, a drive unit that drives the rotating shaft, and a vane that is reciprocally mounted in a vane groove provided in the cylinder member and abuts against the piston to divide the inside of the cylinder bore into a suction chamber and a compression chamber, wherein the piston has a dual structure consisting of a cylindrical inner piston that rotates eccentrically due to the crankshaft and a cylindrical outer piston that is rotatably fitted around the outer periphery of the inner piston, and the inner piston and the outer piston are formed from a member having a self-lubricating coating or a self-lubricating material.

[0010] According to the above configuration, in the double-structure piston, the inner piston is rotated eccentrically by the crankshaft, but the outer piston oscillates without rotating eccentrically, thereby reducing the sliding resistance of the piston rotation and sliding within the cylinder member.

[0011] Furthermore, because the inner and outer pistons are formed from members or materials with a self-lubricating coating, they are not affected by changes in the viscosity of the lubricating oil or the oil film thickness that occur with temperature changes, and the sliding speed is always stable, which further reduces the frictional resistance of the pistons' rotational sliding within the cylinder member.

[0012] Furthermore, since no lubricating oil is used, there is no need to provide a reservoir for storing lubricating oil within the case, which allows the rotary compressor to be made smaller and reduces the environmental impact.

[0013] When the rotary compressor is used in a refrigeration / air conditioning device, a heat pump unit, or the like, the lubricating oil is not mixed into the refrigerant gas, so that a decrease in the heat exchange efficiency in the heat exchanger can be prevented.

[0014] The rotary compressor of claim 2 is the invention of claim 1, characterized in that a recess extending in the axial direction is provided on the outer periphery of the outer piston, the tip of the vane contacts the recess, and the vane is made of a member having a self-lubricating coating or a self-lubricating material. According to the above configuration, the tip of the vane engages with the recess of the outer piston, suppressing eccentric rotation of the outer piston and allowing only swinging motion of the outer piston without rotation, thereby reducing frictional resistance of the piston's rotational sliding within the cylinder member and reducing piston wear.

[0015] A rotary compressor according to a third aspect of the present invention is characterized in that, in the invention of the second aspect, a plurality of annular grooves are provided on the inner peripheral surface of the outer piston. According to the above configuration, by filling the annular groove with grease, it is possible to reduce the sliding resistance between the outer peripheral surface of the inner piston and the inner peripheral surface of the outer piston.

[0016] The rotary compressor of claim 4 is characterized in that, in any one of claims 1 to 3, piston ring mounting grooves are provided on both end surfaces of the piston, and piston rings are fitted in the piston ring mounting grooves. According to the above-described configuration, the piston ring mounting groove and the piston ring can ensure sealing between both end surfaces of the piston and the cover member that closes the cylinder bore. [Effects of the Invention]

[0017] According to the present invention, the above-mentioned various actions and effects can be obtained. [Brief explanation of the drawings]

[0018] [Figure 1] 1 is a perspective view of a rotary compressor according to an embodiment of the present invention. [Figure 2] FIG. 2 is a vertical cross-sectional view of the compressor. [Figure 3] FIG. 3 is a cross-sectional view taken along line III-III in FIG. 2. [Figure 4] FIG. DETAILED DESCRIPTION OF THE INVENTION

[0019] DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, a mode for carrying out the present invention will be described based on an embodiment (see FIGS. 1 to 4). In FIG. 1, reference character F indicates the front, and character L indicates the left. [Example]

[0020] As shown in Figures 1 to 4, in a horizontal rotary compressor 1, a sealed container 4 is formed by a main body housing 2 (case) and a cup-shaped lid 3 fixed to the end of the main body housing 2, and a compression mechanism 5 and a drive unit 6 are incorporated inside this sealed container 4.

[0021] The compression mechanism 5 has a cylinder member 7 having a circular cylinder hole 7a, a cylindrical piston 8 eccentrically rotatably incorporated along the inner peripheral wall of the cylinder hole 7a, a crankshaft 9 that rotates the piston 8 eccentrically, a rotating shaft 10 that is integrally connected to the crankshaft 9 and has an axis X that extends horizontally, a first cylinder cover 11, and a second cylinder cover 12, and has the function of compressing refrigerant gas. The drive device 6 for driving the rotary shaft 10 is composed of an electric motor in which a rotor 13 and a stator 14 are housed in a case 6a.

[0022] The housing of this compressor 1 is composed of a main housing 2, which is a cylindrical body with a bottom and an open rear end, and which houses a compression mechanism section 5, and a cup-shaped lid body 3 fixed to the rear end of the cylindrical body, forming a sealed container 4. A hexagonal flange 2a of the main body housing 2 and a hexagonal flange 3a of the cover 3 are connected together by bolting.

[0023] As shown in Figures 3 and 4, in the compression mechanism 5, the cylinder member 7 is formed with an intake port 15 for introducing low-pressure refrigerant gas from the outside of the cylinder bore 7a, and a discharge port 16 for discharging high-pressure refrigerant gas from the inside of the cylinder bore 7a to the outside.

[0024] A vane 18 is mounted in a vane groove 17 formed in the lower part of the cylinder member 7 so as to be able to reciprocate radially, and the vane 18 is urged toward the piston 8 by a compression spring 20 mounted on a retaining member 19 fixed to the lower end of the cylinder member 7, with the tip of the vane 18 always engaging a recess 34 on the outer periphery of the piston 8. The cylinder bore 7a is divided by the vane 18 into a suction chamber 21 communicating with the suction port 15 and a compression chamber 22 communicating with the discharge port 16.

[0025] The first cylinder cover 11 and the second cylinder cover 12 are arranged to sandwich the cylinder member 7 from both the front and rear in the axial direction. The first cylinder cover 11 closes one axial end face (front face) of the cylinder member 7, and the second cylinder cover 12 closes the other axial end face (rear face) of the cylinder member 7.

[0026] The first cylinder cover 11 has an insertion hole 23 through which the rotating shaft 10 is rotatably inserted. A counterweight 10a and the first cylinder cover 11 are attached to the rear end of the rotating shaft 10, and the rear end of the rotating shaft 10 is connected to the crankshaft 9.

[0027] The second cylinder cover 12 is formed with a suction hole 24 communicating with the suction port 15 and a discharge hole 25 communicating with the discharge port 16. The suction hole 24 and the discharge hole 25 each extend through in the axial direction. A flapper valve 26 that opens and closes the discharge port 16 is attached to the second cylinder cover 12 via a fixing member 27, and the flapper valve 26 is elastically biased toward the closed position.

[0028] An inlet pipe 29, into which refrigerant gas is introduced, is connected to suction hole 24 via a connecting metal fitting 28 (see FIGS. 1 and 2). Discharge hole 25 is connected to a discharge gap 40 between lid body 3 and second cylinder cover 12 (see FIGS. 1 and 2). A discharge pipe 31, which discharges compressed high-pressure refrigerant gas, is attached to the rear wall of lid body 3 via a connecting metal fitting 30 and is connected to discharge gap 40.

[0029] The piston 8 has a double structure consisting of a cylindrical inner piston 32 and a cylindrical outer piston 33 that is rotatably and slidably fitted onto the outer periphery of the inner piston 32, and the inner piston 32 and the outer piston 33 can slide and rotate relative to each other, and the outer periphery of the inner piston 32 slides and rotates relative to the inner periphery of the outer piston 33.

[0030] An axially extending recess 34 is provided on the outer periphery of the lower end of the outer piston 33, and the tip of the vane 18 is arranged so as to contact the recess 34, and the tip of the vane 18 is slidably engaged with the recess 34.

[0031] The inner piston 32 rotates eccentrically around the eccentric crankshaft 9 in conjunction with the rotation of the rotary shaft 10. The outer piston 33 oscillates around the crankshaft 9 along the inner circumferential wall of the cylinder bore 7a without rotating on its own axis because the eccentric rotation is suppressed by the engagement between the tip of the vane 18 and the recess 34.

[0032] An annular piston ring mounting groove 35 is provided on the front end surface and the rear end surface of the inner piston 32 to seal the gap with the inner surfaces of the cylinder covers 11, 12, and a pair of piston rings 36 is fitted in the piston ring mounting groove 35.

[0033] With the inner piston 32 inserted and mounted in the outer piston 33, annular piston ring mounting grooves (not shown) are formed on the front and rear end surfaces of these pistons 32, 33, and a pair of piston rings 38 are mounted in these piston ring mounting grooves. A plurality of annular grooves 39 are formed on the inner peripheral surface of the outer piston 33, and these annular grooves 39 are filled with grease for lubrication.

[0034] Here, the rotary compressor 1 is an oil-free compressor, as the sliding members of the compression mechanism 5 are made of members having a self-lubricating coating or self-lubricating materials.

[0035] The inner piston 32 and the outer piston 33 may be made of a self-lubricating material, such as a fluororesin such as Teflon (registered trademark) or a carbon fiber composite material obtained by combining carbon fiber with carbon or metal powder, or may be made of a steel member having a self-lubricating coating (for example, a fluororesin coating or a DLC coating) formed on the surface thereof.

[0036] The cylinder member 7 may be made of a self-lubricating material such as cast iron or stainless steel, or may be made of a steel member with a self-lubricating coating (for example, a fluororesin coating or a DLC coating) formed on the surface thereof. The vane 18 may be made of a self-lubricating material such as a carbon fiber carbon composite material or a fluororesin, or may be made of ductile cast iron with a self-lubricating coating (for example, a fluororesin coating or a DLC coating) formed on the surface.

[0037] The crankshaft 9 may be made of ductile cast iron or cast steel with a self-lubricating coating (for example, a fluororesin coating or a DLC coating) formed on the surface thereof. The piston rings 36, 38 may be made of a fluororesin-based material, or may be made of a metal material with a fluororesin coating or DLC coating formed on the surface thereof. The cylinder covers 11 and 12 may be made of a self-lubricating fluororesin or the like. The member may be made of a metal member having a self-lubricating coating formed on the surface thereof.

[0038] The operation and effects of the rotary compressor 1 described above will now be described. The piston 8 has a dual structure consisting of a cylindrical inner piston 32 that rotates eccentrically due to the crankshaft 9, and a cylindrical outer piston 33 that is rotatably fitted around the outer periphery of the inner piston 32, and the tip of the vane 18 is abutted against and engaged with the recess 34 of the outer piston 33. As a result, the inner piston 32 is rotated eccentrically due to the crankshaft 9, but the outer piston 33 oscillates without rotating eccentrically, thereby reducing the sliding resistance of the pistons when they rotate inside the cylinder member 7.

[0039] Furthermore, since the inner and outer pistons 32, 33 are formed from members or materials having a self-lubricating coating, they are not affected by changes in the viscosity of the lubricating oil or the oil film thickness that occur due to temperature changes, and the sliding speed is always stable, thereby further reducing the frictional resistance of the pistons' rotational sliding within the cylinder member 7.

[0040] Since no lubricating oil is used, there is no need to provide a reservoir for storing lubricating oil inside the case 2, which allows the rotary compressor to be made smaller and reduces the environmental impact. When the rotary compressor 1 is used in a refrigeration air conditioning device, a heat pump unit, or the like, the lubricating oil is not mixed into the refrigerant gas, so that a decrease in the heat exchange efficiency in the heat exchanger can be prevented.

[0041] A plurality of annular grooves 39 are provided on the inner peripheral surface of the outer piston 33, and by filling the annular grooves 39 with grease, it is possible to reduce the sliding resistance between the outer peripheral surface of the inner piston 32 and the inner peripheral surface of the outer piston 33.

[0042] Piston ring mounting grooves 35 are provided on both end faces of the inner piston 32, and piston rings 36 are mounted in the piston ring mounting grooves 35. Piston rings 38 are mounted in piston ring mounting grooves formed by recesses on the outer peripheral surface of the inner piston 32 and on both end faces of the outer piston 33. This ensures sealing between both end faces of the inner piston 32 and the outer piston 33 and the cylinder covers 11, 12.

[0043] The embodiment described above is merely an example, and those skilled in the art can implement the invention in various modified forms. [Explanation of symbols]

[0044] 1 Rotary compressor 2 Main body housing 6. Drive unit 7 Cylinder parts 7a Cylinder hole 8 pistons 9 Crankshaft 10 Rotation axis 17 Vane groove 18 vanes 21 Suction chamber 22 Compression chamber 32 Inner piston 33 Outer piston 34 Recess 35 Piston ring mounting groove 36, 38 Piston rings 39 Annular groove

Claims

1. A rotary compressor comprising: a cylinder member having a cylinder bore housed in a case; a piston that rotates eccentrically along an inner peripheral wall of the cylinder bore; a crankshaft that rotates the piston eccentrically; a rotary shaft that is integrally connected to the crankshaft; a drive device that drives the rotary shaft; and a vane that is reciprocally mounted in a vane groove provided in the cylinder member and abuts against the piston to divide the interior of the cylinder bore into a suction chamber and a compression chamber, a rotary compressor, characterized in that the piston has a dual structure consisting of a cylindrical inner piston that rotates eccentrically about the crankshaft and a cylindrical outer piston that is rotatably fitted around the outer periphery of the inner piston, and the inner piston and the outer piston are formed from a member having a self-lubricating coating or a self-lubricating material.

2. 2. The rotary compressor according to claim 1, wherein a recess extending in the axial direction is provided on the outer periphery of the outer piston, a tip end of the vane contacts the recess, and the vane is made of a member having a self-lubricating coating or a self-lubricating material.

3. 3. The rotary compressor according to claim 2, wherein a plurality of annular grooves are formed on the inner peripheral surface of the outer piston.

4. 4. The rotary compressor according to claim 1, wherein piston ring mounting grooves are provided on both end surfaces of the piston, and piston rings are fitted in the piston ring mounting grooves.

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