JP2007056721A - Swash plate compressor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a swash plate compressor in which at least one of a swash plate and shoes comprises a hard membrane formed of a DLC with increased wear resistance, seizure resistance, and adhesiveness. <P>SOLUTION: In this swash plate compressor, the rotating motion of a drive shaft is converted into the reciprocating motion of pistons by the swash plate 72 rotatable integrally with the drive shaft and the shoes 78 sliding on the swash plate 72. The swash plate compressor comprises the hard membrane 86 sliding on one of the swash plate 72 and the shoes 78 on at least the other. The hard membrane 86 is formed on a ferrous alloy base material and is formed of a diamond-like carbon substantially not containing hydrogen. In the hard membrane 86, a graphite rich layer 90 in which the ratio of graphite components is larger than that at the portion of the hard membrane 86 nearest the base material 80 is contained in the portion of the hard membrane 86 nearest the surface thereof. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a swash plate compressor.

  For example, a swash plate type compressor as a fluid machine applied to a refrigeration circuit of an air conditioning system for automobiles, etc., as a piston that receives power supply from a drive shaft through a swash plate and a shoe reciprocates in a cylinder bore. A series of processes including a suction step of refrigerant as a working fluid from the suction chamber into the cylinder bore, a compression step of the sucked working fluid, and a discharge step of the compressed working fluid from the cylinder bore to the discharge chamber are executed.

More specifically, the drive shaft passes through an annular swash plate, and the swash plate is fixed so as to be inclined or tiltable with respect to the drive shaft. On the other hand, a pair of shoes each having a substantially hemispherical shape is disposed on the tail portion of each piston, and the pair of shoes slides on the outer peripheral portion with the outer peripheral portion of the swash plate sandwiched therebetween.
The sliding surfaces of the swash plate and the shoe are lubricated by an oil film made of refrigerating machine oil (lubricating oil) contained in the refrigerant. However, in order to improve the wear resistance and seizure resistance of the sliding surface, the sliding surfaces of A film made of PTFE (polytetrafluoroethylene) was formed on the sliding surface of the plate.

In recent years, in order to further improve wear resistance and seizure resistance, a coating made of amorphous carbon containing hydrogen (DLC) is called DLC (Diamond Like Carbon) on the sliding surfaces of the swash plate and the shoe. Film) is formed (for example, Patent Document 1 and Patent Document 2).
JP 2001-280236 A JP 2001-271741 A

However, when the swash plate of Patent Document 1 and the shoe of Patent Document 2 are combined, that is, when a DLC film containing hydrogen is formed on the sliding surfaces of both the swash plate and the shoe, abnormal wear or burning of the DLC film occurs. There is a risk of sticking. This is due to the following reason.
When the rotational speed is high immediately after the compressor is operated at a low temperature, the oil film is washed away by the refrigerant, and the sliding surfaces of the swash plate and the shoe are likely to be in a dry state. For this reason, when a compressor repeats an operation | movement and a stop under low temperature, oil film cutting | disconnection will arise and DLC films will come into direct contact.

Here, since the main component of the DLC film is a non-metallic carbon atom, it has been considered that wear and seizure due to adhesion are less likely to occur than when the metal films are in direct contact with each other. However, in reality, when the DLC films containing hydrogen slide with each other, abnormal wear or seizure of the DLC film occurs due to adhesion even if the surface pressure is low.
Accordingly, the present inventors have advanced research and development of a swash plate and a shoe having a DLC film not containing hydrogen, and the DLC film not containing hydrogen does not adhere to each other but is applied to one of the swash plate and the shoe. However, in this research and development process, it was found that a DLC film that does not contain hydrogen in the swash plate and shoe is sufficient. We faced the problem that it was difficult to form with good adhesion.

  And further research and development, in the DLC film that does not contain hydrogen, if a graphite rich layer with a large proportion of the graphite component is previously formed on the surface, even if the graphite rich layer disappears due to wear, It has been discovered that the ratio of the graphite component on the newly exposed surface is larger than that at the beginning of the formation of the hard film, thereby improving the wear resistance and seizure resistance.

It has also been discovered that the adhesion of the DLC film is improved by selecting the type of substrate, forming a cured layer on the substrate surface, and forming an intermediate layer between the cured layer and the DLC film.
The present invention has been made on the basis of the above-mentioned circumstances. The object of the present invention is to provide a hard film made of DLC having at least one of a swash plate and a shoe improved in wear resistance, seizure resistance and adhesion. An object of the present invention is to provide a swash plate compressor.

In order to achieve the above object, the present inventors formed DLC films not containing hydrogen on swash plates and shoes under various conditions, and evaluated the wear resistance, seizure resistance and adhesion of these DLC films. Went. As a result, the inventors have conceived the following invention.
That is, according to the present invention, in the swash plate compressor in which the rotational motion of the drive shaft is converted into the reciprocating motion of the piston by the swash plate rotatable integrally with the drive shaft and the shoe sliding on the swash plate, A hard film sliding on the other of at least one of the swash plate and the shoe is formed, the hard film is formed on a base material made of an iron-based alloy, and is made of diamond-like carbon substantially free of hydrogen, and The swash plate compressor is characterized in that a portion of the hard film on the most surface side includes a graphite rich layer having a larger proportion of the graphite component than the portion of the hard film on the most substrate side ( Claim 1).

As a preferred embodiment, the graphite rich layer has a thickness in the range of 0.1 to 1 μm.
As a preferred embodiment, the surface region of the substrate on which the hard film is formed has a maximum roughness Rz of 2 μm or less (Claim 3).
As a preferred embodiment, the base material is made of one selected from chromium molybdenum steel and stainless steel, and a nitrided layer is formed by radical nitriding treatment on the surface region of the base material on which the hard film is formed. The nitride layer has a Vickers hardness Hv in the range of 700 to 1500 (claim 4).

As a preferred embodiment, an intermediate film made of one of chromium nitride and titanium nitride is further provided between the hard film and the base material (Claim 5).
As a preferred embodiment, the first hard film provided as the hard film on the swash plate has a thickness in the range of 1 to 8 μm, and the hardness of the first hard film is the thickness of the first hard film. The Vickers hardness Hv at the portion of the first hard film closest to the substrate is in the range of 1500 to 3000, and the Vickers hardness Hv at the graphite rich layer of the first hard film changes. Is in the range of 700-2000 (Claim 6).

  As a preferred embodiment, the second hard film provided as the hard film on the shoe has a thickness in the range of 1 to 5 μm, and the hardness of the second hard film is the thickness of the second hard film. The Vickers hardness Hv at the portion of the second hard film closest to the base material is in the range of 1500 to 3000, and the Vickers hardness Hv at the graphite rich layer of the second hard film changes. Is in the range of 700-2000 (Claim 7).

  As a preferred aspect, the shoe has a flat and circular sliding surface that is slid over the entire area by the swash plate, and at least the hard film is formed on the sliding surface. 8).

  According to the swash plate compressor according to the first aspect of the present invention, a hard film made of DLC (diamond-like carbon) substantially free of hydrogen is formed on at least one of the swash plate and the shoe. Since the surface includes a graphite rich layer, the friction coefficient of the hard film is lowered. As a result, good wear resistance and seizure resistance are ensured at the sliding portion between the swash plate and the shoe, and the power consumption of the compressor is reduced.

  In this compressor, even if the graphite rich layer disappears due to wear, the hard film made of DLC substantially free of hydrogen contains the graphite rich layer in advance, so that the surface of the newly exposed hard film The ratio of the graphite component at the site becomes larger. That is, when sliding, the graphite rich layer becomes a seed, and the diamond component spontaneously changes to the graphite component at the hard film portion immediately below the graphite rich layer, and the newly exposed hard film surface portion also becomes graphite. The proportion of ingredients increases. For this reason, the hard film made of DLC substantially not containing hydrogen has good wear resistance and seizure resistance over a long period of time, and the durability of the compressor is improved.

Moreover, in this compressor, even when a hard film is formed on both the swash plate and the shoe, the hard film is made of DLC not containing hydrogen, so that abnormal wear and seizure due to adhesion of the hard films are prevented. The For this reason, this swash plate type compressor operates stably with the sliding state between the swash plate and the shoe maintained well.
In the swash plate compressor according to claim 2, since the graphite rich layer has a thickness in the range of 0.1 to 1 μm, the diamond component is surely changed by the graphite component at the newly exposed hard film surface. To do.

In the swash plate compressor according to the third aspect, since the surface region of the base material on which the hard film is formed has a maximum roughness Rz of 2 μm or less, the adhesion of the hard film is improved. In particular, when the maximum roughness Rz is 0.8 μm or less, the adhesion of the hard film is further improved.
That is, if there is a local height difference in the surface area of the substrate on which the hard film is formed, the hard film peels off from the protruding part of the surface area during sliding, and the peeled hard film part is separated from the abrasive. The remaining hard film is worn out at an early stage. In this compressor, since the surface region of the base material on which the hard film is formed has a maximum roughness Rz of 2 μm or less, the hard film is prevented from being locally peeled and left by the peeled hard film portion. The hard film does not wear.

In the swash plate type compressor according to claim 4, the nitride layer formed on the surface of the base material made of one selected from chromium molybdenum steel and stainless steel has a Vickers hardness Hv in the range of 700 to 1500. The adhesion of the hard film is improved.
That is, when the hardness of the surface region of the base material forming the hard film is low, the hard film is easily deformed and peeled during sliding. In this compressor, since the nitride layer has a Vickers hardness Hv in the range of 700 to 1500, deformation of the hard film is prevented during sliding, and adhesion of the hard film is improved.

In the swash plate compressor according to claim 5, the adhesion of the hard film is further improved by forming an intermediate film made of one of chromium nitride and titanium nitride between the hard film and the nitride layer of the base material. . In particular, if an intermediate film made of one of chromium nitride and titanium nitride is formed between the hard film and the nitride layer of the base material, the adhesion of the hard film is further improved.
In the swash plate compressor according to claim 6, the first hard film is formed as a hard film on the swash plate, and the Vickers hardness Hv in the graphite rich layer of the first hard film is in the range of 700 to 2000. When the Vickers hardness Hv at the first hard film portion on the side is in the range of 1500 to 3000, the adhesion of the first hard film is further improved, and the shear strength of the first hard film is increased. Deformation of the first hard film is prevented. As a result, the coefficient of friction between the swash plate and the shoe is further reduced.

  In the swash plate compressor according to claim 7, the second hard film is formed as a hard film on the shoe, the Vickers hardness Hv in the graphite rich layer of the second hard film is in the range of 700 to 2000, and the most substrate side When the Vickers hardness Hv at the second hard film portion is in the range of 1500 to 3000, the adhesion of the second hard film is further improved, and the shear strength of the second hard film is increased to increase the second hard film. 2 Deformation of the hard film is prevented. As a result, the coefficient of friction between the swash plate and the shoe is further reduced.

  In the swash plate type compressor according to the eighth aspect, since the sliding surface of the shoe is flat, the surface pressure (extreme pressure) applied to the sliding surface during sliding is reduced, and between the swash plate and the shoe. This further improves the wear resistance and seizure resistance at the sliding portion.

FIG. 1 shows a swash plate compressor of one embodiment applied to a refrigeration circuit of an automotive air conditioning system.
The refrigeration circuit includes a circulation flow path 2 through which an HFC refrigerant such as R134a (hereinafter simply referred to as a refrigerant) circulates. The swash plate compressor is inserted in the circulation flow path 2, and a condenser 4, an expansion valve 6, and an evaporator 8 are sequentially inserted downstream of the swash plate compressor in the flow direction of the refrigerant.
The swash plate compressor is a variable capacity type, and includes a cylinder block 10, and a crankcase 12 is provided at one end of the cylinder block 10. A cylinder head 16 is provided at the other end of the cylinder block 10 via a valve plate 14, and the crankcase 12 and the cylinder head 16 are connected to each other by a connecting bolt that penetrates the cylinder block 10 and the valve plate 14. .

  A drive shaft 20 is disposed in the center of the crank chamber 18 defined by the cylinder block 10 and the crankcase 12, and one end side of the drive shaft 20 passes through the crankcase 12 and is connected to the crankcase via a bearing 22. 12 is rotatably supported. On the other hand, the other end of the drive shaft 20 enters a center hole 24 formed through the center of the cylinder block 10 in the axial direction, and is rotatably supported by the cylinder block 10 via a bearing 26.

  The driven side unit of the electromagnetic clutch 28 is fixed to one end of the drive shaft 20 protruding from the crankcase 12, and the rotor 30 constituting the drive side unit of the electromagnetic clutch 28 is rotatable to the crankcase 12 via a bearing 32. It is supported by. The rotor 30 incorporates a solenoid, a drive pulley 34 is fixed to the outer periphery thereof, and a belt 37 is looped between the drive pulley 34 and the vehicle engine 36. Accordingly, the drive pulley 34 is rotationally driven by the belt 37 during the operation of the engine 36. At this time, when the electromagnetic clutch 28 is turned on, the rotation of the drive pulley 34 is transmitted to the drive shaft 20, and the drive shaft 20 is Rotated in the direction.

For example, seven cylinder bores 38 are formed in the cylinder block 10. These cylinder bores 38 are arranged at equal intervals in the circumferential direction of the cylinder block 10, and each cylinder bore 38 passes through the cylinder block 10 in the axial direction in parallel with the drive shaft 20.
On the other hand, a discharge chamber 40 is defined in the center of the cylinder head 16, and an annular suction chamber 42 is defined around the discharge chamber 40. The discharge chamber 40 and the suction chamber 42 are respectively connected to the forward path and the return path of the circulation flow path 2 through a discharge port and a suction port (not shown) formed on the outer wall of the cylinder head 16.

The valve plate 14 sandwiched between the cylinder block 10 and the cylinder head 16 is formed with a discharge hole 44 and a suction hole 46 communicating with each cylinder bore 38 and the discharge chamber 40 and the suction chamber 42, respectively. The discharge hole 44 and the suction hole 46 are opened and closed by reed valves 48 and 50 as check valves, respectively.
Further, a high-pressure channel 52 is formed between the discharge chamber 40 and the crank chamber 18 so as to pass through the cylinder block 10 and the valve plate 14. An orifice filter 54 is disposed. The orifice filter 54 has an orifice tube 56 having an extremely small inner diameter, and the orifice tube 56 can reduce the pressure in the discharge chamber 40 to the crank chamber 18 and transmit it. The orifice filter 54 has a cylindrical filter material 58 that surrounds the end of the orifice tube 56 on the discharge chamber 40 side in order to prevent the orifice tube 56 from being clogged.

  On the other hand, the suction chamber 42 and the crank chamber 18 are connected through a low-pressure side passage that partially includes the central hole 24 of the cylinder head 10, and the low-pressure side passage is connected to an on-off valve disposed in the central hole 24. 60 is opened and closed under a predetermined condition. More specifically, the on-off valve 60 is closed when the pressure in the suction chamber 42 exceeds a predetermined upper limit value, thereby increasing the pressure in the crank chamber 18, while the pressure in the discharge chamber 40 reaches a predetermined upper limit value. When it exceeds, it opens, and the pressure in the crank chamber 18 is lowered.

  A piston 62 is slidably fitted in each cylinder bore 38 described above, and the reciprocating motion of the piston in the cylinder bore 38 is a process of sucking refrigerant from the suction chamber 42 to the cylinder bore 38 and sucking in the cylinder bore 38. A series of processes including a refrigerant compression process and a compressed refrigerant discharge process from the cylinder bore 38 to the discharge chamber 40 are performed. In other words, the reciprocating motion of the piston 62 includes the refrigerant suction process from the return path of the circulation flow path 2 to the compressor, the refrigerant compression process in the compressor, and the refrigerant discharge process from the compressor to the circulation flow path 2. Implement a series of processes.

  A base rotor 64 is concentrically fixed to the drive shaft 20 to impart reciprocating motion to the piston 62 described above, and a thrust bearing 66 is disposed between the base rotor 64 and the end wall of the crankcase 12. Yes. A tilt rotor 70 is connected to the base rotor 64 by a hinge 68, and the drive shaft 20 passes through the center of the tilt rotor 70. An annular swash plate 72 is fitted to the tilt rotor 70 from the outside. The swash plate 72 can tilt with respect to the drive shaft 20 via the base rotor 64, the hinge 68, and the tilt rotor 70, and It can rotate together.

A coil spring 74 inserted through the drive shaft 20 is disposed between the base rotor 64 and the tilt rotor 70, and the coil spring 74 presses and biases the tilt rotor 70 toward the cylinder block 10.
On the other hand, the end portion of each piston 62 protruding from the cylinder block 10 into the crank chamber 18 is formed as a tail portion 76. The tail portion 76 has a U-shape opening in the direction of the drive shaft 20 and in the circumferential direction, and a pair of hemispherical recesses are formed on the inner surfaces of the tail portions 76 that are separated from each other in the axial direction of the piston 62. A spherical seat is formed. A pair of hemispherical shoes 78 are disposed on the pair of spherical seats, and the outer peripheral portion of the swash plate 72 is slidably sandwiched between the shoes 78.

  More specifically, FIG. 2 schematically shows only the swash plate 72 and the shoe 78 of the swash plate compressor, and the swash plate 72 has main surfaces parallel to each other on both sides in the thickness direction. The outer peripheral area becomes a sliding surface with respect to the shoe 78. On the other hand, the shoe 78 has a circular and flat sliding surface that is slid by the sliding surface of the swash plate 72, and a hemispherical convex surface that is continuous with the outer edge of the sliding surface and can match the spherical seat. .

In FIG. 2, the swash plate and a part of the shoe are notched, and one of the seven pairs of shoes is omitted.
In the circle in FIG. 2, an enlarged cross section of a portion where the swash plate 72 and the shoe 78 slide together is shown. Each of the swash plate 72 and the shoe 78 is made of a base material 80 a made of SCM435 made of chrome molybdenum steel. 80b.

Nitride layers 82 a and 82 b mainly composed of iron nitride are formed on the surface of the substrate 80 by radical nitriding the substrate 80. The nitride layer 82 has a thickness in the range of 30 μm to 80 μm, and the nitride layer 82 has a Vickers hardness Hv in the range of 700 to 1500. The maximum roughness Rz of the nitride layer 82 is 2 μm or less.
Intermediate films 84a and 84b are formed on the nitride layers 82a and 82b by the PVD method. The intermediate films 84a and 84b are made of chromium nitride (CrN), and the thickness of the intermediate film 84 is in the range of 2 μm to 5 μm.

Immediately above the intermediate film 84, hard films 86a and 86b made of DLC (diamond-like carbon) substantially not containing hydrogen are formed, and the thickness of the hard film 86a of the swash plate 72 is in the range of 1 μm to 8 μm. The thickness of the hard film 86b of the shoe 78 is in the range of 1 μm to 5 μm.
Here, “substantially not containing hydrogen” means that hydrogen was not intentionally included when the hard film 86 was formed. Quantitatively speaking, the hydrogen concentration in the hard film 86 is unavoidable. It means that it is 0.5 mass% or less as a general impurity level.

DLC refers to a carbon material mainly composed of carbon elements bonded at short distances by sp ² bonds and sp ³ bonds and having an amorphous structure as a whole. That is, it refers to a carbon material having an amorphous structure in which a graphite component (sp ² bond) and a diamond component (sp ³ bond) are mixed.
More specifically, each hard film 86 has a laminated structure, and is composed of three layers of lower layers 88a and 88b, middle layers 90a and 90b, and upper layers 92a and 92b in this order from the intermediate film 84 side. In the hard film 86a of the swash plate 72, the Vickers hardness Hv of the lower layer 88a closest to the base material 80a is in the range of 1500 to 3000, and the Vickers hardness Hv of the uppermost layer 92a is 700 to 2000. It is in the range. The Vickers hardness Hv in the middle layer 90a is intermediate between the Vickers hardness Hv of the lower layer 88a and the upper layer 92a. That is, the Vickers hardness Hv of the hard film 86a increases stepwise as it approaches the intermediate layer 84a from the surface, as shown by the solid line A in FIG.

  On the other hand, in the hard film 86b of the shoe 78, the Vickers hardness Hv of the lower layer 88b is in the range of 1500 to 3000, and the Vickers hardness Hv of the upper layer 92b is in the range of 700 to 2000. The Vickers hardness Hv in the middle layer 90b is intermediate between the Vickers hardness Hv of the lower layer 88b and the upper layer 92b. That is, the Vickers hardness Hv of the hard film 86b also increases stepwise as it approaches the intermediate layer 84b from the surface.

The Vickers hardness Hv in the upper layer 92a of the swash plate 72 is smaller than the Vickers hardness Hv in the upper layer 92b of the shoe 78, and the difference in Vickers hardness Hv between the upper layers 92a and 92b is 500 or more and 1000 or less. Is in range.
In the upper layer 92, the ratio of the graphite bond to the diamond bond is larger than that in the middle layer 90 and the lower layer 88, and the thickness of the upper layer 92 is in the range of 0.1 μm to 1 μm.

The swash plate 72 and the shoe 78 described above can be manufactured as follows, for example.
First, an iron-based alloy material made of SCM435 that has been roughly processed into a predetermined shape is prepared, and one or both of grinding and lapping are applied to the region of the iron-based alloy material that forms the hard film to reduce the surface roughness. The base material 80 is obtained by adjusting.
Next, nitrogen is diffused on the surface of the obtained base material 80 by radical nitriding to form a nitrided layer 82.

  Alternatively, after the radical nitriding treatment, one or both of finish grinding and lapping can be performed to adjust the surface roughness. That is, an iron-based alloy material made of SCM435 roughly processed into a predetermined shape is prepared, and one or both of grinding and lapping are applied to the region of the iron-based alloy material forming the hard film to obtain the base material 80. . Next, nitrogen is diffused on the surface of the obtained base material 80 by radical nitriding treatment to form a nitrided layer. Thereafter, one or both of grinding and lapping are applied to the nitride layer to obtain a nitride layer 82 with adjusted surface roughness.

  After this, the base material 80 is disposed in the chamber of the PVD apparatus together with the two types of target materials for the intermediate film (CrN) and the hard film (DLC), and then by the PVD method (physical vapor deposition method), First, the intermediate film 84 is formed on the nitride layer 82. Then, a hard film 86 made of DLC is also formed on the formed intermediate film 84 by the PVD method, and the swash plate 72 or the shoe 78 is obtained.

When the hard film 86 is formed, the lower layer 88, the middle layer 90, and the upper layer 92 are sequentially formed by changing the film formation conditions step by step.
Hereinafter, the operation of the above-described refrigeration circuit will be described.
In this refrigeration circuit, when the swash plate compressor is operated by receiving power supply from the engine 36, the compressor sucks and compresses a low-temperature and low-pressure gas refrigerant (HFC refrigerant) from the return path of the circulation flow path 2, and then compresses it. The gas refrigerant is discharged to the forward path of the circulation flow path 2. The discharged high-temperature and high-pressure gas refrigerant is condensed when passing through the condenser 4 and becomes a liquefied state. The liquefied refrigerant undergoes adiabatic expansion when passing through the expansion valve 6, and its temperature and pressure are reduced to enter a gas-liquid mixed state. When the refrigerant in the gas-liquid mixed state flows into the evaporator 8, the liquid refrigerant in the gas-liquid mixed state vaporizes in the evaporator 8, and the gas refrigerant flows out of the evaporator 8. The gas refrigerant flowing out of the evaporator 8 is sucked into the compressor through the return path of the circulation flow path 2.

  In addition, a condenser fan and an evaporator fan (not shown) that form wind passing outside the condenser 4 and the evaporator 8 are arranged in the vicinity of the condenser 4 and the evaporator 8, respectively. The refrigerant | coolant which passes the condenser 4 is cooled because the container 4 receives ventilation. Further, the air passing through the evaporator 8 is deprived of vaporization heat by the liquid refrigerant in the evaporator 8 to become cold air, and the cold air is blown out to the passenger compartment, thereby cooling the passenger compartment.

Hereinafter, the operation of the swash plate compressor will be described in detail.
When the engine 36 is in operation, power from the engine 36 is transmitted to the drive pulley 34 of the swash plate compressor. When the electromagnetic clutch 28 is turned on at this time, the drive pulley 34 is integrated with the drive pulley 34. Thus, the drive shaft 20 is rotationally driven. Along with the rotation of the drive shaft 20, the swash plate 72 is also rotationally driven through the base rotor 64 and the tilt rotor 70, and the rotational motion of the swash plate 72 is converted into the reciprocating motion of the piston 62 through the shoe 78. . As the piston 62 reciprocates, the suction process in which the refrigerant in the suction chamber 42 is sucked into the cylinder bore 38 through the reed valve 50, the compression process in which the refrigerant is compressed in the cylinder bore 38, and the compressed refrigerant A discharge process of discharging into the discharge chamber 40 through the reed valve 48 is performed.

Thus, while the swash plate compressor performs the suction, compression, and discharge processes, the discharge amount of the compressed refrigerant discharged from the compressor to the forward path of the circulation flow path 2 by the autonomous opening / closing operation of the on-off valve 60. Is increased or decreased.
More specifically, for example, when the pressure in the discharge chamber 40 rises above a predetermined upper limit with an increase in the number of revolutions of the engine 36, the on-off valve 60 is closed and the gap between the crank chamber 18 and the suction chamber 42 is increased. As a result, the crank chamber 18 is reduced in pressure. Accordingly, when the pressure (back pressure) in the crank chamber 18 becomes larger than the pressure in the suction chamber 42, that is, the pressure in the cylinder bore 38 performing the suction process, the front (valve plate) 14 side) is applied. For this reason, the stroke length of the piston 62 is reduced, and the discharge amount of the compressed refrigerant from each cylinder bore 38 into the discharge chamber 40 is reduced.

The forward urging force applied to the piston 62 is also transmitted to the swash plate 72 via the tail portion 76 and the shoe 78, so that the swash plate 72 is brought into a virtual plane orthogonal to the drive shaft 20 by this urging force. In contrast, it is tilted so as to approach parallel. That is, FIG. 1 shows a cross section of the compressor when the refrigerant discharge amount is minimum.
On the other hand, when the heat load in the evaporator 8 increases and the pressure in the suction chamber 42 rises above a predetermined upper limit value, the on-off valve 60 opens and the crank chamber 18 and the suction chamber 42 communicate with each other. The pressure in the crank chamber 18 is reduced to the pressure in the suction chamber 42. Therefore, since the forward biasing force applied to the piston 62 is reduced, the stroke length of the piston 62 is increased, and the discharge amount of the compressed refrigerant from each cylinder bore 38 into the discharge chamber 40 is increased.

As the forward biasing force applied to the piston 62 decreases, the swash plate 72 tilts so as to incline with respect to a virtual plane orthogonal to the drive shaft 20.
In addition, while the swash plate compressor performs the suction, compression, and discharge processes, the lubricating oil accumulated at the bottom of the discharge chamber 40 passes through the orifice filter 54 disposed in the high-pressure side passage 26 and enters the crank chamber 18. Refluxed and used for lubrication of the sliding portion between the swash plate 72 and the shoe 78, the bearings 22 and 26, and the thrust bearing 66.

  In the swash plate compressor described above, the pressure in the discharge chamber 40, that is, the pressure in the cylinder bore 38 reaches approximately 3 to 4 MPa, and a very large compression reaction force is applied to the sliding portion between the swash plate 72 and the shoe 78. . That is, although a very large surface pressure is applied to the hard film 86, since the hard film 86 is made of DLC not containing hydrogen, adhesion between the hard films 86 is prevented, and abnormal wear and seizure of the hard films 86 are prevented. Is prevented. As a result, this swash plate compressor operates stably and has excellent durability.

Further, since the upper layer 92 positioned on the surface of the hard film 86 is formed as a graphite rich layer having a large proportion of the graphite component, the hard film 86 has a small coefficient of friction. As a result, good wear resistance and seizure resistance are ensured at the sliding portion between the swash plate 72 and the shoe 78, and the power consumption of the compressor is reduced.
In this swash plate compressor, even if the upper layer 92 as a graphite rich layer formed in advance disappears due to wear, the hard film 86 made of DLC substantially containing no hydrogen contained the graphite rich layer in advance. As a result, the ratio of the graphite component in the newly exposed surface portion of the hard film 86 increases. That is, when sliding, the graphite rich layer becomes a seed, and the diamond component spontaneously changes to the graphite component at the portion of the hard film 86 immediately below the graphite rich layer, and the newly exposed surface portion of the hard film 86. However, the proportion of the graphite component increases. For this reason, the hard film 86 made of DLC substantially not containing hydrogen has good wear resistance and seizure resistance over a long period of time, and the durability of the compressor is improved.

The present invention is not limited to the above-described embodiment, and various modifications can be made.
For example, in the refrigeration circuit to which the swash plate type compressor of one embodiment described above is applied, although the HFC refrigerant circulates as the refrigerant, the type of the refrigerant is not particularly limited, for example, a natural refrigerant such as CO ₂ or the like May be used as a refrigerant.
In the embodiment described above, the base material 80 is made of SCM435, and the nitride layer 82 is formed on the surface of the base material 80. However, the material of the base material 80 is not particularly limited, and other types of SCM, structural carbon. Iron-based alloys such as steel, structural alloy steel, structural special steel, bearing steel, and free-cutting steel can be used. Further, the nitride layer 82 may not be formed on the surface of the substrate 80.

  However, if the hardness of the surface region of the base material 80 on which the hard film 86 is formed is low, the hard film 86 is easily deformed and peeled off during sliding. For this reason, in order to improve the adhesiveness of the hard film 86, the material of the base material 80 is Hv at a portion from the surface to a depth of 0.5 mm by heat treatment (quenching-tempering), carburizing treatment, nitriding treatment, or the like. It is preferable to use an iron-based alloy having a (Vickers hardness) of 550 or more. It is preferable to further form a nitride layer 82 formed by radical nitriding on the surface of the substrate 80.

  The surface roughness of the nitride layer 82 formed on the surface of the substrate 80 is not particularly limited, but preferably has a maximum roughness Rz of 2 μm or less, and more preferably has a maximum roughness Rz of 0.8 μm or less. preferable. If there is a local height difference in the surface region of the base material 80 forming the hard film 86, the hard film 86 peels off from the protruding portion of the surface region during sliding, and the peeled hard film 86 portion is an abrasive. Thus, the remaining hard film 86 is worn out at an early stage. In this compressor, since the surface region of the base material 80 on which the hard film 86 is formed has a maximum roughness Rz of 2 μm or less, the hard film 86 is prevented from being locally peeled, and the peeled hard film 86 The hard film 86 left by the portion is not worn. According to experiments, the maximum roughness Rz of the nitride layer 82 is more preferably 0.8 μm or less.

The hardness of the nitride layer 82 is not particularly limited, but is preferably in the range of 700 to 1500 in terms of Vickers hardness Hv, and local dents are prevented. As a result, the hard film 86 is prevented from being locally recessed and peeled, and the adhesion of the hard film 86 is improved.
Further, the thickness of the nitride layer 82 is not particularly limited, but is preferably in the range of 30 μm to 80 μm. This is because when the thickness of the nitride layer 82 is 30 μm or less, the adhesion of the hard film 86 is not sufficiently improved, and when it exceeds 80 μm, the adhesion of the hard film 86 does not change.

When the nitride layer 82 is formed by radical nitriding, the base material 80 is made of a material selected from chromium molybdenum steel such as SCM435, stainless steel such as SUS410, and structural alloy steel. preferable. This is because nitrogen easily diffuses into these chromium molybdenum steel and stainless steel.
In the above-described embodiment, the intermediate film 84 made of chromium nitride is formed between the hard film 86 and the nitride layer 82 of the substrate 80, but the sliding between the swash plate 72 and the shoe 78 is performed. If the condition is mild, the intermediate film 84 may not be formed. However, since the adhesion of the hard film 86 to the base material 80 is improved through the intermediate film 84, it is preferable to form the intermediate film 84. The material of the intermediate film 84 is preferably chromium nitride, but titanium nitride (TiN) may be used instead of chromium nitride, and the thickness of the intermediate film 84 is preferably in the range of 2 μm to 5 μm. .

In the embodiment described above, the hard film 86 is formed on both the swash plate 72 and the shoe 78, but the hard film 86 may be formed on only one of them. This is because if at least one graphite rich layer is formed, the graphite component of the graphite rich layer is transferred to the other by sliding, and the transferred graphite component functions as a solid lubricant.
Here, when the hard film 86a is formed only on the swash plate 72 and the hard film 86b is not formed on the shoe 78, a hardened shoe 78 made of an iron-based alloy such as SUJ2 may be used. The hard film 86 of the swash plate 72 may be formed at least in a sliding area with the shoe 78.

  In the embodiment described above, the hard film 86 has a laminated structure, but instead of the hard film 86, as shown in FIG. 4, the Vickers hardness Hv is approached from the surface toward the intermediate layer 84. Alternatively, a hard film 94 having an inclined structure in which the thickness increases continuously may be formed. The Vickers hardness Hv of the hard film 94 is indicated by a broken line B in FIG. 3. In this case, the hard film 94 on the most surface side is located at the hard film 94 on the intermediate film 84 side. In comparison, the proportion of the graphite component is increased.

In order to surely change the graphite component by the diamond component, the structure of the hard film is preferably an inclined structure in which the hardness changes continuously rather than a laminated structure in which the hardness changes stepwise.
In any of the laminated structure and the inclined structure, in the hard films 86a and 94a of the swash plate 72, the Vickers hardness Hv of the most surface side portion (upper layer 92), that is, the graphite rich layer is 700 or more and 2000 or less. It is preferable that the Vickers hardness Hv at the portion (lower layer 88) located closest to the base material 80a is in the range of 1500 to 3000.

Further, in the hard films 86b and 94b of the shoe 78, the most surface portion (upper layer 92b), that is, the Vickers hardness Hv of the graphite rich layer is in the range of 700 to 2000, and the portion (most located on the substrate 80b side). The Vickers hardness Hv in the lower layer 88b) is preferably in the range of 1500 or more and 3000 or less.
In the case of such a laminated structure and an inclined structure, the residual stress in the hard films 86 and 94 is alleviated, the adhesion of the hard films 86 and 94 to the base material 80 is further improved, and the shear strength of the hard films 86 and 94 is increased. This is because the deformation of the hard film 86 during sliding is prevented and the friction coefficient between the swash plate 72 and the shoe 78 is further reduced.

  Although the total thickness of the hard film 86 is not particularly limited, the thickness of the hard film 86a on the swash plate 72 is preferably in the range of 1 μm to 8 μm. The thickness is preferably in the range of 1 μm to 5 μm. If the thickness of the hard films 86a and 86b is less than 1 μm, it will be difficult to ensure sufficient wear resistance and seizure resistance. If the thickness of the hard film 86 exceeds 5 μm or 8 μm, it takes time to form the film. This is because the internal residual stress of the hard film 86 is increased and the adhesion of the hard film 86 is lowered.

And it is preferable that the thickness of the upper layer 92 as a graphite rich layer in the hard film | membrane 86 exists in the range of 0.1-1 micrometer. This is because when the thickness of the graphite rich layer is in the range of 0.1 to 1 μm, the diamond component is surely changed by the graphite component at the newly exposed surface portion of the hard film 86.
In the above-described embodiment, the grinding method of the iron-based alloy material when preparing the base material 80 is not particularly limited, and, as shown in FIGS. 5A to 5C, one linear direction ( Parallel), two linear directions intersecting each other (cross stitch), circumferential directions (concentric circles), and a combination of these directions can be ground, but grinding is preferably performed.

In the above-described embodiment, the PVD method for forming the hard film 86 is not particularly limited, but it is preferable to use, for example, the UBMS (Unbalanced Magnetron Sputtering) method disclosed in Japanese Patent Application Laid-Open No. 2000-119843.
In the UBMS method, the first magnet installed in the center of the back surface of the circular target material made of solid carbon and the second magnet arranged around the first magnet have different magnetic characteristics, so that the first A part of the magnetic field lines formed by the second magnet extends from the target material toward the base material 80 (intermediate layer 84). A part of the magnetic field lines guides a part of the plasma generated during sputtering of the target material to the vicinity of the surface of the intermediate layer 84, and the ion assist effect of the plasma guided to the vicinity of the surface of the intermediate layer 84 makes the DLC harder. The hard film 86 made of is easily formed on the intermediate layer 84.

According to the UBMS method, the hardness of the hard film 86 and the ratio of the graphite component can be changed by adjusting film forming conditions such as a bias voltage applied to the substrate 80.
Further, according to the UBMS method, after the intermediate film 84 is formed, the hard film 86 is continuously formed in the chamber of the PVD apparatus, thereby preventing the surface of the intermediate film 84 from being oxidized. The adhesion of the hard film 86 is further improved.

In one embodiment described above, the sliding surface of the shoe 78 is shown in FIG. 6A in order to reduce the surface pressure (extreme pressure) at the sliding portion between the swash plate 72 and the shoe 78. However, as shown schematically in FIG. 6B, the sliding surface of the shoe 78 may protrude by about 1 μm due to manufacturing restrictions.
Although the swash plate compressor of the above-described embodiment is an internal control type variable displacement swash plate compressor in which the on-off valve 60 is opened and closed autonomously, the swash plate compressor of the present invention is not limited to the on-off valve 60. Instead of this, it is also applicable to an external control type variable displacement swash plate compressor having an electromagnetic on-off valve that is opened and closed by a drive circuit provided outside, and further, a fixed displacement swash plate compressor It is also applicable to.

  Finally, the swash plate compressor of the present invention can be applied to a refrigeration circuit of a home / commercial air conditioning system, a refrigeration / refrigerator, a heat pump system, etc. in addition to a refrigeration circuit of an automotive air conditioning system. It is.

It is a figure which shows the longitudinal cross-section of the swash plate type compressor of one Example applied to the freezing circuit of the air conditioning system for motor vehicles. 1 is a perspective view schematically showing a part of a swash plate and a shoe applied to the compressor of FIG. 1, and a part of a cross section of a sliding portion between the swash plate and the shoe is shown in a circle. FIG. It is the figure which showed typically the relationship between the position in the film thickness direction in a hard film, and Vickers hardness Hv. It is a figure which expands and shows a part of cross section of the sliding site | part between the swash plate of a modification, and a shoe. It is a figure for demonstrating the grinding method of the iron type alloy material processed into a swash plate, (a) is the iron type alloy material ground in one linear direction, (b) is two straight lines which mutually cross | intersect. Directionally ground iron-based alloy material, (c) shows the iron-based alloy material ground in the circumferential direction. It is the side view which showed the shoe typically, (a) shows the shoe of an example, and (b) shows the side of the shoe of a modification.

Explanation of symbols

72 Swash plate 78 Shoe 80, 80a, 80b Base material 82, 82a, 82b Nitride layer 84, 84a, 84b Intermediate film 86, 86a, 86b Hard film 88, 88a, 88b Lower layer 90, 90a, 90b Middle layer 92, 92a, 92b Upper layer (graphite rich layer)

Claims (8)

In the swash plate compressor in which the rotational motion of the drive shaft is converted into the reciprocating motion of the piston by a swash plate that can rotate integrally with the drive shaft and a shoe that slides on the swash plate,
A hard film that slides on the other of at least one of the swash plate and the shoe,
The hard film is
Formed on a base material made of iron-based alloy,
Made of diamond-like carbon substantially free of hydrogen, and
A swash plate compressor, wherein the hard film portion on the most surface side includes a graphite rich layer having a larger proportion of the graphite component than the hard film portion on the most base side.   2. The swash plate compressor according to claim 1, wherein the graphite rich layer has a thickness in a range of 0.1 to 1 [mu] m.   The swash plate compressor according to claim 1 or 2, wherein the surface region of the base material on which the hard film is formed has a maximum roughness Rz of 2 µm or less. The base material consists of a kind selected from chromium molybdenum steel and stainless steel,
The surface region of the base material on which the hard film is formed is formed with a nitride layer by radical nitriding, and the nitride layer has a Vickers hardness Hv in a range of 700 to 1500. The swash plate type compressor according to any one of Items 1 to 3.   The swash plate compressor according to any one of claims 1 to 4, further comprising an intermediate film made of one of chromium nitride and titanium nitride between the hard film and the base material. The first hard film provided as the hard film on the swash plate has a thickness in the range of 1 to 8 μm,
The hardness of the first hard film varies in the thickness direction of the first hard film, and the Vickers hardness Hv at the portion of the first hard film closest to the substrate is in the range of 1500 to 3000. The swash plate compressor according to any one of claims 1 to 5, wherein a Vickers hardness Hv of the first hard film in the graphite rich layer is in a range of 700 to 2000. The second hard film provided as the hard film on the shoe has a thickness in the range of 1 to 5 μm,
The hardness of the second hard film varies in the thickness direction of the second hard film, and the Vickers hardness Hv at the portion of the second hard film closest to the substrate is in the range of 1500 to 3000. The swash plate compressor according to any one of claims 1 to 6, wherein a Vickers hardness Hv of the second hard film in the graphite-rich layer is in a range of 700 to 2,000. The shoe has a flat and circular sliding surface that is slid over the entire area by the swash plate,
The swash plate compressor according to any one of claims 1 to 7, wherein the hard film is formed on at least the sliding surface.

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