Single-headed piston type swash-plate-operated compressor and a method of producing a swash plate

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a single-headed piston type refrigerant compressor of the type in which rotation of a swash plate is converted into a reciprocation of a plurality of single-headed pistons via a plurality of pairs of shoes arranged between an outer periphery of the swash plate and the single-headed pistons. The present invention also relates to a method of producing a swash plate suitable for being incorporated in the above-mentioned type of single-headed piston type refrigerant compressor.

2. Description of the Prior Art

A swash-plate-operated refrigerant compressor, either a double-headed piston type refrigerant compressor or a single-headed piston type refrigerant compressor, has a housing assembly including a cylinder block provided with a plurality of cylinder bores formed therein, a plurality of pistons respectively slidably fitted in the cylinder bores, a drive shaft supported by the housing assembly to be rotatable about an axis of rotation, and a swash plate fixedly mounted on the drive shaft within a crank chamber at a constant inclination with respect to a plane perpendicular to the axis of rotation of the drive shaft or mounted on the drive shaft so that its inclination can be adjustably changed in the crank chamber. A part of each piston, i.e., a substantially middle part if the piston is of a double-headed type or an end part opposite the compressing end surface if the piston is of a single-headed type, is connected to a peripheral part of the swash plate via a pair of shoes to provide an operative engagement between each piston and the swash plate. This operative engagement of each piston and the awash plate permits the conversion of rotating motion of the drive shaft and the swash plate into a reciprocating motion of each piston.

In this regard, it is an important technical problem to avoid seizure between the front and the rear surface of the swash plate and the pair of shoes as well as to reduce friction between contacting portions of the swash plate and the shoes to the least possible extent. A refrigerant gas entraining a lubricating oil mist is circulated through the swash plate compressor to lubricate movable components of the compressor. However, in an initial stage of operation of the compressor at a low temperature, the refrigerant gas washes off the lubricating oil remaining on the sliding surfaces of the swash plate before the lubricating oil mist reaches the swash plate and hence the surfaces of the swash plate are in a dried-surface condition having no lubricating oil, and therefore the swash plate and the shoes must unavoidably start to slide relative to each other without lubrication. Thus, the swash plate must be exposed to a very severe operating condition during the initial stage of sliding motion thereof. Moreover, a new refrigerant, such as R134a, which has recently become used instead of the conventional refrigerant for the protection of the ozonosphere is more effective in creating a dried-surface condition than the conventional refrigerant. Accordingly, demand for an improvement in the lubricating property of the surfaces of the swash plate has progressively increased.

Conventional methods intended to satisfy the above-mentioned demand by applying a surface treatment process to a swash plate have been proposed in Japanese Unexamined Patent Publication (Kokai) No. 60-22080 (Japanese Examined Patent Publication No. 5-10513), International Publication WO95/25224 and Japanese Unexamined Patent Publication (Kokai) No. 8-199327.

The typical conventional method disclosed in Japanese Unexamined Patent Publication (Kokai) No. 8-199327 includes forming of a sprayed metal coating of a copper-base or aluminum-base material on a swash plate made of a base metal, and forming of a plated coating of lead-base material or a film of a polytetrafluoroethylene over the sprayed metal coating. The plated film or the film of the polytetrafluoroethylene is formed over the surface of the sprayed metal coating in order to improve the antiseizing property of the sprayed metal coating and to prevent the sprayed metal coating from cracking.

Although the foregoing cited references disclose diverse techniques for the surface treatment of a swash plate, nothing is suggested in these techniques about means for securing compatibility between the surface treatment and management of thickness of the swash plate. For example, the afore-mentioned Japanese Unexamined Patent Publication (Kokai) No. 8-199327 discloses the technique of plating or coating the uppermost surface of a swash plate, but teaches nothing about the management of the thickness of the plated layer or the film in relation to an accurate management of the entire thickness of the swash plate.

Generally, in the swash-plate-operated refrigerant compressor, a special consideration is provided to determination of the amount of stroke of the pistons, in order to reduce a top clearance between each piston and a valve plate assembly when the piston is at its top dead center, i.e., the minimum volume of the cylinder bore during the compression stroke of the piston, to the smallest possible amount near zero. In view of the piston driving principle of the swash plate compressor, the determination of the amount of stroke of each piston largely depends on a production accuracy in the thickness of the swash plate with respect to a designed thickness. Therefore, if an appropriate surface treatment method is applied to the surface of the swash plate to reduce sliding friction between the surfaces of the awash plate and the shoes, a final object of improving the compression efficiency of the swash plate type compressor cannot be achieved if the surface treatment method makes it difficult to control the thickness of the swash plate.

SUMMARY OF THE INVENTION

Therefore, an object of the present invention is to provide a single-headed piston type swash-plate-operated refrigerant compressor in which sliding contact of a swash plate with shoes is improved so as to obtain a good antiseizing property, an enhanced abrasion resistance and a thickness accuracy, to thereby result in an achievement of a good compression efficiency.

Another object of the present invention is to provide a novel method of producing a swash plate for a single-headed piston type swash-plate-operated refrigerant compressor,-in which both an application of a surface treatment to a swash plate and easy controlling of a thickness of the swash plate can be concurrently achieved to eventually produce a swash plate having a high thickness accuracy.

In accordance with one aspect of the present invention, there is provided a single-headed piston type swash-plate-operated refrigerant compressor which comprises:

a rotatably supported drive shaft having an axis of rotation thereof;

a swash plate having an axially front and rear surfaces thereof, and mounted on the drive shaft for rotation together with the drive shaft;

at least one single-headed piston arranged on the rear side of the swash plate; and

a pair of shoes arranged to keep in slide-contact with the front and rear surfaces of the swash plate to operatively engage an end part of the single headed piston with a peripheral part of the swash plate to thereby convert a rotating motion of the swash plate into a reciprocating motion of the single headed piston;

wherein the front and the rear surface of the swash plate are provided with respective uppermost layers thereof, having physical surface properties different from one another in a manner such that a slide-contact performance between the rear surface of the swash plate and the corresponding one of the pair of shoes is superior to that between the front surface of the swash plate and the corresponding other of the pair of shoes.

Preferably, the physical surface properties of the front and rear surfaces of the swash plate are made different by forming the uppermost layers of the front and rear surfaces of different materials.

Alternatively, the physical surface properties of the front and rear surfaces of the swash plate are made different by applying different surface treatment processes to the uppermost layers of the front and rear surfaces.

In the single-headed piston type swash-plate-operated refrigerant compressor, a suction reaction force resulting from application of a force to the piston to suck a refrigerant gas into an associated cylinder bore in which the piston is fitted acts mainly on the front surface of the swash plate through a front side shoe of the pair of shoes, and a compression reaction force resulting from application of a force on the piston to compress the refrigerant gas within the associated cylinder bore acts mainly on the rear surface of the swash plate through a rear side shoe of the pair of shoes. Both the suction reaction force and the compression reaction force could cause abrasion and seizing in a contacting area between the swash plate and the shoes. Practically, the compression reaction force is far greater than the suction reaction force. Therefore, it is necessary to improve the slide-contact performance of the rear surface of the swash plate more than the slide-contact performance of the front surface of the swash plate. When improving the slide-contact performance by forming the front and rear surfaces of the swash plate with appropriate material or by applying an appropriate surface treatment process to these surfaces, the improvement of the slide-contact performance of the rear surface of the swash plate should be made prior to that of the front surface of the swash plate. When improving the slide-contact performance of the rear surface of the swash plate, if it is tried to form a given layer capable of improving slide-contact performance in the rear surface, delicate control of production accuracy in, for example, determining the thickness of the layer is required.

In accordance with the present invention, during the production of a swash plate, formation of the uppermost layer of the front surface of the swash plate in conducted first by considering the fact that the slide-contact performance of the front surface of the swash plate may be inferior to that of the rear surface thereof and, subsequently, forming of the uppermost layer formed in the rear surface of the swash plate can be achieved while adjustably controlling the thickness of the uppermost layer of the rear surface by using the first-formed front surface as a reference plane. Thus, the controlling of the thickness of the uppermost layer formed in the rear surface of the swash plate and the thickness of the swash plate per se during the production thereof can be of very high quality.

If it is required to form the above-mentioned layers to improve the slide-contact performance on both the front and rear surfaces of the swash plate, both surfaces require a simultaneous control of layer thickness and accordingly, a reference plane must be formed in some part of the swash plate other than the front and the rear surfaces. In such a case, the measurement of the thickness of the formed layer or the swash plate might include an error and hence an accurate control of the thickness of the layer or the swash plate will be made difficult.

In a single-headed piston type swash-plate-operated variable capacity compressor in which an inclination of the swash plate can be controlled by supplying a high-pressure refrigerant gas from a discharge pressure region into a crank chamber formed in the compressor to receive therein the swash plate and by controlling an amount of extraction of the refrigerant gas from the crank chamber, the compressed refrigerant gas to be discharged into the discharge pressure region has a high pressure and a high temperature. Therefore, when the high-pressure refrigerant gas is supplied from the discharge pressure region into the crank chamber, the viscosity of a lubricating oil contained in the crank chamber tends to be reduced by the high-pressure and high-temperature refrigerant gas, and accordingly it is difficult to dissipate heat from the crank chamber. Accordingly, an undesirable condition that leads the surfaces of the swash plate to a dried condition might be formed in the crank chamber. Thus, the awash plate produced in accordance with the present invention is very effective for preventing an occurrence of seizing and abrasion in the contacting area between the swash plate and the shoes of the single-headed piston type swash-plate-operated variable compressor.

Preferably, a solid lubricant layer containing a solid lubricant at least in a part thereof is formed in the uppermost layer of the rear surface of the awash plate. The solid lubricant contained in the solid lubricant layer improves the slide-contact performance exhibited by the rear surface of the swash plate in slide-contact with the rear side shoe and improves the antiseizing property and abrasion resistance of the rear surface. The thickness of the solid lubricant layer can be measured and controlled by using the front surface of the swash plate as a reference plane.

The described single-headed piston type swash-plate-operated compressor may be provided with a piston which is made of an aluminum-base material, a pair of shoes which are made of an iron-base material, and a swash plate having the front surface thereof formed of a nonferrous material and the rear surface thereof coated by a solid lubricant layer containing a solid lubricant at least in part thereof. In this regard, since the piston and the shoes are made of different materials, respectively, seizing does not occur when the slide-contacting between the piston and the shoes is performed. Similarly, since the shoes and the rear surface of the swash plate are made of different materials, respectively, seizing does not occur during the slide-contacting between the shoes and the rear surface of the swash plate. Particularly, the solid lubricant contained in the solid lubricant layer formed on the rear surface of the swash plate improves the slide-contact performance exhibited by a contacting area between the shoes and the rear surface of the swash plate, and the antiseizing property and abrasion resistance of the swash plate. The thickness of the solid lubricant layer is measured and controlled by using the front surface of the swash plate as a reference plane.

The nonferrous material forming the front surface of the swash plate may be any one of copper-base materials, tin-base materials and aluminum-base materials including alumite.

In the described single-headed piston type swash-plate-operated compressor, the base material of the swash plate may be an iron-base material, and an intermediate layer of a copper-base or a tin-base material may be formed between a part of the iron-base material of the swash plate, and the solid lubricant layer formed on the rear surface of the swash plate. The intermediate layer of the copper-base cr the tin-base material can prevent the uppermost layer of the rear surface of the swash plate from being immediately exposed and from coming into direct contact with the shoes made of an iron-base material to cause seizing even it a part of the solid lubricant layer coating the uppermost layer of the rear surface of the swash plate is damaged by an unpredictable cause. Although not as effective as the solid lubricant layer, the intermediate layer is effective in improving slide-contact performance exhibited by a contact area between the shoes and the swash plate.

If the intermediate layer is a sprayed metal coating of a copper-base material, the solid lubricant layer coating the intermediate layer serves as a protective layer. If the sprayed metal coating of a copper-base material forms the boundary of the rear surface of the swash plate, local seizing and cracking are liable to occur in the sprayed metal coating due to the sliding contact of the shoe of-an iron-base material with the rear surface of the swash plate because the sprayed metal coating is hard and is difficult to be distorted according to external force exerted thereon. The solid lubricant layer formed over the sprayed metal coating of a copper-base material formed on the rear surface of the swash plate reduces frictional resistance of a contact part of the swash plate and stress induced in the sprayed metal coating, so that the sprayed metal coating is prevented from cracking.

In the described single-headed piston type swash-plate-operated compressor, the base material of the swash plate may be an aluminum-base material, and the intermediate layer of a tin-base material or alumite may be formed between a part of the aluminum-base material of the swash plate, and the solid lubricant layer formed on the rear surface of the swash plate.

The intermediate layer made of a tin-base material or alumite can prevent the aluminum-base material of the swash plate from being exposed and from coming into contact with the shoe and causing seizing when the solid lubricant layer formed on the rear surface of the swash plate is damaged by an unpredictable cause.

The intermediate layer of alumite is effective in enhancing the adhesion of the solid lubricant layer to the aluminum-base material of the swash plate.

The base material of the swash plate may be an aluminum-base material, and the solid lubricant layer may be formed on the rear surface of the base material of the swash plate. Preferably, the solid lubricant layer is formed on the rear surface of the aluminum-base material of the swash plate which surface is finished by a surface roughening process. The surface roughening process enhances the adhesion of the solid lubricant layer to the aluminum-base of the swash plate.

The above-described solid lubricant may be at least one of lubricating materials including molybdenum disulfide, tungsten disulfide, graphite, boron nitride, antimony oxide, lead oxide, lead, indium, tin and fluorocarbon resins. Those lubricating materials have proved effective in improving the slide-contact performance exhibited by a contacting area between the shoes and the swash plate.

In accordance with a further aspect of the present invention, there is provided a method of producing a swash plate, for a single-headed piston type swash-plate-operated refrigerant compressor in which a rotating motion of a swash plate mounted on a drive shaft rotatable about an axis of rotation extending from a front to a rear side of the compressor is converted through a pair of shoes into a reciprocating motion of a piston, which comprises:

A: a first step of forming a front surface in the swash plate so that the front surface is in direct contact with the first shoe of the pair of shoes and to serve as a reference plane;

B: a second step of forming a solid lubricant layer in a rear surface of the swash plate opposite to the front surface so that the solid lubricant layer is in direct contact with the second shoe of the pair of shoes and contains a solid lubricant at least in part thereof;

C: a third step of measuring at least one of the thickness of the solid lubricant layer formed on the rear surface or the thickness of the swash plate by using the front surface formed by the first step as the reference plane; and

D: a fourth step of applying a grinding operation to the solid lubricant layer to adjust the thickness of the solid lubricant layer and that of the swash plate measured in the third step to desired thicknesses.

According to the described method, it is possible to measure the thickness of the solid lubricant layer formed on the rear surface of the swash plate and that of the swash plate by using the reference plane completed in the preceding step. Accordingly, the swash plate can be produced so that the solid lubricant layer of the swash plate and the swash plate per se can have respective thicknesses precisely coinciding with desired thickness values by grinding the solid lubricant layer.

BRIEF DESCRIPTION OF THE DRAWINGS

The above and other objects, features and advantages of the present invention will be made more apparent from the ensuing description of the preferred embodiments thereof, with reference to the accompanying drawings wherein:

FIG. 1

is a longitudinal cross-sectional view of a single-headed piston type swash-plate-operated compressor to which the present invention is applied;

FIG. 2

is an enlarged fragmentary sectional view of the compressor in a state for operation at a minimum discharge capacity;

FIG. 3

is a schematic sectional view illustrating a relation between a drive shaft, a swash plate and a single-headed piston;

FIG. 4

is an enlarged sectional view illustrating a relation between the swash plate and the shoes;

FIG. 5

is a schematic, fragmentary sectional view of assistance in explaining a method of controlling the thickness of a formed layer of the swash plate according to the present invention; and

FIG. 6

is a schematic, fragmentary sectional view of assistance in explaining a method of controlling the thickness of a formed layer according to a prior art.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

Preferred embodiments of the present invention will be described hereinafter.

A single-headed piston type swash plate compressor embodying the present invention for an automotive air conditioning system will be described prior to the description of the construction of a swash plate, which is an essential part of the present invention, and a method of producing the swash plate.

Basic Construction of Single-headed Piston Type Swash-Plate-Operated Refrigerant Compressor

Referring to

FIG. 1

, a clutchless swash plate compressor has a cylinder block

12

, a front housing

11

fixedly joined to the front end of the cylinder block

12

, and a rear housing

13

fixedly joined to the rear end of the cylinder block

12

with a valve plate

14

sandwiched between the cylinder block

12

and the rear housing

13

. The front housing

11

and the cylinder block

12

define a crank chamber

15

. A drive shaft

16

is extended across the crank chamber

15

and is supported for rotation on the front housing

11

and the cylinder block

12

. A pulley

17

is supported for rotation on an angular-contact bearing

18

mounted on a front end part of the front housing

11

, and is fixed to a front end part of the drive shaft

16

projecting from the front housing

11

. A belt

19

is wound around the pulley

17

to connect the pulley

17

operatively to an engine

20

of a vehicle, i.e., a drive-power source, without using any clutch mechanism, such as a solenoid clutch.

A lip seal

21

is fitted in a space between the outer circumference of the front end part of the drive shaft

16

and the front housing

11

to seal the front end of the crank chamber

15

. A rotating support member

22

is fixedly mounted on the drive shaft

16

in the crank chamber

15

. A swash plate

23

, i.e., a cam plate, is arranged in the crank chamber

15

. The drive shaft

16

is extended through a central through hole

23

a

, formed in the swash plate

23

to support the swash plate thereon, so that the swash plate

23

is able to slide axially along and to incline to the axis L

1

of the drive shaft

16

.

The rotating support member

22

and the swash plate

23

are interlocked by a hinge mechanism

10

. The swash plate

23

is provided with a counterweight

23

b

on the opposite side of the hinge mechanism

10

with respect to the drive shaft

16

. The hinge mechanism

10

comprises a pair of support arms

24

(only one of them is shown) projecting from the rear surface of the rotating support member

22

, and a pair of guide pins

25

(only one of them is shown) projecting from the front surface of the swash plate

23

. Each support arm

24

is provided in its end part with a guide hole

24

a

, and each guide pin

25

is provided in its end part with a spherical part

25

a

. The spherical parts

25

a

of the guide pins

25

are fitted in the guide holes

24

a

of the corresponding support arms

24

, respectively.

The swash plate

23

can be inclined to the drive shaft

16

and can be rotated together with the drive shaft by the combined action of the support arms

24

and the guide pins

25

. When the swash plate

23

is inclined, the guide holes

24

a

guide the spherical parts

25

a

for sliding movement, and the drive shaft

16

allows the swash plate

23

to slide thereon. The inclination of the swash plate

23

decreases as the swash plate

23

approaches the cylinder block

12

. A coil spring

26

wound around the drive shaft

16

and arranged between the rotating support member

22

and the swash plate

23

biases the swash plate

23

toward the cylinder block

12

so as to assist the decrease of the inclination of the swash plate

23

. A limiting projection

22

a

formed on the rear surface of the rotating support member

22

comes into contact with a part of the swash plate

23

as shown in

FIG. 1

to determine a maximum inclination at which the swash plate

23

can be inclined.

The cylinder block

12

is provided in its central part with a cavity

27

. A suction passage

32

is formed in a central part of the rear housing

13

so as to be connected to the cavity

27

. A positioning surface

33

is formed around one end of the suction passage

32

on the side of the cavity

27

. The cavity

27

and the suction passage

32

form part of a suction pressure region of the compressor.

A passage disconnecting piston

28

is fitted slidably in the cavity

27

. A suction passage opening spring (coil spring)

29

is arranged between the passage disconnecting piston

28

and a shoulder formed in the cavity

27

to bias the passage disconnecting piston

28

toward the swash plate

23

. A rear end part of the drive shaft

16

is inserted in the passage disconnecting piston

28

and is supported in a radial bearing

30

fitted in the passage disconnecting piston

28

. The radial bearing

30

is retained in the passage disconnecting piston

28

by a snap ring

31

and is axially movable together with the drive shaft

16

along the axis L. The rear end part of the drive shaft

16

is supported in the radial bearing

30

for rotation on the passage disconnecting piston

28

fitted in the cavity

27

. A closing surface

34

is formed on the rear end of the bottom wall of the passage disconnecting piston

28

. The closing surface

34

comes into contact with and is separated from the positioning surface

33

as the passage disconnecting piston

28

moves axially. When the closing surface

34

is in contact with the positioning surface

33

, the suction passage

32

is disconnected from a space in the cavity

27

.

A thrust bearing

35

is supported slidably on the drive shaft

16

between the swash plate

23

and the passage disconnecting piston

28

. The swash plate

23

, the thrust bearing

35

and the passage disconnecting piston

28

are kept in contact with each other by the resilience of the coil spring

26

and the suction passage opening spring

29

. Therefore, as the swash plate

23

slides toward the passage disconnecting piston

28

and the inclination of the swash plate

23

increases, the passage disconnecting piston

28

is forced to move toward the positioning surface

33

against the resilience of the suction passage opening spring

29

and, eventually, the closing surface

34

of the passage disconnecting piston

28

comes into contact with the positioning surface

33

to limit the further inclination of the swash plate

23

. In this state, the swash plate

23

is inclined at a minimum inclination slightly greater than 0°.

The cylinder block

12

is provided with a plurality of cylinder bores

12

a

around the drive shaft

16

, and single-headed pistons

36

are fitted for reciprocation in the cylinder bores

12

a

, respectively. A front end part of each piston

36

(an end part opposite the compression end surface) is linked by a pair of shoes

37

to a peripheral part of the swash plate

23

. Thus, each piston is operatively connected to the swash plate

23

by the shoes

37

to convert a rotating motion of the swash plate

23

into a reciprocating motion of the piston

36

operatively connected to the swash plate

23

by the shoes

37

.

When the inclination of the swash plate

23

changes, the stroke of the pistons

36

and the discharge capacity change accordingly. The top dead center of the piston

36

in the cylinder bore

12

a

remains substantially constant and only the lower dead center of the piston changes. Top clearance in the cylinder bore

12

a

when the piston

36

is at the top dead center is nearly equal to zero.

The rear housing

13

is provided with a substantially annular suction chamber

38

, which forms a part of the suction pressure region, and a substantially annular discharge chamber

39

, which forms a discharge pressure region, formed around the annular suction chamber

38

. The suction chamber

38

communicates with the cavity

27

by means of a port

45

formed in the valve plate

14

. When the closing surface

34

of the passage disconnecting piston

28

is brought into contact with the positioning surface

33

, the port

45

is disconnected from the suction passage

32

.

The valve plate

14

is provided with suction ports respectively opening into the cylinder bores

12

a

, suction valves

41

respectively for opening and closing the suction ports

40

, discharge ports

42

, and discharge valves

43

respectively for opening and closing the discharge ports

42

. A refrigerant gas supplied from an external device into the suction chamber

38

is sucked through the suction port

40

and the suction valve

41

into the cylinder bore

12

a

by the suction stroke of each piston

36

. The refrigerant gas taken into the cylinder bore

12

a

is discharged through the discharge port

42

and the discharge valve

43

by the compression stroke of the piston

36

into the discharge chamber

39

. A compression reaction force that acts on the rotating support member

22

through the piston

36

when the piston

36

compresses the refrigerant gas is born by a thrust bearing

44

arranged between the rotating support member

22

and the inner surface of the front end wall of the front housing

11

.

A passage

46

is formed in the drive shaft

16

along its axis. The passage

46

has a front end

46

a

opening into a region near the lip seal

21

in the crank chamber

15

, and a rear end

46

b

opening into a space defined by the passage disconnecting piston

28

. The passage disconnecting piston

28

is provided in its side wall with a pressure relief passage

47

opening into the cavity

27

. The passage

46

and the pressure relief passage

47

form a bleed passage.

A supply passage

48

is formed through the cylinder block

12

and the rear housing

13

to connect the discharge chamber

39

and the crank chamber

15

. A capacity control valve

49

is placed in the supply passage

48

. A pressure sensing passage

50

is formed in the rear housing

13

so as to connect the capacity control valve

49

and the suction passage

32

.

Referring to

FIG. 2

, a valve housing

51

and a solenoid unit

52

are joined together in a middle part of the capacity control valve

49

. A valve chamber

53

is formed between the valve housing and the solenoid unit

52

. A valve element

54

is placed in the valve chamber

53

. A valve hole is extended along the axis of the valve housing

51

and opposite to the valve element

54

. A valve opening spring

56

is placed between the valve element

54

and a wall defining the valve chamber

53

to bias the valve element

54

in a direction to open the valve hole

55

. The valve chamber

53

communicates with the discharge chamber

39

by means of the supply passage

48

.

A pressure sensing chamber

58

is formed in an upper part of the valve housing

51

and is connected to the pressure sensing passage

50

, A bellows

60

, i.e., a pressure sensing device, is contained in the pressure sensing chamber

58

. The pressure sensing chamber

58

and the valve chamber

53

are separated from each other by a partition wall

57

of the valve housing

51

, and a through hole

61

is formed in the partition wall

57

to connect the chambers

58

and

53

. A section of the through hole

61

on the side of the valve element

54

serves as the valve hole

55

. A pressure sensing rod

62

is slidably fitted in the through hole

61

. The valve element

54

and the bellows

60

are operatively connected by the pressure sensing rod

62

. A section of the pressure sensing rod

62

on the side of the valve element

54

is reduced to form a passage for the refrigerant gas in the valve hole

55

.

A port

63

is formed in the valve housing

51

in a part between the valve chamber

53

and the pressure sensing chamber

58

so as to intersect the valve hole

55

perpendicularly. The port

63

communicates with the crank chamber

15

by means of the supply passage

48

; that is, the valve chamber

53

, the valve hole

55

and the port

63

are parts of the supply passage

48

. A stationary core

64

is fitted in an upper part of a core chamber

65

formed in the solenoid unit

52

to define a solenoid chamber

66

. A movable core

67

having the shape of a bottomed cylinder is fitted axially movably in the solenoid chamber

66

. A spring

68

is arranged between the movable core

67

and the bottom wall of the core chamber

65

. The spring constant of the spring

68

is smaller than that of the valve opening spring

56

.

The stationary core

64

is provided with an axial through hole

69

opening into the solenoid chamber and the valve chamber

53

. A solenoid rod

70

formed integrally with the valve element

54

is fitted slidably in the through hole

69

. One end of the solenoid rod

70

on the side of the movable core

67

is held in contact with the movable core

67

by the biasing forces of the valve opening spring

56

and the spring

68

. The movable core

67

and the valve element

54

are connected operatively by the solenoid rod

70

. A cylindrical solenoid

74

is arranged around the stationary core

64

and the movable core

67

so as to extend over both the cores

64

and

67

.

As shown in

FIG. 1

, the swash plate compressor is connected to an external refrigerant circuit

76

by the suction passage

32

through which the refrigerant gas is taken into the suction chamber

38

, and a discharge flange

75

through which the refrigerant gas is discharged from the discharge chamber

39

. The external refrigerant circuit

76

is provided with a condenser

77

, an expansion valve

78

and an evaporator

79

. The awash plate compressor, the condenser

77

, the expansion valve

78

and the evaporator

79

are the components of the automotive air conditioning system.

An evaporator temperature sensor

81

, a passenger compartment temperature sensor

82

, an air conditioning system operating switch

83

, a passenger compartment temperature setting device

84

and the solenoid

74

of the capacity control valve

49

are connected to a control computer

85

. The control computer

85

controls the current to be supplied to the solenoid

74

on the basis of measured temperatures measured by the temperature sensors

81

and

82

, a signal indicating the condition of the air conditioning system operating switch

83

, and a set temperature signal indicating a set temperature set by operating the passenger compartment temperature setting device

84

.

The description of the operation of the swash-plate-operated refrigerant compressor will be provided below.

When the air conditioning system operating switch

83

is in an on-state and a passenger compartment temperature measured by the passenger compartment temperature sensor

81

is not lower than a set temperature, the control computer

85

gives a command to energize the solenoid

74

. Then a predetermined current is supplied to the solenoid

74

, and an attraction of a magnitude proportional to the current supplied to the solenoid

74

acts between the cores

64

and

67

. The attraction is transmitted through the solenoid rod

70

to the valve element

54

and acts in a direction to reduce the opening of the capacity control valve

49

against the resilience of the valve opening spring

56

. A movable end of the bellows

60

is displaced according to the variation of the suction pressure prevailing in the suction passage

32

and acting through the pressure sensing passage

50

on the pressure sensing chamber

58

. The bellows

60

responds to the suction pressure when the solenoid

74

is energized. The displacement of the movable end of the bellows is transmitted through the pressure sensing rod

62

to the valve element

54

. The opening of the capacity control valve

49

is dependent on the balance of the force produced by the solenoid unit

52

, the force produced by the bellows

60

and the force produced by the valve opening spring

56

.

For example, the difference between the passenger compartment temperature measured by the passenger compartment temperature sensor

82

and the set temperature set by the passenger compartment temperature setting device

84

is large when cooling load is high. The control computer

85

controls the current to be supplied to the solenoid

74

to vary the set-suction pressure on the basis of the measured passenger compartment temperature and the set passenger compartment temperature; that is, the control computer

85

increases the current according to the increase of the difference between the measured passenger compartment temperature and the set passenger compartment temperature. Consequently, the attraction acting between the stationary core

64

and the movable core

67

increases to increase the force acting on the valve element

54

to reduce the opening of the capacity control valve

49

, and the valve element

54

is operated for an opening and closing operation at a lower suction pressure. Thus, the capacity control valve

49

operates to hold the suction pressure on a lower level when the current supplied to the solenoid

74

is increased.

When the valve element

54

is shifted in a direction to reduce the opening of the capacity control valve

49

, the flow rate of the refrigerant gas flowing from the discharge chamber

39

through the suction passage

48

into the crank chamber

15

is reduced. On the other hand, the refrigerant gas flows from the crank chamber

15

through the passage

46

and the pressure relief passage

47

into the suction chamber

38

and the pressure in the crank chamber

15

drops. When the cooling load is high, the suction pressure in the cylinder bores

12

a

is high, and the difference between the pressure in the crank chamber

15

and the suction pressure in the cylinder bores

12

a

decreases, whereby the inclination of the swash plate

23

tends to increase.

In a state where the effective sectional area of the supply passage

48

is zero, i.e., a state where the valve hole

55

is closed completely by the valve element

54

of the capacity control valve

49

, the supply of the high-pressure refrigerant gas from the discharge chamber

39

into the crank chamber

15

is stopped. Then, the pressure in the crank chamber

15

approaches the pressure in the suction chamber

38

and the swash plate

23

is inclined at its maximum inclination.

When the cooling load is low, the difference between the passenger compartment temperature and the set temperature is small. The control computer

85

gives a command to supply lower currents for lower passenger chamber temperature. Therefore, the attraction acting between the stationary core

64

and the movable core

67

is low and the force acting on the valve element

54

in a direction to reduce the opening of the capacity control valve

49

is reduced. The valve element

45

is operated for opening and closing by a higher suction pressure. Thus, the capacity control valve

49

operates to hold the suction pressure on a higher level when the current supplied to the solenoid

74

is reduced.

When the valve element

54

is operated so as to increase the opening of the capacity control valve

49

, the flow rate of the refrigerant gas flowing from the discharge chamber

39

into the crank chamber

15

increases to raise the pressure in the crank chamber

15

. In a state where the cooling load is low, the suction pressure in the cylinder bores

12

a

is low and the difference between the pressure in the crank chamber

15

and the suction pressure in the cylinder bores

12

increases and, consequently, the inclination of the awash plate

23

tends to decrease.

As the cooling load approaches zero, the temperature of the evaporator

79

approaches a frosting temperature at which frost starts to accumulate on the evaporator

79

. The frosting temperature reflects a condition in which frost is likely to accumulate on the evaporator

79

. Upon the drop of the temperature ot the evaporator

79

below the frosting temperature, the control computer

85

provides a command to de-energize the solenoid

74

. The control computer

85

provides a command to de-energize the solenoid

74

also when the air conditioning system control switch

83

is opened.

Supply of the electric current to the solenoid

74

is stopped to de-energize the solenoid

74

and the magnetic attraction acting between the stationary core

64

and the movable core

67

disappears. Consequently, the valve element

54

is shifted down by the resilience of the valve opening spring

56

against the resilience of the spring

68

acting thereon through the movable core

67

and the solenoid

74

to fully open the valve hole

55

. Thus, the high-pressure refrigerant gas flows at a high flow rate from the discharge chamber

39

through the supply passage

48

into the crank chamber

15

and the pressure in the crank chamber

15

rises. Consequently, the inclination of the swash plate

23

is reduced to the minimum angle of inclination.

The operation of the capacity control valve

49

varies according to the intensity of the electric current supplied to the solenoid

74

. The capacity control valve

49

is operated at a low suction pressure when the electric current is large and is operated at a high suction pressure when the electric current is small. The compressor changes the angle of inclination of the swash plate

23

and its discharge capacity to maintain the suction pressure at the set suction pressure. Namely, the capacity control valve

49

operates for both changing the set suction pressure by changing the input current and making the compressor operate at its minimum capacity regardless of the suction pressure. The compressor provided with the capacity control valve

49

changes the refrigerating capacity of a refrigeration circuit.

When the swash plate

19

is set at the minimum inclination, the closing surface

34

of the passage disconnecting piston

28

comes into contact with the positioning surface

33

to disconnect the suction passage

32

from the cavity

27

. In this state, the effective sectional area of the suction passage

32

is zero and the flow of the refrigerant gas from the external refrigerant circuit

76

into the suction chamber

38

is intercepted. The minimum angle of inclination of the swash plate

23

is slightly greater than 0°. The swash plate

23

is inclined at the minimum inclination when the passage disconnecting piston

28

is located at a disconnecting position where the passage disconnecting piston

28

disconnects the suction passage

32

from the cavity

27

. The position of the passage disconnecting piston

28

varies between the disconnecting position and a connecting position to connect the suction passage

32

and the cavity

27

according to the variation of the inclination of the swash plate

23

.

Since the minimum angle of inclination of the swash plate

23

is not equal to 0°, the refrigerant gas is discharged from the cylinder bores

12

a

into the discharge chamber

39

while the compressor is operating with the swash plate

23

inclined at the minimum inclination. The refrigerant gas discharged from the cylinder bores

12

a

into the discharge chamber

39

flows through the supply passage

48

into the crank chamber

15

and flows further through the passage

46

and the pressure relief passage

47

into the suction chamber

38

. Then the refrigerant gas is taken from the suction chamber

38

into the cylinder bores

12

a

and then discharged again into the discharge chamber

39

. Thus, a circulation circuit passing the discharge chamber

39

, i.e., the discharge pressure region, the supply passage

48

, the crank chamber

15

, the passage

46

, the pressure relief passage

47

, the cavity

27

, the suction chamber

38

, i.e., the suction pressure region, and the cylinder bores

12

a

is formed in the compressor when the swash plate

23

is inclined at the minimum inclination. In this state, there is pressure difference between the discharge chamber

39

, and the crank chamber

15

and the suction chamber

38

. Therefore, lubricating oil entailed by the refrigerant gas can be supplied to the sliding surfaces of the components of the compressor as the refrigerant, gas circulates through the circulating circuit.

Construction of the Swash Plate

The surface construction of the swash plate, which is an important feature of the present invention, will be described with reference to

FIGS. 3 through 5

.

Referring to

FIG. 3

, the swash plate

23

has a central land part

91

and a peripheral part

92

surrounding the land part

91

and having the shape of a flange. The thickness of the land part

91

is greater than that of the peripheral part

92

. The land part

91

is provided with the central through hole

23

a

and the counterweight

23

b

. The peripheral part

92

of the swash plate

23

has a front surface

92

a

facing the rotating support member

22

arranged in the crank chamber

15

, and a rear surface

92

b

facing the head parts

36

a

of the single-headed pistons

36

. As shown in

FIGS. 3 and 4

, the tail end part

36

b

of each single-headed piston

36

opposite the head part

36

a

of the same is provided with a pair of spherical surfaces

36

c

for guiding the pair of shoes

37

for sliding movement along a guide circle indicate by long and short dash lines in FIG.

4

. The shoes

37

are held between the pair of spherical surfaces

36

c

and the peripheral part

92

of the swash plate

23

inserted in the space between the spherical surfaces

36

c

. Thus, the shoes

37

are held for turning on the tail end part

36

b

of the single-headed piston

36

, and the tail end part

36

b

is linked to the peripheral part

92

of the swash plate

23

by the shoes

37

.

FIG. 4

illustrates surface layers formed on the opposite surfaces

92

a

and

92

b

of the peripheral part

92

of the swash plate

23

. A front layer

93

is formed on the front surface of the peripheral part

92

, a first rear layer

94

is formed on the rear surface of the peripheral part

92

, and a second rear layer

95

is formed on the first rear layer

94

. The front layer

93

is the outermost surface layer on the front side of the swash plate

23

. The second rear layer

95

is the outermost surface layer on the rear side of the swash plate

23

, and the first rear layer

94

is an intermediate layer sandwiched between the outermost layer and the peripheral part of the swash plate

23

. In this specification, a part of the swash plate

23

excluding the front layer

93

, the first rear layer

94

and the second rear layer

95

, i.e., a part consisting of the land part

91

and the peripheral part

92

, will be called a ‘body’.

The body of the swash plate

23

is made of an iron-base or an aluminum-base material. Each of the single-headed pistons

36

is made of an aluminum-base material in a lightweight member. The shoes

37

are made of an iron-base material, such as a bearing steel. In this specification, the term, ‘iron-base material’ indicates pure iron or an alloy containing iron as a principal component, and the term, ‘aluminum-base material’ indicates pure aluminum, an alloy containing aluminum as a principal component or an intermetallic compound containing aluminum. Aluminum alloys suitable for forming the body of the swash plate are Al—Si alloys, Al—Si—Mg alloys, Al—Si—Cu—Mg alloys and aluminum alloys not containing Si.

Front Layer and First Rear Layer

The front layer

93

and the first rear layer

94

are formed of the same material. The front layer

93

and the first rear layer

94

are copper-base alloy layers, tin-base base alloy layers or alumite layers (layers formed by the anodic oxidation of aluminum), depending on the material of the body (

91

,

92

). Preferably, the respective thicknesses of the front layer

93

and the first rear layer

94

are in the range of 2 to 500 micrometers (μm). Preferably, the copper-base alloy layers are formed by a metal spraying process. The metal spraying process may be conducted by either a method of forming a layer in which a molten metal produced by entirely melting a metal powder to be sprayed is solidified or a method of partly melting a metal powder to be sprayed without changing the structure of the metal powder. Although pure copper (Cu) may be used for the metal spraying process, it is preferable to use a Cu—Sn alloy containing Cu and 2 through 15% by weight tin (Sn), which serves as a strengthening element. The Cu-base alloy may contain

2

through 30% by weight lead (Pb), which provides conformability and a low frictional property. The Cu-base alloy may further contain 0.1% by weight or less phosphorus (P) and 5% by weight of less silver (Ag). A copper spraying process applicable to the present invention is described in detail in International Publication WO95/25224.

The tin-base alloy layers of a tin-base alloy can be formed by a similar metal spraying process. A pure tin may be used instead of the tin-base alloy.

The alumite layers can be formed by subjecting the body of an aluminum-base material to a standard anodizing process. Preferably, the thickness of the alumite layer, i.e., an anodic coating, is in the range of 2 through 20 micrometers (μm). Generally, the anodic coating is dense, hard and has high abrasion resistance and excellent adhesion to a base of an aluminum alloy.

Second Rear Layer

The second rear layer

95

, i.e., an outermost rear layer, is a solid lubricant layer containing a solid lubricant at least in a part thereof. Preferably, the thickness of the solid lubricant layer is in the range of 0.5 through 50 μm, more preferably, in the range of 0.5 through 10 μm.

Concretely, the solid lubricant layer is a layer of an inorganic or an organic solid lubricant or a resin layer containing an inorganic or an organic solid lubricant. Possible inorganic solid lubricants are molybdenum disulfide, tungsten disulfide, graphite, boron nitride, antimony oxide, lead oxide, lead (Pb), indium (In) and tin (Sn). Possible organic solid lubricants are fluorocarbon resins, such as polytetrafluoroethylene resins (PTFE resins), and unsaturated polyester resins.

Swash plates each provided with a front layer

93

, a first rear layer

94

and a second rear layer

95

in Examples 1 to 7 and prior art swash plates in Comparative examples 1 and 2 will be described hereinafter.

EXAMPLE 1

A copper-base alloy containing 5 through 10% by weight Sn and 1 through 10% by weight Pb was sprayed at a powder feed rate of 50 gram/min with a spraying gun (Diamond jet gun available from the manufacturing company in Japan, named “Daiichi Metakon”) over the opposite surfaces of the body of an iron-base material of a swash plate. The front and the rear surface of the peripheral part

92

of the body were ground, after the sprayed copper-base alloy coatings cooled off, to form a front layer

93

and a first rear layer

94

of about 150 μm in thickness. The surfaces of the front layer

93

and the first rear layer

94

were cleaned and degreased, and then the surface of the first rear layer

94

was coated with a coating layer of a material prepared by dispersing molybdenum disulfide particles of particle sizes in the range of 0.5 through 20 μm in a polyamidimide resin by a spray coating process. The coating layer was baked at 200° C. The rear surface

92

b

of the peripheral part of the swash plate was ground to form a 10 μm thick second rear layer

95

.

The swash plate thus fabricated was incorporated into the foregoing single-headed piston type swash plate compressor and the single-headed piston type swash plate compressor was operated for the operational suitability test of the swash plate. During the operational suitability test, a lubricating oil was supplied at a rate equal to about 10% of a rate at which the lubricating oil is supplied for the practical operation of the single-headed piston type swash plate compressor, and the drive shaft

16

was rotated at about 3,000 rpm for fifteen minutes. The front and the rear surface of the swash plate was observed to examine the front and rear surfaces for cracking and seizing after the operational suitability test. No defect was found.

EXAMPLE 2

A tin-base alloy was sprayed at a powder feed rate of 50 gram/min with the same spraying gun over the opposite surfaces of the body of an iron-base material of a swash plate. The front and the rear surface of the peripheral part

92

where ground, after the sprayed tin-base alloy coatings cooled off, to form a front layer

93

and a first rear layer

94

of about 150 μm in thickness. Subsequently, the surfaces of the front layer

93

and the first rear layer

94

were cleaned and degreased, and then the surface of the first rear layer

94

was coated with a coating layer of a material prepared by dispersing molybdenum disulfide particles of particle sizes in the range of 0.5 to 20 μm in a polyamidimide resin by a spray coating process. The coating layer was baked at 200° C. The rear surface

92

b

of the swash plate was ground to form a 10 μm thick second rear layer

95

.

The swash plate thus produced was incorporated into the foregoing single-headed piston type swash plate compressor and the single-headed piston type swash plate compressor was operated for the same operational suitability test of the swash plate. No defects, such as cracks and abrasively damaged parts in the layers, were found.

EXAMPLE 3

Tin-base alloy coatings were formed by plating on the opposite surfaces of the body of an aluminum-base material of a swash plate. The front and the rear surface of the peripheral part

92

were ground to form a front layer

93

and at first rear layer

94

of about 150 μm in thickness. The surfaces of the front layer

93

and the first rear layer

94

were cleaned and degreased, and then the surface of the first rear layer

94

was coated with a coating layer of a material prepared by dispersing molybdenum disulfide particles of particle sizes in the range of 0.5 through 20 μm in a polyamidimide resin by a spray coating process. The coating layer was baked at 200° C. The rear surface

92

b

of the peripheral part of the swash plate was ground to form a 10 μm thick second rear layer

95

.

The swash plate thus produced was incorporated into the foregoing single-headed piston type swash plate compressor and the single-headed piston type swash plate compressor was operated for the same operational suitability test of the swash plate. No defects, such as cracks and abrasively damaged parts, were found.

EXAMPLE 4

The body of an aluminum-base material of a swash plate was immersed in a sulfuric acid solution or an oxalic acid solution and was subjected to an anodizing process to form an oxide film (alumite layer) over the surface of the body made of the aluminum-base material. The body of the swash plate was washed with water. The respective measured thicknesses of the alumite layers forming the front layer

93

and the rear layer

94

were about 15 μm. The surfaces of the alumite layers were cleaned and degreased, and then the surface of the first rear layer

94

was coated with a coating layer of a material prepared by dispersing molybdenum disulfide particles of particle sizes in the range of 0.5 through 20 μm in a polyamidimide resin by a spray coating process. The coating layer was baked at 200° C. The rear surface

92

b

of the peripheral part of the swash plate was ground to form a 10 μm thick second rear layer

95

.

The swash plate thus fabricated was incorporated into the foregoing single-headed piston type swash-plate-operated refrigerant compressor and the single-headed piston type swash-plate-operated refrigerant compressor was operated for the same operational suitability test of the swash plate. No defects, such as cracks and abrasively damaged parts, were found.

EXAMPLE 5

Surface of a body made of an aluminum-base material of a swash plate was cleaned and degreased, and only the rear surface of the body was roughened by a sand blasting process. Only the rear surface of the body was coated with a coating layer of a material prepared by dispersing molybdenum disulfide particles of particle sizes in the range of 0.5 through 20 μm in a polyamidimide resin by a transfer coating process. The coating layer was baked at 200° C. The rear surface

92

b

of the swash plate was ground to form a 10 μm thick solid lubricant layer of the polyamidimide resin containing molybdenum disulfide. The swash plate in Example 5 does have any layers corresponding to the front layer

93

and the first rear layer

94

of the swash plate in Example 4, and the solid lubricant layer of the polyamidimide resin containing molybdenum disulfide corresponding to the second rear layer

95

is formed directly on the body of the aluminum-base material.

Preferably, the surface roughness Rz of the body of the swash plate is in the range of 0.4 through 15 μm, more preferably, in the range of 4 through 10 μm. The surface roughening process improves the adhesion of the solid lubricant layer to the surface of the body. The transfer coating method applies a resin containing a solid lubricant to a transfer surface of a transfer pad, and presses the transfer surface of the transfer pad against the surface of the body of the swash plate to transfer the resin containing a solid lubricant from the transfer surface to the surface of the body of the swash plate.

The swash plate thus produced was incorporated into the foregoing single-headed piston type awash plate compressor and the single-headed piston type swash plate compressor was operated for the same operational suitability test of the swash plate. No defects, such as cracks and abrasively damaged parts, were found.

EXAMPLE 6

A tin-base alloy coating was formed by plating only on the rear surfaces of the body of an aluminum-base material of a awash plate. A peripheral part

92

was ground to form a first rear layer

94

of about 150 μm in thickness. The surface of the plated first rear layer

94

was cleaned and degreased, and then the surface of the first rear layer

94

was coated with a coating layer of a material prepared by dispersing molybdenum disulfide particles of particle sizes in the range of 0.5 through 20 μm in a polyamidimide resin by a spray coating process. The coating layer was baked at 200° C. The rear surface

92

b

of the swash plate was ground to form a 10 μm thick second rear layer

95

.

The swash plate thus produced was incorporated into the foregoing single-headed piston type awash plate compressor and the single-headed piston type awash plate compressor was operated for the same operational suitability test of the swash plate. No defects, such as cracks and abrasively damaged parts, were found in the front and the rear surface of the swash plate.

EXAMPLE 7

The body of an aluminum-base material of a awash plate was immersed in a sulfuric acid solution or an oxalic acid solution and was subjected to an anodizing process using the body as an anode to form an oxide film (alumite layer) over the rear surface of the body made of the aluminum-base material. The body of the swash plate was washed with water. The measured thickness of the alumite layer forming the rear layer

94

was about 15 μm. The surface of the alumite layer was cleaned and degreased, and then the surface of the first rear layer

94

was coated with a coating layer of a material prepared by dispersing molybdenum disulfide particles of particle sizes in the range of 0.5 through 20 μm in a polyamidimide resin by a spray coating process. The coating layer was baked at 200° C. The rear surface

92

b

of the swash plate was ground to form a 10 μm thick second rear layer

95

.

The swash plate thus produced was incorporated into the foregoing single-headed piston type swash plate compressor and the single-headed piston type swash plate compressor was operated for the same operational suitability test of the swash plate. No defects, such as cracks and abrasively damaged parts, were found.

COMPARATIVE EXAMPLE 1

A swash plate in Comparative example 1 was produced by coating a body similar to that of the swash plate in Example 1 with only the same front layer

93

and the same first rear layer

94

as those of the copper-base alloy of Example 1 formed by the metal spraying process. The swash plate in Comparative example 1 corresponds to a swash plate obtained by omitting the second rear layer

95

of the polyamidimide resin containing molybdenum disulfide from the swash plate in Example 1.

The swash plate was incorporated into the foregoing single-headed piston type swash plate compressor and the single-headed piston type swash plate compressor was operated for the same operational suitability test of the swash plate. Cracks were found in the first rear surface

94

of the copper-base alloy formed by metal spraying.

COMPARATIVE EXAMPLE 2

A swash plate in Comparative example 2 was produced by coating a body similar to that of the swash plate in Example 4 with only the same front layer

93

and the same first rear layer

94

as those of alumite of Example 4. The swash plate in Comparative example 2 corresponds to a swash plate obtained by omitting the second rear layer

95

of the polyamidimide resin containing molybdenum disulfide from the swash plate in Example 4.

The swash plate was incorporated into the foregoing single-headed piston type swash plate compressor and the single-headed piston type swash plate compressor was operated for the same operational suitability test of the swash plate. Abrasively damaged parts were found in the first rear surface

94

of alumite.

The materials of the swash plates in Examples 1 through 7 and Comparative examples 1 and 2, and the results of the suitability tests of those swash plates are indicated in Table 1 below.

No defects were found in the rear surface of the swash plates in Examples 1 through 7 provided with the second rear surface layer, i.e., the solid lubricant layer. Cracks or abrasively damaged parts were found in the rear surface of the awash plates in Comparative examples 1 and 2 of the same material as the front surface of the same.

TABLE 1

Materials

Base

First

Second

Test results

Front

Material

rear

rear

Front

Rear

layer

(Body)

layer

layer

surface

surface

Example 1

Cu-base,

Fe-base

Cu-base,

MoS2 +

Defectless

Defectless

Metal

Metal

Polyamid-

sprayed

Sprayed

imide

Example 2

Sn-base,

Fe-base

Sn-base,

MoS2 +

Defectless

Defectless

Metal

Metal

Polyamid-

sprayed

sprayed

imide

Example 3

Sn-base,

Al-base

Sn-base,

MoS2 +

Defectless

Defectless

Plated

Plated

Polyamid-

imide

Example 4

Alumite

Al-base

Alumite

MoS2 +

Defectless

Defectless

Polyamid-

imide

Example 5

None

Al-base

None

MoS2 +

Defectless

Defectless

Polyamid-

imide

Example 6

None

Al-base

Sn-base,

MoS2 +

Defectless

Defectless

Plated

Polyamid-

imide

Example 7

None

Al-base

Alumite

MoS2 +

Defectless

Defectless

Polyamid-

imide

Compar-

Cu-base,

Fe-base

Cu-base,

None

Defectless

Cracked

ative

Metal

Metal

Example 1

sprayed

sprayed

Compar-

Alumite

Al-base

Alumite

None

Defectless

Seizing

ative

Example 2

Note: Shoes of a bearing steel were used.

(Facility in Controlling the Thickness of Layers or the Swash Plate)

The swash plates in Examples 1 to 7 are provided with the solid lubricant layer (a layer of a polyamidimide resin containing molybdenum disulfide) only on the rear side of the peripheral part

92

. The thickness of the solid lubricant layer is adjusted to 10 μm by grinding after forming a solid lubricant coating and baking the solid lubricant coating. The solid lubricant layer is ground for thickness adjustment by using the front surface

92

a

, i.e., the surface of the front layer

93

not coated with any solid lubricant layer, as a reference plane as illustrated in FIG.

5

. Such thickness adjustment is possible because the front surface of the peripheral part

92

of the swash plate is not provided with any solid lubricant layer. The advantage of forming said lubricant layers only on the rear side of the peripheral part of the swash plate is apparent as contrasted with the disadvantage of forming solid lubricant layers on both sides of the peripheral part

92

of the swash plate.

FIG. 6

illustrates a swash plate formed by forming first layers

96

a

and

96

b

, such as sprayed layers of copper or tin or alumite layers, on the front and the rear side of a peripheral part

92

of the body of a swash plate, and forming second layers

97

a

and

97

b

, i.e., solid lubricant layers, on the first layers

96

a

and

96

b

, respectively. When grinding the second layers

97

a

and

97

b

formed on the front and the rear side of the peripheral part

92

to adjust the thickness of the second layers

97

a

and

97

b

(hence the thickness of the peripheral part

92

of the swash plate), a surface other than the surface of the peripheral part

92

must be used as a reference plane.

When measuring and controlling the thickness of the solid lubricant layer

97

b

on the rear side of the peripheral part

92

during a swash plate producing process, for example, the rear end surface

91

a

of the land part

91

is used as a reference plane, a block gage

98

is put on the reference plane, the tip of the plunger of a dial indicator

99

is brought into contact with the surface of the solid lubricant layer

97

b

. The height H

1

of the rear end surface

91

a

, i.e., the reference plane, from the surface of the solid lubricant layer

97

b

is compared with the height H

2

of the same from the surface of the first layer

96

a

. The thickness of the solid lubricant layer

97

a

on the front side of the peripheral part

92

is measured and managed similarly. A surface apart from the measured surface must be used as the reference plane when the solid lubricant layers are formed respectively on both the sides of the peripheral part

92

and, therefore, the improvement of accuracy in thickness measurement is limited and hence the severe management of the thickness of the layer and hence that of the thickness of the swash plate is difficult.

When only the solid lubricant layer, i.e., the second rear surface

95

is formed on the rear side of the peripheral part

92

as shown in

FIG. 5

, the surface of the front layer

92

finished by grinding and not coated with any layer can be used as the reference plane. The front layer

93

and the first rear layer

94

are formed and finished by grinding, and the distance between the surface of the front layer

93

and that of the first rear surface

94

, i.e., a primary thickness T

1

, is measured by using the surface of front layer

93

as a reference plane. The second rear layer

95

is formed on the first rear layer

94

, and the distance between the surface of the front layer

93

and that of the second rear layer

95

, i.e., a secondary thickness T

2

, is measured. The thickness of the second rear layer

95

can be accurately determined by calculating the difference (T

2

−T

1

), i.e., the difference between the secondary thickness T

2

and the primary thickness T

1

. Since the surface nearest to the peripheral part

92

which needs thickness management can be used as the reference plane in the construction shown in

FIG. 5

, accuracy in measuring the thickness of the layer can be improved, severe control of the thickness of the layer can be achieved, and the control of the thickness of the swash plate can easily be achieved.

The embodiment of the present invention and Examples 1 through 7 have the following advantageous effects.

The front and the rear surface of the peripheral part

92

of the swash plate are finished with different materials or different surface treatment processes, respectively, and the second rear layer

95

is formed after completing the surface layer on the front side, Accordingly, the thickness of the second rear layer

95

can be controlled by using the surface of the front layer as a reference plane. The thickness of the peripheral part

92

of the swash plate can accurately be measured by using the surface of the front layer after forming the second rear layer

95

, so that the thickness of the swash plate can severely be managed.

Since the accuracy of thickness control of the swash plate is improved remarkably, the top clearance in the swash plate compressor with the piston

36

at its top dead center can accurately be set at a value nearly equal to zero, whereby the compression efficiency of the swash plate compressor is improved.

Antiseizing properties of the swash plate

23

to prevent seizing between the swash plate

23

and the shoes

37

when the interior of the crank chamber is led into a dry state can be improved (Examples 1 through 7).

The solid lubricant layer, i.e., the outermost layer on the rear side of the swash plate, effectively prevents the development of cracks in the sprayed layer of a copper-base alloy or the abrasive damaging of the alumite layer formed on the rear side of the swash plate (Examples 1 and 4 and Comparative examples 1 and 2).

It is known from the comparison of the swash plates in Example 1 and Comparative example 1 and those in Example 4 and Comparative example 2 that it is scarcely necessary to form a solid lubricant layer on the front side of the swash plate in the single-headed piston type swash plate compressor, because the magnitude of sliding friction between the rear surface of the swash plate and the mating shoe

37

resulting from a compression reaction force acting on the piston

36

while the piston

36

is in the compression stroke is far greater than the magnitude of sliding friction between the front surface (the surface of the front layer

93

) of the swash plate and the mating shoe

37

while the piston

36

is in the suction stroke.

If the body of the swash plate

23

is made of an iron-base material having a specific gravity greater than that of an aluminum-base material (Examples 1 and 2), the swash plate

23

has a large inertia. The large inertia of the swash plate does not deteriorate the response of the swash plate for changing its inclination even when the clutchless compressor unavoidably operates at a high operating speed according to the operation of the engine

20

at a high engine speed.

The following modifications are possible in the present invention.

A variable-capacity compressor is formed to have a refrigerant compressing unit, and a solenoid clutch interposed between the compressing unit and an external drive-power source, e.g., a vehicle engine.

A swash plate having front and rear opposite surfaces onto which solid lubricant layers are applied and used for a swash-plate-operated refrigerant compressor including at least one piston to compress a refrigerant gas when a rotating motion of the swash plate is converted through a pair of shoes into a reciprocating motion of the piston, is produced by a method which comprises the steps of:

forming a temporary surface to be used as a first reference plane on one of the opposite surfaces of the swash plate;

forming a first solid lubricant layer containing a solid lubricant at least in part thereof on the other of the opposite surfaces of the swash plate;

measuring the thickness of the first solid lubricant layer or that of the swash plate by using the temporary surface formed by the first step as a reference plane;

grinding the first solid lubricant layer to adjust the thickness of the first solid lubricant layer or that of the swash plate measured in the third step to a desired thickness to form a second reference plane;

forming a second solid lubricant layer containing a solid lubricant at least in part thereof on the above-mentioned temporary surface;

measuring the thickness of the second solid lubricant layer or the swash plate by using the second reference plane formed by the fourth step; and

grinding the second solid lubricant layer to adjust the thickness of the layer or the swash plate to a predetermined thickness.

Advantageous effects exhibited by the present invention are provided below.

In the single-headed piston type swash-plate-operated compressor according to the present invention stated in any one of the accompanying claims, the accuracy of the thickness of the swash plate is secured and the compression efficiency of the single-headed piston type swash plate compressor is reliably improved while the slide-friction between the swash plate and the shoes is improved and the antiseizing property and the abrasion resistance of the swash plate are improved.

The swash plate production method of the present invention facilitates the controlling of the thickness of the swash plate of the single-headed piston type swash-plate-operated compressor even if the swash plate is provided on its rear side with the solid lubricant layer for improving the slide-friction between the rear surface of the swash plate and the shoes, which enables machining accuracy in adjusting the thickness of the swash plate to a desired value.

It should be understood that many changes and modifications will occur to a person skilled in the art without departing from the scope and spirit of the present invention claimed in the accompanying claims.

Number	Name	Date
5056417	Kato et al.	Oct 1991
5630355	Ikeda et al.	May 1997
5655432	Wilkosz et al.	Aug 1997
5875702	Kawagoe et al.	Mar 1999
5960542	Umemura et al.	Oct 1999

Number	Date	Country
0 776 986 A1	Jun 1997	EP
60-22080	Feb 1985	JP
60-19972	Feb 1985	JP
60022080	Feb 1985	JP
08199327	Aug 1996	JP
8-199327	Aug 1996	JP
09209926	Aug 1997	JP
WO9525224	Sep 1995	WO

Single-headed piston type swash-plate-operated compressor and a method of producing a swash plate

Information

Patent Number

Date Filed

Date Issued

Inventors

Original Assignees

Examiners

Agents

CPC

US Classifications

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US

International Classifications

Abstract

Description

Claims

Priority Claims (1)

US Referenced Citations (5)

Foreign Referenced Citations (8)

Non-Patent Literature Citations (1)