EP0220798A1

EP0220798A1 - Wobble plate type compressor with variable displacement mechanism

Info

Publication number: EP0220798A1
Application number: EP19860305956
Authority: EP
Inventors: Yukihiko Taguchi
Original assignee: Sanden Corp
Current assignee: Sanden Corp
Priority date: 1985-08-09
Filing date: 1986-08-01
Publication date: 1987-05-06
Also published as: JPS6231782U

Abstract

A wobble plate type compressor (1) has a housing (2) having a cylinder block (4) provided with a plurality of cylinders (13). Pistons (12) are slidable in the cylinders and are arranged to be reciprocated by a drive mechanism including a wobble plate (10). A slant angle control means has a control valve mechanism (16) including a first valve (163a) to control the communication between the crank chamber (22) and the discharge chamber (52), a second valve (163c) to control the communication between the crank chamber (22) and the suction chamber (51), and a pressure sensing means (162) to control operation of the first and second valves. The pressure sensing means (162) is disposed within a pressure chamber (162c) unconnected with the suction chamber and having a port (161h) to which refrigerant pressure at a position in a refrigerant circuit between an inlet port of the compressor and an evaporator can be introduced in use.

Description

The present invention relates to a wobble plate type compressor and more particularly, to a wobble plate type compressor with a variable displacement mechanism suitable for use in an automobile air conditioning system.
In recent years, a requirement of compressors for automobile air conditioning systems has been the inclusion of a variable displacement mechanism for improving the conditions in the car and decreasing the power loss of the engine. Such mechanisms for controlling the volume of the compressor enable subsequent change of the compression volume in response to changes in the heat load of the air conditioning system.
In a wobble plate type compressor, a variable displacement mechanism is changed by varying the slant angle of the wobble plate to the drive shaft, i.e., the piston stroke of the pistons connected to the wobble plate is changed due to changes in the slant angle of wobble plate. The volume of the compressor is changed in accordance with changes in the stroke of the piston.
Referring to Figure 1, the construction of a conventional wobble plate type compressor with a variable displacement mechanism is shown. The compressor 1 includes a compressor housing 2 having an annular casing 3, a cylinder block 4 which is attached to one end opening of the casing 3 and a cylinder head 5 which is attached to the other end surface of the cylinder block 4 via a valve plate 6. An opening 21 is formed in the centre of the end of the casing 3 for a drive shaft 7 which is rotatably supported in the casing 3 by a bearing 18 disposed in the opening 21. The inner end of the drive shaft 7 extends within a central bore 41 formed in the centre of the cylinder block 4 and rotatably supported by a bearing 19.
A rotor 8 is connected to the drive shaft 7 within the casing 3 and is engaged with an inclined plate 9 through a hinge portion 81, and the angle of the inclined plate 9 to the drive shaft 7 is changed by movememnt of the hinge portion 81. A wobble plate 10 is disposed on the other side of the inclined plate 9 via a bearing 91. A plurality of cylinders 13 are equiangularly formed in the cylinder block 4 and a piston is reciprocably disposed within each cylinder 13, connected to the wobble plate 10 by a respective connecting rod 11. One end of the connecting rod 11 is connected to the wobble plate 10 with a ball joint and the other end of the connecting rod 11 is connected to the piston 12.
A guide bar 15 extends through the crank chamber 22 of the casing 3 and is fixed in the housing 2. The lower end portion of the wobble plate 10 is engaged with the guide bar 15 to allow reciprocal motion of the wobble plate 10 while preventing rotational motion.
The cylinder head 5 is provided with a suction chamber 51 and a discharge chamber 52, which communicate with the cylinders 13 through suction holes 61 and discharge holes 62, respectively, formed through the valve plate 6. A by-pass passage 42 is formed in the cylinder block 4 to accomplish communication between the discharge chamber 52 and the crank chamber 22 of the casing 3, and communication between the chambers is controlled by a valve mechanism 14 disposed in the cylinder head 5. Furthermore, a by-pass passage 71 is formed in the drive shaft 7 to allow communication between the crank chamber 22 and the central bore 41, and the central bore 41 communicates with the suction chamber 51 through a passageway 43 formed in the cylinder block 4. Communication between the crank chamber 22 and the suction chamber 51 is also controlled by the valve mechanism 14.
The control valve mechanism 14 comprises a valve housing 141, bellows 142 containing a gas under a predetermined pressure and an operating pin 143 attached to the top of the bellows 142. A valve housing 141 defines three chambers in a row; a first chamber 141a, a second chamber 141b, and a third chamber 141c. The first chamber 141a communicates with the discharge chamber 52 through a first hole 141d and also communicates with the crank chamber 22 through a second hole 141e and the by-pass passage 42. The second chamber 141b communicates with the interior of the crank chamber 22 through a third hole 141f, by-pass passage 71 and passageway 43, and also communicates with the suction chamber 51 through a fourth hole 141g. The third chamber 141c, in which the bellows 142 is disposed, communicates with the suction chamber 51 through a fifth hole 141h. The operating pin 143 is slidably supported in a central portion 141i of the control valve mechanism 14 to extend through the three chambers, and is provided with a first valve portion 143a at one end and also a second valve portion 143b formed at the other end, to control the communication between the discharge chamber 52 and the crank chamber 22 and the suction chamber 51 and the crank chamber 22 respectively.
In operation, when an electromagnetic clutch, which may be assembled on the compressor is operated, the drive shaft 7 is connected with a driving source, e.g., an engine of a car through the clutch. When the drive shaft 7 is driven, the inclined plate 9 is driven by the rotor 8 and the wobble plate 10 is wobbled back and forth by the movement of the inclined plate 9. The piston 12 is thus reciprocated by the movement of the wobble plate 10 and, as a result of the reciprocating motion of the piston, refrigerant gas taken into the cylinders 13 from the suction chamber 51 is compressed and discharged to the discharge chamber 52.
Since the third chamber 141d of the valve mechanism 14 is normally connected to the suction chamber 51, if the pressure in suction chamber 51 is increased and the pressure in the third chamber 141d is higher than that of the gas in the bellows 142, the bellows 142 shrinks in accordance with the differential between the pressures. Accordingly, the operating pin 143 moves downwardly, and the first valve portion 143a of the operating pin 143 is positioned lower than the hole 141d. Therefore, the discharge chamber 52 is disconnected from the crank chamber 22 and, at the same time, since the second valve portion 143b also moves downwardly, the crank chamber 22 is connected with the suction chamber 51 through the second chamber 141b and holes 141f, 141g. The pressure in the crank chamber 22, which acts on the rear of the pistons 12, is thus decreased, and the slant angle of wobble plate 10 to drive shaft 7 is increased due to the resulting increased stroke of the pistons 12. The slant angle of the wobble plate 10 is at its largest angle, when the stroke of the pistons 12, i.e., the displacement of the compressor, is also at its maximum.
When the stroke of the pistons 12 is increased, the pressure in the suction chamber 51 is decreased, and if the pressure in the suction chamber 51 is decreased below that of the gas in the bellows 142, the bellows 142 expands and the hole 141g disposed in the third chamber 141c is closed by the second valve portion 143b. At the same time, the first hole 141d is opened since the first valve portion 143a moves upwardly above the upper end of hole 141d, and the discharge chamber 52 is communicated with the crank chamber 22 through the first chamber 141a. The pressure in the crank chamber 22 is thus increased, and the slant angle of the wobble plate 10 to the drive shaft 7 is reduced. The stroke of the pistons 12 also decreases and, therefore, the pressure in the suction chamber 51 is increased.
As mentioned above, the control valve mechanism 14 controls the slant angle of the wobble plate 10, i.e., the stroke of the pistons 12 is controlled in accordance with the pressure in the suction chamber 51 to maintain the pressure in the suction chamber 51. Accordingly, the pressure in the suction chamber 51 is substantially constant regardless of the rotational speed of the engine of the car.
Referring to Figure 2, in the above-mentioned compressor the relationship between the pressure in the suction chamber and the temperature of the air flowing into an evaporator, in accordance with the rotational speed of the driving source is shown. As clearly shown in the figure by the solid line, the pressure in the suction chamber of the compressor is maintained substantially constant without influence from the temperature of the air flowing into the evaporator, i.e., the air in the interior of the car while operating the variable displacement mechanism. The dotted lines show the pressure at maximum capacity for two diferent rotational speeds N₁,N₂, the speed increasing from N₁ through N_n.
On the other hand, referring to Figure 3, when the temperature of the air at the outlet side of the evaporator, i.e., the temperature of air in the interior of a car becomes lower, the circulating volume of refrigerant in the refrigerating circuit reduces. The influence of the pressure loss in the refrigerant circuit between the outlet side of the evaporator and a compressor is not felt at all, and the pressure at the outlet side of the evaporator is controlled to be constant as well as the pressure in the suction chamber. However, when the temperature of the air flowing into the evaporator, i.e., the temperature of the air in the interior of the car increases, the circulating volume of refrigerant is increased, and the pressure loss in the refrigerant circuit between the outlet side of the evaporator and the compressor is increased.
As mentioned above, in an conventional wobble plate type compressor with a variable displacement mechanism, since the stroke of the piston is controlled so that the pressure in the suction chamber is substantially constant, the cooling performance may be decreased by the influence of the pressure loss in the refrigerant circuit between the outlet side of the evaporator and the compressor, when the heating load increases.
It is a primary object of the present invention to provide a wobble plate type compressor with a variable displacement mechanism which has improved cooling capacity.
It is another object of the present invention to provide a wobble plate type compressor with a variable displacement which can maintain a suitable amount of pressure at an outlet side of an evaporator without influence from the heating load on the refrigerating circuit.
A wobble plate type compressor in accordance with the present invention includes a housing having a cylinder block provided with a plurality of cylinders; a suction chamber and a discharge chamber; a crank chamber adjacent the cylinder block; a piston slidable in each cylinder and arranged to be reciprocated by a drive mechanism including a wobble plate; an input drive rotor; and a drive shaft connected to the input rotor to drive the input rotor; slant angle control means having a control valve mechanism including a first valve to control the communication between the crank chamber and the discharge chamber, a second valve to control the communication between the crank chamber and the suction chamber, and a pressure sensing means to control operation of the first and second valves, chracterized in that the pressure sensing means is disposed within a pressure chamber unconnected with the suction chamber and having a port to which refrigerant pressure at a position in a refrigerant circuit between an inlet port of a compressor and an evaporator can be introduced in use.
One example of a compressor constructed in accordance with the invention will now be described with reference to the accompanying drawings, in which:-

Figure 1 is a cross-sectional view of a conventional wobble plate type compressor with a variable displacement mechanism;
Figure 2 is a graph showing the relationship between the pressure in the suction chamber and the temperature of the air flowing into an evaporator in a refrigerant circuit provided with a wobble plate type compressor with a convention variable displacement mechanism;
Figure 3 is a graph showing the relationship between the pressure at the outlet side of an evaporator and the temperature of the air flowing into an evaporator in a refrigerant circuit provided with a wobble plate type compressor with a conventional variable displacement mechanism;
Figure 4 is a cross-sectional view of a wobble plate type compressor with a variable displacement mechanism in accordance with the embodiment of the invention;
Figure 5 is a schematic view of a refrigerant circuit in which a wobble plate type compressor with a variable displacement mechanism of Figure 4 is used;
Figure 6 is a graph showing the relationship between the pressure at the outlet side of an evaporator and the temperature of the air flowing into the evaporator in the refrigerant circuit shown in Figure 5; and
Figure 7 is a graph showing, respectively, the characteristics of cooling down when a wobble plate type compressor with a variable displacement mechanism in accordance with the embodiment of the invention and a wobble plate compressor with a conventional variable displacement mechanism are used in the same car.

Since the compressor 100 shown in Figure 4 is substantially of the same construction as the compressor 1 shown in Figure 1, except for the control valve mechanism, the same reference numerals are used to indicate the same parts of the compressor. The description of the construction and operation of the compressor except for the control valve mechanism will not be repeated in order to simplify the description.
The control valve mechanism 16 comprises a valve housing 161, a bellows 162 containing a gas under a predetermined pressure and an operating pin 163 attached to one end portion of the bellows 162. A valve housing 161 is provided with three chambers; a first chamber 161a, a second chamber 161b and a third chamber 161c. These three chambers are formed in a row within the housing 161 and a pin 163 extends within the valve housing 161, extending through all three chambers. The first chamber 161a is provided with a first hole 161d at its top to communicate with the discharge chamber 52 and is also provided with the second hole 161e at its periphery to communicate with the crank chamber 22 through a by-pass passage 42. A ball valve element, which comprises a ball 163a fixed on the end portion of the pin 163, a valve seat 164 and a spring 163b, is disposed within the chamber 161a to control the communication between the first hole 161d and the second hole 161e. The spring 163b usually urges the ball 163b against the valve seat 164 to disconnect the first and second holes 161d, 161e. The second chamber 161b is provided with a third hole 161f to communicate with the crank chamber 22 through the central bore 41 of the cylinder block 4 and the passageway 43, and is also provided with a fourth hole 161g to communicate with the suction chamber 51. The throttle valve element, which comprises a valve element 163c formed at the middle of the pin 163 and a valve seat 165 formed in an interior surface of the second chamber 161b, is disposed in the second chamber 161b to control communication between the third and fourth holes 161f and 161g. The third chamber 161c is divided from the second chamber 161b by a partition plate 163j and is provided with a fifth hole 161h which connects the interior of the third chamber 161c and an accumulator 140 of the refrigerating system (see Fig. 5).
As can be seen from Figure 5, the outlet port of the compressor 100 is connected to a condenser 110. An evaporator 130 is connected with the condenser 110 through an orifice 120, and the inlet port of the compressor 100 is connected with the evaporator 130 through an accumulator 140 which is also connected with the interior of the third chamber 161c of the control valve mechanism 16. The pressure in accumulator 140 is thus directly introduced into the interior of the third chamber 161c.
In operation, when the pressure in the accumulator 140 i.e., the pressure in the third chamber 161 of the valve mechanism 16, is higher than a predetemined pressure in the bellows 162, the bellows 162 shrinks due to the pressure difference between the third chamber 161c and the interior of the bellows 162. If the bellows 162 shrinks, the operating pin 163 moves downwardly and, at that time, the ball 163a of the operating pin 163 is pushed downwardly to contact the valve seat 164 thereby closing the communication between the first and second holes 161d, 161e. Thus, the discharge chamber 52 is disconnected from the crank chamber 22. Also, the throttle valve element 163c moves downward together with the operating pin 163 thereby to open the communication between the third and the fourth holes 161f, 161g. The crank chamber 22 is thus connected with the suction chamber 51 through the holes 161f, 161g, the central bore 41, and the passageway 42, and as a result of this connection, the pressure in the crank chamber 22 and that on the rear of the pistons 12, decreases. Therefore, the slant angle of the wobble plate 10 to the drive shaft 7 is increased, the stroke of the piston 12 is increased and, thus, the compression capacity of the compressor 100 is increased. When the compression capacity of the compressor 100 is at its largest the pressure in suction chamber 51 is equal to the pressure in the crank chamber 22.
On the other hand, when the pressure in the accumulator 140 is lower than a predetermined pressure in the bellows 162, the bellows 162 is expanded due to the pressure difference between the third chamber and the interior of the bellows 162 and when the bellows 162 expands, the operating pin 163 is moved upwardly, and the ball 163a is moved upwards against the recoil strength of the spring 163b to open communication between the first and the second holes 161d, 161e. Thus the discharge chamber 52 is connected with the crank chamber 22 through the first and second holes 161e, and the by-pass passage 42 and, as a result of this connection, the pressure in the crank chamber 22 is increased. On the other hand, the throttle valve element 163c of the operating pin 163 moves upwards and contacts the valve seat 165 to close the communication between the third and fourth holes 161f, 161g. Therefore, the crank chamber 22 is disconnected from the suction chamber 51. If the pressure in the crank chamber 22 is increased, the slant angle of the wobble plate 10 to drive shaft 7 is decreased, the stroke of the piston 12 is decreased and, therefore the compression capacity of the compressor 100 is decreased.
In the above-mentioned embodiment of the invention, since the slant angle of the wobble plate 10 is changed in accordance with the pressure in the accumulator, as shown by a solid line in Figure 6, the pressure of the refrigerant gas at the outlet side of the evaporator can be maintained constant without influence from the temperature of the air flowing into the evaporator, i.e., the heat load of the refrigerating circuit. Therefore, the characteristic of the cooling performance of the air conditioning system under high heat load conditions is improved, as shown in Figure 7. In Figure 7, the solid line indicates the cooling performance of the air conditioning system provided with the compressor of this example, and the dotted line indicates the cooling performance of the prior air conditioning system.

Claims

1. A wobble plate type compressor (1) including a housing (2) having a cylinder block (4) provided with a plurality of cylinders (13); a suction chamber (51) and a discharge chamber (52); a crank chamber (22) adjacent the cylinder block; a piston (12) slidable in each cylinder (13) and arranged to be reciprocated by a drive mechanism including a wobble plate (10); an input drive rotor (8); and a drive shaft (7) connected to the input rotor to drive the input rotor; slant angle control means having a control valve mechanism (16) including a first valve (163a) to control the communication between the crank chamber (22) and the discharge chamber (52), a second valve (163c) to control the communication between the crank chamber (22) and the suction chamber (51), and a pressure sensing means (162) to control operation of the first and second valves, characterized in that the pressure sensing means (162) is disposed within a pressure chamber (162c) unconnected with the suction chamber (51) and having a port (161h) to which refrigerant pressure at a position in a refrigerant circuit between an inlet port of the compressor and an evaporator can be introduced in use.

2. A wobble plate type compressor according to claim 1, wherein the pressure sensing means (162) is a bellows.

3. A refrigeration circuit including a compressor according to claim 1 or claim 2; and an accumulator (140) connected to the suction chamber (51) of the compressor, the accumulator also being connected to the port (161h) in the pressure chamber containing the pressure sensing means (162).