JPS62298670A - Variable capacity type compressor - Google Patents

Abstract

PURPOSE:To have inclination control of a swash plate with simple construction by keeping the suction gas pressure within a crank case, and furnishing the swash plate with a spring which is to give restoration moment. CONSTITUTION:Through a dry plug 11, a swash plate 21 is mounted on a drive shaft 6 rotated by engine through a pulley 10, and with rotation of this swash plate 21, a piston 29 is reciprocated in a cylinder 30 through a piston rod 28. After pressurization of a refrigerant sucked from an inlet 33 within an actuation chamber P, it is discharged from an outlet 34. In this device, a low pressure chamber 35 is put in communication with a cranking chamber 42 through a communication path 43 so as to make the pressure in both chambers 35, 42 equal. To said swash plate 21 on its one side, is applied a force which is to incline the swash plate 21 by applying the pressure difference between the front and back of each piston 29, and also in case the suction gas pressure is below a certain level, a force in the direction of lessening the inclination angle of the swash plate is applied by a spring 19.

Description

[Detailed Description of the Invention] 3. Detailed Description of the Invention [Field of Industrial Application] The present invention relates to a variable displacement compressor, and in particular to a variable displacement axial compressor suitable for use in automobile air conditioners, etc. It concerns piston compressors.

[Conventional technology]

Variable displacement axial piston compressors used in refrigeration cycle compressors such as vehicle air conditioners are equipped with a swash plate mechanism, cam mechanism, etc. on the drive shaft, and the oscillating rotational movement of the swash plate is transferred to the piston by the cam mechanism. The refrigerant gas sucked into the cylinder is compressed and discharged by converting it into reciprocating motion.
Further, the compressor capacity (cylinder capacity) is controlled by changing the piston stroke in accordance with the tilt angle control of the swash plate.

This type of variable displacement compressor is disclosed in, for example, Japanese Patent Publication No. 58-4195 and Japanese Patent Application Laid-open No. 54-94107.

It is disclosed in US Pat. No. 4,174,191 and the like.

This type of variable displacement compressor variably controls the compressor capacity depending on the heat load of the refrigeration cycle of the air conditioner. For example, when the heat load of the refrigeration cycle is large, the inclination angle of the swash plate is increased. to increase the piston stroke and compressor capacity, and on the other hand,
When the heat load of the refrigeration cycle is small, the inclination angle of the swash plate and the compressor capacity are variably controlled to be small so that the cylinder suction gas pressure does not fall below a predetermined value (for example, the gas pressure value that does not cause frost formation on the evaporator). That's what I do. Capacity control of such a compressor is
For example, in the compressor described in Japanese Patent Publication No. 58-4195, various swash plate inclination angle control means have been used. A hydraulic control valve that controls the increase/decrease of blow pie gas pressure in the crankcase, and a hydraulic piston assembly that acts on the swash plate in the direction that increases the swash plate inclination angle (increases the piston stroke). When the blow pie gas pressure in the crankcase is increased, the inclination angle of the swash plate is controlled to be small by this increased pressure and the force of the spring member.

When the blow pie gas pressure in the crankcase is reduced and the hydraulic pressure in the hydraulic piston assembly is increased, a force is applied to the swash plate that resists the spring force and the pressure in the crankcase.
The angle of inclination of the swash plate is increased. Note that this hydraulic pressure is determined when the suction gas pressure of the compressor is a predetermined value (
For example, in the case of refrigerant gas, it is set so that it does not fall below 2.1 kg/a1).

In addition, the compressor described in JP-A-54-94107 has a spring member that acts on the swash plate in a direction that increases the angle of inclination of the swash plate, and a spring member that acts on the swash plate in a direction that reduces the angle of inclination of the swash plate. A pressure control mechanism is used to control the pressure inside the crankcase with respect to the resultant force of the gas compression force in the spring member and the cylinder, and to balance these forces to obtain a desired swash plate inclination angle. It is.

Further, the compressor described in U.S. Pat. No. 4,174,191 uses a spring member and a swash plate inclination angle control actuator that act on the swash plate in a direction where the swash plate inclination angle is maximum, and the compressor uses the spring member and the swash plate inclination angle control actuator. The inclination angle of the swash plate is controlled by the balance between the pressing force of the actuator and the gas compression force in the compressor cylinder that resists these forces.

[Problem that the invention seeks to solve]

However, in order to control the inclination angle of the swash plate, each of the conventional examples described above uses a pressure control mechanism such as a hydraulic control valve mechanism that controls the pressure in the crankcase, an actuator for controlling the swash plate inclination angle, etc. in addition to a spring member. Complicated flow channels for pressure control and pressure control have become essential, and the number of parts and flow channels in the entire device has increased, resulting in a complex structure that requires assembly work time and tends to increase manufacturing and product costs. Furthermore, the aforementioned Japanese Patent Application Publication No. 1983
In the swash plate inclination angle control system such as No. 94107 and U.S. Pat. No. 4,174,191, the spring force of the spring member acts in the direction of increasing the swash plate inclination angle. When the compressor starts, the plate increases to its maximum inclination angle and the compressor piston moves to its maximum stroke position.
Since the air conditioner is suddenly operated at maximum capacity regardless of the heat load state of the refrigeration cycle, the engine load increases rapidly, and in the case of a small capacity engine, there is a problem in that the shock is large and the riding comfort becomes poor. Other methods for controlling the swash plate inclination angle by controlling the pressure inside the crankcase include the NIS Technical Vapor Series 850040 (published May 1, 1985 (SAE Technical Paper 5e).
ries850040).

This method controls the swash plate inclination angle without using a spring member. When trying to reduce the swash plate inclination angle, high pressure gas is introduced into the crankcase to reduce the pressure inside the crankcase. However, with this method, in addition to the refrigerant leaking between the piston and cylinder, high-pressure gas flows into the crankcase, so there is a problem that the lubricating oil separated from the leaking refrigerant flows out of the compressor. was there.

The present invention has been made in order to solve the above problems, and its purpose is to simplify the structure of the compressor, and to control the desired swash plate inclination angle and, ultimately, the compressor capacity. An object of the present invention is to provide a variable displacement compressor.

[Means for solving problems]

In order to achieve the above object, the present invention provides a swash plate control means for a variable displacement axial piston compressor that changes the piston stroke length and cylinder capacity by changing the inclination angle of the swash plate as follows. It is composed of elements. That is, as a first element, by communicating the low-pressure gas chamber that introduces suction gas into the cylinder of the compressor from the outside with the inside of the crankcase where the swash plate or the like is inserted, the pressure inside the crankcase can be adjusted to reduce the pressure inside the crankcase. equalize the pressure. As a second element, a tilting moment is applied to the swash plate to tilt the swash plate by applying a gas action force due to a pressure difference between the cylinder internal pressure applied to each piston and the crankcase internal pressure to one side of the swash plate. A spring member is disposed on the other side to provide a restoring moment in a direction opposite to the tilting moment, and the swash plate is held at a predetermined inclination angle by balancing the tilting moment and the restoring moment. . As a third element, the spring member has a spring characteristic that overcomes the tilting moment and variably controls the swash plate in the direction of decreasing the tilt angle when the suction gas pressure is about to decrease below a predetermined value. The compressor capacity is set to be variably controlled by this variable inclination angle control up to a capacity range in which the suction gas pressure does not fall below a predetermined value.

[Effect]

According to the present invention having such a configuration, a gas action force due to a pressure difference between the pressure inside each cylinder (gas compression force) acting on a plurality of pistons and the pressure inside the crankcase is applied to one side of the swash plate. A tilting moment is generated to tilt the swash plate, and a restoring moment opposite to the tilting moment is generated on the other side of the swash plate by a spring. The tilt angle is maintained to control the stroke of the piston and the capacity of the compressor (cylinder). Since the pressure inside the crankcase is set to be equal to the pressure of the suction gas of the compressor, the pressure inside the crankcase changes in accordance with the change in the suction gas pressure, and furthermore, the tilting moment is generated in the swash plate. The magnitude of the gas acting force on the piston will also change.

This gas action force has a characteristic that it decreases as the suction gas pressure of the compressor decreases. In the present invention, when the suction gas pressure is about to decrease below a predetermined value, the restoring moment due to the spring force of the spring member is reduced. The inclination angle of the swash plate is controlled to be small by overcoming the gas action force and the tilting moment applied to the swash plate. As a result, the stroke of the piston and the compressor capacity are variably controlled to be small, and this capacity control reduces the suction gas pressure. It is regulated so that it does not fall below a predetermined value.

Therefore, according to the present invention, the capacity of the compressor can be controlled simply by installing a through hole for making the internal pressure of the crankcase equal to the suction gas pressure and a spring member that balances the tilting moment of the swash plate. Its structure can be greatly simplified compared to the swash plate control mechanism used in

〔Example〕

An embodiment of the present invention will be described based on FIGS. 1 to 5.

FIG. 1 is a cross-sectional view of an axial piston compressor that is an embodiment of the present invention. In the figure, 1 is a front cover of the compressor, 2 is a rear cover, and 3 is a cylinder block. The compressor is fitted on three sides of the cylinder block between the front cover 1 and the rear cover 2 via bolts (not shown), and an O-ring 4.5 is interposed between the cover 1.2 and the cylinder block 3. Secrecy inside the crankcase 42 is maintained. 6 is a drive shaft, and the drive shaft 6 is rotatably supported by radial bearings 7 and 8 provided at the end of the front cover 1 and the center of the cylinder block 3, respectively. One end of the drive shaft 6 protrudes from the front cover 1.

Magnetic clutch 9 and pulley 1 provided on this protruding end
0 transmits the rotational force of the engine and rotates. A drive lug 11 is fixed to a portion of the drive shaft 6 between the bearings 7 and 8 in a direction perpendicular to the shaft.
A cylindrical slider 12 is mounted on the outer peripheral surface of the drive shaft 6 at the first mounting position. The slider 12 has a flange 13 extending toward the front side, and the slider 12 includes:
There is a notch (not shown) in the axial direction, and this notch is fitted into the drive lug 11, so that the slider 12 rotates together with the drive @6 through the drive lug 11, and also slides on the drive shaft 6 in the axial direction. It is possible to do so. Further, the drive shaft 6 is provided with a stepped portion 6a, and between the stepped portion 6a and a bearing portion 7 provided inside the front cover 1,
A thrust bearing mechanism 14 is installed. The thrust bearing mechanism 14 is composed of a stationary race 15 in contact with the bearing side of the front cover 1, rollers 16, and a rotating race 17 attached via the rollers 16.

Of these, the rotating side race 17 is provided inside the front cover 1 so as to cover the rollers 16 and the stationary side race 15, and the collar portion 18 of the rotating side race 17 is located near the front cover 1, and the collar portion 18 of the rotating side race 17 is attached to the aforementioned collar of the slider 12. A spring 19 for controlling the inclination angle of the swash plate 21, which will be described later, is installed between the collar parts 13 and 18. Spring 19 is.

Press the slider 12 to the right in the drawing (in the direction of the arrow). Further, a pin 20 is fixed to the drive lug 11, and a guide groove 23 of an engagement piece 22 formed on the swash plate 21 is attached to the pin 20.
is engaged. The swash plate 21 has a boss 24 formed in the center thereof to be fitted to the drive shaft 6 with a predetermined gap therebetween.
The center of the inner peripheral surface of the boss 24! ! ! At the inclined center of the swash plate 21, support bins (not shown) are loosely engaged with both sides of the slider 12.

The swash plate 21 is rotatably attached to the slider 12 via this support pin. With this configuration, when the slider 12 moves in the axial direction, the diagonal body 21 tilts in the directions of arrows C and D around the support pin (not shown) while being guided to the bin 20 by @23. In addition, the tilting operation of the swash plate 21 is caused by the tilt (N movement axis 6) when the slider 12 moves in the direction of arrow A.
The degree of inclination (based on the vertical line) becomes smaller, and arrow B
The inclination is set to increase when moving in the direction.

25 is a thrust bearing 526 provided on the sliding surface side of the swash plate 21
is a radial bearing provided on the outer surface of the boss portion 24 of the swash plate 21, and a drive plate 27 is attached via a radial bearing 26 and a thrust bearing 25. J! ! The movable plate 27 performs a reciprocating motion (cam motion) in response to the rotational force when the swash plate 21 swings and rotates when the drive shaft 6 rotates.

The force acting on the driving plate 277'1 to the left in the figure is supported by the thrust bearing 25M, while the force acting in the right direction in the figure is supported by the fixing ring 27a fixed to the swash plate 21.

The drive plate 27 is connected to a piston 29 in a cylinder 30 provided in the cylinder block 3 via a piston rod 28. In the cylinder block 3, a plurality of cylinders 30 (for example, 5 cylinders) are arranged at equal intervals on a circle concentric with the center of the radial bearing 8 described above, and each cylinder 30 houses a piston 29, and drives the cylinder block 3. When the plate 27 swings,
A piston 29 reciprocates within the cylinder 30 via the piston rod 28. Both ends of the piston rod 28 are rotatably connected to the drive plate 27 and the piston 29 by means of a ball joint.

Reference numeral 31 denotes a suction valve plate provided on the rear end surface of the cylinder block 3, and a cylinder head 32 is mounted further to the rear side of the cylinder block 3 so as to be interposed between the cylinder block 3 and the rear cover 2. There is. 33 is a refrigerant inlet provided in the rear cover 2, and 34 is a refrigerant outlet. The refrigerant inlet 33 communicates with an annular low-pressure gas chamber 35 formed in the rear cover 2, and the refrigerant discharge port 34 communicates with an annular high-pressure gas chamber 36 that is partitioned separately from the low-pressure gas chamber 35. In addition, the cylinder head 32 includes each cylinder 3.
A suction passage hole 37 communicating with the cylinder 30 and the low pressure gas chamber 35 is provided, and a discharge passage hole 38 is provided communicating the cylinder 30 with the high pressure gas chamber 35. Discharge valve plate 3
9. A discharge valve support plate 40 is installed. However,
A specially selected evaporative refrigerant from a refrigeration cycle (not shown) flows into the low-pressure gas chamber 35 of the rear cover 2 through a refrigerant inlet 33, and the refrigerant that has flowed in flows through a suction hole 37. The compressed refrigerant sucked into the cylinder 30 and discharged from the other cylinder 30 is passed through the discharge passage hole 38.
It flows out to the refrigeration cycle side through the high pressure gas chamber 36 and the outlet 34. A shaft seal 41 seals between the front cover 1 and the drive shaft 6, and the inside of the crankcase 42 is kept airtight by the shaft seal 41 and the aforementioned O-rings 4 and 5. Note that the drive plate 27 has this drive plate 27.
A rotation prevention mechanism (not shown) is provided to prevent the drive shaft 6 from rotating together with the drive shaft 6.

42 is the aforementioned slider 12. Spring member 19° Swash plate 2
1. The crankcase 42 is formed by the inner space of the front cover 1, and the swash plate 21 performs a tilting operation and a predetermined rocking rotation operation within the crankcase 42. performs a rocking motion. 43 is a through hole that communicates between the low pressure gas chamber 35 on the rear cover 2 side and the crankcase 42; It is provided to penetrate through the wall thickness.

Next, the basic operation of the compressor having the above configuration and the stroke control operation of the piston 29 that is used to control the compressor capacity will be explained.

First, the basic operation of the compressor will be explained. Drive shaft 6 together with drive lug 11. When the swash plate 21 rotates, the drive plate 27 swings in the axial direction of the drive shaft 6, this movement is transmitted to the piston 29 by the piston rod 28, and the piston 29 reciprocates within the cylinder 30. When the piston 29 moves from the top dead center (the position of the piston at the top position Wt in FIG. 1) toward the bottom dead center by the rotation of the drive shaft 6 and the swash plate 21, the refrigerant flows from the refrigerant inlet 33° to the low pressure gas chamber 35. Push up the suction valve plate 37 through the cylinder 30
flows into the working chamber P of. When the drive shaft 6 further rotates and the piston 29 moves toward the bottom dead center or the top dead center, the suction valve plate 31 closes and the refrigerant in the working chamber P is compressed. and,
When the refrigerant in the working chamber P reaches the discharge gas pressure, the discharge valve 3
9 to open the discharge passage hole 38. It is pumped into the refrigerant cycle through the high pressure gas chamber 36 and the refrigerant outlet 34.

Note that since a minute gap is created between the piston 29 and the cylinder 30, a minute amount of refrigerant in the cylinder working chamber P passes through this minute gap and flows into the crankcase 42 during the compression stroke. The lubricating oil is separated in the rank case 42 and only the refrigerant gas is discharged to the low pressure gas chamber 35 side through a communication hole 43 provided in the cylinder block 3.

Next, we will discuss the mechanism of compressor capacity control in the second section.
This will be explained based on the drawings to FIG. FIG. 2 shows the drive shaft 6. of the compressor components shown in FIG. Swash plate 21. Drive plate 27. Only the piston head 28 and piston 29 are taken out, and the positional relationship of the points where the force acting on the pistons is
It expresses the magnitude of force, etc. In the same figure,
Since the upper piston 29 is at the top dead center, the discharge gas pressure Pd is acting on the piston head 29, and the lower piston 29 is at the bottom dead center, so the suction gas pressure Ps is acting on the piston head 29. Furthermore, since the inside of the crankcase 42 communicates with the low pressure gas chamber 35 through the communication hole 43, the pressure inside the crankcase 42 is at the same level as the pressure inside the low pressure gas chamber 35.
As a result, the suction gas pressure Ps acts on the crankcase side of each piston 29.

Furthermore, when the rotation angle of the drive shaft 6 when each piston 29 is at the top dead center is zero, the internal pressure Pc of the cylinder working chamber P corresponding to the piston 29 is equal to the rotation angle OR of the drive shaft 6. , the piston stroke St is 5t=f(θR), so the temperature and pressure of the suction gas are Ts.

Let Ps be the insulation index and K be the insulation index.

, where StM^X is the maximum stroke flame of the piston 29.

StM^x=f(θR) lI*=π. Further, when the pressure receiving area of each piston 29 is Ap, the force Fai acting on each piston 29 is as follows: FO1=AP(Pc-Ps), and this force acts on the swash plate 21 via the drive plate 27. . In a compressor with Z number of cylinders, the resultant force FQ of the force FGL acting on each piston 29 is Fo = Σ Fat i = 1, the force Fat of each piston and the arrangement circle of the balls of the ball joint on the drive plate 27 side. Since the diameter is determined, the point of action of the resultant force FG is determined based on these relationships. What is the fulcrum when the swash plate 17 tilts?

Since it is the center O of the pin 20, let LO be the distance between the line of action of Fa (parallel to the axis) and the center ○.

Tilting (rotation) moment M that increases the swash plate inclination angle es
a is.

Ma:= La-F.

It is. This tilting moment Ma is driven by Il! The force acting on the axial center of No. 16, when expressed by F'0, the distance between the fulcrum 0 and the axial center is LS, so Ls L
s, therefore, the spring 19 shown in FIG.
If the spring force is set so that the force FS pushing o toward the right (in the six directions of arrows) is equal to F'o, the swash plate 21 will maintain the current swash plate inclination angle θS. That is, at this time, the gas action force F'.

Tilting moment Ma based on and restoring moment M based on spring force Fs of spring 19! will be balanced. Note that F'a changes depending on the rotation angle θR of the drive shaft 2, but the range of change is small under general operating conditions. Therefore, F'a may be expressed as an average value Fq' between 0≦θR and 2π, and the spring force that balances this is defined as FS.

Figure 3 shows that the swash plate inclination angle O8 is the maximum inclination angle θSMAX.
When , the discharge gas pressure P discharged from the piston 29
This figure shows the change in the average value 71 of the gas acting force plG with respect to the change in the suction gas pressure Pg using d as a parameter. According to this, the suction gas pressure Ps is PS=P
If it is around 80, the gas acting force F'c is constant regardless of the magnitude of the discharge gas pressure PdO value. Pso is the necessary suction pressure to prevent frost from adhering to the evaporator of the refrigeration cycle, and Ps when R12 is used as the refrigerant.
o is +1.9 to 2.0 kgf/cdg. Here, Pgo=2, 0 kg f/cd g, and Pd=P da (P d s =
Gas average value F' of 30 kg f/cl g)
Assume that a is F'oo and the spring force 〒1 is set equal to )''uo. Under such setting conditions.

The compressor discharge pressure Pd is Pdx (Pdz =
8,0 kgf/alg) ~Pd
4 (P d 4 = 48 kg f /d g
), the suction gas pressure Ps is Pst(Psx
=1.95kgf /a#g) ~Paw (Psz
= 2, 1 kg f / C51g), F'oo=:Fs, and the tilting moment Ma based on the gas action force F'a and the restoring moment Ml based on the spring force are balanced, and the swash plate 21 reaches the maximum inclination angle θSM Eight X
is maintained.

Furthermore, even when the suction gas pressure Ps is greater than or equal to Pgs-Psz, the gas action force 71 becomes greater than F'oo.On the other hand, when the suction gas pressure Pa attempts to decrease to a pressure value of Pst to Psz or less, is, gas action force F'o is F
Therefore, the relationship is lower 7τ × lower 1, and the restoring moment M is smaller than the swash plate tilting moment Ma.
r is larger.

The swash plate 21 is displaced so that the inclination angle θS becomes smaller by the difference. As a result, the piston stroke length is shortened, the compressor capacity is variably controlled to be small, and the suction gas pressure Ps is raised by the amount that the compressor capacity is reduced. In this case, too, the suction gas pressure Ps will not become less than Psz~Psx. Therefore, in the example of FIG. 3, if the spring force is set to Fs equal to F'oo, When Pd is in the range of Pdx to Pda, the suction gas pressure Ps is Psi(1,
95kgf/CIIg) ~Paw (2,1kgf/
Figure 3 shows that when the swash plate is set to the maximum inclination angle of 63 M^X, regardless of the value of Pd, the swash plate is set to the maximum inclination angle of 63 M^X. Z-P! We have explained the relationship between the spring force 〒1 and the gas action force F'oo that can make I≧Pso, but similarly when the tilt angle θS of the swash plate is changed to various sizes, the deflection force that can make Ps≧Pso 〒τ and the gas acting force F'ao can be determined. When the swash plate inclination angle θS is changed to various sizes in this way, Ps=Pso=2, Okg
FIG. 4 shows F'aoiPd, which is f/cxlg, as a parameter. In the same figure, for example, if we look at Pd=Pdz, a point on one curve a (a point along the locus of curve a) is Ps=Pso when operating at the swash plate inclination angle with respect to that point, and the gas force at this time is The average value of is F'oo corresponding to this point. Furthermore, at a point in the area above this curve a, when operating at the swash plate inclination angle corresponding to that point, Pg > Pso, and the average value of the gas force at this time is F' corresponding to this point. ao and song IIA
At points in the region below a, Ps<Pso, and the average value of the gas force at this time is F'o corresponding to this point.

In addition, for curves b to 8 corresponding to each parameter of Pdz to Pdδ, similarly to the above-mentioned Pd=Pd1,
The point on each song sb~θ is Ps=Pso when operating at the swash plate inclination angle with respect to that point, and the average value of the gas force at this time is F'oo corresponding to this point. It shows. In other words, the characteristic curves a-e in FIG. 4 are the characteristic curves of the tilting moment obtained by changing the swash plate inclination angle O8 when the discharge pressure Pd is P d 1 to Pds. This is shown in place of oo.

Accordingly, from the characteristic curve of each parameter Pdx to Pda shown in FIG. 4, the swash plate inclination angle θS is θ5HIN to
In the range of θ88^X, the necessary spring force Fs to maintain Fs2:Pso regardless of the value of the discharge pressure Pd is:
It is necessary to set the size to the upper region including the envelope of the curve group in FIG. 4.

The spring 19 of this embodiment has an envelope spring characteristic, and under such spring setting conditions, the compressor performs the following operation. This operation will be explained based on FIGS. 4 and 5. First, as shown in the refrigeration cycle load curve of FIG. 5, when the heat load Qp of the refrigeration cycle is large, the cooling capacity Qs required of the refrigerator is also large, so the suction gas pressure Ps is also high. For this reason, the average gas action force 'mF'a exceeds the spring force Fs, so that the compressor is operated at the maximum swash plate inclination angle O8. When the vehicle interior is cooled and the heat load gradually decreases, Ps decreases accordingly, and Ql! = Q
When it comes to EO, Ps=Pso. At this time, if the discharge pressure is P d = P d s, the swash plate inclination angle θS is one song! ! The operation is performed at the inclination angle θsp of the point of contact P between e and the spring characteristic curve (that is, lower τ = F'ho). When Qp further decreases, the discharge pressure Pd becomes Pd
δ, and Ps tends to be lower than Pso.1 For example, when the inclination angle of the swash plate 21 is θS=θsp, the discharge pressure becomes Pd=Pd+, and the suction pressure 'Ps becomes Ps
When attempting to become point Q' of The slider 12 shown in FIG. 1 is pushed in the direction of arrow A by the force of the spring 19, and the swash plate 21 rises so that its inclination angle O5 is smaller than θsp (that is, the compressor is made smaller). (variably controlled).

Then, when the discharge pressure becomes P d = P d 4, the suction pressure PS moves from point Q' to point Q. Here, F'o becomes Ps=Pso when Pd=Pd+.

Let R be the point of contact between the curve d and the spring characteristic ah, then θgo
>θ5R, the point Q exists in the region above the curve d. At this time, although it is not possible to operate with pg=Pso, the inclination angle of the swash plate is maintained at a position where the suction pressure Ps is Ps>Pan, so frost will not adhere to the evaporator. Furthermore, even if heat load conditions and compressor rotational speed conditions are taken into consideration, the balance point of Fs and F'ao will not deviate significantly from the Ps=Pao curve, and even if it does, it will not deviate from the Ps=Pso curve. Due to the characteristic ah relationship of the spring (as mentioned above, the curve is the envelope of the group of curves Ps=Pso (curves 8 to e)), the suction pressure Ps never becomes Ps<Pao. That is.

There is no frost on the evaporator under any operating conditions. Note that in order to obtain curved characteristics, it is sufficient to use a nonlinear spring that has a spring force based on a single curved line. For example, by using a conical coil spring, an unequal pitch coil spring, or a chain coil spring, this can be achieved. It is possible to obtain similar spring characteristics. Approximately, a nonlinear spring having the spring characteristic ah can also be formed by combining a plurality of linear springs.

As described above, according to the above embodiment, the suction gas pressure Ps can be set so as not to fall below a predetermined value only by the spring force, so the structure is simplified and the capacity control of this type of compressor can be automatically performed. Moreover, the productivity of the compressor can be greatly improved.

In the above embodiment, the characteristics of the spring 19 that provides a restoring moment to the swash plate 21 are set to be the envelope of each discharge pressure Pdr~Pc1t, which is Ps''Pso, so that the suction of the compressor is Gas pressure is Ps<
Pso is avoided, but as an alternative to this, the spring characteristics may be set as follows. Namely, in Fig. 4, the point g of θS; θSMAX on the curve ah
Even when a spring with a linear characteristic connecting the point f of The balance point Ps between the acting force F'oo and this spring force can always satisfy Ps≧Pso. In this case, since the spring may be a linear spring, the structure of the spring can be simplified and productivity can be improved.

In the above embodiment, the spring 19 is attached so as to wrap around the outer periphery of the drive #I6, and the spring force is applied to the center of the swash plate 21 via the slider 12. As shown, a spring receiver 45 may be provided at one end of the outer edge of the swash plate 21, and a spring that applies a spring force in the direction of arrow A may be installed at this position.In this case, the distance from the fulcrum 0 to the spring is less than Ls. Great place! Since the spring is provided at L's, the spring force F's becomes L's, and the spring force can be set to F's<Fs. Therefore, according to such a spring mounting structure.

Since a small spring force is sufficient, the wire diameter of the spring can be made smaller than in the above-described embodiments, and as a result, the rigidity of the spring mounting portion can be reduced, making it possible to reduce the size and weight of the entire device.

FIG. 6 shows another embodiment of the present invention, in which the same reference numerals as in the embodiment of FIG. 1 indicate the same or common elements. In this embodiment, the swash plate 21' does not rotate in the circumferential direction, and a guide groove 23 is provided in a pin 20' fixedly arranged inside the crankcase.
is guided so that the swash plate 21' performs only the tilting operation, while the drive plate 27' rotates together with the drive shaft 6 via the universal ball joint 51, and the cylinder block 3' and the cylinder 30' (piston 29 and piston rod 28) rotate in synchronization with a drive plate 27', and the piston 29' reciprocates while rotating. In Figure 1, 52 is a cylinder head, and this cylinder head 52 is Fixedly installed, this cylinder head 5
The cylinder block 3' and cylinder 30' rotate relative to each other on two sides. Further, 53 is a suction port that sucks refrigerant from the refrigeration cycle, 54 is a low pressure gas chamber, 55 is a suction boat, 56 is a discharge port, 57 is a discharge valve, 58 is a high pressure gas chamber, and 59 is a discharge port that returns the refrigerant to the refrigeration cycle. It is the exit. Therefore, in the compressor shown in this embodiment, the drive plate 27' itself rotates together with the drive shaft 6, and the rotating piston 27' rotates together with the drive shaft 6.
The swash plate 21' rotatably supports the driving plate 27' and controls its inclination angle (piston stroke control l).
).

In the case of this embodiment, a communication passage 60 is provided inside the crankcase 50 that communicates the low pressure gas chamber 54 with the crankcase 50.
so that the pressure inside the crankcase 5° is the suction gas pressure Ps, the suction gas pressure Ps and the gas compression force PC inside the cylinder 30 are applied before and after the piston 29', and on the other hand, one part of the drive shaft 6 is A spring 19' is provided at the swash plate 21' to give a restoring moment (moment that reduces the inclination angle θS), and this spring 19'
By providing the spring characteristic *h, the inclination angle θS of the swash plate 21' can be controlled so that the suction gas pressure Ps does not become less than Ps=Pso.

〔Effect of the invention〕

As described above, according to the present invention, the swash plate inclination angle control mechanism can be easily configured with only the passage for maintaining the suction gas pressure inside the crankcase and the spring member that provides a restoring moment to the swash plate. The swash plate inclination angle can be controlled with this structure. Moreover, the productivity of the compressor can be improved by simplifying the structure and reducing the number of parts.

[Brief explanation of the drawing]

Fig. 1 is a cross-sectional view of a variable displacement compressor showing an embodiment of the present invention, Fig. 2 is a structural schematic diagram illustrating swash plate inclination angle control of the above embodiment, and Figs. 3 and 4 are the above embodiments. A compressor operating characteristic diagram for explaining the principle of compressor capacity control as an example. Figure 5 is a characteristic diagram showing the relationship between qualitative evaporator heat load and compressor suction gas pressure in the refrigeration cycle. Figure 6 is FIG. 3 is a sectional view showing another embodiment of the present invention. 3... Cylinder block, 6... Drive shaft, 19...
・Spring member, 20...Swash plate tilt fulcrum (pin), 21・
... Swash plate, 27 ... Drive plate, 28 ... Connection mechanism (piston rod), 29 ... Piston, 30 ... Cylinder, 35 ... Low pressure gas chamber, 36 ... High pressure gas chamber ,
42... Crank case, 43... Communication path, a-e
... Characteristic curve of tilting moment, h ... Envelope curve,
Pd1~Pdg...Compressor discharge pressure, P
s...Compressor suction gas pressure, Pa...Cylinder internal pressure, Mo...Tilt Morse (force 12) Heart 1 Note 2 De -m-! X ton 3θ --Sison 43-0-Etsu S shi compilation Zl\] Ml --1 Hanaseri hair-men L 3rd illustration 4FiJ I's-"餉久〜e ---f; 9aton Beggar's note v4 is also good. H - 11 Jokekakusaru Pd+ <Fds---Konkrun ψ discharge, 4 balls or θ
S - One stitch of axillary moth fee βq4 effect 0 -- Gasi is used for Fig.

Claims (1)

[Scope of Claims] 1. A cylinder block including a plurality of cylinders arranged around the axis of a drive shaft, a piston incorporated in each cylinder, and a cylinder block tilted within a predetermined inclination angle with respect to the drive shaft. a swash plate that operates, a drive plate that forms a cam mechanism together with the swash plate and converts the relative rotational force of the swash plate into reciprocating motion, one end of which is connected to the piston and the other end of which is connected to the surface of the drive plate. a coupling mechanism coupled thereto for transmitting cam movement of the drive plate to the piston; the swash plate regulates the drive plate to a predetermined inclination angle to control the stroke of the piston; In a variable control compressor, a low-pressure gas chamber that introduces suction gas into each cylinder communicates with the inside of the crankcase that houses the cam mechanisms such as the swash plate and the drive plate, and the pressure inside the crankcase is controlled. In order to tilt the swash plate by making it equal to the suction gas pressure and applying a gas acting force to one side of the swash plate due to a pressure difference between the cylinder internal pressure and the crankcase internal pressure applied before and after each of the pistons. A spring member is disposed on the other side to generate a tilting moment and a restoring moment in a direction opposite to the tilting moment, and the swash plate is held at a predetermined tilt angle by the balance between the tilting moment and the restoring moment. Further, when the suction gas pressure is about to drop below a predetermined value, the spring member has a restoring moment that overcomes the tilting moment, and variably controls the swash plate in a direction in which the tilt angle becomes smaller. A variable displacement compressor having spring characteristics, and configured to variably control the compressor capacity up to a capacity range in which the suction gas pressure does not fall below a predetermined value through variable control of the swash plate inclination angle. 2. In the variable displacement compressor according to claim 1, the spring member has a restoring moment due to its spring force that increases the compressor discharge pressure and the swash plate inclination angle when the suction gas pressure is set to a predetermined value. A variable capacity compressor having nonlinear spring characteristics that match the envelope of a group of characteristic curves of tilting moment of a swash plate obtained by changing the swash plate.