JP2600305B2 - Variable displacement swash plate compressor - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a variable displacement swash plate type compressor having a double-headed piston.

2. Description of the Related Art In a double-headed piston type compressor disclosed in Japanese Patent Application Laid-Open No. 58-16272, a swash plate is supported so as to be rotatable integrally with a rotating shaft and swingable back and forth. Is controlled based on suction pressure information reflecting the cooling load. However, since the swing center of the swash plate is set at a fixed position on the rotating shaft, the top dead center of the compression stroke of the double-headed piston fluctuates according to the inclination angle of the swash plate in both the front and rear compression chambers. Substantial compression and discharge cannot be performed in the compression operation region on the small capacity side where the inclination angle is close to zero.

The applicant of the present application has proposed a compressor in which this disadvantage is improved, as disclosed in Japanese Patent Application No.
298630 filed. The center of swing of the swash plate in this compressor is set at the radial position of the rotary shaft corresponding to the cylinder bore of the cylinder block that houses the double-headed piston, so that the compression stroke top dead center in the cylinder bore on one side of the double-headed piston is set. Is defined at a fixed position, and substantial compression and discharge are performed even in the compression operation region on the small capacity side where the swash plate tilt angle is close to zero.

The swash plate tilt angle changes the volume of the control pressure chamber which is switched and connected to the discharge pressure area or the suction pressure area, and the swash plate oscillating power and the pressure in the control pressure chamber due to the pressure in the front and rear cylinder bores via the swash plate. The sliding control body is slidably supported on a rotating shaft. The acting force applied to the rotating shaft by the swash plate that swings due to the pressure is received by the guide hole on the rotating shaft through the guide pin on the swash plate, and the swash plate tilt angle is determined by the guide relationship between the guide pin and the guide hole. It is controlled.

[Problems to be Solved by the Invention] However, the guide hole disclosed in Japanese Patent Application No. 62-298630 cannot provide a monotonous increase in the control pressure on the maximum capacity side, and in this region, a correction spring is used. It is necessary to correct the control pressure in the raising direction, and a configuration in which a correction spring is interposed between the rotating shaft and the sliding control body causes a complicated mechanism. Further, when the ratio between the discharge pressure and the suction pressure, that is, the compression ratio is high, the control pressure must be increased by increasing the spring force of the correction spring, and correction must be performed when the compression ratio is low. The swash plate tilt angle range cannot be completely included in the operation range of the correction spring. In addition, if the spring force of the correction spring is excessively large, the control pressure at the low compression ratio exceeds the discharge pressure at the low compression ratio, and the control becomes impossible.

Further, in this type of compressor, when the operation is started from a state in which the swash plate is stopped at the minimum tilt angle, the swash plate hardly shifts to the maximum tilt angle, and the responsiveness for obtaining the cooling action is poor.

SUMMARY OF THE INVENTION It is an object of the present invention to improve the variable displacement controllability of a variable displacement compressor in which a top dead center of a compression stroke in one cylinder bore accommodating a double-headed piston is a fixed position.

[Means for Solving the Problems] In the present invention, therefore, the swash plate oscillating power generated by refrigerant gas compression and the pressure in the control pressure chamber are opposed via the swash plate and the sliding control body, and the oscillating force is caused by the opposition. A guide pin is mounted on the swash plate side, and a guide hole having a guide relationship with the guide pin is provided on the rotary shaft side, and a guide hole having a variable displacement position of the guide pin in the axial direction of the rotary shaft is provided. The guide curve has an inflection point that increases monotonically with the displacement of the guide pin in the direction of increasing the swash plate inclination and changes from negative to positive on the way, and has a linear control pressure against a change in the discharge capacity at a certain compression ratio. The control pressure chamber is provided with a correction spring for biasing the sliding control body in the direction of increasing the swash plate inclination, and the correction spring acts only near the minimum inclination of the swash plate. Spring special Sex was set.

[Operation] The acting force of the swash plate on the rotation shaft is received by the guide hole on the rotation shaft side via the guide pin on the swash plate side, and the inclination angle of the swash plate is controlled by the guide relationship between the guide hole and the guide pin. The guide pin is displaced along the guide curve, but has a point of inflection that monotonically increases with the displacement of the guide pin in the direction of increasing the swash plate tilt angle and changes from negative to positive on the way, and the discharge capacity at a certain compression ratio. By adopting a guide curve that produces a linear control pressure change with respect to fluctuations, the control pressure is suppressed between the suction pressure and the discharge pressure within the movable range of the sliding control body, and the swash plate tilt angle It increases monotonically with the displacement of the guide pin in the increasing direction. Further, depending on the compression ratio, the control pressure is reduced and corrected by the presence of the correction spring in the control pressure chamber even on the minimum displacement side where the control failure occurs, and when the operation is stopped, the swash plate is shifted and held to the maximum tilt angle side by the correction spring. The compensating spring for compensating the reduction of the control pressure is accommodated in a comparatively large space such as the control pressure chamber, so that the mechanism does not become complicated and the compressor does not become large.

[Embodiment] An embodiment of the present invention will be described below with reference to the drawings.

A front housing 2 and a rear housing 3 are joined and fixed to both front and rear end surfaces of the cylinder block 1, and a rotation shaft 4 is rotatably supported by the front housing 2 and the cylinder block 1 via a front shaft portion 4a. . A rear shaft portion 4b is connected and fixed to the inner end side of the front shaft portion 4a via a bearing receiving plate 8 and connecting members 5, 6, and guide holes 5a, 6a are formed in the connecting members 5, 6. A thrust bearing 27 is interposed between the bearing receiving plate 8 and the inner end surface of the cylinder block 1.

A guide bush 7 is slidably fitted to the rear shaft portion 4b. A shaft pin 7a (only one of which is shown) is protrudingly provided on the left and right sides of the base end of the guide bush 7, and is connected to the shaft pin 7a. The swash plate 9 is supported rotatably. A bridge 9a is formed on the front surface of the swash plate 9, and a guide pin 9b is fitted at an intermediate portion thereof so as to protrude to both sides, and a rotor 9c is provided at both ends of the guide pin 9b. Installed. The bridge 9a is sandwiched between the two connecting members 5, 6, and both the rotors 9c are fitted into the guide holes 5a, 6a of the connecting members 5, 6, whereby the swash plate 9 is moved into the swash plate chamber 1a. And rotates with the rotating shaft 4.

The rotating shaft 4, the swash plate 9 and the guide bush 7 are connected to each other with a guide relationship between the guide pin 9b and the guide holes 5a and 6a and a rotatable relationship of the swash plate 9 with respect to the guide bush 7 which can slide back and forth. Thereby, the swash plate 9 can swing with the sliding of the guide bush 7, and the swing center C is set on the peripheral side of the swash plate 9. A double-headed piston 10 is provided in the front-side cylinder bore 1b and the rear-side cylinder bore 1c correspondingly formed on the rotation trajectory of the swash plate 9.
Are accommodated, and the plurality of double-headed pistons 10
And the swash plate 9 are engaged via the shoes 11 and 12, and the double-headed piston 10 reciprocates back and forth as the swash plate 9 rotates.

Partition plates 13 and 14 and valve forming plates 15 and 16 are interposed between the cylinder block 1 and the front and rear housings 2 and 3, and suction chambers 17 and 18 and a discharge chamber are disposed inside the front and rear housings 2 and 3. 19 and 20 are sectioned. Refrigerant gas in the suction pipe line 21 constituting the external refrigerant gas circuit enters the swash plate chamber 1a from the inlet 22 with the reciprocation of the double-headed piston 10, enters the front-side suction passage 1d, the rear-side suction passage 1e, and the front-side suction chamber. 17
The air is sucked into the front-side compression chamber Pf and the rear-side compression chamber Pr through suction ports 13a and 14a opened and closed by the rear-side suction chamber 18 and the suction valves 15a and 16a, and is subjected to a compression action. The refrigerant gas discharged from the compression chambers Pf, Pr to the discharge chambers 19, 20 via the discharge ports 13b, 14b opened and closed by the discharge valves 28, 29 flows out to the discharge passage 1f, and flows through the discharge passage 1f. Exit 23
Is discharged from

The swing center C of the swash plate 9 is set on the peripheral edge side of the swash plate 9 and is set near the rear cylinder bore 1c, whereby the top dead center of the compression stroke of the double-headed piston 10 in the front compression chamber Pf is set. Varies according to the tilt angle of the swash plate 9, but the top dead center of the compression stroke of the double-headed piston 10 in the rear compression chamber Pr is defined at the fixed position shown in FIGS. Therefore,
When the inclination angle of the swash plate is small in the front-side compression chamber Pf, compression and expansion without substantial suction and discharge are performed only. However, in the rear-side compression chamber Pr having a constant top dead center in the compression stroke, the swash plate 9 is not used. Substantially compression involving suction and discharge is performed irrespective of the inclination angle of.

A spool-shaped slide control body 24 is slidably fitted in the rear-side suction chamber 18 in the front-rear direction, and a part of the rear-side suction chamber 18 is partitioned into a control pressure chamber 18a by its flange portion 24a. The cylindrical portion 24b is rotatably supported by the guide bush 7 via a thrust bearing 25 and a radial bearing 26. As a result, the pressure in the control pressure chamber 18a is converted into the swash plate oscillating power generated by the pressure in the front compression chamber Pf and the pressure in the rear compression chamber Pr via the slide control body 24, the guide bush 7, and the swash plate 9. Oppose.

The control pressure chamber 18a, the rear discharge chamber 20 in the discharge pressure area, the swash plate chamber 1a in the suction pressure area, and the suction pipe line 21 are connected to a capacity control valve mechanism (not shown). It is controlled by the fluctuation of the suction pressure in the suction pipe 21. That is, the control pressure chamber 18a is switched to a high pressure equivalent to the discharge pressure or a low pressure equivalent to the suction pressure by opening and closing a valve in the capacity control valve mechanism based on the suction pressure in the suction pipe line 21, and the swash plate 9 is moved to the first position. The swing is switched between a maximum tilt angle position shown in the figure and a minimum tilt angle position shown in FIG.

In the control pressure chamber 18a, a correction spring 30 is interposed between the slide control body 24 and the rear housing 3, and when the slide control body 24 comes to the left chain line position as shown in FIG. When the inclination angle of the swash plate decreases from this position, the spring action of the correction spring 30 acts on the slide control body 24.

The swash plate 9 is swung by the guide holes 5a and 6a on the rotary shaft 4 side and the swash plate 9
The guide holes 5a and 6a which are guided through engagement with the rotor 9c on the side and provide this guiding action are oblique to the axis l of the rotating shaft 4. The displacement curve of the guide pin 9b, that is, the guide hole
The guide curve S for 5a and 6a is shown in FIG.
With the displacement position x of b as a variable, the displacement position x ₀ has an inflection point s ₀ , and 0 ≦ x <x ₀ means that the inclination α of the tangent to the guide curve S is the variable x
Monotonically increasing section that decreases as x increases, x ₀ <x ≦ x ₁
Is a positive monotone increasing section in which the slope α increases as the variable x increases. Guide pin displaced position x ₁ and 9b is the position of the pivot pin 7a indicated by the solid line in FIG. 4, i.e. inclination angle of the inclined plate β corresponds to the case of the maximum discharge displacement is maximized. The displacement position x = 0 of the guide pin 9b corresponds to the position of the shaft pin 7a indicated by the chain line on the right side, that is, the case where the swash plate inclination angle β is minimum, and the discharge capacity is minimum.

The horizontal axis z of the graph shown in FIG. 7 represents the displacement position of the sliding control body 24, and the vertical axis P represents the control pressure in the control pressure chamber 18a. The horizontal axis V of the graph shown in FIG. 6 represents the discharge capacity, Vmax represents the maximum discharge capacity, and Vmin represents the minimum discharge capacity. Straight D ₂ shown by the solid line in FIG. 6 is a straight line as a basis for guiding the guide curve S, the minimum control pressure P ₂ mi corresponding to the minimum discharge displacement Vmin
n is set to the suction pressure Ps or more, and the maximum control pressure P ₂ max corresponding to the maximum discharge capacity Vmax is set to the discharge pressure Pd ₂ or less.

 The control pressure P is represented by the following equation (1).

P = [M · sin α / L−ΣFj] / A + P (1) where Fj is the refrigerant gas pressure in each compression chamber Pf, Pr, and M is the moment generated by the refrigerant gas pressure Fj in each compression chamber Pf, Pr. , L are the distances shown in FIG. 4, and A is the pressure receiving area in each compression chamber Pf, Pr.

The discharge capacity V has a one-to-one correspondence with the displacement z of the sliding control body 24 and is expressed by the following equation (2).

V = A · 2z + Vmin (2) That is, the control pressure P, which is a function of the discharge capacity V, is a sliding control body.
When the control pressure P is differentiated by the discharge capacity V in one-to-one correspondence with the displacement z of 24, the following expression (3) is obtained.

dP / dV = dP / dz · dz / dV = dP / dz · 1 / 2A = (Pmax−Pmin) / (Vmax−Vmin) (3) Further, the guide curve S (x) and the displacement z are as follows. It is connected by the following equation (4).

(X + L ₁ −z) ² + S (x) = L ₀ ² (4) where L ₀ is the distance between the guide pin 9b and the shaft pin 7a (constant), and L ₁ is the displacement of the sliding control body 24 Shaft pin 7a when z = 0
And the distance on the rotation axis l between the guide pin 9b and the guide pin 9b.

 Differentiating equation (4) with displacement x gives the following equation (5).

2 (x + L ₁ −z) (1−dz / dx) + 2S · dS / dx = 2 (x + L ₁ −z) (1−dz / dx) + 2Sα = 0 (5) Further, FIG. The distance L is specified by straight lines l ₁ and l ₂ determined by the guide curve S (x), and the distance L specified by the guide curve S, which is a function of the displacement z and the inclination α, is a function of the displacement z and the inclination α. Incidentally, the straight line l ₁ is the guide groove
The direction line of the reaction force from 5a, 6a to the guide pin 9b is shown, and this reaction force is in the direction of arrow P in FIG. Therefore, the guide curve S is expressed by the equation (1) representing the control pressure P, the equation (3) representing the gradient of the control pressure P differentiated by the displacement z, the equation (4) representing the relationship between the displacement z and the displacement x, and calculated from equation expressing the relationship between the displacement z and the displacement x and inclination alpha (5) setting, as a monotonically increasing curve guide curve S has an inflection point s ₀ as described above by setting a basic linear D ₂ Is done.

Curves D ₁ , D ₃ and D ₄ shown by solid lines in FIG. 6 show control pressure curves corresponding to the respective discharge pressures Pd ₁ , Pd ₃ and Pd ₄ when the action of the correction spring 30 is excluded. The curves D ₁ , D ₃ , D ₄ are equal to or higher than the suction pressure Ps and equal to or lower than the respective discharge pressures Pd ₁ , Pd ₃ , Pd ₄ . Straight line D ₀ is the compensation spring 30
Represents the spring characteristics of The addition of the spring action of compensating spring 30 having the spring characteristic in the curves D _1, D _3, D ₄ and basal rectilinear D _2, the curves D _1, D _3, D ₄ and basal rectilinear D ₂ are minimum capacity side Is corrected as shown by the chain line.

As shown in FIG. 7, the guide curve S set based on the straight line D is a control pressure curve C ₁ , C ₂ , C ₃ shown by a solid line for each discharge pressure Pd ₁ , Pd ₂ , Pd ₃ , Pd ₄ . , leading to C _4. Although the control pressure curve C ₂ indicated by the solid line is a monotonic increasing curve can be controlled at a minimum capacity side, the other control pressure curve C _1, C _3, C ₄ monotonously decreases at minimum capacity side,
The curve is monotonically increasing on the maximum capacity side, and has an uncontrollable region on the minimum capacity side. However, each control pressure curve C ₁ , C ₂ , C ₃ , C ₄ is corrected by the spring characteristic D ₀ of the correction spring 30 so as to be indicated by a dashed line on the minimum displacement side, and the corrected control pressure curves C ₁ , C
₂ , C ₃ and C ₄ are all monotonically increasing curves and are higher than the suction pressure Ps. Therefore, the fluctuation of the discharge pressure, in other words, the fluctuation of the compression ratio and the maximum displacement position z ma from the displacement position z = 0 of the sliding control body 24
A smooth tilting operation of the swash plate 9 can be obtained in all the regions over x.

Further, since the correction spring 30 for lowering and correcting the control pressure is interposed in the control pressure chamber 18a having a relatively large margin, the mechanism is not complicated and the size of the compressor is not increased. The inclination angle of the swash plate 9 at the time of operation stop is maintained at the maximum inclination side due to the presence of the swash plate 9, and the swash plate 9 quickly shifts to the maximum inclination angle after the operation is started.

The present invention is, of course, not limited to the above embodiment. For example, in order to obtain a control pressure curve that increases monotonously with an increase in the displacement z of the sliding control body 24, an arc curve or an elliptic arc curve close to the base straight line D It is also possible to adopt smooth curves such as
A guide curve substantially similar to that of the above embodiment can be obtained.

[Effects of the Invention] As described in detail above, the present invention provides a guide curve of a guide hole in which the displacement position of the guide pin in the axial direction of the rotating shaft is a variable, with respect to the displacement of the guide pin in the direction of increasing the swash plate inclination angle. Has an inflection point that increases monotonically and changes from negative to positive on the way,
In addition, a curve that linearly changes the control pressure with respect to the change of the discharge capacity at a certain compression ratio is provided, and a spring for lowering and correcting the control pressure on the minimum capacity side is interposed in the control pressure chamber, so the mechanism is complicated. An excellent effect is obtained that the variable capacity controllability in the entire region from the minimum inclination angle to the maximum inclination angle of the swash plate can be improved without causing the formation of the swash plate and the generation of the uncontrollable region.

[Brief description of the drawings]

BRIEF DESCRIPTION OF THE DRAWINGS The drawings show an embodiment of the present invention, FIG. 1 is a side sectional view of a compressor, FIG. 2 is a sectional view taken along line AA of FIG. 1, FIG. FIG. 4 is a graph for explaining a guide curve, FIG. 5 is a side sectional view showing a state where a swash plate is at a minimum tilt angle, FIG. 6 is a graph showing a relationship between a discharge capacity and a control pressure,
FIG. 7 is a graph showing the relationship between the displacement of the sliding control body and the control pressure. Cylinder block: 1, rotating shaft: 4, guide hole:
5a, 6a, swash plate ... 9, guide pin ... 9b, rotor ... 9
c, control pressure chamber 18a, sliding control body 24, correction spring
30, the guide curve ...... S, the inflection point ...... s _0.

Claims (1)

(57) [Claims] A rotary shaft is rotatably accommodated and supported in a cylinder block which accommodates a double-headed piston in a reciprocally movable manner, and a swash plate for reciprocatingly driving the double-headed piston is relatively non-rotatable on a peripheral side of the rotary shaft. The center of oscillation is set near the rear cylinder bore, and the reciprocating area of the double-headed piston is set on the rotation area of the center of oscillation associated with the rotation of the rotating shaft. In a swash plate compressor in which the top dead center of the compression stroke in the rear cylinder bore is a fixed position, a sliding control body that changes the volume of a control pressure chamber for capacity control that is switched to a pressure equivalent to a discharge pressure or a suction pressure is provided. The swash plate, which is slidably supported on the rotating shaft, opposes a swash plate oscillating power generated by refrigerant gas compression and a pressure in the control pressure chamber via a swash plate and a sliding control body, and the swash plate is swung by the opposition. ~ side With the attachment of the guide pins,
A guide hole having a guide relationship with the guide pin is provided on the rotating shaft side, and a guide curve of the guide hole in a direction in which the inclination angle of the swash plate increases as a guide curve of the guide hole with the displacement position of the guide pin in the axial direction of the rotating shaft as a variable. A curve that has an inflection point that increases monotonically with the displacement and changes from negative to positive in the middle, and that causes a linear control pressure change with respect to a change in the discharge capacity at a certain compression ratio. A variable displacement type swash plate compressor in which a correction spring for urging the sliding control body in the direction of increasing the plate tilt angle is interposed, and the correction spring has a spring characteristic that operates only near the minimum tilt angle of the swash plate.