JPH0676793B2 - Variable capacity swash plate compressor - Google Patents

Description

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

[Prior Art] In a double-headed piston type compressor disclosed in Japanese Patent Laid-Open No. 58-162782, a swash plate is supported integrally with a rotating shaft so as to be rotatable and swingable back and forth. Is controlled based on the suction pressure information that reflects the cooling load. However, since the swing center of the swash plate is set to a fixed position on the rotation axis, the top dead center of the compression stroke of the double-headed piston fluctuates according to the swash plate tilt angle in both the front and rear compression chambers. In the compression action area on the small capacity side where the inclination angle is close to zero, substantial compression and discharge cannot be performed.

The applicant of the present invention has proposed a compressor, which improves on this drawback, in Japanese Patent Application 62-29.
I am applying for No. 8630. The center of swing of the swash plate in this compressor is set at the radial position of the rotary shaft that corresponds to the cylinder bore of the cylinder block that houses the double-headed piston, and thus the top dead center of the compression stroke in the cylinder bore on one side of the double-headed piston. Is defined as a fixed position, and substantial compression and discharge are performed even in the compression action 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 that is switched and connected to the discharge pressure region or the suction pressure region, and the swash plate swinging force and the pressure in the control pressure chamber due to the pressure in the front and rear cylinder bores through the sliding control body and the swash plate. It is controlled by the competition with
The sliding control body is slidably supported on the rotary shaft. The acting force applied to the rotary shaft by the swash plate swinging due to this pressure resistance is received by the guide hole on the rotary shaft side via the guide pin on the swash plate side, and the swash plate tilt angle is changed 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 bring about a monotonic increase of the control pressure on the maximum capacity side, and a correction spring is used in this region. It is necessary to correct the control pressure, and the structure in which the correction spring is interposed between the rotary shaft and the sliding control body causes the mechanism to become complicated. Further, when the ratio between the discharge pressure and the suction pressure, that is, the compression ratio is high, the spring force of the correction spring must be increased to raise the control pressure for correction, and when the compression ratio is low, correction is required. The swash plate tilt angle range cannot be entirely included in the working range of the correction spring. Moreover, if the spring force of the correction spring is excessively large, the control pressure in the case of the low compression ratio exceeds the discharge pressure in the case of the low compression ratio, and the control becomes impossible.

An object of the present invention is to improve the capacity variable controllability of a variable capacity compressor in which the top dead center of the compression stroke of one cylinder bore that houses a double-headed piston is a fixed position.

[Means for Solving the Problems] Therefore, according to the present invention, the swash plate swinging force generated by the refrigerant gas compression and the pressure in the control pressure chamber are opposed via the swash plate and the sliding control body, and the swinging is performed by this opposition. A guide pin is attached to the swash plate side, and a guide hole having a guide relationship with the guide pin is provided on the rotating shaft side, and a guide hole having a variable displacement position of the guide pin in the axial direction of the rotating shaft is provided. As a guide curve, it has an inflection point that increases monotonously with the displacement of the guide pin in the direction of increasing swash plate inclination and changes from negative to positive on the way, and at a certain compression ratio, it is a linear control pressure against the change of the discharge capacity. It was a curve that caused a transition.

[Operation] The acting force of the swash plate on the rotation shaft is received in the guide hole on the rotation shaft side via the guide pin on the swash plate side, and the swash plate inclination angle is controlled by the guide relationship between the guide hole and the guide pin.

Although the guide pin is displaced along the guide curve, it has an inflection point that increases monotonously with the displacement of the guide pin in the direction of increasing swash plate inclination and changes from negative to positive on the way, and at a certain compression ratio By adopting as a guide curve a curve that causes a linear control pressure change with respect to fluctuations, the control pressure can be 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.

[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 rotary shaft 4 is attached to the front housing 2 and the cylinder block 1.
Are rotatably supported via the front shaft portion 4a.
A rear shaft portion 4b is connected and fixed to the inner end side of the front shaft portion 4a through a bearing receiving plate 8 and connecting members 5 and 6, and guide members 5 and 6a are formed in the connecting members 5 and 6, respectively. 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 is shown) is provided on the left and right of the base end portion of the guide bush 7, and
A swash plate 9 is rotatably supported on the 7a. A bridge 9a is formed on the front surface of the swash plate 9, guide pins 9b are fitted to the middle portion of the swash plate 9 so as to project to both sides, and a rotor 9c is provided at both ends of the guide pin 9b. Installed. The bridge 9a is sandwiched between both connecting bodies 5 and 6, and both rotors 9c are fitted into the guide holes 5a and 6a of the connecting bodies 5 and 6, whereby the swash plate 9 is inside the swash plate chamber 1a. With rotating shaft 4
Rotate with.

The rotating shaft 4, the swash plate 9 and the guide bush 7 are guide pins.
9b and the guide holes 5a, 6a are connected to each other in a guide relationship and in a rotatable relationship of the swash plate 9 with respect to the guide bush 7 which is slidable forward and backward, whereby the swash plate 9 slides as the guide bush 7 slides. The swash plate 9 is swingable, and the swing center C is set on the peripheral side of the swash plate 9. Swash plate 9
A double-sided piston 10 is housed in the front-side cylinder bore 1b and the rear-side cylinder bore 1c that are formed correspondingly on the rotation locus of the above, and the plurality of double-sided pistons 10 and the swash plate 9 are connected via shoes 11 and 12. The two-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 provided in the front and rear housings 2 and 3. 19,20 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 as the double-headed piston 10 reciprocates, and the front side suction passage 1d, the rear side suction passage 1e, and the front side suction chamber It is sucked into the front side compression chamber Pf and the rear side compression chamber Pr via the suction ports 13a, 14a opened and closed by the suction valve 17 and the rear side suction chamber 18, and the suction valves 15a, 16a to be compressed. Then, the discharge port opened and closed by the discharge valves 28 and 29 from both compression chambers Pf and Pr.
The refrigerant gas discharged into both discharge chambers 19 and 20 through 13b and 14b flows out into discharge passage 1f and is discharged from outlet 23 through discharge passage 1f.

The swing center C of the swash plate 9 is set on the peripheral side of the swash plate 9 and is set near the rear cylinder bore 1c,
As a result, the double-headed piston 10 in the front-side compression chamber Pf
Although the top dead center of the compression stroke varies depending on the tilt angle of the swash plate 9,
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, in the front-side compression chamber Pf, when the swash plate tilt angle is small, compression and expansion are only performed without substantial suction and discharge, but in the rear-side compression chamber Pr with a constant top dead center of the compression stroke, there is no slant. Substantial compression with suction and discharge takes place regardless of the inclination of the plate 9.

A spool-shaped sliding control body 24 is fitted in the rear suction chamber 18 so as to be slidable in the front-rear direction, and a part of the rear suction chamber 18 is partitioned and formed in the control pressure chamber 18a by the flange portion 24a thereof. In addition, the tubular portion 24b is the thrust bearing 2
5 and the radial bushing 26 through the guide bush 7
It is rotatably supported by. This allows control pressure chamber
The pressure in 18a opposes the swash plate swinging force generated by the pressure in the front side compression chamber Pf and the pressure in the rear side compression chamber Pr via the slide control body 24, the guide bush 7 and the swash plate 9.

The control pressure chamber 18a, the rear discharge chamber 20 in the discharge pressure region, the swash plate chamber 1a in the suction pressure region, and the suction pipe line 21 are connected to a volume control valve mechanism (not shown), and the displacement of the slide control body 24 in the front and rear is prevented. It is controlled by the fluctuation of the suction pressure in the suction pipe line 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 / closing the valve body in the displacement 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. Swing switching is arranged between the maximum tilt angle position shown in the figure and the minimum tilt angle position shown in FIG.

This swing is guided through the engagement of the guide holes 5a, 6a on the rotary shaft 4 side and the rotary type 9c on the swash plate 9 side, and the guide holes 5a, 6a that provide this guiding action are the axis l of the rotary shaft 4. Is crossed with respect to. Displacement curve of the guide pin 9b, that is, the guide holes 5a and 6a
As shown in FIG. 3, the guide curve S of FIG. 3 has an inflection point s ₀ at the displacement position x ₀ with the displacement position x of the guide pin 9b as a variable, and
≦ x ≦ x ₀ is a negative monotonic increase section in which the slope α of the tangent of the guide curve S decreases as the variable x increases, and x ₀ <x ≦ x ₁ is a positive monotonic increase in which the slope α increases as the variable x increases. It becomes a section. The displacement position x ₁ of the guide pin 9b corresponds to the position of the shaft pin 7a shown by the solid line in FIG. 3, that is, the case where the swash plate inclination angle β is maximum, and the discharge capacity is maximum. Displacement position of guide pin 9b x
= 0 corresponds to the case where the position of the shaft pin 7a indicated by the chain line on the right side, that is, the swash plate inclination angle β is minimum, and the discharge capacity is minimum.

The horizontal axis z of the graph shown in FIG. 6 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. Fifth
The horizontal axis V of the graph shown in the figure represents the discharge capacity, Vmax represents the maximum discharge capacity, and Vmin represents the minimum discharge capacity. The straight line D is a base line for guiding the guide curve S. The minimum control pressure Pmin corresponding to the minimum discharge volume Vmin is equal to or higher than the suction pressure Ps, and the maximum control pressure Pmax corresponding to the maximum discharge volume Vmax is equal to or lower than the discharge pressure Pd. Is set to.

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

P = [M · sin α / L−ΣFj] / A + Ps (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. 3, and A is the pressure receiving area in each compression chamber Pf, Pr.

The discharge volume V has a one-to-one correspondence with the displacement z of the sliding control body 24,
It 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 volume V is the sliding control body 24.
When the control pressure P is differentiated by the discharge volume V in a one-to-one correspondence with the displacement z of, 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 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),
L ₁ is the distance on the rotation axis l between the shaft pin 7a and the guide pin 9b when the displacement z of the sliding control body 24 is zero.

Differentiating the equation (4) by the 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, it is shown in FIG. The distance L is specified by the straight lines D ₁ and D ₂ defined by the guide curve S (x), and the distance L specified by the guide curve S that is a function of the displacement z and the inclination α is a function of the displacement z and the inclination α. Direct D ₁ is guide groove 5
It represents a direction line of a reaction force from a and 6a to the guide pin 9b, and this reaction force is in the direction of arrow P in FIG. Therefore, the guide curve S is expressed by the formula (1) representing the control pressure P, the formula (3) representing the slope of the control pressure P differentiated by the displacement z, the formula (4) representing the relationship between the displacement z and the displacement x, and The guide curve S is set as the monotonically increasing curve having the inflection point s ₀ as described above, which is obtained from the equation (5) expressing the relationship between the displacement z, the displacement x, and the slope α, and by setting the basic straight line D. It

The guide curve S set in this way yields the control pressure curve C ₁ shown in FIG. The curve C ₁ monotonically increases between the minimum control pressure Pmin and the maximum control pressure Pmax, and has an inflection point c ₀ at a displacement position z ₀ corresponding to the inflection point position x _{0 in} FIG. That is, the sliding control body 24 is prevented while avoiding complication of the mechanism when the control spring is corrected by interposing the correction spring between the rotary shaft and the sliding control body.
It is possible to obtain a smooth tilting motion of the swash plate 9 in all regions from the displacement position z = 0 to the maximum displacement position zmax. Moreover, the configuration without the correction spring enables the length of the rear end portion of the rotary shaft 4, that is, the rear shaft portion 4b to be increased, which enables the length of the radial bearing 26 to be increased. Increases durability.

Of course, the present invention is not limited to the above embodiment, and for example, in order to obtain a control pressure curve that monotonically increases as the displacement z of the sliding control body 24 increases, an arc curve or an elliptic arc curve close to the basic straight line D is obtained. It is also possible to adopt smooth curves such as
A guide curve similar to that of the above-mentioned embodiment can be obtained.

[Effects of the Invention] As described in detail above, according to the present invention, as the guide curve of the guide hole having the displacement position of the guide pin in the axial direction of the rotary shaft as a variable, the displacement of the guide pin in the increasing direction of the swash plate inclination angle Since it is a curve that has a monotonically increasing inflection point and changes from negative to positive in the middle, and causes a linear control pressure change with respect to the change in discharge capacity at a certain compression ratio, it does not complicate the mechanism. This has an excellent effect of improving the variable capacity controllability in the entire region from the minimum tilt angle to the maximum tilt angle of the swash plate.

[Brief description of drawings]

The drawings show an embodiment embodying the present invention. FIG. 1 is a side sectional view of a compressor, FIG. 2 is a sectional view taken along the line AA of FIG. 1, and FIG. 3 is a guide curve. FIG. 4 is a side sectional view showing the minimum swash plate tilt angle state, FIG. 5 is a graph showing the relationship between the discharge capacity and the control pressure, and FIG. 6 is a relationship between the displacement of the sliding control body and the control pressure. It is a graph which shows. Cylinder block 1, rotating shaft 4, guide holes 5a, 6a, swash plate 9, guide pin 9b, rotor 9c, control pressure chamber 18a, sliding control body 24, guide curve S, inflection point s ₀ .

Claims (1)

[Claims] 1. A cylinder block rotatably accommodating and supporting a double-headed piston, and a swash plate for reciprocatingly driving the double-headed piston, which is relatively non-rotatable, on its peripheral side. Is supported so that it can swing back and forth around the center of the cylinder, and this swing center position is set near the rear cylinder bore, and the reciprocating region of the double-headed piston is set on the rotation region of the swing center accompanying the rotation of the rotary shaft. However, in a swash plate compressor with the top dead center of the compression stroke in the rear cylinder bore set as a fixed position, a sliding control body that changes the volume of the control pressure chamber for capacity control that can be switched to a pressure equivalent to the discharge pressure or the suction pressure is provided. The swash plate slidably supported by the rotary shaft, and the swash plate swinging force generated by the refrigerant gas compression and the pressure in the control pressure chamber are opposed to each other via the swash plate and the slide control body, and the swash plate is swung by the opposing force. ~ side With the attachment of the guide pins,
A guide hole having a guide relationship with the guide pin is provided on the rotary shaft side, and a guide curve of the guide hole in which the displacement position of the guide pin in the axial direction of the rotary shaft is a variable is used as a guide curve of the guide pin in the increasing direction of the swash plate inclination angle. A variable displacement swash plate compressor with a curve that has a monotonic increase with displacement and an inflection point that changes from negative to positive along the way, and that causes a linear control pressure transition with respect to discharge volume fluctuation at a certain compression ratio .