JPH0656148B2 - 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 compressor disclosed in Japanese Patent Laid-Open No. 58-162782, a swash plate is supported integrally with a rotary 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 has improved this drawback, in Japanese Patent Application No. 62-
I have applied for No. 298630. 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. And
The acting force on the guide hole is received by the cylinder block via a thrust bearing interposed between the rotary shaft and the cylinder block.

[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 in 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 in the raising direction, and the structure in which the correction spring is interposed between the rotary shaft and the sliding control body complicates the mechanism. Further, if the ratio of the discharge pressure to 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 if the spring force of the correction spring is excessive, high compression will result. In the case of the ratio, the corrected control pressure becomes excessively large, and the force acting on the thrust bearing due to this excessive control pressure becomes excessively large, so that an early deterioration of the function of the thrust bearing cannot be avoided.

Moreover, at a specific compression ratio represented by the ratio between the discharge pressure and the suction pressure, the control pressure on the minimum capacity side is lower than the suction pressure, and the control performed using the refrigerant gas pressure that cannot be lower than the suction pressure is the minimum. Since it becomes impossible on the capacity side, it is also necessary to correct the increase of the control pressure on the minimum capacity side. If a correction spring for increasing the control pressure on the minimum displacement side is used, the amount of control pressure on the maximum displacement side increases, and the control pressure on the maximum displacement side may exceed the discharge pressure. If the control pressure exceeds the discharge pressure, the control performed using the refrigerant gas pressure that cannot be higher than the discharge pressure becomes uncontrollable on the contrary on the maximum discharge side.

It is an object of the present invention to improve the variable capacity controllability of a variable capacity compressor in which the top dead center of the compression stroke in one cylinder bore that accommodates 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 increasing direction of the swash plate, and has an inflection point that changes from negative to positive on the way, and the control pressure is quadratic in the negative monotonically increasing region. A curve that increases in a curve, a curve that linearly increases the control pressure with respect to the displacement of the guide pin in the increasing direction of the swash plate inclination at a specific compression ratio, or a curve that keeps the control pressure at a substantially constant value. As a curve to have in the area It was

[Operation] The acting force of the swash plate on the rotary shaft is received through the engagement relationship between the guide pin on the swash plate side and the guide hole on the rotary shaft side,
The tilt angle of the swash plate is controlled by the guide relationship between the guide hole and the guide pin. When the compression ratio is low, the control pressure linearly increases or is constant on the maximum capacity side with respect to the displacement of the guide pin in the direction of increasing the swash plate inclination angle. In the case of a high compression ratio, the control pressure linearly increases on the maximum capacity side with respect to the displacement of the guide pin in the direction of increasing the swash plate inclination, and does not become excessive. Therefore, the load on the thrust bearing does not become excessive, and the reliability of the thrust bearing can be improved. On the other hand, on the minimum capacity side, the control pressure is controlled by the guide action of the guide hole of the curve set to increase the control pressure in a quadratic curve at a specific compression ratio against the displacement of the guide pin in the increasing direction of the swash plate tilt angle. It increases monotonically at all compression ratios and can be set above the suction pressure. Therefore,
Smooth variable capacity control is possible regardless of the compression ratio.

[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 via 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 of which is shown) is provided on the left and right of the base end portion of the guide bush 7, and the shaft pin 7a is provided with the shaft pin 7a. The swash plate 9 is rotatably supported. A bridge 9a is formed on the front surface of the swash plate 9, guide pins 9b are fitted in the middle portion of the swash plate 9 so as to project to both sides, and the rotor 9 is provided at both ends of the guide pin 9b.
c is attached. The bridge 9a includes both connecting bodies 5 and 6.
It is sandwiched between the two rotors 9c and
6 are fitted in the guide holes 5a, 6a, whereby the swash plate 9 rotates together with the rotary shaft 4 in the swash plate chamber 1a.

The rotary shaft 4, the swash plate 9 and the guide bush 7 are connected to each other in 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 is slidable forward and backward. , By this, swash plate 9
Can swing with the slide 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 housed in the front-side cylinder bore 1b and the rear-side cylinder bore 1c, which are formed correspondingly on the rotation locus of the swash plate 9, and the plurality of double-headed pistons 10 and the swash plate 9 are connected to the shoe 11, The two-headed piston 10 reciprocates back and forth as the swash plate 9 rotates.

Between the cylinder block 1 and the front and rear housings 2, 3, partition plates 13, 14 and valve forming plates 15, 1 are provided.
6 is interposed, and suction chambers 17 and 18 and discharge chambers 19 and 20 are defined in the front and rear housings 2 and 3, respectively. Refrigerant gas in the suction pipe line 21 constituting the external refrigerant gas circuit enters the swash plate chamber 1a through the inlet 22 as the double-headed piston 10 reciprocates, and the front side suction passage 1d, the rear side suction passage 1e, the front side suction chamber 1e. 17 and the rear side suction chamber 18, and the suction ports 13a and 14a opened and closed by the suction valves 15a and 16a to be sucked into the front side compression chamber Pf and the rear side compression chamber Pr to be compressed. The discharge chambers 1f and 1b are opened and closed by the discharge valves 28 and 29 from the compression chambers Pf and Pr, and the discharge chambers 1 and 2 are opened.
The refrigerant gas discharged to 9, 20 flows out to the discharge passage 1f and is discharged from the outlet 23 via the 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, so that the top dead center of the compression stroke of the double-headed piston 10 in the front compression chamber Pf. Varies depending on 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, in the front compression chamber Pf, when the swash plate inclination is small, only compression and expansion without substantial suction and discharge are performed, but in the rear compression chamber Pr where the top dead center of the compression stroke is constant, there is no inclination. Substantial compression with suction and discharge takes place regardless of the inclination of the plate 9.

A spool-shaped sliding control body 24 is provided in the rear suction chamber 18.
Is slidably fitted in the front-rear direction, and the flange portion 24a defines a part of the rear suction chamber 18 in the control pressure chamber 18a, and the tubular portion 24b forms the thrust bearing 25 and the radial bearing 26. It is supported by the guide bush 7 so as to be rotatable relative thereto.
As a result, the pressure in the control pressure chamber 18a is controlled by the sliding control body 24,
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 is opposed via 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 sliding 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 opened and closed by opening and closing the valve body in the displacement control valve mechanism based on the suction pressure in the suction pipeline 21.
Is controlled to be switched to a high pressure equivalent to the discharge pressure or a low pressure equivalent to the suction pressure, and the swash plate 9 is swingably arranged between the maximum tilt angle position shown in FIG. 1 and the minimum tilt angle position shown in FIG.

The swing of the swash plate 9 is guided through the engagement of the guide holes 5a, 6a on the rotary shaft 4 side and the rotor 9c on the swash plate 9 side, and the guide holes 5a, 6a for providing this guiding action are Axis l
Is crossed with respect to. The displacement curve of the guide pin 9b, that is, the guide curve S of the guide holes 5a and 6a, 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, as shown in FIG. x <x ₀ is the guide curve S
The gradient α of the tangent line is a negative monotonically increasing section where the gradient x decreases as the variable x increases, and x ₀ <x ≦ x ₁ is a positive monotonic increasing section where the gradient α increases as the variable x increases.

The displacement position xmax 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. 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 volume 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.
The horizontal axis V of the graph shown in FIG. 5 represents the discharge volume, and Vmax
Represents the maximum discharge capacity, and Vmin represents the minimum discharge capacity. A curve D ₁ shown in FIG. 5 is a basic curve for guiding the guide curve S, and the minimum control pressure P ₁ min corresponding to the minimum discharge volume Vmin is the suction pressure Ps or more and the maximum corresponding to the maximum discharge volume Vmax. The control pressure P ₁ max is set to be equal to or lower than the discharge pressure Pd ₁ . The basic curve D ₁ is the discharge volume range Vmin ≦ V corresponding to the displacement section 0 ≦ x <x ₀ of the guide pin 9b.
<V ₀ , a quadratic curve that increases with an increase in the discharge capacity V, that is, an increase in the displacement of the guide pin 9b, a displacement section x ₀ <x
In the range of discharge volume V ₀ <V ≦ Vmax corresponding to ≦ xmax, a constant value straight line is set.

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

P = [M · sin α / L−ΣFj] / B + Ps (1) where Fj is the refrigerant gas pressure in each compression chamber Pf, Pr,
M is the moment generated by the refrigerant gas pressure Fj in each compression chamber Pf, Pr, L is the distance shown in FIG. 3, and B 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 and is represented by the following equation (2).

V = B · 2z + Vmin (2) That is, the control pressure P which is a function of the discharge volume V is the sliding control body 2
There is a one-to-one correspondence with the displacement z of 4 and the control pressure P is differentiated by the displacement z, which is expressed by the following equation (3).

dP / dz = dP / dV · dV / dz = dP / dV · 2B (3) The differential dP / dV in the equation (3) represents the tangent slope of the basic curve D _{1 in} FIG. The slope of V from the minimum discharge volume Vmin to the vicinity of V ₀ linearly increases,
The gradient from the discharge volume V near V ₁ to the maximum discharge volume Vmax is zero. That is, if the equation (3) is expressed more accurately, the following equations (3-a) and (3-b) are obtained.

dP / dz = ρ (V−σ) 2B> 0 V ₀ > V ≧ Vmin ... (3-a) dP / dz = 0 Vmax ≧ V> V ₀ ... (3-b) where ρ and σ is a constant expressing the quadratic curve portion of the basic curve D ₁ .

Further, the guide curve S (x) and the displacement z are connected by the following equation (4).

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

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) , The distance L shown in FIG. 3 is specified by the straight lines l ₁ and l ₂ defined by the guide curve S (x), and the distance L measured by the guide curve S that is a function of the displacement z and the inclination α is the displacement z and the inclination. It is a function of α. The straight line l ₁ represents the direction of the reaction force from the guide holes 5a 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-a) and the formula (3-b) representing the gradient of the control pressure P differentiated by the displacement z, and the displacement z and the displacement x. Formula (4) representing the relationship,
And the displacement z, the displacement x, and the slope α are obtained from the equation (5). By setting the basic curve D ₁ , the guide curve S becomes a monotonically increasing curve having the inflection point s ₀ as described above. Is set. That is, the negative monotonically increasing section 0 ≦ x in which the inclination α of the tangent to the guide curve S decreases as the variable x increases.
For <x ₀ , an upwardly convex guide curve S ₁ is used to provide a quadratic control pressure for the lowest compression ratio Pd ₁ / Ps, and the tangent slope α of the guide curve S increases as the variable x increases. In the positive monotonically increasing section x ₀ <x ≦ x max, a downwardly convex guide curve S ₂ that provides a constant control pressure P ₁ max in the case of a compression ratio P ₁ max / P ₁ min is used.

The guide curve S set on the basis of the basic curve D ₁ yields the control pressure curves D ₂ , D ₃ , D ₄ , D ₅ and D ₆ shown in FIG. Each control pressure curve _{D 2, D 3, D 4} , D 5, D 6 is the discharge pressure _{Pd 2, Pd 3, Pd 4} , Pd 5, Pd 6, i.e. the compression ratio _{Pd 2 / Ps, Pd 3 /} Ps, Pd ₄ / Ps, P
Corresponding to d ₅ / Ps, Pd ₆ / Ps, each control pressure curve D ₂ , D ₃ , D ₄ , D ₅ , D ₆ is equal to or higher than the suction pressure Ps and each discharge pressure Pd ₂ , Pd ₃ , Pd ₄ , Pd. ₅ and Pd ₆ or less, and increases monotonically with the increase of the ejection capacity in the entire area of the ejection capacity V. Curves C ₁ , C ₂ and C shown in FIG.
₃ , C ₄ , C ₅ , C ₆ are discharge pressures Pd ₁ , Pd ₂ , Pd
₃ shows a control pressure curve expressed with the displacement z of the sliding control body 24 as a variable with respect to ₃ , Pd ₄ , Pd ₅ , and Pd ₆ .

The control pressure curves C _{2 to} C ₆ monotonically increase with an increase in the displacement z in the entire region of the displacement z, and when the compression ratio is Pd ₂ / Ps or more, the displacement position z = 0 of the sliding control body 24 to the maximum displacement position. z _max
A smooth tilting motion of the swash plate 9 can be obtained in all areas. The control pressure curve C ₁ corresponding to the lowest compression ratio Pd ₁ / Ps is a monotonically increasing curve represented by a quadratic curve with respect to the increase of the displacement z on the side of the minimum capacity, but the displacement z on the side of the maximum capacity.
Becomes a constant value straight line with the increase of, and the minimum compression ratio Pd ₁ /
With Ps, the maximum capacity cannot be controlled. However, in the case of a high compression ratio, the sliding control body 24 shifts to the swash plate inclination maximum side, and the compression ratio decreases as the sliding control body 24 starts shifting to the minimum capacity side, When the compression ratio is low, the sliding control body 24 shifts to the side of the minimum capacity, and the sliding control body 24 stays in the displacement region that produces the control pressure represented by the quadratic curve. Therefore, a smooth tilting motion of the swash plate 9 can be obtained at any compression ratio.

The guide curve S is set so that the control pressure on the maximum displacement side in the case of the maximum compression ratio Pd ₆ / Ps is suppressed to a value relatively lower than the discharge pressure. The configuration in which the guide curve S is set so that the control pressure on the maximum capacity side in the case of the maximum compression ratio is controlled to a value relatively lower than the discharge pressure is the thrust bearing 2
Reduce the load on 7. The force F acting on the thrust bearing via the engaging portion K between the guide holes 5a and 6a and the rotor 9c is expressed by the following equation (6).

F = ΣFj + [{ΣFj (Xy-r · cosγ / cosβ) / cosβ} + M ₁ −M ₂ ] / Xy (6) Fj (j = 1 to 5) in the equation (6) is Each double-headed piston 10
Represents the force due to the gas pressure against X, and Xy is the guide hole 5a,
Instantaneous center X (straight line 1) of the engaging portion K between 6a and rotor 9c
₁ )) to the axis l, r is the distance from the swing center C to the axis l, r is the angle (π / 2−α) between the straight line l ₁ and the axis l, and M ₁ is the swash plate. 9, an unbalanced moment due to inertia of the double-headed piston 10, M ₂ represents an unbalanced moment due to inertia of the double-headed piston 10.

The total sum ΣFj of Fj is represented by the control pressure P as in the following equation (7). However, H represents the pressure receiving area of the sliding control body 24.

ΣFj = rHP (7) Therefore, the force F is expressed by the following equation (6 ′).

F = rHP + [{ΣFj (Xy-r · cos γ / cos β) / cos β} + M ₁ −M ₂ ] / Xy (6 ′) According to the formula (6 ′) The force F acting on the thrust bearing 27 increases as the swash plate inclination angle β increases, and increases as the control pressure P increases. Swash plate inclination β
And when the control pressure P is high and the compression ratio is high, the control pressure P
Is excessively large, the thrust bearing 27 is overloaded, and the function of the thrust bearing 27 is inevitably deteriorated at an early stage. However, by setting the guide curve S so as to suppress the control pressure on the maximum displacement side at the maximum compression ratio to a value relatively lower than the discharge pressure, the control pressure P is prevented from becoming excessive, and the thrust bearing 27 Is not overloaded. Therefore, the thrust bearing 2
The early deterioration of the function of 7 is avoided, and the thrust bearing 2
The reliability of 7 is high.

Further, since the correction spring for correcting the control pressure, which is conventionally provided in the guide bush 7, is no longer necessary, the parts for forming the control pressure correction mechanism together with the correction spring are eliminated, and the number of parts is greatly increased. Reduction and simplification of the mechanism are achieved. Along with this, the rear shaft portion 4b of the rotary shaft 4 can be lengthened, the radial bearing 26 can be increased in size, and the reliability of the radial bearing 26 can be improved.

The present invention is of course not limited to the above-mentioned embodiment, and for example, a straight line portion that monotonically increases the straight line portion of the constant value of the basic curve D ₁ within a range in which the control pressure on the maximum capacity side at a high compression ratio does not become too high. It is also possible to

[Advantages of the Invention] As described in detail above, according to the present invention, a guide curve of a guide hole having a displacement position of the guide pin in the axial direction of the rotary shaft as a variable is used to displace the guide pin in the increasing direction of the swash plate tilt angle. On the other hand, it has an inflection point that monotonically increases and changes from negative to positive on the way, and a curve that increases the control pressure in a quadratic curve in the negative monotonically increasing region.The swash plate tilt angle increases at a specific compression ratio. Since the curve that linearly increases the control pressure with respect to the displacement of the guide pin in the direction or the curve that keeps the control pressure at a constant value is used in the positive monotonically increasing region, compression does not occur without complicating the mechanism. This has an excellent effect that the capacity variable controllability in the entire range can be improved and the reliability of the thrust bearing that receives the load in the thrust direction of the rotary shaft can be improved.

[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. Guide holes 5a, 6a, the swash plate 9, the guide pins 9b, rotor 9c, the control pressure chamber 18a, the sliding control element 24, basic curve _{D 1,} the control pressure curves _{C 1, C 2, C 3} , C 4, C ₅ ,
C _6, guide curve S, the curve _S 1, _{S 2,} 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 the guide pin of the guide pin in the direction of increasing the tilt angle of the swash plate is used as a guide curve of the guide hole with the displacement position of the guide pin in the axial direction of the rotary shaft as a variable. It has an inflection point that increases monotonically with the displacement of and changes from negative to positive along the way,
A curve that increases the control pressure as a quadratic curve in the negative monotonically increasing region, and a curve or control pressure that linearly increases the control pressure with respect to the displacement of the guide pin in the increasing direction of the swash plate tilt angle at a specific compression ratio. Variable capacity swash plate compressor with a curve that keeps the constant value in the positive monotonic increasing region.