Variable Capacity Compressor

Abstract

A variable capacity compressor including swash plate connected to rotor via link mechanism can calculate a moment of rotational motion acting on swash plate and set the total moment of rotational motion in inclination angle increasing direction acting on swash plate at minimum inclination angle to a small value. The shape or the like of swash plate 111 or the like are set so that moment MRX+MS becomes a moment which orients swash plate in inclination angle increasing direction in a range from θmin (0°) to θb and becomes a moment which orients swash plate in inclination angle decreasing direction in a range from an inclination angle exceeding θb to θmax. The moment acting in inclination angle increasing direction of swash plate by setting the shape or the like of link arm 121 or the like is determined by calculating the sum of moment components.

Description

TECHNICAL FIELD

The present invention relates to a variable capacity compressor for use in a vehicle air-conditioning system or the like.

BACKGROUND ART

There is known a variable capacity compressor which variably controls a discharge capacity by changing the stroke amount of a piston rotating synchronously with a drive shaft and reciprocating with a variable inclination angle (angle of inclination) relative to the axis line of the drive shaft.

In this type of variable capacity compressor, a moment in an inclination angle increasing direction acts on a swash plate due to a reciprocating inertia force of the piston. In order to counteract the moment, however, generally a product of inertia of the swash plate is set so that a moment of rotational motion in an inclination angle decreasing direction acts on the swash plate by the rotation of the swash plate.

At the minimum inclination angle or in the vicinity of the minimum inclination angle of the swash plate, however, the product of inertia of the swash plate is sometimes set so that the moment of rotational motion in the inclination angle increasing direction acts on the swash plate by the rotation of the swash plate for a specific purpose.

In Patent Document 1, a large product of inertia of the swash plate is set at the minimum inclination angle 0° in order to use the inclination angle increasing moment caused by the rotational motion of the swash plate for capacity recovery in a positive manner. On the other hand, in Patent Document 2, a relatively small product of inertia of the swash plate is set at the minimum inclination angle 0° in order to reduce the inclination angle increasing moment caused by the rotational motion of the swash plate so as to reduce power consumption during compressor off time.

CITATION LIST

Patent Documents

Patent Document 1: Japanese Laid-Open Patent Application Publication No. H07-293429

Patent Document 2: Japanese Laid-Open Patent Application Publication No. 2000-2180

SUMMARY OF THE INVENTION

Problems to be Solved by the Invention

During the rotation of the drive shaft, the moment of rotational motion acting on the swash plate is able to be calculated by a formula such as, for example, one disclosed in Patent Document 1, with respect to the swash plate and a member that is fixed to the swash plate.

For a variable capacity compressor, however, having a structure in which a link arm is not fixed to the swash plate and rotates about a first connecting pin (pin 11) when the inclination angle of the swash plate changes, for example, as disclosed in Japanese Laid-Open Patent Application Publication No. 2002-188565, the formula disclosed in Patent Document 1 is not enough to calculate the total moment of rotational motion acting on the swash plate including an influence of the link arm. Therefore, conventionally, for example, the total moment has been calculated in consideration of only an inclination angle increasing moment caused by a centrifugal force of the link arm, which thereby causes a gap between the calculated value and the actual value in the total moment of rotational motion acting on the swash plate during the rotation of the drive shaft.

The present invention has been made in view of the above conventional problem. Therefore, it is an object of the present invention to provide a variable capacity compressor in which a swash plate and a rotor are connected to each other via a link mechanism with both ends rotatably connected to the swash plate and the rotor, the variable capacity compressor capable of accurately calculating the total moment of rotational motion acting on the swash plate including an influence of a link arm and setting the total moment of rotational motion in an inclination angle increasing direction acting on the swash plate at the minimum inclination angle to a relatively small value.

Means for Solving the Problems

Therefore, according to claim 1 of the present invention, there is provided a variable capacity compressor which variably controls a discharge capacity of refrigerant by connecting a rotor fixed to a drive shaft rotatably supported within a housing to a swash plate slidably attached to the drive shaft so that an inclination angle relative to an axis line of the drive shaft is variable via a link arm with both ends rotatably connected to the rotor and the swash plate, allowing tilting of the swash plate while causing the swash plate to rotate synchronously with the rotor, converting the rotation of the swash plate to reciprocating motion parallel to the drive shaft of a piston inserted into a cylinder bore to draw and discharge the refrigerant, and controlling the inclination angle of the swash plate to control a stroke amount of the piston, having the following configuration.

A shape, weight, and center of gravity of the swash plate, or those of the swash plate and a connected body integral therewith, are set so that a moment of rotational motion caused by the swash plate, or the swash plate and the connected body integral therewith, when the drive shaft rotates in the position of a minimum inclination angle θmin of the swash plate acts in an inclination angle decreasing direction of the swash plate.

A shape, weight, and center of gravity of the link arm, or those of the link arm and a connected body integral therewith, are set so that a total moment of rotational motion caused by the link arm, the swash plate, and the connected body integral therewith acts in an inclination angle increasing direction of the swash plate.

The moment of rotational motion acting in the inclination angle increasing direction of the swash plate by setting the shape, weight, and center of gravity of the link arm, or those of the link arm and the connected body integral therewith, is determined by calculating a sum of moment components about the center of gravity and moment components caused by a centrifugal force acting on the center of gravity.

Moreover, the invention according to claim 2 has the following configuration: a minimum inclination angle θmin of the swash plate is set to 0° supposing that the inclination angle of the swash plate is 0° when the swash plate is orthogonal to the axis line of the drive shaft; and the moment of rotational motion caused by the link arm, the swash plate, and the connected body integral therewith acts in the inclination angle increasing direction of the swash plate in a range from the minimum inclination angle θmin to a predetermined inclination angle θb and acts in the inclination angle decreasing direction of the swash plate in a range from an inclination angle just exceeding the predetermined inclination angle θb to a maximum inclination angle Amax; and the predetermined inclination angle θb is set to a minimum inclination angle range where a compression reaction force is applied when the piston compresses the refrigerant.

Effect of the Invention

According to the invention of claim 1, the total moment of rotational motion in the inclination angle increasing direction acting on the swash plate at the minimum inclination angle of the swash plate is able to be set small and accurately, thereby improving the control accuracy of the inclination angle of the swash plate in the vicinity of the minimum inclination angle of the variable capacity compressor.

According to the invention of claim 2, the moment of rotational motion in the inclination angle increasing direction acting on the swash plate acts only on the minimum inclination angle region and the inclination angle smoothly increases when the inclination angle of the swash plate is less than θb, while sufficiently securing an inclination angle region (θ>θb) corresponding to a counter moment of a moment caused by an inertia force of a reciprocating motion of a piston or the like.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a sectional view illustrating an internal structure of a variable capacity compressor according to the present invention.

FIGS. 2A and 2B are a side view and a drawing of view A, respectively, of a link arm used in the variable capacity compressor.

FIG. 3 is a perspective view of an assembly of a drive shaft and a rotor used in the variable capacity compressor.

FIG. 4 is a perspective view of a swash plate used in the variable capacity compressor.

FIG. 5 is a view illustrating a coordinate system used to calculate a moment of rotational motion with respect to an assembly of the drive shaft, the rotor, the swash plate, and the link arm used in the variable capacity compressor.

FIG. 6 is a view illustrating a X″Y″Z″ coordinate system of the link arm.

FIG. 7 is a view used to calculate the center-of-gravity location G (G_Y, G_Z) of the link arm.

FIG. 8 is a diagram illustrating respective moments of rotational motion acting on the swash plate.

MODE FOR CARRYING OUT THE INVENTION

Hereinafter, an embodiment of the present invention will be described with reference to drawings. FIG. 1 illustrates an internal structure of a variable capacity compressor according to the present invention.

A variable capacity compressor 100, which is a clutchless compressor, includes a cylinder block 101 having a plurality of cylinder bores 101a in a peripheral portion, a front housing 102 connected to one end of the cylinder block 101, and a cylinder head 104 connected to the other end of the cylinder block 101 via a valve plate 103.

A drive shaft 110 is provided across a crank chamber 140, which is defined by the cylinder block 101 and the front housing 102, and a swash plate 111 is disposed around the axial center of the drive shaft 110. The swash plate 111 is connected to a rotor 112 fixed to the drive shaft 110 via a link mechanism 120 and an inclination angle (the angle of inclination) relative to the axis line of the drive shaft 110 is variable.

Between the rotor 112 and the swash plate 111, there is mounted an inclination angle decreasing spring 114 which biases the swash plate 111 toward the minimum inclination angle up to the minimum inclination angle. On the opposite side of the swash plate 111, there is mounted an inclination angle increasing spring 115 which biases the swash plate 111 in a direction of increasing the inclination angle of the swash plate 111. The biasing force of the inclination angle increasing spring 115 is set larger than the biasing force of the inclination angle decreasing spring 114 at the minimum inclination angle, by which the swash plate 111 is located at an inclination angle larger than the minimum inclination angle when the drive shaft 110 does not rotate and the biasing force of the inclination angle decreasing spring 114 is balanced with the biasing force of the inclination angle increasing spring 115.

One end of the drive shaft 110 passes through a boss portion 102a projecting outward of the front housing 102 so as to extend to the outside thereof and is connected to a power transmission device, which is not illustrated. In addition, a shaft seal device 130 is inserted between the drive shaft 110 and the boss portion 102a to block the inside from the outside.

The drive shaft 110 and the rotor 112 are supported by bearings 131 and 132 in a radial direction and supported by a bearing 133 and a thrust plate 134 in a thrust direction.

Then, the power from an external drive source such as a vehicle engine is transmitted to the power transmission device, and the drive shaft 110 is rotatable in synchronization with the rotation of the power transmission device. Incidentally, a gap between an abutting portion of the drive shaft 110 abutting against the thrust plate 134 and the thrust plate 134 is adjusted to a predetermined gap by using an adjustment screw 135.

A piston 136 is disposed in a cylinder bore 101a, an outer peripheral portion of the swash plate 111 is accommodated in a recess, which is formed in the inside of the end of the piston 136 projecting toward the crank chamber 140, and the swash plate 111 works with the piston 136 via a pair of shoes 137. Therefore, the rotation of the swash plate 111 enables the piston 136 to reciprocate within the cylinder bore 101a.

In the cylinder head 104, a suction chamber 141 and a discharge chamber 142 circularly enclosing the suction chamber 141 are divisionally formed in the center portion. The suction chamber 141 communicates with the cylinder bore 101a via a communication hole 103a and a suction valve (not illustrated) provided in the valve plate 103. The discharge chamber 142 communicates with the cylinder bore 101a via a discharge valve (not illustrated) and a communication hole 103b which is formed in the valve plate 103.

A compressor housing is formed by fastening the front housing 102, the cylinder block 101, the valve plate 103, and the cylinder head 104 via a gasket, which is not illustrated, by using a plurality of through bolts 105.

Moreover, a muffler is provided in the upper part of the cylinder block 101 in the view. The muffler is formed by fastening a cover member 106 and a formed wall 101b, which is divisionally formed in the upper part of the cylinder block 101, via a seal member, which is not illustrated, by using bolts. A check valve 200 is disposed in a muffler space 143. The check valve 200 is disposed in a connection between a communication passage 144 and the muffler space 143. The check valve 200 operates in response to a pressure difference between the communication passage 144 (on the upstream side) and the muffler space 143 (on the downstream side): closes the communication passage 144 if the pressure difference is less than a predetermined value; and opens the communication passage 144 if the pressure difference is more than the predetermined value. Therefore, the discharge chamber 142 is connected to a discharge-side refrigerant circuit of the air-conditioning system via a discharge passage formed of the communication passage 144, the check valve 200, the muffler space 143, and a discharge port 106a.

In the cylinder head 104, a suction port 104a and a communication passage 104b are formed, and the suction chamber 141 is connected to a suction-side refrigerant circuit of the air-conditioning system via a suction passage formed of the communication passage 104b and the suction port 104a. The suction passage extends in a straight line across a part of the discharge chamber 142 from the outside in the radial direction of the cylinder head 104.

The cylinder head 104 is further provided with a control valve 300. The control valve 300 controls an introduction amount of discharge gas into the crank chamber 140 by adjusting the opening degree of a communication passage 145, which communicates between the discharge chamber 142 and the crank chamber 140. Moreover, the refrigerant in the crank chamber 140 flows into the suction chamber 141 through a communication passage 101c, a space 146, and an orifice 103c formed in the valve plate 103.

Accordingly, the control valve 300 is able to variably control the discharge capacity of the variable capacity compressor 100 by varying the pressure of the crank chamber 140, i.e., the back pressure of the piston 136 and changing the inclination angle of the swash plate 111, i.e., the stroke amount of the piston 136.

During air conditioning operation, i.e., in the operating state of the variable capacity compressor 100, the amount of current to a solenoid built in the control valve 300 is adjusted on the basis of an external signal, and the discharge capacity is variably controlled so that the pressure of the suction chamber 141 is at a predetermined value. The control valve 300 is able to optimally control the suction pressure according to an external environment.

During non-air conditioning operation, i.e., in the non-operating state of the variable capacity compressor 100, the communication passage 145 is forcibly opened by turning off the current to the solenoid built in the control valve 300 to control the discharge capacity of the variable capacity compressor 100 to the minimum.

Subsequently, the link mechanism 120 according to the present invention will be described.

The rotor 112 is fixed to the drive shaft 110 and the rotor 112 is provided with a pair of first arms 112a projecting toward the swash plate 111 side in parallel with the drive shaft 110. One end 121a, which is formed substantially in a cylindrical shape, of the link arm 121 is guided into the inside of the pair of first arms 112a.

Specifically, a first connecting pin 122 as a connecting means is inserted into a through hole 112b formed in a first arm 112a and into a through hole 121b formed in one end 121a of the link arm 121, by which the link arm 121 is rotatable about the axis line of the first connecting pin 122 while being guided by the pair of first arms 112a.

In addition, the first connecting pin 122 is press-fitted and retained in the through hole 121b formed in the link arm 121 and a minute gap is formed between the outer periphery of the first connecting pin 122 and the through hole 112b which is formed in the first arm 112a, thereby enabling a relative rotation.

The other end 121c of the link arm 121 has a pair of arms projected from one end 121a which is formed in a cylindrical shape, and a second arm 111a which is projected from the swash plate 111 is guided into the inside of the arms. A second connecting pin 123 as a connecting means is inserted into the through hole 121d formed at the other end 121c of the link arm 121 and the through hole 111b formed in the second arm 111a, by which the link arm 121 is connected to the swash 111, thus enabling the link arm 121 and the swash plate 111 to relatively rotate about the axis of the second connecting pin 123.

In addition, the second connecting pin 123 is press-fitted and retained in the through hole 111b of the second arm 111a and a minute gap is formed between the outer periphery of the second connecting pin 123 and the through hole 121d which is formed in the link arm 121, thereby enabling a relative rotation.

The link mechanism 120 is composed of the first arm 112a, the second arm 111a, the link arm 121, the first connecting pin 122, and the second connecting pin 123. Therefore, the swash plate 111 is connected to the rotor 112 fixed to the drive shaft 110 via the link mechanism 120 so as to receive a rotational torque of the rotor 112, by which the inclination angle of the swash plate 111 is variable along the drive shaft 110.

A through hole 111c of the swash plate 111, which is formed passing through the drive shaft 110, is formed in a shape where the swash plate 111 is able to tilt within a range from the maximum inclination angle (Amax) to the minimum inclination angle (θmin). Specifically, the through hole 111c includes a maximum inclination angle restricting portion for restricting the maximum inclination angle by abutting against the drive shaft 110 and a minimum inclination angle restricting portion for restricting the minimum inclination angle in the same manner.

Supposing that the inclination angle of the swash plate is set to 0° when the swash plate 111 is orthogonal to the drive shaft 110, the minimum inclination angle restricting portion of the through hole 111c is formed so that the swash plate 111 is able to be displaced up to substantially 0° in the inclination angle. In addition, the term, “substantially 0°” means a range of 0°±0.5°.

Regarding the variable capacity compressor constructed as described above, the following describes a moment related to the inclination angle of the swash plate 111.

First, the calculation of the moment of rotational motion caused by the link arm acting on the swash plate 111 will be described with reference to FIGS. 5 to 7.

When the connecting portion such as the first connecting pin 122 for connecting the link arm 121 to the rotor is fixed to the link arm 121 side, the moment is calculated as a moment of a connected body between the link arm 121 and the connecting portion such as the first connecting pin 122. Moreover, also when the connecting portion such as the second connecting pin for connecting the link arm 121 to the swash plate 111 is fixed to the link arm 121 side, the moment is calculated as a moment of a connected body between the link arm 121 and the connecting portion such as the second connecting pin 123 in the same manner.

a. Coordinate System

In an assembly of the drive shaft 110, the rotor 112, the swash plate 111, and the link mechanism 120 of the variable capacity compressor 100, three coordinate systems (XYZ, X′Y′Z′, X″Y″Z″) will be discussed as illustrated in FIGS. 5 and 6.

The first is an XYZ coordinate system with the axis of the drive shaft 110 as the Z axis in a plane including the axis of the drive shaft 110 and the center axis line of the piston 136 located at a top dead center position, a line passing through the center of the first connecting pin 122 and orthogonal to the axis of the drive shaft 110 as the Y axis, and a line passing through the intersection of the Z axis and the Y axis and orthogonal to the Z axis and the Y axis as the X axis.

The second is an X′Y′Z′ coordinate system with the origin at the center of gravity G of the link arm 121, having an X′ axis parallel to the X axis, a Y′ axis parallel to the Y axis, and a Z′ axis parallel to the Z axis. In addition, the link arm 121 has a symmetrical shape with respect to a plane including the axis of the drive shaft 110 and the center axis line of the piston 136 located at the top dead center position and also has a symmetrical shape with respect to a plane orthogonal to the above plane and passing through the center of the through hole 121b (i.e., the first connecting pin 122) and the center of the through hole 121d (i.e., the second connecting pin 123). Therefore, the center of gravity G is located in a YZ plane and on a line passing through the center of the first connecting pin 122 and the center of the second connecting pin 123.

The third is an X″Y″Z″ coordinate system with the origin at the center of gravity G of the link arm and with a line passing through the center of the first connecting pin 122 and the center of the second connecting pin 123 as the Z″ axis in a plane including the axis of the drive shaft 110 and the center axis line of the piston 136 located at the top dead center position, an axis orthogonal to the Z″ axis as the Y″ axis, and an axis line orthogonal to the Z″ axis and the Y″ axis as the X″ axis.

The link arm 121 rotates about the first connecting pin 122 in the YZ plane according to the displacing operation of the swash plate 111 and the position of the second connecting pin 123 changes accordingly. The angle of inclination β of the link arm 121 in the case of the inclination angle θ of the swash plate 111 is an angle between the Y″ axis and the Z″ axis.

b. Moment about Center of Gravity G of Link Arm

When the rotor 112 rotates, a moment of rotational motion acts about the first connecting pin 122 connected to the rotor 112 by the link arm 121.

The moment vector M_L about the first connecting pin 122 is the time derivative of the angular momentum H_L and therefore expressed by the following equation.

[Math. 1]

M_L={dot over (H)}_L={dot over (H)}_GL+r×ma  (1)

where:

{dot over (H)}_GF: Moment vector about center of gravity of link arm

r: Position vector of center of gravity of link arm relative to center of first connecting pin

m: Weight of link arm

a: Acceleration vector of center of gravity of link arm

Since the link arm 121 is symmetrical as described above, the principal axis of inertia coincides with the X″Y″Z″ axis. Therefore, the moment of inertia tensor I_L is expressed by the following equation.

$\begin{array}{cc}\left[\mathrm{Math}.2\right]& \\ I_L=\left(\begin{array}{ccc}{I}_{X^{″}X^{″}}& 0& 0\\ 0& I_{Y^{″}Y^{″}}& 0\\ 0& 0& I_{Z^{″}Z^{″}}\end{array}\right)& \left(2\right)\end{array}$

If the equation (2) is coordinate-transformed to that in the X′Y′Z′ coordinate system, the moment of inertia tensor I_L′ is expressed by the following equation.

[Math. 3]

(_L′=RI_LR⁻¹  (3)

R: Rotation matrix
Therefore, the angular momentum vector H_GL about the center of gravity G is determined by the following equation.

$\begin{array}{cc}\left[\mathrm{Math}.4\right]& \\ \begin{array}{c}{H}_{\mathrm{GL}}=I_L^{\prime }\omega \\ ={\mathrm{RI}}_LR^{-1}\omega \\ =\left(\begin{array}{ccc}1& 0& 0\\ 0& \cos \beta & \sin \beta \\ 0& -\sin \beta & \cos \beta \end{array}\right)\left(\begin{array}{ccc}{I}_{X^{″}X^{″}}& 0& 0\\ 0& I_{Y^{″}Y^{″}}& 0\\ 0& 0& I_{Z^{″}Z^{″}}\end{array}\right)\\ \left(\begin{array}{ccc}1& 0& 0\\ 0& \cos \beta & -\sin \beta \\ 0& \sin \beta & \cos \beta \end{array}\right)\left(\begin{array}{c}0\\ 0\\ {\omega }_Z\end{array}\right)\\ =\left(\begin{array}{c}0\\ \frac{1}{2}{\omega }_Z\left(I_{Z^{″}Z^{″}}-I_{Y^{″}Y^{″}}\right)\sin 2\beta \\ {\omega }_Z\left(I_{Y^{″}Y^{″}}{\sin }^2\beta +I_{Z^{″}Z^{″}}{\cos }^2\left(\beta \right)\right)\end{array}\right)\end{array}& \left(4\right)\end{array}$

• • ω_z: Rotational angular velocity of drive shaft

Therefore, the moment M_GL about the center of gravity is obtained by the following equation.

$\begin{array}{cc}\begin{array}{c}{M}_{\mathrm{GL}}={\stackrel{.}{H}}_{\mathrm{GL}}\\ =-\omega \times H_{\mathrm{GL}}\\ =\left(\begin{array}{c}0\\ 0\\ -{\omega }_Z\end{array}\right)\left(\begin{array}{c}0\\ \frac{1}{2}{\omega }_Z\left(I_{Z^{″}Z^{″}}-I_{Y^{″}Y^{″}}\right)\sin 2\beta \\ {\omega }_Z\left(I_{Y^{″}Y^{″}}{\sin }^2\beta +I_{Z^{″}Z^{″}}{\cos }^2\left(\beta \right)\right)\end{array}\right)\\ =\left(\begin{array}{c}\frac{1}{2}{\omega }_Z^2\left(I_{Z^{″}Z^{″}}-I_{Y^{″}Y^{″}}\right)\sin 2\beta \\ 0\\ 0\end{array}\right)\end{array}& \left(5\right)\end{array}$

c. Moment Caused by Centrifugal Force Acting on Center of Gravity of Link Arm

The second term r×ma in the equation (1) is the cross product of a position vector and a force vector, which is a moment of force.

Since the link arm 121 rotates about the first connecting pin 122 in the YZ plane, the moment vector is oriented in the X-axis direction.

Therefore, the force ma is a centrifugal force applied to the center of gravity and r is a distance between the center of the second connecting pin and the center of gravity of the link arm in the Z-axis direction.

The center-of-gravity location G (G_Y, G_Z) of the link arm 121 is able to be determined as follows with reference to FIG. 7.

G_Y=L_Y+L_G cos β

G_Z=L_G sin β  [Math. 6]

Therefore, the centrifugal force F_C and the moment M_FL about the first connecting pin 122 caused by the centrifugal force F_C are able to be determined by the following equation.

[Math. 7]

F_C=mG_Yω_Z²=m(L_Y+L_G cos β)ω_Z²

M_FL=r×ma=−F_CG_Z=−mL_G sin β(L_Y+L_G cos β)ω_Z²  (6)

d. Moment of Rotational Motion Caused by Link Arm about First Connecting Pin

The moment M_L of rotational motion caused by the link arm 121 about the first connecting pin 122 is able to be determined by the following equation from the equations (1), (5), and (6).

$\begin{array}{cc}\left[\mathrm{Math}.8\right]& \\ \begin{array}{c}{M}_L=M_{\mathrm{GL}}+M_{\mathrm{FL}}\\ =\left(\begin{array}{c}\frac{1}{2}{\omega }_Z^2\left(I_{Z^{″}Z^{″}}-I_{Y^{″}Y^{″}}\right)\sin 2\beta \\ 0\\ 0\end{array}\right)+\left(\begin{array}{c}\frac{1}{2}{\omega }_Z^2\left(I_{Z^{″}Z^{″}}-I_{Y^{″}Y^{″}}\right)\sin 2\beta -\\ {\mathrm{mL}}_G\sin \beta \left(L_Y+L_G\cos \beta \right){\omega }_Z^2\\ 0\\ 0\end{array}\right)\end{array}& \left(7\right)\\ \therefore M_{\mathrm{LX}}={\omega }_Z^2\left\{\frac{1}{2}\left(I_{Z^{″}Z^{″}}-I_{Y^{″}Y^{″}}\right)\sin 2\beta -{\mathrm{mL}}_G\sin \beta \left(L_Y+L_G\cos \beta \right)\right\}& \end{array}$

e. Moment of Link Arm about Instant Center of Swash Plate Displacing

The instant center of swash plate displacing R_C is the intersection of a line passing through the center of rotation K of the swash plate 111 in the YZ plane and orthogonal to the Z axis and a line passing through the center of the first connecting pin 122 and the center of the second connecting pin 123.

The product of a force F_R in the rotational direction of the second connecting pin 123, which is generated by the moment M_LX about the first connecting pin 122, and a distance L_R between the center of the second connecting pin and the instant center is a moment M_RX about the instant center of swash plate displacing R_C caused by the link arm 121, and the moment M_RX is able to be determined by the following equation.

$\begin{array}{cc}\left[\mathrm{Math}.9\right]& \\ F_R=\frac{M_{\mathrm{LX}}}{L_P}\begin{array}{c}{M}_{\mathrm{RX}}=F_RL_R\\ =\frac{L_R}{L_P}M_{\mathrm{LX}}\end{array}& \left(8\right)\end{array}$

L_P: Distance between center of first connecting pin and center of second connecting pin

Moment of Changing Inclination Angle of Swash Plate (FIG. 8)

As described above, the swash plate 111 controls the discharge capacity by changing the inclination angle of the swash plate 111 by controlling the pressure of the crank chamber 140 acting on the piston 136 against the inclination angle increasing moment caused by a gas compression reaction force of the piston 136 by using the control valve 300. The moments described below act on the change in the inclination angle of the swash plate 111. Specifically, the moments include a moment caused by a resultant force between a biasing force of the coil spring 114 and a biasing force of the coil spring 115, a moment M_P caused by an inertia force generated by reciprocating motion of the piston 136 or the like, and a moment M_R of rotational motion acting on the swash plate 111.

Incidentally, the moment M_P and the moment M_R increase in proportion to the square of the rotational speed of the drive shaft 110 and therefore are almost negligible in a region in which the rotational speed is low, while affecting the change in the inclination angle of the swash plate 111 in a region of high rotational speed.

The moment M_P acts in the inclination angle increasing direction, while the moment M_R is basically a counter moment of the moment M_P, though the moment M_R acts in the inclination angle increasing direction in a region of a small inclination angle.

FIG. 8 illustrates the moments of rotational motion acting on the swash plate 111 at a predetermined rotational speed of the drive shaft.

The second connecting pin 123 is press-fitted into the swash plate 111, and the moment M_S of the rotational motion generated by the rotation of the swash plate 111 on the basis of the setting of the product of inertia of the swash plate 111 includes that of the second connecting pin 123. Thus, the shape, weight, and center of gravity of the swash plate 111 are set so as to have the characteristics illustrated by M_S in FIG. 8. Specifically, the integral construction of the second connecting pin 123 and the swash plate 111 is set so as to cause a moment of rotational motion which orients the swash plate 111 in the inclination angle decreasing direction at the minimum inclination angle θmin (0°) (M_S<0).

In addition, if the connecting member such as the second connecting pin or the like is secured to the link arm 121, the moment M_S is calculated as a moment of the swash plate 111 only.

When the rotor 112 rotates, the link arm 121 causes the moment of rotational motion acting about the first connecting pin 122. As illustrated in FIG. 8, the moment serves as a moment M_RX of rotational motion which orients the swash plate 111 in the inclination angle increasing direction via the second connecting pin 123 (M_RX>0).

Therefore, the moment M_R of rotational motion acting on the swash plate 111 is calculated by M_S+M_RX.

The shape, weight, and center of gravity of the link arm 121 are set so as to satisfy M_S+M_RX>0 at the minimum inclination angle θmin (0°), here.

Thus, the assembly where the link arm 121 is connected to the integral construction of the second connecting pin 123 and the swash plate 111 receives the moment of rotational motion which orients the swash plate 111 in the inclination angle increasing direction in a range from the minimum inclination angle θmin (0°) to an inclination angle θb, while the assembly receives the moment of rotational motion which orients the swash plate 111 in the inclination angle decreasing direction in a range from an inclination angle just exceeding the inclination angle θb to the maximum inclination angle (θmax).

Although being set so as to satisfy M_S+M_RX>0, the shape, weight, center of gravity of the link arm 121 are set so as to minimize the influence of M_S+M_RX as possible.

The moment M_S+M_RX of the rotational motion, which orients the swash plate 111 in the inclination angle increasing direction, contributes to increasing the inclination angle of the swash plate from the region of less than the inclination angle θb, but when the inclination angle reaches an inclination angle region where the compression reaction force is generated when the piston 136 compresses the gas, the moment M_S+M_RX is no longer needed. Therefore, the inclination angle θb is set to the minimum inclination angle region where the compression reaction force is generated when the piston 136 compresses the gas. Specifically, the inclination angle θb is set to an inclination angle region which causes the discharge capacity to be within a range of 2% to 5% where the maximum discharge capacity corresponding to the maximum inclination angle θmax is 100%.

Accordingly, if the inclination angle of the swash plate 111 is less than θb, for example when the variable capacity compressor 100 is run in the non-operating state, switching the variable capacity compressor 100 from this state to the operating state causes the moment M_S+M_RX of rotational motion to assist the increase in the inclination angle of the swash plate caused by the biasing force of the coil spring 115, by which the inclination angle of the swash plate is smoothly increased. In addition, if the inclination angle of the swash plate 111 exceeds θb, the moment M_S+M_RX of rotational motion immediately serves as the counter moment of the moment M_P caused by an inertia force to contribute to decreasing the moment imbalance.

Since the moment of rotational motion in the inclination angle increasing direction acting on the swash plate 111 is limited to the range of 2% to 5% in the discharge capacity, an adverse effect caused by the moment of rotational motion in the inclination angle increasing direction can be substantially avoided even in the case where the variable capacity compressor 100 rotates at high speed.

In this manner, the moment of rotational motion in the inclination angle increasing direction acting on the swash plate acts only on a required minimum inclination angle region, thereby smoothly increasing the inclination angle in the case where the inclination angle of the swash plate is less than θb and sufficiently securing the inclination angle region (θ>θb) corresponding to the counter moment of the moment caused by an inertia force generated by reciprocating motion of the piston or the like.

The above configuration is achieved, as described in the aforementioned moment calculation process, by making settings so that the link arm 121 causes the moment M_LX of rotational motion acting about the first connecting pin 122 and the moment M_LX serves as the moment M_R (substantially constant regardless of a change in the inclination angle as illustrated in FIG. 8) in the inclination angle increasing direction of the swash plate 111 to act via the connection between the link arm 121 and the swash plate 111, while the moment M_S of rotational motion is set so as to act in the inclination angle decreasing direction of the swash plate 111, where the moment M_S of rotational motion is caused by the swash plate 111 and the second connecting pin 123 when the drive shaft 110 rotates in the position of the minimum inclination angle θmin of the swash plate 111.

Moreover, the moment M_P+M_S+M_RX arising from the drive shaft rotation is able to be maintained at a value close to zero with these settings, thereby minimizing an influence on the discharge capacity control by the control of the pressure in the crank chamber 140 (back pressure of the piston 136) with the control valve 300 as possible and improving the control accuracy.

If calculation is made in consideration of only the inclination angle increasing moment caused by the centrifugal force of the link arm in a simple manner in the variable capacity compressor including the link mechanism to be the target of the present invention, the total moment of rotational motion when the drive shaft rotates cannot be accurately calculated. Particularly, as disclosed in Patent Document 2, in the case of preventing an increase of the inclination angle increasing moment caused by the rotational motion of the swash plate by setting a small product of inertia of the swash plate at the minimum inclination angle, the influence of the inclination angle increasing moment acting on the swash plate by the link arm is relatively large, which causes the inclination angle of the swash plate to deviate from the target in the case where the swash plate is located in the vicinity of the minimum inclination angle.

In this respect, in the above embodiment, the moment of rotational motion in the inclination angle increasing direction of the swash plate with the settings of the shape, weight, and center of gravity of the link arm is determined by calculating the sum of the moment components about the center of gravity of the link arm and the moment components caused by the centrifugal force acting on the center of gravity of the link arm, by which the moment of rotational motion is able to be accurately calculated.

This enables accurate settings of the inclination angle of the swash plate in the vicinity of the minimum inclination angle, thereby enabling high-accuracy control of the discharge capacity of refrigerant represented by the control characteristic of the inclination angle, i.e., the stroke amount of the piston.

Although the link arm is a single member in the above embodiment, the link arm may include a plurality of members.

Moreover, the link arm is symmetrical in shape in the above embodiment, but may be asymmetrical in shape.

Furthermore, although the connecting means of the link arm is a pin in the above embodiment, the link arm may have a structure without the use of a pin or pins. For example, a structure where the tip of one end of the link arm is rotatably supported may be provided on the rotor side without using the first connecting pin.

Furthermore, although the swash plate is directly supported by the drive shaft in the above embodiment, the swash plate may be supported by a swash plate support (sleeve) slidably fitted to the drive shaft in an alternative swash plate structure.

Moreover, the minimum inclination angle restricting portion is formed in the through hole 111c of the swash plate in the embodiment, but a circlip or the like may be attached to the drive shaft to restrict the minimum inclination angle.

Although the clutchless compressor is used in the embodiment, the variable capacity compressor may be equipped with an electromagnetic clutch. Moreover, the present invention is also applicable to a variable capacity compressor driven by a motor.

REFERENCE SIGNS LIST

• 100: Variable capacity compressor
• 101: Cylinder block
• 101a: Cylinder bore
• 102: Front housing
• 104: Cylinder head
• 110: Drive shaft
• 111: Swash plate
• 111a: Second arm
• 111c: Through hole
• 112: Rotor
• 112a: First arm
• 114: Inclination angle decreasing spring
• 115: Inclination angle increasing spring
• 116: Spring support member
• 116a: Cylindrical portion
• 120: Link mechanism
• 121: Link arm
• 122: First connecting pin
• 123: Second connecting pin
• 136: Piston
• 140: Crank chamber
• 141: Suction chamber
• 142: Discharge chamber
• 145: Communication passage
• 300: Control valve
• M_P: Moment caused by inertia force generated by reciprocating motion of piston 136 or the like
• M_RX: Moment of rotational motion acting on swash plate 111 by link arm 121
• M_S: Moment of rotational motion acting on swash plate 111 and second connecting pin 123

Claims

1. A variable capacity compressor which variably controls a discharge capacity of refrigerant by connecting a rotor fixed to a drive shaft rotatably supported within a housing to a swash plate slidably attached to the drive shaft so that an inclination angle relative to an axis line of the drive shaft is variable via a link arm with both ends rotatably connected to the rotor and the swash plate, allowing tilting of the swash plate while causing the swash plate to rotate synchronously with the rotor, converting the rotation of the swash plate to reciprocating motion parallel to the drive shaft of a piston inserted into a cylinder bore to draw and discharge the refrigerant, and controlling the inclination angle of the swash plate to control a stroke amount of the piston, wherein:

a shape, weight, and center of gravity of the swash plate, or those of the swash plate and a connected body integral therewith, are set so that a moment of rotational motion caused by the swash plate, or the swash plate and the connected body integral therewith, when the drive shaft rotates in the position of a minimum inclination angle θmin of the swash plate acts in an inclination angle decreasing direction of the swash plate;

a shape, weight, and center of gravity of the link arm, or those of the link arm and a connected body integral therewith, are set so that a total moment of rotational motion caused by the link arm, the swash plate, and the connected body integral therewith acts in an inclination angle increasing direction of the swash plate; and

the moment of rotational motion acting in the inclination angle increasing direction of the swash plate by setting the shape, weight, and center of gravity of the link arm, or those of the link arm and the connected body integral therewith, is determined by calculating a sum of moment components about the center of gravity and moment components caused by a centrifugal force acting on the center of gravity.

2. The variable capacity compressor according to claim 1, wherein a minimum inclination angle θmin of the swash plate is set to 0° supposing that the inclination angle of the swash plate is 0° when the swash plate is orthogonal to the axis line of the drive shaft, and the moment of rotational motion caused by the link arm, the swash plate, and the connected body integral therewith acts in the inclination angle increasing direction of the swash plate in a range from the minimum inclination angle θmin to a predetermined inclination angle θb and acts in the inclination angle decreasing direction of the swash plate in a range from an inclination angle just exceeding the predetermined inclination angle θb to a maximum inclination angle θmax, and the predetermined inclination angle θb is set to a minimum inclination angle range where a compression reaction force is applied when the piston compresses the refrigerant.