JP2002070731A - Variable displacement controller for refrigeration cycle - Google Patents

Abstract

PROBLEM TO BE SOLVED: To protect a refrigeration cycle through eliminating a fear of breaking piping or components in the refrigeration cycle by avoiding an abnormal pressure increase in start of the refrigeration cycle. SOLUTION: A pressure control valve 2 in the variable displacement compressor at least comprises a low-pressure chamber 73 communicating with a suction space, a high-pressure chamber 84 communicating with a discharge space, a pressure adjustment chamber 86 communicating with a crank chamber, a valve 90 for simultaneously opening and closing the passage between the pressure adjustment chamber and the low-pressure chamber, and the passage between the pressure adjustment chamber and the high pressure chamber, an electromagnetic coil 63 for generating electromagnetic force, a plunger 64 moved by the electromagnetic force from the electromagnetic coil and moves the valve, and a spring 94 for thrusting the valve toward the direction opposed to that of thrusting by the plunger. When a heat load is higher than the prescribed load in starting of the variable displacement compressor, a control signal supplied to the electromagnetic coil 63 is corrected so that a thrusting force Fm, which moves the valve to close the passage between the pressure adjustment chamber and the high-pressure chamber, is reduced.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention has a drive swash plate fixed to a drive shaft so as to be tiltable, and a piston for varying the volume of the compression chamber by rotation of the drive swash plate. It has a variable displacement compressor that changes the inclination angle of the drive swash plate by adjusting the pressure difference from the back pressure of the piston, thereby changing the piston stroke and thereby changing the refrigerant capacity flowing to the refrigeration cycle. The present invention relates to a variable capacity control device for a refrigeration cycle.

[0002]

2. Description of the Related Art As a variable displacement compressor used for an air conditioner for a vehicle, particularly, an external control type compressor for controlling a discharge capacity by an external signal is disclosed in Japanese Patent Application Laid-Open No. 5-99136. ing. This has a pressure control valve that senses the pressure in the suction chamber and controls the suction pressure to a predetermined pressure. This pressure control valve controls the opening and closing of the communication between the discharge chamber and the crank chamber. A first control valve, a second control valve for controlling opening and closing of communication between the crank chamber and the suction chamber, a transmission rod for operating the first and second control valves, and moving the transmission rod It has an electromagnetic actuator and a pressure-sensitive member (diaphragm, bellows, etc.) for operating the second control valve by receiving the pressure in the suction chamber.

[0003] By using such a compressor in a refrigeration cycle, when the refrigerant pressure in the low pressure line, that is, the suction pressure becomes higher than a target pressure, the pressure in the crank chamber is reduced. In order to increase the discharge capacity by increasing the tilt angle of the swing plate, and conversely, when the pressure in the low pressure line becomes smaller than the target refrigerant pressure, the swing plate is increased by increasing the pressure in the crank chamber. , The discharge angle is reduced to reduce the discharge capacity, thereby enabling control to match the low pressure to the target refrigerant pressure.

[0004]

However, as described above, when a pressure control valve using a diaphragm or bellows as a pressure-sensitive member is used in a refrigeration cycle using carbon dioxide as a refrigerant, the pressure in the refrigeration cycle is reduced. Is about 10 times higher than that of a conventional refrigeration cycle using chlorofluorocarbons, so that it is difficult to satisfy the pressure resistance of the pressure-sensitive member.

[0005] Therefore, the present applicant has been developing variable capacity control device, for sufficiently endure the refrigeration cycle even when the carbon dioxide as a refrigerant, carbon dioxide (CO ₂₎
In a refrigeration cycle using a refrigerant as a refrigerant, in a high-load environment where the ambient temperature exceeds the critical temperature (31 ° C.) of the refrigerant, even if the refrigeration cycle is stopped, the pressure in the cycle becomes 7 Equilibrium at 0.3 to 9.0 MPa. For this reason, when the air conditioner switch is turned on from this state and the compressor of the refrigeration cycle is started, the pressure in the low-pressure line is equal to the target pressure (for example, the pressure corresponding to 0 ° C.).
48 MPa), the tilt angle of the swinging plate of the variable displacement compressor is increased, and control is performed to maximize the discharge capacity, and the high-pressure pressure rises abnormally immediately after the compressor is started. This may cause damage to piping and components of the refrigeration cycle.

In order to cope with such a situation, conventionally, the high pressure is sensed by a pressure sensor, and when the pressure exceeds a predetermined value (for example, 15 MPa), the compressor is stopped. In order to cope with abnormally high pressure by operating the compressor again, it is considered that, if such a control is to be taken, every time the compressor starts, an abnormal increase in high pressure occurs, The refrigeration cycle frequently repeats the operation and the stop, which causes inconvenience.

Accordingly, in the present invention, in providing a variable capacity control device for a refrigeration cycle having a pressure resistance suitable for using carbon dioxide as a refrigerant, it is possible to avoid an abnormal increase in high-pressure pressure when the refrigeration cycle is started. It is an object of the present invention to protect a refrigeration cycle and eliminate frequent operation stoppages (on / off) of the cycle due to an abnormal rise in pressure, thereby improving the reliability of the refrigeration cycle.

[0008]

In order to achieve the above object, a refrigeration cycle variable displacement control apparatus according to the present invention comprises: a cylinder block; a drive shaft provided in the cylinder block; A drive swash plate having a variable inclination angle with respect to the drive shaft, a plurality of cylinders provided in the cylinder block and having an axis parallel to the drive shaft, slidably disposed on the cylinder, A plurality of pistons reciprocating in the cylinder with the rotation of the piston, a compression chamber defined by the cylinder and the piston, a crank chamber formed on the side of the piston opposite to the compression chamber, and a suction stroke of the piston. Variable displacement compression having a suction space communicating with the compression chamber, and a discharge space communicating with the compression chamber in a compression stroke of the piston. A radiator that cools the refrigerant compressed by the variable capacity compressor, an expansion device that decompresses the refrigerant cooled by the radiator, and an evaporator that evaporates the refrigerant depressurized by the expansion device. A low-pressure chamber that is used in a provided refrigeration cycle and communicates with the suction space;
A high-pressure chamber communicating with the discharge space, a pressure adjustment chamber communicating with the crank chamber, and opening / closing between the pressure adjustment chamber and the low-pressure chamber, and at the same time, opening and closing between the pressure adjustment chamber and the high-pressure chamber. A valve body that closes / opens, an electromagnetic coil that generates an electromagnetic force, a plunger that is slidably inserted into the electromagnetic coil and moves by the electromagnetic force of the electromagnetic coil to move the valve body; A pressure control valve having at least a spring for urging the valve body in a direction opposite to the direction of urging by the plunger; and a low-pressure line from an outlet side of an expansion device of the refrigeration cycle to a suction side of the variable displacement compressor. Pressure detecting means for detecting the pressure of the pressure, and when the pressure detected by the pressure detecting means is higher than a target pressure, opening between the pressure adjusting chamber and the low pressure chamber and the pressure adjusting chamber and the high pressure Between the room The valve body is moved in a direction to be closed, and when the pressure detected by the pressure detecting means is lower than a target pressure, the space between the pressure adjustment chamber and the low-pressure chamber is closed, and the pressure adjustment chamber is closed. Control signal control means for controlling a control signal supplied to the electromagnetic coil to move the valve body in a direction to open between the high-pressure chamber,
Heat load detecting means for detecting a heat load at the time of starting the variable capacity compressor; determining means for determining that the heat load detected by the heat load detecting means has become higher than a predetermined load; and the determining means When it is determined that the heat load has become higher than the predetermined load, the direction between the pressure adjustment chamber and the low-pressure chamber is opened and the direction between the pressure adjustment chamber and the high-pressure chamber is closed. Control signal correcting means for correcting the control signal so as to reduce the urging force for moving the valve element is provided (claim 1).

Therefore, according to the above configuration, the pressure in the low pressure line of the refrigeration cycle is detected, and the control signal to be supplied to the electromagnetic coil in the comparison between the detected pressure and the target pressure is controlled to move the valve body. As a result, a portion having low pressure resistance, such as a conventional low-pressure pressure detector, can be omitted, and the pressure resistance of the refrigeration cycle can be increased. In addition, when the heat load at the time of starting the variable capacity compressor is higher than the predetermined load, the control signal correcting means applies an urging force (electromagnetic force) applied to the valve body in a direction to close between the pressure adjustment chamber and the high pressure chamber. Force), the pressure in the high-pressure chamber rises with the increase in the pressure in the high-pressure line of the refrigeration cycle. The force acting in the opposite direction to the urging force acting on the valve element can be made larger than the urging force (electromagnetic force), and the valve element is closed in the direction between the pressure adjustment chamber and the low-pressure chamber, that is, It is possible to move the pressure adjusting chamber and the high-pressure chamber in a direction to open. As a result, the high-pressure refrigerant can be released to the crank chamber and the pressure in the crank chamber can be increased at a stage before the pressure in the high-pressure line abnormally increases. It is possible to suppress the rise.

Here, the control signal supplied to the electromagnetic coil is changed by controlling the duty ratio, and the control signal correction means includes at least one of the voltage, current, or duty ratio of the control signal. It is preferable to change one of them to reduce the urging force (claim 2). Also,
Such a device is useful particularly when carbon dioxide having a low critical temperature is used as a refrigerant (claim 3).

[0011]

Embodiments of the present invention will be described below with reference to the drawings. In FIG. 1, a refrigeration cycle 1
Is a variable displacement compressor (hereinafter referred to as a compressor) 3 having a pressure control valve 2 for varying a discharge capacity and capable of compressing a refrigerant to a supercritical region, a radiator 4 for cooling the refrigerant, a high pressure line An internal heat exchanger 5 for exchanging heat between the refrigerant and the low pressure line, an expansion device 6 for decompressing the refrigerant, an evaporator 7 for evaporating and evaporating the refrigerant, and an accumulator 8 for separating the refrigerant flowing out of the evaporator 7 into gas and liquid. It is configured. In the refrigeration cycle 1, the discharge side of the compressor 3 is connected to the high-pressure passage 5a of the internal heat exchanger 5 via the radiator 4, and the outlet side of the high-pressure passage 5a is connected to the expansion device 6, and the compressor 3 The path leading from the discharge side of the expansion device 6 to the inflow side of the expansion device 6 is a high-pressure line 9.
And The outlet side of the expansion device 6 is connected to an evaporator 7, and the outlet side of the evaporator 7 is connected to an accumulator 8.
Is connected to the low-pressure passage 5b of the internal heat exchanger 5 through the second heat exchanger. The outflow side of the low-pressure passage 5 b is connected to the suction side of the compressor 3, and the path from the outflow side of the expansion device 6 to the suction side of the compressor 3 is a low-pressure line 10.

In the refrigeration cycle 1, carbon dioxide (CO ₂ ) is used as a refrigerant, and the refrigerant compressed by the compressor 3 enters a radiator 4 as a high-temperature and high-pressure supercritical refrigerant. To dissipate heat and cool. Thereafter, the internal heat exchanger 5 exchanges heat with the low-temperature refrigerant flowing out of the evaporator 7 to be further cooled and sent to the expansion device 6 without being liquefied. Then, the pressure is reduced in the expansion device 6 to become a low-temperature and low-pressure wet steam, and heat exchange with the air passing therethrough in the evaporator 7 to form a gaseous state. It is heated by heat exchange and returned to the compressor 3.

From the outlet side of the expansion device 6, the compressor 3
A pressure sensor 12 for detecting a low pressure is provided in the low pressure line 10 between the suction sides of the pressure sensors. This pressure sensor 1
2, the low pressure Ps detected by the outside air temperature (T
a), the temperature sensor 13 for detecting the vehicle interior temperature (Tin)
c), a temperature setting signal (Tset) from a temperature setting device 15 of an operation panel (not shown), and an insolation (Q) detected by the insolation detecting sensor 16.
sun), etc., to the control unit 17.

The control unit 17 includes an input circuit 18 for inputting various signals described above as data, a read-only memory (ROM), and a random access memory (R).
AM), a central processing unit (CPU) that calls a program stored in the memory unit 19 to process the data, and saves the data to the memory unit 19 to calculate control data. 20) an output circuit 21 for outputting a duty ratio of a control signal based on the control data calculated by the central processing unit 20; a constant voltage circuit 23 for producing a desired constant voltage from a battery power supply 22; 23, and a duty ratio control circuit 24 that outputs a control signal having a duty ratio output from the output circuit 21.

The compressor 3 is, for example, a variable displacement swash plate type compressor as shown in FIG. 2. The outer peripheral block 30 of the compressor 3 includes a front block 31 defining a crank chamber 34, and a plurality of cylinders. It comprises a central block 32 defining a space 35, and a rear block 33 defining a suction space 36 and a discharge space 37.

A drive shaft 38 disposed through the outer peripheral block 30 is rotatably held by the front block 31 and the center block 32 via bearings 39a and 39b. The engine is connected to a running engine via a belt, a pulley, and an electromagnetic clutch, and when the electromagnetic clutch is turned on, the rotation of the engine is transmitted and rotated. Also,
The drive shaft 38 rotates with the rotation of the drive shaft 38,
A swash plate 40 is provided which can be inclined with respect to the drive shaft 38.

A plurality of cylinders 35 formed in the central block 32 are formed around the drive shaft 38 at predetermined intervals, and are formed in a cylindrical shape having a central axis parallel to the axis of the drive shaft 38. The cylinder 35
, A piston 41 whose one end is held by the swash plate 40 is slidably inserted.

In the above configuration, when the drive shaft 38 rotates, the swash plate 40 rotates with a predetermined inclination.
The end of the swash plate 40 swings at a predetermined width in the axial direction of the drive shaft 38. As a result, the piston 41 fixed to the radial end portion of the swash plate 40 reciprocates in the axial direction of the drive shaft 38 to change the volume of the compression chamber 42 defined in the cylinder 35, The refrigerant is sucked from the suction space 36 through a suction port 43 having a suction valve 44, and the compressed refrigerant is discharged to a discharge space 37 through a discharge port 45 having a discharge valve 46.

The displacement of the compressor 3 is determined by the stroke of the piston 41. The stroke is determined by the pressure applied to the front of the piston 41, ie, the pressure of the compression chamber 42, and the pressure applied to the back of the piston, ie, the crank chamber 34.
It is determined by the pressure difference between the internal pressure (crank chamber pressure). Specifically, if the pressure in the crank chamber 34 is increased, the differential pressure between the compression chamber 42 and the crank chamber 34 is reduced, so that the inclination angle (swing angle) of the swash plate 40 is reduced.
For this reason, the stroke of the piston 41 is reduced and the discharge capacity is reduced. Conversely, if the pressure in the crank chamber 34 is reduced, the differential pressure between the compression chamber 42 and the crank chamber 34 increases, so that the swash plate 40 The inclination angle (oscillation angle) increases, so that the stroke of the piston 41 increases and the discharge capacity increases.

The pressure in the crank chamber 34 is controlled by a pressure control valve 2 provided in a rear block 33 of the compressor 3. The pressure control valve 2 is specifically as shown in FIGS. 3 and 4 and includes a drive unit 60, a central block unit 70, and a valve body unit 80.

The driving unit 60 is provided with the central block 7
0, a cylindrical case 61 housed in the case 61 and fixed to one end of the central block 70, and a cylindrical case 62 wound around the cylinder 62. And one end face which is slidably inserted into the cylinder 62 and abuts the valve drive rod 68 on the side of the central block 70 and the other end face on which a spring mounting hole 65 is formed. A plunger 64, a spring 66 inserted into the spring mounting hole 65, one end of which contacts the plunger 64, and the case holding the other end of the spring 66 and sealing the other end of the cylinder 63. And a cover 67 fixed to the other end of the cover 61.

The central block 70 includes a cylindrical projection 71a for fixing the cylinder 63 and the case 61.
A cylindrical block 71 having an outer ring portion 71b to which it is caulked and fixed at one end side;
And a through-hole 74 through which the valve body drive rod 68 slidably passes, a low-pressure chamber 73 formed in the center of the block 71 in a cylindrical shape, and extends radially from the low-pressure chamber 73. It has a plurality of low pressure side communication holes 72. still,
The plurality of low pressure side communication holes 72 are formed in the suction space 3 of the compressor 3 through first grooves 75 formed in the rear block 33.
6, the pressure in the low-pressure chamber 73 substantially matches the pressure in the low-pressure line of the refrigeration cycle 1.

The valve body 80 includes a substantially cylindrical outer case 81 and an inner case 8 mounted on the outer case 81.
A pressure adjustment chamber 86 is formed on the central block side of the outer case 81, and an opening / closing portion 91 of a valve body 90 is housed therein.
Is slidably inserted. A high-pressure chamber 84 is defined between the small diameter portion 92 of the valve element formed between the opening / closing portion 91 of the valve element and the sliding portion 93 and the inner case 82. The pressure adjustment chamber 86 communicates with the crank chamber 34 via a crank chamber communication hole 85 opened in the outer case 81 and a second groove 95 formed in the rear block 33. It communicates with the discharge space 37 via a high-pressure side communication hole 83 formed through the outer case 81 and the inner case 82 and a third groove 96 formed in the rear block 33.

The inner diameter of the pressure adjusting chamber 86 is the same as that of the low pressure chamber 7.
3, the inner diameter of the inner case 82 is smaller than the inner diameter of the pressure adjustment chamber 86, and the outer diameter of the opening / closing portion 91 accommodated in the pressure adjustment chamber 86 is smaller than that of the low pressure chamber 73. The inner diameter is formed larger than the inner diameter and the inner diameter of the inner case 82.
A low-pressure side valve seat 76 on which a valve body 90 is seated is formed between the pressure adjusting chamber 86 and the pressure adjusting chamber 86 (the low pressure chamber 73 faces the opening of the pressure adjusting chamber 86). A high-pressure side valve seat 77 on which the valve element 90 is seated is formed between the valve body 86 and the high pressure chamber 86 (the periphery of an opening portion where the high pressure chamber 84 faces the pressure adjustment chamber 86). Therefore, the opening / closing portion 91 of the valve element 90 housed in the pressure adjustment chamber 86 is seated on the low-pressure side valve seat 76 or the high-pressure side valve seat 77, so that the pressure adjustment chamber 8
6 and the low-pressure chamber 73 or the high-pressure chamber 84 are communicated (open) or shut off (closed).

A low-pressure space 87 is formed between the end of the sliding portion 93 of the valve element 90 and the inner case 82, and a cover 89 for fixing the inner case 82 to the outer case 81 is formed. It communicates with the suction space 36 through the formed communication hole 88 and the communication space 97 formed in the rear block 33. The low-pressure space 87 accommodates a spring 94 that urges the valve body 90 to press the low-pressure side valve seat 76. Incidentally, the urging force of the spring 94 is set to be larger than the urging force of the spring 66, and when the electromagnetic coil 63 is not energized, as shown in FIG. It comes into contact with the side valve seat 76.

Therefore, since a low pressure can be applied to both end surfaces in the moving direction of the valve body 90, there is no pressure difference between both ends in the moving direction of the valve body 90, so that the valve body 90 can be moved smoothly. Since the driving force of the valve body 90 can be suppressed, the size of the electromagnetic coil 63 itself can be suppressed.

FIG. 5 is a flowchart showing a control operation example of the compressor control by the control unit 17. Hereinafter, this control operation example will be described with reference to a flowchart. The control unit 17 includes an outside air temperature Ta, a vehicle interior temperature Tinc, and the like. After inputting the various signals (Step 100), the thermal load (H) is calculated based on, for example, Equation 1 (Step 102). In Equation 1, K1 to K4 are operation constants, K5 is a correction term, and H
The larger the value, the higher the heat load.

[0028]

(Equation 1)

Then, in the next step 104, it is determined whether or not the refrigeration cycle 1 is at the time of starting. If it is determined that it is not at the time of starting, the process proceeds to step 106,
Normal control for adjusting the discharge capacity so that the pressure of the low-pressure line 10 becomes the target pressure is performed.

In the normal control, when the pressure Ps detected by the pressure sensor 12 is higher than the target pressure Psa, the pressure control valve 2 is increased in a direction to increase the discharge capacity of the compressor 3.
Is operated, and when the detected pressure Ps of the pressure sensor 12 is smaller than the target pressure Psa, control for operating the pressure control valve 2 in a direction to reduce the discharge capacity of the compressor 3 is performed. That is, based on the low pressure Ps and the target pressure Psa, the duty ratio is calculated from the equation shown in Equation 2,
A control signal having this duty ratio is formed by the duty ratio control circuit 24. In the following Expression 2, A is a proportional constant, B is an integration constant, and C is a correction term. When the low pressure Ps is larger than the target pressure Psa, the duty ratio becomes large. For example, FIG.
Is supplied to the electromagnetic coil 63 of the pressure control valve 2, and when the low pressure Ps is smaller than the target pressure Psa, the duty ratio becomes small. For example, in FIG. A control signal having a small duty ratio as shown is supplied to the electromagnetic coil 63 of the pressure control valve 2.

[0031]

(Equation 2)

Here, a predetermined fixed value may be used as the target pressure Psa, or the outside air temperature Ta and the vehicle interior temperature Tin.
c, Psa = K6 · F (H) + based on the heat load H calculated from the solar radiation Qsun, the set temperature Tset, and the like.
It may be determined as K7. In addition, K6
Is an operation constant, and K7 is a correction term.

Therefore, in the normal control, when the detected pressure Ps of the pressure sensor 12 is higher than the target pressure Psa, a control signal having a large duty ratio is supplied to the electromagnetic coil 63 of the pressure control valve 2 and the plunger 64 is turned on. Attracted by the electromagnetic coil 63, the valve body 90 is moved via the valve body drive rod 68 against the spring force of the spring 94. For this reason, the opening / closing part 91 is seated on the high-pressure side valve seat 77,
The state shown in FIG. Thereby, the crank chamber 34
Is the suction space 36 through the pressure adjustment chamber 86 and the low pressure chamber 73.
And the same pressure as the low pressure, the stroke of the piston 41 increases and the displacement of the compressor 3 increases as the low pressure decreases.

When the pressure Ps detected by the pressure sensor 12 is lower than the target pressure Psa, a control signal having a small duty ratio is supplied to the electromagnetic coil 63 of the pressure control valve 2 and the plunger 64 is energized. The spring force of the spring 94 exceeds the electromagnetic force, and the opening / closing portion 91 is moved to the low pressure side valve seat 76.
And the state shown in FIG. 3 is obtained. As a result, the crank chamber 34 communicates with the discharge space 37 via the pressure adjusting chamber 86 and the high-pressure chamber 84 and becomes the same pressure as the high-pressure pressure. Becomes smaller, and the discharge capacity of the compressor 3 decreases.

By the way, in the CO ₂ cycle using the pressure control valve 2 described above, for example, in the case of starting from a state where the operation is stopped under a high load environment where the outside air temperature is high, the pressure of the low pressure line is reduced to the target pressure. Therefore, the duty ratio is increased, the electromagnetic force acting on the plunger is also increased, and the urging force for pressing the opening / closing portion 91 against the high-pressure side valve seat 77 is also increased. In such an initial stage of startup, the high-pressure line 9
And the pressure in the low-pressure line 10 is almost non-existent, so that even if the crank chamber 34 communicates with the suction space 36, there is almost no pressure difference between the crank chamber and the discharge space, and the discharge capacity is small. It will start to move. However, although the discharge amount is small, the refrigerant is continuously supplied from the low-pressure line 10 to the high-pressure line 9, so that a high-low pressure difference gradually occurs, and the pressure in the crank chamber gradually decreases as the pressure of the low-pressure line 10 decreases. The differential pressure between the pressure applied to the front surface of the piston 41 (the pressure in the compression chamber 42) and the pressure applied to the back surface of the piston (the pressure in the crank chamber 34) gradually increases, and accordingly, the stroke amount of the piston 41 increases. As a result, the discharge capacity increases. Since the pressure increase at the initial stage of the cycle starts in a shorter time than when the low pressure reaches the target pressure, there is a risk that an abnormal increase in the high pressure is induced at the initial stage of the refrigeration cycle. That is, when the refrigeration cycle is stopped under an environment of high load, even if the pressure of the high-pressure line 9 and the pressure of the low-pressure line 10 are balanced, the equilibrium pressure is extremely high. Therefore, the rising speed of the high-pressure pressure is faster than the speed at which the low-pressure pressure reaches the target pressure, and there is a concern that the high-pressure pressure may rise abnormally.

In order to cope with such a situation, in the present configuration, if it is determined in step 104 that the refrigeration cycle 1 is to be started, then in step 108, the calculation in step 102 is performed. It is determined whether or not the heat load (H) is equal to or more than a predetermined load (α). The predetermined load amount α is a heat load amount that is not likely to abnormally increase when the high pressure exceeds a predetermined value before the low pressure reaches the target pressure in the initial stage of the refrigeration cycle 1. It is determined by experiments and the like.

If the heat load (H) is smaller than the predetermined load (α), there is no abnormal increase in the high pressure so as to exceed the specified value at the start of the cycle. If the heat load (H) is equal to or more than the predetermined load (α), there is a possibility that the high pressure may abnormally increase at the time of startup. Correction control for reducing the output value of the control signal is performed.

In this output value reduction correction control, the electromagnetic force acting on the plunger 64 against the spring force of the spring 94, that is, the force acting on the valve element 90 from the plunger 64 via the valve element driving rod 68 is controlled. It is controlled to be small. That is, when the low pressure is significantly higher than the target pressure and the state shown in FIG. 4 is formed, as shown in FIG. 7, the electromagnetic force Fm applied to the plunger 64 and the spring 66 (shown in FIG. 4) ), The force (Fm + Fs1) applied to the opening / closing portion 91 via the valve body driving rod 68 by the spring force Fs1 and the contact surface of the opening / closing portion 91 with the valve body driving rod 68 due to the refrigerant pressure Pc of the crank chamber 34. Is acting as a force for urging the opening / closing portion 91 toward the high-pressure side valve seat 77, that is, an urging force for closing the valve body 90 between the pressure adjusting chamber 86 and the high-pressure chamber 84. , Sliding part 93
The spring force Fs2 from the spring 94 and the refrigerant pressure Pd in the discharge space 37 cause the high pressure chamber 84 to open and close the opening 91
And the force Fd applied to the back of the high pressure side valve seat 7
7, which acts as a biasing force for opening the valve body 90 between the pressure adjusting chamber 86 and the high-pressure chamber 84, and Fm + Fs1 + Fc> Fd + F.
s2, but the reduction correction control is
The relationship Fm + Fs1 + Fc <Fd + Fs2 is realized by reducing the electromagnetic force Fm applied to the opening / closing section 91 via the valve drive rod 68.

Here, as a method of reducing the electromagnetic force Fm, a control signal to the pressure control valve 2, that is, at least one of the current, voltage, or duty ratio of the output from the duty ratio control circuit 24 is reduced. If the voltage and current of the control signal output from the duty ratio control circuit 24 during normal control have the relationship shown in FIGS. 8A and 8B, the voltage value itself is changed to that shown in FIG. And the average current value may be corrected and controlled to be small as shown in FIG. Alternatively, the duty ratio itself shown in FIG. 8A may be reduced as shown in FIG. 11A, and correction control may be performed so as to form a current having such a duty ratio.

The decrease amount of the control signal for reducing the electromagnetic force Fm is determined when the pressure (high pressure) Pd of the high pressure line 9 becomes lower than the operating pressure of the high pressure cut switch for stopping the compressor 3. , Fm + Fs1 + Fc <Fd + F
s2, which is such an amount that the valve body 90 can be displaced in a direction for communicating the high-pressure chamber 84 and the pressure adjusting chamber 86. Even if the predetermined amount is reduced irrespective of the heat load, the heat load is The amount of decrease may increase as the value increases.

Therefore, for example, when the cycle is started from a state where the low pressure is extremely high, such as a refrigeration cycle mounted on a vehicle left under the sun, If so, the duty ratio increases, and the pressure between the pressure adjustment chamber 86 and the high-pressure chamber 84 is smaller than the force that urges the valve body in a direction that opens the space between the pressure adjustment chamber 86 and the high-pressure chamber 84 due to the high pressure. And the electromagnetic force for urging the valve element in the direction to close the
Operates at full stroke and causes a sudden increase in pressure. However, when the above-described correction control for reducing the output value to the pressure control valve 2 is performed, the pressure control valve The output from the duty ratio control circuit 24 supplied to the motor is corrected so as to reduce the electromagnetic force Fm at a high load, so that the high pressure reaches a predetermined pressure lower than the pressure at which the high pressure cut switch is operated. At this point, the valve element 90 is moved to the high pressure chamber 84 by the force Fd urged by the high pressure.
Direction in which the pressure control chamber 86 communicates with the pressure control chamber 86, that is, the low pressure chamber 7
3 and the pressure adjustment chamber 86 are displaced in a direction of shutting off. Then, since the high-pressure refrigerant is released to the crank chamber 34, the crank chamber pressure increases, thereby reducing the piston stroke, reducing the discharge amount at the time of starting, and avoiding an abnormal increase in the high-pressure pressure. Will be able to

Thereafter, when the high pressure decreases, Fd
Becomes smaller, the pressure adjusting chamber 86 and the high-pressure chamber 84 again.
Is cut off, the crank chamber 34 is connected to the suction space 36, the crank chamber pressure is reduced, and the piston 41 is caused to make a full stroke.

Therefore, when starting a cycle under a high load, it is possible to start the cycle while suppressing a sudden abnormal rise of the high pressure, and thereafter, the process shifts to a full stroke to perform the capacity control corresponding to the high load. In addition, the inconvenience of frequently stopping the cycle at the time of startup is eliminated. Further, since an abnormal rise in high pressure at the time of starting can be suppressed, damage to the piping and components of the refrigeration cycle 1 can be avoided to protect the cycle, thereby improving the cycle reliability. Will be able to do it.

[0044]

As described above, according to the present invention,
In a refrigeration cycle equipped with a variable displacement compressor, a low pressure chamber communicating with the suction space, and a high pressure chamber communicating with the discharge space,
A pressure regulating chamber communicating with the crank chamber, a valve body for opening / closing between the pressure regulating chamber and the low-pressure chamber, and closing / opening between the pressure regulating chamber and the high-pressure chamber, and an electromagnetic generating electromagnetic force. A coil, a plunger slidably inserted into the electromagnetic coil, and moved by the electromagnetic force of the electromagnetic coil to move the valve body, and a spring for biasing the valve body in a direction opposite to the biasing direction of the plunger. A pressure control valve provided at least, a pressure detecting means for detecting a pressure in a low pressure line from an outflow side of the expansion device of the refrigeration cycle to a suction side of the variable capacity compressor, and a pressure detected by the pressure detecting means is higher than a target pressure. Is higher, the valve body is moved in a direction to open between the pressure adjustment chamber and the low-pressure chamber and to close between the pressure adjustment chamber and the high-pressure chamber, and the pressure detected by the pressure detection means becomes the target pressure. Lower than pressure regulation Control signal control means for controlling a control signal supplied to the electromagnetic coil to move the valve body in a direction to close the chamber between the low pressure chamber and open the space between the pressure adjustment chamber and the high pressure chamber. When the heat load at the time of starting the variable capacity compressor is higher than a predetermined load, a direction in which the space between the pressure adjustment chamber and the low pressure chamber is opened and a space between the pressure adjustment chamber and the high pressure chamber is closed. Since the control signal is corrected so as to reduce the urging force for moving the valve element, the valve element is opposed to the pressure adjusting chamber by the pressure before the pressure of the high-pressure line abnormally rises. It can be moved in a direction to close the space between the chambers, that is, in a direction to open the space between the pressure adjustment chamber and the high-pressure chamber, thereby releasing the high-pressure refrigerant to the crank chamber and reducing the discharge capacity. It is possible to reduce abnormal pressure of high pressure. It is possible.
For this reason, an abnormal pressure rise at the time of starting the refrigeration cycle can be avoided, and the protection of the refrigeration cycle can be ensured without fear of damage to piping and components of the refrigeration cycle.

In the case where the high pressure is sensed, the compressor is stopped when the high pressure is abnormally increased, and the compressor is moved again when the high pressure is reduced.
Since the abnormal increase in the high pressure can be suppressed, frequent ON / OFF of the compressor can be eliminated, and the reliability of the refrigeration cycle can be improved.

[Brief description of the drawings]

FIG. 1 is a schematic configuration diagram of a refrigeration cycle according to an embodiment of the present invention.

FIG. 2 is a sectional view of the variable displacement compressor according to the embodiment of the present invention.

FIG. 3 is a cross-sectional view illustrating a state where power is not supplied to the pressure control valve according to the embodiment of the present invention.

FIG. 4 is a cross-sectional view showing a state when power is supplied to the pressure control valve according to the embodiment of the present invention.

FIG. 5 is a flowchart illustrating a control operation example of compressor control by a control unit.

FIGS. 6A and 6B are diagrams showing examples of control signals supplied to the pressure control valve at the time of normal control. FIG. 6A shows a control signal having a large duty ratio, and FIG. 3 shows a control signal with a small ratio.

FIG. 7 is a diagram illustrating a force relationship applied to the valve body when the pressure control valve according to the embodiment of the present invention is energized.

FIG. 8 is a diagram showing a pulse wave for forming an input current supplied to the pressure control valve before correction and an input current formed by the pulse wave.

FIG. 9 is a diagram illustrating a case where a pulse wave (voltage value) for forming an input current supplied to the pressure control valve before correction is directly corrected.

FIG. 10 is a diagram illustrating a case where the input current supplied to the pressure control valve before correction is directly corrected.

FIG. 11 is a diagram illustrating a case where a duty ratio of a control signal input to the pressure control valve is corrected.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Refrigeration cycle 2 Pressure control valve 3 Compressor 4 Radiator 5 Internal heat exchanger 6 Expansion device 7 Evaporator 8 Accumulator 10 Low pressure line 12 Pressure sensor 31 Front block 32 Central block 33 Rear block 34 Crank chamber 35 Cylinder 36 Suction space 37 Discharge space 40 Swash plate 41 Piston 42 Compression chamber 63 Electromagnetic coil 64 Plunger 73 Low pressure chamber 84 High pressure chamber 86 Pressure adjustment chamber 90 Valve element 91 Opening / closing part 94 Spring

 ────────────────────────────────────────────────── ─── Continuing on the front page (72) Inventor Sakae Hayashi 39, Higashihara, Chiyo-ji, Konan-cho, Osato-gun, Saitama Prefecture F term (in reference) 3H045 AA04 AA27 BA13 BA37 CA02 CA03 CA13 CA26 DA25 DA43 EA13 EA16 EA33 EA38 EA42 3H059 AA03 BB35 CA01 CD05 CD11 DD13 EE13 FF11 FF12 3H076 AA06 BB32 BB43 CC05 CC12 CC16 CC17 CC20 CC84 CC92 CC93 CC94 CC95 CC98 3H106 DA03 DA23 DB02 DB12 DB22 DB32 DC02 DC17 GC09 GB45

Claims (3)

[Claims] 1. A cylinder block, a drive shaft provided in the cylinder block, a drive swash plate that rotates with the drive shaft and has a variable inclination angle with respect to the drive shaft, and a drive swash plate provided in the cylinder block. A plurality of cylinders having an axis parallel to the axis, a plurality of pistons slidably disposed in the cylinder, and reciprocating in the cylinder with the rotation of the driving swash plate; and a plurality of pistons defined by the cylinder and the piston. Compression chamber, a crank chamber formed on the side opposite to the compression chamber of the piston, a suction space communicating with the compression chamber in a suction stroke of the piston, and a discharge space communicating with the compression chamber in a compression stroke of the piston. And a radiator for cooling the refrigerant compressed by the variable capacity compressor, and a refrigerant cooled by the radiator In a refrigeration cycle having at least an expansion device for reducing pressure and an evaporator for evaporating the refrigerant reduced in pressure by the expansion device, a low-pressure chamber communicating with the suction space, and a high-pressure chamber communicating with the discharge space, A pressure adjustment chamber communicating with the crank chamber, a valve body for opening / closing between the pressure adjustment chamber and the low pressure chamber, and closing / opening between the pressure adjustment chamber and the high pressure chamber; An electromagnetic coil that generates a force, a plunger that is slidably inserted into the electromagnetic coil, moves by the electromagnetic force of the electromagnetic coil to move the valve element, and a biasing direction of the valve element by the plunger. A pressure control valve having at least a spring that urges in the opposite direction, and a pressure detection unit that detects a pressure in a low pressure line from an outlet side of the expansion device of the refrigeration cycle to a suction side of the variable capacity compressor, Previous When the pressure detected by the pressure detecting means is higher than the target pressure, open the space between the pressure adjustment chamber and the low-pressure chamber and close the space between the pressure adjustment chamber and the high-pressure chamber. When the valve body is moved and the pressure detected by the pressure detecting means is lower than the target pressure, the space between the pressure adjustment chamber and the low pressure chamber is closed and the space between the pressure adjustment chamber and the high pressure chamber is closed. Control signal control means for controlling a control signal supplied to the electromagnetic coil so as to move the valve element in a direction in which the valve is opened; and heat load detection means for detecting a heat load when the variable capacity compressor is started. Determining means for determining that the heat load detected by the heat load detecting means is higher than a predetermined load; and determining the pressure when the heat load is determined to be higher than the predetermined load by the determining means. Adjustment Control signal correction for correcting the control signal so as to reduce the urging force for moving the valve body in a direction to open between the chamber and the low pressure chamber and to close between the pressure adjustment chamber and the high pressure chamber. Means for controlling a variable capacity of a refrigeration cycle. 2. The control signal supplied to the electromagnetic coil is changed by controlling a duty ratio, and the control signal correction unit controls a voltage, a current, or a duty ratio of the control signal. 2. The variable displacement control device for a refrigeration cycle according to claim 1, wherein at least one of them is changed so as to reduce the urging force. 3. The variable displacement control device for a refrigeration cycle according to claim 1, wherein the refrigerant is carbon dioxide.