JP5474284B2 - Capacity control system for variable capacity compressor - Google Patents

Description

  The present invention relates to a capacity control system for a variable capacity compressor applied to an air conditioning system.

  For example, a reciprocating variable displacement compressor used in a vehicle air conditioning system includes a housing, and a discharge chamber, a suction chamber, a crank chamber, and a cylinder bore are defined in the housing. A swash plate is tiltably connected to a drive shaft extending in the crank chamber, and a conversion mechanism including the swash plate converts the rotation of the drive shaft into a reciprocating motion of a piston disposed in the cylinder bore. The reciprocating motion of the piston performs the steps of sucking the working fluid from the suction chamber into the cylinder bore, compressing the sucked working fluid, and discharging the compressed working fluid into the discharge chamber.

The stroke length of the piston, that is, the discharge capacity of the compressor, becomes variable by changing the pressure (control pressure) of the crank chamber, and in order to control the discharge capacity, an air supply passage that connects the discharge chamber and the crank chamber is used. A capacity control valve is disposed, and a throttle is disposed in a bleed passage that connects the crank chamber and the suction chamber.
For example, the capacity control valve disclosed in Patent Document 1 has a built-in pressure-sensitive member for sensing suction pressure. In a variable capacity compressor using this capacity control valve, feedback control is performed on the discharge capacity by sensing the suction pressure. To do. For example, the pressure-sensitive member is constituted by a bellows, and expands to reduce the discharge capacity when the suction pressure decreases, thereby increasing the opening of the air supply passage.

  In the capacity control device disclosed in Patent Document 2, the discharge capacity is feedback controlled so that the pressure difference (working pressure difference) between the pressure in the discharge chamber (discharge pressure) and the pressure in the suction chamber approaches the target value. Is done. That is, in the capacity control device of Patent Document 2, the amount of current supplied to the capacity control valve is changed with the operating pressure difference as a control target, and the discharge capacity changes accordingly. For example, when the operating pressure difference is to be reduced, the control device operates to increase the discharge capacity and bring the operating pressure difference closer to a predetermined value.

Further, in the air conditioner disclosed in Patent Document 3, similarly to the capacity control of Patent Document 2, the energization amount to the capacity control valve is changed with the operating pressure difference as a control target, and the discharge capacity changes accordingly.
Therefore, the capacity control device of the variable capacity compressor is different from the suction pressure control system in which the suction pressure is controlled as represented by Patent Document 1 and the operating pressure difference as represented by Patent Documents 2 and 3. Are roughly divided into those of the differential pressure control method.
Japanese Patent Laid-Open No. 9-268973 Japanese Patent Laid-Open No. 2001-132650 Japanese Patent Laid-Open No. 2001-153042

  The suction pressure control method for controlling the suction pressure is a discharge capacity control method suitable for an air conditioning system, and is currently most widely used. In the suction pressure control method, the target value of the suction pressure to be controlled is changed to a higher value when the discharge capacity is decreased. However, for example, when the heat load applied to the refrigeration cycle is large and the rotation speed of the compressor is low, the discharge pressure may not be sufficiently reduced because the suction pressure is already high. Further, when the actual suction pressure exceeds the upper limit of the suction pressure control range, the discharge capacity may not be controlled at all.

It was the differential pressure control system typified by Patent Documents 2 and 3 that has been devised to eliminate such drawbacks of the suction pressure control system. According to the differential pressure control system, regardless of the thermal load, The discharge capacity is quickly changed by external control. However, the differential pressure control system has the following drawbacks.
When the discharge capacity is feedback controlled so that the pressure difference between the two pressure monitoring points becomes the target value, if the pressure difference is to be reduced, the discharge capacity is increased so that the pressure difference approaches a predetermined value. From such a control operation, when the capacity control of the differential pressure control method is performed in a state where the refrigerant amount is insufficient from the appropriate amount in the refrigerant circulation path, the pressure difference between the pressure monitoring points is determined when the refrigerant amount is appropriate. Therefore, the discharge capacity is increased to maintain the pressure difference at the target value. In the pressure difference feedback control, the variable capacity compressor is operated in a state where the refrigerant amount is insufficient and the refrigerant circulation amount is insufficient.If the operating pressure difference does not reach the target value, the discharge capacity is accelerated. The compressor eventually continues to operate at maximum capacity. Such an operation may cause damage to the compressor.

  The suction pressure control method is superior from the viewpoint of dealing with the shortage of the refrigerant amount. When the refrigerant amount becomes insufficient, the pressure decreases on the high-pressure side and the low-pressure side of the refrigeration cycle, and the suction pressure tends to fall below a predetermined value.According to the suction pressure control method, in order to maintain the suction pressure at a predetermined value, This is because the discharge capacity is reduced and finally the capacity is shifted to the minimum capacity. That is, the suction pressure control method has a fail-safe function.

As described above, the differential pressure control method has a drawback that the ability to cope with the shortage of the refrigerant amount is insufficient as compared with the suction pressure control method, and a technique for solving this disadvantage with a simple configuration is desired. The present invention has been made based on the above-described circumstances, and an object of the present invention is to provide a variable capacity compressor capable of estimating a suction pressure with a simple configuration while performing discharge capacity control by a differential pressure control method. It is to provide a capacity control system. As a result, the range in which the variable capacity compressor can be operated, such as dealing with the shortage of the refrigerant amount, is defined, and the reliability of the variable capacity compressor is ensured.

In order to achieve the above-mentioned object, according to the present invention, a refrigerant, an expander, and an evaporator are inserted into a circulation path through which a refrigerant circulates to constitute a refrigeration cycle of an air conditioning system, and based on a change in control pressure. In the capacity control system of the variable capacity compressor whose capacity changes, the pressure of the refrigerant in any part of the discharge pressure region of the refrigeration cycle is set as the discharge pressure, and the part in the suction pressure region of the refrigeration cycle A valve body capable of receiving and opening the valve hole in response to the suction pressure and the electromagnetic force of the solenoid in a direction opposite to the discharge pressure when the refrigerant pressure is the suction pressure; , wherein the valve body and the electromagnetic force acts in accordance with the control current discharge pressure and the forces exerted by the pressure difference between the suction pressure supplied to the solenoid is in the balance position shifts And, the target evaporator outlet air temperature to set the displacement control valve capable of adjusting the capacity of said variable capacity compressor by varying the control pressure by opening and closing the valve hole, the target outlet air temperature of the evaporator Based on the difference between the setting means, the outlet air temperature detecting means for detecting the outlet air temperature of the evaporator, and the target outlet air temperature and the outlet air temperature, the control current supplied to the solenoid or Based on the current adjustment means for adjusting the duty ratio related to the control current, the discharge pressure detection means for detecting the discharge pressure , and the discharge pressure detected by the control current and the discharge pressure detection means, the capacity comprising a suction pressure calculating means relational expression of the forces acting on the valve body of the control valve calculates the suction pressure, and said current adjustment means, the said target outlet air temperature outlet When the valve body and the control current is supplied to the solenoid based on the difference between the air temperature capacity of the variable capacity compressor moves it is adjusted to balance position is calculated by the intake pressure calculating means After the suction pressure becomes lower than the lower limit pressure, the control current when the suction pressure becomes lower than the lower limit pressure or the duty ratio related to the control current is maintained, or the discharge capacity decreases. Thus, a capacity control system for a variable capacity compressor is provided (claim 1).

Preferably, the discharge pressure detecting means includes high pressure detecting means for detecting the pressure of the refrigerant at any part of the high pressure region of the refrigeration cycle, and the pressure of the refrigerant detected by the high pressure detecting means. The discharge pressure is detected by correcting (Claim 2) .

Preferably, the suction pressure calculation means sets a first index pressure based on the calculated suction pressure, and the current adjustment means determines that the first index pressure is lower than a lower limit pressure instead of the suction pressure. After that, the control current or the duty ratio when the first index pressure becomes lower than the lower limit pressure is maintained or the discharge capacity is changed (Claim 3).
Preferably, the suction pressure calculating means sets one of an upper limit value and a lower limit value of the calculated error range of the suction pressure as the first index pressure, and the calculated suction pressure and the first index are set. The difference from the pressure changes based on the control current or the duty ratio .

Preferably, the air conditioning system is applied to the vehicle, and the heat load detecting means for detecting internal and external thermal load of vehicles, the operating condition detecting means for detecting at least one operating state of the vehicle and the variable displacement compressor wherein the lower pressure is at least is changed based on one of the operating state detected by the detection thermal load and the operating condition detecting means by said heat load detecting means (claim 5).

Preferably, the current adjusting means changes the control current or the duty ratio so that the discharge capacity decreases when the suction pressure calculated by the suction pressure calculating means becomes lower than the lower limit pressure. When the control current becomes smaller than the first lower limit value as a result of the change or when the duty ratio becomes smaller than a value corresponding to the first lower limit value, the control is performed so that the discharge capacity is minimized. The current or the duty ratio is changed (claim 6).

Preferably, the current adjusting means maintains the control current or the duty ratio when the discharge pressure exceeds the upper limit pressure after the discharge pressure detected by the discharge pressure detection means exceeds the upper limit pressure. Or change so that the discharge capacity is reduced.
Preferably, the discharge pressure detecting unit sets a second index pressure with reference to the detected discharge pressure, and the current adjusting unit is configured to set the second index pressure after the second index pressure exceeds an upper limit pressure. The control current or the duty ratio when the index pressure exceeds the upper limit pressure is maintained, or the discharge capacity is changed (Claim 8).

Preferably, the air conditioning system is applied to the vehicle, and the heat load detecting means for detecting internal and external thermal load of vehicles, the operating condition detecting means for detecting at least one operating state of the vehicle and the variable displacement compressor wherein the discharge pressure detecting means, wherein the second indicator pressure, sensed by setting the one of the upper and lower limits of the variation range of the discharge pressure, sensed the discharge pressure and the second index The difference from the pressure changes based on at least one of the thermal load detected by the thermal load detector and the operating state detected by the operating state detector (Claim 9).

Preferably, the air conditioning system is applied to the vehicle, prior SL includes an operation state detection means for detecting at least one operating state of the vehicle and a variable displacement compressor, wherein the upper limit pressure is sensed by said operating condition detecting means It is changed based on the operating state.
Preferably, the current adjusting means changes the control current or the duty ratio so that the discharge capacity decreases when the discharge pressure detected by the discharge pressure detecting means exceeds the upper limit pressure. As a result of the change, when the control current becomes smaller than the second lower limit value or when the duty ratio becomes smaller than a value corresponding to the second lower limit value, the control current is set to minimize the discharge capacity. Alternatively, the duty ratio is changed (claim 11).

Preferably, the current adjustment means includes target setting means for setting a target value of the control current or the duty ratio , and current detection means for detecting a current flowing through the solenoid or a duty ratio related to the current, The current adjusting means adjusts a control current supplied to the solenoid so that a current or a duty ratio detected by the current detecting means approaches the target value, and the suction pressure calculating means serves as the control current. The suction pressure is calculated based on the current detected by the current detection means and the discharge pressure detected by the discharge pressure detection means (claim 12).

Preferably, the variable capacity compressor is rotatably supported within the housing in which a discharge chamber, a crank chamber, a suction chamber, and a cylinder bore are defined, a piston disposed in the cylinder bore, and the housing. A drive shaft, a conversion mechanism including a variable tilt swash plate element for converting rotation of the drive shaft into reciprocating motion of the piston, an air supply passage communicating the discharge chamber and the crank chamber, and the crank chamber; and a bleed passage for communicating the suction chamber, the displacement control valve is interposed in one of the air supply passage and the bleed passage (claim 13).

In the capacity control system of the variable capacity compressor according to claim 1 of the present invention, the suction pressure is calculated with a simple configuration. By using the calculated suction pressure, the discharge capacity control can be optimized.
In particular, the suction pressure is prevented from being abnormally reduced, and the reliability of the variable capacity compressor is ensured against a shortage of refrigerant. This is due to the following reason.
In the conventional differential pressure control that controls the operating pressure difference, if the suction pressure drops abnormally due to the lack of refrigerant, the discharge pressure also decreases at the same time and the operating pressure difference becomes smaller. The discharge capacity was increased so as to increase. On the other hand, in the capacity control system of the variable capacity compressor according to the first aspect, after the suction pressure becomes lower than the lower limit pressure, the control pressure is maintained or discharged without increasing the operating pressure difference. Change to reduce capacity. As a result, according to this capacity control system, it is possible to prevent the variable capacity compressor from operating at a maximum discharge capacity or a capacity close thereto when the refrigerant is insufficient, and to ensure the reliability of the variable capacity compressor.
In the capacity control system of the variable capacity compressor according to claim 2, since the discharge pressure detection means detects the discharge pressure based on the pressure detected by the high pressure detection means, the degree of freedom of the configuration of the capacity control system is high. Become. On the other hand, the discharge pressure can be detected with high accuracy by correcting the pressure detected by the high-pressure detecting means and detecting the discharge pressure. As a result, the suction pressure is calculated with high accuracy.

In the capacity control system of the variable capacity compressor according to claim 3 , by setting an appropriate first index pressure, the suction pressure is surely prevented from being lowered abnormally, and the reliability of the variable capacity compressor against a shortage of refrigerant, etc. Sex is secured.
In the capacity control system of the variable capacity compressor according to claim 4 , by setting an upper limit value or a lower limit value of the error range of the calculated suction pressure as the first index pressure, it is possible not to cause variation in manufacturing of the refrigeration cycle. The suction pressure is surely prevented from being abnormally reduced.

In the capacity control system of the variable capacity compressor according to the fifth aspect , the optimum discharge capacity control is realized by changing the lower limit pressure based on the heat load or the operation state of the vehicle or the variable capacity compressor. For example, if the lower limit pressure is set high when the heat load is high, the compressor is prevented from operating continuously at the maximum discharge capacity, and the reliability of the compressor is ensured. Further, by setting the lower limit pressure high when the rotation speed of the compressor or the engine is high, it is possible to prevent an excessive load from being applied to the compressor and to ensure the reliability of the compressor.

In the capacity control system of the variable capacity compressor according to claim 6, when the suction pressure is continuously lower than the lower limit pressure, the control current or the duty ratio becomes smaller than the first lower limit value or the value corresponding to the first lower limit value. The discharge capacity of the variable capacity compressor is minimized. That is, when the suction pressure is continuously lower than the lower limit pressure due to refrigerant shortage, the discharge capacity of the variable capacity compressor is minimized. As a result, according to this capacity control system, the reliability of the variable capacity compressor is further ensured against the refrigerant shortage.

In the capacity control system of the variable capacity compressor according to the seventh aspect , the discharge pressure is prevented from rising abnormally, and the reliability of the variable capacity compressor and the refrigeration cycle is ensured.
In the capacity control system of the variable capacity compressor according to claim 8 , by setting an appropriate second index pressure, the discharge pressure can be reliably prevented from rising abnormally, and the reliability of the variable capacity compressor and the refrigeration cycle can be reliably prevented. Is secured.

In the capacity control system of the variable capacity compressor according to claim 9 , by setting an upper limit value or a lower limit value of the detected variation range of the discharge pressure as the second index pressure, the manufacturing variation of the refrigeration cycle and the discharge pressure are set. Regardless of the correction amount when detecting the discharge pressure, the discharge pressure is reliably prevented from rising abnormally.
In the capacity control system of the variable capacity compressor according to the tenth aspect, the optimum discharge capacity control is realized by changing the upper limit pressure based on the operation state of the vehicle or the variable capacity compressor. For example, when the rotational speed of the compressor or the engine is high, setting the upper limit pressure low prevents the compressor from being overloaded and ensures the reliability of the compressor.

In the capacity control system of the variable capacity compressor according to claim 11, when the discharge pressure continuously exceeds the upper limit pressure, the control current or the duty ratio is smaller than the second lower limit value or a value corresponding to the second lower limit value. Thus, the discharge capacity of the variable capacity compressor is minimized. That is, when some abnormality occurs in the refrigeration cycle and the discharge pressure continuously exceeds the upper limit pressure, the discharge capacity of the variable capacity compressor is minimized. As a result, according to this capacity control system, the reliability of the variable capacity compressor and the refrigeration cycle is further ensured.

In the capacity control system of the variable capacity compressor according to claim 12 , the suction pressure is calculated with high accuracy by calculating the suction pressure based on the current detected by the current detection means and the discharge pressure.
The variable capacity compressor to which the capacity control system of the variable capacity compressor of claim 13 is applied is a reciprocating type, and the piston stroke defined by the minimum inclination angle of the swash plate element can be set very small. Discharge volume is very small. For this reason, when the refrigerant is insufficient, the capacity control system minimizes the discharge capacity, so that the variable capacity compressor is effectively protected.

Hereinafter, the capacity control system A of the variable capacity compressor of one embodiment will be described.
FIG. 1 shows a refrigeration cycle 10 of a vehicle air conditioning system to which a capacity control system A is applied. The refrigeration cycle 10 includes a circulation path 12 through which a refrigerant as a working fluid circulates. A compressor 100, a radiator (condenser) 14, an expander (expansion valve) 16, and an evaporator 18 are sequentially inserted in the circulation path 12 in the flow direction of the refrigerant. The refrigerant circulates in the circulation path 12 according to the discharge capacity of the machine 100. That is, the compressor 100 performs a series of processes including a refrigerant suction process, a suction refrigerant compression process, and a compressed refrigerant discharge process.

The evaporator 18 also constitutes a part of an air circuit of the vehicle air conditioning system, and the air flow passing through the evaporator 18 is cooled by taking heat of vaporization by the refrigerant in the evaporator 18.
The compressor 100 to which the capacity control system A is applied is a variable capacity compressor, for example, a swash plate type clutchless compressor. The compressor 100 includes a cylinder block 101, and the cylinder block 101 is formed with a plurality of cylinder bores 101a. A front housing 102 is connected to one end of the cylinder block 101, and a rear housing (cylinder head) 104 is connected to the other end of the cylinder block 101 via a valve plate 103.

  The cylinder block 101 and the front housing 102 define a crank chamber 105, and a drive shaft 106 extends longitudinally through the crank chamber 105. The drive shaft 106 passes through an annular swash plate 107 disposed in the crank chamber 105, and the swash plate 107 is hinged to a rotor 108 fixed to the drive shaft 106 via a connecting portion 109. Accordingly, the swash plate 107 can tilt while moving along the drive shaft 106.

A portion of the drive shaft 106 extending between the rotor 108 and the swash plate 107 is provided with a coil spring 110 that urges the swash plate 107 toward the minimum inclination angle. A coil spring 111 that urges the swash plate 107 toward the maximum inclination angle is attached to a portion of the drive shaft 106 that extends between the swash plate 107 and the cylinder block 101.
The drive shaft 106 penetrates through a boss portion 102a protruding outside the front housing 102, and is connected to a pulley 112 as a power transmission device at the outer end of the drive shaft 106. The pulley 112 is rotatably supported by a boss portion 102a via a ball bearing 113, and a belt 115 is wound around the engine 114 as an external drive source.

A shaft seal device 116 is disposed inside the boss portion 102a to block the inside and the outside of the front housing 102 from each other. The drive shaft 106 is rotatably supported by bearings 117, 118, 119, and 120 in the radial direction and the thrust direction. Power from the engine 114 is transmitted to the pulley 112, and can rotate in synchronization with the rotation of the pulley 112.
A piston 130 is disposed in the cylinder bore 101a, and a tail portion protruding into the crank chamber 105 is formed integrally with the piston 130. A pair of shoes 132 is disposed in a recess 130a formed in the tail portion, and the shoes 132 are in sliding contact with the outer peripheral portion of the swash plate 107 so as to be sandwiched therebetween. Therefore, the piston 130 and the swash plate 107 are interlocked with each other via the shoe 132, and the piston 130 reciprocates in the cylinder bore 101a by the rotation of the drive shaft 106.

  A suction chamber 140 and a discharge chamber 142 are defined in the rear housing 104, and the suction chamber 140 can communicate with the cylinder bore 101 a through a suction hole 103 a provided in the valve plate 103. The discharge chamber 142 communicates with the cylinder bore 101a through a discharge hole 103b provided in the valve plate 103. The suction hole 103a and the discharge hole 103b are opened and closed by a suction valve and a discharge valve (not shown), respectively.

  A muffler 150 is provided outside the cylinder block 101, and the muffler casing 152 is joined to a muffler base 101b formed integrally with the cylinder block 101 via a seal member (not shown). The muffler casing 152 and the muffler base 101b define a muffler space 154, and the muffler space 154 communicates with the discharge chamber 142 via a discharge passage 156 that passes through the rear housing 104, the valve plate 103, and the muffler base 101b.

  A discharge port 152a is formed in the muffler casing 152, and a check valve 200 is disposed in the muffler space 154 so as to block between the discharge passage 156 and the discharge port 152a. Specifically, the check valve 200 opens and closes according to the pressure difference between the pressure on the discharge passage 156 side and the pressure on the muffler space 154 side, and closes when the pressure difference is smaller than a predetermined value, and the pressure difference is predetermined. If it is larger than the value, it opens.

Therefore, the discharge chamber 142 can communicate with the forward portion of the circulation path 12 via the discharge passage 156, the muffler space 154, and the discharge port 152a, and the muffler space 154 is interrupted by the check valve 200. On the other hand, the suction chamber 140 communicates with the return path portion of the circulation path 12 via a suction port 104 a formed in the rear housing 104.
A capacity control valve (electromagnetic control valve) 300 is accommodated in the rear housing 104, and the capacity control valve 300 is inserted in the air supply passage 160. The air supply passage 160 extends from the rear housing 104 to the cylinder block 101 through the valve plate 103 so as to communicate between the discharge chamber 142 and the crank chamber 105.

On the other hand, the suction chamber 140 communicates with the crank chamber 105 via the extraction passage 162. The extraction passage 162 includes a clearance between the drive shaft 106 and the bearings 119 and 120, a space 164, and a fixed orifice 103 c formed in the valve plate 103.
The suction chamber 140 is connected to the capacity control valve 300 independently of the air supply passage 160 through a pressure sensitive passage 166 formed in the rear housing 104.

  More specifically, as shown in FIG. 2, the capacity control valve 300 includes a valve unit and a drive unit that opens and closes the valve unit. The valve unit has a cylindrical valve housing 301, and an inlet port (valve hole 301 a) is formed at one end of the valve housing 301. The valve hole 301 a communicates with the discharge chamber 142 via the upstream portion of the air supply passage 160 and opens to the valve chamber 303 defined inside the valve housing 301.

A cylindrical valve body 304 is accommodated in the valve chamber 303. The valve body 304 can move in the valve chamber 303 in the axial direction of the valve housing 301, and can close the valve hole 301 a by contacting the end face of the valve housing 301. That is, the end surface of the valve housing 301 functions as a valve seat.
Further, an outlet port 301 b is formed on the outer peripheral surface of the valve housing 301, and the outlet port 301 b communicates with the crank chamber 105 through a downstream portion of the air supply passage 160. The outlet port 301b also opens into the valve chamber 303, and the discharge chamber 142 and the crank chamber 105 can communicate with each other through the valve hole 301a, the valve chamber 303, and the outlet port 301b.

The drive unit has a cylindrical solenoid housing 310, and the solenoid housing 310 is coaxially connected to the other end of the valve housing 301. The open end of the solenoid housing 310 is closed by an end cap 312, and a solenoid 316 wound around a bobbin 314 is accommodated in the solenoid housing 310.
Further, a concentric cylindrical fixed core 318 is accommodated in the solenoid housing 310, and the fixed core 318 extends from the valve housing 301 toward the end cap 312 to the center of the solenoid 316. The end cap 312 side of the fixed core 318 is surrounded by a sleeve 320, and the sleeve 320 has a closed end on the end cap 312 side.

The fixed core 318 has an insertion hole 318 a at the center, and one end of the insertion hole 318 a opens into the valve chamber 303. Further, a movable core accommodating space 324 for accommodating the cylindrical movable core 322 is defined between the fixed core 318 and the closed end of the sleeve 320, and the other end of the insertion hole 318a is opened to the movable core accommodating space 324. doing.
A solenoid rod 326 is slidably inserted into the insertion hole 318a, and a valve body 304 is integrally and coaxially connected to one end of the solenoid rod 326. The other end of the solenoid rod 326 projects into the movable core housing space 324, and the other end of the solenoid rod 326 is fitted into a through hole formed in the movable core 322 so that the solenoid rod 326 and the movable core 322 are integrated. Has been. An open spring 328 is disposed between the stepped surface of the movable core 322 and the end surface of the fixed core 318, and a predetermined gap is secured between the movable core 322 and the fixed core 318.

The movable core 322, the fixed core 318, the solenoid housing 310, and the end cap 312 are made of a magnetic material and constitute a magnetic circuit. The sleeve 320 is made of a non-magnetic stainless steel material.
A pressure-sensitive port 310 a is formed in the solenoid housing 310, and a suction chamber 140 is connected to the pressure-sensitive port 310 a through a pressure-sensitive passage 166. A pressure-sensitive groove 318b extending in the axial direction is formed on the outer peripheral surface of the fixed core 318, and the pressure-sensitive port 310a and the pressure-sensitive groove 318b communicate with each other. Accordingly, the suction chamber 140 and the movable core housing space 324 communicate with each other through the pressure-sensitive port 310a and the pressure-sensitive groove 318b, and the suction chamber 140 is arranged in the valve closing direction on the back side of the valve body 304 via the solenoid rod 326. (Hereinafter referred to as suction pressure Ps).

A control device 400 provided outside the compressor 100 is connected to the solenoid 316, and when the control current I is supplied from the control device 400, the solenoid 316 generates an electromagnetic force F (I). The electromagnetic force F (I) of the solenoid 316 attracts the movable core 322 toward the fixed core 318 and acts on the valve body 304 in the valve closing direction.
In the capacity control valve 300, preferably, the pressure receiving area (seal area Sv) of the valve body 304 on which the pressure of the discharge chamber 142 (hereinafter referred to as discharge pressure Pd) acts when the valve body 304 closes the valve hole 301a. The area of the valve body 304 on which the suction pressure Ps acts, that is, the cross-sectional area of the solenoid rod 326 is formed to be equal.

In this case, the pressure in the crank chamber 105 (hereinafter referred to as crank pressure Pc) substantially does not act on the valve body 304 in the opening / closing direction. Therefore, the forces acting on the valve body 304 are the discharge pressure Pd, the suction pressure Ps, the electromagnetic force F (I) of the solenoid 316, and the biasing force fs of the release spring 328, and the discharge pressure Pd and the release spring 328 The urging force fs acts in the valve opening direction, and the other suction pressure Ps and the electromagnetic force F (I) of the solenoid 316 act in the valve closing direction opposite to the valve opening direction.
This relationship is expressed by equation (1), and equation (1) is transformed into equation (2).

From these formulas (1) and (2), when the difference between the discharge pressure Pd and the suction pressure Ps is the operating pressure difference ΔP, if the electromagnetic force F (I), that is, the control current I is determined, the operating pressure difference ΔP is I understand that it will be decided. FIG. 3 shows the relationship between the control current I and the operating pressure difference ΔP (= Pd−Ps).
As apparent from FIG. 3, the operating pressure difference ΔP increases as the control current I supplied to the solenoid 316 increases, and the operating pressure difference ΔP can be feedback controlled by adjusting the control current I. If the control current I is zero, the valve element 304 is separated by the biasing force fs of the opening spring 328 and the valve hole 301a is forcibly opened. As a result, the refrigerant is introduced from the discharge chamber 142 into the crank chamber 105, and the discharge capacity is kept to a minimum.

FIG. 4 is a block diagram showing a schematic configuration of the capacity control system A including the control device 400.
The capacity control system A has one or more external information detecting means for detecting external information. The external information detecting means includes an evaporator target outlet air temperature setting device 401 and a temperature sensor 402 as an evaporator outlet air temperature detecting means. including.

  The evaporator target outlet air temperature setter 401 is based on various external information including the passenger compartment temperature setting, and the target value of the air temperature Te at the outlet of the evaporator 18 that is the target of discharge capacity control of the compressor 100 ( The evaporator target outlet air temperature) Tes is set and input to the control device 400. The evaporator target outlet air temperature setting device 401 can be constituted by, for example, a part of an air conditioner ECU that controls the operation of the entire air conditioning system.

The temperature sensor 402 is installed at the outlet of the evaporator 18 in the air circuit, and detects the air temperature Te immediately after passing through the evaporator 18 (see FIG. 1). The detected air temperature Te is input to the control device 400 as one of external information.
Further, the external information detection means includes discharge pressure detection means, and the discharge pressure detection means has a pressure sensor 403 that constitutes a part thereof. The discharge pressure detecting means is means for detecting the discharge pressure Pd acting on the valve body 304. The pressure sensor 403 is mounted on the inlet side of the radiator 14 and detects the refrigerant pressure (hereinafter referred to as a detection pressure Ph) at the site, and inputs it to the control device 400 (see FIG. 1).

The discharge pressure Pd and the detection pressure Ph are discharge pressures in the general sense of the pressure in the discharge pressure region of the refrigeration cycle 10. The discharge pressure region of the refrigeration cycle 10 refers to a region from the discharge chamber 142 to the inlet of the radiator 14.
On the other hand, the suction pressure region of the refrigeration cycle 10 refers to a region extending from the outlet of the evaporator 18 to the suction chamber 140. The discharge pressure region also includes the cylinder bore 101a in the compression process, and the suction pressure region also includes the cylinder bore 101a in the suction process.

The control device 400 includes, for example, an independent ECU (electronic control unit), but may be included in an air conditioner ECU or an engine ECU that controls the operation of the engine 114. Further, the evaporator target outlet air temperature setting device 401 may be included in the control device 400.
The control device 400 includes a discharge pressure calculation determination unit 404, a control signal calculation unit 405, a solenoid drive unit 406, and a suction pressure calculation unit 407.

The discharge pressure calculation determination unit 404 constitutes a discharge pressure detection unit together with the pressure sensor 403, and calculates the discharge pressure Pd by correcting the detection pressure Ph detected by the pressure sensor 403.
The reason why the detection pressure Ph is corrected in this manner is that the refrigerant pressure differs between the discharge chamber 142 and the inlet of the radiator 14 even in the same discharge pressure region, particularly when the heat load is large. It is. Specifically, the discharge pressure Pd is calculated by the following equation: Pd = Ph + ΔPd in consideration of the pressure loss ΔPd between the position where the pressure sensor 403 is mounted and the discharge chamber 142.

The discharge pressure Pd can be calculated by a function f (Ph) having the detected pressure Ph as a variable. The function f (Ph) can be obtained in advance, and FIG. 5 shows a graph of Pd = f (Ph).
FIG. 5 also shows the upper and lower limits of the variation range of the discharge pressure Pd based on the function f (Ph). Variations in the discharge pressure Pd occur based on manufacturing variations of the pressure sensor 403 and the circulation path 12, and the variation range of the discharge pressure Pd increases as the detected pressure Ph increases. The upper limit and the lower limit of the variation range of the discharge pressure Pd can be set by, for example, the discharge pressure detection unit 404.

Further, in FIG. 5, a straight line corresponding to Pd = Ph is also shown for reference.
In addition, the discharge pressure calculation determination unit 404 not only calculates the discharge pressure Pd, but also compares the calculated discharge pressure Pd with a predetermined upper limit pressure P2, and outputs the comparison result to the control signal calculation unit 405. Further, the discharge pressure calculation determination unit 404 inputs the calculated discharge pressure Pd to the suction pressure calculation unit 407.

The control signal calculation means 405 sets the deviation ΔT (= Tes−Te) between the evaporator target outlet air temperature Tes set by the evaporator target temperature setter 401 and the evaporator outlet air temperature Te detected by the temperature sensor 402. Based on this, the control current I to be supplied to the solenoid 316 is calculated. That is, the control signal calculation unit 405 sets a target value for the control current I.
Here, since there is a relationship represented by the equations (1) and (2) between the control current I and the operating pressure difference ΔP that is the control target, calculating the control current I This corresponds to calculating the pressure difference ΔP.

Then, the control signal calculation unit 405 generates a discharge capacity control signal based on the calculated control current I, and outputs the discharge capacity control signal to the solenoid driving unit 406. Further, the control signal calculation means 405 inputs the calculated control current I to the suction pressure calculation means 407.
The solenoid driving means 406 supplies current to the solenoid 316 with the control current I calculated by the control signal calculating means 405 based on the discharge capacity control signal, and drives the capacity control valve 300. That is, the control signal calculation unit 405 and the solenoid drive unit 406 constitute a current adjustment unit that adjusts the control current I supplied to the solenoid 316.

FIG. 6 shows the configuration of the solenoid driving means 406.
The solenoid driving means 406 includes a switching element 420, and the switching element 420 is inserted in series with the capacity control valve 316 in a power supply line extending between the power supply 450 and the ground. The switching element 420 can be intermittently connected to the power supply line, and current is supplied to the solenoid 316 by PWM (pulse width modulation) at a predetermined drive frequency (for example, 400 to 500 Hz) by the operation of the switching element.

A diode 421 is connected in parallel with the solenoid 316 to form a flywheel circuit.
A predetermined drive signal is input to the switching element 420 from the control signal generating means 422, and the duty ratio in PWM is changed corresponding to this signal.
Further, a current sensor 423 is inserted in the power supply line, and the current sensor 423 detects a current flowing through the solenoid 316. The current sensor 423 is not limited to an ammeter as long as it can detect a physical quantity corresponding to a current, and may be a voltmeter.

  The current sensor 423 inputs the detected current to the control current comparison / determination unit 424, and the control current comparison / determination unit 424 includes the control current I calculated by the control signal calculation unit 405, the current detected by the current sensor 423, and Compare Based on the comparison result, the control current comparison / determination unit 424 changes the drive signal generated by the control signal generation unit 422 so that the detected current approaches the calculated control current I.

  That is, the solenoid drive unit 406 adjusts the current supplied to the solenoid 316 by changing the duty ratio by PWM (pulse width modulation) at a predetermined drive frequency (for example, 400 to 500 Hz). The solenoid drive unit 406 detects the current flowing through the solenoid 316 and performs feedback control so that the current approaches the control current I calculated by the control signal calculation unit 405.

When the solenoid driving unit 406 adjusts the current with the duty ratio, the control signal calculating unit 405 may calculate the duty ratio as a parameter related to the control current I. In this case, the control signal calculating unit 405 The generated discharge capacity control signal is a signal for causing the solenoid driving unit 406 to supply a current with a predetermined duty ratio.
That is, the discharge capacity control signal may be a signal corresponding to the control current I or a signal corresponding to the duty ratio.

  The suction pressure calculation means 407 calculates based on the discharge pressure Pd detected by the discharge pressure detection means and the control current I calculated by the control signal calculation means 405. An equation for calculating the suction pressure Ps is shown in Equation (3).

The suction pressure calculation means 407 compares and determines the calculated suction pressure Ps and a preset lower limit pressure P1, and outputs the determination result to the control signal calculation means 405 .
Hereinafter, the operation (usage method) of the capacity control system A will be described.
FIG. 7 is a flowchart showing a main routine executed by the control device 400. The main routine is started when, for example, the engine key of the vehicle is turned on, and is stopped when the vehicle is turned off.

In this main routine, when it is started, first, initial conditions are set (S10). Specifically, the control current I supplied to the solenoid 316 of the capacity control valve 300 is set to I _{0 at} which the discharge capacity of the compressor 100 is the minimum capacity. I ₀ may be zero.
Next, it is determined whether or not the air conditioner switch (A / C) of the vehicle air conditioning system is on (S11). That is, it is determined whether or not the occupant is requesting cooling or dehumidification of the passenger compartment. When the air conditioner switch is on (in the case of Yes), the discharge pressure calculation determination unit 404 reads the detected pressure Ph detected by the pressure sensor 403 and calculates the discharge pressure Pd (S12). Then, it is determined whether or not the discharge pressure Pd is equal to or lower than a preset upper limit pressure P2 (S13).

If the determination result in S13 is Yes, the suction pressure Ps is calculated from the discharge pressure Pd and the control current I (S15). The initial value of the control current I is I _0.
After S15, it is determined whether or not the calculated suction pressure Ps is equal to or higher than a preset lower limit pressure P1 (S16). If the result of determination in S16 is that the suction pressure Ps is greater than or equal to the lower limit pressure P1, the air conditioning control routine S17 is executed. On the other hand, if the result of determination in S16 is that the suction pressure Ps is lower than the lower limit pressure P1, the lower limit pressure control routine S18 is executed.

If the determination result in S13 is No, an upper limit pressure control routine S20 is executed.
When the air conditioner switch is turned off and the determination result in S11 is No, the control current I is reset (S21).
As described above, the capacity control system A can selectively execute any one of the air conditioning control routine S17, the lower limit pressure control routine S18, and the upper limit pressure control routine S20 depending on the situation.

FIG. 8 is a flowchart showing details of the air conditioning control routine S17 in FIG.
In the air conditioning control routine S17, first, the evaporator target outlet air temperature Tes that is the target of the discharge capacity control of the compressor 100 is set and read (S200). Next, the evaporator outlet air temperature Te detected by the temperature sensor 402 is read (S201), and a deviation ΔT between the evaporator target outlet air temperature Tes and the actual evaporator outlet air temperature Te is calculated (S202). ). Based on the calculated deviation ΔT, for example, the control current I is calculated by a predetermined calculation formula for PI control (S203).

During S203 arithmetic expression but contains the control current I on the left side, the initial value of the control current I is I _0.
Each time the air-conditioning control routine S17 is executed once, the deviation ΔT is calculated in S202, and the subscript n of the deviation ΔT in the arithmetic expression of S203 indicates that the deviation ΔT is calculated in this S202. Show. Similarly, the subscript n-1 indicates that the deviation ΔT has been calculated in the previous S202.

Thereafter, the calculated control current I is compared with the preset lower limit I1 (S204). If the determination result in S204 is No, the lower limit I1 is read as the control current I (S205), and the control current I is output (S206).
On the other hand, if the determination result in S204 is Yes, the upper limit value I2 larger than the preset lower limit value I1 is compared with the control current I (S207). If the determination result in S207 is No, the upper limit value is determined. I2 is read as the control current I (S208) and output (S206).

Therefore, if I1 ≦ I ≦ I2 as a result of the determination in S204 and S207, the control current I calculated in S203 is output as it is.
According to the air conditioning control routine S17 described above, the difference ΔT between the evaporator target outlet air temperature Tes set by the evaporator target outlet air temperature setting unit 401 and the evaporator outlet air temperature Te detected by the temperature sensor 402 is set. Based on this, the control current I supplied to the solenoid 316 is adjusted. That is, according to the air conditioning control routine S17, the discharge capacity is controlled so that the evaporator outlet air temperature Te approaches the evaporator target outlet air temperature Tes, and the comfort of the passenger compartment is ensured.

FIG. 9 is a flowchart showing details of the lower limit pressure control routine S18 in FIG.
In the lower limit pressure control routine S18, first, the control current I currently supplied to the solenoid 316 is read (S250). Then, a predetermined value ΔI1 is subtracted from the read control current I (S251).
Thereafter, it is determined whether or not the subtracted control current I is equal to or greater than a preset first lower limit value Is1 (S252). If the determination result in S252 is Yes, the subtracted control current I is output (S253). On the other hand, if the determination result in S252 is No, 0 is read as the control current I (S254), and then the control current I is output (S253). That is, the control current I supplied to the solenoid 316 becomes zero.

According to the lower limit pressure control routine S18 described above, the discharge capacity is controlled so that the suction pressure Ps does not become lower than the lower limit pressure P1. Further, when the lower limit pressure control routine S18 is repeated and the control current I becomes smaller than the first lower limit value Is1, it is determined that the refrigerant is completely insufficient, and the discharge capacity of the compressor 100 is minimized.
Although not shown in FIG. 9, when the determination result in S252 is No and the control current I is set to 0 in S254, the subsequent control current I is maintained at 0. That is, even when the air conditioning system is restarted, the discharge capacity of the compressor 100 is maintained at a minimum.

FIG. 10 is a flowchart showing details of the upper limit pressure control routine S20 in FIG.
In the upper limit pressure control routine S20, first, the control current I currently supplied to the solenoid 316 is read (S280). Then, a predetermined value ΔI2 is subtracted from the read control current I (S281).
Thereafter, it is determined whether or not the subtracted control current I is equal to or greater than a preset second lower limit value Is2 (S282). If the determination result in S282 is No, 0 is read as the control current I (S283), and then the control current I is output (S284). That is, when the subtracted control current I is smaller than the second lower limit value Is2, the control current I supplied to the solenoid 316 becomes zero.

If the determination result in S282 is Yes, the subtracted control current I is output (S284).
According to the upper limit pressure control routine S20 described above, the discharge capacity is controlled so that the discharge pressure Pd does not become higher than the upper limit pressure P2. That is, when the discharge pressure Pd becomes higher than the upper limit pressure P2, the control current I is decreased so that the discharge capacity is decreased.

Even if the upper limit pressure control routine S20 is repeated, if the determination result in S13 of the main routine is not Yes and the discharge pressure Pd is higher than the upper limit pressure P2, the control current I is the second as a result of subtraction in S281. It becomes smaller than the lower limit value Is2. In such a case, it is determined that some abnormality has occurred in the refrigeration cycle 10, and the discharge capacity of the compressor 100 is minimized.
Although not shown in FIG. 10, when the determination result in S282 is No and the control current I is set to 0 in S283, the subsequent control current I is maintained at 0. That is, even when the air conditioning system is restarted, the discharge capacity of the compressor 100 is maintained at a minimum.

  In the capacity control system A described above, the suction pressure Ps is calculated with a simple configuration. The discharge capacity control is optimized by using the calculated suction pressure Ps. That is, in the normal time, the comfort of the passenger compartment is ensured by the air conditioning control routine S17, and depending on the level of the suction pressure Ps or the discharge pressure Pd, the lower limit pressure control routine S18 or the upper limit pressure control routine S20 is executed to perform compression. The reliability of the machine 100 and the air conditioning system is ensured.

  In the capacity control system A, the discharge pressure detection means detects the discharge pressure Pd based on the detected pressure Ph detected by the pressure sensor 403, thereby increasing the degree of freedom of the configuration of the capacity control system A. On the other hand, the discharge pressure Pd can be detected with high accuracy by correcting the detection pressure Ph and detecting the discharge pressure Pd. As a result, the suction pressure Ps is calculated with high accuracy.

According to the capacity control system A, the suction pressure Ps is prevented from being abnormally reduced, and the reliability of the compressor 100 against a refrigerant shortage or the like is ensured. This is due to the following reason.
In the conventional differential pressure control in which the operating pressure difference ΔP is controlled, when the suction pressure Ps is abnormally decreased due to a lack of refrigerant, the discharge pressure Pd is also decreased at the same time, and the operating pressure difference ΔP is reduced. The discharge capacity was increased so that the operating pressure difference ΔP was increased.

  On the other hand, in the capacity control system A, after the suction pressure Ps becomes lower than the lower limit pressure P1, the operating pressure difference ΔP is not increased and the control current I or a parameter corresponding to the control current I is used. The duty ratio is changed so that the discharge capacity decreases. As a result, according to the capacity control system A, it is possible to prevent the compressor 100 from being operated at the maximum discharge capacity or a capacity close thereto when the refrigerant is insufficient, and the reliability of the compressor 100 is ensured.

  In the capacity control system A, when the suction pressure Ps is continuously lower than the lower limit pressure P1, the control current I tends to be smaller than the first lower limit value Is1, or the duty ratio is a value corresponding to the first lower limit value Is1. When it is going to become, the discharge capacity of the compressor 100 becomes the minimum. That is, when the suction pressure Ps is continuously lower than the lower limit pressure P1 due to refrigerant shortage, the discharge capacity of the compressor 100 is minimized. As a result, according to the capacity control system A, the reliability of the compressor 100 against the refrigerant shortage is further ensured.

In the capacity control system A, the upper limit pressure control routine S20 prevents the discharge pressure Pd from increasing abnormally, and the reliability of the compressor 100 and the refrigeration cycle 10 is ensured.
In the capacity control system A, when the discharge pressure Pd continuously exceeds the upper limit pressure P2, the control current I tends to become smaller than the second lower limit value Is2, or the duty ratio corresponds to the second lower limit value Is2. When it is going to be smaller than the value, the discharge capacity of the compressor 100 is minimized. That is, when some abnormality occurs in the refrigeration cycle 10 and the discharge pressure Pd continuously exceeds the upper limit pressure P2, the discharge capacity of the compressor 100 is minimized. As a result, according to the capacity control system A, the reliability of the compressor 100 and the refrigeration cycle 10 is further ensured.

In the capacity control system A, the compressor 100 is a reciprocating type, and the stroke of the piston 130 defined by the minimum inclination angle of the swash plate 107 can be set very small, so the minimum discharge capacity is very small. For this reason, when the refrigerant is insufficient, the capacity control system minimizes the discharge capacity, so that the compressor 100 is effectively protected.
The present invention is not limited to the above-described embodiment, and various modifications can be made.

  For example, in the capacity control system A, the detected discharge pressure Pd is compared with the upper limit pressure P2 in S13 of the main routine, but the detected discharge pressure Pd varies as shown in FIG. Therefore, an appropriate index (second index pressure) may be set in consideration of the variation, and the second index pressure may be compared with the upper limit pressure P2. By comparing the appropriate second index pressure with the upper limit pressure P2, the discharge pressure Pd is reliably prevented from rising abnormally, and the reliability of the compressor 100 and the refrigeration cycle 10 is ensured.

Specifically, by setting the upper limit value or the lower limit value of the variation range of the detected discharge pressure Pd as the second index pressure, the discharge pressure Pd is reliably prevented from rising abnormally.
In particular, when the heat load is high, the mass flow rate of the refrigerant flowing in the circulation path 12 increases, and the pressure difference between the discharge chamber 142 and the pressure sensor 403 increases. For this reason, when the thermal load is high and the detection pressure Ph is high, if the detection pressure Ph is corrected and the discharge pressure Pd is detected, the variation range of the discharge pressure Pd increases as shown in FIG.

  As described above, the variation range increases or decreases depending on the level of the detected pressure Ph. Therefore, when the upper limit or lower limit of the variation range is set as the second index pressure, the difference between the detected discharge pressure Pd and the upper limit or lower limit of the variation range is not set constant, but the detected pressure Ph is high or low. It may be changed based on external information related to This reliably prevents the discharge pressure Pd from rising abnormally even when the heat load is high.

  Specifically, the second index pressure is set to the vehicle internal or external heat load such as the outside air temperature, the vehicle operating state such as the engine 114 rotational speed, or the compressor operating state such as the compressor 100 rotational speed. Can be changed based on. In this case, the external information detection means is a thermal load detection means for detecting the internal and external heat load of the vehicle such as an outside air temperature sensor, a means for detecting the driving state of the vehicle such as a rotation speed sensor, or the rotation speed of the compressor 100. Means for detecting

  In the capacity control system A, although the calculated suction pressure Ps and the lower limit pressure P1 are compared in S16 of the main routine, an appropriate index (first index pressure) is set based on the error of the calculated suction pressure Ps. Then, the first index pressure and the lower limit pressure P1 may be compared. By setting an appropriate first index pressure, it is possible to reliably prevent the suction pressure Ps from being abnormally reduced, and to ensure the reliability of the compressor 100 against a refrigerant shortage or the like.

Specifically, by setting the upper limit value or the lower limit value of the calculated error range of the suction pressure Ps as the first index pressure, the suction pressure Ps can be reliably prevented from decreasing abnormally. As in the case of the second index pressure, the difference between the first index pressure and the calculated suction pressure Ps may also change based on external information.
Here, the error of the suction pressure Ps is not only the variation in the detected discharge pressure Pd as shown in FIG. 5, but also the operating pressure difference ΔP as shown in FIG. Occurs due to manufacturing variations. Therefore, the first index pressure may be changed based on the control current I and the duty ratio.

In the capacity control system A, the lower limit pressure P1 or the upper limit pressure P2 may be changed based on the heat load inside and outside the vehicle.
If the lower limit pressure P1 is set high when the outside air temperature is high, it is possible to avoid the compressor 100 being continuously operated at the maximum capacity. Thereby, the reliability of the compressor 100 is further ensured.

In the capacity control system A, the lower limit pressure P1 or the upper limit pressure P2 may be changed based on the operation state of the vehicle or the compressor 100.
Specifically, as shown in FIG. 11, the lower limit pressure P1 or the upper limit pressure P2 may be changed according to the rotational speed of the compressor 100 or the engine 114.
If the lower limit pressure P1 in the region where the rotational speed is high is set higher than the region where the rotational speed is low, the discharge capacity is reduced in the region where the rotational speed is high, and an excessive load is prevented from being applied to the compressor 100. . As a result, the compressor 100 is prevented from being damaged and its life is extended.

If the upper limit pressure P2 in the region where the rotational speed is high is set lower than the region where the rotational speed is low, the discharge capacity is reduced in the region where the rotational speed is high, and an excessive load is prevented from being applied to the compressor 100. . As a result, the compressor 100 is prevented from being damaged and its life is extended.
In the capacity control system A, when the calculated suction pressure Ps becomes lower than the lower limit pressure P1 or the detected discharge pressure Pd becomes higher than the upper limit pressure P2, the control current I is decreased stepwise to increase the discharge capacity. The specific method for reducing the discharge capacity is not limited to the above-described embodiment.

  In the capacity control system A, after the suction pressure Ps becomes smaller than the lower limit pressure P1, the control current I or the duty ratio is changed so that the discharge capacity decreases, but the suction pressure Ps is smaller than the lower limit pressure P1. The control current I at the time or the duty ratio may be maintained. That is, after the suction pressure Ps becomes lower than the lower limit pressure P1, it is only necessary to prevent the discharge capacity from increasing.

In the capacity control system A, when the determination result of S252 of the lower limit pressure control routine S18 or S282 of the upper limit pressure control routine S20 is No, the compressor 100 maintains the minimum discharge capacity even when the air conditioning system is started. However, restart may be allowed.
External information detected by the above-described thermal load detecting means includes the outside air temperature, the outside air humidity, the amount of solar radiation, the blowing amount of the fan for the evaporator 18, the inside / outside air switching door position, the outlet position, the air mix door position, The vehicle interior temperature setting, the vehicle interior temperature, the vehicle interior humidity, the evaporator inlet air temperature, the evaporator inlet air humidity, the surface temperature of each part of the vehicle interior, and the like can be raised.

The external information detected by the means for detecting the operating state of the engine 114 or the compressor 100 includes the vehicle speed, the accelerator opening, the throttle opening, the gear shift position, the brake depression amount, as well as the engine and compressor speeds. The radiator cooling water temperature, the engine oil temperature, the temperature of each part of the compressor 100, the vibration of the compressor 100, and the like can be raised.
In the solenoid driving means 406 of the capacity control system A, a diode is arranged in parallel with the solenoid 316 and the current sensor 423, and the current sensor 423 is arranged in the flywheel circuit. However, the current sensor 423 is arranged outside the flywheel circuit. You may arrange in. In this case, although the current measurement accuracy by the current sensor 423 is reduced, the reduction in measurement accuracy can be compensated by correcting based on other external information.

  In the control system A, the suction pressure calculation means 407 calculates the suction pressure based on the control current I or the operating pressure difference ΔP (I) calculated by the control signal calculation means 405. It is preferable to calculate the suction pressure Ps based on the actual control current I detected by the current sensor 423 of the driving unit 406. This is because the suction pressure Ps is calculated with high accuracy by calculating the suction pressure Ps based on the current detected by the current sensor 423 and the discharge pressure Pd.

When the suction pressure calculation means 407 calculates the suction pressure Ps based on the control current I or the operating pressure difference ΔP (I) calculated by the control signal calculation means 405, the calculation is performed for the suction pressure Ps. There is no need to provide the current sensor 423.
Further, since the control current I has a correlation with the duty ratio and changes when the duty ratio is changed, the control signal calculation unit 405 inputs the duty ratio as a discharge capacity control signal to the suction pressure calculation unit 407. Also good. In this case, the suction pressure calculating means 407 calculates the control current I based on the duty ratio while referring to external information, and calculates the suction pressure Ps based on the calculated control current I or the operating pressure difference ΔP (I). can do.

  In the capacity control system A, the pressure sensor 403 is disposed at the inlet of the radiator 14, but the pressure sensor 403 may detect the refrigerant pressure at any part of the high-pressure region of the refrigeration cycle 10. The high pressure region of the refrigeration cycle 10 is a region obtained by adding a region from the radiator 14 to the inlet of the expander 16 to the discharge pressure region. In this case, the discharge pressure calculation determination unit 404 may calculate the discharge pressure Pd by correcting the refrigerant pressure (high pressure) in the high pressure region detected by the pressure sensor 403.

In the capacity control system A, the pressure sensor 403 is used to detect the refrigerant pressure. However, the physical quantity related to the refrigerant pressure is detected by the external information detecting means, and the discharge pressure Pd is determined based on the external information. You may calculate.
In the capacity control system A, the discharge pressure Pd and the suction pressure Ps act against the valve body 304 of the capacity control valve 300, but the crank pressure Pc may further act.

  The compressor 100 to which the capacity control system A is applied is a clutchless compressor, but the capacity control system A can also be applied to a compressor equipped with an electromagnetic clutch. Although the compressor 100 is a swash plate type reciprocating compressor, it may be a rocking plate type reciprocating compressor. The oscillating plate compressor has an element for oscillating the oscillating plate. The swash plate 107 and these elements are collectively referred to as a swash plate element. The compressor 100 may be driven by an electric motor.

Furthermore, the capacity control system A can be applied to a scroll type or vane type variable capacity compressor. That is, the control pressure for changing the discharge capacity is changed by the valve opening degree of the capacity control valve using the capacity control valve in which the discharge pressure Pd, the suction pressure Ps and the solenoid electromagnetic force F (I) act on the valve body. If it can be made, it can be applied to any variable capacity compressor.
The control pressure is the crank chamber pressure (crank pressure Pc) in the case of a reciprocating compressor.

In the compressor 100 applied to the capacity control system A, the fixed orifice 103c is disposed as the throttle element in the extraction passage 162 in order to regulate the flow rate of the extraction passage 162 and increase the crank pressure Pc. A throttle with variable flow rate may be used, and a valve may be arranged to adjust the valve opening.
In the capacity control system A, the capacity control valve 300 is disposed in the air supply passage 160 that connects the discharge chamber 142 and the crank chamber 105. However, when the compressor 100 is a swash plate type or a swing plate type, Instead of arranging the capacity control valve 300 in the passage 160, a capacity control valve may be arranged in the extraction passage 162 connecting the crank chamber 105 and the suction chamber 140. That is, the present invention is not limited to the inlet control that controls the opening degree of the air supply passage 160, and may be the outlet control that controls the opening degree of the extraction passage 162.

In the refrigeration cycle to which the capacity control system A is applied, the refrigerant is not limited to R134a or carbon dioxide, and other new refrigerants may be used. That is, the capacity control system A can also be applied to a conventional field air conditioning system.
The capacity control system A can be applied to refrigeration cycles in general, such as refrigeration cycles for indoor air conditioning systems other than vehicle air conditioning systems.

In the capacity control system A, the lower limit pressure P1 and the upper limit pressure P2 are provided to limit the increase in the discharge capacity so that the compressor 100 does not enter a dangerous operation region, but only the lower limit pressure P1 is set. May be. That is, only the air conditioning control routine S17 and the lower limit pressure control routine S18 may be executed .

It is a figure which shows schematic structure of the refrigerating cycle of the vehicle air conditioning system to which the capacity | capacitance control system of one Embodiment is applied with the longitudinal cross-section of a variable capacity compressor. It is a figure for demonstrating the connection state of the capacity | capacitance control valve in the compressor of FIG. 2 is a graph showing a relationship between a control current I and an operating pressure difference ΔP in the capacity control valve of FIG. 1. It is a block diagram showing a schematic structure of a capacity control system of one embodiment. 5 is a graph showing a relationship between a detected pressure detected by a pressure sensor and a discharge pressure calculated by a discharge pressure calculating means in the capacity control system of FIG. FIG. 5 is a block diagram for explaining a schematic configuration of solenoid driving means in the capacity control system of FIG. 4. 6 is a control flowchart showing a main routine executed by the capacity control system of FIG. 4. It is a control flowchart of the air-conditioning control routine contained in the main routine of FIG. FIG. 8 is a control flowchart of a lower limit pressure control routine included in the main routine of FIG. 7. It is a control flowchart of an upper limit pressure control routine included in the main routine of FIG. It is a graph for demonstrating an example of the setting method of a minimum pressure and an upper limit pressure.

Explanation of symbols

316 Solenoid 401 Evaporator target outlet air temperature setting device 402 Temperature sensor 403 Pressure sensor (discharge pressure detection means)
404 Discharge pressure calculation determination means (discharge pressure detection means)
405 Control signal calculation means (current adjustment means)
406 Solenoid driving means (current adjusting means)
407 Suction pressure calculation means

Claims (13)

In a capacity control system of a variable capacity compressor that is inserted together with a radiator, an expander and an evaporator in a circulation path through which a refrigerant circulates to constitute a refrigeration cycle of an air conditioning system, and whose capacity changes based on a change in control pressure,
The discharge pressure when the pressure of the refrigerant in any part of the discharge pressure region of the refrigeration cycle is the discharge pressure and the pressure of the refrigerant in any part of the suction pressure region of the refrigeration cycle is the suction pressure And a valve body that can open and close the valve hole in response to the suction pressure and the electromagnetic force of the solenoid in a direction opposite to the discharge pressure, and is received by a pressure difference between the discharge pressure and the suction pressure. The valve body on which a force and an electromagnetic force corresponding to a control current supplied to the solenoid act is moved to a balance position, and the control pressure is changed by opening and closing the valve hole to change the control pressure. A capacity control valve with adjustable capacity;
An evaporator target outlet air temperature setting means for setting a target outlet air temperature of the evaporator;
Evaporator outlet air temperature detection means for detecting the outlet air temperature of the evaporator;
Current adjusting means for adjusting the control current supplied to the solenoid or a duty ratio related to the control current based on a difference between the target outlet air temperature and the outlet air temperature;
A discharge pressure detecting means for detecting the discharge pressure ;
Suction pressure calculation means for calculating the suction pressure from the relational expression of the force acting on the valve body of the capacity control valve based on the control current and the discharge pressure detected by the discharge pressure detection means ,
The current adjusting means adjusts the capacity of the variable capacity compressor by supplying the control current to the solenoid based on the difference between the target outlet air temperature and the outlet air temperature and moving the valve body to a balance position. When the suction pressure calculated by the suction pressure calculating means is lower than the lower limit pressure, the control current or the control current when the suction pressure is lower than the lower limit pressure is set. A capacity control system for a variable capacity compressor, wherein the related duty ratio is maintained or the discharge capacity is changed to be reduced. The discharge pressure detecting means includes high pressure pressure detecting means for detecting the pressure of the refrigerant at any part of the high pressure region of the refrigeration cycle, and corrects the refrigerant pressure detected by the high pressure detection means. The capacity control system for a variable capacity compressor according to claim 1, wherein the discharge pressure is detected as a result. The suction pressure calculating means sets a first index pressure based on the calculated suction pressure;
The current adjusting means may be configured such that the control current or the duty ratio when the first index pressure becomes lower than the lower limit pressure after the first index pressure becomes lower than the lower limit pressure instead of the suction pressure. The capacity control system for a variable capacity compressor according to claim 1 or 2, wherein the capacity is changed or the discharge capacity is changed. The suction pressure calculating means sets one of an upper limit value and a lower limit value of the calculated error range of the suction pressure as the first index pressure, and calculates the suction pressure and the first index pressure. 4. The capacity control system for a variable capacity compressor according to claim 3, wherein the difference changes based on the control current or the duty ratio . The air conditioning system is applied to a vehicle,
A heat load detecting means for detecting internal and external thermal load of vehicles, and a driving state detection means for detecting at least one operating state of the vehicle and the variable displacement compressor,
5. The lower limit pressure is changed based on at least one of a thermal load detected by the thermal load detector and an operating state detected by the operating state detector. A capacity control system for the variable capacity compressor according to claim 1. The current adjusting means changes the control current or the duty ratio so that the discharge capacity decreases when the suction pressure calculated by the suction pressure calculating means is lower than the lower limit pressure, and the change As a result, when the control current becomes smaller than the first lower limit value or when the duty ratio becomes smaller than a value corresponding to the first lower limit value, the control current or the 6. The capacity control system for a variable capacity compressor according to claim 1, wherein the duty ratio is changed. The current adjusting means maintains the control current or the duty ratio when the discharge pressure exceeds the upper limit pressure after the discharge pressure detected by the discharge pressure detection means exceeds the upper limit pressure, or The capacity control system for a variable capacity compressor according to any one of claims 1 to 6, wherein the capacity is changed so as to decrease the discharge capacity. The discharge pressure detecting means sets a second index pressure based on the detected discharge pressure;
The current adjusting means maintains the control current or the duty ratio when the second index pressure exceeds the upper limit pressure or the discharge capacity decreases after the second index pressure exceeds the upper limit pressure. The capacity control system for a variable capacity compressor according to claim 7, wherein the capacity control system is changed as follows. The air conditioning system is applied to a vehicle,
A heat load detecting means for detecting internal and external thermal load of vehicles, and a driving state detection means for detecting at least one operating state of the vehicle and the variable displacement compressor,
The discharge pressure detecting means sets one of an upper limit value and a lower limit value of the detected variation range of the discharge pressure as the second index pressure, and determines the detected discharge pressure and the second index pressure. 9. The variable capacity compressor according to claim 8, wherein the difference changes based on at least one of a thermal load detected by the thermal load detection unit and an operation state detected by the operation state detection unit. Capacity control system. The air conditioning system is applied to a vehicle,
Comprising a driving state detection means for detecting at least one operating condition of the previous SL vehicle and a variable displacement compressor,
10. The capacity control system for a variable capacity compressor according to claim 7, wherein the upper limit pressure is changed based on an operation state detected by the operation state detection means. When the discharge pressure detected by the discharge pressure detection unit exceeds the upper limit pressure, the current adjustment unit changes the control current or the duty ratio so that the discharge capacity decreases, and As a result, when the control current becomes smaller than the second lower limit value or when the duty ratio becomes smaller than a value corresponding to the second lower limit value, the control current or the duty is set so that the discharge capacity is minimized. The capacity control system for a variable capacity compressor according to any one of claims 7 to 10, wherein the ratio is changed. The current adjusting means includes
Target setting means for setting a target value of the control current or the duty ratio ;
Current detection means for detecting a current flowing through the solenoid or a duty ratio related to the current,
The current adjusting means adjusts a control current supplied to the solenoid so that the current or the duty ratio detected by the current detecting means approaches the target value;
The suction pressure calculation means calculates the suction pressure based on a current detected by the current detection means as the control current and a discharge pressure detected by the discharge pressure detection means. Item 12. A capacity control system for a variable capacity compressor according to any one of Items 1 to 11. The variable capacity compressor is:
A housing in which a discharge chamber, a crank chamber, a suction chamber and a cylinder bore are defined;
A piston disposed in the cylinder bore;
A drive shaft rotatably supported in the housing;
A conversion mechanism including a variable swash plate element that converts rotation of the drive shaft into reciprocating motion of the piston;
An air supply passage communicating the discharge chamber and the crank chamber;
A bleed passage for communicating the crank chamber and the suction chamber;
13. The capacity control system for a variable capacity compressor according to claim 1, wherein the capacity control valve is inserted into one of the supply passage and the extraction passage.