JP2009052806A - Refrigerating cycle device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To lower a temperature of a cooled space in a short time in a refrigerating cycle device comprising a variable capacity type compressor and a pressure control valve. <P>SOLUTION: A flow rate sensor detecting a flow rate Gr of discharged refrigerant is disposed in this refrigerating cycle device comprising the variable capacity type compressor and the pressure control valve, and control electric current Ic output to an electromagnetic capacity control valve of the variable capacity type compressor is switched from a first control electric current Ic1 calculated on the basis of a control target value to make a pressure of the discharged refrigerant not over a reference maximum high pressure, to a second control electric current Ic2 calculated on the basis of a control target value to exert the desired cooling capacity, when the flow rate Gr of the discharged refrigerant reaches the reference discharged refrigerant flow rate Gr1 corresponding to the leakage amount Grmin leaking from a bleed port of the pressure control valve or more. As the desired cooling capacity can be exerted simultaneously with a timing when the pressure control valve can control the high pressure-side refrigerant pressure, a temperature in a vehicle compartment can be lowered in a short time. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a refrigeration cycle apparatus including a variable displacement compressor and a pressure control valve.

  Conventionally, a variable displacement compressor configured to be able to adjust the refrigerant discharge capacity by changing the discharge capacity, and the high-pressure side refrigerant pressure to be close to the target high pressure determined according to the high-pressure side refrigerant temperature downstream of the radiator There is known a vapor compression refrigeration cycle apparatus including a pressure control valve whose valve opening is adjusted as described above.

  For example, in the refrigeration cycle apparatus of Patent Document 1, the refrigerant discharge capacity of the variable capacity compressor is adjusted so that the low-pressure side refrigerant pressure approaches the target low pressure, that is, the refrigerant evaporation temperature in the evaporator approaches the target refrigerant evaporation temperature. The cooling capacity required by Further, the coefficient of performance (COP) of the cycle is maximized by adjusting the valve opening of the pressure control valve (expansion device) to bring the high-pressure side refrigerant pressure closer to the target high pressure.

Patent Document 2 discloses a pressure control valve that is applied to this type of refrigeration cycle apparatus, provided with a bleed port that slightly leaks refrigerant from the high-pressure side to the low-pressure side even when the valve is closed. Has been. Thereby, for example, even when the target high pressure is increased and the pressure control valve is fully closed, the high pressure side refrigerant pressure is extremely increased by slightly leaking the refrigerant from the high pressure side to the low pressure side. Trying to prevent.
JP 2002-323265 A JP 2002-122367 A

  By the way, in the pressure control valve provided with the bleed port as in Patent Document 2, as the passage area of the bleed port increases, the amount of leakage that leaks from the bleed port when the valve is closed also increases. Therefore, if the passage area of the bleed port is increased more than necessary, for example, when the refrigerant discharge capacity of the compressor is reduced as in low load operation, the high pressure side refrigerant pressure is increased to the target high pressure at which COP is maximized. It becomes impossible to do.

  Therefore, it is necessary to set the passage area of the bleed port to an appropriate value or less. According to the study by the present inventors, in order to increase the high-pressure side refrigerant pressure to the target high pressure at which COP is maximized during low-load operation, specifically, the passage diameter of the bleed port is equivalent to φ0.7 mm or less. It turns out to be desirable.

  However, when the pressure control valve of Patent Document 2 is applied to the refrigeration cycle apparatus of Patent Document 1 and this refrigeration cycle apparatus is used as a vehicle air conditioner, the pressure control valve is generally disposed in the engine room. Therefore, the ambient temperature of the pressure control valve may be higher than the high-pressure side refrigerant temperature on the downstream side of the radiator.

  For example, under an operating condition (hereinafter referred to as “cool down”) in which the vehicle air conditioner is activated simultaneously with the start of the vehicle to rapidly reduce the cabin temperature, the ambient temperature of the pressure control valve is about 60 ° C. to 80 ° C. It may be heated to a high temperature. In such a case, the ambient temperature is easily erroneously detected as the high-pressure side refrigerant temperature, the target high pressure is set unnecessarily high, and the pressure control valve is closed.

  Further, at the time of cool-down, since the target refrigerant evaporation temperature needs to be lowered in order to rapidly lower the passenger compartment temperature, the refrigerant discharge capacity of the variable capacity compressor is also increased. Therefore, if the passage area of the bleed port is set to an appropriate value or less in order to maximize the COP as described above, the high pressure side refrigerant pressure cannot be prevented from being extremely increased, and the high pressure side refrigerant can be prevented. The pressure may exceed the pressure resistance of the cycle component equipment.

  Therefore, in this type of refrigeration cycle apparatus, not only the refrigerant discharge capacity of the variable capacity compressor is adjusted so that the refrigerant evaporation temperature of the evaporator approaches the target refrigerant evaporation temperature, but also the actual capacity of the variable capacity compressor. The discharged refrigerant pressure is detected, and the discharged refrigerant pressure is adjusted by a feedback control method or the like so that the detected discharged refrigerant pressure does not exceed the reference maximum high pressure Pdmax set lower than the withstand pressure of the cycle constituent device.

  Specifically, as shown in FIG. 6, the first control current Ic1 determined so that the discharged refrigerant pressure does not exceed the reference maximum high pressure Pdmax and the refrigerant evaporation temperature of the evaporator are determined so as to approach the target refrigerant evaporation temperature. Of the second control current Ic2, the minimum control is performed in which the smaller discharge capacity is the control current Ic. The control current Ic obtained by this minimum control is output to an electromagnetic capacity control valve that changes the discharge capacity of the variable capacity compressor.

  6 shows the first control current Ic1 (thin solid line + thick solid line), the second control current Ic2 (thin broken line + thick broken line), and the control current Ic actually output to the electromagnetic capacity control valve at the time of cool-down. It is a graph which shows a time-dependent change of (thick solid line + thick broken line). In this variable displacement compressor, the discharge capacity increases as the control current Ic increases.

  The middle part of FIG. 6 is a graph showing temporal changes in the discharged refrigerant pressure Pd and the inside air temperature Tr in the passenger compartment during cool-down, and the lower part of FIG. 6 shows the flow rate of refrigerant circulating in the cycle during cool-down. Fig. 5 is a graph showing a change with time of the discharge refrigerant flow rate Gr of the variable capacity compressor. In this pressure control valve, the passage diameter of the bleed port is φ0.4 mm.

  As is apparent from the upper part of FIG. 6, in the initial stage of the cool-down, the first control current Ic1 becomes smaller than the second control current Ic2, and then the second control current Ic2 becomes the first control current Ic1. Smaller than. That is, the control current Ic actually output to the electromagnetic capacity control valve changes as shown by the thick solid line and the thick broken line in FIG. As the control current Ic changes, the discharge refrigerant pressure Pd and the internal temperature Tr change as shown in the middle part of FIG.

  However, when the present inventors investigated the change with time of the discharged refrigerant flow rate Gr at the time of cool-down, as shown in the lower part of FIG. 6, in the above-mentioned minimum control, the second control current Ic2 is more than the first control current Ic1. It has been found that the timing T1 at which this becomes smaller is delayed from the timing T2 at which the discharged refrigerant flow rate Gr becomes greater than the leakage amount Grmin that leaks from the bleed port when the pressure control valve is closed.

  In a state where the discharge refrigerant flow rate Gr is larger than the leakage amount Grmin as after the timing T2, the pressure control valve shifts from the closed state to the open state, and the valve opening degree is adjusted to adjust the high pressure side refrigerant. The pressure can be controlled. Therefore, after the timing T2, it is not necessary to change the discharge capacity with the first control current Ic1 so that the discharge refrigerant pressure Pd does not exceed the reference maximum high pressure Pdmax.

  That is, the delay of the timing T1 with respect to the timing T2 is switched from the first control current Ic1 for preventing the discharged refrigerant pressure to exceed the reference maximum high pressure Pdmax to the second control current Ic2 for exhibiting the required cooling capacity. This is a cause of prolonging the time for reducing the temperature in the passenger compartment, which is the space to be cooled.

  In view of the above points, an object of the present invention is to reduce the temperature of a space to be cooled in a short time in a refrigeration cycle apparatus including a variable capacity compressor and a pressure control valve.

In order to achieve the above object, the present invention provides a variable displacement compressor (11) configured to be able to change a discharge capacity, and a radiator (12) that dissipates the refrigerant discharged from the variable displacement compressor (11). ) And the refrigerant flowing out from the radiator (12) under reduced pressure, and the valve is opened so that the high-pressure side refrigerant pressure approaches the target high pressure determined according to the high-pressure side refrigerant temperature downstream of the radiator (12). A refrigeration cycle apparatus comprising a pressure control valve (14) whose degree is adjusted, and an evaporator (15) for evaporating the refrigerant decompressed and expanded by the pressure control valve (14),
Further, the discharge capacity changing means (11a) for changing the discharge capacity of the variable capacity compressor (11) and the discharge capacity using any one of at least two control target values (Pdmax, TEO). A discharge capacity control means (20a) for controlling the operation of the changing means (11a), and a flow rate detection means (26) for detecting the refrigerant flow rate (Gr) circulating in the cycle,
The discharge capacity control means (20a) is a control target value used for controlling the operation of the discharge capacity changing means (11a) among a plurality of control target values (Pdmax, TEO) based on the detection value of the flow rate detection means (26). (Pdmax, TEO) is switched.

  According to this, the discharge capacity control means (20a) controls the operation of the discharge capacity change means (11a) among the plurality of control target values (Pdmax, TEO) based on the detection value of the flow rate detection means (26). Since the control target values (Pdmax, TEO) used for the above are switched, the control target values (Pdmax, TEO) can be switched when the refrigerant flow rate actually circulating in the cycle changes.

  Therefore, for example, the temperature of the cooling target space is set at an ideal timing in accordance with the change in the flow rate of the refrigerant circulating in the cycle, such as the timing at which the pressure control valve (14) shifts from the closed state to the open state. In order to decrease in a short time, it is possible to switch to an appropriate control target value. As a result, the temperature of the cooling target space can be reduced in a short time.

  Further, in the refrigeration cycle apparatus having the above-described characteristics, the discharge capacity control means (20a) is configured such that when the detection value of the flow rate detection means (26) is smaller than a predetermined value, two or more control target values (Pdmax, TEO) ), The control target value that minimizes the discharge capacity is used, and if the detection value of the flow rate detection means (26) is equal to or greater than a predetermined value, a control target other than the control target value that minimizes the discharge capacity is used. A value may be used.

  Further, the pressure control valve (14) has a bleed port for leaking refrigerant from the high pressure side to the low pressure side even when the valve is closed, and the predetermined value is a bleed port when the pressure control valve (14) is closed. It may be a leakage amount (Grmin) leaking from the air.

  According to this, as the timing at which the refrigerant flow rate actually circulating in the cycle changes, specifically, the timing at which the pressure control valve (14) shifts from the closed state to the open state is detected, and appropriate control is performed. It can be switched to the target value.

  In the refrigeration cycle apparatus having the above characteristics, one of the control target values is the reference maximum high pressure (Pdmax) of the high-pressure side refrigerant pressure, and the discharge capacity control means (20a) sets the reference maximum high pressure (Pdmax). When used, the operation of the discharge capacity changing means (11a) may be controlled so that the discharge refrigerant pressure of the variable capacity compressor (11) is equal to or lower than the reference maximum high pressure (Pdmax).

  Further, another one of the control target values is the target refrigerant evaporation temperature (TEO) of the refrigerant evaporation temperature in the evaporator (15), and the discharge capacity control means (20a) sets the target refrigerant evaporation temperature (TEO). When used, the operation of the discharge capacity changing means (11a) may be controlled so that the refrigerant evaporation temperature approaches the target refrigerant evaporation temperature (TEO).

  According to this, specifically, the high pressure side refrigerant pressure is cycled by using the reference maximum high pressure (Pdmax) as the control target value in the operating condition in which the pressure control valve is likely to be closed like the above-described cool down. It is possible to prevent the breakdown voltage of the component equipment from being exceeded.

  Furthermore, at the timing when the reference maximum high pressure (Pdmax) does not need to be set as the control target value, it is possible to switch to the target refrigerant evaporation temperature (TEO) and the control target value for exerting the required cooling capacity. As a result, the temperature of the space to be cooled can be reliably reduced in a short time.

  Further, in the refrigeration cycle apparatus having the above-described characteristics that employs the target refrigerant evaporation temperature (TEO) as the control target value, heat exchange fin temperature detection means (24) for detecting the temperature (Te) of the heat exchange fin of the evaporator (15). ) Or a blown air temperature detecting means for detecting the temperature of the air blown from the evaporator (15).

  According to this, since the temperature corresponding to the refrigerant evaporation temperature in the actual evaporator (15) can be detected, the discharge capacity changing means can be easily set so that the refrigerant evaporation temperature approaches the target refrigerant evaporation temperature (TEO). The operation of (11a) can be controlled.

  Further, as the refrigeration cycle apparatus having the above-described characteristics, the refrigerant may be carbon dioxide.

  In addition, the code | symbol in the bracket | parenthesis of each means described in this column and the claim shows the correspondence with the specific means as described in embodiment mentioned later.

  An embodiment of the present invention will be described with reference to FIGS. In this embodiment, the refrigeration cycle apparatus 10 of the present invention is applied to a vehicle air conditioner. FIG. 1 is an overall configuration diagram of a refrigeration cycle apparatus 10 according to the present embodiment. The refrigeration cycle apparatus 10 employs carbon dioxide as a refrigerant, and constitutes a supercritical refrigeration cycle in which the discharge refrigerant pressure of the compressor 11 is equal to or higher than the critical pressure of the refrigerant (supercritical state).

  The compressor 11 sucks, compresses and discharges the refrigerant in the refrigeration cycle apparatus 10, and is driven to rotate by a driving force transmitted from a vehicle travel engine (not shown) via a pulley and a belt. . Further, in the present embodiment, a known swash plate type variable displacement compressor configured such that the discharge capacity can be continuously changed by a control signal output from an air conditioning controller 20 described later is adopted as the compressor 11. .

  The discharge capacity is the geometric volume of the working space where the refrigerant is sucked and compressed, that is, the cylinder volume between the top dead center and the bottom dead center of the piston stroke.

  Specifically, the compressor 11 includes a swash plate chamber (not shown) that introduces suction refrigerant and discharge refrigerant, an electromagnetic capacity control valve 11a that adjusts the ratio of suction refrigerant and discharge refrigerant introduced into the swash plate chamber, It has a swash plate (not shown) that displaces the tilt angle in accordance with the pressure in the swash plate chamber. The piston stroke (discharge capacity) is changed according to the inclination angle of the swash plate.

  The electromagnetic capacity control valve 11a incorporates a pressure responsive mechanism that generates a force due to the suction refrigerant pressure Ps of the compressor 11 and an electromagnetic mechanism that generates an electromagnetic force opposite to the force due to the suction refrigerant pressure Ps. The valve opening (ratio between the suction refrigerant and the discharge refrigerant) is adjusted by changing the balance between the force due to the suction refrigerant pressure Ps and the electromagnetic force, thereby changing the pressure in the swash plate chamber.

  Further, the electromagnetic force of the electromagnetic mechanism is determined by the control current Ic output from the air conditioning control device 20, and when the control current Ic is increased, the pressure in the swash plate chamber decreases and the inclination angle of the swash plate increases. , Piston stroke (discharge capacity) increases. Conversely, when the control current Ic is decreased, the pressure in the swash plate chamber increases and the tilt angle of the swash plate decreases, thereby reducing the piston stroke (discharge capacity).

  That is, the suction refrigerant pressure Ps also increases / decreases in accordance with the increase / decrease of the discharge capacity, so that the target value (target low pressure) of the intake refrigerant pressure Ps is determined by the control current Ic. Specifically, the output of the control current Ic is normally changed by duty control because of the configuration of the current control circuit, but the value of the control current Ic is directly or continuously (analog) regardless of duty control. May be changed.

  Further, by adjusting the control current Ic in this way, the compressor 11 can continuously change the discharge capacity in a range of approximately 0% to 100%. Therefore, in the present embodiment, the discharge capacity changing means is configured by the electromagnetic capacity control valve 11a, and the discharge capacity is controlled by the hardware and software configurations of the air conditioning control device 20 that control the operation of the electromagnetic capacity control valve 11a. Control means 20a is configured.

  In the compressor 11 of the present embodiment, the discharge capacity can be reduced to about 0%. Therefore, as described above, the compressor 11 has a clutchless configuration in which the compressor 11 is always connected to the vehicle running engine via a pulley and a belt. can do. Of course, power may be transmitted from the vehicle running engine via the electromagnetic clutch.

  A radiator 12 is connected to the refrigerant discharge side of the compressor 11. The radiator 12 is a heat-dissipating heat exchanger that performs heat exchange between the high-temperature and high-pressure refrigerant discharged from the compressor 11 and the outside air (air outside the passenger compartment) blown by the cooling fan 12a to radiate the high-pressure refrigerant. The cooling fan 12a is an electric blower in which the rotation speed (the amount of blown air) is controlled by a control voltage output from an air conditioning control device 20 described later.

  As described above, since the refrigeration cycle apparatus 10 of the present embodiment constitutes a supercritical refrigeration cycle, the refrigerant passing through the radiator 12 dissipates heat in a supercritical state without condensing.

  A high-pressure side refrigerant flow path 13 a of the internal heat exchanger 13 is connected to the downstream side of the radiator 12. The internal heat exchanger 13 exchanges heat between the refrigerant at the outlet side of the radiator 12 that passes through the high-pressure side refrigerant flow path 13a and the refrigerant at the suction side of the compressor 11 that passes through the low-pressure side refrigerant flow path 13b, thereby The refrigerant passing through the passage 13a is cooled. Thereby, the enthalpy difference (refrigeration capacity) of the inlet side refrigerant | coolant in the evaporator 15 mentioned later and an outlet side refrigerant | coolant can be increased.

  Furthermore, various configurations can be adopted as specific configurations of the internal heat exchanger 13. Specifically, a configuration in which the refrigerant pipes that form the high-pressure side refrigerant flow path 13a and the low-pressure side refrigerant flow path 13b are brazed and joined together to exchange heat, or the inside of the outer pipe that forms the high-pressure side refrigerant flow path 13a. It is possible to employ a double-pipe heat exchanger configuration in which the low-pressure side refrigerant flow path 13b is disposed.

  A pressure control valve 14 is connected to the outlet side of the high-pressure side refrigerant flow path 13 a of the internal heat exchanger 13. The pressure control valve 14 decompresses and expands the high-pressure refrigerant flowing out from the internal heat exchanger 13, and the valve opening (throttle opening) is adjusted by a mechanical mechanism so that the high-pressure side refrigerant pressure becomes the target high pressure. It has become so.

  Specifically, the pressure control valve 14 has a temperature sensing part 14a provided between the radiator 12 outlet side and the high-pressure side refrigerant flow path 13a inlet side of the internal heat exchanger 13, and this temperature sensing part. A pressure corresponding to the temperature of the high-pressure refrigerant on the outlet side of the radiator 12 is generated inside 14 a, and the balance between the internal pressure of the temperature sensing part 14 a and the outlet-side refrigerant pressure of the high-pressure side refrigerant flow path 13 a of the internal heat exchanger 13 The valve opening degree of the pressure control valve 14 is adjusted.

  Thereby, the high-pressure side refrigerant pressure is adjusted to a target high pressure determined by the high-pressure side refrigerant temperature on the outlet side of the radiator 12. A pressure control valve 14 having such a high-pressure control function is known in Japanese Unexamined Patent Publication No. 2000-81157. In addition, the pressure control valve 14 of this embodiment is arrange | positioned in the engine room with the heat radiator 12. FIG.

  Further, the pressure control valve 14 is provided with a bleed port (not shown) for leaking the refrigerant from the high pressure side to the low pressure side even when the valve is closed. Such a bleed port can be easily formed by providing a communication hole for communicating the upstream side and the downstream side of the valve body of the pressure control valve 14. In the present embodiment, the passage diameter of the bleed port is φ0.4 mm.

  An evaporator 15 is connected to the outlet side of the pressure control valve 14. The evaporator 15 is an endothermic heat exchanger that exchanges heat between the low-pressure refrigerant decompressed by the pressure control valve 14 and the blown air blown from the blower fan 15a to evaporate the low-pressure refrigerant and exert an endothermic effect. is there. The blower fan 15 a is an electric blower in which the rotation speed (the amount of blown air) is controlled by a control voltage output from the air conditioning control device 20.

  In the present embodiment, a heat exchanger having a well-known fin-and-tube structure is employed as the evaporator 15. Furthermore, the evaporator 15 is arrange | positioned in the case 16 which forms the air passage of vehicle interior blowing air in the indoor air conditioning unit of a vehicle air conditioner.

  Further, inside the case 16 and on the downstream side of the air flow of the evaporator 15, the air that adjusts the air volume ratio of the cold air that passes through the heater core 17 and the heater core 17 that reheats the cold air cooled by the evaporator 15. A mix door 18 is arranged. The heater core 16 is a heating unit that reheats the cold air using the cooling water of the vehicle running engine as a heat source, and the air mix door 18 constitutes a temperature adjustment unit that adjusts the temperature of the conditioned air blown into the vehicle interior. Yes.

  Further, an air outlet (not shown) that blows conditioned air into the vehicle interior, which is a space to be cooled, is disposed at the most downstream portion of the air flow of the case 16. Specifically, this air outlet includes a face air outlet that blows air-conditioned air toward the upper body of an occupant in the passenger compartment, a foot air outlet that blows air-conditioned air toward the feet of the occupant, and a vehicle front window glass inner surface. A defroster outlet for blowing air conditioned air is provided.

  An accumulator 19 is connected to the outlet side of the evaporator 15. The accumulator 19 is a gas-liquid separator that separates the refrigerant flowing out of the evaporator 15 into a liquid-phase refrigerant and a gas-phase refrigerant and stores excess refrigerant in the cycle.

  The accumulator 19 is provided with a gas-phase refrigerant outlet through which the gas-phase refrigerant flows out. The gas-phase refrigerant outlet is connected to the inlet side of the low-pressure side refrigerant flow path 13b of the internal heat exchanger 13 described above. The outlet side of the refrigerant channel 13b is connected to the refrigerant suction side of the compressor 11.

  Next, an outline of the electric control unit of the present embodiment will be described. The air conditioning control device 20 includes a known microcomputer including a CPU, a ROM, a RAM, and the like and peripheral circuits thereof. The air conditioning control device 20 performs various calculations and processes based on the control program stored in the ROM, and controls the operations of the various electric actuators 11a, 12a, 15a and the like described above.

  An air conditioning sensor group 21 to 26 and an operation panel 30 disposed in the passenger compartment are connected to the input side of the air conditioning control device 20. The air conditioning sensor group 21 to 26 is provided with a detection signal and an operation panel 30. The operation signals of the various operation switches 31 to 33 are input.

  Specifically, the air conditioning sensor group includes an outside air temperature sensor 21 that detects the outside air temperature Tam, an inside air temperature sensor 22 that detects the inside air temperature Tr, a solar radiation sensor 23 that detects the amount of solar radiation Ts incident on the vehicle interior, and an evaporator. An evaporator temperature sensor 24 which is a heat exchange fin temperature detecting means for detecting the temperature Te of the 15 heat exchange fins, a high pressure sensor 25 for detecting a discharge refrigerant pressure Pd discharged from the compressor 11, and a discharge from the compressor 11. A flow rate sensor 26 that is a flow rate detecting means for detecting the discharged refrigerant flow rate Gr is provided.

  Note that the evaporator temperature sensor 24 of the present embodiment detects a temperature corresponding to the refrigerant evaporation temperature in the actual evaporator 15. Therefore, instead of the evaporator temperature sensor 24, a blown air temperature sensor, which is a blown air temperature detection means for detecting the temperature of the air blown from the evaporator 15, may be used.

  The flow sensor 26 detects the flow rate of the refrigerant circulating in the cycle. Therefore, the flow rate detection position in the flow rate sensor 26 is not limited to the refrigerant discharge side of the compressor 11 and may be arranged at any place in the cycle.

  Furthermore, the flow sensor 26 of the present embodiment has a throttle portion that allows a part of the refrigerant circulating in the cycle to pass therethrough, a differential pressure detector that detects a pressure loss (differential pressure) in the throttle portion, and a throttle portion And a temperature / pressure detector that detects the temperature and pressure of the downstream refrigerant, and the refrigerant is estimated by the refrigerant density estimated from the detected value (differential pressure) of the differential pressure detector and the detected value of the temperature / pressure detector. It is configured by a differential pressure type flow rate sensor that detects a flow rate.

  Specifically, as an operation switch of the operation panel 30, an air conditioner switch 31 that outputs an operation command signal for the vehicle air conditioner, an auto switch 32 that outputs an automatic control request signal for requesting automatic control of the air conditioning state, A temperature setting switch 33 or the like serving as temperature setting means for setting a target temperature is provided.

  Further, on the output side of the air-conditioning control device 20, an electromagnetic capacity control valve 11a of the compressor 11, an electric motor of the cooling fan 12a and the blower fan 15a, a servo motor for driving the air mix door 18 described above, and each outlet are provided. An electric actuator such as a servo motor that drives an opening / closing door that opens and closes is connected, and the operation of these devices is controlled by an output signal of the air conditioning controller 20.

  Next, the operation of the present embodiment having the above-described configuration will be described with reference to FIGS. 2 and 3 are flowcharts showing the control processing executed by the air conditioning control device 20. This control process starts when the auto switch 32 is turned on (ON) in a state where a vehicle start switch (ignition switch) (not shown) is turned on.

  First, as shown in FIG. 2, in step S1, flags, timers, and the like are initialized, and in the next step S2, a vehicle environmental state signal, that is, a detection signal detected by the sensor groups 21 to 26, and an operation panel 30 operation signals are read.

Next, in step S3, a target blowing temperature TAO of the vehicle cabin blowing air is calculated. The target blowing temperature TAO is calculated by the following formula F1 based on the air conditioning thermal load fluctuation and the set temperature Tset set by the temperature setting switch 33.
TAO = Kset × Tset−Kr × Tr−Kam × Tam−Ks × Ts + C (F1)
Note that Tr is the internal temperature detected by the internal temperature sensor 22, Tam is the external temperature detected by the external temperature sensor 21, Ts is the amount of solar radiation detected by the solar sensor 23, and Kset, Kr, Kam, and Ks are control gains. And C are constants for correction.

  Next, the control state of an air-conditioning control apparatus is determined in step S4 and S5. That is, the control signal output to the various electric actuators connected to the output side of the air conditioning controller 20 is determined.

  In this embodiment, in step S4, a control signal to be output to the electric actuator excluding the electromagnetic capacity control valve 11a of the compressor 11 is determined, and in step S5, the discharge capacity control means 20a is connected to the compressor 11. The control signal output to the electromagnetic capacity control valve 11a is determined.

  In step S4, the control signal etc. output to the electric motor of the ventilation fan 15a, the servo motor of the air mix door 18, and the servo motor of the open / close door that opens and closes each outlet are determined. Specifically, for the control signal (control voltage) output to the electric motor of the blower fan 15a, the control signal stored in the air conditioning control device 20 in advance is referred to TAO based on the target blowing temperature TAO. Accordingly, the air flow is determined to be an appropriate amount.

  For the control signal output to the servo motor of the air mix door 18, the target opening degree SW of the air mix door 18 is calculated based on the detection signal of the evaporator temperature sensor 24 and the coolant temperature of the vehicle running engine. Then, the control signal is determined so that the opening degree of the air mix door 18 becomes the target opening degree SW.

  For the control signal output to the servo motor of the open / close door that opens and closes each outlet, the control signal stored in advance in the air-conditioning control device 20 is referred to based on the target outlet temperature TAO, and the control signal appropriate for the TAO is selected. Decide to open and close the outlet.

  Next, in step S5, the control current In (discharge capacity of the compressor 11) to be output to the electromagnetic capacity control valve 11a of the compressor 11 is determined. Details of step S5 will be described with reference to FIG.

  First, in step S51, the first control current Ic1 is determined so that the discharged refrigerant pressure Pd detected by the high pressure sensor 25 is equal to or lower than the reference maximum high pressure Pdmax. The reference maximum pressure Pdmax is set to a value lower than the withstand pressure of the cycle component equipment, and is set to 13.7 MPa in the present embodiment.

  Specifically, the first control current is changed by a feedback control method that changes the control current output to the electromagnetic capacity control valve 11a according to the deviation Pn (Pdmax−Pd) between the reference maximum high pressure Pdmax and the discharge refrigerant pressure Pd. Ic1 is determined. Therefore, the reference maximum pressure Pdmax of this embodiment is one of the control target values used to avoid the high-pressure side refrigerant pressure from exceeding the pressure resistance of the cycle component equipment.

  Next, in step S52, the second control current Ic2 is determined so that the cooling capacity required in the evaporator 15 can be exhibited. Specifically, based on the target blowing temperature TAO, the target refrigerant evaporation temperature TEO is determined with reference to a control map as shown in FIG. 4 stored in the air conditioning control device 20 in advance. In the present embodiment, TEO increases as TAO increases.

  Further, in step S52, a deviation En (Te-TEO) between the temperature Te of the heat exchange fin detected by the evaporator temperature sensor 24 and the target refrigerant evaporation temperature TEO is calculated, and Te is calculated based on the deviation En. The second control current Ic2 is determined by a feedback control method such as proportional-integral control (PI control) so as to approach TEO.

  Therefore, the target refrigerant evaporation temperature TEO of the present embodiment is one of control target values used for exhibiting the cooling capacity required in the evaporator 15. Note that TEOmin shown in FIG. 4 is a lower limit value of the target refrigerant evaporation temperature TEO set to prevent frost formation on the evaporator 15, and is 3 ° C. in this embodiment.

  Next, in steps S53 to S55, the control current that is actually output to the electromagnetic capacity control valve 11a, whichever of the first control current Ic1 and the second control current Ic2, has a smaller discharge capacity of the compressor 11. Minimum control to Ic is performed. Specifically, as the control current Ic increases / decreases, the discharge capacity also increases / decreases, so the lower value of Ic1 and Ic2 is adopted as Ic.

  By performing such minimum control, the first control current Ic1 for preventing the discharged refrigerant pressure Pd from exceeding the reference maximum high pressure with respect to the second control current Ic2 for exerting the required cooling capacity is It will be prioritized and cycle safety and durability can be improved.

  Next, in step S56, it is determined whether or not the discharge refrigerant flow rate Gr detected by the flow sensor 26 is greater than or equal to a predetermined reference discharge refrigerant flow rate Gr1. If the discharged refrigerant flow rate Gr is equal to or higher than the reference discharged refrigerant flow rate Gr1 in step S56, the control current Ic is forcibly changed to the second control current Ic2 in step S57, and the process proceeds to step S6.

  In step S56, if the discharge refrigerant flow rate Gr is not less than the reference discharge refrigerant flow rate Gr1 in step S56, the control current Ic is not changed and the process proceeds to step S6. In this embodiment, the leak amount Grmin (specifically, 50 kg / h) leaking from the bleed port when the pressure control valve 14 is closed is set as the reference discharge refrigerant flow rate Gr1.

  Next, in step S6, a control signal is output from the air conditioning control device 20 to the electric actuator so that the control state determined in steps S4 and S5 is obtained. In the next step S7, the process waits for the control period τ, and when it is determined that the control period τ has elapsed, the process returns to step S2.

  Therefore, in the vehicle air conditioner according to the present embodiment, the air conditioning control device 20 controls the operation of each electric actuator according to the target blowing temperature TAO as described above, so that the vehicle interior is appropriately air-conditioned. be able to. Moreover, since the discharge capacity control means 20a of the air conditioning control device 20 switches the control target value based on the discharged refrigerant flow rate Gr detected by the flow sensor 26, the temperature in the vehicle compartment (inside temperature Tr) is reduced in a short time. Can be made.

  This will be described with reference to FIG. FIG. 5 is a graph corresponding to FIG. 6 described above. In the present embodiment, as described in step S5, when the discharge refrigerant flow rate Gr is smaller than the reference discharge refrigerant flow rate Gr1, the reference maximum high pressure Pdmax is used as the control target value, and the discharge refrigerant flow rate Gr is the reference discharge refrigerant. In the case of the flow rate Gr1 or more, the target refrigerant evaporation temperature TEO is used as the control target value.

  Therefore, as shown in the upper control current Ic (solid line + bold broken line) in FIG. 5, the timing T2 when the discharged refrigerant flow rate Gr becomes equal to or greater than the leakage amount Grmin leaking from the bleed port, that is, the pressure control valve 14 is opened from the closed state. The control target value can be switched from the reference maximum high pressure Pdmax to the target refrigerant evaporation temperature TEO simultaneously with the timing at which the state is reached and the valve opening is adjusted so that the high-pressure side refrigerant pressure can be controlled.

  As a result, there is no delay in switching from the first control current Ic1 for preventing the discharged refrigerant pressure to exceed the reference maximum high pressure to the second control current Ic2 for exhibiting the required cooling capacity. The target value can be switched at an ideal timing. As a result, as shown in the lower part of FIG. 5, the discharge refrigerant flow rate Gr after the timing T2 can be increased with respect to the prior art, and the internal temperature Tr can be reduced in a short time as shown in the middle part of FIG. .

  Note that the middle and lower broken lines in FIG. 5 indicate the internal temperature Tr, the discharged refrigerant pressure Pd, and the discharged refrigerant flow rate Gr in the prior art (that is, corresponding to the solid line in FIG. 6).

  Further, as is clear from the middle stage of FIG. 5, even if the control target value is switched based on the discharge refrigerant flow rate Gr detected by the flow sensor 26 as in this embodiment, the discharge refrigerant pressure Pd is the reference maximum. The high pressure Pdmax is not exceeded, and the safety and durability of the cycle are not impaired.

(Other embodiments)
The present invention is not limited to the above-described embodiment, and can be variously modified as follows.

  (1) In the above-described embodiment, an example in which the pressure control valve 14 having the temperature sensing part 14a between the radiator 12 outlet side and the high-pressure side refrigerant flow path 13a inlet side of the internal heat exchanger 13 will be described. However, a refrigerant passage that allows the refrigerant on the downstream side of the radiator 12 to pass therethrough is formed in the pressure control valve 14, and a temperature sensing rod is disposed in the refrigerant passage to change the internal pressure of the temperature sensing portion 14a. Good.

  Furthermore, an electric variable throttle device that can adjust the valve opening degree by the control device of the air conditioning control device 20 may be adopted as the pressure control valve. In this case, a temperature sensor for detecting the temperature of the refrigerant on the downstream side of the radiator 12 is provided, the target high pressure is determined based on the detected value of the temperature sensor, and the valve opening is set so that the high pressure side refrigerant pressure approaches the target high pressure. Can be controlled.

  (2) In the above-described embodiment, an example is described in which the reference maximum high pressure Pdmax and the target refrigerant evaporation temperature TEO are adopted as the control target values. However, the control target values are not limited to this. Furthermore, you may add another control target value different from said control target value.

  For example, the second target refrigerant evaporation temperature TEO2 determined based on the outside air temperature Tam may be adopted as another control target value. As for the second target refrigerant evaporation temperature TEO2, the outside air temperature Tam decreases with a decrease in the outside air temperature Tam in the low temperature region, the outside air temperature Tam increases in the intermediate temperature region, and further, the outside air temperature Tam in the high temperature region. What is necessary is just to reduce with a raise.

  As a result, when the outside air temperature Tam is low, the dehumidifying ability can be secured to prevent fogging of the window glass, and when the outside air temperature Tam is high, the cooling ability can be secured.

  (3) In the above-described embodiment, the passage diameter of the bleed port of the pressure control valve 14 is set to φ0.4 mm, but the passage diameter of the bleed port is preferably set to φ0.2 or more and φ0.7 mm or less. In the above-described embodiment, the bleed port is formed by the communication hole. For example, a groove is formed in the valve body or the seat so that the refrigerant is slightly leaked from the high pressure side to the low pressure side when the valve is closed. You may do it.

  (4) In the above-described embodiment, an example in which a differential pressure type flow sensor is adopted as the flow sensor 26 has been described, but the type of the flow sensor 26 is not limited to this. For example, a mass flow sensor such as a hot wire flow sensor may be employed.

  (5) In the above-described embodiment, an example in which the refrigeration cycle apparatus 10 of the present invention is applied to a vehicle air conditioner has been described, but the application of the present invention is not limited to this. For example, the present invention may be applied to a commercial refrigeration apparatus, a household refrigerator, and the like. Further, the refrigerant is not limited to carbon dioxide, and a chlorofluorocarbon refrigerant or an HC refrigerant may be employed.

  (6) In the above embodiment, the radiator 12 is an outdoor heat exchanger that exchanges heat between the refrigerant and the outside air, and the evaporator 15 is an indoor heat exchanger that is applied to cool the interior of the vehicle. The present invention is applied to a heat pump cycle in which the evaporator 15 is configured as an outdoor heat exchanger that absorbs heat from a heat source such as outside air, and the radiator 12 is configured as an indoor heat exchanger that heats a heated fluid such as air or water. May be.

1 is an overall configuration diagram of a refrigeration cycle apparatus applied to a vehicle air conditioner according to an embodiment. It is a flowchart which shows control of the vehicle air conditioner of one Embodiment. It is a flowchart which shows the principal part of control of the vehicle air conditioner of one Embodiment. It is a characteristic view for determining target refrigerant evaporation temperature of one embodiment. It is a graph which shows a time-dependent change of 1st control current Ic1, 2nd control current Ic2, control current Ic, discharge refrigerant pressure Pd, internal temperature Tr, and discharge refrigerant flow Gr of one embodiment. It is a graph which shows the time-dependent change of the 1st control current Ic1, the 2nd control current Ic2, the control current Ic of the prior art, the discharge refrigerant pressure Pd, the internal temperature Tr, and the discharge refrigerant flow rate Gr.

Explanation of symbols

DESCRIPTION OF SYMBOLS 11 ... Compressor, 11a ... Electromagnetic capacity control valve, 12 ... Radiator, 14 ... Pressure control valve,
15 ... evaporator, 20a ... discharge capacity control means, 24 ... evaporator temperature sensor,
26: flow sensor, Pdmax: reference maximum pressure, TEO: target refrigerant evaporation temperature.

Claims (8)

A variable capacity compressor (11) configured to be able to change the discharge capacity;
A radiator (12) for radiating the refrigerant discharged from the variable capacity compressor (11);
While opening the refrigerant flowing out of the radiator (12) under reduced pressure, the valve opening degree is set so that the high-pressure side refrigerant pressure approaches the target high pressure determined according to the high-pressure side refrigerant temperature downstream of the radiator (12). A pressure control valve (14) to which is adjusted;
A refrigeration cycle apparatus comprising an evaporator (15) for evaporating the refrigerant decompressed and expanded by the pressure control valve (14),
Furthermore, a discharge capacity changing means (11a) for changing the discharge capacity of the variable capacity compressor (11),
A discharge capacity control means (20a) for controlling the operation of the discharge capacity changing means (11a) using any one of at least two control target values (Pdmax, TEO);
A flow rate detection means (26) for detecting a refrigerant flow rate (Gr) circulating in the cycle,
The discharge capacity control means (20a) controls the operation of the discharge capacity change means (11a) among the plurality of control target values (Pdmax, TEO) based on the detection value of the flow rate detection means (26). A refrigeration cycle apparatus characterized by switching control target values (Pdmax, TEO) to be used. When the detection value of the flow rate detection means (26) is smaller than a predetermined value, the discharge capacity control means (20a) determines the discharge capacity among the two or more control target values (Pdmax, TEO). Use the control target value that makes the smallest value, and if the detected value of the flow rate detection means (26) is equal to or greater than the predetermined value, use a control target value other than the control target value that makes the discharge capacity the smallest. The refrigeration cycle apparatus according to claim 1. The pressure control valve (14) has a bleed port for leaking refrigerant from the high pressure side to the low pressure side even when the valve is closed,
The refrigeration cycle apparatus according to claim 2, wherein the predetermined value is a leakage amount (Grmin) leaking from the bleed port when the pressure control valve (14) is closed. One of the control target values is a reference maximum high pressure (Pdmax) of the high-pressure side refrigerant pressure,
When the reference maximum high pressure (Pdmax) is used, the discharge capacity control means (20a) is configured so that the discharge refrigerant pressure of the variable capacity compressor (11) is equal to or lower than the reference maximum high pressure (Pdmax). The refrigeration cycle apparatus according to any one of claims 1 to 3, wherein the operation of the capacity changing means (11a) is controlled. One of the control target values is a target refrigerant evaporation temperature (TEO) of the refrigerant evaporation temperature in the evaporator (15),
When the discharge capacity control means (20a) uses the target refrigerant evaporation temperature (TEO), the discharge capacity change means (11a) of the discharge capacity change means (11a) so that the refrigerant evaporation temperature approaches the target refrigerant evaporation temperature (TEO). The refrigeration cycle apparatus according to any one of claims 1 to 4, wherein the operation is controlled. The refrigeration cycle apparatus according to claim 5, further comprising heat exchange fin temperature detection means (24) for detecting a temperature (Te) of the heat exchange fin of the evaporator (15). The refrigeration cycle apparatus according to claim 5, further comprising blown air temperature detection means for detecting the temperature of the air blown from the evaporator (15). The refrigeration cycle apparatus according to any one of claims 1 to 7, wherein the refrigerant is carbon dioxide.

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