JP4089630B2 - Refrigeration cycle for vehicles - Google Patents

Description

The present invention relates to a refrigeration cycle for a vehicle using a refrigerant having a high pressure equal to or higher than a critical pressure (supercritical state) such as a CO ₂ refrigerant, and is particularly suitable for application to a cycle having an internal heat exchanger. Is something.

CO ₂ refrigerant can be solved a problem that the ozone layer destruction by refrigerants (R134a, etc.) fluorocarbon, but the other hand, in the supercritical refrigeration cycle using CO ₂ refrigerant, compared to a normal refrigeration cycle using chlorofluorocarbon refrigerants Therefore, the theoretical efficiency is low due to the difference in the physical properties of the refrigerant. Therefore, an internal heat exchanger is installed to improve efficiency, and heat exchange is performed between the low-pressure compressor intake refrigerant and the high-pressure radiator outlet refrigerant, increasing the refrigerant enthalpy difference between the evaporator inlet and outlet. It is known to make (for example, refer to Patent Document 1).
Japanese Patent Laid-Open No. 2003-2048

  By the way, when an internal heat exchanger is provided in the supercritical refrigeration cycle, the compressor intake refrigerant is heated by the radiator outlet refrigerant and has a degree of superheat, so that the temperature of the compressor discharge refrigerant rises excessively.

  Therefore, when the discharge refrigerant temperature exceeds the limit temperature of the compressor, this temperature rise is judged to reduce the compression function (specifically, the capacity of the variable capacity compressor, etc.) It is necessary to reduce the compressor discharge pressure by performing control such as increasing the opening of the expansion valve, thereby suppressing the discharge refrigerant temperature below the compressor limit temperature.

  Here, when the cycle control for suppressing the discharge refrigerant temperature (hereinafter referred to as discharge refrigerant temperature control) is performed, the cooling capacity decreases with a decrease in the compressor discharge pressure. If the detection error of the refrigerant temperature is large, the rate of decrease in the cooling capacity increases.

  Since the detection of the discharge refrigerant temperature has the advantage that a pipe seal portion is not required, a configuration in which a temperature sensor is closely arranged on the outer surface of the discharge refrigerant passage such as a compressor discharge side pipe is usually used. However, with this temperature detection configuration, since the temperature sensor is disposed on the outer surface of the discharge refrigerant passage, the temperature detected by the temperature sensor is influenced by the ambient temperature and the vehicle running wind in addition to the refrigerant temperature. .

  For this reason, when the vehicle speed is low, including when the vehicle is stopped, such as when waiting for a signal, the ambient temperature of the temperature sensor is higher and the air wind speed around the temperature sensor is lower than when the vehicle is traveling normally above the specified vehicle speed. The temperature rises. Therefore, the temperature difference (detection error) between the actual discharged refrigerant temperature inside the discharged refrigerant passage and the temperature sensor detected temperature is smaller at the time of low vehicle speed than during normal traveling.

  As a result, when the target value, which is the limit temperature of the discharge refrigerant temperature, is set to a predetermined fixed value based on the compressor heat resistance temperature, etc., the actual discharge refrigerant temperature is lower at low vehicle speeds than during normal travel. Since it is determined that the target value (limit temperature) has been reached at the temperature, and the discharged refrigerant temperature control is executed, the cooling capacity is lowered early.

  In particular, when the compressor is driven by a vehicle engine, when the vehicle is stopped, the cooling speed is lowered due to the idling operation of the vehicle engine and the cooling capacity is lowered. It will be even lower.

  In addition, although the above-mentioned trouble was explained about the case where an internal heat exchanger is provided in the supercritical refrigeration cycle, the discharge refrigerant temperature during normal running and at low vehicle speed also in the supercritical refrigeration cycle without an internal heat exchanger. The above problems due to the difference in detection error occur to some extent.

  In view of the above-described points, an object of the present invention is to prevent the discharge refrigerant temperature control from being performed at a temperature at which the actual discharged refrigerant temperature is lower than that during normal traveling at a low vehicle speed.

In order to achieve the above object, according to the first aspect of the present invention, a compressor (1) that is driven by a vehicle travel engine and sucks and compresses a refrigerant composed of CO ₂ ;
A radiator (2) for cooling the refrigerant discharged from the compressor (1);
Decompression means (4) for decompressing the outlet side refrigerant of the radiator (2);
An evaporator (5) for evaporating the low-pressure refrigerant decompressed by the decompression means (4);
An internal heat exchanger (3) for exchanging heat between the outlet side refrigerant of the radiator (2) and the suction side refrigerant of the compressor (1) ,
The refrigerant that has passed through the evaporator (5) is sucked into the compressor (1) after passing through the internal heat exchanger (3),
Furthermore, in the vehicle refrigeration cycle where the refrigerant pressure on the high pressure side is equal to or higher than the critical pressure of the refrigerant,
A temperature detection means (11) disposed on the outer surface of the discharge refrigerant passage of the compressor (1) for detecting the discharge refrigerant temperature of the compressor (1);
Control means (S60, S80) for controlling the refrigeration cycle operating condition to the side of suppressing the discharged refrigerant temperature when the detected temperature of the temperature detecting means (11) exceeds a predetermined target value;
During normal driving when the vehicle speed is equal to or higher than a predetermined value, the target value (Tb) during normal driving is set as the target value. On the other hand, at low vehicle speed when the vehicle speed is less than the predetermined value , at least the vehicle speed is zero. and at low speed it includes a time stop comprising, as the target value, the target value switching means for switching the target value of the normal running predetermined amount higher low-speed drive of the target value than (Tb) (Tc) (S20~ S50).

  Incidentally, as described above, the temperature detected by the temperature detecting means (11) is higher at the low vehicle speed than at the normal travel time as described above. Therefore, the actual discharge refrigerant in the discharge refrigerant passage is at the low vehicle speed than at the normal travel time. The temperature difference (detection error) between the temperature and the temperature detected by the temperature detection means (11) is reduced.

  In claim 1, paying attention to this point, the target value (Tc) of the discharged refrigerant temperature control at the time of low vehicle speed is set to a temperature higher by a predetermined amount than the target value (Tb) of the discharged refrigerant temperature control at the time of normal traveling. Therefore, the actual discharged refrigerant temperature when starting the discharged refrigerant temperature control at the time of low vehicle speed and normal driving can be made the same temperature.

  In other words, when the discharge refrigerant temperature control is executed at the low vehicle speed, it is possible to avoid the actual discharge refrigerant temperature from becoming lower than that at the time of traveling, thereby preventing the cooling capacity from being excessively reduced at the low vehicle speed.

  As in the invention described in claim 2, in the vehicle refrigeration cycle according to claim 1, specifically, the predetermined amount is the detected temperature error of the temperature detecting means (11) during normal traveling and the low vehicle speed. What is necessary is just to determine based on the difference with the detection temperature error of the temperature detection means (11) at the time.

  As in the third aspect of the invention, in the refrigeration cycle for the vehicle according to the first or second aspect, at low vehicle speeds, specifically, at low vehicle speeds when the vehicle speed is less than the predetermined value and the vehicle speed is low. It covers both when the vehicle stops at zero.

  As in the fourth aspect of the invention, in the refrigeration cycle for the vehicle according to the first or second aspect, the low vehicle speed may specifically be only when the vehicle stops when the vehicle speed becomes zero.

  As in the invention described in claim 5, in the vehicle refrigeration cycle according to any one of claims 1 to 4, the control of the refrigeration cycle operating condition means that the operation of the compressor (1) is a discharge flow rate. It is to control to the decline side.

  According to this, the compressor discharge pressure can be reduced by reducing the discharge flow rate of the compressor (1) during the discharge refrigerant temperature control, and the rise in the discharge refrigerant temperature can be suppressed.

  As in the sixth aspect of the invention, in the refrigeration cycle for a vehicle according to any one of the first to fourth aspects, the control of the refrigeration cycle operating condition is to increase the opening of the decompression means (4). Is to control to the side.

  According to this, the high pressure (compressor discharge pressure) can be reduced by increasing the opening of the decompression means (4) during discharge refrigerant temperature control, and the rise in discharge refrigerant temperature can be suppressed.

As in the invention according to claim 7, in the vehicle refrigeration cycle according to any one of claims 1 to 4, the outlet side refrigerant of the evaporator (5) bypasses the internal heat exchanger (3). A bypass valve (21) that allows the flow of
The control of the refrigeration cycle operating conditions means that the outlet side refrigerant of the evaporator (5) controls the bypass valve (21) to the side that flows by bypassing the internal heat exchanger (3).

  According to this, in the supercritical refrigeration cycle for a vehicle that can improve the cooling capacity by increasing the refrigerant enthalpy difference between the evaporator inlet and outlet by the action of the internal heat exchanger (3), the evaporator ( The outlet side refrigerant of 5) flows by bypassing the internal heat exchanger (3), thereby reducing the degree of superheat of the refrigerant sucked by the compressor, thereby suppressing the increase in the discharge refrigerant temperature.

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

(First embodiment)
FIG. 1 is a configuration diagram of a refrigeration cycle for vehicle air conditioning showing a first embodiment of the present invention, and this refrigeration cycle uses CO ₂ whose high pressure is not less than a critical pressure (supercritical state) as a refrigerant. . Therefore, this refrigeration cycle constitutes a supercritical refrigeration cycle.

  The compressor 1 obtains driving force from a vehicle travel engine (not shown) and sucks and compresses refrigerant. The compressor 1 obtains a driving force through an electromagnetic clutch 1a serving as a clutch means for intermittently driving the driving force.

  The compressor 1 of the present embodiment is a variable capacity compressor that can change its capacity by an external control signal, and includes an electromagnetic capacity control valve 1b. The variable capacity compressor 1 is known as, for example, a swash plate compressor, and by changing the control current value applied to the electromagnetic capacity control valve 1b, the control pressure of the swash plate chamber is changed. The change of the inclination angle of the plate → the change of the piston stroke → the change of the capacity is performed. The change in the compressor capacity changes the discharge refrigerant flow rate per unit rotation speed.

  A radiator 2 is provided on the discharge side of the compressor 1. The radiator 2 cools the refrigerant by exchanging heat between the discharged refrigerant in the supercritical state at high temperature and high pressure discharged from the compressor 1 and the outside air (outdoor air). Outside air is blown to the radiator 2 by an electric cooling fan 2a.

  A high-pressure side passage 3a of the internal heat exchanger 3 is provided on the outlet side of the radiator 2, and an electric expansion valve 4 serving as a decompression unit is provided on the outlet side of the high-pressure side passage 3a. The electric expansion valve 4 serves as a pressure control valve whose opening degree is electrically controlled so that the high pressure of the cycle becomes the target high pressure.

  An evaporator 5 is provided on the outlet side of the electric expansion valve 4. The evaporator 5 is disposed in a case 6 that forms an air passage of an indoor air conditioning unit of the vehicle air conditioner, and constitutes a cooling means for cooling the air in the case 6. An electric blower 7 is arranged on the upstream side of the air flow of the evaporator 5 so that the inside air or the outside air introduced through an inside / outside air switching box (not shown) is blown into the case 6.

  Note that a heater core (not shown) serving as a heating means for heating air is disposed in the case 6 on the downstream side of the air flow of the evaporator 5, and conditioned air whose temperature is adjusted by the degree of heating of the heater core is provided in the case 6. The air flow is blown out from the outlet (not shown) at the downstream end of the air flow into the vehicle compartment.

  An accumulator 8 is provided on the outlet side of the evaporator 5. The accumulator 8 is a gas-liquid separation unit that separates the liquid refrigerant and gas refrigerant of the outlet refrigerant of the evaporator 5 and stores excess refrigerant in the cycle, and directs the separated gas refrigerant to the suction side of the compressor 1. To derive.

  On the outlet side of the accumulator 8, a low pressure side flow path 3 b of the internal heat exchanger 3 is provided. Accordingly, the outlet pipe of the accumulator 8 is connected to the suction side of the compressor 1 through the low pressure side flow path 3b.

  The internal heat exchanger 3 exchanges heat between the refrigerant flowing out of the accumulator 8 (compressor suction refrigerant) and the outlet side refrigerant of the radiator 2 to reduce the enthalpy of the refrigerant flowing into the evaporator 5, thereby reducing the refrigerant of the evaporator 9. This increases the enthalpy difference (refrigeration capacity) of the refrigerant on the inlet side and the outlet side, and prevents the liquid refrigerant from being sucked into the compressor 1.

  Next, an outline of the electric control unit in the present embodiment will be described. The air-conditioning control device 10 is composed of a microcomputer and its peripheral circuits, etc., and performs predetermined arithmetic processing according to a preset program to control the operation of the air-conditioning equipment.

  Specifically, air-conditioning equipment such as an electromagnetic clutch 1 a of the compressor 1, a capacity control valve 1 b, a cooling fan 2 a of the radiator 2, an electric expansion valve 4, and an electric blower 7 are provided on the output side of the air-conditioning control device 10. Connected and controls the operation of these air conditioners.

  On the input side of the air-conditioning control device 10, the refrigerant temperature sensor 11 discharged from the compressor 1, the refrigerant temperature sensor 12 at the outlet side of the radiator 2, the refrigerant pressure sensor 13 at the outlet side of the radiator 2, and the air blown from the evaporator 5 A temperature sensor 14 or the like is connected. The air conditioning control device 10 also receives detection signals from a sensor group 15 including well-known outside air temperature sensors, inside air temperature sensors, solar radiation sensors, and the like. Various air conditioning operation signals are input to the air conditioning control device 10 from an air conditioning operation panel 16 disposed in the vicinity of an instrument panel in the vehicle interior.

  Specifically, a temperature setting switch for setting a set temperature in the vehicle interior, an air conditioner switch for issuing an operation command signal for the compressor 1, an air volume changeover switch for the electric blower 7, a blowout mode changeover switch for the indoor air conditioning unit, an inside / outside air changeover Operation members such as a box inside / outside air introduction mode changeover switch are provided on the air conditioning operation panel 16.

  The air-conditioning control device 10 is electrically connected to the engine control device 17 so as to communicate electric signals with the engine control device 17. Vehicle-side detection signals such as vehicle speed, engine speed, and engine water temperature are input from the engine control device 17 to the air conditioning control device 10.

  Next, the operation of this embodiment in the above configuration will be described. First, the basic operation of the refrigeration cycle will be described. When the air-conditioner switch of the air-conditioning operation panel 16 is turned on, the electromagnetic clutch 1a is energized by the air-conditioning control device 10 to enter a connected state. Thereby, the driving force of the vehicle engine is transmitted to the compressor 1 via the electromagnetic clutch 1a, and the compressor 1 is driven.

  The high-temperature and high-pressure refrigerant compressed by the compressor 1 flows into the radiator 2 in a supercritical state where the pressure is higher than the critical pressure. Here, the high-temperature and high-pressure supercritical refrigerant exchanges heat with the outside air blown by the cooling fan 2a to dissipate heat into the outside air, thereby reducing enthalpy.

  And the exit refrigerant | coolant of the heat radiator 2 passes the high voltage | pressure side flow path 3a of the internal heat exchanger 3, and goes to the expansion valve 4. FIG. Here, the outlet refrigerant of the radiator 2 exchanges heat with the low-temperature and low-pressure refrigerant of the low-pressure side passage 3b when passing through the high-pressure side passage 3a of the internal heat exchanger 3, and radiates heat to the low-pressure refrigerant side.

  The refrigerant that has further dissipated heat after passing through the high-pressure channel 3a of the internal heat exchanger 3 is then depressurized in the throttle passage of the expansion valve 4 to be in a low-temperature and low-pressure gas-liquid two-phase state. This low-temperature and low-pressure gas-liquid two-phase refrigerant then flows into the evaporator 5 where it absorbs heat from the blown air of the electric blower 7 and evaporates. Thereby, the blowing air of the electric blower 7 can be cooled by the evaporator 5, and the cool air can be blown out into the vehicle interior.

  The low-pressure refrigerant that has passed through the evaporator 5 then flows into the accumulator 8, where the liquid refrigerant and gas refrigerant of the low-pressure refrigerant are separated, and the gas refrigerant is led out from the outlet of the accumulator 8 toward the suction side of the compressor 1. Is done.

  The low-pressure gas refrigerant (compressor suction refrigerant) at the outlet of the accumulator 8 absorbs heat from the outlet refrigerant of the radiator 2 in the low-pressure side passage 3b of the internal heat exchanger 3, so that the outlet refrigerant of the radiator 2 is cooled, Enthalpy decreases. The superheated gas refrigerant that has absorbed heat in the internal heat exchanger 3 is sucked into the compressor 1 and compressed again.

  Next, the refrigeration cycle automatic control based on the detection signal of the refrigerant state of each part of the refrigeration cycle will be described with reference to FIG. FIG. 2 is a flowchart of a control routine executed by the air conditioning control device 10, and this control routine starts when the air conditioner switch of the air conditioning operation panel 16 is turned on. First, in step S10, an initial target value Ta is set as the discharge temperature target value of the compressor discharge refrigerant. This initial target value Ta is a fixed value set in consideration of the heat resistant temperature of the compressor 1 and the heat resistant temperature of the rubber hose of the compressor 1 discharge side piping.

  Next, in steps S20 and S30, it is determined whether or not the vehicle speed is in a low vehicle speed state equal to or lower than a predetermined vehicle speed. In the present embodiment, the low vehicle speed state includes both a low vehicle speed state where the vehicle speed is equal to or lower than a predetermined vehicle speed and a complete stop state.

  Specifically, it is determined in step S20 whether the vehicle speed is higher than a second predetermined vehicle speed, for example, 20 km / h. When the vehicle speed is higher than 20 km / h, it is during normal travel, and the process proceeds to step S40, where the target value Tb during normal travel is set as the discharge temperature target value of the refrigerant discharged from the compressor. The target value Tb during normal driving is the same value (Ta = Tb) as the initial target value Ta.

  On the other hand, when the vehicle speed is lower than 20 km / h, the process proceeds from step S20 to step S30, and the first predetermined vehicle speed, for example, 15 km / h lower than the second predetermined vehicle speed is compared with the vehicle speed. When the vehicle speed is lower than 15 km / h, the vehicle speed is low, and the process proceeds to step S50, where the target value Tc at the low vehicle speed is set as the discharge temperature target value of the refrigerant discharged from the compressor.

  The target value Tc at the low vehicle speed is a temperature that is corrected to the high temperature side by a predetermined temperature α with respect to the target value Tb during normal traveling. That is, at low vehicle speeds, the temperature detected by the discharge temperature sensor 11 rises compared to that during normal driving due to an increase in the ambient temperature of the discharge temperature sensor 11 and a decrease in the wind speed of the passing air around the discharge temperature sensor 11. Therefore, Tc = Tb + α is set.

  Here, α is a value corresponding to the detected temperature difference of the discharge temperature sensor 11 that occurs between the normal travel and the low vehicle speed. Specifically, the actual discharge refrigerant temperature and the discharge temperature sensor during the normal travel. The difference (A−B) between the temperature difference A between the detected temperature 11 and the detected refrigerant temperature at the low vehicle speed and the detected temperature of the discharged temperature sensor 11 is α, and this difference (A− B) The target value Tc at the time of low vehicle speed is made higher than the target value Tb at the time of normal driving by the amount of α.

  When the vehicle speed is 15 km / h or more and less than 20 km / h in the first determination in steps S20 and S30 after the start of the control routine in FIG. 2, the initial target value Ta is used as it is as the discharge temperature target value. Use.

  In the next step S60, the discharge temperature target value set as described above, that is, any one of Ta, Tb, and Tc is compared with the discharge temperature Td detected by the discharge temperature sensor 11, and the discharge temperature is compared. (Sensor detection value) It is determined whether Td is higher than the discharge temperature target value. When the actual discharge temperature Td is equal to or lower than the discharge temperature target value, the process proceeds to step S70, and normal refrigeration cycle control is performed.

  Specifically, the normal refrigeration cycle control includes control of the high pressure Pd by opening control of the electric expansion valve 4 and control of the evaporator outlet temperature Te by capacity control of the compressor 1. The high pressure Pd is controlled by calculating a target high pressure Po that maximizes the cycle COP (coefficient of performance) based on the radiator outlet side refrigerant temperature Tf detected by the refrigerant temperature sensor 12 on the radiator 2 outlet side, and the radiator 2 outlet The opening degree of the electric expansion valve 4 is controlled so that the high pressure Pd detected by the refrigerant pressure sensor 13 on the side becomes the target high pressure Po. When the actual high pressure Pd is higher than the target high pressure Po, the opening degree of the electric expansion valve 4 is increased. Conversely, when the actual high pressure Pd is lower than the target high pressure Po, the opening degree of the electric expansion valve 4 is increased. Decrease.

  The evaporator blowout temperature Te is controlled by calculating the target temperature TEO of the evaporator blowout air from the target temperature TAO of the air blown into the vehicle interior, the outside air temperature Tam, etc., and the evaporation detected by the blowout air temperature sensor 14 of the evaporator 5. The capacity | capacitance of the compressor 1 is controlled so that the evaporator blowing temperature Te may become the evaporator target temperature TEO.

  That is, when the evaporator outlet temperature Te is higher than the evaporator target temperature TEO, the control current value output to the capacity control valve 1b of the compressor 1 is increased to increase the capacity of the compressor 1, thereby evaporating. The cooling capacity of the evaporator 5 is increased by increasing the circulating refrigerant flow rate to the evaporator 5. On the contrary, when the evaporator outlet temperature Te is lower than the evaporator target temperature TEO, the control current value output to the capacity control valve 1b of the compressor 1 is decreased to decrease the capacity of the compressor 1, thereby The flow rate of the circulating refrigerant to the evaporator 5 is reduced to reduce the cooling capacity of the evaporator 5.

  The minimum temperature of the evaporator target temperature TEO is determined to be slightly higher than 0 ° C. (about 1 ° C.) in order to prevent the evaporator 5 from being frosted.

  On the other hand, if it is determined in step S60 that the discharge temperature (sensor detection value) Td is higher than the discharge temperature target value, the process proceeds to step S80, where control is performed to lower the discharge temperature Td to be equal to or lower than the discharge temperature target value. Specifically, the capacity of the compressor 1 is forcibly decreased by a predetermined amount regardless of the detection value of the blown air temperature sensor 14 to lower the discharge pressure, thereby reducing the discharge temperature Td to the discharge temperature target value ( Control to suppress to the limit temperature from heat resistance).

  In step S80, the high pressure is controlled so as to maximize the COP by controlling the opening of the electric expansion valve 4.

  By the way, in this embodiment, at a low vehicle speed, the detection temperature of the discharge temperature sensor 11 is usually affected by an increase in the ambient temperature of the discharge temperature sensor 11 and a decrease in the wind speed of the passing air around the discharge temperature sensor 11. Considering that the temperature rises compared to when traveling, the temperature difference A between the actual discharged refrigerant temperature during normal traveling and the detected temperature of the discharge temperature sensor 11, and the actual discharged refrigerant temperature and discharged temperature sensor during low vehicle speed. The target value Tc at the low vehicle speed is made higher than the target value Tb at the time of normal traveling by the difference (A−B) = α of the temperature difference B from the detected temperature 11.

  Thereby, even when the vehicle speed is low, the actual discharge temperature when the detected temperature of the discharge temperature sensor 11 reaches the discharge temperature target value can be set to the same temperature as during normal driving.

  As a result, even when the discharge temperature (sensor detection value) Td becomes higher than the discharge temperature target value at the low vehicle speed and the discharge temperature control by the capacity control of the compressor 1 is executed, the actual discharge temperature is lower than that during normal driving. Can be prevented.

  In other words, the discharge temperature control by the capacity control of the compressor 1 is prevented from being performed more than necessary due to the influence of an increase in the ambient temperature of the discharge temperature sensor 11 and a decrease in the wind speed of the passing air around the sensor at a low vehicle speed. it can. Therefore, it is possible to solve the problem that the cooling capacity is excessively lowered at a low vehicle speed.

  In the control routine of FIG. 2, the difference between 20 km / h and 15 km / h is provided as the vehicle speed determination value in steps S20 and S30, so that the discharge temperature target value is not frequently changed. This is because hysteresis is set. In step S40, once the target value Tb for normal driving is set as the discharge temperature target value, the target for normal driving is used as the discharge temperature target value as long as it is higher than 15 km / h even if the vehicle speed drops below 20 km / h. The value Tb is maintained.

  In step S50, once the target value Tc at low vehicle speed is set as the discharge temperature target value, the discharge temperature target value is set as long as the vehicle speed is 20 km / h or less even if the vehicle speed increases to 15 km / h or more. The target value Tc at the time of low vehicle speed is maintained.

  By the way, each step in the control routine of FIG. 2 constitutes a function realization means, and among these, steps S60 and S80, when the detected temperature of the discharge temperature sensor 11 exceeds a predetermined target value, The control means of the present invention is configured to control the discharge refrigerant temperature to be suppressed.

  In steps S20 to S50, the target value Tb for normal driving is set as the target value for discharge temperature control during normal driving when the vehicle speed is a predetermined value or higher, and the discharge temperature is set for low vehicle speeds when the vehicle speed is less than the predetermined value. The target value switching means of the present invention is configured to set a target value Tc at a low vehicle speed that is a predetermined amount higher than the target value Tb at the time of normal traveling as a target value for control.

(Second Embodiment)
In the first embodiment, discharge temperature control is performed by capacity control (capacity reduction) of the compressor 1, but the second embodiment is based on capacity control of the compressor 1 and opening degree control of the expansion valve 4. Another discharge temperature control is performed.

  FIG. 3 shows a second embodiment, in which a bypass passage 20 is provided in parallel with the low-pressure side passage 3b of the internal heat exchanger 3, and a bypass valve 21 configured by an electromagnetic valve or the like is provided in the bypass passage 20. The bypass valve 21 is controlled to be opened and closed by the air conditioning controller 10.

  Specifically, the bypass valve 21 is kept closed during normal control in step S70 of FIG. Thereby, since the outlet refrigerant of the accumulator 8 flows through the low-pressure side flow path 3b of the internal heat exchanger 3, the outlet refrigerant of the radiator 2 is cooled by the action of the internal heat exchanger 3, thereby improving cycle efficiency. it can.

  On the other hand, the bypass valve 21 is maintained in the open state during the discharge temperature control in step S80 of FIG. Here, since the pressure loss of the bypass passage 20 is sufficiently small as compared with the low-pressure side flow path 3b of the internal heat exchanger 3, most of the outlet refrigerant of the accumulator 8 flows through the bypass passage 20 and flows into the internal heat exchanger. Bypass 3

  As a result, the compressor 1 is mixed with a small flow rate refrigerant that has been heated by passing through the low pressure side passage 3b of the internal heat exchanger 3 and a large flow rate refrigerant that bypasses the internal heat exchanger 3. Since the refrigerant is sucked, the superheat degree SH of the refrigerant sucked from the compressor can be reduced as compared with the case where the entire amount of the outlet refrigerant of the accumulator 8 is heated by the internal heat exchanger 3. Thereby, the discharge temperature of the compressor 1 can be controlled within the target value.

  In the second embodiment, the bypass valve 21 is configured as a three-way valve type that switches between the refrigerant flow to the low pressure side flow path 3b of the internal heat exchanger 3 and the refrigerant flow to the bypass passage 20, and the discharge temperature in step S80. At the time of control, the entire amount of the outlet refrigerant of the accumulator 8 may be passed through the bypass passage 20.

(Other embodiments)
In the first embodiment, in step S80, control for suppressing the discharge temperature Td to the discharge temperature target value is performed by capacity control (capacity reduction) of the compressor 1, but capacity control of the compressor 1 is performed. Instead of this, the discharge temperature control may be performed by controlling the opening degree of the expansion valve 4.

  That is, in step S80, the opening degree of the expansion valve 4 is forcibly increased by a predetermined amount, separated from the high pressure control for maximizing the COP, to lower the high pressure and raise the low pressure. Thereby, the compression ratio may be reduced to lower the discharge temperature.

  Further, for the discharge temperature control, the capacity control of the compressor 1 according to the first embodiment and the opening degree control of the expansion valve 4 may be performed simultaneously. Similarly, the control of the bypass valve 21 according to the second embodiment may be combined with the capacity control of the compressor 1 and the opening degree control of the expansion valve 4 to be performed simultaneously.

  In the first and second embodiments described above, the case where the refrigeration cycle according to the present invention is applied to a cycle dedicated to cooling operation has been described. However, the present invention is not limited to this, and heating operation or dehumidification operation is performed. Of course, the heat pump cycle may be applicable.

  In the first and second embodiments described above, the refrigeration cycle has been described in which the variable capacity compressor 1 is used to change the discharge refrigerant flow rate of the compressor 1 by the capacity control of the compressor 1. The present invention may be applied to a refrigeration cycle in which an electric compressor capable of continuously controlling the rotational speed is used as 1 and the discharge refrigerant flow rate is changed by controlling the rotational speed of the electric compressor 1.

  In the first and second embodiments described above, the low vehicle speed is determined based on the vehicle speed. However, since the vehicle speed and the engine speed are correlated, the low vehicle speed is determined based on the engine speed. You may do it.

  Further, the low vehicle speed according to the present invention may be only when the vehicle is completely stopped. Therefore, it is determined that the operation lever of the automatic transmission is in the neutral “N” position, and the vehicle is determined to be at the low vehicle speed. May be.

  Further, in the first and second embodiments described above, the high pressure is detected by the refrigerant pressure sensor 13 disposed on the outlet side of the radiator 2, but the discharge side of the compressor 1 reaches the inlet side of the expansion valve 4. Since the refrigerant pressure is substantially constant in the high pressure side flow path, the refrigerant pressure sensor 13 may be disposed at any location in the high pressure side flow path without being limited to the outlet side of the radiator 2.

In addition to CO ₂ , for example, a refrigerant such as ethylene, ethane, or nitric oxide may be used as the supercritical cycle refrigerant.

It is a lineblock diagram showing the refrigeration cycle for vehicles by a 1st embodiment of the present invention. It is a flowchart which shows the operation control of the refrigerating cycle by 1st Embodiment of this invention. It is a block diagram which shows the refrigerating cycle for vehicles by 2nd Embodiment of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Compressor, 2 ... Radiator, 3 ... Internal heat exchanger, 4 ... Expansion valve (pressure reduction means), 5 ... Evaporator,
11: Discharge refrigerant temperature sensor (temperature detection means).

Claims (7)

A compressor (1) driven by a vehicle travel engine and sucking and compressing a refrigerant composed of CO ₂ ;
A radiator (2) for cooling the refrigerant discharged from the compressor (1);
Decompression means (4) for decompressing the outlet side refrigerant of the radiator (2);
An evaporator (5) for evaporating the low-pressure refrigerant decompressed by the decompression means (4) ;
An internal heat exchanger (3) that performs heat exchange between the outlet side refrigerant of the radiator (2) and the suction side refrigerant of the compressor (1) ,
The refrigerant that has passed through the evaporator (5) is sucked into the compressor (1) after passing through the internal heat exchanger (3) ,
Furthermore, in the vehicle refrigeration cycle where the refrigerant pressure on the high pressure side is equal to or higher than the critical pressure of the refrigerant,
A temperature detecting means (11) disposed on the outer surface of the discharge refrigerant passage of the compressor (1) for detecting the discharge refrigerant temperature of the compressor (1);
Control means (S60, S80) for controlling the refrigeration cycle operating condition to the suppression side of the discharged refrigerant temperature when the detected temperature of the temperature detecting means (11) exceeds a predetermined target value;
During normal driving when the vehicle speed is equal to or higher than a predetermined value, a target value (Tb) for normal driving is set as the target value. On the other hand, at low vehicle speed when the vehicle speed is less than the predetermined value , at least the vehicle speed is Target value switching means for switching to a target value (Tc) at a low vehicle speed that is a predetermined amount higher than the target value (Tb) at the time of normal traveling as the target value at a low vehicle speed including when the vehicle stops at zero. S20 to S50). A vehicular refrigeration cycle. The predetermined amount is determined based on a difference between a detected temperature error of the temperature detecting means (11) during the normal running and a detected temperature error of the temperature detecting means (11) at the low vehicle speed. The refrigeration cycle for vehicles according to claim 1. 3. The vehicle refrigeration cycle according to claim 1, wherein the low vehicle speed includes both a low vehicle speed traveling when the vehicle speed is less than the predetermined value and a stop when the vehicle speed is zero. 4. . 3. The vehicle refrigeration cycle according to claim 1, wherein the low vehicle speed is only when the vehicle is stopped when the vehicle speed is zero. The vehicle refrigeration according to any one of claims 1 to 4, wherein the control of the refrigeration cycle operating condition is to control the operation of the compressor (1) to the discharge flow rate lowering side. cycle. The vehicle refrigeration cycle according to any one of claims 1 to 4, wherein the control of the refrigeration cycle operating condition is to control an opening degree of the decompression means (4) to an increase side. . A bypass valve (21) for allowing the outlet side refrigerant of the evaporator (5) to flow bypassing the internal heat exchanger (3);
The control of the refrigeration cycle operating condition is to control the bypass valve (21) so that the outlet side refrigerant of the evaporator (5) flows bypassing the internal heat exchanger (3). The vehicular refrigeration cycle according to any one of claims 1 to 4.

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