JP2007183086A - Supercritical refrigeration cycle - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a supercritical refrigeration cycle that can appropriately suppress an abnormal rise in compressor discharge refrigerant temperature and an abnormal rise in high pressure side pressure without using a variable displacement compressor. <P>SOLUTION: A compressor and a pressure reducing means of the supercritical refrigeration cycle comprise a fixed displacement compressor 1 and an electric expansion valve 4 with electrically controllable travel, respectively. A bypass passage 9 is defined to interconnect a high pressure side refrigerant passage and a low pressure side refrigerant passage, and a mechanical pressure-sensitive valve 9a configured to open when the pressure of the high pressure side refrigerant passage rises to a predetermined pressure set in advance is disposed in the bypass passage 9. When a discharge refrigerant temperature of the compressor 1 rises to a predetermined high temperature, a control device 10 controls the electric expansion valve 4 to increase the travel. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a supercritical refrigeration cycle in which the refrigerant pressure on the high pressure side is equal to or higher than the critical pressure of the refrigerant, and is suitable for vehicles.

  Conventionally, in this type of supercritical refrigeration cycle, Patent Literature 1 controls the opening degree of a pressure control valve that constitutes a decompression unit so that the refrigerant pressure on the high pressure side becomes a target high pressure, and this pressure control valve. And a relief valve is connected in parallel, and when the refrigerant pressure on the high pressure side rises above a predetermined value, the relief valve opens to prevent excessive rise of the refrigerant pressure on the high pressure side.

  Patent Document 2 describes that cycle capacity control (refrigerant flow rate control) is performed using a variable capacity compressor in a supercritical refrigeration cycle.

Meanwhile, as the refrigerant used in the supercritical refrigeration cycle, CO ₂ is typically, although the CO ₂ refrigerant can be solved a problem that ozone depletion by the refrigerant (R134a and the like) of the fluorocarbon, whereas, CO ₂ In a supercritical refrigeration cycle using a refrigerant, theoretical efficiency is low due to a difference in physical properties of the refrigerant as compared with a normal refrigeration cycle using a chlorofluorocarbon refrigerant.

Therefore, an internal heat exchanger is installed to improve efficiency, and heat exchange is performed between the low-pressure side compressor suction refrigerant and the high-pressure side radiator outlet refrigerant to increase the refrigerant enthalpy difference between the inlet and outlet of the evaporator. It is known to allow (see, for example, Patent Document 3).
JP-A-11-248272 JP-A-8-110104 JP 2003-74996 A

  However, 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.

  Although none of Patent Documents 1 to 3 describes a measure for suppressing the abnormal increase in the discharged refrigerant temperature, as in Patent Document 2, in a supercritical refrigeration cycle using a variable capacity compressor, When the discharge refrigerant temperature exceeds the compressor limit temperature, this temperature increase is judged and the capacity of the variable displacement compressor is forcibly reduced, thereby lowering the high-pressure side pressure and lowering the discharge refrigerant temperature. Can be considered.

  However, in the supercritical refrigeration cycle using a CO2 refrigerant, the high-pressure side pressure is significantly increased by about 8 times compared to a normal refrigeration cycle using a chlorofluorocarbon refrigerant. It is necessary to make a pressure-resistant structure. Therefore, an increase in the size and weight of the compressor is inevitable.

  In addition, when a variable displacement compressor is used, the size of the compressor is further increased by adding a variable displacement mechanism, and the weight is also increased. As a result, it becomes difficult to secure the mountability of the compressor in a vehicle having a large mounting space restriction, such as a light vehicle or a small vehicle.

  An object of the present invention is to provide a supercritical refrigeration cycle that can appropriately suppress an abnormal rise in compressor discharge refrigerant temperature and an abnormal rise in high-pressure side pressure without using a variable capacity compressor in view of the above points. And

In order to achieve the above object, in the present invention, in the supercritical refrigeration cycle in which the refrigerant pressure on the high pressure side is equal to or higher than the critical pressure of the refrigerant, the compressor is constituted by a fixed capacity compressor (1) having a constant discharge capacity, The decompression means is constituted by an electric expansion valve (4) whose opening degree can be electrically controlled,
A high-pressure side refrigerant passage from the discharge side of the compressor (1) to the inlet side of the electric expansion valve (4), and a low-pressure side from the outlet side of the electric expansion valve (4) to the suction side of the compressor (1) A bypass passage (9) communicating with the refrigerant passage;
A mechanical pressure responsive valve (9a) provided in the bypass passage (9) and opened when the pressure of the high-pressure side refrigerant passage rises above a predetermined pressure set in advance;
Temperature detecting means (11) for detecting the refrigerant temperature discharged from the compressor (1);
A detection signal from the temperature detection means (11) is input, and a control means (10) for controlling the electric expansion valve (4) is provided.
The first feature of the control means (10) is that the electrical expansion valve (4) is controlled to increase its opening when the discharged refrigerant temperature rises above a predetermined high temperature.

  According to this, it is possible to avoid an abnormal increase in the refrigerant temperature discharged from the compressor (1) by controlling the opening of the electric expansion valve (4).

  In addition, the high pressure side refrigerant pressure has a characteristic that it is faster than the fluctuation of the refrigerant temperature with respect to the fluctuation of the cycle operation condition, but the mechanical pressure responsive valve (9a) opens and closes directly in response to the pressure change. Compared with the case where an electric pressure sensor is used, the responsiveness of the opening / closing operation to the fluctuation of the high-pressure side refrigerant pressure is high. Therefore, the mechanical pressure responsive valve (9a) can quickly open the valve in response to an abnormal increase in the high-pressure side refrigerant pressure, thereby avoiding an abnormal increase in the high-pressure side refrigerant pressure.

  Therefore, even when the fixed capacity compressor (1) is used as the compressor of the supercritical refrigeration cycle, the cycle protection control can be appropriately executed.

  Further, the use of the fixed capacity compressor (1) can reduce the size of the compressor and reduce the weight of the compressor (1), and the ease of mounting the compressor (1) on a vehicle or the like is facilitated.

  In the first feature, the mechanical pressure responsive valve (9a) is specifically connected in parallel with the electric expansion valve (4).

In the present invention, in the supercritical refrigeration cycle in which the refrigerant pressure on the high pressure side is equal to or higher than the critical pressure of the refrigerant, the compressor is configured with a fixed capacity compressor (1) having a constant discharge capacity,
The decompression means includes a throttle passage (43) that decompresses and expands the high-pressure refrigerant, a valve body (44) that adjusts the opening of the throttle passage (43), and generates an electromagnetic attraction force to position the valve body (44). A linear solenoid type electric expansion valve (4) having a linearly displaced electromagnetic coil (44);
A force corresponding to the differential pressure between the high-pressure refrigerant on the upstream side of the throttle passage (43) and the low-pressure refrigerant on the downstream side of the throttle passage (43) acts as a force in the valve opening direction on the valve body (44). And
Furthermore, temperature detection means (11) for detecting the refrigerant discharge temperature of the compressor (1),
A control means (10) for receiving a detection signal of the temperature detection means (11) and controlling the linear solenoid type electric expansion valve (4);
The control means (10) has a second feature that the linear solenoid type electric expansion valve (4) is controlled to increase its opening degree when the discharged refrigerant temperature rises above a predetermined high temperature.

  According to the second feature of the present invention, the linear solenoid type electric expansion valve (4) itself can serve as the mechanical pressure responsive valve (9a) in the first feature.

  That is, the linear solenoid type electric expansion valve (4) according to the second feature has a valve body that has a force corresponding to the differential pressure between the high-pressure refrigerant upstream of the throttle passage (43) and the low-pressure refrigerant downstream of the throttle passage (43). Since it acts as a force in the valve opening direction on (44), when the high-pressure side refrigerant pressure rises, the force corresponding to the differential pressure increases to bring the valve element (44) in the valve opening direction. Can be displaced. Here, the displacement of the valve body (44) in the valve opening direction is performed quickly in direct response to the increase in the high-pressure side refrigerant pressure, so that the throttle passage (43) opens as the high-pressure side refrigerant pressure increases. The degree can be increased rapidly to avoid an abnormal increase in the high-pressure side refrigerant pressure.

  Therefore, according to the second feature of the present invention, the mechanical pressure responsive valve (9a) and the bypass passage (9) in the first feature are not required, and the same effect as the first feature is exhibited. it can.

  In the second feature, the valve body (44) is specifically disposed downstream of the throttle passage (43), and the dynamic pressure of the refrigerant flow passing through the throttle passage (43) corresponds to the differential pressure. It acts on the valve body (44) as a force.

  Further, in the second feature, the linear solenoid type electric expansion valve (4), specifically, the valve element (44) is displaced in the valve closing direction by increasing the electromagnetic attractive force of the electromagnetic coil (44). It is supposed to be.

  According to this, when the disconnection failure of the energization circuit of the electromagnetic coil (44) occurs, the valve element (44) is displaced in the valve opening direction due to disappearance of the electromagnetic attractive force of the electromagnetic coil (44). The open state of (4) can be secured. Therefore, it is possible to avoid problems such as occurrence of abnormal high pressure due to closing of the electric expansion valve (4) even when a disconnection failure occurs.

  In the first and second features described above, specifically, when the discharge refrigerant temperature rises to a predetermined high temperature, the opening of the electric expansion valve (4) is slightly opened until the discharge refrigerant temperature drops to a certain temperature. I try to increase it by degrees.

  By controlling such an opening degree of the expansion valve to be increased by a minute opening degree, a hunting phenomenon in which the discharge refrigerant temperature fluctuates greatly can be avoided.

  In the first and second features described above, more specifically, during normal operation in which the discharged refrigerant temperature does not rise to a predetermined high temperature, the actual high-pressure side refrigerant pressure becomes equal to the outlet refrigerant temperature of the radiator (2). The opening degree of the electric expansion valve (4) is controlled so as to be a target high pressure determined based on this.

  In addition, the code | symbol in the bracket | parenthesis of each said means and each means of a claim 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 the first embodiment. This refrigeration cycle uses CO ₂ whose refrigerant has a high pressure equal to or higher than a critical pressure (supercritical state). Therefore, this refrigeration cycle constitutes a supercritical refrigeration cycle.

  The compressor 1 sucks and compresses refrigerant by obtaining a driving force from a vehicle running engine (not shown) via a belt and a pulley. The transmission of the driving force to the compressor 1 is interrupted by an electromagnetic clutch 1a that constitutes a clutch means.

  Here, the compressor 1 is a fixed capacity type compressor in which the discharge capacity (geometric volume) of the refrigerant is always constant. Accordingly, the refrigerant discharge capacity (refrigerant circulation flow rate in the cycle) of the compressor 1 is adjusted by adjusting the operation rate of the compressor intermittent operation by the intermittent operation of the electromagnetic clutch 1a.

  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 cycle high-pressure side pressure becomes the target high-pressure during normal cycle operation. Further, as will be described later, the electric expansion valve 4 serves as a control valve for suppressing the discharge refrigerant temperature when the discharge refrigerant temperature of the compressor 1 rises abnormally.

  Specifically, the electric expansion valve 4 includes, for example, an electric actuator mechanism including a stepping motor and a valve mechanism driven by the electric actuator mechanism. The opening degree of the valve mechanism depends on the operating angle of the electric actuator mechanism. It can be finely adjusted by minute amounts.

  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. Inside air or outside air introduced through an inside / outside air switching box (not shown) is blown into the case 6 and cooled by the evaporator 5.

  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. This accumulator 8 is gas-liquid separation means for separating liquid refrigerant (saturated liquid phase refrigerant) and gas refrigerant (saturated gas phase refrigerant) as outlet refrigerant of the evaporator 5 and storing excess refrigerant in the cycle. The gas refrigerant separated in step (3) is led out toward the suction side of the compressor 1.

  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 high-pressure refrigerant on the outlet side of the radiator 2, and reduces the enthalpy of the refrigerant flowing into the evaporator 5. While increasing the enthalpy difference (refrigeration capacity) of the refrigerant | coolant in a refrigerant | coolant inlet side and an outlet side, it prevents that a liquid refrigerant is inhaled by the compressor 1. FIG.

  A bypass passage 9 is connected in parallel to the electric expansion valve 4, and this bypass passage 9 directly connects the high-pressure side refrigerant passage and the low-pressure side refrigerant passage. Here, the high-pressure side refrigerant passage is a passage from the discharge side of the compressor 1 to the inlet side of the electric expansion valve 4. The low-pressure side refrigerant passage is a passage from the outlet side of the electric expansion valve 4 to the suction side of the compressor 1.

  A mechanical pressure responsive valve 9a is disposed in the bypass passage 9, and the bypass passage 9 is opened and closed by the mechanical pressure responsive valve 9a.

  The mechanical pressure responsive valve 9a is a normally closed valve mechanism (relief valve) that normally maintains a closed state, and the pressure on the inlet side of the electric expansion valve 4, that is, the high-pressure side refrigerant pressure is cycle protection. For this reason, when the pressure rises above a predetermined value set for this purpose, the mechanical pressure responsive valve 9a is opened to suppress an increase in the high-pressure side refrigerant pressure. Therefore, the passage area when the mechanical pressure responsive valve 9 a is opened is sufficiently larger than the passage area of the electric expansion valve 4.

  The mechanical pressure responsive valve 9a is an on-off valve having a pure mechanical pressure responsive mechanism that responds to the high-pressure side refrigerant pressure. Specifically, a pressure responsive member such as a diaphragm that is displaced in response to the high-pressure side refrigerant pressure, and a spring means such as a coil spring that applies a spring load in a direction opposite to the high-pressure side refrigerant pressure to the pressure responsive member; The mechanical pressure responsive valve 9a can be configured using a valve mechanism connected to the pressure responsive member and displaced in accordance with the displacement of the pressure responsive member.

  Next, an outline of the electric control unit in the first embodiment will be described. The air-conditioning control device 10 is a control means including a microcomputer and its peripheral circuits, 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 the electromagnetic clutch 1a of the compressor 1, the cooling fan 2a of the radiator 2, the electric expansion valve 4, and the electric blower 7 is connected to the output side of the air-conditioning control device 10. Control the operation of air conditioning equipment.

  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. These various sensors 11 to 15 constitute various detection means of the present embodiment. In addition, various air conditioning operation signals are input to the air conditioning control device 10 from the operation members of the air conditioning operation panel 16 disposed near the instrument panel (instrument panel) in the passenger compartment.

  Specifically, the set temperature signal in the passenger compartment by the temperature setting switch, the compressor operation command signal by the air conditioner switch, the air volume switching signal of the electric blower 7 by the air volume switching switch, and the blowing mode switching of the indoor air conditioning unit by the blowing mode switching switch An air conditioning operation signal such as a signal and an inside / outside air introduction mode switching signal of the inside / outside air switching box by the inside / outside air switching switch is input from 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 engine speed, engine water temperature, and vehicle speed are input from the engine control device 17 to the air conditioning control device 10.

  Next, the operation of the first 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, and the liquid refrigerant and gas refrigerant of the low-pressure refrigerant are separated, and the liquid refrigerant is stored on the bottom side in the accumulator 8. On the other hand, the gas refrigerant gathers on the upper side in the accumulator 8 and is led out from the outlet on the accumulator 8 toward the suction side of the compressor 1.

  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 apparatus 10, and this control routine starts upon activation of the refrigeration cycle (compressor 1).

  First, it is determined whether the compressor discharge refrigerant temperature Td detected by the temperature sensor 11 is equal to or higher than a predetermined high temperature To (S10). The predetermined high temperature is a limit temperature set in consideration of the heat resistance temperature of the compressor 1, the heat resistance temperature of the rubber hose of the discharge side piping of the compressor 1, and is 150 ° C., for example.

  During normal operation, the compressor discharge refrigerant temperature Td is lower than a predetermined high temperature To. Therefore, the determination in step S10 is NO during normal operation, and the high pressure Pd is controlled by controlling the opening of the electric expansion valve 4 (S20).

  Specifically, the high pressure Pd is controlled by setting the target high pressure Po at which the cycle COP (coefficient of performance) is maximized by the radiator outlet side refrigerant temperature Tf detected by the refrigerant temperature sensor 12 on the outlet side of the radiator 2. The opening degree of the electric expansion valve 4 is controlled so that the actual high-pressure side pressure Pd detected by the refrigerant pressure sensor 13 on the outlet side of the radiator 2 becomes the target high-pressure pressure Po.

  That is, when the actual high-pressure side pressure Pd is higher than the target high-pressure pressure Po, the opening degree of the electric expansion valve 4 is increased. Conversely, when the actual high-pressure side pressure Pd is lower than the target high-pressure pressure Po, electric expansion is performed. The opening degree of the valve 4 is decreased.

  Next, the evaporator temperature is controlled by intermittent control of the operation of the compressor 1 (S30). Specifically, the evaporator temperature is controlled by calculating the target temperature TEO of the evaporator blown air based on the target temperature TAO of the air blown into the vehicle interior, the outside air temperature Tam, etc., and the actual evaporation detected by the temperature sensor 14. The operation of the compressor 1 is intermittently controlled so that the compressor outlet temperature Te becomes the evaporator target temperature TEO.

  That is, when the evaporator outlet temperature Te is higher than the evaporator target temperature TEO, the compressor 1 is operated. Conversely, when the evaporator outlet temperature Te is lower than the evaporator target temperature TEO, the compressor 1 is stopped. Thus, the operation rate of the compressor 1 is controlled by intermittently controlling the operation of the compressor 1, thereby adjusting the circulating refrigerant flow rate to the evaporator 5. As a result, the cooling capacity of the evaporator 5 is adjusted, and the evaporator outlet temperature Te can be controlled to the evaporator target temperature TEO. The minimum temperature of the evaporator target temperature TEO is determined to be slightly higher than 0 ° C. (around 3 ° C.) in order to prevent the evaporator 5 from being frosted.

  On the other hand, when the compressor discharge refrigerant temperature Td becomes equal to or higher than the predetermined high temperature To, the determination in step S10 becomes YES, and the opening degree of the electric expansion valve 4 is increased by a predetermined amount (S40). Specifically, the opening degree of the electric expansion valve 4 is increased by a predetermined amount from the opening degree before the determination in step S40. In this embodiment, the stroke of the valve mechanism of the electric expansion valve 4 is increased by 0.01 mm to increase the valve mechanism opening by a predetermined amount. Here, since the total stroke of the valve mechanism of the electric expansion valve 4 is 2.0 mm, an increase in stroke of 0.01 mm corresponds to an increase in opening of 1/200.

  Next, the evaporator temperature is controlled by intermittent control of the compressor 1 (S50). Since the control of the evaporator temperature may be the same as that in step S30 described above, a detailed description thereof will be omitted.

  Next, it is determined whether or not the elapsed time t after increasing the expansion valve opening is equal to or longer than the predetermined time to (S60), and waits while the elapsed time t is less than the predetermined time to, and the elapsed time t is the predetermined time. If it is greater than or equal to, the process proceeds to step S70. In this step S70, it is determined whether or not the compressor discharge refrigerant temperature Td has decreased to a value (To−α) that is equal to or lower than the predetermined high temperature To minus the predetermined temperature α.

  The predetermined time to is a time required for the compressor discharge refrigerant temperature Td to actually decrease after the expansion valve opening is increased. Further, the predetermined temperature α is a temperature of about 1 to 3 ° C., and is intended to prevent hunting of the opening / closing operation of the electric expansion valve 4.

  If the determination in step S70 is NO, the process returns to step S40, and the opening degree of the electric expansion valve 4 is increased by a predetermined amount. Accordingly, the opening degree of the electric expansion valve 4 is increased by a predetermined amount until the compressor discharge refrigerant temperature Td decreases to a temperature equal to or lower than (To−α). When the compressor discharge refrigerant temperature Td falls to a temperature equal to or lower than (To−α), the process returns to step S10, and the determination in step S10 is YES, so that the control during normal operation in steps S20 and S30 is performed again.

  As described above, the compressor discharge refrigerant temperature Td can be controlled to be equal to or lower than the predetermined high temperature To by performing the opening degree control of the electric expansion valve 4, so that a fixed capacity type compressor can be used as the compressor 1. Since the fixed capacity compressor 1 does not have a variable capacity mechanism as compared with the variable capacity compressor, the physique can be reduced in size and weight, and the mounting space in the vehicle can be reduced.

  Further, when the refrigerant pressure on the cycle high pressure side rises above a predetermined pressure set in advance, the mechanical pressure responsive valve 9a opens quickly in response to the increase in the refrigerant pressure on the high pressure side. Thereby, the bypass passage 9 directly communicates between the inlet side passage (high pressure side refrigerant passage) of the electric expansion valve 4 and the outlet side passage (low pressure side refrigerant passage) of the electric expansion valve 4.

  Here, since the passage area when the mechanical pressure responsive valve 9a is opened is sufficiently larger than the passage area on the electric expansion valve 4 side, the refrigerant pressure on the high pressure side is reduced by opening the mechanical pressure responsive valve 9a. . As a result, the abnormal state in which the refrigerant pressure on the high-pressure side rises above a predetermined pressure set in advance can be eliminated.

  Since the change in the refrigerant pressure is not accompanied by the movement of heat unlike the change in the refrigerant temperature, the refrigerant pressure changes abruptly as compared with the change in the refrigerant temperature. Therefore, in order to reliably avoid an abnormal increase in the refrigerant pressure, the quick response of the valve mechanism is very important.

  When the increase in the refrigerant pressure on the high-pressure side is electrically detected by the pressure sensor and the valve opening operation of the valve mechanism is electrically controlled, the response delay of the pressure sensor becomes a problem, and the prompt response of the valve mechanism However, according to the present embodiment, the mechanical pressure responsive valve 9a opens the valve mechanism in direct response to a change in the refrigerant pressure by a pressure responsive member such as a diaphragm. Therefore, it is possible to reliably avoid an abnormal increase in the refrigerant pressure.

(Second Embodiment)
In the first embodiment described above, an electric expansion valve of a type that finely adjusts the opening degree of the valve mechanism by a minute amount by an electric actuator mechanism such as a stepping motor is used as the electric expansion valve 4. A bypass passage 9 is connected in parallel to the valve 4 and a mechanical pressure responsive valve 9a is disposed in the bypass passage 9. In the second embodiment, the linear expansion type electric valve shown in FIG. This linear solenoid type electric expansion valve 4 itself has a function equivalent to that of the mechanical pressure responsive valve 9a.

  Thereby, as shown in FIG. 4, the bypass passage 9 and the mechanical pressure responsive valve 9a of 1st Embodiment are abolished.

  The linear solenoid type electric expansion valve 4 according to the second embodiment will be described in detail with reference to FIG. 3. Reference numeral 40 denotes a housing of the expansion valve 4, and the overall shape thereof is cylindrical. In the housing 40, a refrigerant passage is configured inside one end side (upper side in FIG. 4) of the cylindrical shape in the axial direction.

  Specifically, the high-pressure refrigerant chamber 41 connected to the outlet side of the high-pressure side passage 3a of the internal heat exchanger 3 shown in FIG. 4 and the low-pressure refrigerant after depressurization flow toward the inlet side of the evaporator 5. A low-pressure refrigerant chamber 42 and a throttle passage 43 positioned between the chambers 41 and 42 are formed on one end side in the axial direction of the housing 40. In addition, 41a is an inlet hole of the high-pressure refrigerant chamber 41, and 42a is an outlet hole of the low-pressure refrigerant chamber 42.

  The throttle passage 43 is a small-diameter circular hole whose passage area is significantly smaller than both the refrigerant chambers 41, 42, and decompresses and expands the high-pressure refrigerant in the high-pressure refrigerant chamber 41.

  A valve body 44 that adjusts the opening degree of the throttle passage 43 is disposed opposite to the downstream side of the throttle passage 43, that is, on the low-pressure refrigerant chamber 42 side. The valve body 44 has a cylindrical shape that extends in the axial direction of the housing 40. FIG. 3 shows a state of the maximum opening position (fully opened position) in which the valve body 44 is displaced to the position farthest from the throttle passage 43 (the lowermost position in FIG. 3).

  An electromagnetic coil 45 is arranged in a cylindrical shape on the other axial end side of the cylindrical shape inside the housing 40. In the housing 40, a region 40a located around the electromagnetic coil 45 is a magnetic part constituting the magnetic circuit.

  A large-diameter portion 44a is formed on the other end side in the axial direction of the housing 40 of the valve body 44. The large-diameter portion 44a is made of a magnetic material and serves as a movable iron core. The end surface of the large-diameter portion (magnetic body portion) 44a is opposed to the end surface of the inner peripheral magnetic body portion 40b of the housing 40 with a gap 46 having a predetermined dimension.

  When the electromagnetic coil 45 is energized, an electromagnetic attractive force acts between the end surface of the inner peripheral magnetic body portion 40 b of the housing 40 and the end surface of the large-diameter portion 44 a of the valve body 44, so that the valve body 44 approaches the throttle passage 43. It is displaced in the axial direction to the side (upper side in FIG. 3). As a result, the gap between the upper end of the valve body 44 and the throttle passage 43 changes, and the opening degree (passage area) of the throttle passage 43 changes.

  Next, the operation of the second embodiment will be described. In the linear solenoid type electric expansion valve 4 according to the second embodiment, the electromagnetic attractive force between the end surface of the inner peripheral magnetic body portion 40b of the housing 40 and the end surface of the large diameter portion 44a of the valve body 44 causes the valve body 44 to move. It acts as a force in the valve closing direction to be displaced toward the throttle passage 43 side (upper side in FIG. 3).

  On the other hand, the force corresponding to the differential pressure between the high-pressure refrigerant chamber 41 and the low-pressure refrigerant chamber 42, that is, the dynamic pressure of the refrigerant flow ejected into the low-pressure refrigerant chamber 42 through the throttle passage 43 causes the valve element 44 to It acts as a force in the valve opening direction that causes the valve to be displaced away from the throttle passage 43.

  For this reason, when the amount of current to the electromagnetic coil 45 is increased, the electromagnetic attractive force between the end surface of the inner peripheral magnetic body portion 40b of the housing 40 and the end surface of the large diameter portion 44a of the valve body 44 is increased. 44 is displaced to the throttle passage 43 side (upper side in FIG. 3), and the opening degree (passage area) of the throttle passage 43 is decreased.

  Conversely, when the amount of current to the electromagnetic coil 45 is reduced, the electromagnetic attractive force between the end surface of the inner peripheral magnetic body portion 40b of the housing 40 and the end surface of the large diameter portion 44a of the valve body 44 is reduced. 44 is displaced to the side away from the throttle passage 43 (lower side in FIG. 3) by the valve opening side force due to the dynamic pressure, and the opening degree (passage area) of the throttle passage 43 is increased.

  The specific valve opening degree control of the linear solenoid type electric expansion valve 4 according to the second embodiment may be basically the same as that of the first embodiment shown in FIG. Therefore, the description of the specific valve opening control according to the second embodiment is omitted.

  By the way, when the electric expansion valve 4 is constituted by an electric actuator mechanism comprising a stepping motor or the like and a valve mechanism driven by this electric actuator mechanism as in the first embodiment, the position of the valve mechanism is the stepping motor. It is fixed at a predetermined control position by an electric actuator mechanism composed of, for example.

  Therefore, the position of the valve mechanism is fixed at a fixed position unless the control signal of the electric actuator mechanism is changed. Therefore, according to the first embodiment, the electric expansion valve 4 itself cannot serve as a mechanical pressure responsive valve.

  On the other hand, in the linear solenoid type electric expansion valve 4 according to the second embodiment, the position of the valve body 44 is opened by the electromagnetic attraction force determined by the amount of current to the electromagnetic coil 45 and the dynamic pressure acting on the valve body 44. It is determined by the force in the valve direction.

  Therefore, in a state where the position of the valve body 44 is controlled to a predetermined position determined by the amount of current to the electromagnetic coil 45, if the high-pressure side refrigerant pressure suddenly rises for some reason, The valve opening side force due to pressure is increased rapidly. As a result, the valve body 44 is quickly displaced to the side away from the throttle passage 43 (the lower side in FIG. 3), and the valve opening is rapidly increased.

  As a result, an abnormal increase in the high-pressure side refrigerant pressure can be avoided by increasing the valve opening degree of the linear solenoid type electric expansion valve 4 itself. Therefore, the linear solenoid type electric expansion valve 4 itself can have the same function as the mechanical pressure responsive valve 9a of the first embodiment.

  In the second embodiment described above, the valve body 44 is displaced toward the side closer to the throttle passage 43 (the valve closing side) by the electromagnetic attractive force of the electromagnetic coil 45. Therefore, when the electromagnetic coil 45 is disconnected, etc. The electromagnetic attraction force disappears and the valve body 44 is displaced to the side away from the throttle passage 43 (the valve opening side). Therefore, the valve body 44 can be kept open even when the electromagnetic coil 45 is disconnected. Therefore, an abnormal increase in the high-pressure side refrigerant pressure due to the opening of the valve body 44 can be prevented in advance, which is safe.

(Other embodiments)
In the second embodiment described above, an example in which the spring force is not applied to the valve body 44 is shown, but the end surface of the inner peripheral magnetic body portion 40b of the housing 40 and the end surface of the large diameter portion 44a of the valve body 44 are shown. A spring may be arranged in the gap 46 between them, and a force to the side away from the throttle passage 43 (opening side) may be applied to the valve body 44 by this spring.

  Further, in the second embodiment described above, the valve body 44 is displaced toward the side closer to the throttle passage 43 (valve closing side) by the electromagnetic attractive force of the electromagnetic coil 45. The valve body 44 may be displaced to the side away from the throttle passage 43 (the valve opening side) by the electromagnetic attraction force of the coil 45. However, in this case, a spring that generates a spring force that displaces the valve body 44 toward the side closer to the throttle passage 43 (the valve closing side) is essential.

  In the first embodiment described above, the mechanical pressure responsive valve 9a is provided with the bypass passage 9 connected in parallel with the electric expansion valve 4, and the mechanical pressure responsive valve 9a is provided in the bypass passage 9. As long as the bypass passage communicates the high-pressure side refrigerant passage and the low-pressure side refrigerant passage of the cycle, the mechanical pressure responsive valve 9a may be provided in any bypass passage.

  For example, the mechanical pressure responsive valve 9a may be provided in a bypass passage that connects the discharge side and the suction side of the compressor 1. In this case, both the bypass passage and the mechanical pressure responsive valve 9a may be incorporated in the compressor 1.

  Further, when the mechanical pressure responsive valve 9a is provided in the bypass passage 9 connected in parallel with the electric expansion valve 4, the electric expansion valve 4, the bypass passage 9 and the mechanical pressure responsive valve 9a are configured as an integral structure. May be.

In the first embodiment described above, the supercritical refrigeration cycle is configured by using the CO ₂ refrigerant, but the supercritical refrigeration cycle is performed by using a refrigerant other than CO ₂ such as ethylene, ethane, and nitrogen oxide. It may be configured. This is the same in the second embodiment.

  In the first and second embodiments described above, the high pressure side pressure is detected by the refrigerant pressure sensor 13 disposed on the outlet side of the radiator 2, but from the discharge side of the compressor 1 to the inlet side of the expansion valve 4. Since the refrigerant pressure is substantially constant in the high-pressure side passage to reach, the refrigerant pressure sensor 13 may be disposed anywhere in the high-pressure side passage without being limited to the outlet side of the radiator 2.

  In the first and second embodiments described above, the case where 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 the heat pump cycle capable of heating operation or dehumidifying operation is used. Of course, the present invention may be applied, and the present invention can be applied to uses other than those for vehicles.

  In the first embodiment described above, the passage area when the mechanical pressure responsive valve 9a is opened is set sufficiently larger than the passage area of the electric expansion valve 4. However, the present invention is not limited to this. If the mechanical pressure responsive valve 9a is opened and the increase in the high-pressure side refrigerant pressure can be suppressed, the passage area when the mechanical pressure responsive valve 9a is opened is greater than the passage area of the electric expansion valve 4. Need not be set large.

1 is a schematic diagram of an overall configuration of a refrigeration cycle for a vehicle according to a first 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 sectional drawing of the electric expansion valve in 2nd Embodiment of this invention. It is a schematic diagram of the whole structure of the refrigeration cycle for vehicles by 2nd Embodiment of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Compressor, 2 ... Radiator, 3 ... Internal heat exchanger, 4 ... Electric expansion valve (pressure reduction means),
DESCRIPTION OF SYMBOLS 5 ... Evaporator, 9 ... Bypass passage, 9a ... Mechanical pressure responsive valve, 10 ... Control apparatus (control means), 11 ... Discharge refrigerant temperature sensor (temperature detection means), 43 ... Restriction passage, 44 ... Valve body,
45: Electromagnetic coil.

Claims (7)

A compressor (1) for sucking and compressing refrigerant;
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),
The refrigerant that has passed through the evaporator (5) is sucked into the compressor (1),
Furthermore, in the supercritical refrigeration cycle where the refrigerant pressure on the high pressure side is equal to or higher than the critical pressure of the refrigerant,
The compressor is composed of a fixed capacity type compressor (1) having a constant discharge capacity,
The pressure reducing means is composed of an electric expansion valve (4) whose opening degree can be electrically controlled,
A high-pressure side refrigerant passage extending from the discharge side of the compressor (1) to the inlet side of the electric expansion valve (4), and from the outlet side of the electric expansion valve (4) to the suction side of the compressor (1) A bypass passage (9) communicating with the low-pressure side refrigerant passage leading to
A mechanical pressure responsive valve (9a) provided in the bypass passage (9) and opened when the pressure of the high-pressure side refrigerant passage rises above a predetermined pressure set in advance;
Temperature detecting means (11) for detecting the refrigerant temperature discharged from the compressor (1);
A control means (10) for receiving the detection signal of the temperature detection means (11) and controlling the electric expansion valve (4);
The supercritical refrigeration cycle, wherein the control means (10) controls the electric expansion valve (4) to increase its opening when the discharge refrigerant temperature rises above a predetermined high temperature. The supercritical refrigeration cycle according to claim 1, wherein the mechanical pressure responsive valve (9a) is connected in parallel with the electric expansion valve (4). A compressor (1) for sucking and compressing refrigerant;
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),
The refrigerant that has passed through the evaporator (5) is sucked into the compressor (1),
Furthermore, in the supercritical refrigeration cycle where the refrigerant pressure on the high pressure side is equal to or higher than the critical pressure of the refrigerant,
The compressor is composed of a fixed capacity type compressor (1) having a constant discharge capacity,
The pressure reducing means includes a throttle passage (43) for decompressing and expanding high-pressure refrigerant, a valve body (44) for adjusting the opening of the throttle passage (43), and an electromagnetic suction force to generate the valve body (44). A linear solenoid type electric expansion valve (4) having an electromagnetic coil (44) for linearly displacing the position of
A force corresponding to the differential pressure between the high-pressure refrigerant upstream of the throttle passage (43) and the low-pressure refrigerant downstream of the throttle passage (43) acts as a force in the valve opening direction on the valve body (44). And
Furthermore, temperature detection means (11) for detecting the refrigerant discharge temperature of the compressor (1),
A control means (10) for receiving the detection signal of the temperature detection means (11) and controlling the linear solenoid type electric expansion valve (4);
The control means (10) controls the linear solenoid type electric expansion valve (4) to increase its opening degree when the discharged refrigerant temperature rises above a predetermined high temperature. cycle. The valve body (44) is disposed on the downstream side of the throttle passage (43), and the dynamic pressure of the refrigerant flow passing through the throttle passage (43) is a force corresponding to the differential pressure. The supercritical refrigeration cycle according to claim 3, wherein The supercritical refrigeration cycle according to claim 3 or 4, wherein the valve element (44) is displaced in the valve closing direction when the electromagnetic attractive force of the electromagnetic coil (44) is increased. . When the discharge refrigerant temperature rises to the predetermined high temperature, the control means (10) increases the opening of the electric expansion valve (4) by a small opening until the discharge refrigerant temperature decreases by a certain temperature. The supercritical refrigeration cycle according to any one of claims 1 to 5, wherein: The control means (10) is configured such that an actual high-pressure side refrigerant pressure is determined based on an outlet refrigerant temperature of the radiator (2) during a normal operation in which the discharge refrigerant temperature does not rise to the predetermined high temperature. The supercritical refrigeration cycle according to any one of claims 1 to 6, wherein the opening degree of the electric expansion valve (4) is controlled so as to be a high pressure.

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