Vehicle air conditioning system

Abstract

This improves heating performance under extremely low ambient temperature conditions without requiring expensive refrigerant pressure sensors. [Solution] The vehicle air conditioning system 1 includes a condenser 101 connected to the refrigerant discharge side of the compressor 100, an expansion valve 102 connected to the refrigerant outlet side of the condenser 101, an evaporator 103 into which the refrigerant that has passed through the expansion valve 102 flows, a gas-liquid separator 104 connected to the refrigerant outlet side of the evaporator 103, a refrigerant temperature sensor 122 for detecting the temperature of the refrigerant drawn into the compressor 100, and a control unit 50 that calculates an estimated refrigerant pressure based on pressure estimation information including the temperature of the refrigerant detected by the refrigerant temperature sensor 122 and the characteristics of the refrigerant, and controls the compressor 100 using the calculated estimated refrigerant pressure so that the pressure of the refrigerant drawn into the compressor 100 is higher than atmospheric pressure.

Description

Technical Field

[0001] The present disclosure relates to a vehicle air conditioner mounted on a vehicle such as an automobile.

Background Art

[0002] For example, as disclosed in Patent Documents 1 and 2, there are a heating mode in which the refrigerant compressed by a compressor is radiated to heat the air supplied into the vehicle interior, and a cooling mode in which the refrigerant condensed by a condenser is expanded and allowed to flow into an evaporator to cool the air supplied into the vehicle interior. A vehicle air conditioner that can be operated in a plurality of modes including such modes is known.

[0003] The vehicle air conditioner of Patent Document 1 sets a limit target value for the suction refrigerant temperature or suction refrigerant pressure of the compressor, and obtains a detection value by a sensor for the suction refrigerant temperature (suction refrigerant temperature) or suction refrigerant pressure (suction refrigerant pressure) of the compressor. It has a low-pressure protection function for adjusting the rotational speed of the compressor so that the detection value by the sensor does not fall below a predetermined limit target value. By having the low-pressure protection function, at the time of starting the compressor, the rotational speed of the compressor is adjusted with the limit target value as the limit upper value, and when the detection value drops to the limit upper value, the limit target value can be gradually decreased toward the limit lower value.

[0004] Further, in the vehicle air conditioner of Patent Document 2, an air-refrigerant indoor heat exchanger connected to the discharge side of the compressor, heat dissipation means for promoting heat dissipation of this air-refrigerant indoor heat exchanger, and a heat medium-refrigerant heat exchanger connected to the suction side of the compressor and performing heat exchange with the heat medium of the heat source are used. Operation is performed by a refrigeration cycle. Then, after the start of the heating operation of the refrigeration cycle, the pressure on the suction side of the compressor is detected by pressure detection means, and when the pressure detected by the pressure detection means drops, the heat dissipation by the heat dissipation means is stopped, and only when the pressure on the suction side of the compressor has been dropping for a longer time, it is disclosed that the refrigerant compression operation by the compressor is also stopped.

Prior Art Documents

Patent Documents

[0005] [Patent Document 1] Patent No. 6619572 [Patent Document 2] Special Publication No. 6-7031 [Overview of the Initiative] [Problems that the invention aims to solve]

[0006] Incidentally, as disclosed in Patent Documents 1 and 2, there is a Mollier diagram (shown in Figure 6) that shows the state of the refrigerant (R-1234yf) in a refrigeration cycle. As shown in Figure 6, this Mollier diagram shows the characteristics of the refrigerant, and the spacing between isobars becomes narrower as the pressure decreases. Therefore, due to the characteristics of the refrigerant, the impact of the accuracy of pressure detection in the low-pressure range of the refrigeration cycle on system performance is greater than in the high-pressure range. In particular, when heating operation under extremely low ambient temperature conditions, if negative pressure avoidance control is intentionally performed to ensure heating performance, if the accuracy of the refrigerant pressure detected by the refrigerant pressure sensor at the outlet of the heat-absorbing refrigerant heat exchanger is low, the compressor suction pressure may fall below the specified value, causing the compressor to stop unintentionally and potentially making it impossible to ensure heating performance.

[0007] Furthermore, refrigerant pressure sensors are precision instruments, and unlike industrial refrigerant pressure sensors, they are used in environments with significant vibration and ambient temperature fluctuations, which can lead to a decrease in detection accuracy.

[0008] Here, a refrigerant pressure sensor is provided in the refrigeration cycle of the vehicle air conditioning system to detect the pressure on the low-pressure side. By controlling the refrigeration cycle so that the pressure on the low-pressure side detected by this low-pressure refrigerant pressure sensor does not fall below or exceed a specified value, the compressor can be protected.

[0009] However, as mentioned above, the accuracy of detecting the low-pressure side has a significant impact on system performance, requiring a refrigerant pressure sensor with high accuracy and small tolerances. However, high accuracy and small tolerance refrigerant pressure sensors are expensive, and installing such sensors increases the cost of the vehicle's air conditioning system.

[0010] This disclosure is made in view of the above points, and its purpose is to improve heating performance under extremely low ambient temperature conditions without requiring the installation of expensive refrigerant pressure sensors. [Means for solving the problem]

[0011] To achieve the above objective, one aspect of this disclosure may be based on a vehicle air conditioning system mounted on a vehicle. The vehicle air conditioning system includes a compressor for compressing a refrigerant; a condenser connected to the refrigerant discharge side of the compressor into which the refrigerant discharged from the compressor flows; an expansion valve connected to the refrigerant outlet side of the condenser for expanding the refrigerant that has flowed out of the condenser; an evaporator into which the refrigerant that has passed through the expansion valve flows; a gas-liquid separator connected to the refrigerant outlet side of the evaporator for separating the refrigerant that has flowed out of the evaporator into gas-liquid phase and supplying the gaseous refrigerant to the suction side of the compressor; a refrigerant temperature sensor for detecting the temperature of the refrigerant drawn into the compressor; and a control unit that calculates an estimated refrigerant pressure based on pressure estimation information including the temperature of the refrigerant detected by the refrigerant temperature sensor and the characteristics of the refrigerant, and controls the compressor using the calculated estimated refrigerant pressure so that the pressure of the refrigerant drawn into the compressor is higher than atmospheric pressure.

[0012] In this configuration, the high-temperature, high-pressure refrigerant compressed by the compressor flows into the condenser and condenses by exchanging heat with the outside air. By placing this condenser inside the vehicle's interior, it becomes possible to heat the air and supply it to various parts of the interior. The refrigerant condensed in the condenser is depressurized as it passes through the expansion valve, and the depressurized refrigerant flows into the evaporator and evaporates by exchanging heat with the outside air. By placing this evaporator inside the vehicle's interior, it becomes possible to cool the air and supply it to various parts of the interior. By changing the mixing ratio of the air that has passed through the condenser and the air that has passed through the evaporator, it is possible to generate conditioned air at the desired temperature. The refrigerant that flows out of the evaporator flows into a gas-liquid separator where it is separated into gaseous and liquid phase refrigerants. The gaseous phase refrigerant is supplied to the suction side of the compressor, compressed by the compressor, and then discharged as high-temperature, high-pressure refrigerant.

[0013] In this refrigeration cycle, which includes a compressor, condenser, expansion valve, evaporator, and gas-liquid separator, the temperature of the refrigerant drawn into the compressor is detected by a refrigerant temperature sensor. Based on the detected refrigerant temperature and pressure estimation information including the refrigerant characteristics, the control unit calculates the estimated refrigerant pressure. This makes it possible to intentionally and accurately control the refrigerant pressure on the compressor's suction side to near atmospheric pressure using the estimated refrigerant pressure based on the temperature detected by the refrigerant temperature sensor, which has higher detection accuracy than the pressure sensor, without using the refrigerant pressure detected by the pressure sensor. As a result, heating performance under extremely low ambient temperature conditions is improved.

[0014] The control unit can control the compressor so that the refrigerant on the refrigerant outlet side of the evaporator does not become overheated. As a result, the state of the refrigerant from the refrigerant outlet side of the evaporator to the gas-liquid separator becomes saturated or in a gas-liquid mixed phase state, resulting in a correlation between the refrigerant pressure and temperature. Therefore, the calculation accuracy when estimating the refrigerant pressure from the refrigerant temperature detected by the refrigerant temperature sensor can be improved.

[0015] The refrigerant temperature sensor may be provided between the evaporator and the gas-liquid separator. This allows for the detection of the refrigerant temperature on the low-pressure side closer to the compressor, thereby improving the accuracy of the calculation when estimating the refrigerant pressure.

[0016] The vehicle air conditioning system may further include a pressure sensor for detecting the pressure of the refrigerant drawn into the compressor. When heating is started, the control unit can calculate an estimated refrigerant pressure based on pressure estimation information including the temperature of the refrigerant detected by the refrigerant temperature sensor and the characteristics of the refrigerant, and use the calculated estimated refrigerant pressure to control the compressor so that the pressure of the refrigerant drawn into the compressor becomes higher than atmospheric pressure. By including a pressure sensor, control can be performed based on the refrigerant pressure detected by the pressure sensor, and especially when heating is started at a low outside temperature, the compressor can be controlled using an estimated refrigerant pressure calculated based on the temperature of the refrigerant detected by the refrigerant temperature sensor.

[0017] The pressure sensor and the refrigerant temperature sensor may be provided between the evaporator and the gas-liquid separator. The control unit can also determine whether the refrigerant on the refrigerant outlet side of the evaporator is in an overheated state, and if it is determined that it is not in an overheated state, it can calculate the estimated refrigerant pressure. This makes it possible to calculate the estimated refrigerant pressure when the refrigerant pressure and temperature are correlated. [Effects of the Invention]

[0018] As explained above, according to the technology of this disclosure, the estimated refrigerant pressure can be calculated from the refrigerant temperature, and the compressor can be controlled using the calculated estimated refrigerant pressure so that the pressure of the refrigerant drawn into the compressor is higher than atmospheric pressure. Therefore, heating performance under extremely low ambient temperature conditions can be improved without the need to install expensive refrigerant pressure sensors. [Brief explanation of the drawing]

[0019] [Figure 1] Figure 1 shows a refrigeration cycle for a vehicle air conditioning system according to an embodiment of the present invention. [Figure 2] FIG. 2 is a diagram showing the indoor-side configuration of the vehicle air conditioner according to an embodiment of the present invention. [Figure 3] FIG. 3 is a block diagram of the vehicle air conditioner. [Figure 4] FIG. 4 is a Mollier diagram of the accumulator cycle. [Figure 5] FIG. 5 is a flowchart showing the control of the refrigeration cycle. [Figure 6] FIG. 6 is a Mollier diagram of the refrigerant.

MODE FOR CARRYING OUT THE INVENTION

[0020] Hereinafter, embodiments of the present invention will be described in detail based on the drawings. Note that the following description of the preferred embodiments is merely exemplary in nature and is not intended to limit the present invention, its applications, or its uses.

[0021] FIG. 1 is a diagram showing a refrigeration cycle (also referred to as a refrigeration cycle device) S of a vehicle air conditioner according to an embodiment of the present invention. FIG. 2 is a diagram showing the vehicle air conditioner 1. The vehicle air conditioner 1 shown in FIG. 2 is an example, and the structure of the vehicle air conditioner 1 is not limited to the structure shown in FIG. 2.

[0022] The vehicle air conditioner 1 is a device mounted on a vehicle such as an automobile, and is configured to air-condition the vehicle interior. The vehicle on which the vehicle air conditioner 1 is mounted may be, for example, a passenger car or a freight car. Further, the vehicle on which the vehicle air conditioner 1 is mounted may be an electric vehicle equipped with a driving force generating motor and a power battery for supplying power to the driving force generating motor, or a hybrid vehicle equipped with both an internal combustion engine and a driving force generating motor and a power battery. In the case of a hybrid vehicle, for example, it may be a plug-in type hybrid vehicle capable of charging the power battery from an external charging facility. <000​In describing this embodiment, the configuration of the interior unit A of the vehicle air conditioning system 1 will be explained first. This interior unit A is configured to introduce either or both of the air inside the vehicle's interior (recirculating air) and the air outside the vehicle's interior (outside air), adjust the temperature, and then supply it to various parts of the vehicle's interior. The vehicle's interior includes, although not shown, a front seat consisting of a driver's seat and a passenger seat, and a rear seat located behind the front seat.

[0024] The indoor unit A comprises an air conditioning casing 30, a control unit (control section) 50 (shown in Figure 3), a cooling heat exchanger 32, and a heating heat exchanger 33. The air conditioning casing 30 is housed inside an instrument panel (not shown) located, for example, at the front end of the passenger compartment. The air conditioning casing 30 comprises, in order from the upstream side to the downstream side in the airflow direction, a blower casing 20, a temperature control unit 31, and a blower direction switching unit 40.

[0025] The ventilation casing 20 has an outside air inlet 2a and an inside air inlet 2b. The outside air inlet 2a communicates with the outside of the vehicle via, for example, an intake duct (not shown), and is designed to introduce outside air. The inside air inlet 2b opens inside the instrument panel and is designed to introduce inside air into the vehicle and circulate it within the vehicle. The amount of outside air introduced through the outside air inlet 2a is the amount of outside air introduced. The amount of inside air introduced through the inside air inlet 2b is the amount of inside air circulated.

[0026] Inside the air casing 20, air inlet 2a and air inlet 2b are opened and closed by air inlet 2a and air inlet 2b, respectively. Air inlet 6 and air inlet 7 are driven by air inlet 9 to rotate to any desired angle. This switches the intake mode. Air inlet 9 is controlled by a control unit 50 as described later, and is a conventionally known torque-variable type electric actuator.

[0027] As shown in Figure 2, the ventilation casing 20 is equipped with a blower 5 as an air conditioning device. When the blower 5 is operated, air circulates inside the ventilation casing 20, and conditioned air is supplied to the temperature control unit 31 located downstream of the ventilation casing 20.

[0028] The temperature control unit 31 is designed to allow air to circulate inside and is responsible for adjusting the temperature of the air conditioning air introduced from the blower casing 20. Inside the temperature control unit 31 are a cooling heat exchanger 32, a heating heat exchanger 33, and an air mix damper 34. The cooling heat exchanger 32 and the heating heat exchanger 33 are air conditioning components.

[0029] Specifically, a cold air passage R1 is formed inside the temperature control unit 31 on the upstream side in the direction of airflow, and a cooling heat exchanger 32 is housed in this cold air passage R1. The cooling heat exchanger 32 is a device for exchanging heat between the refrigerant and the air introduced into the vehicle cabin. Furthermore, the downstream side of the cold air passage R1 branches into a warm air passage R2 and a bypass passage R3, and a heating heat exchanger 33 is housed in the warm air passage R2.

[0030] The air mix damper 34 is positioned between the cooling heat exchanger 32 and the heating heat exchanger 33, and opens and closes the upstream end of the hot air passage R2 and the upstream end of the bypass passage R3. The air mix damper 34 can be made of, for example, a plate-shaped member and has a pivot shaft (not shown) that is rotatably supported against the side wall of the temperature control unit 31. The air mix damper 34 is driven by the air mix actuator 35 to rotate to any desired angle. The air mix actuator 35 is controlled by the control unit 50 shown in Figure 3 and is a torque-variable electric actuator. A link member (not shown) is provided between the pivot shaft of the air mix damper 34 and the air mix actuator 35 to transmit the force output from the air mix actuator 35 to the pivot shaft of the air mix damper 34.

[0031] When the air mix damper 34 fully opens the upstream end of the warm air passage R2 and fully closes the upstream end of the bypass passage R3, the entire amount of cold air generated in the cold air passage R1 flows into the warm air passage R2 and is heated, so warm air flows into the air outlet direction switching section 40. On the other hand, when the air mix damper 34 fully closes the upstream end of the warm air passage R2 and fully opens the upstream end of the bypass passage R3, the entire amount of cold air generated in the cold air passage R1 flows into the bypass passage R3, so cold air flows into the air outlet direction switching section 40. When the air mix damper 34 is in the rotated position that opens the upstream ends of both the warm air passage R2 and the bypass passage R3, cold air and warm air flow into the air outlet direction switching section 40 in a mixed state. The amount of cold air and warm air flowing into the air outlet direction switching section 40 is changed by the rotation position of the air mix damper 34, thereby generating conditioned air at the desired temperature. Furthermore, the air mix damper 34 is not limited to the plate-shaped damper described above; any configuration that allows for the adjustment of the cold air volume and the hot air volume is acceptable. For example, it may be a rotary damper, a film damper, a louver damper, etc. Also, the temperature control configuration does not have to be one of those described above; any configuration that allows for the adjustment of the cold air volume and the hot air volume is acceptable.

[0032] The air outlet direction switching section 40 is the part through which the temperature-controlled conditioned air from the temperature control section 31 flows, and also supplies the temperature-controlled conditioned air to various parts of the passenger compartment. The air outlet direction switching section 40 has a defroster outlet 42, a vent outlet 43, and a heat outlet 45. The defroster outlet 42 is connected to a defroster nozzle 41 formed on the instrument panel. This defroster outlet 42 is for supplying conditioned air to the interior surface of the front windshield glass (window glass) G. Inside the defroster outlet 42, there is a defroster damper 42a for opening and closing the defroster outlet 42.

[0033] The vent outlet 43 is connected to a vent nozzle 44 formed in the instrument panel. The vent nozzle 44 is for supplying conditioned air to the upper bodies of the front seat occupants and is provided in the center of the instrument panel in the vehicle width direction and on both the left and right sides. Inside the vent outlet 43 is a vent damper 43a for opening and closing the vent outlet 43.

[0034] The heat outlet 45 is connected to a heat duct 46 that extends to near the occupant's feet. The heat duct 46 is for supplying conditioned air to the occupant's feet. Inside the heat outlet 45 is a heat damper 45a for opening and closing the heat outlet 45.

[0035] The defroster damper 42a, vent damper 43a, and heat damper 45a each have a pivot shaft (not shown) that is rotatably supported with respect to the side wall of the air outlet direction switching section 40. The defroster damper 42a, vent damper 43a, and heat damper 45a are opened and closed by the air outlet direction switching actuator 47. The air outlet direction switching actuator 47 is a torque-variable electric actuator. A link member (not shown) is provided between the pivot shafts of the defroster damper 42a, vent damper 43a, and heat damper 45a and the air outlet direction switching actuator 47, which transmits the force output from the air outlet direction switching actuator 47 to the pivot shafts of the defroster damper 42a, vent damper 43a, and heat damper 45a.

[0036] The airflow direction switching actuator 47 is controlled by the control unit 50. The defroster damper 42a, vent damper 43a, and heat damper 45a are linked together via a link (not shown), and can be switched to any of several airflow modes, such as a defroster mode in which the defroster damper 42a is open and the vent damper 43a and heat damper 45a are closed, a vent mode in which the defroster damper 42a and heat damper 45a are closed and the vent damper 43a is open, a heat mode in which the defroster damper 42a and vent damper 43a are closed and the heat damper 45a is open, a def-heat mode in which the defroster damper 42a and heat damper 45a are open and the vent damper 43a is closed, and a bi-level mode in which the vent damper 43a and heat damper 45a are open and the defroster damper 42a is closed.

[0037] In this embodiment, the blower unit is capable of switching between an internal air circulation mode, an external air intake mode, and an internal / external air two-layer flow mode, which is enabled by first and second internal / external air switching dampers 6 and 7 to open only the internal air inlet 2b, an external air intake mode, and an internal / external air two-layer flow mode, which is enabled to open both the internal air inlet 2b and the external air inlet 2a. However, the present invention can also be applied to a blower unit that can switch between an internal air circulation mode and an external air intake mode without having an internal / external air two-layer flow mode.

[0038] The first internal / external air switching damper 6 and the second internal / external air switching damper 7 are driven by the internal / external air switching actuator 9 shown in Figure 2. In this embodiment, the first internal / external air switching damper 6 and the second internal / external air switching damper 7 are driven as follows: In the outside air introduction mode, only outside air is introduced into the air casing 20 by the first internal / external air switching damper 6 and the second internal / external air switching damper 7, and in the internal air circulation mode, only internal air is introduced into the air casing 20 by the first internal / external air switching damper 6 and the second internal / external air switching damper 7. In the internal / external air two-layer flow mode, both outside air and internal air are introduced into the air casing 20 by the first internal / external air switching damper 6 and the second internal / external air switching damper 7. The internal / external air two-layer flow mode is used during heating.

[0039] Switching between internal air circulation mode, external air intake mode, and dual internal / external airflow mode is performed by the conventionally known automatic air conditioning control system. By using the dual internal / external airflow mode, in winter, relatively dry external air can be supplied to the defrost vents to effectively clear condensation from the front windshield, while relatively warm internal air can be supplied to the heat vents to improve heating efficiency.

[0040] Furthermore, a fan 5a and a blower motor 5b that rotates the fan 5a are provided on the lower side of the air casing 20. When voltage is applied to the blower motor 5b, the rotational force of the blower motor 5b is transmitted to the fan 5a, causing the fan 5a to rotate. A control unit 50 is connected to the blower motor 5b, and the control unit 50 applies voltage to the blower motor 5b so that it reaches a desired rotational speed.

[0041] As shown in Figure 3, the vehicle air conditioning system 1 includes, for example, an outside air temperature sensor (outside air temperature detection means) 51, an inside air temperature sensor (inside air temperature detection means) 52, a solar radiation sensor (solar radiation detection means) 53, an evaporator temperature sensor 54, and an air conditioning operation switch 55. The outside air temperature sensor 51, the inside air temperature sensor 52, the solar radiation sensor 53, and the evaporator temperature sensor 54 are connected to the control unit 50 and output signals to the control unit 50. The air conditioning operation switch 55 is also connected to the control unit 50 so that the control unit 50 can detect the operation status by the occupant.

[0042] The outside air temperature sensor 51 is installed, for example, outside the vehicle, at the front or side of the vehicle, and detects the temperature of the air around the vehicle (outside air temperature). The inside air temperature sensor 52 is installed, for example, inside the vehicle, near the instrument panel, and detects the temperature of the air inside the vehicle (inside air temperature). The solar radiation sensor 53 is installed, for example, inside the vehicle, near the instrument panel, and detects the amount of solar radiation irradiating the vehicle.

[0043] The interior temperature sensor 52, the exterior temperature sensor 51, and the solar radiation sensor 53 can detect information related to the temperature the occupants feel. Specifically, the interior temperature output from the interior temperature sensor 52 is approximately equal to the ambient temperature for the occupants. A high interior temperature means the occupants feel warm, and a low interior temperature means the occupants feel cold. Similarly, a high exterior temperature output from the exterior temperature sensor 51 means the occupants feel warm, and a low exterior temperature means the occupants feel cold. Furthermore, a high amount of solar radiation output from the solar radiation sensor 53 means the occupants feel warm, and a low amount of solar radiation means the occupants feel cold.

[0044] The evaporator outlet temperature sensor 54 is positioned downstream of the cooling heat exchanger 32 in the airflow direction and detects the surface temperature of the cooling heat exchanger 32. The evaporator outlet temperature sensor 54 also functions as an evaporator outlet temperature detection means for detecting the temperature of the evaporator outlet, which is the temperature of the air flowing out of the cooling heat exchanger 32. Since the evaporator outlet temperature sensor 54 is in contact with or close to the downstream surface of the cooling heat exchanger 32 in the airflow direction, the evaporator outlet temperature sensor 54 can detect the temperature of the downstream surface of the cooling heat exchanger 32 in the airflow direction, that is, the temperature of the air flowing out of the cooling heat exchanger 32.

[0045] The air conditioning control switches 55 are located on the instrument panel, for example, and consist of switches such as an ON / OFF switch for the vehicle air conditioning system 1, an airflow switch to increase or decrease the amount of air blown, a temperature setting switch to set the temperature of the passenger compartment, an internal / external air switch to switch between internal air circulation, external air intake, and internal / external air mixing modes, an auto switch to select whether or not to use automatic air conditioning control, an air outlet mode switch to switch the direction of airflow, a defroster switch, and the like.

[0046] The control unit 50 controls the indoor / outdoor air switching actuator 9, air mix actuator 35, air outlet direction switching actuator 47, blower motor 5b, and the refrigerant compressor, first expansion valve, second expansion valve, etc., described later, based on signals (output values) output from the outdoor air temperature sensor 51, indoor air temperature sensor 52, solar radiation sensor 53, evaporator temperature sensor 54, and other sensors, as well as the operating status of the air conditioning operation switch 55. The control unit 50 has a microcomputer including a central processing unit, ROM (Read-only memory), and RAM (Random-access memory), as well as various storage devices, and controls each part by a program pre-stored in the storage device.

[0047] In other words, when automatic air conditioning control is selected by the auto switch of the air conditioning control switch 55, the system determines the target discharge temperature of the conditioned air supplied to the passenger compartment based on the temperature outside the passenger compartment, the temperature inside the passenger compartment, the amount of solar radiation, the engine coolant temperature, the surface temperature of the cooling heat exchanger 32, the set temperature, etc. It also calculates the opening degree of the air mix damper 34 to achieve this target discharge temperature, and controls the air mix actuator 35 to rotate the air mix damper 34 so that the air mix damper 34 opens to this degree. As a result, the temperature of the conditioned air becomes the target discharge temperature.

[0048] Furthermore, the control unit 50 controls the airflow direction switching actuator 47 so that the airflow mode is mainly vent mode during cooling, and so that the airflow direction switching actuator 47 is mainly heat mode during heating. In addition, even during cooling or heating, if the setting is weak, the control unit 50 controls the airflow direction switching actuator 47 so that it is bi-level mode or defrost mode. Furthermore, when the defroster switch on the air conditioning operation switch 55 is turned ON, the control unit 50 controls the airflow direction switching actuator 47 so that the airflow mode is defroster mode.

[0049] For example, when heating a vehicle that has been left idle for a long time in winter, or when cooling a vehicle that has been left idle for a long time in summer, the difference between the target outlet temperature and the interior temperature becomes large. In such cases, the control unit 50 controls the blower motor 5b to increase the airflow, but the occupant can also adjust the airflow to their liking by operating the airflow selector switch. In addition, in automatic air conditioning control, the blower motor 5b is controlled so that the airflow decreases as the difference between the target outlet temperature and the interior temperature decreases. The control of the blower motor 5b is performed by changing the applied voltage, but it is not limited to this; it is sufficient if the rotation speed of the blower motor 5b can be changed.

[0050] The refrigeration cycle S shown in Figure 1 comprises a compressor 100 for compressing the refrigerant (R-1234yf), a condenser 101, an expansion valve 102, an evaporator 103, and a gas-liquid separator (accumulator) 104. The compressor 100, although not shown, is an electric compressor having a motor and a compression mechanism rotated by the motor. The compressor 100 is controlled by a control unit 50, which is responsible for starting, stopping, and changing the rotation speed of the compression mechanism.

[0051] The upstream end of the first refrigerant piping 111 is connected to the refrigerant discharge port (discharge port for high-temperature, high-pressure refrigerant) of the compressor 100. The downstream end of the first refrigerant piping 111 is connected to the refrigerant inlet of the condenser 101. Therefore, the condenser 101 is a heat exchanger connected to the refrigerant discharge side of the compressor 100 via the first refrigerant piping 111, into which the refrigerant discharged from the refrigerant discharge port of the compressor 100 flows.

[0052] The condenser 101, although not shown in the diagram, can have a structure that includes, for example, a core section made up of multiple tubes and fins stacked alternately, and a header tank that distributes the refrigerant to the tubes. The refrigerant flowing through the multiple tubes of the condenser 101 exchanges heat with the air (external air) passing outside the condenser 101, thereby releasing heat and causing the refrigerant to condense.

[0053] The upstream end of the second refrigerant pipe 112 is connected to the refrigerant outlet side of the condenser 101. The downstream end of the second refrigerant pipe 112 is connected to the refrigerant inlet of the expansion valve 102. Therefore, the expansion valve 102 is connected to the refrigerant outlet side of the condenser 101 and is a device that expands the refrigerant that has flowed out of the condenser 101. The expansion valve 102 may be an electrically operated expansion valve whose opening degree is controlled by the control unit 50.

[0054] The upstream end of the third refrigerant pipe 113 is connected to the refrigerant outlet side of the expansion valve 102. The downstream end of the third refrigerant pipe 113 is connected to the refrigerant inlet of the evaporator 103. Therefore, the evaporator 103 is a heat exchanger into which the refrigerant that has passed through the expansion valve 102 flows.

[0055] The evaporator 103, although not shown in the figure, can have a structure that includes, for example, a core section made up of multiple tubes and fins stacked alternately, and a header tank that distributes the refrigerant to the tubes. The refrigerant flowing through the multiple tubes of the evaporator 103 exchanges heat with the air (outside air) passing outside the evaporator 103, and absorbs heat, causing the refrigerant to evaporate.

[0056] The upstream end of the fourth refrigerant pipe 114 is connected to the refrigerant outlet side of the evaporator 103. The downstream end of the fourth refrigerant pipe 114 is connected to the refrigerant inlet of the gas-liquid separator 104. The gas-liquid separator 104 is connected to the refrigerant outlet side of the evaporator 103 via the fourth refrigerant pipe 114 and is a device for separating the refrigerant flowing out of the evaporator 103 into gas and liquid phases and supplying the gas phase refrigerant to the suction side of the compressor 100. The first refrigerant pipe 111, the second refrigerant pipe 112, the third refrigerant pipe 113, and the fourth refrigerant pipe 114 are components that constitute the refrigeration cycle S.

[0057] The refrigeration cycle S of this embodiment includes a gas-liquid separator 104 and can therefore be called an accumulator cycle. A Mollier diagram of the accumulator cycle is shown in Figure 4, and in the accumulator cycle, the refrigerant is in the state shown in Figure 4.

[0058] For example, by using the evaporator 103 as a cooling heat exchanger 32, the air circulating inside the temperature control unit 31 can be cooled. On the other hand, by using the condenser 101 as a heating heat exchanger 33, the air circulating inside the temperature control unit 31 can be heated. In this way, the evaporator 103 and the condenser 101 can be used as heat exchangers in the air conditioning system, and during heating, the heat released from the condenser 101 can be used to heat the interior of the vehicle.

[0059] The vehicle air conditioning system 1 includes a refrigerant state detection unit 120 that detects the pressure of the refrigerant drawn into the compressor 100 and the temperature of the refrigerant drawn into the compressor 100. The refrigerant state detection unit 120 includes a pressure sensor (refrigerant pressure sensor) 121 for detecting the pressure of the refrigerant drawn into the compressor 100, and a temperature sensor (refrigerant temperature sensor) 122 for detecting the temperature of the refrigerant drawn into the compressor 100. The pressure sensor 121 and the temperature sensor 122 are installed between the evaporator 103 and the gas-liquid separator 104. Specifically, since the temperature and pressure of the refrigerant flowing through the fourth refrigerant piping 114 are approximately equal to the temperature and pressure of the refrigerant drawn into the compressor 100, the temperature sensor 122 is installed to detect the temperature of the refrigerant flowing through the fourth refrigerant piping 114, and the pressure sensor 121 is installed to detect the pressure of the refrigerant flowing through the fourth refrigerant piping 114. This allows the refrigerant pressure and temperature to be detected at approximately the same location. The refrigerant state detection unit 120 may also be installed at the refrigerant outlet of the evaporator 103 or the refrigerant inlet of the gas-liquid separator 104, etc.

[0060] If we consider the case where the refrigerant state detection unit 120 is installed on the main body of the evaporator 103, in this case, the actual refrigerant temperature will be detected with a delay due to heat conduction in the evaporator 103, and temperature correction will become difficult due to errors in the heat conduction rate caused by the refrigerant flow rate, flow velocity, ambient temperature, etc. Also, if we consider the case where the refrigerant state detection unit 120 is installed to detect the temperature of the medium (water, air) after passing through the evaporator 103 located on the low-pressure side, in this case, there will be losses during heat exchange, reducing the accuracy of temperature measurement, and errors in heat exchange efficiency will occur due to the refrigerant flow rate, flow velocity, etc. Furthermore, if we consider the case where the refrigerant state detection unit 120 is installed to detect the refrigerant temperature before the refrigerant inlet of the evaporator 103 located on the low-pressure side, errors will occur due to pressure loss up to the refrigerant outlet of the evaporator 103. Therefore, in order for the refrigerant state detection unit 120 to detect the temperature of the refrigerant drawn into the compressor 100 without delay and with accuracy, it is preferable to install the refrigerant state detection unit 120 between the evaporator 103 and the gas-liquid separator 104.

[0061] During heating operation, the control unit 50 controls the compressor 100 to prevent the refrigerant on the refrigerant outlet side of the evaporator 103 from becoming overheated (superheated). Specifically, it is possible to estimate the state of the refrigerant on the refrigerant outlet side of the evaporator 103 based on the temperature of the refrigerant detected by the temperature sensor 122 of the refrigerant state detection unit 120. The control unit 50 acquires the temperature of the refrigerant detected by the refrigerant state detection unit 120 and controls the rotational speed of the compressor 100 to prevent the estimated state of the refrigerant based on the acquired refrigerant temperature from becoming overheated. As a result, the state of the refrigerant from the refrigerant outlet side of the evaporator 103 to the gas-liquid separator 104 becomes saturated or in a gas-liquid mixed phase state, so that the refrigerant pressure and temperature become correlated as shown in the Mollier diagram. The control unit 50 may also control the compressor 100 to prevent the refrigerant on the refrigerant outlet side of the evaporator 103 from becoming overheated during heating operation when heat is absorbed from the outside air at extremely low ambient temperatures. Extremely low ambient temperatures refer to conditions where the ambient temperature is 5°C or below, or 3°C or below.

[0062] The control unit 50 acquires pressure estimation information, including the temperature of the refrigerant detected by the temperature sensor 122 of the refrigerant state detection unit 120, and the characteristics of the refrigerant. After acquiring the pressure estimation information, the control unit 50 calculates the estimated refrigerant pressure based on that information and uses the calculated estimated refrigerant pressure to control the compressor 100 so that the pressure of the refrigerant drawn into the compressor 100 is higher than atmospheric pressure. This control, which raises the pressure of the refrigerant drawn into the compressor 100 to higher than atmospheric pressure, is a protective control of the compressor 100 and is also called negative pressure avoidance control (negative pressure avoidance operation). This negative pressure avoidance control can be performed at the start of heating, which absorbs heat from the outside air, or after heating has started.

[0063] Furthermore, the control unit 50 can also perform control based on the ambient temperature. Specifically, the control unit 50 acquires the ambient temperature detected by the ambient temperature sensor 51. If the ambient temperature detected by the ambient temperature sensor 51 is below a predetermined temperature, the control unit 50 determines the starting rotation speed of the compressor 100 so that the pressure of the refrigerant flowing into the compressor 100 during the initial startup is higher than atmospheric pressure. A temperature below a predetermined temperature is, for example, when the ambient temperature is extremely low. An extremely low ambient temperature is, for example, when the ambient temperature is 5°C or below, or 3°C or below. In the case of such ambient temperatures, after startup, the pressure flowing into the compressor 100 quickly falls below atmospheric pressure. If the pressure flowing into the compressor 100 quickly falls below atmospheric pressure after startup, the control unit 50 controls the compressor 100 to achieve the starting rotation speed determined above when the compressor 100 is started.

[0064] Figure 5 shows the control flow of the refrigeration cycle S by the control unit 50. This control flow starts after the ON / OFF switch of the vehicle air conditioning system 1 is turned ON. In step S1, the refrigerant state detection unit 120 detects the refrigerant state on the refrigerant outlet side of the evaporator 103. The refrigerant state refers to the refrigerant temperature detected by the temperature sensor 122, the refrigerant pressure detected by the pressure sensor 121, etc.

[0065] In step S2, the control unit 50 acquires the temperature of the refrigerant detected by the temperature sensor 122. In step S3, the control unit 50 calculates the estimated refrigerant pressure from the temperature of the refrigerant detected by the refrigerant state detection unit 120, using the relationship between temperature and pressure within the refrigerant saturation curve, based on the temperature of the refrigerant detected by the refrigerant state detection unit 120. The relationship between temperature and pressure within the refrigerant saturation curve is a characteristic of the refrigerant and is included in the pressure estimation information. Since the state of the refrigerant from the refrigerant outlet side of the evaporator 103 to the gas-liquid separator 104 is saturated or in a gas-liquid mixed phase state, the relationship between temperature and pressure within the refrigerant saturation curve satisfies a predetermined relationship as shown in Figure 6, and the estimated refrigerant pressure can be calculated using the equation (relational expression) that represents this relationship. In addition, although not shown in Figure 5, the control unit 50 may also determine whether the refrigerant on the refrigerant outlet side of the evaporator 103 is in a superheat state, and if it is determined that it is not in a superheat state, it may calculate the estimated refrigerant pressure in step S3. Thus, the control unit 50 is equipped with a pressure estimation unit (not shown) that estimates the refrigerant pressure based on the temperature of the refrigerant.

[0066] After calculating the estimated refrigerant pressure in step S3, the process proceeds to step S4. In step S4, the estimated refrigerant pressure obtained in step S3 is used as the low-pressure side pressure for protection control. Although not shown in the figures, the part that performs protection control of the compressor 100 (protection control unit) may be composed of a separate control unit from the control unit 50. The protection control unit and the pressure estimation unit may also be separate.

[0067] (Effects of the embodiment) As described above, the vehicle air conditioning system 1 according to this embodiment has a refrigeration cycle S including a compressor 100, a condenser 101, an expansion valve 102, an evaporator 103, and a gas-liquid separator 104, which enables air conditioning inside the vehicle using the refrigeration cycle S.

[0068] When the refrigeration cycle S is operating, the pressure and temperature of the refrigerant drawn into the compressor 100 are detected by the refrigerant state detection unit 120. Based on the pressure estimation information, including the temperature and characteristics of the refrigerant detected by the refrigerant state detection unit 120, the estimated refrigerant pressure is calculated by the control unit 50. The refrigerant temperature used in this calculation is the temperature when the refrigerant is in a saturated state or a gas-liquid mixed state. Therefore, there is a correlation between the refrigerant pressure and temperature, and by using the relationship between temperature and pressure within the saturation curve, the calculation accuracy when calculating the estimated refrigerant pressure can be improved.

[0069] Once the estimated refrigerant pressure is calculated, the control unit 50 uses this estimated refrigerant pressure to control the compressor 100 so that the pressure of the refrigerant drawn into the compressor 100 is higher than atmospheric pressure. This makes it possible to intentionally and accurately control the refrigerant pressure on the suction side of the compressor 100 to near atmospheric pressure using the estimated refrigerant pressure based on the temperature detected by the refrigerant temperature sensor 122, which has higher detection accuracy than the pressure sensor 121, without using the refrigerant pressure detected by the pressure sensor 121. As a result, heating performance is improved under extremely low ambient temperature conditions.

[0070] The control unit 50 can control the compressor 100 so that the refrigerant on the refrigerant outlet side of the evaporator 103 does not become overheated. As a result, the state of the refrigerant from the refrigerant outlet side of the evaporator 103 to the gas-liquid separator 104 becomes saturated or in a gas-liquid mixed phase state, resulting in a correlation between the refrigerant pressure and temperature. Therefore, the calculation accuracy when estimating the refrigerant pressure from the refrigerant temperature detected by the temperature sensor 122 can be improved.

[0071] The embodiments described above are merely illustrative in all respects and should not be interpreted restrictively. Furthermore, any modifications or changes that fall within the equivalent scope of the claims are all within the scope of the present invention. The vehicle air conditioning system 1 can also be installed in vehicles other than automobiles. The embodiments described above can be modified without departing from the spirit of the present invention. For example, the vehicle air conditioning system 1 may be equipped with an electric heater or the like. [Industrial applicability]

[0072] As explained above, the vehicle air conditioning system described herein can be used, for example, as an air conditioning system for automobiles. [Explanation of Symbols]

[0073] 1. Vehicle air conditioning system 50 Control Unit (Control Section) 100 Compressors 101 Condenser 102 Expansion valve 103 Evaporator 104 Gas-liquid separator 120 Refrigerant state detection unit 121 Pressure Sensor 122 Temperature Sensor

Claims

1. A vehicle air conditioning system installed in a vehicle, A compressor that compresses the refrigerant, A condenser connected to the refrigerant discharge side of the compressor, into which the refrigerant discharged from the compressor flows, An expansion valve connected to the refrigerant outlet side of the condenser, which expands the refrigerant that has flowed out of the condenser, An evaporator into which the refrigerant that has passed through the expansion valve flows, A gas-liquid separator is connected to the refrigerant outlet side of the evaporator, separates the refrigerant discharged from the evaporator into gas-liquid phases, and supplies the gaseous refrigerant to the suction side of the compressor. A refrigerant temperature sensor for detecting the temperature of the refrigerant drawn into the compressor, A vehicle air conditioning system comprising: a control unit that calculates an estimated refrigerant pressure based on pressure estimation information including the temperature of the refrigerant detected by the refrigerant temperature sensor and the characteristics of the refrigerant, and controls the compressor using the calculated estimated refrigerant pressure so that the pressure of the refrigerant drawn into the compressor becomes higher than atmospheric pressure.

2. In the vehicle air conditioning system according to claim 1, The control unit controls the compressor so that the refrigerant on the refrigerant outlet side of the evaporator does not become overheated, in this vehicle air conditioning system.

3. In the vehicle air conditioning system according to claim 2, The refrigerant temperature sensor is installed between the evaporator and the gas-liquid separator in a vehicle air conditioning system.

4. In the vehicle air conditioning system according to claim 2, The compressor further comprises a pressure sensor for detecting the pressure of the refrigerant being drawn into the compressor. A vehicle air conditioning system comprising: a control unit that, at the start of heating, calculates an estimated refrigerant pressure based on pressure estimation information including the temperature of the refrigerant detected by the refrigerant temperature sensor and the characteristics of the refrigerant, and controls the compressor using the calculated estimated refrigerant pressure so that the pressure of the refrigerant drawn into the compressor becomes higher than atmospheric pressure.

5. In the vehicle air conditioning system according to claim 2, It is further equipped with an outside air temperature sensor that detects the outside air temperature, The control unit, when the ambient temperature detected by the ambient temperature sensor is below a predetermined temperature, determines the starting rotation speed of the compressor so that the pressure of the refrigerant flowing into the compressor during the initial startup is higher than atmospheric pressure, and controls the compressor to achieve the determined starting rotation speed, in a vehicle air conditioning system.

6. In the vehicle air conditioning system according to claim 4, The pressure sensor and the refrigerant temperature sensor are provided between the evaporator and the gas-liquid separator in a vehicle air conditioning system.

7. In the vehicle air conditioning system according to claim 1, The control unit determines whether the refrigerant on the refrigerant outlet side of the evaporator is in an overheated state, and calculates the estimated refrigerant pressure if it is determined that it is not in an overheated state, in a vehicle air conditioning system.

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