Small working condition control method and device for vehicle air conditioning system

Abstract

The invention provides a small working condition control method and device for a vehicle air conditioning system, and relates to the technical field of air conditioners. Judging whether an air conditioning system of the vehicle is in a heating mode or a refrigerating mode; when the air conditioning system of the vehicle is in the heating mode, whether the outlet water temperature of cooling liquid of a vehicle motor is higher than a first temperature or not is judged; under the condition that the outlet water temperature is higher than the first temperature, the cooling liquid is provided for a warm air core body of an air conditioning system of the vehicle; and when the air conditioning system of the vehicle is in the refrigeration mode, under the condition that the refrigerating capacity is larger than the refrigeration threshold value, the opening degree of an electronic expansion valve EXV is adjusted according to the target air outlet temperature and the actual air outlet temperature of the air conditioning system. Therefore, the endurance mileage of the vehicle is increased, the comfort of the vehicle is improved, the complaint of a user on the bad influence of frequent start and stop on the comfort under the small working condition of the vehicle air conditioning system is eliminated, and the problem of frequent start and stop of the system caused by excessive refrigeration or heating capacity is thoroughly solved.

Description

Technical Field

[0001] This invention relates to the field of air conditioning technology, and in particular to a method and device for controlling a vehicle air conditioning system under low operating conditions. Background Technology

[0002] In recent years, the new energy vehicle market has continued to develop. New energy vehicles have obvious advantages over traditional vehicles in terms of low cost per unit mileage, low noise, and fast acceleration.

[0003] However, when using vehicle air conditioning systems under less demanding operating conditions, most existing thermal management systems do not effectively utilize waste heat, and the refrigeration module is prone to frequent compressor start-stop cycles during cooling. This can cause range anxiety for users of new energy vehicles, impacting comfort. Therefore, there is a need for more effective control methods and devices for vehicle air conditioning systems under less demanding operating conditions. Summary of the Invention

[0004] (a) Technical problems to be solved Therefore, in view of the improvement needs existing in the related technology, (1) the first aspect of this application provides a method for controlling a vehicle air conditioning system under low operating conditions, including: Confirm that the ambient temperature is within the first temperature range; Determine whether the vehicle's air conditioning system is in heating or cooling mode; When the vehicle's air conditioning system is in heating mode, determine whether the coolant outlet temperature of the vehicle's motor is higher than the first temperature. When the outlet water temperature is higher than the first temperature, coolant is supplied to the heating core of the vehicle's air conditioning system; When the vehicle's air conditioning system is in cooling mode, and the cooling capacity is greater than the cooling threshold, the opening of the electronic expansion valve EXV is adjusted according to the target air outlet temperature and the actual air outlet temperature of the air conditioning system.

[0005] (2) In the vehicle air conditioning system small operating condition control method of (1) above, preferably, the amount of coolant supplied is controlled according to the ambient temperature and the target air outlet temperature.

[0006] (3) In the vehicle air conditioning system small operating condition control method of (2) above, preferably, it further includes controlling the amount of coolant supplied according to the outlet water temperature.

[0007] (4) In the vehicle air conditioning system small operating condition control method of (2) or (3) above, preferably, when coolant is supplied to the heating core of the vehicle air conditioning system, the heating device of the air conditioning system is on standby.

[0008] (5) In the vehicle air conditioning system small operating condition control method of (2) or (3) above, preferably, when the outlet water temperature is greater than the second temperature, the outlet water temperature is reduced before the coolant is supplied to the heater core.

[0009] (6) In the vehicle air conditioning system small working condition control method of (1) above, preferably, when the vehicle air conditioning system is in cooling mode, the opening degree of EXV is controlled by the difference between the target air outlet temperature and the actual air outlet temperature.

[0010] (7) In the vehicle air conditioning system small operating condition control method of (1) above, preferably, when the outlet water temperature is lower than the temperature of the heater core, the coolant is supplied to the cooling circuit of the vehicle motor.

[0011] (8) In the vehicle air conditioning system small operating condition control method of (1) above, preferably, the first temperature range is 5-20℃.

[0012] (9) In the vehicle air conditioning system small operating condition control method of (1) above, preferably, the first temperature is 20°C.

[0013] (10) In addition, a second aspect of this application provides a vehicle air conditioning system low-condition control device for a vehicle, comprising: a four-way valve, the four-way valve including a first inlet, a second inlet, a first outlet and a second outlet; the four-way valve receives coolant from the motor side through the first inlet and supplies coolant to the motor side through the first outlet, the second inlet receives coolant from the air conditioning side and supplies coolant to the air conditioning side through the second outlet; and a control unit controls the four-way valve to perform the vehicle air conditioning system low-condition control method provided in the first aspect of this application as described above. Attached Figure Description

[0014] To more clearly illustrate the technical solutions of the embodiments of the present invention, the accompanying drawings used in the description of the embodiments will be briefly introduced below. Obviously, the accompanying drawings described below are embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0015] Figure 1 is a schematic diagram of the system 100 used in the vehicle air conditioning system low-condition control method of this application.

[0016] Figure 2 This is the basic flowchart of the vehicle air conditioning system small-condition control method of this application.

[0017] Explanation of reference numerals in the attached figures: 100: System; 1: Motor (Heating Kettle); 2: Battery-Powered Kettle; 3: Small 3-in-1; 4: Large 3-in-1; 5: Evaporator; 6: Heater Core; 7: First Motor Water Pump; 8: Second Motor Water Pump; 9: Electric Compressor; 10: Battery Pack; 11: Chiller; 12: Condenser; 13: Condenser; 14: Heating Water Pump; 15: Positive Temperature Coefficient Heater (WPTC); A (A1, A2, A3): Three-way Valve; B (B1, B2, B3, B4): Four-way Valve; C (C1, C2): Electronic Expansion Valve (EXV). Detailed Implementation

[0018] The following is attached to the instruction manual. Figure 1 The following examples illustrate preferred embodiments of the vehicle air conditioning system low-condition control method of the present invention. The embodiments illustrated below are intended to facilitate understanding of the invention and not to limit its scope. Furthermore, those skilled in the art will understand that the present invention can be modified and improved without departing from its spirit.

[0019] The terms "first," "second," etc., used in the specification and claims of this invention are used to distinguish similar objects and are not used to describe a specific order or sequence. It should be understood that such terms can be used interchangeably where appropriate so that embodiments of the invention can be implemented in orders other than those illustrated or described herein, and the objects distinguished by "first," "second," etc., are generally of the same class and the number of objects is not limited; for example, the first object can be one or more.

[0020] It should be understood that the terminology used in this specification is for the purpose of describing particular embodiments only and is not intended to limit the invention. As used in this specification, unless the context clearly indicates otherwise, the singular forms “a,” “an,” and “the” are intended to include the plural forms.

[0021] The terms “comprising” and “including” indicate the presence of the described feature, whole, step, operation, element and / or component, but do not exclude the presence or addition of one or more other features, wholes, steps, operations, elements, components and / or collections thereof.

[0022] Figure 1 is a schematic diagram of the system 100 used in the vehicle air conditioning system low-condition control method of this application.

[0023] like Figure 1As shown, the system 100 includes: a motor (heating kettle) 1, a battery-powered kettle 2, a small three-in-one unit 3, a large three-in-one unit 4, an evaporator 5, a heater core 6, a first motor water pump 7, a second motor water pump 8, an electric compressor 9, a battery pack 10, a cooler 11, a condenser 12, a condenser 13, a heating water pump 14, a water positive temperature coefficient heater 15 (hereinafter referred to as WPTC), three-way valves A (A1, A2, A3), four-way valves B (B1, B2, B3, B4), and electronic expansion valves C (C1, C2) (hereinafter referred to as EXV).

[0024] like Figure 1 As shown, the three-way valve A is installed on the side of the vehicle's motor, regulating whether the coolant entering from end A1 flows through end A2 via the condenser or bypasses the condenser from end A3. The four-way valve B includes two inlets, B1 and B4, and two outlets, B2 and B3, switching between cooling and heating functions by changing the direction of coolant flow. The three-way valve A and the four-way valve B are common knowledge in the field, therefore further detailed descriptions are omitted.

[0025] In the vehicle air conditioning system low-condition control method of this application, firstly, the ambient temperature T1 is confirmed to be within the first temperature range (S1).

[0026] For example, when the ambient temperature T1 is in the range of 5℃-20℃, the system load demand is not large, whether for heating or cooling, and the waste heat utilization efficiency of the system is relatively high. Therefore, the first temperature range can be, for example, the range of 5℃-20℃, but is not limited to this.

[0027] Next, determine whether the vehicle's air conditioning system is in heating or cooling mode (S2).

[0028] In heating mode, the waste heat generated by the motor, electronic control, and three-in-one circuits is used to heat the cab.

[0029] When the vehicle's air conditioning system is in heating mode, determine whether the coolant outlet temperature T2 of the vehicle's motor is higher than the first temperature (S3).

[0030] Assuming the motor can operate normally at the first temperature, if the outlet water temperature T2 is higher than the first temperature, it means that while the motor meets its own temperature requirements, it has surplus heat that can be used to heat the cab.

[0031] When the motor outlet water temperature T2 is higher than the first temperature, coolant is supplied to the heating core 6 of the vehicle's air conditioning system (S4).

[0032] Specifically, the four-way valve is controlled according to the motor outlet water temperature T2, so that the waste heat from the motor and other circuits is introduced into the cab, thereby achieving the technical effect of meeting the low-load heating needs of the cab.

[0033] For example, if the initial temperature is 20°C, as long as the motor outlet water temperature T2 is higher than 20°C, the excess heat above 20°C can be supplied to WPTC15 and the heater core 6 via the B4 end of the four-way valve. Therefore, even without using WPTC15 for heating, the low-load heating needs of the cab can be met. However, the initial temperature is not limited to 20°C and can be appropriately determined according to different systems and user requirements.

[0034] In traditional vehicle air conditioning systems operating under low-load conditions, despite the use of various integrated thermal management systems, many of these systems fail to effectively utilize waste heat. Even if the coolant temperature of the vehicle's motor meets its own requirements, waste heat is not fully utilized, and the heating module still relies on either air-cooled or water-heated PTCs, wasting unnecessary energy and causing range anxiety. Furthermore, the cooling module is prone to frequent compressor start-stop cycles under low-load conditions, leading to comfort complaints.

[0035] The vehicle air conditioning system low-load control method according to this embodiment makes full use of waste heat to improve driving range while also improving comfort. It eliminates customers' range anxiety and solves the problem of comfort complaints under low-load conditions, which can be described as killing two birds with one stone.

[0036] Alternatively, in another embodiment of this application, in the above (S4), the amount of coolant supplied can also be controlled according to the ambient temperature T1 and the target outlet air temperature.

[0037] Specifically, the amount of coolant supplied is controlled based on the difference between the ambient temperature T1 and the target outlet air temperature. If the difference is large, more coolant (i.e., more waste heat) is needed to supply the heating core 6 of the air conditioning system to meet the target outlet air temperature. On the other hand, if the difference is small, the amount of coolant supplied to the heating core 6 of the air conditioning system needs to be appropriately controlled; otherwise, if too much coolant is supplied, the excessive waste heat will cause the temperature in the cab to exceed the predetermined temperature, resulting in discomfort for the user.

[0038] Therefore, according to the above-described embodiments of this application, even if the temperature of the vehicle motor's coolant meets its own temperature requirements, the residual heat is not fully utilized or is overutilized, thereby effectively utilizing electrical energy, eliminating customers' range anxiety and ensuring comfort under low-load conditions.

[0039] In another embodiment of this application, the amount of coolant supplied can be further controlled according to the outlet water temperature.

[0040] Specifically, the amount of coolant supplied is also related to the outlet water temperature. When the motor temperature is low, resulting in a low outlet water temperature, more coolant (i.e., more waste heat) is needed to supply the heating core 6 of the air conditioning system. On the other hand, when the motor temperature is high and the outlet water temperature is high, the amount of coolant supplied to the heating core 6 of the air conditioning system needs to be appropriately controlled. Otherwise, if too much coolant is supplied, the excessive waste heat will cause the temperature in the cab to exceed the predetermined temperature, resulting in discomfort for the user.

[0041] Therefore, according to the above-described embodiments of this application, even if the temperature of the vehicle motor's coolant meets its own temperature requirements, the residual heat is not fully utilized or is overutilized, thereby effectively utilizing electrical energy, eliminating customers' range anxiety and ensuring comfort under low-load conditions.

[0042] Furthermore, when coolant is supplied to the heating element of the vehicle's air conditioning system, the heating device of the air conditioning system can be controlled to standby mode.

[0043] With coolant supplied to the heating core of the vehicle's air conditioning system, the residual heat from the motor side is sufficient to meet the heating needs of the air conditioning system, eliminating the need for heating devices such as the WPTC to continue operating. Therefore, the heating devices in the air conditioning system can enter standby mode instead of being completely shut down or continuing to operate.

[0044] Therefore, according to the above-described embodiments of this application, electrical energy is effectively utilized, eliminating customers' range anxiety, avoiding frequent start-stop of the heating device, and ensuring comfort under low-load conditions.

[0045] Furthermore, if the outlet water temperature is higher than the second temperature, the coolant is supplied to the heater core to lower the outlet water temperature, and the second temperature is higher than the first temperature.

[0046] Specifically, the coolant supply is controlled based on the ambient temperature T1, the target air outlet temperature, and the coolant outlet temperature. However, if the coolant outlet temperature is too high, for example, exceeding the second temperature, it is difficult to prevent excessive waste heat from being supplied to the vehicle's air conditioning system's heater core 6 simply by controlling the coolant supply. In this case, the coolant outlet temperature can be pre-lowered before supplying coolant to the heater core. For example, if the coolant outlet temperature is lower than the second temperature, the waste heat can be directly supplied to the vehicle's air conditioning system's heater core 6 through a three-way valve or a four-way valve; if the coolant outlet temperature is higher than the second temperature, the waste heat can be cooled by passing it through the radiator before being supplied to the vehicle's air conditioning system's heater core 6 through the three-way valve or a four-way valve. Furthermore, if the motor's waste heat supply causes overheating (exceeding the second temperature), the motor's coolant outlet temperature can be reduced by calibrating the non-linear relationship between the actual air outlet temperature and the temperature damper opening, combined with the radiator's electronic fan speed control, to meet comfort requirements.

[0047] Therefore, according to the above-described embodiments of this application, when the outlet water temperature is too high, the outlet water temperature is appropriately reduced in advance to avoid excessive heat being supplied to the heating core 6 of the vehicle's air conditioning system, which would cause the temperature to exceed the predetermined temperature, thus ensuring comfort under low-load conditions.

[0048] Alternatively, in another embodiment of this application, in the above (S4), when the outlet water temperature is lower than the temperature of the heater core, the coolant is supplied to the cooling circuit of the vehicle motor.

[0049] In other words, in the vehicle air conditioning system low-condition control method of this application, not only can waste heat be supplied from the motor side to the heating core 6 of the air conditioning system, but conversely, when the vehicle motor temperature does not meet its own temperature requirements and the temperature of the heating core 6 of the air conditioning system exceeds the user's expected temperature, if the outlet water temperature on the motor side is lower than the temperature of the heating core on the air conditioning side, the WPTC will not stop working. Instead, the waste heat from the air conditioning system side will be supplied to the motor side through the four-way valve. Thus, whether it is the motor side or the air conditioning side, as long as one side does not meet its own temperature requirements and the other side has waste heat, the waste heat can be supplied to the other side, maintaining a balanced state of mutual supply, thereby realizing the use of the waste heat of both sides for heating and heat preservation.

[0050] Therefore, according to the above-described embodiments of this application, when there is residual heat on either the motor side or the air conditioning side while the other side does not meet its own temperature requirements, the residual heat can be provided to the side that needs it, solving the problem of excessive heating temperature and meeting the heating requirements, thereby effectively utilizing electrical energy, eliminating customers' range anxiety and ensuring comfort under low-load conditions.

[0051] The main design calibration ideas are shown in Table 1 below (the motor outlet water temperature in the table is the calibration value, which can be determined according to different systems and customer requirements).

[0052] Table 1

[0053] As shown in Table 1, the lower the ambient temperature, the higher the outlet water temperature will be to ensure the motor temperature, thus potentially providing more waste heat. Specifically, for example, when T≤5℃, the motor outlet water temperature is ≥38℃, and the waste heat discharge motor outlet water temperature is ≤33℃. In this case, the waste heat is activated, and the WPTC is in standby mode. When 5<T1≤10℃, the motor outlet water temperature is ≥35℃, and the waste heat discharge motor outlet water temperature is ≤31℃. In this case, the waste heat is activated, and the WPTC is in standby mode. When 10<T1≤15℃, the motor outlet water temperature is ≥32℃, and the waste heat discharge motor outlet water temperature is ≤29℃. In this case, the waste heat is activated, and the WPTC is in standby mode. When 15<T1≤20℃, the motor outlet water temperature is ≥29℃, and the waste heat discharge motor outlet water temperature is ≤27℃. In this case, the waste heat is activated, and the WPTC is in standby mode. When 20℃<T1, the motor outlet water temperature is ≥26℃, and the waste heat discharge motor outlet water temperature is ≤20℃. In this case, the waste heat is activated, and the WPTC is in standby mode.

[0054] Of course, the examples and values ​​shown in the table above are just examples and are not limited to them. Those skilled in the art can set them appropriately according to the actual situation, as long as the waste heat can be effectively utilized.

[0055] In addition, when determining whether the vehicle's air conditioning system is in heating mode or cooling mode (S2), if the vehicle's air conditioning system is in cooling mode and the cooling capacity is greater than the cooling threshold, the opening of the electronic expansion valve EXV is adjusted according to the target air outlet temperature and the actual air outlet temperature of the air conditioning system (S5).

[0056] Optionally, in another embodiment of this application, in the above (S5), when the vehicle's air conditioning system is in cooling mode, the opening degree of EXV is controlled by the difference between the target air outlet temperature and the actual air outlet temperature.

[0057] Specifically, the EXV valve (electronic expansion valve) works by regulating the temperature and pressure of the cooling system by controlling the flow of coolant. An EXV valve consists of an electric controller and a valve. The electric controller sends signals based on system demand to control the opening and closing of the valve, thereby regulating the coolant flow. When the refrigeration system needs more coolant, the electric controller sends a signal to open the valve, allowing coolant to flow; when the system needs less coolant, the electric controller sends a signal to close the valve, reducing the coolant flow.

[0058] When the system determines that it is in cooling mode and the compressor speed is already at the minimum speed, but the cooling capacity is still excessive and cannot meet the comfort requirements, the following methods can be used to achieve precise control of comfort. Method 1: Based on the target outlet air temperature, calibrate the nonlinear relationship between the target outlet air temperature and the opening of the temperature damper. This linear relationship can solve the problem of excess cooling capacity under most low-load conditions.

[0059] Method 2: When the temperature damper in Method 1 is already at its minimum opening limit and the actual outlet air temperature differs significantly from the target outlet air temperature, the EXV opening can be controlled by adjusting the subcooling and high-pressure levels to maintain the outlet air temperature. Subcooling is crucial in the refrigeration system. Without subcooling, the refrigerant will flash in the liquid line, reducing cooling efficiency. Typically, a subcooling of 3°C-5°C is suitable for air-cooled condensers. Subcooling ensures the refrigerant remains liquid in the liquid line, preventing flashing and thus improving refrigeration efficiency.

[0060] Specifically, the main strategy is as follows: When the system is in automatic cooling operation mode, the compressor speed is at its minimum operating speed, the calculated temperature damper opening is less than or equal to the minimum damper opening limit, the high pressure is greater than or equal to 1.3 MPa, and the subcooling is greater than or equal to 2°C, the opening of the cooling EXV is increased by 1% or 2% from its current opening. The opening of the cooling EXV is then adjusted back and forth according to the actual parameters to meet the comfort requirements of having excess cooling capacity under low load without frequent shutdowns. Furthermore, the minimum damper opening limit in method 2 above is calibrated according to the specific air conditioning system, as is the high pressure value. A 1% opening of the cooling EXV is the calibrated value.

[0061] Therefore, according to the above embodiments of this application, the opening degree of EXV can be adjusted by the degree of subcooling to ensure that the operating efficiency of the compressor at low speed does not cause frequent system shutdowns and customer complaints, thereby completely eliminating the adverse effects of frequent system start-stops on customer comfort under low load conditions.

[0062] In another embodiment of this application, a vehicle air conditioning system low-condition control device is also provided for a vehicle, comprising: A four-way valve, comprising a first inlet, a second inlet, a first outlet, and a second outlet; The four-way valve receives coolant from the motor side through the first inlet and supplies coolant to the motor side through the first outlet. It also receives coolant from the air conditioning side through the second inlet and supplies coolant to the air conditioning side through the second outlet. The control unit controls the four-way valve to execute the vehicle air conditioning system's minor operating condition control method as described above.

[0063] For example, the vehicle air conditioning system low-condition control device executes the following vehicle air conditioning system low-condition control method: Confirm that the ambient temperature is within the first temperature range; Determine whether the vehicle's air conditioning system is in heating or cooling mode; When the vehicle's air conditioning system is in heating mode, determine whether the coolant outlet temperature of the vehicle's motor is higher than the first temperature. When the outlet water temperature is higher than the first temperature, coolant is supplied to the heating core of the vehicle's air conditioning system; When the vehicle's air conditioning system is in cooling mode, and the cooling capacity is greater than the cooling threshold, the opening of the electronic expansion valve EXV is adjusted according to the target air outlet temperature and the actual air outlet temperature of the air conditioning system.

[0064] In traditional vehicles, most thermal management systems do not effectively utilize waste heat. Heating modules still rely on air-cooled or water-heated PTC systems, which not only consumes electricity and causes range anxiety but also leads to user complaints about comfort under low-load conditions. Simultaneously, the cooling module is prone to frequent compressor start-stop cycles under low-load conditions, further reducing comfort. The vehicle proposed in this application addresses both range considerations and the comfort issues under low-load conditions. This improves vehicle range and comfort, eliminates user complaints about the negative impact of frequent start-stop cycles on comfort caused by excessive cooling or heating capacity, and completely resolves the problem of frequent system start-stop cycles due to overcapacity in cooling or heating.

[0065] The preferred embodiments of this application have been described in detail above. However, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for controlling a vehicle air conditioning system under low operating conditions, characterized in that, include: Confirm that the ambient temperature is within the first temperature range; Determine whether the vehicle's air conditioning system is in heating or cooling mode; When the vehicle's air conditioning system is in the heating mode, it is determined whether the outlet temperature of the coolant in the vehicle's motor is higher than a first temperature. When the outlet water temperature is higher than the first temperature, the coolant is supplied to the heating core of the vehicle's air conditioning system so that the waste heat is supplied to the water positive temperature coefficient heater WPTC and the heating core through the B1 end of the four-way valve via the B4 end. When the vehicle's air conditioning system is in the cooling mode, if the cooling capacity is greater than the cooling threshold, the opening of the electronic expansion valve EXV is adjusted according to the target air outlet temperature and the actual air outlet temperature of the air conditioning system. The method further includes: If the vehicle motor temperature does not meet its own temperature requirements and the temperature of the heating core of the air conditioning system exceeds the user's expected temperature, if the water outlet temperature on the motor side is lower than the temperature of the heating core on the air conditioning side, the WPTC will not stop working and the residual heat on the air conditioning system side will be supplied to the motor side through the four-way valve. If the outlet water temperature is greater than the second temperature, the outlet water temperature is reduced before the coolant is supplied to the heater core, where the second temperature is greater than the first temperature.

2. The vehicle air conditioning system low-condition control method according to claim 1, characterized in that, The amount of coolant supplied is controlled based on the ambient temperature and the target outlet air temperature.

3. The vehicle air conditioning system low-condition control method according to claim 2, characterized in that, This further includes controlling the amount of coolant supplied based on the outlet water temperature.

4. The vehicle air conditioning system low-condition control method according to claim 2 or 3, characterized in that, When the coolant is supplied to the heating element of the vehicle's air conditioning system, the heating device of the air conditioning system is in standby mode.

5. The vehicle air conditioning system low-condition control method according to claim 1, characterized in that, When the outlet water temperature is higher than the second temperature, reducing the outlet water temperature before supplying the coolant to the heater core includes: When the outlet water temperature is higher than the second temperature, the coolant is cooled down by passing through the radiator and then supplied to the heating core of the vehicle's air conditioning system through a three-way valve and a four-way valve.

6. The vehicle air conditioning system low-condition control method according to claim 1, characterized in that, When the vehicle's air conditioning system is in cooling mode, the opening degree of EXV is controlled by the difference between the target outlet air temperature and the actual outlet air temperature.

7. The vehicle air conditioning system low-condition control method according to claim 1, characterized in that, When the outlet water temperature is lower than the temperature of the heater core, the coolant is supplied to the cooling circuit of the vehicle motor.

8. The vehicle air conditioning system low-condition control method according to claim 1, characterized in that, The first temperature range is 5-20℃.

9. The vehicle air conditioning system low-condition control method according to claim 1, characterized in that, The first temperature is 20°C.

10. A vehicle air conditioning system low-condition control device, characterized in that, For use in vehicles, including: A four-way valve, comprising a first inlet, a second inlet, a first outlet, and a second outlet; The four-way valve receives coolant from the motor side through the first inlet and supplies coolant to the motor side through the first outlet; it receives coolant from the air conditioner side through the second inlet and supplies coolant to the air conditioner side through the second outlet. The control unit controls the four-way valve to execute the vehicle air conditioning system low-condition control method as described in any one of claims 1-9.

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