Transcritical CO2 System for Vehicle Thermal Management and Its Control Method

Abstract

The present invention discloses a transcritical CO2 system for vehicle thermal management and its control method. The system includes: a compressor, an outdoor heat exchanger, an indoor secondary heat exchanger, an indoor main heat exchanger, a regenerator, a battery heat exchange plate, a gas-liquid separator, a first solenoid valve, a second solenoid valve, a third solenoid valve, a fourth solenoid valve, a fifth solenoid valve, a first bi-directional all-pass throttle valve, a second bi-directional all-pass throttle valve, a third bi-directional all-pass throttle valve, a fourth bi-directional all-pass throttle valve, an outdoor fan, and an indoor blower. The present invention can solve the technical problems of difficult energy matching between the battery and the passenger compartment and poor system stability and difficult control caused by large water path lag in the current transcritical CO2 thermal management system for vehicles; by proposing a new configuration structure, the present invention completely releases the problem of energy distribution in the battery circuit and can greatly improve the system stability.

Description

Technical Field

[0001] The present invention belongs to the technical field of new energy vehicle heat pump air conditioners and thermal management, and particularly relates to a transcritical CO2 system for vehicle thermal management and a control method thereof. Background Art

[0002] The driving range of electric vehicles strongly depends on the charge and discharge characteristics of the battery, and the charge and discharge characteristics of the battery are affected by the battery temperature field. Fine temperature management of the battery, motor, and electronic control equipment of new energy vehicles is an effective means to ensure their comprehensive driving range. On the other hand, electric vehicles lack waste heat that can be utilized for winter heating, and the current winter heating efficiency is low and energy consumption is high, which becomes another constraint on the driving range of electric vehicles. In addition, the field of electric vehicle thermal management systems also faces the problem of replacing high greenhouse effect working fluids. To address the above three problems, the transcritical CO2 thermal management system has become one of the effective technical routes to solve the bottleneck problems.

[0003] Currently, in the technical solutions of existing vehicle transcritical CO2 thermal management systems, a scheme of connecting two indoor evaporators in series and then connecting them in parallel with the battery heat exchange cold plate is adopted, or a heat exchanger is used as an evaporator and then connected in parallel with the battery heat exchange cold plate to achieve the functions of heating and cooling the battery and refrigerating and heating the passenger compartment. However, the above existing layout method will cause difficulties in energy matching between the battery and the passenger compartment, and rely on the throttle valve in the parallel branch to adjust energy. The battery heat exchange cold plate mostly adopts a secondary circuit (exemplarily, ethylene glycol aqueous solution), which has a very large thermal inertia, resulting in poor system stability and difficult energy distribution control.

[0004] In summary, there is an urgent need for a new transcritical CO2 system for vehicle thermal management and a control method thereof. Summary of the Invention

[0005] The purpose of the present invention is to provide a transcritical CO2 system for vehicle thermal management and a control method thereof to solve one or more of the above existing technical problems. Specifically, the present invention specifically provides a transcritical CO2 system to solve the technical problems of difficult energy matching between the battery and the passenger compartment and poor system stability and difficult control caused by large water path lag in the current vehicle transcritical CO2 thermal management system. By proposing a new configuration structure, the present invention completely releases the energy distribution problem of the battery circuit and can greatly improve the system stability.

[0006] To achieve the above object, the present invention adopts the following technical solutions:

[0007] A transcritical CO2 system for vehicle thermal management provided by the present invention includes: a compressor, an outdoor heat exchanger, an indoor secondary heat exchanger, an indoor primary heat exchanger, a regenerator, a battery heat exchange plate, a gas-liquid separator, a first solenoid valve, a second solenoid valve, a third solenoid valve, a fourth solenoid valve, a fifth solenoid valve, a first bi-directional full-pass throttle valve, a second bi-directional full-pass throttle valve, a third bi-directional full-pass throttle valve, a fourth bi-directional full-pass throttle valve, an outdoor fan, and an indoor blower;

[0008] The indoor secondary heat exchanger, the indoor primary heat exchanger, and the indoor blower are disposed in an air-conditioning box, and the air-conditioning box is provided with an air damper; the outdoor fan is used to provide forced convection air volume for the outdoor heat exchanger outside the passenger compartment; the indoor blower is used to provide air volume for the passenger compartment in the air-conditioning box;

[0009] The outlet of the compressor is connected to the high-pressure side inlet of the regenerator through the first solenoid valve and the outdoor heat exchanger; one path of the high-pressure side outlet of the regenerator is connected to the inlet of the primary heat exchanger through the battery heat exchange cold plate and the fourth bi-directional full-pass throttle valve, and the other path of the high-pressure side outlet of the regenerator is connected to the inlet of the indoor secondary heat exchanger through the fifth solenoid valve and the first bi-directional full-pass throttle valve. After the outlets of the primary heat exchanger and the indoor secondary heat exchanger converge, they are connected to the inlet of the compressor through the fourth solenoid valve, the gas-liquid separator, and the low-pressure side of the regenerator; wherein, the second bi-directional full-pass throttle valve is disposed between the outlet of the indoor secondary heat exchanger and the fourth solenoid valve;

[0010] One end of the second solenoid valve is connected between the outlet of the compressor and the first solenoid valve, and the other end is connected between the fifth solenoid valve and the first bi-directional full-pass throttle valve; one end of the third solenoid valve is connected between the outdoor heat exchanger and the first solenoid valve, and the other end is connected between the gas-liquid separator and the fourth solenoid valve.

[0011] A further improvement of the system of the present invention is that a proportional adjustment air damper is disposed between the indoor primary heat exchanger and the indoor secondary heat exchanger.

[0012] A further improvement of the system of the present invention is that in the mode of cooling the passenger compartment and cooling the battery simultaneously, the first solenoid valve, the fourth solenoid valve, and the fifth solenoid valve are all opened, and the second solenoid valve and the third solenoid valve are all closed; the second bi-directional full-pass throttle valve is in a full-pass state;

[0013] In the mode of only cooling the passenger compartment, the first solenoid valve, the fourth solenoid valve, and the fifth solenoid valve are all opened, the second solenoid valve and the third solenoid valve are all closed; the second bi-directional full-pass throttle valve is in a full-pass state; the water-side flow rate of the battery heat exchange cold plate is closed;

[0014] In the case of only the battery cooling mode, the first solenoid valve and the fourth solenoid valve are both opened, the second solenoid valve, the third solenoid valve, and the fifth solenoid valve are all closed; the second two-way full-pass throttle valve is in the full-pass state; the air damper of the air-conditioning box and the indoor blower are both closed.

[0015] A further improvement of the system of the present invention lies in that when heating the passenger compartment while heating the battery, the first solenoid valve, the fourth solenoid valve, and the fifth solenoid valve are closed, and the second solenoid valve and the third solenoid valve are both opened; the first two-way full-pass throttle valve, the second two-way full-pass throttle valve, and the fourth two-way full-pass throttle valve are all in the full-pass state;

[0016] In the case of only the passenger compartment heating mode, the first solenoid valve, the fourth solenoid valve, and the fifth solenoid valve are closed, and the second solenoid valve and the third solenoid valve are both opened; the first two-way full-pass throttle valve, the second two-way full-pass throttle valve, and the fourth two-way full-pass throttle valve are all in the full-pass state; the water-side flow of the battery heat exchange cold plate is closed;

[0017] In the case of only the battery heating mode, the first solenoid valve, the fourth solenoid valve, and the fifth solenoid valve are closed, and the second solenoid valve and the third solenoid valve are both opened; the first two-way full-pass throttle valve, the second two-way full-pass throttle valve, and the fourth two-way full-pass throttle valve are all in the full-pass state; the air damper of the air-conditioning box and the indoor blower are closed.

[0018] A further improvement of the system of the present invention lies in that in the defrosting and defogging mode, the first solenoid valve, the fourth solenoid valve, and the fifth solenoid valve are closed, and the second solenoid valve and the third solenoid valve are both opened; the third two-way full-pass throttle valve is in the fully open or throttling state based on a preset situation; the second two-way full-pass throttle valve is in the throttling state;

[0019] In the defrosting mode, the first solenoid valve and the fourth solenoid valve are both opened, the second solenoid valve, the third solenoid valve, and the fifth solenoid valve are all closed; the fourth two-way full-pass throttle valve is in the full-pass state; the third two-way full-pass throttle valve is in the throttling state; the air damper of the air-conditioning box and the indoor blower are closed.

[0020] A further improvement of the system of the present invention lies in that when heating the passenger compartment while recovering the waste heat of the battery, the first solenoid valve, the fourth solenoid valve, and the fifth solenoid valve are closed, and the second solenoid valve and the third solenoid valve are both opened; the fourth two-way full-pass throttle valve is in the throttling state.

[0021] A control method for a transcritical CO2 system for vehicle thermal management according to the present invention includes the following steps:

[0022] Obtain the CO2 temperature T1 at one end of the battery heat exchange cold plate close to the fourth two-way full-pass throttle valve, the air outlet temperature T2 of the air handling unit, the outlet CO2 temperature T3 of the indoor main heat exchanger in the refrigeration mode, the outlet temperature T4 of the indoor secondary heat exchanger in the refrigeration mode, the water outlet temperature T5 of the battery heat exchange plate, and the discharge pressure P of the compressor;

[0023] The control method for the simultaneous cooling of the passenger compartment and the battery cooling mode is as follows: The third two-way full-pass throttle valve establishes a PID adjustment relationship with T1; the fourth two-way full-pass throttle valve establishes an adjustment relationship with the preset outlet superheat of the indoor main heat exchanger to ensure that the temperature of T4 is always the insulation temperature corresponding to the local pressure plus x degrees, where x is the preset outlet superheat; the first two-way full-pass throttle valve establishes a PID adjustment relationship with P, and the rotational speed of the compressor establishes a PID adjustment relationship with T2;

[0024] The control method for only the battery cooling mode is as follows: The third two-way full-pass throttle valve establishes a PID adjustment relationship with P, and the compressor establishes an adjustment relationship with T5;

[0025] The control method for only the passenger compartment refrigeration mode is as follows: The first two-way full-pass throttle valve establishes a PID adjustment relationship with T2, the compressor establishes a PID adjustment relationship with P, and the third two-way full-pass throttle valve establishes an adjustment relationship with the preset outlet superheat of the indoor main heat exchanger to ensure that the temperature of T4 is always the saturation temperature corresponding to the local pressure plus x degrees, where x is the preset superheat; the fourth two-way full-pass throttle valve is in the full-pass state, and the water flow through the battery heat exchange cold plate is closed.

[0026] A further improvement of the method of the present invention lies in that the control method for the simultaneous heating of the passenger compartment and the battery heating mode is as follows: The proportional adjustment air damper establishes a PID condition relationship with T1; the compressor establishes a PID adjustment control relationship with T2; the third two-way full-pass throttle valve establishes a PID adjustment control relationship with P; among them, when the proportional adjustment air damper is completely closed and T1 still cannot reach the target value, enter the selection mode; the selection mode includes that if the battery heating is still in the priority, the rotational speed of the indoor blower is adjusted to automatic adjustment with priority, and the air volume is reduced by one gear every preset time interval until T1 meets the temperature requirement; if the battery is no longer in the priority, the state of the proportional adjustment air damper being completely closed is maintained for operation;

[0027] The control method for only the battery heating mode is as follows: The third two-way full-pass throttle valve establishes a PID adjustment relationship with P, and the compressor establishes an adjustment relationship with T5;

[0028] The control method for only the passenger compartment heating mode is as follows: The compressor establishes a PID adjustment control relationship with T2; the third two-way full-pass throttle valve establishes a PID adjustment control relationship with P; the fourth two-way full-pass throttle valve is in the full-pass state, and the water flow through the battery heat exchange cold plate is closed.

[0029] A further improvement of the method of the present invention lies in that the control method for the defrosting and demisting mode is as follows: A PID regulation control relationship is established between the compressor and T2, where T2 is the target value; A PID regulation control relationship is established between the second two-way full-pass throttle valve and T1; Monitor the P value. If T1 still fails to reach the control target after the P value exceeds 14 MPa, turn off the outdoor fan so that no air passes through the outdoor heat exchanger.

[0030] The control method for the defrosting mode is as follows: The fourth two-way full-pass throttle valve is in the full-pass state, the opening degree of the third two-way full-pass throttle valve is adjusted to a preset opening degree, turn off the outdoor fan so that no air passes through the outdoor heat exchanger, and turn off the indoor blower; If the temperature of the battery is greater than 10 °C, then turn on the water flow of the battery heat exchange cold plate before the defrosting starts, and use the waste heat of the battery for defrosting during the defrosting stage.

[0031] A further improvement of the method of the present invention lies in that the control method for the heating of the passenger compartment and the recovery of battery waste heat is as follows: Turn off the outdoor fan, and establish an adjustment relationship between the compressor and T2; A PID control relationship is established between the fourth two-way full-pass throttle valve and P; The third two-way full-pass throttle valve is in the full-pass state, and the temperature at the T1 position is monitored; When the temperature of T1 is less than the set value, turn on the outdoor fan, change the third two-way full-pass throttle valve to establish a PID regulation relationship with P, and change the fourth two-way full-pass throttle valve to establish a PID control relationship with T1.

[0032] Compared with the prior art, the present invention has the following beneficial effects:

[0033] The transcritical CO2 system for vehicle thermal management provided by the present invention has the battery heat exchange plate always connected in series with the indoor main heat exchanger, which can ensure that the CO2 working medium in the battery heat exchange cold plate is always in a state with a small dryness, can increase the heat exchange characteristics, and can improve the control complexity of the energy distribution between the battery and the passenger compartment; It can completely open the heat extraction amount of the battery, changing from the CO2 system actively distributing energy to the battery to the battery actively absorbing energy from the CO2 system. Among them, the indoor main heat exchanger and the indoor secondary heat exchanger are connected in parallel in the refrigeration mode, which can increase the heat exchange capacity and reduce the pressure drop, improving the system performance; The indoor main heat exchanger and the indoor secondary heat exchanger are connected in series in the heating mode, which can ensure countercurrent heat exchange, adapt to the characteristics of the CO2 working medium, and improve the system performance.

[0034] In the present invention, a proportional adjustment air door is provided between the indoor main heat exchanger and the indoor secondary heat exchanger, which can ensure the water temperature for heating the battery by adjusting the opening degree of the proportional adjustment air door under the condition that both the passenger compartment and the battery have heating requirements. Description of the Drawings

[0035] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the following briefly introduces the accompanying drawings required for the description of the embodiments or the prior art; obviously, the accompanying drawings in the following description are some embodiments of the present invention, and for those of ordinary skill in the art, without creative efforts, other accompanying drawings can also be obtained based on these drawings.

[0036] Figure 1 is a schematic diagram of a transcritical CO2 system for vehicle thermal management according to an embodiment of the present invention;

[0037] In the figure, 1. Compressor; 2. Outdoor heat exchanger; 3. Indoor secondary heat exchanger; 4. Indoor main heat exchanger; 5. Regenerator; 6. Battery heat exchange plate; 7. Gas-liquid separator; 8. First solenoid valve; 9. Second solenoid valve; 10. Third solenoid valve; 11. Fourth solenoid valve; 12. First bi-directional full-pass throttle valve; 13. Fifth solenoid valve; 14. Second bi-directional full-pass throttle valve; 15. Third bi-directional full-pass throttle valve; 16. Battery heat exchange plate water circuit; 17. Outdoor fan; 18. Air conditioning box; 19. Fourth bi-directional full-pass throttle valve; 20. Indoor blower; 21. Proportional adjustment air damper. Detailed implementation manners

[0038] In order to enable those skilled in the art to better understand the solution of the present invention, the following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, rather than all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts shall fall within the protection scope of the present invention.

[0039] It should be noted that the terms "first", "second", etc. in the specification and claims of the present invention and the above accompanying drawings are used to distinguish similar objects, and do not necessarily need to describe a specific order or sequence. It should be understood that such used data can be interchanged under appropriate circumstances so that the embodiments of the present invention described herein can be implemented in an order other than those illustrated or described herein. In addition, the terms "including" and "having" and any variations thereof are intended to cover non-exclusive inclusion. For example, a process, method, system, product or device including a series of steps or units does not necessarily have to be limited to those clearly listed steps or units, but may include other steps or units not clearly listed or inherent to these processes, methods, products or devices.

[0040] The following further describes the present invention in detail in conjunction with the accompanying drawings:

[0041] Please refer to Figure 1, a transcritical CO2 system for vehicle thermal management according to an embodiment of the present invention includes: a compressor 1, an outdoor heat exchanger 2, an indoor secondary heat exchanger 3, an indoor main heat exchanger 4, a regenerator 5, a battery heat exchange plate 6, a gas-liquid separator 7, a first solenoid valve 8, a second solenoid valve 9, a third solenoid valve 10, a fourth solenoid valve 11, a fifth solenoid valve 13, a first bi-directional all-pass throttle valve 12, a second bi-directional all-pass throttle valve 14, a third bi-directional all-pass throttle valve 15, a fourth bi-directional all-pass throttle valve 19, an outdoor fan 17, an air conditioning box 18, and an indoor blower 20.

[0042] Among them, the outdoor heat exchanger 2 is a heat exchange device for heat exchange with air outside the passenger compartment; the indoor main heat exchanger 4 is the main heat exchange device for heat exchange with air in the air conditioning box 18 to increase the appropriate cold or warm air in the passenger compartment; the indoor secondary heat exchanger 3 is the secondary heat exchange device for heat exchange with air in the air conditioning box 18 to increase the appropriate cold or warm air in the passenger compartment; the battery heat exchange plate 6 is a heat exchange device for providing suitable temperature cold or hot water required for battery thermal management; the outdoor fan 17 is a device for providing forced convection air volume for the outdoor heat exchanger 2 outside the passenger compartment; the air conditioning box 18 is for providing comfortable cold or warm air in the passenger compartment, and may include a heat exchange device, an air duct, and a damper adjustment device assembly; the indoor blower 20 is a device for providing appropriate air volume for the passenger compartment in the air conditioning box 18.

[0043] In the embodiment of the present invention, the outlet of the compressor 1 is sequentially connected to the first solenoid valve 8, the outdoor heat exchanger 2, and the high-pressure side of the regenerator 5, and then is divided into two paths. One path passes through the battery heat exchange cold plate, the fourth bi-directional all-pass throttle valve 19, and the indoor main heat exchanger 4, and the other path passes through the fifth solenoid valve 13, the first bi-directional all-pass throttle valve 12, the indoor secondary heat exchanger 3, and the second bi-directional all-pass throttle valve 14. After the two paths converge, they flow back to the compressor 1 through the fourth solenoid valve 11, the gas-liquid separator 7, and the low-pressure side of the regenerator 5. One end of the second solenoid valve 9 is connected between the compressor 1 and the first solenoid valve 8, and the other end is connected between the fifth solenoid valve 13 and the first bi-directional all-pass throttle valve 12. One end of the third solenoid valve 10 is connected between the outdoor heat exchanger 2 and the first solenoid valve 8, and the other end is connected between the gas-liquid separator 7 and the fourth solenoid valve 11.

[0044] In the embodiment of the present invention, for the transcritical CO2 system used for vehicle thermal management, the battery heat exchange plate is always connected in series with the indoor main heat exchanger, which can ensure that the CO2 working medium in the battery heat exchange cold plate is always in a state with a small dryness, increasing the heat exchange characteristics; it can improve the complexity of energy distribution control for the battery and the passenger compartment; it can completely open the heat extraction of the battery, changing from the CO2 system actively distributing energy to the battery actively absorbing energy from the CO2 system. In addition, the indoor main heat exchanger and the indoor secondary heat exchanger are connected in parallel in the refrigeration mode, which can increase the heat exchange capacity and reduce the pressure drop, improving the system performance; the indoor main heat exchanger and the indoor secondary heat exchanger are connected in series in the heating mode, which can ensure countercurrent heat exchange, adapt to the characteristics of the CO2 working medium, and improve the system performance.

[0045] In the embodiment of the present invention, a proportional adjustment damper 21 is provided between the indoor main heat exchanger 4 and the indoor secondary heat exchanger 3, which can ensure the water temperature for heating the battery by adjusting the opening degree of the proportional adjustment damper 21 under the condition that both the passenger compartment and the battery have heating requirements.

[0046] The transcritical CO2 system for vehicle thermal management provided by the embodiment of the present invention includes a passenger compartment refrigeration and battery cooling mode, a only passenger compartment refrigeration mode, a passenger compartment heating and battery heating mode, a only passenger compartment heating mode, a only battery cooling mode, a only battery heating mode, a defrosting and defogging mode, and a passenger compartment heating and battery waste heat recovery mode.

[0047] Specifically, in the embodiment of the present invention, for the passenger compartment refrigeration and battery cooling mode: the first solenoid valve 8, the fourth solenoid valve 11, and the fifth solenoid valve 13 are opened, the second solenoid valve 9 and the third solenoid valve 10 are closed. The CO2 working medium is compressed by the compressor 1 and then passes through the high-pressure side of the first solenoid valve 8, the outdoor heat exchanger 2, and the regenerator 5, and then is divided into two paths. One path passes through the third two-way full-pass throttle valve 15, the battery heat exchange plate 6, the fourth two-way full-pass throttle valve 19, and the indoor main heat exchanger 4, and the other path passes through the fifth solenoid valve 13, the first two-way full-pass throttle valve 12, the indoor secondary heat exchanger 3, and the second two-way full-pass throttle valve 14. The two paths converge and then flow back to the compressor 1 through the fourth solenoid valve 11, the gas-liquid separator 7, and the low-pressure side of the regenerator 5. The second two-way full-pass throttle valve 14 is in a full-pass state.

[0048] Specifically, in the embodiment of the present invention, for the only battery cooling mode: the fifth solenoid valve 13 is closed, and the valve states of the other CO2-side components are the same as those in the passenger compartment refrigeration and battery cooling mode, and the flow path is also the same. In this mode, the outdoor fan 17 is turned off and all dampers of the air conditioning box 18 are closed.

[0049] Specifically, in the embodiment of the present invention, for the only passenger compartment refrigeration mode: the valve states of the CO2 side are the same as those in the passenger compartment refrigeration and battery cooling mode, and the flow path is also the same. In this mode, it is achieved by closing the flow of the battery heat exchange plate waterway 16.

[0050] Specifically, in the embodiment of the present invention, the occupant compartment heating and battery heating mode is as follows: the first solenoid valve 8, the fourth solenoid valve 11, and the fifth solenoid valve 13 are closed, the second solenoid valve 9 and the third solenoid valve 10 are opened. The CO2 working medium is compressed by the compressor 1 and then flows into the indoor secondary heat exchanger 3 through the second solenoid valve 9 and the first bi-directional full-pass throttle valve 12, and then flows into the indoor main heat exchanger 4 through the second bi-directional full-pass throttle valve 14 to realize the heating function of the occupant compartment. It flows from the indoor main heat exchanger 4 through the fourth bi-directional full-pass throttle valve 19 into the battery heat exchange cold plate to further heat the battery, and then enters the outdoor heat exchanger 2 through the third bi-directional full-pass throttle valve 15 to throttle down the pressure and temperature to absorb the heat of the air, and then flows into the compressor 1 through the third solenoid valve 10 and the gas-liquid separator 7 to complete a cycle. The first bi-directional full-pass throttle valve 12, the second bi-directional full-pass throttle valve 14, and the fourth bi-directional full-pass throttle valve 19 are all in the full-pass state.

[0051] Specifically, in the embodiment of the present invention, the battery heating mode only is as follows: the valve states on the CO2 side are the same as those in the occupant compartment heating and battery heating mode, and the flow paths are also the same. In this mode, it is achieved by closing the outdoor fan 17 and all the dampers of the air conditioner box 18.

[0052] Specifically, in the embodiment of the present invention, the occupant compartment heating mode only is as follows: the valve states on the CO2 side are the same as those in the occupant compartment heating and battery heating mode, and the flow paths are also the same. In this mode, it is achieved by closing the flow rate of the battery heat exchange plate waterway 16.

[0053] Specifically, in the embodiment of the present invention, the defrosting and defogging mode is as follows: the valve states on the CO2 side are the same as those in the occupant compartment heating and battery heating mode, and the flow paths are also the same. In this mode, the third bi-directional full-pass throttle valve 15 is determined to be in the fully open or throttling state according to the specific situation, which is related to the amount of dehumidification required. The second bi-directional full-pass throttle valve 14 is in the throttling state to reduce the temperature and pressure to realize the cooling and dehumidification of the main heat exchanger.

[0054] Specifically, in the embodiment of the present invention, the defrosting mode is as follows: the first solenoid valve 8 and the fourth solenoid valve 11 are opened, the second solenoid valve 9, the third solenoid valve 10, and the fifth solenoid valve 13 are closed. The CO2 working medium is compressed by the compressor 1 and then passes through the first solenoid valve 8, the outdoor heat exchanger 2, and the high-pressure side of the regenerator 5, and then passes through the third bi-directional full-pass throttle valve 15, the battery heat exchange plate 16, the fourth bi-directional full-pass throttle valve 19, and the main heat exchanger, and then flows back to the compressor 1 through the fourth solenoid valve 11, the gas-liquid separator 7, and the low-pressure side of the regenerator 5. The fourth bi-directional full-pass throttle valve 19 is in the full-pass state, and the third bi-directional full-pass throttle valve 15 is in the throttling state. The indoor blower 20 and the dampers of the air conditioner box 18 are in the closed state. In this mode, the CO2 working medium can absorb the heat from the battery heat exchange cold plate to achieve the purpose of rapid defrosting.

[0055] Specifically, in the embodiment of the present invention, the heating mode of the passenger compartment and the waste heat recovery of the battery are as follows: the valve state on the CO2 side is the same as that in the heating mode of the passenger compartment and the battery heating, and the flow path is also the same. In this mode, the fourth two-way full-pass throttle valve 19 is in the throttling state to realize the recovery of the battery heat. Here, the waste heat of the battery, motor, etc. can still be recovered simultaneously by switching the water circuit, and the switching of the water circuit is a conventional operation method.

[0056] A control method for the above-mentioned transcritical CO2 system for vehicle thermal management according to an embodiment of the present invention includes the following steps:

[0057] Record the CO2 temperature at one end of the battery heat exchange cold plate close to the fourth two-way full-pass throttle valve 19 as T1, the outlet CO2 temperature of the indoor main heat exchanger 4 in the refrigeration mode as T3, the outlet air temperature of the air conditioning box 18 as T2, the outlet temperature of the indoor secondary heat exchanger 3 in the refrigeration mode as T4, the water outlet temperature of the battery heat exchange plate 6 as T5, the water outlet is the pipeline 16, and the exhaust pressure of the compressor 1 as P.

[0058] The control method for the passenger compartment refrigeration and battery cooling mode is as follows: the third two-way full-pass throttle valve 15 establishes a PID adjustment relationship with T1, and the fourth two-way full-pass throttle valve 19 establishes an adjustment relationship with the preset outlet superheat of the indoor main heat exchanger 4, that is, to ensure that the temperature of T4 is always the insulation temperature corresponding to the local pressure plus x degrees, where x is the preset outlet superheat (exemplarily, the recommended value of x is 5), so as to ensure that the secondary indoor heat exchanger is in a slightly two-phase state and increase the heat exchange capacity of the indoor secondary heat exchanger 3. Since the indoor secondary heat exchanger 3 is downstream on the air side, the heat exchange temperature difference is small. The first two-way full-pass throttle valve 12 establishes a PID adjustment relationship with the exhaust pressure P of the compressor 1, and the speed of the compressor 1 establishes a PID adjustment relationship with the outlet air temperature of the air conditioning box 18.

[0059] The control method for only the battery cooling mode is as follows: the third two-way full-pass throttle valve 15 establishes a PID adjustment relationship with the exhaust pressure P, and the compressor 1 establishes an adjustment relationship with T5. The specific value of T5 is related to the state of the battery and is selected according to the actual state of the battery within the range of 10 to 30 °C.

[0060] The control method for only the passenger compartment refrigeration mode is as follows: the first two-way full-pass throttle valve 12 establishes a PID adjustment relationship with the outlet air temperature T2, the compressor 1 establishes a PID adjustment relationship with the exhaust pressure P, and the third two-way full-pass throttle valve 15 establishes an adjustment relationship with the preset outlet superheat of the indoor main heat exchanger 4, that is, to ensure that the temperature of T4 is always the saturation temperature corresponding to the local pressure plus x degrees, where x is the preset superheat (exemplarily, the recommended value of x is 5), and the fourth two-way full-pass throttle valve 19 is in the full-pass state, and the water flow through the battery heat exchange cold plate is closed. The closing method can be achieved by closing the water pump or by switching or bypassing the water flow, depending on the actual battery and motor cooling water circuits of the system.

[0061] The control method for the passenger compartment heating and battery heating modes is as follows: Since the battery heat exchange cold plate is downstream of the indoor main heat exchanger 4 in the heating mode, it is easy for the CO2 working medium temperature at the outlet of the indoor main heat exchanger 4 to be low due to the low inlet air temperature, resulting in the phenomenon that the battery cannot be heated. Therefore, the proportional regulating damper 21 and T1 establish a PID conditional relationship, and by indirectly reducing the heat exchange capacity of the indoor main heat exchanger 4 and the indoor secondary heat exchanger 3 in the HVAC, the heat exchange temperature difference between the outlet CO2 working medium temperature T1 of the main heat exchanger and the inlet air temperature is changed, so as to achieve the function of controlling T1 to heat the battery. The recommended value of T1 is 45°C. The compressor 1 and T2 establish a PID adjustment control relationship, and the third two-way full-pass throttle valve 15 and the exhaust pressure P establish a PID adjustment control relationship. When the proportional regulating damper 21 is fully closed and T1 still cannot reach the target value, enter the selection mode. If the battery heating is still in priority, at this time, the blower speed in the HVAC is adjusted to automatic adjustment with priority, and the air volume is reduced by one gear every 5 minutes until T1 meets the temperature requirement; if the battery is no longer in a state of urgent heating, the state of the fully closed proportional regulating damper 21 is maintained for operation.

[0062] The control method for only the battery heating mode is: The third two-way full-pass throttle valve 15 and the exhaust pressure P establish a PID adjustment relationship, and the compressor 1 and T5 establish an adjustment relationship.

[0063] The control method for only the passenger compartment heating mode is: The compressor 1 and T2 establish a PID adjustment control relationship, the third two-way full-pass throttle valve 15 and the exhaust pressure P establish a PID adjustment control relationship, the fourth two-way full-pass throttle valve 19 is in a full-pass state, and the water flow through the battery heat exchange cold plate is closed. The closing method can be achieved by closing the water pump or by switching or bypassing the water flow, depending on the actual battery and motor cooling water circuits of the system.

[0064] The control method for the defrosting and defogging modes is: The compressor 1 and T2 establish a PID adjustment control relationship, T2 is the target quantity, the second two-way full-pass throttle valve 14 and T1 establish a PID adjustment control relationship, the recommended value of T1 is 0°C, and the value of the exhaust pressure P is monitored. If T1 still cannot reach the control target after the exhaust pressure P value exceeds 14 MPa, the outdoor fan 17 is turned off, and the air intake grille at the front of the vehicle is closed to ensure that no air enters the outdoor heat exchanger 2.

[0065] The control method for the defrosting mode is as follows: The fourth two-way full-pass throttle valve 19 is in the full-pass state, the opening degree of the third two-way full-pass throttle valve 15 is adjusted to 75% of the full-opening value, the outdoor fan 17 is turned off, and the air inlet grille at the front of the vehicle is closed to ensure that no air enters the outdoor heat exchanger 2, and the indoor blower 20 is turned off. If the temperature of the battery is greater than 10 °C, the water flow of the battery heat exchange cold plate is turned on before the defrosting starts, and the waste heat of the battery is used for defrosting during the defrosting stage.

[0066] The control method for the passenger compartment heating and battery waste heat recovery mode is as follows: After starting this mode, the outdoor fan 17 is turned off, and the air inlet grille at the front of the vehicle is closed. The compressor 1 establishes an adjustment relationship with T2 to ensure the supply air temperature. The fourth two-way full-pass throttle valve 19 establishes a PID control relationship with the exhaust pressure P to ensure performance. The third two-way full-pass throttle valve 15 is in the full-pass state, and the temperature at the T1 position is monitored. When the T1 temperature is less than the set value T01, the recommended set value of T01 is 8 °C, which can be adjusted according to the actual capacity of the battery. The closed blower is turned on, and the air inlet grille at the front of the vehicle is opened. The third two-way full-pass throttle valve 15 is changed to establish a PID adjustment relationship with the exhaust pressure P, and the fourth two-way full-pass throttle valve 19 is changed to establish a PID control relationship with the exhaust pressure T1. The control relationship of the compressor 1 remains unchanged. Among them, in the control of the passenger compartment heating and battery waste heat recovery mode, when the T1 temperature is less than the set value T01, before turning on the closed blower and opening the air inlet grille at the front of the vehicle, first disconnect the PID control relationship established between the fourth two-way full-pass throttle valve 19 and the exhaust pressure P, increase the opening degree of the two-way full-pass throttle valve by 10% of the original opening degree, and keep running at a fixed opening degree for n minutes. The recommended value of n is 3. After that, change the control logic before turning off the blower and closing the air inlet grille at the front of the vehicle to ensure the stability of the switching process.

[0067] In the modes of crew compartment refrigeration + battery cooling, only crew compartment refrigeration, and only battery cooling, the temperature value of T4 is always detected. When the temperature value of T4 is less than 2°C, the indoor blower speed is increased by one gear. If the water flow of the battery heat exchange cold plate waterway is in the open state at that time, the water flow is increased by 20%, and the rest is controlled by the control method at that time. To prevent frosting and icing on the indoor secondary heat exchanger and the main heat exchanger due to the evaporation temperature being lower than 0°C. In the crew compartment refrigeration and battery cooling control mode, the calibration of the optimal exhaust pressure P value is related to the values of T1, T3, T4, and the outlet temperature of the outdoor heat exchanger. In the only crew compartment refrigeration control mode, the calibration of the optimal exhaust pressure P value is related to the values of T3, T4, and the outlet temperature of the outdoor heat exchanger. In the only battery cooling control mode, the calibration of the optimal exhaust pressure P value is related to the value of T5 and the outlet temperature of the outdoor heat exchanger. In the crew compartment heating, battery heating, and only battery heating control modes, the calibration of the optimal exhaust pressure P value is related to the CO2 working medium outlet temperature on the side of the battery heat exchange cold plate close to the third two-way full-pass throttle valve and the ambient temperature. In the control mode of crew compartment heating and waste heat recovery, before turning on the closed blower and opening the air intake grille at the front of the vehicle, the calibration of the optimal exhaust pressure P value is related to the CO2 outlet temperature at one end of the indoor main heat exchanger close to the fourth two-way full-pass throttle valve and the value of T1; after turning on the closed blower and opening the air intake grille at the front of the vehicle, the calibration of the optimal exhaust pressure P value is related to the CO2 outlet temperature at one end of the indoor main heat exchanger close to the fourth two-way full-pass throttle valve, T1, and the ambient temperature value.

[0068] The present invention discloses a vehicle carbon dioxide heat management system and its control method. The first two-way full-pass throttle valve, the indoor secondary heat exchanger, and the second two-way full-pass throttle valve are sequentially connected in series to form one path; the third two-way full-pass throttle valve, the battery heat exchange plate, the fourth two-way full-pass throttle valve, and the indoor main heat exchanger are sequentially connected in series to form one path; the two paths form a large parallel connection, and a fifth solenoid valve is arranged between the first two-way full-pass throttle valve and the third two-way full-pass throttle valve. Through the series connection of the battery heat exchange cold plate and the indoor main heat exchanger, the transformation of the battery energy from the traditional scheme of active distribution by the system side to the on-demand extraction by the battery water side is realized. By controlling the superheat at the outlet of the main heat exchanger, the problems of system control delay and poor stability caused by the large lag of the waterway in the energy distribution control are solved. Through the system layout and reasonable control method of the present invention, it is ensured that both refrigeration and heating adapt to the heat exchange characteristics of CO2, the performance is guaranteed, and at the same time, the stability of the control is guaranteed.

[0069] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit it. Although the present invention has been described in detail with reference to the above embodiments, those of ordinary skill in the art should understand that: modifications or equivalent substitutions can still be made to the specific implementation manners of the present invention, and any modification or equivalent substitution that does not depart from the spirit and scope of the present invention shall be covered by the protection scope of the claims of the present invention.

Claims

1. A transcritical CO2 system for vehicle thermal management, characterized in that, Including: A compressor (1), an outdoor heat exchanger (2), an indoor secondary heat exchanger (3), an indoor main heat exchanger (4), a regenerator (5), a battery heat exchange plate (6), a gas-liquid separator (7), a first solenoid valve (8), a second solenoid valve (9), a third solenoid valve (10), a fourth solenoid valve (11), a fifth solenoid valve (13), a first bi-directional all-pass throttle valve (12), a second bi-directional all-pass throttle valve (14), a third bi-directional all-pass throttle valve (15), a fourth bi-directional all-pass throttle valve (19), an outdoor fan (17), and an indoor blower (20); The indoor secondary heat exchanger (3), the indoor main heat exchanger (4), and the indoor blower (20) are disposed inside an air-conditioning box (18), and the air-conditioning box (18) is provided with an air door; the outdoor fan (17) is used to provide forced convection air volume for the outdoor heat exchanger (2) outside the occupant compartment; the indoor blower (20) is used to provide air volume for the occupant compartment inside the air-conditioning box (18); The outlet of the compressor (1) is connected to the high-pressure side inlet of the regenerator (5) through the first solenoid valve (8) and the outdoor heat exchanger (2); one path of the high-pressure side outlet of the regenerator (5) is connected to the inlet of the main heat exchanger through the battery heat exchange cold plate and the fourth bi-directional all-pass throttle valve (19), and the other path of the high-pressure side outlet of the regenerator (5) is connected to the inlet of the indoor secondary heat exchanger (3) through the fifth solenoid valve (13) and the first bi-directional all-pass throttle valve (12). After the outlets of the main heat exchanger and the indoor secondary heat exchanger (3) converge, they are connected to the inlet of the compressor (1) through the fourth solenoid valve (11), the gas-liquid separator (7), and the low-pressure side of the regenerator (5); wherein, a second bi-directional all-pass throttle valve (14) is disposed between the outlet of the indoor secondary heat exchanger (3) and the fourth solenoid valve (11); One end of the second solenoid valve (9) is connected between the outlet of the compressor (1) and the first solenoid valve (8), and the other end is connected between the fifth solenoid valve (13) and the first bi-directional all-pass throttle valve (12); one end of the third solenoid valve (10) is connected between the outdoor heat exchanger (2) and the first solenoid valve (8), and the other end is connected between the gas-liquid separator (7) and the fourth solenoid valve (11).

2. The transcritical CO2 system for vehicle thermal management according to claim 1, characterized in that A proportional adjustment air door (21) is disposed between the indoor main heat exchanger (4) and the indoor secondary heat exchanger (3).

3. The transcritical CO2 system for vehicle thermal management according to claim 2, characterized in that, In the case of simultaneous refrigeration of the occupant compartment and battery cooling mode, the first solenoid valve (8), the fourth solenoid valve (11), and the fifth solenoid valve (13) are all opened, and the second solenoid valve (9) and the third solenoid valve (10) are all closed; the second bi-directional all-pass throttle valve (14) is in a fully open state; In the case of only the passenger compartment refrigeration mode, the first solenoid valve (8), the fourth solenoid valve (11), and the fifth solenoid valve (13) are all opened, and the second solenoid valve (9) and the third solenoid valve (10) are all closed; the second two-way all-pass throttle valve (14) is in the all-pass state; the water-side flow of the battery heat exchange cold plate is closed. In the case of only the battery cooling mode, the first solenoid valve (8) and the fourth solenoid valve (11) are all opened, and the second solenoid valve (9), the third solenoid valve (10), and the fifth solenoid valve (13) are all closed; the second two-way all-pass throttle valve (14) is in the all-pass state; the air damper of the air conditioner box (18) and the indoor blower (20) are all closed.

4. The transcritical CO2 system for vehicle thermal management according to claim 3, characterized in that, In the case of the passenger compartment heating and battery heating mode, the first solenoid valve (8), the fourth solenoid valve (11), and the fifth solenoid valve (13) are closed, and the second solenoid valve (9) and the third solenoid valve (10) are all opened; the first two-way all-pass throttle valve (12), the second two-way all-pass throttle valve (14), and the fourth two-way all-pass throttle valve (19) are all in the all-pass state. In the case of only the passenger compartment heating mode, the first solenoid valve (8), the fourth solenoid valve (11), and the fifth solenoid valve (13) are closed, and the second solenoid valve (9) and the third solenoid valve (10) are all opened; the first two-way all-pass throttle valve (12), the second two-way all-pass throttle valve (14), and the fourth two-way all-pass throttle valve (19) are all in the all-pass state; the water-side flow of the battery heat exchange cold plate is closed. In the case of only the battery heating mode, the first solenoid valve (8), the fourth solenoid valve (11), and the fifth solenoid valve (13) are closed, and the second solenoid valve (9) and the third solenoid valve (10) are all opened; the first two-way all-pass throttle valve (12), the second two-way all-pass throttle valve (14), and the fourth two-way all-pass throttle valve (19) are all in the all-pass state; the air damper of the air conditioner box (18) and the indoor blower (20) are closed.

5. The transcritical CO2 system for vehicle thermal management according to claim 4, characterized in that, In the defrosting and defogging mode, the first solenoid valve (8), the fourth solenoid valve (11), and the fifth solenoid valve (13) are closed, and the second solenoid valve (9) and the third solenoid valve (10) are all opened; the third two-way all-pass throttle valve (15) is in the fully open or throttling state based on a preset condition; the second two-way all-pass throttle valve (14) is in the throttling state. In the defrosting mode, the first solenoid valve (8) and the fourth solenoid valve (11) are all opened, and the second solenoid valve (9), the third solenoid valve (10), and the fifth solenoid valve (13) are all closed; the fourth two-way all-pass throttle valve (19) is in the all-pass state; the third two-way all-pass throttle valve (15) is in the throttling state; the air damper of the air conditioner box (18) and the indoor blower (20) are closed.

6. The transcritical CO2 system for vehicle thermal management according to claim 5, characterized in that, When in the mode of heating the passenger compartment while recovering the waste heat of the battery, the first solenoid valve (8), the fourth solenoid valve (11) and the fifth solenoid valve (13) are closed, and the second solenoid valve (9) and the third solenoid valve (10) are both open; the fourth bi-directional all-pass throttle valve (19) is in the throttling state.

7. A control method for a transcritical CO2 system for vehicle thermal management according to claim 6, characterized in that, It includes the following steps: Obtain the CO2 temperature T1 at one end of the battery heat exchange cold plate close to the fourth bi-directional all-pass throttle valve (19), the outlet air temperature T2 of the air conditioner box (18), the outlet CO2 temperature T3 of the indoor main heat exchanger (4) in the refrigeration mode, the outlet temperature T4 of the indoor secondary heat exchanger (3) in the refrigeration mode, the water outlet temperature T5 of the battery heat exchange plate (6), and the exhaust pressure P of the compressor (1); The control method for the mode of cooling the passenger compartment while cooling the battery is: The third bi-directional all-pass throttle valve (15) establishes a PID adjustment relationship with T1; the fourth bi-directional all-pass throttle valve (19) establishes an adjustment relationship with the preset outlet superheat of the indoor main heat exchanger (4) to ensure that the temperature of T4 is always the insulation temperature corresponding to the local pressure plus x degrees, where x is the preset outlet superheat; the first bi-directional all-pass throttle valve (12) establishes a PID adjustment relationship with P, and the rotational speed of the compressor (1) establishes a PID adjustment relationship with T2; The control method for only the battery cooling mode is: The third bi-directional all-pass throttle valve (15) establishes a PID adjustment relationship with P, and the compressor (1) establishes an adjustment relationship with T5; The control method for only the passenger compartment refrigeration mode is: The first bi-directional all-pass throttle valve (12) establishes a PID adjustment relationship with T2, the compressor (1) establishes a PID adjustment relationship with P, and the third bi-directional all-pass throttle valve (15) establishes an adjustment relationship with the preset outlet superheat of the indoor main heat exchanger (4) to ensure that the temperature of T4 is always the saturation temperature corresponding to the local pressure plus x degrees, where x is the preset superheat; the fourth bi-directional all-pass throttle valve (19) is in the all-pass state, and the water flow through the battery heat exchange cold plate is closed.

8. The control method of a transcritical CO2 system for vehicle thermal management according to claim 7, characterized in that The control method for the mode of heating the passenger compartment while heating the battery is: The proportional regulating air damper (21) establishes a PID condition relationship with T1; the compressor (1) establishes a PID adjustment control relationship with T2; the third bi-directional all-pass throttle valve (15) establishes a PID adjustment control relationship with P; wherein, when the proportional regulating air damper (21) is completely closed and T1 still cannot reach the target value, enter the selection mode; the selection mode includes that if the battery heating is still in priority, the rotational speed of the indoor blower (20) is adjusted to automatic adjustment with priority, and the air volume is reduced by one gear every preset time interval until T1 meets the temperature requirement; if the battery is no longer in priority, the state of the proportional regulating air damper (21) being completely closed is maintained for operation; The control method for only the battery heating mode is: The third bi-directional all-pass throttle valve (15) establishes a PID adjustment relationship with P, and the compressor (1) establishes an adjustment relationship with T5; The control method for the heating mode of the passenger compartment only is as follows: The compressor (1) establishes a PID regulation control relationship with T2; the third two-way all-pass throttle valve (15) establishes a PID regulation control relationship with P; the fourth two-way all-pass throttle valve (19) is in the all-pass state, and the water flow through the battery heat exchange cold plate is closed.

9. The control method of a transcritical CO2 system for vehicle thermal management according to claim 7, wherein The control method for the defrosting and demisting mode is as follows: The compressor (1) establishes a PID regulation control relationship with T2, where T2 is the target value; the second two-way all-pass throttle valve (14) establishes a PID regulation control relationship with T1; monitor the P value, if the T1 still cannot reach the control target after the P value exceeds 14 MPa, then turn off the outdoor fan (17) so that no air passes through the outdoor heat exchanger (2); The control method for the defrosting mode is as follows: The fourth two-way all-pass throttle valve (19) is in the all-pass state, the opening of the third two-way all-pass throttle valve (15) is adjusted to a preset opening, the outdoor fan (17) is turned off so that no air passes through the outdoor heat exchanger (2), and the indoor blower (20) is turned off; if the temperature of the battery is greater than 10 °C, then turn on the water flow of the battery heat exchange cold plate before the defrosting starts, and use the waste heat of the battery for defrosting during the defrosting stage.

10. The control method of a transcritical CO2 system for vehicle thermal management according to claim 7, wherein The control method for the heating of the passenger compartment and the recovery of battery waste heat is as follows: Turn off the outdoor fan (17), and the compressor (1) establishes a regulation relationship with T2; the fourth two-way all-pass throttle valve (19) establishes a PID control relationship with P; the third two-way all-pass throttle valve (15) is in the all-pass state, and the temperature at the T1 position is monitored; when the T1 temperature is less than the set value, turn on the outdoor fan (17), change the third two-way all-pass throttle valve (15) to establish a PID regulation relationship with P, and change the fourth two-way all-pass throttle valve (19) to establish a PID control relationship with T1.

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