Tianfluground water heat pump air-conditioning system for bus and control method of Tianfluground water heat pump air-conditioning system

Abstract

An exhaust port of a compressor is connected with an inlet pipe of a four-way valve, the other three pipelines of the four-way valve are connected with an outdoor core body, a gas-liquid separator and a heating plate type heat exchanger respectively, and the two ends of the refrigerant side of the heating plate type heat exchanger are connected with first one-way valves in parallel; the other end of the heating plate heat exchanger is connected with an indoor core through a refrigerant pipeline, the other end of the indoor core is connected with a two-way filter, and an outlet of the two-way filter is connected with a second one-way valve and a main-path electronic expansion valve, and the other end of the second one-way valve is connected with a third one-way valve and a battery-side electronic expansion valve. The other end of the third one-way valve is connected with the main path electronic expansion valve and the drying filter, and the other end of the drying filter is connected with the outdoor core body. The problem that a heating head is hot and feet are cold in a conventional bus air conditioning system is solved, and the system is simple in structure, easy to implement and applied to products.

Description

Technical Field

[0001] The present invention belongs to the field of new energy vehicle battery management, and specifically relates to a natural fluorine ground water heat pump air conditioning system for buses and a control method thereof. Background Art

[0002] At present, the vast majority of conventional heat pump air conditioning systems in the bus air conditioning industry use top-mounted air conditioning plus bottom electric auxiliary heating or fuel heaters. Conventional heat pump air conditioning hot air is delivered from the top. Since the hot air floats, the warm air cannot be delivered to the bottom of the passenger compartment. Therefore, most electric air conditioners in the bus air conditioning industry currently have the problem of heating the top and cold the feet, which seriously affects the comfort of passengers. When the ambient temperature is low, the electric auxiliary heating intervention heating not only greatly increases the power consumption, but also the electric auxiliary heating outlet temperature is too high, which also has a negative impact on comfort. The existing technologies are: (1) Roof-mounted heat pump air conditioning system + bottom-mounted electric heating.

[0003] (2) Roof-mounted heat pump air conditioning system + fuel heater.

[0004] shortcoming: (1) The roof-mounted heat pump air conditioning system + bottom-mounted electric heating solution used in the market has uneven temperature distribution in the passenger compartment regardless of the heating conditions, with the head being hot and the feet being cold, which is very uncomfortable. In addition, when the ambient temperature is low, the use of electric heating consumes a lot of electricity, affecting the battery life.

[0005] (2) The existing roof-mounted heat pump air conditioning system + fuel heater on the market also has the problem of uneven temperature distribution in the passenger compartment, with the head being hot and the feet being cold, resulting in poor comfort. At the same time, the heating cost is greatly increased after using the fuel heater when the ambient temperature is low. The air outlet temperature of the fuel heater is too high, resulting in poor body sensation. Summary of the invention

[0006] The technical problem to be solved by the present invention is: how to solve the problem of large temperature difference between the upper and lower parts of the passenger cabin during winter heating by a heat pump air conditioner, resulting in a hot head and cold feet in the passenger cabin. The present invention can make the temperature of the passenger cabin more uniform, the air supply more comfortable and energy-saving when the heat pump air conditioning system is running in winter, thereby improving the comfort of the air conditioning. A natural fluorine and ground water heat pump air conditioning system and a control method for buses are provided.

[0007] To achieve the above object, the present invention is achieved through the following technical solutions: A natural fluorine and ground water heat pump air conditioning system for buses comprises a compressor, the exhaust port of the compressor is connected to the inlet pipe of a four-way valve, the other three pipelines of the four-way valve are respectively connected to an outdoor core, a gas-liquid separator and a heating plate heat exchanger, the first one-way valve is connected in parallel at both ends of the refrigerant side of the heating plate heat exchanger, the other end of the heating plate heat exchanger is connected to an indoor core through a refrigerant pipeline, the other end of the indoor core is connected to a two-way filter, the outlet of the two-way filter is respectively connected to a second one-way valve and a main electronic expansion valve, wherein the other end of the second one-way valve is respectively connected to a third one-way valve and a battery-side electronic expansion valve, the battery-side electronic expansion valve is connected to the battery plate heat exchanger, the other end of the third one-way valve is respectively connected to the main electronic expansion valve and a drying filter, and the other end of the drying filter is connected to the outdoor core; The heating plate heat exchanger is a natural fluorine and ground water plate heat exchanger. The water side outlet of the heating plate heat exchanger is divided into at least two heating water circuits. Each heating water circuit includes a water pump connected in series, a liquid heat PTC and a different number of water-heating forced radiators. The water-heating forced radiators are located at the bottom of the passenger compartment. After the heating water circuits converge, they return to the heating plate heat exchanger to form a closed loop on the water side.

[0008] A left defrost temperature sensor, a right defrost temperature sensor and a return air temperature sensor are respectively arranged on the indoor core.

[0009] An outdoor defrost temperature sensor and an outdoor temperature sensor are arranged on the outdoor core.

[0010] The exhaust port of the compressor is connected to the inlet pipe of the four-way valve through a high-pressure charging valve, an exhaust temperature sensor and a high-pressure pressure switch, and a low-pressure pressure switch is provided on the low-pressure side of the compressor.

[0011] The gas-liquid separator is respectively connected with a low-pressure charging valve and an intake temperature sensor.

[0012] The battery plate heat exchanger is connected with a battery pressure sensor; the battery plate heat exchanger is provided with a water inlet and a water outlet.

[0013] A control method for a natural fluorine ground water heat pump air conditioning system for a bus using the system includes a cooling mode control method and a heating mode control method: The refrigeration mode control method is as follows: When the air conditioning system is in cooling mode, the refrigerant is discharged from the compressor and enters the outdoor core. After flowing out of the outdoor core, the refrigerant is divided into two paths. One path flows to the battery plate heat exchanger through the third one-way valve and the battery-side electronic expansion valve in sequence, and the other path flows to the indoor core through the main electronic expansion valve; among them, the refrigerant flowing through the battery plate heat exchanger enters the gas-liquid separator after heat exchange; the refrigerant flowing through the indoor core enters the gas-liquid separator after heat exchange through the first one-way valve and the heating plate heat exchanger, and finally returns to the compressor; In cooling mode, the opening of the main electronic expansion valve is controlled by the target exhaust temperature. The control formula is as follows: T 目标 =aF+b Among them, T 目标 The target exhaust temperature is calculated by the formula, a is the coefficient, b is the constant, and F is the compressor operating frequency. a and b use different values ​​in different environmental ranges. When the actual exhaust temperature T 实际 >T 目标 When T 实际 <T 目标 , the main circuit electronic expansion valve is closed; The heating mode control method is as follows: When the air conditioning system is in heating mode, after the refrigerant is discharged from the compressor, it first passes through the heating plate heat exchanger on the heating side. At this time, the first one-way valve on the heating side is in a closed state. After the refrigerant flows out of the heating plate heat exchanger, it enters the indoor core. After being cooled again by the indoor core, it is divided into two paths. One path enters the battery plate heat exchanger after throttling by the main electronic expansion valve and the third one-way valve in turn, and the other path enters the outdoor core after throttling by the main electronic expansion valve. After heat exchange, the two refrigerants merge into the gas-liquid separator and finally return to the compressor. In heating mode, the opening of the main electronic expansion valve is controlled by the target exhaust temperature. The control formula is as follows: T 目标 =T 芯 +f*F+e Among them, T 目标 The target exhaust temperature is calculated by the formula, and the actual core temperature T 芯 , f is the coefficient, e is the constant, and F is the compressor operating frequency.

[0014] When the air conditioning system is in heat pump heating mode, the ambient temperature is divided into different zones T a 、T b and T c , -15℃<T a ≤-5℃、-5℃<T b ≤5℃、T c >5℃, each temperature zone corresponds to a different duty cycle of the indoor fan, and the duty cycles of the three ranges are -15℃<T a ≤-5℃Duty cycle 20%, -5℃<T b ≤5℃ Duty cycle 25%, T c >5℃ duty cycle 30%.

[0015] After the heating mode is turned on, the water pump in the heating water circuit connected in parallel with the heating plate heat exchanger is turned on first. After a certain period of time, the heating water circuit system circulation is stable, and the ceiling air conditioner is turned on. The ceiling air conditioner determines the duty cycle of the indoor ceiling fan according to the current ambient temperature. After the ceiling air conditioner is turned on, the bottom-mounted water-heating forced radiator executes the anti-cold wind logic, that is: when the return water temperature of the heating water circuit is lower than T1, the water-heating forced radiator will not output air. The return water temperature T1 is preferentially set to 20°C. When the return water temperature is greater than T1, the water-heating forced radiator will output air according to the set gear.

[0016] When the ambient temperature is higher than T2, the liquid heat PTC will not start. The T2 setting temperature is 5°C. In addition, whether the liquid heat PTC starts is determined by the temperature difference between the set return water temperature and the actual return water temperature. 设 -T 回 ≥a, the liquid thermal PTC third gear starts; T 设 -T 回 ≥b, the liquid heat PTC operates in two gears; T 设 -T 回 ≥c, first gear operation, T 设 -T 回 Closed when ≥d.

[0017] Compared with the prior art, the present invention has the following beneficial effects: the natural fluorine and ground water heat pump air conditioning system of the present invention is a combination of a refrigerant system and a water system. The heat pump raises the water temperature and then transports it to the radiator at the bottom of the passenger compartment. The bottom forced radiator transports the heat from the bottom to the entire passenger compartment. The principle of hot air floating is used to achieve the purpose of improving the temperature uniformity of the entire vehicle, and solve the problem of the conventional bus air conditioning system with hot head and cold feet. The principle of this system has a simple structure and is easy to implement, and has been applied to products. The present invention is suitable for all vehicles that require heat pump air conditioning. At the same time, the natural fluorine and ground water heat pump air conditioning system takes into account the functions of high-temperature refrigeration, normal temperature refrigeration, normal temperature heating, low temperature heating, defrosting, battery thermal management, etc. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 It is the system principle diagram of the present invention; Figure 2 It is the principle diagram of the refrigeration mode of the present invention; Figure 3 It is a principle diagram of the heating mode of the present invention. DETAILED DESCRIPTION

[0019] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0020] In the description of the present invention, it is necessary to understand that the terms "upper", "lower", "front", "back", "left", "right", "top", "bottom", "inside", "outside", etc., indicating the orientation or position relationship are based on the orientation or position relationship shown in the drawings, and are only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as a limitation on the present invention.

[0021] like Figure 1 As shown, a natural fluorine and ground water heat pump air conditioning system for buses includes a compressor 1, the exhaust port of the compressor 1 is connected to the inlet pipe of the four-way valve 10, and the other three pipelines of the four-way valve 10 are respectively connected to the outdoor core 2, the gas-liquid separator 5 and the heating plate heat exchanger 3, the first one-way valve 4 is connected in parallel at both ends of the refrigerant side of the heating plate heat exchanger 3, the other end of the heating plate heat exchanger 3 is connected to the indoor core 6 through the refrigerant pipeline, the other end of the indoor core 6 is connected to the two-way filter 7, the outlet of the two-way filter 7 is respectively connected to the second one-way valve 8 and the main electronic expansion valve 9, wherein the other end of the second one-way valve 8 is respectively connected to the third one-way valve 11 and the battery side electronic expansion valve 12, the battery side electronic expansion valve 12 is connected to the battery plate heat exchanger 28, the other end of the third one-way valve 11 is respectively connected to the main electronic expansion valve 9 and the drying filter 13, and the other end of the drying filter 13 is connected to the outdoor core 2.

[0022] The heating plate heat exchanger 3 is a natural fluorine and ground water plate heat exchanger. The water side outlet of the heating plate heat exchanger 3 is divided into at least two heating water circuits. Each heating water circuit includes a water pump 14 connected in series, a liquid heat PTC 15 and a different number of water-heating forced radiators 16. The water-heating forced radiators 16 are located at the bottom of the passenger compartment. The number of water-heating forced radiators 16 is configured according to the actual load. After the multiple heating water circuits converge, they return to the heating plate heat exchanger 3 to form a closed loop on the water side.

[0023] The system of the present invention is provided with a heating plate heat exchanger 3, which is connected in series with the indoor core 6. The refrigerant of the heat pump air conditioning system firstly heats the water through the heating plate heat exchanger 3. When the water temperature reaches a predetermined temperature, the hot water is transported by the water system to the water heating forced radiator 16 at the bottom of the passenger compartment. The heat is transported to the entire passenger compartment through the water heating forced radiator 16. At the same time, the refrigerant passes through the indoor core 6, and part of the heat is transported from the top to the passenger compartment, forming a heating form of three-dimensional heating at the top and the bottom at the same time.

[0024] Furthermore, a left defrost temperature sensor 17 , a right defrost temperature sensor 18 and a return air temperature sensor 19 are respectively provided on the indoor core 6 .

[0025] Furthermore, an outdoor defrost temperature sensor 20 and an outdoor temperature sensor 21 are provided on the outdoor core 2 .

[0026] Furthermore, the exhaust port of the compressor 1 is connected to the inlet pipe of the four-way valve 10 through a high-pressure charging valve 22, an exhaust temperature sensor 23 and a high-pressure pressure switch 24, and a low-pressure pressure switch 25 is provided on the low-pressure side of the compressor 1.

[0027] Furthermore, the gas-liquid separator 5 is connected to a low-pressure charging valve 26 and an intake air temperature sensor 27 respectively.

[0028] Furthermore, a battery pressure sensor 29 is connected to the battery plate heat exchanger 28. The battery plate heat exchanger 28 is provided with a waterway inlet 30 and a waterway outlet 31.

[0029] A control method for a natural fluorine ground water heat pump air conditioning system for a bus includes a cooling mode control method and a heating mode control method.

[0030] like Figure 2 As shown, the cooling mode control method is as follows: When the air conditioning system is in cooling mode, the refrigerant is discharged from the compressor 1 and enters the outdoor core 2. After flowing out of the outdoor core 2, the refrigerant is divided into two paths. One path flows to the battery plate heat exchanger 28 through the third one-way valve 11 and the battery-side electronic expansion valve 12 in sequence, and the other path flows to the indoor core 6 through the main electronic expansion valve 9. Among them, the refrigerant flowing through the battery plate heat exchanger 28 enters the gas-liquid separator 5 after heat exchange; the refrigerant flowing through the indoor core 6 enters the gas-liquid separator 5 after heat exchange through the first one-way valve 4 and the heating plate heat exchanger 3, and finally returns to the compressor 1.

[0031] In cooling mode, the opening of the main electronic expansion valve 9 is controlled by the target exhaust temperature. The control formula is as follows: T 目标 =aF+b Where T 目标 is the formula for calculating the target exhaust temperature, a is a coefficient, b is a constant, F is the compressor operating frequency, a and b use different values ​​in different environmental intervals, when the actual exhaust temperature T collected by the exhaust temperature sensor 23 实际 >T 目标 When the main circuit electronic expansion valve 9 opens wide, when T 实际 <T 目标 , the main electronic expansion valve 9 is closed.

[0032] The coefficient can be calibrated according to the actual configuration. The application examples of the preferred correlation coefficient are as follows: a b Temperature range 0.18 43 5℃≤Outdoor<13℃ 0.28 44 13℃≤Outdoor<21℃ 0.32 46 21℃≤Outdoor<29℃ 0.32 50 29℃≤Outdoor<33℃ 0.32 53 33℃≤Outdoor<38℃ 0.28 56 38℃≤Outdoor<42℃ 0.24 62 42℃≤Outdoor<46℃ 0.18 72 46℃≤Outdoor like Figure 3 As shown, the heating mode control method is as follows: When the air-conditioning system is in heating mode, after the refrigerant is discharged from the compressor 1, it first passes through the heating plate heat exchanger 3 on the heating side. At this time, the first one-way valve 4 on the heating side is in a closed state. The refrigerant flows out of the heating plate heat exchanger 3 and enters the indoor core 6. After being cooled again by the indoor core 6, it is divided into two paths. One path enters the battery plate heat exchanger 28 after throttling by the main electronic expansion valve 9 and the third one-way valve 11, and the other path enters the outdoor core 2 after throttling by the main electronic expansion valve 9. The two refrigerants merge after heat exchange and enter the gas-liquid separator 5, and finally return to the compressor 1.

[0033] When the air conditioning system is in heat pump heating mode, the ambient temperature is divided into different zones T a , T b , T c For example, -15℃~20℃ is divided into -15℃<T a ≤-5℃、-5℃<T b ≤5℃、T c >5℃, each temperature zone corresponds to a different duty cycle of the indoor fan (low duty cycle, low proportion of overhead heating), and the duty cycles of the three preferred intervals are -15℃<T a ≤-5℃Duty cycle 20%, -5℃<T b ≤5℃ Duty cycle 25%, T c >5℃ duty cycle 30%.

[0034] After the heating mode is turned on, in the heating water circuit connected in parallel with the heating plate heat exchanger 3, the water pump 14 is turned on first. After a certain period of time, the heating water circuit system circulation is stable, and the ceiling air conditioner is turned on. The ceiling air conditioner determines the duty cycle of the indoor ceiling fan according to the current ambient temperature. After the ceiling air conditioner is turned on, the bottom-mounted water-heating forced radiator 16 executes the anti-cold wind logic, that is: when the return water temperature of the heating water circuit is lower than T1, the water-heating forced radiator 16 does not output air, and the return water temperature T1 is preferentially set to 20°C. When the return water temperature is greater than T1, the water-heating forced radiator 16 outputs air according to the set gear.

[0035] At the same time, the liquid thermal PTC 15 determines whether it needs to be turned on based on the ambient temperature and the temperature inside the vehicle. The logic for turning on the liquid thermal PTC 15 is as follows: When the ambient temperature is higher than T2, the liquid heat PTC will not start. The T2 setting temperature is 5°C. In addition, whether the liquid heat PTC starts is determined by the temperature difference between the set return water temperature and the actual return water temperature. For example, when the liquid heat PTC has three gears, when the set water temperature T 设 -T 回 ≥a, the liquid thermal PTC third gear starts; T 设 -T 回 ≥b, the liquid heat PTC operates in two gears; T 设 -T 回≥c, first gear operation, T 设 -T 回 Close when ≥d. Preferably, a, b, c, d are 8, 6, 4, 2 respectively.

[0036] When the heat pump is defrosting, the liquid thermal PTC intervenes to supplement the heat required for defrosting, while maintaining the water temperature to ensure the comfort of the passenger compartment during defrosting.

[0037] In heating mode, the opening of the main electronic expansion valve 9 is controlled by the target exhaust temperature. The control formula is as follows: T 目标 =T 芯 +f*F+e Where T 目标 The target exhaust temperature is calculated by the formula, and the actual core temperature T of the indoor core 6 is detected by the return air temperature sensor 19. 芯 , f is a coefficient, e is a constant, F is the operating frequency of the compressor, a and e are calibrated according to the actual configuration of the air-conditioning system, and the preferred calibration values ​​of f and e are 0.3 and 13 respectively.

[0038] The beneficial effects of the present invention are: 1. The present invention has the function of natural fluorine and ground water heating, and improves heating energy efficiency and user comfort by introducing natural fluorine and ground water heat pump air conditioning system; 2. The present invention not only integrates the battery thermal management function but also has the waste heat recovery function by adding a relevant one-way valve structure to the air conditioning system; 3. By optimizing the expansion valve control in heating mode, the operation of the natural fluorine and ground water heat pump air conditioning system is more stable and more reliable; 4. Through the optimization of the control system, the defrosting of the heat pump system during heating operation is made more intelligent, eliminating the impact of system defrosting on comfort; 5. The present invention can realize functions such as high-temperature cooling, normal-temperature cooling, high-temperature heating, normal-temperature heating, battery thermal management, waste heat recovery, and defrosting of the air-conditioning system.

[0039] The above-described embodiments are only preferred embodiments of the present invention. It should be noted that, for those skilled in the art, several changes and improvements may be made without departing from the overall concept of the present invention, and these should also be regarded as the protection scope of the present invention.

Claims

1. A natural fluorine ground water heat pump air conditioning system for buses, characterized by: It comprises a compressor (1), wherein the exhaust port of the compressor (1) is connected to the inlet pipe of a four-way valve (10), and the other three pipelines of the four-way valve (10) are respectively connected to an outdoor core (2), a gas-liquid separator (5) and a heating plate heat exchanger (3); the first one-way valve (4) is connected in parallel to both ends of the refrigerant side of the heating plate heat exchanger (3); the other end of the heating plate heat exchanger (3) is connected to an indoor core (6) through a refrigerant pipeline; the other end of the indoor core (6) is connected to a two-way filter (7); the outlet of the two-way filter (7) is respectively connected to a second one-way valve (8) and a main electronic expansion valve (9); wherein the other end of the second one-way valve (8) is respectively connected to a third one-way valve (11) and a battery-side electronic expansion valve (12); the battery-side electronic expansion valve (12) is connected to a battery plate heat exchanger (28); the other end of the third one-way valve (11) is respectively connected to the main electronic expansion valve (9) and a drying filter (13); and the other end of the drying filter (13) is connected to the outdoor core (2); The heating plate heat exchanger (3) is a natural fluorine and ground water plate heat exchanger. The water side outlet of the heating plate heat exchanger (3) is divided into at least two heating water paths. Each heating water path includes a water pump (14) connected in series, a liquid heat PTC (15), and a different number of water heating forced radiators (16). The water heating forced radiators (16) are located at the bottom of the passenger compartment. After the heating water paths are merged, they return to the heating plate heat exchanger (3) to form a closed loop on the water side.

2. A natural fluorine and ground water heat pump air conditioning system for buses according to claim 1, characterized in that: A left defrost temperature sensor (17), a right defrost temperature sensor (18) and a return air temperature sensor (19) are respectively arranged on the indoor core (6).

3. A natural fluorine and ground water heat pump air conditioning system for buses according to claim 1, characterized in that: An outdoor defrosting temperature sensor (20) and an outdoor temperature sensor (21) are arranged on the outdoor core (2).

4. A natural fluorine and ground water heat pump air conditioning system for buses according to claim 1, characterized in that: The exhaust port of the compressor (1) is connected to the inlet pipe of the four-way valve (10) via a high-pressure charging valve (22), an exhaust temperature sensor (23) and a high-pressure pressure switch (24), and a low-pressure pressure switch (25) is provided on the low-pressure side of the compressor (1).

5. The natural fluorine and ground water heat pump air conditioning system for buses according to claim 1, characterized in that: The gas-liquid separator (5) is respectively connected to a low-pressure charging valve (26) and an intake air temperature sensor (27).

6. A natural fluorine and ground water heat pump air conditioning system for buses according to claim 1, characterized in that: The battery plate heat exchanger (28) is connected to a battery pressure sensor (29); the battery plate heat exchanger (28) is provided with a waterway inlet (30) and a waterway outlet (31).

7. A method for controlling a natural fluorine-ground water heat pump air conditioning system for a bus using the system described in any one of claims 1 to 6, characterized in that: Including cooling mode control method and heating mode control method: The refrigeration mode control method is as follows: When the air conditioning system is in cooling mode, the refrigerant is discharged from the compressor (1) and enters the outdoor core (2). After flowing out of the outdoor core (2), the refrigerant is divided into two paths. One path flows to the battery plate heat exchanger (28) through the third one-way valve (11) and the battery-side electronic expansion valve (12) in sequence, and the other path flows to the indoor core (6) through the main electronic expansion valve (9). The refrigerant flowing through the battery plate heat exchanger (28) enters the gas-liquid separator (5) after heat exchange. The refrigerant flowing through the indoor core (6) enters the gas-liquid separator (5) after heat exchange through the first one-way valve (4) and the heating plate heat exchanger (3), and finally returns to the compressor (1). In cooling mode, the opening of the main electronic expansion valve (9) is controlled by the target exhaust temperature. The control formula is as follows: T 目标 =aF+b Among them, T 目标 The target exhaust temperature is calculated by the formula, a is the coefficient, b is the constant, and F is the compressor operating frequency. a and b use different values ​​in different environmental ranges. When the actual exhaust temperature T 实际 >T 目标 When T 实际 <T 目标 , the main circuit electronic expansion valve (9) is closed; The heating mode control method is as follows: When the air conditioning system is in heating mode, after the refrigerant is discharged from the compressor (1), it first passes through the heating plate heat exchanger (3) on the heating side. At this time, the first one-way valve (4) on the heating side is in a closed state. After the refrigerant flows out of the heating plate heat exchanger (3), it enters the indoor core (6). After being cooled again by the indoor core (6), it is divided into two paths. One path is throttled by the main electronic expansion valve (9) and the third one-way valve (11) in sequence and then enters the battery plate heat exchanger (28). The other path is throttled by the main electronic expansion valve (9) and then enters the outdoor core (2). After heat exchange, the two refrigerants merge and enter the gas-liquid separator (5), and finally return to the compressor (1). In heating mode, the opening of the main electronic expansion valve (9) is controlled by the target exhaust temperature. The control formula is as follows: T 目标 =T 芯 +f*F+e Among them, T 目标 The target exhaust temperature is calculated by the formula, and the actual core temperature T 芯 , f is the coefficient, e is the constant, and F is the compressor operating frequency.

8. The control method of the natural fluorine and ground water heat pump air conditioning system for buses according to claim 7, characterized in that: When the air conditioning system is in heat pump heating mode, the ambient temperature is divided into different zones T a 、T b and T c , -15℃<T a ≤-5℃、-5℃<T b ≤5℃、T c >5℃, each temperature zone corresponds to a different duty cycle of the indoor fan, and the duty cycles of the three ranges are -15℃<T a ≤-5℃Duty cycle 20%, -5℃<T b ≤5℃ Duty cycle 25%, T c >5℃ duty cycle 30%.

9. The method for controlling a natural fluorine-ground water heat pump air conditioning system for a bus according to claim 7, characterized in that: After the heating mode is turned on, in the heating water circuit connected in parallel with the heating plate heat exchanger (3), the water pump (14) is turned on first. After a certain period of time, the heating water circuit system circulation is stable, and the ceiling air conditioner is turned on. The ceiling air conditioner determines the indoor ceiling fan duty cycle according to the current ambient temperature. After the ceiling air conditioner is turned on, the bottom-mounted water heating forced radiator (16) executes the cold wind prevention logic, that is: when the return water temperature of the heating water circuit is lower than T1, the water heating forced radiator (16) does not output air. The return water temperature T1 is preferentially set to 20°C. When the return water temperature is greater than T1, the water heating forced radiator (16) outputs air according to the set gear.

10. The control method of the natural fluorine and ground water heat pump air conditioning system for buses according to claim 7, characterized in that: When the ambient temperature is higher than T2, the liquid heat PTC will not start. The T2 setting temperature is 5°C. In addition, whether the liquid heat PTC starts is determined by the temperature difference between the set return water temperature and the actual return water temperature. 设 -T 回 ≥a, the liquid thermal PTC third gear starts; T 设 -T 回 ≥b, the liquid heat PTC operates in two gears; T 设 -T 回 ≥c, first gear operation, T 设 -T 回 Closed when ≥d.

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