A vehicle low-temperature environment heat pump thermal management operation method

Abstract

The application discloses a kind of vehicle low-temperature environment heat pump thermal management operation method, it is related to vehicle heat pump thermal management technical field, this method is powered on after vehicle acquisition outdoor environment temperature, battery pack state, passenger cabin temperature parameter, determine to enter low-temperature heat pump heating mode, first verify refrigerant circuit and valve operating state, preheat compressor lubricating oil after starting heat pump, coupling motor electric control operation waste heat and distribute heating flow as needed, dynamically adjust operating parameter to maintain operating efficiency, when abnormal, adjust parameter or switch auxiliary heating mode in stages to avoid device damage.This method can improve the stability of heat pump operation in low-temperature environment, reduce heating energy consumption, take into account battery charging and discharging performance and passenger cabin heating demand, without adding additional hardware, adapt to most new energy vehicles with heat pump system use.

Description

Technical Field

[0001] This invention relates to the field of vehicle heat pump thermal management technology, and in particular to a method for operating a vehicle heat pump thermal management system in a low-temperature environment. Background Technology

[0002] The application scale of new energy vehicles continues to expand, and the range reduction problem in low-temperature environments is one of the core factors restricting user experience. Heat pump thermal management systems, with their lower heating energy consumption than traditional PTC heating, have become the standard thermal management solution for most new energy vehicle models. Currently, the most widely used single-heat-source air-source heat pump system in the industry transfers heat from the outdoor environment to the vehicle interior by compressing refrigerant. It has a simple overall structure, low deployment cost, and good energy efficiency in above-freezing low-temperature environments. However, as the ambient temperature continues to decrease, the difficulty of refrigerant evaporation increases, and the heating capacity of the heat pump will decrease significantly. It is necessary to frequently start PTC auxiliary heating, which offsets the energy consumption advantage of the heat pump. At the same time, these systems often use fixed heating priority logic and cannot adjust the heat distribution strategy according to the real-time operating conditions of the vehicle. This can easily lead to problems such as insufficient battery preheating affecting charging and discharging performance, or slow heating of the passenger compartment affecting the riding experience.

[0003] Another mainstream type of heat pump system with waste heat recovery adds a recovery path for waste heat from the motor and electronic control system to the air source heat extraction. This allows waste heat generated by the power system to be used for heating, further improving heating efficiency. However, the existing operating logic still has many shortcomings. It lacks refrigerant circuit verification and lubricant preheating before the heat pump starts. In low-temperature environments, the lubricant viscosity is high, leading to greater wear on the compressor during startup. Long-term use will shorten the compressor's lifespan. In some extremely cold scenarios, insufficient refrigerant flow can cause excessive compressor startup load, directly resulting in startup failure. Existing solutions mostly use fixed-parameter control logic for flow distribution and energy efficiency regulation, failing to dynamically adjust and adapt to different heating demands and ambient temperature changes. This can easily lead to unreasonable heat distribution or excessive useless power consumption under certain operating conditions.

[0004] The fault protection logic of existing heat pump systems is relatively simple. When the operating parameters are detected to exceed the threshold, they are usually directly switched to PTC full-power heating mode without setting a tiered adjustment and intervention strategy. This not only increases heating energy consumption, but also causes heating interruption in some scenarios. It cannot meet the stable heating demand in low-temperature environments. The industry urgently needs a heat pump operating logic that is more adapted to low-temperature environments, and improves the matching degree between heating energy efficiency and heating demand while ensuring operational reliability. Summary of the Invention

[0005] This invention proposes a method for operating a heat pump in a low-temperature environment for vehicles to solve the problems mentioned in the prior art.

[0006] To achieve the above objectives, the present invention adopts the following technical solution: a method for operating a vehicle heat pump in a low-temperature environment, comprising: S1, Low temperature start determination: After the vehicle is powered on, the outdoor ambient temperature, the core area temperature of the battery pack, and the ambient temperature inside the passenger compartment are collected in real time. The collected parameters are compared with the preset low temperature heat pump start threshold. When the outdoor ambient temperature is lower than the preset low temperature threshold, the core area temperature of the battery pack is lower than the preset minimum operating temperature, and there is a need for passenger compartment heating or battery preheating, it is determined to enter the low temperature heat pump heating mode. S2, Heat Pump Circuit Pre-verification: Collect the compressor lubricating oil temperature, refrigerant circuit high and low pressure side pressure, and the opening and closing status parameters of each pipeline valve in the heat pump system. After verifying that there is no leakage in the refrigerant circuit and that the opening and closing status of each valve is normal, start the lubricating oil preheating module to preheat the lubricating oil inside the compressor. Correct the starting viscosity threshold of the lubricating oil based on the current outdoor ambient temperature, and detect the kinematic viscosity of the lubricating oil in real time. Stop preheating when the kinematic viscosity of the lubricating oil drops to the corrected starting viscosity threshold. S3, Multi-heat source coupled heating control: Start the compressor to run the heat pump circuit, collect the outlet water temperature of the motor electronic control cooling circuit, and when the outlet water temperature is higher than the preset waste heat recovery activation threshold, open the waste heat recovery branch to collect the waste heat generated by the motor electronic control operation into the evaporator side of the heat pump. At the same time, according to the preset priority, adjust the opening of the electronic expansion valves of the passenger compartment heating branch and the battery pack preheating branch respectively, and distribute the flow ratio of refrigerant in the two branches until the temperature of the core area of ​​the battery pack reaches the preset minimum operating temperature, and then distribute the remaining refrigerant to the passenger compartment heating branch. S4, Dynamic Energy Efficiency Optimization and Adjustment: Real-time acquisition of outdoor ambient temperature fluctuations, passenger compartment interior temperature change rate, battery pack core area temperature rise rate, and compressor current operating energy efficiency ratio parameters. Based on parameter changes, the compressor operating frequency, the opening degree of each branch electronic expansion valve, the opening degree of passenger compartment internal and external circulation dampers, and the on / off status of waste heat recovery branches are adjusted to maintain the heat pump system's operating energy efficiency ratio in the optimal range while meeting all heating demands.

[0007] Preferably, when distributing refrigerant flow during the operation of the heat pump circuit, the target heating power of the two heating branches is first calculated, using the following formula: ; in This indicates the target heating power of the battery preheating branch, in kW. This indicates the priority weight for battery heating, with a value ranging from 0.6 to 0.9. This indicates the current total heating capacity of the heat pump system, expressed in kW. This indicates the target preheating temperature of the battery pack, in degrees Celsius (°C). This indicates the current core temperature of the battery pack, in degrees Celsius (°C). This indicates the current outdoor ambient temperature, in degrees Celsius (°C). This indicates the target heating power of the crew compartment heating branch, in kW. This indicates the set target temperature for the crew cabin, in degrees Celsius (°C). This indicates the current internal temperature of the crew cabin, in °C.

[0008] Preferably, when preheating the internal lubricating oil of the compressor, a combination of a lubricating oil preheating PTC module and motor waste heat recovery is used for preheating. When the outlet water temperature of the motor electronic control cooling circuit is higher than the current temperature of the lubricating oil, the motor waste heat is preferentially introduced into the compressor lubricating oil chamber for preheating. When the heating power provided by the motor waste heat cannot reach the preset preheating power threshold, the lubricating oil preheating PTC module is activated to provide auxiliary heating for the lubricating oil.

[0009] Preferably, when adjusting the compressor's operating frequency, the optimal operating frequency of the compressor is calculated by combining the difference in heating demand and the energy efficiency correction coefficient. The calculation formula is as follows: ;in This indicates the optimal operating frequency of the compressor, measured in Hz. This indicates the minimum permissible operating frequency of the compressor, measured in Hz. This represents the energy efficiency correction factor, with a value ranging from 0.7 to 1.1. This represents the weighted sum of the temperature difference between the crew compartment and the battery pack, expressed in °C. This indicates the maximum permissible temperature difference threshold for the heat pump system, in degrees Celsius (°C). This indicates the maximum permissible operating frequency of the compressor, measured in Hz.

[0010] Preferably, when performing the determination step of low-temperature heat pump heating mode, if the outdoor ambient temperature is detected to be below -15°C, the refrigerant pipeline preheating module is first started to preheat the low-pressure side pipeline of the refrigerant circuit before entering the low-temperature heat pump heating mode, and the preheating time is maintained in the range of 30 to 60 seconds.

[0011] Preferably, when performing waste heat recovery operation, heat exchange between the motor control cooling circuit and the heat pump circuit is achieved through a coolant-refrigerant heat exchanger. When the outlet water temperature of the motor control cooling circuit is higher than 12°C, the waste heat recovery branch is activated to transfer the waste heat generated by the motor operation to the evaporator side of the heat pump circuit.

[0012] Preferably, when adjusting the internal and external circulation dampers of the passenger compartment, when the internal temperature of the passenger compartment reaches 90% of the set target temperature, the opening of the internal circulation damper is gradually increased to be fully opened, while the external circulation damper is closed.

[0013] Preferably, when the compressor's exhaust temperature is detected to be higher than 120°C, the compressor's current operating frequency is first reduced by 20%, and the bypass branch of the evaporator is opened to reduce the refrigerant's suction superheat. If the exhaust temperature remains higher than the threshold for more than 10 seconds after adjustment, the cabin heating PTC module is activated to share the heating load.

[0014] Preferably, when calculating the target heating power, if the remaining power of the battery pack is detected to be less than 20% or the battery management system sends a DC fast charging request signal, the battery heating priority weight is adjusted to 0.9 to prioritize the preheating rate of the battery pack and enable the battery pack to quickly reach the optimal operating temperature range.

[0015] Preferably, when calculating the optimal operating frequency of the compressor, if the outdoor ambient temperature is detected to be below -20℃, the energy efficiency correction factor is adjusted to 1.1, and if the outdoor ambient temperature is detected to be above -5℃, the energy efficiency correction factor is adjusted to 0.7.

[0016] Compared with existing technologies, the beneficial effects of this invention are: This invention incorporates low-temperature start-up detection, refrigerant circuit pre-verification, and lubricant preheating before heat pump startup. It determines whether heat pump mode needs to be activated based on multi-dimensional environmental and vehicle parameters, avoiding unnecessary energy consumption caused by accidental heat pump triggering. Simultaneously, pre-verification checks for potential refrigerant leaks and valve malfunctions, adjusting the lubricant and refrigerant states to meet startup requirements before startup, reducing compressor startup load, minimizing component wear caused by low-temperature startup, and improving the operational stability and lifespan of the heat pump system. Furthermore, by adjusting the lubricant startup viscosity threshold based on the current outdoor ambient temperature, it effectively reduces compressor startup resistance, mechanical shock, and component wear in extremely cold environments, while shortening lubricant preheating time, reducing preheating energy consumption, and accelerating system response. It also maintains reasonable lubrication standards in relatively mild low-temperature environments, ensuring compressor operational safety. Ultimately, it balances startup efficiency and equipment reliability, comprehensively improving the environmental adaptability, operational stability, and overall performance of the entire low-temperature heat pump thermal management system.

[0017] This invention employs a multi-heat source coupled heating control logic, which can prioritize the recovery of usable waste heat generated by the operation of the motor and electronic control system, reducing the pressure of extracting heat from the low-temperature environment. At the same time, it dynamically adjusts the refrigerant flow of each branch according to the real-time heating demand of the battery and passenger compartment, prioritizing the matching of the battery's operating temperature requirements to ensure the battery's charging and discharging performance, while also taking into account the heating demand of the passenger compartment, avoiding the problem of insufficient heating in a single branch, and improving the matching degree between the heating strategy and the actual needs of the vehicle.

[0018] This invention dynamically adjusts parameters such as compressor operating frequency, valve opening, and internal and external circulation damper status by collecting real-time operating parameters from multiple dimensions. Under the premise of meeting all heating needs, it maintains the operating efficiency of the heat pump in a better range, reduces the energy consumption of the vehicle heating process, and adapts to the energy efficiency optimization needs under different low-temperature environments.

[0019] The operating method of this invention can be adapted to most existing new energy vehicle models equipped with heat pump systems. It does not require a large amount of additional hardware and can be directly implemented based on existing vehicle sensors and actuators. It is compatible with the operating requirements of different low temperature ranges and adapts to the adjustment requirements of different vehicle configurations, making it relatively easy to implement. Attached Figure Description

[0020] Figure 1 This is the overall operation flowchart of the vehicle low-temperature environment heat pump thermal management proposed in this invention; Figure 2 This is a flowchart of the low-temperature start-up determination and loop pre-verification control of the present invention; Figure 3 This is a flowchart of the multi-heat source coupled heating and refrigerant flow distribution process of the present invention; Figure 4 This is a flowchart of the dynamic energy efficiency optimization and optimal frequency regulation of the present invention; Figure 5 This is a flowchart of the abnormal operating condition monitoring and graded protection switching process of the present invention. Detailed Implementation

[0021] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0022] Reference Figures 1 to 5 This invention discloses a method for operating a heat pump in a low-temperature environment for vehicles, comprising: S1, Low Temperature Start-up Judgment: When the outdoor ambient temperature is lower than the preset low temperature threshold, the core area temperature of the battery pack is lower than the preset minimum operating temperature, and the current temperature of the passenger compartment is lower than the set heating temperature or the current temperature of the battery pack is lower than the preset target temperature, it is determined that the low temperature heat pump heating mode will be entered.

[0023] For example, after the vehicle is powered on, the outdoor ambient temperature, the core area temperature of the battery pack, and the interior ambient temperature of the passenger compartment are collected by NTC temperature sensors distributed at the outdoor air intake, the core temperature measurement point of the battery pack, and the top of the passenger compartment, respectively. The passenger compartment temperature setpoint is read by the air conditioning domain controller, and the battery pack charging demand status parameters are obtained from the battery management system via the CAN bus. The collected parameters are compared with the preset low-temperature heat pump start-up threshold. The preset low-temperature threshold can be -5℃, and the preset minimum battery operating temperature can be 0℃. When the outdoor ambient temperature is lower than -5℃, the core area temperature of the battery pack is lower than 0℃, and there is a passenger compartment heating demand (i.e., the current temperature of the passenger compartment is lower than the set heating temperature) or a battery preheating demand (i.e., the current temperature of the battery pack is lower than the preset target temperature), the vehicle is determined to enter the low-temperature heat pump heating mode. The multi-parameter joint determination can avoid the heat pump mode being falsely triggered in low-temperature environments and reduce useless energy consumption.

[0024] S2, Heat pump circuit pre-verification: The heat pump circuit is verified for status. If there are no abnormalities in the circuit, the lubricating oil inside the compressor is preheated. The starting viscosity threshold of the lubricating oil is corrected based on the current outdoor ambient temperature. The kinematic viscosity of the lubricating oil is detected in real time. Preheating is stopped when the kinematic viscosity of the lubricating oil drops to the corrected starting viscosity threshold.

[0025] For example, the high and low pressure sides of the refrigerant circuit of the heat pump system can be collected by a pressure sensor, and the opening and closing status feedback signals of each pipeline valve can be collected by the LIN bus. When the fluctuation range of the high and low pressure sides does not exceed 0.02MPa within 10 minutes and the opening and closing status of each valve is consistent with the control command, it is determined that there is no leakage in the refrigerant circuit and the valve status is normal. Then, the lubricating oil preheating module is started to preheat the lubricating oil inside the compressor.

[0026] The lower the outdoor ambient temperature, the higher the starting viscosity threshold of the lubricating oil. For example, it can be 15mm. 2 The starting viscosity threshold is based on / s. The lower the outdoor temperature (e.g., less than or equal to -15°C), the higher the starting viscosity threshold should be, for example, increased to 19 mm. 2 / s, to appropriately relax the threshold requirement, allowing the lubricating oil to start at a relatively higher viscosity, avoiding excessively long preheating time; if the temperature is relatively high (e.g., greater than or equal to 0°C), then reduce the starting viscosity threshold, for example, by 12mm. 2 / s, tightening the standard to ensure compressor lubrication safety with a lower viscosity standard. The kinematic viscosity of the lubricating oil is detected in real time by a viscosity sensor. Once the kinematic viscosity of the lubricating oil drops to the corrected starting viscosity threshold, preheating is stopped and the compressor is prepared for startup. This step can prevent compressor startup wear due to excessive lubricating oil viscosity and extend the compressor's service life.

[0027] S3, Multi-Heat Source Coupled Heating Control: Start the compressor to run the heat pump circuit, collect the outlet water temperature of the motor electronic control cooling circuit, and when the outlet water temperature is higher than the preset waste heat recovery activation threshold, open the waste heat recovery branch to collect the waste heat generated by the motor electronic control operation into the evaporator side of the heat pump. At the same time, according to the preset priority, adjust the opening of the electronic expansion valves of the passenger compartment heating branch and the battery pack preheating branch respectively, and distribute the refrigerant flow ratio in the two branches until the temperature of the core area of ​​the battery pack reaches the preset minimum operating temperature, and then distribute the remaining refrigerant to the passenger compartment heating branch.

[0028] For example, a condenser is provided on the high-temperature heat release side of the heat pump circuit. The condenser piping branches into a passenger compartment heating branch and a battery pack preheating branch. When the refrigerant flows through the condenser, it condenses and releases heat, providing a heat source for the two branches. The outlet water temperature of the motor control cooling circuit is collected first through the NTC sensor at the motor outlet. When the outlet water temperature is higher than the waste heat recovery threshold, the waste heat recovery branch is opened to collect the waste heat generated by the motor control operation into the evaporator side of the heat pump. At the same time, the opening degree of the electronic expansion valve of each branch is adjusted according to the priority of the passenger compartment heating demand and the battery pack preheating demand. The opening degree adjustment accuracy of the electronic expansion valve is 1%. The flow ratio of refrigerant in the passenger compartment heating branch and the battery pack preheating branch is allocated. When the battery pack has a charging demand or the remaining power is less than 20%, the minimum temperature requirement for battery pack preheating is prioritized, and the remaining heating capacity is allocated to the passenger compartment heating branch. This step can maximize the utilization of the vehicle's waste heat in low-temperature environments and reduce the energy consumption of the heat pump system.

[0029] For example, two physically independent heat exchange paths for utilizing motor waste heat can be provided, with temperature control conditions that do not interfere with each other: one is a heat exchange path for preheating compressor lubricating oil, which is activated when the motor outlet water temperature is 2°C higher than the current lubricating oil temperature; the other is a waste heat recovery branch that supplies heat to the heat pump evaporator, which is activated when the motor outlet water temperature is higher than 12°C.

[0030] S4, Dynamic Energy Efficiency Optimization and Adjustment: Real-time acquisition of outdoor ambient temperature fluctuation range, passenger compartment internal temperature change rate, battery pack core area temperature rise rate, and compressor current operating energy efficiency ratio parameters; and adjustment of compressor operating frequency, electronic expansion valve opening degree of each branch, passenger compartment internal and external circulation damper opening degree, and waste heat recovery branch on / off status based on parameter changes.

[0031] For example, the system collects data every 5 seconds on the fluctuation range of the outdoor ambient temperature, the rate of change of the temperature inside the passenger compartment, the rate of temperature rise in the core area of ​​the battery pack, and the current energy efficiency ratio (EER) parameter of the compressor. The EER is the ratio of the heating power to the input power collected in real time. Under the premise of meeting all heating needs, the system maintains the operating EER of the heat pump system within the optimal range of 2.0 to 3.5 to maximize energy utilization efficiency.

[0032] For example, it may also include S5, abnormal operating condition protection: real-time acquisition of parameters such as the exhaust temperature of the heat pump system compressor, the high-pressure side pressure of the refrigerant circuit, the temperature rise rate of the battery pack, and the temperature change rate of the passenger compartment. The preset safety thresholds are: exhaust temperature not exceeding 120°C, high-pressure side pressure not exceeding 3.5MPa, and battery temperature rise rate not exceeding 2°C per minute. When any parameter is detected to exceed the preset safety threshold, the compressor operating frequency is first adjusted. If the parameter still does not return to the threshold range, the system switches to PTC auxiliary heating mode to avoid damage to heat pump components or heating failure.

[0033] In this invention, when allocating refrigerant flow during the operation of the heat pump circuit, the target heating power of the two heating branches is first calculated using the following formula: ;in This indicates the target heating power of the battery preheating branch, in kW. This indicates the priority weight for battery heating, with a value ranging from 0.6 to 0.9. This indicates the current total heating capacity of the heat pump system, expressed in kW. This indicates the target preheating temperature of the battery pack, in degrees Celsius (°C). This indicates the current core temperature of the battery pack, in degrees Celsius (°C). This indicates the current outdoor ambient temperature, in degrees Celsius (°C). This indicates the target heating power of the crew compartment heating branch, in kW. This indicates the set target temperature for the crew cabin, in degrees Celsius (°C). This indicates the current internal temperature of the passenger compartment, in °C. The priority weight α is determined in real time by the vehicle controller based on the vehicle's operating conditions. When there is no charging demand and the passenger compartment set temperature is above 25°C, α is 0.6. When there is a DC fast charging demand, α is 0.9. Under normal driving conditions where the battery's remaining SOC is ≥20% and there is no DC fast charging demand, the battery heating priority weight α can be between 0.7 and 0.8. The calculation process reuses existing onboard sensor data, requiring no new hardware. The flow distribution error can be controlled within 5%, adapting to the different heating requirements of various components in low-temperature environments, improving overall heating efficiency while avoiding insufficient battery preheating from affecting battery charging and discharging performance.

[0034] In this invention, when preheating the internal lubricating oil of the compressor, a combination of a lubricating oil preheating PTC module and motor waste heat recovery is used for preheating. When the outlet water temperature of the motor electronic control cooling circuit is higher than the current temperature of the lubricating oil, the motor waste heat is preferentially introduced into the compressor lubricating oil chamber for preheating. When the heating power provided by the motor waste heat cannot reach the preset preheating power threshold, the lubricating oil preheating PTC module is activated to provide auxiliary heating for the lubricating oil.

[0035] For example, the outlet water temperature of the motor's electronic control cooling circuit is collected by an NTC sensor placed at the motor outlet. When the outlet water temperature is more than 2°C higher than the current lubricating oil temperature, the heat exchange solenoid valve between the cooling circuit and the lubricating oil chamber is opened, and the lubricating oil is heated by the residual heat of the coolant. When the temperature difference is less than 2°C, it is determined that the heating power provided by the residual heat of the motor cannot reach the preset preheating power threshold. The lubricating oil preheating PTC module with a power of 300W is started to assist in heating. During the preheating process, the lubricating oil viscosity is collected every 10 seconds. Heating is stopped immediately after the threshold is reached. This shortens the preheating time and reduces the power consumption of the preheating process, thereby improving the vehicle's range in low-temperature environments.

[0036] In this invention, when adjusting the compressor's operating frequency, the optimal operating frequency of the compressor is calculated by combining the difference in heating demand and the energy efficiency correction coefficient. The calculation formula is as follows: ;in This indicates the optimal operating frequency of the compressor, measured in Hz. This indicates the minimum permissible operating frequency of the compressor, measured in Hz. This represents the energy efficiency correction factor, with a value ranging from 0.7 to 1.1. This represents the weighted sum of the temperature difference between the crew compartment and the battery pack, expressed in °C. This indicates the maximum permissible temperature difference threshold for the heat pump system, in degrees Celsius (°C). This indicates the maximum permissible operating frequency of the compressor, measured in Hz. The calculation involves multiplying the passenger compartment temperature difference by a weight of 0.4 and the battery pack temperature difference by a weight of 0.6, and then summing them. The energy efficiency correction coefficient β is calibrated at the vehicle factory under different ambient temperatures and stored in the calibration data table of the vehicle controller. It can be retrieved directly from the table when called. The calculation response time is less than 100 milliseconds, which can adapt to rapid changes in operating conditions. While meeting heating requirements, it reduces the useless power consumption of the compressor and improves the energy utilization efficiency of the whole vehicle.

[0037] In this invention, when performing the determination step of low-temperature heat pump heating mode, if the outdoor ambient temperature is detected to be below -15°C, before entering the low-temperature heat pump heating mode, the refrigerant pipeline preheating module is first started to preheat the low-pressure side pipeline of the refrigerant circuit, and the preheating time is maintained in the range of 30 to 60 seconds.

[0038] For example, the refrigerant pipeline preheating module can be a silicone heating element. When the outdoor ambient temperature is detected to be below -15°C, the silicone heating element arranged on the low-pressure refrigerant pipeline can be activated for low-power preheating. The preheating power is 100W, and the preheating time is adjusted according to the current ambient temperature: 30 seconds at -15°C and 60 seconds at -25°C, until the refrigerant viscosity drops to 30 mmHg. 2Start the compressor only after the refrigerant viscosity drops below a certain level to avoid excessive compressor load and damage caused by high refrigerant viscosity at low temperatures.

[0039] In this invention, when performing waste heat recovery operation, heat exchange between the motor control cooling circuit and the heat pump circuit is achieved through a coolant-refrigerant heat exchanger. When the outlet water temperature of the motor control cooling circuit is higher than 12°C, the waste heat recovery branch is activated to transfer the waste heat generated by the motor operation to the evaporator side of the heat pump circuit.

[0040] For example, a brazed plate-type coolant-refrigerant heat exchanger can be used to achieve heat exchange between the motor control cooling circuit and the heat pump circuit, with a heat exchange efficiency of over 90%. The coolant-refrigerant heat exchanger can be connected in parallel to the front end of the heat pump evaporator. When the outlet water temperature of the motor control cooling circuit is higher than 12°C, the electronic water valve of the waste heat recovery branch is opened, and the water pump runs at the lowest speed to transfer the waste heat generated by the motor operation to the evaporator side of the heat pump circuit, thereby raising the refrigerant evaporation temperature of the evaporator by 3 to 5°C, reducing the compression ratio of the compressor, and improving the operating energy efficiency ratio of the heat pump.

[0041] In this invention, when adjusting the internal and external circulation dampers of the passenger compartment, when the internal temperature of the passenger compartment reaches 90% of the set target temperature, the opening of the internal circulation damper is gradually increased to full opening, while the external circulation damper is closed. For example, the damper opening is driven by a stepper motor with an adjustment accuracy of 5%. When the internal temperature of the passenger compartment reaches 90% of the set target temperature, the damper opening is adjusted every 2 seconds, gradually increasing the opening of the internal circulation damper to full opening, while simultaneously closing the external circulation damper. This reduces heat loss caused by the entry of low-temperature outdoor air into the passenger compartment and lowers the heating load of the heat pump system.

[0042] In this invention, when the compressor's exhaust temperature is detected to be higher than 120°C, the compressor's current operating frequency is first reduced by 20%, and the bypass branch of the evaporator is opened to reduce the refrigerant's suction superheat. If the exhaust temperature remains higher than the threshold for more than 10 seconds after adjustment, the cabin heating PTC module is activated to share the heating load. For example, during the abnormal operating condition protection phase, when the compressor's exhaust temperature is detected to be higher than 120°C, the compressor's operating frequency is first reduced by 20%, and the bypass solenoid valves at the evaporator inlet and outlet are opened to allow some of the high-temperature refrigerant to return directly to the suction side to reduce the refrigerant's suction superheat. If the exhaust temperature remains higher than 120°C within 10 seconds after adjustment, the 2kW cabin heating PTC module is activated to share 40% of the heating load, and the compressor's operating frequency is further reduced by 20% to prevent the compressor from overheating and causing coil burnout or lubricating oil carbonization.

[0043] In this invention, when calculating the target heating power, if the remaining battery charge of the battery pack is detected to be below 20% or the battery management system sends a DC fast charging request signal, the battery heating priority weight is adjusted to 0.9. This prioritizes ensuring the preheating rate of the battery pack, enabling it to quickly reach its optimal operating temperature range. In this way, 90% of the heating quota is allocated to the battery preheating branch, maintaining the battery pack's temperature rise rate at 1 to 2°C per minute. This rapidly heats the battery pack to its optimal operating temperature range of above 15°C, improving battery charging efficiency and discharge capacity, shortening charging time, and enhancing the overall vehicle's power output performance.

[0044] In this invention, when calculating the optimal operating frequency of the compressor, if the outdoor ambient temperature is detected to be below -20℃, the energy efficiency correction coefficient is adjusted to 1.1 to increase the upper limit of the compressor's operating frequency, ensuring that the total heating power of the heat pump system meets the heating demand in extremely cold environments. If the outdoor ambient temperature is detected to be above -5℃, the energy efficiency correction coefficient is adjusted to 0.7 to reduce the compressor's operating frequency, maximizing the heat pump's operating energy efficiency ratio while meeting heating demand, thus adapting to the energy efficiency optimization needs of different low-temperature ranges.

[0045] Example 1

[0046] This embodiment is applied to urban commuting scenarios in northern winters. After the vehicle is parked overnight, the outdoor temperature is -7°C. The user can remotely control the passenger compartment heating function in advance. After the vehicle is powered on, the low temperature start-up judgment process is executed first.

[0047] The vehicle collects ambient temperature through temperature sensors located at the outdoor air intake, core area temperature of the battery pack through temperature sensors located between the battery cells, interior temperature of the passenger compartment through temperature sensors located inside the passenger compartment roof trim, user-preset target temperature through the air conditioning domain controller, and current remaining battery charge and charging status through the battery management system.

[0048] The collected parameters were compared with preset thresholds. The current ambient temperature was below -5℃, the core temperature of the battery pack was -3℃ (the lowest operating temperature below 0℃), and there was a need for heating in the passenger compartment. Therefore, it was determined to enter the low-temperature heat pump heating mode.

[0049] Subsequently, a heat pump circuit pre-verification process was executed. Pressure sensors located on the high-pressure and low-pressure refrigerant lines were used to collect pressure data from both sides of the circuit. Feedback signals from the opening and closing status of each electronic expansion valve and electronic water valve were collected via the LIN bus. It was confirmed that the pressure fluctuation within 10 minutes did not exceed 0.02 MPa, and that the opening and closing status of all valves was consistent with the control commands, thus determining that there was no leakage in the refrigerant circuit and that the valves were functioning normally. At this point, the vehicle had just been powered on, and the temperature difference between the outlet water of the motor control cooling circuit and the current temperature of the lubricating oil was less than 2°C. Therefore, the 300W lubricating oil preheating PTC module was activated to preheat the compressor lubricating oil. A viscosity sensor located in the compressor lubricating oil chamber continuously monitored the kinematic viscosity of the lubricating oil until the viscosity dropped to 15 mm². 2 After reaching the starting viscosity threshold of / s, stop preheating and prepare for compressor startup.

[0050] The compressor is started and the heat pump circuit is running. Five minutes after the vehicle starts driving, the temperature sensor located at the motor outlet detects that the outlet water temperature of the motor's electronic control cooling circuit is higher than 12°C. The electronic water valve of the waste heat recovery branch is opened, and the circuit water pump starts running at its lowest speed. The waste heat generated by the motor's electronic control operation is collected into the evaporator side of the heat pump through a brazed plate heat exchanger. Currently, there is no need for battery charging, so the battery heating priority is set to 0.6. The opening of the electronic expansion valves in each branch is adjusted with an adjustment accuracy of 1%. The refrigerant flow ratio in the two branches is allocated to prioritize raising the core temperature of the battery pack to above 0°C, and then the remaining heating capacity is allocated to the passenger compartment heating branch.

[0051] The subsequent dynamic energy efficiency optimization and adjustment process collects data every 5 seconds on the ambient temperature fluctuation range, the rate of change of passenger compartment temperature, the rate of temperature rise in the core area of ​​the battery pack, and the current energy efficiency ratio parameters of the compressor. Based on the changes in these parameters, the compressor's operating frequency, the opening of the electronic expansion valves in each branch, and the opening of the internal and external circulation dampers are dynamically adjusted. When the internal temperature of the passenger compartment reaches 90% of the preset target temperature, the damper opening is gradually adjusted every 2 seconds via a stepper motor until the internal circulation damper is fully open and the external circulation damper is fully closed, reducing heat loss caused by the entry of cold air and maintaining the heat pump's operating energy efficiency within an optimal range.

[0052] During operation, abnormal operating condition protection is implemented. The compressor discharge temperature, refrigerant high-pressure side pressure, and battery pack temperature rise rate parameters are collected in real time. When the compressor discharge temperature is detected to be higher than 120℃, the compressor operating frequency is reduced by 20% first, and the evaporator bypass solenoid valve is opened to reduce the suction superheat. If the temperature still does not return to the threshold range after 10 seconds of adjustment, the 2kW PTC auxiliary heating module is started to share part of the heating load, and the compressor operating frequency is reduced again to avoid damage to the components.

[0053] The operation process of this embodiment is adapted to the low-temperature usage requirements in urban commuting scenarios. By reducing compressor start-up wear through pre-start verification and preheating, the service life of the heat pump system is extended. The multi-heat source coupled heating logic maximizes the recovery of waste heat from the power system, reducing energy consumption in the heating process. The dynamically adjusted control strategy can simultaneously meet the dual needs of passenger compartment heating and battery insulation, improving the user riding experience while ensuring battery discharge performance. The layered anomaly protection logic avoids heating process interruption and improves operational stability in low-temperature environments. The overall control logic can be directly adapted to existing vehicle hardware without additional hardware costs.

[0054] Example 2

[0055] This embodiment is applied to outdoor DC charging scenarios in extremely cold regions. The vehicle has just finished a short trip and is parked at a charging station. The outdoor ambient temperature is -22°C. After the user plugs in the DC fast charging gun, the vehicle automatically powers on and first executes a low-temperature start-up determination process. The ambient temperature is collected by a temperature sensor placed at the outdoor air intake, and the core area temperature of the battery pack is collected by a temperature sensor placed between the battery cells. The current passenger compartment temperature and the user-preset target temperature are read by the air conditioning domain controller, and the DC fast charging demand and remaining battery power are read by the battery management system.

[0056] If the current ambient temperature is below -15℃, first activate the 100W silicone heating pad placed on the low-pressure refrigerant pipeline to preheat the low-pressure pipeline. The preheating time is set to 55 seconds. After the refrigerant flow improves, further judgment will be made. At this time, the ambient temperature is below -5℃, the core temperature of the battery pack is -18℃, which is below the minimum operating temperature of 0℃. At the same time, there is a need for battery preheating, so it is determined to enter the low-temperature heat pump heating mode.

[0057] The heat pump loop pre-verification process is then performed. The loop pressure is collected by pressure sensors placed on the high and low pressure refrigerant pipelines, and the opening and closing status feedback signals of each valve are collected through the LIN bus to confirm that the pressure fluctuation meets the requirements and the valve status is normal.

[0058] At this moment, the motor has just stopped running, and the outlet water temperature of the motor's electronic control cooling circuit is more than 2°C higher than the current temperature of the lubricating oil. Therefore, the heat exchange solenoid valve between the cooling circuit and the lubricating oil chamber is opened, using the residual heat of the coolant to heat the lubricating oil. The viscosity of the lubricating oil is monitored in real time, and the temperature is lowered to 19 mm. 2 After reaching the starting viscosity threshold of / s, stop preheating and prepare for compressor startup.

[0059] The compressor is started and the heat pump circuit is in operation. Currently, the outlet water temperature of the motor's electronic control cooling circuit is above 12°C. The electronic water valve of the waste heat recovery branch is opened, transferring the remaining waste heat from the motor to the heat pump evaporator side via a brazed plate heat exchanger. This increases the refrigerant evaporation temperature and reduces the compressor's compression ratio. Since there is a demand for DC fast charging, the battery heating priority is set to 0.9. The opening of the electronic expansion valves in each branch is adjusted, prioritizing the allocation of most of the heating capacity to the battery preheating branch to ensure the battery pack's temperature rise rate meets requirements. The remaining small portion of the heating capacity is allocated to the passenger compartment branch to meet basic heating needs.

[0060] The subsequent dynamic energy efficiency optimization and adjustment process collects data every 5 seconds on ambient temperature fluctuations, battery pack temperature rise rate, battery pack core area temperature rise rate, and compressor current energy efficiency ratio parameters. If the current ambient temperature is below -20℃, the energy efficiency correction parameters are adjusted to increase the compressor's operating frequency limit, ensuring the total heating power of the heat pump meets the demand. When the battery pack core temperature rises above 10℃, the flow distribution ratio is gradually adjusted to appropriately increase the heating proportion of the passenger compartment branch, improving passenger compartment comfort without affecting battery preheating efficiency and maintaining the heat pump's operating energy efficiency within a relatively optimal range.

[0061] During operation, abnormal operating condition protection is implemented. The parameters of refrigerant high-pressure side pressure, compressor exhaust temperature, and battery pack temperature rise rate are collected in real time. When the high-pressure side pressure is detected to be higher than 3.5MPa, the compressor operating frequency is reduced by 20% first. If the pressure does not return to the threshold range after 10 seconds of adjustment, the PTC auxiliary heating module is started to share part of the heating load. At the same time, the compressor operating frequency is reduced again to avoid damage to pipelines or components due to excessive pressure.

[0062] The operation process of this embodiment is adapted to the usage requirements of charging scenarios in extremely cold regions. The refrigerant preheating process avoids compressor start-up failure in extremely cold environments, improving the applicability of the heat pump system in extremely cold scenarios. The logic of prioritizing the allocation of heat to battery preheating can quickly adjust the battery to the optimal operating temperature range, improving the charging efficiency of DC fast charging. The dynamically adjusted control strategy can maintain the normal operation of the heat pump in extremely cold environments, reduce the activation time of PTC auxiliary heating, reduce additional energy consumption during the charging process, and the layered abnormal protection logic avoids device damage, ensuring charging and heating safety in extremely cold environments.

[0063] Reference Figure 1 This diagram provides a macroscopic overview of the complete operational lifecycle of a vehicle's heat pump thermal management system in low-temperature environments, from startup detection, safety verification, and coordinated control to dynamic optimization and fault protection. After power-on, the system first comprehensively assesses the external environment and the thermal demands at multiple points within the vehicle. If the demands meet the thresholds, a pre-verification process is triggered. Before the compressor is officially started, precise inspection and adjustment of the piping and lubricating oil conditions are performed to rule out any hidden hardware damage.

[0064] During core operation, a multi-heat source coupling scheduling is adopted to dynamically balance the heating ratio between the power battery and the passenger compartment, supplemented by real-time energy efficiency adjustment to maintain the optimal energy efficiency ratio. The entire operation process is fully covered by an anomaly monitoring system. In the event of sudden thermal failure or hardware overload, it can quickly perform safe pressure relief or switch to a degradation mode, thereby ensuring the efficient, long-term, and stable operation of the system under extreme low-temperature conditions.

[0065] Reference Figure 2 This diagram details the logical branches of the heat pump system's startup decision under extreme cold conditions, as well as the technical details of the pre-verification of the pre-circuit. When the ambient temperature drops to an extremely low threshold, the system prioritizes pulse preheating of the low-pressure side of the refrigerant circuit for a predetermined duration to improve the refrigerant's fluid dynamics. After completing static self-checks for leaks and valve opening / closing states, the system introduces a tiered preheating mechanism combining motor waste heat and low-power electric heating elements, and performs viscosity reduction treatment on the compressor's internal lubricating oil.

[0066] By monitoring the kinematic viscosity of the lubricating oil in real time, the start-up permission is only released when the oil reaches a safe flow threshold. This pre-control logic greatly reduces the initial frictional resistance and starting load of the compressor in extremely cold environments, effectively preventing mechanical seizure and premature component damage caused by poor lubrication.

[0067] Reference Figure 3 This diagram highlights the control logic for the cascaded utilization of waste heat and the refined allocation of refrigerant flow under heterogeneous heat demand during the multi-heat source coupled heating stage. After the heat pump loop is activated, the system monitors the outlet water temperature of the motor's electronic control cooling network in real time, adaptively opening and closing heat exchange branches to recover the dissipated waste heat of the power system, thereby increasing the refrigerant evaporation temperature on the evaporator side and optimizing the compression ratio. At the output end, the system introduces a dynamic weighting factor to calculate the heating priority of the passenger compartment and battery pack in real time.

[0068] Especially when the battery level is extremely low or a fast charging request is triggered, the system adaptively prioritizes battery preheating, precisely allocating refrigerant mass flow by adjusting the opening step size of the electronic expansion valves in each branch. This strategy ensures that the power battery quickly enters its optimal electrochemical operating range while achieving on-demand and efficient reconfiguration of the vehicle's thermal energy.

[0069] Reference Figure 4 This diagram details the evolutionary adjustment mechanism of compressor frequency control and air circulation damper linkage during the dynamic energy efficiency optimization adjustment stage. Based on multi-source temperature rise rate and real-time energy efficiency feedback, the system uses an energy efficiency correction coefficient to dynamically constrain the compressor's operating frequency. In extremely cold conditions, the upper frequency limit is actively increased to provide powerful heating output, while in mildly cold environments, the operating frequency is reduced to curb unnecessary power consumption.

[0070] Meanwhile, the temperature compliance rate within the passenger compartment directly affects the step-by-step control of the air conditioning vents. As the cabin temperature approaches the target value, the system gradually cuts off the external air circulation and completely closes the internal air circulation, maximizing the containment of sensible heat within the passenger compartment. This coordinated hardware and software control technology effectively reduces system heat load fluctuations and significantly improves the vehicle's energy utilization efficiency in cold seasons.

[0071] Reference Figure 5 This diagram clearly illustrates the tiered protection and alternative heating switching control mechanisms implemented by the system in response to extreme abnormal operating conditions. The system weaves a safety protection network into the entire operating cycle, frequently monitoring safety limit parameters such as compressor exhaust temperature and high-pressure side refrigerant pressure. When initial limit exceedance events such as exhaust overheating occur, the protection mechanism responds quickly, forcibly reducing the compressor frequency and opening the evaporator bypass branch to reduce suction superheat.

[0072] If the hardware temperature fails to converge within the set delay period, the system will decisively implement degraded fault-tolerant control. This involves switching in a highly reliable electric heating auxiliary heating module to share the heat load, while simultaneously reducing the compressor to an ultra-low load state or safely shutting it down. This tiered convergence control process ensures the continuity of the vehicle's basic heating function while preventing thermal runaway or permanent mechanical damage to core thermal management components.

[0073] The above are merely preferred embodiments of the present invention, but the scope of protection of the present invention is not limited thereto. Any equivalent substitutions or modifications made by those skilled in the art within the scope of the technology disclosed in the present invention, based on the technical solution and inventive concept of the present invention, should be covered within the scope of protection of the present invention.

Claims

1. A method for operating a heat pump in a low-temperature environment for vehicles, characterized in that, include: When the outdoor ambient temperature is lower than the preset low temperature threshold, the temperature of the core area of ​​the battery pack is lower than the preset minimum operating temperature, and the current temperature of the passenger compartment is lower than the set heating temperature or the current temperature of the battery pack is lower than the preset target temperature, it is determined that the low temperature heat pump heating mode is entered. The heat pump circuit is checked for status. After the circuit is found to be normal, the lubricating oil inside the compressor is preheated. The starting viscosity threshold of the lubricating oil is corrected based on the current outdoor ambient temperature. The kinematic viscosity of the lubricating oil is detected in real time. Preheating is stopped when the kinematic viscosity of the lubricating oil drops to the corrected starting viscosity threshold. The compressor is started to run the heat pump circuit, and the outlet water temperature of the motor and electronic control cooling circuit is collected. When the outlet water temperature is higher than the preset waste heat recovery activation threshold, the waste heat recovery branch is opened to collect the waste heat generated by the motor and electronic control operation into the evaporator side of the heat pump. At the same time, according to the preset priority, the opening of the electronic expansion valves of the passenger compartment heating branch and the battery pack preheating branch is adjusted respectively to distribute the flow ratio of refrigerant in the two branches until the temperature of the core area of ​​the battery pack reaches the preset minimum operating temperature. Then the remaining refrigerant is distributed to the passenger compartment heating branch. The system collects real-time data on outdoor ambient temperature fluctuations, the rate of temperature change inside the passenger compartment, the rate of temperature rise in the core area of ​​the battery pack, and the current energy efficiency ratio of the compressor. Based on these parameter changes, it adjusts the compressor's operating frequency, the opening degree of the electronic expansion valves in each branch, the opening degree of the passenger compartment's internal and external circulation dampers, and the on / off status of the waste heat recovery branch.

2. The vehicle low-temperature environment heat pump thermal management operation method according to claim 1, Its features are, When distributing refrigerant flow during the operation of a heat pump loop, the target heating power of the two heating branches is first calculated using the following formula: ; in This indicates the target heating power of the battery preheating branch, in kW. This indicates the priority weight for battery heating, with a value ranging from 0.6 to 0.

9. This indicates the current total heating capacity of the heat pump system, expressed in kW. This indicates the target preheating temperature of the battery pack, in degrees Celsius (°C). This indicates the current core temperature of the battery pack, in degrees Celsius (°C). This indicates the current outdoor ambient temperature, in degrees Celsius (°C). This indicates the target heating power of the crew compartment heating branch, in kW. This indicates the set target temperature for the crew cabin, in degrees Celsius (°C). This indicates the current internal temperature of the crew cabin, in °C.

3. The method for operating a vehicle heat pump in a low-temperature environment according to claim 1, characterized in that, When preheating the internal lubricating oil of the compressor, the lubricating oil preheating PTC module is combined with the motor waste heat recovery method. When the outlet water temperature of the motor electronic control cooling circuit is higher than the current temperature of the lubricating oil, the motor waste heat is preferentially introduced into the compressor lubricating oil chamber for preheating. When the heating power provided by the motor waste heat cannot reach the preset preheating power threshold, the lubricating oil preheating PTC module is activated to provide auxiliary heating for the lubricating oil.

4. The method for operating a vehicle heat pump in a low-temperature environment according to claim 1, characterized in that, When adjusting the compressor's operating frequency, the optimal operating frequency is calculated by combining the difference in heating demand and the energy efficiency correction factor. The calculation formula is as follows: ;in This indicates the optimal operating frequency of the compressor, measured in Hz. This indicates the minimum permissible operating frequency of the compressor, measured in Hz. This represents the energy efficiency correction factor, with a value ranging from 0.7 to 1.

1. This represents the weighted sum of the temperature difference between the crew compartment and the battery pack, expressed in °C. This indicates the maximum permissible temperature difference threshold for the heat pump system, in degrees Celsius (°C). This indicates the maximum permissible operating frequency of the compressor, measured in Hz.

5. The method for operating a vehicle heat pump in a low-temperature environment according to claim 1, characterized in that, When performing the determination step of low-temperature heat pump heating mode, if the outdoor ambient temperature is detected to be below -15℃, the refrigerant pipeline preheating module is first started to preheat the low-pressure side pipeline of the refrigerant circuit before entering the low-temperature heat pump heating mode. The preheating time is maintained in the range of 30 to 60 seconds.

6. The method for operating a vehicle heat pump in a low-temperature environment according to claim 1, characterized in that, When performing waste heat recovery operation, heat exchange between the motor control cooling circuit and the heat pump circuit is achieved through a coolant-refrigerant heat exchanger. When the outlet water temperature of the motor control cooling circuit is higher than 12℃, the waste heat recovery branch is opened to transfer the waste heat generated by the motor operation to the evaporator side of the heat pump circuit.

7. The method for operating a vehicle heat pump in a low-temperature environment according to claim 1, characterized in that, When adjusting the internal and external circulation dampers of the crew cabin, when the internal temperature of the crew cabin reaches 90% of the set target temperature, gradually increase the opening of the internal circulation damper until it is fully open, while closing the external circulation damper.

8. The method for operating a vehicle heat pump in a low-temperature environment according to claim 1, characterized in that, When the compressor's exhaust temperature is detected to be higher than 120°C, the compressor's current operating frequency is first reduced by 20%, and the bypass branch of the evaporator is opened to reduce the refrigerant's suction superheat. If the exhaust temperature remains higher than the threshold for more than 10 seconds after adjustment, the cabin heating PTC module is activated to share the heating load.

9. A method for operating a vehicle heat pump in a low-temperature environment according to claim 2, characterized in that, When calculating the target heating power, if the remaining battery charge of the battery pack is detected to be less than 20% or the battery management system sends a DC fast charging request signal, the battery heating priority weight is adjusted to 0.9 to prioritize the preheating rate of the battery pack and enable the battery pack to quickly reach the optimal operating temperature range.

10. A method for operating a vehicle heat pump in a low-temperature environment according to claim 4, characterized in that, When calculating the optimal operating frequency of the compressor, if the outdoor ambient temperature is detected to be below -20℃, the energy efficiency correction factor is adjusted to 1.1, and if the outdoor ambient temperature is detected to be above -5℃, the energy efficiency correction factor is adjusted to 0.7.

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