Method for controlling an expansion valve of a heat pump arrangement with a heating and a cooling circuit of a thermal management system for a hybrid or electric vehicle

Abstract

The invention relates to a method for controlling an expansion valve (5) of a heat pump arrangement (1) for a heating and a cooling circuit of a thermal management system for a hybrid or electric vehicle, wherein the heat pump arrangement (1) comprises a refrigerant circuit (2) with a flow path for a refrigerant and a control loop comprising the first and second measuring devices (20, 22), the expansion valve (5), a comparator (28), a controller, and an actuator (32), comprising the steps of: supplying the control loop with reference variables (24), wherein the reference variables (24) comprise a target pressure and a target temperature for the high-pressure side and a target pressure and a target temperature for the low-pressure side; acquiring controlled variables (25), wherein the actual pressure and the actual temperature on the high-pressure side are measured via the first measuring device (20) and the actual pressure and the actual temperature on the low-pressure side are measured via the second measuring device (22);Feeding the recorded control variables (25) as feedback variables (26) to the comparator (28) and determining a control deviation as the difference between the specified reference variables (24) and the feedback variables (26); feeding the control deviation to a controller and determining a controller output variable (30) which is fed as an input variable to the actuator (32) and whereby, as a result, the actuator adjusts the flow rate of the expansion valve (5) by means of a manipulated variable (34).

Description

[0001] The present invention relates to a method for controlling an expansion valve of a heat pump arrangement with a heating and a cooling circuit of a thermal management system for a hybrid or electric vehicle.

[0002] The continuous development of hybrid or electric vehicles also includes the area of ​​thermal management of such vehicles.

[0003] According to current technology, hybrid or electric vehicles require up to one-third of their energy storage capacity during winter operation to heat the passenger compartment and condition the energy storage device, in most cases a battery. Since an electric motor as the prime mover only provides minimal waste heat, a conventional electric heating resistor is often used in the simplest case to heat the passenger compartment. This drastically reduces the vehicle's range. A similar problem arises in summer when using a conventional air conditioning system in a hybrid or electric vehicle.

[0004] In order to counteract these problems and thus achieve optimized thermal management of the vehicle, a heat pump arrangement for a hybrid or electric vehicle with a refrigerant circuit is known from DE 10 2021 205 922 A1, wherein the refrigerant circuit has a flow path for a refrigerant, a compressor for compressing the refrigerant from a low pressure level to a high pressure level, a high pressure refrigerant heat exchanger for releasing heat from the refrigerant, wherein the high pressure refrigerant heat exchanger is integrated into a high temperature heat accumulator, an expansion valve for reducing the pressure of the cooled refrigerant to the low pressure level and a low pressure refrigerant heat exchanger for absorbing heat from the refrigerant, wherein the low pressure refrigerant heat exchanger is integrated into a low temperature heat accumulator.

[0005] The expansion valve's function is to adjust the pressure and flow rate of the refrigerant in the refrigerant circuit by adjusting the flow cross-section, e.g., by adjusting the expansion valve's throttle body. Particularly in electronically controlled expansion valves with shape memory actuation without a stepper motor in a refrigerant circuit, it is common practice to detect the position of the throttle body using a sensor (e.g., a Hall sensor) for precise position control. This allows the position of the throttle body to be adjusted, and consequently, the pressure and flow rate of the refrigerant.

[0006] A disadvantage of this known method for position control of an expansion valve, however, is that an additional sensor (e.g. Hall sensor) is required, which must be integrated into the expansion valve and thus also requires higher costs, as well as weight and installation space.

[0007] Another disadvantage is that if the sensor fails, the valve switches off the entire refrigerant circuit due to its "normally closed position", since the system is controlled based on the position signal. In a thermal management system that includes the air conditioning and the heat pump, the heating or cooling functions (for the drive train, interior and battery) would therefore fail. In the aforementioned "fault scenario", an electric vehicle would only be drivable to a very limited extent or would no longer be drivable at all. In particular, a safety-critical condition can arise if heat has to be supplied under certain operating conditions, e.g. to defrost or demist the windshield. Another operating condition concerns battery temperature control at very low or high temperatures or during rapid charging.

[0008] It is an object of the invention to provide a method for controlling an expansion valve of a heat pump arrangement with a heating and a cooling circuit of a thermal management system of a hybrid or electric vehicle, which method can dispense with additional sensors integrated in the expansion valve and their position signals and can be implemented simply and cost-effectively.

[0009] This need can be met by the subject matter of the present invention according to independent claim 1. Advantageous embodiments of the present invention are described in the dependent claims.

[0010] The heat pump arrangement according to the invention is intended to be used in particular in a hybrid or electric vehicle, but it can also be used in any other common vehicle.

[0011] According to the present invention, the heat pump assembly comprises a refrigerant circuit. The refrigerant circuit has a flow path for a refrigerant, a compressor, a first measuring device, a second measuring device, a high-pressure refrigerant heat exchanger, an expansion valve without sensors for position detection, and a low-pressure refrigerant heat exchanger.

[0012] The electronically controlled expansion valve serves to reduce the pressure of the cooled refrigerant to the low-pressure level. The expansion valve comprises a valve housing and a throttle body, the throttle body being adjustable to set a controlled flow of refrigerant in the valve housing. This position of the throttle body is not detected in the method according to the invention. The expansion valve does not have a sensor for detecting the position of the throttle body relative to the valve housing. By eliminating the position sensor, costs, weight, and installation space can be reduced.

[0013] The expansion valve is preferably an electronically controlled expansion valve with actuation by means of a shape memory wire or a solenoid coil (without a stepper motor).

[0014] Furthermore, the method according to the invention offers a possibility of realizing an emergency function for expansion valves that are operated with an integrated sensor for position detection, so that the heat pump arrangement can continue to operate in the event of a failure of the position sensor.

[0015] The method according to the invention for controlling the expansion valve is characterized by the fact that easily measured variables can be used as control variables of the control loop. For this purpose, the first measuring device is provided, which has a pressure and a temperature sensor on the high-pressure side at the high-pressure outlet of the compressor for detecting the current system pressure and temperature.

[0016] Furthermore, the second measuring device is provided, which has a pressure and temperature sensor on the low-pressure side at the low-pressure inlet of the compressor for detecting the current system pressure and the current temperature.

[0017] In a further aspect of the invention, a method for controlling an expansion valve of a heat pump arrangement is proposed, which provides a possibility of realizing an emergency function in electronically controlled expansion valves that are operated with an integrated sensor for position detection, so that the heat pump arrangement can continue to operate in the event of a failure of the position sensor. Brief description of the drawings

[0018] The invention is described below by way of example with reference to the drawings. Fig. 1 shows a schematic representation of a heat pump arrangement, Fig. 2 shows a schematic representation of an electronically controlled expansion valve without a sensor for position detection Fig. 3 shows a process flow diagram for controlling the expansion valve according to the method according to the invention, Fig. 4 shows in a tabular overview relationships between different operating points with assigned high and low pressures, as well as a cooling or heating capacity and opening positions of the expansion valve, Fig. 5 shows a line diagram showing a cooling capacity as a function of the opening of the expansion valve; and Fig. 6 shows a line diagram which depicts a heating output depending on the opening of the expansion valve. Detailed description of the invention

[0019] In Fig. 1 shows a schematic diagram of a heat pump arrangement 1.

[0020] The heat pump assembly 1 is part of a thermal management system of a vehicle, wherein the thermal management system of the vehicle has a heating circuit 1a and a cooling circuit 1b. Both the heating circuit and the cooling circuit include a flow path for a coolant.

[0021] The heat pump assembly 1 comprises a closed refrigerant circuit 2. The refrigerant circuit 2 comprises a flow path for a refrigerant, a compressor 3, a first measuring device 20 for detecting a system pressure and a system temperature on the high-pressure side, a second measuring device 22 for detecting a system pressure on the low-pressure side, a high-pressure refrigerant heat exchanger 4, an electronically controlled expansion valve 5 with a throttle body 5a, a low-pressure refrigerant heat exchanger 6, and an accumulator / expansion tank 13.

[0022] The high-pressure refrigerant heat exchanger 4 serves to release heat from the refrigerant and is integrated into a high-temperature heat accumulator 10 and functionally forms a condenser.

[0023] The low-pressure refrigerant heat exchanger 6 serves to absorb heat from the refrigerant, wherein the low-pressure refrigerant heat exchanger is integrated into a low-temperature heat accumulator 12 and functionally forms an evaporator.

[0024] The accumulator / expansion tank 13 ensures that the compressor 3 is only supplied with refrigerant in the gas phase.

[0025] Compressor 3 serves to compress the refrigerant from a low-pressure level to a high-pressure level. In the present embodiment, compressor 3 is designed as a turbocompressor, but can be designed as any compressor. Compressor 3 has a low-pressure inlet 7 on the low-pressure side, i.e., the evaporator side, and a high-pressure outlet 8 on the high-pressure side, i.e., the condenser side.

[0026] Fig. 2 shows a schematic representation of the expansion valve 5. The expansion valve 5 is designed as an electronically controllable valve with actuation by means of a shape memory wire 5d (without a stepper motor) and comprises a valve housing 5b with a conical valve seat at the end, which has a flow opening 5c ​​for the refrigerant. For this purpose, a throttle body 5a with a conical end section is adjustably held in the valve housing 5b. The throttle body 5a with the conical end section and the valve housing 5b form, in a manner known per se, a conical seat which is designed as a throttle and is adjusted accordingly depending on the position of the throttle body 5a in relation to the conical valve seat. The expansion valve 5 does not have a sensor for detecting the position of the throttle body 5a in relation to the valve housing. In the following description, reference is made to the degree of opening in %.100% corresponds to a fully open flow opening, and 0% corresponds to a completely closed flow opening. The expansion valve 5 comprises an electronic module 5e. The electronic module 5e imprints a current as a manipulated variable for the expansion valve control process into the shape memory wire 5d, as a result of which the position of the throttle body 5a is adjustable.

[0027] During operation of the heat pump arrangement 1, the compressor 3 draws in low-pressure refrigerant from the accumulator / expansion tank 13 via the low-pressure inlet 7. The refrigerant supplied to the compressor 3 via the low-pressure inlet 7 is compressed by the compressor 3 and brought to a high-pressure level. The high-pressure refrigerant is supplied to the high-pressure heat exchanger 4 via the high-pressure outlet 8, where it is cooled while releasing heat to the high-temperature heat accumulator 10. The refrigerant cooled by the high-pressure refrigerant heat exchanger 4 is reduced to a low-pressure level via the expansion valve 5. The refrigerant is then reheated in the low-pressure refrigerant heat exchanger 6 while absorbing heat and supplied to the accumulator 13.

[0028] In addition to the high-pressure refrigerant heat exchanger 4, a high-temperature coolant heat exchanger 9 is also integrated into the high-temperature heat accumulator 10, which is part of the heating circuit of the vehicle's thermal management system.

[0029] In addition to the low-pressure refrigerant heat exchanger 6, a low-temperature coolant heat exchanger 11 is also integrated into the low-temperature heat accumulator 12, which is part of the cooling circuit of the vehicle's thermal management system.

[0030] The thermal management system of the vehicle can be cooled via the low-temperature coolant heat exchanger 11 by the low-temperature latent heat accumulator 12 in a cooling operating mode and heated via the high-temperature coolant heat exchanger 9 by the high-temperature heat accumulator 10 in a heating operating mode.

[0031] When integrating the heat pump arrangement 1 into a thermal management system of an electric vehicle, depending on the operating mode, the high-pressure refrigerant heat exchanger 4 can be coupled to a heating circuit via the high-temperature heat accumulator 10 and the high-temperature coolant heat exchanger 9, or the low-pressure refrigerant heat exchanger 6 can be coupled to a cooling circuit of the vehicle via the low-temperature heat accumulator 12 and the low-temperature coolant heat exchanger 11.

[0032] A high-pressure side 14 of the heat pump assembly 1 provides warm coolant, and a low-pressure side 15 of the heat pump assembly 1 provides cold coolant. The following components and assemblies can be thermally conditioned on the vehicle side using the heat pump assembly: • electric drive train (motor, power electronics, charger and, depending on the application, transmission) • Battery • Passenger compartment • Radiator Controlling the flow of the expansion valve:

[0033] In the heat pump arrangement 1 described above, fixed relationships between certain parameters arise in different operating modes. These parameters include: - the system pressure on the high pressure side - the system pressure on the low pressure side of the intake side of the compressor 3, - the system temperature on the high pressure side - the system temperature on the low pressure side - the degree of opening of the expansion valve. - Depending on the thermal conditioning (heating or cooling) the performance - Valve characteristic curve - Impressed control current valve

[0034] These connections are in the Fig. 4 shows several operating points as examples. All operating points required for sufficiently precise control of the expansion valve 5 are stored in a memory in a control unit (not shown). Operating points not stored in the memory are calculated by interpolation of known operating points.

[0035] At a selected operating point, in the method according to the invention, the parameters assigned to the operating point and stored in the memory, such as the system pressure and the system temperature, are added as reference variables to the Fig. 3 shown control circuit.

[0036] For example, for "WLTC driving @ -7 degrees C," a heating output of 7800 watts can be set as the operating point in heating mode with an expansion valve opening of 12.5%. With this aforementioned opening setting, the system pressure on the low-pressure side of measuring device 22 is 2.88 bar, and the system pressure on the high-pressure side of measuring device 20 is 23.34 bar. (WLTC - Worldwide Harmonized Light-Duty Vehicles Test Cycles)

[0037] Accordingly, at the selected operating point “Driving WLTC @ -7 degrees”, the system pressure 2.88 bar for the low-pressure side and the system pressure 23.34 bar for the high-pressure side are applied as reference variables to the control loop according to the Fig. 3 supplied.

[0038] The Fig. 5 and Fig. 6 show in a line diagram for both the thermal conditioning heating (heating mode) and cooling (cooling mode) that there is a clear assignment between the previously mentioned parameters.

[0039] Fig. 3 shows the control circuit for controlling the expansion valve.

[0040] The control loop's 24 reference variables are the setpoints: the system target pressure and the system target temperature (high pressure / low pressure). These reference variables are fed into the control loop.

[0041] The controlled variables 25 are the actual values: system actual pressure and system actual temperature. These are recorded by the first and second measuring devices 20, 22 using corresponding pressure and temperature sensors.

[0042] As output variables of the first and second measuring devices 20, 22, these are fed as feedback variables 26 to a comparator 28, which determines a control difference as the difference between predetermined reference variables and the feedback variables and feeds it as an output variable to a controller.

[0043] In a known manner, a controller output variable 30 is formed from the control difference in the controller, which is an input variable of the actuating device 32. In the method according to the invention, the actuating device 32 comprises the electronics module 5e and the shape memory wire 5d as well as the throttle body coupled thereto. Depending on the controller output variable, a corresponding current is impressed into the shape memory wire 5d by means of the electronics as a manipulated variable 34. Consequently, the throttle body 5a is adjusted as an actuator in the valve housing 5b depending on the impressed current. The set position of the throttle body 5a corresponds to an opening degree of the expansion valve in %. The opening degree in % sets the controlled variables 25, which in turn are fed as input variables to the measuring device 20, 22. List of reference symbols 1 Heat pump arrangement 2 Refrigerant circuit 3 turbo compressor 4 high-pressure heat exchangers 5 Expansion element 6 low-pressure heat exchangers 7 Low pressure inlet 8 High pressure outlet 9 high-temperature coolant heat exchangers 10 high-temperature heat storage units 11 Low-temperature coolant heat exchangers 12 low-temperature heat storage units 13 Refrigerant expansion tank 14 High pressure side (of the heat pump arrangement) 15 Low pressure side (of the heat pump arrangement) 20 first measuring device 22 second measuring device 24 management variables 25 controlled variables 26 feedback variables 28 comparators 30 Controller output variable 32 Adjusting device 34 Control variable QUOTES CONTAINED IN THE DESCRIPTION

[0000] This list of documents submitted by the applicant was generated automatically and is included solely for the convenience of the reader. This list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions. Cited patent literature

[0000] DE 10 2021 205 922 A1

[0004]

Claims

[1] Method for controlling an expansion valve (5) of a heat pump arrangement (1) for a heating and a cooling circuit of a thermal management system for a hybrid or electric vehicle, wherein the heat pump arrangement (1) comprises a refrigerant circuit (2) with a flow path for a refrigerant with a compressor (3), a high-pressure refrigerant heat exchanger (4), an expansion valve (5), a low-pressure refrigerant heat exchanger (6), a first measuring device (20) on the high-pressure side of the refrigerant circuit (2), and a second measuring device (22) on the low-pressure side of the refrigerant circuit (2), with a control circuit which comprises the first and second measuring devices (20, 22), a comparator (28), a controller and an actuating device (32), with the steps: - supplying the control loop with reference variables (24), wherein the reference variables (24) comprise a target pressure and a target temperature for the high-pressure side and a target pressure and a target temperature for the low-pressure side - detecting controlled variables (25), wherein the actual pressure and the actual temperature on the high-pressure side are measured via the first measuring device (20) and the actual pressure and the actual temperature on the low-pressure side are measured via the second measuring device (22) - feeding the recorded control variables (25) as feedback variables (26) to the comparator (28) and determining a control difference as the difference between the specified reference variables (24) and the feedback variables (26) - feeding the control difference to a controller and determining a controller output variable (30) which is fed as an input variable to the actuating device (32) and as a result of which the actuating device adjusts the flow of the expansion valve (5) by means of a manipulated variable (34). [2] Method for controlling an expansion valve (5) of a heat pump arrangement (1) according to claim 1, characterized by in that the expansion valve (5) comprises a valve housing (5b) and a throttle body (5a) which is adjustable in the valve housing (5b), and wherein the throttle body (5a) and the valve housing (5b) form a conical valve seat (5c) with an adjustable flow opening, and wherein the adjusting device (32) comprises an electronic module (5e) and a shape memory wire (5d) which is connected to the throttle body (5a) for adjusting the throttle body (5a) in relation to the valve body (5b), and wherein a current is impressed into the shape memory wire (5d) as a manipulated variable (34) for regulating the flow by means of the electronic module (5e). [3] Method for controlling an expansion valve (5) of a heat pump arrangement (1) according to claim 2, characterized bythat the position of the throttle body (5a) in relation to the valve body (5b), which is set by means of the setting device (32), sets the controlled variables (25) as an opening degree in %, which in turn are fed as input variables to the measuring device (20, 22). [4] Method for controlling an expansion valve (5) of a heat pump arrangement (1) according to one of the preceding claims, characterized by that the reference variables (24) supplied to the control loop can be selected as operating points, wherein the reference variables (24) and the operating points are correlated with one another and there is a clear assignment and these are stored in a memory. [5] Method for controlling an expansion valve (5) of a heat pump arrangement (1) according to claim 4, characterized by that unsaved operating points are determined by interpolation of known operating points. [6] Method for controlling an expansion valve (5) of a heat pump arrangement (1) according to one of claims 4 or 5, characterized by that the operating points are assigned fixed, previously known relationships of parameters, the parameters being: the system pressure occurring on the high-pressure side, the system pressure occurring on the low-pressure side on the intake side of the compressor (3), the system temperature on the high-pressure side, the system temperature on the low-pressure side, the degree of opening of the expansion valve (5), the power depending on the thermal conditioning (heating or cooling), the characteristic curve of the expansion valve (5), the impressed control current of the expansion valve (5).

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