Heat pump unit, thermal management sytem, vehicle, and method

Abstract

The invention relates to a heat pump unit (10) for a vehicle, in particular an electric vehicle or a hybrid vehicle, having a refrigerant circuit, wherein the refrigerant circuit comprises: at least one evaporator (11) and a condenser (12) for transferring thermal energy, a compressor unit (13) for compressing a fluid, at least one expansion valve (14) for adjusting the pressure of the fluid, at least one first temperature sensor (T1) for detecting first temperature information at a first measurement position, the first temperature sensor (T1) being situated downstream of the expansion valve (14) of the refrigerant circuit, and a computing unit which is designed to determine the pressure of the refrigerant at the first measurement position on the basis of the first temperature information.

Description

[0001] ZF Friedrichshafen AG File 304495 Friedrichshafen 2024-09-25

[0002] Heat pump unit, thermal management system, vehicle and process

[0003] The present invention relates to a heat pump unit, in particular for an electric vehicle or for a hybrid vehicle, a thermal management system, a vehicle and a method.

[0004] Heat pumps, especially for vehicles, are well-known. Heat pumps typically include a compressor, which can be driven mechanically or electrically, designed to draw in a gaseous fluid or refrigerant, compress it, and then feed it via a pipe or hose to a heat exchanger, such as a condenser. In the condenser, thermal energy is extracted from the fluid. This cools the fluid or refrigerant until it falls below a boiling point, causing it to undergo a phase change and at least partially return to a liquid state. The liquid fluid is then expanded by passing through an expansion valve. Finally, the fluid is fed to another heat exchanger, an evaporator, where energy is added, causing it to return to a gaseous state.The compressor draws in the fluid, and the process begins again.

[0005] Conventional heat pumps require at least one pressure sensor to determine the refrigerant pressure and / or to detect superheat before the refrigerant enters the compressor. Superheat describes the temperature difference between the isothermal temperature of the refrigerant when it exists as a wet vapor mixture at a given pressure and the actual temperature of the refrigerant at the compressor inlet. Therefore, to determine superheat in conventional heat pumps, the pressure and temperature at the compressor inlet must be measured. Furthermore, heat pump systems are designed for a maximum process pressure in the high-pressure range. This pressure must not be exceeded, for example, for component safety reasons (ZF Friedrichshafen AG File 304495, Friedrichshafen, September 25, 2024). Currently, the maximum pressure is monitored using a pressure sensor.So far, only heat pumps with pressure and temperature sensors are known for controlling and monitoring the heat pump unit. However, pressure sensors require significantly more installation space compared to temperature sensors. Furthermore, this can save costs, as smaller pressure sensors in particular are expensive, and using only one type of sensor is more economical.

[0006] It has therefore become clear that there is a need to provide an improved heat pump unit.

[0007] Therefore, it is an object of the present invention to provide a heat pump unit that has a compact design.

[0008] This problem is solved by a heat pump unit having the features of claim 1, by a thermal management system having the features of claim 9, by a vehicle having the features of claim 10 and by a method having the features of claim 11.

[0009] According to a first aspect of the present invention, a heat pump unit for a vehicle, in particular for an electric vehicle or for a hybrid vehicle, is provided with a refrigerant circuit, wherein the refrigerant circuit comprises: at least one evaporator and one condenser for transferring thermal energy, a compressor unit for compressing a fluid, at least one expansion valve for adjusting the pressure of the fluid, at least one first temperature sensor for detecting a first temperature information at a first measuring position, wherein the first temperature sensor is arranged downstream of the expansion valve of the refrigerant circuit, and a computing unit configured to determine a pressure of the refrigerant at the first measuring position based on the first temperature information.

[0010] In contrast to the known prior art, this method allows for a heat pump unit with a compact, and in particular space-saving, design. The compact design is achieved by eliminating the need for pressure sensors in the heat pump unit according to the present invention. In the present invention, the pressure is determined by the temperature. For this purpose, the first temperature reading is acquired via at least the first temperature sensor. From this first temperature reading, the current pressure at the first measuring position is determined. More precisely, a temperature sensor is positioned so that it constantly measures the temperature of the refrigerant at the point in the heat pump unit where the refrigerant is present as wet vapor. From the temperature reading, or...The refrigerant pressure can be determined from the temperature reading, for example, using material properties. Optionally, additional temperature sensors can be used at other measuring points to determine further temperature and pressure values. Consequently, no pressure sensors are required in the heat pump unit.

[0011] The heat pump unit is preferably a heat pump for a vehicle, in particular an electric vehicle or a hybrid vehicle. The heat pump unit includes a refrigerant circuit. The refrigerant circuit is designed to be circulated by a fluid or refrigerant. The refrigerant can be liquid and / or gaseous. The refrigerant circuit comprises an evaporator for evaporating a fluid and a condenser for liquefying a fluid. The evaporator and the condenser can also be referred to as heat exchangers. The two heat exchangers are designed to transfer thermal energy from a refrigerant circuit to a coolant circuit. For example, the heat exchangers can each be thermally coupled to a cooling circuit of a vehicle's thermal management system. In particular, a high-temperature circuit can be thermally coupled to the condenser and a low-temperature circuit to the evaporator.

[0012] The compressor unit is specifically designed to compress a fluid. The compressor unit can also be referred to as a compressor. The compressor unit preferably includes a drive unit. The drive unit can, for example, be an electric motor. The compressor unit and the drive unit are preferably formed as a single unit. In one embodiment, the compressor unit optionally includes a scroll compressor, a rotary piston compressor, or a turbo compressor. Other suitable compressor types are also possible.

[0013] The heat pump unit further comprises at least one expansion valve for adjusting the fluid pressure. The expansion valve may include a valve, an orifice, and / or a throttle. Alternatively, the expansion valve may include a pressure control valve, in particular a directly controllable pressure control valve. The expansion valve is arranged downstream of the condenser in the refrigerant flow direction. The expansion valve is designed to reduce the pressure acting on the refrigerant. Preferably, the expansion valve actively regulates the refrigerant pressure using the pressure determined by the processing unit based on at least the first temperature information.

[0014] The first temperature sensor is located in or at the first measuring position. The position of the first temperature sensor and the first measuring position can be essentially identical. The first temperature sensor, or the first measuring position, is located downstream of the expansion valve. Preferably, the first measuring position is located between the expansion valve and the compressor unit in the refrigerant circuit. The first temperature sensor detects the first temperature information. It is possible for the first temperature sensor to be configured to detect multiple first temperature values, in particular a plurality of first temperature values. A temperature value can be understood as information that includes at least a temperature value. The temperature can be measured or specified in Celsius or Kelvin.

[0015] The first measuring position is preferably located in a low-pressure section of the refrigerant circuit. The low-pressure section is the part of the refrigerant circuit that extends between the expansion valve and the compressor unit. ZF Friedrichshafen AG File 304495 Friedrichshafen 2024-09-25

[0016] The processing unit is preferably designed to obtain the initial temperature information. This means that the first temperature sensor is preferably connected to the processing unit via a signal transmission connection. The signal transmission connection can be wireless or wired.

[0017] In one embodiment, the computing unit is designed to determine the pressure based on the refrigerant's material properties. For this purpose, it is advantageous if the first measuring position is located in a substantially isothermal region where the temperature is largely constant. In particular, it is possible to determine the pressure based on the refrigerant's material properties, which are stored as a characteristic curve, for example, a state diagram or phase diagram, and / or a table. More precisely, in an isothermal region of the cycle, a corresponding pressure value can be assigned to a measured temperature value based on the material properties. The first measuring position is preferably located in the wet vapor region of the refrigerant.

[0018] In one embodiment, the refrigerant circuit includes a second temperature sensor for acquiring a second temperature reading at a second measuring position. This second temperature sensor is located directly upstream of or within the evaporator, and the processing unit is configured to determine the superheat of the refrigerant based on the first and second temperature readings. For this purpose, the first temperature sensor is preferably located directly upstream of the compressor unit, particularly at a compressor inlet. This means that no other components are located between the temperature sensor and the compressor unit. Superheat describes the temperature difference between the isothermal temperature of the refrigerant when it exists as a wet vapor mixture at a given pressure and the actual temperature of the refrigerant at the compressor inlet.Determining the pressure without a pressure sensor is achieved by measuring the temperature in the wet vapor region of the low-pressure area and converting it using the refrigerant's material properties. ZF Friedrichshafen AG File 304495 Friedrichshafen 2024-09-25.

[0019] In one embodiment, the refrigerant circuit includes a third temperature sensor for acquiring a third temperature reading at a third measuring position and a fourth temperature sensor for acquiring a fourth temperature reading at a fourth measuring position. The third and fourth temperature sensors are arranged downstream of the compressor unit, and the processing unit is configured to determine a further pressure based on the third and fourth temperature readings. The third and fourth measuring positions are preferably located in a high-pressure region. The high-pressure region extends between the compressor unit and the expansion valve. In other words, the third and fourth measuring positions are located in the high-pressure region of the refrigerant circuit.In particular, the third measuring position can be located immediately after the compressor unit and the fourth measuring position in the condenser. The heat pump unit is designed for a maximum process pressure in the high-pressure range. This pressure must not be exceeded for safety reasons. Here, the pressure in the high-pressure range can be determined and monitored without a pressure sensor. If the maximum pressure is exceeded, intervention can occur, for example, by switching off the compressor unit.

[0020] In one embodiment, the first, second, third, and / or fourth temperature sensors are arranged in the wet vapor region of the refrigerant circuit. The wet vapor region is the area of ​​the refrigerant circuit in which the refrigerant exists as wet vapor or as a substantially gaseous fluid. The wet vapor region extends within the refrigerant circuit between the evaporator and the condenser. Isothermal changes of state occur in the wet vapor region. Temperature information can be acquired in the wet vapor region, allowing conclusions to be drawn about the pressure in the area of ​​the respective measuring position. Preferably, the first and second temperature sensors, or the first and second measuring positions, are arranged upstream of the compressor unit in the direction of flow.Preferably, the third temperature sensor and the fourth temperature sensor, or the third measuring position and the fourth measuring position, are arranged downstream of the compressor unit in the direction of flow.

[0021] In one embodiment, the first, second, third, and / or fourth temperature sensors are configured as thermocouples or thermistors. Thermocouples have a very small measuring junction and a short response time. Furthermore, thermocouples are resistant to mechanical stress. Thermistors are characterized by their small size and high measurement accuracy. The temperature sensors are designed to acquire temperature information. Temperature information is understood to mean information that includes or relates to a temperature value. Temperature information can also include temperature data. The temperature sensors can be configured, for example, as invasive or non-invasive sensors. The temperature sensors are arranged, at least indirectly, in a circuit of the fluid or refrigerant.The temperature sensors can be configured to transmit a signal; for example, they can be configured to transmit a signal wirelessly or via a signal line, particularly to the processing unit. This means that the temperature sensors can preferably be connected to the processing unit wirelessly or via a cable.

[0022] In one embodiment, the expansion valve is designed as an electrically controlled valve. More precisely, the expansion valve can be designed as a direct-acting valve. For example, the expansion valve can include a solenoid coil. Direct-acting valves can, for example, use an electromagnet as an actuator. The electromagnet is directly connected to the sealing element or a valve piston. When no voltage is applied to the electromagnet, a compression spring holds the valve closed by pressing the valve piston against a valve seat. During operation, the flow direction of the refrigerant through the valve is fixed such that, in a closed state of the valve, the differential pressure that builds up between an inlet and an outlet of the valve additionally presses the valve piston against the valve seat.To open the valve, the valve piston must be lifted from the valve seat by the actuator or electromagnet. The actuator therefore exerts a force against the compression spring and against the differential pressure acting on the valve piston. The minimum force required by the electromagnetic actuator to open the valve depends on the spring force of the compression spring, the size of the valve seat, and the maximum differential pressure of the valve in the closed state. The directly controlled expansion valve can thus be directly controlled depending on the measured pressure. This allows for a very short response time of the expansion valve. The processing unit can include a control unit or be connected to a control unit via signal transmission.

[0023] In one embodiment, the processing unit determines the dew point of the fluid or refrigerant based on the measured pressure and temperature information. This makes it possible, for example, to regulate the fluid pressure using the control unit, based on the determined dew point. This ensures that the fluid is completely evaporated in the evaporator or converted into a gaseous state. The dew point, in this context, can be understood as the point at which the fluid transitions into a liquid state.

[0024] In one embodiment, the refrigerant circuit is designed without pressure sensors. This means that no pressure sensors are used or installed in the refrigerant circuit. More precisely, the pressures are determined solely via temperature information. This saves installation space, allowing for a more compact design of the heat pump unit. In this way, the cost and weight of the heat pump unit can be reduced.

[0025] Another aspect of the present invention relates to a thermal management system with a heat pump unit according to one of the preceding embodiments. ZF Friedrichshafen AG File 304495 Friedrichshafen 2024-09-25

[0026] Another aspect of the present invention relates to a vehicle with a heat pump unit according to one of the preceding embodiments and / or a thermal management system according to the preceding embodiment.

[0027] Another aspect of the present invention relates to a method for determining a pressure in a heat pump unit according to one of the preceding embodiments, comprising the steps of: acquiring a first temperature information of a refrigerant by a first temperature sensor, transmitting the first temperature information to a computing unit, determining a pressure of the refrigerant based on the first temperature information using material data of the refrigerant.

[0028] Individual features and embodiments of the present invention can be combined with other features in other embodiments to form new embodiments. Advantages and further developments mentioned for the features or embodiments also apply analogously to the new embodiments. Further developments and advantages mentioned in connection with the apparatus also apply analogously to the method and vice versa.

[0029] The present invention will now be described in detail with reference to the accompanying figures. These figures show

[0030] Fig. 1: a schematic representation of a heat pump unit; and

[0031] Fig. 2: a schematic representation of a process.

[0032] Figure 1 shows a schematic representation of a heat pump unit 10. The flow direction of a refrigerant in a refrigerant circuit of the heat pump unit 10 is indicated by arrows. The heat pump unit 10 is preferably a heat pump for a vehicle, in particular an electric vehicle or a hybrid vehicle. The refrigerant circulating in the refrigerant circuit can be liquid or gaseous. The heat pump unit 10 comprises an evaporator 11 (ZF Friedrichshafen AG File 304495 Friedrichshafen 2024-09-25) for evaporating the refrigerant, a condenser 12 for liquefying the refrigerant, a compressor unit 13 for compressing the refrigerant, and an expansion valve 14 for adjusting the refrigerant pressure.

[0033] The evaporator 11 and the condenser 12 are designed to transfer thermal energy from the refrigerant circuit to a coolant circuit. In particular, a high-temperature circuit can be thermally coupled to the condenser 13 and a low-temperature circuit to the evaporator 11. The evaporator 11 and the condenser 12 can, for example, be designed as plate heat exchangers.

[0034] The compressor unit 13 is specifically designed to compress the refrigerant. The compressor unit 13 can also be referred to as a compressor. The compressor unit 13 is arranged downstream of the evaporator 11 and upstream of the condenser 12 in the direction of flow. The compressor unit includes a drive unit, for example, an electric motor.

[0035] The expansion valve 14 is arranged downstream of the condenser 12 and upstream of the evaporator 11 in the direction of refrigerant flow. The expansion valve 14 is specifically designed to reduce the pressure acting on the refrigerant. The expansion valve 14 reduces the pressure acting on the refrigerant so that the refrigerant completely transitions into a liquid state.

[0036] A first temperature sensor T1 is arranged at a first measuring position M1 in the refrigerant circuit. The first measuring position M1 is located between the evaporator 11 and the compressor unit 13. Preferably, the first measuring position M1 is located directly in front of the compressor unit 13. The first temperature sensor T1 is designed to acquire a first temperature reading. A second temperature sensor T2 is arranged at a second measuring position M2 in the evaporator 11. In other words, the second measuring position is located in the evaporator 11. The second temperature sensor T2 is designed to acquire a second temperature reading at the second measuring position M2. (ZF Friedrichshafen AG File 304495 Friedrichshafen 2024-09-25)

[0037] A third temperature sensor T3 is arranged at a third measuring position M3 between the compressor unit 13 and the condenser 12. The third temperature sensor T3 is designed to record a third temperature reading at the third measuring position M3. A fourth temperature sensor T4 is arranged at a fourth measuring position M4 in the condenser 12. The fourth temperature sensor T4 is designed to record a fourth temperature reading at the fourth measuring position M3. The temperature sensors are each located in a wet vapor region of the refrigerant. More precisely, the temperature sensors are each located in an isothermal section of the refrigerant circuit. This means that the temperature is essentially constant in the sections where the temperature sensors are located.

[0038] The temperature readings from the individual temperature sensors can be used to determine the refrigerant pressure at the corresponding measuring position. Furthermore, the first temperature reading from the first temperature sensor T1 and the second temperature reading from the second temperature sensor T2 can be used to detect refrigerant superheating. The third temperature reading from the third temperature sensor T3 and the fourth temperature reading from the fourth temperature sensor T4 can be used to monitor the maximum refrigerant pressure. For example, if a limit pressure is reached or exceeded, compressor unit 13 can be deactivated.

[0039] Figure 2 is a schematic representation of a method for determining the pressure of a heat pump unit 10. In a first step S1, a heat pump unit 10 is provided with at least one first temperature sensor T1. In a second step S2, the first temperature sensor T1 acquires initial temperature information about a refrigerant. In a third step S3, the initial temperature information is transmitted to a processing unit. In a fourth step S4, the pressure of the refrigerant is determined based on the initial temperature information. The pressure is determined by the processing unit. In particular, the pressure of the refrigerant can be determined based on the refrigerant's material properties. ZF Friedrichshafen AG File 304495 Friedrichshafen 2024-09-25

[0040] Other embodiments of the present invention are possible and can be understood and carried out by persons skilled in the art when applying the claimed subject matter by studying the figures, the disclosure, and the appended claims. In particular, the respective parts / functions of each embodiment described above can also be combined with one another. Furthermore, various steps of the method can be carried out in a different order than disclosed herein. In the claims, the word "comprising" does not exclude other elements or steps, and the indefinite article "a" or "an" does not exclude a plurality. The mere fact that certain measures are mentioned in interdependent claims does not mean that a combination of these measures cannot be advantageous. Any reference numerals in the claims should not be interpreted as limiting the scope of the claims.

[0041] ZF Friedrichshafen AG File 304495 Friedrichshafen 2024-09-25

[0042] List of reference signs

[0043] 10 heat pump units

[0044] 11 evaporators

[0045] 12 Capacitor

[0046] 13 Compressor unit

[0047] 14 Expansion valve

[0048] T1 first temperature sensor

[0049] T2 second temperature sensor

[0050] T3 third temperature sensor

[0051] T4 fourth temperature sensor

[0052] M1 first measuring position

[0053] M2 second measuring position

[0054] M3 third measuring position

[0055] M4 fourth measuring position

Claims

ZF Friedrichshafen AG File 304495 Friedrichshafen 2024-09-25 Patent claims 1. Heat pump unit (10) for a vehicle, in particular an electric vehicle or a hybrid vehicle, with a refrigerant circuit, wherein the refrigerant circuit comprises: at least one evaporator (11) and one condenser (12) for transferring thermal energy, a compressor unit (13) for compressing a fluid, at least one expansion valve (14) for adjusting the pressure of the fluid, at least one first temperature sensor (15) for detecting a first temperature information at a first measuring position (M1), wherein the first temperature sensor (T1) is arranged downstream of the expansion valve (14) of the refrigerant circuit, and a computing unit configured to determine a pressure of the refrigerant at the first measuring position (M1) based on the first temperature information.

2. Heat pump unit (10) according to claim 1, wherein the computing unit is configured to determine the pressure based on material properties of the refrigerant.

3. Heat pump unit (10) according to one of the preceding claims, wherein the refrigerant circuit comprises a second temperature sensor (T2) for detecting a second temperature information at a second measuring position (M2), wherein the second temperature sensor (T2) is arranged directly in front of the evaporator (11) or in the evaporator (11) and the computing unit is configured to determine superheating of a refrigerant in the refrigerant circuit on the basis of the first temperature information and the second temperature information.

4. Heat pump unit (10) according to one of the preceding claims, wherein the refrigerant circuit includes a third temperature sensor (T3) for detecting a ZF Friedrichshafen AG File 304495 Friedrichshafen 2024-09-25 comprises a third temperature information at a third measuring position (M3) and a fourth temperature sensor (T4) for acquiring a fourth temperature information at a fourth measuring position (M4), wherein the third temperature sensor (T3) and the fourth temperature sensor (T4) are arranged downstream of the compressor unit (13), wherein the computing unit is configured to determine a further pressure based on the third temperature information and the fourth temperature information.

5. Heat pump unit (10) according to one of the preceding claims, wherein the first temperature sensor (T1), the second temperature sensor (T2), the third temperature sensor (T3) and / or the fourth temperature sensor (T4) are arranged in a wet vapor area of ​​the refrigerant circuit.

6. Heat pump unit (10) according to one of the preceding claims, wherein the first temperature sensor (T1), the second temperature sensor (T2), the third temperature sensor (T3) and / or the fourth temperature sensor (T4) are configured as thermocouples or thermistors.

7. Heat pump unit (10) according to one of the preceding claims, wherein the expansion valve (14) is designed as an electrically controlled valve.

8. Heat pump unit (10) according to one of the preceding claims, wherein the refrigerant circuit is designed without a pressure sensor.

9. Thermal management system with a heat pump unit (10) according to one of the preceding claims.

10. Vehicle with a heat pump unit (10) according to one of claims 1 to 8 and / or a thermal management system according to claim 9.

11. Method for determining a pressure in a heat pump unit (10) according to any one of claims 1 to 8, comprising the steps: ZF Friedrichshafen AG File 304495 Friedrichshafen 2024-09-25 Acquisition of initial temperature information of a refrigerant by a first temperature sensor, Transmitting the initial temperature information to a computing unit, determining the pressure of the refrigerant based on the initial temperature information using the material properties of the refrigerant.

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