Thermal system for a motor vehicle and method for operating the thermal system

Abstract

The invention relates to a thermal system (10) for a motor vehicle, comprising a temperature control circuit (12) for controlling the temperature of a motor vehicle battery (18), an air-conditioning circuit (14) for air-conditioning a passenger compartment by means of an air-conditioning heat exchanger (26), and a heat exchanger (16) thermally coupling the temperature control circuit (12) to the air-conditioning circuit (14), the air-conditioning circuit (14) has a bypass line (32) which is connected to the output side of the compressor (24) via a first adjustable expansion valve (34), the bypass line (32) being guided back to the input side of the compressor (24) bypassing the heat exchanger (16) and the air-conditioning heat exchanger (26). By means of a recirculation in the air-conditioning circuit (14) by means of the first expansion valve (34) and the bypass line (32), good control of the motor vehicle battery (18) and good cabin air conditioning can be achieved with low equipment costs.

Description

Technical Field

[0001] The invention relates to a thermal system and a method for operating such a thermal system, by means of which a motor vehicle battery can be temperature-controlled and a passenger compartment of the motor vehicle can be air-conditioned. Background Art

[0002] It is known from WO 2019 / 069018 A1 that a temperature control circuit for controlling the temperature of a motor vehicle battery of a motor vehicle is thermally coupled to an air-conditioning circuit for air conditioning the passenger compartment of the motor vehicle via an evaporator referred to as a “cooler”, wherein the air-conditioning circuit can selectively flow past the cooler by means of a valve and extend through the evaporator connected to the air-conditioning circuit.

[0003] For example, during a cold start of a motor vehicle, there are situations where the motor vehicle battery should not be cooled but heated. After reaching the designed operating temperature of the motor vehicle battery, cooling is usually only necessary, in which case the heat generated in the motor vehicle battery should be used to air condition the passenger compartment. However, in order for the motor vehicle battery to reach its operating temperature at which it can operate efficiently as quickly as possible, it should be avoided with the lowest possible equipment expenditure that the power output for air conditioning the passenger compartment affects the heating power for heating to the operating temperature. Summary of the invention

[0004] The object of the present invention is to specify measures which allow good temperature control of the vehicle battery and good air conditioning of the passenger compartment with low equipment expenditure.

[0005] According to the invention, this object is achieved by a thermal system having the features of claim 1 and a method having the features of claim 10. Preferred embodiments of the invention are given in the dependent claims and the following description, which can each describe an aspect of the invention individually or in combination, wherein the scope of protection is determined by the claims.

[0006] One aspect of the present invention relates to a thermal system for a motor vehicle, which comprises a temperature control circuit / / temperature regulating circuit for controlling the temperature of a motor vehicle battery, an air-conditioning circuit for air-conditioning a passenger compartment via an air-conditioning heat exchanger, and a heat exchanger thermally coupling the temperature control circuit to the air-conditioning circuit, wherein the air-conditioning circuit has a bypass line connected to the output side of a compressor via an adjustable first expansion valve, wherein the bypass line is led back to the input side of the compressor while bypassing the heat exchanger and the air-conditioning heat exchanger.

[0007] By means of the bypass line, part or all of the mass flow of the air conditioning circuit can be circulated in the area of ​​the compressor and accordingly prevented from flowing through the heat exchanger. As a result, the heat absorption from the temperature control circuit can be reduced or even completely prevented, so that more heat is available in the temperature control circuit for heating the vehicle battery. As a result, the thermal power available for air conditioning the passenger compartment is reduced accordingly and is used instead for rapid heating of the vehicle battery. Since the vehicle battery is heated to the operating temperature particularly quickly in this way, the vehicle occupants can usually accept the time delay of air conditioning the passenger compartment. In particular, when the temperature of the vehicle battery gradually increases, it is possible to adjust the thermal power output from the temperature control circuit to the air conditioning circuit by correspondingly adjusting the bypass mass flow through the bypass, so as to air condition the passenger compartment at least with the reduced thermal power. An optimal balance can be adjusted between the heating power required in the temperature control circuit for heating the vehicle battery and the thermal power required in the air conditioning circuit for air conditioning the passenger compartment, which balance can depend in particular on the difference between the current temperature of the vehicle battery and the efficiency associated therewith and the operating temperature of the vehicle battery. By means of the recirculation in the air-conditioning circuit by means of the first expansion valve and the bypass line, good temperature control of the vehicle battery and good air conditioning of the passenger compartment can be achieved with low equipment expenditure.

[0008] The first expansion valve can be designed to compensate for the pressure increase achieved in the compressor, so that the operating conditions do not change significantly with respect to the compressor. Preferably, the first expansion valve can completely open the bypass line in the initial state, so that the entire mass flow of the air conditioning circuit is conducted through the heat exchanger, also referred to as the "cooler", and as much heat as possible can be absorbed from the temperature control circuit. Preferably, the first expansion valve can be designed to adjust the bypass mass flow through the bypass line steplessly between 0% and 100%.

[0009] The compressor is designed in particular to compress a gaseous medium, in particular an evaporating refrigerant medium. Therefore, a significantly higher pressure will be present on the output side of the compressor than on the input side of the compressor. By means of compression, the temperature of the medium can also be increased, at which temperature the medium can be supplied to the air conditioning heat exchanger.

[0010] An air conditioning heat exchanger can be designed to air condition, in particular heat, the air that is led into the passenger compartment of a motor vehicle. In the air conditioning heat exchanger, the pressure of the medium can drop due to pressure losses and the temperature of the medium can drop due to the dissipated heat. The air conditioning heat exchanger is in particular part of an air conditioning system of a motor vehicle.

[0011] The heat exchanger, also referred to as a "cooler", is part of both the air conditioning circuit and the temperature control circuit, wherein the medium flowing through the heat exchanger of the air conditioning circuit and the medium flowing through the heat exchanger of the temperature control circuit are preferably separated from each other but can exchange heat with each other. It is not necessarily necessary to provide that the medium of the air conditioning circuit and the medium of the temperature control circuit undergo a physical state change in the heat exchanger. However, it can be provided that the corresponding medium evaporates on the side of the heat exchanger assigned to the air conditioning circuit and / or the corresponding medium condenses on the side of the heat exchanger assigned to the temperature control circuit.

[0012] The motor vehicle battery can be part of a temperature control circuit and, depending on the current temperature of the motor vehicle battery relative to the expected operating temperature of the motor vehicle battery, can act as a heat sink or heat source. The motor vehicle battery can, in particular, have battery cells arranged in a housing, wherein preferably the medium of the temperature control circuit can be guided into the housing of the motor vehicle battery in order to flow through the battery cells.

[0013] In particular, the regulating position of the first expansion valve can be adjusted by the PI regulating element to adjust the bypass mass flow. As a result, the expected regulating position of the first expansion valve is not controlled suddenly, but in a ramp-like manner. As a result, sudden pressure fluctuations in the pipeline of the air conditioning circuit can be avoided.

[0014] Preferably, the first expansion valve can be adjusted as a function of the heating demand in the temperature control circuit. The control device can calculate the required heating demand in the temperature control circuit and, by adjusting the first expansion valve, only allow such an amount of medium from the air conditioning circuit to be introduced into the heat exchanger that does not result in the required heating demand not being met. In this case, the control device can take into account the current temperature of the vehicle battery, the designed operating temperature of the vehicle battery, the heating power specified in the temperature control circuit and / or the mass flow of the medium in the temperature control circuit.

[0015] Particularly preferably, the bypass line is led back to the input side of the compressor via the collector, in particular only via the collector. Apart from the line and / or the collector, no other functional components of the air conditioning circuit are arranged between the outlet of the bypass line and the inlet of the compressor, so that the bypass mass flow is neither delivered to the evaporator nor to the condenser or heat exchanger element, such as an air conditioning heat exchanger. As a result, the connection point of the bypass line to the remaining line of the air conditioning circuit - at which the bypass line is led back into the remaining line of the air conditioning circuit - can be arranged particularly close to the compressor, so that the bypass line can be implemented correspondingly short. A certain amount of the medium of the air conditioning circuit can be buffered in the collector, and phase separation can also be achieved in principle. As a result, the collector can also reduce pressure fluctuations caused by the first expansion valve.

[0016] Particularly preferably, the air conditioning heat exchanger and the heat exchanger are connected to each other in the air conditioning circuit via an unbranched connecting pipe. This can avoid additional bypass pipes in the air conditioning circuit. Preferably, in the air conditioning circuit, the medium first flows through the air conditioning heat exchanger and then flows through the heat exchanger.

[0017] In particular, a second adjustable expansion valve is provided in the connecting line. If the second expansion valve is closed, the medium can be blocked in the area of ​​the line leading to the compressor, so that the connecting line does not run without medium. In addition, the flow through the heat exchanger can be adjusted directly at the inlet of the heat exchanger on the air conditioning circuit side, without the connecting line having to be run without medium first.

[0018] Preferably, the second expansion valve can be adjusted according to the adjustment position of the first expansion valve. This ensures that the mass flow at the outlet of the compressor corresponds to the sum of the mass flow through the bypass line and the mass flow through the heat exchanger. This avoids dead times and time delays in the line sections of the air conditioning circuit.

[0019] Particularly preferably, the temperature control circuit has a heater for heating a temperature control medium for the motor vehicle battery. In particular, the heater can be operated electrically and heats the medium of the temperature control circuit, in particular water. If the motor vehicle battery reaches its designed operating temperature, the heater can simply be switched off, so that the cooling function of the temperature control circuit for cooling the motor vehicle battery is not impaired. The heater avoids heat transfer from other heat sources, in particular from an air conditioning circuit.

[0020] In particular, the air conditioning heat exchanger is designed as a heating register / heating coil of an air conditioning heat pump for air conditioning the air guided into the passenger cabin. The air conditioning of the passenger cabin can be carried out according to the heat pump principle, wherein the associated heating register can be easily flowed through by the medium of the air conditioning circuit for heat exchange with the air guided into the passenger cabin.

[0021] Another aspect of the invention relates to a method for operating a thermal system which can be designed and improved as described above, in which the mass flow conducted through the heat exchanger in the air conditioning circuit is regulated as a function of the heating demand of the temperature control circuit. By means of the recirculation in the air conditioning circuit by means of the first expansion valve and the bypass line, good temperature control of the vehicle battery and good cabin air conditioning can be achieved with low equipment expenditure. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] The present invention is explained below by way of example according to preferred embodiments with reference to the accompanying drawings, wherein the features shown below may describe an aspect of the present invention both individually and in combination, wherein the scope of protection is determined by the claims. The accompanying drawings show:

[0023] Figure 1 A schematic diagram of the thermal system is shown. DETAILED DESCRIPTION

[0024] exist Figure 1 The thermal system 10 shown in FIG. 1 can be used in a motor vehicle. The thermal system 10 has a temperature control circuit 12 and an air conditioning circuit 14 which are thermally coupled to each other via a heat exchanger 16, also referred to as a "cooler". The temperature control circuit 12 includes a motor vehicle battery 18, which is usually to be cooled by a liquid medium pumped by means of a pump 20. For this purpose, the heat generated in the motor vehicle battery 18 and absorbed by the liquid medium can be output to the medium of the air conditioning circuit 14 in the heat exchanger 16. If the motor vehicle battery 18 is to be heated to the designed operating temperature first, for example when the motor vehicle is cold started, the liquid medium can be heated by a heater.

[0025] The air conditioning circuit 14 comprises a compressor 24, by means of which a medium, in particular a gaseous medium, can be conveyed. The medium compressed by the compressor to a high pressure and a high temperature can be conveyed to an air conditioning heat exchanger 26. The air conditioning heat exchanger 26 can be part of an air conditioning device 28, by means of which the air conveyed to the passenger compartment of the motor vehicle can be air-conditioned, in particular heated. Subsequently, the medium having a low pressure and a low temperature after the air conditioning heat exchanger 26 can be conveyed to the heat exchanger 16 in order to absorb heat from the temperature control circuit 12 for the purpose of cooling the motor vehicle battery 18. The medium of the temperature control circuit 12 leaving the heat exchanger 16 can be conveyed to the compressor 24 again via a collector 30.

[0026] In order that the air conditioning circuit 14 does not affect the heating of the motor vehicle battery 18, the air conditioning circuit 14 has a bypass 32 connected to the output side of the compressor 24, which bypasses the air conditioning heat exchanger 26 and the heat exchanger 16 and is connected to the input side of the compressor 24 via the collector 30. With the help of the first expansion valve 34, the bypass mass flow branched via the bypass 32 can be adjusted. The bypass mass flow is basically transported by the compressor 24 via the collector 30 in a cyclic manner, and heat output from the temperature control circuit 12 to the bypass mass flow cannot be carried out. Preferably, as an addition to the connecting line 36 between the air conditioning heat exchanger 26 and the heat exchanger 16, a second expansion valve 38 is provided, and the flow rate of the second expansion valve is adapted to the bypass mass flow adjusted by the first expansion valve 34.

Claims

1. A thermal system (10) for a motor vehicle, the thermal system comprising: A temperature control circuit (12) for controlling the temperature of a motor vehicle battery (18), an air conditioning circuit (14) for air conditioning the passenger cabin via an air conditioning heat exchanger (26), and A heat exchanger (16) thermally couples the temperature control circuit (12) with the air conditioning circuit (14), It is characterized in that The air conditioning circuit (14) has a bypass line (32) which is connected to the output side of the compressor (24) via a first adjustable expansion valve (34), wherein the bypass line (32) is led back to the input side of the compressor (24) bypassing the heat exchanger (16) and the air conditioning heat exchanger (26).

2. The thermal system (10) according to claim 1, wherein: The regulating position of the first expansion valve (34) can be adjusted by a PI regulating element to adjust the bypass mass flow.

3. The thermal system (10) according to claim 1 or 2, wherein: The first expansion valve (34) can be adjusted according to the heating demand in the temperature control circuit (12).

4. The thermal system (10) according to any one of claims 1 to 3, wherein: The bypass line (32) is led back to the input side of the compressor (24) via the collector (30), in particular exclusively via the collector (30).

5. The thermal system (10) according to any one of claims 1 to 4, wherein: The air conditioning heat exchanger (26) and the heat exchanger (16) are connected to each other in the air conditioning circuit (14) via an unbranched connecting line (36).

6. The thermal system (10) according to claim 5, wherein: An adjustable second expansion valve (38) is arranged in the connecting pipeline (36).

7. The thermal system (10) according to claim 6, wherein: The second expansion valve (38) can be adjusted according to the adjustment position of the first expansion valve (34).

8. The thermal system (10) according to any one of claims 1 to 7, wherein: The temperature control circuit (12) has a heater (22) for heating a temperature control medium for a motor vehicle battery (18).

9. The thermal system (10) according to any one of claims 1 to 8, wherein: The air conditioning heat exchanger (26) is designed as a heating regulator of an air conditioning heat pump for temperature regulating air guided into the passenger compartment.

10. A method for operating a thermal system (10) according to any one of claims 1 to 9, wherein: The mass flow conducted through the heat exchanger (16) in the air conditioning circuit (14) is regulated as a function of the heating demand of the temperature control circuit (12).

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