DE102023130210B4 - Thermosystem for a motor vehicle and method for operating the thermosystem - Google Patents

Abstract

Thermal system (10) for a motor vehicle,
with a temperature control circuit (12) for temperature control of a motor vehicle battery (18),
with a climate circuit (14) for air conditioning a passenger compartment via a climate heat exchanger (26), and
with a heat exchanger (16) thermally coupling the temperature control circuit (12) with the air conditioning circuit (14),
wherein the climate circuit (14) has a bypass line (32) connected via a controllable first expansion valve (34) to an outlet side of a compressor (24), wherein the bypass line (32) is routed past the heat exchanger (16) and the climate heat exchanger (26) back to an inlet side of the compressor (24),
characterized by the fact that
the bypass line (32) is routed back to the inlet side of the compressor (24) via a collector (30).

Description

The invention relates to a thermal system and a method for operating such a thermal system, with the respective aid of which a motor vehicle battery can be temperature controlled and a passenger compartment of the motor vehicle can be air-conditioned.

From WO 2019/069 018 A1, a thermal system according to the preamble of claim 1 is known. It is known to thermally couple a temperature control circuit for temperature control of a motor vehicle battery via an evaporator referred to as a "chiller" with an air conditioning circuit for air conditioning a passenger compartment of the motor vehicle, wherein the air conditioning circuit can optionally bypass the chiller and pass through an evaporator then connected in the air conditioning circuit by means of valves.

There are situations, such as during a cold start of a vehicle, where the vehicle battery needs to be heated rather than cooled. Once the battery reaches its designated operating temperature, cooling is usually the only remaining requirement, and the heat generated within the battery should be used to cool the passenger compartment. To ensure the battery reaches its operating temperature as quickly as possible, at which point it can operate with high efficiency, the heat required for cooling the battery should not be compromised by the heat dissipated for air conditioning, and this should be achieved with minimal equipment.

DE 10 2018 010 019 A1 reveals further state of the art.

The object of the invention is to demonstrate measures that enable good temperature control of a motor vehicle battery and good air conditioning of a passenger compartment with minimal equipment effort.

According to the invention, the problem is solved 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 specified in the dependent claims and the following description, each of which can individually or in combination represent an aspect of the invention, the scope of protection being determined by the claims.

According to claim 1, the thermal system for a motor vehicle comprises a temperature control circuit for temperature control 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 with the air conditioning circuit, wherein the air conditioning circuit has a bypass line connected to an output side of a compressor via a controllable first expansion valve, wherein the bypass line is routed past the heat exchanger and the air conditioning heat exchanger back to an input side of the compressor.

With the aid of the bypass line, part or all of the mass flow of the air conditioning circuit can be recirculated in the compressor area and thus prevented from flowing through the heat exchanger. This reduces or even completely prevents heat absorption from the temperature control circuit, making more heat available in the temperature control circuit for heating the vehicle battery. The heat output available for air conditioning the passenger compartment is thereby reduced and instead used for rapidly heating the vehicle battery. Because the vehicle battery heats up to operating temperature particularly quickly, the slight delay in the passenger compartment's air conditioning is generally acceptable to vehicle occupants. In particular, if the vehicle battery temperature gradually increases, the heat output drawn from the temperature control circuit to the air conditioning circuit can be adjusted by appropriately modifying the bypass mass flow, thus ensuring that the passenger compartment can be air-conditioned with a reduced heat output. An optimized balance can be established between the heating power required in the temperature control circuit to heat the vehicle battery and the heat output required in the air conditioning circuit to temperature-control the passenger compartment. This balance depends particularly on the difference between the current temperature of the vehicle battery and its operating temperature, and the associated efficiency. The recirculation in the air conditioning circuit, achieved with the first expansion valve and the bypass line, enables effective temperature control of the vehicle battery and effective air conditioning of the passenger compartment with minimal equipment.

The first expansion valve can be designed to reverse a pressure increase achieved in the compressor, so that the operating conditions for the compressor do not change significantly. preferably, the first expansion valve can completely close the bypass line in an initial state, so that the entire mass flow of the air conditioning circuit is routed through the heat exchanger, also known as the "chiller," and can absorb as much heat as possible from the temperature control circuit. Preferably, the first expansion valve is designed to continuously adjust the bypass mass flow through the bypass line between 0% and 100%.

The compressor is specifically designed to compress a gaseous medium, particularly a vaporized refrigerant. Therefore, the pressure at the compressor's outlet can be significantly higher than at its inlet. Compression can also increase the temperature of the medium, which can then be supplied to the air conditioning heat exchanger at this higher temperature level.

The air conditioning heat exchanger can be designed to condition, and in particular heat, the air directed into the passenger compartment of the vehicle. Within the air conditioning heat exchanger, pressure losses can cause the pressure of the medium to decrease, and the temperature of the medium can decrease due to the heat released. The air conditioning heat exchanger is, in particular, a component of the vehicle's air conditioning system.

The heat exchanger, also known as a "chiller," is part of both the air conditioning circuit and the temperature control circuit. Preferably, the media flowing through the heat exchanger in the air conditioning circuit and the temperature control circuit are separated from each other but can still exchange heat. A change in the state of matter of the media in the air conditioning circuit and the temperature control circuit within the heat exchanger is not strictly necessary. However, it is possible to provide for evaporation on the side of the heat exchanger assigned to the air conditioning circuit and/or condensation of the respective medium on the side assigned to the temperature control circuit.

The vehicle battery can be part of the temperature control circuit and, depending on its current temperature relative to the intended operating temperature, can act as either a heat sink or a heat source. The vehicle battery can, in particular, have battery cells arranged within a housing, with the medium of the temperature control circuit preferably being introduced into the housing of the vehicle battery to circulate around the battery cells.

According to claim 1, the bypass line is routed back to the compressor's inlet side via a manifold, and in particular exclusively via the manifold. Apart from the lines and/or the manifold, no further functional components of the air conditioning circuit are provided between the outlet of the bypass line and the compressor's inlet, so that the bypass mass flow is not fed to an evaporator, a condenser, or a heat exchanger element such as the air conditioning heat exchanger. A connection point where the bypass line is routed back into the rest of the air conditioning circuit can therefore be located particularly close to the compressor, allowing the bypass line to be correspondingly short. A quantity of the air conditioning circuit's refrigerant can be buffered in the manifold, and phase separation can also be provided. The manifold can thus also dampen pressure fluctuations caused by the first expansion valve.

In particular, the position of the first expansion valve for setting a bypass mass flow can be controlled via a PI controller. The intended position of the first expansion valve is thus not reached abruptly, but rather gradually via a ramp. This prevents sudden pressure fluctuations in the air conditioning circuit lines.

Preferably, the first expansion valve is controllable depending on the heating demand in the temperature control circuit. A control system can calculate the heating demand required in the temperature control circuit and, with the help of the control of the first expansion valve, introduce only as much refrigerant from the air conditioning circuit into the heat exchangers as is necessary to ensure that the required heating demand is not undershot. The control system can take into account the current temperature of the vehicle battery, the designated operating temperature of the vehicle battery, a heating output provided within the temperature control circuit, and/or a mass flow rate of the refrigerant in the temperature control circuit.

Preferably, the air conditioning heat exchanger and the heat exchanger within the air conditioning circuit are connected to each other via an unbranched connecting line. This eliminates the need for additional bypass lines in the air conditioning circuit. Preferably, the medium flows through the air conditioning heat exchanger first, followed by the heat exchanger within the air conditioning circuit.

In particular, a controllable second expansion valve is provided in the connecting line. When the second expansion valve is closed, the medium can be retained in a section of the line up to the compressor, so that the The connecting line does not run dry. Furthermore, it is possible to adjust the flow rate through the heat exchanger directly at the inlet of the heat exchanger on the side of the air conditioning circuit, without having to drain the connecting line first.

Preferably, the second expansion valve is controllable depending on the control position of the first expansion valve. This ensures that the mass flow rate at the compressor outlet corresponds to the sum of the mass flow rates through the bypass line and the heat exchanger. Dead times and time delays along the air conditioning circuit can thus be avoided.

The temperature control circuit preferably includes a heater for heating a temperature control medium for the vehicle battery. The heater can be electrically operated and heat the medium of the temperature control circuit, particularly water. Once the vehicle battery has reached its designated operating temperature, the heater can be easily switched off, so that the cooling function of the temperature control circuit for cooling the vehicle battery is not impaired. The heater prevents heat input from other heat sources, particularly from the air conditioning system.

In particular, the climate control heat exchanger is designed as a heating element of a climate control heat pump for temperature control of the air supplied to the passenger compartment. The passenger compartment can be temperature controlled according to the heat pump principle, whereby the associated heating element can be easily supplied with air from the climate control system for heat exchange with the air supplied to the passenger compartment.

Another aspect of the invention relates to a method for operating a thermal system, which can be designed and further developed as described above, in which a mass flow routed through the heat exchanger in the air conditioning circuit is regulated depending on the heating demand of the temperature control circuit. The recirculation in the air conditioning circuit achieved with the aid of the first expansion valve and the bypass line enables effective temperature control of a vehicle battery and effective air conditioning of a passenger compartment with minimal equipment.

• 1: eine schematische Prinzipdarstellung eines Thermosystems.

The invention is now explained by way of example with reference to the accompanying drawing, using a preferred embodiment as an illustration, wherein the features shown below can represent an aspect of the invention, either individually or in combination, and the scope of protection is defined by the claims. It shows:

• 1 : a schematic representation of the principle of a thermosystem.

The 1 The illustrated thermal system 10 can be used in a motor vehicle. The thermal system 10 comprises a temperature control circuit 12 and an air conditioning circuit 14, which are thermally coupled via a heat exchanger 16, also referred to as a "chiller." The temperature control circuit 12 includes a vehicle battery 18, which is typically cooled by a liquid medium circulated by a pump 20. For this purpose, heat generated in the vehicle battery 18 and absorbed by the liquid medium can be transferred to the medium of the air conditioning circuit 14 via the heat exchanger 16. If the vehicle battery 18 needs to be heated to a designated operating temperature, for example, during a cold start of the vehicle, the liquid medium can be heated by a heater.

The air conditioning circuit 14 includes a compressor 24, which can pump a medium, particularly a gaseous medium. The medium, compressed by the compressor to high pressure and high temperature, can be fed to an air conditioning heat exchanger 26. The air conditioning heat exchanger 26 can be part of an air conditioning unit 28, which can be used to condition, and in particular heat, the air supplied to the passenger compartment of the motor vehicle. The medium, now at low pressure and low temperature after the air conditioning heat exchanger 26, can subsequently be fed to the heat exchanger 16 to absorb heat from the temperature control circuit 12 for cooling purposes of the motor vehicle battery 18. The medium leaving the heat exchanger 16 from the temperature control circuit 12 is fed back to the compressor 24 via a manifold 30.

To prevent the air conditioning circuit 14 from interfering with the heating of the vehicle battery 18, the air conditioning circuit 14 has a bypass line 32 connected to an outlet side of the compressor 24. This bypass line runs past the air conditioning heat exchanger 26 and the heat exchanger 16, via the manifold 30, and is connected to the inlet side of the compressor 24. A first expansion valve 34 allows the bypass mass flow rate diverted via the bypass line 32 to be adjusted. The bypass mass flow rate is essentially circulated by the compressor 24 via the manifold 30 without any heat being transferred from the temperature control circuit 12 to the bypass mass flow rate. Preferably, a second bypass line 36 is also connected between the air conditioning heat exchanger 26 and the heat exchanger 16. Expansion valve 38 is provided, the flow rate of which is adapted to the bypass mass flow set by the first expansion valve 34.

Claims (10)

Thermosystem (10) for a motor vehicle, comprising a temperature control circuit (12) for temperature control of a motor vehicle battery (18), an air conditioning circuit (14) for air conditioning a passenger compartment via an air conditioning heat exchanger (26), and a heat exchanger (16) thermally coupling the temperature control circuit (12) to the air conditioning circuit (14), wherein the air conditioning circuit (14) has a bypass line (32) connected to an outlet side of a compressor (24) via a controllable first expansion valve (34), wherein the bypass line (32) is routed past the heat exchanger (16) and the air conditioning heat exchanger (26) back to an inlet side of the compressor (24), characterized in that the bypass line (32) is routed back to the inlet side of the compressor (24) via a collector (30). Thermosystem (10) according to Claim 1 , characterized in that a control position of the first expansion valve (34) for setting a bypass mass flow can be controlled via a PI control element. Thermosystem (10) according to Claim 1 or 2 , characterized in that the first expansion valve (34) is controllable depending on a heating requirement in the temperature control circuit (12). Thermosystem (10) according to one of the Claims 1 until 3 , characterized in that the bypass line (32) is routed back to the inlet side of the compressor (24) exclusively via the collector (30). Thermosystem (10) according to one of the Claims 1 until 4 , characterized in that the climate heat exchanger (26) and the heat exchanger (16) are connected to each other within the climate circuit (14) via an unbranched connecting line (36). Thermosystem (10) according to Claim 5 , characterized in that a controllable second expansion valve (38) is provided in the connecting line (36). Thermosystem (10) according to Claim 6 , characterized in that the second expansion valve (38) is controllable depending on a control position of the first expansion valve (34). Thermosystem (10) according to one of the Claims 1 until 7 , characterized in that the temperature control circuit (12) has a heater (22) for heating a temperature control medium for the motor vehicle battery (18). Thermosystem (10) according to one of the Claims 1 until 8 , characterized in that the climate heat exchanger (26) is designed as a heating register of a climate heat pump for tempering air supplied into the passenger compartment. Method for operating a thermal system (10) according to one of the Claims 1 until 9 , in which a mass flow directed through the heat exchanger (16) in the climate circuit (14) is regulated depending on a heating requirement of the temperature control circuit (12).