Vehicle heat management system and procedures for operating it

Abstract

Vehicle heat management system with: a heat pump arrangement (2) comprising a compressor (12), a cabin condenser (14) and a cooler (18) for collecting heat energy from a battery coolant circuit (4) and a powertrain coolant circuit (6), wherein the cooler (18) has an inlet connected to an upstream first electric expansion valve (26); the battery coolant circuit (4), which thermally couples a battery (58) and an electric battery heater (62); the powertrain coolant circuit (6) which is in thermal connection with at least one powertrain component (48), a control system configured to operate based on at least one of the following factors: ambient temperature, cabin temperature, and desired start time: to control the heat pump arrangement (2) such that it operates in one of the modes, efficient mode, heat enhancement mode or a combination of the efficient mode and the heat enhancement mode, wherein the compressor (12) generates more heat in the heat enhancement mode than in the efficient mode; and to control the heat pump arrangement (2) so that it operates in heat enhancement mode with or without activation of the electric battery heater (62), and to ensure that when the vehicle is started at low ambient temperature, the battery coolant circuit (4) and / or the powertrain coolant circuit (6) is in thermal contact with the radiator (18) for a limited period of time, wherein in the heat enhancement mode a portion of a compressed refrigerant gas is routed from a compressor outlet via a compressor bypass (70) with a third electric expansion valve (72) bypassing the cabin condenser (14) directly to the inlet of the cooler (18).

Description

[0001] The invention relates to a vehicle heat management system according to claim 1 and a method for operating the same according to claim 5.

[0002] The complexity of thermal management systems in the automotive industry (PHEV & BEV) is increasing dramatically, as is the demand for cooling and heating. In conventional cars, waste heat from the electric motor is used to warm the passenger cabin. In battery electric vehicles (BEVs), a high-voltage, air-side heater is typically used to warm the passenger cabin, leading to packaging issues within the heating, ventilation, and air conditioning (HVAC) system and increasing costs.

[0003] To reduce the overall system costs and avoid packaging issues, an existing compressor is used as a heat source to heat the passenger cabin or battery, as disclosed in US 2019 / 0070924A1. However, this approach results in delays in cabin heating for the following reasons: a) The thermal mass of other components (such as compressor, pressure pipe, accumulator / collector / heat exchanger, etc.) must be heated along with the heating of the cabin air; b) The heating output depends on the power consumption of the compressor, which is a function of the suction density, the pressure ratio (ratio of compressor outlet to inlet pressure) and the compressor speed; c) When the compressor is started from the equilibrium point at a low ambient temperature, the suction pressure / density is usually low and the pressure ratio is lower, therefore the heating capacity of the compressor is very limited; d) Heat loss to the environment is greater if the compressor and pressure pipe are not thermally insulated.

[0004] From US 2017 / 0 106 725 A1, DE 11 2015 000 552 T5, DE 10 2016 210 130 A1 and DE 10 2018 127 539 A1, vehicle heat management systems for motor vehicles with electric or hybrid drive are known, which use a heat pump arrangement and various heat exchangers to provide waste heat from different sources for heating the vehicle cabin.

[0005] Document DE 10 2020 100 428 A1 relates to an air conditioning and battery cooling arrangement with high cooling capacity and passive battery cooling, and to a method for operating an air conditioning and battery cooling arrangement in which there is no direct connection between the compressor outlet and the cooler inlet.

[0006] Even at very low ambient temperatures such as -20°C, users demand rapid thermal comfort in the passenger cabin. Starting the systems according to current best practices at such low ambient conditions, directly with a high / target HVAC airflow, leads to a delay in warm-up and can also result in very limited / insufficient heat generation by the compressor.

[0007] Accordingly, it is an object of the present invention to provide a vehicle heat management system for BEVs that enables faster cabin heating. Furthermore, it is an object of the invention to provide a method for operating the vehicle heat management system in order to accelerate cabin heating.

[0008] These tasks are solved by a vehicle heat management system according to claim 1 and by an operating method according to claim 5. Further developments according to the invention are the subject of the dependent claims.

[0009] By coupling thermal energy from the battery heater into the battery coolant circuit, heat in powertrain components or the battery (thermal mass) and / or ambient air is still present in the heat pump assembly for a very short duration of 1 to 5 minutes, in combination with the heat boost mode. In heat boost mode, a portion of the compressed coolant gas at the compressor outlet is routed to the inlet of the radiator / chiller via a thermal expansion valve to increase the compressor's suction pressure. This, in turn, causes more waste heat to be generated by the compressor, which is then used to heat the vehicle cabin.At the same time, low-temperature heat from the battery coolant circuit - with battery heating activated or not activated - and / or low-temperature heat from the powertrain coolant circuit is coupled into the radiator to further increase the suction pressure of the compressor and thus shorten the warm-up time of the vehicle cabin.

[0010] This involves pre-conditioning the vehicle cabin before starting the journey by using criteria such as ambient temperature, required cabin temperature and available time for pre-conditioning the cabin, in order to enable the most energy-efficient mode to increase the warm-up rate of the vehicle cabin.

[0011] The heating output depends on the compressor's power consumption, which is a function of the suction density, the pressure ratio (ratio of compressor outlet to inlet pressure), and the compressor speed. The compressor outlet pressure is a function of the cabin condenser air outlet temperature; therefore, to achieve the desired cabin heating output, the airflow through the cabin condenser and the air outlet temperature should be controlled. Thus, in a preferred embodiment, the airflow through the cabin condenser and the cabin condenser air outlet temperature are controlled to increase the compressor intake and outlet pressures during heat amplification mode, thereby increasing the compressor's heat generation and thus the cabin's heating rate.

[0012] In a preferred embodiment, the electric battery heater is positioned upstream or downstream of the battery with a coolant bypass arrangement for the battery, so that the battery is not in thermal contact with the electric battery heater. This allows the full heating capacity of the electric battery heater to be quickly coupled to the radiator, resulting in increased compressor suction pressure and, consequently, a faster cabin warm-up time.

[0013] Preferably, the battery bypass is only activated for a limited period of time until a desired compressor inlet pressure is reached during the heat boost operating mode.

[0014] Operating the compressor with overshoot of the compressor speed for a short duration, a few seconds, leads to a faster increase in the suction pressure / suction density at the compressor and thus to a faster increase in compressor power and cabin heating power.

[0015] As mentioned previously, the heating output depends on the compressor's power consumption, which is a function of the suction density, pressure ratio, and compressor speed. The compressor discharge pressure is a function of the cabin condenser air outlet temperature; therefore, to achieve the desired cabin heating output, the airflow through the cabin condenser and the air outlet temperature should be controlled. In some operating conditions, it is preferable to use an air mixing damper to achieve the desired HVAC air outlet temperatures.

[0016] According to another preferred embodiment, the control system causes the heat pump arrangement to operate in a heat pump mode, with the compressor operating in efficient mode, in heat enhancement mode, or in a combination of both. These different operating modes allow the cabin heating to be optimized with respect to the ambient temperature, the target cabin temperature, and available waste heat sources.

[0017] Furthermore, the present disclosure relates to a method for operating the vehicle heat management system to warm the vehicle cabin by selectively activating the heat pump mode, the heat enhancement mode or a combination of heat pump mode and heat enhancement mode based on the ambient temperature, cabin temperature and time available until the desired start of driving the vehicle, wherein the heat pump arrangement is operated in a heat pump mode and the compressor is operated in the efficient mode or in the heat enhancement mode or in a combination of heat pump mode and heat enhancement mode.

[0018] Preferably, the cabin heating process is started before the vehicle begins driving, so that the cabin is thermally pre-conditioned. This way, when the driver enters the cabin, it is already at a comfortable temperature.

[0019] The present invention achieves a faster cabin heating rate and comparable heating performance to a heat pump system with air-side high-voltage heating. Since no air heater is required, costs are reduced. Likewise, a slimmer HVAC system design is possible because the high-voltage air heater is eliminated.

[0020] Preferred embodiments of the invention are described below with reference to the drawing.

[0021] The Fig. 1, Fig. 2 to Fig. 3 represent a first embodiment of the present invention, wherein Fig. 1 represents a basic design as a starting point for the present invention;

[0022] Fig. 4 is a comparison of the heating of the cabin from the prior art and the present invention;

[0023] The Fig. 5, Fig. 6 to Fig. Figure 7 represents a second embodiment, wherein Fig. 5 represents a basic design as a starting point for the present invention;

[0024] Fig. 8 and Fig. Figure 9 represents the effect of adjusting the airflow in the HVAC 16 to the suction pressure of the compressor 12;

[0025] Fig. 10 and Fig. 11 represent the effect of using an air mixing flap 90, which is provided in the HVAC 16 between the cabin evaporator 20 and the cabin condenser 14;

[0026] Fig. 12 and Fig. Figure 13 presents two different scenarios for pre-conditioning the vehicle cabin before the vehicle starts driving.

[0027] The Fig. 1, Fig. 2 to Fig. Figure 3 illustrates the various operating modes according to a first embodiment of a battery coolant circuit 4, a powertrain coolant circuit 6, a coolant circulation arrangement, and a control system. The heat pump arrangement 2 includes a compressor 12, a cabin condenser 14 arranged in a heating, ventilation, and air conditioning system 16 for a vehicle cabin, a radiator 18 for collecting heat energy from the battery coolant circuit 4 and the powertrain coolant circuit, a cabin evaporator 20 arranged in the HVAC 16, and an external heat exchanger 22, which operates as an evaporator in the heat pump arrangement 2. The HVAC 16 further includes a cabin blower 24 for transporting the heated air into the vehicle cabin and for controlling the temperature of the cabin condenser 14 and thus the outlet pressure of the compressor 12.A first electric expansion valve 26 is arranged at the inlet of the cooler 18, and a second electric expansion valve 28 is arranged at the inlet of the cabin evaporator 20. A first pressure temperature sensor 30 is arranged at the outlet of the cooler 18. A second pressure temperature sensor 34 is arranged at the outlet of the compressor 12. A third pressure temperature sensor 34, followed by a check valve 35, is provided at the outlet of the cabin evaporator 20. A manifold 36, a cabin condenser 14, and a compressor 12 are connected to the cooler 18, the cabin evaporator 20, and an external heat exchanger 22—all three of which operate as evaporators—as is known from compressor heat pumps.The manifold assembly 36 contains a plurality of valves and a coolant reservoir 38. It stores liquid coolant from the cabin condenser 14 and supplies the appropriate quantity of liquid coolant to the radiator 18, the cabin evaporator 20, and / or the external heat exchanger 22, depending on whether the heat pump assembly 2 is in cooling / air conditioning mode or heating mode. A fourth pressure / temperature sensor 40 is provided at the outlet of the external heat exchanger 22. The outlet of the external heat exchanger 22 can be connected to the inlet of the compressor 12 via a first shut-off valve 42.

[0028] The powertrain coolant circuit 6 connects a powertrain coolant pump 46 with at least one powertrain component 48 to a low-temperature cooler (LTR) 52 via a powertrain coolant 4-way valve 50. The LTR 52 is located adjacent to the outer heat exchanger 22. A powertrain coolant bypass 54 connects the inlet of the powertrain coolant pump 46 to the powertrain coolant 4-way valve 50. The powertrain coolant circuit 6 can be thermally connected to the cooler 18 via the powertrain coolant 4-way valve 50.

[0029] The battery coolant circuit 4 connects a battery coolant pump 56 to the battery 58 via a battery coolant 4-way valve 60 to the LTR 42. An electric battery heater 62 is provided between the battery 58 and the battery coolant pump 56. The battery coolant bypass 64 connects the inlet of the battery coolant pump 56 to the battery coolant 4-way valve 60. The battery coolant circuit 4 can be thermally connected to the radiator 18 via the battery coolant 4-way valve 60.

[0030] In the Fig. In the heat pump mode of the heat pump arrangement 2 shown in Figure 1, low-temperature heat coupled into the external heat exchanger 22 and the radiator 18 is radiated as high-temperature heat into the HVAC system 16 via the cabin condenser 14. It is evident that at low ambient temperatures, e.g., -20°C, there is a delay before the vehicle cabin begins to warm up, until waste heat from the compressor 12 and heat from the electric battery heater 62 are available.

[0031] To shorten this delay in heating the cabin, a heat amplification mode is applied, as described in Fig. 2 shown. In addition to the ones in Fig. In the components shown in Figure 1, a compressor bypass 70 connects the outlet of the compressor 12 to a 3-way block connection 74 at the inlet of the cooler 18. A second shut-off valve 76, with a smaller opening than the first shut-off valve 42, is provided in parallel with the first shut-off valve 42. In heat amplification mode, the compressor bypass 70 directs a portion of the hot compressed refrigerant gas back to the cooler 18 to increase the suction pressure of the compressor 12. This, in turn, causes more waste heat from the compressor to be used to heat the vehicle cabin. Simultaneously, low-temperature heat from the battery coolant circuit 4 – with or without the electric battery heater 62 activated – and / or low-temperature heat from the powertrain coolant circuit 6 is coupled into the cooler 18 to further increase the suction pressure of the compressor 12 and thus shorten the vehicle cabin heating time.

[0032] The heat pump mode of Fig. 1 and the heat amplification mode of Fig. 2 can also be combined, as shown in Fig. Figure 3 is shown. In this combination mode, both the external heat exchanger 22 and the cooler 18 are operated as evaporators in the heat pump arrangement 2.

[0033] The effect of this combination mode on the warm-up rate of the vehicle cabin at low ambient temperatures of -20°C is shown in Fig. Figure 4 shows the heating energy / power in kW over time in seconds of the present invention – Graph 80 – compared with a reference system – Graph 82 – without applying any measures of the present invention. For both in Fig. The following conditions apply to the 4 heat management systems shown: - Target heating output of 6.5 kW - T air_in = -20°C - Airflow: 270 kg / h - Heat amplification mode: p d / p s= 25 bar / 5 bar Compressor speed limit: 8600 rpm

[0034] The in the Fig. 5, Fig. 6 to Fig. The second embodiment of the invention, as illustrated in Figure 7, differs from the first embodiment according to the following: Fig. 1, Fig. 2 to Fig. 3 simply by the arrangement of a battery coolant bypass 64. In the second embodiment, the battery coolant bypass 64 connects the outlet of the electric battery heater 62 to the outlet of the battery coolant of the battery 58 instead of the inlet of the battery coolant pump 56 to the outlet of the battery coolant of the battery 58. This allows the full heating capacity of the electric battery heater 62 to be immediately coupled to the radiator 18, resulting in an immediate increase in the suction pressure of the compressor 12 and, furthermore, an increased heating rate of the cabin. This battery coolant bypass 64 is only activated for a limited period until a desired compressor inlet pressure is reached during the heat boost operating mode.

[0035] The Fig. 8 and Fig. Section 9 represents a measure to further increase the vehicle cabin's warm-up rate by optimizing the HVAC airflow generated by the cabin blower 24. Conventionally, the HVAC airflow is ramped up quickly to achieve the desired cabin airflow target. Using the same approach for the heat amplification mode results in a delay in warm-up and can also lead to very limited / insufficient heat generation by the compressor. The heating output depends on the compressor's power consumption, which is a function of the suction density, the pressure ratio (ratio of compressor outlet to inlet pressure), and the compressor speed. The compressor outlet pressure is a function of the cabin condenser air outlet temperature; therefore, to achieve the desired cabin heating output, the cabin condenser airflow and the air outlet temperature should be controlled.By controlling the cabin blower 24, the airflow through the cabin condenser 14 and the cabin condenser air outlet temperature can be adjusted to the suction pressure of the compressor 12, as shown in . Fig. 8 shown. This gradually increases the compressor intake pressure and the compressor outlet pressure during the heat boost mode, resulting in increased heat generation by the compressor 12 - as shown in Fig. 9 shown - thus increasing the warm-up rate of the cabin.

[0036] Operating compressor 12 with overshoot of the compressor speed for a short duration, a few seconds, during the heat amplification mode leads to a faster increase in the suction pressure / suction density at compressor 12 and thus to a faster increase in compressor power and cabin heating power.

[0037] As mentioned previously, the heating output depends on the compressor's power consumption, which is a function of the suction density, pressure ratio, and compressor speed. The compressor outlet pressure is a function of the cabin condenser air outlet temperature; therefore, to achieve the desired cabin heating output, the airflow through the cabin condenser and the air outlet temperature should be controlled. Under certain operating conditions, it is advantageous to use a 90° air mixing damper to achieve the desired HVAC air outlet temperatures. As described in the Fig. 10 and Fig. Figure 11 shows different cabin temperatures or HVAC air outlet temperatures T set generated by using the air mixing flap provided between the cabin evaporator 20 and the cabin condenser 14. In Fig. 10 T set = 75°C and in Fig. 11 T set= 50°C. In both cases, the ambient temperature T is air_in -20°C. Fig. 10 The airflow into the HVAC system is 16,285 kg / h and T set The temperature is 75°C, the air mixing flap 90 is closed, and the airflow from the HVAC 16 into the vehicle cabin is 285 kg / h. Fig. 11. The airflow into the HVAC system is 16.385 kg / h and T set 50°C, the air mixing flap 90 is open to a certain degree and the airflow from the HVAC 16 into the vehicle cabin is 385 kg / h.

[0038] The heat generation of compressor 12 depends on the power consumption of the compressor, which is a function of the suction density, i.e., pressure ratio (ratio of compressor outlet to inlet pressure, p). d / p s ) and compressor speed. The compressor outlet pressure p dis a function of the cabin condenser air outlet temperature; therefore, in order to achieve a desired heating output for the cabin, the airflow through the cabin condenser 14 and the air outlet temperature should be adjusted to a saturation temperature of the desired compressor outlet pressure p. d The air mixing flap 90 is used to achieve a desired cabin condenser air outlet temperature and a desired HVAC air outlet temperature into the cabin.

[0039] Fig. 12 and Fig. Figure 13 presents two different scenarios for pre-conditioning the vehicle cabin before the vehicle starts moving. Pre-conditioning means that the cabin begins to warm up before the vehicle starts moving. Pre-conditioning the vehicle cabin using criteria such as ambient temperature, required cabin temperature, and available pre-conditioning time is used to select the most energy-efficient operating mode. The use of the ambient heat pump mode (as in Fig. (1 shown) for heating the passenger cabin is more efficient, but results in a very slow cabin warm-up, and the required heating output cannot be achieved. Using the heat amplification mode (by using a compressor as a heat source, as shown in Fig. Mode 2 (shown) for heating the passenger cabin is less efficient, but results in a relatively faster warm-up of the cabin, and the required heating output can be achieved. Therefore, a combination of these modes is used to pre-condition the vehicle based on the available time.

[0040] In both scenarios, which are in the Fig. 12 and Fig. Figure 13 assumes an ambient temperature of -20°C and a desired cabin temperature of 22°C. The driver enters the desired cabin temperature and the departure time via an app on a smartphone. Fig. In scenario A, shown in Figure 12, the journey begins in 10 minutes. This is quite short, and to reach the desired cabin temperature within these 10 minutes, the control system selects the heat boost mode to warm the cabin for 10 minutes. Fig.In scenario B, as depicted in Figure 13, the journey begins in 30 minutes. The control system selects a waiting period of 10 minutes, then activates heat pump mode for 15 minutes, and finally heat boost mode for 5 minutes to achieve the desired cabin temperature of 22°C precisely at the entered departure time. Depending on the available time until departure, the ambient temperature, and the desired cabin temperature, the control system selects the most energy-efficient heating mode(s). Reference sign 2 Heat pump arrangement 4 Battery coolant circuit 6 Powertrain coolant circuit 12 Compressor 14 Cabin condenser 16 Heating, ventilation and air conditioning (HVAC) system 18 coolers or chillers 20 cabin evaporators 22 Outer heat exchanger 24 cabin blowers 26 First electric expansion valve 28 Second electric expansion valve 30 First pressure temperature sensor 34 Second pressure temperature sensor 35 Check valve 36 Collective order 38 Coolant reservoirs 40 Fourth pressure temperature sensor 42 First shut-off valve 46 Drivetrain coolant pump 48 powertrain component(s) 50 Powertrain Coolant 4-Way Valve 52 LTR - Low-temperature cooler 54 Powertrain coolant bypass 56 Battery coolant pump 58 Battery 60 Battery Coolant 4-Way Valve 62 Electric battery heater 64 Battery coolant bypass 70 Compressor bypass 72 Third electric expansion valve 74 3-way block connection 76 Second shut-off valve 80 Heating power over time, present invention, combination mode 82 Heating power over time, reference mode, without invention 90 Air mixing flap 100 smartphones p s Suction pressure of 12 p d Outlet pressure of 12 p d / p s Pressure ratio of 12

Claims

Vehicle heat management system comprising: a heat pump arrangement (2) comprising a compressor (12), a cabin condenser (14) and a radiator (18) for collecting heat energy from a battery coolant circuit (4) and a powertrain coolant circuit (6), wherein the radiator (18) has an inlet connected to an upstream first electric expansion valve (26); the battery coolant circuit (4) thermally coupling a battery (58) and an electric battery heater (62);the powertrain coolant circuit (6) which is in thermal connection with at least one powertrain component (48), a control system which is configured to control the heat pump arrangement (2) based on at least one of the factors, an ambient temperature, a cabin temperature and a desired driving start time, such that it operates in one of the modes, efficient mode, heat enhancement mode or a combination of the efficient mode and the heat enhancement mode, wherein the compressor (12) generates more heat in the heat enhancement mode than in the efficient mode;and to control the heat pump arrangement (2) so that it operates in heat enhancement mode with or without activation of the electric battery heater (62), and to cause the battery coolant circuit (4) and / or the powertrain coolant circuit (6) to be in thermal contact with the radiator (18) for a limited period of time when the vehicle is started at low ambient temperatures, wherein in heat enhancement mode a portion of a compressed refrigerant gas is routed from a compressor outlet via a compressor bypass (70) with a third electric expansion valve (72) directly to the inlet of the radiator (18), bypassing the cabin condenser (14). Vehicle heat management system according to claim 1, wherein the electric battery heater (62) is positioned after or before the battery (58) with a battery coolant bypass (64) so ​​that the battery (58) is not in thermal contact with the electric battery heater (62). Vehicle heat management system according to claim 2, wherein the battery coolant bypass (64) is activated for a limited period of time until a desired compressor inlet pressure is reached during the heat enhancement mode. Vehicle heat management system according to one of the preceding claims, wherein the heat pump arrangement (2) further comprises a cabin evaporator (20) and an air mixing flap (90) arranged between the cabin evaporator (20) and the cabin condenser (14) for directing ambient air into the vehicle cabin, wherein the control system is configured to activate the air mixing flap (90) to control the air outlet temperature of the cabin condenser (14) to a saturation temperature of the desired compressor outlet pressure. Method for operating the vehicle heat management system according to one of claims 1 to 4, for heating the vehicle cabin by selectively activating the heat pump mode, the heat enhancement mode or a combination of heat pump mode and heat enhancement mode based on the ambient temperature, cabin temperature and time available until the desired start of driving the vehicle, wherein the heat pump arrangement (2) is operated in a heat pump mode and the compressor (12) is operated in the efficient mode or in the heat enhancement mode or in a combination of heat pump mode and heat enhancement mode. Method according to claim 5, wherein the heat pump arrangement (2) is operated in the heat enhancement mode before the vehicle starts driving. Method according to claim 5 or 6, wherein the airflow through the cabin condenser (14) and the cabin condenser air outlet temperature are adjusted to the suction pressure of the compressor (12) by controlling the cabin blower (24), thereby gradually increasing the compressor intake pressure and compressor outlet pressure during the heat amplification mode, resulting in increased heat generation by the compressor (12). Method according to one of claims 5 to 7, wherein the control system causes the compressor speed to be increased for a limited period during the heat enhancement mode at the beginning of the cabin warm-up. Method according to one of claims 5 to 8, wherein the warming of the cabin is started before the vehicle begins to drive.

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