Method for preconditioning a hybrid or electric vehicle having a heat pump device

Abstract

The invention relates to a method for pre-conditioning an electrically operated motor vehicle by heating via a thermal management system having a control unit and a heat pump device (1), in which an electric drive train (17) is operated at low efficiency during parking in order to generate waste heat, in that the electric machine is operated at a current vector that is not suitable for operation, and in that the electric drive train (17) is operated at a current vector that is not suitable for operation. The converter is operated at an increased switching frequency of the switch, and the waste heat reaches the high-pressure side (14) of the heat pump device (1) via the coolant. And a separation unit is arranged between the permanent magnet motor and the driving shaft.

Description

TECHNICAL FIELD

[0001] The present invention relates to a method for pre-conditioning an electrically operated motor vehicle by heating via a thermal management system, the thermal management system having a controller and a heat pump device, wherein the electric drive train is inefficiently operated to generate waste heat when parked in such a way that the electric machine is operated with a current vector that is not suitable for operation and the inverter is operated with an increased switching frequency of the switches of the inverter. BACKGROUND

[0002] The thermal system of an electrically operated vehicle is commonly composed of a heat pump system. However, at subzero temperatures, the ambient temperature is no longer sufficient to evaporate the coolant in the air conditioning circuit. An external heat source such as an electric heater is therefore necessary in order to heat the system in the stationary state as well as during driving.

[0003] An exemplary heat pump device for a hybrid vehicle or an electric vehicle is known from WO 2022 258 311 Al, which comprises a refrigerant circuit having a flow path for a refrigerant, a compressor, a high-pressure refrigerant heat exchanger integrated into a high-temperature latent heat store, an expansion element, and a low-pressure refrigerant heat exchanger integrated into a low-temperature latent heat store.

[0004] Methods for targeted heating of electric vehicles are also known. Thus, in electric vehicles, one or more dedicated PTC heaters (PTC, positive temperature coefficient) are usually installed in the electric vehicle. The PTC heaters are usually fitted directly in the HVAC box (Heating, Ventilation and Air Conditioning) for air conditioning of the interior space of the electric vehicle behind the thermal water exchanger of the electric vehicle, for example close to the air outlet. The PTC heaters immediately heat the cold air flowing into the vehicle interior at cold start and are usually automatically turned off after the desired temperature value has been reached. PTC heaters are usually used in order to increase the temperature in the passenger compartment, to heat the traction battery, to heat the water-glycol cooling circuit, or in order to heat the power conditioning of the electric vehicle.

[0005] However, this has the disadvantage that additional high-power (approx. 7-9 kW) components are required in the vehicle for this purpose alone. This increases the cost and the overall weight of the vehicle.

[0006] DE 10 2017 223 114 A1 shows the use of a purposefully heated power inverter and / or electric motor of an electric vehicle instead of a PTC heater, wherein the power inverter and / or electric motor here for example generate the loss power that would otherwise be generated by the PTC heater. Of course, the power inverter and electric motor are already present in the electric vehicle anyway and do not have to be installed in the electric vehicle independently like the PTC heater. It is proposed to increase the switching frequency of the transistors that are switched during discontinuous pulse width modulation compared to the normal switching frequency of the transistors in at least one inverter branch.

[0007] DE 10 2013 017 464 A1 shows a temperature regulation system for a vehicle, wherein there is at least one thermal store as a latent heat store with different operating points, and a heating system is used for regulation.

[0008] EP 3 192 167 B1 describes a method for air conditioning of an interior space of a vehicle.

[0009] The method can have the step of operating the electric drive in such a way that the drive control device operates the electric machine such that a rotating field is generated in the electric machine without the shaft of the electric machine rotating. The frequency of the rotating field can be so high that it does not cause rotation of the shaft of the electric machine because too low a torque is generated. The step is suitable for pre-conditioning of the interior space of a motor vehicle and for when the motor vehicle is parked as a result of traffic. SUMMARY

[0010] The object is achieved by a method for pre-conditioning an electrically operated motor vehicle by heating via a thermal management system, which has a controller and a heat pump device, wherein the electric drive train is inefficiently operated when parked to generate waste heat in such a way that the electric machine is operated with a current vector that is not suitable for operation and the inverter is operated with an increased switching frequency of the switches of the inverter and the waste heat reaches the high-pressure side of the heat pump device via a coolant.

[0011] The object is achieved by a method for pre-conditioning an electrically operated motor vehicle by heating via a thermal management system, which has a controller and a heat pump device, wherein the electric drive train is inefficiently operated when parked to generate waste heat in such a way that the electric machine is operated with a current vector that is not suitable for operation and the inverter is operated with an increased switching frequency of the switches of the inverter and the waste heat reaches the high-pressure side of the heat pump device via a coolant.

[0012] The system regulation via the as low as possible inefficient operation of the electric machine and the inverter eliminates the necessity of an external heating element. By this, sufficient heat can be generated by the vehicle without further additional components in the sense of a park heating. By the method the waste heat of the electric machine and its inverter can be used in a heat exchanger.

[0013] The pre-conditioning allows an increase in the net range in winter and, more importantly, an increase in comfort.

[0014] The preheated vehicle is not only comfortable for the human user, but also minimizes battery aging by pre-conditioning.

[0015] If necessary, the electric drive train comprises a decoupling unit between the permanent magnet motor and the drive shaft of the drive train. Thereby it is also possible to run the permanent magnet motor inefficiently.

[0016] It is advantageous here when using an asynchronous motor or a permanently magnetized motor running decoupled that the current vector for the running is turned slowly with a frequency below 1 Hz, because then a uniform distribution of the waste heat in the entire stator is achieved.

[0017] The running at small frequencies prevents the occurrence of noise and vibrations and minimizes wear.

[0018] The pre-conditioning is activated by the controller by the driver approaching the vehicle with the key to a predefined distance.

[0019] Before activating the pre-conditioning, the controller first queries the state of charge of the vehicle.

[0020] Method for pre-conditioning according to claim 1, wherein the pre-conditioning is carried out when the vehicle is parked. BRIEF DESCRIPTION OF DRAWINGS

[0021] Figure 1 Schematic diagram showing a heat pump device coupled with the heating and cooling circuit of a thermal management system of a vehicle. DETAILED DESCRIPTION

[0022] Figure 1 Schematic diagram showing a heat pump device 1 integrated into a thermal management system of an electric vehicle, wherein the high-pressure refrigerant heat exchanger via the high-temperature latent heat store and the high-temperature coolant heat exchanger, as well as the low-pressure refrigerant heat exchanger via the low-temperature latent heat store and the low-temperature coolant heat exchanger, can be selectively coupled with the cooling circuit or the heating circuit of the vehicle depending on the operating mode.

[0023] The high-pressure side 14 of the heat pump device 1 provides here hot coolant, and the low-pressure side 15 of the heat pump device 1 provides cold coolant.

[0024] The following components and assemblies are to be thermally conditioned on the vehicle side:

[0025] The electric drive train 17 (motor, power electronics, charger and depending on the application also a transmission) generates waste heat in operation, which must be dissipated by the thermal management system or can be used for pre-conditioning.

[0026] The battery 18 generates waste heat in operation and during charging, which must likewise be compensated by appropriate cooling. But the battery can also be heated by the thermal management system, for example under winter cold-start conditions.

[0027] The passenger compartment 23 is supplied with hot or cold air via a so-called "HVAC box," which is blown into the interior of the passenger compartment through outflow nozzles. The required cooling or heating power is achieved via a heat exchanger 20, which is circulated with hot or cold coolant as needed.

[0028] The radiator 21 in the front structure of the vehicle is through which air flows and exhausts excess heat from the thermal management system into the environment.

[0029] Two pumps, 22a and 22b, ensure the necessary mass flow of coolant for operation.

[0030] An additional air-side electric auxiliary heater 19 can be installed within the "HVAC box" and used during the dehumidification operation of the air conditioning unit to reheat the air previously cooled in the heat exchanger 20 (to achieve condensation of air moisture) to the desired inflow temperature before entering the passenger compartment 23. Furthermore, the electric auxiliary heater 19 provides a "backup" solution for situations where sufficient heating power cannot be provided by the heat pump unit 1 in winter, or where particularly rapid preheating of the passenger compartment 23 is desired.

[0031] In principle, the electric powertrain 17 serves as a parking heater, in which the surrounding coolant is heated by waste heat from the converter and electric motor installed in the vehicle. The heat generated is used to evaporate the coolant in the heat pump unit 1. Here, pre-regulation can be activated both when stationary and during driving, i.e., during regenerative braking, coasting, inertial driving, forward movement, and reversing. Here, the additional waste heat generated during driving is achieved through existing technology by selecting the least efficient operating point not only at the converter but also at the motor.

[0032] For pre-adjustment in a static state, the following methods are proposed based on the type of motor.

[0033] If an asynchronous motor or a separately excited synchronous motor is used, permanent magnets are not installed.

[0034] Due to the lack of permanent magnet flux, a slowly rotating current vector can be set with reference to the stator's α-β coordinate system. This slow rotation occurs at approximately 0.5 Hz.

[0035] Because of the very low frequency of the stator current, almost no torque is generated; however, the load is evenly distributed across all phases of the motor.

[0036] Additionally, maximizing converter losses can be achieved by increasing the switching frequency.

[0037] If the electric machine is a machine with permanent magnets, then when the electric powertrain 17 comprises a decoupling unit between the electric machine and the powertrain, only the rotating current vector can be used. If the slowly rotating current vector is applied again, the rotor of the permanent magnet machine rotates slowly under load independently of the transmission with the current vector.

[0038] If there is no decoupling unit, heating with a stationary current vector takes place, which in the ideal case generates no torque and in the worst case a minimal torque. Because the load is not distributed uniformly in the phases in the stationary current vector, the maximum heating power is reduced accordingly. The maximization of the inverter losses can again be achieved by increasing the switching frequency of the switches in the inverter.

[0039] An alternative embodiment of the application consists in connecting the star point of the permanent magnet machine via a switching element to the HVDC line. Thereby it is possible to distribute the electrical load uniformly on all phases independently of the mechanical construction of the powertrain.

[0040] The waste heat generated via the electric powertrain 17 is fed into the high-pressure side of the heat pump device 1 and used for heating the vehicle.

[0041] In today's vehicles the air conditioning can be operated via a wireless connection and a mobile phone. Here, the possibility exists to switch on the air conditioning temporarily or to define a specified departure time for the air conditioning.

[0042] The method for the pre-conditioning of the interior temperature of a vehicle according to the application is additionally or alternatively started as soon as a person approaches his vehicle. The approach of the driver with his key to the vehicle is detectable just in time with the key on the mobile phone with the open positioning via GPS or with the activated wireless connection via Bluetooth or near field identification.

[0043] In a defined distance from the vehicle, the controller of the thermal management system recognizes the request of the driver for the pre-conditioning and starts the electric machine and the inverter with the pre-conditioning condition. Likewise the pump of the thermal management system and the blower motor are activated by the controller.

[0044] The usual wireless key and the corresponding sensor device allow the pre-conditioning in a corresponding manner. A manual setting via an app is then no longer necessary. Individually, the distance from which the pre-conditioning is started can be set once via a program or in the vehicle itself.

[0045] Before the pre-conditioning, the controller queries whether the state of charge of the vehicle is suitable for allowing the pre-conditioning.

[0046] In one embodiment, the method of the pre-conditioning during the standstill is combined with the low-efficiency operation of the electric machine and its inverter during driving.

[0047] This can be the case, firstly, if the preconditioning mode has not yet ended before departure. It can also be the case, for example, during a coasting run of the vehicle, that waste heat is generated in the electric machine by inefficient operation (elongated current vector and / or increased PWM switching frequency).

[0048] In principle, preconditioning is also usable during driving, i.e. also during regenerative braking, coasting, inertia driving, forward travel and reversing.

Claims

1. Method for pre-conditioning of an electrically operated motor vehicle by heating via a thermal management system, which has a controller and a heat pump device (1), wherein an electric drive train (17) is inefficiently operated for generating waste heat at standstill in such a way that the electric machine is operated with a current vector which is not suitable for operation and the waste heat reaches the high-pressure side (14) of the heat pump device (1) via a coolant, characterized in that the inverter is operated with an increased switching frequency of the switches and the current vector for operation is slowly rotated with a frequency below 1 Hz, wherein an asynchronous electric machine or a permanently excited electric machine which is operated separately is used, wherein the electric drive train (17) comprises a separate unit between the permanently excited electric machine and the drive shaft of the drive train.

2. Method for pre-conditioning according to claim 1, wherein the pre-conditioning is activated by the controller by the driver approaching the vehicle with a key to a predefined distance.

3. Method for pre-conditioning according to claim 1, wherein the controller first queries the state of charge of the vehicle before the pre-conditioning is activated.

4. Method for pre-conditioning according to claim 1, wherein the pre-conditioning is carried out at standstill of the vehicle and during driving, i.e. during regenerative braking, coasting, inertia driving, forward and reverse driving. ​

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