Method for heating a motor vehicle

Abstract

The invention relates to a method for heating a motor vehicle having a three-phase electric motor (1) as a traction motor, wherein a pulse-controlled inverter (3) is provided for supplying power to the electric motor (1), wherein a coolant circuit (12) is provided for coolant cooling of the electric motor (1) and the pulse-controlled inverter (3), which conducts heat by means of a coolant to a heat exchanger for heating the passenger compartment and / or to a vehicle battery (13), wherein when the electric motor (1) is stationary, a positive d-current and / or a negative d-current is applied to the d-axis, thereby generating loss heat which is input into the coolant.

Description

Technical Field

[0001] The invention relates to a method for heating a motor vehicle. Background Art

[0002] Motor vehicles with a combustion engine generate waste heat during operation of the combustion engine that is sufficient to heat the passenger compartment and / or the vehicle battery. In motor vehicles with an electric motor as traction motor, this possibility does not exist. However, the waste heat generated by the electric motor and the associated control electronics can likewise be used to heat the passenger compartment and / or the vehicle battery via the coolant circuit. This heat source is therefore not available when the motor vehicle is stationary, since the electric motor correspondingly does not generate any heat in the stationary state. Summary of the invention

[0003] The object of the present invention is to provide a method for heating a motor vehicle with an electric motor as traction motor which allows heating of the passenger compartment and / or the vehicle battery even when the motor vehicle is stationary.

[0004] This object is achieved by the method according to the invention for heating a motor vehicle.

[0005] An embodiment of the invention relates to a method for heating a motor vehicle, the motor vehicle having a three-phase electric motor as a traction motor, wherein a pulse-controlled inverter is provided for supplying power to the electric motor, wherein a coolant circuit is provided for coolant cooling of the electric motor and the pulse-controlled inverter, the coolant circuit conducting heat to a heat exchanger for heating the passenger compartment and / or to a vehicle battery by means of a coolant, wherein when the electric motor is stationary, a positive d-current and / or a negative d-current is applied to the d-axis, thereby generating heat loss, which is input into the coolant. As a result, the electric motor can be energized without generating a torque for driving the motor vehicle (which would drive the motor vehicle). Nevertheless, the energization still causes heat loss to be generated, which is input into the coolant that can be used for heating. Thus, the electric motor provided with a targeted current supply can be used as a heating source, even though the electric motor does not drive the motor vehicle in this operating mode.

[0006] It is also advantageous in an embodiment that the electric motor is supplied with a d current on the d axis and loss heat is generated both in the electric motor and in the pulse inverter, which is utilized as waste heat, wherein the q current on the q axis is equal to zero. Driving is performed only by generating torque based on the q current. Therefore, in the absence of the q current, the d current does not drive the motor vehicle and still generates loss heat. The names "d current" and "q current" are observations in the d / q coordinate system for describing the three-phase electric motor based on the d / q transformation. The d / q transformation is generally used to convert a three-phase parameter such as a U-axis, a V-axis, and a W-axis in a three-phase electric motor (also referred to as a three-phase motor) into a two-axis coordinate system with a d-axis and a q-axis.

[0007] In a further embodiment, it is expedient that by setting the d current no torque is applied to the wheels of the motor vehicle which would drive the motor vehicle, thereby generating power losses inductively without the motor vehicle having to be moved.

[0008] It is also advantageous that the heat loss of the electric motor is generated as power losses in the windings of the electric motor and / or as eddy current losses in the laminated core; and / or the heat loss in the pulse-controlled inverter is generated as forward losses of the power switch and the freewheeling diode and / or as switching losses when the power switch is switched and / or as power losses when the power switch is in operation and / or losses in the intermediate circuit capacitor.

[0009] It is also advantageous if the pulse-controlled inverter has an electronic circuit with a power switch and a freewheeling diode, wherein the current of the power switch and the current of the freewheeling diode are modulated. Thus, the desired d current can be modulated in time to achieve appropriate heating and not damage the electric motor.

[0010] It is also advantageous if the pulse inverter has a high-side power transistor, a low-side power transistor, a low-side diode and a high-side diode, wherein the current of the high-side power transistor and the current of the low-side diode are controlled in a modulated manner and / or wherein the current of the low-side power transistor and the current of the high-side diode are controlled in a modulated manner. By means of this corresponding modulation, heating can be achieved with a defined current supply without causing damage to the electric motor.

[0011] Preferably, the current of the power transistor and the current of the diode are pulse modulated, in particular by a square wave signal with a constant amplitude or a modulated amplitude. This corresponding modulation allows heating to be achieved at a limited current supply without damaging the electric motor. BRIEF DESCRIPTION OF THE DRAWINGS

[0012] The present invention will be described in detail below with reference to the accompanying drawings using exemplary embodiments. In the drawings:

[0013] Figure 1 A schematic diagram showing the connection of an electric motor to a pulse-controlled inverter is shown in order to explain the method according to the invention,

[0014] Figure 2 shows a schematic illustration for operating an electric motor in order to generate lost heat when the electric motor is at a standstill,

[0015] Figure 3 shows a schematic illustration for alternatively operating an electric motor to generate lost heat when the electric motor is at a standstill,

[0016] Figure 4 A schematic diagram for alternatively operating an electric motor to generate lost heat when the electric motor is at a standstill is shown, and

[0017] Figure 5 A schematic illustration is shown for alternatively operating an electric motor in order to generate lost heat when the electric motor is at a standstill. DETAILED DESCRIPTION

[0018] Figure 1 An electric motor 1 is schematically shown as a three-phase electric machine which is supplied with current from a high-voltage vehicle electrical system 2 and a pulse-controlled inverter 3. For this purpose, the three individual phases of the electric motor 1 can be supplied with current I in an individually controllable manner.

[0019] The electric motor 1 has resistance elements which can be inductive or resistive (see reference numerals 4 , 5 ).

[0020] The current of the electric motor 1 with its three phases can be represented in a three-coordinate system, so that the current I U ,I V and I W It is also possible to use a current I d and I q .

[0021] The pulse-controlled inverter 3 has power switch modules 6, which are equipped with a high-side power switch 7, a low-side power switch 8, a high-side diode 9 and a low-side diode 10. The power switches can be designed as MOSFET power switches or (for example) Figure 1 The power switch module 6 is designed as an IGBT power switch 11 . In this case, the diode is integrated into the IGBT power switch 11 . The power switch module 6 can be formed by two IGBT power switches 11 .

[0022] The torque M of the electric motor 1 has a plurality of terms. In one term, the corresponding torque component of M is related to I d *I q is proportional to I, while in the other term the torque component is proportional to I q This means that in I q = 0, no torque M is transmitted. d It may still be different from zero, thus generating heat loss by induction.

[0023] M~A*I d *I q +B*I q

[0024] The factors A and B are proportional to the number of pole pairs p, the flux F of the permanent magnets, and / or the tangent inductance S in the d / q axis, where:

[0025] A=3 / 2*p*(S s，d -S s，q ), and B = 3 / 2*p*F.

[0026] Correspondingly, in I q = 0 utilizes the heating when the motor vehicle is stationary.

[0027] The method according to the invention for heating a motor vehicle having a three-phase electric motor 1 as a traction motor therefore provides the following mode of operation, wherein a pulse-controlled inverter 3 is provided for supplying power to the electric motor 1, wherein a coolant circuit 12 is provided for coolant cooling of the electric motor 1 and the pulse-controlled inverter 3, which conducts heat by means of a coolant to a heat exchanger for heating the passenger compartment and / or to a vehicle battery 13. In this case, the vehicle battery 13 is part of the high-voltage onboard electrical system 2.

[0028] When the electric motor 1 is stationary, a positive d current and / or a negative d current is applied to the d axis, so that heat loss is generated, which is fed into the coolant. The vehicle battery 13 and / or the passenger compartment can then be heated.

[0029] Here, the electric motor 1 is supplied with a d current on the d axis and waste heat is generated both in the electric motor and in the pulse inverter, which is utilized as waste heat, wherein the q current on the q axis is equal to zero. Setting the d current to zero ensures that no torque capable of driving the motor vehicle is applied to the wheels of the motor vehicle.

[0030] The heat loss of the electric motor 1 is generated as power loss of the winding of the electric motor 1 and / or as eddy current loss in the laminations; and / or the heat loss in the pulse inverter 3 is generated as forward loss of the power switches 7, 8 and the freewheeling diodes and / or as switching losses when the power switches 7, 8 are switched and / or as power losses when the power switches 7, 8 are in operation and / or losses in the intermediate circuit capacitor.

[0031] Here, according to Figure 1 The pulse-controlled inverter 3 has an electronic circuit with power switches 7 , 8 and freewheeling diodes 9 , 10 , wherein the currents in the power switches 7 , 8 and the currents in the freewheeling diodes 9 , 10 are modulated.

[0032] In the illustrated embodiment, the pulse inverter 3 has a high-side power transistor 7, a low-side power transistor 8, a high-side diode 9 and a low-side diode 10, wherein the current of the high-side power transistor 7 and the current of the low-side diode 10 are controlled in a modulated manner, and / or wherein the current of the low-side power transistor 8 and the current of the high-side diode 9 are controlled in a modulated manner.

[0033] In this case, the currents of the power transistors 7 , 8 and the currents of the diodes 9 , 10 can be pulse-modulated, in particular using square-wave signals with a constant amplitude or a modulated amplitude.

[0034] Figures 2 to 4 An example of such current modulation is shown.

[0035] exist Figure 2 In the process, the high-side power transistor current and the low-side diode current are alternately modulated into a square wave signal, so that I q =0 and for example I d =644A. Correspondingly, the current I of the U phase, V phase, and W phase are also shown. PH,U ,I PH,V and I PH,W Here, I PH,U is always positive (about 644A), and the current I PH,V and I PH,W is always negative (about -180A and about -450A), so Iq = 0 and I d It is 644A.

[0036] exist Figure 3 In FIG. 1 , the low-side power transistor current and the high-side diode current are alternately modulated into a square wave signal, so that Iq=0 and, for example, Id=-644A. Correspondingly, the current I of phases U, V, and W is also shown. PH,U ,I PH,V and I PH,W Here, I PH,Uis always negative (about -644A), and the current I PH,V and I PH,W is always positive (about 180A and about 450A), so I q =0 and I d It is -644A.

[0037] exist Figure 4 In the embodiment, the low-side power transistor current and the high-side diode current are alternately modulated into a high-frequency square wave signal, which is applied alternately so that the high-side power transistor current and the low-side diode current are alternately modulated into a high-frequency square wave signal, so that I q =0 and I d As a square wave signal, it switches between +400 A and -400 A. Correspondingly, the current I of phases U, V, and W is also shown. PH,U ,I PH,V and I PH,W The current is also implemented as a corresponding square wave signal, resulting in I q =0 and I d Transitions between +400A and -400A.

[0038] exist Figure 5 In the embodiment, the low-side power transistor current and the high-side diode current are alternately modulated into a high-frequency signal with a sine waveform amplitude, which is applied alternately so that the high-side power transistor current and the low-side diode current are alternately modulated into a high-frequency signal with a sine waveform amplitude, so that I q =0 and I d As a sine wave signal, it switches between +400A and -400A. Correspondingly, the current I of phases U, V, and W is also shown. PH,U ,I PH,V and I PH,W The current is also implemented as a corresponding sine wave signal, so that I q =0 and I d Sine switching is performed between +400A and -400A.

[0039] Reference numerals list

[0040] 1 Electric motor

[0041] 2 High-voltage on-board power grid

[0042] 3-pulse inverter

[0043] 4 Resistor

[0044] 5. Resistor

[0045] 6 Power switch module

[0046] 7 High-side power switch / power transistor

[0047] 8 Low-side power switches / power transistors

[0048] 9 High-side diode

[0049] 10 Low-side diode

[0050] 11 IGBT power switch

[0051] 12 Coolant circuit

[0052] 13 Vehicle Battery

Claims

1. A method for heating a motor vehicle, the motor vehicle having a three-phase electric motor (1) as a traction motor, wherein a pulse-controlled inverter (3) is provided for supplying power to the electric motor (1), wherein a coolant circuit (12) is provided for coolant cooling of the electric motor (1) and the pulse-controlled inverter (3), the coolant circuit conducting heat by means of a coolant to a heat exchanger for heating the passenger compartment and / or to a vehicle battery (13), characterized in that When the electric motor (1) is stationary, a positive d-current and / or a negative d-current is applied to the d-axis, thereby generating heat loss, which is input into the coolant. The pulse inverter (3) has an electronic circuit, which has a power switch and a freewheeling diode, wherein the current of the power switch and the current of the freewheeling diode are modulated. The pulse inverter (3) comprises a high-side power transistor (7), a low-side power transistor (8), a high-side diode (9) and a low-side diode (10), wherein the current of the high-side power transistor (7) and the current of the low-side diode (10) are controlled in a modulated manner, and / or wherein the current of the low-side power transistor (8) and the current of the high-side diode (9) are controlled in a modulated manner.

2. The method according to claim 1, characterized in that: The electric motor (1) is supplied with a d current on the d axis and waste heat is generated both in the electric motor (1) and in the pulse-controlled inverter (3), which is utilized as waste heat, wherein the q current on the q axis is equal to zero.

3. The method according to claim 1 or 2, characterized in that: By setting the d current, a torque capable of driving the motor vehicle is not applied to the wheels of the motor vehicle.

4. The method according to claim 1 or 2, characterized in that: The heat loss of the electric motor (1) is generated as power losses in the windings of the electric motor (1) and / or as eddy current losses in the laminations; and / or the heat loss in the pulse inverter (3) is generated as forward losses of the power switch and the freewheeling diode and / or as switching losses when the power switch is switched and / or as power losses when the power switch is in operation and / or losses in the intermediate circuit capacitor.

5. The method according to claim 1, characterized in that The currents of the power transistors (7, 8) and the currents of the diodes (9, 10) are pulse modulated.

6. The method according to claim 5, characterized in that The pulse modulation is performed using a square wave signal having a constant amplitude or a modulated amplitude.

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