Method for influencing the temperature of at least one transmission of an electric vehicle

Abstract

Method for influencing the temperature of at least one transmission of an electric vehicle, wherein the electric vehicle has at least one electric machine, at least one transmission connected downstream of the electric machine and at least one oil circuit for cooling and / or lubricating the electric machine and the transmission, wherein the oil circuit comprises at least one electric oil pump, wherein the electric oil pump is activated (P_ON) when the temperature of the electric machine (T) is greater than the temperature of the oil in the transmission (T3) and when the transmission speed (n) exceeds a limit value (G2).

Description

Field of the invention

[0001] The present invention relates to a method for influencing the temperature of at least one transmission of an electric vehicle, wherein the electric vehicle has at least one electric machine, at least one transmission connected downstream of the electric machine and at least one oil circuit for cooling and / or lubricating the electric machine and the transmission, wherein the oil circuit comprises at least one electric oil pump. State of the art

[0002] Electric vehicles use electric motors to generate drive torque. These vehicles can be designed as pure electric vehicles, which use one or more electric motors for propulsion, or as hybrid vehicles, which use a combustion engine and a motor-driven electric motor in parallel as the drive motor.

[0003] In electrical machines, it is necessary to dissipate the waste heat generated during the conversion of electrical energy into kinetic energy in order to operate the drive within a specified temperature range. Furthermore, it is necessary to lubricate a gearbox downstream of the electrical machine and dissipate waste heat generated by friction and other loss processes in the gearbox.

[0004] The prior art discloses a wide variety of devices for cooling and lubricating vehicle transmissions. In the most common design, transmissions are equipped with an oil sump, with the transmission oil contained therein serving both as a lubricant and as a coolant for the transmission. For this purpose, electric vehicles often have an (electric) oil pump that provides a flow of transmission oil, which, in addition to cooling and lubricating the transmission, also cools the electric motor.

[0005] It is well known that the efficiency of a transmission increases with increasing transmission oil temperature. This is especially true at high speeds and low torques, such as during normal driving on a highway.

[0006] For example, DE 10 2021 100 958 B3 discloses a control system for a cooling system of a first electric machine within a drive train of a motor vehicle. The cooling system comprises a first closed cooling circuit with a first cooling fluid and a first fluid pump for conveying the first cooling fluid through the first cooling circuit, serving at least to cool the first electric machine. The control system comprises a control unit connected to the first fluid pump for controlling the pump speed.

[0007] The document DE 10 2020 130 785 A1, for example, discloses a cooling device for cooling an electrical machine with a housing for accommodating a stator and a rotor of the electrical machine, an inlet channel leading to an interior of the housing for supplying a cooling medium, an outlet channel leading away from the interior of the housing, a first temperature sensor provided in the outlet channel for measuring the outlet temperature of the cooling medium, a conveying element connected to the inlet channel and to the outlet channel, and an evaluation unit for calculating an average temperature of the stator on the basis of a thermal calculation model.The thermal calculation model takes into account only measured values ​​​​outside the housing and, when calculating an average temperature of the stator, the outlet temperature of the cooling medium, a volume flow of the cooling medium conveyed by the conveying element and a load point of the electrical machine. Summary of the invention

[0008] Based on this, it is the object of the invention to provide a method for influencing the temperature of at least one transmission of an electric vehicle, whereby an increase in the efficiency of the transmission can be achieved in certain driving situations of the electric vehicle.

[0009] The object is achieved by a method for influencing the temperature of at least one transmission of a vehicle according to claim 1. Advantageous embodiments of the present invention are described in the dependent claims.

[0010] The method according to the invention serves to influence the temperature of at least one transmission of an electric vehicle and is used in particular in an electric vehicle with at least one electric machine, at least one transmission connected downstream of the electric machine and at least one oil circuit for cooling and / or lubricating the electric machine and the transmission, wherein the oil circuit has at least one electric oil pump.

[0011] An oil circuit is essentially an oil line arrangement for circulating oil.

[0012] According to the invention, the electric oil pump is activated when the temperature of the electric machine is higher than the temperature of the oil in the transmission and when the transmission speed exceeds a limit value.

[0013] In this way, the temperature of the oil can be increased via the waste heat of the electric motor and the temperature of the transmission can be increased via the oil in a defined driving situation of the electric vehicle, thus increasing the efficiency of the transmission.

[0014] Particularly preferably, the electric oil pump is deactivated when the temperature of the electric machine is less than or equal to the temperature of the oil in the transmission or when the transmission speed falls below the limit value.

[0015] The temperature of the electrical machine is determined via the temperature of at least one magnet of the electrical machine and / or via the temperature of at least one winding head of the electrical machine.

[0016] The electric oil pump is preferably also activated when the temperature of the electric machine, namely the temperature of a magnet of the electric machine or the temperature of a winding head of the electric machine, reaches or exceeds a critical limit value.

[0017] By means of the method according to the invention it is possible to minimize transmission losses at high speeds and low torques of the electric vehicle. Brief description of the drawings

[0018] The invention is described below by way of example with reference to the drawings. Fig. 1 shows a schematic block diagram of a process. Detailed description of the invention

[0019] In Fig. 1 schematically shows a process flow of a method according to the invention using a block diagram.

[0020] The method according to the invention serves to influence the temperature of at least one transmission of an electric vehicle and is particularly applicable in an electric vehicle with at least one electric machine, at least one transmission downstream of the electric machine, and at least one oil circuit for cooling and / or lubricating the electric machine and the transmission. The oil circuit has at least one electric oil pump.

[0021] The electric oil pump is activated P_ON when the temperature of the electric machine T is greater than the temperature of the oil in the transmission T3 and when the transmission speed n exceeds a limit value G2. The threshold value for a temperature difference between the temperature of the electric machine T and the temperature of the oil in the transmission T3 is set in the Fig. 1 using the term “G1”.

[0022] The electric oil pump is deactivated when the temperature of the electric machine T is less than or equal to the temperature of the oil in the gearbox T3 or when the gearbox speed n falls below the limit value G2.

[0023] The temperature of the electrical machine T is determined via the temperature of at least one magnet of the electrical machine T2 and / or via the temperature of at least one winding head of the electrical machine T1.

[0024] Furthermore, the electric oil pump is activated P_ON when the temperature of the electric machine T, namely the temperature of a magnet of the electric machine T2 or the temperature of a winding head of the electric machine T1, reaches or exceeds a critical limit value.

[0025] The electric oil pump P_ON is also activated as a result of a special event E - for example in a lubrication mode, when reversing, when driving uphill, etc. List of reference symbols T Temperature of an electrical machine T1 Temperature of a winding head of an electrical machine T2 Temperature of a magnet of an electrical machine T3 Temperature of oil in a gearbox G1 Threshold value for a temperature difference between the electric machine and the oil in the gearbox G2 limit G3 Critical limit value of a winding head G4 Critical limit of a magnet n Speed ​​of an axis E Special Event P_ON Oil pump activated

Claims

[1] Method for influencing the temperature of at least one transmission of an electric vehicle, wherein the electric vehicle has at least one electric machine, at least one transmission connected downstream of the electric machine and at least one oil circuit for cooling and / or lubricating the electric machine and the transmission, wherein the oil circuit comprises at least one electric oil pump, wherein the electric oil pump is activated (P_ON) when the temperature of the electric machine (T) is greater than the temperature of the oil in the transmission (T3) and when the transmission speed (n) exceeds a limit value (G2). [2] Method according to claim 1, characterized by that the electric oil pump is deactivated when the temperature of the electric machine (T) is less than or equal to the temperature of the oil in the gearbox (T3) or when the gearbox speed (n) falls below the limit value (G2). [3] Method according to claim 1 or 2, characterized bythat the temperature of the electrical machine (T) is determined via the temperature of at least one magnet of the electrical machine (T2) and / or via the temperature of at least one winding head of the electrical machine (T1). [4] Method according to claim 1, 2 or 3, characterized by that the electric oil pump is activated (P_ON) when the temperature of the electric machine (T), namely the temperature of a magnet of the electric machine (T2) or the temperature of a winding head of the electric machine (T1), reaches or exceeds a critical limit value (G3, G4).

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