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

Abstract

The invention relates to a method for influencing the temperature of at least one transmission of an electric vehicle, the electric vehicle having 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, and wherein the electric oil pump is activated (PON) when the temperature (T) of the electric machine is higher than the temperature (T3) of the oil in the transmission and the transmission speed (n) exceeds a limit value (G2).

Description

TECHNICAL FIELD

[0001] The invention relates to a method for influencing the temperature of at least one transmission of an electrically operated vehicle, wherein the electrically operated 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. BACKGROUND

[0002] In electrically operated vehicles, electric machines are used for generating a drive torque. Here, the electrically operated vehicle can be designed as a purely electric vehicle, which uses one or more electric machines exclusively for driving; or the electrically operated vehicle can also be designed as a hybrid vehicle, which uses a combustion engine and an electric machine operating in electric machine mode in parallel as drive motor.

[0003] In electric machines, it is necessary to discharge the waste heat generated when electrical energy is converted into kinetic energy in order to enable the drive to be operated within a predefined temperature range. Furthermore, it is necessary to lubricate the transmission connected downstream of the electric machine and likewise to discharge the waste heat generated in the transmission as a result of friction and other loss processes.

[0004] The prior art discloses various different devices for cooling and lubricating vehicle transmissions. In the most common embodiment, the transmission is embodied with an oil sump, wherein the transmission oil located therein is used both as lubricant and as coolant for the transmission. For this purpose, in electrically operated vehicles, a (electric) oil pump usually provides a transmission oil flow, which serves not only for cooling and lubricating the transmission but also for cooling the electric machine.

[0005] It is known that the efficiency (utilization factor) of a transmission increases as the transmission oil temperature increases. This applies in particular at high rotational speeds and low torques, for example when the vehicle is being driven conventionally on a motorway. SUMMARY

[0006] On the basis thereof, it is an object of the invention to specify a method for influencing the temperature of at least one transmission of an electrically operated vehicle, whereby an increase in the transmission efficiency can be achieved in specific driving situations of the electrically operated vehicle.

[0007] 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 invention are described in the dependent claims.

[0008] The method according to the invention serves for influencing the temperature of at least one transmission of an electrically operated vehicle and is used in particular in an electrically operated vehicle which 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 has at least one electric oil pump.

[0009] The oil circuit basically refers to an oil line arrangement for oil circulation.

[0010] According to the application, 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 the transmission rotational speed exceeds a limit value.

[0011] In this way, the temperature of the oil can be increased via the waste heat of the electric machine and the temperature of the transmission can be increased via the oil in a defined driving situation of the electric vehicle, thereby increasing the efficiency of the transmission.

[0012] 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 the transmission rotational speed is below the limit value.

[0013] The temperature of the electric machine is determined via the temperature of at least one magnet of the electric machine and / or via the temperature of at least one winding head of the electric machine.

[0014] Preferably, the electric oil pump is also activated when the temperature of the electric machine, i.e. the temperature of the magnets of the electric machine or the temperature of the winding heads of the electric machine, reaches or exceeds a critical limit value.

[0015] By means of the method according to the application, the transmission losses can be minimized at high rotational speeds and low torques of the electric vehicle. BRIEF DESCRIPTION OF DRAWINGS

[0016] The application is described below by way of example with reference to the accompanying drawings.

[0017] Figure 1 A block diagram of the method is shown schematically. DETAILED DESCRIPTION

[0018] In Figure 1 The method flow of the method according to the application is shown schematically according to the block diagram.

[0019] The method according to the application serves to influence the temperature of at least one transmission of an electric vehicle and is applied in particular in an electric vehicle having 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. The oil circuit has at least one electric oil pump.

[0020] The P_ON electric oil pump is activated when the temperature T of the electric machine is higher than the temperature T3 of the oil in the transmission and the transmission rotational speed n exceeds a limit value G2. The threshold value of the temperature difference between the temperature T of the electric machine and the temperature T3 of the oil in the transmission is in the range of 5 to 20 K, preferably 10 to 15 K. Figure 1 The threshold value of the temperature difference between the temperature T of the electric machine and the temperature T3 of the oil in the transmission is shown in the shown schematic block diagram with the wording "G1".

[0021] The electric oil pump is deactivated when the temperature T of the electric machine is less than or equal to the temperature T3 of the oil in the transmission or when the transmission speed n is below a limit value G2.

[0022] The temperature T of the electric machine is determined via the temperature T2 of at least one magnet of the electric machine and / or via the temperature T1 of at least one winding head of the electric machine.

[0023] Furthermore, the P_ON activation of the electric oil pump is carried out when the temperature T of the electric machine, i.e. the magnet temperature T2 of the electric machine or the winding head temperature T1 of the electric machine, reaches or exceeds a critical limit value.

[0024] The P_ON activation of the electric oil pump is also carried out due to a specific event E, for example in the lubrication mode, when reversing, when driving uphill, etc.

[0025] List of reference signs

[0026] T temperature of the electric machine

[0027] T1 temperature of the winding head of the electric machine

[0028] T2 temperature of the magnet of the electric machine

[0029] T3 temperature of the oil in the transmission

[0030] G1 threshold value for the temperature difference between the electric machine and the oil in the transmission

[0031] G2 limit value

[0032] G3 critical limit value of the winding head

[0033] G4 critical limit value of the magnet

[0034] n shaft speed

[0035] E specific event

[0036] P_ON activation of the oil pump

Claims

1. A method for influencing the temperature of at least one transmission of an electrically powered vehicle, wherein the electrically powered 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 (T) of the electric machine is higher than the temperature (T3) of the oil in the transmission and when the transmission rotational speed (n) exceeds a limit value (G2).

2. The method according to claim 1, characterized in that the electric oil pump is deactivated when the temperature (T) of the electric machine is less than or equal to the temperature (T3) of the oil in the transmission or when the transmission rotational speed (n) is below the limit value (G2).

3. The method according to claim 1 or 2, characterized in that the temperature (T) of the electric machine is determined via the temperature (T2) of at least one magnet of the electric machine and / or via the temperature (T1) of at least one winding head of the electric machine.

4. The method according to claim 1, 2 or 3, characterized in that the electric oil pump is activated (P_ON) when the temperature (T) of the electric machine, i.e. the temperature (T2) of the magnets of the electric machine or the temperature (T1) of the winding heads of the electric machine, reaches or exceeds a critical limit value (G3, G4).

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