DE102020007635A1 - Electrical machine with a cooling circuit and method for its operation - Google Patents

Abstract

The invention relates to an electrical machine (2) with a cooling circuit (1), comprising an oil sump (3), a pump (5) for sucking in cooling oil from the oil sump (3) and a heat exchanger (6) for cooling the cooling oil, wherein the oil sump (3) is divided into a first container (3.1) and a second container (3.2), the first container (3.1) and the second container (3.2) being separated from one another and being connected to the pump (5 ) are connected, a control unit being provided which is configured to switch the valve (4) in normal operation in such a way that only the first container (3.1) is connected to the pump (5), and the supply of the cooling oil is switched off to control and/or regulate the second container (3.2) via the valve (4) in the event of an increased cooling requirement depending on a temperature and power in the electrical machine (2).

Description

The invention relates to an electrical machine with a cooling circuit according to the preamble of claim 1 and a method for its operation according to claim 4.

In the case of electrical machines for driving road vehicles, there is only a low cooling requirement during normal operation. Thus, the cooling system could be operated with high coolant flow temperatures. However, power peaks require an increased cooling capacity, which must therefore be kept as a reserve in the flow temperature during operation. This leads to increased expenditure for the cooling system, which is not necessary in regular operation, and to colder coolant temperatures. Cold temperatures in the transmission oil reduce the efficiency in the transmission and the bearings.

It is known to regulate the cooling capacity in a cooling circuit by controlling pumps.

DE 10 2016 200 081 A1 relates to an electrical machine comprising a rotor with a rotor laminated core, a stator with stator end windings which are arranged on opposite end faces of the stator, and a housing with a reservoir for a cooling liquid. When the electrical machine is at a standstill, a sump can form in particular on the bottom of the housing, in particular an oil sump, which serves as a reservoir for a cooling liquid which is filled with oil or an oil mist. According to the method for cooling the electrical machine, the rotor is operated in such a way that an electrically insulating cooling liquid is drawn in from the coolant reservoir and conveyed through the at least one screw-spindle-shaped cooling channel and the outer cooling channel, with the rotation of the rotor turning the electrically insulating cooling liquid into a cooling liquid -air mixture is generated. A feed pump is arranged inside the coolant line, which sucks in oil from the sump and conveys it back to the sump via a heat exchanger.

The invention is based on the object of specifying an electrical machine with an improved cooling circuit and an improved method for operating it.

The object is achieved according to the invention by an electrical machine with a cooling circuit according to claim 1 and by a method for its operation according to claim 4.

Advantageous configurations of the invention are the subject matter of the dependent claims.

According to the invention, an electrical machine with a cooling circuit is provided, comprising an oil sump, a pump for sucking in cooling oil from the oil sump and a heat exchanger for cooling the cooling oil. According to the invention, the oil sump is divided into a first container and a second container, the first container and the second container being separate from one another and connected to the pump via a valve, a control unit being provided that is configured to operate the valve in normal operation to switch so that only the first container is connected to the pump, and to control and/or regulate the supply of cooling oil from the second container via the valve when there is an increased need for cooling, depending on a temperature and power in the electric machine.

In this way, the use of coolant in normal operation can be significantly reduced. Bearings and gears become more efficient due to the higher coolant temperatures achieved in this way and the pressure loss in the system decreases, which means that a reduced pump output is necessary. In the event that an increased coolant requirement is required for a short period of time, the second tank can be switched on, which prevents a reduction in performance (so-called derating) and increases continuous performance.

Splitting the cooling oil into two tanks allows the oil volume to heat up quickly during normal operation, improving lubrication and reducing drag losses. As soon as increased power is required from the electrical machine, less hot cooling oil from the second container is available through the valve.

This allows for more sustained power, longer peak power retention, and faster system cooldown.

Exemplary embodiments of the invention are explained in more detail below with reference to a drawing.

• 1 eine schematische Ansicht eines Kühlkreislaufs für eine elektrische Maschine,

It shows:

• 1 a schematic view of a cooling circuit for an electrical machine,

1 is a schematic view of a cooling circuit 1 for an electric machine 2, in particular a drive machine for an electrically driven motor vehicle. The cooling circuit 1 runs through the electric machine 2 and is configured to carry a cooling oil. Furthermore, the cooling circuit 1 includes an oil sump 3 into which the cooling oil flows after passing through the electrical machine 2 . The oil sump 3 is divided into a first container 3.1 and a second container 3.2 divides that are separate from each other. The first container 3.1 and the second container 3.2 are connected to a pump 5 via a valve 4 in order to remove cooling oil from the first container 3.1 and the second container 3.2. The pump 5 delivers the cooling oil through a heat exchanger 6 to cool the cooling oil. The cooling oil is supplied to the electrical machine 2 from the heat exchanger 6 .

The valve 4 can be configured so that either only the first container 3.1 is connected to the pump 5 or that the first container 3.1 and the second container 3.2 are connected to the pump 5. In an alternative embodiment, the first container 3.1 can be connected directly to the pump 5 and the second container 3.2 can be connected via the valve 4.

The first container 3.1 is intended for normal operation of the electrical machine 2 with little cooling capacity requirement and cooling capacity volume flow. In normal operation, the valve 4 is switched in such a way that the second container 3.2 is separated from the cooling circuit 1. Therefore, no power loss is introduced into the cooling oil by the second container 3.2 in normal operation and it is only switched on by means of the valve 4 when an increased cooling requirement occurs in the electric machine 2. A control unit can be provided that controls and/or regulates the supply of the cooling oil from the second container 3.2 via the valve 4 depending on the temperature and power in the electrical machine 2.

In this way, the use of coolant in normal operation can be significantly reduced. Bearings and gears become more efficient due to the higher coolant temperatures achieved in this way and the pressure loss in the system decreases, which means that a reduced pump output is necessary. In the event that an increased coolant requirement is required for a short time, the second container 3.2 can be switched on, which prevents a reduction in performance (so-called derating) and increases the continuous performance.

The division of the cooling oil into two containers 3.1, 3.2 allows the oil volume to heat up quickly during normal operation, which improves lubrication and reduces drag losses. As soon as increased power is required from the electrical machine 2, less hot cooling oil from the second container 3.2 is available through the valve 4.

This allows for more sustained power, longer peak power retention, and faster system cooldown.

The second container 3.2 is filled via an overflow of the first container 3.1.

In an alternative embodiment, the second container 3.2 can be configured as an oil sump 3 of a separate cooling circuit in order to flow through a cooling jacket of the electrical machine 2 with the cooling oil of this separate cooling circuit, for example. In this case there would be two cooling circuits 1 which would then also require two pumps 5 .

Reference List

1

cooling circuit

2

electric machine

3

oil sump

3.1

first container

3.2

second container

4

Valve

5

pump

6

heat exchanger

QUOTES INCLUDED IN DESCRIPTION

This list of documents cited by the applicant was generated automatically and is included solely for the better information of the reader. The list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions.

Patent Literature Cited

• DE 102016200081 A1 [0004]

Claims (4)

Electrical machine (2) with a cooling circuit (1), comprising an oil sump (3), a pump (5) for sucking in cooling oil from the oil sump (3) and a heat exchanger (6) for cooling the cooling oil, characterized in that the The oil sump (3) is divided into a first container (3.1) and a second container (3.2), the first container (3.1) and the second container (3.2) being separated from one another and connected to the pump (5) via a valve (4). are connected, a control unit being provided that is configured to switch the valve (4) in normal operation in such a way that only the first container (3.1) is connected to the pump (5), and the supply of the cooling oil from the to control and/or regulate the second container (3.2) via the valve (4) when there is an increased need for cooling, depending on a temperature and power in the electrical machine (2). Electrical machine (2) with a cooling circuit (1) according to claim 1 , characterized in that the first container (3.1) has an overflow from which the second container (3.2) can be filled with cooling oil. Electrically driven motor vehicle, comprising an electric machine (2) with a cooling circuit (1) according to claim 1 or 2 . Method for operating an electrical machine (2) with a cooling circuit (1) according to claim 1 or 2 , characterized in that the valve (4) is switched in normal operation so that only the first container (3.1) is connected to the pump (5), and that the supply of cooling oil from the second container (3.2) via the valve (4) is controlled and/or regulated when there is an increased need for cooling, depending on a temperature and power in the electrical machine (2).

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