WO2022175070A1

WO2022175070A1 - Transmission cooling

Info

Publication number: WO2022175070A1
Application number: PCT/EP2022/052255
Authority: WO
Inventors: Benjamin KRANK; Felix Bolotnikov; Bernhard Wolf; Joachim Maerz; Martin Lasch
Original assignee: Bayerische Motoren Werke Aktiengesellschaft
Priority date: 2021-02-18
Filing date: 2022-02-01
Publication date: 2022-08-25
Also published as: DE102021103789A1

Abstract

The invention relates to a traction unit (8) having transmission cooling, the traction unit having a prime mover which is directly connected to a drive transmission device, the prime mover and the drive transmission device being accommodated in a shared traction unit-transmission housing apparatus (4), a transmission oil chamber (1) being provided in the traction unit-transmission housing apparatus (4) for accommodating a transmission lubricant, at least one gear pair being arranged in the transmission oil chamber (1) for transmitting drive power from the prime mover, said traction unit-transmission housing apparatus (4) having a heat exchanger device (12), the heat exchanger device (12) being separated from the transmission oil chamber (1) by a transmission housing wall and being sealed so as to be fluid-tight with respect to said chamber, characterised in that the heat exchanger device (12) has a cooling chamber (3), wherein the cooling chamber (3) is delimited at least in part by said transmission housing wall, and the cooling chamber (3) can be connected in a fluid-conducting manner to a motor vehicle coolant circuit such that a cooling medium of the motor vehicle coolant circuit can flow though the cooling chamber at least at times.

Description

transmission cooling

The invention relates to a traction unit with transmission cooling for an electric drive unit and an electric motor vehicle drive system with such transmission cooling.

The invention is explained below using a motor vehicle transmission in an electric vehicle; this is not to be understood as a limitation of the invention to such an application. In electric vehicles, the cooling of the transmission usually differs based on the power installed to drive the motor vehicle. In a higher performance class (drive power greater than / equal to 100 kW), there is usually an active cooling of the gear oil in the drive gear. This is achieved by means of its own heat exchanger and coolant circuit. For example, the gear oil cooling circuit of the BMW iX3 model is designed in this way. In low power classes of electric vehicles, for example up to a continuous power of 60 kW or less provided for driving the motor vehicle, there is often no explicit cooling of the transmission oil, since in such a case an existing engine cooling system can be sufficient to cool the transmission oil as well. Furthermore, in the case of drive machines in the low power range, heat can be dissipated from the drive gear to the environment, i.e. through the relative wind.

Active oil cooling of the drive transmission, as explained in connection with the upper performance class, causes considerable effort, since an oil pump, a heat exchanger and, as a rule, an oil filter are installed. The present invention relates to gear cooling for drive gears with a high cooling requirement, in particular those of the higher performance class, it being an object of the invention to specify simple gear cooling for such a drive gear.

This object is achieved by a transmission cooling system according to patent claim 1 and by a motor vehicle drive system with such a transmission cooling system. An advantage which is achievable with a transmission cooling according to the invention is one Simplification of the cooling of the drive unit, which can also be referred to as a traction unit, whereby cost savings and an increase in functional reliability can be achieved as a result.

A basic principle of the invention is to increase the heat dissipation from the transmission oil, for which purpose it is proposed in particular to bring the coolant of a motor vehicle cooling circuit as close as possible to a transmission device from which heat is to be extracted from the transmission oil and thus to cool the transmission housing of this transmission device over a large area in the area of the transmission oil chamber . Furthermore, the heat exchange between the transmission device and this coolant is provided at a location where the flow rate of the transmission oil is high during scheduled operation and where there are regularly large quantities of transmission oil, which is in particular in an area geodetically located below the traction unit in the scheduled installation position of the traction unit Unit. Furthermore, ribs or a rib-like structure is preferably provided which, compared to a transmission housing wall without such a structure, leads to an increase in the wall surface, which can be contacted by transmission oil in particular in the above-mentioned area and thus enables increased absorption of heat from the transmission oil .

In the context of the invention, a traction unit with a transmission cooling means a drive device which is set up to provide drive power in order to overcome driving resistances of a motor vehicle. Furthermore, such a traction unit has a drive machine, preferably the drive machine is designed as an electromechanical energy converter, preferably as a so-called electric motor/generator (electric motor generator). The traction unit also has a drive transmission device, which is set up to transmit and convert the drive power provided by the drive machine. The drive gear device is preferably designed as a toothed wheel gear device, preferably as a drive gear device with a single transmission ratio and preferably with at least two switchable transmission ratios. The drive machine can be connected to the drive transmission device at least temporarily, and the drive machine is preferably connected to the drive transmission device in order to transmit the drive power (rotational speed, torque). An output shaft of the drive machine is preferably aligned concentrically with a transmission input shaft of the drive transmission device and is preferably connected to it in a torsionally rigid manner and particularly preferably permanently in a torque-conducting manner. The prime mover is in particular arranged immediately adjacent to the drive transmission device and in particular, the prime mover and the drive transmission device are accommodated in a common traction unit transmission housing device. In particular, such a traction unit transmission housing device is to be understood as a one-part or preferably multi-part housing device in which both the drive machine and the drive transmission device are arranged.

Furthermore, a transmission oil chamber is arranged in the traction unit transmission housing device, with drive means of the drive transmission device for transmission of the drive power being arranged in this transmission oil chamber, in particular gear wheels and transmission shaft. The gear oil chamber is also provided for receiving a gear lubricant in order to achieve lubrication and/or cooling of the drive gear device. Accordingly, at least one pair of gearwheels for transmitting drive power from the drive machine is arranged in the transmission oil chamber.

This traction unit-transmission housing device has a heat exchanger device, the heat exchanger device being separated from the transmission oil chamber by means of a transmission housing wall and sealed off in a fluid-tight manner with respect to the transmission oil chamber. Functionally, the heat exchanger device is set up in particular to absorb heat from the transmission oil chamber and to emit it into a heat sink.

In connection with the invention, it is proposed that the heat exchanger device has a cooling space, the cooling space being delimited at least in sections by this transmission housing wall, ie a region of the wall of the drive transmission device. Figuratively speaking, the heat exchanger device is arranged directly on a wall of the drive transmission device; in particular, this wall separates the cooling chamber from the transmission oil chamber in the area of the heat exchanger device. Furthermore, the cooling chamber of the heat exchanger device can be fluidly connected to a motor vehicle coolant circuit or is preferably permanently connected to such a motor vehicle coolant circuit in such a way that coolant from the motor vehicle coolant chamber can be fed to the cooling chamber, so that this coolant absorbs heat from the transmission oil. More preferably, the heat exchanger device has at least one inlet for coolant from a motor vehicle coolant circuit and an outlet for this coolant into a motor vehicle coolant circuit. More preferably, the heat exchanger device is set up in such a way that a cooling medium from a motor vehicle coolant circuit can flow through it at least at times. More preferably, a motor vehicle coolant circuit is a device of the motor vehicle which supplies at least one other device of the motor vehicle, apart from the traction unit, with coolant, preferably a device such as an electrochemical energy store or preferably an air conditioning device for a motor vehicle cabin. In particular, such a design of the traction unit makes it possible to use a motor vehicle coolant circuit efficiently, in particular additionally, for cooling or temperature control of the traction unit, thus enabling particularly reliable and efficient operation of the traction unit.

In a preferred embodiment of the invention, the housing wall has at least one and preferably a large number of heat-conducting ribs opposite the heat-exchanger device, ie in particular on the side of this housing wall facing away from the heat-exchanger device. More preferably, the heat-conducting ribs are arranged in the transmission oil chamber and more preferably arranged in such a way that they contact the transmission oil in the transmission oil chamber, in particular when the traction unit is in scheduled operation. More preferably, the at least one heat-conducting rib is aligned, starting from the housing wall, in such a way that it extends into the transmission oil chamber. In particular, with such an embodiment, the surface over which heat can be absorbed from the transmission oil is enlarged, so that the heat dissipation from the transmission oil is improved.

In a preferred embodiment, the heat exchanger device has a cooling medium deflection structure. The coolant deflection structure is set up, in particular, for a coolant which flows from the motor vehicle coolant circuit through the cooling chamber of the heat exchanger device to be deflectable in the heat exchanger device, or is deflected as it flows through it, so that this coolant absorbs more heat when it flows through the heat exchanger device than when it flows directly or in a straight line Flow without deflection. More preferably, the cooling medium deflection structure is set up in such a way that it deflects a particularly intended flow of cooling medium as it flows through the heat exchanger device. Put another way, the heat exchanger device, in particular its cooling chamber, is designed in such a way that an imaginary flow of coolant can flow through it along a coolant path, from a coolant inlet into the heat exchanger device to a coolant outlet through which the coolant exits the heat exchanger device. Furthermore, the cooling medium deflection structure is set up and forms the cooling medium flow on it To deflect the cooling medium path by at least 90° and preferably to direct it several times. Particularly in such an embodiment of the invention, a particularly good heat transfer from the transmission oil into the cooling medium can be achieved.

In a preferred embodiment, the heat exchanger device is arranged geodetically below in relation to a planned installation position of the traction unit. Investigations have shown that gear oil is more likely to be found in this report during scheduled operation of the traction unit, or flows through it at "high" speed, and thus, in particular, such an embodiment of the invention enables efficient heat transfer from the gear oil to the cooling medium.

In a preferred embodiment, a cooling medium control valve is provided, which is provided for controlling or regulating the volume flow of cooling medium through the cooling chamber of the heat exchanger device. The cooling medium control valve is preferably arranged upstream of the cooling chamber and more preferably downstream, based on a planned flow through the heat exchanger device with cooling medium. The cooling medium control valve is preferably arranged in the heat exchanger device and more preferably it is arranged at a distance from it. Functionally, the cooling medium accumulation valve is thus set up in particular for controlling a flow of cooling medium through the heat exchanger device. In particular, a cooling medium control valve makes it possible to control the cooling of the traction unit as required. More preferably, the cooling medium control valve prevents or reduces a flow of cooling medium through the heat exchanger device in a warm-up phase and thus enables the traction unit to be heated up quickly to an operating temperature. This has a particularly favorable effect on the efficiency of the traction unit.

A motor vehicle drive system with a traction unit according to one of the previously explained embodiments is also preferably proposed. Furthermore, this motor vehicle drive system is set up to drive a passenger car. This passenger car has a motor vehicle coolant circuit which, according to the type explained above, is designed for cooling or tempering at least one further component of the motor vehicle. More preferably, the traction unit, in particular its heat exchanger device, is preferably permanently or preferably at least temporarily fluidly connected to this motor vehicle coolant circuit. More preferably, the cooling medium of the motor vehicle coolant circuit flows through the cooling chamber of the heat exchanger device at least at times. Especially A particularly efficient motor vehicle drive system can be represented by means of such a configuration.

Individual features and embodiments of the invention are explained in more detail below with reference to the partially schematic figures, with other combinations of features than those shown are also possible in principle, showing:

Fig. 1: Sectional view through the traction unit,

Fig. 2: Sectional view through the heat exchanger device,

Fig. 3: Perspective view of the traction unit gear housing device.

FIG. 1 shows a sectional view of a traction unit. The final drive gear is arranged in the traction unit 8 and transmits drive power from the prime mover (not shown) to a differential gear (not shown). From the differential gear, the drive power is transmitted in direction 6a/6b to the left and right drive wheels (not shown). The final drive gear wheel 2 is arranged in the gear oil chamber 1 and is lubricated and cooled by gear oil during scheduled operation of the traction unit 8 . During the transmission of drive power, unavoidable losses occur in the traction unit 8, which lead to heating of the gear oil in particular. In particular in the case of a traction unit 8 with high performance, the transmission oil can heat up to such an extent that it would fail without active temperature control.

In the direction of gravity 7 and thus at the bottom of the traction unit 8, the heat exchanger device 12 is arranged, which is designed to absorb heat from the transmission oil and deliver it to a cooling medium which flows through the cooling chamber 3 of the heat exchanger device 12. The cooling medium deflection structure 9 , which leads to the deflection of the cooling medium flow in the cooling chamber 3 , is arranged in the heat exchanger device 12 .

To improve the conduction of heat from the transmission oil chamber 1 into the cooling chamber 3, heat-conducting ribs 5 are arranged on the traction unit transmission housing device 4, i.e. on the wall between the transmission oil chamber 1 and the cooling chamber 3 occurs enlarged.

FIG. 2 shows a sectional view of the traction unit 8 from below. For orientation purposes, the directions 6a/6b are also shown, which lead to the right or point to the left drive wheel. The final drive gear wheel is also shown, so only part of the traction unit gear housing device 4 is shown in this view. The heat exchanger device 12 is formed in one piece with the traction unit transmission housing device 4 . It can also be seen how the cooling medium device 9 deflects a flow of cooling medium in the cooling chamber 3 on its way from the cooling medium inlet 10 to the cooling medium outlet 11.

FIG. 3 shows a perspective view of the traction unit gear housing device 4 . For better orientation, the direction of gravity 7 and the direction 6a to the left drive wheel are shown. It can also be seen at which location in the transmission oil chamber 1 the heat-conducting ribs 5 are arranged for absorbing heat from the transmission oil.

In other words, the basic principle of the invention is based in particular on three measures, preferably two or more of these measures to increase the heat dissipation from the transmission oil, with the heat being dissipated from the transmission oil in cooling medium from a motor vehicle cooling circuit. The measures are essentially:

1. The coolant or cooling medium of the motor vehicle cooling circuit is brought as close as possible to the transmission chamber of the traction unit and cools the housing, the so-called traction unit transmission housing device, "over a large area" in the area of the transmission oil chamber.

2. The transmission cooling is used in the transmission oil room where the flow speed of the transmission oil is “high” during scheduled operation of the traction unit (Finaldrive gear wheel is in rotation) and there are regularly large amounts of transmission oil, which is usually at the bottom of the traction unit the case is.

3. Heat-conducting ribs, which protrude into the gear oil chamber, additionally increase the surface area for heat dissipation from the gear oil.

Furthermore, the above points 1. and 2. can be realized in particular by cooling the outer surface and end face of the traction unit gear housing device in the vicinity of the final drive gear. The transmission cooling takes place primarily in the lower area, since the effect of gravity brings the transmission oil together at this point and thus a lot of transmission oil is available for heat transport.

At the same time, there is a high flow rate in the gear oil in the area of the Finaldrive gear wheel due to the movement of this gear wheel, which leads to a high heat transfer into the gear oil and in the wall of the traction unit gear housing device. Additional heat-conducting ribs in the area of this wall (see above) lead to a further improvement in heat transfer (point 3). Furthermore, these heat-conducting ribs are designed in such a way that they protrude into the undercut of the geometry of the Finaldrive gear wheel, but in particular into the transmission oil chamber. The heat-conducting ribs or the at least one heat-conducting rib are preferably oriented in the circumferential direction relative to the Finaldrive gear wheel, in particular the fluid friction losses are not significantly influenced by this orientation of the at least one heat-conducting rib. Furthermore, the offset waveform of the heat-conducting ribs shown in FIG. 3 enables a radial flow through the rib arrangement. The described arrangement of the heat-conducting ribs is space-neutral, ie it does not require any additional installation location or space in the transmission oil chamber compared to an embodiment without heat-conducting ribs.

Reference list:

Claims

Expectations

1. Traction unit (8) with a transmission cooling system, which has a drive machine which is directly connected to a drive transmission device, the drive machine and the drive transmission device being accommodated in a common traction unit-transmission housing device (4) and in which the traction unit-transmission housing device (4 ) a transmission oil chamber (1) is provided for accommodating a transmission lubricant and at least one pair of gearwheels for transmitting drive power from the drive motor is arranged in the transmission oil chamber (1), this traction unit transmission housing device (4) having a heat exchanger device (12), the Heat exchanger device (12) is separated from the transmission oil chamber (1) by means of a transmission housing wall and is sealed off from the latter in a fluid-tight manner, characterized in that the heat exchanger device (12) has a cooling chamber (3), the cooling chamber (3) being at least partially delimited by this transmission housing wall and wherein the cooling space (3) can be fluidly connected to a motor vehicle coolant circuit in such a way that a cooling medium of the motor vehicle coolant circuit can flow through the cooling space at least temporarily.

2. Traction unit (8) according to Claim 1, characterized in that the housing wall has at least one heat-conducting rib (5) opposite the heat exchanger device (12), so that the heat-conducting rib (5) extends from the housing wall into the transmission oil chamber (1). extends.

3. Traction unit (9) according to one of the preceding claims, characterized in that a cooling medium deflection structure (9) is arranged in the heat exchanger device (12), that the cooling medium deflection structure (9) has an imaginary flow of cooling medium, the heat exchanger device (12) moving along a cooling medium path from towards this imaginary cooling medium flow from a cooling medium inlet (10). a cooling medium outlet (11) and that the cooling medium flow is deflected by at least 90 on this cooling medium path.

4. traction unit (8) according to any one of the preceding claims, characterized in that the heat exchanger device (12) based on a planned installation position of the traction unit (8) arranged geodetically below.

5. Traction unit (8) according to any one of the preceding claims, characterized in that it comprises a cooling medium control valve which is used for

Control of a flow of cooling medium through the heat exchanger device (12) is set up.

6. Motor vehicle drive system with a traction unit (8) according to one of the preceding claims, wherein the motor vehicle drive system is set up to drive a passenger car and is fluid-conductingly connected to a motor vehicle coolant circuit of this passenger car permanently or at least intermittently in a fluid-conducting manner, and wherein cooling medium of the motor vehicle coolant circuit thus flows through the cooling chamber at least at times is.