DE102022110968A1 - Hydraulic system with relief valve to reduce pump motor load - Google Patents

Abstract

The invention relates to a hydraulic system (1) for a motor vehicle drive device, with a first pump (3) connected on the output side to a first line (2), a second pump (5) connected on the output side to a second line (4), and a simultaneous The electric motor (6) used to drive both pumps (3, 5), the first pump (3) being designed to generate a higher system pressure in the first line (2) than the second pump (5) in the second line (4), wherein a primary valve (7) is inserted between the two lines (2, 4) in such a way that in a first position of the primary valve (7) the lines (2, 4) are connected to one another and in a second position of the primary valve (7) the first line (2) is separated from the second line (4), and there is also a relief valve (8) which, depending on a pressure present in the first line (2), automatically turns the second line (4) into a tank (9) opens towards...

Description

The invention relates to a hydraulic system for a motor vehicle drive device, preferably for a transmission and/or a drive machine of the motor vehicle drive device, with a first pump connected on the output side to a first line, a second pump connected on the output side to a second line and one for driving both pumps simultaneously used electric motor, wherein the first pump is designed to generate a higher system pressure in the first line than the second pump in the second line (at a certain speed of the electric motor), and wherein a primary valve is inserted between the two lines in such a way that in in a first position of the primary valve the two lines are connected to one another and in a second position of the primary valve the first line is separated from the second line. The structural unit/arrangement consisting of the two pumps and the common electric motor is also known as a tandem pump.

Generic hydraulic systems are already well known. For example, the reveals DE 10 2020 131 788 A1 a hydraulic system with a tandem pump.

In the embodiments known from the prior art, it has been found that the system pressure, i.e. the pressure in the first line, is relatively high in certain driving situations of the motor vehicle (e.g. reversing under full load), so that there is a relatively high leakage on the part the consumer connected to the first line comes. This in turn leads to a relatively high volume flow requirement on the first line and therefore a high pump speed has to be implemented. Because of the forced coupling of the electric motor to both pumps at the same time, this in turn has the consequence that the amount of hydraulic fluid from the second pump into the second line is unnecessarily increased. This also leads to an increase in the load on the electric motor. Since the load on the high-pressure side, i.e. in the first line, is already relatively high, this unnecessary increase in load on the low-pressure side, i.e. in the second line, is relatively critical.

This can lead to an overload of the electric motor and thus to a malfunction of the pumps.

It is therefore the object of the present invention to provide a hydraulic system which ensures safe functioning of the electric motor and the pumps associated with it during all operating states of the motor vehicle.

This is solved according to the invention in that there is also a relief valve which, depending on a pressure present in the first line, automatically opens the second line to a tank.

As a result, the load on the electric motor is significantly reduced in a critical pressure state of the first line. The electric motor therefore has a significantly longer service life and can be made significantly smaller.

Further advantageous embodiments are claimed in the subclaims and explained in more detail below.

For a simpler construction of the relief valve, it is advantageous if it has a (preferably spring-loaded) rest position in which the second line is connected to a line section that can be connected or is connected to a coolant and / or lubricant supply device and from a directly (before entering the Cooling and/or lubricant supply device) is separated from the relief line leading to the tank.

Furthermore, it is advantageous if the relief valve is designed such that when a maximum pressure within the first line is exceeded, it switches from its rest position to a relief position, in which relief position the second line is opened towards the tank. This results in a defined control/switching of the relief valve.

If the second line is separated from the line section that can be connected or connected to the coolant and/or lubricant supply device in the relief position of the relief valve, the electric motor is relieved of the load as quickly as possible in the event of a corresponding overload.

Alternatively, it is also advantageous if the second line in the relief position is connected directly via the relief valve or directly to the line section that can be connected or connected to the coolant and/or lubricant supply device. As a result, a certain minimum amount is conveyed into the coolant and/or lubricant supply device even in the relief position.

In addition, it is advantageous if a flow diaphragm is integrated in the second line on an inlet side of the relief valve, which is hydraulically connected to the second pump, or is formed directly by the relief valve. This allows the volume flow to be as high as possible cleverly distributed between the tank and the coolant and/or lubricant supply device.

It has proven to be particularly useful if the relief valve is designed as a 3/2-way valve and/or the primary valve is designed as a 2/2-way valve.

In other words, according to the invention there is a relief valve that is passively controlled with the system pressure. This allows the load on the low-pressure side to be greatly reduced, which in turn means a load reduction on the engine (electric motor). The motor and the associated electronics can therefore be made smaller and cheaper.

The invention will now be explained in more detail below with reference to figures.

• 1 einen Schaltplan eines Teils eines erfindungsgemäßen Hydrauliksystems nach einem ersten Ausführungsbeispiel, wobei ein seitens einer Niederdruckseite eingesetztes Entlastungsventil als 3/2-Wegeventil einer mit einer Kühl- und Schmiermittelversorgungseinrichtung verbundenen oder verbindbaren Leitung eingesetzt ist,
• 2 einen Schaltplan eines Teils eines erfindungsgemäßen Hydrauliksystems nach einem zweiten Ausführungsbeispiel, wobei das Entlastungsventil derart ausgebildet ist, dass es in einer Entlastungsstellung eine mit einer Pumpe der Niederdruckseite verbundene Leitung sowohl mit einem Tank als auch mit der Kühl- und Schmiermittelversorgungseinrichtung verbindet,
• 3 einen Schaltplan eines Teils eines erfindungsgemäßen Hydrauliksystems nach einem dritten Ausführungsbeispiel, wobei das Entlastungsventil nun unmittelbar in einer Entlastungsleitung, die von der mit der Kühl- und Schmiermittelversorgungseinrichtung direkt verbundenen Leitung abzweigt, eingesetzt ist, sowie
• 4 einen Schaltplan eines Teils eines erfindungsgemäßen Hydrauliksystems nach einem vierten Ausführungsbeispiel, wobei aufbauend auf das dritte Ausführungsbeispiel eine Strömungsblende vor dem Entlastungsventil eingesetzt ist.

Show it:

• 1 a circuit diagram of a part of a hydraulic system according to the invention according to a first exemplary embodiment, wherein a relief valve used on a low-pressure side is used as a 3/2-way valve of a line connected or connectable to a coolant and lubricant supply device,
• 2 a circuit diagram of part of a hydraulic system according to the invention according to a second exemplary embodiment, wherein the relief valve is designed such that in a relief position it connects a line connected to a pump on the low-pressure side both to a tank and to the coolant and lubricant supply device,
• 3 a circuit diagram of part of a hydraulic system according to the invention according to a third exemplary embodiment, wherein the relief valve is now inserted directly in a relief line which branches off from the line directly connected to the coolant and lubricant supply device, and
• 4 a circuit diagram of part of a hydraulic system according to the invention according to a fourth exemplary embodiment, with a flow orifice being inserted in front of the relief valve based on the third exemplary embodiment.

The figures are only of a schematic nature and serve exclusively to understand the invention. The same elements are given the same reference numbers. In principle, the various features of the different exemplary embodiments can also be freely combined with one another.

The hydraulic system 1 according to the invention is initially based on the 1 described in more detail for the first exemplary embodiment. It should be noted that the further exemplary embodiments of 2 until 4 largely the same as the first exemplary embodiment. For the sake of brevity, only the differences between the respective exemplary embodiments will be discussed below 2 until 4 compared to the first exemplary embodiment 1 explained.

1 illustrates that the hydraulic system 1 according to the invention uses a so-called tandem pump. This tandem pump is a structural unit consisting of two pumps 3, 5 and an electric motor 6 driving these pumps 3, 5. That electric motor 6 has a schematically shown drive shaft 16 (also referred to as a rotor shaft), which is directly rotary with drives of a first pump 3 and a second pump 5 is mechanically connected. The speed of the electric motor 6 therefore directly determines the speed of the respective pump 3, 5. The drive shaft 16 serves directly to drive a rotating part of the respective pump 3, 5, so that the two pumps 3, 5 are driven during operation at the same speed that the electric motor 6 directly sets.

The first pump 3 is connected on the output side, that is to say with its output, to a first line 2 / connected to the first line 2. On the input side, that is to say with an input, the first pump 3 is connected to a tank 9 / connected to the tank 9. During operation, the first pump 3 serves to supply at least one consumer 17, more preferably several consumers 17, with a hydraulic medium having a specific pressure/system pressure.

It should also be noted that the first pump 3, also known as a high-pressure pump, preferably supplies several consumers 17 with hydraulic fluid via the first line 2. Those consumers 17 can be clutch actuation devices, transmission switching devices, parking lock actuation devices, etc.

The second pump 5 is connected on the output side, that is to say with its output, to a further second line 4 / connected to the second line 4. On the input side, that is to say with its input, the second pump 5 is connected to the tank 9/connected to the tank 9. It can also be seen that the second line 4 is in operation with a coolant and lubricant supply device device 10 is further connected or, more precisely, can be connected by means of a relief valve 8 described in more detail below.

It should be noted that the first pump 3 is designed to generate a higher pressure than the second pump 5 at the same speed of the electric motor 6. When setting a corresponding speed, there is therefore a higher pressure/system pressure in the first line 2 than in the second line 4.

The second pump 5, also referred to as a low-pressure pump, supplies the coolant and lubricant supply device 10 with hydraulic fluid via the second line 4. The coolant and lubricant supply device 10, like the consumers 17, is preferably used in a motor vehicle drive device, such as a transmission and/or a drive machine.

The first line 2 and the second line 4 can be coupled to one another by means of a primary valve 7, which is designed as a 2/2-way valve. It can be seen that the primary valve 7 is designed as a solenoid valve. In a rest position of the primary valve 7 (also referred to as the first position), the two lines 2, 4 are connected to one another and in a forced position/activated position of the primary valve 7 (also referred to as the second position), the first line 2 is separated from the second line 4 .

In addition, the primary valve 7 is provided with a pressure return 18 connected to the first line 2. The primary valve 7 is therefore preferably designed as a pressure control valve.

According to the invention, the relief valve 8 is used in such a way that it automatically opens the second line 4 to the tank 9 depending on the pressure present in the first line 2. The relief valve 8 is moved from its rest position, in which a delivery volume conveyed by the second pump 5 is supplied in its entirety to the coolant and lubricant supply device 10, into a relief position in which the second line 4, that is, the output side of the second pump 5, is at least partially. here completely, to which tank 9 is open, switchable.

It is in 1 It can be seen that the relief valve 8 in the first exemplary embodiment is designed such that in the relief position it completely separates the second line 4, that is the second pump 5, from a (first) line section 11 that is permanently connected to the coolant and lubricant supply device 10 .

The relief valve 8 switches depending on a pressure present in the first line 2. The switchover from the rest position to the relief position takes place (by means of a control connection) when a maximum pressure in the first line 2 is exceeded. The reverse switchover from the relief position back to the rest position takes place when this maximum pressure in the first line 2 is undershot.

The switchover between the rest position and the relief position thus takes place automatically in such a way that when the maximum pressure in the first line 2 is exceeded, the relief valve 8 automatically switches to the relief position from the rest position. The relief valve 8 is biased into the rest position by means of a spring 20. If a corresponding spring force of the spring is exceeded due to the pressure applied in the first line 2, a piston of the relief valve 8, which is not shown for the sake of clarity, is moved into the relief position.

The relief valve 8 is designed as a 3/2-way valve.

In the second exemplary embodiment 2 In contrast to the first exemplary embodiment, the relief valve 8 is changed in such a way that in the relief position it no longer diverts the entire flow of the second pump 5 to the tank 9, but rather divides the flow and sends a first part of the flow to the coolant and lubricant supply device 10 forwards in order to ensure an appropriate minimum supply of the coolant and lubricant supply device 10. A second part of the flow is directed to tank 9.

Combined with 3 It can also be seen that the relief valve 8 compared to 1 does not necessarily have to be used in the second line 2, which forms the direct connection between the second pump 5 and the coolant and lubricant supply device 10, but in principle can also be used in a (second) line section 19, which is connected by the second line 4 can be used in the direction of a relief line 12, which in turn is directly connected to the tank 9.

Furthermore, in the fourth embodiment 4 It can be seen that it is also possible to insert a flow orifice 15 in front of the relief valve 8, that is to say on an inlet side 13 of the relief valve 8, which faces the second pump 5. An output side 14 of the relief valve 8 is further connected directly to the tank 9.

In other words, according to the invention, with a relief valve 8 that is passively controlled with the system pressure, the load on the low-pressure side (second line 4) can be greatly reduced, which in turn means a load reduction on the engine. The motor and electronics can therefore be made smaller and cheaper.

In 1 a first version is shown. There the relief valve 8 is designed as a 3/2 switching valve. During normal operation (ie system pressure <12 bar), the relief valve 8 is in its rest position/basic position, in which the volume flow is directed towards cooling (coolant and lubricant supply device 10). If the system pressure exceeds a threshold value (maximum pressure, eg 15 bar), the pressure force on the valve slide/valve piston of the relief valve 8 is so great that the relief valve 8 moves into the other position (relief position). In this case, the volume flow is transferred directly to tank 9 (short circuit) and the low-pressure pump no longer sees any load.

If cooling does not need to be completely prevented when reversing under full load, the valve concept is not necessary 2 for use. Even in the switched valve position (relief position), a certain volume flow flows towards cooling. A targeted distribution of the volume flow can be achieved via the valve design.

The execution in 3 is an alternative for execution in 1 . An advantage over the execution of the 1 is that the load on the low-pressure pump is lower in normal operation because the cooling oil volume flow does not have to flow over the control edge of the relief valve 8.

The execution in 4 is an alternative for execution in 2 . Here the volume flow can be distributed between tank 9 and cooling via a diaphragm (flow diaphragm 15). Of course, the aperture effect can also be achieved directly using a suitable valve design.

Reference symbol list

1

Hydraulic system

2

first line

3

first pump

4

second line

5

second pump

6

Electric motor

7

Primary valve

8th

Relief valve

9

tank

10

Coolant and lubricant supply device

11

first line section

12

Relief line

13

Entrance page

14

Home page

15

Flow diaphragm

16

drive shaft

17

consumer

18

Pressure return

19

second line section

20

Feather

QUOTES INCLUDED IN THE DESCRIPTION

This list of documents listed 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.

Cited patent literature

• DE 102020131788 A1 [0002]

Claims (7)

Hydraulic system (1) for a motor vehicle drive device, with a first pump (3) connected on the output side to a first line (2), a second pump (5) connected on the output side to a second line (4) and one for driving both pumps simultaneously ( 3, 5) used electric motor (6), the first pump (3) being designed to generate a higher system pressure in the first line (2) than the second pump (5) in the second line (4), and between the A primary valve (7) is inserted into both lines (2, 4) in such a way that the lines (2, 4) are connected to one another in a first position of the primary valve (7) and the first line is connected to one another in a second position of the primary valve (7). (2) is separated from the second line (4), characterized in that there is also a relief valve (8) which, depending on a pressure present in the first line (2), automatically connects the second line (4) to a tank (2) 9) opens. Hydraulic system (1). Claim 1 , characterized in that the relief valve (8) has a rest position in which the second line (4) is connected to a line section (11) which can be connected or connected to a coolant and/or lubricant supply device (10) and from a line section (11) directly to the Tank (9) leading relief line (12) is separated. Hydraulic system (1). Claim 1 or 2 , characterized in that the relief valve (8) is designed such that when a maximum pressure within the first line (2) is exceeded, it switches from its rest position to a relief position, in which relief position the second line (4) to the tank (9) is open. Hydraulic system (1). Claim 3 , characterized in that the second line (4) in the relief position of the relief valve (8) is separated from the line section (11) which can be connected or connected to the coolant and/or lubricant supply device (10) or is connected indirectly to this line section (11). the relief valve (12) or is directly connected. Hydraulic system (1) according to one of the Claims 1 until 4 , characterized in that on an inlet side (13) of the relief valve (12), which is hydraulically connected to the second pump (5), a flow orifice (15) is integrated in the second line (4) or directly through the relief valve (8 ) is trained. Hydraulic system (1) according to one of the Claims 1 until 5 , characterized in that the relief valve (8) is designed as a 3/2-way valve. Hydraulic system (1) according to one of the Claims 1 until 6 , characterized in that the primary valve (7) is designed as a 2/2-way valve.

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