DE102020131788A1 - Hydraulic system with low pressure pump bypass circuit - Google Patents

Abstract

The invention relates to a hydraulic system (1) for a motor vehicle transmission, 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 with two pumps (3, 5) drivingly connected electric motor (6), wherein the first pump (3) is designed to generate a first system pressure in the first line (2) and the second pump (5) to generate a pressure opposite to the first system pressure increased, second system pressure in the second line (4), and wherein a valve (7) is inserted between the two lines (2, 4) so that in a first position of the valve (7) the lines (2, 4) are connected to one another and in a second position of the valve (7) the first line (2) is connected to a return tank (8) and / or is depressurized, while the second line (4) is separated from the first line (2) is separated.

Description

The invention relates to a hydraulic system for a transmission of a motor vehicle, such as a car, truck, bus or other utility vehicle.

In principle, it is known for hydraulic systems in which several consumers are to be supplied with different and varying working pressures that losses are caused by throttling the system pressure to the respective working pressure at the consumer and by throttling the excess volume flow from one system pressure level to tank pressure level or to a second lower level occur.

So there are already so-called “load sensing” systems that have the task of reducing throttling losses. A corresponding increase in efficiency takes place in these systems by adapting the measures to reduce the system losses to the respective specific hydraulic system, taking into account the requirements of the consumers. There are also versions of these systems that use two pumps, with these pumps supplying the consumers separately for high pressure and low pressure areas. It has also already been proposed to drive these two pumps by a common electric motor, the pumps always having the same speed.

A disadvantage of the last-mentioned embodiment, however, is that the common speed of the two pumps at certain operating points leads to volume flows that are not required at all, which is why the required power is unnecessarily increased. This in turn has to be taken into account when dimensioning the components, such as the electric motor.

It is therefore the object of the present invention to eliminate the disadvantages known from the prior art and, in particular, to provide a hydraulic system which is as simple and compact as possible and whose efficiency is further improved.

This is achieved according to the invention by the subject matter of claim 1. According to claim 1, a hydraulic system for a motor vehicle transmission, ie for supplying various consumers in or on a motor vehicle transmission, is claimed, which hydraulic system has a first pump connected to a first line on the output side, a second pump connected to a second line on the output side and a is equipped with both pumps driving / torque-transmitting connected electric motor, wherein the first pump is designed to generate a first system pressure in the first line and the second pump is designed to generate a, compared to the first system pressure, increased, second system pressure in the second line, and wherein a valve is inserted between the two lines so that in a first position of the valve the lines are connected to one another and in a second position of the valve the first line is connected to a return tank and / or is depressurized while the second line is disconnected from the first line.

The presented valve according to the invention thus not only disconnects the connection between the two pumps in one (the second) valve position, but also connects the volume flow with the lower pressure level to the return tank or switches it to an unpressurized circulation. This reduces the torque on the low-pressure side and avoids or dampens the power peak that otherwise occurs on the electric motor. Because of the mechanical connection between the two pumps, it would not be possible to reduce the pressure on the low-pressure side by reducing the speed. In this way, the electric motor can be made smaller, which leads to advantages in terms of installation space and costs.

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

If the valve is equipped as a valve with three connections and two valve positions (analogous to a 3/2-way valve), the structure of the hydraulic system is kept as simple as possible.

The valve works particularly efficiently if it is designed in such a way that the first position corresponds to a (preferably spring-preloaded) rest position.

It is also advantageous if the second line, viewed along its course away from an outlet of the second pump, has a non-return valve on a side facing away from the second pump and the valve, which (is arranged such that there is) a backflow of liquid blocks towards the output of the second pump.

In addition, it is advantageous if the first line is connected to a first (low-pressure) consumer, which preferably forms a cooling and / or lubricating supply (preferably within a transmission).

In this regard, it is again expedient if the second line is provided with at least one, preferably one, clutch actuation device and / or a second (high pressure) consumer forming a gear shifting device is connected.

The structure of the hydraulic system is also kept as simple as possible in that the drive shaft of the electric motor is (directly) connected to both a pump drive (/ drive shaft) of the first pump and a pump drive (/ drive shaft) of the second pump.

In addition, it is advantageous if the valve is provided with a pressure return (preferably connected to the second line).

Thus, according to a further preferred embodiment, the valve is designed as a pressure regulating valve.

In other words, a hydraulic system with a low-pressure pump bypass circuit is thus implemented according to the invention. Here, a valve is arranged in the hydraulic line that connects the two pumps to one another, which in the first position enables the two pumps to be connected to the area of the lower pressure level and in a second position disconnects this connection and at the same time the pump on the side of the connects lower pressure levels to the tank or switches to an unpressurized circulation. In this way, the electric motor can be made smaller, which leads to advantages in terms of installation space and costs.

The invention will now be explained in more detail below with reference to figures, in which context various exemplary embodiments are also shown.

• 1 einen Schaltplan eines Teils eines, nach einem ersten Ausführungsbeispiel ausgebildeten, erfindungsgemäßen Hydrauliksystems, wobei zwei, jeweils an eine Leitung angeschlossene, durch einen gemeinsamen Elektromotor angetriebene Pumpen sowie ein die beiden Leitungen koppelndes Ventil gut zu erkennen sind, sowie
• 2 einen Schaltplan eines Teils eines Hydrauliksystems nach einem zweiten Ausführungsbeispiel, das sich gegenüber dem ersten Ausführungsbeispiel unter anderem dadurch unterscheidet, dass in einer zweiten Ventilstellung des Ventils eine mit einer ersten Pumpe verbundene erste Leitung nicht, wie in 1, mit einem Rückführtank direkt verbunden, sondern in einen drucklosen Umlauf geschaltet ist.

Show it:

• 1 a circuit diagram of a part of a hydraulic system according to the invention, designed according to a first exemplary embodiment, wherein two pumps, each connected to a line, driven by a common electric motor and a valve coupling the two lines can be clearly seen, and
• 2 a circuit diagram of part of a hydraulic system according to a second embodiment, which differs from the first embodiment, among other things, in that in a second valve position of the valve a first line connected to a first pump is not, as in 1 , is directly connected to a return tank, but switched to a pressureless circulation.

The figures are merely of a schematic nature and are used exclusively for understanding the invention. The same elements are provided with the same reference symbols.

A basic structure of the hydraulic system according to the invention 1 is initially associated with 1 explained. In this context, it should be noted that the hydraulic system 1 is preferably used in a motor vehicle for supplying several consumers, which are not shown here for the sake of clarity, more preferably in a transmission. In an area of the hydraulic system marked with "ND" 1 , speak to a first line 2 , connects at least one first consumer during operation, which preferably forms a coolant and lubricant supply device. In an area of the hydraulic system marked with "HD", i.e. on a second line 4th , a second consumer connects at least during operation. It is further preferred to connect to this second line 4th even several second consumers. Every second consumer is preferably implemented as a clutch actuation device or a gear actuation device / gear shift device. The at least one second consumer therefore requires a higher system pressure than the at least one first consumer, so that the second line 4th is also referred to as the high pressure line, while the first line 2 is designated as a low pressure line.

To supply the lines 2 , 4th is per line 2 , 4th a pump 3 , 5 intended. The first line 2 closes at an exit 9 a first pump 3 at. The second line 4th closes at an exit 10 a second pump 5 at. Both pumps 3 , 5 are used to generate different system pressures in the lines 2 , 4th educated. The first pump 3 is configured to generate a first system pressure that is lower than a second system pressure that is generated by the second pump 5 is produced.

Furthermore, both are pumps 3 , 5 by a common electric motor 6th driven. The electric motor 6th has a mechanical coupling that works together with the pump drives 13th , 14th of the two pumps 3 , 5 connected is. To put it more concretely, the electric motor 6th a schematically shown drive shaft 12th (Rotor shaft) with the indicated pump drives 13th , 14th of pumps 3 , 5 is connected together. The two pumps 3 , 5 are thus in operation by the electric motor 6th driven at a common speed.

Both lines are according to the invention 2 , 4th via a valve 7th , which is designed in terms of its connections and valve positions according to a 2/3-way valve, coupled or can be coupled. At a first connection 21a of the valve 7th is the first line 2 connected. At a second connection 21b of the valve 7th is the second line 4th connected. At a third connection 21c of the valve 7th is a recovery tank in this version 8th connected.

The valve 7th is designed in such a way that there is a first position in which the two lines 2 , 4th are directly connected to each other, implemented as a rest position. The first position of the valve 7th is by a bias spring 19th supported. In a second position of the valve 7th is the second line 4th from the first line 2 severed. At the same time is the first line 2 in this second position with the return tank 8th , for example the tank 18th corresponds, connected. The second line 4th is also in the second position of the recycle tank 8th severed.

It can also be seen that both pumps 3 , 5 each with their input 16 , 17th with a tank 18th are connected. tank 18th and return tank 8th are in turn connected to one another or carried out together in the usual way. Is also in 1 recognizable that the valve 7th is implemented in a typical manner as a solenoid valve.

The moreover one is the valve 7th in this version, with the formation of a pressure control valve, with a pressure return 15th provided in such a way on a for the sake of clarity, not shown sliding element / a piston of the valve 7th acts that it pushes the piston on one of the biasing springs 19th facing active side with the second line 4th connects.

Also on the part of the second line 4th a check valve 11 available. The check valve 11 is in a section of the second line 4th arranged on a portion of the second line 4th that connects to the output 10 and the valve 7th connected. The check valve 11 is used in such a way that there is a return of hydraulic medium from the at least one second consumer to the second pump 5 locks.

The second embodiment according to 2 is essentially constructed like the first exemplary embodiment, so that, for the sake of brevity, only the differences between these two exemplary embodiments are described below.

It is with 2 recognizable that the valve 7th is now arranged in a slightly different way and further connected. In this context it becomes clear that the third connection 21c of the valve 7th , which in the first embodiment is still with the return tank 8th was connected, now with an entrance 16 the first pump 3 connected is. In the first position of the valve 7th are still the two lines 2 , 4th connected with each other. The first line is in the second position 2 and consequently the outcome 9 the first pump 3 with the entrance 16 same pump 3 connected. The second line 4th is still from the first line in this second position 2 severed. As the entrance 16 turn with the tank 18th connected, it occurs in the second position of the valve 7th to a pressureless circulation of the by the first pump 3 pumped hydraulic fluid.

In this second embodiment, there are also both inputs 16 , 17th of pumps 3 , 5 via a common feed line 20th with the tank 18th connected.

In other words, according to the invention, in the hydraulic line, the two pumps 3 , 5 connects to each other, a valve 7th arranged, the connection of the two pumps in the first position 3 , 5 with the range of the lower pressure level and in a second position this connection separates and at the same time the pump 3 on the side of the lower pressure level, eg the side that is used to provide a cooling and lubricating oil volume flow, with the tank 8th connects or switches into a pressureless circuit.

The presented solution for avoiding power peaks in a hydraulic system 1 with two hydraulically connectable jointly driven pumps 3 , 5 preferably includes an electromagnetically actuated 3/2-way valve 7 with optional pressure return 15th . Should the volume flows of both pumps 3 , 5 used for cooling and lubrication, so is the valve 7th in its inoperative basic position (first position). Now the volume flow of a pump 5 is required for another consumer with a higher pressure level, the valve 7th actuates and blocks the connection between the two pumps 3 , 5 so that a higher pressure level on a pump 5 can arise. Due to the higher pressure level, there would now be a higher torque on the drive motor 6th arise that would have to be taken into account in the design. Through the presented valve 7th but according to the invention not only the connection between the two pumps 3 , 5 separated, but also the volume flow with the lower pressure level with the tank 8th connected ( 1 ) or switched to unpressurized circulation ( 2 ). This reduces the torque on the low-pressure side and avoids or dampens the power peak that otherwise occurs on the drive motor 6th . Due to the mechanical connection between the two pumps 3 , 5 it would not be possible to reduce the pressure on the low-pressure side by reducing the speed. That way the engine can 6th be dimensioned smaller, which leads to space and cost advantages.

List of reference symbols

1

Hydraulic system

2

first line

3

first pump

4th

second line

5

second pump

6th

Electric motor

7th

Valve

8th

Recovery tank

9

Output of the first pump

10

Second pump output

11

check valve

12th

drive shaft

13th

Pump drive of the first pump

14th

Pump drive of the second pump

15th

Pressure return

16

Input of the first pump

17th

Second pump input

18th

tank

19th

Preload spring

20th

Feed line

21a

first connection

21b

second connection

21c

third connection

Claims (9)

Hydraulic system (1) for a motor vehicle transmission, 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 with both pumps (3 , 5) drivingly connected electric motor (6), the first pump (3) being designed to generate a first system pressure in the first line (2) and the second pump (5) being designed to generate a second system pressure that is higher than the first system pressure in the second line (4), and wherein a valve (7) is inserted between the two lines (2, 4) so that the lines (2, 4) are connected to one another in a first position of the valve (7) and in a second position of the valve (7) the first line (2) is connected to a return tank (8) and / or is depressurized, while the second line (4) is separated from the first line (2). Hydraulic system (1) Claim 1 , characterized in that the valve (7) is equipped with three connections (21a, 21b, 21c) and two valve positions. Hydraulic system (1) Claim 1 or 2 , characterized in that the valve (7) is designed such that the first position corresponds to a rest position. Hydraulic system (1) according to one of the Claims 1 to 3 , characterized in that the second line (4), viewed along its course from an outlet (10) of the second pump (5), has a check valve (11) on a side facing away from the second pump (5) and the valve (7) ) which blocks a backflow of liquid towards the outlet (10) of the second pump (5). Hydraulic system (1) according to one of the Claims 1 to 4th , characterized in that the first line (2) is connected to a cooling and / or lubricating supply. Hydraulic system (1) according to one of the Claims 1 to 5 , characterized in that the second line (4) is connected to a clutch actuation device and / or a gear shift device. Hydraulic system (1) according to one of the Claims 1 to 6th , characterized in that the electric motor (6) with its drive shaft (12) is connected both to a pump drive (13) of the first pump (3) and to a pump drive (14) of the second pump (5). Hydraulic system (1) according to one of the Claims 1 to 7th , characterized in that the valve (7) is provided with a pressure return (15) connected to the second line (4). Hydraulic system (1) according to one of the Claims 1 to 8th , characterized in that the valve (7) is designed as a pressure control valve.

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