DE102020004243A1 - Hydraulic system for a transmission of a motor vehicle, in particular a motor vehicle - Google Patents

Abstract

The invention relates to a hydraulic system (10) for a transmission of a motor vehicle, with an electric hydraulic pump (12) for conveying a hydraulic fluid, with at least one hydraulic cylinder (22), by means of which a shifting element of the transmission can be actuated by actuating the hydraulic cylinder (22), and with a solenoid-operated working pressure valve (34) which has: a first connection (A1) which is fluidically connected directly to a sump (40) for receiving the hydraulic fluid; a second connection (A2) which is fluidically connected directly to the electric hydraulic pump (12); a third connection (A3) via which the hydraulic fluid conveyed by means of the hydraulic pump (12) for actuating the hydraulic cylinder (22) can be fed to the hydraulic cylinder (22); in a flow path (SP) running from the second connection (A2) to the first connection (A1) in at least one switching state of the working pressure valve (34), through which at least in the at least one switching state the second connection (A2) is connected to the first connection ( A1) is short-circuited.

Description

The invention relates to a hydraulic system for a transmission of a motor vehicle, in particular a motor vehicle.

Of the WO 2012/025192 A1 a hydraulic control for an automatic transmission of a motor vehicle can be seen as known, with a parking lock actuation system, which has a parking lock slide and a parking lock piston-cylinder unit with a parking lock piston and a first parking lock pressure chamber.

The object of the present invention is to create a hydraulic system for a transmission of a motor vehicle, so that particularly low costs and particularly efficient operation of the hydraulic system can be achieved.

This object is achieved by a hydraulic system with the features of claim 1. Advantageous configurations with expedient developments of the invention are specified in the remaining claims.

The invention relates to a hydraulic system for a transmission, in particular for an automatic transmission, of a motor vehicle, in particular a motor vehicle. This means that the motor vehicle is preferably designed as a motor vehicle, in particular as a passenger vehicle, and has the transmission in its fully manufactured state. For example, in its fully manufactured state, the motor vehicle also has a drive motor by means of which the motor vehicle can be driven via the transmission. In particular, at least one wheel of the motor vehicle, also referred to as a vehicle wheel, and the transmission can be driven by the drive motor. For example, at least or precisely two vehicle wheels of the motor vehicle can be driven by the drive motor via the transmission. The respective wheel is a ground contact element by means of which the motor vehicle can be or is supported on a ground in the vertical direction of the vehicle downwards. If the motor vehicle is driven along the floor while the motor vehicle is supported in the vertical direction of the vehicle downwards on the floor via the wheel, the wheel rolls on the floor. The drive motor can be an internal combustion engine or an electric machine, so that the motor vehicle can preferably be a hybrid or an electric vehicle, in particular a battery-electric vehicle (BEV).

The hydraulic system comprises an adjustable electric hydraulic pump for delivering a hydraulic fluid. The feature that the hydraulic pump is adjustable means that a speed and / or a delivery rate of the pump can be controlled. The feature that the hydraulic pump, which is also simply referred to as a pump, is electric, is to be understood in particular that the hydraulic pump can be operated electrically, that is to say can be operated using electrical energy or electrical current. The hydraulic fluid is preferably a liquid. By electrically operating the hydraulic pump, the hydraulic fluid is conveyed by means of the hydraulic pump. The hydraulic system also includes a hydraulic cylinder, which is also referred to as a piston-cylinder unit. By means of the hydraulic cylinder, at least one shift element of the transmission can be actuated, in particular hydraulically, by actuation, in particular by hydraulic actuation, of the hydraulic cylinder. By means of the switching element, for example, at least two transmission elements of the transmission can be connected to one another in a rotationally fixed manner. In other words, the switching element can be switched or adjusted, for example, between a coupling state and a decoupling state. In the coupling state, the gear elements are connected to one another in a rotationally fixed manner by means of the shift element. In the decoupling state, the switching element releases the transmission elements for rotation relative to one another about a transmission element axis of rotation. For example, by actuating the switching element, the switching element can be switched from the decoupling state to the coupling state and / or from the coupling state to the decoupling state. The shifting element can be a positive shifting element such as a claw or claw clutch or a frictional shifting element such as a friction or multi-disc brake. The hydraulic cylinder comprises, for example, a housing and a piston which is arranged in the housing such that it can be moved in a translatory manner. For example, the housing forms or delimits a cylinder in which, for example, the piston is arranged such that it can be moved in a translatory manner. For example, the housing and the piston each partially and each directly delimit an actuation space into which the hydraulic fluid can be introduced. The hydraulic cylinder can be or is actuated by introducing the hydraulic fluid. For example, the hydraulic fluid is applied to the piston, in particular directly, when the hydraulic fluid is introduced into the actuation chamber. As a result, the piston is moved in a translatory manner relative to the housing.

The hydraulic system also includes a solenoid operated line pressure valve. The feature that the working pressure valve, also referred to simply as a valve, is solenoid-operated, can in particular be understood to mean the following: The valve can be a valve housing and a valve element have which, in particular translationally, is movably received in the valve housing. The valve can have at least one first valve connection and at least one second valve connection. The valve element can, for example, be moved relative to the housing between at least one first position and at least one second position, in particular in a translatory manner.

The valve also has a magnet, in particular designed as an electromagnet, as an actuator, which can be supplied with electrical energy or electrical current. By supplying the actuator with electrical energy or electrical current, the actuator provides a magnetic field, for example, by means of which, for example, the valve element from one of the positions to the other position and / or from the other position to the one position relative to the housing, in particular translationally, can be moved. In other words, the magnetic field can bring about a movement of the valve element from one position into the other position and / or from the other position into one position.

The working pressure valve, in particular its valve housing, now has a first connection, a second connection and a third connection. Exactly one of the connections can be one of the valve connections mentioned above, or exactly two of the connections can be the valve connections mentioned above. The first connection is now fluidically connected directly to a sump for receiving the hydraulic fluid. The sump is, for example, a tank, the hydraulic fluid being or being received in the sump. The second connection is fluidically connected directly to the electric hydraulic pump. The feature that the first connection is fluidically connected directly to the sump is to be understood in particular that the first connection is fluidically connected to the sump via a first channel, wherein in the first channel, based on its complete, in particular uninterrupted from the The first connection to the sump extending extension is free of an adjustable valve device, which is adjustable between a first state blocking at least part of a flow cross-section of the first channel through which the hydraulic fluid can flow and a second state which releases the part. Accordingly, the feature that the second connection is fluidically connected directly to the electric hydraulic pump is to be understood, for example, as meaning that the second connection is fluidically connected to the hydraulic pump via a second channel. In the second channel, based on its complete, in particular uninterrupted extension from the second connection to the hydraulic pump, there is no switchable or adjustable valve device that is located between an at least part of a flow cross-section of the second channel through which the hydraulic fluid can flow and a state which blocks part of the Flow cross-section of the second channel releasing state is switchable or adjustable. By means of the first channel, for example, the hydraulic fluid can be conducted from the first connection to or into the sump. With the second channel, for example, the hydraulic fluid conveyed by means of the hydraulic pump can be guided from the hydraulic pump to the second connection. The connections can each be traversed by the hydraulic fluid, in particular when the connections are or are released. The hydraulic fluid conveyed by means of the hydraulic pump for actuating the hydraulic cylinder can be fed to the hydraulic cylinder via the third connection. This means that the hydraulic fluid conveyed by means of the hydraulic pump flows, for example, from the hydraulic pump to the second connection and can flow through the second connection. The hydraulic fluid can flow from the second connection to the third connection and flow through the third connection, whereupon the hydraulic fluid can flow from the third connection to the hydraulic cylinder and in particular can flow into the actuation chamber. This actuates the hydraulic cylinder.

The working pressure valve also has in at least one switching state of the working pressure valve from the second connection to the first connection, in particular continuously or without interruption, through which at least in the at least one switching state the second connection is short-circuited with the first connection, so that the Hydraulic fluid flowing through the second connection, bypassing the third connection, can be guided from the second connection to the first connection and thereby diverted into the sump by bypassing the third connection, has exactly one control edge, with the first connection being able to be released and locked by means of precisely one control edge. The feature that the second connection is short-circuited with the first connection through the flow path can be understood in particular to mean that the hydraulic fluid which flows through the second connection and thus flows into the valve, in particular the valve housing, via the second connection, from the second connection can flow via the flow path or along the flow path directly to the first connection and then flow through the first connection so that the hydraulic fluid flowing through the flow path on its way from the second connection to the first Connection bypasses the third connection, that is, does not flow through the third connection. Thus, the hydraulic fluid conveyed through the second connection, for example by means of the hydraulic pump, in particular from the sump, flows from the second connection directly to the first connection, through the first connection and back into the sump via the first connection without closing the third connection flow through and thus without actuating the hydraulic cylinder. In this way, for example, at least part of the hydraulic fluid conveyed through the second connection by means of the hydraulic pump can be diverted so that at least the mentioned part does not flow through the third connection, but is (again) led (back) to the sump. This can take place in particular when a pressure of the hydraulic fluid at the third connection and / or at the second connection is so great that the pressure of the hydraulic fluid exceeds a particularly predeterminable or predetermined threshold value, so that exactly one control edge initially blocking the first connection releases the first port.

The invention is based in particular on the following findings: A classic and, for example, directly controlled pressure control valve can, for example, regulate or control an inflow quantity of a hydraulic medium, in particular designed as an oil or liquid, coming from a pump, that is to say adjust, which, however, leads to the hydraulic system according to the invention can, that a volume flow of the hydraulic fluid, for example designed as oil, comes to a standstill, whereby the hydraulic pump can in particular be braked to a standstill. In addition, pressure peaks and drops in pressure can occur, especially in regulated pressure.

In principle, it is conceivable to use orifices in a pump line or in a channel in order to ensure a minimum speed of the electrically operated hydraulic pump. However, this leads to high losses, in particular to high pressure or flow losses, at high pressures.

However, the aforementioned problems and disadvantages can now be avoided. The solenoid-operated working pressure valve can be used as a directly controlled pressure relief valve that does not limit an inflow, in particular of the hydraulic fluid to the hydraulic cylinder, but regulates or controls or sets a system pressure of the hydraulic fluid via the first connection, also known as a tank or sump connection, for example. Since the working pressure valve in the flow path does not have several control edges and thus not two control edges, but only one control edge in the form of precisely one control edge, a first channel coming from the pump and leading to the working pressure valve can be prevented from being closed, so that an abrupt standstill of the hydraulic medium and thus also of the hydraulic pump can be avoided. The working pressure valve can be controlled or regulated directly, that is to say operated, by means of the magnet which functions or is designed, for example, as a regulating magnet, in particular instead of a pilot control using a spring and a pressure regulating connection. Costly orifices can be avoided so that the hydraulic system can be operated in a particularly energy-efficient manner in a particularly cost-effective manner. In this way, for example, the energy consumption and thus in particular the CO ₂ emissions of the motor vehicle can be kept within a particularly low range, in particular compared to a pilot-controlled working pressure system.

The invention is therefore characterized in particular by the combination of the solenoid-operated, and non-pilot-operated, working pressure valve with the adjustable electric hydraulic pump, the working pressure valve having precisely one control edge.

Further advantages, features and details of the invention emerge from the following description of preferred exemplary embodiments and on the basis of the drawing.

• 1 ausschnittsweise eine schematische Darstellung einer ersten Ausführungsform eines erfindungsgemäßen Hydrauliksystems für ein Getriebe eines Kraftfahrzeugs;
• 2 ausschnittsweise eine schematische Darstellung einer zweiten Ausführungsform des Hydrauliksystems;
• 3a eine schematische Darstellung eines magnetbetätigten Arbeitsdruckventils des Hydrauliksystems;
• 3b ausschnittsweise eine schematische Detaildarstellung des Arbeitsdruckventils gemäß 3a;
• 4a eine schematische Darstellung eines Regelmagnetventils des Hydrauliksystems; und
• 4b ausschnittsweise eine schematische Detaildarstellung des Regelmagnetventils gemäß 4a.

The drawing shows in:

• 1 a section of a schematic representation of a first embodiment of a hydraulic system according to the invention for a transmission of a motor vehicle;
• 2 a section of a schematic representation of a second embodiment of the hydraulic system;
• 3a a schematic representation of a solenoid-operated working pressure valve of the hydraulic system;
• 3b excerpts from a schematic detailed representation of the working pressure valve according to FIG 3a ;
• 4a a schematic representation of a control solenoid valve of the hydraulic system; and
• 4b excerpts from a schematic detailed representation of the control solenoid valve according to FIG 4a .

Identical or functionally identical elements are provided with the same reference symbols in the figures.

1 shows a section of a first embodiment of a hydraulic system in a schematic representation 10 for a transmission, in particular an automatic transmission, of a motor vehicle, in particular a motor vehicle preferably designed as a passenger vehicle. The motor vehicle is preferably designed as an electric vehicle, in particular as a battery-electric vehicle, and thus has, in a completely manufactured state, at least one electric machine as a traction machine and the transmission, via which at least or precisely two wheels of the motor vehicle of the motor vehicle and thus the motor vehicle as a whole, in particular can be driven purely electrically by the electric machine. The hydraulic system 10 has an electric hydraulic pump 12th which is also referred to simply as a pump. By means of the hydraulic pump 12th can be a preferably liquid and thus preferably designed as hydraulic fluid hydraulic fluid, in particular from a fluid sump 14th , are promoted. The hydraulic pump 12th a conveyor element 16 which is received, for example, in a pump housing and is movable, in particular rotatable, relative to the pump housing. By moving the conveyor element 16 relative to the pump housing is by means of the delivery element 16 the hydraulic fluid promoted. The hydraulic pump 12th also has an electric motor 18th on, which can be operated by means of electrical energy or electrical current. By operating the electric motor 18th is by means of the electric motor 18th the conveying element 16 driven and thereby moved relative to the pump housing. In 1 is by a double arrow 20th illustrates that the hydraulic pump 12th is designed as a reversing pump. This means that the conveying element 16 by means of the electric motor 18th can be moved, in particular rotated, in a first direction of movement, in particular in a first direction of rotation, relative to the pump housing. In addition, the conveying element 16 by means of the electric motor 18th in a second direction of movement opposite to the first direction of movement, in particular in a second direction of rotation opposite to the first direction of rotation, in particular rotated. By moving the conveyor element 16 the hydraulic fluid is moved in the first direction of movement by means of the hydraulic pump 12th conveyed in a first conveying direction, in particular through the pump housing. By moving the conveyor element 16 The hydraulic fluid is moved in the second direction of movement, for example by means of the hydraulic pump 12th conveyed in a second conveying direction opposite to the first conveying direction, in particular through the pump housing.

The hydraulic system 10 also has at least one hydraulic cylinder 22nd on, by means of which by actuating the hydraulic cylinder 22nd at least one switching element of the transmission can be actuated. The hydraulic cylinder 22nd is also referred to as a piston-cylinder unit and has a housing 24 and a piston 26th on, which is along a direction of movement relative to the housing 24 , in particular translationally, is movable. Also includes the hydraulic cylinder 22nd a piston rod 28 which with the piston 26th relative to the housing 24 is movable. The piston 26th and the case 24 each partially and directly delimit an actuation space, also referred to as a working chamber 30th of the hydraulic cylinder 22nd . This is done by means of the hydraulic pump 12th pumped hydraulic fluid in the actuation space 30th initiated, the hydraulic cylinder is thereby initiated 22nd actuated. In doing so, the piston 26th related to the image plane of 1 to the right relative to the housing 24 moves, causing the piston rod 28 at least a piece of the case 24 is pushed out.

The hydraulic cylinder 22nd also has a particularly mechanical spring element 32 on, which along the direction of movement on the one hand on the piston 26th and on the other hand on the housing 24 is in each case directly or indirectly supportable or supported. By moving the piston 26th related to the image plane of 1 to the right is the spring element 32 tensioned, in particular compressed, whereby the spring element 32 provides a spring force. By means of the spring force, the piston 26th and with this the piston rod 28 related to the image plane of 1 relative to the housing 24 be moved to the left, for example, initially in the actuation space 30th absorbed hydraulic fluid from the actuation space 30th is promoted out.

The hydraulic system 10 also has a solenoid operated working pressure valve 34 on, which is also simply referred to as a valve. As will be explained in more detail below, the hydraulic cylinder 22nd , in particular its operating space 30th , via the valve with the hydraulic pump 12th pumped hydraulic fluid are supplied. The working pressure valve 34 has, for example, a valve housing 36 and a valve element 38 on, which is at least partially, in particular at least predominantly or completely, in the valve housing 36 is recorded. The valve element 38 can be relative to the valve housing 36 , in particular in a translatory manner, moved, in particular moved back and forth. The working pressure valve 34 , especially the valve body 36 , has a first connection A1 on which immediately with a swamp 40 is fluidically connected for receiving the hydraulic fluid. This means that the hydraulic fluid is in the sump 40 recorded or recordable. By the swamp 40 can it be the Fluid sump 14th act, or the swamp 40 is an addition to the fluid sump 14th provided sump, which, for example, fluidically from the fluid sump 14th separate or to be separated. For example, the swamp 40 be a tank in which this is the first port A1 hydraulic fluid flowing through is at least temporarily absorbed or absorbed.

The working pressure valve 34 , especially the valve body 36 , also has a second connector A2 which directly connects to the hydraulic pump 12th is fluidically connected. The hydraulic system 10 have a first channel K1, which at one end is directly connected to the connection A2 and the other day directly with the hydraulic pump 12th is fluidically connected, with the first channel K1 not having an adjustable or switchable valve device for varying a flow cross-section of the channel K1 through which the hydraulic fluid can flow. The working pressure valve 34 , especially the valve body 36 , also has a third connector A3 on what that with the hydraulic pump 12th pumped hydraulic fluid for actuating the hydraulic cylinder 22nd the hydraulic cylinder 22nd is feedable. For example, the valve element 38 between a first position and a second position relative to the valve housing 36 , in particular translationally, are moved. For example, the connections are in the first position A2 and A3 fluidically connected to one another, so that the hydraulic fluid, which is generated by means of the hydraulic pump 12th conveyed and conveyed through the channel K1 and thus to the connection A2 is promoted and through the connection A2 conveyed through and thereby into the valve housing 36 is fed in from the port A2 to the connection A3 stream and connect A3 can flow through. From the connection A3 can do this by means of the hydraulic pump 12th sponsored and the connection A3 hydraulic fluid flowing through to the hydraulic cylinder 22nd flow into the control room 30th pour in. At the in 1 The first embodiment shown is the connector A3 directly to the hydraulic cylinder 22nd , especially with the control room 30th , fluidically connected. The hydraulic system 10 a second channel K2, which at one end is directly connected to the connection A3 and the other day directly with the control room 30th is fluidly connected, so that in the first embodiment the connection A2 directly to the hydraulic pump 12th is fluidically connected, and the actuation space 30th or the hydraulic cylinder 22nd is immediate with the connection A3 fluidically connected. This means that no adjustable or switchable valve device is arranged in the channel K2, by means of which a flow cross section of the channel K2 through which the hydraulic fluid can flow can be varied. It can be seen that in the first position the actuation space 30th over the connection A3 with the connector A2 is fluidically connected, so that in the actuation space 30th the hydraulic fluid can be conveyed in. In the second position, however, are, for example, the connection A3 and thus the operating space 30th by means of the valve element 38 from the connection A2 separated so that no hydraulic fluid in the actuation space 30th by means of the hydraulic pump 12th can be conveyed in. In particular, it is conceivable that in the second position the connection A3 by means of the valve element 38 is closed and thus fluidically blocked.

The working pressure valve 34 , especially the valve body 36 , can also have a control connection S1 have which, in particular directly, with the connection A3 can be fluidically connected. For example, is about the control connection S1 the valve element 38 with one on the connector A3 The prevailing pressure of the hydraulic fluid can be acted upon, in particular directly, as a result of which, for example, in particular when the said pressure exceeds a predeterminable or predefined threshold value, the valve element 38 from a first valve position into a second valve position relative to the valve housing 36 , in particular translationally, is movable. The first valve position is, for example, the aforementioned first position. The connection is, for example, in the first position and / or in the first valve position A2 from the swamp 40 , in particular by means of the valve element 38 , fluidically separated. It is preferably provided that in the second position and / or in the second valve position the connection A2 fluidically with the connection A1 is connected, making for example the connections A1 and A2 are short-circuited with each other. Alternatively or additionally, the second valve position can be the aforementioned second position.

3a shows the working pressure valve 34 . In 3b is the working pressure valve 34 shown partially in an enlarged, schematic detailed view. Out 3b it is particularly easy to see that the working pressure valve 34 in at least one switching state of the working pressure valve 34 from the second port A2 to the first connection A1 running flow path SP through which the second port A2 at least in the at least one switching state with the first connection A1 is short-circuited or can be short-circuited, so that the second connection A2 flowing through and thus via the second connection A2 into the valve body 36 incoming hydraulic fluid bypassing the third connection A3 from the second port A2 to the first connection A1 and thereby bypassing the third connection A3 the first connection A1 flow through it and then into the swamp 40 can be derived, exactly one control edge 42 having. For example, the working pressure valve takes 34 the at least one switching state in the above-mentioned second valve position or the second valve position causes the at least one switching state. The control edge 42 is in the present case by the valve element, for example at least partially designed as a piston 38 educated. By means of exactly one control edge 42 is the first connection A1 releasable and lockable. For example, the connection is in the first position and / or in the first valve position A1 by means of the control edge 42 blocked, that is, closed and thus, for example, from the connection A2 and the connection A3 fluidically separated. In the second position and / or in the second valve position, however, there is the control edge 42 or the valve element 38 the connection A1 free, so the connection A1 - while he is for example by means of the valve element 38 from the connection A3 is fluidically separated or while he is with the connection A3 is fluidically connected - in particular via the flow path SP fluidically with the connection A2 connected is. This can do this via the connection A2 into the valve body 36 incoming hydraulic fluid - without the connection A3 to flow through and thus without over the connection A3 in the control room 30th to flow in - via the flow path SP directly from the connector A2 to the connection A1 flow or by means of the hydraulic pump 12th be promoted. Costly screens can be avoided. Because in the flow path SP also only one control edge in the form of the exact one control edge 42 is arranged, in particular at high pressures of the fluid, excessive pressure losses of the fluid while it is from the connection A2 to the connection A1 and thereby through the flow path SP or along the flow path SP flows should be avoided.

By short-circuiting the connections A1 and A2 In particular, the following can be avoided: The piston 26th can for example be moved to the right in relation to the image planes of image 1 until the piston moves again 26th to the right is avoided, for example, by a stop. Thus, the hydraulic pump 12th only as long as hydraulic fluid in the actuation space 30th like the piston 26th can be moved to the right. After moving the plunger completely 26th to the right so that the piston 26th cannot be moved any further to the right, the pump can therefore no longer enter the actuation space 30th convey in, so that a volume or mass flow of the hydraulic fluid from the pump to the actuation chamber 30th come to a standstill and - if no appropriate countermeasures have been taken - the pump or its delivery element 16 can be braked to a standstill. This or an excessively long standstill of the pump or the delivery element 16 can now be avoided, however. After moving the plunger completely 26th to the right rises, for example, at the connection A3 and / or at the connection A2 the pressure of the hydraulic fluid so that the pressure of the hydraulic fluid exceeds, for example, the aforementioned threshold value. The valve element 38 is thereby moved by means of the pressure from the first position or from the first valve position into the second position or into the second valve position, whereby the first by means of the control edge 42 , in particular in the first valve position or in the first position, blocked connection A1 released and thus with the connection A2 is short-circuited. As a result, the flow path is formed SP along which the hydraulic fluid from the port A2 to the connection A1 flow while by means of the hydraulic pump 12th can be promoted. The hydraulic pump 12th or their conveying element 16 can thus continue to rotate and thereby remove the hydraulic fluid from the connection A2 to the connection A1 and doing it in the swamp 40 promote.

2 shows a second embodiment of the hydraulic system 10 . In the second embodiment, the hydraulic system 10 the hydraulic cylinder 22nd for actuating the switching element and at least one further hydraulic cylinder 44 to actuate at least one second shift element of the transmission. The previous and following statements on the first switching element and the first hydraulic cylinder 22nd can easily access the second switching element and the second hydraulic cylinder 44 transmitted and vice versa. In the second embodiment, the third is port A3 each directly with a first control solenoid valve 46 and with a second control solenoid valve additionally provided 48 fluidically connected. Via the control solenoid valve 46 is the connection A3 with the control room 30th of the hydraulic cylinder 22nd fluidically connected or connectable. Via the control solenoid valve 48 is the connection A3 with an operating room 50 of the hydraulic cylinder 44 fluidically connectable or connected. This means that the operating room 30th via the control solenoid valve 46 with the connection A3 hydraulic fluid flowing through can be supplied. As a result, the operating space is 50 via the control solenoid valve 48 with the connection A3 hydraulic fluid flowing through it can be supplied.

4a shows in a schematic representation a control solenoid valve also referred to as a pressure control solenoid valve 52 which is in 4b excerpts in an enlarged, schematic Detail view is shown. Basically the control solenoid valve could 52 instead of the working pressure valve 34 are used, however, the control solenoid valve 52 - as in 4b can be seen - in the flow path SP at least or exactly two control edges 42 and 54 so that the flow path SP of the control solenoid valve 52 hydraulic fluid flowing through opposite the working pressure valve 34 and its flow path SP would experience a greater pressure drop. This means that the use of the working pressure valve 34 , especially instead of the control solenoid valve 52 , a more energy-efficient operation of the hydraulic system 10 and thus the motor vehicle as a whole. In addition, costly orifices can be avoided, reducing the cost of the hydraulic system 10 can be kept particularly low.

Out 4b it can be seen that the control edge 54 the connection A2 is assigned so that the control edge 54 for example the connection A2 can release and block. By means of the control solenoid valve designed or functioning as a pressure control solenoid valve 52 For example, a pressure of the hydraulic fluid, in particular to the respective switching element or to the respective hydraulic cylinder, can be regulated, with the two control edges 42 and 54 Act. It is thus conceivable, for example, to use the control solenoid valve 52 than the respective control solenoid valve 46 respectively 48 to use. The control solenoid valve 46 , 48 and or 52 is - as the name suggests - magnet-operated.
For example, by means of the hydraulic pump 12th generated pressure of the hydraulic fluid, in particular in the first position and / or in the first valve position and thus for example via the connections A2 and A3 directly on the respective switching element or directly on the hydraulic cylinder 22nd and or 44 issue. The pressure is adjusted, in particular a regulation or control, by releasing excess hydraulic fluid, for example in the form of oil, via the control edge, which is also referred to as a sump or edge 42 . In this way, particularly efficient operation can be achieved, and so can the costs of the hydraulic system 10 can be kept particularly low.

List of reference symbols

10

Hydraulic system

12th

hydraulic pump

14th

Fluid sump

16

Conveying element

18th

Electric motor

20th

Double arrow

22nd

Hydraulic cylinder

24

casing

26th

piston

28

Piston rod

30th

Operating room

32

Spring element

34

Working pressure valve

36

Valve body

38

Valve element

40

swamp

42

Control edge

44

Hydraulic cylinder

46

Control solenoid valve

48

Control solenoid valve

50

Operating room

52

Control solenoid valve

54

Control edge

A1

first connection

A2

second connection

A3

third connection

S1

Control connection

SP

Flow path

QUOTES INCLUDED IN THE DESCRIPTION

This list of the 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.

Patent literature cited

• WO 2012/025192 A1 [0002]

Claims (3)

Hydraulic system (10) for a transmission of a motor vehicle, with an adjustable electric hydraulic pump (12) for conveying a hydraulic fluid, with at least one hydraulic cylinder (22), by means of which a switching element of the transmission can be actuated by actuating the hydraulic cylinder (22), and with a solenoid-operated working pressure valve (34), the working pressure valve (34) having: - A first connection (A1) which is fluidically connected directly to a sump (40) for receiving the hydraulic fluid; - A second connection (A2) which is fluidically connected directly to the electric hydraulic pump (12); - A third connection (A3) via which the hydraulic fluid conveyed by means of the hydraulic pump (12) for actuating the hydraulic cylinder (22) can be fed to the hydraulic cylinder (22); wherein the working pressure valve (34) in at least one switching state of the working pressure valve (34) running from the second connection (A2) to the first connection (A1) flow path (SP) through which at least in the at least one switching state the second connection (A2 ) is short-circuited to the first connection (A1) so that the hydraulic fluid flowing through the second connection (A2) can be guided from the second connection (A2) to the first connection (A1) along the flow path (SP), bypassing the third connection (A3) and thereby can be diverted into the sump (40) by bypassing the third connection (A3), has exactly one control edge (42), the first connection (A1) being able to be released and locked by means of the precisely one control edge (42). Hydraulic system (10) Claim 1 , characterized in that the third connection (A3) is fluidically connected directly to the hydraulic cylinder (22). Hydraulic system (10) Claim 1 , characterized in that the third connection (A3) is in each case directly fluidly connected to a first solenoid control valve (46) and a second solenoid control valve (48).

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