WO2013017202A1

WO2013017202A1 - Hydraulic controller for an automatic transmission of a motor vehicle

Info

Publication number: WO2013017202A1
Application number: PCT/EP2012/002999
Authority: WO
Inventors: Michael Baraga; Markus Brandenburg; Henrik Kalczynski; Thomas Kull
Original assignee: Daimler Ag
Priority date: 2011-08-04
Filing date: 2012-07-17
Publication date: 2013-02-07
Also published as: DE102011109377A1

Abstract

The invention is based on a hydraulic controller for an automatic transmission with a pilot control valve (20) which can be used to set a pilot control pressure which can be conducted as control pressure both to a first valve unit (19) and to a second valve unit (45). According to the invention, the hydraulic controller has a third valve unit (80) to which the pilot control pressure set by means of the pilot control valve (20) can be conducted as control pressure. In addition, a counter pressure acting counter to the control pressure can be applied via a counter pressure line (85) to the third valve unit (80) and therefore actuation of the third valve unit (80) can be prevented even in the event of a high control pressure. It is therefore advantageously possible to use just one pilot control valve to activate three valve units.

Description

Hydraulic control for an automatic transmission of a motor vehicle

The invention relates to a hydraulic control for an automatic transmission of a motor vehicle according to the preamble of claim 1.

DE 10 2009 018 982 A1 describes a hydraulic control for a

Automatic transmission of a motor vehicle in the form of a hybrid vehicle. The hydraulic control comprises a pilot valve, with which a pilot pressure can be set, which can be passed as a control pressure both to a first valve unit for actuating a separating clutch, as well as to a second valve unit for actuating a parking brake.

In contrast, it is the object of the invention to propose a hydraulic control for an automatic transmission, which requires few hydraulic components. According to the invention, the object by a hydraulic control with the

Characteristics of claim 1 solved.

According to the invention, the hydraulic control has a third valve unit, to which the pilot control pressure set by means of the pilot control valve can be conducted as control pressure. In addition, it is possible to apply a counterpressure acting against the control pressure to the third valve unit via a counterpressure line, thereby preventing actuation of the third valve unit. Thus, it is advantageously possible with only one

Pilot valve three control units safely to control. At the same time by the application of the back pressure to the third valve unit, the actuation of the third

Valve unit be prevented, so that the first or especially the second

Valve unit can be operated without the third valve unit is operated simultaneously. This allows a large number of different control options of the individual valve units with only one pilot valve and thus a large

Functional range of the hydraulic control with few hydraulic components. For actuation of the first, second and third valve unit respectively a first, second and third pressure range provided. This is to be understood in the case of a switching valve that changes in the state or the behavior of the switching valve result from changes in the control pressure within the pressure range assigned to the switching valve. In this case, a change in the switching position of the slide valve is achieved by changing the control pressure from one boundary to the other limit of the pressure range. An increase in the control pressure above an upper limit or a reduction below a lower limit of the respective associated pressure range then has no further

Effect on the switching position of the slide switch. In the case of a valve unit designed as a control slide, the adjusted pressure or the flow rate changes with changes within the pressure range. It is also possible that in the case in which the control pressure is outside the assigned pressure range, it still has influence on the adjusted pressure or the flow rate. The

Pressure ranges may overlap, but it is also possible that there is an area between each of the pressure ranges that is not associated with any of the pressure ranges. The first, second and third pressure region are in particular in the direction

increasing pressure arranged one after the other. For example, the first valve unit is a pressure range of about 0 to 3 bar, the second valve unit a pressure range of 4 to 5 bar and the third valve unit associated with a pressure range of 6 to 8 bar.

Due to the back pressure on the third valve unit, an actuation of the third valve unit can be reliably avoided, in particular in the case of a desired actuation of the second valve unit. By the division of the pressure areas this should actually not happen. However, it may due to component tolerances, wear or aging of the hydraulic components to shifts and / or overlaps of the

Pressure ranges and thus come to unwanted operations of the third valve unit. By applying the back pressure to the third valve unit, safe operation of the hydraulic control can be enabled.

However, it is also possible that the third pressure range is arranged between the first and the second pressure range. For example, the first valve unit, a pressure range of about 0 to 3 bar, the third valve unit, a pressure range of 4 to 5 bar and the second valve unit, a pressure range of 6 to 8 bar are assigned.

By preventing the actuation of the third valve unit by the back pressure, the first or second valve unit can be actuated without the activation having effects on the third valve unit. In the example mentioned, the second Valve unit can be controlled without the third valve unit is actuated. Thus, the second and third valve unit can be controlled independently of each other by only one pilot valve.

The automatic transmission is designed, for example, as a transmission with several coupled planetary gear sets. It is designed in particular as an automatic transmission according to DE 10 2008 055 626 A1 of the applicant. The automatic transmission can also be used, for example, as an automated change-speed gearbox, as

Double clutch transmission or be designed as a continuously variable transmission.

The pilot valve is designed, for example, as a control solenoid valve, in particular as a so-called direct control valve. The pilot valve is with a

Supply pressure, for example in the form of a working pressure or a

Valve supply pressure supplied and derived therefrom according to the control by an electronic transmission control from a desired pilot pressure.

The valve units are in particular as slide valves, for example as

Slide gate or control slide executed.

Under an actuation of the third valve unit is in particular a change of a switching position of the third valve unit or a change of one of the third

Valve unit set pressure or flow to understand.

The third valve unit is designed in particular as a slide switch, on the slider on one side of the pilot pressure as the control pressure and on a

opposite side of the slide can act on the back pressure. In addition, the third valve unit in particular has a spring which can apply a force acting counter to the pilot pressure on the slide. By an appropriate design of the effective areas on the slide, the pressure ranges of the pilot and the counter pressure and optionally the spring can be ensured that an actuation of the valve unit can be prevented by applying a back pressure to the third valve unit. In this case, an actuation of the valve unit to understand the change in the switching position of the switching valve.

In an embodiment of the invention, the back pressure, which can act on the third valve unit against the control pressure, derived from a pressure, mainly a fulfills another function. By the phrase "mainly having a different function" is meant, in particular, that this pressure is not primarily adjusted to derive therefrom the backpressure

set, for example, to control a further valve unit or in particular to actuate a switching element of the automatic transmission, for example in the form of a multi-plate clutch or multi-disc brake. The pressure of which

Is derived backpressure is selected in particular so that the back pressure in the situations in which a control of the second valve unit is useful or necessary, is sufficiently high, to an unwanted operation of the third

Valve unit to prevent.

In an embodiment of the invention, the hydraulic control to a switching valve, by means of which the back pressure can be derived from a first or a second pressure. The switching valve is designed in particular as an automatically switching valve, which derives the back pressure from the higher of the two pressures mentioned. The switching valve is designed in particular as a ball switching valve. Thus, the operation of the third valve unit can be prevented not only in response to a pressure but in response to two pressures. The

Control of the second valve unit without affecting the third valve unit is thus possible in many situations.

In an embodiment of the invention, the back pressure is derived from an actuation pressure of a switching element of the automatic transmission. Thus, the control of the second valve unit without impact on the third valve unit can be made possible when certain gears of the automatic transmission is engaged and thus certain switching elements are actuated. This is particularly advantageous if the

Control of the second valve unit is necessary or useful only in certain courses.

The invention can be used particularly advantageously when the first valve unit is provided for adjusting a lubricating pressure, the second valve unit a

Switching valve is assigned in the form of a Fliehölventils, by means of which an inflow to a Fliehölraum a switching element of the automatic transmission can be increased and the third valve unit is associated with a parking brake actuation system.

The first valve unit is designed in particular so that an increasing control pressure causes an increasing lubrication pressure. In the above example of the Valve units associated pressure ranges means that when driving the parking lock actuation system or the centrifugal oil valve, a high lubricating pressure is set.

A parking lock of the parking lock actuation system must only be controlled, in particular closed when no gear is engaged in the automatic transmission. Thus, it represents for the parking brake actuation system no functional restriction, if in some gears because of the back pressure no control of the parking brake is possible. On the other hand, filling the Fliehölhauben is only necessary if certain gears are engaged in the automatic transmission. The parking lock is activated only when no gear is engaged in the automatic transmission. Thus, the centrifugal oil valve can be controlled in all necessary situations. The activation of the

Parking lock actuation system and the centrifugal oil valve by a common

Control solenoid valve does not restrict the functionality of the two systems.

Further advantages, features and details of the invention will become apparent from the following description of exemplary embodiments and with reference to the drawings, in which the same or functionally identical elements are provided with identical reference numerals.

Showing:

Fig. 1 is a hydraulic diagram of a hydraulic control of a

Automatic transmission.

1, a hydraulic control for an automatic transmission of a

Motor vehicle to a main pump 10 which is driven by an internal combustion engine 11. The main pump 10 sucks operating fluid in the form of transmission oil from a tank 13 via a suction filter 12. In Fig. 1 drains to a tank are shown at several points. This is to be understood that transmission oil from these drains enters the tank 13 directly or indirectly. The main pump 10 delivers gear oil into a working pressure line 14, which supplies a working pressure slide 15 with gear oil. In the working pressure line 14, a check valve 16 is arranged, which is designed so that transmission oil from the main pump 10 for

Working pressure slide 15 can flow, but not vice versa. The working pressure slide 15 is designed as a normally constructed control slide on which acts as a control pressure set by a control solenoid valve working pressure 17 pressure. Together with a spring force, which is a basic pressure of the

Adjusting working pressure, the control pressure acts against the recirculated from the working pressure line 14 working pressure. By changing the pressure set by the control solenoid valve working pressure 17, the level of the working pressure can be adjusted. When the working pressure reaches the desired value set by the control solenoid valve working pressure 17, a connection between the working pressure line 14 and a lubricating pressure slide 19 is established by the working pressure slide 15 via a lubricating pressure line 18. The lubricating pressure slide 19 is thus only supplied with gear oil when the

Working pressure has reached its set by the control solenoid valve working pressure 17 setpoint. The working pressure slide 15 thus regulates the working pressure in the

Working pressure line 14 to the set by the control solenoid valve working pressure 17 setpoint.

The lubricating pressure slide 19 is also designed as a standard constructed control slide on which acts as a control pressure set by a control solenoid lubrication pressure 20 pressure. The control solenoid lubrication pressure 20 may thus be referred to as a pilot valve. Together with a spring force which sets a base pressure of the lubricating pressure, the control pressure acts against the returned from the lubricating pressure line 18 lubricating pressure. By changing the of

Regulating solenoid valve lubrication pressure 20 set pressure, the height of the

Lubricating pressure can be adjusted. When the lubrication pressure reaches the set value, the lubrication pressure slide 19 establishes a connection between the

Lubricating pressure line 18 and a return line 21 made. About the

Return line 21 is gear oil to an intake passage 22, which connects the main pump 10 with the suction filter 12, returned. The lubricating pressure slide 19 thus controls the lubricating pressure in the lubricating pressure line to the set by Regelmagnetventil- lubricating pressure 20 setpoint. The lubricating pressure slide 19 is designed so that the maximum required lubrication pressure is achieved at a control pressure of about 3 bar. The lubricating pressure slide is thus assigned a pressure range of 0 to 3 bar. If the control pressure continues to rise, so does the set

Lubricating pressure continues.

The control solenoid valve working pressure 17 and the control solenoid valve lubrication pressure 20 are both configured as so-called direct control valves. In direct control valves, a force acts from an electronic control device, not shown controlled electromagnet directly as a control force on a slider. Against the control force act a spring force and a recirculated pressure whose height is to be set by the direct control valve according to the control of the electronic control device. The pressure set by a direct control valve is derived from a supply pressure. In the case of the control solenoid valve working pressure 17 and the control solenoid valve lubrication pressure 20, the working pressure in the

Working pressure line 14 as supply pressure.

The hydraulic control can also have a connection, not shown, via which a controllable Drehmomentverteilvorrichtung for an all-wheel drive of the motor vehicle can be supplied with working pressure.

The hydraulic control has in addition to the main pump 10 via an additional pump 23 which can be driven by an electric motor 24 controlled by the electronic control device. The auxiliary pump 23, on the one hand, the main pump 10 in situations where the delivery rate of the main pump 10 is insufficient, support, with a maximum achievable pressure of the auxiliary pump 23 is significantly lower than a maximum pressure of the main pump 10. On the other hand, the

Booster pump 23 to ensure a basic supply of the hydraulic control with the internal combustion engine 11 and thus standing main pump 10. The

Additional pump 23 also sucks on the suction filter 12 from the tank 13 transmission oil. It conveys transmission oil into an auxiliary pump line 25, which is connected via a check valve 26 to the working pressure line 14. The check valve 26 is arranged so that transmission oil can flow from the auxiliary pump line 25 into the working pressure line 14, but not vice versa. Thus, the auxiliary pump 23 in the case in which the working pressure is less than its maximum achievable pressure, promote together with the main pump 10 in the working pressure line 14. The auxiliary pump line 25 is also connected to an auxiliary pump slide 27. By means of the

Additional pump spool 27, a connection between the auxiliary pump line 25 and the lubricating pressure line 18 can be made, wherein between

Auxiliary pump spool 27 and lubricating pressure line 18, a check valve 28 is arranged so that transmission oil from the auxiliary pump spool 27 in the

Lubricating pressure line 18 can flow, but not vice versa. In a illustrated basic position of the auxiliary pump slide 27, the said connection between the auxiliary pump line 25 and the Schmierdruckleituhg 18 is interrupted, in a switched position of the auxiliary pump slide 27, said connection is made. On the auxiliary pump slide 27 acts as a control pressure of the working pressure in the working pressure line 14 against a spring force. The spring force is designed so that the auxiliary pump slide 27 remains in the normal position until the working pressure exceeds the maximum achievable pressure of the auxiliary pump 23. If this pressure is reached, the connection between the auxiliary pump line 25 and the

Lubricating pressure line 18 made via the auxiliary pump slide 27 and the

Booster pump 23 can promote transmission oil in the lubricating pressure line 18, in which a significantly lower pressure than the working pressure prevails. Thus, the auxiliary oil pump 23 may also support the main pump 10 when the working pressure is greater than their maximum achievable pressure and therefore they can no longer promote the working pressure line 14.

Via the working pressure line 14 are also solenoid valves 29, 30, 31, 32, 33 and 34 for the actuation of switching elements of the automatic transmission in the form of

Multi-plate clutches and brakes supplied with working pressure. The multi-plate clutches and brakes are shown schematically by gear change piston-cylinder units 35, 36, 37, 38, 39 and 40, by means of which the multi-plate clutches and - brakes can be closed and opened. The speed change piston-cylinder units 35, 38 and 40 are multi-disc brakes, and the speed change piston-cylinder units 36, 37 and 39 are associated with multi-plate clutches. The control solenoid valves 29, 30, 31, 32, 33 and 34 are constructed identically, so that only the control solenoid valve 29 is explained in more detail. The control solenoid valve 29 is also designed as a direct control valve, which is controlled by the electronic control device, not shown. The control solenoid valve 29 is supplied via a connection with working pressure. It is used to set an actuating pressure in a gear change pressure chamber 41 of the gear change piston-cylinder unit 35, to which it is connected via a line 42. The actuating pressure in the line 42 is returned as control pressure to the control solenoid valve 29. In order to avoid pressure oscillations in the line 42, the actuation pressure is additionally fed back to two further connections of the control solenoid valve 29. As a further measure to avoid pressure oscillations, the line 42 is connected via the control solenoid valve 29 to a pressure accumulator 43. About a tank discharge line 87 is the control solenoid valve 29 and the

Control solenoid valves 30, 31, 32, 33 and 34 connected to the tank 13. In the

Tankabflussleitung 87, a spring-loaded check valve 44 is arranged. The check valve 44 is arranged so that transmission oil can flow into the tank 13. It is also designed so that it opens the flow in the direction of the tank 13 only when there is a minimum pressure, for example, 0.2 to 0.4 bar in the tank discharge line 87. This ensures that in the tank discharge line 87 always at least the said minimum pressure is applied. This causes the line 42 and the

Gear change pressure chamber 41 can not idle, but are always filled with gear oil.

By appropriate control of the control solenoid valve 29 can thus a

Operating pressure in the gear change pressure chamber of the gear change piston-cylinder unit 35 and dismantled and so the gear change piston-cylinder unit 35th

assigned multi-disc brake can be closed and opened. By appropriate control of the control solenoid valves 29, 30, 31, 32, 33 and 34 can thus the

The multi-plate clutches and brakes of the automatic transmission are closed and opened, allowing the individual gears to be engaged and disengaged. The control solenoid valves 29, 30, 31, 32, 33 and 34 and the speed change piston-cylinder units 35, 36, 37, 38, 39 and 40 may thus be referred to as a speed change system 61. With the gear change system 61 shown here, a total of nine forward gears and one reverse gear can be switched.

The lubricating pressure line 18 is connected via a centrifugal oil valve 45 and a first supply line 63, which is designed as a controllable slide switch, with a converter inlet 46 of a hydrodynamic torque converter 47. On the centrifugal oil valve 45 acts as a control pressure set by the control solenoid valve lubrication pressure 20 against a spring force. The spring force is designed so that the centrifugal oil valve 45 changes when a pressure limit of, for example, 4 bar is exceeded from a basic position shown in a switching position. The set by the control solenoid valve lubrication pressure 20 thus acts both on the lubricating pressure slide 19, and the centrifugal oil valve 45 as the control pressure. The centrifugal oil valve 45 is thus assigned a pressure range of 3 to 5 bar.

In the illustrated basic position of the centrifugal oil valve 45, the lubricating pressure line 18 is connected via the centrifugal oil valve 45 via two connections with the Wandlerzufluss 46. In a first portion 48 of the first supply line 63 between Fliehölventil 45 and converter inflow 46, a diaphragm 49 is disposed in a second, to the first portion 48 parallel portion 50 is no corresponding hydraulic component arranged. The second section 50 is connected to the lubricating pressure line 18 only in the basic position of the centrifugal oil valve 45. By contrast, the first section 48 is always connected to the lubricating pressure line 18. This ensures that in the switching position of the centrifugal oil valve 45, in which, as described above, a very high lubricating pressure acts over the Aperture 49, the pressure at the converter inlet 46 is lowered so far that damage to the torque converter 47 can be reliably avoided.

After flowing through the torque converter 47, the transmission oil flows via a converter outflow 51 to a transmission oil cooler 52. The transmission oil cooler 52 supplies various lubrication points 53 in the automatic transmission with cooled transmission oil.

The torque converter 47 has a lockup clutch 54, which is controlled by a control solenoid valve converter 55. The control solenoid valve converter 55, according to a control by the electronic control device in a line 56 which is connected to a not shown pressure chamber of the lock-up clutch 54, an actuating pressure. The torque converter 47 is thus designed as a so-called 3-channel converter. The control solenoid valve converter 55 is also designed as a direct control valve and is supplied with working pressure. As a special feature, the control solenoid valve converter 55 is supplied with a corresponding pressure to an internal pressure of the torque converter 47, which counteracts the actuating pressure at the lockup clutch 54, as pilot control. Said pressure acts in the same direction to the force of the solenoid of the solenoid valve converter 55 and is tapped in a line 58, which via a first aperture 59 with the

Wandlerzufluss 46 and is connected via a second aperture 60 with the Wandlerabfluss 51. With a suitable choice of the orifices 59 and 60, the pressure in the line 58 corresponds to the internal pressure of the torque converter 47. The operation of the return and the derivative of the internal pressure are described in detail in DE 10 2004 012 117 A1.

The speed change piston-cylinder units 36, 37 and 39 of the multi-plate clutches each have a Fliehölraum 62, which via a Fliehölleitung 64 with the

Transmission cooler 52 and thus at least indirectly connected to the first supply line 63. The centrifugal oil space 62 is arranged relative to the gear change pressure chamber 41 with respect to a gear change piston 65, which acts on the multi-plate clutches. If the centrifugal oil space 62 is sufficiently filled with gear oil, the same result from the rotation of the gear change piston-cylinder units 36, 37 and 39

Pressure increases in the gear change pressure chamber 41 and 62 in the centrifugal oil chamber.

In some situations, for example in certain circuits in the automatic transmission, a functioning centrifugal oil balance, ie, sufficiently filled centrifugal oil spaces 62, is important. In these situations, over a corresponding pressure of the Regelmagnetventil lubricating pressure 20 the centrifugal oil valve 45 are brought into its switching position as described above. In this switching position, a connection between the lubricating oil line 18 and a second supply line 66, which opens into the centrifugal oil line 64, is produced via the centrifugal oil valve 45. Thus, the centrifugal oil pipe 64 is supplied not only via the first supply line 63 but also via the second supply line 66 gear oil. Thus, the Fliehölräume 62 of the gear change piston-cylinder units 36, 37 and 39 can be filled very quickly and thus a functioning Fliehölausgleich be achieved.

In the second supply line 66, a diaphragm 67 is arranged. About this aperture 67 and the aperture 49 in the first portion 48 of the first supply line 63 can

Flow rates of the transmission oil in the first and second supply line 63, 66 can be adjusted. In the centrifugal oil line 64, a check valve may be so arranged that a return flow of transmission oil from the second supply line 66 in the direction

Transmission cooler 52 is prevented.

The hydraulic control also has a parking lock actuation system 68, by means of which a parking lock, not shown, can be switched on and laid out. The parking lock actuation system 68 has a parking lock piston-cylinder unit 69 with a parking lock piston 70 which is at least indirectly connected to a so-called, not shown, parking pawl. By moving the

Park Sperrenkolbens 70 in a first operating direction 71, the parking brake off and when moving in a, the first operating direction 71 opposite set second operating direction 72 inserted. If the parking lock is engaged, this position is referred to below as P position, the parking brake is not engaged, this position is referred to as non-P position. The parking lock piston cylinder unit 69 has a first parking brake pressure chamber 73. By supplying transmission oil to the first parking lock pressure space 73, the parking lock piston 70 can be displaced toward non-P (first operation direction 71). The parking lock piston-cylinder unit 69 has a second parking brake pressure chamber 74 on a side opposite the first parking brake pressure chamber 73 with respect to the parking brake piston 70. By supplying transmission oil to the second parking brake pressure space 74, the parking lock piston 70 can be displaced in the direction P (second operation direction 72). The parking lock piston-cylinder unit 69 also has a parking brake spring 75, which is arranged so that it applies a spring force in the direction P on the parking lock piston 70. The parking brake piston-cylinder unit 69 also has a controllable detent 76, by means of which a position of the parking brake piston 70 can be set. The detent 76 has for this purpose a controlled by the electronic control device solenoid 77, which can engage in a contour 78 of a connected to the parking brake piston 70 piston rod 79. The detent 76 is designed so that it can be overpressed in the direction P. The said contour 78 is so

stated that it can push back the solenoid 77 in a displacement of the parking brake piston 70 in the direction P. Overriding the detent 76 in the direction of non-P, however, is not possible.

Gear oil can be fed into the second parking brake pressure chamber 74 via a parking brake slide 80 supplied with working pressure and thus an actuating force in the direction P can be applied in addition to the force of the parking brake spring 75. The parking lock slide 80 is designed as a slide valve with two positions. In a P-position, not shown, the working pressure line 14 via the

Park lock slide 80 connected to the second parking brake pressure chamber 74 so that this gear oil is supplied.

When moving the parking brake piston 70 in the direction P transmission oil from the first parking brake pressure chamber 73 must be removed. In order for this to be possible quickly and only with little resistance, the parking lock actuation system 68 has a drain slide 81 designed as a slide switch with two positions with large openings

Flow cross-sections, which is connected to the first parking brake pressure chamber 73. In an illustrated emptying position, the first parking brake pressure chamber 73 is connected to the tank 13 via the emptying slide 81. Thus, the gear oil from the first parking brake pressure chamber 73 does not have to be discharged via the parking lock slide 80 with significantly smaller flow cross sections in the tank 13, but can flow without great resistance via the drain valve 81 into the tank 13. In a filling position of the emptying slide 81, not shown, a parking lock connecting line 82, which connects a connection of the parking lock slide 80 with the emptying slide 81, is connected via the emptying slide 81 to the first parking lock pressure chamber 73. Thus, the first parking brake pressure chamber 73 in the filling position of the emptying slide 81 gear oil can be supplied and so the

Parking lock piston 70 are moved toward non-P. As a control pressure for switching between the filling and the emptying of the emptying slide 81, the pressure acts in the parking lock connecting line 82, which acts against a spring force of an emptying spring 83. The emptying slide 81 is designed so that it passes through the Spring force of the emptying spring 83 can be brought into the emptying position, so this represents its basic position.

About the parking lock slide 80, the parking brake connecting line 82 can be connected to the working pressure line 14. The parking lock slide 80 is then in a non-P position shown. The emptying slide 81 is initially still in the emptying position in which he completes the parking brake connecting line 82 so far that can build up a pressure in the parking brake connecting line 82. This then acts in the parking brake connection line 82 of the

Working pressure, which then acts as a control pressure on the emptying slide 81 and this brings against the spring force in the filling position. Thus, at sufficiently high working pressure the first parking brake pressure chamber 73 supplied gear oil and the parking brake is, if the detent is disabled, the solenoid 77 so does not engage in the contour 78, designed. For this purpose, gear oil from the second parking brake pressure chamber 74 may flow into the tank 13, which is why in the non-P position of the parking slide valve 80, the second parking brake pressure chamber 74 via the

Parking lock slide 80 is connected to the tank 13.

On the parking lock slider 80 acts as a control pressure set by Regelmagnetventil- lubricating pressure 20 against a spring force of Parksperrenschieber- spring 84. This pressure acts as a control pressure on the lubricating pressure slide 19 as the first valve unit, the centrifugal valve 45 as the second valve unit and the

Parking lock slider 80 as the third valve unit. The parking lock slider spring 84 is arranged so that it can bring the parking lock slider 80 in the non-P position, so this represents the basic position of the parking brake slide 80. Of the

Parking lock slider 80 is designed so that, if no further pressures act on it, it assumes the P position from a control pressure of approx. 7 bar. Since that

Regulating solenoid valve lubrication pressure 20 can set a maximum of 8 bar is the

Parking lock slide 80 thus assigned a pressure range of 6 to 8 bar.

The parking lock slide 80 is also connected to a back pressure line 85, that in the back pressure line 85 pressure in the same direction with the spring force of

Parking lock slide spring 84 can act as back pressure against the control pressure. With a correspondingly high back pressure so that the parking lock slide 80 remains in the non-P position, even if a control pressure is set, in which the

Fliehölventil 45 is in its switching position, in the fast filling of the

Fliehölhaube 62 is possible. This is guaranteed even if due to Tolerances, wear or aging have shifted the mentioned pressure ranges and overlap. The back pressure line 85 is connected via a ball switching valve 86 to the gear change pressure chambers 41 of the speed change piston-cylinder units 37 and 39. The ball switching valve 86 is arranged so that the higher of the two acts in the mentioned spinning chambers 41 as back pressure on the parking lock slide 80. Is one of the two gear change piston-cylinder units 37 and 39 associated with multi-plate clutches operated and thus closed, the back pressure is sufficiently large to prevent the change of the parking brake slide 80 in the P position. The hydraulic control is designed to be one of the two

Clutches in all gears is closed, in which a control of the

Fliehölventils 45 may be necessary.

If the parking brake at very low or no working pressure, so for example when the internal combustion engine 11 and thus standing main pump 10 are inserted, so the parking brake spring 75 is used. For this purpose, the solenoid 77 and thus the detent 76 is deactivated and the parking brake spring 75 can

Move the parking brake piston 70 in the direction of the P position. From the first parking brake pressure chamber 73 while transmission oil must be removed. Since no or only a very low working pressure is available, the parking lock slide 80 is in its normal position. So he can not be brought into the P position, but is in the non-P position. In the non-P position of the parking slide valve 80 is about the parking lock slide 80 except on slide gap no connection between the parking brake connecting line 82 and the tank 13. About the

Parksperrenschieber 80, the transmission oil could therefore drain only very slowly towards the tank 13. Since no or only a slight pressure prevails in the parking brake connecting line 82 in this case, the emptying slide 81 is in its emptying position as described above. Thus, the transmission oil from the first parking lock pressure chamber 73 can be very quickly discharged via the discharge slide 81 to the tank 13 and the parking brake are inserted with it.

Claims

claims

Hydraulic control for an automatic transmission of a motor vehicle with a pilot valve (20) and a first and a second valve unit (19, 45), wherein a pre-control pressure set by means of the pilot valve (20) as the control pressure to the first and second valve unit (19, 45) can be conducted is

marked by

a third valve unit (80), to which said pilot pressure as the control pressure can be conducted, and a counter pressure line (85), by means of which a against the

Control pressure acting back pressure applied to the third valve unit (80) and thus actuation of the third valve unit (80) can be prevented.

Hydraulic control according to claim 1 or 2,

characterized in that

said back pressure is derived from a pressure which mainly serves another function.

Hydraulic control according to claim 2,

characterized in that

a switching valve (86) is provided, by means of which the backpressure can be derived from a first or a second pressure.

Hydraulic control according to claim 2 or 3,

characterized in that

the back pressure is derived from an actuation pressure of a shift element (37, 39) of the automatic transmission.

5. Hydraulic controller according to one of the preceding claims,

characterized in that

the first valve unit (19) is provided for adjusting a lubricating pressure.

6. Hydraulic controller according to one of the preceding claims,

characterized in that

the second valve unit (45) is associated with a switching valve, by means of which an inflow to a Flieholraum a switching element of the automatic transmission can be increased.

7. Hydraulic controller according to one of the preceding claims,

characterized in that

the third valve unit (80) is associated with a parking lock actuation system.