EP1618322A1

EP1618322A1 - Hydraulic circuit for controlling a drive chain

Info

Publication number: EP1618322A1
Application number: EP04713472A
Authority: EP
Inventors: Gunther Petrzik
Original assignee: Getrag Getriebe und Zahnradfabrik Hermann Hagenmeyer GmbH and Co
Current assignee: Magna PT BV and Co KG
Priority date: 2003-04-30
Filing date: 2004-02-21
Publication date: 2006-01-25
Also published as: US7300375B2; US20060150762A1; DE10320524A1; WO2004097265A1

Abstract

The invention relates to a hydraulic circuit (50) for controlling a double-clutch gear box comprising to gear groups (52, 54), each group being provided with a separation clutch (K1, K2) and several clutch couplings (60, 62) for engaging and disengaging gears. For each drive group (52, 54), said hydraulic circuit comprises its own hydraulic branch (68, 70) which is connected respectively to a pump (66) by means of a safety valve (72, 74). Each hydraulic branch (68, 70) is provided with a clutch control valve (76, 78) for controlling the associated separation clutch (K1, K2) and with at least one gear-switch control valve (80, 82) for controlling the associated clutch couplings (60, 62). Each safety valve (72, 74) is embodied in the form of a proportional pressure control valve.

Description

Hydraulic circuit for controlling a drive train

The present invention relates to a hydraulic circuit for controlling a drive train of a motor vehicle and, in particular, relates to a hydraulic circuit for controlling a double clutch transmission which has two transmission groups, each with a separating clutch and a plurality of shifting clutches for engaging and disengaging gear stages, the hydraulic circuit for each transmission group having its own hydraulic branch has, which are each connected to a pump via a safety valve, and wherein each hydraulic indicator each has a clutch control valve for controlling the assigned clutch and at least one shift control valve for controlling the assigned clutch.

Such a hydraulic circuit is known from DE 101 34 115

AI. Dual clutch transmissions have been known for a long time. Recently, however, there has again been a greater interest in double clutch transmissions, since the overlapping actuation of the two clutches for the traction force of uninterrupted gear changes is now easier to control in terms of control technology. This applies in particular to double clutch transmissions that use wet multi-plate clutches as separating clutches.

In general, dual clutch transmissions offer a good compromise between high comfort and high efficiency. As said, the overlapping actuation of the two separating clutches enables gears to be changed without interrupting the tractive force. For example, this is generally not possible with conventional automated manual transmissions. On the other hand, double clutch transmissions offer higher efficiency than, for example, classic converter automatic transmissions, since double clutch transmissions require an energy-consuming hydrodynamic converter.

From the aforementioned DE 101 34 115 AI a hydraulic circuit for controlling such a double clutch transmission is known. The hydraulic circuit is divided into two branches for the two gear groups. Each branch has a pilot valve in the form of a non-proportional directional valve on the input side. The pilot valve has a safety-relevant function, since it enables the gear group that is not active to be “switched off” completely.

Each branch has a flow control valve with a fixed throttle for controlling a cylinder for actuating the associated disconnect clutch. Each transmission group has two shift rods for actuating assigned clutches. To actuate the shift rods, each hydraulic branch has a proportional pressure valve per shift rod. The proportional pressure valves and the flow valve are connected to the outlet side of the safety directional valve.

Furthermore, a central directional valve device in the form of a multiplex valve is provided between the proportional pressure valves and the four shift rods.

The known hydraulic circuit arrangement has various disadvantages. The known hydraulic circuit has a comparatively large number of valves. The use of flow valves to control the disconnect clutches requires a valve hysteresis that is difficult to control and high valve damping. It is generally possible for a vibrating oil column to excite a valve spool of such a valve, so that a high level of damping is usually integrated. This leads to a loss of dynamics.

By using a multiplex valve coupling the two hydraulic branches, the entire double clutch transmission is inoperative if it fails.

In general, it is difficult in hydraulic circuits for drive trains of motor vehicles to actuate safety-relevant devices hydraulically. This is due to the fact that, due to the high safety requirements, digital regulations are generally forbidden, which can be parameterized and have a high control quality. Safety-related devices of a drive train are, for example, separating clutches and shift clutches of an automated manual transmission and a double clutch transmission, but also variator arrangements for CVT transmissions and toroidal transmissions.

It is therefore the object of the present invention to provide an improved hydraulic circuit for controlling a drive train of a motor vehicle, and in particular an improved hydraulic circuit for controlling a dual clutch transmission.

The above-mentioned object is achieved in the above-mentioned hydraulic circuit for controlling a double clutch transmission according to one aspect of the invention in that the safety valves are each designed as proportional pressure control valves.

This allows a second control level to be set up. The respective downstream valve arrangements of the respective branch can be simplified, and this also results in options for optimizing the control of the disconnect clutches or the shift clutches that are easy to control in terms of safety.

The above task is solved completely in this way.

According to a second aspect of the present invention, the above object is achieved in the above-mentioned hydraulic circuit for controlling a double clutch transmission in that the two hydraulic branches are decoupled from one another in such a way that that in the event of failure of any element of one transmission group or one hydraulic branch, the vehicle remains conditionally ready to drive by means of the other transmission group or the other hydraulic branch.

By decoupling the two hydraulic branches, it can be achieved that each transmission group can be operated as a separate transmission independently of the other transmission group. If a transmission group fails (for example the transmission group for the even gears 2, 4, 6, etc.), the double clutch transmission can nevertheless be operated on the basis of the other transmission group by means of the hydraulic circuit according to the invention, in the example mentioned using gears 1, 3 , 5, etc.

It is therefore possible that the vehicle remains ready to drive, for example, to be able to drive to a workshop or the like.

Furthermore, the above object is achieved according to a third aspect of the present invention by a hydraulic circuit for controlling a drive train of a motor vehicle, with a proportional pressure control valve that can be connected on the input side to a pump, and a digitally controlled proportional directional valve that is connected on the input side to the proportional pressure control valve and that can be connected on the output side to an actuator arrangement for actuating a safety-relevant device of the drive train.

Through the serial combination of a pressure control valve and a downstream, digitally controlled proportional valve, two control levels can be implemented to operate the safety-relevant device. On the one hand, the proportional pressure control valve on the inlet side serves for safety and is designed in particular as a pressure relief valve. The safety-relevant device can be deactivated by switching off the pressure control valve (usually by means of a fail-safe arrangement).

In normal operation, the proportional pressure control valve is then preferably operated in saturation, so that essentially the nominal hydraulic pressure is available on the output side. The digitally controlled proportional directional valve establishes a second, inner control level. Due to the increased safety of the proportional pressure control valve, the proportional directional valve can be controlled digitally.

The directional valve has no pressure feedback of the working connection. For this reason, the directional control valve cannot be excited to vibrate the spool by a vibrating oil column. High damping can thus be dispensed with and high dynamics result. Furthermore, the digital control of the directional control valve can take place essentially free of hysteresis. Finally, digital control enables parameterization, so that parameters of the digital controller can be adjusted for different operating states, so that the overall quality of control rises sharply.

Overall, the above task is thus completely solved.

In particular in the first and second aspects of the present invention relating to a hydraulic circuit for controlling a Double coupling gearbox, the following advantageous configurations are possible.

According to a preferred embodiment, the proportional pressure control valves are designed as pressure-limiting pressure control valves.

This ensures that the hydraulic pressure in the respective hydraulic branch does not rise above a certain maximum value. This increases security.

According to a further advantageous exemplary embodiment, at least one of the clutch control valves is designed as a proportional directional valve.

In contrast to pressure control valves, directional control valves enable more dynamic and hysteresis-free control.

This is especially true when the clutch control valves are digitally controlled. This also enables the control parameters to be parameterized. It is also possible to correct and teach in the valve-specific properties. The control parameters can be set, for example, on the basis of offset current, temperature, clutch wear, friction conditions, pressure conditions.

It is particularly preferred if a sensor is provided for a physical variable assigned to the respective separating clutch, the output of which is sensed and fed to a digital controller. In the case of the disconnect clutch, the physical variable can in particular be the pressure.

The combination of the proportional pressure control valve as an input-side safety valve and a digitally controlled directional valve results in two control levels. This makes it possible to use the digital control in the motor vehicle. In the event of some failures, the controllability of the respective hydraulic branch or the transmission group is retained, for example if the digital pressure control fails.

Since the pressure control valve is preferably operated in such a way that the valve is fully open during nominal operation, no control-related vibrations can occur during nominal operation, so that no high damping is required.

According to a further preferred embodiment, a pressure relief valve is connected between the clutch control valves and actuators for actuating the separating clutches.

The additional pressure relief valve further increases operational safety.

It is particularly advantageous if the pressure relief valves upstream of the actuators of the separating clutches are coupled in such a way that a simultaneous frictional engagement of the two separating clutches is excluded.

This further increases the safety of the hydraulic circuit. For example, the coupling can take place by the pressure limiting valves being configured as differential pressure control valves. are formed, the connections of which are connected to one another crosswise.

Overall, it is also preferred if at least one of the switching control valves is designed as a proportional directional valve.

Here too, the proportional directional control valve can be controlled digitally, the control variable for the clutches usually being the switching path. In general, however, there are the same advantages as with digital control of the proportional directional valve for the disconnect clutch.

According to one embodiment of the invention, the gear stages of each transmission group can be switched by means of at least two individual shift rods, the associated hydraulic branch for each shift rod having at least one proportional directional control valve as a shift control valve.

This embodiment enables individual actuation of the respective clutch clutches or clutch clutch packs, that is to say the usual combination of two clutch clutches, by means of the individual shift rods. However, mechanical locking of the shift rods against each other is usually required.

According to a first alternative embodiment, the gear stages of each transmission group can be switched by means of a shift shaft, the associated hydraulic branch for each shift shaft being at least one proportional directional valve Has switching control valve and has at least one selection actuator for selection movements of the switching shaft.

Such an arrangement can be referred to as a double H arrangement. Only one shift shaft is assigned to each transmission group, whereby an axial movement of the shift shaft is generally used for shifting and a rotation of the shift shaft to select the respective clutch packs.

It is particularly advantageous that the selection actuator can be designed in a particularly simple manner. For example, the selector actuator can be a single-acting hydraulic cylinder that can be controlled by means of a simple directional valve (not proportional). Alternatively, it is also possible to actuate the selection actuator magnetically or electromechanically or the like.

Each hydraulic branch preferably has a selector control valve for the respective selector actuator.

This results in a strict separation between the two hydraulic branches.

Alternatively, a single common selector control valve for the selector actuators is provided for the two hydraulic branches.

This simplifies the valve effort. According to a further alternative embodiment, the gear stages of a transmission group can each be operated by means of a shift drum.

In this embodiment, one shift drum is provided for each transmission group. The shift drum can also be operated by means of a digitally controlled proportional directional valve, with the advantages mentioned above.

Overall, it is also advantageous if a low-pressure circuit for cooling or lubrication is also connected to the pump via a central valve.

This measure also makes it possible to connect the low-pressure circuit to a central pump, which is also used to supply the high-pressure hydraulic branches.

It is particularly advantageous if the central valve is a proportional directional valve.

As a result, the pressure available for the low-pressure circuit can be easily adapted to the other operating conditions. For example, the supply to the low pressure circuit can be interrupted for a short time if a high volume flow is available for clutch actuation.

It is also advantageous if the central valve for the low pressure circuit has a switching position in which the low pressure circuit is connected to the pump via an orifice. This measure can permanently provide a reduced volume flow for the low pressure circuit for lubrication or cooling in that switching position. It is therefore advisable to design this switch position as a fail-safe position.

It is also advantageous if the low-pressure circuit has at least one jet pump.

In this way, even with a comparatively low volume flow from the central valve, a high volume flow can be set up for cooling or lubrication.

It goes without saying that the features mentioned above and those yet to be explained below can be used not only in the combination indicated in each case, but also in other combinations or on their own without departing from the scope of the present invention.

Embodiments of the invention are shown in the drawing and are explained in more detail in the following description. Show it:

Figure 1 is a schematic representation of a first embodiment of a hydraulic circuit for controlling a drive train for a motor vehicle according to the third aspect of the present invention.

2 is a block diagram of a hydraulic circuit for a dual clutch transmission according to the first and second aspects of the present invention; 3 is a hydraulic circuit diagram of a hydraulic circuit according to the first and second aspects of the present invention;

Fig. 4 shows a modification of the hydraulic circuit of Fig. 3;

5 shows a hydraulic circuit diagram of an alternative arrangement for switching control;

6 shows a hydraulic circuit diagram of a further alternative arrangement for switching control;

7 shows a hydraulic circuit diagram of a further alternative arrangement for switching control; and

FIG. 8 shows a modification of the arrangement from FIG. 7.

A drive train for a motor vehicle 10 is shown in schematic form in FIG. 1.

The drive train has an internal combustion engine 12, a transmission 14, a differential 16 and driven wheels 18.

A hydraulic circuit 20 is provided to control the drive train, in particular the transmission 14. Only a section of the hydraulic circuit 20 is shown, which serves to control a safety-relevant device 22 of the transmission 14. The safety-relevant device can be, for example, a disconnect clutch or a clutch of an automated transmission or a double clutch transmission. However, it can also be a variator of a CVT transmission or a variator of a toroidal transmission or the like.

In the present context, a safety-relevant device is to be understood as any device of the transmission 14, the incorrect operation of which can impair the safety of the operation of the motor vehicle 10.

A central control device 24 is also shown in FIG. 1, which controls the hydraulic circuit 20 and possibly further devices of the drive train and / or of the vehicle.

The hydraulic circuit 20 has a pump 30 which is motor-operated and is supplied from a tank 32.

A proportional pressure control valve is connected to the pump 30. A proportional directional control valve 36 is connected to the output of the proportional pressure control valve and is connected on the output side to an actuator of the safety-relevant device 22.

A sensor 38 measures a physical quantity of the safety-relevant device 22, for example the pressure inside a multi-plate clutch, the path of a clutch, or the like. The physical variable determined by the sensor 38 is scanned by means of an A / D converter 40 and fed to a digital controller 42. The digital controller can be a P, a PI or PID controller.

The output of the digital controller 42 is fed to a D / A converter 44, the output of which is connected to an electrical or electromagnetic actuating device of the proportional directional valve 36.

The proportional directional valve is a 3/3-way valve with three connections and three switch positions. In the switching position shown, hydraulic energy is taken from the safety-relevant device 22 and fed to the tank 32.

The digitally controlled proportional directional valve 36 allows the physical size of the safety-relevant device 22, which is measured by means of the sensor 38, to be controlled in a highly dynamic and precise manner. Because the directional control valve 36 has no pressure feedback of the working connection. As a result, the directional control valve cannot be excited to vibrate. The damping can be kept small, so that there is a high dynamic. Furthermore, there is no valve hysteresis in this type of control.

The proportional pressure control valve 34 forms, together with a conventional analog controller 46, a higher-level control loop. The analog controller 46 is connected on the input side to the sensor 38 and on the output side to the electrical or electromagnetic actuating device of the valve 34. In the event of failure of the digital controller 42, the proportional directional valve 36 can possibly be set to switch through and the proportional control valve can take over the regulation of the safety-relevant device 22 in this case.

In normal operation, the proportional pressure control valve 34 is fully controlled so that the valve is fully open. In this normal state, the control function of the proportional pressure control valve 34 is consequently switched off, so that no vibrations can occur.

The proportional pressure control valve 34 is designed as a single-stage pressure relief valve, in particular as a pressure reducing valve. As a result, the proportional pressure control valve 34 also forms a safety valve for limiting the physical size of the safety-relevant device 22, which is influenced by the hydraulic circuit 20. Furthermore, the valve 34 has a switch-off position, so that the hydraulic system behind it can be blocked.

Overall, the hydraulic circuit 20 offers precise and dynamic regulation of the physical size of the safety-relevant device 22, with high security. A digital control, such as is carried out on the proportional directional control valve 36, is basically only possible for the safety-relevant device 22 of the vehicle 10 by connecting the proportional pressure control valve 34 with a pressure limiting function upstream.

It is understood that the digital controller 42 can be implemented by software. It can also be integrated in the central control device 24. The valves 34, 36 can also be connected directly to the central control device 24.

2 shows a hydraulic circuit 50 for controlling a double clutch transmission according to the first and the second aspect of the present invention.

The dual clutch transmission has a first transmission group 52 and a second transmission group 54.

The first transmission group 52 has a first separating clutch Kl, which is actuated by means of a hydraulic motor (clutch cylinder) 56. In a corresponding manner, the second transmission group 54 has a second clutch K2, which is actuated by means of a hydraulic motor 58.

Furthermore, the first transmission group has clutches (in the present case synchronizers) for engaging and disengaging gear stages of the transmission group 52, which are schematically designated by 60.

Correspondingly, the second gear group 54 has clutches 62 for engaging and disengaging the gear stages of that gear group.

The hydraulic circuit 50 has a pump 66, which in the usual way contains a suction filter, a pressure supply and a pressure limitation.

A first hydraulic branch 68 and a second hydraulic branch 70 are connected in parallel to the pump 66. The first hydraulic branch 68 has a first safety valve 72 on the input side. Correspondingly, the second hydraulic branch 70 has a second safety valve 74 on the input side.

The safety valve 72 is connected on the output side to a clutch control valve 76 for actuating the hydraulic motor 56. In a corresponding manner, the second safety valve 74 is connected on the output side to a clutch control valve 78 for actuating the hydraulic motor 58.

Furthermore, the first hydraulic branch 68 has first shift control valves 80, which are connected to the outlet of the first safety valve 72. Correspondingly, the second hydraulic branch 70 has second switching control valves 82, which are connected to the outlet of the safety valve 74.

The shift control valves 80, 82 are used to control the shift clutches 60, 62 of the first and the second gear group 52, 54 by means of hydraulic motors, which are not described in more detail.

The hydraulic circuit 50 also has a low-pressure circuit 84, which is connected to the pump 66 via a central valve 86, parallel to the first and second hydraulic branches 68, 70.

The low-pressure circuit 84 serves, among other things, to cool the clutches K1, K2. Since the clutches K1, K2 are preferably wet multi-plate clutches, and since the clutches K1, K2 are actuated during gear changes under load, a high cooling capacity is required during the gear changes. The low-pressure circuit also serves to cool the gear oil via a cooler and to lubricate the wheel sets and bearings of the dual clutch transmission. A fine filter for depth filtering is also connected to the low pressure circuit.

It is advantageous in the hydraulic circuit 50 of FIG. 2 that the two hydraulic branches 68, 70 are completely decoupled from one another. Accordingly, if one component of one gear group 52, 54 or the respectively assigned hydraulic branch 68, 70 fails, the respective other gear group can be operated without restriction via the assigned hydraulic branch. Accordingly, in the event of such a failure, the vehicle can be kept conditionally ready to drive by means of the still functioning transmission group 52, for example in order to start a workshop or the like.

It can also be seen that the hydraulic branches 68, 70 for the clutches K1, K2 and the clutches 60, 62 each work according to a control concept which is based on the control concept presented in FIG. 1. This applies in particular if the safety valves 72, 74 are designed as proportional pressure control valves, corresponding to the pressure control valve 34 in FIG. 1. Furthermore, the clutch control valves 76, 78 and / or the shift control valves 80, 82 can be designed as digitally controlled proportional directional valves, corresponding to the Directional control valve 36 of FIG. 1.

In this embodiment, the same advantages apply as described above for FIG. 1. Such an implementation of the hydraulic circuit 50 is shown in FIG. 3. The same elements are provided with the same reference numbers as in FIG. 2. The further details are therefore dealt with below.

The hydraulic circuit 50 of FIG. 3 has a network pressure control circuit 90 for regulating the hydraulic network pressure provided by the pump 66. The network pressure control circuit 90 has an unspecified two-stage pressure relief valve and also an unspecified one-stage pressure relief valve, to which a bypass filter 92 is connected in parallel. External oil cooler is shown at 93.

To increase safety, a first pressure relief valve 94 is connected in parallel to the clutch actuator 56 at the outlet of the clutch control valve 76. In a corresponding manner, a second pressure relief valve 96 is connected to the outlet of the second clutch control valve 78, in parallel to the second clutch actuator 58.

A digital pressure sensor 98 measures the internal pressure of the clutch K1 via a first rotary union 99. In a corresponding manner, a second digital pressure sensor 100 measures the internal pressure of the clutch K2 via a second rotary union 101.

The general structure for regulating the clutch pressure P of the clutches K1 and K2 essentially corresponds to the control circuit shown with reference to FIG. 1. The valve 76 (or 78) corresponds to the valve 36 and the valve 72 (or 74) corresponds to the valve 34. The first transmission group 52 comprises two clutches 60-1 and 60-2 (for example for engaging and disengaging gear stages 2, 4, 6 and R).

A double-acting shift cylinder 103-1 is provided for actuating the one clutch 60-1. A corresponding, identically constructed double-acting shift cylinder 103-2 is provided for actuating the clutch 60-2. Correspondingly, double-acting shift cylinders 105-1 and 105-2 are used to actuate clutches 62-1 and 62-2 of the second gear group (e.g. for engaging and disengaging gear stages 1, 3, 5 and, if applicable, 7).

A digital displacement sensor 102-1, 102-2, 104-1, 104-2 is provided on the shift cylinders 103, 105 to detect the path of the shift clutches 60, 62.

A separate proportional directional control valve 80-1, 80-2 or 82-1, 82-2 is provided for actuating the switching cylinders 102, 104. The directional control valves 80-1 and 80-2 are connected in parallel to the output of the proportional pressure control valve 72 (first safety valve). Accordingly, the proportional directional control valves 82-1, 82-2 are connected in parallel to the output of the second safety valve 74.

The proportional directional valves 80, 82 are each designed as 4/4 directional valves in order to be able to regulate switching points for actuating the respective switching clutches 60, 62 in both directions. Otherwise, the structure of the first safety valve 72 and each of the proportional directional control valves 80, 82 corresponds to the control concept described with reference to FIG. 1. The valve 72 corresponds to the valve 34 and the valves 80-1, 80-2, 82-1 and 82-2 each correspond to the valve 36.

The physical variable that is regulated here is the path of the shift clutches 60, 62. The advantages described in relation to the control system of FIG. 1 apply correspondingly to the regulation of the shift clutches 60, 62.

The low-pressure circuit 84 according to FIG. 3 has a proportional directional valve 86 as a central valve.

The proportional directional valve 86 can e.g. control the pressure or the volume flow for the low-pressure circuit 84 proportionally, for example depending on the engine speed, switching state, temperature of the hydraulic oil, heat input into the transmission, etc.

As a rule, the constant adjustment serves to adapt the cooling oil flow to the available volume flow. In a switch position, the volume flow available for pump 66 for cooling is switched through. This is possible because at the point in time when cooling power is required in the clutches K1, K2, the clutches K1, K2 are in the slip point at which there is essentially no displacement of the respective actuator 56 or 58 (that is, in words no volume flow is necessary for positioning). On the other hand, a high volume flow is required when switching the switching clutches 60, 62, so that the directional control valve 86 is switched over to locks, so that no cooling takes place. As this is only necessary for a very short time, no impairment of the cooling and lubricating performance is to be expected.

In a third position, an aperture 108 is provided in order to provide basic cooling. This is also the fail-safe position. This ensures that the drive train is adequately cooled and lubricated under all circumstances.

An arrangement of two jet pumps 106 is provided at the outlet of the proportional directional valve 86 in order to increase the volume flow required for cooling, in particular, the couplings K1, K2.

A digital controller 109 is shown centrally, which receives signals from the sensors 98-104 and supplies the valves 76-82 with control signals. The digital controller 109 corresponds to the digital controller 42 of FIG. 1. It is only indicated schematically in FIG. 3. It goes without saying that the digital controller 109 can be part of a central control device, similar to the control device 24 of FIG. 1.

The proportional valves 72, 74, 86 control the hydraulic power flow from the network to the consumers, specifically to the hydraulic branches 68, 70 and the low pressure branch 84. This establishes a first control level. The second control level for controlling the actuators 56, 58, 103, 105 can be switched without pressure by the valves 72, 74, so that there is a high level of security.

The valves 72, 74 consequently form safety valves and, due to their design as proportional pressure control valves, in particular pressure reducing valves with pressure limitation, can each be used as central control valves. This applies in particular in the event that the digital control (digital controller 109) fails.

Since the pressure in the clutches K1 and K2 is measured internally, specifically via the rotary unions 99, 101, the control quality can be increased further.

Modifications to the hydraulic circuit 50 which has been described with reference to FIG. 3 are explained below.

For all modifications, only the differences from the hydraulic circuit 50 are described.

4 shows a modification in which, instead of the pressure limiting valves 94, 96, differential pressure control valves 94 ', 96' are provided, which are cross-coupled to one another via a coupling 110.

In this way it can be achieved that the two clutches Kl and K2 never come into frictional engagement at the same time. In other words, this limits the total pressure in order to avoid a transmission blockage. 5, instead of four individual shift rods for actuating the shift clutches (as a rule shift clutch packs) 60, 62, only one shift shaft 114 is provided per transmission group. For example, in the illustrated gear group 52 ', an axial displacement of the shift shaft 114 in direction 116 leads to shifting operations, whereas a rotation of the shift shaft 114 leads to the selection of the two shift gates in direction 118.

Accordingly, only a single digitally controlled proportional directional valve 80 '(4/4-way valve) is provided for switching operations and only a single double-acting switching cylinder 103'.

A simple selector actuator 122 is provided for dialing movements, for example in the form of a single-acting hydraulic cylinder, as shown. Instead of the single-acting hydraulic cylinder, any other magnetic or electromechanical device for performing the selection movements 118 can also be provided, for example a rotary magnet, an electric motor or the like.

FIG. 6 shows an arrangement in which the gears of a transmission group 52 ″ are actuated by means of a single shift drum 126, which has a stator 128 and a rotor 130. A digitally controlled, proportional directional control valve 80 ″ is again provided for actuating the shift drum 126.

FIG. 7 shows a further modification in which, similar to the arrangement in FIG. 5, a shift shaft 114A, 114B is provided for each transmission group. A selection actuator in the form of a single-acting hydraulic cylinder 122A, 122B is provided for the switching shafts 114A, 114B of the hydraulic branches 68, 70.

A simple 3/2-way valve 140A, 14OB is provided for each of the hydraulic cylinders 122A, 122B. The directional control valves 140A, 140B are shown as proportional directional control valves and can be regulated in a manner similar to that which was explained at the beginning with reference to FIG. 1. The directional control valves 140A, 140B can, however, also be simple, non-proportional directional control valves.

FIG. 7 also shows that the transmission group 52, which is assigned to the hydraulic branch 68, includes the gears 1, 3, 5 and R. The other gear group 54, which is assigned to the hydraulic branch 70, has the gears 2, 4, 6 and also the reverse gear.

This arrangement can be implemented with a six-speed transmission. The special feature is that the reverse gear R can be actuated by means of both hydraulic branches 68, 70. This further increases redundancy. If one of the gearbox groups and / or one hydraulic branch fails, the vehicle therefore remains capable of limited driving using the gears then available (i.e. 1, 3, 5 and R or 2, 4, 6 and R). This ensures that the reverse gear can always be operated in this case.

The fail-safe position set up by the single-acting hydraulic cylinders 140A, 14OB relates in each case to the alley in which two forward gears are available (ie 3.5 or 4.6). As a result, even if the hydraulic cylinders 122A, 122B or the associated valves 140A, 140B fail, it is ensured that two forward gears can be shifted. As a result, the operating range of the transmission is increased in the event of conditional readiness to drive.

FIG. 8 shows a modification to the arrangement in FIG. 7. In the modification of FIG. 8, instead of the two selector control valves 140A, 140B, a single selector control valve 140 'is provided, which is used for selector movements of both switching shafts 114A, 114B. This reduces the valve outlay, although the strict separation of the two hydraulic branches 68, 70 is thereby somewhat eliminated. However, since the selector actuators 122A, 122B have a safe fail-safe position, this is less problematic.

Claims

claims

1. Hydraulic circuit (50) for controlling a double clutch transmission, which has two transmission groups (52, 54), each with a separating clutch (Kl, K2) and a plurality of clutches (60, 62) for engaging and disengaging gear stages, the hydraulic circuit (50) for each transmission group (52, 54) has its own hydraulic branch (68, 70), each of which is connected to a pump (66) via a safety valve (72, 74), and each hydraulic indicator (68, 70) has a clutch control valve (76, 78) for controlling the assigned clutch (K1, K2) and at least one shift control valve (80, 82) for controlling the assigned clutch (60, 62),

characterized in that

the safety valves (72, 74) are each designed as proportional pressure control valves (72, 74).

2. Hydraulic circuit according to claim 1, characterized in that the proportional pressure control valves (72, 74) are designed as pressure-limiting pressure control valves (72, 74).

3. Hydraulic circuit according to claim 1 or 2, characterized in that at least one of the clutch control valves (76, 78) is designed as a proportional directional valve (76, 78).

4. Hydraulic circuit according to one of claims 1-3, characterized in that the clutch control valves (76, 78) are digitally controlled.

5. Hydraulic circuit according to claim 4, characterized in that a sensor (98, 100) is provided for a physical variable (P) assigned to the respective separating clutch (K1, K2), the output of which is sampled and fed to a digital controller (88).

6. Hydraulic circuit according to one of claims 1-5, characterized in that a pressure relief valve (94, 96) is connected between the clutch control valves (76, 78) and actuators (56, 58) for actuating the separating clutches (Kl, K2).

7. Hydraulic circuit according to claim 6, characterized in that the actuators (56, 58) of the clutch clutches (Kl, K2) upstream pressure relief valves (94 ') are coupled such that a simultaneous frictional engagement of the two clutch clutches (Kl, K2) is excluded ,

8. Hydraulic circuit according to one of claims 1-7, characterized in that at least one of the switching control valves (80, 82) is designed as a proportional directional valve (80, 82).

9. Hydraulic circuit according to one of claims 1-8, characterized in that the gear stages of each transmission group (52, 54) by means of at least two individual shift rods (60-1, 60-2; 62-1, 62-2) are switchable and that the associated hydraulic branch (68, 70) for each shift rod (60, 62) has at least one proportional directional valve (80, 82) as a shift control valve.

10. Hydraulic circuit according to one of claims 1-8, characterized in that the gear stages of each transmission group (52, 54) can be shifted by means of a shift shaft (114) and that the respective hydraulic branch (68, 70) for the associated shift shaft (114) Has at least one proportional directional control valve (80 ') as a switching control valve (80') and at least one selection actuator (122) for selection movements (118) of the switching shaft (114).

11. Hydraulic circuit according to claim 10, characterized in that each hydraulic branch (68, 70) has a selector control valve (140A, 140B) for the respective selector actuator (122).

12. Hydraulic circuit according to claim 10, characterized in that for the two hydraulic branches (68, 70) a single common selector control valve (140 ') is provided for the selector actuators (122).

13. Hydraulic circuit according to one of claims 1-8, characterized in that the gear stages of a transmission group (52, 54) can be actuated by means of a shift drum (126).

14. Hydraulic circuit according to one of claims 1-13, characterized in that a low pressure circuit (84) for cooling or lubrication via a central valve (86) is also connected to the pump (66).

15. Hydraulic circuit according to claim 14, characterized in that the central valve (86) is a proportional directional valve (86).

16. Hydraulic circuit according to claim 15, characterized in that the central valve (86) for the low pressure circuit (84) has a switching position in which the low pressure circuit (84) is connected to the pump (66) via an orifice (104).

17. Hydraulic circuit according to one of claims 14 to 16, characterized in that the low-pressure circuit (84) has at least one jet pump (106).

18. Hydraulic circuit (50) in particular according to one of claims 1-17, for controlling a double clutch transmission of a vehicle (10), the double clutch transmission having two transmission groups (52, 54), each with a separating clutch (Kl, K2) and a plurality of shift clutches (60, 62) for engaging and disengaging gear stages, the hydraulic circuit (50) having its own hydraulic branch (68, 70) for each transmission group (52, 54), each of which has a pump (66 ), and each hydraulic branch (68, 70) each has a clutch control valve (76, 78) for controlling the assigned clutch (K1, K2) and at least one shift control valve (80, 82) for controlling the assigned clutch (60, 62) having,

characterized in that the two hydraulic branches (68, 70) are decoupled from one another in such a way that in the event of failure of any element of one transmission group (52, 54) or one hydraulic branch (68, 70) of the hydraulic circuit (50), the vehicle (10) by means of the other transmission group ( 52, 54) or the other hydraulic branch (68, 70) remains ready to drive.

19.Hydraulic circuit for controlling a drive train of a motor vehicle (10), with a proportional pressure control valve (34), which can be connected on the input side to a pump (30), and a digitally controlled, proportional directional valve (36), which on the input side with the proportional pressure control valve ( 34) and is connected on the output side to an actuator arrangement for actuating a safety-relevant device (22) of the drive train.