DE10316419B4 - Method for detecting a leakage of a hydraulic release system of a double clutch of a parallel shift transmission - Google Patents

Abstract

A method for detecting a leakage of a hydraulic release system of a double clutch of a parallel transmission, wherein the release system has the two clutches associated respective hydraulically actuated master cylinder and slave cylinder, characterized in that the disengagement of the slave cylinder of the non-active clutch is monitored, the difference of the disengagement of the slave cylinder to a Target position of the slave cylinder is determined in response to a master cylinder position, the amount of change in the disengagement position of the slave cylinder of the non-active clutch and / or the disengagement positions of the other slave cylinder is monitored, the difference of disengagement of this slave cylinder to a desired position of this slave cylinder in response to a master cylinder position is determined at least two times before and behind a snoop position of the associated master cylinder, the sum of the differences this disengagement position of the other slave cylinder is formed and a change of a transfer position of both clutches is determined by this sum is subtracted from the difference of the disengagement position of the slave cylinder of the non-active clutch, the amount of changes in these transfer functions of both clutches is determined and the leakage is detected, if at least one of the amounts exceeds a threshold.

Description

The present invention relates to methods having the features according to the preamble of claim 1.

From the DE 199 36 886 A1 such as DE 198 53 333A1 are known methods for detecting a leakage of a hydraulic release system.

A parallel shift transmission (also called PSG) is a variant of a dual-clutch transmission, in which the gears are arranged alternately in two partial transmissions, each having its own clutch.

By such an arrangement, it is possible to select a gear in the load-free partial transmission, while the torque is transmitted from the other partial transmission. The actual switching process is realized in that the torque is transmitted from one clutch to the other.

The requirements for such a parallel gearbox in terms of functionality and comfort correspond to those of the known automatic transmission, also called step machine. However, the parallel shift transmission has consumption advantages over the stepped automatic transmission, since such stepped automatic machines have a plurality of clutches which constantly run during operation and thus generate power losses due to fluid friction, and thus increase consumption.

In a parallel shift transmission, however, the clutch of the just torque-free subtransmission generates no slippage, as long as no gear is preselected in this sub-transmission.

The dual clutch of such a parallel transmission can be operated with an electric motor actuator and a hydraulic release system. Such an arrangement has the advantage that, in the event of failure of the energy driving the electromotive actuator, the couplings remain open, in particular when this is designed to be self-locking, and the critical case can not occur that both couplings are closed at the same time.

The hydraulic release system with a donor cylinder and slave cylinder associated with each clutch has, inter alia, the advantage that the lines of the hydraulic circuit in the respective vehicle can be installed vehicle-specific and therefore the release system does not have to be adapted independently for different vehicle types.

When using such a hydraulic release system but must still be ensured that not both clutches are closed simultaneously, which could occur even with a creeping pressure loss in the release system of the currently not active clutch.

The present invention is therefore based on the object to provide a method for detecting a leakage of a hydraulic disengagement of a dual clutch parallel transmission, which allows the detection of such pressure loss, but is not affected by system-inherent properties, such as operating temperature change induced behavior of the hydraulic system. In addition, a method is to be developed which avoids a leakage-induced closing of the double clutch of a parallel shift transmission.

This object is achieved by a method having the features according to claim 1.

The invention now provides a method for detecting a leakage of a hydraulic disengagement system of a double clutch of a parallel transmission, in which the release system has the two clutches associated respective hydraulically actuated master cylinder and slave cylinder, wherein the method according to the amount of change in the disengaged position of the slave cylinder of the non-active Clutch and / or the amount of changes in the transfer functions of both clutches is determined and leakage is detected when at least one of said amounts exceeds a predetermined value.

Under the non-active clutch, the open clutch of the sub-transmission is understood in which a gear is selected, but which is not involved in the transmission due to the open coupling. If now the disengagement position of the slave cylinder of the non-active clutch changes by a value which exceeds a predetermined value, it can be assumed that a leakage in the hydraulic release system of the non-active clutch.

It can also be assumed that such a leakage, when the amount of changes in the below-described transfer functions of both clutches exceeds a predetermined value. The significance of the leak detection is higher if both conditions are cumulatively fulfilled.

After a modification of the method according to the invention also the amount of change of the transfer function of the active clutch can be determined and / or the amount of change the transmission functions of both clutches are determined and are then assumed to be a leak when at least one of the amounts exceeds a predetermined value. The significance of the leakage detection is significantly increased, in particular, if one of the stated amounts exceeds the predetermined value in a reproduced manner, that is to say if it is repeatedly determined in successive cycles that a threshold value violation has occurred.

According to a modification of the method according to the invention, the difference between the slave cylinder positions of both clutches determines the current disengagement positions of the slave cylinder determined, determines their difference as a measured variable S, and from this measurand S using a linear dependence of the slave cylinder positions of the corresponding master cylinder positions a difference of arithmetic slave cylinder positions determined force-free clutches and a leakage determined by a change in the difference. In other words, it means that the two slave cylinder positions are detected and it is concluded, for example, that the slave cylinder position of at least one of the slave cylinders has changed due to a leakage in the hydraulic circuit and thus a leak in the hydraulic release system of at least one of the must be present both clutches.

Based on the observation of the direction of the change in the difference can be determined in which of the respective clutches associated Ausrücksystemen leakage has occurred. If, in addition, the speed of the change in the difference is evaluated, it is also possible, for example on the basis of a very large gradient, to conclude the change in the difference to a line break or the like.

According to a modification of the method according to the invention, it is provided that by means of a differential pressure sensor, a pressure difference in the hydraulic circuits of the release system of both clutches is determined and based on a change in the differential pressure leakage in the release system of the non-active clutch is detected. In other words, this means that, for example, between the two hydraulic lines, which drive the respective slave cylinder, a differential pressure sensor can be attached, which detects the pressure difference in the two hydraulic lines as a measured variable and thus provides a characteristic that compared with a characteristic from a reference map becomes. The reference map describes the target pressure difference as a function of the current master cylinder positions. A characteristic comparison allows a closing for leakage on the basis of a difference formation and a threshold value difference exceeding the difference value.

Finally, it is provided according to a further modification of the method according to the invention that the travel of the clutch actuator between a known position of a respective clutch release bearing and the respective clutch associated stop is determined and determined on the basis of a change in the travel leakage in the release system of the non-active clutch is, with the stop can be reached only after an over-travel of the open clutch. For this purpose, the coupling may have a stop which can be achieved by a necessary over the travel of the clutch actuator to open the clutch travel out towards the clutch opening and the achievement of this attack can be detected, for example, a load current increase of the clutch actuator. This can be used as an inspection criterion for an open clutch and prior art position of the respective clutch release bearing the path length to reach the stop. As part of a cyclic measurement, the distance from the known release bearing position can be moved cyclically to the stop by the actuator, so that a change in the travel in the release system of the clutch can be detected in a leakage and thus can be concluded in this way to a leak.

Since the coupling is subject to wear and this wear is compensated in an advantageous manner via a device for wear adjustment of the clutch, this would lead to a change in the travel due to the wear adjustment, so that it is advantageous if the position of the stop together with a wear-related Adjustment of the clutch is changed.

In addition to the above-described detection of a leak in the hydraulic release system, it is also necessary to respond to an example, line break-induced sudden pressure drop in the release system in such a way that such a pressure loss does not lead to an uncontrolled snapping of the two clutches. For this purpose, it may be provided that the leakage-related closing of the double clutch of a parallel transmission is avoided, that in the hydraulic circuit of Ausrücksystems a valve is provided which is closed at a sudden pressure difference such that this suddenly occurring pressure difference is not up to the slave cylinders can propagate the respective release systems of the couplings and thus an uncontrolled snapping the clutches is avoided.

Finally, it is also provided according to the invention that after the detection of a leak in the hydraulic release system an emergency program of the transmission control is activated, which executes various error handling routines depending on the significance of the operation of the leak detection. These fault handling routines may count, for example, the shutdown of the torque tracking of the clutch, or even the activation of a routine that is switched only with traction interruption, which would immediately sensitize the driver to the fact that a system error is present. Also, after a further error handling routine, the relevant partial transmission can be deactivated, that is to say that driving is only permitted in the still active partial transmission. Also occurred fault conditions can be stored, so that a corresponding fault memory entry a review in the workshop of equipped with such a parallel transmission vehicle is made possible. With the mentioned error handling routines it is achieved that due to a change in the switching behavior of the parallel shift transmission, the driver of such a vehicle receives an indication to have a fault check carried out, but an emergency driving operation of the vehicle is still possible.

The invention will be explained in more detail below with reference to the drawing. This shows in:

1 a schematic representation of a parallel shift transmission with dual clutch and Ansteuerungsaktorik;

2 a diagram of slave cylinder travel plotted against the master cylinder path;

3 a diagram similar 2 to explain the characteristic shift;

4 a diagram for explaining the positioning of a differential pressure sensor;

5 a diagram for explaining the leak detection based on a pressure difference change;

6 an illustration for explaining the leak detection based on a change in the travel of the clutch actuator to reach the stopper; and

7 a schematic representation of an emergency valve.

1 The drawing shows the schematic structure of a parallel gearbox with dual clutch and Ansteuerungsaktorik. Shown are two couplings 1 . 2 , two slave cylinders 3 . 4 , two units 5 . 6 each consisting of a clutch actuator and a master cylinder and provided thereon respective displacement sensors 7 . 8th , Also is the slave cylinder 3 a displacement sensor 9 provided and on the slave cylinder 4 a corresponding displacement sensor 10 ,

With the respective slave cylinder sensors 9 . 10 the slave cylinder position can be detected. The displacement sensors provided on the master cylinders 7 . 8th serve the position control of the electromotive clutch actuator and can be incremental measuring sensors of the electric motors of the clutch actuators in an advantageous manner.

2 The drawing shows a linearized idealized transmission behavior of the slave cylinder path or slave path x _K , plotted on the encoder cylinder or encoder x _G. In 2 is the linearized behavior with a solid half-line, which has the slope c _K shown, as well as a real transmission behavior based on the dotted line.

The transmission behavior from the master cylinder to the slave cylinder can starting from a position in which a pressure or volume compensation with the reservoir is possible (this is called the so-called sniffing) by the in 2 The illustrated linearized function are idealized. The snoop position of the master cylinder is a structurally predetermined size. The slave cylinder position in the depressurized state of the disengagement system may, for example, change depending on the state of wear of the clutch, the engine speed and the component temperature. Also, due to changes in the temperature of the hydraulic fluid in the release system, the slave cylinder position changes, for example, in a warming towards a greater release position. A cooling of the hydraulic fluid leads to a change in the slave cylinder position towards a smaller release position. Even with a leak, the slave cylinder performs a change in position in the direction of a smaller disengagement position.

This behavior is in 3 the drawing shown schematically, wherein the upper parallel shifted half-line corresponds to a characteristic shift, for example, due to heating and the lower parallel shifted half-line represents a characteristic shift due to leakage.

x_K

Nehmerweg

x_G

Geberweg

NP_K

Nehmerposition bei kraftfrei geschlossener Kupplung

TP_K

Nehmerposition bei Trennpunkt der Kupplung

SP_G

Schnüffelbohrungsposition (Geberposition bei kraftfrei geschlossener Kupplung)

TP_G

Nehmerposition bei Trennpunkt der Kupplung.

The figures can be taken from the following names:

x _K

slave travel

x _G

control travel

NP _K

Slave position with force-free closed coupling

TP _K

Slave position at disconnection point of the coupling

SP _G

Sniffer hole position (encoder position with force-free closed coupling)

TP _G

Slave position at disconnection point of the coupling.

To detect a leak can be monitored with disengaged, ie non-active clutch, the change in the disengagement position of the slave cylinder of the non-active clutch. If the non-active clutch is referred to as K2, then the change in the disengagement position of the non-active clutch results from the following relationship: Δ _K2 = x _K2 - NP _K2 - c _K2 · (x _G2 - SP _G2 )

The amount of changes in the transfer functions of both clutches is given as Δ Δ = _{12 K2} - ΣΔ _K1, wherein, using the term K1 for the active coupling, the cumulative drift of the transfer function of the active couplings between each two consecutive sniffing operations ΣΔ _K1 = Σ [x _K1 -NP _K1 -c _K1 * (x _G1 -SP _K1 )] results. The totaling is required because the position NP _K1 , the slave position when force-free closed clutch when pressure or volume compensation (sniffing) 1 can change.

Leakage can then be detected when the amount of change in the disengagement position of the slave cylinder of the non-active clutch exceeds a predetermined threshold, ie the condition B1: -Δ _K2 > GW _K2 is satisfied.

The level of significance for leakage detection is higher when the amount of change in the transfer functions of both clutches exceeds a predetermined threshold, that is, the condition B2: -Δ ₁₂ > GW ₁₂ is satisfied. In particular, when both conditions are met or one of the two conditions is reproducibly true, it must be assumed that there is a leakage in the release system of the respective clutch.

In addition to the just-described monitoring of the non-active clutch and a corresponding monitoring of the active clutch can be made. For this purpose, the amount of change in the transfer function of the active clutch can be determined and / or the amount of change in the transfer functions of both clutches can be determined and then closed for leakage if at least one of the amounts exceeds a predetermined value. The conditions that speak for the detection of a leak are based on the following mathematical relationships B3: -ΣΔ _K1 > GW _K1 B4: + Δ ₁₂ > GW ₁₂ .

On the basis of the distance measuring sensors 9 and 10 it is possible to detect the taker paths x _K1 and x _K2 and thus to form a difference S from the slave path x _K2 and x _K1 . Alternatively, a relative sensor for direct detection of the measured variable can also be provided.

The measured variable S results from the following equation: S = x _K2 - x _K1 = NP _K2 - NP _K1 + c _K2 * MAX (x _G2 - SP _G2 ; 0) - c _K1 * MAX (x _G1 - SP _G1 ; 0) where c _K1 and c _{K2 are} the line slopes of the transmission behavior of the clutch K1 and clutch K2, as shown by 2 has already been explained.

On the basis of an observation of the difference (D) of the two slave cylinder positions NP _K1 and NP _K2 in force-free closed couplings can be concluded on a leak. The difference D describes the recalculated from the current disengagement positions distance of the two coupling zero points (slave position with closed clutch) and results from the following mathematical relationship: D = NP _K2 - NP _K1 = S - c _K2 * MAX (x _G2 - SP _G2 ; 0) + c _K1 * MAX (x _G1 - SP _G1 ; 0).

If a leakage occurs, there is a change in the difference D such that, taking into account D = NP _K2 - NP _K1 = S - c _K2 · MAX (x _G2 - SP _G2 ; 0) + c _K1 · MAX (x _G1 - SP _G1 ; 0) when increasing D from leakage in the release system in the clutch 1 can be assumed and with a reduction of D from a leakage in the release system of the clutch 2 , The change in the difference D is continuously monitored during operation of the parallel transmission, which is particularly necessary when a gear is preselected in the non-active part of the transmission and therefore the clutch must remain open.

For this purpose, initially an initialization of the leakage monitoring is carried out, advantageously after a respective switching operation, and the following value assignment is carried out at the time T0: Δ ₀ = 0; D ₀ = D (T ₀ ).

• • Δ = Δ₀ + D – D₀ ≤ –Grenze => Leckageverdacht Kupplung 2
• • Δ = Δ₀ + D – D₀ ≥ +Grenze => Leckageverdacht Kupplung 1

If a difference change is detected in the cyclical monitoring operations, it can be determined by means of the direction of the change in the difference D in which of the hydraulic clutches associated with the respective clutches a leakage has occurred, this being illustrated by the following mathematical relationship:

• • Δ = Δ ₀ + D - D ₀ ≤ limit => Leakage suspected Coupling 2
• • Δ = Δ ₀ + D - D ₀ ≥ + limit => leakage suspected Coupling 1

Since the respective slave cylinder can repeatedly reach their pressure compensation positions (sniffer positions), the leakage monitoring is briefly interrupted when such a sniffing operation takes place. But so that a slow leakage can be detected, the current value Δ is stored and continue to be used after a re-commissioning of the monitoring process after snooping. For this purpose, the size Δ _{0 is} newly occupied, namely Δ ₀ = Δ = Δ ₀ + D - D ₀ and continue with this value after the resumption of leakage monitoring. Leakage can be assumed when the thus determined Δ value moves very quickly beyond the limits, ie the gradient of the change is very high, or the Δ value reproducibly exceeds the threshold values with a substantially constant gradient.

In the normal driving operation of a vehicle equipped with a parallel transmission, the clutch of the active output shaft is at least partially closed, the clutch of the non-active output shaft open. This leads to different instantaneous operating points of the respective clutches on the pressure-displacement characteristic, as shown in FIG 5 the drawing is shown.

A creeping pressure loss due to leakage leads to a change in the ratio of the pressures in both release systems and their hydraulic lines due to a shift of the operating point s ₂₀ -> s _{21 of} the opened clutch. The shift of the operating point s _{10 of} the active clutch due to a slip control or torque tracking is set by the clutch control or transmission control active, so it is known. This makes it possible on the basis of the change of the differential pressure Δ (Δp) = Δ (p (s ₂ ) -p (s ₁ )) determine in both the clutches associated release systems a possible leakage in the open clutch.

The use of the differential pressure has the advantage that the actual pressure-displacement curve does not need to be known exactly, since the actual operating points of both clutches are determined after each switching operation, sniffing process and touch-point adaptation and only the change of the differential pressure is monitored. This also has the particular advantage that the influence of thermal changes is less, since such thermal changes to the differential pressure lower influences than on absolute values, since these changes have an equal impact on both release systems. Also, advantageously only one differential pressure sensor is required, as shown schematically in FIG 4 the drawing is shown.

The following is based on 6 the drawing explains the method for detecting a leak on the basis of the travel of the clutch actuator between a known position of a clutch release bearing and a respective clutch associated stop. The left drawing in the upper half of the 6 shows the closed state of the coupling, while the right drawing shows the state "cover stop reached" and the middle drawing shows the opened state of the coupling. As it is based on the force-displacement diagram in the lower half of the drawing 6 can be seen, the clutch actuator after reaching the position B, to which the clutch is already open, pass another path towards the stop, the stop can be detected by the high increase of the actuator force at the position C. The stop therefore represents a reference position and the travel of the clutch actuator from the known position of the clutch release bearing to the clutch associated stop changes when there is a loss of volume in the hydraulic line of the open clutch, so the hydraulic release system of the non-active clutch. On the basis of the change of the travel of the clutch actuator from the disengaged position of the clutch release bearing and the stop can therefore be concluded that there is a leakage in the release system.

As has already been explained above, in a hydraulic clutch release system of the double clutch of a parallel shift transmission, it is necessary to avoid inadvertently closing both clutches, since this could lead to a negative behavior on the driveability of the vehicle equipped with such a transmission.

In addition to the detection of a creeping pressure drop due to leakage, it is therefore also necessary to take precautions against a sudden pressure drop in the release system to avoid an uncontrolled snapping the clutch.

To solve this problem, it is therefore proposed according to the invention to arrange a load-dependent valve in the hydraulic line in front of the slave cylinder, so that a sudden pressure drop can not progress to the slave cylinder and thus an uncontrolled snapping the clutch is avoided.

7 shows a schematic representation of such emergency valve in the form of a ball valve. In the open state while the ball is biased biased by the spring shown schematically pressed against a ramp assembly and held in position. The pressurized fluid may flow around the ball upon actuation of the clutch. If a critical pressure difference is exceeded, the ball snaps out of the ramp assembly and is pressed against the schematically shown throttle acting diameter constriction of the hydraulic line. As a result, no liquid can flow through the throttle and the pressure in front of the throttle is maintained.

It is possible to adjust the critical pressure difference over the geometry of the ramp arrangement or on the biasing force of the spring. Integration of the emergency valve into the disengagement mechanism eliminates uncontrolled clutch slippage and allows the transmission controller sufficient time to detect and respond to the hydraulic failure, for example by laying out the submitted gear without sets a safety-critical state. The illustrated emergency valve is characterized by a simple structure, easy installation in the release system and high reliability.

Claims (12)

A method for detecting a leakage of a hydraulic release system of a double clutch of a parallel transmission, wherein the release system has the two clutches associated respective hydraulically actuated master cylinder and slave cylinder, characterized in that the disengagement of the slave cylinder of the non-active clutch is monitored, the difference of the disengagement of the slave cylinder to a Target position of the slave cylinder is determined in response to a master cylinder position, the amount of change in the disengagement position of the slave cylinder of the non-active clutch and / or the disengagement positions of the other slave cylinder is monitored, the difference of disengagement of this slave cylinder to a desired position of this slave cylinder in response to a master cylinder position is determined at least two times before and behind a snoop position of the associated master cylinder, the sum of the differences this disengagement position of the other slave cylinder is formed and a change of a transfer position of both clutches is determined by this sum is subtracted from the difference of the disengagement position of the slave cylinder of the non-active clutch, the amount of changes in these transfer functions of both clutches is determined and the leakage is detected, if at least one of the amounts exceeds a threshold. A method according to claim 1, characterized in that the amount of change in the transfer function of the active clutch is determined and / or the amount of change in the transfer functions of the clutch is determined and the leakage is detected when at least one of the amounts exceeds a threshold. A method according to claim 1 or 2, characterized in that the leakage is detected when at least one of the amounts exceeds the threshold reproduced. A method for detecting a leakage of a hydraulic disengagement system of a double clutch of a parallel transmission, wherein the release system has the two clutches associated respective hydraulically actuated master cylinder and slave cylinder, characterized in that the current disengagement positions of the slave cylinder are determined, their difference is determined as a measured variable S, and off this Measured variable S is determined by using a linear dependence of the slave cylinder positions of the corresponding master cylinder positions a difference of arithmetic slave cylinder positions in force-free clutches, wherein a leakage is determined by a change in the difference. A method according to claim 4, characterized in that based on the direction of the change in the difference is determined in which of the respective clutches associated hydraulic Ausrücksystemen leakage has occurred. A method according to claim 4 or 5, characterized in that based on the gradient of the change in the difference, a failure of a hydraulic release system is detected. A method for detecting a leakage of a hydraulic disengagement of a double clutch of a parallel transmission, wherein the release system associated with the two clutches each hydraulically actuated master cylinder and slave cylinder, characterized in that by means of a differential pressure sensor, a pressure difference in the hydraulic circuits of the disengagement of both clutches is determined and on the basis a change in the differential pressure in comparison with a reference characteristic field, a leakage in the release system of the non-active clutch is detected, wherein the reference map describes the target pressure difference as a function of the current master cylinder positions. A method for detecting a leakage of actuated by a clutch actuator hydraulic release system of a dual clutch parallel transmission, characterized in that the travel of the clutch actuator between a known position of a respective clutch release bearing and a respective clutch associated stop is determined and on the basis of a change in the travel Leak in the release system of the non-active clutch is detected, the stop can be reached only after an over-travel of the open clutch. A method according to claim 8, characterized in that the position of the stopper is changed together with a wear-related adjustment of the clutch. Method for the reaction to a leakage in the hydraulic release system of a double clutch of a parallel shift transmission according to one of claims 1 to 9, characterized in that after the detection of the leakage an emergency program of the transmission control is activated, which executes various error handling routines depending on the significance of the condition of leakage detection , A method according to claim 10, characterized in that the switching behavior of the parallel shift transmission is changed such that the driver of a vehicle equipped with such a transmission receives an indication to perform an error check, but an emergency driving operation of the vehicle is still possible. A method according to claim 10 or 11, characterized in that is switched after the leak detection only with traction interruption and / or the relevant sub-transmission is deactivated.

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