DE10316419A1 - Leak identification method in hydraulic double clutch comprises determining values of modifications of clutch position of receiving actuator of inactive clutch and transmission functions of two clutches - Google Patents

Abstract

The clutch system for a double clutch of a parallel gearbox comprises hydraulic control transmitting and receiving actuators allocated to the two clutches. The leak identification method comprises determining the value (B1) of the modification of the clutch position of the receiving actuator of the inactive clutch and/or the value (B2) of the modifications of the transmission functions of the two clutches. The leak is noted when one of the values exceeds a predetermined value.

Description

The present invention relates to a method for detecting a leak a hydraulic clutch release system of a double clutch Parallel shift. The invention also relates to a method for Avoiding leakage-related closing of the double clutch of such Parallel shift.

A parallel gearbox (also called PSG) is a variant of one Double clutch transmission, in which the gears alternate in two sub-transmissions are arranged, each having its own clutch.

With such an arrangement, it is possible to shift a gear in a no-load condition Preselect sub-transmission while the torque from the other sub-transmission is transmitted. 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 regarding Functionality and comfort correspond to those of the well-known automatic transmission, also called step machine. The parallel gearbox points however the step machine on consumption advantages because such step machines have multiple clutches that run continuously during operation and thus generate power loss due to fluid friction and thus consumption increase.

In the case of a parallel gearbox, however, the clutch produces straight torque-free partial transmission no slip, as long as no gear in this Partial gearbox is selected.

The double clutch of such a parallel gearbox can with one actuated by an electric motor and a hydraulic release system become. Such an arrangement has the advantage that if the the clutches that drive the electromotive actuator especially if it is self-locking, remain open and not the critical case can occur that both clutches are simultaneously getting closed.

The hydraulic release system with one assigned to each clutch Master cylinder and slave cylinder have the advantage, among other things, that the Lines of the hydraulic circuit in the respective vehicle are laid vehicle-specifically and therefore the release system cannot be used for different Vehicle types must be adapted independently.

When using such a hydraulic release system, however still make sure that not both clutches at the same time be closed, which is also in the case of a gradual loss of pressure in the Release system of the currently inactive clutch could occur.

The present invention is therefore based on the object Method of detecting leakage from a hydraulic release system to create a double clutch of a parallel gearbox that the Detection of such a pressure drop is allowed, but by system inherent Properties such as operating temperature changes Behavior of the hydraulic system is not affected. Beyond that a method can also be developed which involves leakage-related closing avoids the double clutch of a parallel gearbox.

To achieve this object, the invention relates to the method Leakage detection has the following features: a hydraulic release system a double clutch of a parallel transmission, the release system the respective hydraulically operated assigned to the two clutches Has master cylinder and slave cylinder, and the amount of change in Disengagement position of the slave cylinder of the inactive clutch and / or the amount the changes in the transfer functions of both clutches is determined and the leak is determined if at least one of the amounts contains one exceeds a predetermined value. Advantageous process designs are described in the further claims. In addition, the invention regarding the method for avoiding leakage-related closure the double clutch has the following features: a release system with two Couplings assigned to respective hydraulically operated master cylinders and Slave cylinders, one in the hydraulic circuit of the release system provided valve that is closed to a sudden pressure difference such that a sudden pressure difference occurs on the slave cylinders is avoided, with advantageous configurations thereof in the further Claims are described.

The invention now provides a method for detecting a leak a hydraulic clutch release system of a double clutch Parallel gearbox, in which the release system is the two clutches assigned respective hydraulically operated master cylinders and slave cylinders having, according to the procedure, the amount of change in the release position of the slave cylinder of the inactive clutch and / or the amount of Changes in the transfer functions of both clutches is determined and one Leakage is then determined when at least one of the amounts mentioned exceeds a predetermined value.

Under the inactive clutch is the open clutch of the partial transmission understood, in which a course is selected, but which is due to the open Clutch is not involved in the power transmission. If now Disengagement position of the slave cylinder of the inactive clutch by one value changed, which exceeds a predetermined value, can from a Leakage in the hydraulic clutch disengagement system be assumed.

Such a leak can also be assumed if the amount the changes in the transfer functions explained below of both clutches exceeds a predetermined value. The significance of the Leakage determination is higher if both conditions are met cumulatively.

After a modification of the method according to the invention, the Amount of change in the transfer function of the active clutch determined and / or the amount of change in the transfer functions of both Couplings are determined and then assumed a leak if at least one of the amounts has a predetermined value exceeds. The significance of the leakage detection is particularly then significantly increased if any of the amounts mentioned exceeds the predetermined value reproduced exceeds, if so several times in successive cycles it is determined that a threshold has been exceeded.

After a modification of the method according to the invention, the difference the slave cylinder positions of both clutches determined and a leak determined by changing the difference. It means this with in other words, that the two slave cylinder positions are recorded and at a difference that changes repeatedly, for example it is concluded that the slave cylinder position is at least one of the Slave cylinder has changed due to a leak in the hydraulic circuit and thus a Leakage in the hydraulic release system of at least one of the two Couplings must be present.

By observing the direction of the change the difference can be determined in which of the associated couplings A leakage has occurred in the release systems. If additionally that The rate of change of the difference is evaluated, too for example on the basis of a very large gradient of change in the Difference can be concluded on a line break or the like.

After a modification of the method according to the invention, it is provided that 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 a change in the differential pressure a leak in the release system of the inactive clutch is detected. In other words, it means that, for example, between the two hydraulic lines that the respective Activate slave cylinder, a differential pressure sensor can be attached, the measured variable is the pressure difference in the two hydraulic lines recorded and thus provides a parameter that is based on a parameter from a Reference map is compared. The reference map describes the Setpoint pressure difference depending on the current master cylinder positions. On Parameter comparison can be made on the basis of a difference and one If the differential value exceeds the threshold, leakage is closed.

Finally, it is after a further modification of the invention Method provided that the travel of the clutch actuator between a known position of a respective clutch release bearing and a stop assigned to the respective clutch is determined and on the Based on a change in the travel path, a leak in the release system of the inactive clutch is detected. For this purpose, the clutch can Have stop that by a through the travel of the clutch actuator necessary to open the clutch in the direction Clutch opening can be achieved and reaching this stop detected for example via a rise in the load of the clutch actuator can be. This can be done with an open clutch and known Position of the respective clutch release bearing the path length until it is reached of the attack can be used as a test criterion. As part of a cyclical Measurement can cover the distance from the known release bearing position cyclically to the stop by the actuator, so that at a leak a change in the travel in the release system of the Coupling can be determined and thus concluded that there is a leak can be.

Because the clutch is subject to wear and tear, this wear in advantageously via a device for adjusting the wear of the clutch is compensated, this would result in a change in the travel path wear adjustment, so it is beneficial if the position of the attack together with a wear-related adjustment of the Clutch is changed.

In addition to the detection of a leak in the Hydraulic release system, it is also necessary, for example to respond to a sudden pressure drop in the release system due to a cable break in such a way that such a pressure drop does not result in an uncontrolled Snap both clutches leads. For this purpose it is after the Invention also provided that the leakage-related closing of the Double clutch of a parallel transmission is avoided in the hydraulic circuit of the release system, a valve is provided, which is suddenly at a occurring pressure difference is closed such that this suddenly occurring pressure difference is not up to the slave cylinders of the respective Disengagement systems of the clutches can propagate and thus an uncontrolled Snapping the clutches is avoided.

Finally, it is also provided according to the invention that according to the Detecting a leak in the hydraulic release system is an emergency program the transmission control is activated, which depending on the Significance of the operation of the leak detection various Executes error handling routines. For example, these error handling routines count the deactivation of the clutch torque tracking, or else also activating a routine that only with traction interruption is switched, which would immediately sensitize the driver to the fact that there is a system error. Can also be done after another Error handling routine, the relevant sub-transmission can be deactivated, i.e. driving only still be allowed in the still active partial transmission. Can too occurred error conditions are saved so that a corresponding error memory entry a check in the workshop of the one such parallel gearbox equipped vehicle is made possible. With the mentioned error handling routines is achieved because of a Change in the shift behavior of the driver's parallel gearbox such a vehicle receives a message, carry out a fault check to let, but an emergency operation of the vehicle is still possible.

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

Figure 1 is a schematic representation of a parallel transmission with double clutch and control actuator.

Fig. 2 is a diagram of the slave cylinder path, plotted over the Geberzylinderweg;

Fig. 3 is a diagram similar to Figure 2 for explaining the characteristic shift.

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

5 is a diagram for explaining the leakage detection on the basis of a pressure difference change.

Fig. 6 is an illustration for explaining the leakage detection based on a change in the travel of the clutch actuator to reach the stop, and

Fig. 7 is a schematic representation of an emergency valve.

Fig. 1 of the drawing shows the schematic structure of a parallel transmission with double clutch and control actuator. Shown are two clutches 1 , 2 , two slave cylinders 3 , 4 , two units 5 , 6 , each consisting of a clutch actuator and a master cylinder and respective displacement sensors 7 , 8 provided thereon. A displacement sensor 9 is also provided on the slave cylinder 3 and a corresponding displacement sensor 10 on the slave cylinder 4 .

The slave cylinder position can be detected with the respective slave cylinder sensors 9 , 10 . The displacement sensors 7 , 8 provided on the master cylinders serve to control the position of the electromotive clutch actuator and can advantageously be incremental measurement sensors of the electric motors of the clutch actuators.

Fig. 2 of the drawing shows a linearized, idealized transmission characteristics of the slave cylinder or slave travel path x _K, plotted against the Geberzylinderweg or master travel x _G. In FIG. 2 this is the linearized behavior by a solid half-line having slope _K c, shown, as well as a real transfer characteristic based on the dotted line.

The transfer behavior from the master cylinder to the slave cylinder can be idealized starting from a position in which pressure or volume compensation with the storage container is possible (here one speaks of the so-called sniffing) by the linearized function shown in FIG. 2 of the drawing. The sniffing position of the master cylinder is a design variable. The slave cylinder position in the depressurized state of the release system can change, for example, 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 disengaging system, the slave cylinder position changes, for example when heated in the direction of a larger disengaging position. A cooling of the hydraulic fluid leads to a change in the slave cylinder position towards a smaller disengagement position. Even in the event of a leak, the slave cylinder changes position towards a smaller disengagement position.

This behavior is shown schematically in FIG. 3 of the drawing, the upper, half-straight line shifted in parallel corresponding to a shift in the characteristic curve, for example due to heating, and the lower, half-straight line shifted in parallel representing a shift in the characteristic curve due to leakage.

The following names can be found in the figures:

x _K : Nehmerweg
x _G : encoder path
NP _K : Slave position when clutch is de-energized
TP _K : slave position at the disconnection point of the clutch
SP _G : Sniffer bore position (encoder position when clutch is de-energized)
TP _G : slave position at the disconnection point of the clutch.

To determine a leak, the change in the disengagement position of the slave cylinder of the non-active clutch can be monitored when the clutch is disengaged, ie, inactive. If the non-active clutch is referred to as K2, the change in the disengaged 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 results as:

Δ ₁₂ = Δ _K2 - ΣΔ _K1 ,

where using the designation K1 for the active clutch, the cumulative drift of the transfer function of the active clutches between two successive sniffing processes as

ΣΔ _K1 = Σ [x _K1 - NP _K1 - c _K1 . (X _G1 - SP _K1 )]

results. The summation is necessary because the position NP _K1 , the slave position when the clutch 1 is deenergized, can change during pressure or volume compensation (sniffing).

Leakage can then be determined when the amount of change in the disengagement position of the slave cylinder of the non-active clutch exceeds a predetermined threshold value, i.e. the condition:

B1: - Δ _K2 > GW _K2

is satisfied.

The level of significance for the leakage determination is higher if the amount of changes in the transfer functions of both clutches exceeds a predetermined threshold value, i.e. the condition:

B2: - Δ ₁₂ > GW ₁₂

is satisfied. In particular, if both conditions are fulfilled or one of the two conditions is reproducibly true, a leak in the release system of the clutch in question can be assumed.

In addition to the monitoring of the inactive clutch just described, the active clutch can also be monitored accordingly. 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 function of both clutches can be determined and a leak can be concluded if at least one of the amounts exceeds a predetermined value. The conditions that speak for the detection of a leak result from the following mathematical relationships:

B3: - ΣΔ _K1 > GW _K1 ,

B4: + Δ ₁₂ > GW ₁₂ .

On the basis of the displacement sensors 9 and 10 , it is possible to detect the slave paths x _K1 and x _K2 and thus to form a difference S from the slave paths x _K2 and x _K1 . As an alternative to this, a relative sensor can also be provided for the direct detection of the measured variable.

The measured variable S is based on 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 straight gradients of the transmission behavior of the clutch K1 and clutch K2, as has already been explained with reference to FIG. 2.

An observation of the difference (D) between the two slave cylinder positions NP _K1 and NP _K2 in the case of clutches that are de-energized enables a leak to be concluded. The difference D describes the distance between the two clutch zero points calculated back from the current disengagement positions (slave position when the clutch is closed) 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 leak occurs, the difference D changes 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)

if D is increased, a leak in the release system in clutch 1 can be assumed, and if D is reduced, there is a leak in the release system of clutch 2 . The change in the difference D is continuously monitored during the operation of the parallel gearbox, this being particularly necessary if a gear is preselected in the non-active sub-gearbox and the clutch must therefore remain open.

For this purpose, the leakage monitoring is first initialized, advantageously after a respective switching operation, and the following value assignment is carried out at time T0:

Δ ₀ = 0; D ₀ = D (T ₀ ).

If a change in the difference is ascertained in the cyclically carried out monitoring processes, then the direction of the change in the difference D can be used to determine in which of the hydraulic clutch release systems associated with the respective clutches a leakage occurred, which can be explained on the basis of the following mathematical relationship :

Δ = Δ ₀ + D - D ₀ ≤ - limit => leakage suspected clutch 2 ,

Δ = Δ ₀ + D - D ₀ ≥ + limit => suspected leakage clutch 1 .

Since the respective slave cylinders can repeatedly reach their pressure compensation positions (sniffing positions), the leakage monitoring is briefly interrupted when such a sniffing process takes place. However, so that a slow leakage can be recognized, the current value Δ is stored and used again when the monitoring process is restarted after sniffing. For this purpose, the size Δ _{0 is} newly assigned, namely:

Δ ₀ = Δ = Δ ₀ + D - D ₀

and after this resumption of the leakage monitoring continues with this value. Leakage can be assumed if the Δ value determined in this way moves very quickly beyond the limits, that is to say the gradient of the change is very high, or if the Δ value reproducibly exceeds the threshold values with a largely constant gradient.

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

A gradual pressure loss due to leakage leads to a change in the ratio of the pressures in both release systems or their hydraulic lines due to a shift in the operating point s ₂₀ → s _{21 of} the opened clutch. The shift of the operating point s _{10 of} the active clutch as a result of a slip control or torque tracking is actively specified by the clutch control or transmission control and is therefore known. This makes it possible, based on the change in differential pressure:

Δ (Δp) = Δ (p (s ₂ ) - p (s ₁ ))

detect a possible leak in the opened clutch in both release systems assigned to the clutches.

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

The method for detecting a leak based on the travel path of the clutch actuator between a previously known position of a clutch release bearing and a stop assigned to the respective clutch is explained below with reference to FIG. 6 of the drawing. The left drawing in the upper half of FIG. 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 can be seen from the force-displacement diagram in the lower half of the drawing in FIG. 6, after reaching position B, to which the clutch is already open, the clutch actuator can travel a further distance in the direction of the stop, the Stop can be detected by the high increase in actuator force at position C. The stop therefore represents a reference position and the travel path of the clutch actuator from the known position of the clutch release bearing to the stop associated with the clutch changes when there is a loss of volume in the hydraulic line of the opened clutch, i.e. the hydraulic release system of the non-active clutch. On the basis of the change in the travel path of the clutch actuator from the disengagement position of the clutch release bearing and the stop, a leak in the disengagement system can therefore be concluded.

As already explained above, it is a hydraulic one Disengagement system of the double clutch of a parallel gearbox requires that inadvertent closing of both clutches avoided in any case is because this leads to a negative behavior on the driveability of the one such a gear equipped vehicle.

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

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

Fig. 7 shows a schematic representation of such an emergency valve in the form of a ball valve. In the open state, the ball is biased by the schematically illustrated spring against a ramp arrangement and thus held in position. The pressure fluid can flow around the ball when the clutch is actuated. If a critical pressure difference is exceeded, the ball snaps out of the ramp arrangement and is pressed against the diameter restriction of the hydraulic line, which is shown schematically as a throttle. As a result, liquid can no longer flow through the throttle and the pressure in front of the throttle is maintained.

It is possible to determine the critical pressure difference via the geometry of the Ramp arrangement or set by the biasing force of the spring. A Integration of the emergency valve in the release mechanism ensures that a uncontrolled snapping of the clutch is avoided and thus the Transmission control receives enough time to close the defect in the hydraulics recognize and react to it, for example by presenting the gear is designed without a safety-critical state occurring. The Emergency valve shown is characterized by a simple structure, a easy assembly in the release system and high functional reliability.

With regard to features of the In addition, the invention is expressly based on the claims and the drawing directed.

The claims filed with the application are Proposed wording without prejudice for obtaining further patent protection. The The applicant reserves the right to add more, so far only in the description and / or To claim drawings disclosed combination of features.

Relationships used in subclaims point to the others Training the subject of the main claim by the features of respective subclaim; they are not considered a waiver of achieving one independent, objective protection for the combinations of features of to understand related subclaims.

Since the subjects of the subclaims with regard to the prior art reserves the right to make its own and independent inventions on the priority day Applicant before becoming the subject of independent claims or To make divisional declarations. You can continue to work independently Inventions contain one of the objects of the previous Have independent claims independent design.

The exemplary embodiments are not intended to limit the invention understand. Rather, there are numerous within the scope of the present disclosure Changes and modifications possible, especially such variants, elements and combinations and / or materials, for example by combination or modification of individual in connection with that in general Description and embodiments as well as the claims described and in features or elements contained in the drawings or Process steps for the person skilled in the art with regard to solving the problem can be found and through combinable features to a new item or new ones Lead process steps or process step sequences, also insofar as they Test and work procedures concern.

Claims (13)

1. A method for detecting a leak of a hydraulic release system of a double clutch of a parallel transmission, the release system having the respective hydraulically actuated master cylinder and slave cylinder assigned to the two clutches, characterized in that the amount of change in the release position of the slave cylinder of the non-active clutch and / or the The amount of changes in the transfer functions of both clutches is determined and the leakage is determined if at least one of the amounts exceeds a predetermined value. 2. The method according to claim 1, characterized in that the amount the change in the transfer function of the active clutch is determined and / or the amount of change in transfer functions both clutch is determined and the leakage is determined if at least one of the amounts exceeds a predetermined value. 3. The method according to claim 1 or 2, characterized in that the Leakage is detected when at least one of the amounts reproduced predetermined value exceeds. 4. Method for detecting leakage of a hydraulic Release system of a double clutch of a parallel gearbox, the Release system assigned to the two clutches has hydraulically operated master cylinder and slave cylinder, thereby characterized that the difference in arithmetic Slave cylinder positions is determined with power-free closed clutches, one Leakage is determined by changing the difference. 5. The method according to claim 4, characterized in that based on the Direction of change in the difference is determined, in which the hydraulic couplings assigned to the respective couplings A leakage has occurred in the release systems. 6. The method according to claim 4 or 5, characterized in that a failure of a based on the gradient of the difference hydraulic release system is determined. 7. Method of detecting leakage from a hydraulic Release system of a double clutch of a parallel gearbox, the Release system assigned to the two clutches, each has hydraulically operated master cylinder and slave cylinder, thereby characterized in that by means of a differential pressure sensor Pressure difference in the hydraulic circuits of the release system of both clutches is determined and on the basis of a change in the differential pressure compared to a reference map, a leak in the Release system of the non-active clutch is determined. 8. Method for detecting a leakage by means of a Clutch actuator operated hydraulic release system of a double clutch of a parallel gearbox, characterized in that the Travel of the clutch actuator between a previously known position a respective clutch release bearing and one of the respective Coupling associated with the clutch is determined and based on a Change in travel a leak in the release system inactive clutch is detected. 9. The method according to claim 8, characterized in that the position of the stop together with a wear-related adjustment the clutch is changed. 10. Method of avoiding leakage-related closure of the Double clutch of a parallel transmission, one of which is the release system with two hydraulically assigned to the two clutches actuated master cylinders and slave cylinders, one in Hydraulic circuit of the release system provided valve, which at a suddenly occurring pressure difference is closed such that a suddenly occurring pressure difference on the slave cylinders avoided becomes. 11. Procedure for responding to a leak in the hydraulic Release system of a double clutch of a parallel transmission according to one of the Claims 1 to 10, characterized in that after the finding the transmission control emergency operation program is activated, which depends on the significance of the condition of the Leak detection executes various error handling routines. 12. The method according to claim 11, characterized in that the Switching behavior of the parallel transmission is changed such that the Driver of a vehicle equipped with such a transmission receives a hint to perform an error check, but a Emergency operation of the vehicle is still possible. 13. The method according to claim 11 or 12, characterized in that after the leak has been determined, only with an interruption in tractive power is switched and / or the relevant partial transmission is deactivated.