WO2006029783A1

WO2006029783A1 - Device and method for actuating a clutch

Info

Publication number: WO2006029783A1
Application number: PCT/EP2005/009755
Authority: WO
Inventors: Michael Schultheiss; Josef Steuer
Original assignee: Daimlerchrysler Ag
Priority date: 2004-09-14
Filing date: 2005-09-10
Publication date: 2006-03-23
Also published as: DE102004044193A1; DE102004044193B4

Abstract

Disclosed is a device for actuating a clutch in an automatic motor vehicle transmission. Said device controls the flow of power on the clutch during an engagement process while limiting the applied torque of a driving machine during an engagement process. The aim of the invention is to create a device which allows the motor vehicle to react rapidly to an acceleration request of a vehicle driver, which is adjusted before or during an engagement process. Said aim is achieved by the fact that the inventive device estimates a point in time (t3) from which the clutch is able to transmit torque. At said point in time, the device switches from a first limiting mode to a subsequent mode that is characterized by an increased limiting moment (62), thus allowing the applied torque (63) of the driving machine to be augmented before the engagement process is completed. The inventive device and method are used in a motor vehicle.

Description

Device and method for actuating a clutch

The invention relates to a device for actuating a clutch in an automatic transmission of a motor vehicle for transferring the transmission from a neutral position to a driving position according to the preamble of claim 1 and a method for actuating a clutch according to the preamble of claim 13.

The transfer of a transmission from a neutral position to a driving position is often referred to as a so-called switch-on. In an automatic transmission with a hydrodynamic torque converter as a starting element while one or more clutches or brakes are closed in the transmission and thus made positive connection between the input and the output of the transmission, ie a drive connection between a transmission input shaft and a transmission output shaft. A then occurring speed difference between a speed of the engine of the motor vehicle and the speed at the input of the transmission leads to a speed difference within the torque converter.

The aforementioned clutches or brakes so do not serve as a starting element. In the not .vorveröffentlichten German patent application with the official file number 10333602.8 a device and a method for actuating a clutch in an automatic transmission for transferring the transmission from a neutral position to a driving position are described. The device controls the power flow through the clutch by means of an actuator. Depending on at least one parameter sensed during the closing process, the device estimates a time from which the coupling can transmit a torque. At this time, the device switches the actuator from a high pressure mode to a follow mode.

It is also known that a device for actuating the clutch during a switch-on limits a torque output of the drive motor of the motor vehicle in drive connection with the clutch. The device sends to a corresponding request to a control device of the prime mover, which then implements the request. For example, the torque is limited to zero, so as to prevent an undesirable increase in the rotational speed of the prime mover and an increased load on the clutch. The limitation is only canceled when the clutch is fully closed, the switch-on is thus completely completed.

In contrast, it is the object of the invention to provide a device and a method which sets a rapid response of the motor vehicle to a before or during a power-up

Allow acceleration request of a driver. According to the invention the object is achieved by a device having the features of patent claim 1 and a method according to claim 13. According to the invention, the device estimates a time from which the clutch can transmit a torque. A clutch designed as a friction clutch can, for example, be transmitted from the point in time on which the friction surfaces of the clutch are brought into contact for the first time. This point in time can be determined, for example, as a function of a parameter sensed during the closing process. It is also possible, for example, to determine the required time duration up to the stated time in a development phase of the motor vehicle by measurements and to store it in the device. During operation of the motor vehicle, the stored value for the time duration can be read out and used to determine the time mentioned.

At or a time after this time, the device changes from a first limiting mode to a following mode characterized by an increased limiting torque. With the change to the follower mode, the prime mover can deliver a higher torque when requested by the driver than in the first limiting mode, which is transmitted via the clutch to driven vehicle wheels. This torque leads to an acceleration of the motor vehicle, whereby the driver receives very quickly a reaction of the motor vehicle to his request. The motor vehicle thus reacts very spontaneously to the request of the vehicle driver.

Since the estimation of the time point from which the clutch can transmit torque may be subject to a certain degree of uncertainty, the change to the following mode can also take place only after a period of time after that time. The time span can be, for example, between 10 and 50 ms.

The transmission may for example be designed as a planetary gearbox or a CVT transmission.

The coupling can be controlled hydraulically or in any other manner that appears appropriate to a person skilled in the art, for example pneumatically, electrically or electromagnetically. The coupling does not serve as a starting element. By closing the clutch rather a drive connection between a transmission input shaft and a transmission output shaft is made.

In an embodiment of the invention, the device is provided to determine the said time in dependence of a sensed during the closing process parameter. Thus, the estimation of said time can be very accurate, since a reaction of the sensed characteristic can be detected on the actual torque transfer to the clutch. Operational temporary and permanent disturbances and fluctuations, in particular by different temperature values in the clutch as well as by wear within the clutch related changes of said time can be compensated easily and safely.

If the sensed parameter is at least substantially determined by a variable dependent on a speed difference within the clutch, the same can be determined particularly simply and accurately. Furthermore, the parameter changes directly with a changing torque transmission via the clutch. If the time from which the clutch can transmit torque is recognized when a parameter determined at least essentially by the amount of the rotational speed difference is smaller than a predefined proportion of a maximum sensed value, this parameter is assumed in the time span which has elapsed since the beginning of the closing operation By selecting the amount as the parameter, both positive and negative speed differences can be uniformly treated. Furthermore, in particular by reference to a maximum despite fluctuations in the speed difference and in particular also in opening and closing operations in rapid succession advantageously said time can be accurately determined.

In particular, the parameter is at least substantially proportional to the magnitude of the speed difference, and the proportion of the maximum value at which the following mode is switched is between 70% and 95%. This can advantageously be avoided that random fluctuations in the speed difference lead to a too early detection of torque transmission of the clutch.

In an embodiment of the invention, the clutch is actuated hydraulically. The device is intended to fill in a closing operation, the clutch in a characterized by an increased pressure filling phase with a fixed duration. The duration of the filling phase is determined in a development phase of the motor vehicle and stored in the device. The duration can be determined as a function of operating variables of the motor vehicle at the beginning of the closing operation, such as, for example, a temperature of a transmission oil or the rotational speed of the drive machine. It is also possible that the duration is adjusted during operation of the motor vehicle. The Duration of the filling phase is fixed at the beginning of the closing process. In the filling phase, a pressure chamber of the clutch should be filled with gear oil so that at the end of the filling phase, the friction surfaces of the clutch just touch and thus torque can be transmitted. In a subsequent application phase, the device continues to close the clutch. The estimated time from which it is assumed that the clutch can transmit torque corresponds to the transition point between filling phase and application phase.

This allows an estimate of the time from which the clutch can transmit torque, which is not as accurate as the estimate as a function of a sensed characteristic, but which is very easy to implement.

In an embodiment of the invention, the limiting torque in the first limiting mode is 0 Nm. This ensures that the prime mover does not deliver torque to the clutch during the switch-on process. In this phase, the so-called idle governor of the control device of the engine is then active, which ensures that the drive machine remains at a constant speed and thereby emits no torque. In the technical implementation, the device may also request a negative torque from the controller of the prime mover. Also in this case, the idle governor is active.

In a refinement of the invention, the limiting torque in the following mode assumes a constant value greater than 0 Nm. This is particularly easy to implement in the facility. This embodiment can be used in particular when the control device of the drive machine can not set a requested torque exactly. In an embodiment of the invention, the device is provided to determine the limiting torque in the following mode as a function of operating variables and characteristic values of the motor vehicle. Operating variables of the motor vehicle, for example, the output torque of the prime mover or speeds of the prime mover and the transmission. Characteristics of the motor vehicle are, for example, moments of inertia of the prime mover or the transmission. In the device, a mathematical model can be stored, which evaluates the operating variables and the characteristic values and thus determines the torque at the clutch. This can be determined very accurately, which torque may leave the prime mover, without the torque on the clutch exceeds the transmittable torque of the clutch.

In an embodiment of the invention, the device is provided to determine a function of the output torque of the engine under consideration of the moments of inertia of components between the engine and clutch, such as the transmission input shaft, a transmitted torque of the clutch. Subsequently, the device determines the limiting torque for the following mode from the transmitted torque of the clutch without taking into account the moments of inertia. The torque transmitted by the clutch causes a transmission input shaft to decelerate. The necessary torque can be additionally applied by the drive machine, without this additional torque arrives at the clutch. This makes it possible to limit the torque of the prime mover only as much as absolutely necessary.

In an embodiment of the invention, the prime mover drives a pump to supply the transmission with gear oil. The device is intended to determine an estimated value for the torque required to drive the pump. The device can determine the estimated value, for example, from a characteristic curve or a characteristic field as a function of the generated oil pressure and / or the rotational speed of the engine. Alternatively, a mathematical model of the pump may be stored in the device and the estimate determined using the model. The device determines the limiting torque in the following mode depending on the said estimated value. The torque required to drive the pump can no longer be transferred to the coupling. Therefore, for example, the limiting torque can be increased by the estimated value.

Further advantages of the invention will become apparent from the description and the drawings. Embodiments of the invention are shown in simplified form in the drawing and explained in more detail in the following description. In the drawing show:

1 shows a drive train of a motor vehicle with an automatic transmission in the form of a continuously variable belt transmission and

Fig. 2 + 3 is a representation of the time course of a switch-on

A drive train of a motor vehicle has a drive machine 11 in the form of an internal combustion engine. The prime mover 11 is connected via an engine output shaft 12 to an impeller 13 of a hydrodynamic torque converter 14. A turbine 15 of the torque converter 14 is connected to a transmission input shaft 16 of an automatic transmission 17 in the form of a continuously variable transmission connected. The transmission input shaft 16 is connected to a fixed bevel gear 19 of a primary Doppelkegelrads 20. The primary Doppelkegelrad 20 has a loose bevel gear 21, which is arranged axially relative to the fixed bevel gear 19 to the transmission input shaft 16 slidably.

The primary Doppelkegelrad 20 and a secondary Doppelkegelrad 22 are spanned by a belt 23 in the form of a belt thrust band. The secondary Doppelkegelrad 22 also has a fixed bevel gear 24 and a displaceably arranged to Los bevel gear 25. By a corresponding displacement of the loose bevel gears 21 and 25, the position of the belt 23 within the double bevel gears 20 and 22 changed and thus the ratio between the primary Doppelkegelrad 20 and the secondary Doppelkegelrad 22 can be changed.

The fixed bevel gear 24 has a base body 26, which is designed as a hollow shaft. About this main body 26, the fixed bevel gear 24 is connected to a reversible kit 27 in the form of a planetary gear. The main body 26 is rotatably connected to a sun gear 28 of the turning set 27. The reversible kit 27 also has a planet carrier 29, planet gears 30 and a ring gear 31. The ring gear 31 is connected by means of a connecting element 33 with a transmission output shaft 32. By means of a coupling 34, the sun gear 28 with the connecting element 33 and thus the main body 26 of the fixed bevel gear 24 to the transmission output shaft 32 are connected and thus the transmission 14 are transferred from a neutral position to a driving position. When the clutch 34 and the corresponding output power of the engine 11, the motor vehicle moves forward. The transmission output shaft 32 is performed by the base body 26, that is arranged coaxially within the base body 26. Via a gear stage 35, the transmission output shaft 32 is connected to a differential gear 36, which transmits in a known manner via side shafts 37, the torque and the rotational speed of the engine 11 to not shown driven vehicle wheels.

The engine 11 and the automatic transmission 20 are driven by a device 38. To control the engine 11, the device 38 is in signal connection with actuators and sensors of the engine 11, not shown. Thus, the device 38, for example by means of a setting of a throttle set a torque output of the engine 11 set. The device 38 may also limit the output torque of the prime mover to a limiting torque.

The device 38 is in signal communication with a selector lever 39, by means of which the driver can select driving steps of the automatic transmission 17. With the selector lever 39, at least the drive position "D" for forward drive, "R" for reverse drive and "N" for neutral are adjustable. In the driving position "D", the clutch 34 is closed and in the driving position "N", the connection between the main body 26 and the transmission output shaft 32 and thus the drive connection between the transmission input shaft 16 and transmission output shaft 32 is interrupted. The driving steps "D" and "R" thus represent driving positions of the transmission 17.

The device 38 is also connected to an accelerator pedal 40 in signal connection, by means of which the driver a driver's desired torque of the engine 11 and thus a Can set acceleration request. About speed sensors 42, 43, 44, 45 and 46, the device 38 speeds of the motor output shaft 12, the fixed bevel gear 19, the fixed bevel gear 24, the transmission output shaft 32 and the side shaft 37 detect. From the speeds other sizes can be calculated. For example, from the rotational speeds of the fixed bevel gears 19 and 24, the ratio of the transmission 17 or from the speed of the side shaft 37, the speed of the motor vehicle can be calculated.

The gear 17 is hydraulically controlled. For this purpose, a pump 47 is driven by the motor output shaft 12. The pump

47 supplies a hydraulic control 48 with hydraulic fluid in the form of transmission oil. The hydraulic control 48 is connected to the reversible kit via a hydraulic line 50. By supplying and discharging hydraulic fluid, the clutch 34 can be closed and opened. The Doppelkegelräder 20 and 22 have pressure chambers 51 and 53, which via hydraulic lines 52 and 54 with the hydraulic control

48 are connected. The hydraulic line 54 to the pressure chamber 53 of the secondary Doppelkegelrads 22 is formed within the output shaft 32 through a channel 55 which has an opening 56 in the direction of the main body 26. By supplying and removing hydraulic fluid in the pressure chambers 51 and 53, the loose bevel gears 21 and 25 can be moved and thus the ratio of the transmission 17 can be changed.

The supply and discharge of hydraulic fluid via the hydraulic lines 50, 52 and 54 is controlled by unillustrated solenoid valves in the hydraulic control 48. The solenoid valves are connected to the device 38 in signal connection. Thus, the device 38 can control the flow of force through the clutch 34. FIGS. 2 and 3 show the time profiles of different operating variables of the drive train during a switch-on process, that is, when the clutch 34 is closed.

In FIG. 2, a torque in [Nm] is plotted on an ordinate 60 and the time in [s] is plotted on an abscissa 61. A solid line 62 represents the limiting torque to which the device 38 limits the output torque of the engine 11, a dotted line 63 an output torque of the engine 11, and a broken line 64 a desired torque of the driver.

In FIG. 3, a speed in [l / s] and a pressure in [bar] are plotted on an ordinate 65, and the time in [s] is plotted on an abscissa 66. A dotted line 67 represents the rotational speed of the transmission output shaft 32, a solid line the rotational speed of the fixed bevel gear 24 and a dot-dash line 69 the rotational speed of the prime mover 11. A dashed line 70 represents the pressure exerted by the device 38 on the clutch The speed of the fixed bevel gear 24 corresponds to the input speed and the speed of the transmission output shaft 32 of the output speed of the clutch 34th

The start up procedure begins tl to the time point at which the vehicle driver the selector lever 39 from the drive position "N" in the drive range "D ^w moved (not shown). The motor vehicle is stationary at this time, so that the output speed of the clutch is 0. The drive machine 11 is operated at idle and the limiting torque has a value that is greater than a maximum torque of the engine 11. At time t 1, the limiting torque is abruptly reduced to 0. At the same time, the device 38 controls a high, until the time t2 constant pressure to the clutch 34. The phase between tl and t2 is referred to as a so-called Vorfüllphase in which hydraulic fluid is to be promoted as quickly as possible in a pressure chamber of the clutch 34. Between the times t1 and t2, the vehicle driver actuates the accelerator pedal 40, so that the desired torque increases. However, since the limiting torque is 0, this desired torque is not implemented. All other sizes remain unchanged.

At the time t2, the device 38 reduces the actuated pressure to a further constant value and thus passes into a so-called filling phase. Between times t2 and t3, the clutch 34 is completely filled and the friction surfaces begin to contact, whereby the clutch 34 begins to transmit torque. As a result, between times t2 and t3, the input speed of clutch 34 begins to drop. During the entire time, means 38 calculates and observes the speed difference 71 between the input speed and the output speed of the clutch 34. At time t3, the speed difference 71 becomes smaller than a predetermined percentage of the differential speed 72 at time t1. The time t3 is thus defined as the time from which the clutch 34 can safely transmit torque. At this time, the device 38 changes from the first limiting mode to the following mode.

As a result, the limiting torque at time t3 is increased to a fixed value, which may be, for example, between 50 and 100 Nm. Then the dispensed rises Torque of the engine 11 with a slight time delay also on. Due to the increase in the output torque of the engine 11, both the speed of the engine 11, and the output speed of the clutch 34 increase. So the vehicle starts to accelerate. Thus, with the increase in the rotational speed of the engine 11 and the acceleration of the motor vehicle, the vehicle driver receives feedback on his accelerator operation.

At time t3, unit 38 begins to reduce the applied pressure on clutch 34 along a steep ramp to a rising ramp start value. The device 38 thus enters into a so-called docking phase. The slope of the rising ramp can be dependent on the desired moment of the driver, in particular be larger with increasing desired torque. At time t4, the speed difference 71 between the input speed and the output speed of the clutch 34 has dropped to 0. Slip no longer occurs on the clutch 34. As a result, the device 38 controls a steeper pressure ramp to a holding pressure on the clutch 34. At the same time, the limiting torque is increased along a ramp to the same value as before the switch-on process, so that the output torque of the drive machine 11 adjusts to the desired torque of the vehicle driver. At time t5, the actuated pressure at the clutch 34 reaches the holding pressure, whereby the switch-on is completed.

The device 38 may also limit the output torque of the engine 11 outside of a switch-on process. In the following mode, the limiting torque can also be determined as a function of operating variables and parameters of the motor vehicle.

For this purpose, the device 38 first determines the torque currently transmitted to the computer in accordance with a mathematical model

Coupling 34 (M _Kup ):

^M κ _up = ( ^M _A M - J _A M * (Om - M _pump ) * i _Var * μ _wall ) - J _prim * ω _prim * i _mt - J _sec * ω _sec

With

M _AM : output torque of the engine 11,

J _m : moment of inertia of the prime mover 11,

COAM: time derivative of the engine speed

11, ^ _Pump 'drive torque of the pump 47, i _Var : translation of between the primary and the secondary bevel gear 20, 22, Mw _and ' • torque gain of the torque converter 14, which is determined by the ratio of the input and

Output speed results from a stored characteristic,

J _{r! M} : moment of inertia of the transmission input shaft 16 and the primary double bevel gear 20,

(OpHm ^• time derivation of the speed of the

Transmission input shaft 16, J _sec : moment of inertia of the secondary bevel gear 22 and

α> sec: time derivative of the speed of input clutch 34. Based on the consideration that the transmitted torque from the clutch 34 is a deceleration of

Transmission input shaft 16 and the primary and secondary Doppelkegelrads 20, 22 causes and the necessary torque can be applied in addition by the prime mover 11, the device 38 calculated in the following mode, the limiting torque (M _limit ) according to the following equation:

M Kup

^M Gr _eπ , = ^J AM * ^ω ΛM + M Pump ^l Var MtVaπd

These calculations are carried out continuously in the following mode and the limiting torque is set accordingly.

If, during a switch-on operation, the clutch 34 is closed in such a way that the filling phase is interrupted after a defined period of time, the curves of the operating variables can, in the optimal case, be identical to the curves in FIGS. 2 and 3. This is the case when the fixed period of time is chosen exactly so that the filling phase is stopped when the clutch 34 can transmit a torque.

Claims

DaimlerChrysler AGPatent claims

1. A device for actuating a clutch (34) in an automatic transmission (17) of a motor vehicle for transferring the transmission (17) from a neutral position to a driving position, wherein by closing the clutch (34) has a drive connection between a transmission input shaft (16) and a transmission output shaft (32) is manufactured and the device is provided to control a flow of force through the clutch (34), characterized in that the device is provided to, in a closing operation of the clutch (34)

- An output torque of one with the clutch (34) in drive connection

Limit drive unit (11) to a limiting torque,

- Estimate a time (tl), from which the clutch (34) can transmit torque and

to change from a first limiting mode to a following mode characterized by an increased limiting torque at or a time interval after this point in time (t3).

2. Device according to claim 1, characterized in that the device is provided to determine said time (t3) in dependence of a sensed during the closing process characteristic (68).

3. Device according to claim 2, characterized in that the sensed parameter (68) is at least substantially determined by a speed difference (71) within the clutch (34) dependent size.

4. Device according to claim 3, characterized in that the device is provided to change to the following mode, as soon as an at least substantially determined by the amount of the speed difference (71) characteristic (68) smaller than a predetermined proportion of a maximum sensed value ( 72) which this characteristic (68) has assumed in the time elapsed since the beginning (t1) of the closing operation.

5. Device according to claim 3 or 4, characterized in that the characteristic (68) is at least substantially proportional to the amount of the speed difference (72) and the proportion between 70% and 95%.

6. Device according to claim 1, characterized in that the coupling (34) is hydraulically actuated and the device is provided, in a closing operation, the clutch (34) in a characterized by an increased pressure filling phase with a fixed duration to fill and in a subsequent application phase to further close the clutch (34), said time corresponds to the transition time between filling phase and application phase.

7. Device according to one of the preceding claims, characterized in that the limiting torque in the first limiting mode is 0 Nm.

8. Device according to one of the preceding claims, characterized in that the limiting torque in the follow mode assumes a constant value greater than 0 Nm.

9. Device according to one of claims 1 to 7, characterized in that the device is provided to determine the limiting torque in the following mode as a function of operating variables and parameters of the motor vehicle.

10. Device according to claim 9, characterized in that the device is intended to

- In dependence of the output torque of the drive machine taking into account the moments of inertia of components (16, 20, 22) between the engine (11) and clutch (34) to determine a transmitted torque of the clutch and

- Determine the limiting torque in the following mode from the transmitted torque of the clutch (34) without taking into account the moments of inertia.

11. Device according to claim 9 or 10, characterized in that between the drive machine (11) and the clutch (34) a hydrodynamic torque converter (14) is arranged and the device is provided to the limiting torque in the follow mode depending on operating variables and characteristics of the hydrodynamic torque converter (14) to determine.

12. Device according to claim 9, 10 or 11, characterized in that the drive machine (11) drives a pump (47) and the device is provided for,

- To determine an estimated value for the drive of the pump (47) necessary torque and

- To determine the limiting torque in the following mode depending on the said estimate.

13. A method for operating a clutch (34) in an automatic transmission (17) of a motor vehicle for transferring the transmission (17) from a neutral position to a driving position, wherein a force flow through the clutch (34) is controlled, characterized in a Closing operation of the clutch (34)

- An output torque of one with the clutch (34) in drive connection

Drive machine (11) is limited to a limiting torque,

- A time (t3) is estimated, from which the clutch (34) can transmit torque and at or a time interval after this time (t3) is changed from a first limiting mode to a following mode characterized by an increased limiting torque.