Method for controlling a separating clutch

Abstract

A method for controlling a separating clutch in a power train of a vehicle having a drive motor and a retarder. The clutch is arranged such that a rotor of the retarder is switched into a drive connection with the motor and/or power train via the clutch and a working chamber of the retarder can be filled with an operating medium to build up a braking power such that braking torque is exerted by the retarder onto the power train and/or motor. A control system switches the clutch into a closed or an open position. The switching of the clutch into the closed position occurs depending on an input signal to the controller, and the clutch is switched back into the open position depending on essentially no medium being present in the working chamber of the retarder and that predetermined limits of an operating and/or environmental parameter are not exceeded.

Claims

1. A method for controlling a separating clutch in a power transmission of a motor vehicle, comprising the steps of: arranging a separating cutch between a drive motor and/or a power transmission and a retarder such that a rotor of the retarder can be switched into a drive connection with the drive motor and/or the power transmission by the separating clutch; filling of a working chamber of the retarder with an operating medium in order to build up a braking power such that a braking torque is exerted by the retarder onto the power transmission and/or the drive motor; switching the separating clutch into a closed position or an open position under a control of a control system, the switching of the separating clutch into the closed position occurs depending on at least one input signal to the controller, and the separating clutch is switched back into the open position depending on essentially no working medium being present in the working chamber of the retarder and that predetermined limits of at least one additional operating and/or environmental parameter are not exceeded.

2. The method of claim 1, wherein the input signal to the controller is generated by way of a foot pedal, a lever or an actuator.

3. The method of claim 1, wherein the switching of the separating clutch into the open position only occurs when at least one of the following operational and/or environmental parameters is met and/or the predetermined limits are not exceeded: incline of a roadway time or distance until an inclined stretch of a road is reached an input signal is generated by the driver last retarder brake incidents or switching into the closed position were not generated within a defined time interval and predetermined limits of operating brakes of the vehicle were exceeded due to prior braking.

4. The method of claim 3, wherein an inclinometer and/or GPS data are used for determination of the environmental parameters.

5. The method of claim 3, wherein the incline of the roadway is >1.5% or a stretch of the road of <300 m and/or a time of <10 s until reaching the inclined stretch of road is calculated.

6. The method of claim 3, wherein a distance sensor and/or a proximity control are used for determining of the environmental parameters.

7. The method of claim 3, further comprising the step of measuring an operating temperature of the operating brakes with a temperature sensor.

8. The method of claim 1, further comprising the step of preventing the switching of the clutch into the open position by means of a manually triggered signal.

9. The method of claim 1, further comprising the step of preventing the switching of the clutch into the open position when a drive motor speed and/or a power transmission speed and/or a rotor shaft speed is exceeded.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) The above-mentioned and other features and advantages of this invention, and the manner of attaining them, will become more apparent and the invention will be better understood by reference to the following description of an embodiment of the invention taken in conjunction with the accompanying drawings, wherein:

(2) FIG. 1 is a schematic illustration of a motor vehicle for use with an embodiment of a method according to the present invention; and

(3) FIG. 2 is a flow chart providing an exemplary illustration of a process sequence of the method according to the invention.

(4) Corresponding reference characters indicate corresponding parts throughout the several views. The exemplification set out herein illustrates one embodiment of the invention, in one form, and such exemplification is not to be construed as limiting the scope of the invention in any manner.

DETAILED DESCRIPTION OF THE INVENTION

(5) FIG. 1 illustrates a power train 1 of a vehicle including a drive motor 8, a transmission 6 and a hydrodynamic brake 2 or a retarder 2 arranged on the output side of transmission 6. Retarder 2 is connected via a booster, which is not illustrated herein, with transmission 6. The retarder 2 is therefore a so-called secondary retarder 2.

(6) The output of drive motor 8 is controllable by a foot pedal 3. The more foot pedal 3 is pressed down, the higher is the output of drive motor 8 via clutch 7 to transmission 6.

(7) Retarder 2 is switchable into a drive connection with transmission 6 via a separating clutch 4. Thus, an indirect coupling occurs into vehicle power train 1. Retarder 2 is switchable into a direct drive connection with power train 1 and can be disengaged from this drive connection in that separating clutch 4 is closed or opened. When separating clutch 4 is closed, rotor 2.1 of retarder 2 is accelerated via a transmission output shaft, for example a booster.

(8) In a filled state, a circulatory disturbance occurs, so that a torque is transferred by the working medium in the working chamber from rotor 2.1 to stator 2.2, which in turn causes a braking effect or braking torque upon rotor 2.1. According to the present invention, rotor 2.1 of retarder 2 is driven by closing of separating clutch 4 even under certain constraints in an empty state of brake 2, or respectively in a largely empty state of brake 2, in order to move retarder 2, so to speak, into a standby operation.

(9) Braking performance of retarder 2 is adjustable by way of a brake actuator 5, which is operable by the driver, meaning it is adjustable in a closed control system or controllable in an open control system. Alternatively or in addition, a control device, for example a cruise control system or a proximity control, may be provided which controls the braking power depending on certain operational conditions or predefined specifications.

(10) Alternatively to the illustrated arrangement, retarder 2 may also be designed as a primary retarder meaning that, viewed in direction of the drive connection of drive motor 8 to the drive wheels, it is located before transmission 6 or the transmission input and is driven with motor speed.

(11) FIG. 2 illustrates a flow chart showing an exemplary process sequence of the inventive method. Separating clutch 4 is always being closed if an input signal 10 is issued. An input signal may be the positioning of foot pedal 3, or a gas pedal. A signal for closing of the clutch is generated when the driver releases the foot pedal, in other words, when the pressure on foot pedal 3 is terminated. An input signal may however also come from lever switch 5 of the retarder that is operated by the driver, or the input signal comes from an actuator.

(12) Switching of the separating clutch back into the open position only occurs depending on essentially no working medium, or substantially no working medium, being present in the working chamber of retarder 2 and moreover, that predetermined limits of at least one additional operating and/or environmental parameters 11 are not exceeded. It is thus not sufficient that the driver presses foot pedal 3 again in order to switch the clutch into the open position. Instead an additional parameter is requested via the control system which will ultimately decide the opening of the clutch.

(13) Switching of separating clutch 4 into the open position occurs only when at least one of the following operating and/or environmental parameters 11 is met and/or definable threshold values are not exceeded. If, for example, a slope in the roadway is determined, then the clutch remains closed. Moreover, the time to reach a sloping road section can be used as a criterion. A relevant input signal 10 can also be issued alternatively or in addition by the driver.

(14) Technical conditions can however also require that it is useful or necessary to keep separating clutch 4 more effectively closed. For example, if the last retarder braking actions were generated within a defined time interval. Thus, opening occurs only if in a prior time interval not too many braking actions or switching into the closed position occurred.

(15) Furthermore, measured values from all sensors in the power train can be used for this purpose. If certain threshold values of operating parameters of the vehicle are exceeded, due to previous braking actions, the separating clutch does not open.

(16) If the parameter state is in order “i.o.”—meaning that no threshold value is exceeded and all parameters are adhered to, the separating cutch can be switched into the open or closed position, depending on signal status 0 or 1. In the sense of the current invention the parameter state, is a state determined by the controller, which can consist of one or several operating parameters, measured values and/or environmental parameters. The sum total of all values and/or individual assessments either leads to an “i.o.” (in order) status or a “not i.o.” (not in order) status. The separating clutch will not open if a “not i.o.” (not in order) is indicated.

(17) If the threshold values or operating parameters are exceeded, then no switching (see signal 12) of the separating clutch occurs from the “closed position” to the “open position”, even if no input signal is present. The separating clutch will be opened only when the operating parameters are again “i.o.” (in order).

(18) It is not illustrated which conditions have to be met so that the separating clutch switches from the open to the closed position. We refer to DE 10 2007 024 698 A1 which already specifies in detail a possible method for control of a hydrodynamic brake with which sufficiently short reaction times of the retarder are achieved in order to switch same to operational readiness.

(19) By anticipatory switching of the separating clutch, in other words precautionary closing of the separating clutch as described in DE10 2007 024 698 A1, as well as precautionarily keeping the separating clutch closed or rather not opening it is achieved that in non-braking operation the no-load losses are minimized and that the separating clutch can be designed to be compact and durable.

(20) The input signal to the controller is generated by way of a foot pedal, a lever or an actuator.

(21) Provision may further be made that switching of the separating clutch into the open position only occurs, if at least one of the following operational and/or environmental parameters is met and/or determinable limits are not exceeded:

(22) Incline of the roadway

(23) time or distance until an inclined stretch of road is reached

(24) an appropriate input signal 10 is generated by the driver

(25) the last retarder brake incidents were not generated within a defined time interval

(26) certain limits of the operating brakes of the vehicle were exceeded due to prior braking.

(27) Provision may be made as an option or in addition, that an inclinometer and/or GPS data are used for determination of environmental parameters.

(28) One design may provide that, when reaching an incline of >1.5% or a stretch of road of <300 m and/or a time of <10 s until reaching the inclined stretch of road, the retrieved environmental parameter has been passed through and opening of the separating clutch is prevented. It is however also conceivable that a distance sensor and/or a proximity control is used for determining of environmental parameters.

(29) Moreover, a temperature sensor can be used to measure the operating temperature of the operating brake.

(30) It may be additionally provided that switching the clutch into the open position by means of a manually triggered signal is prevented. Thus, on recognition of an increased braking probability the driver can prevent decoupling of the retarder. This can occur by means of a relevant signal, such as activation of a switch.

(31) Moreover, switching of the clutch into the open position can be prevented in the event that a drive motor and/or a power train speed and/or rotor shaft speed is exceeded.

(32) While this invention has been described with respect to at least one embodiment, the present invention can be further modified within the spirit and scope of this disclosure. This application is therefore intended to cover any variations, uses, or adaptations of the invention using its general principles. Further, this application is intended to cover such departures from the present disclosure as come within known or customary practice in the art to which this invention pertains and which fall within the limits of the appended claims.

COMPONENT IDENTIFICATION LIST

(33) 1 Drive train 2 Retarder 3 Foot pedal 4 Separating clutch 5 Brake actuator 6 Transmission 7 Clutch 8 Motor 9 Wheels 10 Input signal 11 Parameter state 12 Clutch position