Source: https://insight.rpxcorp.com/pat/US9108637B2
Timestamp: 2019-11-13 13:27:14
Document Index: 330682348

Matched Legal Cases: ['§120', '§365', 'Application No. 10', 'art9', 'art15', 'art21', 'art\n10', 'art\n15', 'art\n16', 'art\n22']

Patent US 9,108,637 B2
1. A method for controlling a friction clutch of a hybrid drivetrain of a motor vehicle having a combustion engine, which is coupled by means of a freewheel to a transmission input shaft of a transmission to transmit engine torque, the method comprising the following steps:
transmitting drag torque from the input shaft to the friction clutch;
transmitting starting torque from an electric machine to the friction clutch;
transmitting, via the friction clutch, a summed torque, formed of the starting torque and the drag torque, to the combustion engine for starting the combustion engine by means of the electric machine; and
, slipping the friction clutch to limit the summed torque present at the friction clutch to a predefined transmission torque which can be transmitted via the friction clutch.
A hybrid drivetrain and method for controlling a friction clutch of a hybrid drivetrain of a motor vehicle having a combustion engine which is coupled by means of a freewheel to a transmission input shaft of a transmission to transmit the engine torque, and having an electric machine which starts the combustion engine and/or propels the motor vehicle, which friction clutch transmits to the combustion engine a summed torque formed of a starting torque for starting the combustion engine by means of the electric machine and a drag torque which acts on the combustion engine when the drivetrain is in drag mode. To be able to operate the friction clutch reliably and to avoid over-dimensioning of the friction clutch as a result of high summed torques, a torque present at the friction clutch is limited to a predefined transmission torque which can be transmitted via the friction clutch.
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2. The method as recited in claim 1, wherein the friction clutch is operated by means of a self-arresting clutch actuator.
3. A drivetrain, comprising:
a combustion engine which is coupled by means of a freewheel to a transmission input shaft of a transmission to transmit engine torque;
an electric machine which transmits a starting torque and/or propels the motor vehicle; and
, a friction clutch arranged to receive a summed torque, formed of the starting torque and a drag torque from the input shaft, for starting the combustion engine by means of the electric machine, wherein the friction clutch is designed for a predefined transmission torque which limits the summed torque.
4. A drivetrain, comprising:
, a friction clutch arranged to;
receive a summed torque, formed of the starting torque and a drag torque transmitted by the input shaft, for starting the combustion engine by means of the electric machine; and
, slip to limit the summed torque to a predefined transmission torque.
This patent is filed under 35 U.S.C. §120 and §365(c) as a continuation of International Patent Application No. PCT/DE2012/000647 filed Jun. 26, 2012, which application claims priority from German Patent Application No. 10 2011 107 069.2 filed Jul. 11, 2011, which applications are incorporated herein by reference in their entireties.
The invention relates to a hybrid drivetrain and to a method for controlling a friction clutch of a hybrid drivetrain of a motor vehicle having a combustion engine which is coupled by means of a freewheel to a transmission input shaft of a transmission in order to transmit the engine torque, and having an electric machine which starts the combustion engine and/or propels the motor vehicle, which friction clutch transmits to the combustion engine a transmission torque formed of a starting torque for starting the combustion engine by means of the electric machine and a drag torque which acts on the combustion engine when the drivetrain is in drag mode.
Hybrid drivetrains are well known from series applications. In such cases, in addition to a combustion engine which drives a transmission input shaft, an electric machine is provided which serves as a generator in the deceleration phase of the drivetrain, and furthermore, in an electric-motor operating mode drives the combustion engine and/or the motor vehicle using the hybrid drivetrain alone or as support in combination with the combustion engine. In these cases, a friction clutch operates between the combustion engine and the electric machine, which uncouples these from each other.
In a special hybrid drivetrain, a freewheel is positioned between the crankshaft of the combustion engine and the transmission input shaft of the transmission, which is situated such that it blocks in the direction of transmission of torque from the combustion engine to the transmission, and rolls over in the drag direction. To be able to transmit drag torque to the combustion engine, for example, to decelerate the motor vehicle in addition to possible recovery of the electric machine, the friction clutch is at least partially engaged for this purpose. Furthermore, the friction clutch is engaged if the combustion engine is to be started in a cold or warm start by means of the electric machine, for example, when the motor vehicle is standing still, or while the motor vehicle is being propelled exclusively by means of the electric machine or is coasting. To this end, a starting torque, which is formed exclusively by the electric machine and/or from the kinetic energy of the motor vehicle, is transmitted via the friction clutch. The summed torque is therefore made up proportionately of drag torque and starting torque, and may far exceed the requisite torque necessary for starting the combustion engine or for supporting drag torque when the friction clutch is conventionally engaged, so that the components of the friction clutch, such as, for example, leaf springs, riveted joints, the clutch plate and the like, which are positioned between the pressure plate and the housing must be appropriately largely dimensioned. For example, when lining friction coefficients of the friction linings of the clutch plate change, especially high torques, which are unnecessary at this level can be transmitted.
The object of the invention is to provide an improved method for controlling a friction clutch in a hybrid drivetrain, and a hybrid drivetrain having a smaller-dimensioned friction clutch.
The invention is a method for controlling a friction clutch of a hybrid drivetrain of a motor vehicle having a combustion engine which is coupled by means of a freewheel to a transmission input shaft of a transmission to transmit the engine torque, and having an electric machine which starts the combustion engine and/or propels the motor vehicle, which friction clutch transmits to the combustion engine a summed torque formed by a starting torque for starting the combustion engine by means of the electric machine and a drag torque which acts on the combustion engine when the drivetrain is in drag mode; the summed torque present at the friction clutch being limited to a predefined transmission torque which can be transmitted via the friction clutch. By limiting the transmissible torque, the friction clutch can be designed for the transmission torque actually needed, and thus, for a smaller transmission capacity, which can save costs. In this case, the friction clutch is engaged only far enough, by specifying an actuator distance of the clutch travel, depending on coefficients of friction of the friction linings of the clutch plate and clamping forces of a clutch actuator, for the necessary transmission torque to be transmitted. Higher torque proportions are blocked out by the slipping operation of the friction clutch. In an embodiment, the friction clutch does not engage completely until the coefficients of friction assume a minimum calculated value, and the calculated tolerance values are at the limiting values.
In order to avoid energy tosses while the friction clutch is being held, the clutch actuator is designed to be self-arresting, for example, as a spindle actuator having a self-arresting thread pitch of the spindle.
The friction clutch is controlled by means of a control device, which issues an actuator travel for the clutch actuator from a predefined transmission torque by means of a characteristic curve. The characteristic curve is set up from the coefficient of friction and the actuator travel, and is adapted as needed, for example, regularly and/or after a number of clutch procedures. An adaptation of the characteristic curve can be made, for example, by determining the Y axis section in the form of a contact point at which the friction clutch just begins to transmit torque, and a slope in the form of an actuator travel ascertained at a predefined torque.
In addition, the invention is a drivetrain for carrying out the proposed method, having a combustion engine which is coupled by means of a freewheel to a transmission input shaft of a transmission to transmit the engine torque, and having an electric machine which starts the combustion engine and/or propels the motor vehicle, a friction clutch at which a summed torque formed of a starting torque for starting the combustion engine by means of the electric machine and a drag torque which acts on the combustion engine when the drivetrain is in drag mode is present, the friction clutch being designed for a predefined transmission torque, which limits the summed torque while maintaining a safety margin. Because of the limited transmission torque, the friction clutch can be designed for smaller torques to be transmitted. It goes without saying that appropriate safety margins which allow for tolerances of the individual clutch components are provided here.
FIG. 1is a partial section of a hybrid drivetrain of the present invention; and
FIG. 2is a block diagram illustrating a summed torque.
FIG. 1shows a partial section of hybrid drivetrain1of a motor vehicle having a combustion engine, of which only crankshaft2is depicted, transmission input shaft3of the transmission, not shown in greater detail, friction clutch4and electric machine5. Crankshaft2is linked to intermediate shaft8via torsional vibration damper7, and conveys the torque of the combustion engine into transmission input shaft3through input part9of freewheel10. The electric machine accommodated on housing6by means of stator11is connected non-rotatingly to the output part of freewheel10by means of rotor13. In addition, rotor13is non-rotatingly connected to input part15of friction clutch4. The output part of friction clutch4is formed by clutch plate16, which is non-rotatingly connected to intermediate shaft8.
Clutch actuator17displaces pressure plate19axially by means of cup spring18, and braces pressure plate19, which is supported by means of leaf springs20non-rotatingly and axially movably on supporting part21, which is received rotatably relative to housing component22by means of bearing12, against axially fixed opposing pressure plate23, so that friction linings24of clutch plate16are tensioned, and by forming a frictional engagement with pressure plate19and opposing pressure plate23, the transmission torque is transmitted from rotor13or transmission input shaft3, while bypassing freewheel10, which is rolled over in this direction of torque, to the intermediate shaft, and from there via torsional vibration damper7to crankshaft2.
The combustion engine is started when the motor vehicle is standing still, through friction clutch4, by applying the starting torque by means of electric machine5, with the friction clutch being engaged just far enough so that the starting torque of the combustion engine is transmitted. In addition, the combustion engine can be started when the motor vehicle is moving, in that the kinetic energy which is present when a gear ratio of the transmission is engaged, which is supplied, for example, by coasting or propulsion solely by electric machine5, is conducted to crankshaft2via friction clutch4. Finally, when friction clutch4is transmitting torque, drag torque can be transmitted from transmission input shaft3to rotor13, which serves to produce electrical energy or provide drag braking of the motor vehicle by means of the combustion engine. Thus, as shown inFIG. 2: starting torque from electric machine5is transmitted to clutch4; drag torque from input shaft3is transmitted to clutch4; and clutch4transmits a summed torque, formed of a starting torque for starting the combustion engine by means of electric machine5and a drag torque which acts on the combustion engine when the drivetrain is in drag mode, to the engine via crankshaft2. In both cases, friction clutch4is engaged just far enough, or is operated with slip, so that only the predefined transmission torque is transmitted. The transmission torque is designed so that both the starting torque and a desired drag torque are reliably transmitted; in addition, the friction clutch serves as overload protection to protect itself, so that overloading of the friction clutch is prevented by adjusting slip when greater drag torque is present. By specifying the transmission torque, the friction clutch can be adjusted for the maximum requisite torques and designed accordingly. In this way, it is not necessary to design for peak torques, which enables the friction clutch to be dimensioned smaller despite being designed for a long, reliable service life.
2crankshaft
3transmission input shaft
4friction clutch
5electric machine
7torsional vibration damper
8intermediate shaft
9input part
10freewheel
11stator
13rotor
14output part
15input part
16clutch plate
17clutch actuator
18cup spring
19pressure plate
20leaf spring
21supporting part
22housing component
23opposing pressure plate
24friction lining
Ruder, Willi, Dilzer, Martin
US 20140128218A1
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