Patent Grant
7287634
This patent claims priority of German Patent Application No. 103 61 491.5, filed Dec. 23, 2003, which application is incorporated herein by reference.
The invention relates to a torque transmission device, especially for a drive train comprising an internal combustion engine and a twin-clutch transmission having two transmission input shafts and one transmission output shaft, each transmission input shaft being connectable to an internal combustion engine via a clutch of the torque transmission device.
Twin clutch transmissions having two transmission input shafts are known in which a torque transmission device has one wet clutch for each transmission input shaft, the wet clutches being hydrostatically actuated via suitable piston units and the pressure needed for this purpose, and in some cases the pressure for cooling the clutches when necessary, being generated by a hydraulic fluid pump. Pumps of this type have high outputs and consume accordingly great amounts of energy. Rotary transmission leadthroughs having seals that seal between rotating and stationary components are provided between the pump and the piston units for the development of a pressure produced by the pump via a hydraulic fluid for actuating the clutches. Appropriate precautions for the service life of these seals must be taken.
The object of the present invention is the improvement of a torque transmission device and a drive train to the effect that it is possible to transmit a high output power of the internal combustion engine via the clutches of the two transmission input shafts while consuming little energy while a simple and safe operation of the clutches at a high transmission output power over a long service life is simultaneously possible. Moreover, the production costs are to be low and the manufacture and assembly simple.
The objective is achieved via a torque transmission device in the drive train of a motor vehicle for the transmission of torque between an internal combustion engine having a crankshaft and a twin-clutch transmission having at least two transmission input shafts with two friction clutches, employing the features described below.
Each transmission input shaft is coupleable to the crankshaft via a friction clutch. The mounting of the transmission input shafts may be concentric, with a second transmission input shaft designed as a hollow shaft disposed around a first transmission shaft, or be with transmission input shafts arranged parallel to each other.
Each friction clutch is provided with friction units on the driving and driven ends that may act on each other via an axial pressure along a rotational axis of at least one of the transmission input shafts to form a frictional engagement as friction partners. For example, disks that are driven by an input part and act on an output part may be stacked alternately to form a multi-disk assembly, it being possible for the driven-end and/or driving-end disks to have friction linings in order to increase the friction coefficient of the friction partners.
The friction units of the two friction clutches are preferably mounted radially one over the other, but may, in appropriately designed drive train spaces, be axially spaced from each other and have equal or different diameters. In order to provide a uniform transmission performance of the two friction clutches, the frictional power of the two friction clutches may be harmonized with each other; for example, the annular frictional partners of the radially outer friction clutches may have a slight difference between inner and outer diameter, and/or the friction unit of the radially outer friction clutch may have fewer friction elements. The selection of different friction materials may also be advantageous.
The friction units of each friction clutch are moved against a stop via an actuation part assigned to each particular frictional unit. At the actuation part, it is also possible to provide a disk or lever part that is attached to a rotating, axially fixed part of the clutch and may swivel in relation to it and, when acted on in the axial direction, presses the friction partners of the driving end and driven end against a stop so that the friction clutch at first slips and then sticks. It may be advantageous to compress the friction clutch only to a certain extent, that is, to engage it until the desired torque is transmitted from the internal combustion engine to the corresponding transmission input shaft.
Mounted with the actuation part of each friction clutch is an actuation device that is rotationally fixedly joined to a stationary housing part, an actuation bearing being interposed between them, and acts axially on each particular actuation part; both friction clutches are operated in a wet operating mode. In this way an actuation system without rotary transmission leadthroughs may be proposed because the hydraulic operative connection pressure supply device/stationary line/rotational line/pressure piston for acting on the clutch—as is known from twin clutches of the prior art—may be bypassed by means of a mechanical actuation bearing for the rotational decoupling of actuation device and clutch. In this way a torque transmission system is also available whose friction clutches may be equipped with the appropriate actuation system, independent of the actuation of the twin-clutch transmission, whether hydraulic, pneumatic, by means of electrical actuators or a combination thereof.
A torque transmission device having an actuation device that is electro-hydraulic may therefore be advantageous. In this context, at least one actuation device may be formed of a hydraulic master device, which comprises a piston/cylinder unit and is actuated by an electric motor, at least one hydraulic slave device, which comprises a piston/cylinder unit, acting axially on the corresponding actuation bearing and a hydraulic fluid line linking master and slave devices. The slave device may have a plurality of subunits distributed around the circumference of at least one transmission input shift for acting on an actuation bearing, both slave devices having subunits distributed around the circumference for acting on both friction clutches, and it being possible to mount them alternately distributed around the circumference and on an approximately equal circumference. Alternatively, a slave device for a friction clutch may comprise a pressurizable annular cylinder having disposed therein an axially displaceable annular piston, it being possible for each of two slave devices radially disposed one over the other to act on a friction clutch. A system in which the one outer annular piston is mounted in an axially displaceable and sealing manner on a radially interior annular piston, a separate pressure chamber being provided for both pistons so that both clutches may be actuated independently of each other.
Especially for drive trains having an hydraulically actuated twin-clutch transmission comprising a pump and a control section to control the hydraulic components of the shifter, it may be advantageous to incorporate slave devices for acting on the actuation bearing directly in a wall of the transmission housing, whereby they are controlled by the control section with pressure supplied by the pump and actuate the clutches. It may be advantageous to use a system of this type also for a single clutch in conjunction with a hydraulically controlled automatic transmission, such as an automated shift transmission (ASG) or a continuously variable transmission (CVT). In this context, a piston/cylinder unit may be accommodated in the wall of the transmission and/or in the corresponding control section, or at least one piston may be placed in an axially displaceable manner within a cylinder that is incorporated in the housing wall or the control section.
A further exemplary embodiment may provide an electromechanical actuation device, an electromotive rotary drive unit that is disposed essentially perpendicular to one of the transmission input shafts acting on at least one friction clutch, the rotary movement being converted via a transmission into a translatory movement along one of the transmission input shafts to act on the corresponding actuation bearing. The German patent application having the file number 103 40 528.3, whose contents are fully incorporated by reference into the present application, is cited in this regard. Alternatively, an electromotive rotary drive mechanism that is disposed essentially parallel to or concentric with one of the transmission input shafts may act on at least one friction clutch, the rotary movement being converted via a transmission into a translatory one along this transmission input shaft to act on the corresponding actuation bearing. The published German patent application 100 33 649 A1, for example, is mentioned in this regard.
Obviously, the two friction clutches being operated in wet operating mode in special applications may be normally engaged clutches that are disengaged when an axial force is applied. However, in standard applications, these friction clutches are compressed clutches; that is, they are disengaged while they are not being acted on by the actuation device and are engaged by being acted one with an axial force.
Especially advantageous is the actuation of the clutches that are operated in wet mode with an actuation device of the proposed embodiments that is independent of the speed of the internal combustion engine in conjunction with a so-called start/stop device in which the internal combustion engine is immobilized while the vehicle is stationary or driving downhill and when there is a load requirement, especially via the gas pedal, the internal combustion engine is started and with at least one clutch the drive is started or continued. While clutches actuated by means of a pump must be moved from the completely disengaged state after the start of the internal combustion engine and the subsequent pressure buildup by the pump from this position back to the engagement point and then, once friction moment can be transmitted to the transmission, an operation of this type occurs more quickly in the actuation devices according to the invention because, independent of the operating state of the internal combustion engine, at least one clutch may be kept at the engagement point and, after the start of the internal combustion engine, a torque that is transferable to the transmission via this clutch is immediately available.
To cool at least one of the friction clutches, especially if a great frictional heat is produced by slip, it may be advantageous to provide a flow of coolant via a pump for cooling at least one friction clutch. For a mode of operation that is essentially independent of the transmission, this pump may be disposed in the area of a clutch bell housing formed between a wall of the internal combustion engine and a wall of the twin-clutch transmission. In this context a flow of coolant may be sucked in from an oil sump that is shared with the transmission or from the transmission itself, or a separate oil circulation for the friction clutches may be provided. It may also be advantageous, especially if there is no hydraulic pump to control the transmission, to configure the output of the pump in such a manner that the flow of coolant may be provided. The pump may be driven by the crankshaft or a component connected thereto. For example, when the pump is mounted on the transmission housing, a clutch component may be geared with the pump in the vicinity of the transmission. In an advantageous way, this involves a component joined to the disk carrier that drives the internal gear of an internal-gear pump disposed radially further to the outside by means of a gear wheel, the internal-gear pump being advantageously disposed within an area that conserves space, for example, between two transmission lugs of the transmission. In this context, the pump may be disposed on a housing wall of the transmission and, depending specifically on the particular transmission concept, within the space of the clutch bell housing or in the transmission space. Also an integration in the housing wall or, when there is a common space with the transmission, in a corresponding fixture of the common space may be advantageous. Of course, the pump may also be electrically driven. The drive by the crankshaft or an electric motor may be produced via a gear connection, a belt drive, a chain drive or the like.
The internal-gear pump may be driven via an internal gear having an internal toothing, this internal toothing meshing with an external toothing of a sun gear and a suction crescent being provided to suck in the coolant. In an advantageous manner, the sun gear may be radially supported via its external toothing on a complementary segment of the suction crescent so that a separate mounting of the sun gear may be eliminated. If desired, the use of a gerotor pump may also be advantageous. To minimize the required power of the pump, its flow volume may be controlled via a suction throttling, it being possible to produce the suction throttling via an electromagnetic valve. In this way, a flow volume may, for example, be proportional up to a predetermined speed of the drive speed and starting at a limit speed be kept at a constant value. Historical values have shown that a limitation of the coolant pressure to 5 bar, preferably 3 bar, and a flow volume of no more than 36 1/min, preferably 24 1/min, may be advantageous. In an advantageous manner, an oil cooler may be connected between a pump and the friction units of the friction clutches. The coolant may leak into the sump through an appropriate opening in the chamber, whereby it may be advantageous to use a scoop tube that is fixedly mounted on the housing to collect coolant that has been forced radially outward due to centrifugal force and conduct it into the sump. A scoop tube of this type may advantageously be combined with other functional elements, such as a slave unit, into one component. Of course, for special applications, other pumps, such as radial piston pumps, vane pumps, diaphragm pumps and the like may also be advantageous.
According to the theory of the invention, the entire clutch bell housing may be filled with coolant or hydraulic fluid, such as commercially available ATF; a space shared with the transmission may also be provided. However, it is especially advantageous if a separate chamber sealed off in a fluid-tight manner from the clutch bell housing is formed in the clutch bell housing between a wall of the internal combustion engine and a wall of the twin-clutch transmission, in which chamber at least the two friction clutches are housed. These chambers may be formed by a component that encompasses both friction clutches, for example, a pot-shaped input part such as a disk carrier, it being possible to rotatably mount a part connected thereto on a stationary part, such as a component of the actuation device or of the transmission housing, in a leak-proof manner. Alternatively, to form the chamber, a disk part may be firmly attached to the transmission housing and be swiveling and fluid tight on a rotating part, such as on the hub of an input part.
The assembly of the two friction clutches according to the invention may be designed as a component that is directly held on the crankshaft. In this context, the actuation system may also be mounted directly on this unit and when assembled may be rotationally fixedly joined to the transmission to form a torque damper, the individual clutch assemblies being joined to and mounted on the actuation system in swiveling manner. In further exemplary embodiments, the clutch assembly may be held and supported on the crankshaft, while the actuation device is premounted on the transmission housing. The coolant pump may be premounted simultaneously with the actuation device. An axial or radial mounting of them on the transmission housing may be provided.
To reduce or eliminate torsional vibrations migrating from the internal combustion engine into the transmission, a dual-mass flywheel disposed between crankshaft and input part of the two friction clutches may be provided on the torque transmission device. This dual-mass flywheel may be integrated into the chamber filled with hydraulic fluid or be mounted outside the chamber. The dual-mass flywheel may also form a part of the housing for the chamber and/or have a drive part for the pump. The holding of the dual-mass flywheel on the crankshaft may be accomplished via an axially flexible disk part of a so-called “flexplate”. Of course, the torque transmission device without a dual-mass flywheel may also be held in this manner on the crankshaft. It may be especially advantageous, in conjunction with the mass ratios of a twin clutch, to form two masses that swivel against at least an energy accumulator acting in the circumferential direction and are on the driven and driving side of the flywheel so that they are coupleable with each other at least temporarily, the coupling being accomplished via a friction device that depends on centrifugal force. The use of a coupling with mass ratios in which the driving side moment of inertia is greater than that of the driven side may be especially advantageous, for example, a first coupleable mass having a moment of inertia of 0.1±0.04 kgm2 on the driving side and a second mass on the driven side has a moment of inertia of 0.04+0.04 kgm2. It has also proven advantageous to sustain the two masses up to a range from 1200 to 1800 rpm.
The assembly of the torque transmission device may be provided in such a way that the complete module comprising slave device and in some cases a dual-mass flywheel is held on one or both transmission input shafts of the twin-clutch transmission and, when the internal combustion engine and transmission are joined, is rotationally fixedly connected to an axially flexible drive component that is joined to the crankshaft, such as a “flexplate”. It may also be advantageous to connect parts of the dual-mass flywheel or the entire dual-mass flywheel to the crankshaft separately from the clutch unit and to produce a connection between internal combustion engine and transmission via fasteners, such as plug and socket connectors, that permit an axial displaceability and a rotationally fixed entrainment of the connected parts. To guide the torque transmission device, a pilot bearing may be provided on it by means of which the torque transmission device is held on the crankshaft in a swiveling manner. An axial support of the torque transmission device on the crankshaft via, for example, a friction bearing, may also be advantageous. It may be especially advantageous to adjust the torque transmission device or its axially displaceable components in the assembly in a merely coarse manner, to connect the actuation device to the transmission housing in a rotationally fixed, but axially displaceable manner and, when operating the torque transmission device for the first time, to finally position it via a self-regulating, axially acting pressure of the coolant on the axially displaceable components, for example, by running them against suitably disposed stops.
The invention is explained in detail in relation to the following figures. Shown are:
The coupling of drive shaft 4 and transmission input shafts 2,3 is accomplished via axial compression of friction partners 12a, 12b, 13a, 13b, each via an actuation part 14a, 14b assigned to a clutch 10, 11, against a stop 15a, 15b provided on the opposite side of actuation parts 14a, 14b. Stops 15a, 15b may be formed of a retaining ring that is axially fixedly joined to the input or output part or formed of lugs that are appropriately molded into the input or output part and may be designed in an annular configuration or distributed around the circumference. The actuation parts 14a, 14b are preferably formed on input parts 10b, 11b of friction clutches 10, 11 as—seen physically—single-armed levers and preferably technically seen as components having a force rim and tabs or similar disk parts that connect to each other distributed around the circumference, the solid lines in
Torque transmission device 1 is provided in such a way that it may be mounted as a module on the dual-mass flywheel 80, which is rotationally fixedly joined to crankshaft 4.
For this purpose, actuation devices 50a, 50b are fixedly swivel-mounted on a disk-shaped component so that housing 50c of actuation devices 50a, 50b may be rotationally fixedly mounted on a wall of the twin-clutch transmission. In this context, common housing 50cis joined to slave devices 51a, 51b via at least one collar 50d in an appropriate recess of the transmission or in such a manner that the torque produced by the load moments of actuation bearings 16a, 16b may be supported on the housing. Furthermore, a bearing 50e, such as a rolling bearing or friction bearing, that stabilizes the actuation force within the clutch so that practically no axial forces are introduced into the transmission housing is provided between housing 50c and receptacle 20a for accommodating transmission housing 50c.
The friction clutches 10, 11 are preferably friction clutches that run wet, which means that they are intended for operation in the oil bath. To this end, it may be advantageous if both clutches have a common input part 17 that is preferably formed with a pot shape on one side so that a housing 18 for friction units 10a, 11a that is open on one side is produced. Common input part 17 may be designed as a formed sheet metal part and have a recess in the area of rotation axis 2a in which an axial collar 17a made of another material, such as a hardened material, is placed providing for the centering of the clutch on one of the two transmission input shafts 2, 3 (shown here: transmission input shaft 2). For this purpose, a pilot bearing 17b may be provided between transmission input shaft 2 and axial collar 17a. Moreover, on the outer circumference of collar 17a, a rotationally connected contact with output part 80a of dual-mass flywheel 80 is provided, for example, as a plug and socket connection 80b for mounting torque transmission device 1 on the dual-mass flywheel. Moreover, axial collar 17a with interposition of a bearing, such as friction bearing 4c, forms the stop of torque transmission device 1 on the crankshaft 4.
The axial clearance between torque transmission device 1 and crankshaft 4 is set in such a manner that, when actuation devices 50a, 50b are first actuated, torque transmission device 1 is distanced from transmission housing 56 along collars 50d via pressure buildup of slave devices 51a, 51b, and/or a pressure is built up in chamber 30, which is at least partially filled with the coolant.
In the shown exemplary embodiment, provision is made that dual-mass flywheel 80 and wet clutches 10, 11 are isolated from each other so that the dual-mass flywheel may be continuously operated dry and friction clutches 10, 11 may be continuously operated wet. For this purpose, a disk part 20, such as a diaphragm, is provided that is sealed off from clutch bell housing 4b and from input part 17, in this case, for example, on axial collar 17a, by means of a seal 17c.
To cool the oil contained in chamber 30, a pump 270, which as a gear pump is driven by input part 17 of friction clutches 10, 11, is contained within clutch bell housing 4b. For this purpose, on component 19, which is connected to input part 17, receptacle 20a, which is connected thereto, is provided with an axial collar 20b that is supported in a swiveling manner at its interior circumference via bearing 20c and at its exterior circumference drives internal gear 272, the pump housing being fixedly attached to transmission housing 56. The more detailed explanation of the operation of pump 270 is given in
Another inventive concept is provided in
It has been shown that it may be especially advantageous, for example, in order to save energy, to provide the pump with a flow volume control valve 275 by means of which the flow volume is adapted to the cooling requirement of clutches 10, 11. The flow volume control valve may, for example, be electrically controlled and controlled as a function of the speed of one of the shafts 2, 3, 4. For this purpose
Torque transmission device 800, which is illustrated in
As is evident in
Moreover, a friction clutch or friction device 815 that also functions as a converter lockup clutch at low speeds, for example, below the idle speed of the engine, is provided between the two parts 803 and 804 formed as inertial bodies or flywheel masses. Friction clutch 815 has flyweights 816 that are carried by an axial collar 817 of primary part 803. In the illustrated exemplary embodiment, radial guide pins 818 are provided for this purpose on axial collar 817. Flyweights 816, which are formed around the circumference as segments, are pressed radially inward via springs 819 that are pretensioned and in this case are supported via friction linings or friction areas 820 against an axial collar 821 that is carried by secondary part 804 (at least below a certain speed). In the depicted exemplary embodiment, axial collar 821 is formed by a pot-shaped formed sheet metal part 822 that is rotationally fixedly joined to secondary part 804.
Friction clutch or converter lockup clutch 815 acts parallel to torsionally elastic damper 801 so that it may be bypassed corresponding to the design or pretensioning of spring 819, at least starting at a specific minimum speed. In this way, among other things, the resonance problems present when starting the engine may in particular be overcome.
Because of the relatively large angular dimension of the segment-type flyweights 816, they have strengthening effect like a braking band. In the depicted exemplary embodiment, three flyweights 816 of this type are provided that are seen each extending practically 120 degrees around the circumference.
From
| Number | Date | Country | Kind |
|---|---|---|---|
| 103 61 491 | Dec 2003 | DE | national |
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| Number | Date | Country |
|---|---|---|
| 10033649 | Feb 2001 | DE |
| 10316445 | Oct 2003 | DE |
| 10316419 | Nov 2003 | DE |
| 10301405 | Jul 2004 | DE |
| Number | Date | Country | |
|---|---|---|---|
| 20050139442 A1 | Jun 2005 | US |
