WO2012119751A1

WO2012119751A1 - Dual-mass flywheel arranged in the drive train of a motor vehicle

Info

Publication number: WO2012119751A1
Application number: PCT/EP2012/000977
Authority: WO
Inventors: Herbert Meyer
Original assignee: Audi Ag
Priority date: 2011-03-10
Filing date: 2012-03-05
Publication date: 2012-09-13
Also published as: DE102011013483A1; DE102011013483B4

Abstract

The invention relates to a dual-mass flywheel (ZMS) arranged in the drive train of a motor vehicle, having a rotation-symmetrical primary part which is connected to the crankshaft of an internal combustion engine, having a secondary part which outputs directly or indirectly on a gear shaft, and having a spring and dampening unit for absorbing the rotary oscillations originating from the crankshaft, wherein the resonance frequency of the dual-mass flywheel is variable. For favorable adaptation of the ZMS to different operating conditions, according to the invention the spring unit (26) is arranged pre-tensioned between the primary part (12) and the secondary part (18) so that it produces a rigid connection below a defined engine torque and that furthermore a second spring unit (30) is connected downstream of the spring unit (26) which is substantially effective only below the defined engine torque.

Description

description

In the drive train of a motor vehicle arranged

Dual Mass Flywheel

The invention relates to a arranged in the drive train of a motor vehicle two-mass flywheel according to the preamble of claim 1.

Dual mass flywheels (DMF) as torsional vibration dampers in the drive train of motor vehicles are widely known. The interpretation of the Torsionskennlinie determining spring unit (usually annularly arranged helical compression springs) of the DMF is such that its resonant frequency is outside the regular engine operation of idle speed to full load speed to ensure an always effective torsional vibration damping. For example, the resonant frequency may be well below the idle speed at an engine speed, so that this condition is passed through only briefly when starting the engine or when it is stopped.

The torsional characteristics of dual-mass flywheels today are usually designed so that the alternating torque of the engine from idle speed to maximum speed and the maximum thrust torque is transmitted to the maximum torque torsionally soft. This design leads to the known resonant frequency of the two-mass oscillator. The resonance frequency may not be excited by the combustion engine, since the resulting vibration amplitudes

CONFIRMATION COPY and moments endanger the components and lead to serious comfort impairments. If you want to turn off in a ZMS, which is designed for the 4-cylinder operation, two cylinders to bypass the part-load operation of the 4-cylinder engine with poor efficiency, then the resonant frequency described above is hit at twice the speed because the excitation frequency halved.

Today common DMFs for 4-cylinder engines can have a resonant frequency in the range of 12Hz, so this at about 350rpm. Engine speed is hit. This value then increases to 700 rpm in 2-cylinder operation. Since it is a damped vibration system, the increase in amplitude in the range of the resonance against the exciting amplitude of the motor is up to 1400rpm. so high that at least loss of comfort in terms of roar and hum of the body arise. Therefore, operation with only 2 cylinders is only permitted above this speed. The CO2 savings potential is therefore clearly limited.

By the generic DE 10 2007 044 474 A1 a ZMS is known in which by means of an electrically or hydraulically operated adjusting device, the spring unit or at least one spring of the spring unit for varying the resonant frequency of the ZMS acted upon or is adjustable in its bias. In particular, this should improve the vibration damping when starting the engine and during its run-up. The object of the invention is to form the Torsionsdämpferkennlinie arranged in the drive train of a motor vehicle ZMS with structurally simple means so that the excitation of its resonant frequency can no longer take place at any moment point so that disturbing or component hazardous vibrations can occur. In particular, a arranged in the drive train of a motor vehicle ZMS with structurally simple Means are designed so that the operation of the internal combustion engine in the lower load range is also possible near its resonance frequency.

The solution to this problem is achieved according to the invention with the features of claim 1. Advantageous and particularly expedient developments of the invention are specified in the further claims.

According to the invention it is proposed that the spring unit is arranged biased between the primary part and the secondary part, that it produces a rigid connection below a defined engine torque and that further the spring unit is driven downstream of a second spring unit, which is essentially effective only below the defined engine torque , With the proposal according to the invention, the ZMS is limited in its effect on the load range above the selected biasing torque. The task of vibration isolation of the drive train up to this biasing moment is transmitted to the ZMS downstream torsion damper. Thus, the resonance frequency of the ZMS at the low torque operating points of the internal combustion engine, as they arise after switching off of cylinders, not excitable. The ZMS behaves almost rigidly. The vibration decoupling is done completely in the downstream torsion damper. To split the effect of the two torsional damper no actuator or the like is necessary.

The characteristic curve of the dual-mass flywheel is therefore modified to such an extent by the installation of the torsion springs in the strongly preloaded state that a movement in the DMF takes place only from a freely definable engine torque. This moment can be, for example, the moment to which a 2-cylinder operation is intended. At higher torques, the R4 Operation resumed and the ZMS works as known with its intended characteristic. In order to decouple the torsional vibrations occurring in the R2 mode or in the range of low torques from the drive train, a torsion damper is provided after the DMF whose characteristic curve extends at least up to the preloaded moment in the DMF. As an embodiment in a vehicle with manual transmission, the usual torsional damper of clutch plates for powertrains with Einmassenschwungrad offers. Since only low torques have to be covered, a very good decoupling for all low load ranges in push and pull operation can be achieved here as well. A damper for decoupling in idle can also be provided. In order to ensure the transition of the movement from one torsion damper to the other without disturbing torque shocks from the excitation of the internal combustion engine when striking one of the two dampers, the abutment torque of the second torsional damper must be selected slightly above the breakaway torque of the first torsional damper. When designing the preload torque is also to be considered that in the torsion damper of the DMF not only the mean moment of the internal combustion engine acts, but also the moment that is generated by the alternating acceleration of the crank mechanism from the combustion force on the secondary inertial mass.

This method is of course not limited to the 2-cylinder operation of a 4-cylinder engine, but can be applied to all known engine designs and suggestions by more or less cylinder at the shutdown. The transient torque of the EMS in a DMF must then be adjusted (as well as the downstream torsion damper). Due to the bias of the springs, the ZMS becomes EMS until a certain moment. By a suitable choice of the characteristic of the downstream torsional damper, a two-cylinder operation is possible up to low speeds. The coupling of the secondary side increases the mass moment of inertia of the flywheel and thus reduces the alternating torque delivered into the drive train. The effect of the downstream torsional damper is thereby improved. The effect of a built-in or on the ZMS order styling device such as a centrifugal pendulum is not hindered.

The consumption-saving potential can be fully exploited.

The second spring unit can be switched on in an advantageous manner between the first secondary part interacting with the primary part and a second secondary part. This requires only the output side changes to the drive train, the second secondary part can already be a driven-side gear part, such as a correspondingly modified input flange, etc. If, in a manner known per se, the secondary part of the DMF is followed by a friction clutch with a driver disk and a spring unit is arranged in the driver disk, then the second spring damper unit, which acts below the defined engine torque, can be formed by the spring unit in the driver disk with virtually no additional structural expenditure. This then only requires a suitable adaptation of the two spring units in the above sense.

Furthermore, the two spring units can be formed in a manner known per se by means of compression springs arranged annularly around the primary part, the secondary part and optionally the driver disk, between which the each abortive driver of the secondary parts are clamped backlash, the spring rate of the springs is tuned accordingly.

Finally, it is proposed in an advantageous embodiment of the invention that during operation of the internal combustion engine with disengageable cylinders in the low-load range, the second spring unit is designed for the resulting lower engine torque and the first spring unit to the higher engine torque during operation of the internal combustion engine with all cylinders. For example, if a four-cylinder engine is operated in the low load range to save fuel and increase efficiency with only two cylinders, the second spring unit may be tuned to accommodate the changed vibration excitation throughout the low load RPM range. As a result, the internal combustion engine can also be operated at low speeds without reaching the critical range of the resonance frequency of the ZMS.

An embodiment of the invention is explained in more detail below with further details. The sketchy drawing shows in:

1 shows a vibration model of a prior art ZMS in the drive train of a motor vehicle with a linear torsional characteristic. and

Fig. 2 shows another vibration model of a ZMS with a

Torsionskennlinie, which only allows a rotation from a certain torque, with a downstream torsion damper, whose torsional characteristic just above this torque mentioned no longer allows the further rotation.

FIG. 1 schematically shows the vibration model of a dual-mass flywheel 10 (DMF) which is switched on in a drive train of a motor vehicle as a torsional vibration damper whose primary part 12, which is fixedly connected to the crankshaft, not shown, of a reciprocating internal combustion engine has a torsionally elastic limited elasticity via a spring unit 14 and a damper unit 16 a secondary part 18 is coupled.

The secondary part 18 is connected for example via an integrated friction clutch (not shown) and a transmission input shaft 19 (acting as a torsion spring) with the speed change gear 20 and via this with the other drive train 21 of the motor vehicle 22, which components complement the illustrated vibration model accordingly ,

The spring unit 14 with the damper unit 16 is vibrationally tuned so that the drawn in the graph below torsion (torque over angle of rotation) 24 increases linearly with increasing motor torque M above the swing angle phi, for example. Up to the stop moment Mmax, the DMF is effective as a torsional vibration damper.

Fig. 2 shows a modified to Fig. 1 vibration model in which between the primary part 12 of the DMF 10 ^' and the secondary part 18 a parallel to the damper unit 6, the first spring unit 26 is turned on.

The spring unit 26 is composed of several, biased between the primary part 12 and the secondary part 18 in the circumferential direction backlash built screw compression springs together. The bias of the compression springs of the spring unit 26 is designed so that the rotational connection between the Primary part 12 and the secondary part 18 below a defined engine torque M (is still running) is rigid, so no torsional vibration damping takes place. The secondary part 18, a second secondary part 28 is driven downstream, which is connected via a second spring unit 30 and also a damper unit 32 to the first secondary part 18 is limited torsionally elastic coupled.

The second spring unit 30 lower spring rate is designed so that it acts as a vibration isolation at lower engine torque.

The graph drawn below the vibration model according to FIG. 2 shows the torsion characteristic 24 ^'of the DMF 10 ^' and the torsion characteristic curve 34a, 34b of the downstream torsion damper 11, which is composed as follows:

In the lower load range of the internal combustion engine at low torques M, the spring unit 30 (see arrows) acts with the damper unit 32 (characteristic 34 a, 34 b) vibration-isolating. The region 34a of the characteristic curve represents, for example, the very flat spring stage required for vibration decoupling during idling and neutral gear.

The area 34b shows the position of the stop torque of the torsion damper 11 just above the engine torque Mi.

The first spring unit 26 is set rigidly up to this moment Mi by bias and allows no relative movement between the primary part 12 and the first secondary part 18 to. With increasing moment M, the first spring unit 26 with the damper unit 16 becomes active and the torsional vibration damping now takes place between the primary part 12 and the secondary part 18. The spring unit 26 has the same spring rate as the spring unit 14 of FIG. 1.

In an internal combustion engine with disengageable cylinders (for example, in two-cylinder operation with low power requirement and in four-cylinder operation with high power requirement), the biasing torque of the DMF 10 ^' is chosen so that the low torque in two-cylinder operation just does not lead to a movement of the torsion damper. Although the high alternating torques generated by the gas force also apply to the prestressed torsion damper and the first secondary part, the bias voltage increases the possible approach to the resonance frequency.

This design advantageously takes into account the changed excitation frequency of the engine when the cylinders are switched off or in the two-cylinder mode. The bias prevents the ZMS resonance, which is very close to the speed range selectable by the driver, to be excited. The drive train is decoupled in this operating state by the second torsional damper 11 of disturbing vibrations. With increasing loads through the connection of the cylinder and the excitation frequency increases again and the resonance point is again far below the approachable speed range.

The second secondary part 28 of the torsion damper 11 may be in a manner not shown in an embodiment with integrated friction clutch whose drive plate, in which the second spring unit 30 may be integrated in a conventional manner. This is just the well-known To modify spring unit to a suitably tuned spring unit 30.

In a drive train without integrated friction clutch, the second secondary part 28 and its spring and damper unit 30, 32 may be arranged, for example, in an input flange of the downstream variable speed transmission 20.

The spring unit 26 may be formed in a conventional manner by circularly about the rotationally symmetrical primary part 12 and secondary part 18 arranged helical compression springs which are inserted into corresponding recesses of the primary part 12 and engage in the backlash and under the defined bias driver of the secondary part 18, for example in the aforementioned DE 10 2007 044 474 A1 in FIG. 1.

The spring unit 30 may be formed as known per se in driver disks of friction clutches also by circularly arranged helical compression springs, which are matched in their spring hardness corresponding to the spring unit 30.

The damper units 16 and 32 may be in a known manner friction damper, as are common in two-mass flywheels or Mitnehmerscheiben of friction clutches. The invention is not limited to the embodiment shown in the vibration model Fig. 2. The second spring unit only has to be arranged at one point between the DMF and the gear mass.

Claims

claims

In the drive train of a motor vehicle arranged dual-mass flywheel, with a rotationally symmetrical primary part, which is connected to the crankshaft of an internal combustion engine, with a secondary part, which aborts indirectly or directly on a transmission shaft, and with a spring and damper unit for absorbing the vibrations emanating from the crankshaft, characterized in that the spring unit (26) biased between the primary part (12) and the secondary part (18) is arranged to produce a rigid connection below a defined engine torque and further that the spring unit (26) drivingly a second spring unit (30 ), which is essentially effective only below the defined engine torque.

Dual-mass flywheel according to claim 1, characterized in that the second spring unit (30) between the first, with the primary part (12) cooperating secondary part (18) and a second secondary part (28) is turned on.

Dual-mass flywheel according to claim 1, wherein the secondary part (18) a friction clutch is connected downstream with a drive plate and in the drive plate, a spring unit is arranged, characterized in that the effective below the defined engine torque second spring unit (30) is formed by the spring unit in the drive plate ,

4. dual mass flywheel according to one of the preceding claims, characterized in that the two spring units (26, 30) in a conventional manner by annularly around the primary part (12), the secondary part (18) and optionally the drive plate arranged helical compression springs are formed between the each abeating driver are clamped backlash, the spring rate of the springs is tuned accordingly.

5. Dual mass flywheel according to one of the preceding claims, characterized in that during operation of the internal combustion engine with deactivatable cylinders in the low-load range, the second spring unit (30) to the resulting lower engine torque and the first spring unit (26) to the higher engine torque during operation the internal combustion engine is designed with all cylinders.