GB2145495A

GB2145495A - Method and apparatus for damping torsional vibrations in a combustion engine - gear box unit

Info

Publication number: GB2145495A
Application number: GB08420392A
Authority: GB
Inventors: Hans Jurgen Drexl
Original assignee: Fichtel and Sachs AG
Current assignee: ZF Friedrichshafen AG
Priority date: 1983-08-23
Filing date: 1984-08-10
Publication date: 1985-03-27
Also published as: IT8467843A0; DE3330332A1; JPS6065934A; IT8467843A1; ES8603043A1; GB8420392D0; SE8404166D0; BR8404186A; ES535345A0; SE8404166L; IT1179070B; FR2551154A1

Abstract

In a driving unit comprising an internal combustion engine 10 and a gear box 26 a torque transmitting frictional clutch 16 is provided between the output of the combustion engine and the input of the gear box. To torsional vibrations a predetermined slip is maintained between the output of the combustion engine and the input of the gear box by controlling the engagement pressure of the clutch, at least in some ranges of speed of the engine. The clutch control may be electrical, pneumatic or hydraulic. Sensors 40, 42 measure the slip. <IMAGE>

Description

SPECIFICATION Method and apparatus for daniping torsional vibrations in a combustion engine gear box unit This invention relates to a driving unit comprising an internal combustion engine, such as of the piston type, having an engine output shaft, further comprising a gear box having a gear box input shaft, further comprising a torque transmitting frictional clutch. Such driving units are particularly used in motor vehicles. In such driving units torsional vibrations are excited by the combustion engines.

It is necessary to damp such torsional vibrations such, that the subsequent units connected to the engine, more particularly to the gear box, are not subject to non-tolerable torsional vibrations. Moreover, it is desired to prevent noise resulting from such torsional vibrations.

STATEMENT OF THE PRIOR ART In the past one has integrated torsional vibration dampers in the clutch discs of clutches provided between the combustion engine on the one hand and the gear box on the other hand. Such a construction is known for example from German Patent 1 680 049.

In this known construction there is provided a first torsional vibration damper for the idling operation and a second separate vibration damper for the operation under load. Even by this considerable expense it has not always been possible to damp the arising torsional vibrations to the desired degree. The damping problem becomes still more difficult due to the fact that the various components of combustion engine driving units are more and more reduced in weight. By this reduction in weight the effect of torsional vibrations is still increased.

OBJECT OF THE INVENTION It is a primary object of the present invention to have a driving unit of the type as defined above in which torsional vibrations are suppressed to a high degree. Moreover, the suppression of torsional vibration is to be obtained with reduced expense. Further the components for suppression or the torsional vibrations are to be small in view of space saving.

SUMMARY OF THE INVENTION In view-of the above objects this invention provides a method of operation for a driving unit comprising an internal combustion engine having an engine output shaft, a gear box having a gear box input shaft and a torque transmitting frictional coupling unit interconnecting said engine output shaft and said gear box input shaft. According to this method the torque transmission of the frictional coupling unit is controlled such as to maintain a predetermined slip between the engine output shaft and the gear box input shaft at least in those ranges of R.P.M. in which torsional vibrations are expected. The method is of particular importance for combustion engines of the reciprocating piston type because such engines are particularly subject to torsional vibration.It has been found that the maintainance of a small slip within the frictional coupling unit results in a very effective suppression of torsional vibrations. It has been further found that even a small slip which has no negative result with respect to a heat generation warrants a highly effective suppression of torsional vibrations.

The method of this invention is applicable even with known clutches which are usually provided between the engine and the gear box in view of starting the gear change.

It has further been found that a satisfactory suppression of torsional vibrations is obtained even at a slip value below 100 R.P.M. In view of reducing heat generation and wear of the friction faces a slip of about 25 to about 50 R.P.M. is preferred.

A driving unit of this invention comprises an internal combustion engine, such as of the reciprocating piston type and a gear box. The combustion enging has an engine output shaft. The gear box has a gear box input shaft. A torque transmitting frictional coupling unit is provided for interconnecting the engine output shaft and the gear box input shaft. The torque transmitting frictional coupling unit may be a clutch unit which is useful also in view of starting and speed changing. Slip sensing means are provided sensing the slip between the engine output shaft and the gear box input shaft. Slip setting means are provided for setting a desired slip between the engine output shaft and the gear box input shaft. Comparative means are connected to the slip sensing means on the one hand and the slip setting means on the other hand.

These comparative means compare the set slip from the slip setting means and the measured slip from the slip sensing means and supply a comparison result signal. Torque transmission control means are provided which control the torque transmission in response to the comparison result signal such that the measured slip is continuously approached to the set slip.

In ordinary motor vehicle clutches the torque transmission through the clutch is dependent on the engagement force by which the clutch disc is engaged between the friction faces of the clutch housing and the pressure plate. With these ordinary clutches the torque transmission can be controlled by controlled variation of the clutch engagement force.

The various features of novelty which characterize the invention are pointed out with particularity in the claims annexed to and forming a part of this disclosure. For a better understanding of the invention, its operating advantages and specific objects attained by its use, reference should be had to the accompanying drawings and descriptive matter in which there are illustrated and described embodiments of the invention.

BRIEF DESCRIPTION OF THE DRAWINGS The invention will explained in greater detail below by reference to an example of embodiment. In detail the enclosed Figure 1 shows diagrammatically a driving unit according to the invention.

Figure 2 shows a modified embodiment.

DESCRIPTION OF THE PREFERRED EMBODI MENT According to the figure 1 the driving unit comprises a combustion engine of the reciprocating piston type 10. The combustion engine 10 has an engine output shaft 12. This engine output shaft 1 2 is connected for common rotation to a clutch housing 14 of a clutch 1 6. The clutch 16 comprises a pressure plate 18 which is axially guided within the clutch housing 14 so as to rotate with the clutch housing 14. The pressure plate 18 is urged to the left as seen in the figure by a diaphragm spring 20. A clutch disc 22 is engaged between the pressure plate 1 8 and the clutch housing 14 by the action of the diaphragm spring 20. The clutch disc 22 is mounted on a gear box input shaft 24 of a gear box 26.The clutch disc 22 is axially movable with respect to the gear box input shaft 24 and connected thereto for common rotation. The pressure plate 1 8 is combined with an armature 28 of a stationary electromagnetic coil 30. The electromagnetic coil 30 is connected to a current supply unit 32 which is again connected to the battery 34 of the motor vehicle. In view of releasing the clutch 1 6 on starting or gear changing the electromagnetic coil 30 can be energized through the electric supply unit by activating a clutch pedal unit 38. When the electromagnetic coil 30 is energized the armature 28 is pulled to the right against the action of the diaphragm spring 20 so that the clutch disc 22 is released from frictional engagement with the clutch housing 14 and the pressure plate 18.

According to this invention a predetermined slip is maintained between the engine output shaft 1 2 and the gear box input shaft 24 or with other words - between the clutch housing 1 4 and the pressure plate 18 on the one hand and the clutch disc 22 on the other hand. The predetermined slip is controlled by the electromagnetic coil 30. The torque transmission of the clutch 1 6 is dependent on the sum of the spring force of the diaphragm spring 20 on the one hand and the pulling force exerted by the electromagnetic coil 30 on the armature 28 on the other hand. This sum is controlled by controlled variation of the energizing current in the electromagnetic coil 30 such that the desired slip is maintained within the clutch 16.

In detail there is provided a first R.P.M.

sensor 40 on the engine output shaft 1 2 and a second R.P.M. sensor 42 on the gear box input shaft 24. These R.P.M. sensors 40 and 42 are connected to a first comparator 44 which supplies a signal representing the difference in R.P.M. of the engine output shaft 1 2 and the gear box input shaft 24 i.e. a signal representing the 'slip'. The group of components comprising the R.P.M. sensors 40, 42 and the first comparator 44 can be regarded as a 'slip sensor'. The slip signal representing the measured slip is supplied from the first comparator 44 to a second comparator 46. This second comparator 46 is moreover connected to a slip setting unit which supplies a signal representing the desired slip to the second comparator 46.The desired slip is dependent on the absolute R.P.M. of the engine output shaft 12 as indicated by the connection between the first R.P.M. sensor 40 and the slip setting unit 48.

The second comparator 46 compares the signal coming from the first comparator 44 and representing the measured slip on the one hand and the signal arising from slip setting unit 48 and representing the desired slip on the other hand. This difference is to become zero and therefore the comparison result signal from the second comparator 46 is fed back to the electric supply unit 32 such as to control the pulling force exerted by the electromagnetic coil 30 onto the armature 28 in view of approaching the slip in the clutch 1 6 to the desired slip.

If one wants a slip in the clutch 1 6 only in certain R.P.M. ranges or in one certain R.P.M. range a corresponding program may be supplied to the slip setting unit 48. This program may provide a zero value for the desired slip for all R.P.M. ranges outside those ranges in which a predetermined slip is wanted.

Driving units are known, in which the operation of the clutch 1 6 is effected automatically in dependency of various parameters such as the R.P.M. of the engine 10 and the R.P.M.

of the gear box 26. In such cases there are already provided R.P.M. sensors on the engine output shaft and the gear box input shaft 24. Such sensors may be according to this invention additionally used for maintaining the controlled slip.

While in the preferred embodiment the controlled slip is provided in the clutch 1 6 which has the additional function of separating the shafts 12 and 24 on starting and gear changing it is to be understood that a monofunctional coupling unit can also be provided which has the only purpose of maintaining a predetermined slip between the shafts 1 2 and 24. If a clutch is also provided such a monofunctional coupling unit may be arranged in series with the clutch between the engine and the gear box.

In the modified embodiment of figure 2 28' is a tube member connected to the pressure plate 1 8. This tube member 28' has a radial flange 29 which is the rotating part of a clutch release bearing 31. The non-rotating part of the clutch release bearing 31 is designated by 33. A pulling unit 35 is connected to the non rotating part 33. The pulling unit 35 is connected to the electric supply unit 32.

For the rest the embodiment of Fig. 2 is identic with the embodiment of Fig. 1. It is to be noted that the pulling unit 35 could also be a hydraulic, pneumatic or mechanic pulling unit.

The embodiment of Fig. 2 is the preferred one.

While a specific embodiment of the invention has been shown and described in detail to illustrate the application of the inventive principles, it will be understood that the invention may be embodied otherwise without departing from such principles. More particularly it is to be noted that any kind of electric, electromechanic, hydraulic and pneumatic clutch operation is possible.

The reference numbers as used in the claims are only used in view of better understanding but are not at all restrictive.

Claims

1. For a driving unit comprising: an internal combustion engine (10), such as of the reciprocating piston type, having an engine output shaft (12), a gear box (236) having a gear box input shaft (24) and a torque transmitting frictional coupling unit (16) interconnecting said engine output shaft (12) and said gear box input shaft (24), a method of operation in which the torque transmission of said frictional coupling unit is controlled such as to maintain a predetermined slip between said engine output shaft (12) and said gear box input shaft (24) at least in those ranges of R.P.M. in which torsional vibrations are expected.

2. A method as claimed in claim 1 wherein torque transmission is controlled such as to maintain a slip of less than about 100 R.P.M.

3. A driving unit comprising: an internal combustion engine (10), such as of the reciprocating piston type, having an engine output shaft (12), a gear box (26) having a gear box input shaft (24), a torque transmitting frictional coupling unit (16) interconnecting said engine output shaft (12) and said gear box input shaft (24); slip sensing means (40, 42, 44) sensing the slip between said engine output shaft (12) and said gear box input shaft (24); slip setting means (48) for setting a desired slip between said engine output shaft (12) and said gear box input shaft (24); comparative means (46) connected to said slip sensing means (40, 42, 44) and to said slip setting means (48) and torque transmission control means (30) responsive to a comparison result signal from said comparative means (46).

4. A driving unit as set forth in claim 3 said torque transmitting frictional coupling unit being a clutch unit (16) useful for separating torque transmission between said engine output shaft (12) and said gear box input shaft (24).

5. A driving unit substantially as described in Fig. 1 or Fig. 2 of the accompanying drawings.