192 clutches and power-stop control – Transmission control and clutch control
Reexamination Certificate
1998-12-10
2001-06-12
Bonck, Rodney H. (Department: 3681)
192 clutches and power-stop control
Transmission control and clutch control
C192S003520, C477S167000, C477S176000
Reexamination Certificate
active
06244402
ABSTRACT:
BACKGROUND OF THE INVENTION
Power shift transmissions in general have one hydrodynamic converter as starting device. Such converters require great space and involve power loss to hydraulic and churning losses. In order to reduce the length of the transmission and prevent such power losses, the converter has been eliminated in a special development of the invention described in European patent No. 0 214 989 B2, its function as starting component being assumed by a transmission brake. Such a brake is, however, severely stressed.
SUMMARY OF THE INVENTION
The problem on which the invention is based is to provide a compact, economical and wear resistant starting device of long service life and high efficiency.
According to the invention, this problem is solved by a front-mounted, regulated multiple disc clutch wherein a one-way clutch prevents the motor vehicle from rolling opposite to the travel direction intended by the gear selection.
To design the multiple disc clutch as compact as possible, the loading of the clutch must be kept low. At the same time, the clutch must be operated only as briefly as possible under drag in order to minimize its wear and thermal stress. In any case, the vehicle must not be held with the clutch on hills. To avoid such a load the power shift transmission has said one-way clutch which prevents the vehicle from rolling opposite to the travel direction intended by a gear selection.
Another solution of the problem, on which the invention is based and for which separate protection is claimed, is to design the regulated gear clutch as compact, economical and wear resistant starting device. This is advantageous insofar as there is already a gear clutch in power shift transmissions. Such a gear clutch serving as starting device must be dimensioned only somewhat larger. The regulation ensures that the gear clutch be thermally loaded and used up as little as possible. Length and weight of the power shift transmission are considerably reduced in this solution, since the hydrodynamic converter is eliminated and also no separate front mounted clutch is needed.
The gear clutch is preferably a regulated multiple disc clutch.
In such a gear clutch designed to act as integrated starting clutch and is a regulated multiple disc clutch, a one-way clutch advantageously prevents the rolling of the vehicle opposite to the travel direction intended by a gear selection.
In an advantageous development of the invention, the one-way clutch is designed as free wheel unit, especially as sprag unit or pawl unit.
The one-way clutch (free wheel unit) is preferably mounted on the input shaft of the power shift transmission, that is, on the side of the multiple disc clutch facing the transmission, especially in the area of the multiple disc clutch.
Alternatively to a free wheel unit, an unintended rolling opposite to the travel direction can be prevented by an electronic gearshift system which acts upon shifting components. One possibility here is to activate the service brake in case of an unintended rolling. The brake system must here, of course, be synchronized with the transmission system. Another possibility is to design the one-way clutch in the transmission combined with the starting clutch as closed system (transmission brake). The braking action is preferably obtained by adjusting in the transmission a combination of shifting components which blocks the output of the transmission. The electronic control of said transmission brake must be effected as an overlapping control, that is, when the starting clutch begins to grip, the braking action of a shifting component is released to the same extent the starting clutch absorbs the torque. How strong the retaining torque overlap must be depends on the drive force of the vehicle due to a downhill gradient. The retaining torque of the transmission brake, which is determined by the overlapping control, is advantageously adapted to this drive force. Thus, there are no frictional losses that are great enough to destroy the mechanical power and produce unneeded thermal load.
When the vehicle weight is known, this drive force can be determined by its effect upon the vehicle, that is, by the acceleration of the vehicle during a very brief testing time within which the vehicle hardly noticeably rolls away. This requires measuring of the angular velocity of the transmission output shaft and a power calculation from the change in angular velocity.
Alternatively, the drive force resulting from a slope can be determined by measuring the torque of the transmission output shaft resulting therefrom.
In another development of the invention, the slope output power is determined, when the vehicle weight is known, by means of a gradient sensor.
When the vehicle weight is known the drive power is advantageously found by a change of the transmission output speed.
The multiple disc clutch may be a wet clutch in order to obtain a good dissipation of heat.
Another solution of the problem on which the invention is based and for which separate protection is claimed is to design a regulated transmission brake as a compact, economical and wear resistant starting device wherein by activating the service brake an overlapping shift prevents the motor vehicle from rolling opposite to the travel direction intended by the gear selection. This is advantageous insofar as there is in any case a transmission brake in power shift transmissions. Said transmission brake serving as starting device must be dimensioned somewhat larger. The regulation ensures that the transmission brake be thermally loaded and used up as little as possible. Length and weight of the power shift transmission are considerably reduced in this solution, since the hydrodynamic converter is eliminated and also no separate front-mounted clutch is needed.
REFERENCES:
patent: 4487303 (1984-12-01), Boueri et al.
patent: 4817462 (1989-04-01), Dach et al.
patent: 4867291 (1989-09-01), Holman et al.
patent: 5474164 (1995-12-01), Berger
patent: 5836849 (1998-11-01), Mathiak et al.
patent: 5911648 (1999-06-01), Dreibholz et al.
patent: 2 003 977 (1971-08-01), None
patent: 40 25 420 C2 (1992-12-01), None
patent: 0 214 989 B1 (1987-03-01), None
patent: 0 251 156 A2 (1988-01-01), None
patent: 0338219 (1989-02-01), None
patent: 0 517 420 A2 (1992-12-01), None
patent: 0 681 123 A2 (1995-11-01), None
Japanese Abstract, vol. 010, No. 277 (M-519) dated Sep. 19, 1986 to Nissan Motor Co. Ltd).
Domian Hans-Jorg
Dreibholz Ralf
Kuhn Walter
Bonck Rodney H.
Davis & Bujold P.L.L.C.
Waddell Tisha D.
ZF Friedrichshafen AG
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