192 clutches and power-stop control – Clutches – Operators
Patent
1996-10-18
1998-10-20
Lorence, Richard M.
192 clutches and power-stop control
Clutches
Operators
192109F, F16H 6106, F16D 4806
Patent
active
058233130
DESCRIPTION:
BRIEF SUMMARY
The invention concerns a pressure-control device to affect the engaging behavior of powershift clutches in a powershift gear with a control valve cooperating with a damping device as pressure-control valve by means of which the pressure cycle can be set upon engaging the clutch concerned.
DE 21 20 545 has disclosed a pressure-control for gearshift clutches in motor vehicles.
Hydraulic fluid is here forced into an intermediate chamber, between a hollow piston and a control piston, so that said pistons move away from each other and thus the pressure-control device can be moved back to its initial position.
However, in the pressure-control device according to DE 21 20 545, it is disadvantageous that the pressure-control device still has not been reset to its initial position when two clutches are consecutively switched during a short interval of time. The pressure control of the second clutch begins, therefore, at the point of a modulation curve at which the pressure in the pressure-control device is, at the moment of actuation of the second clutch, and not, as it would be necessary for a jolt-free switching operation, at a definite point of the modulation curve, since the whole modulation curve must be cycled through for optimal switching.
Therefore, the pressure of the second clutch is not gradually increased but leaps immediately to the pressure momentarily existing in the pressure-control device whereby a so-called impulse is produced.
Another disadvantage of the pressure-control device, disclosed in the publication cited, is the impossibility of quickly filling the clutch cylinder. Said disadvantage results from the fact that the control piston moves from its starting position where the control edge of the valve releases the full aperture cross section of the clutch cylinder to its pressure-control, where only a small throttle cross section is open on the control edge of the valve, as soon as the pressure, behind the pressure-control valve and before the line to the clutch cylinder, has reached a certain value due to the prestress force of a spring.
Said pressure value is relatively low whereby starting from said point the clutch cylinder is filled only still throttled so that the filling operation of the clutch cylinder lasts a relatively long time.
In order to obtain a good switching quality, the filling time must be as short as possible so that the power flow, in the drive train of the motor vehicle, is only briefly interrupted.
Accordingly, the problem on which this invention is based is to provide a pressure-control device which overcomes the disadvantages of the prior art, especially one that makes possible an impulse-free switching and a quick filling of the clutch cylinder.
According to the invention this problem is solved by the fact that, via a first switching valve switched by a magnetic valve, pressure can be controlled in a chamber C3 between a displacement piston and a pressure-control piston and, via a second switching valve switched by the same magnetic valve, a chamber C2 behind the displacement piston can be exhausted, the pressure-control piston being held in its initial position for releasing the full valve aperture cross section from the pressure line to the clutch line.
By the possibility of being able to control pressure in the chamber C3, between displacement piston and pressure-control piston, the displacement piston and the pressure-control piston can be very quickly again returned to their initial positions.
This quick return of the displacement piston and of the control piston, to their initial positions, is also made possible by the fact that the chamber behind the displacement piston can be exhausted so that the displacement piston does not have to be moved against any great resistance.
As result of the release of the full valve aperture cross section from the pressure line to the clutch line in the initial position of the pressure-control piston, it is possible to fill the clutch cylinder quickly.
The magnetic valve can always be advantageously activated in a neutral state
REFERENCES:
patent: 3674121 (1972-07-01), Copeland
patent: 3882980 (1975-05-01), Blake
patent: 4132302 (1979-01-01), Chatterjea
patent: 4478237 (1984-10-01), Blake et al.
patent: 4676349 (1987-06-01), Coutant
patent: 5251443 (1993-10-01), Ehrlinger et al.
Bohner Ulrich
Burkhart Hugo
Lorence Richard M.
ZF Friedrichshafen AG
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