Method and device for controlling a motor vehicle drive train
AssigneeZF Friedrichshafen AG
InventorsMartin Spiess, Christoph Goebel, Willibald Probst
Life of this patent
Estimating the term…
Abstract
Method and device for controlling a motor vehicle drive train. To reverse the travel direction, the input torque is transmitted with pressure modulation from one clutch (Kv) of one travel direction to one clutch (Kr) of the opposite travel direction. If at the time that a reverse travel direction is selected and the speed of travel exceeds a set maximum value (VR,max), the speed of travel is automatically reduced to the maximum value first by continuous change of the ratio of the transmission (2) of the drive train.
Claims14
A method to control a motor vehicle drive train, said train having one transmission (2) with a continuously variable ratio, one reversing gear (22), at least one optionally actuatable clutch (Kv) for a forward motion, one clutch (Kr) for a reverse motion, and one control device (16) for an automatic reversal of an original travel direction, comprising the following steps:
- selecting the automatic reversal of the original travel direction from one of the forward motion to the reverse motion and the reverse motion to the forward motion, by a person on said control device (16);
- selecting the automatic reversal of the original travel direction by a person at a first travel speed above a preset limiting speed (VR,max), and
- carrying out each following steps automatically:
- a) reducing the first travel speed to a lower traveling speed, by continuously regulating and controlling a downshifting of a transmission ratio,
- b) determining one of reaching and falling below the limiting speed (VR,max),
- automatically changing a previously open clutch of a new travel direction to a friction-slip state by a pressure modulation,
- bringing a friction-slip free previously closed clutch of the original travel direction to the friction-slip state, by reducing a closing pressure, overlapping in time the friction-slip state change of the previously open clutch, and
- transmitting an input torque interruption-free and jolt-free from the previously closed clutch to the previously open clutch,
- c) automatically maintaining as friction-slip free the previously closed clutch following a complete opening of said clutch, and
- automatically maintaining a friction-slip operation of the previously open clutch until the vehicle is decelerated to a stop and accelerated in the new travel direction, until both a driven side and a driven-off side of the previously open clutch of the new travel direction have reached a synchronous running,
- d) raising the closing pressure of the previously open clutch after reaching the synchronous running, to a system pressure allowing friction-slip free operation to occur in said previously open clutch, and
- e) automatically skipping step a) and applying steps b) to c), by said control device, upon selection of the new travel direction wherein the vehicle speed is one of at the limiting speed (VR,max) and below the limiting speed (VR,max).
A device to control a motor vehicle drive train, said drive train having one transmission (2) with a continuously variable ratio, one reversing gear (22), at least one optionally actuatable clutch (Kv) for forward motion, and a clutch (Kr) for reverse motion, comprising the following:
- one control device (16) for an automatic reversal of a travel direction, wherein the reversal of the travel direction from one of forward motion to reverse motion and reverse motion to forward motion is selected by a person on said control device and automatically carried out thereby, characterized in that said control device (16) being designed so that after the reversal of the travel direction is selected by the person, at a vehicle speed above a preset limiting speed (VR,max), said control device automatically carries out the following steps:
- a) reducing the first travel speed to a lower traveling speed, by continuously regulating and controlling a downshifting of a transmission ratio,
- b) determining one of reaching and falling below the limiting speed (VR,max),
- automatically changing a previously open clutch of a new travel direction to a friction-slip state by a pressure modulation,
- bringing a friction-slip free previously closed clutch of the original travel direction to the friction-slip state, by reducing a closing pressure, overlapping in time the friction-slip state change of the previously open clutch, and
- transmitting an input torque interruption-free and jolt-free from the previously closed clutch to the previously open clutch,
- c) automatically maintaining as friction-slip free the previously closed clutch following a complete opening of said clutch, and
- automatically maintaining a friction-slip operation of the previously open clutch until the vehicle is decelerated to a stop and accelerated in the new travel direction, until both a driven side and a driven-off side of the previously open clutch of the new travel direction have reached a synchronous running,
- d) raising the closing pressure of the previously open clutch after reaching the synchronous running, to a system pressure allowing friction-slip free operation to occur in said previously open clutch, and
- e) automatically skipping step a) and applying steps b) to d), by said control device, upon selection of the new travel direction wherein the vehicle speed is one of at the limiting speed (VR,max) and below the limiting speed (VR,max).
A method to control a motor vehicle drive train having one transmission (2) with continuously variable ratio, one reversing gear (22), at least one optionally actuatable clutch (Kv) for forward motion and one clutch (Kr) for reverse motion and one control device (16) for automatic reversal of a travel direction comprised of the following steps:
- selecting a reversal of the travel direction from one of forward motion to reverse motion and reverse motion to forward motion by a person on said control device (16),
- automatically carrying out said selecting,
- automatically carrying out each of the following steps when the automatic reversal of travel direction at a travel speed above a preset limit speed (VR,max) is selected:
- a) Lifting a gear ratio and pressure-modulated closing of a previously open clutch of a new travel direction so that the previously open clutch is brought to a friction-slip operation, and
- bringing to friction-slip operation a slip-free previously closed clutch of an old travel direction by a closing pressure reduction with a pressure modulation, overlapping in time with said previously open clutch,
- b) Permanently varying a ratio of the gear so that a parameterized maximum rotational speed difference between an input side and an output side of the clutch device is not exceeded,
- continuously calculating a friction work of both the clutch for forward motion and the clutch for reverse motion,
- comparing the friction work with admissible values and thus a rotational speed difference does not exceed a maximum value,
- c) Maintaining the friction-slip until the vehicle is decelerated to stoppage and is accelerated in the new travel direction until a driven side and a driven off side of the previously open clutch have reached a synchronous running, and
- d) Raising a closing pressure of said previously open clutch to a system pressure at which slip-free operation occurs on said clutch after a synchronous running of a driving clutch side and of a driven clutch side of the new travel direction has been reached.
Dependencies are inferred from the claim text.