Machine element or mechanism – Gearing – Interchangeably locked
Patent
1996-10-30
1998-10-13
Ta, Khoi Q.
Machine element or mechanism
Gearing
Interchangeably locked
94336R, 447 79, 447 86, B60K 4122, F16H 6102
Patent
active
058195858
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF INVENTION
This invention relates to vehicle transmissions which include multi-ratio gearbox and in particular to transmissions which have an automatic ratio selection mode.
SUMMARY OF INVENTION
It is an object of the present invention to provide an improved form of vehicle transmission.
Thus according to the present invention there is provided a vehicle transmission comprising a main drive clutch, a multi-ratio gearbox, a gear engaging mechanism for engaging the operative ratio of the gearbox, a manually operable gear selector allowing an operator to manually select the operative ratio of the gearbox when the transmission is acting in a manual mode, and an electronic control means which controls the disengagement and engagement of the drive clutch at start-up and halting of the associated vehicle and during gear changes and which controls the operation of the gear engaging mechanism in response to movements of the gear selector, the transmission being characterised in that the electronic control means is arranged to override the gear ratio currently selected by the operator to select a more appropriate gear ratio for the current conditions if a predetermined operating condition occurs when in its manual mode.
In a preferred arrangement the transmission also has an automatic mode of operation and the electronic control means also determines which gear ratio is to be selected when the transmission is operating in its automatic mode.
Typically the override of the manual mode will occur if any one of the following predetermined operating conditions occurs: will be implemented. downshift of gear ratio will be implemented. The electronic control means may be set up so that the downshift only occurs if the engine speed resulting from the lower ratio gear selection still remains below a present limit (eg 1050+300 rpm).
The transmission will also preferably allow the operator to override the gear automatically selected by the transmission if he so wishes.
BRIEF DESCRIPTION OF DRAWINGS
The present invention will now be described by way of example only, with reference to the accompanying drawings in which:
FIG. 1 shows in diagrammatic form the general layout of a vehicle transmission embodying the present invention;
FIG. 2 shows in flow diagram form the criteria used in the manual override feature.
FIG. 3 shows diagrammatically the generation of the clutch engagement control signal.
DESCRIPTION OF THE PREFERRED EMBODIMENT
Referring to FIG. 1 this shows an engine 10 with a starter and an associated starter circuit 10a which is coupled through a friction clutch 14 with a five speed lay-shaft type gearbox 12 via a gearbox input shaft 15. In the example described, fuel is supplied to the engine by a throttle 16 which includes a throttle valve 18 operated by accelerator pedal 19. The invention is equally applicable to electronic or mechanical fuel injected petrol or diesel engines.
The clutch 14 is actuated by a release fork 20 which is operated by a slave cylinder 22.
The selection of the operative ratio of the gearbox may be controlled manually or automatically.
A gear selector lever 24 operates in a gate 50 having two limbs 51 and 52 joined by a cross track 53. When the lever 24 is in limb 51 the transmission operates in manual mode and the lever 24 is biassed to return to a central position 51a when released. Each movement of lever 24 from central position 51a to a downchange position 51b selects a downchange of one ratio in the currently operative ratio of the gearbox and each movement to an upchange position 51c selects an upchange of one ratio.
The position of lever 24 in limb 51 and 52 is sensed by a series of sensors (eg micro switches and optical sensors spaced around the gate) which are indicated collectively at 33 and whose signal outputs Vs are fed to electronic control unit 36. Control unit 36 in turn issues signals to a gear engaging mechanism 25 which includes, for example, hydraulic rams and solenoid control valves to move selector members to engage the desired gearbox ratio. One e
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Germain Lee A.
Kongsberg Techmatic UK Limited
Milliken Paul E.
Ta Khoi Q.
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