Machine element or mechanism – Gearing – Interchangeably locked
Patent
1996-01-16
1998-05-12
Ta, Khoi Q.
Machine element or mechanism
Gearing
Interchangeably locked
74336R, 477 77, F16H 5100
Patent
active
057492646
DESCRIPTION:
BRIEF SUMMARY
This invention relates to gear change mechanisms and particularly to arrangements for mechanisms for semi-automatically selecting the gear ratio for a gearbox.
Road vehicles conventionally include a gearbox in which different gear ratios are selected either automatically using torque converters or other mechanisms whereby gear changes are made without direct intervention by the driver, or manually using a gear lever and an associated clutch. In the latter arrangements the gears are arranged conventionally in an H pattern arrangement with the gear selection lever passing through a neutral position for every gear change effected by the driver. During each manual gear change the driver uses a drive clutch to the gearbox and an engine throttle to effect a smooth gear change. To assist in changing gear the gearbox is provided with a synchromesh system.
In European patent publication No. 0350812 there is disclosed a gear change mechanism in which a shaft is moved axially and about its axis by pistons and in which there is automatic control of the clutch mechanism.
An object of the invention is to provide an improved gear change mechanism whereby, using a substantially conventional gearbox, gears can be changed more easily with the possibility of quicker, more trouble-free gear selection.
According to one aspect of the invention a gear change mechanism for a gearbox comprises a drive assembly connectable to the gearbox gear selector, an actuator for actuating the drive assembly, and control means for controlling the operation of the drive assembly according to instructions received from the actuator and programming of the control means; the drive assembly including a shaft drivingly connectable to the gearbox selector, the shaft being movable in its axial direction and about its axis to move to a plurality of positions according to the gear to be selected in the gearbox.
Preferably the shaft is driven in its axial direction by a piston or pistons coaxial with the shaft, pressure fluid being applied selectively to the piston or pistons to move the pistons and the shaft in said axial direction.
The shaft may be movable about its axis by a further piston or pistons movable in a direction at a right angle to and spaced from the axis of the shaft, movement of said piston or pistons being transmitted to the shaft by a coupling whereby the shaft is rotated about its central axis.
The drive assembly and the control means are so arranged that upon actuation of a gear change the shaft is first moved in its axial direction from a gear selected position towards a neutral position in which no gear is selected. Thereafter the shaft may be moved axially from a neutral position to a further gear selected position, or the shaft may be rotated whilst in the neutral position before making an axial movement towards a further gear selected position. The kind of movement made by the shaft will depend on the gear to be selected, for example, in a conventional gearbox layout, movement between first and second gear will be by axial movement only, through the neutral position, whereas a change up from second gear to third gear will comprise an axial movement to neutral, followed by a rotational movement of the shaft whilst in neutral and followed by a further axial movement of the shaft in the same direction as the first axial movement. Changing down will, of course, involve the same movements in reverse order.
Valve arrangements are provided to effect the movement of the shaft in the desired sequence according to the operation of the actuator and the way the control means is arranged.
Preferably the gear change mechanism is actuated by an actuator which includes switch means which selects a change up or a change down mode. Conveniently there are separate switch means for each mode of operation.
In one arrangement the switch means for a road vehicle is carried on the vehicle steering wheel and conveniently the change up switch means is carried on one side of the steering wheel and the change down switch means is carried on the opposite si
REFERENCES:
patent: 5191804 (1993-03-01), Genise
patent: 5417124 (1995-05-01), Huff et al.
patent: 5473959 (1995-12-01), Lasoen
patent: 5560255 (1996-10-01), Willford et al.
patent: 5566579 (1996-10-01), Willford et al.
Actuator is Key to Better Automatics; Apr. 13, 1993, No. 4, Horton Kirby, Author, pp. 26-28.
Kwon Peter T.
Prodrive Engineering Limited
Ta Khoi Q.
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