GB2355501A

GB2355501A - Transmission control with selector lever position for hill ascent and/or descent

Info

Publication number: GB2355501A
Application number: GB9924687A
Authority: GB
Inventors: Brian Ernest Tolley
Original assignee: MG Rover Group Ltd; Land Rover Group Ltd
Current assignee: MG Rover Group Ltd; Jaguar Land Rover Ltd
Priority date: 1999-10-20
Filing date: 1999-10-20
Publication date: 2001-04-25
Anticipated expiration: 2019-10-20
Also published as: GB9924687D0; GB2355501B

Abstract

A selector lever 26 is restricted to longitudinal movement, by a transmission selector gate 45, for selecting park P, drive D, neutral N, fifth and three intermediate ratios while being able to move transversely from position 2 to position 1 for selecting 1<SP>st</SP> gear hold. The 1<SP>st</SP> gear hold position 1 signals, eg via a microswitch (55, fig 4), an electronic controller (25, fig 1) to automatically select hill ascent/descent control so that there is maximum engine braking and an even distribution of retarding torque between road wheels. For off-road use position 1 is engaged against an action of a spring loaded detent ball (38, fig 3) so that a certain degree of manual effort is required. During normal driving the detent ball (38) is engaged in a first detent groove so that a driver would only select park P, drive D etc. In another embodiment hill ascent/descent control is selected manually by a separate control switch (61, fig 5).

Description

2355501 Vehicle Control System The invention relates to vehicle control

systems for use in vehicles having a variable ratio transmission in a drive line between an engine and road wheels of the vehicle, the system including a transmission control arranged to operate the transmission in a plurality of forward gear ratios. Particularly, but not exclusively, it relates to a vehicle in which the lowest of the forward gear ratios is intended for off-road use.

It is common to provide vehicles which are intended for off-road use with an auxiliary or range-change transmission which is mounted on or integrated with the normal variable ratio transmission (manual or automatic) to provide a range of high ratios for on-road use and a range of low ratios for off-road use. Frequently there is an overlap between the two ranges of gear ratios so that in some instances it may be possible to use a single transmission with a range of ratios which allows for both on-road and off-road use. In any event, the control of a variable ratio transmission in conjunction with an auxiliary transmission may be integrated to the extent that, to the driver, only one transmission is apparent. Although the use of a separate auxiliary/range change transmission usually necessitates the use of an additional control for the driver, this does have the advantage of having only a deliberate selection of the high range for road use so that inadvertent selection of an unsuitably low ratio is unlikely.

The present invention has as an object the provision of a control system for use in a vehicle having a variable ratio transmission which includes a low ratio whose use can be inhibited for normal on-road driving.

According to the invention there is provided a vehicle control system for use in a vehicle having a variable ratio transmission in a drive line between an engine and road wheels of the vehicle, the control system including a transmission control arranged to operate the transmission in a plurality of forward gear ratios including a high ratio, a low ratio and at least one intermediate ratio and a selector device co-operating in use with the transmission control and comprising a selector lever pivotal about a first axis substantially perpendicular to a longitudinal axis of the lever between positions which include a high position which in normal use of the vehicle allows the transmission control to select the high ratio in the transmission, and an intermediate position which in normal use if the vehicle allows the transmission control to select a transmission ratio no higher than the intermediate ratio, the lever also being pivotal about a second axis, substantially perpendicular to the first axis and to the longitudinal axis of the lever, between the intermediate position and a low position which in normal use of the vehicle allows the transmission control to select a transmission ratio no higher than the low ratio.

The control system may further comprise a hill descent control which is operative to apply brakes on the road wheels to control the speed of the vehicle in the descent of steep hills, the hill descent control being activated by movement of the lever from the intermediate position into the low position. Alternatively, the hill descent control may be activated by a manually operated switch and inhibited except when the lever is in the low position.

Preferably, the selector lever is movable from the intermediate position to the low position against a spring.

Conveniently, the selector lever is retained in the low position by a spring-loaded detent. Alternatively, the selector lever may be allowed to return under a spring load from low position to the intermediate position.

The invention will now be described by way of example and with reference to the accompanying drawings, of which:

Fig.1 is a schematic diagram of a vehicle control system according to the invention; Fig.2 is a more detailed view of a selector lever and transmission selector gate shown in Fig. 1; Fig.3 is a sectional elevation showing details of the selector lever shown in Figs. 1 and 2 together with an associated selector mechanism; Fig. 4 is a cross-section on the line IV-IV in Fig. 3; and Fig.5 is a sectional view of a gear knob and lever mounted switch for use in a modification.

Referring to Figs. I to 4, a vehicle has an engine 11 connected to a drive line including a variable ratio transmission 12 which in turn drives an intermediate reduction (IRD) drive transmission 13. The output from the IRD transmission 13 is through a front differential incorporated in the IRD transmission 13 and a through a rear differential 14 driven through a forward propshaft 15, a viscous coupling unit 16 and a rearward propshaft 17. The front differential drives front road wheels 18 through two front drive shafts 19 and the rear differential 14 drives rear road wheels 21 through two rear drive shafts 22.

The variable ratio transmission 12, which may be a servo-actuated conventional layshaft (manual) type, an epicychc-type or a continuously variable transmission (CVT) type, incorporates ratios which may be controlled step- wise by an electronic transmission control (ETC) 25 which receives the usual signals of engine load, engine speed and road speed to determine the appropriate ratio. The ETC 25 is also under the control of a selector lever 26 incorporated in a selector assembly 27.

The selector assembly 27 includes a frame 28 which is mounted on the body or chassis of the vehicle and has a pivot pin 29 arranged generally longitudinally of the vehicle and carrying a pivot block 31. Pressed into the pivot block 31 are two pivot pegs 32. The frame 28 includes a quadrant member arranged generally longitudinally of the vehicle, the lever 26 being forked so that it straddles the quadrant member 33 and is pivotally retained on the pivot block 31 by the pivot pegs 32 so as to be pivotal about a first axis 35 which extends generally transversely of the vehicle and lies substantially perpendicular to a longitudinal axis 36 of the lever 26. The lever 26 can also pivot about a second axis 37 formed by the pivot pin 29, this axis also lying substantially perpendicular to the lever longitudinal axis 36, movement in this direction being controlled by a detent ball 38 spring-loaded by a compression spring 40 into engagement with first and second detent grooves in an arm 41 extending from the lever 26, only the first detent groove 39 being visible in Fig.3. Movement of the selector lever 26 in the longitudinal direction of the vehicle about the pivot pegs 32 is limited by a baulk pin 42 which is spring-loaded towards the quadrant member 33. The selector lever 26 carries a selector knob 43 which, in a conventional manner, carries a button or lever (not shown) for engagement by the driver to lift the baulk pin 42 away from the quadrant member 33. By this means the longitudinal movement of the selector lever 26 is limited to a range permitted by recesses in the quadrant member 33 or, by lifting the baulk pin 42, can be moved over the whole arc of 7the quadrant member.

The selector lever 26 moves in a selector gate 45 attached to the selector frame 28 and this is provided with positions marked P R N D 4 3 2 1 as indicated in Fig.2. The vehicle also incorporates a hill descent control (HDC) 51 which is operative to apply brakes 52 on each of the road wheels 18, 21 to control the speed of the vehicle in the descent of steep hills. Such a control is known, for example, from WO-A-96/11826. The HDC 51 is linked to the ETC 25 or may be incorporated as part of the same control.

The position of the selector lever 26 in the selector gate 45 is signalled to the ETC by means of a switch or transducer 54 in the mechanical control of the transmission 12 by a Bowden cable 53 connected to the lever 26 by a ball pin 56.

Positions P, R, N, D, 4, 3 and 2 are signalled by the switch/transducer 54 according to the longitudinal position of the selector lever 26 in the gate 45. However, in the case of position 1 the selector lever 26 is moved transversely from position 2 by pivoting on the longitudinal pivot pin 29 to operate a microswitch 55 carried on the selector frame 28.

There are five forward ratios in the variable ratio transmission 12 so that the highest available forward ratio is fifth, the lowest available forward ratio is first and there are three intermediate ratios, namely second, third and fourth. There is also a reverse ratio. The ETC 25 selects the appropriate ratio according to the position of the selector lever 26 at the marked positions on the selector gate 45, as follows:

P = Park; no ratios in the transmission 12 are engaged and the Bowden cable 53 operates to allow a spring-loaded parking sprag to lock the transmission 12 against forward and reverse rotation.

R = Reverse; the reverse ratio is engaged.

N = Neutral; no ratios are engaged.

D = Drive wherein the ETC operates to automatically select the most appropriate forward ratio, including, when appropriate, fifth 4 = 4th gear hold whereby the ETC 25 allows up changes as far as fourth gear but will not upshift to fifth gear.

3 = 3rd gear hold whereby the ETC 25 allows up changes as far as third gear but will not upshift to fourth or fifth gear.

2 = 2nd gear hold whereby the ETC 25 allows up changes as far as second gear but will not upshift to third, fourth or fifth gear.

1 = 1st gear hold whereby the ETC 25 selects only first gear and will not upshift to second, third, fourth or fifth gear.

Optionally there may be an engine protection override which will allow an upshift from the 1st, 2nd, 3rd or 4th gear hold conditions if an excessively high engine speed would otherwise be incurred.

Movement the selector lever 26 transversely from position 2 to position 1.

requires a certain degree of manual effort to push the detent ball 38 against its spring-load and out of the first detent groove 39. In this way, for normal road use the driver of the vehicle would ordinarily only select positions D, 4, 3 or 2 for the selection of forward ratios in the variable ratio transmission 12. However, for use off-road the lever can be moved from position 2 into position 1 where the detent ball 38 engages the second detent groove. This position not only allows first gear to be selected and held for the ascent of steep hills but also allows first gear to be selected and held for the descent of steep hills. This allows for maximum engine braking and, particularly importantly on shppery surfaces, an even distribution of retarding torque between the wheels 18, 2 1.

In the arrangement shown in Figs.1 to 4 the microswitch 55 on the selector frame 28 also operates in conjunction with the HDC 51 so that hill descent control is active whenever the transmission selector lever 26 is in position 1. Hence the selection of hill descent control is made automatically when gear selector position 1 is selected.

In a modification to the arrangement described above, the selector lever 26 carries a separate hill descent control switch 61 (Fig.5) which is substantially as -7, described in GB-A-2327244. In this case the microswitch 55 is operative in conjunction with the HDC 51 to inhibit operation of the hill descent control except when the selector lever 26 is in the 1 position. Hence the use of hill descent control can be prevented by the driver but hill descent control is inhibited unless 5 the selector lever 26 is in position 1 In both the above instances, the hill descent control cannot be used at normal road speeds, i.e. when position D, 4, 3, or 2 is selected, so cannot affect normal on-road driving.

In an alternative to the arrangement whereby the selector lever 26 is retained in position 1 by the second detent groove, the lever is arranged to spring back into position 2. The effect is the same as the lever 26 remaining at position 1 but this allows for rapid selection of the 3, 4, D, N, R or P positions. Position 1 can be either side of the longitudinal slot provided for the P, R, N, D, 4, 3, and 2 positions to suit left or right-hand drive. If desired, the gate 45 can be provided with two transverse slots which allow transverse movement of the sector lever 26 to either of two positions 1.

It will be appreciated that the marking of the positions P R N D 4 3 2 1 as indicated in Fig.2 may be provided as a separate indication at a position displaced from the gate, e.g. on a console adjacent the gate and/or on a dashboard display.

Also, a greater or lesser number of forward ratios may be provided (or more than one reverse ratio). Furthermore, the Bowden cable 53 could be replaced by a remote servomotor and the microswitch 55 could be replaced by alternative sensors, e.g. a Hall-effect sensor.

Claims

-8CIAIMS

1. A vehicle control system for use in a vehicle having a variable ratio transmission in a drive line between an engine and road wheels of the vehicle, the control system including a transmission control arranged to operate the transmission in a plurality of forward gear ratios including a high ratio, a low ratio and at least one intermediate ratio and a selector device co-operating in use with the transmission control and comprising a selector lever pivotal about a first axis substantially perpendicular to a longitudinal axis of the lever between positions which include a high position which in normal use of the vehicle allows the transmission control to select the high ratio in the transmission, and an intermediate position which in normal use if the vehicle allows the transmission control to select a transmission ratio no higher than the intermediate ratio, the lever also being pivotal about a second axis, substantially perpendicular to the first axis and to the longitudinal axis of the lever, between the intermediate position and a low position which in normal use of the vehicle allows the transmission control to select a transmission ratio no higher than the low ratio.

2. A control system according to claim I and further comprising a hill descent control which is operative to apply brakes on the road wheels to control the speed of the vehicle in the descent of steep hills, the hill descent control being activated by movement of the lever from the intermediate position into the low position.

3. A control system according to claim 1 and further comprising a hill descent control which is operative to apply brakes on the road wheels to control the speed of the vehicle in the descent of steep hills, the hill descent control being activated by a manually operated switch and inhibited except when the lever is in the low position.

4. A control system according to any preceding claim wherein the selector lever is movable from the intermediate position to the low position against a spring.

5. A control system according to any preceding claim wherein the selector lever is retained in the low position by a spring-loaded detent.

7. A control system according to any of claims I to 4 wherein the selector lever is allowed to return under a spring load from low position to the intermediate position.

8. A vehicle control system substantially as described herein with reference to Figsl to 4 or as modified with reference to Fig.5 of the accompanying drawings.