GB2270143A

GB2270143A - Force sensitive lever.

Info

Publication number: GB2270143A
Application number: GB9218324A
Authority: GB
Inventors: Charles John Jones; John Vivian Comfort
Original assignee: Automotive Products PLC
Current assignee: Automotive Products PLC
Priority date: 1992-08-28
Filing date: 1992-08-28
Publication date: 1994-03-02
Also published as: WO1994005933A1; GB9218324D0

Abstract

The lever 24, eg a vehicle gear lever, has a knob 25 with an outer body 51 having a cavity 52 therein to loosely receive an end portion of the lever 24. The cavity 52 houses an elastomeric ring 58 which in use locates the knob concentrically on the end of the lever. At least one force sensitive resistor 61 senses loads acting on the 58 elastomeric ring and is located radially between the elastomeric ring 58 and the end portion of the lever 24. <IMAGE>

Description

FORCE SENSITIVE GEAR LEVER This invention concerns a lever and a transmission for a motor vehicle which is provided with such a lever which is utilised as the gear lever.

Typically a motor vehicle transmission may be of a type comprising a change-speed gear box having a plurality of gear ratios which are mutually exclusively engageable so that at any instant only one of the ratios can be engaged.

A typical gear lever which is utilised for the gear ratio change is operated by either a push or a pull action depending in which group of gears the selected gear is to be found.

Some motor vehicles incorporate a clutch control system which engages and disengages the clutch automatically in response to forces acting on the lever as a result of the vehicle driver initiating a gear change, or to other signals from the vehicle. In addition some motor vehicles may also incorporate an automatic gear ratio change system which responds to the vehicle driver initiating a gear change.

The present invention provides a new type of lever having force sensors which can be utilised as a gear lever and a clutch control system which utilise said force sensors to determine the direction of force acting on the gear knob.

According to the invention there is provided a force sensitive lever which senses force acting on the lever, especially for use with a motor vehicle transmission, the lever comprising a lever and a knob, the knob comprising an outer body having a cavity therein to loosely receive an end portion of the lever, the cavity housing an elastomeric ring which in use locates the hub concentrically to said end portion of the lever, and at least one force sensitive resistor which senses loads acting on the elastomeric ring.

A force sensitive resistor is a device comprising a conductive printed area on polymer thick film that exhibits a decreasing electrical resistivity with an increasing force.

Such components are sold under the trade mark FSR by Interlink Electronics, P.O. Box 40760, Santa Barbara, California, USA.

Preferably the force sensitive resistors are located radially between the elastomeric ring and the end portion of the lever. By placing the elastomeric ring externally of the force sensitive resistors the forces acting on the force sensitive resistors are more evenly spread.

The above type of lever may form part of a control system for a motor vehicle having a clutch, a gear box operated by a gear lever or automatic gear ratio change system, and an engine, the control system including a control unit wherein at least one pair of force sensitive resistors in the gear knob is connected in-series between a reference voltage and a ground voltage, and the voltage from the junction between the two force sensitive resistors is utilised to determine the direction of force acting on the gear knob.

The invention will be described by way of example and with reference to the accompanying drawings in which: Fig 1 is a schematic of a clutch control system according to the invention.

Fig 2 is a longitudinal section through a gear lever according to the present invention, and as used in the system shown in Fig 1.

Fig 3 is a section on the line III-III of Fig 2.

Figs 4-6 are way of connecting individual force sensitive resistors into a clutch control system.

Fig 7 is an alternative means of connecting the pair of force sensitive resistors into a clutch control system.

Fig 8 shows direct connection of the force sensitive resistors into a microprocessor.

Fig 9 shows a schematic system initiating the signals from the lever for operating power assistance to the lever.

Now with reference to Fig 1, a motor vehicle comprises an engine 10 and a gear box 12 coupled to the engine through a clutch 14 via a gearbox input shaft 15. Fuel is supplied to the engine by a throttle 16 which includes a throttle valve 18 operated by accelerator pedal 19. The clutch 14 is actuated by a release fork 20 which is operated by a slave cylinder 22. The gearbox is operated by a gear lever 24.

An engine speed signal generator comprises an engine speed sensor 26 which includes a transducer. The state of the throttle valve 18 is monitored by a throttle valve position throttle valve 18 is monitored by a throttle valve position sensor 30. The state of the gearbox 12 is monitored by a gear position sensor 32. The position of the slave cylinder 22 is monitored by an actuation sensor 34. The speed of the gearbox input shaft 15, which is equal to that of a driven plate 40 of the clutch 14, is monitored by a driven plate speed sensor 42. Since the speed of the vehicle depends on the driven plate speed and the gear engaged, the driven plate speed sensor 42 acts in effect as a vehicle speed sensor.

Signals from the sensors are transmitted to a electronic control unit 36 which includes microprocessors that control the actuation of the clutch via a hydraulic control 38. Such a system is described in W092/08065.

The gear lever 24 includes a gear knob 25 which can send signals to the control unit 36 to initiate operation of the clutch for a gear change.

The gear knob 25 is shown in detail in Figs 2 and 3, mounted on a tubular gear lever 24.

The gear knob 25 comprises an outer body 51 formed from a moulded material, preferably a hard rubber material, which has a cavity 52 therein to receive the end portion of the gear lever 24. The cavity 52 is lined with a plastic insert 53, which is preferably in the form of a inverted cup having a mouth 55 and end wall 57. The insert 53 is moulded from nylon for example and the outer body 51 is assembled with the insert 53, preferably by moulding thereon.

The insert 53 has a plurality of circumferentially spaced slots 54 adjacent its mouth 55, and has a raised coaxial circular boss 56 on its end wall 57. The insert 53 loosely engages the lever 24 so that the gear knob 25 can move radially with respect to the lever and, the boss 56 engages in the hollow centre at the end of the tubular lever 24 to limit the radial movement of the gear knob 25 with respect to the lever 24.

The upper end portion of the plastics insert 53 houses an elastomeric ring 58 which locates the knob 25 concentrically with the lever 24. The elastomeric ring 58 is held in place by a retainer ring 59. At least two force sensitive resistors 61 and perhaps four as shown in Fig 3 are located on diametrically opposite sides of the elastomeric ring 58 on its radially inner surface, so that the force sensitive resistors 61 are located between the elastomeric ring and the end portion of the lever 24. The force sensitive resistors are preferably attached to the upper end portion of the lever 28 by adhesive.

The gear knob 25 is secured to the lever 24 by a sleeve 62 which is a sliding fit on the lever and has resilient catches 63 at its upper end for snap-fit engagement with slots 54 in the insert 53. The sleeve has at least one spigot 64 on its inner surface for engagement with a hole 26 in the lever to secure the sleeve to the lever. Formed integrally within the sleeve 62 are lead out contacts 65, wires 66 and terminals 67 for connection into the control unit 36.

The elastomeric ring 58 transmits any forces acting on the outer body 51 to the force sensitive resistors 61.

In the case where principally "fore" and "aft" forces are to be detected and/or measured the resistors 61 are positioned opposite to each other in "fore" and "aft" positions on the lever 24, and in the case where sideways forces are also measured additional resistors 61 are located on the lateral sides of the tube.

The resistors 61 may be connected into the control unit 36 in a number of different ways so that the resistance changes are detected and utilised to determine the magnitude and/or direction of force applied to the lever 24.

Figs 4-6 show means of connecting the separate force sensitive resistors 61 into the control unit 36. With reference to Fig 4 force sensitive resistor 61 is connected in-series with a padding resistor R1 of fixed value between a reference voltage V1, say + five volts, and a ground voltage of zero volts. The reference voltage may conveniently be the same reference voltage as is used in an analogue-to-digital converter in the control unit 36. Voltage 'S' is taken from the junction 72 between the resistors 61 and R1 to an analogue circuit as shown in Fig 4, or a digital microprocessor circuit, to determine a "push" or "pull" force.The resistors 61 and R1 can be interchanged and the other resistors R2, R3 which determine the input voltage into the negative input of the operational amplifier 73, and resistor R4 across the amplifier 73, are all of fixed value.

The voltage S from said junction 72 forms an input for an operational amplifier 73 and the amplifier output is used to determine "push" and "pull".

Fig 5 and Fig 6 show alternative way of connecting the force sensitive resistor 61 into an operational amplifier.

Fig 7 shows an alternative arrangement for pairs of force in a fore and aft arrangement, are located in series between a reference voltage V1 and a ground voltage eg. zero volts.

The voltage S2 taken from the junction 172 between the two force sensitive resistors 61 is fed into a analogue circuit as shown to determine "push" "pull".

By putting the force sensitive resistors 61 on opposite sides of the lever any pre-load on the resistors due to the tightness of fit of the elastomeric ring 58 on the lever .24 will not effect the voltage at the junction 172 because both resistors 61 will be equally effected.

In Fig 8, the signal S2 is fed into a microprocessor forming part of the control unit 36.

With reference to Fig 9, there is shown a power assisted shift arrangement for a lever according to the present invention. The outputs 67 from the lever 24 having an analogue arrangement as shown in Fig 7 are fed into the control unit 36 which includes a push/pull decoder 70. The decoder sends out a signal S3 which is say positive for a push, or negative for a pull. The signal is fed into a threshold device 71 which compares the signal S3 to a threshold signal St and passes through signals that exceed a predetermined difference from the threshold signal St. This removes small signals S3 caused by vibrations or accidental touching of the knob 24. The filtered signal S4 passes through a gain amplifier 72 and the amplified signal S5 is used to control an actuator 74 connected by a rod 75 to the lever 24 to assist shift of the lever in the direction required.

Claims

1. A force sensitive lever which senses forces acting on the lever and which comprises a lever and a knob, the knob comprising an outer body having a casing therein to loosely receive an end portion of the lever, the cavity housing an elastomeric ring which in use locates the knob concentrically to said end portion of the lever, and at least one force sensitive resistor which senses loads acting on the elastomeric ring.

2. A lever as claimed in claim 1 wherein the force sensitive resistor is located radially between the elastomeric ring and the end portion of the lever.

3. A lever as claimed in claim 1 wherein the cavity is lined by a plastic insert having a boss thereon that engages the end face of the lever to limit the possible movement of the knob relative to the lever when a force is applied to the knob.

4. A lever as claimed in claim 3 further including a sleeve for engaging the outer surface of the lever, and sleeve having a resilient catch means at one end for snap-fit engagement with the mouth of the plastic insert.

5. A gear lever as claimed in claim 4 wherein the sleeve houses contacts for electrical connection to respective force sensitive resistors, and has out wires from said contacts -

6. A lever as claimed in claim 3 or claim 4 wherein the sleeve includes a radially inwardly projecting spigot that is engageable with the lever to prevent rotation of the knob relative to the lever.

7. A gear lever comprising a lever as claimed in any one of claims 1 to 6 having at least two force sensitive resistors which are each connectable to a reference voltage supply and to an input to a clutch control system for operation of a transmission gear ratio change.

8. A clutch control system for a motor vehicle having a clutch, a gear box operated by a gear lever, and an engine, the control system further including a control unit which controls the actuation of the clutch, wherein the gear lever is a gear lever as claimed in claim 7 in which each force sensitive resistor forms part of an operational amplifier included in the control unit, the control unit utilising the signals from the amplifier to determine the direction of force acting on the gear knob.

9. A clutch control system for a motor vehicle having a clutch, a gear box operated by a gear lever, and an engine, the control system further including a control unit which controls the actuation of the clutch, wherein the gear lever is a gear lever as claimed in claim 7, in which at least one pair of force sensitive resistors in the gear knob is connected in-series between a reference voltage and a ground voltage, and the voltage from the junction between the two force sensitive resistors is utilised to determine the direction of force acting on the gear knob.

10. A clutch control system as claimed in claim 9 wherein the gear knob includes four force sensitive resistors spaced over 360 degrees, and opposite pairs of force sensitive resistors are arranged in series.