GB2309495A

GB2309495A - Controlling the braking of a motor vehicle

Info

Publication number: GB2309495A
Application number: GB9601334A
Authority: GB
Inventors: Peter Thomas Meacock
Original assignee: Individual
Current assignee: Individual
Priority date: 1996-01-23
Filing date: 1996-01-23
Publication date: 1997-07-30
Also published as: GB9601334D0

Abstract

A system, for controlling the braking of a motor vehicle, comprises means 1, 2, 3 for sensing the state of a gear selector mechanism, means 5 for sensing movement of the vehicle, and means 9, 23 for operating a braking system of the vehicle if the state of the gear selector mechanism is incompatible with propulsion of the vehicle in the direction of sensed movement. The control system may be disabled by operating an accelerator pedal (in a vehicle with automatic transmission), by a signal from a torque sensing device 7, by a signal from device 29 when the vehicle reaches a predetermined speed, or by opening an auto/manual switch 27.

Description

IMPROVEMENTS IN THE BRAKING OF MOTOR VEHICLES This invention relates to systems for controlling the braking of motor vehicles.

It is the object at least preferred embodiments of the invention to avoid the risk of an accident or damage when a motor vehicle is being started, parked or otherwise driven on a hill or incline and the vehicle is inadvertently allowed to roll downhill, or when the vehicle is standing in a traffic queue.

In one aspect the invention provides a system for controlling the braking of a motor vehicle, the system comprising means for sensing the state of a gear selector mechanism, means for sensing movement of the vehicle and means for operating a braking system of the vehicle if the state of the gear selector mechanism is incompatible with propulsion of the vehicle in the direction of sensed movement.

According to another aspect of the invention there is provided a system for controlling the braking of a motor vehicle, the system comprising means for sensing the state of a gear selector mechanism and generating a first signal representing the direction of movement or non movement selected by that state, means for sensing a movement of the vehicle relative to the ground and generating a second signal representing the direction of that movement, control means for comparing the directions of movement represented by respective first and second signals and generating a first control signal when the direction of movement relative to the ground is different from the selected movement or non-movement, and means for applying the first control signal to a braking mechanism of the vehicle, whereby the mechanism is operated to slow down or to halt the vehicle.

The system may comprise further means for sensing the application to a transmission system of the vehicle of a torque in a sense corresponding to movement of the vehicle in the selected direction and generating a third signal, means for applying the third signal to the control means, whereby the control means generate a second control signal, and means for applying the second control signal to the braking mechanism, whereby the mechanism is released to allow movement of the vehicle in the selected direction.

Alternatively, the system may further comprise means for sensing actuation of an accelerator mechanism and applying a third signal to the control means, whereby the control means generate a second control signal, and means for applying the second control signal to the braking mechanism, whereby the mechanism is released to allow movement of the vehicle in the selected direction.

The invention will now be described, by way of example, with reference to the accompanying drawing, which is a schematic drawing of a system according to the invention for controlling the braking of a motor vehicle.

The system shown in the drawing is designed to effect automatic braking of a motor vehicle whenever a driver attempts to start, drive or to park the vehicle on a hill or incline and inadvertently allows the vehicle to run or roll downhill. The brakes are released as soon as the driver depresses the accelerator and or a torque is applied to the transmission system of the vehicle. eg. by engaging the clutch in a manual transmission.

Referring to the drawing, the present system includes gear neutral or park sensing devices 1, 2 and 3 which are mounted on the vehicle adjacent to a gear selector mechanism or automatic drive selector mechanism in an automatic vehicle (not shown). Each of the devices 1, 2 and 3 includes an electric switch which is arranged to be actuated by movement of a gear or drive lever of the selector mechanism, the switch in the device 1 being actuated by movement of the lever into and out of a reverse gear, the switch in the device 2 being actuated by movement of the lever into and out of neutral or park and the switch in the device 3 being actuated by movement of the gear lever into and out of a forward gear. The switch in each of the devices 1, 2 and 3 is connected in series with an associated resistor and the series circuit so formed is connected to a battery.

Associated with the gear sensing devices 1, 2 and 3 is a device 5 for sensing the direction of movement of the vehicle. Included in the device 5 are two light sources, suitably light emitting diodes, and two photosensors, each arranged to receive light emitted by a respective one of the diodes. The diodes and photosensors are mounted close to an abutment on a rotatable part of the vehicle, suitably an abutment on a ground engaging wheel or a part of the transmission system. Each diode and its associated photosensor are so arranged that rotation of the rotatable part causes the abutment to move between the diode and the photosensor, temporarily interrupting the passage of light from the diode to the photosensor.

At each interruption, a voltage pulse is generated at an output of the associated photosensor.

The arrangement of the diodes and photosensors is such that the interruption of light from one diode is rapidly followed by interruption of the light from the other diode.

Also associated with the gear sensing devices 1, 2 and 3 is a torque sensing device 7 which is coupled to a component in the transmission system of the vehicle and produces an output signal whenever a torque above a predetermined magnitude is applied to that component.

Each of the devices 1, 2, 3, 5, and 7 is connected to a central control circuit 9 of the present system.

In the case of the devices 1, 2 and 3, a first input 11 of the circuit 9 is connected to a resistor in the above-mentioned series circuit in the device 1 and a second input 12 is connected to a resistor in the series circuit of the device 2 and a third input 13 is connected to a resistor in the series circuit of the device 3. The connections are such that a voltage is applied to the associated input of the circuit 9 when the switch in a device 1, 2 or 3 is closed and there is a potential drop across the associated resistor. When a switch in a device 1, 2 or 3 is open, no voltage is applied to the associated input to the circuit 9.

The motion sensing device 5 is connected to third and fourth inputs 15 and 17, respectively, of the circuit 9. The connections are such that voltage pulses from one photosensor in the device 5 are applied to the input 15 and voltage pulses from the other photosensor are applied to the input 17. A fifth input 19 of the circuit 9 is connected to the torque sensing device 7.

The control circuit 9 includes a microprocessor having a memory in which there is stored a program for effecting operation of the present system in the manner hereinafter described.

An output 21 of the circuit 9 is connected to a brake control mechanism 23, which may be a servo device for actuating the brakes on one or more ground wheels of the vehicle or an electromechanical device for operating a handbrake on one or more ground wheels.

In addition to the inputs described above, the circuit 9 has a sixth input 25 connected to an auto/manual switch 27 and a seventh input 29 connected to a speed sensing device 31.

When a motor vehicle including the present control system is parked on a hill with the vehicle facing uphill, the handbrake applied and the switch 27 closed, the devices 1, 2, 3, 5, 7, 23 and 31 and the control circuit 9 are in an operative condition.

Assuming a driver of the vehicle now moves the gear lever into a forward gear position, the switch in the device 3 is closed and an input signal is applied to the second input 13 of the circuit 9. If the driver now releases the handbrake without releasing the clutch and/or without depressing the accelerator pedal sufficiently the vehicle moves rearwardly downhill instead of forwardly. This rearwards movement causes signals to be applied from the motion sensing device 5 to the inputs 15 and 17 of the circuit 9 in a rapid sequence, each signal to the input 15 immediately preceding a signal to the input 17.

The microprocessor in the circuit 9 is programmed to recognise the sequence of signals at the inputs 15 and 17 as representing movement of the vehicle in the reverse direction. At the same time the microprocessor recognises the signal at the input 13 as representing selection of a forward gear. In this situation, the microprocessor causes an output signal to be applied via the output 21 of the circuit 9 to the brake control mechanism 23. The above-mentioned servo-device or electromechanical device is then operated to cause braking.

Assuming that the clutch or automatic transmission is engaged and that the accelerator pedal is now depressed to the necessary extent, the torque sensing device 7 operates and an input signal is applied to the input 19 of the circuit 9. The microprocessor in the circuit 9 recognises this input signal and operates to cancel the output signal at the output 21. The mechanism 23 is then de-activated, the brakes are released, and the vehicle is free to move forwardly uphill or incline.

When the vehicle is parked facing downhill or down an incline and the driver wishes to reverse, an output signal is likewise applied to the brake control mechanism 23 if the gear lever or automatic transmission lever has been moved to the reverse gear position, causing the sensing device 1 to apply a signal to the input 11 of the circuit 9, and the vehicle moves forwardly, causing the appropriate sequence of signals at the inputs 15 and 17 of the circuit.

The brakes are then operated until the clutch is engaged and the accelerator pedal is depressed to the necessary extent or just the accelerator in the case of automatic transmission.

Once the vehicle is moving in the selected direction the driver may open the auto/manual switch 27 so that the control circuit 9 and the associated sensing devices 1, 2, 3, 5, and 7 are no longer operative. The switch 31 is closed when the vehicle reaches a predetermined speed and thereby renders the system inoperative even if there is some malfunction which might otherwise cause the system to operate under conditions other than which it is intended.

It will be appreciated that the present system can also be used to actuate the brake control mechanism 23 when the vehicle is being parked on a hill or incline. Assuming the switch 27 is closed, that the gear lever is in a forward gear position and that the vehicle is moving uphill, an output signal is provided at the output 21 of the circuit 9 if the vehicle stops and begins to move downhill so that the device 5 provides a signal which represents movement of the vehicle in the reverse direction.

It will be appreciated that the present system can also be used to actuate the brake control mechanism 23 when the vehicles gear lever is in a neutral / park position. Assuming the switch 27 is closed and that the gear lever is in a neutral / park position, causing the sensing device 2 to apply a signal to the input 12 of the circuit 9, and the vehicle moves either in a forward or reverse direction causing signals at the inputs 15 and 17 of the circuit the microprocessor in the circuit 9 is programmed to apply an output signal at 21, the brake control mechanism is then activated.

This embodiment of the invention is useful in a situation where a vehicle is stationary in a traffic queue without the handbrake being applied. It will prevent the vehicle rolling forwards or backwards due to driver inattention, and will reduce the risk of it being projected forward into the vehicle in front, if subjected to a rear-end collision.

In a modification of the above system which is suitable for use only with a motor vehicle having an automatic transmission system, the torque sensing device 7 can be replaced by a switch which is coupled to an accelerator pedal and causes a voltage to be applied to the input 19 of the control circuit 9 whenever the pedal is depressed by a predetermined amount.

A system according to the invention can be used on any motor vehicle such as a motor car, van, lorry, coach or tractor. Other types of sensors can be employed in device 5, instead of photodiodes. For example magnetic sensors such as used in ABS braking systems may be utilised; indeed with suitable attention to the control circuitry the ABS sensors may form part of the sensing device.

Each novel and inventive feature disclosed in this specification and/or shown in the drawings may constitute an invention independently of other disclosed and/or illustrated features.

Claims

1. A system for controlling the braking of a motor vehicle, the system comprising means for sensing the state of a gear selector mechanism, means for sensing movement of the vehicle and means for operating a braking system of the vehicle if the state of the gear selector mechanism is incompatible with propulsion of the vehicle in the direction of sensed movement.

2. A system as claimed in claim 1 wherein the means for sensing the state of a gear selector mechanism generates a first signal representing the direction of movement or the non movement selected by that state, the means for sensing movement of the vehicle relative to the ground generates a second signal representing the direction of that movement, the system comprising control means for comparing the first and second signals and for generating a control signal when the direction of movement relative to the ground is different from the selected movement or non-movement, and means for applying the control signal to the means for operating the braking mechanism of the vehicle, whereby the mechanism is operated to retard the vehicle.

3. A system as claimed in claim 2 comprising means for sensing the application to a transmission system of the vehicle of a torque in a sense corresponding to movement of the vehicle in the selected direction and for generating a third signal, means for applying the third signal to the control means, whereby the control means generates a further control signal, and means for applying the further control signal to the braking mechanism, whereby the mechanism is released to allow movement of the vehicle in the selected direction.

4. A system as claimed in claim 2 comprising means for sensing actuation of an accelerator mechanism and applying a third signal to the control means, whereby the control means generates a further control signal, and means for applying the further control signal to the braking mechanism, whereby the mechanism is released to allow movement of the vehicle in the selected direction.

5. A brake control system substantially as herein described with reference to the accompanying drawing.