Monitoring the operation of a vehicle

#THIS INVENTION relates to a method of and apparatus for monitoring the operation of a vehicle. More particularly, it relates to a method of and apparatus for monitoring the operation of a vehicle, in which accelerative, decelerative or centrifugal forces acting on the vehicle in a plane (herein simply referred to as the plane of movement) parallel to the surface on which the vehicle is supported, are sensed.

#As deceleration is negative acceleration in the direction of travel of the vehicle and centrifugal acceleration is acceleration transverse to the direction of travel of the vehicle, accelerative, decelerative, and centrifugal forces acting on the vehicle are, for ease of definition, all referred to herein as `accelerative` forces.

#Applicant is aware of vehicle monitoring devices in which the accelerative forces acting on the vehicle are sensed by pendulum-operated switches or by mercury switches. A difficulty with such switches has been that they are unable to distinguish between true accelerative forces acting on the vehicle, i.e. forces due to changes in the velocity vector of the vehicle in the plane of movement, and gravitational forces acting on the vehicle in this plane when the vehicle is banked or travels up or down an incline. The devices become more sensitive to true accelerative forces when the vehicle is travelling up an incline than they are when the vehicle is travelling along a level road. Likewise, the devices become more sensitive to true decelerative (negative accelerative) forces when the vehicle is travelling down an incline than they are when the vehicle is travelling along a level road. Furthermore, in the case of trucks which have a tippable cab for providing access to the truck's engine, where the device is mounted in the cab, the device will interpret tipping of the cab as heavy acceleration of the truck in some direction, depending on the direction in which the cab is tipped relative to the body of the truck.

#The invention will now be described in more detail, by way of example, with reference to the accompanying diagrammatic drawings.

#In the drawings;

#FIG. 1 illustrates the forces acting on a vehicle when it is travelling along a level road (left hand side of the drawing), when it is travelling up an incline (centre of the drawing), and when it is travelling down an incline (right hand side of the drawing); and

#Referring now to FIG. 1 of the drawings, there is shown at 10.1 a vehicle travelling along a level road. The weight of the vehicle is indicated by vector W, the reaction force of the road on the vehicle by vector R, and the accelerative force applied by the vehicle's engine in the direction of travel by vector F. The accelerative force F is over and above the driving force required to keep the vehicle moving at a steady forward speed. Alternatively, if the vehicle's brakes are applied, then a decelerative force D (shown dotted) will be applied to the vehicle.

#Reference numeral 10.2 indicates the vehicle when it is travelling up an incline. In this case an accelerative force F' over and above the driving force required to keep the vehicle moving at a steady speed along a level road will have to be applied by the vehicle's engine in order to keep the vehicle moving up the incline at a steady speed.

#Reference numeral 10.3 indicates the vehicle when it is travelling down an incline. In this case a decelerative force D' will have to be applied to the vehicle by its brakes in order to keep the vehicle moving down the incline at a steady speed.