GB2322918A - Trailer vehicle with an over-run braking system - Google Patents

Abstract

A trailer vehicle has at least one pair of road wheels, each with a brake, an over-run braking system for applying the brakes, and a motion control braking system for applying the brakes independently of the over-run braking system in response to undesirable lateral or other motion of the trailer vehicle. The motion control braking system comprises motion detector means (6, Fig.1) located on or in the vehicle for transmitting signals representing vehicle motion to a programmable processor means (4), which compares the pattern of signals with stored criteria and sends a braking control signal to brake control means (3) to apply the brakes in response to the criteria being met. The brake control means includes a rod 22 movable against bias of a dual-rate spring 28 by lever 24 pivoted by an electric motor 26.

Description

TRAILER VEHICLE Field of the Invention This invention relates to a trailer vehicle, for example at trailer caravan.

Background to the Invention In our patent No 2 267 134 we disclose and claim a trailer vehicle having wheel brakes operable by an over-run braking system and comprising snaking detection means for providing a control signal in response to the detection of the onset of snaking, and additional brake control means arranged to apply the brakes in response to the control signal. The present invention relates to improvements in that system.

Summary of the Invention According to one aspect of the invention, there is provided a trailer vehicle having at least one pair of road wheels, each wheel having a brake, an over-run braking system which can apply the brakes in response to deceleration of a towing vehicle causing the trailer vehicle to tend to overrun the towing vehicle, and a motion control braking system which can apply the brakes independently of the over-run braking system in response to undesirable lateral or other motion of the trailer vehicle, the motion control braking system comprising motion detector means located on or in the vehicle and arranged to send signals representing vehicle motion to a programmable processor means which is programmed to monitor the signals, to compare the pattern of signals with stored criteria, and to send a braking control signal to brake control means to apply the brakes in response to the criteria being met.

The processor means is preferably provided with a vehicle speed input and is programmable to send braking control signals to the brake control means only when the vehicle speed exceeds a predetermined value.

The speed input is preferably provided by means of a speed sensor on the trailer vehicle, for example linked to a wheel, but may be provided from the towing vehicle, for example as a signal from an electric speedometer.

The processor may comprise timing means for preventing the sending of brake control signals until a predetermined time period has elapsed from commencement of motion of the trailer vehicle. Means for detecting ambient conditions, such as temperature, wind speed and direction and the presence of ice on the road, may also be linked to the processor means, and the processor means may be arranged to vary the criteria, or select different sets of criteria, according to the detected conditions.

The motion control braking means may be arranged to brake the wheels independently of each other, the processor means being arranged to send braking control signals for the separate wheels. Thus, for example, a steering effect may be generated to steer the trailer against yaw.

The processor means may also be employed to serve other control functions within the trailer vehicle. For example, it may be used in conjunction with load cells or other load sensors to measure and display the distribution of the static weight of the caravan, for example on a Liquid Crystal Display or a Cathode Ray Tube, depicting changes in the centre of gravity and polar moments as the trailer vehicle is loaded.

Another application for the processor means is in conjunction with an adjustable suspension system for the trailer vehicle, controlling the ride height to lower the centre of gravity for improved handling and reduced aerodynamic frontal area. The control of the suspension may also be used to counter the tendency of the vehicle to roll on corners and for forced ground clearance and weight transfer.

Aerodynamic control of the vehicle may also be achieved using the processor means to control the movement of aerodynamic devices such as skirts and wings according to the detected handling of the vehicle in use.

detection of the handling can be derived from the accelerometer measurements, amongst others.

Yet another use for the processor means is to receive inputs from devices monitoring such services in the trailer as fluid levels (e.g. drinking water) and battery condition and charge level, and to control the timing of lights and heating systems when the caravan is unoccupied, for example.

The processor may also be used to control theft alarm systems Another aspect of the invention provides a brake control system for a trailer vehicle having an over-run braking system having a brake rod extending longitudinally of the vehicle from the towing hitch, forward movement of the brake rod causing the brakes to be applied, the brake control system comprising a lever extending generally transversely of the vehicle and being linked to the brake rod such that turning of the lever causes longitudinal movement of the brake rod, motor means for causing rotation of the lever in response to a brake control signal, and spring means between a fixed point on the vehicle and a shoulder on the brake rod or on the lever, the spring means comprising a high rate spring and a low rate spring, the high rate spring serving to bias the rod towards the inoperative position thereof, and the low rate spring serving to take up any play in the movement of the rod, for example due to wear.

Brief Description of the Drawings In the drawings, which illustrate exemplary embodiments of aspects of the invention: Figure 1 is a circuit diagram in block form of a motion control braking system forming part of a trailer vehicle in accordance with one exemplary embodiment of the invention; Figure 2 is a diagrammatic plan view of a part of a trailer chassis incorporating a motion control braking system; and Figures 3 and 4 are enlarged views of the spring arrangement in the system shown in Figure 2.

Detailed Description of the Illustrated Embodiments Referring first to Figure 1, the control system comprises a voltage regulator 1 which drops the towing vehicle's (or trailer vehicle's) system voltage from a nominal 12V to 5V DC, with a relay 2 being supplied with 12V power to control the operation of the brake activating motor, described hereinafter with reference to Figure 2. The control signal for the relay is supplied via a driver 3 from a microprocessor 4 which, in the simple example illustrated, has an input from an accelerometer or acceleration sensor 6 via an analogue to digital converter 5, the sensor 6 being an analogue device.

The microprocessor 4 is suitably programmed to perform the following steps, in the simple case illustrated: Read input from the sensor If input is above safety level Then Perform the following while above safety level Apply mechanical braking device Read input from sensor End (Perform) End (If) Read input from driver brake If there is a voltage Then Perform the following while there is a voltage Apply mechanical braking device Read input from driver brake End (Perform) End (If) End Referring now to Figures 2 to 4, a typical trailer caravan chassis consists of an A-frame 20 mounting a pair of road wheels 21, operated by cables (not shown) which are in turn pulled by a brake rod 22 extending longitudinally of the frame 20 and slidable relative thereto. A cross beam 23 is mounted on the A-frame, and a brake-operating lever 24 is mounted on a pivot 25 at one side of the beam 23. The lever 24 is connected to the brake rod 22 through a cleat 24a.

An electric motor 26 is mounted at the other end of the beam 23, controlled by the microprocessor 4 as described with reference to Figure 1, and supplied with power through the relay 2. The electric motor drives a crank which pulls a link 27, in turn pulling the lever 24 and so pushing the brake rod 22 forward of the frame to apply the brakes in the road wheels 21.

A dual rate spring 28 extends between a shoulder 29 on the rod 22 and the cross beam 23. The dual rate spring 28 has a first portion 28a of low rate, which serves to take up any slack in the linkages,;for example arising as a result of wear, and a second portion 28b of high isFte which serves as a return spring for the brakes. It will be appreciatekl that a similar effect can be achieved by other spring configurations, for example by mounting different rate springs coaxially of one another.

In an alternative arrangement, not shown, the motor 26 is of the type used to drive the windscreen wipers of a motor vehicle, providing a reciprocating drive which is linked to the end of the lever 24 through a spring operating under tension. Operation of the motor causes the brakes to be repeatedly applied and released, achieving the effect of an anti-lock braking system.

Claims (18)

1. A trailer vehicle having at least one pair of road wheels, each wheel having a brake, an over-run braking system which can apply the brakes in response to deceleration of a towing vehicle causing the trailer vehicle to tend to over-run the towing vehicle, and a motion control braking system which can apply the brakes independently of the over-run braking system in response to undesirable lateral or other motion of the trailer vehicle, the motion control braking system comprising motion detector means located on or in the vehicle and arranged to send signals representing vehicle motion to a programmable processor means which is programmed to monitor the signals, to compare the pattern of signals with stored criteria, and to send a braking control signal to brake control means to apply the brakes in response to the criteria being met.

2. A trailer vehicle according to Claim 1, wherein the processor means is provided with a vehicle speed input and is programmable to send braking control signals to the brake control means only when the vehicle speed exceeds a predetermined value.

3. A trailer vehicle according to Claim 2, wherein the speed input is provided by means of a speed sensor on the trailer vehicle.

4. A trailer vehicle according to Claim 3, wherein the speed sensor is linked to a wheel of the trailer vehicle.

5. A trailer vehicle according to Claim 2, wherein the speed input is provided from the towing vehicle.

6. A trailer vehicle according to any preceding claim, wherein the processor comprises timing means for preventing the sending of brake control signals until a predetermined time period has elapsed from commencement of motion of the trailer vehicle.

7. A trailer vehicle according to any preceding claim, wherein the processor is linked to means for detecting ambient conditions and is arranged to vary the criteria, or select different sets of criteria, according to the detected conditions.

8. A trailer vehicle according to Claim 7, wherein the means for detecting ambient conditions comprise one or more of temperature sensors, wind speed and direction detectors, and road ice sensors.

9. A trailer vehicle according to any preceding claim, wherein the motion control braking means is arranged to brake the wheels independently of each other and the processor means is arranged to send braking control signals for the separate wheels.

10. A trailer vehicle according to any preceding claim, wherein the processor means is arranged to serve other control functions with the trailer vehicle.

11. A trailer vehicle according to Claim 10, wherein the processor means is connected to load and/or level sensors and is arranged to provide an output to display means representing the distribution of load weight in the trailer.

12. A trailer vehicle according to Claim 10 or 11, comprising an adjustable suspension system controllable by the processor means to vary the ride height of the vehicle.

13. A trailer vehicle according to Claim 10,11 or 12, comprising variable aerodynamic devices controllable by the processor means in response to the movements of the vehicle detected in use.

14. A trailer vehicle according to any of Claims 10 to 13, wherein the processor means receives inputs from devices monitoring stored fluid levels and/or battery condition and charge level.

15. A trailer vehicle according to any of Claims 10 to 14, wherein the processor means is arranged to control the timing of lights and heating systems and/or theft alarm systems.

16. A brake control system for a trailer vehicle having an over-run braking system having a brake rod extending longitudinally of the vehicle from the towing hitch, forward movement of the brake rod causing the brakes to be applied, the brake control system comprising a lever extending generally transversely of the vehicle and being linked to the brake rod such that turning of the lever causes longitudinal movement of the brake rod, motor means for causing rotation of the lever in response to a brake control signal, and spring means between a fixed point on the vehicle and a shoulder on the brake rod or on the lever, the spring means comprising a high rate spring and a low rate spring, the high rate spring serving to bias the rod towards the inoperative position thereof, and the low rate spring serving to take up any play in the movement of the rod, for example due to wear.

17. A trailer vehicle, substantially as described with reference to, or as shown in, the drawings.

18. A brake control system for a trailer vehicle, substantially as described with reference to, or as shown in, the drawings.