SE436114B - Apparatus to eliminate risk of vehicle wheels locking while braking - Google Patents

Abstract

The invention concerns a device for eliminating the risk of wheel-lock on vehicle when breaking. According to the invention, there is an accelerometer (G) on the relevant wheel's (H) spring-hanger (U) which is designed, when the vehicle traverses rough surfaces on the road, to emit a temporary alternating current signal (S) with information on the axle's (A) swings and muffling on the tyre.After passing through a rectifier (in FL) and a differentiator (DVR), the signal (Sd) becomes a measure of the variations taking place in the tyre muffler. A tendency to slippage (locking of the wheel) where a sudden reduction in the wheel's surface breaking action expresses itself as an abrupt reduction in the tyre's muffling capacity, produces a jump in the signal. The signal (Sd) is fed to a break power (B) control device (R), designed to momentarily reduce breaking power when a jump in signal occurs. In this way, it is ensured that breaking power is always maintained at a value which eliminates the risk of wheel-lock.<IMAGE>

Description

10 15 20 25 30 35 HO snoesas-z _. 2 a piezoelectric element, fixedly mounted for continuous measurement vibrations of the wheel axle, which depend on the tire properties, whereby the output signal from each accelerometer goes to a rectifier and from this to a derivative circuit, whose output signal indicating the variations in tire characteristics is applied an input on a braking force controlling device, arranged to momentarily down-regulate the braking force when a nail appears in the derived signal, which nail indicates sudden reduction in the ground braking torque of the wheel and thus the risk of locking, whereby the braking force is constantly maintained during a locking of the wheels carry value.

The invention is described in more detail below with reference to, attached drawing, which schematically shows an example of the invention the arrangement for sensing and lifting the braking the risk. 'IN A sensor G in the form of an accelerometer, one per wheel on same axle, is mounted on the spring suspension device of the wheel H n near the wheel hub. Accelerometer; which detects the tire natural oscillation frequency and damping by measuring the axis vibrations when passing over the unevenness of the road surface, may conveniently be formed of a piezoelectric quartz element, i the case shown facing upwards mounted on the wheel suspension U and in its free upper end supporting a metal plate. When the base point of the piezo element is accelerated as it passes over irregularities in the road surface, the movement of the point is transmitted vertically via the piezo element to the plate, whose mass inertia opposes acceleration motion and thus momentarily compresses the meant. This piezoelectric effect then results in a counter its grounding via the tire, axle and damper spring caused head pressure proportional and measurable current pulse, S with, as a result of the damping of the shaft oscillation, tud. The accelerator output S in the form of a current pulse goes to a low-pass filter LP 1 and then to an amplifier PL. This also contains a rectifier and has an AGC circuit for automatic gain control. The output signal from the amplifier, which is a filtered and rectified signal, receives pass through a second low-pass filter LP.2 for further smoothing. The output LP 2 of the filter is connected partly to the input one on a derivative DVR and partly directly to a first input on a regulator R for the braking force. To a second entrance 10 15 20 25 3 eoaesu9 ~ z on the control device R, the output of the derivative DVR is connected.

The device R will thus be continuously fed with one hand undivided signal S and partly a derived signal Sd, den later with instantaneous variations in accordance with the the damping. in The control device R, which is connected via a line L1 with a valve V for regulating the brake pressure B from a non- hydraulic or compressed air source, is designed to lower the brake force, when against a sudden decrease in the ground brake of the wheel torque corresponding nails appear in the derived signal Sd, to then increase the braking force again, until a new nail comes in.

In the event that the regulator should miss a nail, it takes care of it 'oderivered signal Sod that, if braking force is on but it the attenuating signal is zero for a shorter time, the device responds in the same way as if a nail had appeared in the derivative the signal. 7 As a complement to the hydraulic or pneumatic pressure control one can use a superimposed braking force, generated by a eddy current brake, also controlled by the control unit T. This is indicated in the figure by a line L2 emanating from the device, as in the case shown feeds the spool to one acting on the brake disc electromagnet M. In this case the braking force becomes proportional to vehicle speed and magnetic field strength. Eddy current brake then seems considerably faster than the pressure control obh works as well as this even at low speeds.

The invention is not limited to the embodiments described above. without many different modifications are possible within the framework of the invention. Of course, acoelerometers of another type than piezoelectric use.

Claims (5)

soossae-3,) H Patent claim Device for eliminating the risk of locking of vehicle wheels when applying a braking force using an accelerating force sensing means, characterized by an accelerometer (G) mounted on a non-rotating means connected to the wheel axle (A) , which, at the movements of the mounting point due to the irregularities of the road surface, continuously emits a primary signal (S), which is a measure of the vertical acceleration of the mounting point depending on the damping properties of the wheel tire; an electronic device for converting the primary signal (S) into a secondary signal (Sd), the strength of which is related to the rate of changes in the primary signal and thus in the vertical acceleration; and a braking force regulating device (R) connected to the electronics unit, arranged to respond momentarily in response to a sudden increase in the strength of the secondary signal (Sd), corresponding to a sudden decrease in the ground braking torque of the wheel, thereby lifting the locking risk. Device according to claim 1, characterized in that next to each wheel hub on a wheel axle (A) is an accelerometer (G), preferably a piezoelectric element, fixedly arranged for continuous measurement of the vibrations of the wheel axle (A) in the vertical direction. , said primary signal forming output signal (S) from each accelerometer (G) going to a rectifier (in FL) and from there to a derivation circuit (DVR), said secondary signal forming output signal (Sd) being applied to an input on the brake (the force regulating device (R), arranged to momentarily down-regulate the braking force when a nail appears in the derivative signal (Sd), which nail indicates a sudden decrease in the ground braking torque of the wheel and thus the risk of locking. Device according to Claim 2, characterized in that a low-pass filter (LP1) and an amplifier (FL) operating preferably with automatic gain control are inserted between the accelerometer (G) and the rectifier. Device according to claim 2 or 3, characterized in that the control device (R) at a second input receives the unrivaled signal (Sod) from the rectifier (in FL) for guarding the device (R) skipping a nail in the device. derived the signal (Sd). 5. A device according to any one of the preceding claims, characterized in that the braking force provided on the brake or pneumatic brake acting on the wheel (H) is 8006549-3 s supplemented by an eddy current brake, formed by an acting on the brake disc. the electron magnet (M), which is fed via a line (LZ) from the control device (R).