Fluid-pressure and analogous brake systems – Speed-controlled – Having a valve system responsive to a wheel lock signal
Patent
1997-02-18
1998-10-20
Oberleitner, Robert J.
Fluid-pressure and analogous brake systems
Speed-controlled
Having a valve system responsive to a wheel lock signal
3031191, 303DIG8, 137 14, 1374875, 25112905, B60T 836, F16D 116, F16K 3102
Patent
active
058236406
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND INFORMATION
The invention relates to a method and a device for driving an electromagnetic valve, in particular an electromagnetic valve of a braking system having antilock (wheel lock-up) protection and/or a traction control system.
A method and a device of this kind are disclosed by the German Patent Laid-Open publication no. 4 141 354. It describes a method and a device whereby by varying the frequency, the pulse width or the pulse duration/interpulse (mark-to-space) ratio, the valve is so driven that the valve needle assumes a floating position, however, does not completely open or close.
In addition, a device for driving an electromagnetic valve is disclosed by the German Patent Laid-Open publication no. 4 110 254. It describes interrupting the drive current once or several times when driving the valve to achieve a softer closing of the solenoid valve and to avoid disturbing hydraulic noises.
In hydraulic braking systems having antilock protection and/or a traction control system, noises occur particularly when opening and closing the solenoid valve. However, these noises cannot be avoided with the existing device under the state of the art.
SUMMARY OF THE INVENTION
Given a method and a device for driving an electromagnetic valve,of the type mentioned at the outset, the underlying object of the invention is to minimize the noises that occur when switching (operating) the valve.
The invention provides for the drive current characteristic to be so formed that the valve needle is prevented from hitting forcefully against the limit stop, since the lift stroke is smaller and is not run through as quickly. Also, the usual hydraulic vibrations experienced during valve opening are not produced, so that sound emissions are clearly reduced.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 shows a schematic illustration according to the present invention.
FIG. 2a shows a first signal timing plot of signals according to the present invention.
FIG. 2b shows a second signal timing plot of signals according to the present invention.
DETAILED DESCRIPTION OF THE DRAWINGS
To modulate the pressure prevailing in the individual brakes of a vehicle equipped with antilock protection or a traction control system, it is generally known to use electrically actuated supply valves and discharge valves. For this purpose, it is preferable to use two-way valves, i.e., hydraulic valves, which have only two switching positions (open or closed). The desired pressure build-up or pressure-reduction gradient is achieved by driving the valves with series of pulses and by varying the pulse-duration/interpulse (mark-to-space) ratios.
The supply valve, which is inserted in the brake line between the brake-force sensor or the main cylinder and the brake, is generally switched to allow flow in its neutral position, while the discharge valve, which is used to bleed off pressure, in its neutral position, blocks the hydraulic fluid's path to the return-flow pump or to the pressure-equalizing reservoir.
In place of the supply/discharge valve pairs, valve arrangements having three switch positions (pressure buildup, pressure stabilization, and pressure reduction) may also be used.
In addition, so-called proportional valves are used, which release a flow-through port in proportion to the driving signal. Such proportional valves are expensive and require a complex drive circuit.
The disadvantage associated with the known control aided by the high-speed switching valves is that the rapid armature movements produce local decelerations and accelerations in the hydraulic fluid, so that substantial noises are generated. Such noises are perceived as disturbing in antilock protection or traction control systems. These noises are especially troublesome when an active braking intervention is carried out by the traction control system, especially when it is performed to limit or control driving speed.
FIG. 1 illustrates the relationships based on the example of a supply valve of an antilock protection and/or traction control system. The described d
REFERENCES:
patent: 4361164 (1982-11-01), Sakakitava et al.
patent: 5647387 (1997-07-01), Isutsui
Eichhorn Alexander
Wiss Helmut
Oberleitner Robert J.
Robert & Bosch GmbH
Schwartz Chris
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