Control Circuit for a Solenoid Valve

The present invention relates to a solenoid valve control circuit, in particular, to a control circuit for controlling the actuation current of a solenoid valve.

Published German Patent Application No. 41 10 254 A1 describes how a solenoid valve actuation current is to be interrupted once or a plurality of times when actuating the valve in order to achieve a more gentle closing of the valve and to avoid disturbing hydraulic noises.

According to the principles of the control circuit and method of the present invention, a solenoid valve actuation current is generated so that upon actuation of the valve, initial heavy impacting of the valve body against the stop is avoided, because the travel is executed less quickly. Also, the hydraulic vibrations which otherwise occur during opening are not produced and thus a significant reduction in noise emission is achieved. This is of particular interest with, e.g., Anti-lock Braking System (ABS) and Anti-Spin Regulation (ASR) valves.

With a further refinement of the present invention, the level of the subsequent compression stage and the pressure-change gradient can be influenced.

FIG. 1 is a schematic representation of a control circuit, in accordance with the present invention, coupled to a solenoid valve.

FIG. 2 shows the actuation current generated by the control circuit of the present invention as a function of time.

FIG. 1 shows an embodiment of a control circuit 1, of the present invention, coupled to a solenoid valve 2.

FIG. 2 shows with broken lines the variation 3 in the customary actuation current between two actuation pulses. The actuation current, controlled according to the present invention, between the two actuation pulses is shown by a solid line. In FIG. 2, the actuation current value 5 at which the solenoid valve 2 is triggered (is closed), is shown by a dot-dash line, as is the actuation current value 6 at which the valve drops out (opens). When the valve is switched off, and begins to open, at the time t.sub.1, the actuation current is not adjusted to 0, but rather to a value which is below the value 6 and constitutes, e.g., 20-30% of the actuation for the closed position. Thus, the valve begins to drop out. However, the actuation current 4 is immediately adjusted back again to the range between the current values 5 and 6 and maintained there (starting from t.sub.2) until the valve is to be moved back into the closed position (t.sub.3). This provides the advantages mentioned at the beginning. However, it is also possible to allow the actuation current to rise slowly in accordance with the dashed line 4a or to allow it to drop out slowly in accordance with the dashed line 4b.

In another embodiment of the present invention, the actuation current may be briefly reduced to 0 at time t1 before being adjusted to a level between that of levels 5 and 6, as shown by line 7 of FIG. 2. In yet another embodiment of the present invention, the actuation current may be pulse width modulated.

The process has been illustrated with reference to straight lines, but can also be realized with any desired curve forms.