Patent ID: 12187257

DETAILED DESCRIPTION OF EXAMPLE EMBODIMENTS

FIGS.1aand1bshow a flowchart and a coordinate system for explaining one specific embodiment of the method for electrically switching a two-stage solenoid valve.

The two-stage solenoid valve electrically switched with the aid of the method described below is understood to mean a switching valve, which is switchable only into its energized switching state or into its de-energized switching state. Thus, the two-stage solenoid valve is able only to be switched back and forth between these two switching states. The two-stage solenoid valve is closed either in its energized switching state or in its de-energized switching state, while the two-stage solenoid valve is open in the other of the two switching states. The two-stage solenoid valve may thus be a currentless closed solenoid valve or a currentless open solenoid valve.

The method described below is preferably designed for electrically switching a two-stage solenoid valve of a braking system of a vehicle/motor vehicle. The advantages of the method described below may thus be utilized in spatial surroundings, in which persons present are easily irritated by noises. For example, the two-stage solenoid valve in the form of a wheel inlet valve or a wheel outlet valve of the braking system may be electrically switched. It is noted, however that a feasibility of the method described below is limited neither to particular, spatial surroundings nor to a specific valve type.

In a method step S1of the method for electrically switching the two-stage solenoid valve, the solenoid valve is switched from its de-energized switching state into its energized switching state. This occurs by increasing a current intensity I of a current flowing through at least one solenoid coil of the solenoid valve as a switching signal from (almost) zero to a switching current intensity Isgreater than or equal to a holding current predefined by the design of the solenoid valve. The holding current is understood to mean a current intensity just sufficient enough, with the aid of which the solenoid valve is switchable/maintainable from its de-energized switching state into its energized switching state. The current flowing through the at least one solenoid coil of the solenoid valve having a switching current intensity Is, effectuates a magnetic field, which is sufficient for adjusting an adjustable valve element of the solenoid valve from its initial position corresponding to the de-energized switching state into an end position corresponding to the energized switching state, at least one spring of the solenoid valve counteracting the adjusting movement of the adjustable valve element from the initial position into the end position.

In a method step S2alternatingly carried out with method step S1, the solenoid valve is switched from its energized switching state into its de-energized switching state. This occurs by setting current intensity I of the switching signal during a switching time interval Δtotalto at least one current intensity value between zero and switching current intensity Isand by reducing current intensity I of the switching signal after switching time interval Δtotalto (almost) zero. In addition, current intensity I of the switching signal is increased during switching time interval Δtotalat least twice, each for a predefined pulse time interval Δtpulse, to a predefined current pulse value Ihighbetween zero and switching current intensity Is. In the times of switching time interval Δtotaloutside pulse time intervals Δtpulseon the other hand, current intensity I of the switching signal is set to at least one current intensity value greater than zero and less than predefined current pulse value Ihigh.

FIG.1bshows a coordinate system, whose abscissa is a time axis t, while current intensity I of the current conducted as switching signal through the at least one solenoid coil of the solenoid valve is represented with the aid of the ordinate of the coordinate system.

For example, during the times t from 0 to a point in time t0, the solenoid valve is held in its energized switching state with the aid of switching current intensity Isof 250 mA (milliamperes).

The implementation of method step S2is started from time t0by setting current intensity I of the switching signal during subsequent switching time interval Δtotalbetween times t0and tendto the at least one current intensity value between (almost) zero and switching current intensity Is. During switching time interval Δtotal, at least two so-called high current pulses2are also conducted through the at least one solenoid coil of the solenoid valve by increasing current intensity I of the switching signal at least twice, each for predefined pulse time interval Δtpulse, to predefined current pulse value Ihighbetween zero and predefined switching current intensity Is. Current pulse value Ihighmay, for example, be 120 mA (milliamperes).

During switching time interval Δtotal, current intensity I of the switching signal is at least temporarily no longer sufficient to effectuate the magnetic field counteracting the at least one spring of the solenoid valve. The adjustable valve element of the solenoid valve is therefore pressed by the at least one spring from its end position again in the direction toward its initial position. The at least two high current pulses2conducted through the at least one solenoid coil of the solenoid valve during switching time interval Δtotaleffectuate, however, a short-term “recovery” of the magnetic field, or a short-term increase of its magnetic force, as a result of which the effect of the at least one spring with respect to an acceleration of the adjustable valve element of the solenoid valve is temporarily weakened. The at least two high current pulses2carried out during switching time interval Δtotalthus effectuate a slight delay of the valve element driven with the aid of the at least one spring. The at least two high current pulses2thereby counteract an undesirably strong acceleration of the adjustable valve element. A hard or loud striking of the valve element adjusted with the aid of the at least one spring in its initial position (for example, at a valve seat of the solenoid valve) may thus be prevented with the aid of the at least two high current pulses2. Thus, there is also no need to fear any “valve switching noises” or “valve knocking noises” during the implementation of method step S2. Persons in spatial surroundings of the solenoid valve such as, for example, occupants of a vehicle/motor vehicle equipped with the solenoid valve are therefore also not irritated by such noises. With the aid of the at least two high current pulses2, it is possible to reduce undesirable “valve switching noises” or “valve knocking noises” by at least 50% as compared to the related art.

During switching time interval Δtotal, current strength I of the switching signal is preferably increased at least three times each for predefined pulse time interval Δtpulse, to predefined current pulse valve Ihigh. As a result of a high number of high current pulses2conducted through the at least one solenoid coil of the solenoid valve during switching time interval Δtotal, it is possible to comparatively quickly and relatively frequently switchover between pulse time intervals Δtpulseand so-called intermediate time intervals Δtinter, each intermediate time interval Δtinterbeing limited by two successive pulse time intervals Δtpulse. Each pulse time interval Δtpulsemay thus have a relatively short duration between 1 ms (millisecond) and 10 ms (milliseconds), for example, a duration of 5 ms (milliseconds). Each intermediate time interval Δtintermay accordingly also have a comparatively short duration between 1 ms (millisecond) and 10 ms (milliseconds), for example, a duration of 5 ms (milliseconds). The frequent switchover between pulse time intervals Δtpulseand intermediate time intervals Δtintereffected in this way reliably counteracts an excessively strong acceleration of the adjustable valve element of the solenoid valve during its adjusting movement from the end position into the initial position.

In the specific embodiment of the method depicted with the aid ofFIGS.1aand1b, current intensity I of the switching signal is set during each intermediate time interval Δtinterto a respective intermediate value in such a way that each of the intermediate values is greater than an intermediate value of a subsequent intermediate time interval Δtintersubsequently maintained in the same switching time interval Δttotal. For example, the respective intermediate value between two successive intermediate time intervals Δtintermay be gradually reduced by a permanently predefined step height dstep. Step height dstepmay, for example, be 15 mA (milliamperes). In this way, it is ensurable that despite the comparatively frequent implementation of high current pulses2, the solenoid valve is reliably switched from its energized switching state into its de-energized switching state and still, no “valve switching noises” or “valve knocking noises” are to be feared. One further advantage of the gradual reduction of the intermediate value respectively maintained in intermediate time intervals Δtinterby step height dstepis that in this specific embodiment, the holding current, above which the solenoid valve is switchable/maintainable from its de-energized switching state into its energized switching state, need not be known.

As is apparent based on the coordinate system ofFIG.1b, current intensity I, starting initially from switching current intensity Is, may first be reduced at the beginning of switching time interval Δtotalto an initial current intensity Isfor a predefined time span tinit. Once predefined time span tinithas expired, first high current pulse2is then implemented. Initial current intensity Iinitmay, for example, be 80 mA (milliamperes). Predefined time span tinitmay, for example, be 5 ms (milliseconds). In first intermediate time interval Δtinterfollowing first high current impulse2, current intensity I may then be reduced compared to initial current intensity Iinitby step height dstep.

FIG.2schematically shows a representation of the control device or of a braking system equipped therewith for a vehicle.

Control device10schematically depicted inFIG.2is designed to electrically switch a two-stage solenoid valve12. The two-stage design of solenoid valve12is understood to mean that solenoid valve12is switchable only into its de-energized switching state or into its energized switching state. Thus, solenoid valve12outlined inFIG.2as currentless closed solenoid valve12may also be a currentless open solenoid valve in another specific embodiment.

In the example ofFIG.2, two-stage solenoid valve12switchable with the aid of control device10is, for example, a valve of a braking system for a vehicle, control device10may also be a component of the braking system. It is noted, however, that a usability of control device10is not limited to a particular intended purpose of solenoid valve12switchable therewith. Even the design of solenoid valve12as wheel outlet valve12and14switchable with the aid of control device10is to be interpreted as merely exemplary. For example, a wheel inlet valve16and18, a high pressure switching valve20and/or a switchover valve22may be activatable with the aid of control device10. Moreover, a functionality of control device10is also not limited to the electrical switching of only the one solenoid valve12, as is visually depicted inFIG.2. Instead, multiple valves such as, for example, all valves12through22of the braking system are switchable with the aid of the approach described below. Although only one brake circuit of the braking system is depicted inFIG.2, valves12through22of multiple brake circuits may also be switched with the aid of control device10. Further components of the braking system outlined inFIG.2such as, for example, a pump motor24of at least one pump26, may be switchable with the aid of control device10.

Control device10includes an activation unit10a, which is designed to output a current flowing through at least one solenoid coil of solenoid valve12as switching signal28to solenoid valve12. Solenoid valve12is switchable from its de-energized switching state into its energized switching state with the aid of activation device10aby designing activation unit10a, if necessary, to increase a current intensity of switching signal28from (almost) zero to a switching current intensity greater than-equal to a holding current predefined by the design of the solenoid valve, with the aid of which solenoid valve12is switchable from its de-energized switching state into its energized switching state. The currentless closed solenoid valve12may be switched from its de-energized switching state into its energized switching state with the aid of activation unit10a, for example, as a driver forces brake fluid from a downstream main brake cylinder34into at least one connected brake circuit with the aid of his/her driver brake force32applied to a brake actuation element30. With the aid of the switching of currentless closed solenoid valve12into its energized switching state, it is possible in this case to limit or prevent a pressure build-up in at least one wheel brake cylinder38and40of the respective brake circuit due to the resultant displacement of the brake fluid forced into the respective brake circuit via switched open, currentless closed solenoid valve12into a downstream reservoir chamber/low-pressure reservoir chamber36(seeFIG.2). The actuation of brake actuation element30by the driver may be indicated to control device10with the aid of at least one sensor signal42aof a brake actuation element sensor42. Control device10may also be designed to verify the limitation/prevention of the brake pressure build-up in the respective brake circuit based on at least one sensor signal44aof at least one pressure sensor44. The example of a “regenerative braking” with the aid of the switching of currentless closed solenoid valve12described herein is not to be interpreted as restrictive.

Solenoid valve12is also switchable from its energized switching state into its de-energized switching state with the aid of activation unit10aby designing activation device10a, if necessary, to set the current intensity of switching signal28during a switching time interval to at least one current intensity value between zero and the switching current intensity and to reduce it after the switching time interval to (almost) zero.

Activation unit10ais specifically designed to increase the current intensity during the switching time interval at least twice, each for a predefined pulse time interval, to a predefined current pulse value between zero and the switching current intensity and to set the current intensity of the switching signal in the times of the switching time interval outside the pulse time intervals to at least one current intensity value greater than zero and less than the predefined current pulse valve. Thus, control device10also yields the advantages of the above-explained method.

Control device10/its activating unit10amay, in particular, be designed to carry out the above-described method. For example, activation device10amay be designed to increase the current intensity of the switching signal during the switching time interval at least three times, each for the predefined pulse time interval, to the predefined current pulse value. Activation unit10ais preferably also designed to set the current intensity of the switching signal during the switching time interval to a respective intermediate value during each intermediate time interval between two successive pulse time intervals in such a way that each of the intermediate values is greater than an intermediate value of a subsequent intermediate time interval maintained in the same switching time interval.

A braking system including control device10also yields the above-described advantages. It is expressly noted, however, that the design of such a braking system including control device10visually depicted inFIG.2is to be interpreted as merely exemplary. Components14through44, as well as brake booster46, a brake fluid reservoir48and a filter50are also only examples of braking system components of such a braking system.