| 摘要 |
Direct-current and alternating-current magnets are used for operating hydraulic apparatuses, especially valves having two switching positions, such as directional-control slide valves. In the case of these so-called switching magnets, there is no proportionality between the force and the impressed current of the magnet winding. Since, in the case of the excitation of the magnet coil of such switching magnets, the primary object is to produce a force which is necessary to operate the valve slide into the other switching position, switching magnets can be produced relatively cheaply without any particular constructional complexity. However, if the output size of the valve, as for example the through-flow current or the pressure, is intended to respond in proportion to the excitation current of the magnet coil in order to carry out corresponding control processes, then the switching magnets must be replaced by direct-current operated proportional magnets, in the case of which the magnetic force responds in proportion to the excitation current, and in consequence necessitate a considerably greater manufacturing cost. According to the invention, simple switching magnets can also be used, in conjunction with feedback of the armature stroke or actuating-element stroke (for example control pistons of valves, cylinders) in a control loop, instead of a proportional magnet. In this way, the control of the valve or of the cylinder stroke can be implemented with the aid of a switching magnet which is simple and cheap to produce. <IMAGE>
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