Abstract:
A solenoid valve having a valve disc on a movable armature that is subjected to a restoring spring and a magnet coil. The magnet coil has a pick-up winding with a high-electrical capacity for opening and closing the valve and a holding winding whose capacity is such that it can hold the valve disc in the position in which it is lifted off of the valve seat when the valve is opened or on the valve seat when the valve is closed. A capacitor can be charged with a system voltage that is applied and can be momentarily connected to the pick-up winding in order to open or close the magnetic valve is also provided.

Description:
BACKGROUND OF THE INVENTION 
     The invention relates to a magnetic or solenoid valve, on the movable armature of which is attached the valve disk that is acted upon by a restoring spring, and the magnet coil of which has a pickup winding with a high electrical capacity for opening or closing the valve, and a holding winding, the capacity of which is designed to hold the valve disk in a position where it is raised from the valve seat when the valve is open, and hold the valve disk in a position where it rests against the valve seat when the valve is closed. 
     The magnet coil in such solenoid valves encompasses a pickup winding and a holding winding with center tap. The pickup winding must be designed with high electrical capacity in order to actuate the magnet armature and thus the valve disc with substantial force in the opening and closing direction of the valve to open and close the solenoid valve. Once the valve has been opened or closed, there is a switch to holding capacity, which is sufficient to hold the valve disc in the open or closed position. DE 43 07 878 A1, which concerns such a solenoid valve, reports that it is known from DE 38 24 545 A1 in a contactless switching arrangement to insert in the feed line to the coil a parallel switch from a capacitor and a resistor, whereby when turned on, that is, for the pickup phase, there is a brief, distinct increase in the starting current corresponding to the capacitor capacity. 
     The object of the invention is to provide a solenoid valve in which the electrical control power can be reduced using simple means, especially when opening and closing the solenoid valve. 
     SUMMARY OF THE INVENTION 
     The solenoid valve of the present invention is characterized primarily in that the magnet coil comprises a pickup winding and a holding winding with a center tack, in that for opening and closing a capacitor is respectively connectable to a line branch leading to the pickup winding and to a branch leading to the center tap, and in that a DC/DC converter is disposed upstream of the capacitor such that the capacitor can be switched between a state where it is connected to the converter and a state where it is connected to the pickup winding. These features serve to realize this object. Thus it is possible to assure reliable opening and closing of the solenoid valve using simple circuit engineering means in that the pickup current or pickup capacity is taken from the capacitor, depending on the mechanical design of the solenoid valve either during opening of the valve or closing thereof, while subsequently only a small holding current must be taken from the connected consumer power supply. For the period in which the capacitor is charging a small charging current is also required that is not needed once the capacitor has been charged. 
     Pursuant to a preferred embodiment of the invention, a timer is provided for switching from pickup current operation to holding current operation, wherein the pickup winding and the holding winding are in series and the enter tap line branch is interrupted. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     Exemplary embodiments of the inventive solenoid valve are explained in greater detail in the following using the attached drawings. The drawings illustrate: 
     FIG. 1 is a sectional view of a first embodiment of a solenoid valve; 
     FIG. 2 is a block diagram of the control device for triggering the solenoid valve; 
     FIG. 3 is a sectional view of a second embodiment of the solenoid valve. 
    
    
     DESCRIPTION OF PREFERRED EMBODIMENTS 
     In terms of mechanics, the solenoid valve illustrated in FIG. 1 essentially includes the following conventional individual parts: 
     
       
         
               
               
             
           
               
                   
               
             
             
               
                 Valve housing 1 
                 Magnet armature 8 affixed to valve 
               
               
                   
                 disc shaft 
               
               
                 Valve seat 1.1 
                 Magnet coil 9 
               
               
                 Valve disc seal 2 
                 Magnet yoke 10 
               
               
                 Valve disc 3 
                 Connecting bolts 11 
               
               
                 Valve disc shaft 4 
                 Magnet housing cover 12 
               
               
                 Valve disc restoring compression 
                 Cover screw 13 
               
               
                 spring 5 
               
               
                 Intermediate piece 5.1 
                 Magnet coil terminals 14 - 
               
               
                   
                 schematically illustrated 
               
               
                 Magnetic system base 6 
                 Electronic control unit 15 
               
               
                 Magnet housing 7 
               
               
                   
               
             
          
         
       
     
     The flow direction through the valve housing  1  is indicated by the arrow such that the valve in the currentless state is held in the closed position by the average flow pressure acting on the valve disc  3 . 
     In accordance with FIG. 2, the magnet coil  9  includes a pickup winding  9 . 1  and a holding winding  9 . 2  with center tap. The pickup winding  9 . 1 , which is designed for high electrical capacity, pulls the magnet armature  8  and thus the valve disc  3  upward for opening the valve. Then there is a switching over to the holding winding  9 . 2  that is designed with a lower electrical holding capacity that is sufficient for holding the valve disc  3  in the open position. For closing the valve, the holding winding  9 . 2  is brought into the currentless state so that the compression spring  5  moves the valve shaft  4  and thus the valve disc  3  downward via the intermediate piece  5 . 1  in order to push the valve disc  3  against the valve disc seat  1 . 1 . 
     The terminals L+/L− connected/connectable to the power source (for instance, 24 V DC) are connected via appropriate line segments to the DC/DC converter G 1  for charging a capacitor C (e.g., 15000 μF-50V). The terminal L+ is furthermore connected to a line branch leading to the pickup winding  9 . 1  in which there is a relay switch K 2 . The terminal L− is connected to the line branch leading to the holding winding  9 . 2  in which there is a relay switch K 4 ′. The capacitor C is connectable for the purpose of charging via regulating and control members (not shown in detail) to the converter G 1  and to the line branch containing the relay switch K 2  and to the center tap branch that is located between the two windings  9 . 1  and  9 . 2  and that contains a relay switch K 4  and a diode D 2 . Actuation of the solenoid valve is initiated via a terminal LS connected to the power source in order to actuate the relay switches K 2  and K 4 /K 4 ′, whereby a timer T is allocated to the two relay switches K 4 , K 4 ′. 
     The diodes D 3  and D 4  in the area of the terminals L+/L−/LS prevent an increase in induction voltage in the power supply, that is, they protect against an overload in the power supply. 
     When the solenoid valve is closed, the relay switches K 2  and K 4 ′ are open, while the relay switch K 4 , which is located in the center tap line branch, is closed. The two relay switches K 4  and K 4 ′ are coupled to one another such that the relay switch K 4 ′ is closed when relay switch K 4  is opened and vice versa. 
     While the solenoid valve is in the closed position, a system voltage applied continuously to the terminals L+/L− via the DC/DC converter G 1  interposed therebetween charges the capacitor C, and the converter G 1  is deactivated once the capacitor has been charged completely. If the lower capacitor voltage limit is not achieved, for instance due to spontaneous discharge, the converter G 1  is automatically activated so that the capacitor is recharged to its prespecified voltage, as is described in DE 43 25 578 A1, for instance. 
     For opening the solenoid valve, the relay switch K 2  is closed via the control line a attached to the terminal LS, whereby the correspondingly switched capacitor C is discharged via the pickup winding  9 . 1  so that the pickup winding  9 . 1 , which is designed with high electrical capacity, pulls the magnet armature upward and thus opens the valve. Controlled by the timer T, after a delay time of approximately 0.5 to 1 second, the relay switches K 4 /K 4 ′ coupled to one another are switched such that the relay switch K 4  opens and the relay switch K 4 ′ closes. Thus the two windings  9 . 1  and  9 . 2  are switched in series and are actuated via the terminals L+/L− with the holding current that has a lower capacity and that is sufficient to hold the valve disc over the magnet armature  8  in the open position. During this time the capacitor C is again separated from the center tap line branch and the line branch that leads to the pickup winding  9 . 1  and is recharged in the manner described in the foregoing in accordance with appropriate controls. 
     When the solenoid valve is open, the power taken from the DC system drops to the level of the holding winding, whereby an additional low charging current of approx. 0.1 to 0.4 A is required during the period in which the capacitor is recharged. The individual components are selected such that the capacitor charging time is approximately 30 seconds, for instance. 
     For closing the solenoid valve, there is a switching back to the original condition via the terminal LS and the control line a, that is, the switches K 2  and K 4 ′ are opened and the switch K 4  is closed so that the compression spring  5  can move the valve disc  3  into the closed position. 
     The advantage of the inventive solution is the very low total current consumption despite high pickup power during the pickup time. The electrical feed line can be dimensioned substantially smaller compared to conventional actuation via a relay switch or protective circuit. Likewise, due to the considerably lower current consumption, large numbers of solenoid drives with capacitor charging can be switched at the same time without overtaxing the consumer power supply. An additional advantage of the invention is that magnet coils that are substantially smaller but have improved electrical properties can be used. 
     The pickup winding also heats up less since a high pickup power is required for only a brief period; during continuous operation only a distinctly lower holding capacity is used, whereby power losses caused by the coil heating up are minimized. This results in distinctly lower deviations between the operating current of a cold coil and the operating current of a coil that has already heated up. 
     FIG. 3 illustrates a solenoid valve having the following individual parts: 
     Valve housing  1   a    
     Valve seat  1 . 1   a    
     Valve disc seal  3   a    
     Valve disc  3   a    
     Valve disc shaft  4   a    
     Compression spring  5   a    
     Intermediate piece  5 . 1   a    
     and a magnet system and magnet control system in accordance with FIGS. 1 and 2. 
     In the solenoid valve illustrated in FIG. 3, the valve disc  3   a  is held in the open position as illustrated by the pressure of the medium flowing in the direction of the arrow fa and/or of the compression spring  5   a . The valve is closed in a manner similar to that in which the valve illustrated in FIG. 1 is opened, and this closed condition is maintained by means of the holding winding  9 . 2  until 
     either the average flow pressure together with the force of the compression spring  5   a  is greater than the solenoid holding force of the holding winding  9 . 2 , or 
     until appropriate changeover opens the switches K 4 ′ and K 2  and closes the switch K 4 , whereby the valve and its magnet coil are without current so that the valve is opened by the compression spring acting via the valve shaft  4   a  on the valve disc  5   a  and/or by the average flow pressure acting on the valve disc  3   a.    
     The specification incorporates by reference the disclosure of German priority document 199 47 958.5 filed Oct. 6, 1999 and International priority document PCT/DE00/03336 of Sep. 26, 2000. 
     The present invention is, of course, in no way restricted to the specific disclosure of the specification and drawings, but also encompasses any modifications within the scope of the appended claims.