Method for Actuating a Solenoid Valve Which is Used for Throughflow Rate Control of an Agricultural Spreading Machine

Abstract

A method for actuating a solenoid valve, which is used for throughflow rate control, of an agricultural spreading machine, wherein the solenoid valve has a valve armature, comprising: energizing the solenoid valve in order to cause an opening movement of the valve armature and/or in order to hold the valve armature in an open position in which the solenoid valve is open, interrupting or changing the energization of the solenoid valve in order to cause a closing movement of the valve armature in the direction of a valve seat, and causing a reduction in the movement speed of the valve armature during the closing movement of the valve armature.

Claims

1. A method for actuating a solenoid valve of an agricultural spreading machine which is used for throughflow rate control, wherein the solenoid valve has a valve armature, comprising: energizing the solenoid valve in order to cause an opening movement of the valve armature or hold the valve armature in an open position in which the solenoid valve is open; and Interrupting or changing the energization of the solenoid valve in order to cause a closing movement of the valve armature in the direction of a valve seat; characterized by the step: causing a reduction in the movement speed of the valve armature (24) during the closing movement of the valve armature.

2. The method according to claim 1, characterized in that the solenoid valve is energized to cause the movement speed of the valve armature to decrease during the closing movement of the valve armature.

3. The method according to claim 1, characterized in that the solenoid valve has a coil and the energization of the solenoid valve for holding the valve armature in the open position is pulse-width modulated, wherein the negative induction voltage of the coil during pulse width modulated energization of the solenoid valve to hold the valve armature in the open position is limited to a first voltage limit value and during interruption or alteration of the energization of the solenoid valve to cause a closing movement of the valve armature to a second voltage limit value, wherein the magnitude of the second voltage limit value is greater than the magnitude of the first voltage limit value.

4. The method according claim 1, characterized in that the solenoid valve has a return spring acting on the valve armature, and the return spring causes or supports the closing movement of the valve armature.

5. The method according to claim 1, further comprising: determining an expected contact time at which the valve armature comes into contact with the valve seat without a reduction in the movement speed of the valve armature during the closing movement; wherein the determined contact time to be expected is taken into account in the reduction of the movement speed of the valve armature during the closing movement.

6. The method according to claim 1, further comprising: determining an actual contact time at which the valve armature comes into contact with the valve seat; wherein the determined actual contact time is taken into account when causing a reduction in the movement speed of the valve armature during a subsequent closing movement.

7. The method according to claim 6, characterized in that the actual contact time is determined by a evaluating temporal development of a voltage applied to the solenoid valve.

8. The method according to claim 7, characterized in that evaluating the temporal development of the voltage applied to the solenoid valve comprises detecting a specific voltage change in the temporal development of the voltage applied to the solenoid valve.

9. The method according to claim 1, further comprising determining a contact time of another solenoid valve of the agricultural spreading machine at which the valve armature of the other solenoid valve comes into contact with the valve seat of the another solenoid valve; wherein the determined contact time of the other solenoid valve is taken into account in the reduction of the movement speed of the valve armature during the closing movement.

10. The method according to claim 1, further comprising: suspending the reduction of the movement speed of the valve armature during the closing movement in at least one switching cycle; determining a delay-free contact time at which the valve armature comes into contact with the valve seat during the at least one switching cycle; wherein the determined delay-free contact time is taken into account in the reduction of the movement speed (v) of the valve armature during a subsequent closing movement.

11. A system for actuating a solenoid valve of an agricultural spreading machine used for throughflow rate control, comprising a solenoid valve having a movable valve armature, and a control unit via which the solenoid valve can be energized to cause an opening movement of the valve armature and/or to hold the valve armature in an open position in which the solenoid valve is open; wherein the control unit is adapted to cause the energization of the solenoid valve to be interrupted or changed to cause a closing movement of the valve armature in the direction of a valve seat; characterized in that the control unit is adapted to cause a reduction in the movement speed of the valve armature during the closing movement of the valve armature by a control intervention, in particular by causing the solenoid valve to be energized.

12. The system according to claim 11, characterized in that the solenoid valve has a coil and the control unit is adapted to energize the solenoid valve in a pulse width modulated manner to hold the valve armature in the open position and to limit the negative induction voltage of the coil during energizing the solenoid valve in a pulse-width-modulated manner to hold the valve armature in the open position to a first voltage limit value and during interrupting or changing the energization of the solenoid valve to cause a closing movement of the valve armature to a second voltage limit value, wherein the magnitude of the second voltage limit value is greater than the magnitude of the first voltage limit value.

13. The system according to claim 11, characterized in that the solenoid valve comprises a return spring acting on the valve armature and the return spring is adapted to cause or support the closing movement of the valve armature.

14. The system according claim 11, characterized in that the control unit is adapted, to determine an expected contact time to be expected at which the valve armature comes into contact with the valve seat without a reduction in the movement speed of the valve armature during the closing movement; to determine an actual contact time at which the valve armature comes into contact with the valve seat; to determine a contact time of another solenoid valve of the agricultural spreading machine at which the valve armature of the other solenoid valve comes into contact with the valve seat of the other solenoid valve; or to determine a delay-free contact time at which the valve armature comes into contact with the valve seat during at least one switching cycle in which the reduction of the movement speed of the valve armature is suspended during the closing movement; wherein the control unit is adapted to take into account the determined expected contact time, the determined actual contact time, the determined contact time of the other solenoid valve and/or the determined delay-free contact time when reducing the movement speed of the valve armature during the closing movement.

15. The method according to claim 2, characterized in that the solenoid valve has a coil and the energization of the solenoid valve for holding the valve armature in the open position is pulse-width modulated, wherein the negative induction voltage of the coil during pulse width modulated energization of the solenoid valve to hold the valve armature in the open position is limited to a first voltage limit value and during interruption or alteration of the energization of the solenoid valve to cause a closing movement of the valve armature to a second voltage limit value, wherein the magnitude of the second voltage limit value is greater than the magnitude of the first voltage limit value.

Description

[0032] In the following, preferred embodiments of the disclosure are explained and described in more detail with reference to the accompanying drawings. Therein:

[0033] FIG. 1 shows a schematic view of a system according to the disclosure, wherein the valve armature of the solenoid valve is in a closed position;

[0034] FIG. 2 shows a schematic view of the system illustrated in FIG. 1, wherein the valve armature of the solenoid valve is in an open position;

[0035] FIG. 3 shows a schematic view of the system illustrated in FIG. 1, wherein the valve armature of the solenoid valve carries out a closing movement;

[0036] FIG. 4 shows the time characteristics of the voltage applied to a solenoid valve and the current flowing through the solenoid valve, as well as the resulting armature movement and armature speed without armature braking upstream of the valve seat; and

[0037] FIG. 5 shows the time characteristics of the voltage applied to a solenoid valve and the current flowing through the solenoid valve, as well as the resulting armature movement and armature speed with armature braking upstream of the valve seat.

[0038] FIGS. 1 to 3 show a system 10 for actuating a solenoid valve 12 used for throughflow rate control of an agricultural spreading machine, namely a field sprayer. The illustrated solenoid valve 12 is arranged in a fluid circuit of the agricultural spreading machine, wherein the solenoid valve 12 may be positioned immediately upstream of a nozzle. The nozzle and the solenoid valve 12 may form a valve-nozzle unit. A plurality of corresponding valve-nozzle units are arranged in the fluid circuit of the agricultural spreading machine, through which spray fluid F can be spread onto a farmland.

[0039] The solenoid valve 12 is connected to a control unit 16 of the system 10 via a line 14. The solenoid valve 12 can be opened and closed via the control unit 16.

[0040] The solenoid valve 12 has a fluid inlet 18 and a fluid outlet 20. In the passage between the fluid inlet 18 and the fluid outlet 20, there is a valve armature 24 which can be moved by a magnetic field generated by the coil 22. A return spring 28 is arranged at one front end of the valve armature 24, wherein the return spring 28 is supported on a portion of the housing 30 of the solenoid valve 12.

[0041] In the state shown in FIG. 1, the solenoid valve 12 is not energized so that the return spring 28 presses a front end of the valve armature 24 onto a valve seat 26 so that the passage between the fluid inlet 18 and the fluid outlet 20 is blocked.

[0042] Via the control unit 16, the solenoid valve 12 can be energized such that the magnetic field generated by the coil 22 causes an opening movement of the valve armature 24. To cause the opening movement, it is necessary that the magnetic field generated by the coil 22 applies an opening force to the valve armature 24 that is greater than the restoring force of the return spring 28.

[0043] FIG. 2 shows the solenoid valve 12 in an open state. Thus, by energizing the solenoid valve 12 with an inrush current, an opening movement of the valve armature 24 was caused. By energizing the solenoid valve 12 with a holding current, the valve armature 24 is held in an open position in which the solenoid valve 12 is open. In the open state of the solenoid valve 12, the passage between the fluid inlet 18 and the fluid outlet 20 is open so that spray fluid F can be spread via the nozzle positioned downstream of the solenoid valve 12.

[0044] FIG. 3 shows the system 10 after the energization of the solenoid valve 12 with the holding current to cause a closing movement S of the valve armature 24 in the direction of the valve seat 26 has been interrupted. The interruption of the energization dissolves the magnetic field of the coil 22 so that the return spring 28 moves the valve armature 24 in the direction of the valve seat 26.

[0045] To reduce wear on the solenoid valve 12, the valve armature 24 is actively braked shortly before it impacts the valve seat 26. The control unit 16 causes a reduction in the movement speed v of the valve armature 24 during the closing movement S, before the valve armature 24 reaches the valve seat 26. This is done by energizing the solenoid valve 12 during the closing movement S, so that a magnetic field is generated by the coil 22 which counteracts the closing movement S of the valve armature 24. However, the magnetic field generated by the coil 22 is not that strong so as to interrupt the closing movement S, but merely provides a braking of the valve armature 24 during the closing movement S. By reducing the movement speed v of the valve armature 24, the valve armature 24 impacts the valve seat 26 with a lower movement speed v, so that a smoother impact is achieved. The smoother impact reduces the shock load on the valve armature 24 and the valve seat 26, so that the service life of the solenoid valve 12 is increased.

[0046] FIG. 4 shows curves of the voltage U applied to a solenoid valve and the current I flowing through the solenoid valve as well as the resulting armature movement s and armature speed v over time t without the previously described braking of the valve armature 24 before reaching the valve seat 26. FIG. 5 shows corresponding voltage and current curves U, I as well as the resulting armature movement s and armature speed v when armature braking occurs before reaching the valve seat.

[0047] Both Figures show that energizing the solenoid valve 12 to cause the opening movement of the valve armature 24 occurs in an opening phase t.sub.O. In the opening phase to, a voltage U is applied to the solenoid valve 12 so that current I is impressed in the solenoid valve 12. The magnetic field generated by the coil 22 causes the valve armature 24 to perform a movement along the armature travel s. The armature speed v increases during the opening phase t.sub.O, since the valve armature 24 is increasingly accelerated during the opening movement. After reaching the end position, the solenoid valve 12 continues to be energized to hold the valve armature 24 in the open position in a holding phase t.sub.H. During the opening movement, braking of the valve armature 24 can be caused so that the end position is more gently assumed by the valve armature 24 in the open state. The energization with the inrush current can, for example, be interrupted shortly before the end position is reached during the opening movement of the valve armature 24.

[0048] To close the solenoid valve 12, the energization of the solenoid valve 12 is interrupted so that the valve armature 24 performs a closing movement in a closing phase t.sub.S. Due to an increase in the permissible induction voltage when the energization is interrupted, there is a quick energy reduction in the coil 22 and thus a rapid dissolution of the magnetic field. In the closing phase t.sub.S, the valve armature 24 is accelerated by the return spring 28 until the valve armature 24 impacts the valve seat 26, thus completing the closing phase t.sub.S. In the subsequent closed phase to, the valve armature 24 is in contact with the valve seat 26 so that no fluid can flow through the solenoid valve 12.

[0049] FIG. 5 shows the braking of the valve armature 24 in the closing phase t.sub.S. In the closing phase t.sub.S, a braking voltage UB is applied to the solenoid valve 12, so that a braking current I.sub.B is impressed. The magnetic field generated by the coil 22 ensures a reduction in the movement speed v of the valve armature 24 during the closing movement, before the valve armature 24 reaches the valve seat 26. In this way, the impact speed of the valve armature 24 on the valve seat 26 is reduced, which significantly increases the service life of the solenoid valve 12.

[0050] In order for the braking voltage UB to be applied to the solenoid valve 12 shortly before the valve armature 24 impacts the valve seat 26, the control unit 16 of the system 10 determines the expected contact time at which the valve armature 24 would come into contact with the valve seat 26 without a reduction in the movement speed V of the valve armature 24 during the closing movement S. Based on this contact time to be expected, the control unit 16 causes the application of the braking voltage UB sufficiently early so that an intended reduction of the armature speed v can be implemented before the valve armature 24 impacts the valve seat 26.

LIST OF REFERENCE SIGNS

[0051] 10 system [0052] 12 solenoid valve [0053] 14 line [0054] 16 control unit [0055] 18 fluid inlet [0056] 20 fluid outlet [0057] 22 coil [0058] 24 valve armature [0059] 26 valve seat [0060] 28 return spring [0061] 30 housing [0062] F spray fluid [0063] I current [0064] I.sub.B braking current [0065] S closing movement [0066] s armature movement [0067] t time [0068] t.sub.G closed phase [0069] t.sub.O opening phase [0070] t.sub.H holding phase [0071] t.sub.S closing phase [0072] U voltage [0073] U.sub.B braking voltage [0074] v armature speed