Method for operating a solenoid valve

Abstract

The invention relates to a method for operating a solenoid valve (10), in particular a solenoid valve designed as an application valve for applying a flowable medium onto a substrate, said valve having a closure element (23) which can be moved against the restoring force of a restoring element by means of an electromagnet (26) of the solenoid valve (10). The coil (25) of the electromagnet (26) is supplied with a respective electric control voltage signal (33) in successive cycles such that the solenoid valve (10) carries out switching cycles one after the other in which the solenoid valve (10) is converted from a closed position into an open position as part of a respective opening movement and from the open position back into the closed position as part of a closing movement. After carrying out a specified number of switching cycles, in particular a number of switching cycles which is stored in a storage device, in particular identical switching cycles which are not measurement switching cycles, a switching cycle designed as a measurement switching cycle is carried out. In order to diagnose the operating state of the solenoid valve (10), the curve of the electric current is detected which has been set for the coil (25) of the electromagnet (26) on the basis of the control voltage signal (33) that is supplied to the coil (25) in the measurement switching cycle.

Description

[0001] Method for operating a solenoid valve

[0002] Description

[0003] The present invention relates to a method for operating a solenoid valve, particularly designed as an application valve for applying flowable medium to a substrate, which has a closure member movable by an electromagnet of the solenoid valve against the restoring force of a restoring member. The coil of the electromagnet is cyclically supplied with an electrical control voltage signal one after the other, so that the solenoid valve undergoes successive switching cycles in which the valve is moved from a closed position to an open position during an opening movement and from the open position back to the closed position during a closing movement. Furthermore, the invention relates to a control device with which the method can be carried out.

[0004] Solenoid valves operated according to such a method are used in packaging machines, among other things. They typically undergo tens of thousands of switching cycles during the machine's entire operating life. It is desirable to be able to diagnose the current operating status of the respective solenoid valve during operation, for example, to detect any fault conditions.

[0005] Based on this, the object of the invention is to further develop the method mentioned at the beginning.

[0006] This object is achieved by a method having the features of claim 1.

[0007] A method according to the invention is accordingly characterized in that (in each case) after passing through a predetermined number of, in particular, identical switching cycles, which are not measuring switching cycles, stored in a (in particular electronic) memory, (at least) one switching cycle designed as a measuring switching cycle is passed through, wherein, for the diagnosis of the operating state of the solenoid valve, the course of the electrical current is recorded which occurs in the coil of the electromagnet due to the control voltage signal with which the coil is acted upon in the measuring switching cycle.

[0008] According to the invention, at least one, and generally preferably several, of the switching cycles performed during solenoid valve operation are configured as a special measuring switching cycle, in which or on the basis of which the operating state can then be diagnosed. This approach has the particular advantage that this measuring switching cycle, in particular its parameters, can be adapted as required for a particularly reliable and accurate diagnosis.

[0009] For example, the control voltage signal applied to the solenoid coil can be selected differently during the measuring switching cycle than during the non-measuring switching cycles, thus creating optimized measurement conditions for detecting the electrical current. In other words, the control voltage signal applied to the coil during the or each measuring switching cycle can differ from the respective control voltage signal applied to the coil during one or the predetermined number of non-measuring switching cycles, after which the measuring switching cycle is completed.

[0010] Preferably, however, the respective (deviating) control voltage signal applied to the coil during the measuring switching cycle is selected such that the flow rate flowing or capable of flowing through the solenoid valve during the measuring switching cycle does not change compared to the flow rate flowing through the solenoid valve during one, the or each non-measuring switching cycle. For example, a later, faster opening of the solenoid valve in one, the or each non-measuring switching cycle could be compensated by an earlier, but slower opening in the measuring switching cycle.

[0011] In this way, the measurement switching cycles can be systematically integrated into the otherwise regular operation of the solenoid valve. According to the invention, during the specific measurement switching cycle, the electrical current profile that occurs in the coil is recorded, since this electrical current, or its profile, generally allows conclusions to be drawn about the operating state of the solenoid valve. For example, a worn or generally faulty solenoid valve generally exhibits a different current profile than an intact solenoid valve. For example, by comparing the currently recorded actual current profile with a stored target current profile and / or with stored limit values, such a fault can then be detected.

[0012] Generally speaking, the recorded current profile can be automatically analyzed, preferably by means of an electronic analysis unit, which can be part of an (electronic) control device (in particular a control device for carrying out the method), so that conclusions can be drawn about the operating state of the solenoid valve. This can be done, for example, by comparing the recorded or measured current profile with a predetermined target current profile stored in a memory and / or with one or more stored limit or target values ​​and / or by determining particular local characteristics of the current profile, such as peaks or break areas, using mathematical analysis methods, which preferably run on the analysis unit.

[0013] Preferably, it can be provided that during operation of the solenoid valve several / many measuring switching cycles are run through, in particular in a periodic sequence in which a predetermined number of non-measuring switching cycles is run through between each two (correspondingly with a sufficiently large temporal interval) consecutive measuring switching cycles.

[0014] The predetermined number of non-measuring switching cycles after which one or the (next) measuring switching cycle is run through can, for example, be a number between 400 and 1100.

[0015] As for the control voltage signals applied to the coil during non-measuring switching cycles, these are preferably all identical. In a suitable embodiment of the invention, all switching cycles (regardless of whether they are measuring switching cycles or non-measuring switching cycles) can have a first phase in which the control voltage signal applied to the coil ensures an increasing current (curve) in the coil, in particular an increasing current that leads to an opening movement of the solenoid valve.

[0016] Preferably to an opening movement in which the closure member is transferred by an opening force triggered by the increasing current through the coil from a closed position in which it closes a valve opening, against the restoring force of the restoring member into an opening position releasing the valve opening.

[0017] In this case, the switching cycles each also have a phase following the first phase, in which the control voltage signal applied to the coil causes a decreasing current in the coil. In particular, this decrease in current leads to a closing movement of the solenoid valve and preferably to a closing movement in which the closure element is moved by the restoring force of the restoring element from an open position to a closed position closing the valve opening, thereby overcoming the opening force triggered by the current, which decreases due to the decreasing current.

[0018] Preferably, in particular, the control voltage signal applied to the coil during the or each measuring switching cycle (cf. above) can furthermore have one or more sections, preferably designed as square-wave signal sections, to slow down one or more current increases in the coil (compared to one, several or each non-measuring switching cycles), which correspond / correspond to multiple, clocked switching on and off of the voltage. This can be done in particular with a constant duty cycle or with several different duty cycles, wherein the or each duty cycle has a value between 50% and 90%, preferably between 60% and 80%. The switching on and off can take place in a section of the control voltage signal which ensures a section of increasing current in the coil during the measuring switching cycle.

[0019] By slowing the current rise, it may be possible to properly analyze the detected current profile, especially in the case of particularly fast-switching valves and / or control voltage signals with particularly high voltage values. This is particularly true in the area where the current rise through the coil is slowed. This can then be done automatically, for example, using an electronic analysis unit, as outlined above, so that conclusions can be drawn about the operating state of the solenoid valve.

[0020] Irrespective of the use of the aforementioned sections of the control voltage signals comprising the switching on and off of the voltage to slow down the current rise, moreover, in general, for example for current limitation / current reduction, the control voltage signal, several control voltage signals or each control voltage signal with which the coil is acted upon during the or each switching cycle can also have one or more sections, preferably designed as square-wave signal sections, which correspond to a multiple, clocked switching on and off of the voltage, in particular with a constant duty cycle or with several different duty cycles, preferably with a duty cycle that has a value between 50% and 100%.

[0021] Preferably, all switching cycles (regardless of whether they are measuring switching cycles or non-measuring switching cycles) can last the same length and can be triggered cyclically by an assigned trigger signal, wherein each non-measuring switching cycle begins immediately after the respective assigned trigger signal is triggered with a fixed dead time, during which the control voltage signal applied to the coil has a voltage value of zero, so that no current flows through the coil. In this case, the control voltage signal applied to the coil in the or each measuring switching cycle has a voltage value of zero immediately after the (respectively) assigned trigger signal is triggered.in the area of ​​the same a section for compensating for the current increase slowed down by the (subsequent) clocked switching on and off of the voltage, in which the voltage values ​​are at least temporarily different from zero, so that an increasing compensation current flows through the coil.

[0022] In this way, with suitable coordination and formation of the respective control voltage signals, it could be achieved, for example, that, as already mentioned above, the flow rate that flows or can flow through the solenoid valve during the measuring switching cycle does not change compared to the flow rate that flows through the solenoid valve during one, the or each non-measuring switching cycle.

[0023] Preferably, the section of the control voltage signal which leads to the compensation current is also a section corresponding to the multiple, clocked switching on and off of the voltage.

[0024] Further preferably, the section of the control voltage signal which leads to the compensation current can be selected such that the increasing compensation current which is thereby established in the coil and the resulting force on the closure member are too small to be able to transfer the closure member into a position which releases the valve opening.

[0025] Furthermore, as regards the number of measuring cycles to be completed per predetermined operating time of the solenoid valve, this can be selected automatically, directly or indirectly, depending on the total operating time of the solenoid valve, in particular depending on the total number of switching cycles that the solenoid valve has completed during the total operating time.

[0026] To implement the method according to the invention, an (electronic) control device is expediently provided for controlling a solenoid valve, which can be acted upon by a control voltage signal, so that the closure member of the solenoid valve can be moved back and forth in cycles between a closed position in which it closes a valve opening of the solenoid valve and an open position in which it releases the valve opening, wherein the control device is designed and configured in such a way that it can carry out the method.

[0027] Further features of the present invention will become apparent from the appended claims, the following description of preferred embodiments, and the accompanying drawings. Figure 1 shows a cross section through a solenoid valve that can be operated using the method according to the invention.

[0028] Fig. 2 shows a voltage-time diagram (center) of a control voltage signal applied to the solenoid valve in a non-measuring switching cycle, a current-time diagram (top) showing the current curve in the non-measuring switching cycle due to the control voltage signal, and a diagram (bottom) showing the trigger signal (time-dependent) matching the non-measuring switching cycle,

[0029] Fig. 3 Diagrams analogous to Figure 2, but for one measuring switching cycle,

[0030] Fig. 4 - 7 a schematic sectional view of the valve from Fig. 1 in different operating states of the valve.

[0031] A solenoid valve 10 that can be operated using the method according to the invention is designed in this case as an application valve for applying a flowable medium to a substrate. For example, as a solenoid valve 10 such as those used in machines in the cigarette packaging industry, which serve, for example, to apply adhesive to blanks for cigarette packs. It is understood that the method according to the invention can also be used with other types and / or for other purposes of solenoid valves.

[0032] The solenoid valve 10 according to the present embodiment is part of a valve arrangement (not shown) consisting of several individual valves. However, this need not be the case.

[0033] The solenoid valve 10 is attached together with the other solenoid valves (not shown) to a common distributor body 11, to which the liquid medium is supplied via a supply line from a medium source (not shown).

[0034] The supply line opens into a medium inlet 12 of the distributor body 11, which is fluidically connected to medium channels 13 arranged in the distributor body 11, to which the individual solenoid valves 10 are each connected, so that the liquid medium is supplied to them via the medium channels 13.

[0035] In the present case, the solenoid valve 10 has a nozzle 14 which is arranged on the distributor body 11, in this case on its underside, and via which, namely via a discharge opening 15 thereof, the liquid medium is discharged onto a substrate (not shown).

[0036] The discharge opening 15 of the nozzle 14 is located at the end of a nozzle channel 16, which in turn is connected upstream to a medium channel 17 in the distributor body 11, to which liquid medium is supplied in portions from a medium channel 19 arranged in a housing 18 of the solenoid valve 10.

[0037] The liquid medium is fed to this medium channel 19 of the solenoid valve 10 from the correspondingly upstream medium channel 13 of the distributor body 11 via inlet openings 20 opening into the medium channel 19.

[0038] For the portion-wise dispensing of the liquid medium from the medium channel 19 of the solenoid valve 10 into the medium channel 17 of the distributor body 11, the solenoid valve 10 has an elongated closure member 23 which can be moved axially back and forth in the medium channel 19 and which closes a dispensing opening 21 connected to the medium channel 19 of the solenoid valve 10 in a closed position (see also Figs. 4 and 7) and releases it in an open position (see also Figs. 5 and 6).

[0039] The discharge opening 21 is part of a valve seat 22 of the solenoid valve 10 with, in the present case, in particular a (circular) ring-shaped contact or sealing surface for a closure piece 24 forming a first end of the closure member 23.

[0040] In the closed position of the closure member 23, this first end or this closure piece 24 lies sealingly against the valve seat 22 or the contact surface thereof.

[0041] In the open position of the closure member 23, this or the closure piece 24 is lifted from the valve seat 22, in this case downward, thereby exposing the discharge opening 21. The closure member 23 extends in the housing 18 of the solenoid valve 10 from its end formed by the closure piece 24 through the medium channel 19 and through an interior space 27 enclosed by a coil 25 of an electromagnet 26 to an area beyond the coil 25.

[0042] The closure member 23 is mounted radially in the housing 21 so that it can (only) perform axial reciprocating movements.

[0043] The closing force on the closure member 23 is applied by a return member 28 arranged beyond the medium channel 20 and designed as a compression spring, which on the one hand is supported on a support surface 29 of the housing 18 and on the other hand presses against a plate-like section 30 of the closure member 23.

[0044] The opening force on the closure member 23 is generated by the electromagnet 26, the core or armature of which forms a metallic component 31 which is connected in a rotationally fixed manner to the closure member 23 and which can be moved by the magnetic field or the magnetic force of the electromagnet 26 while the closure member 23 moves along.

[0045] During regular operation, the solenoid valve 10 is switched cyclically, namely by successively applying an electrical control voltage signal 33 to the coil 25 of the solenoid valve 10, triggered by a trigger signal 32, so that the solenoid valve 10 undergoes successive switching cycles 34, in which it is moved from the closed position to the open position during an opening movement and from the open position back to the closed position during a closing movement. Figures 2 and 3 each show a switching cycle 34 with a control voltage signal 33, with which such movements can be effected.

[0046] The control voltage signals 33 are each provided by a control device (not shown) for controlling the solenoid valve 10. Such control devices are known. It is important that fault conditions in the solenoid valve 10 are detected as quickly as possible during operation. For example, fault conditions that lead to improper application of the adhesive portions emerging from the solenoid valve 10 can, if left undetected, result in significant production losses.

[0047] According to the invention, it is therefore provided that (in each case) after passing through a predetermined number of switching cycles 34, which are in particular but not necessarily identical, which are not measuring switching cycles, a switching cycle 34 designed as a measuring switching cycle is passed through, for example after 500, 800 or 1000 such non-measuring switching cycles, wherein, in order to diagnose the operating state of the solenoid valve 10, the course of the electrical current is recorded which is established in the coil 25 of the electromagnet 26 due to the control voltage signal 33 with which the coil 25 is acted upon in the measuring switching cycle 34.

[0048] The diagrams in Figure 2 initially show, by way of example, the relationships when running through a single one of the many non-measuring switching cycles 34.

[0049] It can be seen that when the trigger signal 32 is triggered, the control voltage signal 33 remains at the voltage value U = 0 for a certain time t, namely a dead time described in more detail below, see signal section 35. After the dead time has elapsed, the control voltage signal 33 in the present case is designed as a square wave signal 36 that is clocked several times, sampled with certain duty cycles and repeatedly moves back and forth / oscillates between on and off states.

[0050] A first section 36a of the square-wave signal 36, in which the coil 25 is continuously supplied with a constant voltage (for example due to a duty cycle of 100% applied to a constant voltage), results in the solenoid valve 10 beginning to open. In this case, an increasing current I is generated in the coil 25, which leads to an opening force being exerted on the closure member 23, see reference number IV in the current curve 40 which occurs in the 20 in Fig. 2 and see the position of the closure member 23 in Fig. 4. Due to the still constant voltage, the current I then continues to rise in the coil 25 until the opening force exceeds the closing force which is exerted on the closure member 23 by the return member 28 and as a result the closure member 23 lifts off its valve seat 22 until the solenoid valve 10 is opened under stops of the metallic component 31 orthe armature / core of the electromagnet 26 is fully open at a stop 39 of the solenoid valve 10, see reference number V in Fig. 2 and Fig. 5.

[0051] Section 36a of the control voltage signal 33 is followed by a second section 36b, in which the control voltage signal 33 is sampled with a duty cycle of 80% in this case. This value is also to be understood only as an example. The electrical current I in the coil 25 reaches its maximum value I p in this second section 36b. ea k .

[0052] The second section 36b is followed by a third section 36c of the control voltage signal 33, in which the duty cycle in the present example is less than 30%. This results in a decreasing current I in the coil 25. The control voltage signal 33 is selected such that a current I Hold is established that is sufficient to keep the solenoid valve 10 open for the specified period of time.

[0053] After the third section 36c has expired, the switching cycle 34 is terminated; compare the trigger signal 32, which is set to the value 0 at this time. Accordingly, the current I also drops to the value 0. As a result, the opening force on the closure member 25 is eliminated, and the solenoid valve 10 or closure member 25 begins its closing movement due to the restoring force of the restoring member 28. In this case, the metallic component 31 first detaches from the stop 39 (cf. reference number VI in Fig. 2 and Fig. 6). Subsequently, the closure member 25 moves (in this case upwards) until it strikes the valve seat 22.

[0054] During the closing movement, a counter voltage is induced in the coil 25, which can be seen in the voltage / time diagram in Figure 2, compare reference number 37. Also visible is a voltage peak 38, which occurs when the closure member 23 hits the valve seat 22.

[0055] The diagrams in Fig. 3 now show, by way of example, the relationships when running through a measuring switching cycle 34 which follows a certain number of non-measuring switching cycles 34 and which is designed in such a way that it allows the resulting course of the electrical current I through the coil 25 to be precisely analyzed or resolved, in particular better than would be the case with the non-measuring switching cycle 34.

[0056] For example, in comparison to the non-measuring switching cycle 34 shown in Fig. 2, in the measuring switching cycle 34 of Fig. 3 the increase in the electrical current I during the opening movement is slowed down, which makes it possible, especially in the case of particularly fast-switching valves and / or in the case of control voltage signals with particularly high voltage values, to be able to analyze the course of the detected current I with sufficient accuracy or to be able to detect certain deviations in the current course in error cases compared to non-error states in the first place.

[0057] As can be seen in Fig. 3, due to the slower rise of the current I, a local peak 40a forms in the current curve 40, which represents the beginning of the opening movement of the closure member 23 or the solenoid valve 10 according to Fig. 4. In the regular or normal non-measurement switching cycle according to Fig. 2, this peak does not form due to the faster current rise and would therefore not be detectable.

[0058] In the present example, in order to slow down the current rise as desired, the first section 36a of the control voltage signal 33, which has a constant voltage value during the non-measuring switching cycle 34, which corresponds to a duty cycle of 100%, is sampled with a duty cycle less than 100%, in particular equal to or less than 80%.

[0059] In order to ensure that the same flow rate, or in this case, portion of adhesive, is dispensed from the solenoid valve 10 during such a measuring switching cycle 34 as in the non-measuring switching cycles 34, provision is made to apply a (square-wave) voltage to the coil 25 of the electromagnet 26 within the dead time (cf. signal section 35 in Fig. 3), here using a duty cycle of less than 10%. This pre-magnetizes the coil 25 and essentially pre-tensions the closure member 23. In particular, this can compensate for the slowed current rise during the first section 36a. According to the invention, the current curve 40 detected in the measuring switching cycle 34 (using known detection or measuring methods) is then preferably automatically analyzed, so that conclusions can be drawn about the operating state of the solenoid valve 10 in this way.

[0060] This can be done using an electronic analysis unit, which can, for example, be part of or within the (electronic) control device. For this purpose, the detected or measured current profile can be compared with a predetermined target current profile stored in an (electronic) memory and / or with one or more stored limit or target values, and / or by using mathematical analysis methods, preferably run on the analysis unit, to determine specific local characteristics of the current profile, such as peaks or break points.

[0061] Fig. 3 shows, as an example, a current profile 40' of a no longer properly operational (worn) solenoid valve 10 (see the dashed line). The deviations from the current profile 40 of a fault-free or properly operational solenoid valve 10 are recognizable and can be detected accordingly. In particular, it can be seen that in this case, even in the measurement switching cycle 34, the local peak indicating the beginning of opening in the fault-free state of the solenoid valve 10 (see above) does not develop in the current profile 40'. This can be detected accordingly and indicates a fault.

[0062] Finally, as can also be seen, the course of the countervoltage induced in the coil 25 is also different when the solenoid valve 10 is no longer properly operational (worn), see the dashed line 37'. This can also be detected if necessary.

[0063] ***** List of reference symbols

[0064] 10 Solenoid valve 37' counter voltage

[0065] 11 Distributor body 38 Voltage peak

[0066] 12 Medium inlet 39 Stop

[0067] 13 Medium channel distributor body 40 Current flow

[0068] 14 Nozzle 40a local peak

[0069] 15 Discharge opening 40' Current flow

[0070] 16 nozzle channel

[0071] 17 Medium channel distributor body

[0072] 18 housings

[0073] 19 Medium channel solenoid valve

[0074] 20 Inlet opening

[0075] 21 Dispensing opening

[0076] 22 Valve seat

[0077] 23 Closure organ

[0078] 24 closure piece

[0079] 25 coil

[0080] 26 Electromagnet

[0081] 27 Interior

[0082] 28 Return device

[0083] 29 Support surface

[0084] 30 plate-like section

[0085] 31 metallic component

[0086] 32 trigger signal

[0087] 33 Control voltage signal

[0088] 34 switching cycles

[0089] 35 Signal section dead time

[0090] 36 square wave signal

[0091] 36a first section square wave signal

[0092] 36b second section

[0093] Square wave signal

[0094] 36c third section square wave signal

[0095] 37 Counter voltage

Claims

Patent claims 1. Method for operating a solenoid valve (10), in particular designed as an application valve for applying a flowable medium to a substrate, which has a closing element (23) movable against the restoring force of a return element by an electromagnet (26) of the solenoid valve (10), wherein the coil (25) of the electromagnet (26) is successively supplied with an electrical control voltage signal (33) so that the solenoid valve (10) successively goes through switching cycles in which the solenoid valve (10) is moved from a closed position to an open position and from the open position back to the closed position during a closing movement, characterized in that (each) after going through a predetermined number of switching cycles, in particular identical ones stored in a memory, which are not measurement switching cycles,a switching cycle designed as a measuring switching cycle is performed, whereby the course of the electric current is recorded for the diagnosis of the operating state of the solenoid valve (10), which is set in the coil (25) of the electromagnet (26) due to the control voltage signal (33) with which the coil (25) is supplied in the measuring switching cycle.

2. Method according to claim 1, characterized in that the control voltage signal (33) with which the coil (25) is supplied during the or each measurement switching cycle differs from the respective control voltage signal (33) with which the coil (25) is supplied during one or the predetermined number of non-measurement switching cycles, after which the measurement switching cycle is carried out.

3. Method according to claim 1 or 2, characterized in that several measuring switching cycles are carried out during the operation of the solenoid valve (10), in particular in a periodic sequence in which a predetermined number of non-measuring switching cycles are carried out between each two successive measuring switching cycles.

4. Method according to one or more of the preceding claims, characterized in that the predetermined number of non-measuring switching cycles after which a (next) measuring switching cycle is performed is a number between 400 and 1100.

5. Method according to one or more of the preceding claims, characterized in that all control voltage signals (33) with which the coil (25) is supplied in the non-measuring switching cycles are identical.

6. A method according to one or more of the preceding claims, characterized in that the switching cycles have a first phase in which the control voltage signal (33), with which the coil (25) is supplied, causes an increasing current in the coil (25), in particular an increasing current that leads to an opening movement of the solenoid valve (10), preferably to an opening movement in which the closing element (23) is moved from a closed position, in which it closes a valve opening, against the restoring force of the restoring element to an opening position releasing the valve opening by an opening force triggered by the increasing current through the coil (25), and in that the switching cycles have a phase following the first phase in which the control voltage signal (33), with which the coil (25) is supplied, causes a decreasing current in the coil (25), in particular a decreasing current,which leads to a closing movement of the solenoid valve (10), preferably to a closing movement in which the closing element (23) is moved by the restoring force of the restoring element from an open position to a closed position that closes the valve opening, overcoming the opening force triggered by the current which decreases due to the decreasing current.

7. Method according to one or more of the preceding claims, characterized in that the control voltage signal (33) with which the coil (25) is supplied during the switching cycle or cycles comprises one or more sections, preferably designed as rectangular signal sections, which correspond to multiple, pulsed switching on and off of the voltage, in particular with a constant duty cycle or with several different duty cycles, preferably with a duty cycle that has a value between 50% and 100%.

8. Method according to one or more of the preceding claims, characterized in that the control voltage signal (33) with which the coil (25) is supplied during the or each measurement switching cycle, in particular to slow down one or the current rise in the coil (25) compared to one, the or each non-measurement switching cycle, preferably in the aforementioned first phase of the switching cycle, has one or more sections, preferably designed as rectangular signal sections, which correspond to multiple, pulsed switching on and off of the voltage, in particular with a constant duty cycle or with several different duty cycles, preferably with a duty cycle between 60% and 80%.

9. Method according to claim 8, characterized in that the switching on and off takes place in a section of the control voltage signal (33) which provides for a section of increasing current in the coil (25) in the measuring switching cycle.

10. Method according to one or more of the preceding claims, characterized in that the detected current profile, in particular in the area where the current increase through the coil (25) is slowed down, is preferably automatically analyzed by means of an electronic analysis unit, so that conclusions can be drawn about the operating state of the solenoid valve (10), in particular by comparing the current profile with a predetermined target current profile stored in a memory and / or with one or more stored limit or target values ​​and / or by determining special local characteristics of the current profile, such as peaks or kink areas, by means of mathematical analysis methods.

11. Method according to one or more of the preceding claims, at least according to claim 8, characterized in that all switching cycles have the same duration and are each triggered sequentially by an associated trigger signal, that each non-measuring switching cycle begins immediately after triggering the respective associated trigger signal with a fixed dead time in which the control voltage signal (33), with which the coil (25) is supplied, The voltage value is zero, so that no current flows through the coil (25), and the control voltage signal (33), with which the coil (25) is supplied in the or each measurement switching cycle, has, immediately after triggering the (respectively) associated trigger signal, instead of this dead time or in the area thereof, a section to compensate for the current rise slowed by the (subsequent) clocked switching on and off of the voltage, in which the voltage values ​​are at least temporarily different from zero, so that an increasing compensation current flows through the coil (25).

12. Method according to claims 8 and 11, characterized in that the section of the control voltage signal (33) which leads to the compensation current is also a section corresponding to the multiple, pulsed switching on and off of the voltage.

13. Method according to claim 12, characterized in that the section of the control voltage signal (33) that leads to the compensation current is selected such that the resulting increasing compensation current in the coil (25) and the resulting force on the closing element (23) are too small to move the closing element (23) into a position that releases the valve opening.

14. Method according to one or more of the preceding claims, characterized in that the number of measuring cycles to be traversed per predetermined operating time of the solenoid valve (10) is automatically selected directly or indirectly depending on the total operating time of the solenoid valve (10), in particular depending on the total number of switching cycles that the solenoid valve (10) has undergone during the total operating time.

15. Control device for controlling a solenoid valve (10) which has a closing element (23) movable by an electromagnet (26) of the solenoid valve (10) against the restoring force of a return element, wherein the coil (25) of the electromagnet (26) can be supplied with a control voltage signal (33) so that the closing element (23) can be moved back and forth intermittently between a closed position, in which it closes a valve opening of the solenoid valve (10), and an open position, in which it releases the valve opening, wherein the control device is designed and equipped in such a way that it can perform the procedure according to one or more of the preceding claims.

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