Electropneumatic solenoid valve, field device with a solenoid valve, and diagnostic method for an electropneumatic solenoid valve

Description

[0001] The invention relates to an electropneumatic solenoid valve for a field device of a process plant, such as a power plant, for example a nuclear power plant; a chemical plant, for example a petrochemical plant, such as a refinery; a food processing plant, such as a brewery or a dairy; or the like. The invention also relates to a field device with a single-acting or double-acting pneumatic actuator comprising an electropneumatic solenoid valve. The invention further relates to a diagnostic method for an electropneumatic solenoid valve.

[0002] Electropneumatic solenoid valves are known from the prior art, which comprise an electropneumatic actuator and a 3 / 2-way valve actuated thereby. Such a 3 / 2-way valve (501) is described in Figures 9 and 10shown. When used in an electropneumatic field device, the 3 / 2-way valve (501) can have an air supply channel (511) connected to a pneumatic source, an exhaust air channel (521) connected to a compressed air sink, such as the atmosphere, and a control air channel (551) for supplying and venting a pneumatic actuator. The 3 / 2-way valve (501) further comprises an air chamber (505) into which the air channels (511, 521, 551) open, as well as a valve member (553) movable within the air chamber (505). The valve member (553) can close either the air supply channel (511) or the exhaust air channel (521).

[0003] To actuate the valve member (553), i.e. to move the valve member between an exhaust air duct closing position ( Fig. 10 ) and a supply air duct closed position ( Fig. 9), the valve member is rigidly connected to a solenoid armature (533) of an electromagnetic linear actuator (503) by means of an actuating rod (507). The electromagnetic linear actuator is equipped with a return spring (573) between the solenoid armature (533) and the ferromagnetic core (537) of the actuator. The return spring is provided to return the solenoid armature (533), for example, to the supply air duct closed position ( Fig. 9 ). When the electromagnetic actuator is activated, the magnet armature is magnetically attracted against the force of the return spring (573) and, if sufficiently strong, moves in such a way that the valve element moves into the exhaust air duct closed position ( Fig. 10 ) is spent.

[0004] A non-magnetic gap (534) is provided between the magnet armature and the magnetizable core to prevent the magnet armature (533) from coming into contact with the magnetizable core (537). Such contact would result in extremely high adhesive forces. The gap is dimensioned such that a certain degree of wear and / or settling on the valve member (553) and the cooperating valve seat (523) of the exhaust air duct (521) is tolerated without causing contact between the magnet armature and core and the consequent functional failure of the electro-pneumatic solenoid valve. The magnetic attraction force between the magnet armature and core increases quadratically depending on the inverse of the distance between the core and the magnet armature. Wear therefore acts as a self-reinforcing effect. After initial slight wear, the electro-pneumatic solenoid valve can fail quickly and uncontrollably.To avoid a malfunction during system operation, the 3 / 2-way valve is replaced preventively. Since the actual wear condition is only apparent after the valve has been removed and disassembled, unnecessary replacement costs must be accepted in favor of safe system operation.

[0005] DE 10 2016 120 655 A1 discloses a method for monitoring the condition of a solenoid valve. A measuring unit measures a voltage induced by the return of a plunger within an electromagnet as a function of time after the coil current is switched off, and an evaluation unit compares the voltage with a reference function. The comparison is intended to provide information about the condition of the springs. However, the method described in DE 10 2016 120 655 A1 does not allow any conclusions to be drawn about wear and / or settlement on the valve element.

[0006] JP S55 34093 U relates to a corrosion-resistant solenoid valve for low pressures. DE3807278A1 discloses a prior art diagnostic method.

[0007] It is an object of the invention to overcome the disadvantages of the prior art, in particular to provide a solenoid valve and a diagnostic method for a solenoid valve with increased reliability. This object is achieved by the subject matter of the independent claims.

[0008] Accordingly, an electropneumatic solenoid valve is provided for a field device of a process plant, such as a power plant, for example, a nuclear power plant, a chemical plant, for example, a petrochemical plant, a food processing plant, for example, a brewery, or the like. The electropneumatic solenoid valve comprises an electromagnetic actuator with an energizable coil and a magnet armature movable relative to the coil. The electromagnetic actuator may further comprise an iron core or magnetic core stationary relative to the coil. The electromagnetic actuator may, in particular, be an electromagnetic linear actuator.

[0009] The electropneumatic solenoid valve comprises a (first) air chamber into which three air channels open, wherein the three air channels comprise a first air channel, a second air channel, and a control air channel. The first air channel can, for example, be an air supply channel connected to a pneumatic source, such as a compressed air reservoir, a compressor, or the like. The second channel can be an exhaust air channel connected to a pressure sink, such as the atmosphere. The control air channel can be connected to a pneumatic actuator in order to vent and / or vent it. The electropneumatic solenoid valve is designed, in particular, as a 3 / 2-way valve. If the electropneumatic solenoid valve is designed as a 3 / 2-way valve, a valve member can be accommodated in the air chamber in such a way that the valve member closes either the first air channel or the second air channel.The electropneumatic solenoid valve comprises a valve member which, in a first closed position, closes the first air duct and opens the second air duct; and which, in a second closed position, closes the second air duct and opens the second air duct; and which, in a second closed position, closes the second air duct and opens the first air duct. In particular, the valve member can be designed such that the control air duct is free regardless of the position of the valve member. In particular, the electropneumatic solenoid valve is free of further air ducts opening into the air chamber. Preferably, only the first air duct, the second air duct, and the control air duct open into the air chamber. The first closed position can be referred to as the supply air duct closed position. The second closed position can be implemented as the exhaust air duct closed position.The valve member is in particular an at least partially elastic sealing element.

[0010] The solenoid valve according to the invention comprises a movable driver, in particular an actuating rod or actuating shaft. The driver is movable in a first actuating direction and in a second actuating direction opposite to the first actuating direction. For example, a driver can be designed as an actuating rod and be movable linearly, for example upwards and downwards. The driver connects the valve member to the magnet armature in a force-transmitting manner. Between the driver and the magnet armature, at least one driving prestressing means, such as a spring, is arranged to provide a prestressing force on the driver in a driving direction corresponding to the first actuating direction or corresponding to the second actuating direction. Furthermore, at least one return prestressing means, such as a return spring, is provided to provide a return force on the driver opposite to the driving direction.The return biasing means can be arranged in particular between the driver and the electromagnetic actuator, preferably a core of the electromagnetic actuator which is immovable relative to the coil.

[0011] The driver is free of any material-locking and / or rigid connection to the magnet armature. The driver is movable relative to the magnet armature. In particular, the driver can be linearly movable relative to the magnet armature. The magnet armature and the driver are preferably movable in the same direction relative to the coil. For example, a driver designed as an actuating rod can have linear mobility corresponding to the driving direction, and the magnet armature can have linear mobility corresponding to the actuating directions, which are oriented parallel, in particular coaxially, to one another. If a driver is implemented as an actuating shaft, for example, a mutation movement relative to a rotational axis can occur, and the electromagnetic actuator can be implemented as a rotational axis with a rotatable magnet armature that can rotate about the same or a different rotational axis.

[0012] Preferably, the driver preloading means and the return preloading means can be formed separately from one another. For example, the driver preloading means can be formed as a spring, for example a first spiral spring, and the return preloading means as a return spring, for example a second spiral spring. It is conceivable for the driver preloading means and / or the return preloading means to be formed as a plastic spring. For example, a plastic spring can be realized as an elastomer block. It is conceivable for such a plastic spring to act in functional union as a driver preloading means on the one hand and a return preloading means on the other. For example, by the plastic spring being connected to the driver and being supported on the one hand on the magnet armature and on the other hand on a part of the electromagnetic actuator that is stationary relative to the coil.Such a plastic spring can have different sections, with one section acting as a driver preloading means and another section acting as a return preloading means. It is conceivable that the return preloading means is arranged between the driver and the magnet armature.

[0013] According to a preferred embodiment, the driving direction corresponds to the second actuating direction, i.e., the first actuating direction corresponds to the direction of movement of the magnet armature from the second closed position to the first closed position. The second actuating direction corresponds to the direction of movement of the magnet armature from the first closed position to the second closed position. In this preferred embodiment, the driving preloading means provides the preload force in the direction of the second actuating direction, i.e., in the second closed position, as a driving force from the valve member to a seat of the second air channel.

[0014] By decoupling the valve member from the solenoid armature by means of the driver and the driver preloading means, the closing force of the valve member on the valve seat of the air channel is limited in the driving direction. This advantageously limits the closing force of the valve member on a valve seat, even when the movable solenoid armature comes very close to a core of the electric actuator, for example, to a very small gap. In this way, exponentially self-reinforcing wear phenomena can be avoided. Compared to conventional 3 / 2-way valves, the reliability of the electropneumatic solenoid valve according to the invention can be significantly increased in this way.

[0015] According to one embodiment, the electromagnetic actuator is formed with a magnetizable, in particular ferromagnetic, core that is immobile relative to the coil. A non-magnetic gap is arranged between the core and the magnet armature. In particular, the non-magnetic gap forms a free space in the first and / or second actuating direction between the core and the magnet armature, so that during operation the core is always contact-free relative to the magnet armature. Preferably, an anti-adhesive body, such as a non-adhesive coating or an anti-adhesive disc made of a non-magnetizable material, for example PTFE (Teflon®<), can be arranged in the gap. The anti-adhesive body arranged in the gap can cover the surface of the core and / or the magnet armature in the gap in sections or over its entire area.The electromagnetic actuator is to be measured in particular in such a way that in the first closed position and / or in the second closed position the non-magnetic gap, which may be at least partially filled with an anti-adhesive body, remains between the core and the armature of the electromagnet.

[0016] According to one embodiment of an electropneumatic solenoid valve, the driver has a stop for determining an end position of the magnet armature relative to the driver counter to the driving direction. The position of the stop in the driving direction can be adjustable relative to the driver. In particular, the position of the stop in the driving direction is fixed relative to the driver. The stop can be rigidly connected to the driver, for example, positively or integrally. The stop limits the mobility of the magnet armature relative to the driver counter to the driving direction. In the driving direction, the magnet armature is freely movable relative to the driver by the stop. When the magnet armature is moved counter to the driving direction by the electromagnetic actuator and / or the return biasing means, the magnet armature comes into contact with the stop.By pushing the armature against the stop of the driver, it is ensured that the armature and the driver move together in the opposite direction of the driving direction. This allows the armature to drive the driver along, bringing the valve element into the first closed position.

[0017] According to one embodiment of an electropneumatic solenoid valve, the driver biasing means limits a stop effect, such as a stop force, of the valve member on a valve seat in the driver direction. The driver biasing means can limit the stop force of the valve member on a valve seat, for example, in the driver direction, which can correspond, for example, to the second actuating direction, on the second valve seat. The driver biasing means can limit the stop force of the valve member on the valve seat in the closed position, which is brought about by an electromagnetic actuation of the magnet armature by the electromagnetic actuator. For example, the second closed position can be achieved by actuating the magnet armature by means of the electromagnetic actuator.The closed position can be achieved by the solenoid armature being moved by the electromagnet, the movement being transmitted from the solenoid armature to the driver via the driving preloading means. As long as the valve member moves freely between the first valve seat and the second valve seat, the movement of the driver corresponds to the movement of the solenoid armature. If the valve member comes into contact with a valve seat in the driving direction, this prevents further movement of the driver in the driving direction, whereby further movement of the solenoid armature in the driving direction can occur, for example, into the gap. The movement of the solenoid armature in the driving direction beyond the closed position can be at least partially or completely absorbed by the driving preloading means without the solenoid armature movement being transmitted to the valve member.In this way, the impact effect, in particular the impact force, of the valve member on the valve seat is limited in the driving direction. In this way, on the one hand, the impulse force of the impact of the valve member on the valve member in the driving direction is considerably reduced because the mass of the magnet armature, which is significantly higher relative to the mass of the driver and valve member, is decoupled, so that the mass of the magnet armature does not have an impact on the impulse force when the valve member hits the valve seat in the driving direction. Furthermore, it is avoided that the movement of the magnet armature into the gap space results in a corresponding movement or deformation of the valve member; unlike in the prior art according to . Figure 9, in which there is a material-locking, rigid connection between the magnet armature and the valve member. Furthermore, the stop effect of the valve member in the driving direction on the valve seat is decoupled from the exponentially increasing magnetic force exerted by the electromagnet on the magnet armature as the gap decreases. It is not the magnetic force that is transferred from the magnet armature to the driver, but only the additional spring force of the driver preloading means caused by this (free) travel in the area of the gap.

[0018] Alternatively or additionally, the return biasing means can limit a stop effect, in particular the stop force, of the valve member on a valve seat counter to the driving direction. For example, the electropneumatic solenoid valve can be designed such that when the electropneumatic actuator is de-energized, the force of the return biasing means alone urges the valve member into a closed position, for example into the first closed position, against a valve seat, for example the first valve seat. In such a configuration, the return biasing means can be designed as a spring with a linear characteristic curve or a progressive characteristic curve. In the closed position brought about by the return biasing means, for example the first closed position, a predetermined closing force is provided corresponding to a preload of the return biasing means.The preload force of the return preloading means can be selected according to a preload spring travel which is substantially smaller than the travel of the valve member from the first closed position to the second closed position.

[0019] For example, the advance spring travel can be less than 50%, less than 20%, or even less than 10% of the actuator travel. The preload force provided by the return preloading means in this closed position corresponds to the stop force of the valve member against the valve seat.

[0020] According to one embodiment, an electropneumatic solenoid valve can further comprise a second air chamber and a second valve member arranged therein. The second valve member, like the first, can be carried by the driver. The second valve member can be carried by another driver. The driver, in particular an actuating rod, can be fork-shaped and comprise several prongs, on each of which at least one valve member can be carried. The second valve member is in particular an at least partially elastic sealing element. Three further air channels open into the further air chamber. The further air channels comprise a fourth air channel, a fifth air channel, and a further control air channel. In the first closed position, the second valve member closes the fourth air channel and opens the fifth air channel. In the second closed position, the second valve member closes the fifth air channel and opens the fourth air channel.

[0021] The fifth air duct can, for example, be an air supply duct connected to a pneumatic source, such as a compressed air reservoir, a compressor, or the like. The fourth air duct can be an exhaust air duct connected to a pressure sink, such as the atmosphere. The further control air duct can be connected to a pneumatic actuator in order to ventilate and / or vent it. The electropneumatic solenoid valve is designed, in particular, as a 5 / 2-way valve. If the electropneumatic solenoid valve is designed as a 5 / 2-way valve, the first valve member can be accommodated in the air chamber such that the valve member closes either the first air duct or the second air duct, and the second valve member can be accommodated in the further air chamber such that the second valve member closes either the fourth air duct or the fifth air duct.

[0022] The driver or the further drivers connects the second valve member to the, in particular, precisely one solenoid armature in a force-transmitting manner. At least one driver preloading means, such as a spring, is arranged between the driver for the second valve member and the solenoid armature to provide a preload force on the driver in a driver direction corresponding to the first actuating direction or corresponding to the second actuating direction. Furthermore, at least one return preloading means, such as a return spring, is provided to provide a return force on the driver for the second valve member opposite to the driver direction. The return preloading means can be arranged in particular between the driver for the second valve member and the electromagnetic actuator, preferably a core of the electromagnetic actuator that is immovable relative to the coil.

[0023] The electropneumatic solenoid valve can comprise n (more than two) valve members in n air chambers with respective air channels, wherein the n additional valve members can be supported on the same driver or on several, in particular individual, drivers. The n additional valve members can be implemented in an electropneumatic solenoid valve in accordance with a second valve member described above. In particular, the electropneumatic solenoid valve can be implemented as an n / 2-way valve.

[0024] According to a further development of an electropneumatic solenoid valve, the first air duct and the fifth air duct are pneumatically connected in parallel. Alternatively or additionally, the second air duct and the fourth air duct can be connected in parallel. For example, the first air duct and the fifth air duct can be implemented as ventilation ducts that are connected to a pneumatic source via a common supply duct. For example, the second air duct and the fourth air duct can be implemented as venting ducts that are connected to a pneumatic sink, in particular the atmosphere. According to an alternative development of an electropneumatic solenoid valve, the first air duct and the fourth air duct are pneumatically connected in parallel. Alternatively or additionally, the second air duct and the fifth air duct can be connected in parallel.For example, the second air duct and the fifth air duct can be realized as venting ducts that are connected to a pneumatic sink, in particular the atmosphere.

[0025] According to a further development of an electropneumatic solenoid valve, the driver comprises an elastic coupling between the first valve member and the second valve member. According to this embodiment, the first and second valve members are carried on the same driver. An elastic coupling can form a section of the driver that has increased elasticity relative to the remaining driver. For example, the elastic coupling can have an elasticity that is at least 10%, at least 50%, or at least 100% higher than a section of the driver between the elastic coupling and / or the first valve member and the driver biasing means. In particular, the elastic coupling can limit a stop effect, in particular a closing force, of the further valve member to at least one further valve seat.

[0026] According to another development of an electropneumatic solenoid valve, the driver comprises a rigid coupling between the first valve member and the second valve member. According to this embodiment, the first and second valve members are carried on the same driver. Preferably, the entire driver is rigid. In particular, the elasticity of the driver between the second valve member and the first valve member and / or the driver preloading means is constant. In particular, the driver preloading means can limit a stop effect of the further valve member on a further valve seat in the driver direction and / or the return preloading means can limit a stop effect of the further valve member on a further valve seat counter to the driver direction.

[0027] According to the invention, the electropneumatic solenoid valve comprises analog and / or digital diagnostic electronics which detect the current flowing through the coil in order to provide a diagnostic result based on at least a first local current flow minimum correlating to an impact of the valve member on a valve seat, taking into account a stop time difference between the first local current flow minimum and a second local current flow minimum correlating to an impact of the magnet armature on a stopper.

[0028] The diagnostic electronics can be configured to provide a diagnostic result taking into account a second time difference between the occurrence of the first current flow minimum and a reference time defined by the occurrence of the second local current flow minimum. Based on the time difference, it is possible to make a statement about the wear status of the 3 / 2-way valve. The diagnostic electronics can be configured to output a warning or error message if the time difference falls below a predetermined threshold.

[0029] The analog and / or digital diagnostic electronics of the electropneumatic solenoid valve can be configured, in particular, to carry out a diagnostic procedure as described below. For analog diagnosis, the current value can be converted into electrical voltage via a shunt resistor and its temporal progression continuously monitored. Differentiating elements can detect the kinks and, for example, convert them into individual pulses. A counter element can convert the elapsed time between the two pulses into a digital or analog value. For digital analysis using a microprocessor, microcontroller, or the like, this can continuously digitally convert the voltage signal at the shunt resistor and, using a firmware routine, detect and evaluate the kinks and their time difference. The time difference between the stop kinks can be increased using additional damping elements.This improves detection for the evaluation electronics. The damping elements can dampen either the armature relative to the housing or the valve stem with the sealing element relative to the armature. The time course of the current rise can also be optimized by optimally selecting the amplitude of the switching voltage.

[0030] The invention also relates to a field device for a process plant, such as a power plant, a chemical plant, a food processing plant or the like, comprising a particularly single-acting or double-acting pneumatic control valve actuator and an electro-pneumatic solenoid valve as described above, wherein the first air channel is a ventilation channel for connecting to a pneumatic source and the second air channel is a vent channel for connecting to a pneumatic sink and wherein the control air channel is connected to a control air chamber of the control valve actuator.

[0031] According to one embodiment of a field device, the pneumatic control valve actuator can be designed as a single-acting control valve actuator with spring return. A single-acting control valve actuator preferably comprises precisely one pneumatically pressurizable control air chamber for providing a control valve actuation force that counteracts a return force of the spring return. According to this embodiment, the solenoid valve can be implemented, in particular, as a 3 / 2-way valve.

[0032] According to one embodiment of a field device with a double-acting pneumatic control valve actuator and an electro-pneumatic solenoid valve with a first valve member and a second valve member, in particular as described above, the control air channel is connected to a first control air chamber of the control valve actuator, and the second control air channel is connected to a second control air chamber acting opposite to the first control air chamber. According to this embodiment, the solenoid valve can be implemented in particular as a 5 / 2-way valve. A double-acting pneumatic control valve actuator preferably comprises precisely two oppositely acting control air chambers for actuating a control valve. It can be particularly preferred that in such a field device, the first and fifth air channels are designed as ventilation channels and the second and fourth air channels are designed as vent channels.In this way, a simple operation of the double-acting pneumatic control valve actuator can be ensured by venting the first valve element while the second valve element is pressurizing or vice versa.

[0033] The invention also relates to a diagnostic method for an electropneumatic solenoid valve of a field device of a process plant, such as a power plant, a chemical plant, a food processing plant, or the like. In particular, the diagnostic method for an electropneumatic solenoid valve and / or field device can be designed as described above.

[0034] The diagnostic method comprises a diagnostic routine. According to the diagnostic routine, an electromagnetic actuator with a magnetic armature is activated to actuate a valve member. According to the diagnostic routine, the impact of a valve member on a valve seat is detected as the first reference time, and the impact of the magnetic armature on a stopper, such as a non-magnetic anti-adhesion body, for example a non-adhesion coating or an anti-adhesion disc, in particular on a stationary core of the electromagnetic actuator, is detected as the second reference time. According to the diagnostic routine of the diagnostic method, a stop time difference between the first reference time and the second reference time is determined. The stop time reference is to be compared with a predetermined time difference reference value. It is conceivable that the stop time differences of several consecutively executed diagnostic routines are compared with one another.It is also conceivable that a combination of the aforementioned comparisons is carried out; for example, several different recorded time differences from different diagnostic routines can be compared with one another. Based on the comparison of one or more stop time difference values recorded in one or more diagnostic routines of the diagnostic method, a statement can be made about the wear status of the electropneumatic solenoid valve. The diagnostic method according to the invention therefore allows continuous monitoring of the operating status of the 3 / 2-way valve during operation, so that the solenoid valve can be used over its entire safe service life. Monitoring the functionality and wear status of the electromagnetic solenoid valve also allows for particularly safe operation because unexpected failure due to wear can be reliably ruled out.

[0035] It should be clear that the designation of the reference points as "first" or "second" reference point, as well as "third," "fourth," or further reference points, is not related to the temporal occurrence of the reference points. Rather, the different designations clarify that different reference points correlate with different diagnostically relevant events, and that each specific diagnostically relevant event can be assigned a specific individual reference point.

[0036] In one embodiment of a diagnostic method, the impact of a further valve member on a further valve seat is detected as a fourth reference time in the diagnostic routine. In particular, at least one further stop time difference between the fourth reference time and the first reference time and / or the second reference time is determined. According to one embodiment of the diagnostic method, to activate the electromagnetic actuator, current can flow through a coil of the actuator, and the first reference time and / or the second reference time and / or the fourth reference time can be detected based on a local (first, second and / or third) local minimum of the current flow through the coil. The current flow through the coil of the electromagnetic actuator is related to the movement and position of the magnet armature relative to the electromagnetic drive.If the magnetic armature experiences deceleration, for example when the valve member hits a valve seat and / or when the free movement of the magnetic armature ends, a temporally local current flow minimum of the current flowing through the coil occurs in correlation with the deceleration. For example, the diagnostic method can be carried out taking into account a time difference between at least one (first) local current flow minimum and a reference time. The reference time can be predetermined. In particular, a diagnostic method can be carried out on the basis of at least two local current flow minima, a first local current flow minimum and a second local current flow minimum. The diagnostic method can be carried out taking into account a second time difference that exists between the occurrence of the first current flow minimum and a reference time, which is defined by the occurrence of the second local current flow minimum.According to one embodiment of the diagnostic method, which can be combined with the previous one, the release of the valve member from a second valve seat can be detected as the third reference time for the diagnostic method. A movement time difference between the first reference time and the third reference time can be detected, on the basis of which a further diagnostic function can be performed. For example, by comparing the detected movement time difference with a movement time difference reference and / or movement time difference values of one or more different other diagnostic routines, it can be determined whether the valve member can move freely from the first valve seat and the second valve seat. In particular, the release of the further valve member from another further valve seat can be detected as the fifth reference time.

[0037] According to one embodiment of a diagnostic method that can be combined with the previous one, several diagnostic routines are carried out successively, wherein the stop time differences of the several diagnostic routines are taken into account, in particular compared with each other.

[0038] According to one embodiment of a diagnostic method, a wear condition warning is generated as a diagnostic result when the stop time difference of at least one diagnostic routine approaches zero or is equal to zero. For example, a wear condition warning can be generated if, contrary to expectations, only one local current flow minima occurs instead of two when performing the diagnostic method, because this suggests that the electropneumatic solenoid valve is not functioning properly. For example, the valve element and / or the valve seat may be defective, meaning that reliable closing of the valve element is no longer guaranteed. It is also conceivable that a foreign object has become lodged between the magnet armature and the electromagnetic actuator or between the valve seat and the valve element, so that proper movement is no longer possible.However, a wear condition warning can already be issued if, for example, the evaluation of the stop time differences of several consecutive diagnostic routines reveals a trend and / or pattern according to which the stop time difference experiences a critical change, for example, decreases, i.e. approaches zero.

[0039] According to one embodiment of a diagnostic method that can be combined with the previous one, a malfunction warning can be issued as a diagnostic result if a second time difference between two reference times exceeds a limit value during at least one diagnostic routine. A second or further time difference between the first reference time and the third reference time, or between the second reference time and the third reference time, can be detected and compared with an assigned limit value. It is also conceivable for the first reference time, the second reference time, and / or the third reference time to be compared with another, for example, predetermined, fourth reference time, and for the time difference to be compared with an assigned limit value.

[0040] Further features, characteristics and advantages of the invention will become clear from the following description of a preferred embodiment and the accompanying drawings, in which: Figure 1 shows a sectional view of an electropneumatic solenoid valve according to the invention in the first closed position; Figure 2a shows a partial section of the solenoid valve according to the invention according to Figure 1 in the second closed position; Figure 2b the solenoid valve according to the invention according to Figure 1in the second closed position, wherein the magnet armature has reached its end position; Figure 3a shows a path-time diagram showing the position of the magnet armature starting from the first closed position in the driving direction; Figure 3b shows a path-time diagram showing the position of the valve member of the solenoid valve according to the invention according to Figure 1a starting from the first closed position in the second actuating direction; Figure 3c shows a current-time diagram showing the current flow through the magnet coil of the electropneumatic actuator according to Figure 1 during the movement of the valve member from the first closed position to the second closed position; Figure 4a shows a path-time diagram of the magnet position for a defective electropneumatic actuator; Figure 4b shows a path-time diagram of the valve member position for a defective electropneumatic actuator; Figure 4c shows a current-time diagram for a defective electropneumatic actuator according to Figure 1; Figure 5 shows a sectional view of another electropneumatic solenoid valve according to the invention in the second closed position; Figure 6a shows a sectional view of another solenoid valve according to the invention with several valve members in the second closed position, wherein the magnet armature has reached its end position; Figure 6b shows the solenoid valve according to Figure 6a in the second closed position, with the magnet armature in contact with the stop; Figure 6c a sectional view of the solenoid valve according to Figure 6a in a state in which the first valve member is released from a closed position; Figure 6 shows a sectional view of the solenoid valve according to Figure 6a in a state in which both valve members are released from a closed position; Figure 7 shows a current-time diagram showing the current flow through the solenoid coil of the electropneumatic actuator according to the Figures 6a to 6dduring the movement of the valve member from the first closed position to the second closed position; Figure 8 shows a sectional view of another control valve according to the invention with several valve members; Figure 9 shows a conventional electropneumatic 3 / 2-way valve in a first closed position; and Figure 10 shows the conventional 3 / 2-way valve according to Figure 9 in a second closed position.

[0041] In the following description of preferred embodiments of the invention using exemplary embodiments, as in the figures, the same or similar components are provided with the same or similar reference numerals to simplify readability.

[0042] An electropneumatic solenoid valve according to the invention, which is generically designed as a 3 / 2-way valve, generally bears the reference numeral 1. The essential components of the solenoid valve 1 include an electropneumatic actuator 3, which in the present case is designed as a linear actuator, and an air chamber 5 with exactly three air channels opening into it, namely a first air channel 11, which is designed as a ventilation channel and is connected to a pneumatic source, a second air channel 21, which is designed as a venting channel and is connected to the atmosphere, and a third air channel, which is designed as a control air channel 51 and is connected to a pneumatic actuator (not shown in detail).

[0043] In the electropneumatic solenoid valve 1, the control air channel 51 always remains open regardless of the position of the valve member 53 within the air chamber 5. The solenoid valve 1 has a first closed position ( Figure 1), in which the ventilation channel 11 is closed by the valve member 53. The solenoid valve 1 has a second closed position ( Figures 2a and 2b ), in which the valve member 53 closes the vent channel 21. The solenoid valve is moved into the first closed position ( Figure 1 ). The solenoid valve 1 is moved into the second closed position ( Figure 2a, Figure 2b ). A movement of the valve member 53 in the direction of the first valve seat 13, which surrounds the opening of the first air duct 11, is in the exemplary embodiment shown a movement of the valve member 53 in a first actuating direction S1. A movement of the valve member 53 in the direction of a second valve seat 23, which surrounds the opening of the second ventilation duct 21 into the air chamber 5, is realized in the exemplary embodiment shown in Figure 1illustrated version an adjustment movement in a second adjustment direction S2.

[0044] The valve member 53 is rigidly coupled to a driver, which in the exemplary embodiments illustrated in the figures is implemented as an actuating rod 7. The actuating rod 7 is movably mounted relative to the housing of the solenoid valve 1 for a linear movement in the first actuating direction S1 and / or in the second actuating direction S2. The actuating rod 7 is connected to a magnet armature 33 of the electromagnetic actuator 3 by means of a driver preloading means implemented by a spiral spring 71.

[0045] The electromagnetic actuator comprises a coil 31 through which a control current I can flow in order to build up an electromagnetic field under the influence of which the magnet armature 33 can be actuated. Figure 1, Figure 2a and Figure 2bIn the exemplary embodiment of an electromagnetic actuator 3 as a linear actuator shown, the magnetic armature 33 is arranged coaxially within the magnetic coil 31. The rotational symmetry axis of the coil can, as shown, correspond to the rotational symmetry axis of the actuating rod 7 and / or the valve member 53. The actuating rod 7 is linearly movable, and with it the valve member 53.

[0046] To actuate the electropneumatic actuator 1, an electric current I flows through the coil 31 of the magnetic actuator 3. The electromagnetic field generated by the activation of the magnetic coil 31 causes a magnetic force of attraction on the linearly movable magnetic armature 33, possibly amplified by a magnetic core 35. The magnetic force of attraction of the magnetic actuator 3 on the magnetic armature 33 causes the magnetic armature 33 to move in the driving direction M. The movement of the magnetic armature 33 is transmitted via the driving pretensioning means 71 to the driver 7, i.e. the actuating rod that carries the valve member 53. In the embodiment shown, the driving direction M corresponds to the second actuating direction S2.If, in the illustrated embodiment, the magnetic coil 31 is activated to actuate the magnetic armature 33, this can result in a movement of the magnetic armature 33 in the driving direction M (upwards in the illustrated illustration) and a corresponding, parallel movement of the valve member 53 in the second actuating direction S2. When the electromagnetic actuator 3 is activated, the magnetic armature 33, driver 7 and valve member 53 can move, starting from the first closed position, along a valve actuating path x in the second actuating direction (upwards) until the valve member 53 reaches the second closed position (. Figure 2a ). The valve member 53 reaches the second closed position when it engages with the second valve seat 23, which forms the opening of the second air channel 21 into the air chamber 5.

[0047] Thanks to the decoupling of the driver 7 from the magnet armature 33 by the clamped drive preloading means 71 arranged therebetween, the magnet armature 33 can continue to move in its drive direction M. After the valve member 53 has engaged with the valve seat 23 due to the joint movement of the magnet armature 33, valve member 53, and driver 7 in the drive direction M and can no longer move, the magnet armature 33 can continue to move along a free travel path s. The movement of the magnet armature 33 along the free travel path s can be impeded by a spring, damping, or the like, or can occur unimpeded.

[0048] The magnet armature 33 can continue to move in the driving direction M until the movement of the magnet armature 33 relative to the magnet coil 31 is stopped ( Figure 2b). In the illustrated embodiment, the magnet armature 33 abuts against a non-magnetic stopper 74 in the gap 34 between the magnet armature 33 and the magnet core 35. The non-magnetic stopper 74 prevents contact between the ferromagnetic components of the magnet armature 33 and the magnet core 35.

[0049] During the movement of the magnetic armature 33 along the free travel distance s, the valve member 53 and the driver 7 are in a fixed position relative to the housing of the solenoid valve 1. Since the magnetic armature 33 is supported on the driver 7 via the driver preloading means 71, the driver preloading means 71 is compressed according to the free travel distance s traveled by the magnetic armature 33. The stroke or free travel distance s corresponds to a spring travel of the driver preloading means 71. The movement of the driver 33 along the free travel distance s exerts a closing force on the valve member 53 that corresponds to the free travel distance s multiplied by the spring constant of the driver preloading means 71. This closing force can be many times lower than the magnetic force acting on the magnetic armature 33 when very close to the magnetic core 35.

[0050] In the driving direction M, the driving pre-tensioning means 71 presses against the driver 7 with the pre-tensioning force V. In the illustrated embodiment, the pre-tensioning force V acts against the driving direction M according to the Figures 1, 2a and 2b the restoring preloading means 73 with the restoring force R from the stationary magnetic core 35 onto the driver 7.

[0051] If the Figures 2a and 2b illustrated versions of the electropneumatic solenoid valve 1, the electromagnetic actuator 3 is deactivated by terminating or interrupting the current flow through the coil 31, the magnetic attraction force on the magnet armature 33 in the driving direction M disappears. The preload forces of the return coil spring 73 directed against the driving direction M and the in the position according to Figure 2b The preload force of the driving preload means 71 then causes the magnet armature 33 to move counter to the driving direction M (downward).

[0052] The driving pre-tensioning means 71 clamped between the driver 7 and the magnet armature 33 moves the magnet armature 33 counter to the driving direction M up to a stop 75 formed on the driver 7. The stop 75 limits the linear mobility of the magnet armature 33 relative to the driver 7 counter to the driving direction M. The driver 7, the stop 75, the driving pre-tensioning means 71 and the magnet armature 33 can be coordinated with one another in such a way that it is structurally ensured that the driving pre-tensioning means 71 is always in particularly clamped contact with both the driver 7 on the one hand and the magnet armature 33 on the other. When the magnet armature 33 is in contact with the non-magnetizable stopper 74, the magnet armature 33 is raised from the stop 75 on the driver 7 by the free travel s.

[0053] The return biasing means 73 is designed such that it (i.) moves the magnet armature 33 from the second closed position ( Figure 2a, Figure 2b ) against the driving direction M to the second closed position ( Figure 1 ) and / or (ii.) in the second closed position, can provide a closing force for pressing the valve member 53 against the first valve seat 13.

[0054] The return biasing means 73 is generally provided for force transmission between the movable valve member 53 and a stationary part of the electropneumatic solenoid valve 1. The return biasing means 73 can, for example, be supported on the one hand on the valve member 53, on the driver 7, or on the magnet armature 33. The return biasing means 73 can, on the other hand, be supported, for example, on a housing section of the solenoid valve 1 or on a stationary part of the electromagnetic actuator 3, for example the magnet core 35. The return biasing means 73, in particular in the form of a spiral spring, can be arranged in a clamped manner between the magnet armature 33 and a stationary counterbearing of the electropneumatic solenoid valve 1. In the exemplary embodiments illustrated in the figures, the return biasing means 73 is supported on the one hand on the driver 7 and on the other hand on the magnet core 35.When the return preloading means 73 moves the driver 7 in the first adjustment direction S1, in the present embodiment the magnet armature 33 is moved by the driver 7 by means of the driving preloading means 71.

[0055] In the first closed position ( Figure 1 ), the return preloading means 73 provides a preload force on the driver 7 and the valve member 53 connected thereto, which causes a sealing contact of the valve member 53 with the valve seat 13 at the opening of the first air channel 11 into the air 5. The spring travel of the return preloading means 73 corresponds to the travel distance x of the valve member 53 between the first valve seat 13 and the second valve seat 23.

[0056] The Figures 1, 2a and 2bThe electropneumatic solenoid valve 1 shown is designed to open when de-energized, so that if the current flow I through the coil 31 fails, the reset biasing means 73 moves the valve member 53 into the first closed position S1, opening the ventilation channel 21. It is conceivable within the scope of the invention for a pneumatic solenoid valve according to the invention to be designed as a de-energized solenoid valve, for example in such a way that in the de-energized state the reset biasing means closes the venting channel; this can be realized, for example, by the second air channel 21 being a ventilation channel connected to a pneumatic source and the first air channel 11 being a venting channel connected to a pneumatic sink.

[0057] Figure 3a shows a path-time diagram of the position of the magnet armature 33, where as reference point (distance 0) the Figure 2bshown end stop position of the magnet armature 33 and the distance of the magnet armature away from the stop point is shown. Figure 3b shows a path-time diagram of the valve member 53, where the o-point represents the second closed position according to the Figures 2a and 2b from which the distance of the valve member 53 relative to the second valve seat 23 in the first adjustment direction S1 is shown. Figure 3c shows a current flow-time diagram, illustrating the current flow through coil 31. The numbers shown in the diagrams are to be understood as qualitative comparison values.

[0058] The Figures 3a, 3b and 3c refer to a fully functional electropneumatic solenoid valve according to the invention. Figures 4a, 4b and 4c refer to a defective electropneumatic solenoid valve according to the invention.

[0059] Figure 3cshows the current flow I through the electromagnetic coil 31 when actuating the electropneumatic solenoid valve 1 starting from the first closed position ( Figure 1 ) or rest position in which the valve member 53 is positioned by the force of the return biasing means 73.

[0060] From the time to (0.1 second) the current flow I through the coil 31 increases. As shown in the Figures 3a and 3b As can be seen, there is no movement of the valve element from time to until time t3. As shown in the Figure 3b As can be seen, the movement of the valve member begins at time t3. Between time t0 and time t3, the current flow I increases. As a result, the electromagnetic coil 31 causes an increasingly large magnetic force, which acts on the valve member in the closed position ( Figure 1) located magnet armature 33. At time t3, the magnetic actuating force is sufficiently large to overcome the preload force R of the return preload spring 73, which in the closed position ( Figure 1 ) acts on the driver 7 and the valve member 53 to press it against the first valve seat 13. From t3 onwards, the magnetic actuator 3 causes the magnetic armature 33, driver 7 and valve member 53 to move in the second actuating direction S2.

[0061] Between time t3, which corresponds to the release of the valve member 53 from the first valve seat 13, and time t1, the valve member moves opposite to the first actuating direction S1 toward the second valve seat 53. At time t1, the valve member 53 comes into contact with the second valve seat 23 of the second air channel 21, and the actuating movement of the valve member 53 ends. The distance x, which occurs between time t3 and time t1 ( Figure 3b), corresponds to the distance x of the valve member between the first closed position at the first valve seat 13 ( Figure 1 ) and the second closed position of the valve member 53 at the second valve seat 23 ( Figure 2a, 2b ). After time t1, the valve member 53 is in contact with the second valve seat 23.

[0062] Thanks to the decoupling of the magnet armature 33 from the driver 7 rigidly connected to the valve member 53, the magnet armature can also move after the valve member 53 has reached the second closed position ( Figure 2a ) continues to move in the driving direction until the magnet armature 33 reaches an end stop 74 at time t2. This movement of the magnet armature 33 is counteracted by the driving return means 71. As in Figure 3a in correlation with Figure 3c can be seen, remains after reaching the closed position according to Figure 2athe magnetic armature 33 initially comes into contact with the driving stop 75. If necessary, the magnetic armature 33 may briefly overshoot at time t1, when the valve member 53 reaches the valve seat. The magnetic armature 33 only slowly detaches from the stop 75 after time t1, when the current flow I in the coil 31 provides a sufficiently high magnetic force to also overcome the restoring force V of the driving preloading means 71. The magnetic armature 33 then leaves the stop 75 and moves in the driving direction M up to the stopper 74. When the current value I is reached, at which the armature 33 begins to move, the inductance of the system immediately increases because the air gap begins to decrease. The rate of current rise decreases and even changes direction because the magnetic system now induces a counter voltage. This results in the current maximum in the curve being reached shortly after the start of the armature movement.The current then decreases again until the armature hits its mechanical stop. The kink in the curve indicates the point of impact of the armature.

[0063] At time t2, the armature 33 reaches its final stop at a stopper 74, which forms a non-magnetic and non-magnetizable barrier between the armature 33 and the magnetic core 35. As long as a sufficiently high control current I flows, the armature 33 remains in this end position ( Figure 2b ).

[0064] With constant process parameters (restoring force R of the restoring preloading means, restoring force V of the driving preloading means, free travel s, valve travel x, actuating energy (current U), etc.), it can be expected that the course of the current flow curve, dependent on the time t, will be the same for each actuation cycle in a fully functional electro-pneumatic solenoid valve 1. Smaller tolerances may occur. With constant process parameters, the reference times t0, t1, t2 and / or t3, which are characterized by instantaneous force equilibria, occur reproducibly at consistently long time intervals relative to one another for each cycle (i.e., each diagnostic routine).

[0065] For example, it is to be expected that the time difference dt between the first reference time t1 and the second reference time t2 remains the same for different actuation cycles in a functioning electropneumatic solenoid valve, possibly taking minor tolerances into account. The inventors have discovered that, based on a sufficiently long period dt between the reference times t1 and t2, it can be concluded that the gap 34 between the magnet armature 33 and the magnet core 35 is sufficiently large and that any stopper 74 provided therein is not worn, or at least not excessively worn. The first kink at t1 (0.15 s) characterizes the impact of the sealing element against the upper seat 13, and the second kink at t2 (0.1875 s) characterizes the impact of the armature 33 against the anti-stick disc 74.The time difference dt between the two stops (37.5 ms) is characteristic of a new, not yet worn valve. If the seat lift changes due to wear (settlement effect), the time difference dt between the two stops also changes.

[0066] Based on a time difference between reference time t1 and reference time t3 and / or between reference time t1 and reference time t0, it can be determined whether the travel x of the valve member 53 between the first valve seat 13 and the second valve seat 23 is free and the movement of the valve member 53 and driver is unhindered. If the time difference between reference time t1 and a reference time t0 and / or t3 is noticeably small, for example if the difference time falls below a minimum threshold value, it can be concluded that one of the springs has broken. If the period between reference time t1 and one of the reference times t0 and / or t3 becomes noticeably long, for example if it is above a maximum threshold value, it can be concluded that an obstacle is disrupting the movement of the driver and / or valve member 53 or that an undesirably high frictional force is acting on the driver 7.

[0067] The Figures 4a, 4b and 4c show the diagrams of a defective electropneumatic solenoid valve. The time difference dt* between the reference time t1 and t2 has noticeably decreased. The time difference dt* is smaller than a threshold value. This threshold value can be a predefined threshold value. The threshold value can be set when performing the diagnostic procedure by comparison to a reference time difference dt of one or more previous diagnostic routine cycles. The stroke x of the valve member 53 has increased due to wear, while the armature stroke s has remained the same. The time difference dt* between the stop of the sealing element 53 and the armature stop has critically shortened dt (37.5 ms) to dt* (19.1 ms). When measuring more conspicuous values, as in the Figures 4a, 4b and 4c As shown, the electropneumatic solenoid valve must be replaced.

[0068] In Figure 5Another solenoid valve 1a according to the invention is shown. Another solenoid valve 1b according to the invention is shown in the Figures 6a to 6d . In Figure 8 A further alternative embodiment of a solenoid valve 1c according to the invention is shown in a first, lower closed position. The electromagnetic actuator 3 and the connection of the driver, designed as an actuating rod 7, to the actuator 3 by means of a driver preloading means 71 and a return preloading means 73 correspond to those described above, which is why reference is made to the previous explanations in this regard.

[0069] The solenoid valves 1a and 1b are 5 / 2-way valves. The first valve stage, comprising the first valve member 53 in a first air chamber 5 with a first air channel 11, a second air channel 21, and a control air channel 51, is designed in the solenoid valves 1a and 1b as described above with respect to the solenoid valve 1. The second valve stage is designed correspondingly to the first valve stage.

[0070] That is, the second air chamber 105 corresponds to the first air chamber 5; the fourth air channel 111 is formed corresponding to the first air channel 11 and the fifth air channel 121 is formed corresponding to the second air channel 21; and each air chamber 5 or 105 has a control air channel 51 or 151. Regarding the structural design and functionality of the second valve stage, reference is made to the above description of the first valve stage in the Figures 1, 2a and 2b shown solenoid valve 1.

[0071] In the present embodiments, the first air duct 11 and the fifth air duct 121 are pneumatically connected in parallel and connected to a common supply duct 110. The supply duct 110 can be connected to a pneumatic source (not shown). In this case, the fifth air duct is a ventilation duct 121. The second air duct 21 and the fourth air duct 111 can be pneumatically connected in parallel and connected to the atmosphere or another pressure sink. The fourth ventilation duct in this case is an exhaust air duct 111. The first control air duct 51 can be connected to a first control air chamber of a pneumatic double-acting actuator (not shown). The second control air duct 151 can be connected to a second control air chamber of a pneumatic double-acting actuator (not shown).

[0072] The solenoid valves 1a and 1b differ from the previously described solenoid valve 1 essentially only by the presence of a second valve stage comprising a further valve member 153 in a second air chamber 105 with further air channels 111, 121, and 151 associated with it, two of which can be selectively closed by the second valve member 153. The solenoid valves 1a and 1b differ from one another essentially only by their respective coupling 170 or 171 between the two valve members 53 and 153, which are carried by the same actuating rod 7. Because the two valve members 53 and 153 are attached to the same actuating rod 7, the first valve member 53 and the second valve member 153 move in the same first or second actuating direction S1 or S2.

[0073] The valve members 53 and 153 can move in the first actuating direction S1 until they are both in the first closed position (not shown). In the first closed position, the second valve member 53 is in sealing contact with a valve seat 13 of the first air channel 11, and the second valve member 153 is in sealing contact with a valve seat 113 of the fourth air channel 111.

[0074] The valve members 53 and 153 can move together in the second actuating direction S2 until they are both in the second closed position ( Fig. 5 , Fig. 6a and 6b ). In the second closed position, the first valve member 53 is in sealing contact with a valve seat 23 of the second air channel 21 and the second valve member 153 is in sealing contact with a valve seat 123 of the fifth air channel 121.

[0075] In the Figure 5In the solenoid valve 1a shown, the first valve member 53 and the second valve member 153 are connected to the same actuating rod 7. Between the valve members 53 and 153, the actuating rod 7 is designed as a rigid coupling 170. The rigid coupling 170 comprises a constant elasticity in the driving direction M, which corresponds to the elasticity of the actuating rod 7 between the first valve member 53 and the magnet armature 33 and / or the actuating prestressing means 71. The actuating rod 7 is manufactured in one piece in the driving direction M, starting at the actuating prestressing means 71 and the return prestressing means 73, beyond the first valve member 53 to the second valve member 153, as a solid rod with a constant cross-section and consistent material. When leaving a closed position, the two valve members 53 and 153 release the respective valve seats 13 and 113 or 23 and 123 simultaneously or almost simultaneously.When a closed position is reached, the two valve elements in the unworn state simultaneously occupy the valve seats 13 and 113 or 23 and 123 (first and fourth reference times practically coincide).

[0076] In the Figures 6a to 6d In the solenoid valve 1b shown, the first valve member 53 and the second valve member 153 are connected to the same actuating rod 7.

[0077] Between the valve members 53 and 153, the actuating rod 7 is partially designed with an elastic coupling 171. The elastic coupling 171 has increased elasticity compared to the elasticity of the driver between the first valve member 53 and the armature 33 and / or the driver preloading means 71. Increased elasticity can be realized, for example, by a material recess, such as a radially outer constriction or an opening penetrating the actuating rod transversely (not shown). The elastic coupling 171 can be realized by a section made of a different, more elastic material than that of the remaining driver. The elastic coupling 171 can be formed, for example, by a compression and / or tension spring section. For example, the solenoid valve 1b can be dimensioned such that the elastic coupling 171 in the second closed position ( Fig. 6a and 6b) is tensioned and elastically stretched and that the elastic coupling 171 is relaxed in the first closed position, or is tensioned and elastically compressed.

[0078] Starting from the second closed position ( Fig. 6a and 6b ), the valve members 53 and 153 of the solenoid valve 1b can be moved in the first actuating direction S1, whereby first the first valve member 53 ( Fig. 6c ) and then the second valve member 153 ( Fig. 6d ) releases the respective valve seat 23 or 123. Upon further movement in the first actuating direction S1 up to the first closed position, first the second valve member 153 and then the first valve member 53 can come into sealing contact with the respective valve seat 13 or 113.

[0079] Starting from the first closed position, the valve members 53 and 153 of the solenoid valve 1b can be moved in the second actuating direction S2, whereby first the first valve member 53 and then the second valve member 153 releases the respective valve seat 13 or 113 (third reference time t3 according to Fig. 7 ). With a further movement in the second adjustment direction S2 up to the second closed position ( Fig. 6a and 6b ) can initially (fourth reference time t4 according to Fig. 7 ) the second valve member 153 ( Fig. 6c ) and subsequently (first reference time t1 according to Fig. 7 ) the first valve member 53 ( Fig. 6b ) come into sealing contact with the respective valve seat 23 or 123. With a further increase in force, the armature 33 can be raised relative to the stop 75 in the driving direction M as described above, until the armature 33 hits the stopper 74 ( Fig. 6a ; second reference time t2 according to Fig. 7).

[0080] The wear condition of the second valve stage can be detected based on the first stop time difference dt and a second stop time difference dt' between t4 and t1 or dt" between t4 and t2.

[0081] In the Figure 8 In the illustrated solenoid valve 1c, several valve elements 53, 53', in particular of the same type, are connected to the same actuating rod 7'. Figure 8 The solenoid valve 1c shown acts electrically and mechanically essentially like the solenoid valve 1a described above according to Figure 5 . When leaving a closed position, the two valve members 53 and 53' release the respective valve seats 13 and 13' or 23 and 23' simultaneously or almost simultaneously. When reaching a closed position, the two valve members 53 and 53', in the unworn state, simultaneously occupy the valve seats 13 and 13' or 23 and 23' (the first and fourth reference times practically coincide).

[0082] The solenoid valve 1c differs from the solenoid valve 1a in that the valve members 53 and 53' of the solenoid valve 1c are not coaxially offset from one another in the axial direction of the actuator, like the valve members 53 and 53' of the solenoid valve 1a. The actuating rod 7' forks between the common electromagnetic actuator 3 and the valve members 53 and 53'. The actuating rod 7' has two prongs 173, 173' at its valve-side end. Figure 8The left prong 173 carries the left valve member 53 and the right prong 173' carries the right valve member 53'. The valve members 53 and 53' are offset transversely with respect to the axis of symmetry of the electromagnetic actuator 3, in particular parallel. At least one or more prongs 173, 173' realize the stop 75 in the area of the fork of the actuating rod 7'. In the solenoid valve 1c, it may be preferred that the two lower air channels 11 and 11' are air supply channels. The air channels 11 and 11' can be connected to the same or different pneumatic sources. The two upper air channels 21, 21' can be vent channels, which, as in Figure 8shown by way of example, can open into a common atmosphere channel 120. The left control air channel 51 and the right control air channel 51' can be connected to different or the same pneumatic control valve. For example, the two control air channels 51 and 51 can be connected to the same pneumatic active chamber (control air chamber) of a pneumatic actuator. Alternatively, the right control air channel 51 and the left control air channel 51' can be connected to a respective pneumatic active chamber of different, in particular parallel-connected and aligned, pneumatic actuators.

[0083] It is clear that a solenoid valve 1c may comprise further prongs with further valve members. Alternatively or additionally, the solenoid valve 1c may be Figure 8 along each individual control rod prong 173 and / or 173' further valve stages, as in the designs of solenoid valves 1a according to Figure 5or 1b according to the Figures 6a to 6d can include. List of reference symbols

[0084] 1 Solenoid valve 3 Electropneumatic actuator 5, 5', 105 Air chamber 7, 7' Actuating rod 11, 11', 121 Ventilation channel 13, 13' First valve seat 21, 21', 111 Vent channel 23, 23' Second valve seat 31 (Solenoid) coil 33 Magnet armature 34 Gap space 35 Magnet core 51, 51', 151 Control air channel 53, 53', 153 Valve member 71 Driving preloading means 73 Return preloading means 74 Non-magnetic stopper 75 Stop 110 Feed channel 120 Atmosphere channel 113, 123 Valve seat 170 Rigid coupling 171 Flexible coupling 173, 173'tines IControl current MDrive direction VDrive preload force RReset preload force S1First actuating direction S2Second actuating direction dt, dt*, dt', dt"Time difference sFree actuating travel t1, t2, t3, t4Reference times xValve actuating travel

Claims

1. Electropneumatic solenoid valve (1) for a field device of a process plant, such as a power plant, a chemical plant, a food processing plant, or the like, comprising: an electromagnetic actuator (3) with a coil (31) that can be energized and a solenoid armature (33) movable relative to the coil (31), at least one air chamber (5) into which three air channels (11, 21, 51) open, wherein the three air channels comprise a first air channel (11), a second air channel (21), and a control air channel (51); at least one valve member (53) which, in a first closed position, closes the first air channel (11) and opens the second air channel (21) and which, in a second closed position, closes the second air channel (21) and opens the first air channel (11); at least one driver, in particular an actuating rod (7) or shaft, which is movable in a first actuating direction (S1) and in a second actuating direction (S2) opposite to the first actuating direction (S1) and which connects the valve member (53) to the solenoid armature (33) for force transmission, wherein at least one driver biasing means, such as a spring (71), is arranged between the driver and the solenoid armature (33) to provide a biasing force (V) on the driver in a driving direction (M) corresponding to the first or second actuating direction (S1, S2) and wherein at least one return biasing means, such as a return spring (73), is provided to provide a return force (R) on the driver opposite to the driving direction, characterized by an analog and / or digital diagnostic electronics that detects the current flowing through the coil (31) to provide a diagnostic result based on at least a first local current flow minimum correlating to an impact of the valve member (53) on a valve seat (23) considering a stop time difference between the first local current flow minimum and a second local current flow minimum correlating to an impact of the solenoid armature (33) on a stopper.

2. Electropneumatic solenoid valve (1) according to claim 1, characterized in that a core (35) of the electromagnetic actuator (3) is magnetizable, in particular ferromagnetic, wherein a non-magnetic gap (34) is arranged between the core (35) and the solenoid armature (33), wherein an anti-adhesion body, such as an anti-adhesion coating or an anti-adhesion disc (74), made of a non-magnetizable material is arranged in the gap (34).

3. Electropneumatic solenoid valve (1) according to one of claims 1 or 2, characterized in that the driver has a stop (75) for determining an end position of the solenoid armature (33) relative to the driver opposite to the driving direction.

4. Electropneumatic solenoid valve (1) according to one of the preceding claims, characterized in that the driver biasing means limits a stop effect of the valve member (53) on a valve seat (23) in the driving direction (M) and / or that the return biasing means limits a stop effect of the valve member (53) on a valve seat (23) opposite to the driving direction.

5. Electropneumatic solenoid valve (1) according to one of the preceding claims, characterized in that the solenoid valve (1) further comprises: a second air chamber (105, 5'), into which three further air channels (11', 21', 51', 111, 121, 151) open, wherein the further air channels comprise a fourth air channel (11', 111), a fifth air channel (21', 121), and a further control air channel (51', 151); a second valve member (53', 153) which, in the first closed position, closes the fourth air channel (11', 111) and opens the fifth air channel (21', 121) and which, in the second closed position, closes the fifth air channel (21', 121) and opens the fourth air channel (11', 111); wherein the driver, in particular the actuating rod (7, 7') or shaft, or a second driver carries the second valve member (53', 153).

6. Electropneumatic solenoid valve (1) according to claim 5, characterized in that the first air channel (11) and the fifth air channel (121) are pneumatically connected in parallel and / or that the second air channel (21) and the fourth air channel (111) are connected in parallel.

7. Electropneumatic solenoid valve (1) according to one of claims 5 or 6, characterized in that the driver (7) comprises an elastic coupling (171) between the first valve member (53) and the second valve member (153), wherein in particular the elastic coupling (171) limits a stop effect of the further valve member (153) on at least one further valve seat (113, 123).

8. Electropneumatic solenoid valve (1) according to one of claims 5 or 6, characterized in that the driver (7) comprises a rigid coupling (170) between the first valve member (53) and the second valve member (153), wherein in particular the driver biasing means limits a stop effect of the further valve member (153) on a further valve seat (123) in the driving direction (M) and / or that the return biasing means limits a stop effect of the further valve member (153) on a further valve seat (113) opposite to the driving direction.

9. Field device for a process plant, such as a power plant, a chemical plant, a food processing plant, or the like, comprising: a pneumatic control valve actuator, in particular single-acting or double-acting; and an electropneumatic solenoid valve (1) according to one of the preceding claims, wherein the first air channel (11) is a supply channel for connecting to a pneumatic source and the second air channel (21) is an exhaust channel for connecting to a pneumatic sink and wherein the control air channel (51) is connected to a control air chamber of the control valve actuator.

10. Field device according to claim 9 with a double-acting pneumatic control valve actuator and an electropneumatic solenoid valve (1) according to one of claims 5 to 8, characterized in that the control air channel (51) is connected to a first control air chamber of the control valve actuator and that the second control air channel (151) is connected to a second control air chamber acting opposite to the first control air chamber.

11. Diagnostic method for an electropneumatic solenoid valve (1) according to one of the preceding claims 1 to 8 of a field device of a process plant, such as a power plant, a chemical plant, a food processing plant, or the like, in particular according to one of the preceding claims 9 or 10, comprising a diagnostic routine wherein an electromagnetic actuator (3) with a solenoid armature (33) is activated to actuate a valve member (53); wherein as a first reference time (t1) the impact of the valve member (53) on a valve seat (23) correlating to a first current flow minimum is detected; wherein as a second reference time (t2) the impact of the solenoid armature (33) on a stopper, such as a non-magnetic anti-adhesion body, for example an anti-adhesion coating or an anti-adhesion disc (74), in particular on a stationary core (34) of the electromagnetic actuator (3), correlating to a second current flow minimum is detected; and wherein a stop time difference (dt) between the first reference time (t1) and the second reference time (t2) is determined.

12. Diagnostic method according to claim 11, wherein the diagnostic routine comprises that as a fourth reference time (t4) the impact of a further valve member (153) on a further valve seat (123) is detected; wherein in particular at least one further stop time difference (dt') between the fourth reference time (t4) and the first reference time (t1) and / or the second reference time (t2) is determined.

13. Diagnostic method according to claim 11 or 12, wherein to activate the electromagnetic actuator (3) current flows through a coil (31) of the actuator (3) and wherein the first reference time (t1) and / or the second reference time (t2) and optionally the fourth reference time (t4) is detected based on a local minimum of the current flow (I) through the coil (31).

14. Diagnostic method according to one of claims 11 to 13, wherein as a third reference time (t3) the release of the valve member (53) from a second valve seat (23) is detected, wherein in particular as a fifth reference time (t5) the release of the further valve member (153) from another further valve seat (113) is detected.

15. Diagnostic method according to one of claims 11 to 14, wherein several diagnostic routines are carried out in succession and wherein the stop time differences (dt, dt') of the diagnostic routines are considered, in particular compared, with each other.

16. Diagnostic method according to one of claims 11 to 15, wherein as a diagnostic result a wear condition warning is generated if the stop time difference (dt, dt') of at least one diagnostic routine approaches zero or is equal to zero.

17. Diagnostic method according to one of claims 11 to 16, wherein as a diagnostic result a malfunction warning is generated if a second time difference between two reference times during at least one diagnostic routine exceeds a limit value.

18. Diagnostic method according to one of claims 11 to 17, wherein the stop time difference (dt) is compared with a reference value, in particular a predetermined threshold value, wherein in particular a warning message or an error message is output if the stop time difference (dt) falls below the predetermined threshold value.