Method for actuating an electromechanical switching element

Abstract

The invention relates to a method for actuating an electromechanical switching element at least comprising: a plurality of contacts; a coil having an iron core; and an armature, wherein, in the event that a predefined condition is fulfilled, the switching element is repeatedly pulsed on and off during the switch-off process or pulsed off and on during the switch-on process at a predefined point in time within an overtravel range in such a way that the coil current flowing into the coil oscillates between a predefined maximum value and a minimum value so that the armature moves within the overtravel range, thereby causing the contacts to rub against one another without becoming detached from one another, the minimum value being defined as the current value at the point in time at which the armature begins to detach from the iron core.

Description

[0001] The invention relates to a method for controlling an electromechanical switching element, as well as a universal component.

[0002] When switching electromechanical elements such as relays, two types of faults can occur. In one case, a relay may fail to make contact during a switching operation; in another, the current flow across the contacts may not be interrupted during a switching operation. The reasons for these faults are varied, including mechanical jamming, oxide buildup, and contact welding. However, most of these causes are reversible. For example, if the contacts were once mechanically jammed, they can still be released, and the relay can be used for many thousands of switching cycles. Thus, it is possible to correct a faulty relay state by simply actuating it again.

[0003] In DE102014211400A1, for example, the contactor opens and closes at least once if the contacts of the contactor come into contact with a contact resistance that is not below a defined value.

[0004] In EP3185269B1, the operating current is superimposed with an electrical waveform. The method is only applicable for a switching-off process.

[0005] Known measures include repeating the switching process and applying vibration to the contacts. The necessary measuring technology for recording contact states is also known, e.g., from DE 102010011394 A1, DE 102018114425 A1, or WO 202194418 A1.

[0006] However, the known methods still need improvement in order to prevent or delay failures of switching elements.

[0007] Therefore, an object of this invention is to provide a method for controlling an electromechanical switching element, by which sticking contact elements can be avoided or released. This object is achieved according to the invention by the features of the independent claims. Advantageous embodiments are the subject of the dependent claims.

[0008] A method is proposed for controlling an electromechanical switching element, comprising at least several contacts, a coil with an iron core, and an armature, wherein, in the event that a predetermined condition is met, during the switching-off process, the switching element is repeatedly pulsed on and off, or during the switching-on process, it is repeatedly pulsed off and on at a predetermined time within an overtravel range, such that the coil current flowing into the coil oscillates between a predetermined maximum value and a minimum value, causing the armature to move within the overtravel range and thereby causing the contacts to rub against each other without separating from each other, wherein the minimum value is defined as the current value at the time at which the armature begins to separate from the iron core.

[0009] In a further embodiment, it is provided that the specified condition is a detected fault condition in which the contacts do not make contact when switched on or do not release when switched off, or in which the specified condition is a detection of a deterioration in the contact quality of the contacts.

[0010] In another embodiment, it is provided that the on-time or off-time is selected until the coil current has reached the value it had at a predetermined time after switching off or switching on.

[0011] In a further embodiment, it is provided that the overstroke range is continuously determined for each electromechanical switching element during use, and if this range changes during its service life, the specified time for pulse in or out is adjusted within the overstroke range.

[0012] In a further version, it is provided that continuous monitoring takes place to ensure that the specified condition is met.

[0013] In a further embodiment, a universal component is provided, comprising an electromechanical switching element, comprising several contacts and an armature, wherein the armature is configured to move the contacts in such a way that they touch or separate from each other, and an integrated measuring technology for determining at least one overtravel range in the operation of the electromechanical switching element, and a microcontroller in signal communication with the electromechanical switching element, in which the method is implemented as a software program.

[0014] In another embodiment, the universal component is designed as a relay socket.

[0015] Further features and advantages of the invention will become apparent from the following description of exemplary embodiments of the invention, with reference to the figures in the drawing, which shows details of the invention, and from the claims. The individual features can be implemented individually or in any combination in a variant of the invention.

[0016] Preferred embodiments of the invention are explained in more detail below with reference to the accompanying drawing. It shows: Figures 1-3 show views of an electromechanical switching element in different switching states according to the state of the art. Figure 4 shows a diagram with a normal shutdown process and rubbing of the contacts according to one embodiment of the present invention.

[0017] In the following figure descriptions, identical elements or functions are marked with the same reference symbols.

[0018] The proposed method is used in products with electromechanical switching elements 10, which have multiple contacts 7a, 7b, 7c and an armature 5. In particular, electromechanical switching elements 10 of the proposed invention are installed in universal components such as universal sockets, which are used, for example, in industrial automation (DC industrial networks) or in charging stations for electric vehicles, etc. The electromechanical switching elements 10 used here cannot usually be configured directly after production or based on one or more reference components, since different influences come into play depending on the application scenario, i.e., type of switching element, control voltage, installation position, installation location, etc., which can lead to altered switching characteristics of the switching element.

[0019] Therefore, according to the invention, an electromechanical switching element 10 is controlled directly at its installation location to reduce errors. This means that the control method is implemented within the universal component. For this purpose, both measurement technology and a microcontroller are required and integrated into the universal component. The universal component can be designed as a relay socket.

[0020] The following refers only to a relay 10 as an electromechanical switching element 10. However, the method can also be used for other electromechanical switching elements, e.g., contactors. Besides the embodiment shown here, in which a changeover contact is part of an electromechanical switching element 10, the changeover contact of this type can also be integrated into other devices, such as a changeover switch.

[0021] In Figure 1Figure 1 shows a schematic representation of a three-pole changeover contact according to a general embodiment. Here, the changeover contact is merely an example of a part of an electromechanical switching element 10, or changeover relay. The electromechanical switching element 10 comprises three terminals associated with the changeover contact, which are referred to below, according to common convention, as COM terminal ("common") 2a, NC terminal 2b (normally closed), and NO terminal 2c (normally open). Furthermore, the electromechanical switching element 10 comprises two relay coil terminals 3a and 3b, via which a relay coil 3, also referred to simply as coil 3, of the electromechanical switching element 10 can be energized with a coil current I3.The current flow from the relay coil 3 generates a magnetic field which is guided in a magnetic core 4 and exerts a force on a movable relay armature 5, also referred to as armature 5, which in turn causes a movement of one or more contacts 7a, 7b, 7c (also referred to as contact elements or contact pills) assigned to the respective terminals 2a, 2b, 2c via a slider 6.

[0022] In Figure 1 The diagram shows a state in which relay 10 is open, i.e., contacts 7a and 7b are touching. Figure 2 The diagram shows a state in which the relay is closed, i.e., contacts 7a and 7c are touching. Figure 3A so-called overtravel is shown. Here, contact 7a is in contact with contact 7c (relay 10 is closed) and is pressed against contact 7c by the slider 6 actuated by the armature 5, which is represented by the bending of the upper end of contact 7a. Both when switching on and off relay 10, a region occurs where contacts 7a and 7c touch, but the armature 5 does not touch the coil 3 (more precisely, the iron core 8). This means that the connection between contacts 7a and 7c is already conductive, but the bending of the contact elements is still changing; this region is referred to as the overtravel region in the following.

[0023] In Figure 4A time course of a switching-off process for an electromechanical switching element 10, e.g., a relay, is shown according to the prior art. A normalized measured quantity x / X_max is specified on the ordinate. Here, region B0 denotes the state in which the relay 10 is closed, i.e., the armature 5 is attracted to the coil 3; more precisely, the armature does not touch the coil 3, but rather the yoke or iron core 8, and detaches from it in regions B1 and B2, and the contacts 7a and 7c are in contact (as in Fig. 2 ), so that conductivity exists (labeled with the short dashed line L1). Area B1 denotes the state of over-stroke (as in Fig. 3), in which the armature 5 is detached from the coil 3, but the contacts 7a, 7c are not yet separated from each other. Area B2 shows the state in which the relay 10 is open, i.e., the contacts 7a, 7c are separated from each other, so that there is no longer any conductivity between the contacts 7a, 7c (as in Fig. 1The solid line represents the coil current I3. It can be seen that during the switch-off process, the coil current I3 decreases to a current minimum at time t_01. This current minimum is defined by the release of the armature 5 from the iron core 8 of the coil 3 (and can be detected shortly after release). At time t_01, when the armature 5 begins to release, the coil current I3 increases again, which can be calculated, for example, using the derivative (change from negative to positive). At this time t_01, area B0 transitions into area B1 (overtravel). At time t_12, when contacts 7a and 7c open, the overtravel area B1 is exited (area B2, in which contacts 7a and 7c are open). The period d_02 denotes the time interval between t_01 and t_12, in which the armature 5 is detached from the iron core 8 of the coil 3, but the contacts 7a, 7c are still in contact with each other.

[0024] The object of the invention is to detect a faulty switching state that prevents contacts 7a / 7b or 7a / 7c from separating from each other, or in which contacts 7a / 7b or 7a / 7c touch but do not conduct, and to automatically correct this faulty switching state. This is achieved by re-energizing the armature 5 within the overtravel range B1, which moves contacts 7a and 7c, causing them to rub against each other, as described below. The focus here is particularly on the switching-off process, i.e., contacts 7a and 7c. However, the proposed method can also be applied during switching-on. Depending on the installation, there are two switching-off errors (NO 2c-COM 2a; COM 2a-NC 2b) in the changeover relay, but also switching-on errors for these contact pairs, so that a total of four errors are corrected in the changeover relay: contacts NO 2c-COM 2a do not release, NO 2c-COM 2a do not conduct, COM 2a-NC 2b do not release, COM 2a-NC 2b do not conduct.Since the following section focuses on the switching-off process, the procedure will only be described using contacts 7a and 7c. The corresponding parameters, e.g., I1, t_in, d_in, L2, are additionally shown in [reference]. Figure 4 entered to illustrate how the procedure works.

[0025] The activation, in this implementation a renewed switching-on or pulse (since a complete switching-on process is not performed), occurs at a time t_in within the overshoot range B1, i.e., within the period d_02. Advantageously, the time t_in is chosen so that it lies at a (temporal) interval from t_01 and t_12. The selection of the time t_in can be arbitrary by the microcontroller. From this time t_in, the coil current, subsequently referred to as I1, then increases again (in Figure 4(shown as a dashed line starting at t_in), which prevents contacts 7a and 7c from separating. However, they still experience excitation within the overtravel range and are moved along different trajectories by the spring force, causing the contacts to rub against each other or exert forces on a connection between the contacts. As the coil current I1 increases again, contacts 7a and 7c are pressed together again. When the coil current I1 reaches a predetermined current value, selected at time t_out during the switch-off process, the switch-off occurs again, causing contacts 7a and 7c to experience excitation once more and be moved along different trajectories by the spring force, resulting in the contacts rubbing against each other or forces being exerted on a connection between the contacts. This can be repeated several times.Thus, contacts 7a and 7c rub together without separating, i.e., without completing a full switching cycle. The switching element 10 therefore remains fully conductive even during contact rubbing. The coil current I3 (11) oscillates between a (predefined, freely chosen) maximum current and a minimum current (defined by the release of the armature 5), thereby always causing movement of the armature 5 within the overtravel range B1.

[0026] The time t_off of the shutdown is determined somewhere between the point in Figure 4The maximum current (maximum coil current I3) and the minimum current (present at time t_01) are selected on the ordinate, labeled "1". In this configuration, the switch-off time t_off is chosen at approximately 2 / 3 of the full coil current I3. However, a different switch-off time t_off, and thus a different switch-off coil current I3, can be selected for each control cycle. For example, the excitation can be set within a range of 90% to 40% of the coil current I3.

[0027] The off-time d_off is determined from the selected time t_off and the switch-on time t_in. The switch-on time d_in is the period between the switch-on time t_in and the time t_off2 at which the coil current I1 reaches the same level as the switch-off coil current I3 at time t_off. The sum of d_off and d_in yields the frequency of the (pulse width) signal used for control, and the ratio of d_off and d_in determines the duty cycle of the signal. A high frequency of 50 Hz or more is preferably achieved; in this embodiment, 200 Hz is used.

[0028] The process is advantageously terminated at the earliest when successful contacting of contacts 7a, 7b (during switch-on) or release of contacts 7a, 7c (during switch-off) is detected. Monitoring is advantageously performed continuously or at predetermined intervals. If no such detection is possible after a predetermined period, relay 10 is switched off and an error signal is output.

[0029] The result of the proposed renewed excitation is therefore that contacts 7a, 7c rub against each other several times, but are not opened (separated from each other), so that the conductive connection between them remains, as shown by the dotted line L2 in Figure 4As indicated. The term "multiple" means that the pulsing on and off (during the switching-off process) or the pulsing off and on (during the switching-on process) is repeated several times, preferably until the fault condition is no longer detected, whereby a limitation on the duration or frequency of the rubbing may be provided.

[0030] Furthermore, the excitation does not involve a complete switching cycle. Instead, a renewed excitation occurs within the overtravel range B1, i.e., within the period d_02 between the release of the armature 5 and the release of contacts 7a, 7c at a time t_in, i.e., even before contacts 7a, 7c separate from each other.

[0031] The process is event-based and is advantageously executed when a fault condition is detected, i.e., when contacts 7a and 7c do not release or when a conductive connection can no longer be established due to deposits. The friction resulting from the multiple on / off pulses (during the switch-off process) or the on / off pulses (during the switch-on process) loosens contaminants between the contacts or abrades applied material.

[0032] However, the procedure can also be executed under conditions other than a currently detected fault state, e.g., preventively. It can be executed based on the detection of an impending fault state, i.e., preventively. For example, if oscillation in the coil current I3 is detected at the end of a switching operation, it can be concluded that the switching element 10 is in a degradation state (deterioration of the contact quality of contacts 7a, 7b, 7c). While a fault state has not yet been detected in which contacts 7a, 7c no longer separate from each other (when relay 10 is switched off) or fail to establish a conductive connection (when relay 10 is switched on), the fault state is already incipient and therefore expected. In this case, the procedure can be executed preventively.

[0033] Alternatively, in a less preferred embodiment, the procedure can be carried out preventively after a fixed number of switching operations of relay 10.

[0034] As already mentioned, the procedure can be carried out both during the switch-on process and the switch-off process, since in both processes the fault condition can occur that the contacts 7a / 7c, 7a / 7b do not separate from each other or do not conduct.

[0035] To execute the procedure, data (coil current I3, times t) are collected at the beginning of the electromechanical switching element 10's use, i.e., after installation in the application, during each switching operation to determine the overtravel range B1. As described above, this can be determined from the time difference between the first sign change of the time derivative of the coil current and the first change in the conductivity of contacts 7a / 7c, 7a / 7b. By acquiring the data during as many switching operations as possible, the overtravel range B1 can be adjusted, as it can shift, for example, due to the aging of the relay 10 during its service life. The procedure is therefore adaptive.

[0036] To acquire the data and perform the adjustments, a universal component is provided, which includes both the necessary measuring technology (e.g., for current measurement) and a microcontroller capable of performing the corresponding calculations and controlling relay 10. The procedure is implemented as a software program in the microcontroller. It also serves to control relay 10, for example, via a PWM signal.

[0037] One advantage of this method is that it can prevent a large number of system failures caused by faulty relays 10. Furthermore, the system has a short response time, allowing for uninterrupted operation of the systems. Another advantage is that the friction can be stopped immediately if the system is not switched on again, as there is no oscillation. In addition, its technical implementation as a self-contained, universal switching component ensures minimal application effort for users. Reference symbol list

[0038] 2a COM terminal 2b NC terminal 2c NO terminal 3 Relay coil 3a, 3b Relay coil terminals 4 Magnetic core 5 Relay armature 6 Slider 7a-7c Contact elements 8 Iron core 10 Electromechanical switching element, e.g., relay B0 Armature position Contacts closed B1 Armature position Overtravel (overtravel range) B2 Armature position Contacts open I3 Coil current I1 Coil current during friction I3_max, I1_max Maximum value coil current I3_min Minimum value coil current L1, L2 Conductivity t Time t_off Switch-off time t_off2 Switch-off time friction t_on Switch-on time t_12 Time at which contacts open t_01 Time at which armature releases d_02 Period / Duration Overtravel d_off Switch-off duration d_on Switch-on duration

Claims

1. A method for actuating an electromechanical switching element (10), at least including a plurality of contacts (7a, 7b, 7c), a coil (3) with an iron core (8) and an armature (5), characterized in, that - in the event that a predefined condition is fulfilled - in the switch-off process pulsing on and off or in the switch-on process pulsing off and on of the switching element (10) is carried out repeatedly at a predefined time (t_on) within an overtravel range (B1) in such a way that the coil current (I3, I1) flowing into the coil (3) oscillates between a predefined maximum value (I3_max; I1_max) and a minimum value (I3_min) so that the armature (5) moves within the overtravel range (B1) and the contacts (7a, 7b, 7c) thereby rub against each other without becoming detached from each other, wherein the minimum value (I3_min) is defined as the current value at the time (t_01) at which the armature (5) begins to detach from the iron core (8).

2. The method according to claim 1, wherein the predefined condition is a detected error state in which the contacts do not contact each other at switch-on or do not become detached at switch-off, or wherein the predefined condition is a detection of a deterioration of the contact quality of the contacts (7a, 7b, 7c).

3. The method according to claim 1 or 2, wherein the switch-on duration (d_on) or the switch-off duration is selected until the coil current (I1) had reached the value which it had at a predefined point in time (t_off) after being switched-off or switched-on.

4. The method according to any of the preceding claims, wherein for each electromechanical switching element (10) the overtravel range (B1) is determined continuously during the use, and in the event that the same changes during the service life the predefined point in time (t_on) is adapted for pulsing on and pulsing off within the overtravel range (B1).

5. The method according to any of the preceding claims, wherein a continuous monitoring is effected as to whether the predefined condition is fulfilled.

6. A universal component (100), including: - an electromechanical switching element (10), including a plurality of contacts (7a, 7b, 7c) and an armature (5), wherein the armature is adapted to move the contacts (7a, 7b, 7c) in such a way that they touch each other or become detached from each other, and - an integrated measuring technique for determining at least one overtravel range (B1) in operation of the electromechanical switching element (10), characterized by - a microcontroller in signal connection with the electromechanical switching element (10), in which the method according to any of the preceding claims is implemented as a software program.

7. The universal component (100) according to claim 6, which is formed as a relay socket.

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