EP0535205B1 - Device for monitoring a control unit - Google Patents

Abstract

The invention relates to a monitoring device for a control unit having a safety chain. In accordance with the invention, the monitoring device has a testable switching device which is provided with input and output terminals such that a monitoring loop may be set up from a plurality of testable switching devices and a sequence of digital signals can, in particular, be transmitted via this loop as a continuous signal so that a "digital stand-by current loop" is obtained.

Description

The invention relates to a monitoring device for a control device having a safety chain, in particular for elevator and conveyor systems, with a contactlessly triggerable, electronic, testable switching device comprising a sensor, with the aid of which the state of the sensor can be detected.

A monitoring device of this type is known from EP-A-0 357 888, in which a safety light barrier in the form of a so-called failsafe arrangement is used as the sensor arrangement, in which an error by doubling the components and by comparing the output signals is to be avoided . A switching device which can be actively checked at any time in the sense of the present invention is not described in EP-A-0 357 888. Rather, a functional test is only carried out there if the sensor arrangement on a car passes through an actuation flag permanently installed in the elevator shaft, in accordance with the use of the elevator system.

In various electromechanical systems, in particular in elevator and conveyor systems, individual actions, for example moving the elevator or operating a conveyor device, are generally monitored with the aid of switching devices, of which several often have to have a certain switching state in order to carry out the intended action safely to be able to.

In particular, it must be ensured in an elevator system that all doors remain closed and mechanically locked before the car begins to move and while it is moving. In the case of hydraulic bumpers, for example, it must also be ensured that the buffers are fully extended before the car can be started in normal operation.

In systems of the type under consideration, the various "security points" at which the position of moving components, e.g. Doors, before the initiation of an action and possibly during the course of the same, must often be used mechanical safety switches, in particular several of which are connected in series to form a so-called "safety chain", so that the action can only be started or continued , when all safety switches or - more generally, switching devices assume a predetermined switching state.

With all electromechanical safety switches there are great problems with regard to the creation of perfect electrical contacts, since the mechanical contact of the contact elements can lead to a contact adjustment and, in addition, the setting of the switching point is difficult from the start. In addition, such electromechanical switches result in considerable wear during the course of operation and the risk of contamination. Overall, when using electromechanical safety switches, malfunctions can easily occur that force the monitored system to stop, the frequency of malfunctions in safety chains with numerous switch contacts increasing considerably. The result of this is that, for example, in conveyor systems and elevators, a large part of the malfunctions can be attributed to any switch defects.

There is a certain improvement in the situation described above when using electronic switches or sensors which can be actuated without contact, for example by approaching or moving away of a magnet. With these switches, the switching point is generally easier to set and remains stable even during longer operating times. In addition, the causes of malfunctions, which can be attributed to wear on the contact pieces and other moving components in electromechanical switches, are eliminated. (Unlike mechanical safety switches, however, there is no inevitability when actuated.) Nevertheless, it would also be important for this type of switch to check that it is working properly and, in the event of a fault, to be able to determine as easily as possible which switch in a safety chain caused a malfunction and which Chain has broken. In contrast to mechanical switches, the switching status of magnetically operated electronic switches cannot be determined optically, as is the case with typical mechanical safety switches.

A simple test option would be particularly important in elevator systems, since there are a large number of safety switches that are never operated in normal operation, but should work in an emergency. With these switches, a functional test has so far often only been carried out at large time intervals, since the parts to be monitored had to be moved for the test, which was all the more problematic the more unfavorable the switch or the part in question was accessible to a fitter for testing .

In principle, there is the possibility of individually connecting each switching device to a control system to determine the point of failure, which involves a high outlay in material and installation. The individual switching devices can also be connected to the bus Control connected and in this case be queried in the desired order with regard to their respective switching state, but the query takes more and more time with increasing number of security points.

Based on the prior art and the problems explained above, the invention has for its object to provide an improved monitoring device that enables the implementation of a reliable control for elevator and conveyor systems with a safety chain and high safety requirements with comparatively little effort.

This object is achieved in a monitoring device of the type specified at the outset according to the invention, which has contactlessly triggerable, electronic, testable switching device with control electronics, with the aid of which the state of the sensor is independent of changes in the external states of the monitoring device for test purposes by controlling the sensor can be changed with the help of the control electronics that the switching device has input and output connections for establishing data exchange connections with a higher-level control system, which are designed such that they connect the input and output connections of further switching devices for data exchange with a higher-level control system serving and thus connectable monitoring loop can be connected and by two separate sections for each ascending and returning branch of the monitoring loops are formed such that the monitoring loop each switching device twice, namely outgoing and incoming, runs through and that this enables data exchange by means of a higher-level control and that the switching device has an electronic switching device which, in the event of a safety criterion not being fulfilled, short-circuits the monitoring loop between the ascending and the returning branch in such a way that the switching device in question Status data can be transmitted to a higher-level control system in accordance with the relevant safety criterion.

It is a particular advantage of the monitoring device according to the invention or of the switching device forming this monitoring device that the electronic changeover switch of the control electronics can be used as a switch of a safety chain or a safety switch chain, as in the case of a mechanically operated switching device.

However, it is particularly advantageous if the monitoring device comprises further testable switching devices and a higher-level control, since this opens up the possibility of establishing a monitoring loop by connecting the switching devices to one another. An output of the higher-level control system can then apply a continuous signal to the input-side end of the monitoring loop, the interruption of which can be detected at the output-side end of the monitoring loop at an input of the higher-level control system. In this way, a so-called quiescent current loop can be implemented in a monitoring device according to the invention, which in a further embodiment of the invention takes the form of a continuous signal a defined pulse sequence forms a "digital quiescent current loop".

Further advantageous embodiments of the invention are the subject of further claims.

Fig. 1

ein stark schematisiertes Prinzipschaltbild einer erfindungsgemäßen Überwachungseinrichtung in Form einer einzelnen elektronischen Schalteinrichtung;

Fig. 2

eine detaillierte Darstellung der Schalteinrichtung gemäß Fig. 1; und

Fig. 3

ein schematisches Schaltbild einer eine erfindungsgemäße Überwachungseinrichtung umfassenden Steuervorrichtung für eine Aufzugsanlage.

Further details and advantages of the invention are explained in more detail below with reference to drawings. Show it:

Fig. 1

a highly schematic block diagram of a monitoring device according to the invention in the form of a single electronic switching device;

Fig. 2

a detailed representation of the switching device according to FIG. 1; and

Fig. 3

a schematic circuit diagram of a control device comprising a monitoring device according to the invention for an elevator system.

1 schematically shows a monitoring device according to the invention in the form of a non-contact electronic switching device with sensor electronics 10 and a magnetic field sensor 12, for example a Hall element, which responds to an external magnetic field. This external magnetic field can be generated, for example, by a permanent magnet 14, which is usually attached to a movable component 15 to be monitored, namely, for example, an elevator door. As long as the sensor 12 is outside the effective range of the external magnetic field generated by the permanent magnet 14, the sensor 12 supplies a signal in which an electronic (toggle) switch 48 of the sensor electronics 10, indicated by dashed lines, is held in an "unactuated" state , especially when open. If the Permanent magnet 14 then, starting from the previously described state, approaches sensor 12 to a predetermined minimum distance, then said switch is switched into its “actuated” state, in particular into its closed state, so that output A of sensor electronics 10 and thus a corresponding control signal is emitted to the switching device as a whole, which indicates that the movable component 15 with the permanent magnet 14 is in the position required for carrying out a specific action, in particular for safety reasons.

In order to create a test option for an electronic switching device of the type under consideration, which allows the proper functioning of this electronic switching device to be checked, a magnetic coil 16 is provided, which is dimensioned and arranged with respect to the sensor 12 in such a way that with its help in In the area of the sensor 12, a magnetic field can be generated, which can compensate for the effect of the magnetic field of the permanent magnet 14 present in the detection area of the sensor 12.

If the permanent magnet 14 is now in its position shown in FIG. 1 in front of the sensor 12 and the electronic switching device consequently assumes its actuated state, then with the aid of the sensor electronics 10 such an excitation current can be generated for the magnet coil 16 that the Compensate for magnetic fields of the permanent magnet 14 on the one hand and the magnetic coil 16 on the other hand in the detection range of the sensor 12, which means that the influence of the permanent magnet on the sensor 12 is canceled, so that the switching device for the duration of the control of the solenoid 16 must pass into its unactuated state if its elements are working properly. To check the proper functioning of the electronic switching device, it is therefore only necessary to determine whether, starting from the actuated state of the switching device, the unactuated state of the switching device can be brought about for the duration of the excitation of the solenoid 16. Only if this is actually the case can it be assumed that the electronic switching device and the active sensor element are functioning properly.

It is particularly advantageous if the switching device under consideration is designed in such a way that the functional test takes place before the initiation of an action monitored by the switching device, a corresponding signal being applied to an input E of the sensor electronics 10 depending on the planned action in order to have a bring about appropriate control of the solenoid 16. If necessary, the functional test can also be carried out periodically at suitable short intervals, it being possible for the clock for the test processes to be generated in the sensor electronics itself by means of a suitable clock generator.

While it was assumed above that during the functional test, the permanent magnet 14 must be in such a position that the switching device is in its actuated state, it becomes clear from the preceding explanation that the presence of the magnet coil 16 even if the sensor is located 12 is outside the area of influence of the magnetic field of the permanent magnet 14, test options are given. If the sensor 12 is not influenced by the external magnetic field of the permanent magnet 14, then The flow of an excitation current through the magnet coil 16 must result in the switching device being switched from the unactuated state to the actuated state, since in this case the magnetic field of the permanent magnet 14 which counteracts the magnetic field of the coil is missing. A functional test for the switching device can thus also be carried out, for example, when the elevator door is open when the permanent magnet 14 attached to the door is in a position that is ineffective with respect to the sensor 12.

As shown in FIG. 2, a sensor 12 can be used in the practical implementation of a switching device according to the invention for carrying out the method according to the invention, which has a Hall sensor 18 in the form of an integrated circuit with an open-drain output and a pull-up resistor 20 connected to it includes. One connection of this resistor 20 is connected to a connection terminal to which a supply voltage V _DD is present, while the other connection is connected to a circuit point 22 which forms an input of an internal control circuit 24 of the sensor electronics 10. The control circuit 24, which is part of the sensor electronics 10, supplies an output signal for a control block 26, to which a second input signal for activating the magnetic coil 16 can be fed via a signal line 28, which via a corresponding input circuit 30 with a higher-level control, namely a bus control 32 (cf. FIG. 3), can be connected and can be connected on the output side via an output circuit 34 to further sensor electronics circuits which belong to further contactless electronic switching devices.

Depending on the signals at its inputs, the control block 26 supplies a control signal by which a transistor 36 is controlled to be conductive so that a current can flow through the excitation winding 38 of the magnet coil 16, the excitation winding 38 being connected in parallel with a free-wheeling diode 40 in a conventional manner is.

In the switching device shown in FIG. 2, the sensor electronics 10 further comprises a data input line 42 and a data output line 44, these two lines each being provided with an input circuit and an output circuit. The data input line 42 represents an ascending data path starting from the bus control 32 (FIG. 3), via which the sensor electronics circuits 10 of all switching devices belonging to a safety chain are connected. The signal line 28 and the data input line 42 with their assigned input circuits thus correspond to the input E, which is only indicated schematically in FIG. 1. In a corresponding manner, the data output line 44, which corresponds to the output A in FIG. 1, provides one of the connected switching devices to the bus control 32 returning data path. The data input line 42 is connected to a receiving part 46, which samples the data running over the data input line 42 and forms an input register. The receiving part 46 is additionally provided with an input connected to the control circuit 24. A switchover device or switch 48 is inserted into the data output line 44, which is controlled by the output signal of an OR gate 50, the two inputs of which have the switching point 22 or one output of a Transmitting part 52 are connected, either the data output of the transmitting part 52, which supplies status and address signals, or connects the input side of the data output line 44 to its output side. The transmitting part 52 is connected to the control circuit 24 via a further output and a further input. As indicated in FIG. 2, the sensor electronics 10 comprises a clock generator 54 and is otherwise fed from a schematically indicated voltage supply 56, which generates the regulated supply voltage V _DD of, for example, 5 V from a possibly unregulated input voltage of 24 V. In addition to the sensor 12, the voltage V _DD is also applied to the solenoid 16.

In the switching device under consideration, the open-drain output of the Hall sensor 18 is drawn to the supply voltage V _DD via the resistor 20 in the absence of a magnetic field and to the reference potential in the presence of a magnetic field. These voltages are at the switching point 22. If an excitation current flows through the magnet coil 16 when the switching device is initially actuated, that is to say starting from a state in which the permanent magnet 14 acts on the sensor 18 and the switching point 22 is at reference potential, then this causes this Previously existing magnetic field on the sensor 18 compensated so that the voltage V _{DD is} supplied to the node 22. This signal change indicates that sensor 18 is functioning properly as the most important part of the switching device.

3 shows how the sensor electronics circuits 10.1 to 10.n are switched from n testable electronic switching devices to a safety chain and are associated with the one that forms a higher-level control Bus controller 32 are connected to actuate a switch 58 in a motor circuit 60. In detail, n sensor electronics circuits 10.1, 10.2 to 10.n are provided, to which, as explained for the switching device according to FIG. 2, a sensor 12.1 to 12.n and a magnet coil 16.1 to 16.n are assigned, each sensor cooperates with a permanent magnet 14.1 to 14.n. In the exemplary embodiment according to FIG. 3, the permanent magnets 14.1 to 14.n are each connected to a door 15.1 to 15.n as a movable component to be monitored. The individual magnetic coils 16.1 to 16.n can be activated via lines 28 and 42 for test purposes in order to determine whether the associated switching devices are working properly. In this case, a coil activation signal is applied to line 28 when a functional test is to be carried out, while the individual switching devices or sensor electronics circuits are called up via address 42 in line with the address. The line 44 provides feedback on the correct functioning of the individual switching devices and on their switching status. If all the switching devices are working properly and all the doors are in the correct position, the bus control 32, which can optionally be connected to other bus controls belonging to other safety circuits, as shown in FIG. 3 by pairs of input and output lines for the bus control 32 It is indicated that the switch 58 of the motor circuit 60 is actuated so that the motor contactor 64 located in this circuit attracts and closes the motor circuit 66 via its switch contact 64a, in which a motor 68 and a voltage source 70 are connected in series.

3 shows that the interconnected sections of line 42 and the interconnected sections of line 44 together with a cross-connection 43 between data input line 42 and data output line 44 of the sensor electronics furthest away from bus controller 32 10.n provided that the switches 48 all occupy such a position that they create a continuous connection, form a closed loop. This loop can serve as a monitoring loop, the ascending branch of which is connected on the input side to an output of the bus control 32 and the returning branch is connected at its end to an input of the bus control 32. Via this monitoring loop, the bus controller 32 can send a continuous signal, the presence of which is monitored on the returning branch of the loop, so that in the end there is a type of quiescent current loop. If the bus controller 32 instead of a simple continuous signal, e.g. a certain DC voltage level, a sequence of digital signals on the monitoring loop, then a "digital closed-circuit loop" is obtained, which offers particularly advantageous monitoring options, wherein the bus controller 32 checks whether the signal sequence received on the returning branch corresponds to the transmitted signal sequence.

The circuit arrangement shown in FIG. 3 can be supplemented in a further embodiment of the invention in that a signal converter 72 is inserted between the upper end of the ascending branch and the beginning of the descending branch in the cross connection 43 between the two branches, as indicated by dashed lines through which the sequence of digital signals arriving via the ascending branch of the monitoring loop is converted in a defined manner into a changed digital signal sequence. In particular, this also makes it possible to detect errors which are based on an undesired cross-connection between the ascending and the descending or returning branch of the monitoring loop. Such cross connections can occur, for example, in the event of short circuits in the individual sensor electronics circuits.

From the above description it is clear that the monitoring device according to the invention enables a relatively simple structure of a complete control device and ensures reliable, trouble-free operation of the same.

Claims (11)

1. Device for monitoring a control unit comprising a safety chain, in particular for elevator and conveyor systems, said monitoring device including an electronic, testable switching unit (10, 12) triggerable in a non-contacting manner and comprising a sensor (12), the state of which is detectable with the aid of said switching unit,
   characterized in that said electronic, testable switching unit (10, 12) triggerable in a non-contacting manner comprises control electronics (10), with the aid of which the state of said sensor (12) is alterable at any time for test purposes, independently of alterations in the external states of the monitoring device, by activating said sensor (12) with the aid of said control electronics (10), in that said switching unit (10, 12) comprises input and output terminals for establishing connections serving the exchange of data with a primary control (32), said input and output terminals being designed such that they are connectable to the input and output terminals of further switching units (10, 12) to form a monitoring loop serving the exchange of data with a primary control (32) and connectable to said primary control, and such that they are formed by two separate path sections for a branch ascending from said monitoring loop and a branch leading back to said monitoring loop, respectively, such that said monitoring loop passes through each switching unit (10, 12) twice, namely outgoing and incoming, and that an exchange of data by means of a primary control (32) is thereby enabled, and in that said switching unit (10, 12) comprises an electronic changeover device (48) which in the event of an unfulfilled safety criterion, short-circuits said monitoring loop between the ascending and the returning branches such that the relevant switching unit (10, 12) can transmit status data corresponding to the relevant safety criterion to a primary control (32).
2. Monitoring device as defined in claim 1, characterized in that it comprises further testable switching units (10.2 to 10.n, 12.2 to 12.n) and a primary control (32), in that the input and output terminals of said switching units (10, 12) are connected to one another to form a monitoring loop, the ascending branch thereof being connected to an output of said primary control (32) and the returning branch thereof including the changeover devices (48) of said switching units and being connected to an input of said primary control (32), and in that a continuous signal is producible for the monitoring loop by said primary control (32) at the output thereof, the interruption of said continuous signal being detectable by said primary control (32).
3. Monitoring device as defined in claim 2, characterized in that a defined sequence of pulses is producible by said primary control (32) as continuous signal, said sequence of pulses being examinable at the input of said primary control with respect to its conformity with the sequence of pulses emitted.
4. Monitoring device as defined in claim 2 or 3, characterized in that said primary control (32) comprises addressing devices for addressing a receiver part (46) of each switching unit (10, 12) individually, and in that each switching unit (10, 12) comprises a sender part (52) for supplying status information on the relevant switching unit (10, 12) to said primary control (32) at the input thereof via the returning branch.
5. Monitoring device as defined in claim 3, characterized in that the ends of the ascending branch and of the returning branch of said monitoring loop remote from the control are connected to one another via a signal converter (72) for converting the sequence of digital signals incoming via the ascending branch of said monitoring loop in a defined manner into an altered sequence of digital signals.
6. Monitoring device as defined in claim 1, characterized in that said switching unit (10, 12) comprises a magnetic field sensor (12) for monitoring the state of a mechanical locking mechanism with a displaceable permanent magnet (14).
7. Monitoring device as defined in claim 6, characterized in that a test coil (16) selectively activatable by said control electronics (10) is associated with said sensor (12) of said switching unit for generating a magnetic field compensating the magnetic field of said permanent magnet (14).
8. Monitoring device as defined in claim 1 or 2, characterized in that said control electronics (10) are designed to perform a logical information control of data fed to their input (E).
9. Monitoring device as defined in claim 1 or 2, characterized in that said control electronics (10) are designed as a test device for the logical information control of the function of their associated sensor (12).
10. Monitoring device as defined in claim 2, characterized in that the state of each sensor (12) is interrogatable individually by said primary control (32).
11. Monitoring device as defined in claim 10, characterized in that all the sensors (12) are monitorable with respect to a uniform state by said primary control (32) with the aid of a continuous signal on said monitoring loop.

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