Classifications

• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01H—ELECTRIC SWITCHES; RELAYS; SELECTORS; EMERGENCY PROTECTIVE DEVICES
  • H01H47/00—Circuit arrangements not adapted to a particular application of the relay and designed to obtain desired operating characteristics or to provide energising current
  • H01H47/002—Monitoring or fail-safe circuits

Definitions

• the present invention relates to abutschaltvor- direction for safely switching off an electrical load, especially in an automated system operated, with at least one input for supplying a message signal from a reporting devices, with an evaluation and control unit, and with at least one switching element, of the Evaluation and control unit is controlled to interrupt a power supply path to the consumer,
• a safety switching device is known for example from DE 100 11 211 Al.
• the known safety switching device is a so-called safety switching device, i. a compact device unit, which is generally provided for installation in a control cabinet of an automated system and which typically has a (at least largely) defined scope of functions.
• safety switching devices in particular for evaluating emergency stop buttons, safety doors, safety mats, two-hand switches, limit switches and other position switches as well as other safety-related signaling devices.
• the evaluation and control unit of this safety switching devices is usually set to the evaluation or monitoring of one or more signaling devices of certain types. Depending on the signaling device, the evaluation and control unit generates a control signal with which the power supply path to the consumer can be interrupted in fail-safe manner when the signaling device requests a safety shutdown.
• the at least one switching element is often a positively driven relay, ie an electromechanical switching element which typically has a plurality of normally open contacts and at least one normally closed contact.
• the normally closed contact and the normally open contacts are coupled to one another via a mechanical forced operation so that the normally closed contact and the normally open contacts can not be closed at the same time.
• the closing contacts are closed by the evaluation and control unit and they serve to interrupt the power supply path to the electrical load, if this is necessary due to a safety function.
• a signal is typically fed back via the normally closed contact to the evaluation and control unit so that it can monitor the switching position of the make contacts due to the forced operation.
• the evaluation and control unit can recognize, for example, when a normally open contact is welded and stuck in its closed (or open) switching position. Due to this property, positively driven relays have been well proven in the field of safety switching devices and have been widely used for many years. However, positively driven relays have the disadvantage that they are relatively expensive and relatively large.
• the aforementioned DE 100 11 211 Al proposes a safety switching device in which at least two electronic switching elements are used to interrupt the power supply path to the consumer.
• transistors are proposed as switching elements of the safety switching device. This makes the new safety relay smaller and less expensive. be realized at a lower cost.
• the known from DE 100 11 211 Al safety switching device differs not only by the use of transistors instead of forcibly guided 1 relay from the mass of conventional safety relays. Another difference is that the transistors in the safety switching device from DE 100 11 211 A1 each generate a potential-related output signal, whereas safety switching devices with positively driven relays typically provide potential-free outputs. The latter means that the safety switching device does not deliver an output signal per se, but only switches on a potential connected from the outside or not.
• the known from DE 100 11 211 Al safety switching device generates a "own" output potential, which is based on a mass of the safety switching device.
• Safety relays with potential-free outputs are widely used in practice because this technique has been used for many years. For reasons of spare part compatibility, it is desirable to continue to have safety switching devices with potential-free outputs.
• potential-free outputs have the advantage that they can switch currents and voltages in the load circuit over a very wide range of variation.
• the switching capacity in the safety switching device from DE 100 11 211 Al is limited by the properties of the transistors used. Therefore, there is still a need for safety switching devices with potential-free outputs.
• a safety switching device of the type mentioned in which the switching element is a changeover switch with at least two mutually alternative switching paths, wherein a first switching path in the power supply path to the consumer, and wherein a second (alternative) switching path leads to a monitoring unit.
• the at least one switching element of the safety switching device may be an electromechanical switching element, in particular a three-terminal alternating relay, which provide two mutually alternative switching paths.
• the at least one switching element can also be realized as a semiconductor component or with the aid of semiconductor components.
• the at least one switching element can be a single component, which is the at least two. alternative, switching paths. or it may be a more complex circuit structure, such as multiple simple transistors and / or relays.
• An essential aspect of the invention is the feature that the at least two switching paths of the switching element are alternative to one another, ie the switching paths have a common root, but only one of the switching paths is closed at a time.
• the monitoring unit is an arbitrary part of the safety switching device, with the help of which it can be determined whether the second switching path of the at least one switching element is closed or not.
• the new safety switching device allows a small-scale implementation. In this case it is sufficient to exclude the assumed error with the help of a suitable functional test.
• the new safety switching device does not require positively driven relays to establish a feedback circuit that allows a safe conclusion to the interruption of the power supply path to the consumer. Since simple, non-positively driven relays are much smaller and cheaper than positively driven relay, the new safety switching device can be realized smaller and cheaper than conventional safety switching devices. This also applies, in particular, if a "simple" changeover relay is used as the at least one switching element, but on the other hand, the new safety switching device can be realized with the aid of such changeover relays in such a way that it has potential-free outputs The new safety switching device can therefore be functionally compatible with conventional safety This facilitates the replacement of conventional safety switching devices in an existing plant with the new safety switching device, and enables switching in the load circuit over a wide current, voltage and frequency range.
• a safety switching device can also be realized with potential-related outputs.
• the advantage of the potential-free outputs is lost, the use of a changeover switch allows in this case, a very simple and reliable statement about whether the power supply path to the electrical load is interrupted or not. Therefore, a safety switching device can be realized easily and therefore cost-effectively in these cases.
• the changeover switch is designed such that it closes the second switching path as Defaultschalt- path.
• the first switching path which lies in the power supply path to the consumer, only closed when the changeover switch has been selectively brought into the first switching position.
• the change-over switch falls by itself in the default state- back, - if there is no error des- changeover switch.
• the evaluation and control unit and the monitoring unit are formed together to perform a functional test of the changeover switch before closing the power supply path. It is preferred if the monitoring unit with the evaluation and control unit is connected to possibly prevent a closing of the second switching path.
• the combination of these two embodiments ensures that the power supply path to the consumer can only be closed when the changeover switch in the (preferably immediately before taking place) function test works properly.
• the power supply path to the consumer can be at least once again interrupted, which can be achieved, for example, when using diverse, redundant switching elements and the constructive avoidance of common cause errors
• a safety switching device with the the (highest) safety category 4 of the European standard EN 954-1 or a comparable standard according to PR EN ISO 13849-1 or IEC 61508 can be achieved.
• the technical complexity is relatively low compared to previous safety switching devices, so that the high safety standard can be achieved more cost-effectively.
• the two embodiments can also be implemented independently or separately from one another.
• the functional test includes the generation of a test signal which is routed via the second current path.
• the test signal is selected so that it is in itself unable to drive a consumer connected to the current path.
• the test signal may include one or more short pulses whose pulse duration is shorter than the response time of an applied pulse. closed consumer.
• the test signal may have an amplitude, a frequency or another signal parameter that can not be processed and / or detected by the consumer.
• the safety switching device includes a filter unit which is designed to filter or suppress the test signal at or before the connection point for the consumer. This avoids influencing the consumer by the test signal.
• the monitoring unit is at least partially integrated in the evaluation and control unit.
• This embodiment is particularly preferred if a microcontroller or microprocessor is an essential element of the evaluation and control unit, since the function of the monitoring unit can then be implemented very easily there.
• the new safety switching device includes at least two changeover switches whose first current paths are arranged in series with one another
• the two series-connected first current paths provide a redundancy that allows a shutdown of the consumer even in the event of failure of one of the changeover switches.
• the arrangement of the first current paths in series is a particularly simple and cost-effective implementation.
• the safety switching device includes at least two changeover switches whose second current paths are arranged in series with one another. Preferably, each changeover switch is independent of the other switchable.
• This embodiment is preferred because this allows the monitoring and the functional test for the changeover switch can be realized very easily and with few components.
• the at least one changeover switch is an exchange relay.
• An interchangeable relay in the sense of this embodiment is an electro-mechanical component having at least three terminals, one of the three terminals being a common terminal for both alternative current paths, while the second and third terminal are each associated with only one of the alternative current paths.
• Changeover relay of this type are available as standard components cost, significantly smaller and cheaper than positively driven relays, and therefore they allow a particularly small and inexpensive safety switching device with potential-free outputs.
• the at least one changeover switch includes a semiconductor switching element.
• the changeover switch may be a single semiconductor switching element having two mutually alternative current paths or also a circuit arrangement of, for example, a plurality of transistors, which may be at least two alternatives Rungs provides.
• the advantage of this embodiment is that the at least one switching element in integrated technology and thus can be realized even smaller and cheaper than with a relay.
• the monitoring unit is designed to be multi-channel redundant.
• the evaluation and control unit is designed to be multi-channel redundant.
• This embodiment is particularly advantageous if the new safety switching device for category 4 applications of the European standard EN 954-1 or similar applications is to be used.
• the requirements placed on the intrinsic safety of the safety switching device can be met particularly easily and reliably with a multi-channel redundant structure.
• FIG. 1 shows a robot as an example of an automated system with the new safety switching device
• Figure 2 is a schematic representation of a first embodiment of the neweschaltvorrich- device
• Figure 3 shows several timing diagrams for explaining the operation of an embodiment of the new safety switching device.
• FIG. 1 an automated system in which the new safety switching device is used is designated in its entirety by the reference numeral 10.
• the plant 10 here includes a robot 12 whose working space is secured by a protective fence with a protective door 14.
• the open or closed position of the protective door 14 is detected with a protective door sensor 16.
• the safety door sensor includes a first part 16a attached to the movable part of the safety door 14 and a second part 16b on the fixed frame of the safety door 14.
• the first part 16a includes a transponder which is only accessible from the second safety door Part 16b (reader) can be detected and evaluated.
• the invention is not limited to this kind of protective door sensors and, moreover, not to safety door sensors as display devices.
• the invention can be equally used with other signaling devices, especially emergency stop buttons, as well as speed sensors, light barriers and other.
• Reference numeral 18 denotes a safety switching device according to the present invention. It serves to switch off the robot 12 when the protective door 14 is opened.
• the system 10 is also shown here with an emergency stop button 20 as a further reporting device.
• the emergency stop button 20 is evaluated with another safety switching device 22 according to the present invention.
• the safety switching devices 18 and 22 have in the embodiment shown each potential-free outputs (will be explained in more detail below with reference to Figure 2), which are connected in series with each other to construct a logical AND operation.
• two contactors 24, 26 are arranged, whose normally open contacts are in series with each other in a power supply path 28 to the robot 12.
• the working voltage 30 is for example 24 volts and is looped in this embodiment via the series-connected output contacts of the safety switching devices 18 and 22 to the shooters 24, 26.
• the safety switching devices 18, 22 interrupt the current path via which the input circuits of the contactors 24, 26 are connected to the working voltage 30. As a result, the shooters 24, 26 fall off, the robot 12 is turned off.
• the contactors 24, 26 and (indirectly) the robot 12 are thus consumers in the context of the present invention.
• the system 10 is shown here in a simplified manner.
• here are just two simple Safety circuits for switching off the robot 12 shown.
• the contactors 24, 26 typically still have positively-open contact contacts returned to at least one of the safety switching devices 18, 22 to prevent the robot 12 from turning on when one of the contactors 24, 26 is welded.
• an operation control (not shown) is typically provided which controls the normal operation of the robot 12.
• FIG. 2 shows the safety switching device 22 in further details.
• the safety switching device 18 can in principle be constructed in the same way, or also have a two-channel evaluation and control unit as well as potential-free outputs of conventional design.
• the components of the safety switching device 22 are arranged in a conventional manner in a compact device housing 36.
• the housing 36 has connections, for example in the form of screw or spring terminals.
• two ports are referred to, both of the ._Not-off ⁇ Tas-ters here for turning -Schlitis- - 20 also serve as for supplying a supply voltage 42 for the safety switching apparatus 22nd
• the supply voltage 42 is shown here as a DC voltage, and it is connected via one NC contact of the emergency stop button 20 to the terminals 38, 40.
• the voltage 42 could in principle also be an alternating voltage.
• Reference numerals 46, 48 designate two further connection terminals, to which a series circuit comprising a start button 50 and two normally closed contacts 52, 54 is connected.
• the normally closed contact 52 belongs to the contactor 24 from FIG. 1 and is forcibly guided with the normally open contacts of the contactor 24. In the same way, the normally closed contact 54 is forcibly guided with the normally open contacts of the contactor 26.
• the safety switching device 22 is shown here with a total of four switching elements 56, 56 ', 58, 58'.
• the switching elements 56, 58 and 56 ', 58' are each arranged in series with each other, and they form two power supply paths, via which the two contactors 24, 26 can be excited.
• the second power supply path with the switching elements 56 ', 58' is shown only partially for reasons of clarity, namely without the details of the control of the switching elements 56 ', 58'. However, the control of the switching elements 56 ', 58' takes place in the same way as the control of the switching elements 56, 58. Therefore, the following explanations equally apply to the switching elements 56 ', 58', unless otherwise stated.
• the switch elements 56, 58 are implemented here as changeover switches. Each switching element 56, 58 has three terminals 60, 62, 64, which are designated here only for switching element 56 for reasons of clarity.
• the three terminals 60, 62, 64 form two mutually alternative switching paths.
• a first switching path 66 extends between the terminals 62 and 64 (shown in dashed line in FIG. 2).
• a second, alternative switching path 68 extends from port 60 to port 64 (shown in solid line). Of the Terminal 64 thus forms a common root of the alternative switching paths 66, 68. Only one of the switching paths 66, 68 can be closed at a time. The other one is open in this case.
• the changeover switches 56, 58 in one embodiment of the invention are changeover relays, each with a contact that is switched between the terminals 60, 62. In further embodiments, however, the changeover switches can also be realized as or at least with the aid of semiconductor switching elements.
• the terminal 62 of the switching element 56 is connected to a terminal 70 on the housing 36 of the safety switching device 22.
• the terminal 62 of the switching element 58 is connected to an external terminal 72 of the safety switching device 22.
• the roots 64 of the two switching elements 56, 58 are connected in series with each other.
• the first switching paths 66 of the two switching elements 56, 58 provide a power supply path between the terminals 70, 72 of the safety switching device 22, which may be closed or interrupted depending on the switching position of the switching elements 56, 58.
• "make-the-switching ELEMENTS 56 ', 58' a second power supply path between terminals 74, 76 of the safety switching device 22 ready.
• the contactors 24, 26 are connected in the application according to FIG.
• the working voltage 30 is applied, which is possibly looped through the safety switching device 18 in the same manner as described here.
• the second switching paths 68 of all four switching elements 56, 56 ', 58, 58' are connected in series in this embodiment, and this series circuit is connected to a monitoring unit, which is designated in Figure 2 by the reference numeral 78.
• the monitoring unit 78 may have two channels, which is indicated schematically in FIG. However, it is also possible to design the monitoring unit 78 in one channel.
• the task of the monitoring unit 78 is to feed a test signal 80 into the series connection of the second switching paths 68 of the switching elements 56, 58, 56 ', 58'. If the monitoring unit 78 can read back the test signal 80 via the said switching paths, this means that all the switching elements are in the switching position shown in FIG. The power supply paths to the shooters 24, 26 are therefore interrupted.
• the monitoring unit 78 is connected to a microcontroller 82, which represents an evaluation and control unit in the sense of the present invention.
• a microcontroller 82 represents an evaluation and control unit in the sense of the present invention.
• the microcontroller 82 is configured to adjust the switching position of the switching elements 56, "5_8 _, __ 56_ ', _ 58'. He also performs in the manner described below, functional tests to check the switching function of the switching elements 56, 58, 56 ', 58'.
• the switching elements 56, 58 need to switch a supply voltage, which is applied to a line 84 and a capacitor 86.
• the supply voltage 84, 86 corresponds here largely to the supply voltage 42, at the terminals 38, 40 of the safety switching device 22 is applied.
• the voltage on the line 84 is passed through the input circuit of the switching elements 56, 58 and in each case one transistor 90, 92. With the aid of the transistors 90, 92, the microcontroller 82 can close or interrupt the excitation circuit to each switching element 56, 58. When the excitation circuit is closed and a supply voltage across the capacitor 86 and the line 84, which is higher than the starting voltage of the switching elements 56, 58, switch the changeover switch to the first switching path 66.
• the switching elements fall back into their default switching position, in which the second switching path 68 is closed. The power supply paths to the shooters 24, 26 are then interrupted.
• Reference numeral 88 denotes a voltage and reset circuit. This includes a voltage regulator (not shown separately), which generates an individual supply voltage for the microcontroller 82 from the general supply voltage 42. In addition, the voltage and reset circuit 88 ensures that the _Mikrocpntroller 3.8. after every. Voltage return at the terminals 38, 40 starts in a defined manner (reset function). Therefore, in one embodiment, the voltage and reset circuit still includes a pulse generator (not shown separately) connected to a reset input of the microcontroller 82. The supply voltages for the microcontroller 82 and for the switching elements 56, 58 are thus both generated from the supply voltage 42, which at the input of the safety switching device 22 is present.
• a decoupling network 94 For decoupling of the two internally separated supply voltages, a decoupling network 94 is provided, which in the present embodiment includes a diode and a resistor 95, which together with the capacitor 86 form an RC element.
• the resistor 95 determines the charging time until fully charged the capacitor 86. Therefore, the RC element of the resistor 95 and the capacitor 86 forms a timer, which ensures that the supply voltage for the switching elements 56, 58 only with a certain delay, measured from the application of the supply voltage 42 to the terminals 38, 40, is reached.
• the reference numeral 96 denotes a so-called watchdog, which includes a second timer.
• the watchdog 86 serves on the one hand to monitor the function of the microcontroller 82 in a conventional manner. For this purpose, the watchdog 96 waits for regularly recurring pulses which have to be supplied by the microcontroller 82.
• the watchdog 86 is connected to a plurality of AND gates 98, by means of which it can prevent transmission of the control signals from the microcontroller 82 to the transistors 90, 92.
• the activation of the _ Wegijnmaschine._56.,. _.5-8. takes place in this embodiment diversified, that is, with mutually different control signals.
• the control of the switching element 56 (and the switching element 56 ') takes place here with a dynamic control signal (defined pulse train), which provides the microcontroller 82 at an output 100.
• the control signal 100 is connected via an AND gate and a capacitor 102 to the.
• the transistor 90 is only conductive when the microcontroller 82, the pulse train aum Output 100 is generated at the intended frequency and amplitude, and when the watchdog 96 switches this pulse train to the capacitor 102.
• the switching elements 58, 58 ' are controlled by the microcontroller 82 with a static signal 104.
• the switching elements 56, 58 could also be respectively controlled with a dynamic or in each case a static signal, wherein it is generally preferred if the control signals 100, 104 differ from each other.
• the changeover switches 56, 58 remain in the excited (first) switching position 66, although the input circuit is de-energized (not driven).
• the changeover switches 56, 58 do not go into the first switching position 66 despite excitation of the input circuit, but remain in the second default switching position 68.
• the monitoring unit 78 testing the switching function of the changeover switches 56, 58 together with the microcontroller 82 before the power supply path to the load is closed. For this purpose, the monitoring unit 78 generates the test signal 80 and feeds it in the series connection of the second switching paths 68 a. If all connected changeover switches are in their de-energized default state, the monitoring unit 78 must be able to read back the test signal 80. In the next step, for example, the changeover switch 56 is switched over by the microcontroller 82. The test signal 80 may now no longer be read back if the switching of the changeover switch worked properly and no short-circuit between the terminals 60, 62, 64 is present.
• the top course of time 110 shows the application of the supply voltage 42 of the safety switching apparatus 22, either on power of the system or during the closing of the emergency stop button 20. It is assumed that the emergency stop button 20 at a time t 2 is actuated, so that the supply voltage 42 is disconnected from the safety switching device 22.
• the second time course 112 shows the supply voltage for the microcontroller 82, which is generated with the aid of the voltage and reset circuit 88.
• the microcontroller 82 carries out internal functional tests, as is known from the operation of microcontrollers in safety switching devices.
• the third time course 116 shows the course of the supply voltage to the exciter circuits of the switching elements 56, 58.
• the supply voltage increases here at the beginning slower, which is due to the timing of the RC element 95, 86.
• the dimensioning of the components is selected so that the supply voltage to the switching elements 56, 58 only fully applied when the microcontroller 82 has completed its internal self-tests.
• the fourth time profile 118 is the output signal at the watchdog 96. With this signal, the outputs 100, 104 of the microcontroller 82 are switched through to the transistors 90, 92 at the switching elements 56, 58. Only from the time t 2 , the microcontroller 82 is thus able to control the switching elements 56, 58.
• the fifth course shows the test signal 80, which is fed by the monitoring unit 78 into the circuit of the second switching paths 68.
• control signals 100 and 104 for the switching elements 56, 58 are shown.
• a control signal for a period of time 120 and 122 respectively activated, wherein the periods 120, 122 are offset from one another.
• the control signals in the time periods 120, 122 are at the same time as the test signal 80. If the test signal 80 can no longer be read back by the monitoring unit 78 during the time periods 120 and 122, which is indicated schematically in FIG. 3, the switching was the corresponding switching element 56, 58 successfully.
• the microcontroller 82 may switch the switching elements 56, 58 to their first switching position 66 and thereby close the power supply paths to the contactors 24, 26 (time t 3 ).
• the bottom diagram finally shows the curve 124 of the working voltage 30 at the input circuits of the contactors 24, 26.
• the contactors 24, 26 can be applied from the time t 3 , the robot 12 can go into operation. If at time t x of the emergency stop switch is activated 20, falls (after a not considered here discharge time for the capacitor 86), the supply voltage for the switching elements 56, 58 away. In addition, the control signals 100, 104 for the switching elements 56, 58 are omitted. Both events cause the power supply path to the contactors 24, 26 to be interrupted.
• the functionality of the monitoring unit 78 may be at least partially integrated into the microcontroller 82. It is preferred, for example, if the test signal 80 is coupled by the microcontroller 82 via an optocoupler, a capacitive or an inductive coupling in the monitoring circuit of the second switching paths.
• the designated here as a monitoring unit 78 part can then, for example, include the optocoupler or a transformer.
• embodiments of the invention may include that the changeover switches 56, 58 each have a plurality of parallel switch contacts. In this case, the readback paths of the monitoring unit 78 can be performed in parallel.
• the changeover switches 56, 58 have their own monitoring unit 78, which generates a test signal which is individual for the respective changeover switch.
• the plurality of monitoring units may then be connected to the microcontroller 82 to report the results of the functional tests to the microcontroller 82.
• the second switching paths of the changeover switches 56, 58 may be connected in series with each other, while the second switching paths of the changeover switches 56 ', 58' form a second series circuit formed separately from the series connection of the changeover switches 56, 58.
• the present invention can also be implemented in safety switching devices which have a "conventional" two-or multi-channel evaluation and control unit, as shown, for example, in DE 100 11 211 A1.
• the implementation shown in the above embodiment is here only a particularly preferred embodiment, but also taken in itself represents an inventive development of known safety switching devices.

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• Keying Circuit Devices (AREA)
• Electronic Switches (AREA)
• Push-Button Switches (AREA)
• Safety Devices In Control Systems (AREA)
• Electrical Discharge Machining, Electrochemical Machining, And Combined Machining (AREA)

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• 2005
  • 2005-03-22 DE DE102005014125A patent/DE102005014125A1/de not_active Withdrawn
• 2006
  • 2006-02-18 DE DE502006006977T patent/DE502006006977D1/de active Active
  • 2006-02-18 EP EP06707069A patent/EP1861860B1/fr active Active
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  • 2006-02-18 WO PCT/EP2006/001484 patent/WO2006099925A1/fr active Application Filing
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