Cylinder switch with actuator control

Abstract

According to the invention, a cylinder switch (10) is provided for arrangement on a valve-controlled working cylinder (20), comprising a single sensor element (S) arranged in a switch housing (12) which generates an electrical signal as a result of a body (M) moving past the cylinder switch (10), wherein the cylinder switch (10) is connected to a higher-level controller (PLC) via a first interface (S1) and the control of the working cylinder (20) is effected via a valve (30), wherein switching information for controlling the working cylinder (20) is transmitted from the controller (PLC) to the cylinder switch (10) via the first interface (S1), wherein the cylinder switch (10) is connected directly to the valve (30) via a second interface (S2), wherein the valve (30) can be controlled by the cylinder switch (10) via this second interface (S2),wherein the detection of the position of the body (M) in an intermediate position or in an end position is carried out by the single sensor element (S) arranged in the switch housing (12), wherein the cylinder switch (10) is adapted by means of the valve (30) to detect both end positions of the working cylinder (20).

Description

The invention relates to a cylinder switch according to claim 1.Cylinder switches are sensors that electrically sense the position of a magnet. They are used to detect the end positions or the intermediate positions of a drive, evaluate them and transmit corresponding signals to a control.The mode of operation of cylinder switches is based on the principle of magnetic field detection. A permanent magnet is attached to the piston of a cylinder, which generates a magnetic field. This field penetrates all nonferromagnetic materials, such as aluminum or plastic.For assembly, the cylinder switch is frequently pushed and fixed in a groove integrated in the cylinder. Depending on the manufacturer and design of the cylinder, the groove can have a C-groove, a T-groove or some other shape. A cylinder switch includes at least one magnetic sensor that converts the magnetic field into an electrical signal and an interface for transmitting the signals to a higher-order unit. Cylinder switches may include a display, such as an LED display, to indicate sensed conditions.Areas of application of cylinder switches can be found in automation solutions. Thus, cylinder switches can record, control, monitor and optimize the movement sequences of actuators or transmitter magnets in automated machines or systems.Usually, at least two cylinder switches are used to detect the piston position of a cylinder in the end positions or in any intermediate position without contact.DE 42 01 464 A1 discloses a device for damping a piston which is displaceable in a cylinder. To interrogate the end positions, at least one sensor means is required per end position.Furthermore, intelligent cylinder sensors are known from DE 10 2022 114 889 A1, which evaluate states and state sequences, convert them into diagnostic information and transmit appropriately conditioned information to a higher-order unit.To monitor longer lifting cylinders, a cylinder switch is frequently attached at each end position. It is complicated that each individual cylinder switch has to be connected by means of a cable to an input module of a system control unit or to a distributor unit, which provides a corresponding cabling outlay.A valve which regulates the medium of a cylinder has hitherto to be connected to an output module of the installation control unit in order to obtain control signals. Connecting to similar interfaces entails a corresponding risk of confusion and complicates the wiring and startup of such working cylinders.If the installation is subsequently modified, for example during changes, the problem frequently arises that too little space is available for the cabling or the controller has too small a number of plug-in locations, which leads to the installation controller having to be replaced or components having to be extended in a complicated manner, which is costly and costly.This can be taken into account in the plant planning and a reserve can be scheduled. However, the provision of a reserve also leads to, for example, switch cabinets turning out to be larger and more space being reserved.It is an object of the invention to provide a simplified cylinder switch with which the start-up and the monitoring of a working cylinder is facilitated. In particular, the cabling outlay for connecting a working cylinder to a system controller is to be reduced. Furthermore, the cylinder switch is intended to simplify the cabling outlay which arises when connecting a control valve for actuating a working cylinder.The object is achieved according to the invention by the features of claim 1. Advantageous embodiments of the invention are specified in the dependent claims.According to the invention, there is provided a cylinder switch for mounting on a valve-controlled power cylinder, comprising a sensor element disposed in a switch housing of the cylinder switch which generates an electrical signal as a result of a body moving past the cylinder switch. The cylinder switch is connected to a superordinate control via a first interface. The actuation of the working cylinder takes place exclusively via a valve. The switching information for activating the working cylinder is transmitted from the controller to the cylinder switch via the first interface. According to the invention, the cylinder switch is directly connected to the valve via a second interface, so that the valve can be controlled by the cylinder switch via this second interface.Advantageously, the cylinder switch has an extended instruction set ensuring the communication of the controller with the cylinder switch and the communication of the cylinder switch with the valve.Furthermore, the cylinder switch has a driver circuit which provides additional current for activating the valve.According to the invention, the second interface is either designed in the form of a plug connection, a cable connection, a terminal block or as a radio connection between valve and cylinder switch.In a further embodiment of the invention, the device cable of the cylinder switch is extended by a corresponding number of wires, so that the cable is connected to a Y splitter or, by connecting the corresponding wires to the valve, so that the switching information is transmitted from the cylinder switch via this cable connection on a direct path to the valve.According to the invention, a cylinder switch is provided which is extended such that a valve can be connected to the cylinder switch and this valve can be controlled by the cylinder switch. For this purpose, the instruction set of the cylinder switch is extended such that the system controller can transmit control information to the cylinder switch via a single interface. Furthermore, the cylinder switch is extended by a driver circuit in order to provide the necessary current for activating the valve. The cylinder switch has an interface with which the valve can be connected to the cylinder switch. For this purpose, a plug, a terminal strip or a cable can be integrated.The invention is explained in more detail below on the basis of exemplary embodiments with reference to the drawings.They show schematically: FIG. 1 is a conventional wiring arrangement of a power cylinder; FIG. 2 shows a wiring arrangement according to the invention of a working cylinder; FIG. 3 shows the cylinder switch according to the invention in a schematic overview.In the following description of the preferred embodiments, like reference numerals designate like or comparable components.FIG. 1 shows a conventional arrangement, generally known from the prior art, for connecting a working cylinder 20 to a system controller PLC. The working cylinder 20 shown in a sectional view has a piston 25 with a cylinder rod and a first and a second cylinder switch 10. A magnet M is mounted on the piston 25. With the sensor element S, the magnetic field change caused by the movement of the magnet M with the plunger 25 is detected and converted into an electric signal. The presence of the magnet can be detected within a respective sensor detection range, as well as the approach and the position of the magnet, and thus the respective position of the working cylinder 20, can be determined. The cylinder switches 10 are mounted on the housing of the working cylinder 20 in the end positions of the cylinder 20, respectively. Each cylinder switch 10 has a sensor element S which is arranged in a switch housing 12. Each of these cylinder switches 10 is connected by means of a separate cable to an input module I / O of the installation controller PLC. The valve 30, for example the pilot valve shown here, which regulates the compressed air supply of the cylinder and thus the actuation of the working cylinder 20, is connected to the system controller PLC via an output module I / O. It is disadvantageous that the signals of the cylinder switches 10 and the signals of the valve 30 must be separately connected, mapped and merged again via the respective modules I / O of the system controller PLC.FIG. 2 shows a wiring arrangement according to the invention of a working cylinder 20 for connecting a working cylinder 20 to a system controller PLC. A cylinder switch 10 is arranged on the working cylinder 20. The cylinder switch 10 has a sensor element S which generates an electrical signal as a result of a magnet M moving past the cylinder switch 10. The cylinder switch 10 is connected via a first interface S 1 to a superordinate controller PLC. The actuation of the working cylinder 20 takes place exclusively via a valve 30. According to the invention, the cylinder switch 10 is directly connected to the valve 30 via a second interface S 2, so that the valve 30 can be controlled by the cylinder switch 10 via this second interface S 2. As shown, the drive, consisting of the working cylinder 20, valve 30 and cylinder switch 10, is connected to the control PLC by a single cable. Therefore, according to the invention, only one I / O module is required for connecting the drive to the PLC, which is advantageous since I / O modules on the controller PLC can be saved as a result and the cabling outlay and faults which can occur during the cabling are reduced overall. The connection of the drive to the controller PLC is thereby considerably simplified.FIG. 3 shows the cylinder switch 10 according to the invention in a schematic illustration. In addition to a central logic unit μC, the cylinder switch 10 has a sensor element S for detecting the magnetic field change, a memory 60, an extended instruction set 40 and a driver circuit 50. The extended instruction set 40 enables the cylinder switch 10 to receive signals from the controller PLC, process the signals, and control the valve 30 via the driver circuit 50. The driver circuit 50 provides the necessary current for activating the valve.Merging ACTUAL and TARGET states into the cylinder switch 10 results in the following advantages:The wiring and thus the connection to the controller PLC is simplified. Only one cable per drive is required for the control PLC. This makes it possible to save cables for control PLC and I / O modules on the control PLC. When using M12 cable boxes, wiring faults can also be avoided in particular.The manufacturer of the drive can already equip it with accessories and pre-cable them, so that the installation engineer or assembly technician only has to connect a cable and a control medium for controlling the valve. The start-up is thereby simplified.The control and programming are simplified. The drive, consisting of the working cylinder 20, valve 30 and cylinder switch 10, occurs as a unit. The output signals to the actuators and end position signals of the cylinder switches 10 do not have to be assigned. The controller PLC can thus deactivate or activate a drive without the output signal having to be mapped to an I / O module.Advantages are also found in self-diagnosis. The cylinder switch 10 knows not only the ACTUAL state, i.e. the position or the end position, but also the DESIRED state, i.e. the control specification of the working cylinder 20. Advantageously, the DESIRED and ACTUAL values of a drive are transmitted via the same channel and do not have to be mapped and merged separately. Since the cylinder switch 10 knows the state of the valve 30, the cylinder switch 10 can assign the end positions in a correspondingly automated manner, so that an end position can be linked to the activated valve and an end position to the deactivated valve. As a result of this assignment, it does not matter in which orientation, i.e. cable departure of the cylinder switch 10 in the process direction or counter to the process direction, the cylinder switch 10 is arranged on the working cylinder 20.Knowing the DESIRED state allows the cylinder switch 10 to make a comparison with the ACTUAL value and thus perform an extended diagnostic. If the ACTUAL VALUE does not change after a SETPOINT value change, then missing energy, i.e. compressed air is missing or cable to the valve 30 is missing, or blocking of the drive can be reported. If the time from the setpoint change to the actual value change is monitored, then a changed operating pressure or a sticking of the application, for example by inadequate cleaning, can be deduced. With the time measurement from a change in the setpoint value until the setpoint value is reached until the setpoint value is equal to the actual value, it is possible to proceed to a changed operating pressure, to wear on the drive or to overload of the drive. With corresponding knowledge of the application, these diagnostic data can be used to plan cleaning, maintenance or the replacement of plant parts or to detect fault cases.By connecting the valve 30 to the cylinder switch 10, a learning function can be implemented in the cylinder switch 10. For example, by an auto-attach command, the valve 30 may be alternately activated and deactivated by the cylinder switch. Since the cylinder switch 10 recognizes the end positions, this information can be automatically assigned to the state of the drive.Because a cylinder switch 10 typically has faster data acquisition than a plant controller PLC, the cylinder switch 10 can respond much more quickly and sensitively to changes in response time and run time. Wear and contamination can be detected early with this information, rejects and machine downtime can be avoided and better planned.In summary, the wiring outlay and wiring errors are minimized with a cylinder switch 10 with actuator control. Because of a single communication interface with the controller PLC, less hardware is required, so that with a constant number of I / O modules, more drives can be connected to a controller PLC on a controller PLC. Merging the signals onto the cylinder switch 10 allows for an extended diagnosis. The drive is recognized as a stand-alone unit by the controller PLC and is treated in this way. Unnecessary data traffic between valve 30 and the IO module of the controller PLC can thereby be avoided.The advantages of the invention lie in particular in simplifying the cabling outlay for connecting a working cylinder 20 to a system controller PLC and, by combining functions, equipping the cylinder switch 10 in such a way that control signals from a superordinate controller PLC are detected by the cylinder switch 10, are further processed and are used for direct actuation of a control valve 30. By directly controlling the valve 30 via the cylinder switch 10, wiring errors are eliminated and the wiring outlay is reduced to a minimum.List of reference characters10 Cylinder switch 12 Switch housing 20 Working cylinder 25 Piston 30 Valve 40 Expanded instruction set 50 Driver circuit 60 Memory PLC Superordinate controller I / O module M Body S Sensor element S 1 First interface S 2 Second interface T 2 Driver circuit μC Logic unit

Claims

Cylinder switch (10) for arrangement on a valve-controlled working cylinder (20), having a single sensor element (S) which is arranged in a switch housing (12) which generates an electrical signal as a result of a body (M) moving past the cylinder switch (10), the cylinder switch (10) being connected via a first interface (S1) to a superordinate controller (PLC) and the working cylinder (20) being actuated via a valve (30), switching information for actuating the working cylinder (20) being transmitted from the controller (PLC) to the cylinder switch (10) via the first interface (S1), the cylinder switch (10) being connected directly to the valve (30) via a second interface (S2), wherein the valve (30) can be controlled by the cylinder switch (10) via this second interface (S2), characterized in that the position of the body (M) is detected in an intermediate position or in one of the end positions by the individual sensor element (S) which is arranged in the switch housing (12), wherein the cylinder switch (10) is configured by means of the valve (30) to detect both end positions of the working cylinder (20).Cylinder switch (10) according to Claim 1, wherein the cylinder switch (10) has an extended instruction set (40) with which the communication of the controller (PLC) with the cylinder switch (10) and the communication of the cylinder switch with the valve (30) are ensured, and wherein the cylinder switch (10) is additionally provided with the setpoint value in addition to the detected actual value, wherein the cylinder switch (10) is designed in such a way that diagnostic data can be determined by comparing the actual values with the setpoint values in order to plan maintenance or replacement intervals or in order to be able to detect fault cases at an early stage.The cylinder switch (10) of any preceding claim, wherein the cylinder switch (10) includes a driver circuit (50) that provides additional current to activate the valve (30).Cylinder switch (10) according to one of the preceding claims, wherein the second interface (S2) is either in the form of a plug connection, a cable connection, a terminal block or as a radio connection between valve (30) and cylinder switch (10).Cylinder switch (10) according to one of the preceding claims, wherein the device cable of the cylinder switch (10) is extended by a corresponding number of wires, so that the cable is connected to a Y splitter or by connection of the corresponding wires to the valve (30), so that the switching information is transmitted from the cylinder switch (10) via this cable connection on a direct path to the valve (30).

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