JPS6318397B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a switch device for configuring a centralized control system using multiplex transmission.

Centralized control systems centered on sequence controllers and control computers are widely used in various plants. In this type of system, various input devices such as limit switches, photoelectric switches, proximity switches, level switches, temperature switches, pressure switches, etc. are connected to a central control device using separate signal lines. The amount of wiring connecting input devices and central equipment has become enormous and extremely complicated, which not only becomes a major factor in high costs, but also significantly reduces the workability of wiring work and maintenance, and even makes it difficult to easily change specifications. There are inconveniences such as the need for large-scale wiring work.

Various types of multiplex transmission equipment are known that transmit information from multiple systems over a single line, and there are examples of these multiplex transmission equipment being used in control systems for plants, etc. The situation is exactly the same as above, where the control device and the central control device are connected by a multiplex transmission device, and a large number of input devices are connected to each terminal control device with separate wiring.

The basic purpose of this invention is to solve the problem of the large and complicated wiring connecting a large number of input devices and control devices in the above-mentioned control system, and to develop a switch that can achieve this purpose. It provides equipment.

Hereinafter, one embodiment of the present invention will be described in detail based on the drawings.

1 and 2 show the mechanical structure of a limit switch to which the present invention is applied, and FIG. 3 is a block diagram showing the electrical structure built into this limit switch.

First, the electrical configuration will be explained based on FIG. A pair of input/output terminals 1 and 2 are connected to a power supply line and multiplex transmission line L during use, and this line L is connected to an external DC power supply (not shown), and the limit switch is connected via the line L. In addition to supplying driving power to the internal circuit, line L is also connected to an external multiplex transmission control device (not shown), and signals of predetermined frequencies (referred to as ₁ and ₂ ) sent from this multiplex transmission device are connected to line L. Superimposed on the power supply voltage.

The power supply circuit 3 is a circuit that removes signal components superimposed on the DC voltage of the line L and applies a stabilized voltage to each circuit described below. The filter circuit 4 is a circuit that extracts signal components of frequency ₁ and frequency ₂ superimposed on the DC voltage of line L, respectively.
The output of this filter circuit 4 is detected and shaped by a waveform shaping circuit 5, and the detected output corresponding to the signal of frequency ₁ becomes the reset input of the counter 6,
The detection output corresponding to the signal No. ₂ becomes the clock input of the counter 6. Specifically, as shown in FIG. 4a, the multiplex transmission control device sends out a keying signal (a signal with frequency ₁ that continues for a predetermined time) as a modulated wave to line _L. Then, when keying signals with frequency ₂ as a modulated wave are sent out one after another at regular intervals, they are received and detected by the filter circuit 4 and the waveform shaping circuit 5, and then shaped by the waveform shaping circuit 5. 2
The outputs of the system are as shown in Fig. 4b and c, respectively. In other words, first the keying signal of frequency ₁ is received and counter 6 is reset, and then the frequency
The counter 6 is incremented by 1 each time a keying signal of ₂ is received.

The address setter 8 is for setting a unique address to be assigned to this limit switch. They are compared, and when the two match, an output signal is generated from the matching circuit 7 and supplied to the transmitting circuit 9.

The transmitting circuit 9 is activated in response to the output from the matching circuit 7, and operates to oscillate for a certain period of time, and changes the frequency line ₃ or frequency ₄ depending on the current state (on or off) of the limit switch contact 10. Send signals to line L from terminals 1 and 2. Note that the display 11 displays the state of the contact portion 10 by blinking a light emitting element.

As can be seen from the above explanation, when the address "4" is set in the setting device 8 and the signal shown in _FIG. The output of the counter 6 becomes "4" when 4 times is received, the matching circuit 7 outputs a matching signal, and the transmitting circuit 9 outputs the following:
At that point, if the contact portion 10 is on, a signal of frequency ₃ is sent, and if it is off, a signal of frequency ₄ is sent to the line L for a fixed time (a time shorter than the space time of the keying signal of frequency ₂ ). On the other hand, the external multiplex transmission control device is equipped with a counter that counts the number of times the keying signal of frequency ₂ is transmitted, and after transmitting the keying signal of frequency ₂ (during the space period), the keying signal of frequency ₃ or ₄ is sent to line L. It is equipped with a receiving circuit that checks whether a signal is present. Therefore, in this multiplex transmission control device,
If a signal of frequency ₃ is present on the line L when the keying signal of frequency ₂ is sent four times as in the above case, it is known that the limit switch at address "4" is on.

FIG. 5 shows an input system of a centralized control system using a large number of the above limit switches according to the present invention. In the same figure, LS ₁ to _{LS o} are the limit switches described above, and the respective address setters 8 are set to "1", "2", . . . "n" in order. These limit switches
LS ₁ to LS _o are connected in parallel to line L, and the DC power supply
In addition to operating with power supplied from the PS,
A time division multiplex transmission system centered on the multiplex transmission control device MC is constructed. That is, when the multiplex transmission control device MC first sends out a keying signal of frequency ₁ , the counters 6 of each limit switch LS ₁ to _{LS o} are all reset, and then when a keying signal of frequency ₂ is sent out at a constant cycle, this resets each limit switch. LS ₁ -LS _o are addressed in order, and the on/off states of each limit switch LS ₁ -LS _o are sequentially transmitted to the multiplex transmission control device MC during the space period of the keying signal. In this way, if the limit switch of the present invention is used, there is no need to connect the central control device and each limit switch with separate wiring, and one
By simply connecting each limit switch to one line in a multi-drop manner, a power supply and signal transmission path is formed, making the wiring configuration in a centralized control system extremely simple.

Now, an example of the mechanical configuration of the limit switch will be explained based on FIGS. 1 and 2. In the figure, reference numeral 21 denotes a head housing a mechanism related to the operation shaft 22, and 23 denotes a contact section 24 that turns on and off in conjunction with the rotation of the operation shaft 22 (the contact section 10 in FIG. 3).
25 is a joint box combined with this switch box 23, 26 is a circuit unit including circuit boards 27 and 28 built in the joint box 25, and 29 is a terminal of the contact portion 24. Plug fittings,
30 engages with the plug fitting 29 to connect the circuit unit 2.
6 and the contact portion 24, 31 is a digital switch corresponding to the address setting device 8 in FIG. 3, 32 is a display window corresponding to the display board 33 of the digital switch 31, and 34 is an operating state. A light emitting diode (corresponding to the display 11 in FIG. 3) that displays the information so that it can be confirmed from the outside,
35 is a terminal fitting corresponding to terminals 1 and 2 in Fig. 3;
36 is a conduit hole. As described above, it is easy to house each part of the limit switch of the present invention in a case that has almost the same appearance as a conventional enclosed limit switch, and therefore its mechanical handling is no different from that of the conventional one.

Although the above description is all about limit switches, the present invention can be easily applied to various switch devices such as photoelectric switches, proximity switches, level switches, temperature switches, pressure switches, and ultrasonic switches. can. Furthermore, although the above embodiment is adapted to one type of time division multiplex transmission, the present invention is not limited thereto, and can be applied to various types of multiplex transmission systems. Further, in the above embodiment, the signal component is superimposed on the DC power supply voltage, but it is also easy to superimpose the signal component on the AC power supply voltage, and in this case, there is no terminal polarity, making it easier to handle.

As is clear from the above description, the switch device according to the present invention includes a switch section that responds to a predetermined physical change, an address setting device that can arbitrarily set an address from the outside, and a switch that is connected to a power supply line and multiplex transmission line. a pair of input/output terminals, a power supply circuit that receives a power supply voltage externally applied to the input/output terminals and supplies an operating voltage to each part; a filter circuit that extracts a specific frequency that is extracted from the filter circuit, a receiving circuit that detects addressing data from the specific frequency extracted from this filter circuit, and the addressing data detected by this receiving circuit set in the address setting device. a matching circuit that outputs an output when the address matches the specified address; and a transmitting circuit that operates upon receiving the output of this matching circuit and sends a signal of a predetermined frequency representing the state of the switch unit to the outside from the input/output terminal. A switch box is characterized in that a large number of switch devices of the present invention are connected to one line that serves as a multiplex transmission path and a power supply path, and the status of each of these switch devices is centrally monitored. It can be managed with a control device. Therefore, even in large-scale centralized control systems, input system wiring is extremely simple, wiring and maintenance work efficiency is improved, and it is extremely easy to handle the addition of switch devices due to specification changes. etc., has various effects.

[Brief explanation of the drawing]

FIG. 1 is a structural diagram of a limit switch according to an embodiment of the present invention, FIG. 2 is a partial view taken in the direction of arrow A in FIG. 1, FIG. 3 is a block diagram showing the electrical configuration of the same limit switch, and FIG. FIG. 5 is a block diagram of a control system constructed using a large number of limit switches as described above. 1, 2... Input/output terminal, 3... Power supply circuit, 4...
... Filter circuit, 5 ... Waveform shaping circuit, 6 ... Counter, 7 ... Matching circuit, 8 ... Address setter, 9 ... Transmission circuit, 10 ... Contact section, 23 ...
Switchbotcus.

Claims (1)

[Claims] 1. A switch section that responds to a predetermined physical change;
It has an address setting device that can arbitrarily set an address from the outside, a pair of input/output terminals that are connected to the power supply line and multiplex transmission line, and an operating voltage that is applied to each part by receiving the power supply voltage applied from the outside to the input/output terminals. A power supply circuit for supplying the power supply, a filter circuit for extracting a specific frequency that is superimposed on the power supply voltage from the outside and applied to the input/output terminal, and detecting addressing data from the specific frequency extracted from the filter circuit. a receiving circuit; a matching circuit that outputs an output when the address designation data detected by the receiving circuit matches the address set in the address setter; A switch device characterized in that a transmitting circuit for transmitting a signal of a predetermined frequency representing a state to the outside from the input/output terminal is built into one switch box.