JPH0310448Y2 - - Google Patents

Description

[Detailed Description of the Invention] [Industrial Application Field] This invention relates to an overload indicating circuit for a drive mechanism such as an electric valve equipped with a position-torque limit switch.

[Conventional technology]

A combined position-torque limit switch has been devised as a switch mechanism having a position limit that operates at the stroke end of a valve such as an electric valve and a torque limit that operates due to overload.

When such a position-torque limit switch is used as a component of a control circuit that controls a drive mechanism such as an electric valve, there are specific problems associated with having both position limit and torque limit functions. . That is, the valve is operated in the closing direction by the motor, and when the valve reaches the fully closed position, the position-torque limit switch operates as a position limit to stop the motor, and then a current in the opposite direction is applied to the motor. When operating the valve in the opening direction from the fully closed position by flowing the valve, especially when operating the valve in the opening direction after the valve has remained closed for a relatively long period of time, the valve must be in close contact with the valve seat. A larger torque than usual may be required to pull the valve away from the toilet seat, which puts an excessive load on the motor at the beginning of operating the valve from the fully closed position to the open direction, and as a result, the position/torque limit switch Because the valve operates as a torque limiter, the power supply to the motor is cut off, and the valve sometimes remains closed instead of opening.

As a means to prevent such situations,
In Japanese Patent Publication No. 47-3934 and Japanese Patent Publication No. 49-12207, etc., in the initial stage when the valve operates from the closed state to the opening direction, there is a short time until the valve operates to a certain position, and the position and torque are combined. In order to prevent a limit switch from operating as a torque limiter, a technique has been disclosed in which a latch mechanism (latching device) is provided to mechanically latch a driving body (switch striking plate) that operates the limit switch.

However, when the above-mentioned position/torque limit switch displays that it has been activated only due to overload, the position limit function can be canceled and the switch can be switched so that it can be used as a switch with only the torque limit function. If this is done, the advantages of the limit switch's latch mechanism, which has two types of functions, will not be utilized.

Therefore, in order to display overload while taking advantage of the features of the latch mechanism, an overload display circuit as shown in FIG. 2 has been devised. This overload display circuit includes normally open contacts CL1 and OL1 on the closed side and open side of the position-torque limit switch, normally closed position limit switches CA and OA on the closed side and the open side,
Closed side and open side overload indicators CD and OD are connected in series to the operating power source S2, respectively.

[Problem that the invention attempts to solve]

The operation of the overload display circuit configured as described above will be explained with reference to FIG. 3, which shows its operation timing. When the valve is fully open, the close operation push button switch PBC is pressed at _t1 in FIG. When turned on, the relay coil of the closing direction electromagnetic relay
CC is energized and energized, its first and second normally open contacts CC1 and CC2 are turned on, power is supplied to the motor M from the operating power supply S1 through the second normally open contact CC2, and the motor M operates the valve. Rotate in the direction of activation in the closing direction. During this operation process in the closing direction, if an overload occurs at time t ₂ in Figure 3,
The normally closed contact CL2 of the limit switch for both the closing position and torque is turned off, the relay coil CC of the closing direction electromagnetic relay is deenergized, and the normally open contacts CC1 and CC2 of this relay coil CC are turned off, and the motor M is turned off.
stops rotating. At this time, the close position limit switch CA is in the on state, and at t ₂ the close position limit switch CA is turned on.
Since the normally open contact CL1 of the torque limit switch turns on, the closed side overload indicator CD lights up. Next, when the overload disappears and the closing side operation push button switch PBC is turned on again at time _t3 , the valve is operated in the closing direction by the same operation as described above.

Then, at t ₄ , just before the fully closed state, the closed position limit switch CA detects this and turns off, and at t ₅ , when the fully closed state is reached, the normally closed contact CL2 of the closed position/torque limit switch turns off. The relay coil CC of the closing direction electromagnetic relay is de-energized and the motor M is stopped. At this time, the normally open contact CL1 of the closed position torque limit switch turns on, but since the closed position limit switch CA is already in the OFF state at time t4, the closed side overload indicator CD is energized. There is no.

Next, when the open side operation pushbutton switch PBO is pressed at time t6, the open direction electromagnetic relay OC is energized and the first and second normally open contacts OC1 and OC2 are turned on, respectively, and the second normally open contact OC2 is turned on. When turned on, current flows through the motor M in the opposite direction to that described above, and the valve is operated in the opening direction. Due to the operation of this valve, t ₇
When the close position limit switch CA turns on,
Closed position - Normally open contact of torque limit switch
Due to the action of the latch mechanism described above, CL1 does not turn off until _t8 , a short time after _t7 . Therefore, from t ₇ o'clock to t ₈ o'clock, even though there is no overload, the closed side overload indicator CD is energized and gives an erroneous indication. That is, the open side and closed side positions -
Torque limit switch normally open contacts CL1, OL
1. When the valve operates at the stroke end, even if the valve moves in the opposite direction and the close and open position limit switches CA and OA return to the ON state, the latch mechanism remains in place for a short period of time. There is a problem that recovery is delayed due to this, and during this time an overload is displayed even though there is no overload.

This idea was devised in view of these problems, and was published in Japanese Patent Publication No. 3934/1983 and Japanese Patent Publication No. 49/1983.
It is an object of the present invention to provide an overload display circuit that takes advantage of the features of the latch mechanism of the position-torque limit switch described in Japanese Patent No. 12207, but which does not cause false overload indications.

[Means for solving problems]

In order to achieve the above object, the overload indicating circuit of this invention includes a position-torque limit switch having a position limit that operates at the stroke end of a valve such as an electric valve and a torque limit that operates due to overload. A latching mechanism is provided that latches the operation of the position-torque limit switch at the initial stage when the limit switch starts moving in the opposite direction from the stroke end position, and the operation power supply is connected to the close/open operation switch and the close/open direction electromagnetic relay. Each series circuit of the relay coil and each normally closed contact of the limit switch for both closed and open positions and torque is connected, and each of the first normally open contacts of each of the electromagnetic relays is connected in parallel to each of the operation switches. and an overload indicating circuit in a drive mechanism having an electric circuit in which each of the second normally open contacts of each of the electromagnetic relays is connected in antiparallel to a power supply circuit from an operating power source to a valve drive motor; The operation power supply includes a series circuit of each of the third normally open contacts of each of the electromagnetic relays and a relay coil of a relay with a delay in return to the closed and open sides, and each normally open contact of each of the relays with a delay in return and each of the positions. - Each series circuit of the normally open contact of the torque limit switch and the close, open side limit switch and the relay coil of the close and open side auxiliary relay, and each of the first contacts of each of the auxiliary relays.
Connect the normally open contacts of the auxiliary relays to the series circuits of the closed and open side overload indicators, respectively, and connect the second normally open contacts of the auxiliary relays to the normally open contacts of the respective return delay relays. The gist is a configuration in which each is connected in parallel.

[Effect]

The above structure was created by focusing on the fact that the overload is displayed when the valve is operating and is divided into open side overload and close side overload depending on the direction of operation, that is, the opening and closing direction of the valve. When the limit switch operates at the end of the stroke and then the valve moves in the opposite direction, for example, when the valve is operated from the fully closed state to the open direction, the normally open contact of the torque limit switch in the closed position is turned on by the latch mechanism. Even if the close position limit switch is turned on while the state is maintained,
The normally open contact of the return delay relay connected in series with these relays is connected to the normally open contact of the close direction electromagnetic relay connected in series with the relay coil of the close direction electromagnetic relay, which is previously deenergized. Since the open contact is in the OFF state, the closed side overload indicator is not energized and no erroneous display occurs.
The same applies to the open side overload display.

〔Example〕

An embodiment of this invention will be explained in detail below.

In FIG. 1, the same or equivalent parts as in FIG. 2 are given the same reference numerals. To explain the configuration that corresponds to Fig. 2, the operation power source S
2, the third normally open contact CC of the closing direction electromagnetic relay CC
3, the series circuit of the relay coil CT of the closing side return delay relay, the normally open contact CT1 of this relay, the closing side position - the normally open contact CL1 of the torque limit switch, the closing side position limit switch CA, and the relay of the closing side auxiliary relay. Connect the series circuit with the coil CX, the first normally open contact CX1 of this relay, and the series circuit of the closed side overload indicator CD, and connect the closed side contact in parallel with the normally open contact CT1 of the closed side return delay relay. The second normally open contact CX2 of the auxiliary relay is connected. Similarly, for the open side, the operation power supply S2 is connected to a series circuit of the third normally open contact OC3 of the open direction electromagnetic relay OC, the relay coil OT of the open side return delay relay, and the normally open contact OT1 of this relay. Open side position - the normally open contact OL1 of the torque limit switch, the series circuit of the open side limit switch OA, the relay coil OX of the open side auxiliary relay, and the first normally open contact OX1 of this relay
and the series circuit of the open side overload indicator OD, and the normally open contact OT1 of the open side return delay relay.
The second normally open contact OX2 of the opening side auxiliary relay is connected in parallel with
is connected.

Next, the operation of the example circuit with the above configuration will be explained in the third section.
Points that differ from the diagram will be explained. During operation in the closing direction, each normally open contact CC1 of the closing direction electromagnetic relay
~CC3 is in the on state, and the third normally open contact CC3
The relay coil CT of the return delay relay is energized through the relay, and this normally open contact CT1 is turned on. Since the close position limit switch CA is also on during operation in the close direction, if an overload occurs at this time and the normally open contact CL1 of the close position torque limit switch turns on, the close side auxiliary relay relay Coil CX is energized and each normally open contact of this
CX1 and CX2 are each turned on, and the closed side overload indicator CD lights up. At the same time as this overload occurs, normally open contact CL2 of the closing position torque limit switch turns off and the closing direction electromagnetic relay CC is demagnetized, but the relay coil CT of the return delay relay remains energized for a while. Normally open contact CT of lever
1 is in the on state, the auxiliary relay is securely self-maintained, and the display on the closed side overload indicator CD is maintained.

Then, when operating from the fully closed state to the open direction,
Closed position - Normally open contact of torque limit switch
If the close position limit switch CA is turned on while CL1 is held in the on state by the latch mechanism, the close direction electromagnetic relay CC
is deenergized and the normally open contact CT of the return delay relay
1 is turned off, which causes the auxiliary relay to
CX is also deenergized and its first normally open contact CX1 is also off, and the closed side overload indicator CD is not energized. In other words, there will be no erroneous display.

The overload indication on the open side is also performed in exactly the same manner as described above.

〔effect〕

As described above, the overload indicating circuit of this invention takes advantage of the features of the latch mechanism of the position-torque limit switch as described in Japanese Patent Publication No. 47-3934 and Japanese Patent Publication No. 49-12207. Erroneous overload indications caused by this latch mechanism can be reliably prevented.

Further, since the torque sheet and the position sheet can all be configured in the same circuit, there is an advantage that the circuit can be unified regardless of the type of valve or whether or not there is an overload indication.

[Brief explanation of the drawing]

Fig. 1 is an electric circuit diagram of an embodiment of the overload indicating circuit of this invention, Fig. 2 is an electric circuit diagram of a conventional circuit,
FIG. 3 is a timing chart of FIG. 2. S2...Operating power supply, CC...Relay coil of the electromagnetic relay in the closing direction, CC1 to CC3...Normally open contact of the electromagnetic relay in the closing direction, CL1...Normally open contact of the closing side position-torque limit switch, CA... Closed position limit switch, CT...Relay coil of closed side return delay relay, CT1...Normally open contact of closed side return delay relay, CX...Relay coil of closed side auxiliary relay, CX1, CX2...Closing side auxiliary relay 1st and 2nd normally open contacts, CD...Closing side overload indicator, OC...
...Relay coil of open direction electromagnetic relay, OC1 to OC
3... Normally open contact of the open direction electromagnetic relay, OL1...
Open side position - normally open contact of torque limit switch,
OA...Open side limit switch, OT...Relay coil of open side return delay relay, OT1...Normally open contact of open side return delay relay, OX...Relay coil of open side auxiliary relay, OX1, OX2...Open The first and second normally open contacts of the side auxiliary relay, OD...open side overload indicator.

Claims (1)

[Scope of utility model registration request] A position-torque limit switch is provided that has a position limit that operates at the stroke end of a valve such as an electric valve and a torque limit that operates due to overload, and the switch is provided with a position-torque limit switch that operates at the stroke end of a valve such as a motor-operated valve. - A latch mechanism is provided to latch the operation of the torque limit switch.
Connect each series circuit with each normally closed contact of the open side position-torque limit switch, and connect each first normally open contact of each electromagnetic relay in parallel with each operation switch, and In an overload indicating circuit in a drive mechanism having an electric circuit in which each of the second normally open contacts of each of the electromagnetic relays is connected in antiparallel to a power supply circuit to a valve drive motor, the operation power source is connected to the Each series circuit of each third normally open contact of each electromagnetic relay and the relay coil of the relay with closed and open side return delay;
Each of the normally open contacts of the respective return delay relays, each of the normally open contacts of each of the position-torque limit switches, and each of the relay coils of the closed, open side position limit switches and the closed and open side auxiliary relays. A series circuit is connected to each of the first normally open contacts of each of the auxiliary relays and a closed/open side overload indicator, and each of the normally open contacts of each of the return delay relays is connected to the first normally open contact of each of the auxiliary relays. An overload indicating circuit characterized in that each second normally open contact of each auxiliary relay is connected in parallel.