JPH05138400A - Driving circuit for press machine - Google Patents

Abstract

PURPOSE:To contrive protection of semiconductor element and automatic detection of abnormal time. CONSTITUTION:In a driving circuit for press machine which is formed so that the load 4 on a press machine is driven with an AC power supply 1 impressed through a bidirectional semiconductor element 2, abnormality detecting means 30, 10A, Ra, 10B, Rb which consist of an automatic current suppressing return type overcurrent protection element 30 which is connected to the semiconductor element 2 in series and a pair of photocouplers 10A, 10B which are connected to the semiconductor element 2 in parallel is provided.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a drive circuit for driving loads such as clutches and brakes of a press machine using an AC power source.

[0002]

2. Description of the Related Art The load of a press machine (for example, a clutch
When driving the solenoid of the air supply valve for brake)
From the viewpoint of safety, it is desirable to turn the power on and off with a rotary cam switch or relay. However, in a high-speed press machine such as 400 to 1000 SPM, there is no choice but to perform ON-OFF control with a semiconductor element due to the problem of followability.

Therefore, as shown in FIG. 2, for example, a bidirectional controlled rectifying semiconductor element 2 such as a triac (trade name).
Is connected to the AC power source 1 in series with the load 4 in the electrical circuit 3
And a drive circuit for ON / OFF controlling the semiconductor element 2 by a control signal Tp from the control unit 25.

[0004]

However, since the semiconductor element 2 has a symmetrical fault property, that is, the semiconductor element 2 is broken on the conducting side or the breaking side, the safety and reliability are low.
If it breaks to the conduction side, current continues to flow in the load 4 and control becomes impossible, which is dangerous. On the other hand, if it breaks to the shut-off side, the load 4 is protected, but other auxiliary machines and auxiliary devices are still in the operating state. Therefore, when viewed as a press machine as a whole, it is unfail safe, and there is a risk. Furthermore, even if the semiconductor element 2 is operating normally, when the load 4 is short-circuited, the overcurrent I flows and the semiconductor element 2 burns out.

It is an object of the present invention to provide a press machine capable of detecting an abnormality of a semiconductor element, whether it is broken on the conducting side or the breaking side, and protecting the semiconductor element from an overcurrent even if a load or the like is short-circuited. It is to provide a driving circuit.

[0006]

A drive circuit for a press machine according to the present invention is a drive circuit for a press machine, wherein the load of the press machine is formed by an AC power source applied through a bidirectional semiconductor element. An overcurrent protection element which is connected in series with a bidirectional semiconductor element and has a function of reducing the current when an abnormal excessive current flows to the load and automatically returning to the original state when the abnormal excessive current disappears. And a pair of photocouplers connected in parallel with the bidirectional semiconductor element and outputting a pulse signal having a frequency equal to the frequency of the AC power supply when current stops flowing in the load. Characterize.

[0007]

In the present invention having the above-mentioned structure, when the bidirectional semiconductor element for ON-OFF control is broken to the blocking side, the pair of photocouplers connected in parallel with this semiconductor element work to output a pulse signal. Therefore, if you monitor this pulse signal,
Since the abnormality of the semiconductor element can be detected, fail-safe of the entire press machine can be achieved.

On the other hand, when the load is short-circuited and an abnormal overcurrent flows, the overcurrent protection element operates to reduce the current. Therefore, the semiconductor element can be protected. Moreover, when the overcurrent protection element reduces the current flowing to the semiconductor element connected in series with the overcurrent protection element, the current now flows to the photocoupler, and in this case also, a pulse signal can be output, that is, an abnormality can be detected.

[0009]

Embodiments of the present invention will be described below with reference to the drawings. As shown in FIG. 1, the drive circuit of this press machine has the same basic configuration (1, 2, 3, 4) as that of the conventional example (FIG. 2), and also has an overcurrent protection element 30 and a pair of photocouplers 10.
An abnormality detecting means composed of A and 10B is provided.

The load 4 is not particularly limited, but in this embodiment, it is a solenoid of the clutch / brake air supply valve.

First, the overcurrent protection element 30 is connected to the electric path 3 in series with the bidirectional semiconductor element 2 (triac in this embodiment). This element 30 is provided with a current Ia when an abnormal excessive current Iab flows through the load 4.
It has a function of decreasing b and automatically returning to the original state when the abnormal excessive current Iab disappears. That is, it works in the same way as when the electrical resistance changes. In this embodiment, a Posistar [PTH63 manufactured by Murata Manufacturing Co., Ltd.
Shape].

That is, the resistance value (Ω) at 25 ° C. is 3.3 ± 20%, the maximum voltage is 125 V, and the maximum current is 2.0.
A, non-operating current 440mA, operation starting current 1000mA
Is.

Here, the abnormal current (Iab) flowing through the load 4 is a failure in the conduction side of the semiconductor element 2 (specifically, element elements in each direction), and the abnormal excessive current Iab flowing through the semiconductor element 2. Is a short circuit of the load 4. It also includes the case where the electric circuit (3C, 3C) is short-circuited so as to bypass the load 4 due to the disconnection.

Next, the photocoupler 10A (10B) forms a pulse signal generator together with the resistor Ra (Rb) connected in series with it. Due to the bidirectional nature of the semiconductor element 2, a pair of 10A and 10B is provided, and each pulse signal generator 10
A, Ra, 10B and Rb are branch points 3P1 and 3P of the electric circuit 3.
It is connected in parallel to the semiconductor element 2 by bypass electric paths 3A and 3B between the two.

Therefore, if the semiconductor element 2 is normal, the pulse signals Sa and Sb are not output from any of the photocouplers 10A and 10B. However, if the semiconductor element 2 breaks in one direction (the other direction) to the current interruption side, the photocoupler 1
Pulse signal S from 0A (10B) as an abnormality detection signal
a (Sb) is output. If it breaks to the bidirectional current cutoff side, the pulse signals Sa,
Sb is output.

The pulse signals Sa and Sb have the same frequency as the frequency of the AC power source 1, but have a positional deviation of 180 degrees from each other.

Further, in this embodiment, both pulse signals S
A failure detection circuit 15 is provided which receives a and Sb as inputs and detects a failure of the drive circuit (1, 2, 3, 4) and outputs a failure detection signal ED when there is a failure. This failure detection signal ED is used as an interlock signal for other auxiliary machines and auxiliary devices, and establishes fail-safe for the entire press machine.

Next, the operation of this embodiment will be described. The bidirectional semiconductor element 2 is ON-OFF controlled by the control signal Tp from the control unit 25 to drive the load 4.

This normal current is I, and the resistance value of the overcurrent protection element 30 is small. Further, since the currents to the bypass circuits 3A and 3B are limited by the resistors Ra and Rb, the pulse signals Sa and Sb are not output from any of the photocouplers 10A and 10B. Failure detection circuit 1
5 is judged to be normal.

Here, the semiconductor element 2 is in one direction (the other direction).
If it is broken to the current interruption side, the photocoupler 10A (1
The pulse signal Sa (Sb) is output from 0B). Therefore, the failure detection circuit 15 determines that there is a failure and outputs the failure detection signal ED. This guarantees the fail safe of the entire press machine. If it is broken in both directions, both pulse signals Sa and Sb are output, so that a failure can be similarly detected.

On the other hand, if the semiconductor element 2 is broken to the conducting side, the current I will not flow through the photocoupler 10A (10B). Therefore, the pulse signal Sa (Sb) is not output and the failure can be detected by matching with the control signal Tp.

When the load 4 is short-circuited, the semiconductor element 2
An abnormally large current Iab flows through. Then, the apparent resistance value of the overcurrent protection element 30 increases, and the abnormal overcurrent Iab is reduced. Therefore, the photocoupler 10A (10B)
Outputs a pulse signal Sa (Sb). Therefore,
It is possible to detect a short circuit failure of the load 4 while protecting the semiconductor element 2.

That is, even when the load 4 is short-circuited or the electric circuit (3C, 3C) is short-circuited so as to bypass the load 4, the overcurrent protection element 30 reduces the current, so that the semiconductor element 2 can be protected. And the failure can be detected. The same applies to the case of overload operation of the load 4.

When the overload operation is stopped, the overcurrent protection element 30 is restored, so that it takes less labor than in the case of a fuse or the like.

According to this embodiment, however, a current-suppressing automatic recovery type overcurrent protection element 30 connected in series to the semiconductor element 2 and a pair of photocouplers 10A and 10B connected in parallel to the semiconductor element 2 are provided. Since the above-mentioned configuration is provided with the abnormality detection means, it is possible to detect both the conduction side and the interruption side of the semiconductor element 2. On the other hand, even if the abnormal excessive current Iab is generated due to the short circuit of the load 4, the semiconductor element 2 can be protected without being burnt out, and its failure can be detected.

Further, since the pair of photocouplers 10A and 10B are provided, even if one of the element elements forming the bidirectional semiconductor element 2 fails, the abnormality can be detected.

Further, the overcurrent protection element 30 suppresses the current with respect to the overcurrent Iab, but automatically returns to the original state when the overcurrent Iab disappears, so that no trouble such as replacement of the fusing fuse is required when releasing the overload operation.

Further, since the failure detection circuit 15 which outputs the failure detection signal ED with the both pulse signals Sa and Sb as inputs is provided, any one of the semiconductor element 2, the AC power supply 1, the electric line (3C, 3C) load 4 is provided. Even if something goes wrong, the entire press machine can be made to fail-safe.

[0029]

According to the present invention, there is provided an abnormality detecting means comprising a current-suppressing automatic recovery type overcurrent protection element connected in series to a semiconductor element and a pair of photocouplers connected in parallel to the semiconductor element. Therefore, it is possible to protect the semiconductor element against an abnormal excessive current, and it is possible to quickly detect the abnormality even if any abnormality occurs in the semiconductor element, the load, or the electric circuit. Therefore, fail-safe of the entire press machine can be guaranteed.

[Brief description of drawings]

FIG. 1 is a circuit diagram showing an embodiment of the present invention.

FIG. 2 is a circuit diagram showing a conventional example.

[Explanation of symbols]

 1 AC power supply 2 Bidirectional semiconductor device 3, 3A, 3B, 3C Electric circuit 4 Load 10A, 10B Photocoupler Ra, Rb Resistance 15 Fault detection circuit 25 Control unit 30 Overcurrent protection device

Claims (1)

[Claims] 1. A drive circuit of a press machine formed to drive a load of a press machine with an AC power source applied through a bidirectional semiconductor element, wherein an abnormal excessive current is connected to the bidirectional semiconductor element in series and to the load. And an overcurrent protection element having a function of automatically reducing the current and returning to the original state when the abnormal overcurrent disappears, and being connected in parallel with the bidirectional semiconductor element and connected to the load. A drive circuit for a press machine, comprising: an abnormality detection unit including a pair of photocouplers that output a pulse signal having a frequency equal to the frequency of the AC power supply when current stops flowing.