JPS6322592Y2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a push button switch circuit designed to prevent arc discharge occurring between push button switch contacts.

In circuits that reduce the voltage of AC power using a transformer and then full-wave rectify it to drive and control DC relays, IC elements, etc., such as control circuits for air conditioners that are made up of weak electrical elements, AC power is generally used. An on/off control switch is provided in the power supply circuit. An automatic reset type push button switch is used as the power switch, and a relay contact that is activated when the push button switch is closed is connected in parallel with the push button switch, and after the push button switch is opened, the control is controlled via the relay contact. The circuit is configured to maintain power supply to the circuit. When the power supply is cut off, the power supply to the relay coil is cut off.

However, with such a circuit configuration, when the push button switch is pressed to close the power supply circuit, the power supply voltage is directly applied to the contacts of the push button switch, causing arc discharge between the contacts.
If an arc discharge occurs between the contacts, the switch contacts will naturally burn out, shortening their lifespan, and this will cause an abnormal voltage that will destroy weak electrical elements.

In order to prevent this, a snapping mechanism made of a leaf spring or a spring is incorporated into the contact portion of the push button switch to bring the contacts into contact extremely instantaneously, or an arc-resistant material is used. However, this method has the drawback that the internal structure of the push button switch becomes complicated, making it difficult to assemble and making it very expensive.

In view of the above-mentioned drawbacks of the prior art, the present invention provides a push button switch circuit that can reliably prevent the occurrence of arc discharge between the contacts when the switch is turned on and off, and can be manufactured at a low cost. .

The present invention has a configuration in which a negative resistance sudden change element is connected in series with an automatic reset type switch that controls the power supply circuit intermittently, and a relay contact that maintains the power supply to the load circuit is connected in parallel to the series circuit. By doing so, the above objective was achieved. Hereinafter, one embodiment of the present invention will be described in detail with reference to the accompanying drawings.

Figure 1 shows an automatic return type pushbutton switch that controls the power supply circuit intermittently, and a relay contact that is driven when the pushbutton switch is closed is installed in parallel, so that the pushbutton switch automatically returns, and when the switch is opened, the relay FIG. 2 is a circuit configuration diagram in which power supply to a load circuit is maintained through contacts. In FIG. 1, reference numeral 1 denotes an AC 100V power supply, which is connected to a control circuit 5 via a transformer 3. Reference numeral 2a denotes a push button switch for closing the power supply circuit, which is of a double-pole single throw type and is of an automatic return type, interlocking with the push button switch 2b for cutting off the power supply provided on the control circuit 5 side.
Reference numeral 4 denotes a self-heating sensitive negative resistance sudden change element (hereinafter abbreviated as resistance element) connected in series between the push button switch 2a and the primary winding of the transformer 3, and when the push button switch 2a is closed, the application of the power supply 1 is applied. It has the characteristic of self-heating due to voltage, and instantly changes from a high resistance value (10 to 100KΩ) to a low resistance value (about 1 to 10Ω). Further, the control circuit 5 connected to the secondary winding (low voltage side) of the transformer 3 closes the push button switch 2b when controlling the current path between the full-wave rectifier 7 and the power source 1 to be interrupted. The relay coil 8 to be driven, the contact 8a of the relay coil 8, and the DC output of the full-wave rectifier 7 when the contact 8a is in the closed state drive the relay coil 8, and the series circuit of the push button switch 2a and the resistance element 4. and a relay coil 6 having a normally open contact 6a for short-circuiting. Although not shown in the figure, the control circuit 5 drives and controls various DC circuits or relays through the output terminal 9 of the full-wave rectifier 7.

To explain the resistance element 4 in more detail, this element is made of a thick film element printed and formed on an alumina substrate, and generates heat by itself due to the applied voltage of the power supply 1, and is not subject to thermal transient conditions. The resistance element reaches a sudden temperature change and changes to a low resistance value, and the relationship between the temperature and the temperature at which this resistance element suddenly changes to a low resistance value is shown in Figure 2.
It decreases to about 10Ω at point Tc, where the self-heating temperature is about 70 degrees. Factors that affect the time t required to reach this sudden temperature change include the heat generation amount P of the resistance element.
(V ² /R, RI ² ), the thermal time constant τ of the resistance element itself, and the ambient temperature Ta. In other words, the time t required to bring the temperature to a sudden change, the thermal time constant τ determined by the structure and material of the resistance element, and the amount of heat P applied to the resistance element are in the relationship shown in the characteristic diagrams in Figures 3a and b. The time t can be arbitrarily selected by controlling the thermal time constant τ and the amount of heat generation P, respectively. especially,
If the time t is to be shortened, the thermal time constant τ of the resistance element may be determined to be small; in that case,
The thermal time constant τ can be easily reduced by printing the resistive element as a thick film element.

Next, the operation of the circuit configured as shown in FIG. 1 will be explained.

According to this circuit, before the push button switch 2a is closed, it is in the state shown in FIG. 1, and the resistance element 4 is at a high resistance value. As a result, even if the power supply voltage is applied to the contact gap of the push button switch 2a, the flowing current value is limited to about 10 mA, and no arc discharge occurs in the contact gap.

Then, the push button switch 2a is closed and power is supplied to the control circuit 5. In this case, most of the power supply voltage is The voltage is applied to the resistive element 4, and the resistive element 4 starts to self-heat. Then, as shown in FIG. 2, when the temperature of the resistance element 4 reaches a sudden change temperature (approximately 70 degrees), its resistance value rapidly decreases on the order of microseconds. As a result, the power supply voltage is applied to the transformer 3 via the push button switch 2a and the resistive element 4, and the control circuit 5 is activated. Control circuit 5 drives a not-shown circuit connected to terminal 9 via rectifier 7, and also drives relay 6 via relay contact 8a. As a result, relay contact 6
a is closed, short-circuiting the series circuit of the push button switch 2a and the resistive element 4. That is, push button switch 2a
After the switch is restored, power is supplied to the control circuit 5 through the relay contact 6a, and no arc discharge occurs in the contact gap when the push button switch 2a is closed.

Further, when the circuit in this operating state is to be cut off, this is done by closing the push button switch 2b. That is, the push button switch 2b is closed to drive the relay coil 8, and the relay contact 8a is closed.
The power supply to the relay coil 6 is cut off by opening the circuit.
As a result, the relay contact 6a returns to its original state and cuts off the alternating current supply path. In this case, push button switch 2
Push-button switch 2a is also closed in conjunction with b, but since the series circuit of push-button switch 2a is cut off by the high-resistance means of resistance element 4 as described above, the relay contact 6a cuts off the AC power circuit. There is no risk of arcing occurring between the contacts of the push button switch 2a.

Note that it is possible that the series circuit of the push button switch 2a and the resistor element 4 cannot be short-circuited by the relay contact 6a within the time period from when the push button switch 2a is pressed until it is immediately released. It takes a very short time (approx.
100 μs), which can be achieved within the operator's push button switch operation time.

Further, at the same time as closing the push button switch 2a and driving the relay 6, the push button switch 2b is also closed.
The relay 8 is driven to try to cut off the power supply circuit of the relay 6, but such inconvenience can be avoided by using a relay 8 with a time delay function and driving it later than the relay 6. can be resolved.

Next, the circuit operation shown in Fig. 1 will be explained in more detail with reference to Fig. 4. Fig. 4 is a time chart showing the operation of each contact in the push button switch circuit.
In the case of < _t0 , the state before the push button switch 2a is closed, that is, the state of each contact shown in FIG. 1 is shown.

Next, when the push button switch 2a is closed at T= _t0 , the impedance of the transformer 3 is extremely small compared to the resistance value of the negative resistance sudden change element 4 in the initial state, so almost all of the voltage of the AC power supply 1 is is applied to the negative resistance sudden change element 4 and starts self-heating. After that, as shown in FIG. 2, after a period of time t until the negative resistance sudden change element 4 reaches the sudden change temperature Tc,
The power supply voltage is now applied to transformer 3,
Control circuit 5 is activated. Then, the relay 6 is driven via the relay contact 8a which is in the closed state in the initial state, thereby closing the relay contact 6a. In FIG. 4, after the contact 2a is closed at T= _t0 , the contact 6a is closed after the time t for the negative resistance sudden change element 4 to reach the sudden change temperature Tc and the delay time tm of the relay 6. This indicates that it will close.
By closing the contact 6a, the power supply continues even if the operator releases the push button switch 2a to open it. In order to enter the power supply state, the operator must hold down the push button switch 2a for a longer time than the power supply activation time (t+tm) shown in FIG.
However, by closing the pushbutton switch 2a, the pushbutton switch 2b linked therewith becomes closed, and the relay 8 is driven, but as mentioned above, the relay 8 has a time delay function compared to the relay 6. Therefore, the power supply to the relay 6 is not cut off. In other words, as shown in FIG.
By setting the time longer than the time during which a is pressed (t ₂ -t ₀ in the figure), it is possible to avoid a malfunction in which the relay contact 8a is opened and the relay contact 6a is opened. In summary, in order to achieve a stable power supply state, the operator should set the time for which the push button switch 2a is pressed to be longer than (t+tm) and shorter than the delay time td of the relay 8. Next, regarding the power supply circuit cutoff operation, the fourth
This will be explained using figures. When the operator closes the pushbutton switch 2a again at time T= _t3 when the power supply is stable, the delay time of the relay contact 8
After td, the relay contact 8a opens at T= _t4 .
As a result, the power supply to the relay 6 is cut off, and the relay contact 6a is opened at T= _t5 after the delay time tm of the relay 6 has elapsed. As a result, power is supplied via the push button switch 2a and the negative resistance sudden change element 4. At this point, the negative resistance sudden change element 4 has returned to its initial state and is in a high resistance state, so almost no power is supplied to the control circuit 5, the power supply to the relay 8 is cut off, and the relay contact 8a is again in the closed state. The time from when the contact 6a is opened to when the contact 8a is closed is indicated by te in the figure, and the relay contact 8a is in the closed state at T= _t6 . Relay contact 6
The operator releases the push button switch 2a after T= _t5 when the switch a becomes open, thereby completing the power cutoff. However, if the handler is T=t ₅
If the push button switch 2a is continued to be pressed for a long time thereafter, a malfunction will occur in which the power supply operation is restarted after the power supply circuit is cut off. In other words,
Time t from time T = t ₅ (time required for negative resistance sudden change element 4 to reach sudden change temperature Tc)
As time passes, the resistance of the negative resistance sudden change element 4 decreases, and power is supplied to the transformer 3.
It will switch to power supply state again. Therefore, when cutting off the power circuit, the operator must press push button switch 2.
It is necessary to appropriately set the time for which a is pressed (t ₇ -t ₃ in FIG. 4), the delay time of the relay, and the characteristics of the negative resistance sudden change element. In other words, in Figure 4,
(t ₇ − _{t 5} ) when the negative resistance element is exposed to a sudden change in temperature.
In addition to setting the time t required to reach Tc to be sufficiently long to avoid malfunctions, as shown in Figure 4, the operator can press push button switch 2a.
If you set the button to be held down for at least (td + tm), the power circuit can be shut off reliably.

In addition, in the above embodiment, a resistance element that suddenly changes the resistance value due to self-heating was used as a resistance element, but another heat-generating resistor is connected in series with the push button switch, and a temperature-sensing type resistor is connected in parallel with it. It can also be used by connecting a negative resistance sudden change element.

As is clear from the above-mentioned embodiments, the present invention connects a negative resistance sudden change element in series with a switch that controls the power supply circuit on and off, and includes a relay in the series circuit that is driven when the switch is closed. Normally open contacts are connected in parallel, the current flow during on/off control of the switch is momentarily suppressed by the negative resistance sudden change element, and the power supply circuit is controlled by the normally open contact of the relay connected in parallel with the negative resistance sudden change element. Because of this, arc discharge does not occur between the switch contacts when the switch is turned on and off, and it is possible to prevent burnout of the switch contacts, and there is no adverse effect on other weak current circuits. Furthermore, compared to a conventional snapping mechanism built into the switch itself, the switch is cheaper and has a simpler structure and can be used as is.

[Brief explanation of the drawing]

The attached drawings are for explaining one embodiment of the present invention, and FIG. 1 is a specific circuit diagram of a switch circuit equipped with an arc discharge prevention circuit, and FIG. 2 is a diagram of a negative resistance sudden change element. Electrical resistance-temperature characteristic diagrams, Figures 3a and b are characteristic diagrams for explaining the relationship between the time t required for the negative resistance sudden change element to reach a sudden change temperature, the thermal time constant τ, and the amount of heat generated P. be. Figure 4 shows
2 is a time chart between each contact point in the circuit operation shown in FIG. 1. FIG. 1... AC power supply, 2a, 2b... push button switch, 3... transformer, 4... negative resistance sudden change element,
5... Control circuit, 6, 8... Relay coil, 6
a, 8a... Relay contact, 7... Rectifier, 9...
terminal.

Claims (1)

[Scope of utility model registration request] A negative resistance sudden change element is connected in series with an automatic reset type switch 2a that controls power supply to the load circuit intermittently, and the switch 2a is closed in a series circuit of the switch 2a and the negative resistance sudden change element. A circuit in which relay contacts 6a driven by the switch 2a are connected in parallel, and the load circuit controls an automatic return switch 2b that operates in conjunction with the switch 2a, and a relay that controls on/off the power supply to the relay 6 that drives the relay contact 6a. 8, and a circuit that connects the relay 6 in series with the contact 8a driven by the relay 8. A push button switch circuit characterized in that the delay time of the contact 6a of the relay 6 is longer than the delay time of the contact 6a of the relay 6 to prevent arc discharge from occurring between the contacts of the switch 2a when the switch 2a is controlled on and off.