JPS62171Y2 - - Google Patents

Description

[Detailed Description of the Invention] The present invention relates to a solenoid valve excitation circuit used in a hydraulic solenoid valve of a hydraulic system.

Generally, the solenoid excitation circuits shown in FIGS. 1 to 4 are known as solenoid excitation circuits for suppressing surge voltages generated across the solenoid coils of DC solenoid valves and eliminating sparks at contacts of relays and the like. In these figures, 1 is a DC solenoid coil, 2 is a capacitor, 3 is a surge absorption element, 4 is a diode, 5 is a resistor, 6 is an inductance element, and 7 is a relay etc. that turns on/off the excitation current to the solenoid coil. 8 is a DC power supply, and 9 is a fuse. When these excitation circuits are used in solenoids of hydraulic solenoid valves, the following drawbacks occur.

In other words, in the one shown in FIG. 1, the steep rise of the surge voltage generated from the solenoid coil 1 when the contact 7 is turned off is suppressed to a gentle rise by the series circuit of the capacitor 2 and the resistor 5, and the surge is absorbed. Although the peak value of the surge voltage is suppressed to a low value by the element 3, the larger the value of the resistor 5, the more sparks are generated at the contact 7, resulting in a drawback that the life of the contact is shortened. Another drawback is that the operation of the solenoid valve when turned off is delayed by the time this spark is generated.

In the models shown in Figures 2 and 3, when the contact 7 is opened, current circulates through the coil 1 by the diode 4, which causes a delay in the operation of the solenoid valve, so it is not suitable for use in hydraulic solenoid valves. Not.

The one in Figure 4 is most suitable for a hydraulic solenoid valve considering only when the contact 7 is open, but if the capacitor 2 has a large capacity when the contact 7 is closed, there is a risk that the contact 7 will melt due to the inrush current. . On the other hand, if the capacitance of the capacitor 2 is small, sparks will occur between the contacts when they are opened.

In addition to the above-mentioned individual drawbacks, the devices shown in FIGS. 1 to 4 have common problems. That is, when the capacitor 2 or the surge absorbing element 3 is damaged or conductive, the fuse 9 (or a breaker, not shown) will break the circuit. When using a DC solenoid valve in a hydraulic system, the fuse 9 is usually provided not for each solenoid coil but for each group containing several solenoid coils, since DC solenoids do not suffer from burnout accidents. be. For this reason, when fuse 9 is blown, other solenoid coils and other electrical equipment in the group connected to power supply 8 through that fuse become de-energized, and as mentioned above, only one Damaged conduction of a capacitor or surge absorbing element results in widespread damage.

In addition, if fuse 9 blows and the solenoid valves and other equipment in the group stop operating, it is difficult to find the point of failure that caused it, especially as shown by the dashed-dotted line in Figures 1 to 4. The circuit components shown in the circle are often placed very close to the solenoid, such as inside the terminal block of a solenoid valve. In order to do so, it is necessary to disconnect the wiring from each solenoid valve and examine the inside of the terminal block, which is an extremely complicated process.

Furthermore, if a transistor is used in place of the contact 7 to turn on and off the excitation current of the solenoid coil, depending on the selection of the fusing current value of the fuse 9, etc., damage to the capacitor 2 or the surge absorbing element 3 may result. There is also a possibility that the transistor may be damaged before the fuse 9 etc. blow out.

The purpose of this invention is to eliminate the above-mentioned drawbacks.When opening a contact, a capacitor eliminates the sparks that occur between the contacts, and also eliminates the sudden surge that occurs from the solenoid coil. By suppressing the voltage to a gradual rise and suppressing the peak value of this surge voltage to a low value using a surge absorbing element, this prevents a delay in the operation of the solenoid valve when the contact is opened. To provide an excitation circuit that can effectively block inrush current to a capacitor when closing a capacitor, and can also disconnect a damaged capacitor or surge absorbing element from the circuit when the capacitor or surge absorbing element is damaged and conductive. It is something.

That is, the solenoid valve excitation circuit of the present invention includes a parallel circuit of a capacitor for preventing sparks at the contact and a surge absorbing element, and a constant current diode between both ends of a solenoid that receives excitation current from a DC power source through a contact. and a constant current passing through the constant current diode is supplied to the capacitor when the contact is closed.

The capacitor and the surge absorbing element are the first to
A capacitor for preventing sparks between contacts and a surge absorption element for suppressing the peak value of surge voltage are used as in the case shown in Fig. 4, and a constant current diode has static characteristics as shown in Fig. 5, for example. When a voltage is applied such that the anode is positive and the cathode is negative, a constant current flows within the range of applied voltage, for example 5 to 100V, and when the anode is negative and the cathode is positive, it is a normal diode order. Indicates directional characteristics. In addition, if a current exceeding the rated value flows in either the forward or reverse direction, the constant current diode will naturally be damaged and short-circuited, and furthermore, the fusing current value of the fuse 9 etc. placed on the power supply side will be adjusted to an appropriate value. By selecting a larger value, the damaged and short-circuited constant current diode can be blown out before the fuse 9 is blown to open the circuit.

An embodiment of the present invention will be described in detail below with reference to FIG. In Figure 6, Figures 1 to 4
The same reference numerals as in the figure indicate the same effect. Reference numeral 10 is the constant current diode, and 11 is a resistor.
This resistor 11 is used as necessary to reduce the load on the constant current diode 10.

The area enclosed by the chain line 12 is housed in a terminal block (not shown) of a solenoid valve.

In the one shown in FIG. 6 above, the contact 7 is closed,
When a voltage is applied between A and B, the voltage between A and C is, for example, 5V.
As a result, a constant charge current flows to the capacitor 2 via the constant current diode 10. Furthermore, when the contact 7 is opened, the reverse characteristic of the constant current diode 10 is the same as that of a diode, so the spark at the contact 7 is eliminated due to the relationship between the capacitor 2 and the solenoid 1, and these capacitors 2 and solenoid 1
When the voltage between B and C reaches the operating voltage of the element 3 due to the resonance between them, the element 3 absorbs the voltage. The surge voltage is applied between B and C, and the reverse characteristics of the constant current diode 10 are close to the forward characteristics of a normal diode, as shown in Figure 5, so points A and C are considered to have the same potential with respect to the surge voltage. It will be done. The waveform shown in FIG. 7 is the voltage waveform generated between AC and BC due to the surge voltage of the solenoid 1 when the contact 7 is opened. When the surge voltage from the solenoid 1 reaches the absorption voltage of a surge absorbing resistance element such as the non-linear voltage dependent resistance element 3, it is absorbed by the element 3. At this time, since points A and C are at the same potential with respect to this surge voltage, the constant current diode 10 will not operate due to the first surge voltage, and the capacitor 2 and solenoid after being absorbed by element 3 The current flowing into the capacitor 2 due to the voltage applied in the forward direction of the constant current diode 10 among the low voltages generated by vibration with the constant current diode 10 is limited to a constant current.

In the solenoid 1 as shown in Fig. 6 above, the power supply 8
Usually, multiple solenoids are connected to the When these solenoids are energized at the same time,
Since the voltage applied to each solenoid may become low and there is a risk of voltage shortage, the power supply voltage is raised in advance by raising the tap of the power transformer, so if there are few solenoids that are energized at the same time,
A voltage higher than necessary is applied to the solenoid 1. In this way, high or low voltage is applied to solenoid 1 depending on the excitation status of other solenoids, but since a constant current is supplied to capacitor 2, inrush current to capacitor 2 can be prevented. Its lifespan will be significantly extended. By appropriately selecting the fusing current value of the fuse used on the power supply side, if the capacitor 2 or element 3 is damaged or conductive during energization, the constant current diode 10 cuts off and also serves as a fuse.

Note that when a voltage of, for example, 5V or more is applied between A and C in FIG. 6, the diode 10 supplies only a constant current to the capacitor 2 due to the characteristics of the constant current diode shown in FIG. Therefore, an excessive rush current flowing into the capacitor 2 can be prevented, and the life of the contact 7 can be extended.

The above-mentioned constant current diode 10 is selected depending on the voltage of the power supply 8. For example, the constant current diode 10 that exhibits constant current characteristics at 5 to 100V is selected from 100 to 200V.
When used in a power source, two constant current diodes 10 may be connected in series as shown in FIG. 8, and a resistor 13 may be connected to prevent current reduction due to self-heating.

Although FIG. 8 shows only the inside of the chain line 12 in FIG. 6, various modifications can be made similarly as shown in FIGS. 9 to 30.
In these FIGS. 8 to 30, the same reference numerals as in FIGS. 1 to 4 and FIG. 6 indicate the same elements. Further, reference numeral 14 is a bidirectional Zener diode for surge absorption, and 15 is a surge absorption element 3 or 1.
4 is a diode to make it independent of the power supply voltage, 16 is a light emitting diode for operation display, 17
is a light emitting diode for indicating surge absorption operation, 18
is a light emitting diode that serves both as an indicator for operation and surge absorption operation.

[Brief explanation of the drawing]

Figures 1 to 4 are circuit diagrams showing conventional examples, and Figure 5 is a circuit diagram showing a conventional example.
The figure is a characteristic diagram of a constant current diode, Figure 6 is a circuit diagram showing one embodiment of the present invention, Figure 7 is a waveform diagram showing the operation of the one in Figure 6, and Figures 8 to 30 are other embodiments. FIG. 3 is a circuit diagram of main parts showing an example. 1... Solenoid, 2... Capacitor, 3...
Nonlinear voltage dependent resistance element, 4... diode, 7... contact, 8... power supply, 10... constant current diode, 14... bidirectional Zener diode.

Claims (1)

[Scope of utility model registration request] A parallel circuit of a capacitor and a surge absorbing element is connected via a constant current diode between both ends of a solenoid that receives excitation current from a DC power source, and a constant current is supplied to the capacitor through the constant current diode when energization starts. What is claimed is: 1. A solenoid valve excitation circuit characterized in that: