JPS5936153B2 - Solenoid valve drive device for hydraulic control - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a hydraulic control electromagnetic valve drive device used for controlling operating valves of construction machinery, etc., which are driven by hydraulic pressure, for example.

Conventionally, construction machines controlled by hydraulic drive have used on-off valves as operating valves.

On-off valves are inexpensive, but the controllability of on-off operation is not very good.

On the other hand, when using a proportional valve, controllability is good, but the price is high.

Servo valves have better controllability but are more expensive.

Proportional valves are not only expensive, but also have the disadvantage that when used in poor environments such as construction machinery, the operating oil becomes dirty and deteriorates, making it impossible to operate correctly (in other words, high-purity oil is required). .

An object of the present invention is to provide an electromagnetic valve drive device for hydraulic control that enables proportional operation control using inexpensive on-off valves and has good controllability.

In this invention, an input signal is converted into a pulse signal with an on/off ratio corresponding to its level, and the converted pulse signal is supplied as a drive signal to a spool type solenoid valve.

If the frequency of this drive pulse is selected appropriately, during the on period, for example, the spool will try to move from close to open, and during the off period it will be pulled back, but before the spool has completely returned, it will open again. , the spool substantially stops during opening and closing, and this stopping position is close to the open position if the on period of the pulse is on and off ratio is large (or close to the closed position if the on period is short). Therefore, it is comparatively controlled by the on/off ratio of this spool-type solenoid valve Hapulus.

Generally speaking, in a spool-type solenoid valve, the valve begins to open when the displacement of the spool becomes greater than a value of 2.

Therefore, if the input signal is too small, the on-period of the pulse will be short, and even if driven by such a single drive signal, the spool will be displaced only slightly and the valve will remain completely closed, causing no drive to the valve. This will shorten the life of the valve.

Therefore, in the case of such a small signal, it is preferable not to apply one drive pulse to the solenoid valve.

For this reason, the present invention is provided with means for stopping the supply of the drive signal to the sub-spool type solenoid valve when the input signal is below a predetermined level.

Furthermore, due to the inertia of the spool itself, in order to control the opening of the valve proportionally to the displacement of the spool, it is necessary to increase the frequency of the drive pulse considerably, which may not be preferable.

For this reason, in the present invention, the pilot cylinder is driven by the auxiliary spool type solenoid valve, and the inertia of this cylinder smoothes the on/off control for the solenoid valve, so that the main spool type is controlled by this cylinder.

Next, a hydraulic control electromagnetic valve drive device according to the present invention will be explained with reference to the drawings.

In the present invention, an input signal is converted into a pulse having an on/off ratio corresponding to its level and used as a drive signal.

Conversion into such a pulse signal is performed, for example, as shown in FIG.

That is, the input signal from the terminal 11 is supplied to the non-inverting input terminal of the comparator 12, and the inverting input terminal of the comparator 120 receives the sawtooth wave signal 1 from the sawtooth wave generator 13, for example, as shown in FIG. 2A.
4 are occurring at regular intervals.

If the input signal et is at the level shown in FIG. 2A, the sawtooth wave signal 14 rises from zero level at the beginning of each period, so the input signal level ei is higher and the output of the comparator 12 is at a high level. , sawtooth signal 1
When the 40 level becomes larger than the input signal ei, the output of the comparator 12 is inverted and becomes a low level.

The output of this comparator 12 is applied to the base of a driving transistor 160 through a resistor 15.
The emitter is grounded, and the collector is connected to the power supply terminal 18 through the drive coil 17 of the sub-spool type solenoid valve.

Therefore, while comparator 12 is at a high level, transistor 16 is turned on as shown in FIG. 2B, and when the output of comparator 12 is at a low level, transistor 16 is turned off.

The output of the comparator 12 becomes a pulse signal, and the on/off state of this pulse is the same as the on/off state of the transistor 16 in FIG. 2B.

As the level of the input signal ei increases, the width of the output pulse, ie, the on-period, increases; as the input signal level decreases, the width of the output pulse decreases, and the on/off ratio of the output pulse changes in accordance with the input signal level.

The output pulse of this comparator 12 drives the sub-spool type solenoid valve, but in principle, for example, as shown in FIG.
The output of the comparator 12a is supplied to the non-inverting input terminal of the comparator 12a through the contact a side of the transistor 16.
one excitation coil 1γ of the spool solenoid valve 21 through a
Drive a.

The b side of the changeover switch 19 is connected to the non-inverting input terminal of the comparator 12b through the inverting circuit 22.
The output side of is connected to the base of the driving transistor 16b, and the collector of the l transistor 16b is connected to the other driving coil 17b of the electromagnetic valve 21.

The output of the sawtooth wave generator 13 is applied to the inverting input terminals of the comparators 12 a and 12 b, respectively.

The polarity of the input signal from the input terminal 110 is determined by the polarity determination circuit 23, and if the polarity is positive, the changeover switch 19 closes contact a.
If it is negative, it is switched to the contact side.

For example, when a drive current is applied to the coil 17a of the solenoid valve 21 with the switch 19 connected to the a side, the spool inside the solenoid valve 21 moves from the closed position to one open side.

The opening of the valve in response to this spool displacement has a characteristic as shown in Fig. 4, and the spool displacement corresponds to an area D1.
~ D20, although the range is narrow, the valve opening changes proportionally to the displacement.

When a drive current as shown in FIG. 2B is applied to the drive coil 17a, the spool inside the solenoid valve 21 moves in the opening direction while the current is on, and is closed by the spring inside the solenoid valve when the current is off. be returned to the direction.

If the next pulse is applied before the valve closes, the valve will open and close as shown in Figure 2C.
If this is done properly as shown in FIG. 5, for example, the spool will be displaced back and forth as shown in FIG. 5, and the average displacement will become larger as the pulse width becomes larger.

If this pulse width is appropriately selected, the spool position can be made to fluctuate small at a portion where the valve opening is proportional to the spool displacement, that is, at an appropriate position between D1 and D20 in FIG. The spool valve is now under proportional control.

When the polarity of the input signal 11 becomes negative, the drive coil 17b is similarly driven by the pulse, and the spool of the electromagnetic valve 21 is displaced and opened in the opposite direction to the previous displacement direction.

When the direction of the control oil flowing into and out of the solenoid valve 21 is reversed, the opening of this valve can also be controlled proportionally in accordance with the level of the input signal, as described above.

As shown in FIG. 4, the valve does not open but remains closed unless the displacement of the spool becomes greater than Dl.

Therefore, if the drive pulse input signal level is small and the drive pulse width is narrow, the average spool displacement will be less than D1,
In such a state, the valve is not controlled, but is simply driven in vain.

Although no hydraulic output is generated, pulse drive is performed, which shortens the life of the solenoid valve accordingly.

Therefore, in the present invention, in the case of such a small input signal, the supply of the drive signal to the solenoid valve is stopped.

For example, as shown in FIG. 6, the input signal at the input terminal 11 is not directly supplied to the comparator 12, but is supplied to the non-inverting input terminal of the differential amplifier 25.

A reference voltage e1 is supplied to the inverting input terminal of this amplifier 250 from a terminal 26, and its output side is connected to a diode 27.
It is further grounded through a resistor 28, through a diode 29 having the opposite polarity to the diode 2γ, and further through a resistor 31.

A connection point between the diode 27 and the resistor 28 is connected to the inverting input terminal through a resistor 32 in negative feedback.

The connection point between the diode 27 and the resistor 28 and the connection point between the diode 29 and the resistor 31 are connected through resistors to the non-inverting input terminal of the differential amplifier 33, and this non-inverting input terminal is connected to the reference voltage from the terminal 34. e2 is applied, the inverting input terminal of the differential amplifier 33 is grounded through a resistor, and the output terminal is grounded through a diode 35 and a resistor 36.

The connection point of these diode 35 and resistor 36 is terminal 37
and to the input terminal through a resistor 38.

In this configuration, when the input signal ei of the input terminal 110 is lower than the comparison voltage e1, the output of the differential amplifier 25 is at a low level, and the voltage e2 at the terminal 34 is smaller than this, so the output of the amplifier 33 is also at a low level. The output terminal 37 is at zero level.

However, when the input signal ei at the input terminal 110 exceeds el, the output of the amplifier 25 becomes e ie 1, which appears at the junction of the diode 27 and the resistor 28, and its output and the reference signal e2 at the terminal 340 are added to form a differential signal. It is obtained as the output of the amplifier 33.

Therefore, the output e at terminal 37.

has a characteristic as shown in FIG. 7 for the input signal ei.

In this way, while the input signal level et is smaller than 01, it is supplied as an O level to the comparator 12 in FIG. Valve 21 is not activated.

In this case, the amount of movement of the spool with respect to the input signal has characteristics as shown in FIG.

If the input signal reaches the level e1 at which the solenoid valve 21 starts to be driven, and the spool displacement amount D1 is selected when the valve just starts to open, the solenoid valve will be driven unnecessarily due to a small level. Never.

As described above, the electromagnetic valve can be controlled proportionally by pulse driving, but in that case, it is desirable to make the frequency relatively high in order to perform good control.

However, if the frequency is too high, problems may occur due to problems with the response characteristics of the vibration system caused by the spool and the spring that returns it, and surge pressure generated in the hydraulic circuit, so-called shock.

In order to solve this problem, in the present invention, the pilot cylinder is first controlled by the solenoid valve 21 without directly using the hydraulic pressure of the auxiliary spool type solenoid valve 21, thereby obtaining a smooth characteristic, that is, the control signal as a whole. The main spool-type solenoid valve is controlled by the pilot cylinder with a large inertia of 1-.

For example, as shown in FIG. 9, a sub-spool type solenoid valve 2102
The two input and output ports communicate with one side and the other side of the pilot cylinder 39, respectively.

As a result, the piston of the pilot cylinder 39 is displaced as the solenoid valve 21 moves.

The main spool type solenoid valve 41 is controlled by the piston of the pilot cylinder 39.

In this example, the cylinder 42 is operated by the main spool type solenoid valve 41.
This cylinder 42 controls the controlled device.

The auxiliary solenoid valve 21 may be connected to the operating rod so that it can be manually operated by the operating rod.

In this way, even if the auxiliary spool type solenoid valve 21 is controlled on and off, that is, even if it is controlled in an on-off manner by leaving the proportional control part due to the pulse drive, when the frequency reaches a certain level, the pilot Due to the inertia and oil loss of the spool of the cylinder 39 and the main spool type solenoid valve 41, the inertia of the spool of the main spool type solenoid valve 41 becomes large, and the frequency of the drive pulse is kept relatively low (even if the control is smooth). will be carried out.

That is, since the pilot cylinder 39 has a relatively large inertia, a kind of smoothing effect is performed thereby, and proportional control is performed.

As described above, according to the hydraulic control electromagnetic valve drive device according to the present invention, proportional control can be performed using an inexpensive on-off valve, and its controllability is good.

In this way, for example, even if the input signal is controlled manually, the control can be performed with good operability.

This input signal may be manually controlled, or, for example, the difference between the operating rod and the actual displacement of the controlled machine may be detected as an electrical signal and this may be supplied as the input signal.

In the above, the frequency is kept constant and the pulse width is changed to create a pulse with an on/off ratio according to the input signal, but it is also possible to change the pulse frequency with a constant pulse width, and in either case, it corresponds to a human input signal. It is sufficient if the output has a certain on-off ratio.

Further, the present invention can be applied not only to construction machinery but also as a control valve for general hydraulic control.

[Brief explanation of the drawing]

FIG. 1 is a circuit diagram showing an example of a circuit for converting an input signal into a pulse signal used in this invention, FIG. 2 is a waveform diagram for explaining the operation of FIG. 1, and FIG. A configuration diagram showing an example of a basic hydraulic control solenoid valve drive device, No. 4
The figure is a curve diagram showing the relationship between spool displacement and valve opening.
Fig. 5 is a curve diagram showing the relationship between pulse width and spool displacement, Fig. 6 is a connection diagram showing an example of a circuit for blocking a small input level in this invention, and Fig. 7 is a diagram showing the relationship between pulse width and spool displacement. Figure 8 is a curve diagram showing the relationship between input and spool displacement in the drive device according to the present invention when the circuit shown in Figure 6 is used; Figure 9 is a curve diagram showing the relationship between input and spool displacement in the drive device according to the present invention when the circuit shown in Figure 6 is used. FIG. 3 is a diagram showing an example configuration. 11: Input terminal, 12: Comparator, 13: Sawtooth wave generator, 17: Drive coil, 21' sub-spool type solenoid valve, 39
: Pilot cylinder, 41: Main spool type solenoid valve.

Claims (1)

[Claims] 1. A conversion circuit that generates a pulse signal with an on/off ratio according to the level of the human input signal, a sub-spool type solenoid valve that is supplied with the pulse signal from this conversion circuit and is controlled on/off, and a a blocking means for blocking the supply of the pulse signal to the sub-spool type solenoid valve when the value is below a predetermined value; and a block driven by the sub-spool type solenoid valve;
A hydraulically controlled solenoid valve drive device comprising: a pilot cylinder for smoothing on/off control operations of the sub-spool type solenoid valve; and a main spool type solenoid valve driven by the pilot cylinder.