JP3799507B2 - Industrial proportional solenoid valve - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an electromagnetic proportional valve used for industrial use, and to an electromagnetic proportional valve capable of stable position control.
[0002]
[Prior art]
Generally, a solenoid includes a movable plunger and a fixed iron core, and the movable plunger is attracted to the fixed iron core side by excitation of a coil. When the excitation of the coil is released, the movable plunger adsorbed by the return spring is returned. And if the front end side of this movable plunger is connected to the spool of the valve body, it can be used as a solenoid valve. However, in this solenoid valve, in the supplied current, the suction force with respect to the stroke appears as a curve with a characteristic that the suction force increases on the suction side, so it is difficult to balance the suction force of the solenoid and the load of the return spring. Thus, the movable plunger cannot be stopped at a position in the middle of the stroke.
[0003]
A proportional solenoid is used to solve this problem. The proportional solenoid can take a balance position with a load such as a spring, and forms a horizontal characteristic portion that makes the suction force constant for substantially the entire stroke at the controlled current value. Thus, the attractive force is increased in proportion to the increasing current. Therefore, by controlling the current, the position of the balance with the spring can be continuously changed and adjusted to an arbitrary position. Therefore, the position of the spool in the valve body can be adjusted. Accuracy can be maintained. As a result, the flow rate or pressure of the fluid flowing through the valve can be accurately maintained with the set stroke.
[0004]
Conventionally, an electromagnetic proportional solenoid is often used for the hydraulic electromagnetic valve B1. As shown in FIG. 7, the electromagnetic proportional solenoid 41 is directly attached to the hydraulic valve body 40, and the return spring 45 is connected to the poppet 44 in which the shaft 43 of the movable plunger 42 is movable in the hydraulic valve body 40. Connected through. The oil supplied into the hydraulic valve body 40 flows into a movable part such as a movable plunger 42 inside the solenoid 41 so as to lubricate. For this reason, the movable part in the solenoid 41 is not sealed, and the outside of the solenoid 41 is sealed to prevent oil leakage.
[0005]
In this type of load characteristic, as shown in FIG. 8, the spring load appears linearly with respect to the stroke. Therefore, the suction force of the movable plunger is affected only by the spring load.
[0006]
However, when the fluid flowing into the electromagnetic proportional valve uses not only oil but also general industrial fluids such as water and chemicals, the electromagnetic proportional valve (hereinafter referred to as a valve) B is shown in FIG. As described above, the solenoid 1 is attached so as to be separated from the valve body 3 so that the fluid from the valve body 3 does not flow into the proportional solenoid (hereinafter referred to as solenoid) 1. Therefore, a seal case 2 as a connecting body is disposed between the valve body 3 and the solenoid 1 to prevent leakage of fluid in the valve body 3.
[0007]
The solenoid 1 is provided with a fixed iron core 11 and a movable plunger 12, and the movable plunger 12 is configured to be attracted to the fixed iron core 11 side when a coil 10 wound around the solenoid 1 is energized. Yes. A core 14a is attached to one end of the shaft 13 formed integrally with the movable plunger 12, and a differential transformer 14b is disposed around the core 14a. The core 14a and the differential transformer 14b are included. A displacement sensor 14 for detecting the position of the movable plunger 12 is configured. The other end of the shaft 13 is connected to a spring receiver 22 disposed in a seal case 2 described later. Further, a tapered horizontal characteristic forming portion 11a is formed at the distal end of the fixed iron core 11 on the movable plunger 12 side.
[0008]
A spring chamber 21 in which a return spring 23 is disposed and a connection window portion 24 in which a seal packing 26 is disposed are formed in the seal case 2, and the spring chamber 21 is connected to the shaft 13 of the movable plunger 12 to be inserted. A spring receiver 22 to be connected and a return spring 23 for urging the spring receiver 22 toward the valve body 3 are disposed. One end of the connection window portion 24 is connected to the spring receiver 22 and the other end is connected to the valve body 3. A connecting pin 25 connected to the inner spool 31, a seal packing 26 disposed around the connecting pin 25 to prevent leakage of fluid from the valve body 3, and a seal that presses the seal packing 26 toward the valve body 3 side. A presser 27 is provided.
[0009]
As shown in FIG. 2, the control circuit in the valve B includes a command signal amplifier 4 that receives the first command signal a and amplifies the first command signal, and a displacement sensor 14 that is attached to the solenoid 1 side. Displacement signal amplifier 5 for amplifying input displacement signal b, command signal amplifier 4, differential amplifier 6 for combining signals c and d output from displacement signal amplifier 5, and dither oscillation circuit 7 for oscillating a pulse waveform The comparator 8 that compares the second command signal e output from the differential amplifier 6 with the waveform signal f oscillated from the dither oscillation circuit, and the command signal g output from the comparator 8 And a transistor portion 9 that controls a current flowing through the coil 10. The transistor unit 9 may not be a general transistor but may be a power switching element such as an FET.
[0010]
[Problems to be solved by the invention]
However, the seal packing 26 that prevents the fluid in the valve body 3 from leaking is sealed between the connection pin 25 and the valve body 3 by the seal retainer 27 with a strong fit. In order to increase the frictional resistance and stabilize the stop position of the spool 31, the pressure of the return spring 23 is increased. Therefore, a combined load of the spring load and the friction load is applied to the valve B.
[0011]
The load to which this friction is applied is more difficult to control the applied current than the load by only the spring load, and the positional accuracy of the spool cannot be improved and the hysteresis cannot be reduced.
[0012]
This invention solves the above-mentioned subject, and it aims at providing the industrial electromagnetic proportional valve which can make the hysteresis small while improving the precision of spool position control.
[0013]
[Means for Solving the Problems]
In order to solve the above-described problems, the industrial electromagnetic proportional valve according to the present invention is configured as follows. That is,
A proportional solenoid comprising a valve body having a spool, a fixed iron core and a movable plunger, wherein the movable plunger is attracted to the fixed iron core by excitation of a coil, and the movable plunger is returned by a spring; In an electromagnetic proportional valve configured as
A connecting body is disposed between the valve body and the solenoid,
The connection body is provided with a connection pin that connects the spool and a shaft formed integrally with the movable plunger,
An industrial electromagnetic proportional valve in which a sealing means is disposed at least between the valve body and the connection pin,
The control circuit of the solenoid has control means for minutely changing the current flowing through the coil, and amplification means for amplifying a control voltage for adjusting the current that is minutely changed,
The gain set by the amplifying means is set to be larger than the gradient of the friction spring load line generated along with the minute movement of the movable plunger.
[0014]
Preferably, the control circuit includes a displacement sensor means and a pulse oscillating means, and is a synthesized command signal synthesized by a displacement signal output from the displacement sensor means and a command signal for setting a predetermined stroke. However, any method may be used as long as it is compared with the oscillation waveform output from the pulse oscillation means, and the current flowing through the coil is controlled by adjusting the amplitude of the oscillation waveform.
[0015]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, an embodiment of the present invention will be described with reference to the drawings. The configuration of the electromagnetic proportional valve is the same as that shown in FIG. 1, and its control circuit is the same as that shown in FIG.
[0016]
The main part of the present invention is a valve having the configuration shown in FIG. 1 and the control circuit shown in FIG. 2, and a change in the controlled minute current value with respect to the load applied to the valve, that is, the minute movement amount of the movable plunger 12. It becomes clear by elucidating.
[0017]
The graph of FIG. 3 shows the load (current value) characteristics of the solenoid 1. The horizontal axis shows the stroke amount of the movable plunger, and the vertical axis shows the horizontal suction force (load force). For example, when a suction force of 20 kg is required, it is necessary to pass a current value of about 1.3 A. All the loads Y (current values) by moving the movable plunger 12 by changing the current value are the sum of the load (current value) S by the spring and the load T (current value) by all the frictional resistances. Thus, Y = S + T in the direction in which the movable plunger 12 is attracted (A → B in the graph in the figure), and Y = ST in the direction in which the movable plunger returns (C → D in the graph in the figure). Within the full stroke, the load (current value) range appears over a fairly wide range.
[0018]
Now, the coil 10 is energized and moved in a direction (A → B) in which the movable plunger 12 is attracted, and the commanded current is changed to the total load of the combined spring load and friction load at the position P1. It is controlled to a well-positioned position. In this state, when the movable plunger 12 is slightly moved in the direction of large stroke (C → D) due to disturbance, a friction load is applied at the time of movement, and the movable plunger 12 passes through P2 from the position of P1. It is moved to the position P3. A line connecting the P1 and P3 (NN line) is called a friction spring load line N. That is, on the friction spring load line N, a current value corresponding to a given stroke amount is determined, so that control by current becomes possible. Therefore, the friction spring load line N may be set so that the gain of the differential amplifier 6 becomes the minimum.
[0019]
Next, a case where the gain of the differential amplifier 6 is low will be described with reference to FIG. 4 for comparison with the above description.
[0020]
When the movable plunger 12 currently at the position Q1 is controlled to move to the load line on the suction side, the friction spring load line N is a line passing through Q1, Q2, and Q3 (NN line with respect to the position of Q1. ), And the gain of the differential amplifier 6 is set to a line connecting the Q1 and Q5 (LL line lower than the friction spring load line N). Now, when the movable plunger 12 tries to move from Q1 to the intermediate point Q0 of the friction spring load line N, the load (current value) with respect to the displacement from Q1 to Q0 is on the LL line, and therefore corresponds to the load of Q0. The stroke is shifted to the stroke position Q4 corresponding to the point Q'0 where the line intersects the gain of the differential amplifier 6 (LL line). Accordingly, the actual movement amount X is moved to X1. This X1-X appears as the hysteresis width.
[0021]
Therefore, if the gain of the differential amplifier is lower than the friction spring load line, the stroke position of the movable plunger 12 cannot be controlled, and the hysteresis increases.
[0022]
On the contrary, when the gain of the differential amplifier is larger than the friction spring load line, the stroke position of the movable plunger 12 is on the friction spring load line, so that control by current is possible.
[0023]
As described above, it is understood that the control of the position of the movable plunger 12 in the valve B is in the relationship between the friction spring load line N and the gain of the differential amplifier 6.
[0024]
5 and 6 control the voltage applied to the transistor section 9 with respect to the waveform output from the dither oscillation circuit 7 in order to further improve the positional accuracy of the movable plunger 12, and the dither oscillation circuit in FIG. 7 shows a method in which the oscillation waveform f oscillated from 7 and the second command signal e outputted from the differential amplifier 6 are compared by the comparator 8 and the applied voltage is converted into a pulse signal.
[0025]
In FIG. 5, when the second command signal e from the differential amplifier 6 is compared with the oscillation waveform f1, and subtracting e1 from f1, the command signal g1 having an ON-OFF waveform with a pulse width as shown in (a). Thus, the command signal g1 is sent to the transistor unit 9 so that a current flows through the solenoid 1. If the displacement of the movable plunger moved by this current is excessive with respect to the set position, the width of the waveform of the command signal g1 is narrowed to reduce the current flowing through the solenoid 1. Conversely, if the setting position is insufficient, the width of the waveform of the command signal g1 is increased and feedback is performed so that a large current flows through the solenoid 1. If the stroke position of the movable plunger 12 is too far from the set position, the waveform width of the command signal g1 is reduced. First, the displacement signal b is output from the displacement sensor 14 and input to the displacement signal amplifier 5. The second command signal e <b> 2 is input to the comparator 8 after being combined with the signal c amplified from the first command signal a by the differential amplifier 6. The second command signal e2 is a signal having a lower voltage than the second command signal e1, and when e2 is subtracted from f1 by the comparator 8, as shown in (b), a voltage having a smaller pulse width than the command signal g1. A command signal g2 indicating a value is sent to the transistor unit 9. When a current is passed through the solenoid 1, the current value becomes lower than before, so that the movable plunger 12 is moved in the returning direction.
[0026]
Next, the case of FIG. 6 will be described. In this case, the amplitude of the waveform f output from the dither oscillation circuit 7 is adjusted to control the voltage, and the adjustment of the amplitude of the waveform f is manually operated using, for example, a volume (not shown). When the amplitude of the waveform f1 shown in FIG. 5 is large, a waveform f2 having an amplitude smaller than the amplitude of the waveform f1 adjusted by the volume is output to the comparator 8. The waveform f2 is converted to a command signal g3 by subtracting the second command signal e3 output from the differential amplifier 6. Further, when the waveform f2 is fed back so that the second command signal e4 corresponding to a voltage smaller than the second command signal e3 is inputted, it is converted into a command signal g4 having a pulse width smaller than g3. If the voltage difference between the second command signals e1 and e2 compared with the waveform f1 and the voltage difference between the second command signals e3 and e4 compared with the waveform f2 are the same, the command signal g in each case The fluctuations in the pulse widths of the command signals g3 and g4 are larger than the fluctuations in the pulse widths of the command signals g1 and g2. That is, the smaller the amplitude of the waveform f output from the dither oscillation circuit, the greater the pulse width of the command signal g with respect to the fluctuation of the second command signal e.
[0027]
As described above, when the waveform f output from the dither oscillation circuit 7 and the second command signal e are compared and fed back, the displacement accuracy of the movable plunger can be further increased.
[0028]
The displacement sensor 14 uses a differential transformer in this embodiment, but may be a potentiometer.
[0029]
【The invention's effect】
As mentioned above, the industrial electromagnetic proportional valve of the present invention is
A proportional solenoid comprising a valve body having a spool, a fixed iron core and a movable plunger, wherein the movable plunger is attracted to the fixed iron core by excitation of a coil, and the movable plunger is returned by a spring; Configured
A connection body is disposed between the valve body and the solenoid, and a connection pin that connects the spool and a shaft formed integrally with the movable plunger is disposed on the connection body. Since the sealing means is disposed at least between the valve body and the connection pin, it is particularly suitable for those using a fluid other than hydraulic pressure. The solenoid control circuit includes a control unit that minutely changes a current flowing through the coil, and an amplification unit that amplifies a control voltage for adjusting the minutely changed current, and is set by the amplification unit. Is set to be larger than the gradient of the friction spring load line generated along with the minute movement of the movable plunger, the accuracy of spool position control can be improved, and the valve opening degree Accuracy can be improved and hysteresis can be reduced.
[0030]
Further, the control circuit includes a displacement sensor means and a pulse oscillating means, and a synthesized command signal synthesized by a displacement signal output from the displacement sensor means and a command signal for setting a predetermined stroke, It is compared with the oscillation waveform output from the pulse oscillation means, and the current flowing through the coil can be controlled by adjusting the amplitude of the oscillation waveform. it can.
[Brief description of the drawings]
FIG. 1 is a cross-sectional view of a general industrial electromagnetic proportional valve. FIG. 2 is a control circuit diagram in FIG. 1. FIG. 3 is a graph showing load characteristics for explaining the main part of the present invention. Elucidation diagram for comparing load line and gain [Fig. 5] Fig. 1 shows the conversion of the waveform output from the dither oscillation circuit into a pulse waveform.
FIG. 6 is a diagram for converting the waveform output from the dither oscillation circuit into a pulse waveform;
FIG. 7 is a diagram showing a conventional electromagnetic proportional valve. FIG. 8 is a graph showing load characteristics of the electromagnetic proportional valve in FIG.
B ... Proportional solenoid valve 1 ... Solenoid 2 ... Seal case (connector)
DESCRIPTION OF SYMBOLS 3 ... Valve body 6 ... Differential amplifier 7 ... Dither oscillation circuit 8 ... Comparator 10 ... Coil 11 ... Fixed iron core 12 ... Movable plunger 13 ... Shaft 14 ... Displacement sensor 23 ... Return spring 25 ... Connection pin 26 ... Seal packing (seal Element)
31 ... Spool N ... Friction spring load line e ... Second command signal f ... Oscillation waveform g ... Command signal

Claims (2)

A proportional solenoid comprising a valve body having a spool, a fixed iron core and a movable plunger, wherein the movable plunger is attracted to the fixed iron core by excitation of a coil, and the movable plunger is returned by a spring; In an electromagnetic proportional valve configured as
A connecting body is disposed between the valve body and the solenoid,
The connection body is provided with a connection pin that connects the spool and a shaft formed integrally with the movable plunger,
An industrial electromagnetic proportional valve in which a sealing means is disposed at least between the valve body and the connection pin,
The control circuit of the solenoid has control means for minutely changing the current flowing through the coil, and amplification means for amplifying a control voltage for adjusting the current that is minutely changed,
An industrial electromagnetic proportional valve characterized in that a gain set by the amplifying means is set so as to be larger than a gradient of a friction spring load line generated with a minute movement of the movable plunger. The control circuit includes a displacement sensor means and a pulse oscillation means, and a synthesized command signal synthesized by a displacement signal output from the displacement sensor means and a command signal for setting a predetermined stroke is the pulse. 2. The industrial electromagnetic proportional valve according to claim 1, wherein the current flowing through the coil is controlled by comparing with an oscillation waveform output from an oscillation means and adjusting an amplitude of the oscillation waveform.

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