JPH0226378A - Solenoid valve - Google Patents

Abstract

PURPOSE:To surely push back a plunger to off-position, even if an offset current remains, by coating non-magnetic material with a predetermined thickness on the magnetic pole face in the side of a solenoid. CONSTITUTION:Non-magnetic material 24 is coated on the magnetic pole face 16 of a solenoid 15 opposed to the plunger 14 of a pilot hydraulic pressure changeover mechanism through a return spring 18. The thickness of this non- magnetic material 24 is instituted so that an electromagnetic attractive force due to an offset current generated at switchover of an electromagnetic coil 15 from on-condition to off-condition is under the energizating force of the return spring 18.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an electromagnetic solenoid valve that operates a plunger using an electromagnetic solenoid to switch pilot hydraulic pressure to turn on and off a valve spool.

[Prior Art] Conventionally, as this type of electromagnetic solenoid valve, for example, the one shown in FIG. 3 is known.

In FIG. 3, reference numeral 1 denotes a valve body, and a spool 2 is slidably provided in the valve body 1. At the switching position of the spool 2 shown in the figure, the inlet port 3 and the outlet port 4 are in an off state. When the spool 2 is moved to the left against the return spring 5, the inlet port 3 and the outlet port 4 are brought into communication and turned on.

Switching the spool 2 on and off is performed by a pilot hydraulic pressure switching mechanism 6 and an electromagnetic solenoid 7 mounted on the right side of the valve body 1.

That is, a pilot liquid chamber 8 is formed at the right end of the spool 2, a fixed spool 10 is built into the pilot liquid chamber 8, and rubber valve seats 11 are installed on both sides of the fixed spool 10.
, 12 are connected by a joint pin 13 and are slidably assembled, and a plunger 1 is attached to the right valve seat 11.
4 is fixed to one end, thereby forming a hydraulic pressure switching mechanism 6.

The electromagnetic solenoid 7 is screwed onto the outside of the pilot hydraulic switching mechanism 6, includes an electromagnetic coil 15 that generates an electromagnetic attraction force, a magnetic pole surface 16 facing the plunger 14, and has a magnetic body 17. The plunger 14 is opposed to the magnetic pole surface 16 of the magnetic pole via a return spring 18.

The operation of such an electromagnetic solenoid valve is as follows.

First, when the electromagnetic coil 15 of the electromagnetic solenoid 7 is in a de-energized state, the plunger 14 is held in the first position (off position) shown by the return spring 18, and the valve seat 11 is in contact with the right end of the fixed spool 10. The supply of pilot hydraulic pressure from the internal flow path 19 is cut off. At this time, the pilot liquid chamber 8 is in communication with the drain port 20, and the spool 2 is pushed to the right side by the return spring 5 and is in an OFF state where it is stopped by the stopper ring 21.

Next, when the electromagnetic coil 15 of the electromagnetic solenoid 7 is energized,
The plunger 14 is stroked to the right by the electromagnetic attraction force generated from the magnetic pole surface 16 of the magnetic body 17, and the valve seat 11 opens the internal flow path 19 of the fixed spool 10, while the valve seat 12 closes the internal flow path 22 (first 2 position)
. Therefore, the pilot fluid pressure is supplied to the pilot fluid chamber 8 from the internal flow path 19 of the fixed spool 10 through the internal flow path 23 formed in the axial direction, and at the same time, communication to the drain port 20 is blocked by the valve seat 12. Because of this, pilot fluid pressure is applied to the right side of spool 2. Therefore, the spool 2 is pushed by the pilot hydraulic pressure and strokes to the left, and is switched to the on state where the inlet port 2 and the outlet port 4 are in communication.

[Problems to be Solved by the Invention] However, in such conventional electromagnetic solenoid valves, the spool does not return to the off position due to the offset current when the electromagnetic coil of the electromagnetic solenoid is switched from the on state to the off state. There was a problem that caused a time delay.

FIG. 4 schematically shows the plunger 14, return spring 18, magnetic body 17, and electromagnetic coil 15 shown in FIG. 3. When the electromagnetic coil 15 is controlled on and off as shown in FIG. , controller circuit characteristics,
For example, depending on temperature, drift, etc., even if the drive signal is turned off, the drive current may not be turned off immediately, and an offset of a certain size may remain.

FIG. 6 is a characteristic graph showing the relationship between the electromagnetic attraction force F of the plunger 14 generated by energizing the electromagnetic coil 15 in FIG. There is a relationship in which it decreases in approximately inverse proportion to the square of the square.

Return spring 1 for electromagnetic attraction force F shown by curve A
The spring force of No. 8 is set so as to be below the curve A of the electromagnetic attraction force, as shown by the straight line B.

Therefore, when the electromagnetic coil 15 is energized, the plunger 14
is attracted to the magnetic pole face 16 of the magnetic body 17 and the stroke L=
O, so the electromagnetic attractive force F becomes infinite (in reality, it is a fixed force), and the spring force F at that time is
The plunger 14 is attracted and held by a force obtained by subtracting S from the electromagnetic attraction force.

On the other hand, when the electromagnetic coil 15 is de-energized, the electromagnetic attractive force F shown by the curve A disappears, and the plunger 14 is pushed back to the position shown in FIG. 4 by the spring force shown by the straight line B.

However, as shown in FIG. 5, if the offset current remains even after the drive signal for the electromagnetic coil 15 is turned off,
As shown by the broken line C in Fig. 6, the electromagnetic attractive force also remains according to the offset current, and in this case, the stroke L
The electromagnetic attraction force FO due to the offset at the on position becomes O
If the spring force Fs exceeds the spring force Fs of the return spring 18, the plunger 14 cannot be returned to the OFF position by the return spring 18.

As a result, when the electromagnetic solenoid is turned off, there is a time delay in the return of the spool to the off position due to the offset current, resulting in a problem that the responsiveness of the valve is significantly deteriorated.

Of course, it would be possible to improve the controller circuit so that the offset does not occur when the electromagnetic solenoid is turned off, but this inevitably leads to the problem of complicating the circuit configuration and increasing costs.

The present invention was made in view of these conventional problems, and it is possible to reliably switch the valve to the off position with a simple configuration even if an offset remains when the drive signal is turned off by the controller. The purpose is to provide electromagnetic solenoid valves.

[Means for Solving the Problem] In order to achieve this object, the present invention provides a method in which an electromagnetic coil is energized on the magnetic pole surface of the electromagnetic solenoid that faces the plunger of the pilot hydraulic pressure switching mechanism via a return spring. It is coated with a non-magnetic material to a predetermined thickness such that the electromagnetic attraction force due to the offset current when switched from to the non-energized state is equal to or less than the spring force of the return spring.

[Operation] In the electromagnetic solenoid valve of the present invention having such a configuration, when the electromagnetic coil is energized, the plunger is attracted and held at a position in front of the magnetic pole surface determined by the thickness of the non-magnetic coating. Therefore, even if an offset current remains when the electromagnetic coil is de-energized, the attraction force of the plunger will always fall below the spring force of the return spring, making it possible to reliably return the plunger to the OFF position and turn off the valve. can.

Embodiment FIG. 1 is an explanatory diagram schematically showing an embodiment of the present invention by removing the plunger 14 and the magnetic body on the electromagnetic solenoid side in the pilot hydraulic pressure switching mechanism of the electromagnetic solenoid valve shown in FIG. 3. It is.

In FIG. 1, 14 is a plunger provided in the pilot hydraulic pressure switching mechanism, and a magnetic body 17 provided in an electromagnetic solenoid is provided on the right side of the plunger 14 with magnetic pole faces 16 facing each other. A return spring 18 is installed between the two. Also,
The magnetic body 17 generates an electromagnetic attractive force on the magnetic pole surface 16 by energizing the electromagnetic coil 15 arranged on the outside, which is schematically shown. For an electromagnetic solenoid that operates the plunger 14 by the electromagnetic attraction force generated on the magnetic pole face 16 of the magnetic body 17 by energization of the electromagnetic coil 15, in the present invention, the surface of the magnetic pole face 16 of the magnetic body 17 has a predetermined thickness. The non-magnetic material is coated with ΔL. The non-magnetic material 24 is realized by, for example, Teflon or paint.

Here, when the electromagnetic coil 15 is de-energized, the gap between the plunger 14 and the magnetic pole face 16, which is placed in the first position (off position) of the return spring 18, that is, the stroke L of the plunger 14, is usually set to about several M. On the other hand, the thickness ΔL of the non-magnetic material 24 formed on the magnetic pole surface 16 of the magnetic material 17 is determined according to the electromagnetic attractive force determined by the offset current generated when the electromagnetic coil 15 is turned off by the controller. The thickness difference ΔL of the non-magnetic material 24 may be set to approximately ΔL=0.2j7+#1 for the stroke L=number order.

Next, the present invention will be described in detail with reference to a characteristic graph of the electromagnetic attraction force and the stroke of the plunger 14 in the energized state of the electromagnetic coil 15 shown in FIG.

In FIG. 2, the electromagnetic attraction force F when the electromagnetic coil 15 is energized has a characteristic that decreases approximately in inverse proportion to the square of the distance indicated by the stroke, as shown by a curve A. In contrast to the characteristic of the electromagnetic attractive force F of the curve A, the spring force of the return spring 18 is determined to have the characteristic of the straight line B so as to be lower than the curve A.

On the other hand, it is assumed that the characteristics of the electromagnetic attractive force due to the maximum offset current predicted to occur when the electromagnetic coil 15 is de-energized are the characteristics shown by the broken curve C. The characteristic curve C of the electromagnetic attractive force due to this offset current is the plunger 1
For the on position where the stroke L=O of No. 4, a predetermined pressure,
The spring force of the return spring 14 is exceeded at 11 separated points. Therefore, the magnetic pole face 1 shown in FIG.
The thickness ΔL of the non-magnetic material 24 formed at 6 is set so that the characteristic C of the electromagnetic attractive force due to the offset current is on the right side of the 11th point, for example, the 22nd point, below the characteristic straight line B of the spring force of the return spring 18. Establish.

Assuming that the thickness ΔL of the non-magnetic material 24 formed on the magnetic pole face 16 of the magnetic material 17 is determined in this way, first, the electromagnetic coil 1
5 is energized and the plunger 14 is stroked by electromagnetic attraction force. The tip of the plunger 14 is the magnetic pole surface 16
The stroke stops when it comes into contact with the surface of the non-magnetic material 24 formed above and having a thickness of ΔL, and at this time, the electromagnetic attraction force acting on the plunger 14 moves by ΔL to the right of the on position where the stroke L=O. It is attracted and held with a force obtained by subtracting the spring force from the electromagnetic attraction force of the 20 shifted points.

Next, it is assumed that the energization of the electromagnetic coil 15 is cut off, and an offset current remains in the electromagnetic coil 15 in the energization cut-off state, so that an electromagnetic attraction force shown by a broken curve C is obtained. Plunger 14
is receiving electromagnetic attraction at 22 points located △L away from the magnetic pole surface 16, and since the electromagnetic attraction at 22 points is smaller than the spring force of the return spring 18 shown by the straight line B at that time, the electromagnetic attraction due to the offset current The return spring 18 can overcome the force and push the plunger 14 back to the off position.

Therefore, even if an offset current remains due to the circuit characteristics of the controller when the electromagnetic coil 15 is de-energized, the return spring 18 can reliably push the plunger 14 back to the OFF position.
The spool can be switched to the off position by cutting off the supply of pilot hydraulic pressure and simultaneously communicating with the drain port by returning to the off position.

As is clear from the above embodiments, in the present invention, ΔL is applied to the magnetic pole face 16 of the magnetic body 17 on the electromagnetic solenoid side.
The solenoid valve is characterized by being coated with a non-magnetic material 24 having a thickness of 24, and the other configuration is the same as the electromagnetic solenoid valve shown in the conventional example shown in FIG.

[Effects of the Invention] As explained above, according to the present invention, even if an offset current remains due to the circuit characteristics of the controller when the electromagnetic solenoid is de-energized, the electromagnetic attraction acting on the plunger due to the offset current is prevented. Since the force always falls below the spring force of the return spring, it is possible to reliably push the plunger back to the OFF position and switch the valve spool to the OFF position even if an offset current remains.

In addition, in order to prevent delays in switching response to the OFF position due to offset current, it is only necessary to coat the magnetic pole surface of the electromagnetic solenoid with a non-magnetic material of a predetermined thickness, which improves the valve's OFF response with an extremely simple configuration. Since no special changes are required to the valve structure or controller, it can be realized easily and at low cost.

[Brief explanation of the drawing]

Fig. 1 is an explanatory diagram schematically showing an embodiment of the present invention with respect to the plunger and electromagnetic coil portion of an electromagnetic solenoid valve; Fig. 2 is an explanatory diagram of the characteristics of the electromagnetic attraction force of the plunger according to the present invention; Fig. 3 The figure is a sectional view showing a conventional example: Figure 4 is an explanatory diagram schematically showing the conventional plunger and electromagnetic coil portion; Figure 5 is an explanatory diagram of the offset current that occurs when the electromagnetic solenoid is turned on and off; FIG. 6 is a diagram illustrating the characteristics of conventional electromagnetic attraction force. 1: Valve body 2 Varnish spool 3: Inlet port 4: Outlet port 5.18: Return spring 6: Pilot hydraulic switching mechanism 7: Electromagnetic solenoid 8: Pilot liquid chamber 10: Fixed spool 11.12: Valve seat 13: Joint pin 14 Nibranger 16: Magnetic pole face 17: Magnetic material 24: Non-magnetic material Characteristics Applicant: Fuji Iron Works Co., Ltd.

Claims (1)

[Claims] (1) A spool that is slidably provided in the valve body and switches the inlet port and the outlet port on and off, a pilot liquid chamber formed at one end of the spool, and a spool that is slidably provided in the valve body to switch the inlet port and the outlet port on and off; Pilot hydraulic pressure switching that cuts off the supply of pilot hydraulic pressure to the pilot liquid chamber and connects it to the drain port, and simultaneously cuts off the pilot liquid chamber from the drain port and supplies pilot hydraulic pressure by switching the plunger to the second position. A mechanism and a plunger of the pilot hydraulic pressure switching mechanism are opposed to the magnetic pole surface via a return spring, and the return spring holds the plunger in the first position when the electromagnetic coil is not energized, and the plunger is held in the first position when the electromagnetic coil is energized. and an electromagnetic solenoid that strokes the electromagnetic solenoid to the second position, wherein an attractive force due to an offset current when the electromagnetic coil is switched from a energized state to a de-energized state is applied to a magnetic pole surface of the electromagnetic solenoid. An electromagnetic solenoid valve characterized in that the electromagnetic solenoid valve is coated with a non-magnetic material to a predetermined thickness that is less than or equal to the spring force of the return spring.