JP2743338B2 - Actuator using magnetic fluid - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an actuator using a magnetic fluid, and more particularly to an actuator which has a high response speed and a large driving force when used in a fluid flow control device.

[0002]

2. Description of the Related Art As an example of a conventional flow control device, a configuration shown in a schematic diagram of FIG. 13 is known. That is, the sensor 2 is arranged upstream of the pipe 1 through which the fluid flows, and a signal detected by the sensor 2 is input to the control unit 3, and based on comparison with the set flow rate signal 4, the control unit 3 Outputs a control signal to the valve operating unit 5 and moves the variable opening valve 6 disposed in the pipe 1 in the vertical direction in the figure to control the flow rate of the fluid.

Various methods for controlling the opening / closing degree by the opening degree variable valve 6 are considered.
Solenoid valve type and piezoelectric element type are mainly adopted.
In either case, it is necessary to move the valve with a force that overcomes the pressure of the flowing fluid, and the flow rate control accuracy is increased by moving the valve with a stroke of several tens to several hundreds of microns.

FIG. 14 is a conceptual diagram for explaining a basic operation for reciprocating the load 7 using a conventionally known magnetic fluid. A non-magnetic container 9 enclosing a magnetic fluid 8 is shown in FIG. A disk 10 made of a non-magnetic material is placed in the inside, and an output shaft 11 protruding from one side of the disk 10 made of the non-magnetic material is led out of the container 9 made of a non-magnetic material to support the load 7. Then, a coil 12 is arranged on the other side of the disc 10 made of a non-magnetic material and outside the container 9 made of a non-magnetic material, and both ends of the coil are connected to a power supply 13 to generate a magnetic field.

[0005] The strength of the magnetic field generated by the coil 12 has a magnetic field gradient in the A direction. Therefore, a magnetic pressure difference is generated between the upper surface and the lower surface of the disk 10 made of a non-magnetic material, and the disk 10 made of a non-magnetic material moves upward due to a magnetic levitation force. This lifting motion is transmitted to the load 7 via the output shaft 11, and the load 7 can be raised. When the current flowing through the coil 12 is reduced, the magnetic pressure difference between the upper surface and the lower surface of the disk 10 made of a non-magnetic material is reduced, and the load 10 moves downward by its own weight. Thus, the load can be reciprocated by the amount of current flowing through the coil 12.

When the magnetic field strength is small and M = ＭH (χ = constant), the magnetic levitation force ΔN (kg · m / s ² ) acting on the disk 10 made of a non-magnetic material in the magnetic fluid 8 is lower. It can be expressed by equation (1). ^{ΔN (kg · m / s 2} ) = χ (χ + 1) / 2 · (H 2 2 -H 1 2) · S ... (1) where chi is susceptibility, H _1, H ₂ are made of a non-magnetic material Disk 10
And S is the area (m ² ) of the disk 10 made of a non-magnetic material.

FIGS. 15 and 16 are conceptual views for explaining a basic operation for generating a magnetic repulsive force. A solenoid 15 is provided around a core 14 made of a soft magnetic material, and a core is provided at an opening of the core 14. A plunger 16 of the same material as 14 is arranged. When power is supplied to the solenoid 15 from a power source (not shown), the core 14 and the plunger 16 are magnetized in the same direction, and the core 14 exerts a repulsive force on the plunger 16 of the same material, and the plunger floats in the B direction.

[0008]

Among the three methods used for controlling the degree of opening and closing of the valve, the piezoelectric element method is characterized by a high response speed and good position accuracy. Due to the high cost, it cannot be frequently used for a flow rate control device that requires mass productivity. Although the thermal expansion method and the solenoid valve method are inexpensive, the thermal expansion method has a slow response speed, and the solenoid valve method has a problem in stability of continuous control.

Further, the actuator using only the magnetic levitation force shown in FIG. 14 or the actuator using only the magnetic repulsion force shown in FIGS. 15 and 16 cannot obtain a large driving force as a development target. There is a problem.

Accordingly, the present invention has been made in view of the above, and utilizes both the driving of a non-magnetic material in a magnetic fluid and the magnetic repulsion, and at low cost by combining this with a booster. It is an object of the present invention to provide an actuator having a large driving force and a high response speed and capable of continuous control.

[0011]

FIG. 17 is a conceptual diagram for explaining a basic operation for achieving the above object. An electromagnetic magnet composed of a solenoid 15 disposed around a core 14 having a central hole made of a soft magnetic material, a plunger 16 of the same material as the core 14 disposed in the central hole of the core 14, and an upper part of the electromagnetic magnet A container 9 made of a non-magnetic material, which is provided and filled with a magnetic fluid 8, a disk 10 made of a non-magnetic material, and a disk 10 made of a non-magnetic material and arranged in the magnetic fluid 8 and fixed to a plunger 16. A small-diameter piston 17 made of a non-magnetic material connected to the upper part of the piston 10
And a small-diameter cylinder 18, a large-diameter cylinder 20, and a large-diameter piston 19 having different diameters attached to the container 9 made of the nonmagnetic material, and a floating action caused by a repulsive force of the plunger 16 by the electromagnetic magnet. The load 7 is raised via the output shaft 11 derived from the piston 19 by receiving the upward movement of the plunger 16 in which the magnetic levitation force caused by the magnetic pressure difference acting on the disk 10 made of a non-magnetic material is synergistic. Let it.

In order to further amplify the driving force by the above method, a small-diameter cylinder 18 and a large-diameter cylinder 20 having different diameters are provided between a disc 10 made of a non-magnetic material and an output shaft 11, and a container made of a non-magnetic material. 9, a disk 10 made of a non-magnetic material
The small-diameter piston 1 is composed of a large-diameter piston 19 transmitted through a hydraulic oil 21 filled in a large-diameter cylinder 18 to slide the small-diameter piston 17 fixed to the upper end of the small-diameter piston 1.
The driving force of the plunger 16 is increased by the boosting effect due to the difference between the diameters of the piston 7 and the large-diameter piston 19.

[0013]

According to the actuator using the magnetic fluid, when the power supply energizes the solenoid of the electromagnetic magnet, the core and the plunger of the same material are magnetized in the same direction, and the plunger floats by the repulsive force and is generated from the solenoid at the same time. Due to the magnetic field gradient, a magnetic pressure difference is generated between the upper surface and the lower surface of the disk made of a non-magnetic material in the magnetic fluid, and a magnetic levitation force acts on the disk made of the non-magnetic material in an upward direction to raise the plunger. The ascending movement, which is a combination of the levitation action caused by the repulsive force of the plunger and the magnetic levitation action of the magnetic fluid, is transmitted to a small-diameter piston connected to a disk made of a non-magnetic material, and the small-diameter piston slides. Is transmitted to the large-diameter piston via the hydraulic oil, and the driving force of the plunger is increased by the boosting effect due to the difference in diameter between the small-diameter piston and the large-diameter piston to perform the ascending movement. Further, the strength of the magnetic field varies depending on the amount of current flowing through the solenoid, and accordingly, the repulsive force of the plunger and the magnetic levitation force of the disk made of a non-magnetic material also change, so that the load can be controlled to rise or fall by the current.

Accordingly, the ascending movement of the plunger having a large force, which is a combination of the levitation action caused by the repulsive force of the plunger and the levitation action by the magnetic fluid, is transmitted to the load by the booster, and the target response speed is controlled by controlling the current. The load can be reciprocated by the large driving force.

[0015]

DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of an actuator using a magnetic fluid according to the present invention will be described below with reference to the drawings. The present embodiment utilizes both the buoyancy of a non-magnetic material in a magnetic fluid and the repulsion of a plunger of the same material as the core of a soft magnetic material, and realizes an actuator having a booster added thereto. Has become.

FIG. 1 shows a specific example of an actuator using a magnetic fluid according to the present invention. In FIG. 1, reference numeral 22 denotes a base, and columns 23, 23 are screwed and fixed to both ends of the base 22. In addition, an electromagnetic magnet 28 is disposed substantially at the center of the base 22. The electromagnetic magnet 28 includes a core 14 made of a soft magnetic material and a central hole 14 of the core 14.
The core 14 includes an insert core 31 made of a soft magnetic material, a solenoid 15, and a plunger 16 made of the same material as the core 14. A groove 32a and a hole 32 are formed in the insert core 31 as a passage for the magnetic fluid in order to smooth the movement of the plunger 16, and a head 16a of the same material is fixed to the upper end of the plunger 16.

Above the electromagnetic magnet 28, a container 9 made of a non-magnetic material, in which the magnetic fluid 8 is sealed, is disposed. In the magnetic fluid 8, disks 24, 24 made of a non-magnetic material, A piston rod 17a made of a non-magnetic material is connected to the disks 24, 24. A small-diameter piston 17 fixed to the tip of the piston rod 17a
Are slidably inserted into the small-diameter cylinder 18 filled with the hydraulic oil 21.

A large-diameter cylinder 20 having a different diameter is connected to the small-diameter cylinder 18 and is fixed to an inner wall surface of an outer cylinder 29. The outer cylinder 29 faces the hydraulic oil 21. A large-diameter piston 19 is slidably inserted into a large-diameter cylinder 20. A cover 26 made of a non-magnetic material is fixed to the upper portion of the inner wall of the outer cylinder 29, and the output shaft 11 fixed to the upper surface of the large-diameter piston 19 passes through a center hole 26 a formed in the cover 26. And supports a load not shown. A spring 25 is inserted between the cover 26 and the large-diameter piston 19 to always push the large-diameter piston 19 downward. Reference numeral 27 denotes a pressure adjusting bypass connecting the upper space of the large-diameter piston 19 and the upper space of the magnetic fluid 8.

A small-diameter cylinder 18 through which the small-diameter piston 17 is slidably inserted, an outer cylinder 29 fixed to the small-diameter cylinder 18, and a slidable surface facing the hydraulic oil 21 in the outer cylinder 29. The booster 30 for the output shaft 11 is constituted by the large-diameter piston 19 inserted through the shaft.

The basic operation of this embodiment is as follows. First, by energizing the solenoid 15 of the electromagnetic magnet 28 from a power source (not shown), the plunger 16 made of the same material as the core 14 is magnetized in the same direction, and the magnetic force is generated between the insert core head 31a of the insert core 31 and the plunger head 16a. A repulsive force is generated, and the plunger 16 floats in the direction C due to the repulsive force. At the same time solenoid 1
5 made of non-magnetic material due to the magnetic field gradient generated from 5
A magnetic pressure difference is generated between the upper and lower surfaces of the magnetic fluids 8 on the upper and lower surfaces of the disks 4, 24, and the disks 24, 24 made of a non-magnetic material move upward in the direction D by magnetic levitation.

Therefore, the levitation effect caused by the repulsive force of the plunger 16 and the magnetic levitation effect acting on the discs 24, 24 made of a non-magnetic material are synergistically moved to move the piston rod 17a upward. The piston 17 is transmitted to the small-diameter piston 17 fixed to the tip of the small-diameter cylinder, and the small-diameter piston 17 slides in the small-diameter cylinder 18 filled with the hydraulic oil 21.

The upward movement of the small-diameter piston 17 is transmitted to the large-diameter piston 19 through the hydraulic oil 21, and the large-diameter piston 19 slides in the large-diameter cylinder 20 filled with the hydraulic oil 21. Move. Therefore, the small-diameter piston 17
The driving force of the piston rod 17a is increased by the boosting effect due to the difference between the diameter of the large diameter piston 19 and that of the large diameter piston 19, and the piston rod 17a is led outward from the large diameter piston 19 through the center hole 26a formed in the cover 26. The output shaft 11 performs a rising motion with a large driving force. When the current flowing through the solenoid 15 is reduced, the repulsive force acting between the insert core head 31a and the plunger head 16a and the magnetic pressure difference acting on the disks 24, 24 made of a non-magnetic material are reduced, and the output shaft 11
Is smaller than the force of the spring 25. Therefore, the output shaft 11 moves downward by the force of the spring 25. During the above operation, a container made of a non-magnetic material is generated by sliding of the small-diameter piston 17 and the large-diameter piston 19 when air flows through the upper space of the large-diameter piston 19 and the upper space of the magnetic fluid 8 by the bypass 27. The pressure imbalance in 9 is adjusted and a smooth movement of the small diameter piston 17 and the large diameter piston 19 is obtained.

Therefore, according to the present embodiment, a floating action is caused by the repulsion of the plunger 16 due to the magnetic field generated from the electromagnetic magnet 28 by applying a current to the electromagnetic magnet 28, and the disk 24 made of a non-magnetic material in the magnetic fluid 8. , 24 are transmitted to the piston rod 17a, and the ascending movement is amplified by the booster 30,
The load is transmitted to a load (not shown) as a rising motion of the output shaft 11, and the load can be raised. Electromagnetic magnet 28
When the current flowing through the output shaft 11 is reduced, the output shaft 11 is lowered by the weight of the spring 25 and a load (not shown). Therefore, the load can be reciprocated by controlling the current flowing through the electromagnetic magnet 28.

The effect of the shape of the plunger 16 made of the soft magnetic material shown in FIG. 2 on the magnetic repulsion was examined. That is, the current flowing through the solenoid 15 is 0.4 A, the diameter of the plunger head 16a when the jump height of the plunger 16 is 0.5 × 10 ⁻³ m is a, the thickness of the plunger head 16a is b, and The length was c, the diameter of the cylindrical portion of the plunger 16 was d, and a hole having a diameter e was formed at the center of the plunger 16 to consider the effect of weight reduction. The results are shown in FIGS.

Each of the above figures is a graph in which the effective force, which is a value measured by the electronic balance, and the weight of the plunger 16 are stacked, and the sum of the two is the magnetic repulsive force. From the graphs shown in FIGS. 3 and 4, as the shape of the plunger 16 having the largest effective force, the diameter of the plunger head 16a is equal to the diameter of the core 14 (17.5 × 10 ⁻³ m), and the thickness of the plunger head 16a is It is preferable to make the thickness b thin.

FIG. 5 shows that the overall length c is 10 to 40.
× 10- ³ significant difference in repulsive force in m is not seen, 5
At × 10 ⁻³ m, it was confirmed that it was greatly reduced. This is because the demagnetizing field coefficient of the plunger 16 increases and the magnetization decreases rapidly. Therefore, by making the length of the plunger 16 equal to or longer than the diameter d of the cylindrical portion and forming a hole having a diameter e at the center of the plunger 16, a great effect on weight reduction can be obtained as shown in FIG.

Next, the effect of the shape of the discs 24, 24 made of a non-magnetic material disposed in the magnetic fluid 8 on the magnetic levitation force was examined. The diameter of the cylindrical portion is 6 × 10 as the plunger 16.
- it is used aluminum ³ m, the insert core 31
No magnetic repulsion occurs. A disk 24 made of a non-magnetic material,
24 is an aluminum plate having a diameter of 25 × 10 ⁻³ m and a thickness of 2 × 10 ⁻³ m. Then, a magnetic levitation force was measured by placing the magnetic fluid 8 filled on an electronic balance and fixing the upper ends of the discs 24, 24 made of a non-magnetic material, and applying a current of 0.25A. The results are shown in FIGS.

FIG. 7 is a graph showing the result of examining the effect of the distance between the disks 24, 24 made of non-magnetic material on the magnetic levitation force, and FIG.
The result of examining the effect of the number of
According to FIGS. 7 and 8, it was confirmed that the effective force decreases as the distance between the disks 24 made of a non-magnetic material increases.
This is because when the distance becomes longer, the distance from the core 14 constituting the electromagnetic magnet 28 increases, and the magnetic field strengths H ₁ , H ₁ , on the upper and lower surfaces of the non-magnetic disks 24, 24 shown in the above equation (1). This is because H ₂ becomes smaller. The effective force increases up to three discs 24 made of non-magnetic material, but the rate of increase decreases when the discs are three or more. Therefore, it is optimal that the interval between the disks 24, 24 made of a non-magnetic material is reduced and the number of the disks is about three.

Next, the effect of the magnetic repulsion on the effective force was examined. FIG. 9 shows the result. According to the drawing, the number of the discs 24, 24 made of a non-magnetic material is set to three,
As compared with the case where aluminum was used as the material of the above, the effective force when the soft magnetic material was used as the plunger 16 was about 4.5 times, and it was found that the effect of the repulsive force of the plunger 16 was large.

Therefore, in this embodiment, the spring constant of the spring in the actuator using the magnetic fluid 8 shown in FIG. 1 is 1.5 × 10 ⁻³ (kg / mm), and the diameter of the plunger head 16a is 17.5. × 10- ³ m, 0.5 thickness × 1
Was 0- ³ m. The diameter of the cylindrical portion of the plunger 16 is 6 × 10 ⁻³ m and the length is 20 × 10 ⁻³ m.
A 3.5 × 10 ^-3 m hole was formed in the center of 6 to reduce the weight. The booster 30 is a 6 × 10 ^-3 filled with hydraulic oil 21.
The piston 17 has a small diameter of 17 m and a large diameter piston 19 of 40 × 10 ⁻³ m.

FIG. 10 is a graph showing the effect of current and load on the stroke of the actuator obtained according to the present embodiment. 1.0998k load when I = 0.25A
Stroke 45 × 10- ⁶ m was obtained in g, initial goal was achieved. Also, the stroke increases as the current value increases. The stroke can be controlled by the current value.

FIG. 11 shows an example of the measurement of the indian response by the laser displacement meter. FIG. 12 is a graph showing the effect of the current on the time constant, and shows the value of the time constant s when the current I is changed. From FIG. 12, the time constant s when the current is on tends to increase as the current value increases.
0.45 seconds at 0.25A. On the other hand, when the current is off, the time constant is as slow as 4.25 seconds. It is presumed that the cause of the variation in the time constant when the current is off is the friction between the O-rings of the small-diameter piston 17 and the large-diameter piston 19 constituting the booster 30 and the cylinder.

[0033]

As described above in detail, in the actuator using the magnetic fluid according to the present invention, the plunger made of the same material as the core of the electromagnetic magnet floats due to the repulsion due to the magnetization of the core, and at the same time, the magnetic gradient is generated. Since a disk made of a non-magnetic material in a magnetic fluid moves upward by magnetic levitation force, the upward movement of the plunger, which has a large force that combines the levitation action caused by the repulsive force of the plunger and the magnetic levitation action by the magnetic fluid Is increased by the booster and then transmitted to the load to obtain an actuator capable of reciprocating the load with a target response speed and a large driving force.

In particular, it solves the problem of responsiveness of the conventional thermal expansion system and the drawback that continuous control of the solenoid valve system is not possible. The present invention can be applied to a flow control device which is low and requires mass productivity.

Therefore, the present invention utilizes both the driving of the non-magnetic material in the magnetic fluid and the magnetic repulsive force, and by combining this with a booster, the driving force and the response speed are large at low cost, and continuous control is possible. An enabled actuator is provided.

[Brief description of the drawings]

FIG. 1 is a sectional view of a main part showing a specific example of an actuator using a magnetic fluid according to the present invention.

FIG. 2 is a front view showing an example of the shape of a plunger made of a soft magnetic material employed in this embodiment.

FIG. 3 is a graph showing the effect of plunger head diameter.

FIG. 4 is a graph showing the effect of plunger head thickness on magnetic repulsion.

FIG. 5 is a graph showing the effect of plunger length on magnetic repulsion.

FIG. 6 is a graph showing the effect of weight reduction on magnetic repulsion.

FIG. 7 is a graph showing the effect of disc spacing on magnetic levitation force.

FIG. 8 is a graph showing the effect of the number of disks on the magnetic levitation force.

FIG. 9 is a graph showing the effect of magnetic repulsion on magnetic levitation.

FIG. 10 is a graph showing the effect of current and load on stroke.

FIG. 11 is a graph showing a measurement example of an indian response.

FIG. 12 is a graph showing the effect of a current on a time constant.

FIG. 13 is a schematic diagram showing an example of a conventional general flow control device.

FIG. 14 is a conceptual diagram illustrating a basic operation of a conventional reciprocating motion of a load using a magnetic fluid.

FIG. 15 is a conceptual diagram for explaining a basic operation for generating a magnetic repulsion.

FIG. 16 is a conceptual diagram for explaining a basic operation in which a magnetic repulsion has occurred.

FIG. 17 is a conceptual diagram for explaining a basic operation of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Piping 2 ... Flow sensor 3 ... Flow control part 4 ... Set flow signal 5 ... Valve operation part 6 ... Valve 7 ... Load 8 ... Magnetic fluid 9 ... Container made of non-magnetic material 10 ... Non-magnetic material 11 ... Output shaft ... Coil 13 ... Power supply 14 ... Core 14a ... Center hole 15 ... Solenoid 16 ... Plunger 16a ... Plunger head 17 ... Small diameter piston 18 ... Small diameter cylinder 19 ... Large diameter piston 20 ... Large diameter cylinder 21 ... Hydraulic oil 22 ... Base 23 ... Post 24 ... Disc made of non-magnetic material 25 ... Spring 26 ... Cover 26a ... Center hole 27 ... Bypass 28 ... Electromagnetic magnet 29 ... Outer cylinder 30 ... Power booster 31 ... Insert core 31a ... Insert core head 32 ... holes 32a ... grooves

Claims (4)

(57) [Claims] 1. An electromagnetic magnet comprising a solenoid disposed on the outer periphery of a core made of a soft magnetic material and a plunger of the same material as the core disposed in a center hole of the core.
A container made of a non-magnetic material, which is disposed above the electromagnetic magnet and in which a magnetic fluid is sealed, and connected to a plurality of disks made of a non-magnetic material and a disk made of a non-magnetic material, which are disposed in the magnetic fluid Movement of the plunger, in which a levitation effect caused by a repulsion force of the plunger by the electromagnetic magnet and a magnetic levitation force caused by a magnetic pressure difference acting on the disc made of the nonmagnetic material, and a piston made of the nonmagnetic material thus obtained are synergized. An actuator using a magnetic fluid, comprising, as a component, a booster for increasing a driving force of an output shaft derived from a piston in response to the force. 2. A booster includes a large-diameter piston which transmits the sliding of a small-diameter piston fixed to a tip of a plunger via a hydraulic oil filled in a small-diameter cylinder and a large-diameter cylinder. 2. The actuator using magnetic fluid according to claim 1, wherein the driving force of the plunger is increased by a boosting effect due to a difference in diameter between the small-diameter piston and the large-diameter piston. 3. The actuator using a magnetic fluid according to claim 1, wherein a hole is formed at the center of the cylindrical portion of the plunger which floats with the repulsive force of the electromagnetic magnet to reduce the weight of the plunger. 4. The magnetic fluid according to claim 1, wherein the distance between the plurality of nonmagnetic discs is reduced, and the number of nonmagnetic discs is up to three. Actuator.