JPH09148641A - Housing structure of pre-stress coil spring of magnetostrictive actuator - Google Patents

Abstract

PROBLEM TO BE SOLVED: To enable a pre-stress to be accurately applied to a magnetostrictive actuator. SOLUTION: A magnetipstrictive actuator is equipped with a drive element 5 pinched between two flanges 2 and 2a, a bolt 3 protruding from the flange 2a is inserted into a coil spring 1 inserted into a coil spring insertion hole provided to the flange 2, and the coil spring 1 is compressed by tightening a nut 4 so as to give a pre-stress to the drive element 5, wherein a housing structure where the coil spring 1 is housed is formed like a cylinder conforming to the outer diameter of the coil spring 1. At this point, a Teflon cylinder 7 smaller in friction coefficient than metal is provided outside the coil spring 1 to align the coil spring 1.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a prestressing coil spring housing structure provided in an electromagnetic strain actuator that requires prestressing.

[0002]

2. Description of the Related Art FIG. 3 is a schematic cross-sectional view showing a housing structure of a coil spring provided in a conventional electrostrictive actuator (hereinafter abbreviated as an actuator) requiring prestress. 3A shows an initial state before stress application, and FIG. 3B shows a state when stress is applied. An actuator generally uses a material that expands and contracts in response to an electric field or a magnetic field to form a drive element. When using the actuator, the drive element is given the necessary contraction (pre-stress) so that tensile stress is not applied. . That is, in practice, an optimum prestress suitable for the purpose is applied so that a certain predetermined reference (use) state is maintained.

Further, when the driving element is made of a material which is very compliant (greatly deformable), the mechanism for applying prestress needs to be more compliant than the material, and a coil spring as shown in FIG. 3 is often used. Used. FIG. 3 shows a conventional coil spring housing structure, but it is not actually a special mechanical device, it is simply positioned so that stress can be applied. is there. In FIG. 3, the housing for housing the drive element 5 includes an upper flange 2 and a lower flange 2a for holding the drive element 5 tightly.
Consists of A spring insertion hole 6 is provided in the flange 2, and a bolt 3 with a nut 4 that reaches almost the upper portion of the flange 2 is attached to the flange 2a at a position corresponding to the spring insertion hole 6. Then, as shown in FIG. 3A, the coil spring 1 is located between the nut 4 and the bottom surface of the spring insertion hole 6 while being inserted into the bolt 3 in the spring insertion hole 6, The state is maintained.

In order to apply a prestress to the drive element 5 from the state of FIG. 3A, a predetermined prestress can be applied by rotating the nut 4 and contracting the coil spring 1.

[0005]

However, in the housing structure of the coil spring for pre-stress of the conventional actuator as described above, there is no problem if the coil screw 1 is short or wide, but it is longer than the diameter. If the shape is tall and narrow so that
The inconvenience as shown in the state diagram of (b) when stress is applied occurs. That is, mechanical parallelism and dimensional accuracy of the spring,
Alternatively, there is a problem in that it may be bent by being displaced from the axial direction due to a torque in the tightening work, an error in stroke management, or the like.

This undesired problem leads to a prestress error and a performance error of the driving element 5 due to it.
For example, reference: "Low-frequency sound source using giant magnetostrictive material": IEICE Technical Report; US93-40, Ultrasonic Research Group, 1993.
This is because, as shown in FIG. 1 of August issue, pp. 57-64, the distortion characteristic of the drive element is generally changed by prestress. Therefore, the spring positioning portion of the flange 2, that is, the spring insertion hole 6 is adjusted to the diameter of the coil spring 1,
It is necessary to take measures for forcibly displacing the coil spring 1 in the axial direction, for example, by matching the diameter of the bolt 3 or the diameter of the bolt 3 with the inner diameter of the coil spring 1. However, even in such a case, the coil spring 1 has the spring insertion hole 6,
Alternatively, since the bending direction is forced while contacting the bolt 3, a considerable amount of friction occurs. This is not a problem when the actuator requires only static operation, but when it is used as a dynamic vibration source, the electromechanical conversion efficiency and the resonance frequency of the actuator are affected by the magnitude of friction. It gives an unfavorable problem.

[0007]

A housing structure of a coil spring for prestressing an electromagnetic strain actuator according to the present invention uses an electromagnetic strain element sandwiched between two flanges as a drive element, and one of the flanges is used. The pre-stress of the electromagnetic strain actuator, which has a structure in which the coil spring inserted in the coil insertion hole provided in the above is inserted into the bolt protruding from the other flange of the flanges, and the nut is tightened to pre-stress the drive element. A housing structure of a coil spring for a vehicle, wherein a cylindrical spacer made of a material having a friction coefficient smaller than that of a metal is formed on the outside or inside of the coil spring so as to match the outside diameter or the inside diameter of the coil spring. It is characterized by being positioned.

Further, in the above-mentioned housing structure of the coil spring for prestress of the electromagnetic strain actuator, the cylindrical spacer made of a material having a friction coefficient smaller than that of metal is made of polytetrafluoroethylene (common name: Teflon). Is preferably used.

According to the present invention, a cylindrical spacer formed of a material having a friction coefficient smaller than that of a metal is arranged on the outside or inside of the coil spring so as to match the outside diameter or the inside diameter of the coil spring. Since the housing structure of the coil spring for prestressing is adopted, even if the coil spring and the cylindrical spacer are brought into contact with each other due to the positioning of the coil spring, one side of the contact is Teflon, which is much smaller than the case of friction between metals. Therefore, the adverse effect on the actuator for the purpose of dynamically vibrating the driving element 5 is extremely reduced.

[0010]

BEST MODE FOR CARRYING OUT THE INVENTION

[First Embodiment] FIG. 1 is a schematic cross-sectional view showing a first embodiment of a housing structure of a coil spring for prestress of an electromagnetic strain actuator according to the present invention. The approximate housing structure is the same as the conventional structure shown in FIG.
The reference numeral 6 is the same as the reference numeral described in FIG. In FIG. 1, a Teflon cylinder 7 having its inner diameter matched with the outer diameter of the coil spring 1 inserted particularly in the lower region of the spring insertion hole 6 of the flange 2 is relatively loosely fitted as a kind of spacer to form a shaft of the coil spring 1. It is used as an auxiliary means for aligning the bolt 3 with the shaft. The Teflon used as the Teflon cylinder 7 is a trade name of polytetrafluoroethylene (PTFE) which is a fluororesin (DuPont, USA), but in general, the name Teflon is commonly used in the industry. Therefore, the Teflon cylinder is also used as a noun in the present embodiment.

The length of the Teflon cylinder 7 is set so that the length (natural length) of the portion of the coil spring 1 that does not cover it is shorter than its outer diameter. Therefore, the bending of the coil spring 1 is forced along the Teflon cylinder 7 substantially in the axial direction. As a result, the coil spring 1 flexes in the axial direction without distortion, and accurate prestress according to the stroke of the spring is applied to the drive element 5. Further, even if the coil spring 1 and the Teflon cylinder 7 come into contact with each other due to the positioning, since one side of the contact is Teflon, the friction due to the contact is much smaller than that between the metals. Therefore, the adverse effect on the actuator for the purpose of dynamically vibrating the drive element 5 is extremely small.

[Second Embodiment] FIG. 2 is a schematic sectional view showing a second embodiment of the housing structure of the coil spring for prestress of the electromagnetic strain actuator according to the present invention.
The approximate housing structure is the same as the conventional structure shown in FIG. 3, and reference numerals 1 to 6 are the same as the reference numerals used in FIG. In FIG. 2, the flange 2
The Teflon cylinder 8 whose outer diameter is adjusted to the inner diameter of the coil spring 1 inserted particularly in the lower region of the spring insertion hole 6 is relatively loosely fitted, and the axis of the coil spring 1 and the axis of the bolt 3 are positioned. There is.

The length of the Teflon cylinder 8 is set so that the length of the portion of the coil spring 1 which does not cover it is shorter than the outer diameter thereof. Therefore, the bending of the coil spring 1 is forced along the Teflon cylinder 8 substantially in the axial direction. As a result, the coil spring 1 flexes in the axial direction without distortion, and accurate prestress according to the stroke of the spring is applied to the drive element 5. Further, as in the case of the first embodiment, even if the coil spring 1 and the Teflon cylinder 8 come into contact with each other due to the positioning, since one side of the contact is Teflon, the friction due to the contact is far greater than that between the metals. small. Therefore, the adverse effect on the actuator for the purpose of dynamically vibrating the drive element 5 is reduced.

As described above, according to the first and second embodiments, in the actuator having the structure in which the pre-stress is required for the driving element 5 and the pre-stress is applied by the coil spring 1, the bending of the coil spring is prevented. In order to minimize the mechanical friction with the coil spring by forcing it in the axial direction, for example, Teflon cylinders 7 and 8 made of a material having a smaller friction coefficient than metal are used as the positioning component.
Since this is arranged outside or inside the coil spring 1, it is possible to apply prestress with high accuracy without adversely affecting the dynamic performance of the actuator in particular.

The housing structure of the coil spring provided in the actuator as described above is effective for all actuators that require prestress, and the application of such an actuator is for underwater use and air use. It goes without saying that it does not matter.

[0016]

As described above, according to the present invention, in the actuator of the type in which the coil element is prestressed to the driving element, the coil spring is positioned by the material which is adjusted to the outer diameter or the inner diameter of the spring, and is more frictional than metal. Since it is done with a cylinder made of a material with a small coefficient, the bending of the spring can be forced in the axial direction, so accurate prestress can be reliably given and the performance of the actuator is not adversely affected. The effect is obtained.

[Brief description of the drawings]

FIG. 1 is a schematic cross-sectional view showing a first embodiment of a housing structure according to the present invention.

FIG. 2 is a schematic sectional view showing a second embodiment of the housing structure according to the present invention.

FIG. 3 is a schematic cross-sectional view showing a housing structure of a coil spring provided in a conventional electromagnetic strain actuator that requires prestress.

[Explanation of symbols]

 1 Coil spring 2, 2a Flange 3 Bolt 4 Nut 5 Drive element 6 Spring insertion hole 7,8 Teflon cylinder

Claims (3)

[Claims] 1. An electromagnetic strain element sandwiched between two flanges is used as a driving element, and a coil spring inserted in a coil insertion hole provided in one of the flanges is provided in the other of the flanges. In a housing structure of a coil spring for prestress of an electromagnetic strain actuator, which is inserted through a bolt protruding from a flange and tightens the coil spring with a nut to prestress the drive element, a cylindrical shape is formed according to an outer diameter of the coil spring. And a cylindrical spacer made of a material having a friction coefficient smaller than that of a metal, disposed outside the coil spring, and positioning the coil spring. A housing for a coil spring for prestressing an electromagnetic strain actuator, comprising: Construction. 2. In place of the cylindrical spacer being fitted to the outer diameter of the coil spring and arranged outside thereof,
2. The housing structure for a coil spring for prestressing an electromagnetic strain actuator according to claim 1, wherein the cylindrical spacer is arranged inside the coil spring and inside thereof. 3. The coil spring for prestressing an electromagnetic strain actuator according to claim 1, wherein the cylindrical spacer made of a material having a friction coefficient smaller than that of metal is made of polytetrafluoroethylene. Housing structure.