Magnetic scale manufacturing method and magnetic scale

Abstract

First, an inner tube member is accommodated in an outer tube member. Then, rigid powder, having high rigidity and a hard-to-magnetize characteristic, into the inner tube member. Next, magnetic powder is filled into a recessed portion of the inner tube member. Then, the inner tube member is drawn out of the outer tube member. Then, a composite filler composed of the rigid powder, magnetic powder and outer tube member is subjected to a cold hydrostatic pressure pressing process as pre-processing. Next, the composite filler is heated and solidified into a billet. Then, the billet is subjected to a hot extrusion process so that it is formed into a bar-shaped workpiece. The bar-shaped workpiece is rolled onto a roller, and then the outer tube member is peeled off. Next, the bar-shaped workpiece is subjected to a cutting process so that it is formed into an elongated bar. Then, a magnetic section of the elongated bar is magnetized into a scale structure.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

For better understanding of the objects and other features of the present invention, its preferred embodiments will be described hereinbelow in greater detail with reference to the accompanying drawings, in which:

FIG. 1 is a diagram showing various steps for manufacturing an embodiment of a magnetic scale using a magnetic scale manufacturing method in accordance with an embodiment of the present invention;

FIG. 2 is a view showing another example of a peel-off step in the embodiment of FIG. 1;

FIG. 3 is a view showing examples of magnetization of an elongated bar and magnetic scale in the embodiment;

FIG. 4 is a view showing a shape of a double tube assembly and a sectional shape of an elongated bar in the embodiment;

FIG. 5 is a view showing a shape of another example of the double tube assembly and a sectional shape of another example of the elongated bar in the embodiment;

FIG. 6 is a view showing example shapes of a recessed portion and sectional shapes of the elongated bar;

FIG. 7 is a perspective view and sectional view of another embodiment of the magnetic scale;

FIG. 8 is a perspective view showing principal portions of a slide volume control device using the magnetic scale of the present invention;

FIG. 9 is a perspective view showing principal portions of a suspension section in an automotive vehicle employing the aforementioned magnetic scale of the present invention; and

FIG. 10 is a view showing still other embodiments of the magnetic scale.

Claims

1. A magnetic scale manufacturing method comprising: a first step of forming and providing a double tube assembly of a nested structure with an inner tube member accommodated in an outer tube member, the inner tube member having, in part of an outer periphery thereof, a recessed portion, a distance from an inner wall surface of the outer tube member to an outer wall surface of the recessed portion of inner tube member is greater than a distance from the inner wall surface of the outer tube member to the outer wall surface of another section, than the recessed portion, of the inner tube member;a second step of filling rigid powder, having high rigidity and hard-to-magnetize characteristic, into a center region of the nested structure;a third step of filling magnetic powder into the recessed portion between the inner tube member and the outer tube member;a fourth step of removing the inner tube member after said first step, said second step and said third step having been performed in desired order;a fifth step of heating and solidifying a composite having remained after removal of the inner tube member;a sixth step of stretching the composite, heated and solidified by said fifth step, into a bar-shaped workpiece;a seventh step of peeling off the outer tube member from the bar-shaped workpiece stretched by said sixth step; andan eighth step of magnetizing, into a magnetic scale structure, a magnetic section of the bar-shaped workpiece formed by heating and solidifying the magnetic powder of the bar-shaped workpiece from which the outer tube member has been peeled off.

2. A magnetic scale manufacturing method as claimed in claim 1 wherein the composite heated and solidified in said fifth step is subjected to a hot extrusion process in said sixth step.

3. A magnetic scale manufacturing method as claimed in claim 1 wherein the composite heated and solidified in said fifth step is subjected to a hot rolling process in said sixth step.

4. A magnetic scale manufacturing method as claimed in claim 1 wherein, in said sixth step, the composite heated and solidified in said fifth step is subjected not only to a hot rolling process, but also to extrusion, rolling and drawing processes in permutation and simultaneously.

5. A magnetic scale manufacturing method as claimed in claim 1 wherein the recessed portion of the inner tube member is formed into an undercut structure with respect to an inner-outward direction of the nested structure of the doublet tube assembly.

6. A magnetic scale manufacturing method as claimed in claim 1 wherein the rigid powder is powder of stainless steel, brass or duralumin.

7. A magnetic scale manufacturing method as claimed in claim 1 wherein the magnetic powder is powder of alloy permanent magnet.

8. A magnetic scale comprising: an elongated rigid shaft section having high rigidity and hard-to-magnetize characteristic including a nonmagnetic characteristic; anda magnetic section disposed as a layer uniformly and integrally on said rigid shaft section in a longitudinal direction of said rigid shaft section,said magnetic section having a smaller cross-sectional area than said elongated rigid shaft section, said magnetic section being secured to part of a surface of said rigid shaft section and magnetized to a magnetic scale structure, said magnetic section having opposite side joint surfaces along which said magnetic section is joined with said rigid shaft section, the opposite side joint surfaces being formed into an undercut structure with respect to an inner-outer direction of said shaft section as viewed in cross-section.

9. A magnetic scale as claimed in claim 8 wherein said magnetic section is formed of an alloy permanent magnet material.

10. A magnetic scale as claimed in claim 8 wherein said magnetic section is formed of a copper-nickel alloy.

11. A magnetic scale as claimed in claim 8 wherein said rigid shaft section is formed of metal or high-strength resin, and said magnetic section is a resin-mixed magnet and formed by being insert-molded to said rigid shaft section.

12. A magnetic scale as claimed in 11 wherein said rigid shaft section is formed of the high-strength resin, and wherein said magnetic section is formed through primary molding and said rigid shaft section is formed onto said magnetic section through secondary molding.

13. A magnetic scale as claimed in 8 wherein said magnetic section has a layer thickness in a range from 0.1 mm to 1 mm.

14. A magnetic scale comprising: an elongated rigid shaft section having high rigidity and high magnetic permeability; anda magnetic section disposed as a layer uniformly and integrally on said rigid shaft section in a longitudinal direction of said rigid shaft section,said magnetic section having a smaller cross-sectional area than said elongated rigid shaft section, said magnetic section being secured to part of a surface of said rigid shaft section and magnetized to a magnetic scale structure, said magnetic section having opposite side joint surfaces along which said magnetic section is joined with said rigid shaft section, the opposite side joint surfaces being formed into an undercut structure with respect to an inner-outer direction of said shaft section as viewed in cross-section.

15. A magnetic scale as claimed in claim 14 wherein said magnetic section is formed of an alloy permanent magnet material.

16. A magnetic scale as claimed in claim 14 wherein said magnetic section is formed of a copper-nickel alloy.

17. A magnetic scale as claimed in claim 14 wherein said rigid shaft section is formed of metal or high-strength resin having a material of a high magnetic permeability mixed therein, and said magnetic section is a resin-mixed magnet and formed by being insert-molded to said rigid shaft section.

18. A magnetic scale as claimed in 17 wherein said rigid shaft section is formed of the high-strength resin, and wherein said magnetic section is formed through primary molding and said rigid shaft section is formed onto said magnetic section through secondary molding.

19. A magnetic scale as claimed in 14 wherein said magnetic section has a layer thickness in a range from 0.1 mm to 1 mm.