Arm head

An arm head includes an end portion to which a retainer is pivotally coupled and a surface covered by a coating. The end portion includes a coupling bore. The coupling bore includes an open end. First and second surfaces of the arm head form an annular recess around the open end that extends continuously from the open end. The radial outer surface extends outward in a radial direction from the annular recess. The first surface extends outward in the radial direction from the open end. The first surface is located inward in an axial direction of the coupling bore from the radial outer surface. The second surface extends from the first surface to the radial outer surface at an angle less than 180° with respect to the first surface.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is based upon and claims the benefit of priority from prior Japanese Patent Application No. 2011-051429, filed Mar. 9, 2011, and claims the benefit of priority from prior Japanese Patent Application No. 2011-286774, filed Dec. 27, 2011, the entire contents of which are both incorporated herein by reference.

BACKGROUND OF THE INVENTION

The present invention relates to an arm head of a wiper arm.

A typical wiper arm includes an arm head and a retainer. The arm head includes a distal portion with respect to the longitudinal direction. A coupling bore extends through the distal portion in a direction orthogonal to the longitudinal direction. The retainer is coupled to the arm head and is pivotal about a shaft inserted through the coupling bore. An anti-glare and rust resistant coating is applied to the wiper arm to prevent light reflection and metal corrosion.

The retainer is formed by bending a steel plate into a U-shape. After bending the steel plate, it is difficult to coat the inner side of the retainer. Thus, for example, one side of the steel plate is coated in advance. In this case, the steel plate is bent so that the coated surface is arranged at the inner side. Then, the outer side of the steel plate is coated so that the retainer is entirely coated to prevent metal corrosion (refer to, for example, Japanese National Phase Laid-Open Patent Publication No. 2007-501152).

The coupling bore of the arm head receives the shaft. Thus, the coating is not applied to the wall of the coupling bore. For example, as shown inFIG. 14, an arm head101includes a coupling bore102, and a coating103is applied to the arm head101but not to the wall of the coupling bore102. In this case, a corrosion product104may form inside the coating103on the arm head101near the open end of the coupling bore102. As corrosion advances, the corrosion product104may expand or separate the coating103. Such a corroded portion would stand out and adversely affect the outer appearance of the arm head prematurely.

SUMMARY OF THE INVENTION

It is an object of the present invention to provide an arm head capable of preventing a corrosion product from growing and preventing its outer appearance from deteriorating prematurely.

One aspect of the present invention is an arm head including a longitudinal end portion to which a retainer is pivotally coupled and a surface covered by a coating. The end portion includes a coupling bore. The retainer is pivotal relative to the arm head about an axis of a shaft extending through the coupling bore. The coupling bore includes an open end that opens outward from the arm head. The arm head includes first and second surfaces forming an annular recess around the open end and a radial outer surface. The annular recess extends continuously from the open end. The radial outer surface extends outward in a radial direction from the annular recess. The first surface extends outward in the radial direction from the open end. The first surface is located in the arm head inward in an axial direction of the coupling bore from the radial outer surface. The second surface extends from the first surface to the radial outer surface at an angle less than 180° with respect to the first surface.

A further aspect of the present invention is an arm head covered by a coating and pivotally coupled by a shaft to a retainer. The arm head includes a coupling bore into which the shaft is fitted. The coupling bore includes an open end that opens outward from the arm head. Annular first and second surfaces form an annular recess around the open end. The annular recess is continuously from the open end. A radial outer surface extends outward in a radial direction from the annular recess. The first surface extends outward in the radial direction from the open end. The first surface is located in the arm head inward in an axial direction of the coupling bore from the radial outer surface. The second surface extends from a radially outer edge of the first surface to a radially inner edge of the radial outer surface at an angle less than 180° with respect to the first surface.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

One embodiment of the present invention will now be described with reference toFIGS. 1 to 5. As shown inFIG. 1, a wiper arm1includes a basal portion, which is fixed to a pivot shaft2(schematically shown by a broken line) arranged in the vicinity of a lower end of the windshield of a vehicle, and a distal portion, to which a wiper blade (not shown) is coupled. The wiper arm1is formed by coupling an arm head11, a retainer12, and an arm piece13from the basal side.

A shaft fixing hole11ais formed in the basal portion of the arm head11. The pivot shaft2is in inserted through and fixed to the shaft fixing hole11a. As shown inFIGS. 2 and 3, the arm head11has a distal portion including a coupling bore11bextending in a direction orthogonal to the longitudinal direction of the arm head11. The coupling bore11bincludes open ends11cthat open toward the outer side of the arm head11.

As shown inFIGS. 1 and 2, the retainer12has a basal portion, with respect to the longitudinal direction, including two coupling arms12a. The two coupling arms12aand a rivet14, which serves as a shaft inserted through the coupling bore11b, pivotally couples the retainer12to the arm head11. The retainer12is pivotal about the rivet14in directions toward and away from the windshield, which serves as a wiping surface. Referring toFIG. 2, in the present embodiment, a tubular outer bushing15and inner bushing16, which are formed of metal, are arranged between the wall of the coupling bore11band the rivet14.

As shown inFIG. 2, the inner bushing16includes two end faces respectively projecting out of the open ends11cof the coupling bore11band contacting inner surfaces of the two coupling arms12aof the retainer12. The outer bushing15, which is shorter than the inner bushing16, includes two end faces that do not contact the inner surfaces of the two coupling arms12a. Each end face of the outer bushing15is flush with or projected outward from an outer surface11d(radial outer surface) of a tubular portion11g(annular projection) of the arm head11, which will be described later.

As shown inFIG. 4A, two annular surfaces, namely a first surface11eand a second surface11f, which form an annular recess, are arranged between each open end11cand the corresponding outer surface11d. In the present embodiment, the two surfaces (i.e., the first surface11eand second surface11f) are arranged at an angle of 90° with respect to each other in a cross-section taken along an axial direction of the coupling bore11b. In this manner, the arm head11includes first and second surfaces11eand11f, around the open end11c, forming an annular recess that extends continuously from the open end11c. Further, the radial outer surface11dextends outward in the radial direction from the annular recess. In the description hereinafter, the phrase of “cross-section taken along the axial direction” refers to a “cross-section taken along the axial direction of the coupling bore11b”.

More specifically, as shown inFIGS. 4A and 4B, the arm head11of the present embodiment is formed by applying a coating to a main body17, which is an aluminum die cast component. The surface of the arm head11excluding the wall of the coupling bore11bis covered by a coating18. The coating of the present embodiment is a resin coating of acryl, polyester, epoxy, or the like. InFIG. 4A, the coating18is schematically illustrated with an even thickness, and hatching lines are omitted to visually facilitate understanding.FIG. 4Billustrates the difference in the thickness of the coating18. Specifically, the coating18is thick at a portion (inner angle portion) corresponding to where the two surfaces11eand11finterest at an angle of 90°. Hence, the coating18includes a thick portion18awhere the first surface11eand the second surface11fintersect with each other. The thick portion18ais thicker than other parts of the coating18. The thickness of the coating18varies on the two surfaces11eand11f. Thus, in strict terms, the angle between the two surfaces11eand11fis not 90°. However, in a state in which the coating18is removed (e.g., prior to the application of the coating18), the angle between the two surfaces11eand11fis 90°. The coating18is not applied to the wall of the coupling bore11bof the present embodiment. However, the wall of the coupling bore11bis anodized to suppress corrosion.

The tubular portion11g(annular projection) is arranged around each open end11cof the arm head11, and a top face of the tubular portion11gdefines the outer surface11d. The two surfaces11eand11fare formed between the open end11cand the radially inner edge of the outer surface11d. In other words, the radial outer surface11dis a top face of the tubular portion11g(annular projection) arranged around each open end11c, and the first and second surfaces11eand11fare arranged between the open end11cand the radially inner edge of the radial outer surface11d. Hence, the first surface11eextends outward in the radial direction from the open end11cand is located in the arm head11inward in the axial direction of the coupling bore11bfrom the radial outer surface11d. The second surface11fextends from the first surface11eto the radial outer surface11dat an angle that is less than 180° with respect to the first surface11e.

As shown inFIG. 4A, the first surface11e, which is close to the coupling bore11b, extends along a direction orthogonal to the axial direction of the coupling bore11bin a cross-section taken along the axial direction. That is, the first surface extends from the open end11coutward in the radial direction of the coupling bore11b. The second surface11f, which is close to the outer surface11d, forms an inner circumferential surface of the tubular portion11gand extends in the axial direction of the coupling bore11bin a cross-section taken along the axial direction, that is, in a direction orthogonal to the first surface11e.

Further, as shown inFIG. 4A, an outer circumferential surface11hof the tubular portion11gand a basal surface11iof the tubular portion11gare arranged at an angle of 90° with respect to each other in a cross-section taken along the axial direction.

The above embodiment has the advantages described below.

(1) As shown inFIG. 5, for example, corrosion may occur inside the coating18, specifically, at the edge of the coating18in the vicinity of the open end11c. In the present embodiment, the arm head11includes the first and second surfaces11eand11fthat form an annular recess. The annular recess extends continuously from the open end11c, around the open end11c. The arm head11also includes the radial outer surface11d, which extends outward in the radial direction from the annular recess. The first surface11eextends outward in the radial direction from the open end11cand is located in the arm head11inward in the axial direction of the coupling bore11bfrom the radial outer surface11d. The second surface11fextends from the first surface11eto the radial outer surface11dat an angle that is less than 180° (specifically, 90°) with respect to the first surface11e. Thus, the direction of the force acting on the coating18when a corrosion product21separates the coating18from the main body17temporarily changes at the portion where the two surfaces11eand11fintersect each other. More specifically, the corrosion product21applies a separation force to the coating18of the first surface11ein a direction perpendicular to the first surface11e(so that the coating18is compressed). The corrosion product21also applies a shearing separation force to the coating18of the second surface11fin a direction parallel to the second surface11f. This suppresses and retards growth of the corrosion product21. The thick portion18a(seeFIG. 4B) is formed where the two surfaces11eand11fintersect each other. Thus, the coating18has high rigidity at the thick portion18a. This also suppresses growth of the corrosion product21and retards corrosion. Consequently, expansion (separation) of the coating18that would be caused by growth of the corrosion product21is retarded, and the outer appearance is not deteriorated prematurely.

(2) The first and second surfaces11eand11fare arranged relative to each other at an angle that is less than or equal to 90° (90° in the present embodiment). The corrosion product21advances along one of the surfaces, namely, the first surface11e, and requires a large force along the shearing separation direction of the coating18where the two surfaces11eand11fintersect each other. This further retards advancement of the corrosion product21at where the two surfaces11eand11fintersect each other.

(3) The one of the two surfaces11eand11fcloser to the outer surface11d, namely, the second surface11f, extends parallel to the axis of the coupling bore11b. Thus, the direction in which the second surface11fis removed from a mold is the same as the direction in which the coupling bore11bis removed from a mold. Thus, the arm head11can be formed with fewer molds.

(4) The radial outer surface11dis the top face of the tubular portion11g(annular projection), which is arranged around each open end11c. Thus, even if the corrosion product21advances beyond the two surfaces11eand11fand the outer surface11dand proceeds towards the basal surface11iat which the tubular portion11gis arranged, the advancement of the corrosion product21is retarded where the outer circumferential surface11hand the basal surface11iof the tubular portion11gintersect each other. This retards the advancement of expansion (separation) of the coating18, which would be caused by advancement of the corrosion product21, even where the outer circumferential surface11hand the basal surface11iof the tubular portion11gintersect each other, and premature deterioration of the outer appearance is suppressed.

The above embodiment may be modified as described below.

The forms of the two surfaces11eand11fin the embodiment described above may be changed.

For example, the two surfaces11e,11fmay be changed as shown inFIG. 6. In the example ofFIG. 6, two surfaces (first surface31aand second surface31b) are arranged relative to each other at an angle (acute angle) that is less than 90°. Specifically, the first surface31aextends outward in the radial direction from the open end11cat an angle (acute angle) that is less than 90° with respect to the axis of the coupling bore11bin a cross-section taken along the axial direction. The second surface31b, which forms an inner circumferential surface of the tubular portion11g, extends along the axial direction of the coupling bore11bin a cross-section taken along the axial direction.

This structure also obtains advantages (1) to (4) of the above embodiment. The two surfaces31aand31bare arranged at an acute angle relative to each other. Thus, in order for the coating18(expanded portion not shown) expanded by a corrosion product that has advanced along one of the surfaces, namely, the first surface31a, a larger force in the shearing separation direction of the coating18must be applied to the other one of the surfaces, that is, the second surface31b, for the corrosion product to further grow and advance beyond where the two surfaces intersect each other. Accordingly, the coating18is less likely to be separated at the second surface31b. This further retards advancement of the corrosion product where the two surfaces31aand31bintersect each other.

The above embodiment may also be modified as shown inFIG. 7. In the example ofFIG. 7, two surfaces (first surface32aand second surface32b) are arranged at an angle (acute angle) of less than 90° relative to each other. Specifically, the first surface32aextends outward in the radial direction from the open end11cin a direction orthogonal to the axial direction of the coupling bore11bin a cross-section taken along the axial direction. The second surface32b, which forms an inner circumferential surface of the tubular portion11g, is inclined with respect to the axial direction of the coupling bore11bso that the second surface32bis arranged relative to the first surface32aat an angle (acute angle) of less than 90° in a cross-section taken along the axial direction. In other words, the second surface32bis inclined away from the coupling bore11bin the radial direction of the coupling bore11bas the second surface32bextends into the coupling bore11bfrom the outer surface11din the axial direction.

This structure also obtains advantages (1) and (2) of the above embodiment. The two surfaces32aand32bare arranged at an acute angle relative to each other. Thus, in order for the coating18(expanded portion not shown) expanded by a corrosion product that has advanced along one of the surfaces, namely, the first surface32a, a larger force in the shearing separation direction of the coating18must be applied to the other one of the surfaces, that is, the second surface32b, for the corrosion product to further grow and advance beyond where the two surfaces intersect each other. Accordingly, the coating18is less likely to be separated at the second surface32b. This retards advancement of the corrosion product at where the two surfaces32aand32bintersect each other. In the example ofFIG. 7, an outer circumferential surface33aand a basal surface33bof the tubular portion11gare arranged at an angle (acute angle) that is less than 90° in a cross-section taken along the axial direction. Thus, in addition to advantage (4) of the above embodiment, the advancement of the corrosion product21at where the outer circumferential surface33aand the basal surface33bintersect each other is further retarded in the same manner as where the two surfaces32aand32bintersect each other.

The above embodiment may be modified as shown inFIG. 8. In the example ofFIG. 8, two surfaces (first surface34aand second surface34b) are arranged at an angle (obtuse angle) of less than 180° and greater than 90°. Specifically, the first surface34aextends outward in the radial direction from the open end11cin a direction orthogonal to the axial direction of the coupling bore11bin a cross-section taken along the axial direction. The second surface34b, which forms an inner circumferential surface of the tubular portion11g, is inclined with respect to the axial direction and arranged relative to the first surface34aat an angle (obtuse angle) of less than 180° and greater than 90° in a cross-section taken along the axial direction. In other words, the second surface34bis inclined toward the axis of the coupling bore11bin the radial direction of the coupling bore11bas the second surface34bextends into the coupling bore11bfrom the outer surface11din the axial direction. That is, the second surface34bis inclined with respect to the axis of the coupling bore11band tapered from the radial outer surface11dtowards the first surface34a.

This structure also obtains advantages (1) and (3) of the above embodiment. In the example ofFIG. 8, an outer circumferential surface35aand a basal surface35bof the tubular portion11gare arranged at an angle (obtuse angle) that is less than 180° and greater than 90° in a cross-section taken along the axial direction.

As shown inFIG. 9, the two surfaces11eand11fof the above embodiment described above may be connected by a curved surface36(e.g., arcuate surface having an extremely small radius of curvature).

In the embodiment described above, the outer surface11dis the top face of the tubular portion11garranged around the open end11c. The outer surface11donly needs to be located outward in the radial direction of the coupling bore11bfrom the open end11cand be extended along the radial direction of the coupling bore11band may thus be changed as shown inFIG. 10to an outer surface37a. More specifically, the outer surface37ain the example ofFIG. 10occupies most of the side surface of an arm head37and is continuous with an upper surface37bof the arm head37.

This structure also obtains advantages (1) to (3) of the above embodiment.

The outer surfaces11dand37ado not have to extend along the direction orthogonal to the axial direction of the coupling bore11bin a cross-section taken along the axial direction. The outer surfaces11dand37amay extend along a direction inclined with respect to the direction orthogonal to the axial direction.

In the above embodiment, the coupling bore11bin the arm head11has a fixed diameter in the axial direction but is not limited in such a manner. For example, as shown inFIG. 11, for example, an axial end region of the coupling bore11bmay include an increasing diameter portion42in which the diameter increases at a constant ratio towards the open end41.

In the example ofFIG. 11, anodization is performed on the wall of the coupling bore11bincluding the increasing diameter portion42.

An outer bushing43is inserted into the coupling bore11balong the axial direction of the coupling bore11b. The axial end region of the outer bushing43includes a decreasing diameter portion44in which the diameter decreases at a constant ratio towards the end face in the axial direction of the outer bushing43. As shown inFIG. 12A, in a cross-section taken along the axial direction, a line extending along the insertion direction (direction in which the outer circumferential surface of the outer bushing extends) and a line extending along the decreasing diameter portion44intersect each other at an angle θ1. In the cross-section taken along the axial direction, a line extending along the axial direction of the coupling bore11band a line extending along the increasing diameter portion intersect each other at an angle θ2. The increasing diameter portion42and the decreasing diameter portion44are set so that the angle θ1is greater than the angle θ2. In other words, an inclination angle θ1of the decreasing diameter portion44with respect to the axis of the coupling bore11bis greater than an inclination angle θ2of the increasing diameter portion42with respect to the axis of the coupling bore11b. The outer circumferential surface of the outer bushing43(outer circumferential surface of central part) and the decreasing diameter portion44are continuously connected by a curved portion45(fine curved portion) having a curved cross-sectional shape (arcuate cross-sectional shape). In other words, the bushing43includes the outer circumferential surface, which extends parallel to the axis of the bushing43, and the curved portion45, which connects the outer circumferential surface and the decreasing diameter portion44. That is, the outer circumferential surface of the outer bushing43is continuously connected to the decreasing diameter portion44by the curved portion45, which has a curved cross-sectional shape with a diameter that decrease toward the decreasing diameter portion44.

With such a structure, as shown inFIGS. 12A to 12C, the insertion (press-fitting) of the outer bushing43into the coupling bore11bis facilitated since the increasing diameter portion42guides the outer bushing43. Further, the outer bushing43comes into contact with the increasing diameter portion42during insertion (press-fitting) at the curved portion45, which is a curved surface having round cross-section and not a sharp edge. Thus, the outer bushing43and the increasing diameter portion42(arm head11) are unlikely to be scratched.

Anodization of the coupling bore11bforms an anode oxidization film on the wall of the coupling bore11b. In the example ofFIGS. 11 and 12Ato12C, even if scratches are produced in the wall of the coupling bore11b(anode oxidization film) when the wiper arm1is assembled, the scratches would be shallow.FIG. 13is a graph comparing the depth of scratches between the above example and a comparative example (seeFIG. 12D). In the comparative example shown inFIG. 12D, a line extending along the insertion direction (outer circumferential surface of outer bushing51) and a line extending along a decreasing diameter portion52intersect each other at an angle θ3in a cross-section taken along the axial direction. A line extending along the axial direction of the coupling bore11band a line extending along an increasing diameter portion54intersect each other at an angle θ4in a cross-section taken along the axial direction. The increasing diameter portion54and the decreasing diameter portion52are set so that the angle θ3is less than the angle θ4. Further, the outer bushing51does not include the curved portion45.FIG. 13shows the depth of scratches produced in the anode oxidization film when the outer bushings43and51are coupled to the arm head11repetitively for thirty times with the example ofFIGS. 11 and 12Ato12C and the comparative example ofFIG. 12D. The depth of scratches in the experimental result of the comparative example is approximately 20 μm in average (AVE), approximately 57 μm at maximum (MAX), and approximately 6 μm at minimum (MIN). In contrast, in the example ofFIGS. 11 and 12Ato12C, the depth of scratches is approximately 13 μm in average (AVE), approximately 36 μm at maximum (MAX), and approximately 4 μm at minimum (MIN). Thus, in the example ofFIGS. 11 and 12Ato12C, the scratches produced during the assembly process in the coupling bore11b(anode oxidization film) including the increasing diameter portion42, which is anodized, have decreased depths and are shallow. This suppresses corrosion resulting from such scratches. Further, a corrosion product produced from a scar would be prevented from advancing towards the open end41and the coating. As a result, the deterioration in the outer appearance prematurely can be suppressed.

In the above embodiment, the rivet14is used as a shaft. The rivet14may be changed to a different type of shaft having a similar function.

In the above embodiment, the end faces of the inner bushing16projects out of the coupling bore11bfrom the two open ends11cand come into contact with the inner surfaces of the two coupling arms12aof the retainer12. In other words, the projecting amount (axial length of the inner bushing16) of the inner bushing16is set so that the outer surfaces11dand37aof the tubular portion11gdoes not come into contact with the inner surfaces of the two coupling arms12aof the retainer12. This prevents separation of the coating18that would be caused by friction between the inner surface of the coupling arm12aof the retainer12and the outer surfaces11dand37aof the arm head11when the retainer12pivots with respect to the arm head11.

The invention is not limited to the foregoing embodiments and various changes and modifications of its components may be made without departing from the scope of the present invention. Also, the components disclosed in the embodiments may be assembled in any combination for embodying the present invention. For example, some of the components may be omitted from all components disclosed in the embodiments. Further, components in different embodiments may be appropriately combined.