ELECTROPLATED WHEEL

Abstract

An electroplated wheel comprises a metal base formed to a disc shape and rotationally driven about a rotational axis and a superabrasive grain layer formed to have numerous superabrasive grains fixed by plating on a belt section that extends in a predetermined width on an outer peripheral portion of the metal base. In the electroplated wheel, a plurality of masking portions having no superabrasive grains electrodeposited thereat are formed of gel adhesive fixed as dots to be larger than the superabrasive grains by a dispenser at intersection points of a plurality of concentric array circles imaginarily drawn concentrically of the rotational axis to divide the belt section at equal intervals and a plurality of width-direction array lines imaginarily drawn from one end toward the other end of the belt section to divide the belt section at equal intervals in a circumferential direction.

Description

This application is based on and claims priorities under 35 U.S.C 119 with respect to Japanese patent applications No. 2012-241146 filed on Oct. 31, 2012 and No. 2013-220118 filed on Oct. 23, 2013, the entire contents of which are incorporated herein by reference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to an electroplated wheel in which the concentration ratio of abrasive grains on an electroplated grinding wheel or an electroplated dressing tool is adjusted by masking patterns.

2. Discussion of the Related Art

The concentration ratio of abrasive grains is a value indicating how much abrasive grains are contained in a grinding wheel. Being a high concentration ratio means that much abrasive grains are contained, in which case although the service life as a grinding wheel is extended, the dulling or glazing of the abrasive grains is liable to occur, so that the cutting ability is likely to fall down shortly. On the contrary, at a low concentration ratio, although the cutting ability is heightened, the shedding is liable to occur to result in a short service life. Therefore, it is very important how to adjust the concentration ratio of abrasive grains to be contained in a grinding wheel.

JP4871543B as prior art describes a technology that controls the concentration ratio of abrasive grains by forming masking portions by an ink jet device on a grinding surface of a metal base, by fixing abrasive grains by plating on non-masking portions, by setting the projected area of abrasive grains relative to the area of the metal base in a range of 5 to 40%, and by forming the masking portions with no abrasive grains fixed thereon and the non-masking portions in fixed patterns.

JP3325832B describes a diamond dressing tool on which dimples are fixed as dots to control the concentration ratio by the dimple portions with no abrasive grains thereon, by fixing as dots gel adhesive over a peripheral wall of a conductive matrix to form protrusions, by fixing diamond abrasive grains by electroplating on the peripheral wall of the matrix, and by removing the matrix.

However, in the first mentioned Japanese patent, the masking pattern is merely such that circles with ink applied thereto are arranged as if an equilateral triangle is formed by three circles adjoining. Thus, the maskings arranged on circles that are centered on the rotational axis of the grinding wheel become many at some parts and few at some other parts, so that an anxiety arises in that the concentration of the abrasive grains cannot be made to be uniform.

Further, in the second mentioned Japanese patent, the arrangement pattern of the dimples formed by the masking portions is formed as an equilateral triangle, a lattice shape or the like. Thus, the dimples arranged on circles that are centered on the rotational axis of the grinding wheel become many at some parts and few at some other parts, so that an anxiety arises in that the concentration of the abrasive grains cannot be made to be uniform.

Further, although an electroplated wheel was manufactured in which, as shown in FIG. 14, a plurality of maskings were arranged to be dotted in a lattice fashion. However, in this electroplated wheel, like those described in the aforementioned Japanese patents, the maskings arranged on circles that were centered on the rotational axis of the wheel became many at some parts and few at some other parts, so that it was unable to make the concentration of abrasive grains uniform.

For the reasons described above, according to the patterns of the maskings (or dimples) shown in the aforementioned Japanese patents and in FIG. 14, the cutting ability shortly deteriorates due to plugging at the parts where the maskings are few, whereas wear becomes heavy due to shedding at the parts where the maskings are many. Because the concentration of the abrasive grains cannot be made to be uniform, there arises a problem in that the electroplated wheels are liable to lose the shape and become short in service life.

SUMMARY OF THE INVENTION

The present invention has been made taking the aforementioned problem into consideration, and an object thereof is to provide an improved electroplated wheel capable of maintaining the cutting ability long in a good state as well as being long in service life as a wheel.

Briefly, in order to solve the foregoing problem, the feature of an electroplated wheel according to the present invention in a first aspect resides in comprising a metal base formed to a disc shape and rotationally driven about a rotational axis; a superabrasive grain layer formed to have numerous superabrasive grains fixed by plating on a belt section that extends in a predetermined width on an outer peripheral portion of the metal base; and a plurality of masking portions having no superabrasive grains electrodeposited thereat and formed of gel adhesive fixed as dots to be larger than the superabrasive grains by a dispenser at intersection points of a plurality of concentric array circles and a plurality of width-direction array lines. The plurality of concentric array circles are imaginarily drawn concentrically of the rotational axis to divide the belt section at equal intervals, and the plurality of width-direction array lines are imaginarily drawn from one end toward the other end of the belt section to divide the belt section at equal intervals in a circumferential direction.

With this configuration in the first aspect, the plurality of masking portions arranged at the intersection points of the with-direction array lines and the concentric array circles that are imaginarily drawn on the belt section of the superabrasive layer are arranged uniformly in the circumferential direction and the width direction of the belt section. Thus, when the electroplated wheel is rotated, the plurality of masking portions are brought into contact with an object to be ground, evenly and uniformly over the whole of the superabrasive grain layer without being concentrated locally.

Then, by arranging the plurality of masking portions uniformly in the circumferential direction and the width direction of the belt section, the superabrasive grains over the whole of the superabrasive grain layer in the belt section is made uniform in concentration. Thus, it is possible for the plurality of masking portions that are formed on the width-direction array lines residing on the superabrasive grain layer, to prevent the occurrence of plugging caused as a result that the concentration of the superabrasive grains becomes high, and portions that are between the width-direction array lines adjoining on the superabrasive grain layer without having the masking portions thereon can serve to prevent the loss of shape from occurring.

The feature of the present invention in a second aspect resides in that in the invention of the first aspect, the plurality of concentric array circles are grouped into a plurality of concentric array circle groups each composed of a plurality of different concentric array circles and that the plurality of width-direction array lines are grouped into a plurality of width-direction array line groups each composed of a plurality of different width-direction array lines and being respectively in corresponding relation with the plurality of concentric array circle groups. The plurality of masking portions are formed at the intersection points of the plurality of concentric array circles in each concentric array circle group and the plurality of width-direction array lines in each width-direction array line group corresponding to each such concentric array circle group.

With this construction in the second aspect, because the plurality of masking portions formed at the intersection points of one concentric array circle group and the width-direction array line group being in corresponding relation with the one concentric array circle group and the plurality of masking portions formed at the intersection points of another concentric array circle group and the width-direction array line group being in corresponding relation with such another concentric array circle group are arranged on different concentric array circles, it is possible to arrange the masking portions in such another width-direction array line group in place of the masking portions which are unable to array in the one width-direction array line group. Therefore, it is possible to heighten the concentration of the masking portions to be arrayed in the width direction of the belt section.

The feature of the present invention in a third aspect resides in that in the invention of the first or second aspect, each of the width-direction array lines is constituted by a primary array line and at least one secondary array line which are imaginarily drawn to be close to each other.

With this construction in the third aspect, because each width-direction array line includes the at least one secondary array line in addition to the primary line, it is possible to adjust the ratio of the masking portions to the superabrasive grains on the concentric array circles by arranging the masking portions on the at least one secondary array line.

The feature of the present invention in a fourth aspect resides in that in the invention of any one of the first to third aspects, the plurality of width-direction array lines are straight lines tilted at the same angle relative to the radial direction of the metal base.

With this construction in the fourth aspect, the grinding can be done in the state that the plurality of masking portions arranged along the titled width-direction array lines are not brought into contact with the same portions on an object to be ground and rather, that the contact positions of the masking portions are moved along continuously adjoining portions of the object to be ground. Thus, it is possible to make the grinding resistance uniform.

The feature of the present invention in a fifth aspect resides in that in the invention of any one of the first to fourth aspects, a plurality of auxiliary width-direction array lines are imaginarily drawn to be close to each of the width-direction array lines and that the masking portions are respectively formed at intersection points of the plurality of concentric array circles and the plurality of auxiliary width-direction array lines so that the wear of the superabrasive grain layer becomes uniform.

With this construction in the fifth aspect, by providing the masking portions arranged at the intersection points of the concentric array circle groups and the auxiliary width-direction array lines, it is possible to increase the masking portions on the superabrasive grain layer in dependence on the degree of wear arising. Thus, it is possible to easily adjust the ratio of the masking portions on the superabrasive grain layer, so that the superabrasive grain layer is made to be uniform in wear to be prevented from losing the shape.

The feature of the present invention in a sixth aspect resides in that in the invention of any one of the first to fifth aspects, the electroplated wheel is a grinding wheel for grinding a workpiece.

With this construction in the sixth aspect, since the plurality of masking portions are arranged uniformly in the width direction and the circumferential direction of the superabrasive grain layer formed on the belt section, the plurality of masking portions are brought into contact with the workpiece evenly at the whole part of the superabrasive grain layer when the grinding wheel is rotated in grinding the workpiece. Thus, the grinding wheel can be prevented from losing the shape of the superabrasive grain layer and hence, can be extended in service life.

The feature of the present invention in a seventh aspect resides in that in the invention of any one of the first to fifth aspects, the electroplated wheel is a dressing tool for dressing a grinding wheel.

With this construction in the seventh aspect, since the plurality of masking portions are arranged uniformly in the width direction and the circumferential direction of the superabrasive grain layer formed on the belt section, the plurality of masking portions are brought into contact with the grinding wheel evenly at the whole part of the superabrasive grain layer when the dressing tool is rotated in dressing the grinding wheel. Thus, the dressing tool can be prevented from losing the shape of the superabrasive grain layer and hence, can be extended in service life.

The feature of a manufacturing method according to the present invention in an eighth aspect is for manufacturing an electroplated wheel comprising a metal base formed to a disc shape and rotationally driven about a rotational axis and a superabrasive grain layer formed to have numerous superabrasive grains fixed by plating on a belt section that extends in a predetermined width on an outer peripheral portion of the metal base. The feature of the method resides in a masking portion forming step of forming a plurality of masking portions having no superabrasive grains electrodeposited thereat by fixing gel adhesive as dots to be larger than the superabrasive grains by a dispenser at intersection points of a plurality of concentric array circles and a plurality of width-direction array lines. The plurality of concentric array circles are imaginarily drawn concentrically of the rotational axis to divide the belt section at equal intervals, and the plurality of width-direction array lines are imaginarily drawn from one end toward the other end of the belt section to divide the belt section at equal intervals in a circumferential direction. The feature of the method further resides in an electroplating step of fixing by electroplating the numerous superabrasive grains on the belt section except for the masking portions, wherein at the masking portion forming step, the total projected area of the masking portions is set in a range of 5 to 20% of the total projected area of the superabrasive grain layer.

With this construction in the eighth aspect, by the use of the dispenser, it is possible to easily form, on the belt section at the outer peripheral portion of the metal base, the superabrasive grain layer in which the masking portions are arranged uniformly in the width direction and the circumferential direction of the belt section. Then, by controlling the dispenser, it is possible to easily manufacture the electroplated wheel that is effective in preventing plugging and the loss of shape by setting the total projected area of the masking portions in a range of 5 to 20% of the total projected area of the superabrasive grain layer.

BRIEF DESCRIPTION OF THE ACCOMPANY DRAWINGS

The foregoing and other objects and many of the attendant advantages of the present invention may readily be appreciated as the same becomes better understood by reference to the preferred embodiments of the present invention when considered in connection with the accompanying drawings, wherein like reference numerals designate the same or corresponding parts throughout several views, and in which:

FIG. 1 is a side view showing a part of an electroplated wheel in a first embodiment according to the present invention;

FIG. 2 is a sectional view of the electroplated wheel taken along the line II-II in FIG. 1;

FIG. 3 is a view showing the state that adhesive is fixed as dots on a metal base by a dispenser;

FIG. 4 is a view showing the state that superabrasive grains are filled on the metal base with masking portions provided thereon;

FIG. 5 is a view showing the state that the superabrasive grains are fixed provisionally by plating;

FIG. 6 is a view showing the state that superabrasive grains being superfluous have been removed;

FIG. 7 is a view showing the state that the superabrasive grains have been fixed permanently by plating;

FIG. 8 is an illustration showing the outline of a plating bath; FIG. 9 is a comparison graph showing the dressing resistances of test objects;

FIG. 10 is a comparison graph showing the wear amounts of the test objects;

FIG. 11 is a side view showing a part of an electroplated wheel in a second embodiment according to the present invention;

FIG. 12 is a front view of the electroplated wheel shown in FIG. 11;

FIG. 13 is an illustration showing the state that a dressing is performed on a screw-like grinding wheel; and

FIG. 14 is a side view showing a part of an electroplated wheel in the prior art.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

First Embodiment

Hereinafter, with reference to the drawings, description will be made regarding a first embodiment in which an electroplated wheel according to the present invention is applied to a gear grinding wheel.

As shown in FIGS. 1 and 2, the gear grinding wheel 2 is provided with a metal base 4 taking a disc shape and diamond abrasive grain layers 6 as superabrasive grain layers which are formed on both side surfaces 54 of the metal base 4 in a predetermined width. A belt section 18 is formed on the metal base 4 in the predetermined width, and the diamond abrasive layer 6 is formed in the belt section 18. As the metal base 4, there is used a hardened and tempered steel (SUJ) for example.

In the gear grinding electroplated wheel 2 in the present embodiment, diamond abrasive grains 8 of a grain size in the range of, for example, #30 to #140 or the like are used as the superabrasive grains. Each diamond abrasive grain layer 6 is constituted by an electrocast abrasive grain layer in which the diamond abrasive grains 8 are fixed by plating. Further, as shown in FIG. 8, each of the both side surfaces 54 of the metal base 4 takes a convex curved surface, and an outer peripheral edge 56 of the metal base 4 is formed to make the both side surfaces 54 come close like a peak.

A plurality of masking portions 12 are arranged on the surface of each diamond abrasive grain layer 6. As shown in FIG. 1, the plurality of masking portions 12 having no diamond abrasive grains 8 electrodeposited thereat are formed of gel adhesive 20 (refer to FIG. 3) fixed as dots to be larger than the diamond abrasive grains 8 by a dispenser 22 at intersection points of a plurality of concentric array circles 14 and a plurality of width-direction array lines 16. The plurality of concentric array circles 14 are imaginarily drawn concentrically of a rotational shaft 3 for the gear grinding wheel 2 to divide the belt section 18 at equal intervals, and the plurality of width-direction array lines 16 are imaginarily drawn from one end 50 toward the other end 52 of the belt section 18 to divide the belt section 18 at equal intervals in the circumferential direction. Each masking portion 12 is formed to a hemisphere shape of the diameter being, for example, 1.5 millimeters.

Specifically, the plurality of concentric array circles 14 drawn imaginarily are grouped into a first concentric array circle group composed of a plurality of concentric array circles 14A, 14C, 14E, 14G, 14I that respectively have odd-number orders as counted from the radially outer side, and a second concentric array circle group composed of a plurality of concentric array circles 14B, 14D, 14F, 14H, 14J that respectively have even-number orders as counted from the radially outer side.

The width-direction array lines 16 drawn imaginarily equally divide the belt section 18 at the intervals of 22.5 degrees in the circumferential direction of the belt section 18. The respective width-direction array lines 16 are straight lines that are tilted at the same angle of 67.5 degrees relative to the radial direction at the center in the width direction of the belt section 18. Thus, it is possible to perform a grinding operation as the masking portions 12 arranged on the tilted width-direction array lines 16A, 16B are brought into contact with continuously adjoining portions of an object to be ground without being brought into contact with the same portions on the object to be ground, so that the grinding resistance can be made to be uniform.

Further, the width-direction array lines 16 drawn imaginarily are grouped into first width-direction array lines 16A being in corresponding relation with the first concentric array circle group (14A, 14C, 14E, 14G, 14I) and second width-direction array lines 16B being in corresponding relation with the second concentric array circle group (14B, 14D, 14F, 14H, 14J).

Each group of the first width-direction array lines 16A is composed of a primary array line 16A1 and a secondary array line 16A2 provided to be close to the primary array line 16A1. Likewise, each group of the second width-direction array lines 16B is composed of a primary array line 16B1 and a secondary array line 16B2 provided to be close to the primary array line 16B1. Because each group of the width-direction array lines 16A, 16B is provided with the secondary array line 16A2, 16B2 being adjacent to the primary array line 16A1, 16B1, it is possible to adjust the ratio of the masking portions 12 to the superabrasive grains 8 both being on the concentric array circles 14, by the masking portions 12 that are arranged on the secondary array line 16A2, 16B2.

The masking portions 12 are arranged at the respective intersection points of the first concentric circle group (14A, 14C, 14E, 14G, 14I) and the first width-direction array lines 16A1, 16A2 being in corresponding relation therewith as well as at the intersection points of the second concentric array circle group (14B, 14D, 14F, 14H, 14J) and the second width-direction array lines 16B1, 16B2 being in corresponding relation therewith.

As mentioned above, the masking portions 12 on the first width-direction array lines 16A reside at the intersection points with the first concentric array circle group (14A, 14C, 14E, 14G, 14I) composed of the array circles that respectively have odd-number orders as counted from the radially outer side, and the masking portions 12 on the second width-direction array lines 16B reside at the intersection points with the second concentric array circle group (14B, 14D, 14F, 14H, 14J) composed of the array circles that respectively have even-number orders as counted from the radially outer side. Thus, the masking portions 12 on each first width-direction array line group 16A and the masking portions 12 on each second width-direction array line group 16B are respectively arranged on the concentric array circle group and the concentric array circle group which are shift by one circle in the radial direction.

Therefore, even where on each of the first width-direction array lines 16A, there exists a portion on the diamond abrasive grain layer 6 at which portion the masking portion 12 cannot be arranged in the width direction of the belt section 18 (e.g., the portion between the first concentric array circle 14A and the third concentric array circles 14C as counted from the radially outer side on each first width-direction array line 16A), it is possible to arrange the masking portion 12 on a corresponding radial position (e.g., on the second concentric array circle 14B as counted from the radially outer side) and on the second width-direction array line 16B next thereto in the circumferential direction. By doing so, it is possible to increase the concentration of the masking portions 12 arranged in the width direction of the belt section 18.

Next, a manufacturing method for the gear grinding wheel 2 will be described with reference to FIGS. 3 through 8.

First of all, as shown in FIG. 3, on the surface of each belt section 18 that is provided on the outer peripheral portion of the conductive metal base 4 made of iron or the like, adhesive 20 of nonconductive gel is fixed as dots by a circular nozzle of the dispenser 22 by a predetermined amount per dot (masking portion forming step).

The gel adhesive 20 is fixed as dots at the intersection points of the plurality of concentric array circles 14 that are imaginarily drawn concentrically of the rotational shaft 3 to divide at equal intervals the belt section 18 with the superabrasive grain layer 6 formed thereon of the metal base 4, and the plurality of width-direction array lines 16 that are imaginarily drawn from the one end 50 toward the other end 52 of the belt section 18 to divide the belt section 18 at equal intervals in the circumferential direction.

Because of being gel, each adhesive fixed as dot becomes a nearly hemispherical shape and solidifies in a moment to become a protrusion (masking portion 12). The dimension of each masking portion 12 depends on the quantity of the adhesive 20 fixed as dot, and the density depends on the number of dots. These can easily be adjusted by choosing the dimension of the nozzle and the injection quantity from the dispenser 22. In the present embodiment, an instantaneous adhesive of gel type is used as the nonconductive gel adhesive 20. The nonconductive gel adhesive 20 may be any other one so far as the same meets the purpose of the present invention. Preferably, the nonconductive gel adhesive 20 is 75,000 Pa·s (Pascal second) or less in viscosity in order to make the works easy in forming a good shape (e.g., hemispherical shape). The shape of each masking portion 12 is not limited to the hemispherical shape and may be freely chosen to, for example, a triangle, a quadrilateral, a rhombus or the like. In this case, by making the shape of the nozzle take a triangular pyramid, a quadrangular pyramid or the like, it is possible to choose the shape of each masking portion 12 easily.

Further, it is possible to automatically fix the masking portions 12 as dots at predetermined distribution positions by controlling the movement, of the nozzle portion and the injection of the adhesive by a numerical controller.

That is, the movement of the nozzle is controlled by the numerical controller, so that the gel adhesive 20 is automatically arranged as the masking portions 12 of the nearly hemispherical shape at the intersection points of the first concentric array circle group 14A, 14C, 14E, 14G, 14I and the first width-direction array lines 16A as well as at the intersection points of the second concentric array circle group 14B, 14D, 14F, 14H, 14J and the second width-direction array lines 16B which circles and lines are imaginarily drawn on the surface of the belt section 18 of the metal base 4.

Then, as shown in FIG. 4, when diamond abrasive grains 8 are filled on the surface of the metal base 4, the diamond abrasive grains 8 are brought into direct contact with the wall surface of the metal base 4 at places where the masking portions 12 are not provided, and are prevented from being contacted with the wall surface of the metal base 4 at places where the masking portions 12 are provided.

Then, as shown in FIG. 8, the metal base 4 with the diamond abrasive grains 8 filled thereon is put into an electroplating bath 24 and is electroplated. As a result, as shown in FIG. 5, a plated layer 26 is formed between the diamond abrasive grains 8 and the wall surface of the metal base 4, whereby the diamond abrasive grains 8 are provisionally electrodeposited on the wall surface of the metal base 4 (electrodeposition plating step part 1).

The electroplating bath 24 contains a plating solution 30 that is a mixture of, for example, boric acid, nickel sulfate, nickel chloride and the like. In the plating solution 30, a nickel electrode 32 is provided as a positive electrode. The metal base 4 is used as a negative electrode. The metal base 4 is fastened by a nut 36 to a flange portion 34A of a conductive support member 34 connected to a terminal of the negative electrode, and the metal base 4 is supported from above and bottom to be put between a bottom plate 38 and a bracket 40 made of polyvinyl chloride through masking members 42 made of rubber. In the provisional electrodeposition, the diamond abrasive grains 8 were electrodeposited provisionally under the electrical density of, for example, 0.1 to 0.15 A/dm².

Then, after the provisional electrodeposition of the diamond abrasive grains 8, superfluous diamond abrasive grains 8 are removed. At this time, because the protrusions of the masking portions 12 fixed as dots on the surface of the metal base 4 are made of the nonconductive adhesive 20, the diamond abrasive grains 8 held in contact with the masking portions 12 only are not electrodeposited and hence, can be removed easily. This results in hardly having the diamond abrasive grains 8 fixed at the portions corresponding to the masking portions 12 on the diamond abrasive grain layer 6.

Then, as shown in FIG. 8, the metal base 4 with the diamond abrasive grains 8 fixed provisionally are put again into the electroplating bath 24, and an electrocast layer 28 is formed by electroplating in order to fix the diamond abrasive grains 8 permanently (electrodeposition plating step part 2). Thus, as shown in FIG. 7, the electrocast layer 28 of a sufficient thickness is formed to fix the diamond abrasive grains 8 reliably. The metal base 4 was set in the electroplating bath 24, and the diamond abrasive grains 8 were fixed by forming the electrocast layer 28 by nickel electroplating for the period of, e.g., ninety (90) hours under the electrical density of, e.g., 0.3 A/dm².

Like this, it is possible to easily control the shape, dimension and distribution positions of the masking portions 12 through adjustments when the masking portions 12 of the adhesive 20 are fixed as dots by the dispenser 22. The electrodeposition plating step parts 1 and 2 collectively constitute an electrodeposition plating step.

In the gear grinding wheel 2 in the present embodiment, as shown in FIG. 8, the superabrasive grain layers 6 are formed on the both side surfaces 54 of the metal base 4 each of which takes the convex curved shape at the outer peripheral part, and the both side surfaces 54 are formed to come close to each other toward the outer peripheral edge 56. Then, on each of the superabrasive grain layers 6, the plurality of masking portions 12 are arranged equally in the circumferential direction and the width direction of the belt section 18. Therefore, in grinding side surfaces of each of groove portions of a gear, it is possible to perform the grinding easily by making the outer peripheral edge 56 of the both side surfaces each with the superabrasive grain layer 6 thereon enter each groove portion of the gear. At this time, the plurality of masking portions 12 are brought into contact with the object to be ground, evenly over the whole of each superabrasive grain layer 6. Consequently, it is possible to prevent the loss of shape from occurring at each of the superabrasive grain layers 6 of the gear grinding wheel 2 and hence, to extend the service life of the grinding wheel.

According to the gear grinding wheel 2 constructed as aforementioned, the plurality of masking portions 12 being larger in diameter than ink jets are formed by the dispenser 22 at the intersection points of the plurality of concentric array circles 14 that are imaginarily drawn concentrically of the rotational shaft 3 to divide at equal intervals the belt section 18 where the diamond abrasive grain layer 6 is formed like a belt shape at the outer peripheral portion of the metal base 4, and the plurality of width-direction array lines 16 that are imaginarily drawn from the one end 50 toward the other end 52 of the belt section 18 to divide the belt section 18 at equal intervals in the circumferential direction. Thus, the plurality of masking portions 12 arranged at the intersection points of the width-direction array lines 16 and the concentric array circles 14 both of which are imaginarily drawn on the belt section 18 are arranged uniformly in the circumferential direction and the width direction of the belt section 18. As a result, when the gear grinding wheel 2 is rotated, the plurality of masking portions 12 are brought into contact with the object to be ground, evenly over the whole of the diamond abrasive grain layer 6 without being concentrated locally.

Further, by the uniform arrangement of the plurality of masking portions 12 in the circumferential direction and the width direction of the belt section 18, it is possible to make the concentration of the superabrasive grains 8 in the superabrasive grain layer 6 at the belt section 18 uniform as a whole. Therefore, by the provision of the plurality of masking portions 12 that are formed on the width-direction array lines 16 imaginarily drawn on the superabrasive grain layer 6, it is possible to prevent the occurrence of plugging which is caused as a result of the concentration of the superabrasive grains 8 becoming high. The portions which are between respective width-direction array lines 16A and the width-direction array lines 16B next thereto and at which the masking portions 12 are not provided can serve to prevent the loss of shape from occurring.

Consequently, it is possible to extend the service life of the gear grinding wheel 6. It was derived experimentally that effects of preventing plugging and the loss of shape were high where the total projected area of the masking portions 12 was set in a range of 5 to 20% of the total projected area of the superabrasive grain layer 6.

Second Embodiment

Hereinafter, an electroplated wheel in a second embodiment according to the present invention will be described with reference to the drawings.

The present embodiment differs from the foregoing first embodiment in that the electroplated wheel 102 in the present embodiment is a dressing tool and has a frustconical side surface with a vertex angle of 145 degrees at one side only, that a belt section 118 is provided over the outer peripheral portion on the frustconical side surface, that a diamond abrasive grain layer 106 is formed on the belt section 118, and that auxiliary width-direction array lines 17 drawn imaginarily are provided on the belt section 118.

Further, on the belt section 118 of the diamond abrasive grain layer 106, like the first embodiment, there are provided a first concentric array circle group that are composed of concentric array circles (14A, 14C, 14E, 14G, 14I) drawn imaginarily and having odd-number orders as counted from the radially outer side of the belt section 118, and a second concentric array circles group that are composed of concentric array circles (14B, 14D, 14F, 14H, 14J) drawn imaginarily and having even-number orders as counted from the radially outer side of the belt section 118. Further, on the belt section 118, there are provided first width-direction array lines 16A1, 16A2 drawn imaginarily and being in corresponding relation with the first concentric array circle group, and second width-direction array lines 16B1, 16B2 drawn imaginarily and being in corresponding relation with the second concentric array circle group. These arrangements are the same as those in the first embodiment when the electroplated dressing tool 102 is viewed from one side.

Next, the aforementioned differences will hereafter be described in detail.

As shown in FIGS. 11 and 12, the electroplated dressing tool 102 is provided with a metal base 104 which is configured to generally take a disc shape with a surface 154 on one side formed to a thin frustconical surface and with a surface on the other side formed to a flat surface, and the diamond abrasive grain layer 106 as a superabrasive grain layer which is formed in a predetermined width at a radially outer side of the surface 154 on one side of the metal base 104. The belt section 118 is formed on the outer peripheral portion of the metal base 104 of the electroplated dressing tool 102, and the diamond abrasive grain layer 106 is formed on the belt section 118. As the metal base 104, there is used a hardened and tempered steel (SUJ) for example.

The electroplated dressing tool 102 in the present embodiment is a dressing tool for dressing a screw-like grinding wheel 109 (refer to FIG. 13), and as the superabrasive grains, there are used diamond abrasive grains 8 of the grain size in a range of, for example, #30 to #140 or so.

The first width-direction array lines 16A1, 16A2 of each group provided on the belt section 118 where the diamond abrasive grain layer 106 resides are provided with first auxiliary width-direction array lines 17A1, 17A2, 17A3 imaginarily drawn as auxiliary width-direction array lines arranged next thereto on the forward side in the circumferential direction. Similarly, the second width-direction array lines 16B1, 16B2 of each group provided on the belt section 118 are provided with second auxiliary width-direction array lines 17B1, 17B2, 17B3 imaginarily drawn as auxiliary width-direction array lines arranged next thereto on the forward side in the circumferential direction. The first width-direction array lines 16A1, 16A2 and the first auxiliary width-direction array lines 17A1, 17A2, 17A3 are straight lines that are tilted at the same angle of 67.5 degrees relative to the radial direction at the center part in the width direction of the belt section 118 and are arranged to be at equal intervals with one another in the circumferential direction. Similarly, the second width-direction array lines 16B1, 16B2 and the second auxiliary width-direction array lines 17B1, 17B2, 17B3 are straight lines that are tilted at the same angle of 67.5 degrees relative to the radial direction at the center part in the width direction of the belt section 118 and are arranged to be at equal intervals with one another in the circumferential direction.

The first auxiliary width-direction array lines 17A1, 17A2, 17A3 are in corresponding relation with the first concentric array circle group 14A, 14C, 14E, 14G, 14I, while the second auxiliary width-direction array lines 17B1, 17B2, 17B3 are in corresponding relation with the second concentric array circle group 14B, 14D, 14F, 14H, 14J. Then, masking portions 12 are provided at the intersection points of the auxiliary width-direction array lines and the concentric array circle group which are in corresponding relation to each other.

These masking portions 12 are not arranged at all of the intersection points of the auxiliary width-direction array lines 17A, 17B and the concentric array circle groups corresponding thereto. That is, the masking portions 12 are arranged at those which, of the intersection points of the auxiliary width-direction array lines 17A, 17B and the concentric array circle groups 14 corresponding thereto, are located at the radially outer side, so that it can be realized to equalize the wear of the diamond abrasive grain layer 106.

Specifically, on the outermost concentric array circle 14A in the first concentric array circle group 14A, 14C, 14E, 14G, 14I, the masking portions 12 are arranged at all of three intersection points with three first auxiliary width-direction array lines 17A1-17A3 that are next to the first width-direction array line 16A2 on the left (on the forward side in the rotational direction of the electroplated dressing tool 102).

On the third concentric array circle 14C as counted from the radially outer side, the masking portions 12 are arranged at two intersection points with two first auxiliary width-direction array lines 17A1, 17A2 that are next to the first width-direction array line 16A2 on the left.

On the fifth concentric array circle 14E as counted from the radially outer side, the masking portions 12 are arranged at two intersection points with two first auxiliary width-direction array lines 17A1, 17A2 that are next to the first width-direction array line 16A2 on the left.

On the seventh concentric array circle 14G as counted from the radially outer side, the masking portion 12 is arranged at one intersection point with one first auxiliary width-direction array lines 17A1 that is next to the first width-direction array line 16A2 on the left.

On the ninth concentric array circle 14I as counted from the radially outer side, the masking portion 12 is not arranged at the intersection point with ether of the auxiliary width-direction array lines 17A1-17A3.

Likewise, in the second concentric array circle group 14B, 14D, 14F, 14H, 14J, the masking portions 12 are not arranged at all of the intersection points with the second auxiliary width-direction array lines 17B1, 17B2, 17B3 that are arranged next to the second width-direction array lines 16B1, 16B2 of each group. That is, the masking portions 12 are arranged at those which, of the intersection points of the second concentric array circle group 14B, 14D, 14F, 14H, 14J and the second auxiliary width-direction array lines 17B1-17B3, are located on the radially outer side of the belt section 118 on the electroplated dressing tool 102, so that it can be realized to equalize the wear of the diamond abrasive grain layer 106.

The electroplated dressing tool 102 of the disc shape becomes longer in circumferential length as the radial position goes radially outward. Thus, by increasing the number of the masking portions 12 as the radial position on the belt section 118 with the superabrasive grain layer 106 residing thereon of the electroplated dressing tool 102 goes radially outer side, it is possible to keep the ratio of the masking portions 12 to the superabrasive grain layer 106 uniform. This makes it possible to bring about a uniform contact with the grinding wheel 109 in performing a dressing on the same, and thus, the electroplated dressing tool 102 can be prevented from losing the shape of the diamond abrasive grain layer 106 and hence, can be extended in service life.

Next, description will briefly be made regarding a dressing that is performed on the screw-like grinding wheel 109 by using the electroplated dressing tool 102 in the present embodiment.

First of all, as shown in FIG. 13, two electroplated dressing tools 102 are provided on a drive shaft 113 not to be relatively rotatable by bolts or the like. The two electroplated dressing tools 102 are arranged so that the frustconical surfaces each with the diamond abrasive layer 106 provided thereon face each other. The drive shaft 113 is driven by having a driving torque transmitted thereto from a drive motor (not shown) through a reduction device (not shown). The reduction device is constructed to change the rotational speed of the drive shaft 113 to a desired circumferential speed by a mechanism that changes the reduction ratio of the reduction device. The grinding wheel 10 of the screw-like shape being an object to be ground is non-rotatably assembled to a drive spindle (not shown) that is rotatable at a different circumferential speed from the drive shaft 113. The drive shaft 113 and the drive spindle with the grinding wheel 10 of the screw-like shape assembled thereto are moved by an infeed mechanism (not shown) toward and away from each other in a mutually parallel relation. Further, the drive shaft 113 and the drive spindle with the grinding wheel 109 of the screw-like shape assembled thereto are relatively moved by a traverse feed mechanism (not shown) in the axial direction in synchronized relation with the rotation of the drive spindle with the grinding wheel 10 of the screw-like shape assembled thereto.

In performing a dressing, the electroplated dressing tools 102 and the grinding wheel 109 are rotated in mutually opposite directions to rotate in the same tangential directions at a contact point therebetween with the circumferential speed of the grinding wheel 109 of the screw-like shape set to be lower than the circumferential speed of the electroplated dressing tools 102. Then, while the infeed amount is adjusted by the infeed mechanism, the electroplated dressing tools 102 being rotated are infed against the grinding wheel 109 to dress opposite side surfaces of a thread portion of the grinding wheel 109 at a time, and the electroplated dressing tools 102 and the grinding wheel 109 are traversed relatively in the axial direction, whereby the thread portion of the grinding wheel 109 of the screw shape is dressed at the opposite side surfaces over the entire length thereof.

According to the electroplated dressing tool 102 of the construction described above, in addition to the masking portions 12 that are arranged at the intersection points of each concentric array circle group 14A, 14C, 14E, 14G, 14I (14B, 14D, 14F, 14H, 14J) and the corresponding width-direction array lines 16A1, 16A2 (16B1, 16B2), the masking portions 12 on the auxiliary width-direction array lines 17A1-17A3, 17B1-17B3 are arranged on the radially outer side of the belt section 118 where the wear of the superabrasive grain layer is estimated to be little. Therefore, the wear of the superabrasive grain layer 106 is made to be uniform, and the superabrasive grain layer 106 can be prevented from losing the shape.

Next, description based on experimental data will be made regarding the optimum array positions, occupancy area and the like of the masking portions 12 on the surface of the diamond abrasive grain layer 106 in the dressing tool 102.

Comparison were made between an electroplated dressing tool (test object A) in which, as shown in FIG. 14, a plurality of masking portions 12 are arrayed in a lattice fashion as done in the prior art, and the electroplated dressing tool (test object B) according to the present embodiment shown in FIG. 11. In the test object B, as shown in FIG. 11, the plurality of masking portions 12 are arrayed at the intersection points of the first concentric array circle group 14A, 14C, 14E, 14G, 14I and the first width-direction array line group 16A1, 16A2 and the first auxiliary width-direction array line group 17A1-17A3 which line groups are in corresponding relation with the first concentric array circle group. Further, the plurality of masking portions 12 are arrayed at the intersection points of the second concentric array circle group 14B, 14D, 14F, 14H, 14J and the second width-direction array line group 16B1, 16B2 and the second auxiliary width-direction array line group 17B1-17B3 which line groups are in corresponding relation with the second concentric array circle group. On the first and second auxiliary width-direction array line groups 17A, 17B, the masking portions 12 are arranged at the intersection points that are located on the radially outer side of the belt section 118.

The total projected area of the masking portions 12 relative to the total projected area of the diamond abrasive grains 8 was set to 10% in ratio for both of the test objects A and B. As the total projected area of the masking portions 12 is increased, the load on the diamond abrasive grains 8 becomes large, and hence, the loss of the shape is liable to occur. As the total projected area of the masking portions 12 is decreased, on the contrary, the loading or plugging takes place to deteriorate the cutting ability shortly. For this reason, it was considered that the ratio of the total projected area of the masking portions 12 to the total projected area of the diamond abrasive grains 8 was preferable to be set to around 10%.

By performing actual dressing operations of the test objects A and B under the same dressing condition, comparison experiments were made for respective dressing resistances representing the cutting ability (wherein a larger value indicates being worse in the cutting ability) as well as for respective wear amounts representing the shape sustainability (service life) (wherein a larger value indicates the shape sustainability becoming worse and the loss of shape being liable to occur).

The electroplated wheels being the test objects A and B in the present embodiment was the electroplated dressing tool, and the dressings were performed in the dressing condition wherein settings are made as the diameter of the electroplated dressing tool being 110 mm, the diameter of a vitrified grinding wheel to be dressed being 300 mm, the infeed rate being 0.027 m/s, the dressing tool circumferential speed being 18.8 m/s and the grinding wheel circumferential speed 1.4 m/s.

Regarding the cutting ability as the electroplated dressing tool, as shown in FIG. 9, the dressing resistance on the test object B was 0.5 where the dressing resistance representing the cutting ability of the test object A was regarded as 1, so that it was confirmed that the electroplated dressing tool being the test object B according to the present embodiment became better twice in cutting ability and represented a high cutting ability.

Regarding the shape sustainability of the electroplated dressing tool, as shown in FIG. 10, the wear amount of the test object B was about 0.63 where the wear amount of the test object A was regarded as 1. This value was the same degree as that of one having no masking portions thereon at all, and it was also confirmed that the shape sustainability was also high.

Although in the present embodiments, the auxiliary width-direction array lines 17 are arranged on the forward side in the rotational direction of each group of the width-direction array lines 16, they may be arranged on the backward side of each group of the width-direction array lines 16 in the rotational direction. Further, the auxiliary width-direction array lines 17 may be divided to be arranged on the forward and backward sides in the rotational direction of each group of the width-direction array lines 16.

Further, although in the present embodiments, the width-direction array lines 16 and the auxiliary width-direction array lines 17 are made as straight lines, they may be curved lines such as, for example, circular arcs without being limited to the straight lines.

Further, although in the present embodiments, the respective groups of the width-direction array lines 16 are arranged at the intervals of 22.5 degrees in the circumferential direction of the electroplated wheel, it is possible without being limited to the 22.5-degree intervals to arbitrarily change the angle of the intervals to, for example, 15-degree intervals to meet the performance that is required for an electroplated wheel to be manufactured.

Further, the auxiliary width-direction array lines 17 for the masking portions 12 may be set between the primary array line 16A1, 16B1 and the secondary array line 16A2, 16B2 of each group for the masking portions 12.

Further, in the electroplated dressing tool 102 in the present embodiment, for the purpose of equalizing the wear over the superabrasive grain layer, the masking portions 12 on the auxiliary width-direction array lines 17A, 17B are arranged at the radially outer side on the belt section 118. However, where the surfaces on the superabrasive grain layer where wear is little arise unevenly in dependence on the shape of the object to be ground or dressed, it may be done to arrange one or more auxiliary width-direction array lines on the surfaces that hardly wear, and to increase masking portions arranged on the array lines.

In the foregoing first and second embodiments, the diamond abrasive grain layer 6 is formed by providing the diamond abrasive grains 8 as a single layer by electroplating. However, the abrasive grain layer is not limited to being so formed and may be a superabrasive grain layer in which for example, CBN (Cubic Boron Nitride) abrasive grains are fixed by electroplating or the like.

Further, in the foregoing first and second embodiments, the width-direction array lines of each group are composed of a single primary array line and a single secondary array line. However, the width-direction array lines of each group are not limited to being so composed and may include two or more secondary array lines on which the masking portions are arranged.

Further, in the foregoing first and second embodiments, the first and second width-direction array lines are tilted backward relative to the rotational direction (i.e., to have the radially inner parts thereof behind in the rotational direction). However, the first and second width-direction array lines are not limited to being so tilted and may be tilted, for example, forward (i.e., to have the radially outer parts thereof behind in the rotational direction).

Further, in the foregoing first and second embodiments, the belt section is provided on at least one side surface of the disc-shape metal base. However, the belt section is not limited to being so provided and may be provided on, for example, an outer circumferential surface of the metal base.

Further, in the foregoing first and second embodiments, the concentric array circles 14 are grouped into the first concentric array circle group composed of the plurality of concentric array circles that respectively have odd-number orders as counted from the radially outer side, and the second concentric array circle group composed of the plurality of concentric array circles that respectively have even-number orders as counted from the radially outer side. However, the concentric array circles 14 are not limited to being so grouped and may be grouped into a first concentric array circle group composed of, for example, the first, fourth and seventh concentric array circles 14A, 14D, 14G as counted from the radially outer side, a second concentric array circle group composed of the second, fifth and eighth concentric array circles 14B, 14E, 14H and a third concentric array circle group composed of the third, sixth and ninth concentric array circles 14C, 14F, 14I. Moreover, the concentric array circles 14 may be grouped into four or more concentric array circle groups.

Further, in the foregoing first and second embodiments, the solidified gel adhesives are left as the masking portions. However, the solidified adhesives are not limited to being so left and may be eliminated to form dimples (depressions) that have no abrasive grains on the surface of the superabrasive grain layer.

Obviously, numerous further modifications and variations of the present invention are possible in light of the above teachings. It is therefore to be understood that within the scope of the appended claims, the present invention may be practiced otherwise than as specifically described herein.

Claims

1. An electroplated wheel comprising:

a metal base formed to a disc shape and rotationally driven about a rotational axis;

a superabrasive grain layer formed to have numerous superabrasive grains fixed by plating on a belt section that extends in a predetermined width on an outer peripheral portion of the metal base; and

a plurality of masking portions having no superabrasive grains electrodeposited thereat and formed of gel adhesive fixed as dots to be larger than the superabrasive grains by a dispenser at intersection points of a plurality of concentric array circles and a plurality of width-direction array lines, the plurality of concentric array circles being imaginarily drawn concentrically of the rotational axis to divide the belt section at equal intervals, and the plurality of width-direction array lines being imaginarily drawn from one end toward the other end of the belt section to divide the belt section at equal intervals in a circumferential direction.

2. The electroplated wheel in claim 1, wherein:

the plurality of concentric array circles are grouped into a plurality of concentric array circle groups each composed of a plurality of different concentric array circles;

the plurality of width-direction array lines are grouped into a plurality of width-direction array line groups each composed of a plurality of different width-direction array lines and being respectively in corresponding relation with the plurality of concentric array circle groups; and

the plurality of masking portions are formed at the intersection points of the plurality of concentric array circles in each concentric array circle group and the plurality of width-direction array lines in each width-direction array line group corresponding to each such concentric array circle group.

3. The electroplated wheel in claim 1, wherein each of the width-direction array lines is constituted by a primary array line and at least one secondary array line which are imaginarily drawn to be close to each other.

4. The electroplated wheel in claim 1, wherein the plurality of width-direction array lines are straight lines tilted at the same angle relative to the radial direction of the metal base.

5. The electroplated wheel in claim 1, wherein:

a plurality of auxiliary width-direction array lines are imaginarily drawn to be close to each of the width-direction array lines; and

the masking portions are respectively formed at intersection points of the plurality of concentric array circles and the plurality of auxiliary width-direction array lines so that the wear of the superabrasive grain layer becomes uniform.

6. The electroplated wheel in claim 1, wherein the electroplated wheel is a grinding wheel for grinding a workpiece.

7. The electroplated wheel in claim 1, wherein the electroplated wheel is a dressing tool for dressing a grinding wheel.

8. A manufacturing method for an electroplated wheel comprising a metal base formed to a disc shape and rotationally driven about a rotational axis and a superabrasive grain layer formed to have numerous superabrasive grains fixed by plating on a belt section that extends in a predetermined width on an outer peripheral portion of the metal base, the method comprising:

a masking portion forming step of forming a plurality of masking portions having no superabrasive grains electrodeposited thereat by fixing gel adhesive as dots to be larger than the superabrasive grains by a dispenser at intersection points of a plurality of concentric array circles and a plurality of width-direction array lines, the plurality of concentric array circles being imaginarily drawn concentrically of the rotational axis to divide the belt section at equal intervals, and the plurality of width-direction array lines being imaginarily drawn from one end toward the other end of the belt section to divide the belt section at equal intervals in a circumferential direction; and

an electroplating step of fixing by electroplating the numerous superabrasive grains on the belt section except for the masking portions;

wherein at the masking portion forming step, the total projected area of the masking portions is set in a range of 5 to 20% of the total projected area of the superabrasive grain layer.