JPH11114721A - Built-up gear hob - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce the extent of noise in time of gear driving by improving the machining accuracy of a tooth profile inclusive of a tip of the machined gear as preventing an increase in cost, in this built-in gear hob which consists of a lot of rack-form blades, extending in each axial direction, are combinedly installed in the circumference of a hob body in the circumferential direction. SOLUTION: This built-up gear hob is provided with an exclusive blade 3 cutting a tip part in addition to a rack-form blade 2 cutting a tooth flank of the machined gear, and in this constitution, these blades are apposingly installed on the circumference of a hob body at an equal space in the circumferential direction. A peripheral edge of an edge face 3a of this exclusive blade 3 is formed so as to be rectilinearly extended in the axial direction, and then it is installed so as to be projected up to an intermediate position between a projection 6 and a recess 7 of the rack-form blade 2.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an assembling hob used for gear cutting, and more particularly to a technical field for improving the processing accuracy of a gear tooth profile.

[0002]

2. Description of the Related Art Conventionally, as an assembly hob of this type, one disclosed in, for example, Japanese Utility Model Laid-Open No. Sho 60-178530 is known. That is, as shown in FIG. 5, the assembling hob includes a large number (twelve in the illustrated example) having a reference rack shape on the outer periphery of the cylindrical hob main body 1 which ideally meshes with a not-shown gear to be cut. Rack blade 2,
Are arranged side by side in parallel to the axial direction and at equal intervals in the circumferential direction.

[0003] When, for example, gear cutting of a spur gear is performed using such an assembling hob, a blank processed into a thick disk shape using a lathe or the like is prepared, and the blank and the assembling hob are not shown. Attached to a hobbing machine, it cuts out the obstacles while giving the ideal relational motion between the two, and processes the gear to be cut. That is, the blank and the assembling hob are arranged such that the screw streaks of the assembling hob coincide with the tooth streak direction of the gear to be cut, and the assembling hob is rotated around the hob axis, and the blank is synchronously rotated. By that
Teeth having an ideal involute curve tooth surface can be sequentially formed along the outer periphery of the blank.

[0004]

By the way, in the above-mentioned hobbing, only a portion to be a tooth surface of a gear to be cut is cut by a rack-shaped blade, and a portion to be a tooth tip is not cut. Thus, the outer periphery of the blank formed by machining with a lathe or the like becomes the tooth tip of the gear as it is. For this reason, the rack-shaped blade 2 (see FIG. 3) of the above-mentioned conventional assembly hob has a concave portion 7,
Are formed, so that even when the blank is cut deepest, a gap is formed between the blank and the tooth tip of the gear to be cut.

However, in the hobbing method as described above, when a blank machined by a lathe or the like is replaced with a hobbing machine, the center of rotation is slightly shifted, but the gear may be eccentric. In order to avoid the influence of this eccentricity, it is necessary to provide a sufficiently large clearance for preventing interference between the tooth tips between the gears meshing with each other, and as a result, to sufficiently reduce the noise during the operation of the gears. There is a problem that it cannot be obtained.

Incidentally, as shown in FIG. 6, the recesses 7 ', 7',... Of the rack-shaped blade 2 'are formed in a shape corresponding to the tooth tip of the gear to be machined, so that the tooth surface to the tooth tip can be processed simultaneously. There is also an assembling hob (full topping hob) as described above. In this hob, however, the rack-shaped blade 2 ', especially the recesses 7',
The shape of the bottom part of 7 ',... Becomes complicated, it is extremely difficult to form it with high precision, and the manufacturing cost becomes high.
There is a problem that maintenance work such as resharpening becomes difficult.

SUMMARY OF THE INVENTION The present invention has been made in view of the above circumstances, and an object of the present invention is to improve the structure of an assembling hob so as to prevent the increase in cost and to reduce the tooth tip of a gear to be machined. An object of the present invention is to improve the processing accuracy of a tooth profile including the tooth profile and to reduce noise during operation of the gear.

[0008]

In order to achieve the above object, in the solution of the present invention, a dedicated blade for shaving the tooth tip of a gear to be cut is provided in a state of being arranged in a rack-like blade.

More specifically, the invention according to claim 1 is based on the premise that an assembling hob in which a number of rack-shaped blades are arranged in the circumferential direction on the outer periphery of the hob body. Then, at least one dedicated blade for shaving the tooth tip of the gear to be cut is provided on the outer periphery of the hob main body along with the rack-shaped blade.

According to this configuration, when gear cutting is performed using the assembly hob, the tooth surface of the gear to be cut is cut by the rack-shaped blade as in the conventional case, and the outer periphery of the blank is slightly reduced by the dedicated blade. Since the tooth tip portion can be cut out by shaving, the center of the addendum circle of the gear to be cut can be made to exactly coincide with the rotation center on the hob machine, that is, the rotation center of the gear to be cut. Therefore, eccentricity of the gear can be reliably prevented, and noise during operation can be reduced.

Further, the dedicated blade only needs to cut out only the tooth tip of the gear to be machined, and does not have a complicated shape unlike the conventional full topping hob, so that it can be manufactured at low cost and the cost of the assembly hob can be reduced. Does not lead to growth.

According to the second aspect of the present invention, the dedicated blade according to the first aspect of the present invention is provided so as to protrude to an intermediate position between the convex portion and the concave portion of the rack-shaped blade and to extend linearly in the axial direction.

That is, in general, the convex portion of the rack-shaped blade is formed so as to finish the root of the gear to be machined,
The concave portion is formed deeply so as not to interfere with the outer periphery of the blank, but the dedicated blade is provided so as to protrude to an intermediate position between the convex portion and the concave portion. Can be cut to remove the tooth tip.

Further, since the dedicated blade is formed in a straight line, it is particularly easy to work, and can be manufactured at a low cost and with extremely high precision.

According to a third aspect of the present invention, one dedicated blade according to the second aspect of the present invention is provided. With this,
Since the tooth tip of the gear to be machined is cut out by one dedicated blade, only the one dedicated blade is accurately positioned and provided on the hob main body, so that the center of the tooth tip circle of the gear to be machined is set. The center of rotation can be matched with high accuracy.

In the case of shaving the tooth tip,
In practice, the outer periphery may be slightly cut by the amount of the eccentricity of the blank, and the load on the dedicated blade is considered to be extremely small. Therefore, one dedicated blade is sufficient.

According to a fourth aspect of the present invention, in the first aspect of the invention, the rack-shaped blade and the dedicated blade are arranged at equal intervals in the circumferential direction of the hob body. This makes it possible to equalize the load on the hob main body and the blade, thereby increasing the strength of the entire assembly hob.

[0018]

Embodiments of the present invention will be described below with reference to the drawings.

1 and 2 show an assembly hob A according to an embodiment of the present invention. The assembly hob A is used for gear cutting of a spur gear, a helical gear, or the like.

In both of the figures, reference numeral 1 denotes a cylindrical hob main body. At the center of the hob main body 1, a mounting hole 1a for a hob shaft of a hob machine (not shown) is formed so as to penetrate along the axis X. On the outer periphery, a plurality (1 in the figure) parallel to the axis X direction is provided.
3) are formed at equal intervals in the circumferential direction. The rack-like blades 2, 2,... Similar to the conventional one are provided in twelve of these blade mounting grooves 1b, 1b,. Are respectively fitted with dedicated blades 3 for shaving the tooth tips of the gears to be machined.

Tightening rings 4, 4 are arranged on both end surfaces of the hob body 1, respectively, and are fixed to the hob body 1 by four bolts 5, 5,... Have been. Thereby, each of the blades 2, 2,
, 3 are fixed to the hob main body 1 in the axis X direction. And the assembling hob A thus configured is
It is rotated counterclockwise (in the direction of the arrow) in FIG. 2 around the axis X to cut a blank (not shown) to process the gear.

Each of the rack-shaped blades 2 is the same as the conventional one, but is formed by, for example, forming a high-speed steel or the like by forging and heat-treating the same. As shown in FIG. It is provided so as to extend in the direction of the axis X (the left-right direction in the figure). The mounting handle 2a on the inner peripheral side (lower side in the figure) is shrink-fitted and fixed in the blade mounting groove 1b, while the outer peripheral side (upper side in the figure) is radially outward from the outer circumference of the hob body 1. In the direction of rotation of the hob main body 1, and a cutting edge surface 2a is formed on the protruding end surface thereof.

Are formed at equal intervals in the longitudinal direction (left-right direction in FIG. 3). , Are formed with six substantially triangular concave portions 7, 7,. The tips of the projections 6, 6,...
Finishes the root of the gear to be machined when cut deepest into the blank. On the other hand, the recesses 7, 7,.
The cut gear is formed deeper than the teeth of the cut gear so as not to interfere with the outer periphery of the blank which is the tooth tip of the cut gear.

.. On the tip side of the projections 6, 6,.
A hump is formed to make the root of the gear to be cut slightly larger, so that when cutting the finished gear by grinding or shaving, the cutting edge of a tool such as a shaving cutter does not interfere with the root of the gear. Has become.

The dedicated blade 3 is a feature of the present invention, and is made of, for example, high-speed steel or the like like the rack-shaped blades 2, 2,..., As shown in FIG. The mounting handle 3a (lower side in the figure) is shrink-fitted and fixed in the blade mounting groove 1b. On the other hand, the outer peripheral side (upper side in the figure) of the dedicated blades 3, 3,... The cutting edge surface 3a is formed on the protruding end surface.

The outer peripheral edge of the cutting surface 3a (the uppermost part in the figure)
Are formed so as to extend linearly in parallel with the axis X, and the convex portions 6, 6,.
Are projected from the outer periphery of the hob main body 1 to a radial position corresponding to the tooth tip portion of the gear to be cut, which is intermediate between the concave portions 7, 7,... It is designed to sharpen the tip of the tooth slightly.

Therefore, if the gear hobbing is performed by the hobbing machine using the assembly hob A of this embodiment in the same manner as in the prior art, when the tooth surfaces of the gear to be cut are cut out by the rack-shaped blades 2, 2,. At the same time, the outer periphery of the blank can be slightly shaved by the dedicated blade 3 to cut out the tooth tip portion, whereby the center of the tooth tip circle of the gear to be machined can be accurately positioned at the center of rotation on the hobbing machine, ie, It can be made to coincide with the rotation center of the gear to be cut. Therefore, eccentricity of the gear can be reliably prevented, and noise during operation can be reduced.

At this time, since the tooth tip portion of the gear to be machined is cut out by only one dedicated blade 3,
If only the dedicated blade 3 is accurately positioned so that the outer peripheral edge of the cutting surface 3a is located at a predetermined position radially protruding from the outer periphery of the hob main body 1, the center of the addendum circle of the gear to be machined is obtained. Can be matched with the center of rotation with high accuracy. Note that the dedicated blade 3 slightly cuts the outer periphery of the blank by the amount of the eccentricity of the blank, and the burden is considered to be extremely small.

Further, since the cutting surface 3a of the dedicated blade 3 is formed in a straight line, processing such as grinding is particularly easy, and a very high-precision blade can be manufactured at low cost.

Further, twelve rack blades 2,
, And one dedicated blade 3 are provided on the outer periphery of the hob main body 1 at equal intervals in the circumferential direction, so that the load on the hob main body 1 and each of the blades 2, 2,. Therefore, the strength of the entire assembly hob A can be increased.

(Other Embodiments) The present invention is not limited to the above embodiments, but includes various other embodiments. That is, in the above embodiment, the outer peripheral edge of the cutting surface 3a of the dedicated blade 3 is linear, but is not limited thereto, and may be a curved shape such as a circular shape.

In the above embodiment, the dedicated blade 3
Is provided only one, but is not limited to this, and two or more may be provided.

Further, in the above embodiment, the twelve rack-shaped blades 2, 2,... And the dedicated blade 3 are provided on the outer periphery of the hob body 1 at equal intervals in the circumferential direction. For example, the rack-shaped blades 2, 2,... May be provided at equal intervals in the circumferential direction, and the dedicated blade 3 may be provided between them.

[0034]

As described above, according to the assembling hob according to the first aspect of the present invention, when the tooth surface of the gear to be cut is cut, the tooth tip portion can be cut with the dedicated blade at the same time. In addition, the eccentricity of the gear can be reliably prevented to reduce noise during operation. In addition, since the dedicated blade can be manufactured at a lower cost than a conventional full topping hob, an increase in cost can be prevented.

According to the second aspect of the present invention, since the dedicated blade is formed in a straight line, it can be manufactured at low cost and with extremely high precision.

According to the third aspect of the present invention, since only one dedicated blade is used, high precision can be easily realized.

According to the fourth aspect of the present invention, since the rack-shaped blade and the dedicated blade are provided at equal intervals in the circumferential direction of the hob body, the strength of the entire assembly hob can be increased.

[Brief description of the drawings]

FIG. 1 is a partial longitudinal sectional view showing a configuration of an assembly hob according to an embodiment of the present invention.

FIG. 2 is a partial cross-sectional view of FIG.

FIG. 3 is an enlarged sectional view showing a configuration of a cutting surface of a rack-shaped blade.

FIG. 4 is a diagram corresponding to FIG. 3, showing a configuration of a cutting surface of a dedicated blade.

FIG. 5 is a diagram corresponding to FIG. 1 showing a configuration of a conventional assembly hob.

FIG. 6 is a diagram corresponding to FIG. 3 relating to a conventional full topping hob.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Hob main body 2 Rack-shaped blade 3 Dedicated blade 6 Convex part of the cutting surface of a rack-shaped blade 7 Recess of the cutting surface of a rack-shaped blade X Axis line of the hob main body

Claims (4)

[Claims] 1. An assembling hob in which a number of rack-shaped blades are arranged in a circumferential direction on an outer periphery of a hob body, at least one sheet for shaving a tooth tip portion of a gear to be cut on the outer periphery of the hob body. An assembling hob characterized in that the dedicated blade of (1) is provided alongside the rack-shaped blade. 2. The assembly hob according to claim 1, wherein the special blade protrudes to an intermediate position between the convex portion and the concave portion of the rack-shaped blade and extends linearly in the axial direction. 3. The assembly hob according to claim 2, wherein one dedicated blade is provided. 4. The assembly hob according to claim 1, wherein the rack-shaped blade and the dedicated blade are arranged at equal intervals in a circumferential direction of the hob main body.