FORM 2
THE PATENT ACT 1970
(39 of 1970)
&
The Patents Rules, 2003
COMPLETE SPECIFICATION
(See Section 10, and rule 13)
1 . TITLE OF INVENTION
METHOD FOR MANUFACTURING SCREW-SHAPED TOOL
2. APPLICANT(S)
a) Name
b) Nationality
c) Address
MITSUBISHI HEAVY INDUSTRIES, LTD.
JAPANESE Company
16-5, KONAN 2-CHOME,
MINATO-KU, TOKYO 1088215,
JAPAN
3. PREAMBLE TO THE DESCRIPTION
The following specification particularly describes the invention
and the manner in which it is to be performed : -
TECHNICAL FIELD
The present invention relates to a method for manufacturing a threaded tool for use
in grinding the tooth surfaces of a face gear.
BACKGROUND ART
Gears are frequently used in automotive transmissions and the like. In recent years,
there has been a demand for improvement in gear machining accuracy for the
purpose of reducing the vibrations and noises of transmissions. Generally, gear
machining involves performing gear cutting on a prescribed gear blank to form a
tooth profile, performing heat treatment on the gear after the gear cutting, and then
performing finishing (grinding) to remove strain and the like resulting from the heat
treatment. Usually, each tooth surface of a machining-target gear is ground by
bringing the machining-target gear after its heat treatment and a grinding wheel into
mesh with each other at a crossed axes angle. As tools to be used in such grinding
methods, there are tools of various shapes such as externally toothed shapes,
internally toothed shapes, and threaded (worm) shapes for the shapes of gears to be
ground.
PRIOR ART DOCUMENT
PATENT DOCUMENTS
Patent Document 1: Japanese Patent No. 3637357 (see [Fig. 1], etc., for example)
Patent Document 2: Japanese Patent No. 3665874 (see [Fig. 7], [Fig. 17], etc., for
example)
NON-PATENT DOCUMENT
Non-Patent Document 1: Hiroshi Gunbara,Kazumasa Kawasaki, "Geometrical
Design of Point-Contact Face Gear", Transactions of the Japan Society of Mechanical
Engineers, Part C, Volume 74, Issue 745, No. 08-0151, p. 197-201
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SUMMARY OF THE INVENTION
PROBLEM TO BE SOLVED BY THE INVENTION
In recent years, there has been a demand for further improvement in machining
accuracy not only for external gears but also for face gears (see Non-Patent
Document 1, for example). In this respect, as a tool for use in grinding a
machining-target face gear, use of a threaded grinding wheel has been considered,
the threaded grinding wheel being formed in such a way as to decrease gradually in
diameter from the center of the grinding wheel in the direction of the rotation axis
thereof toward either end in the axial direction thereof (see Patent Documents
1 and 2 listed above, for example).
There is, however, no consideration in either Patent Document 1 or 2 for what
specifications the threaded grinding wheel should have when it is used to finish
(grind) a machining-target face fear. In other words, there has been no consideration
for a method for manufacturing a threaded grinding wheel which can grind a
machining-target face gear accurately.
Thus, the present invention has been made to solve the above-mentioned problem,
and an object thereof is to provide a method for manufacturing a threaded tool
which can manufacture a threaded tool capable of grinding a face gear accurately.
MEANS FOR SOLVING THE PROBLEM
A method for manufacturing a threaded tool according to a first invention for
solving the above-mentioned problem is a method for manufacturing a threaded tool
which is to be formed in such a way as to increase gradually in diameter from axial
ends thereof toward an axial center thereof, for use in gear machining of a
machining-target face gear, characterized in that the method comprises:
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based on a prescribed pinion which meshes with the machining-target face gear,
setting a virtual gear which meshes with the prescribed pinion and has a greater
number of teeth than the number of teeth of the prescribed pinion;
based on the virtual gear, setting a virtual internal gear which is internally toothed
with the same number of teeth as the number of teeth of the virtual gear; and
based on the virtual internal gear, setting the threaded tool which has specifications
for use in gear machining of the virtual internal gear.
EFFECT OF THE INVENTION
According to the present invention, it is possible to realize a method for
manufacturing a threaded tool which can manufacture a threaded tool having
specifications allowing accurate grinding of a machining-target face gear.
BRIEF DESCRIPTION OF THE DRAWINGS
[Fig. 1]
[Fig. 2]
Fig. 1 is a set of views for describing a method for manufacturing a
threaded grinding wheel according to an embodiment of the present
invention, Part (a) of Fig. 1 showing a plan view of a state where a pinion
which meshes with a machining-target face gear is disposed, Part (b) of
Fig. 1 showing a side view of the state.
Fig. 2 is a set of views for describing the method for manufaCturing a
threaded grinding wheel according to the embodiment of the present
invention, Part (a) of Fig. 2 showing a plan view of a state where a virtual
gear which meshes with the pinion is disposed, Part (b) of Fig. 2 showing
a side view of the state.
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[Fig. 3]
[Fig. 4]
[Fig. 5]
[Fig. 6]
Fig. 3 is a set of views for describing the method for manufacturing a
threaded grinding wheel according to the embodiment of the present
invention, Part (a) of Fig. 3 showing a plan view of a state where a virtual
gear is given as a virtual internal gear, and a threaded grinding wheel
which meshes with the virtual internal gear is disposed, Part (b) of Fig. 3
showing a side view of the state.
Fig. 4 is a set of views for describing grinding of the machining-target face
gear using the threaded grinding wheel obtained by the method for
manufacturing a threaded grinding wheel according to the embodiment
of the present invention, Part (a) of Fig. 4 showing a plan view of a state
where the threaded grinding wheel and the machining-target face gear
are in mesh with each other, Part (b) of Fig. 4 showing a side view of the
state.
Fig. 5 is a view for describing a state where the machining-target face gear
is ground by using the threaded grinding wheel obtained by the method
for manufacturing a threaded grinding wheel according to the
embodiment of the present invention.
Fig. 6 is a vertical cross-sectional view of the threaded grinding wheel.
MODES FOR CARRYING OUT THE INVENTION
A mode for carrying out a method for manufacturing a threaded tool according to
the present invention will be described below with reference to Figs. 1 to 6.
A threaded grinding wheel (threaded tool) to be manufactured by a method for
manufacturing a threaded tool according to this embodiment is a tool for use in a
grinding process in gear machining of a face gear. As shown in Fig. 6, a .threaded
grinding wheel 10 is formed in such a way as to increase gradually in diameter from
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its axial ends lOb and 10c toward its axial center. Edges lOa are formed at the
peripheral surface of the threaded grinding wheel 10 in such a way as to extend from
the end lOb on one side toward the end 10c on the other side while inclining with
respect to the direction of the axis. The axial length of the threaded grinding
wheel 10 (grinding-wheel length) is a length H.
Now, a method for manufacturing a threaded grinding wheel with the above
configuration will be specifically described with reference to Figs. 1 to 5.
As shown in Parts (a) and (b) of Fig. 1, there is a prescribed pinion (e.g. a spur gear
or a helical gear) 13 which meshes with a machining-target face gear 11 to be
ground. That is, there is a prescribed pinion 13 which is rotated about a pinion
rotation axis B2 by bringing the pinion 13 into mesh with teeth of the
machining-target face gear 11 and rotating the machining-target face gear 11 about a
workpiece rotation axis Cl.
First, as shown in Parts (a) and (b) of Fig. 2, a virtual gear 14 is set which meshes
with the prescribed pinion 13, has a greater number of teeth than the number of
teeth of the pinion 13, and has the same specifications as the specifications of the
pinion 13 except the number of teeth. The virtual gear 14 is a gear having an outline
of the tooth profile, and may be an external gear, for example.
Then, based on the virtual gear 14, a virtual internal gear 15 (see Parts (a) and (b) of
Fig. 3) is set which is internally toothed with the same number of teeth as the
number of teeth of the virtual gear 14 and has the same specifications as the virtual
gear 14.
Then, as shown in Parts (a) and (b) of Fig. 3, based on the virtual internal gear 15,
a threaded grinding wheel 10 is set which has specifications for use in gear
machining of the virtual internal gear 15. The threaded grinding wheel 10 for
grinding the machining-target face gear 11 is formed in a barrel s~ape and has
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grinding-wheel specifications allowing proper mesh with the specifications of the
machining-target face gear 11, and the edge profile thereof includes a predetermined
helix angle. Since the threaded grinding wheel 10 meshes with the virtual internal
gear 15, the threaded grinding wheel 10 meshes with the machining-target face
gear 11 with the grinding-wheel rotation axis B1 being set at a predetermined
crossed axes angle e with respect to the workpiece rotation axis C1 of the
machining-target face gear 11 as shown in Parts (a) and (b) of Fig. 4.
Thus, in the case of grinding each tooth surface (tooth 12) of the machining-target
face gear 11 by using the threaded grinding wheel 10 manufactured through the
above-described steps, teeth 12 of the machining-target face gear 11 and edges lOa of
the threaded grinding wheel 10 are brought into mesh with each other as shown in
Fig. 5. In the meshing state, the machining-target face gear 11 is rotated about the
workpiece rotation axis C1, while the threaded grinding wheel 10 is synchronously
rotated about the grinding-wheel rotation axis B1 and also the threaded grinding
wheel 10 is swung in the radial direction of the machining-target face gear 11.
As a result, so-called crowning is performed in which each tooth 12 of the
machining-target face gear 11 is machined by the edges lOa of the threaded grinding
wheel 10 to have a slightly curved surface that makes the tooth 12 wider at the center
and thinner at either end along its tooth trace. By using the threaded grinding wheel
10 manufactured through the steps described above, the tooth surface of the
machining-target face gear 11 can be ground accurately.
As described above, the method for manufacturing a threaded tool according to this
embodiment includes: based on a prescribed pinion 13 which meshes with a
machining-target face gear 11, setting a virtual gear 14 which meshes with the
prescribed pinion 13 and has a greater number of teeth than the number of teeth of
the prescribed pinion 13; based on the virtual gear 14, setting a virtual internal gear
15 which is internally toothed with the same number of teeth as the number of teeth
of the virtual gear 14; and based on the virtual internal gear 15, setting a threaded
grinding wheel 15 which has specifications for use in gear machining of the virtual
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internal gear 15. Thus, a threaded grinding wheel 10 which meshes with the
machining-target face gear 11 can be manufactured. Specifically, since the virtual
gear 14 is set in such a way as to mesh with the prescribed pinion 13 and have a
greater number of teeth than the number of teeth of the prescribed pinion 13,
it is possible to manufacture a threaded grinding wheel 10 which meshes with the
machining-target face gear 11 and has edges lOa that, in the meshing state, come into
point contact with teeth 12 of the machining-target face gear 11 instead of line
contact therewith, Le. a threaded grinding wheel 10 which can grind the
machining-target face gear 11 accurately. Moreover, the machining-target face
gear 11 can be ground with the grinding-wheel rotation axis B1 of the threaded
grinding wheel 10 being oriented at the predetermined crossed axes angle 8 with
respect to the workpiece rotation axis Cl. Thus, the grinding speed can be increased,
thereby making it possible to improve the sharpness of grinding action of the
threaded grinding wheel 10 and increase the life thereof.
Note that although a method for manufacturing a threaded grinding wheel has been
described hereinabove, a threaded grinding wheel obtained by the above-described
method for manufacturing a threaded grinding wheel may be dressed by using the
same method as a method for dressing a threaded grinding wheel for machining an
internal gear (e.g. by using a dressing gear, a disk dresser, or the like). In this way,
it is possible to recover the sharp tooth surfaces.
INDUSTRIAL APPLICABILITY
The present invention is a method for manufacturing a threaded tool. and can
manufacture a threaded tool which has specifications allowing accurate grinding of
a machining-target face gear. Thus, the present invention is usefully applicable to
machine tool industries and the like.
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EXPLANATION OF THE REFERENCE NUMERALS
10 threaded grinding wheel (threaded tool)
11 machining-target face gear
12 tooth
13 pinion
14 virtual gear
15 virtual internal gear
M1 grinding-wheel rotation drive source
B1 grinding-wheel rotation axis
B2 pinion rotation axis
C1 workpiece rotation axis
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WE CLAIM:
1. A method for manufacturing a threaded tool which is to be formed in such a
way as to increase gradually in diameter from axial ends thereof toward an
axial center thereof, for use in gear machining of a machining-target face gear,
characterized in that the method comprises:
based on a prescribed pinion which meshes with the machining-target face
gear, setting a virtual gear which meshes with the prescribed pinion and has a
greater number of teeth than the number of teeth of the prescribed pinion;
based on the virtual gear, setting a virtual internal gear which is internally
toothed with the same number of teeth as the number of teeth of the virtual
gear; and
based on the virtual internal gear, setting the threaded tool which has
specifications for use in gear machining of the virtual internal gear.