U.S. patent application number 11/227134 was filed with the patent office on 2006-03-23 for grinding wheel.
This patent application is currently assigned to TOYODA KOKI KABUSHIKI KAISHA. Invention is credited to Tomoyuki Kasuga, Shinji Soma.
Application Number | 20060063478 11/227134 |
Document ID | / |
Family ID | 35445944 |
Filed Date | 2006-03-23 |
United States Patent
Application |
20060063478 |
Kind Code |
A1 |
Soma; Shinji ; et
al. |
March 23, 2006 |
Grinding wheel
Abstract
A grinding wheel 10 comprises a disk core 11 and a grinding
stone 20 surrounding the core 11. The grinding stone 20 includes a
first abrasive portion 30 and a second abrasive portion 40. The
first abrasive portion forms a circumferential surface of the
grinding stone 20 and has small grains. The second abrasive portion
40 forms at least one lateral surface of the grinding stone 20 and
has larger grains than the first abrasive portion 30.
Inventors: |
Soma; Shinji; (Handa-shi,
JP) ; Kasuga; Tomoyuki; (Kariya-shi, JP) |
Correspondence
Address: |
OBLON, SPIVAK, MCCLELLAND, MAIER & NEUSTADT, P.C.
1940 DUKE STREET
ALEXANDRIA
VA
22314
US
|
Assignee: |
TOYODA KOKI KABUSHIKI
KAISHA
Kariya-shi
JP
|
Family ID: |
35445944 |
Appl. No.: |
11/227134 |
Filed: |
September 16, 2005 |
Current U.S.
Class: |
451/541 |
Current CPC
Class: |
B24D 7/14 20130101; B24B
5/42 20130101 |
Class at
Publication: |
451/541 |
International
Class: |
B24B 33/00 20060101
B24B033/00 |
Foreign Application Data
Date |
Code |
Application Number |
Sep 17, 2004 |
JP |
2004-271163 |
Claims
1. A grinding wheel comprising: a disk core; a grinding stone
surrounding the core; a first abrasive portion forming a
circumferential surface of the grinding stone; a second abrasive
portion forming at least one lateral surface of the grinding stone;
and wherein the second abrasive portion has larger grains than the
first abrasive portion.
2. A grinding wheel according to claim 1, wherein: the second
abrasive portion is studded with single layer of the grains.
3. A grinding wheel according to claim 1, wherein: the second
abrasive portion is studded with a multiple layers of the
grains.
4. A grinding wheel according to claim 1, wherein: the external
radius of the second abrasive portion is smaller than the first
abrasive portion.
5. A grinding wheel according to claim 1, wherein: the external
radius of the second abrasive portion is as large as the first
abrasive portion.
6. A grinding wheel according to claim 1, wherein: the corner of
the second abrasive portion forms a chamfer
7. A grinding wheel according to claim 6, wherein: the chamfer is
R-chamfer and its radius is larger than the width of the second
abrasive portion.
8. A grinding wheel according to claim 1, wherein: the corner of
the second abrasive portion is right-angled.
Description
INCORPORATION BY REFERENCE
[0001] The present application claims priority under 35 U.S.C.
.sctn.119 to Japanese Patent Application No. 2004-271163, filed on
Sep. 17, 2004. The contents of that application are incorporated
herein by reference in their entirety.
BACKGROUND OF THE INVENTION
[0002] 1. Field of the Invention
[0003] This invention relates to a grinding wheel.
[0004] 2. Discussion of the background
[0005] A conventional cylindrical grinding machine has a grinding
wheel. In general, the grinding wheel is disk-like and has a
grinding stone surrounding itself. The grinding wheel is attached
to a wheel spindle of a wheel head of the grinding machine and is
rotationally driven by an electric motor connected to the wheel
spindle. The rotational grinding wheel grinds a workpiece with its
circumferential surface of the grinding stone. As shown in FIG. 4,
the grinding wheel 10 may grind not only a cylindrical surface Wa
of the workpiece W but also a face Wb of the workpiece W.
Especially, where the workpiece W is a crankshaft of which
cylindrical surfaces Wa of crank journals and crank pins would be
ground, the grinding wheel may grind faces Wb of crank webs
therebetween with the lateral surfaces of the grinding stone 20.
During grinding the face Wb with the lateral side of the abrasive
portion 20, because the lateral surface 20 widely contacts with the
face Wb radially, coolant hardly penetrates into the contact area
between the workpiece W and the grinding stone 20 (the contact area
will be explained as "grinding area") and the chip is hardly
discharged from the grinding area. Thus, grinding burn may occur to
the workpiece W so that it is hard to improve grinding
efficiency.
SUMMARY OF THE INVENTION
[0006] In view of the foregoing, it is an object of the present
invention to provide a grinding wheel which hardly causes a
workpiece burn and is able to improve grinding efficiency even in
the case of face grinding. In order to achieve the above and other
objects, an aspect of the present invention provides a grinding
wheel comprising a first abrasive portion forming a circumferential
surface and a second abrasive portion forming a lateral surface
whose grain size is larger than the first abrasive portion.
[0007] The second abrasive portion may unite the first abrasive
portion with an adhesive. Or, the grains forming the second
abrasive portion may be implanted in the lateral side of the first
abrasive portion. Additionally, the second abrasive portion may
form a single layer or a multiple layers. Further, the external
radius of the second abrasive portion may be as large as the
external radius of the first abrasive portion. Or, the external
radius of the second abrasive portion may be smaller than the
external radius of the first abrasive portion. The external corner
of the second abrasive portion may form a chamfer.
BRIEF DESCRIPTION OF THE DRAWINGS
[0008] Various other objects, features and many of the attendant
advantages of the present invention will be readily appreciated as
the same becomes better understood by reference to the following
detailed description of the preferred embodiments when considered
in connection with the accompanying drawings, in which:
[0009] FIG. 1 is a section view of an embodiment of a grinding
wheel and its partial section view related to the invention;
[0010] FIG. 2 is partial section views of first and second examples
of the embodiment related to the invention;
[0011] FIG. 3 is partial section views of third and forth examples
of the embodiment related to the invention;
[0012] FIG. 4 is a schematic sketch of a grinding process of a face
of a rotational workpiece.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0013] An embodiment of the present invention will be described
with reference to figures. As shown in FIG. 1, a grinding wheel 10
comprises a disk core 11 and a grinding stone 20 surrounding the
circumference of the core 11. The grinding wheel 10 is used for a
grinding machine, for example a cylindrical grinding machine which
grinds a workpice with the grinding wheel 10 attached to a spindle
of a wheel head of the grinding machine, similar to the
conventional related art shown in FIG. 4. The workpiece W has a
cylindrical surface Wa and a face Wb to be ground by the grinding
wheel 10. One example of the workpiece W is a crank shaft whose
crank journal has a cylindrical surface Wa adjacent to a crank web
of a face Wb. The grinding stone 20 surrounding the core 11
includes a first abrasive portion 30 forming a circumferential
surface and a second abrasive portion 40 forming at least one
lateral surface. Each lateral surface is able to form the second
abrasive portion 40.
[0014] The first abrasive portion 30 is made from small CBN (Cubic
Boron Nitride) grains whose size is between #80 and #120, a bond
(vitrified bond etc.), a filling whose material is weaker than the
grains to adjust the grain distance, and pores. Thus, the first
abrasive portion 30 is able to grind the cylindrical surface Wa of
the workpiece W as precisely as required surface roughness. On the
other hand, the second abrasive portion 40 is made from CBN grains
whose size is between #20 and #60 that is larger than the first
abrasive portion 30, thereby the second abrasive portion 40 is
appropriately able to grind the face Wb of the workpiece W not to
be required as precisely as the cylindrical surface Wa.
[0015] In the above grinding wheel, the lateral surface(s) of the
grinding stone is/are formed by the second abrasive portion 40
whose grain size is larger than the first abrasive portion 30.
Because of the large grains, during the face grinding, coolant is
easily supplied into the grinding area and chip is discharged
better. Therefore, even in the case of the face grinding, the above
grinding wheel 10 hardly causes workpiece burn so that grinding
efficiency improves.
[0016] In general face grinding, grinding allowance is
approximately set 0.2 millimeters, so that the face Wb is able to
be ground well and rapidly with the second abrasive portion 40
whose grain size is larger than the grinding allowance. For
example, the grain size of #60 is 0.25 millimeters in average that
is larger than the general grinding allowance of 0.2 millimeters.
Additionally, the second abrasive portion 40 provides higher wear
resistance and reduces its own wear.
[0017] Where the workpiece W is a crank shaft or the like, more
precise surface roughness is generally required for the cylindrical
surface Wa than the face Wb. Because the circumferential surface of
the grinding wheel 10 forms the first abrasive portion 30 made from
the smaller grains than the second abrasive portion 40, the
cylindrical surface Wa of the workpiece W such as a crank journal
is able to be ground precisely with the first abrasive portion 30.
On the other hand, although the face grinding is not required as
precisely as the cylindrical surface grinding, the precise
perpendicular to the cylindrical surface Wa is required for the
face grinding to grind a crank web Wb. In the case that the coolant
does not penetrate well into the grinding area or the chip is not
discharged well from the grinding area, the workpiece W is
overheated and is deformed, thereby the perpendicular may not be
obtained between the face Wb and the cylindrical surface Wa. Using
the grinding wheel 10 with the large grains on its lateral
surface(s), however, the coolant is easily able to penetrate into
the grinding area so that the workpiece W is cooled down well. And
the chip is discharged from the grinding area well so that the
workpiece W is not overheated. Therefore, the workpiece W is hardly
deformed and the perpendicular is obtained between the face Wb and
the cylindrical surface Wa.
[0018] FIG. 2(a) shows a first example of the second abrasive
portion 40 according to the embodiment. In the first example, the
second abrasive portion 40 is made by the large grains 41 adhering
on the lateral side of the first abrasive portion 30 with vitrified
bond or the like 42. Although the surface of the second abrasive
portion 40 is filled with the grains 41 in FIG. 2(a), the grains 41
may be loosely mounted with appropriate distance between of
themselves. In this case, the grains 41 may be mixed with filling
more brittle than the grains 41.
[0019] The second abrasive portion 40 is flatly studded with single
layer of the large grains 41 that are not piled but stud the
surface of the second abrasive portion 40. As shown in FIG. 2(a),
there form appropriate gaps between each tip of the grains 41 where
cutting edges appear, so that the coolant is easily able to
penetrate into the grinding area and the chip is discharged better
due to the gaps.
[0020] Although the second abrasive portion 40 is flatly studded
with single layer of the large grains 41 in FIG. 2(a), a pile of
layers (a multiple layers) of the grains 41 is also available.
[0021] FIG. 2(b) shows a second example of the second abrasive
portion 40 according to the embodiment. Manufacturing method of the
second example includes following steps of; mixing bond and the
small grains for the first abrasive portion 30; mounting the large
grains 41 on the lateral surface(s) of a molding flask; putting the
mixture of the bond and the small grains into the molding flask;
and sintering them. Thus, the second abrasive portion 40 is adhered
on the lateral surface(s) of the first abrasive portion 30 of the
grinding wheel 10. Although the second abrasive portion 40 is
flatly studded with single layer of the large grains 41 in FIG.
2(a), a multiple layers of the grains 41 is also available. And
although the surface of the second abrasive portion 40 is filled
with the grains 41 in FIG. 2(b), each of the grains 41 may be
loosely mounted with appropriate distance between of themselves. In
this case, the grains 41 may be mixed with filling more brittle
than the grains 41.
[0022] There may form some appropriate shapes at the external
corner of the grinding stone 20. FIG. 3(a) shows a third example of
the embodiment related to the shape at the external corner of the
grinding stone 20. The external corner forms an R-chamfer that
extends from the lateral surface of the second abrasive portion 40
to the circumferential surface of the first abrasive portion 30. So
the external radius of the second abrasive portion 40 is smaller
than the first abrasive portion 30 (see dimension "A" in FIG.
3(a)). Further, the R-chamfer forms a part of a circle in its
section view and the width of the second abrasive portion 40 is
smaller than the radius of the R-chamfer. Therefore, during plunge
cutting, the large grains of the second abrasive portion 40 do not
grind but the small grains of the first abrasive portion 30 grind
the cylindrical surface Wa of the workpiece W, so that the
cylindrical surface Wa of the workpiece W is precisely ground.
[0023] Although the chamfer forms an R-shape in its section view,
it may form a C-shape or taper-shape. Instead of the chamfer, for
the dimension of the external radius of the second abrasive portion
40 being smaller than the first abrasive portion 30, there may form
the radius of the whole circumferential surface of the second
abrasive portion 40 than the first abrasive portion 30. In this
case, there forms a step between the first and second abrasive
portions 30, 40.
[0024] In the third example, because the external radius of the
second abrasive portion 40 with large grains is smaller than the
first abrasive portion 30 with small grains, the cylindrical
surface Wa of the workpiece W is precisely ground during the plunge
cutting. Where the chamfer forms R-shape, there may form a recess
or R-shape between the cylindrical surface Wa and the face Wb of
the workpiece W.
[0025] FIG. 3(b) shows a forth example of the embodiment. In the
forth example, the whole external radius of the second abrasive
portion 40 is set as large as the first abrasive portion 30,
thereby the second abrasive portion 40 forms the same
circumferential surface of the first abrasive portion 30 and forms
a right angle at the corner. Where such grinding wheel 10 is used
for traverse cutting, the second abrasive portion 40 with the large
grains precedes the first abrasive portion 30 with the small
grains. Therefore, the cylindrical surface Wa of the workpiece W is
efficiently ground because it is roughly ground by the first
abrasive portion 40, and then precisely ground by the first
abrasive portion 30. In the forth example, because the external
radius of the second abrasive portion 40 having the large grains is
as large as the first abrasive portion 30 having the small grains,
the traverse cutting performs rough grinding and finish grinding
continuously and effectively. Although the forth example shows the
right-angled corner of the second abrasive portion 40, the corner
may form appropriate chamfer (R, C or tapered) or the like that
does not reach the first abrasive portion 30.
[0026] As described above, according to the embodiment of the
invention, where the face Wb of the workpiece W is ground, there is
produced the grinding wheel 10 that the grinding burn hardly occurs
and the grinding efficiency easily improves.
[0027] Obviously, numerous modifications and variations of the
present invention are possible in light of the above teachings. It
is thereby to be understood that within the scope of the appended
claims, the present invention may be practiced otherwise than as
specifically described herein.
[0028] For example, the second abrasive portion 40 may be made in
advance and then be adhered on the lateral side of the first
abrasive portion 30. Or, the second abrasive portion 40 may form
the shape of backed taper that becomes thinner in direction of
inward of the grinding wheel 10, so that the coolant easily
penetrates into the grinding area and the chip is easily
discharged.
* * * * *