The present application claims priority under 35 U.S.C. §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.
1. Field of the Invention
This invention relates to a grinding wheel.
2. Discussion of the background
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
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.
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.
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:
An embodiment of the present invention will be described with reference to figures. As shown in
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.
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.
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.
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.
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
Although the second abrasive portion 40 is flatly studded with single layer of the large grains 41 in
There may form some appropriate shapes at the external corner of the grinding stone 20.
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.
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.
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.
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.
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.
Number | Date | Country | Kind |
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2004-271163 | Sep 2004 | JP | national |