JPH0822509B2 - Grinding wheel - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial field of application] The present invention relates to a high peripheral speed rotation in which a superabrasive grain layer of diamond, CBN (cubic boron nitride) or the like or a general abrasive grain layer is bonded to a ground surface. A grinding wheel for grinding.

[Prior art]

Conventionally, various grinding wheels for rotary grinding have been proposed and put into practical use. As the above-mentioned grinding wheel, there is one in which a superabrasive grain layer or a general abrasive grain layer is adhered to a base disc made of metal or the like.

As the super-abrasive grain layer, those in which abrasive grains of diamond or CBN are bonded by vitrified bond are used (for example, Japanese Patent Publication No. 58-34431).

Conventionally, steel, cast iron, aluminum alloys, phenolic resins, etc. have been used as the base disk (Japanese Patent Laid-Open No. 61-152374).

Further, the grinding stone using the above-mentioned superabrasive grains has very little abrasion as the abrasive grains themselves are much harder than general abrasive grains. Therefore, there is little dimensional change or variation due to wear, and high-precision grinding is possible. Therefore, it is mainly used for grinding difficult-to-cut materials.

[Problems to be solved]

However, the above conventional grinding wheel for rotary grinding is
Due to the large elongation of the base disk due to the centrifugal force during rotation,
There was a problem that the processing accuracy was lowered. In recent years, the improvement of machining efficiency and the improvement of the life of the grindstone have been strongly demanded, so that the grinding wheel is required to have a higher peripheral speed. Therefore, it is necessary to minimize the elongation of the grinding wheel during rotation.

Moreover, the conventional base disk has a larger coefficient of thermal expansion than the superabrasive layer. Therefore, the base disk expands due to the heat of grinding or the heat of the bearing device, and the entire grinding wheel including the base disk expands thermally. This causes a decrease in the dimensional accuracy of the workpiece.

Further, the conventional base disc, especially made of steel or cast iron, has a large weight (specific gravity). Therefore, when the grinding wheel is rotated by the grinder, the load on the motor and the load on the grindstone shaft are large, and the amount of heat generated by the motor and the bearing is large. Therefore, these heats are also transferred to the base disk, which causes the thermal expansion of the base disk to be further increased as described above.

The above problem also occurs in a grinding wheel using general abrasive grains.

In view of the above-mentioned conventional problems, the present invention is to provide a grinding wheel for rotary grinding, which can perform highly accurate grinding even under a high peripheral speed.

[Means for solving problems]

The present invention relates to a grinding wheel for rotary grinding, in which an abrasive grain layer is adhered to a base disk, wherein the base disk is a plastic made of epoxy resin or polyimide resin, and one of carbon fiber, aramid fiber or It is made of a composite material in which fibers composed of both are dispersed, and the base disk has a coefficient of thermal expansion of 15 × 10
^-6 / ℃ or less, and density (kg / cm ³ ) / modulus of elasticity (kgf / c
The grinding wheel is characterized in that the ratio (N) of m ² ) is 3.5 × 10 ⁻⁹ or less.

In the present invention, the composite material constituting the base disk is a plastic (base material) in which fibers are dispersed.
An epoxy resin or a polyimide resin is used as the plastics. These two kinds of resins can reduce the above-mentioned ratio (N) by dispersing the specific fiber described later, and exert an effect of extremely reducing the elongation of the base disk (the first embodiment). See table).

Further, as the fibers, one or both of carbon fibers and aramid fibers are used. Among these, epoxy resin in which carbon is dispersed is most preferable.

Next, the above fibers are preferably contained in the base disk in an amount of 30 to 70% by volume. If it is less than 30%, the elongation during rotation is large, while if it exceeds 70%, the stability as a product is lacking, which is not preferable. Further, it is preferable to use fibers having a diameter of 1 to 300 μm.

Further, in the present invention, the base disc has a coefficient of thermal expansion of 15 × 10 ⁻⁶ / ° C. or less and a ratio (N) of density (kg / cm ³ ) / longitudinal elastic modulus (kgf / cm ² ). It must be 3.5 × 10 ^-9 or less. If both of these are satisfied, the thermal expansion and elongation of the base disk will be particularly low, and a more excellent grinding wheel can be obtained.

In addition, an adhesive such as an epoxy resin is used to bond the base disk and the abrasive grain layer.

Further, in the present invention, the abrasive grains include superabrasive grains such as diamond and CBN, and general abrasive grains such as alumina and silicon carbide.

Further, the bonding of the abrasive grains in the abrasive grain layer is performed by vitrified bond, resinoid bond or metal bond.

The present invention is particularly effective for a vitrified bond grinding wheel using superabrasive grains.

[Action and effect]

In the grinding wheel of the present invention, a composite material in which the specific fiber is dispersed in the specific plastic is used as the material of the base disk.

In addition, the base disc has a thermal expansion coefficient of 15 compared with a conventional metal base disc made of an aluminum alloy or the like.
× 10 ^-6 / ℃ is low and the ratio (N) is 3.5 ×
It is 10 ^-9 or less.

Therefore, the base disc of the present invention has a low thermal expansion, and particularly the elongation during rotation is about half or less as compared with the conventional product (see Table 1 of Examples).

Further, since the base disc of the present invention is lighter in weight than the conventional base disc, the load on the motor and the grindstone shaft due to the rotation of the grinding wheel is small, and the amount of heat generated by these is small. Therefore, the amount of heat transferred to the base disk is small, the thermal expansion of the grinding wheel is even smaller, and highly accurate grinding can be performed.

Therefore, according to the present invention, it is possible to provide a grinding wheel for rotary grinding which can perform highly accurate grinding even at a high peripheral speed.

〔Example〕

A grinding wheel for rotary grinding using the superabrasive grains according to the present invention was produced, its performance was tested, and the results are shown in Table 1. These will be described in detail below.

First, as the grinding wheel, as shown in FIGS. 1 and 2, a segment tip 1 (FIG. 1) made of a superabrasive grain layer was prepared and bonded to a base disk 2 as shown in FIG. . An epoxy resin adhesive was used as the adhesive. The base disk 2 has a rotary shaft hole 20 at the center.

Then, the above grinding wheels were prepared in three types (No. 1 to 3) by changing the type of the base disk 2. Also, for comparison,
Four types of grinding wheels were manufactured using conventional base disks (No.C
1 to C4).

The segment tip 1 is the same for all the grinding wheels.

That is, the grinding wheel has an outer diameter of 305 mm, a diameter of the hole for the rotating shaft of 76.2 mm, and a thickness of 15 mm. The size of the segment chip is 40mm in length, 15mm in width, and 7mm in thickness.

 The structure of the finished superabrasive layer is as follows.

CBN abrasive grains (# 325/400) ··· 50 parts by volume, vitrified bond ・ ・ ・ · 18 parts by volume, pores ・ ・ ・ ・ ・ ・ 32 parts by volume, and the grinding conditions in the test are: It is as follows.

Grinding wheel peripheral speed: 2700 m / min, table feed speed: 20 m / min, depth of cut: 5 μm / pass, work material: SKH51, work material dimensions:・ ・ ・ Length 300 × width 10 mm, and the materials used for each base disk are those shown in Table 1. Among these materials, aluminum is JIS
-A6061 and JIS-S55C for hard steel.

C represents carbon. The fibrous C has a diameter of 5
The one having a thickness of -20 μm was used. Aramid fiber has a diameter of 5 to 20
The thing with a micrometer was used.

Further, the addition amount (%) of C fiber and the like in the table is the volume ratio in the base disk.

 The results of the above measurements are shown in Table 1.

In the table, the ratio N is a value obtained by dividing the density (kg / cm ³ ) by the longitudinal elastic modulus (kgf / cm ² ).

As is known from Table 1, the base disks of Examples 1 to 3 have considerably lower thermal expansion coefficients than those of Comparative Examples C1 and C2.

Regarding the ratio N, the base disks of Examples 1 to 3 are about half or less of those of Comparative Examples C1 to C4. This ratio N indicates that the lower the value, the smaller the elongation of the base disk. Therefore, regarding elongation, Example 1
The base disks of Nos. 3 to 3 are about half or less of those of Comparative Examples C1 to C4.

Regarding the thermal expansion, the base disk of Comparative Example C3 using Super Invar is lower than those of Examples 2 and 3. However, in Comparative Example C3, since the ratio N is large as described above,
Since the elongation is large, the object of the present invention cannot be achieved like Comparative Examples C1, C2, and C4.

As described above, according to the present invention, it is possible to obtain a grinding wheel for rotary grinding, which uses superabrasive grains having a small thermal expansion and a small elongation even when used at a high peripheral speed.

Further, when comparing the actual grinding performances of the grinding wheels of Example 1 and Comparative Example C1, the surface roughness of the work piece was 0.4 μRa in Example 1 and 1.4 μmRa in Comparative Example C1. It can be seen that the grinding wheel of the invention has excellent processing accuracy.
Here, Ra means the center line average roughness defined by JIS B0601.

Further, since the grinding wheel of Example 1 is lighter than Comparative Example C1, the load on the motor during rotation is small. For example, the motor power in the idle rotation is 0.4 kw for the former and 1.
It is 0kw. The grinding wheel of Comparative Example C3 has a power of 1.3 kW.

Thus, the small motor power means that the motor load and the bearing load for the rotation of the grinding wheel are small. Therefore, when the grinding wheel of the present invention is used, heat generation of the motor and heat generation of the bearing are reduced. As a result, the temperature rise of the base disk is suppressed, the elongation of the base disk due to heat is also suppressed, and more precise grinding can be performed.

In addition, therefore, it is possible to further promote the higher peripheral speed of the grinding wheel for rotary grinding.

[Brief description of drawings]

1 and 2 show a grinding wheel according to an embodiment, FIG. 1 is a perspective view of the superabrasive layer, and FIG. 2 is a plan view of the grinding wheel. 1 …… Segment chip, 2 …… Base disk,

Claims (3)

[Claims] 1. A grinding wheel for rotary grinding, comprising an abrasive grain layer adhered to a base disk, wherein the base disk is made of epoxy resin or polyimide resin in which one of carbon fiber and aramid fiber is formed. Or, a composite material in which fibers composed of both are dispersed is used, and the base disk has a coefficient of thermal expansion of 15 × 10 ^-6 / ° C or less and a density (kg / cm ³ ) / longitudinal elastic modulus (kgf The grinding wheel is characterized in that the ratio (N) of / cm ² ) is 3.5 × 10 ^-9 or less. 2. A grinding wheel according to claim 1, wherein the abrasive grains are superabrasive grains such as diamond and CBN, or general abrasive grains such as alumina and silicon carbide. 3. A grinding wheel according to claim 1, wherein the bonding of the abrasive grains in the abrasive grain layer is a vitrified bond, a resinoid bond or a metal bond.