JPH11188636A - Base disk type grinding wheel - Google Patents

Abstract

PROBLEM TO BE SOLVED: To realize the high peripheral speed grinding at high accuracy by providing a base disk comprising a core and an outer circumferential layer, setting the coefficient of thermal expansion and the specific gravity of the core to be not more than the specified values, and forming the outer circumferential layer of carbon fiber reinforced plastic to reduce the distortion of a grinding wheel caused by the centrifugal force and the temperature change. SOLUTION: An outer circumferential layer 1 is fitted and adhered to a core 2 having a hole 20 for a rotary shaft. The core is <=18×10<-6> / deg.C in coefficient of thermal expansion, and <=4 g/cm<3> in specific gravity, and formed of aluminum-based composite material reinforced by ceramic particles or ceramic fiber, or aluminum alloy containing >=20 wt.% silicon. The material of the outer circumferential layer 1 is carbon fiber reinforced plastic. Even when the base disk is used at high peripheral speed, the deviation of the elongation of the base disk, and the deviation of the radial elongation in the magnet width direction (the direction of the rotary shaft) are small, and the grinding at high accuracy can be realized.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a base disk-type grinding wheel for rotary grinding in which an abrasive layer is bonded to a ground surface, and particularly to a superabrasive layer such as diamond or CBN (cubic boron nitride). The present invention relates to a base disk-type grinding wheel for high peripheral speed rotary grinding.

[0002]

2. Description of the Related Art Conventionally, as a grinding wheel for rotary grinding, a superabrasive layer is generally bonded to a metal base disk, and steel, cast iron, aluminum alloy, etc. are used as the material of the base disk. Used. Grinding stones using superabrasives have less abrasive wear because the abrasives themselves are much harder than general abrasives. Therefore, dimensional changes and variations due to wear are small, and high-precision grinding can be performed.
Therefore, superabrasive grinding wheels are mainly used for grinding difficult-to-cut materials. In addition, the high peripheral speed grinding can increase the efficiency of grinding and extend the life of the grinding wheel. By the way, in performing high peripheral speed grinding exceeding 80 m / s, the mechanical strength of the superabrasive grains themselves is sufficient, but the material of the base disk is required to have characteristics that have not been a problem under the conventional peripheral speed. The Rukoto.

Accordingly, as a base disk material for a grinding wheel for high peripheral speed grinding, Japanese Patent Application Laid-Open Nos.
JP 91541 proposes the use of a fiber reinforced plastic having excellent mechanical and thermal strength and a low specific gravity. Japanese Patent Application Laid-Open No. 3-256677 proposes a composite material in which ceramic fibers or particles are dispersed in a metal matrix. Japanese Patent Application Laid-Open No. 6-91542 discloses that, for the purpose of reducing the material cost of the base disk and improving the accuracy of the mounting surface, fiber-reinforced plastic is used only for the outer peripheral material of the base disk, and the inner peripheral portion (core portion). There has been proposed a technique of using a metal which is inexpensive and has good workability as a raw material of the material. Also,
Japanese Patent Application Laid-Open No. 7-9347 discloses that an outer diameter side member and an inner diameter side member of a base are fitted with an interference that is equal to or larger than the difference between the displacement of the outer diameter side member inner diameter and the inner diameter side member outer diameter during use rotation of the grindstone. Duralumin (coefficient of thermal expansion α = 24 × 10 ⁻⁶ / ° C. at 0 to 100 ° C.) as the inner diameter side member,
A vitrify bond CBN grindstone using a circumferentially wound CFRP having a density of 1.6 g / cm ³ and a circumferential elastic modulus of 19,000 kg / mm ² as an outer diameter side member is disclosed.

[0004]

However, the first problem is to be solved.
JP-A-3-234474 or JP-A-6-91
The base disk made of fiber reinforced plastic proposed in Japanese Patent No. 541 has excellent physical properties, but is expensive in price, and a large and thick base disk may be distorted due to deviation in elongation. Especially outer diameter 500mm
Those having a thickness of 50 mm or more have a problem that production is difficult.

Second, a base disk made of a composite material in which ceramic fibers or particles are dispersed in a metal matrix proposed in Japanese Patent Application Laid-Open No. 3-256677 is as large as a base disk made of fiber-reinforced plastic. In this case, there is a problem in manufacturing stability.

Third, a fiber reinforced plastic is used for the outer periphery of the base disk proposed in Japanese Patent Application Laid-Open No. Hei 6-91542, and a metal (duralumin: thermal expansion) which is inexpensive and has good workability is used for the inner core. According to the base disc-shaped grindstone using a coefficient of about 24 × 10 ⁻⁶ ), it is possible to manufacture even those having an outer diameter of 500 mm or more or a thickness of 50 mm or more by winding the outer periphery of the core material with filament wound carbon fiber reinforced plastic or the like. It becomes possible. However, during high peripheral speed grinding (60 m / s or more), particularly at an ultra-high peripheral speed grinding of 80 m / s or more, the difference in grinding wheel elongation in the radius direction of rotation in the grinding wheel width direction (grinding wheel rotation axis direction) is considered to increase. Therefore, there is a problem that uniform high-precision grinding is difficult. Also,
In order to further increase the peripheral speed of rotary grinding, such a large elongation is a safety problem. Also, Japanese Patent Application Laid-Open No. 7-934
According to the invention according to Japanese Patent Publication No. 7, the outer diameter side member and the inner diameter side member of the base (base disk) are set to have a difference equal to or larger than the difference between the displacement of the outer diameter side member inner diameter and the inner diameter side member outer diameter during use rotation of the grindstone. Although the displacement difference between the inner diameter side and the outer diameter side of the base at the time of high-speed rotation is reduced by fitting and integrating with the interference, the above-mentioned problems have not been completely solved yet. Further, the design of the grindstone becomes complicated, and there is a problem that the degree of freedom in selecting the material on the outer diameter side and the inner diameter side is reduced.

SUMMARY OF THE INVENTION In view of the above circumstances, the present invention has a base disk type which is capable of performing high-precision high peripheral speed grinding, in which the distortion of the grinding stone due to centrifugal force and temperature change, which is remarkable in a wide grinding stone such as a centerless grinding stone, is small. It is intended to provide a grinding wheel.

[0008]

An outline of the present invention will be described. According to the knowledge of the present inventors, superabrasive grindstones originally have a characteristic that they are less likely to be worn than ordinary grindstones, and even if a slight runout or distortion occurs in the grindstone itself, it is transferred to a work material to be processed. There is a possibility that the precision of the grinding operation may be remarkably poor or the rate of failure may be caused. For example, the core material is made of duralumin, and the outer layer is CFR
Even if a P-type double structure base disk is used, the peripheral speed is 60m
In the case of performing high peripheral speed grinding at more than 80 m / s or ultrahigh peripheral speed grinding at more than 80 m / s, the processing accuracy may be reduced due to local deformation (distortion) of the base disk. In particular, with a grindstone having a grindstone width of more than 50 mm, the distortion is increased and the processing accuracy is significantly reduced.

This is because, because of the high peripheral speed, the load on the grinding wheel shaft of the grinding machine increases and the amount of heat generated in the motor and the bearing portion increases, and the heat is transferred to the base disk to increase elongation and distortion. it is conceivable that. Further, such distortion tends to increase particularly in proportion to the width of the grindstone. In addition, as a characteristic thermal distortion generation factor, in large wheels,
It is foreseen that a temperature difference will occur in each part of the grindstone due to the time difference of heat conduction and the distance between the grinding part and the generated heat source such as the diameter of the grindstone hole. This causes a significant problem in workability especially in a wide grinding wheel for centerless grinding or the like.

In addition, when a conventional base disk is used, truing for correcting the shape of a grindstone is not performed near the temperature at the time of operation. Since it is conceivable, the trouble of whetstone management work occurs. In a work environment where there is no air conditioning equipment and the temperature change is large in one day,
Even if it is not super-high peripheral speed grinding in which the peripheral speed exceeds 80 m / s, it is considered that a large temperature change occurs in the grindstone, so that it becomes difficult to control the grinding quality of the work material.

Based on the above findings, the present inventor has searched for a rotary grinding wheel having the following features. (1) Have sufficient safety strength against centrifugal force under high peripheral speed.
(2) Elongation and deformation due to the centrifugal force are uniform in each part of the grindstone and distortion is small. (3) Elongation and distortion due to temperature rise that are likely to occur during high peripheral speed grinding are small and uniform. (4) The specific gravity of the base disk material that greatly contributes to the above characteristics is small.

As a result, the present inventors have developed a grinding wheel for rotary grinding provided with a base disk to which a superabrasive layer is adhered, wherein the base disk is composed of a core material and an outer peripheral layer surrounding the core material, and thermal expansion of the core material is achieved. Coefficient of 18 × 10 ^-6 or less, specific gravity 4g /
cm ³ or less, and preferably a tensile strength of 200 MPa or more, and the outer peripheral layer is made of carbon fiber reinforced plastic (hereinafter referred to as “C
FRP "), it has been found that even when used under a high peripheral speed, it is possible to obtain a grindstone for rotary grinding using superabrasive grains having small thermal expansion and small elongation, and further reached the present invention. Things.

The present invention includes the following elements in a first aspect. That is, the core material of the base disk has a coefficient of thermal expansion of 18
It has characteristics of not more than × 10 ⁻⁶ / ° C. and a specific gravity of not more than 4 g / cm ³ . The material of the outer peripheral layer of the base disk is fiber reinforced plastic.

[0014] The base disk based on the first viewpoint has a small thermal expansion, especially when the temperature of the grinding wheel body rises during high peripheral speed rotation, the expansion is smaller than that of the conventional product, and the deviation in the grinding wheel width direction is reduced. It is possible to significantly reduce it. For this reason, especially in the case of a wide grindstone having a grindstone width of 50 mm or more, in which distortion tends to increase, it is possible to effectively suppress the absolute amount of deviation in the grindstone width direction due to a change in the grindstone rotation speed or temperature during truing or grinding work. it can. Further, a core material based on the first viewpoint is selected to have a higher specific elastic modulus (elastic modulus / specific gravity) than a conventional metal core material made of a normal aluminum alloy or the like, and to elongate the base disk during rotation. Is smaller than conventional products.

In addition, since a material having a specific gravity of 4 g / cm ³ or less is used, elongation and deformation of the base disk due to centrifugal force are reduced, and a load on a motor and a load on a grinding wheel shaft accompanying rotation of a grinding wheel are reduced. And the calorific value of these is small. Therefore, the amount of heat transfer to the base disk is small,
The thermal expansion of the grinding wheel is further reduced, and highly accurate grinding can be performed.

Further, the present invention includes the following elements from a second viewpoint. The core material of the base disk is an aluminum-based composite material reinforced with ceramic particles or ceramic fibers. The third aspect includes the following elements. The material of the core is an aluminum alloy. 4th
Including the following elements from the viewpoint of The material of the core material is an aluminum alloy containing 20% by weight or more of silicon. The fifth aspect includes the following elements. The material of the outer peripheral layer of the base disk is carbon fiber reinforced plastic. Sixth
Including the following elements from the viewpoint of The grindstone width is 50 mm or more. The seventh aspect includes the following elements. At the time of high peripheral speed rotary grinding (especially at a peripheral speed of 80 m / s or more), the difference between the radius of the center portion of the base disk and the radius of the end portion of the disk along the wheel width direction is 10 μm or less.

[0017]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, a preferred embodiment of the present invention will be described. The thermal expansion coefficient α (0 to 100 ° C.) of the core material constituting the inner peripheral layer of the base disk is preferably 18 × 10 ⁻⁶ ° C. or less, more preferably 16 × 10 ⁻⁶ ° C. or less, and 14 × 10 ⁻⁶ ° C.
The following is preferred. The range of α is 12 to 15 × 10 ^-6
C is preferred. At least the coefficient of thermal expansion is 24 × 10 ^-6 ° C
A material having a lower coefficient of thermal expansion than duralumin is used. The specific gravity of the core is preferably 4 g / cm ³ or less, more preferably 3 g / cm ³ or less, and 2 g / cm ³ or less.

An example of a material suitable for the physical properties of the core material is an aluminum-based composite material, which is obtained by dispersing ceramic fibers or particles in an aluminum alloy matrix (base material), and is referred to as FRM, MMC, or the like. Is what it is. As the above ceramics, alumina, silicon carbide, boron, silica, carbon, potassium titanate, barium titanate, or the like can be used. Further, the core material preferably contains the ceramic fibers or particles in an amount of 10 to 70 wt%. If it is 10% or more, the elongation at the time of rotation tends to be small, while if it is 70% or less, the stability as a product tends to be high. The ceramic fibers preferably have a diameter of 1 to 300 μm, and the ceramic particles preferably have a particle diameter of 0.1 to 300 μm.

As a material suitable for the physical properties of the core material, there is an aluminum alloy containing 20% by weight or more of silicon. The alloy preferably contains 20 to 40% by weight of silicon. If the content is 20 wt% or more, the thermal expansion coefficient tends to be small, and if it is 40% or less, the stability (strength and toughness) as a product tends to be high.

As the fiber reinforced plastic layer constituting the outer peripheral layer of the base disk, carbon fiber reinforced plastic (C
FRP) is preferred. CFRP is obtained by dispersing carbon fibers in plastic (base material).
It is preferable to contain 0 to 70 vol%. 30vol
% Or more tends to decrease the elongation during rotation, and 70% or less tends to increase the stability as a product. Further, a filament winding CFRP (hereinafter referred to as “F”) in which carbon fibers are wound in the circumferential direction of the base disk and laminated.
WCFRP "). Preferably, the fibers are wound at an angle of 45 ° or less with respect to the circumferential direction. It is also possible to use another type of CFPR, for example, one obtained by laminating carbon fibers in a grinding wheel thickness direction (grinding wheel rotation axis direction). In addition, the elastic modulus of the rotating grindstone in the radial direction is 15 GPa.
As described above, it is preferable to wind the fiber so that the coefficient of thermal expansion (0 to 100 ° C.) is 50 × 10 ⁻⁶ or less.

For bonding the base disk and the abrasive layer, various adhesives such as epoxy resin can be used. By using superabrasive grains such as diamond and CBN as abrasive grains, the advantages obtained by the present invention can be further utilized, but general abrasive grains such as alumina and silicon carbide may be used. The bonding of the abrasive grains in the abrasive grain layer can be performed by vitrified bond, resinoid bond, metal bond, electrodeposition, or the like. Particularly preferably, the present invention is applied to a super-abrasive high peripheral speed grinding wheel bonded by vitrify bond.

The present invention is suitably applied particularly to a grinding wheel for rotary grinding having a grinding wheel width (thickness, length in the direction of the rotating shaft) of 50 mm or more. Grinding stone width 50mm or more (grinding time is shortened)
When using a grinding wheel for rotary grinding, if the base disk has a high coefficient of thermal expansion and a high specific gravity, the deviation in the width direction of the grinding wheel (the wheel swells like a drum due to centrifugal force) is much smaller than that of a wheel with a small width. In addition, the present invention is suitably applied to a center race grindstone formed in a wide width, but is also applicable to other types of grindstones. In addition, the rotary grinding wheel according to the present invention has a high peripheral speed grinding speed of 60 m / s or more,
/ S or more and 100 m / s or more.

[0023]

[Test Example 1] An embodiment of the present invention will be described below with reference to the drawings. As shown in Table 1, FWCFRP was used as the material of the outer peripheral layer of the base disk, and various materials were used as the core material, and four types of base disks having the structure shown in FIG. 1 (Examples 1, 2 and Comparative Examples 1, 2) were produced. . Note that Comparative Example 2
It is a base disk having a single structure of WCFRP. Table 1 shows the materials of the outer layer used and various core materials, and Table 2 shows the physical properties of these core materials. The method of manufacturing the base disk is as follows. That is, as a base disk, FIG.
An outer peripheral layer 1 made of a carbon fiber reinforced plastic shown in FIG. 2A is manufactured, and the outer peripheral layer 1 is formed as a rotary shaft hole 2 shown in FIG.
The core material 2 having 0 was bonded using an epoxy resin adhesive. In the above base disk, the dimensions of the outer peripheral layer 1 are as follows:
Its outer diameter is 439mm, inner diameter is 250mm and thickness is 21
0 mm. The core 2 has a dimension whose outer diameter is 25.
0 mm, inner diameter is 203.2 mm, and thickness is 210 mm. The outer layer 1 is formed by helically winding carbon fibers in the circumferential direction and impregnating with an epoxy resin.

[0024]

[Table 1]

[0025]

[Table 2]

These four types of base disks are set to 5200 rpm
m (peripheral speed 117 m / s) for 3 minutes and 60 minutes,
The radial elongation of the circumferential surface was measured with a laser displacement meter. The elongation was measured at three positions, that is, the center and both ends of the circumferential surface of the base disk. Further, the temperature of the base disk was measured using a surface thermometer before the rotation test and at the time of the stop after the spin for one hour. Table 3 shows the results of the test rotated for 3 minutes.
Shows the test results after 60 minutes of rotation.

[0027]

[Table 3]

[0028]

[Table 4]

As can be seen from Tables 3 and 4, the base disks of Examples 1 and 2 have considerably smaller elongation after 60 minutes of idling than Comparative Example 1 which is a general double-structured base disk. Also, 6
The difference in displacement (corresponding to the difference in radius) between the central portion and both ends after idling for 0 minutes is 4 to 5 μm in Examples 1 and 2, which is about 1/4 of the maximum of 16 μm in Comparative Example 1, and It can be seen that the difference depending on the position in the width direction is very small. FWCF
In Comparative Example 2 of the RP integrated structure, the total elongation itself after 60 minutes of idling is smaller than in Examples 1 and 2, but the deviation of the elongation due to the position in the grindstone width direction is larger than in Examples 1 and 2 and Comparative Example 1. The maximum is 24 μm.

Accordingly, in the grinding wheel having a structure in which the grindstone pieces are adhered to the outer peripheral surface of the base disks of Comparative Examples 1 and 2 with an adhesive, the elongation deviation due to the position of the base disk along the width direction of the grindstone is large. For this reason, the processing accuracy of the work material is adversely affected, and it is necessary to wait for the grinding operation until the grindstone reaches a constant temperature state in order to cope with the adverse effect, and a reduction in the processing efficiency is inevitable. Further, since the truing for shape correction also needs to be performed in the vicinity of the temperature at the time of work, the work of managing the grindstone occurs. Further, in a work environment in which there is no air conditioner or the like and a large change in room temperature per day, it becomes more difficult to control the grinding quality of the work material.

Further, in Comparative Example 1, since the absolute amount of elongation due to centrifugal force and heat generated during use is large, the tensile stress generated at the joint of the grindstones becomes large, and the grindstone is liable to be damaged, which is disadvantageous in terms of safety. Becomes

This is because the temperature of the base disk increases due to the frictional heat between the base disk and air due to the long-time rotation and the frictional heat between the rotating shaft of the base disk and the bearing of the grinding machine.
It is considered that the base disk has a low elastic modulus in the radial direction and a high coefficient of thermal expansion, so that the distortion of the base disk was increased. Therefore, it is presumed that the same phenomenon as the result of this test occurs even during actual grinding.

Test Example 2 Further, except for the width of the grindstone, as in Comparative Example 1 (the core was made of A2014 aluminum alloy),
Five types of base disks having different grinding wheel widths shown in Table 5 or Table 6 were produced. Using these five types of base disks, base disk distortions after 3 minutes of idling and after 60 minutes of idling were examined in the same manner as in Test Example 1. Tables 5 and 6 show the results of these measurements.

[0034]

[Table 5]

[0035]

[Table 6]

According to Tables 5 and 6, the deviation is as small as 3 to 4 μm when the grinding wheel width is 30 mm, but 10 to 11 μm when the grinding wheel width is 50 mm.
m, which is a level at which a problem starts to occur in the precision of the processed product in the actual grinding operation. FIG. 3 also shows the results of Test Example 1 and Test Example 2. From FIG. 3, it can be seen that the strain deviation increases as the thickness increases between 30 to 70 mm in the grinding wheel width (thickness), and reaches a level at which the strain deviation has a substantial effect on the precision of the workpiece at 50 mm or more. I understand.

[0037]

According to the present invention, even when used under a high peripheral speed, the deviation of the elongation of the base disk and the elongation in the radial direction of rotation along the grinding wheel width direction (the direction of the grinding wheel rotation axis) is small.
Provided is a grinding wheel for rotary grinding capable of high-precision grinding. Therefore, the present invention is suitably applied to a grindstone having a large grindstone width, particularly a grindstone having a grindstone width of 50 mm or more, and the grinding time can be reduced. Further, since the base disk according to the present invention has a small coefficient of thermal expansion, distortion of the base disk due to a temperature difference is small. Therefore, since it is not necessary to wait for the grindstone operation until the grindstone reaches a constant temperature state, the machining efficiency is improved, and the machining accuracy of the work material is always kept good.
In a work environment in which the temperature changes daily are large, the shape of the grindstone changes greatly. However, by using the grindstone according to the present invention, a stable grinding operation can be performed even in such a situation. Further, the truing operation can stably produce a predetermined shape accuracy irrespective of the temperature of the grindstone at any time. Further, according to the present invention, even if the core material of the base disk is a relatively brittle material, since the external impact is not directly transmitted to the core material portion because it is surrounded by the CFRP forming the outer peripheral layer, Work safety is improved.

[Brief description of the drawings]

FIG. 1 is a view for explaining the structure of a base disk-type grinding wheel according to one embodiment of the present invention.

2 (a) and 2 (b) are exploded views of the grindstone shown in FIG. 1, and show (a) an outer peripheral layer of a base disk, and (b) a core material portion of the base disk.

FIG. 3 is a diagram for explaining a relationship between a grindstone width (thickness) and a distortion deviation.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Outer layer 2 Core material 20 Hole for rotary shaft

 ──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Takeshi Nonokawa 3-36, Noritake Shinmachi, Nishi-ku, Nagoya City, Aichi Prefecture Inside Noritake Company Limited (72) Inventor Yoshiharu Terada 3-chome Noritake Shinmachi, Nishi-ku, Nagoya City, Aichi Prefecture No. 1-36 Noritake Company Limited

Claims (7)

[Claims] 1. A base disk-type grinding wheel having an abrasive layer adhered to a base disk, said base disk having a core material and an outer peripheral layer surrounding said core material, said core material having a thermal expansion coefficient of 18 × 10. ^-6 / ° C. or lower and specific gravity of 4 g / cm ³ or lower, wherein the material of the outer peripheral layer is a fiber-reinforced plastic, wherein the base disk-type grinding wheel is characterized by the following characteristics. 2. The base disk-type grinding wheel according to claim 1, wherein the core material is an aluminum-based composite material reinforced by ceramic particles or ceramic fibers. 3. The grinding wheel according to claim 1, wherein the core material is an aluminum alloy. 4. A base disk-type grinding wheel according to claim 3, wherein said core material is an aluminum alloy containing 20 wt% or more of silicon. 5. The base disk-type grinding wheel according to claim 1, wherein a material of said outer peripheral layer is carbon fiber reinforced plastic. 6. A grindstone having a width of 50 mm along a grindstone rotation axis direction.
The base disk-shaped grinding wheel according to any one of claims 1 to 5, characterized in that: 7. A rotary grinding machine having a peripheral speed of 80 m / s or more, wherein a difference between a radius of a center portion of the base disk along a grinding wheel rotation axis direction and a radius of an end portion of the disk is 10 μm or less. A grinding wheel according to claim 6.