JP7561785B2 - Gear grinding wheels - Google Patents

Description

The present invention relates to a gear grinding wheel.

Various grinding wheels (hereafter referred to as gear grinding wheels) used to grind gear materials to manufacture gears have been proposed (for example, Patent Documents 1 and 2). Gear grinding wheels are capable of rotational motion and have a grinding surface that meshes with the tooth surface of a gear, and the gear material is ground by rotating the gear grinding wheel. Recently, in order to improve the grinding efficiency of gear materials, there has been a trend toward increasing the rotation speed of gear grinding wheels during grinding, and there is a demand for gear grinding wheels that can grind gear materials at high speeds. In other words, there is a demand for gear grinding wheels that have durability that can withstand high-speed grinding. In addition to being capable of high-speed grinding, such gear grinding wheels are required to have good grinding precision.

However, the gear grinding wheels proposed to date have room for improvement in terms of grinding efficiency and grinding precision. In addition, it is generally considered preferable to use fine grains as the abrasives that make up the gear grinding wheel in order to improve grinding efficiency, and to increase its strength. However, when fine grains are used as the abrasives that make up the gear grinding wheel, problems such as dulling of the wheel during grinding of gear material with the wheel and reduced grinding precision are likely to occur. In other words, there is a trade-off between improving grinding efficiency and improving grinding precision, and it has not yet been possible to fully satisfy both.

JP 2015-16522 A JP 2021-30419 A

The main objective of the present invention is to provide a gear grinding wheel that has good grinding efficiency and precision for grinding gear materials.

A gear grinding wheel according to one embodiment of the present invention is comprised of a cylindrical reinforcing portion and a usage portion located on the outer peripheral surface side of the reinforcing portion and fixed to the reinforcing portion, the usage portion having a grinding surface for grinding gears, the usage portion and the reinforcing portion both being vitrified grinding wheels containing abrasive grains and a vitrified binder and having pores therein, the average grain size of the abrasive grains contained in the usage portion being 30 μm or more and 200 μm or less, the average grain size of the abrasive grains contained in the reinforcing portion being 16 μm or more and 56 μm or less, and the volume fraction of the abrasive grains in the usage portion being (i) 40% or more and less than 47% or (ii) 47% or more and 50% or less, in which case (i) the volume fraction of the vitrified binder is 10% or more and 16% or less, and the volume fraction of the pores is greater than 37%, and in the case of (ii) the volume fraction of the vitrified binder is 9% or more and 16% or less, and the volume fraction of the pores is 34% or more, the volume fraction of the abrasive grains in the reinforcing portion is 46% or more and 50% or less, the volume fraction of the vitrified binder is 10% or more and 15% or less, and the volume fraction of the pores is 35% or more, and at least a portion of the pores in the reinforcing portion are impregnated with a thermosetting resin.

In the above gear grinding wheel, the abrasive grains in the use portion and the reinforcing portion may both be alumina-based abrasive grains.
In the above gear grinding wheel, the surface on the outer circumferential surface side of the reinforcing portion may be prevented from being exposed.
In the above gear grinding wheel, the use portion and the reinforcing portion may be directly fixed to each other by integral molding.

The gear grinding wheel of the present invention can improve both the grinding efficiency and grinding accuracy of gear materials, which are in a trade-off relationship.

FIG. 1 is a perspective view of a gear grinding wheel according to an embodiment of the present invention. 1 is a cross-sectional view of a gear grinding wheel according to an embodiment of the present invention.

The following describes the embodiments of the present invention with reference to the drawings. Note that the present invention can be implemented in many different ways, and should not be interpreted as being limited to the description of the embodiments exemplified below. In addition, the drawings may show the width, thickness, shape, etc. of each part in a schematic manner compared to the actual embodiment in order to make the explanation clearer, but these are merely examples and do not limit the interpretation of the present invention. In addition, in this specification and each figure, elements similar to those described above with respect to the previous figures are given the same reference numerals, and detailed explanations may be omitted as appropriate. In addition, for convenience of explanation, the terms "upper" and "lower" are used in the explanation, but the up-down direction may be reversed. The same applies to the left-right direction.

＜＜Gear grinding wheels＞＞
A gear grinding wheel according to one embodiment of the present invention (hereinafter referred to as a gear grinding wheel according to one embodiment) is composed of a cylindrical reinforcing portion 2 and a use portion 1 located on the outer circumferential surface side of the reinforcing portion 2. The use portion 1 has a grinding surface capable of grinding a gear material. The cylindrical reinforcing portion 2 is synonymous with a disk-shaped reinforcing portion, a doughnut-shaped reinforcing portion, and a reinforcing portion having a hole portion 3. FIG. 1 is a perspective view showing an example of a gear grinding wheel according to one embodiment. FIG. 2 is a cross-sectional view of the gear grinding wheel according to one embodiment. In FIG. 1, the shape of the grinding surface, which is the outer circumferential surface of the use portion, is omitted.

The gear grinding wheel 10 of one embodiment is used when the gear grinding wheel 10 is rotated sequentially to form teeth on the gear material to be ground, that is, on the grinding surface of the use part. There is no limitation on the grinding method using the gear grinding wheel 10 of one embodiment, and any method and device conventionally known in this field can be appropriately selected and used. The reinforcing part 2 and the use part 1 that constitute the gear grinding wheel 10 of one embodiment are described below.

<Usage area>
The use part 1 is located on the outer peripheral surface side of the reinforcing part 2, and contains abrasive grains and a vitrified binder. The use part 1 has pores therein. The use part 1 is cylindrical with an inner diameter that is the same as or larger than the outer diameter of the cylindrical reinforcing part 2, and the outer peripheral surface of the reinforcing part 2 and the inner peripheral surface of the use part 1 are directly fixed to each other, or indirectly fixed to each other via a joining member such as an adhesive.

The outer peripheral surface of the use portion 1 is a grinding surface capable of grinding the gear material to be ground. There is no limitation on the shape of the grinding surface, and it may be set appropriately depending on the shape of the gear to be manufactured. An example of the grinding surface is a screw shape. An example of the grinding surface has a spiral groove. An example of the grinding surface has a spiral convex portion (see FIG. 2). There is no limitation on the height, inner diameter, and outer diameter of the use portion 1, and it may be set appropriately depending on the shape of the reinforcing portion 2 and the desired shape of the entire gear grinding wheel 10 of one embodiment.

The usage unit 1 satisfies the following (Condition 1) and (Condition 2).
(Condition 1): Abrasive grains A having an average grain size of 30 μm or more and 200 μm or less are included. Hereinafter, when referring to abrasive grains A, this means abrasive grains having an average grain size of 30 μm or more and 200 μm or less.
(Condition 2): When the volume of the usage part 1 is taken as 100%, the volume fraction of abrasive grains A is (i) 40% or more and less than 47%, or (ii) 47% or more and 50% or less. When the volume fraction of abrasive grains A is (i), the volume fraction of the vitrified bond is 10% or more and 16% or less, and the volume fraction of pores is greater than 37%. When the volume fraction of abrasive grains A is (ii), the volume fraction of the vitrified bond is 9% or more and 16% or less, and the volume fraction of pores is 34% or more.

The average particle size of the abrasive grains in this specification refers to the average particle size in accordance with JIS R6001-1:2017 (Table 3 - Standard particle size distribution of coarse grains, third stage test sieve: particle size at nominal opening and minimum mass fraction that must remain on the sieve) and the average particle size in accordance with JIS R6001-2:2017 (Table 4 - Particle size at ds50 in standard particle size distribution of fine powder for precision polishing (sedimentation tube test method)).

The volume ratio of the abrasive grains A and the vitrified binder in the use part 1 in the present specification can be calculated by the following method. The following calculation example is a calculation example in the case where the use part 1 is formed only with the abrasive grains A and the vitrified binder. First, the volumes of the use part 1, the abrasive grains A, and the vitrified binder are calculated. The volumes of the abrasive grains A and the vitrified binder can be calculated from the amount (mixture amount) of the abrasive grains A and the vitrified binder used to form the use part 1, and the density of the abrasive grains and the vitrified binder used. The calculated volumes of the abrasive grains and the vitrified binder are divided by the volume of the use part 1 to calculate the volume ratio (%) of the abrasive grains and the vitrified binder. The volume ratio (%) of the pores is the volume ratio of the use part 1, 100 (%) minus the volume ratio (%) of the abrasive grains A and the volume ratio (%) of the vitrified binder. In addition, when the use part 1 contains any component within the range satisfying (Condition 2), the volume fraction (%) of the any component is calculated, and then this volume fraction (%) is further subtracted to calculate the volume fraction (%) of the pores.
In other words, the volume fraction (%) of the pores is a volume fraction calculated by subtracting the volume fraction (%) of all components used to form the use portion 1 from the volume fraction (100%) of the use portion 1.
The volume fractions of the abrasive grains B, the vitrified binder, and the pores in the reinforcing portion 2 can also be calculated in the same manner.

The gear grinding wheel 10 of one embodiment, which includes a use portion 1 that satisfies (Condition 1) and (Condition 2), can achieve both improved grinding efficiency and improved grinding precision, which are in a trade-off relationship. The gear grinding wheel 10 of one embodiment can be used safely at operating speeds of 90 m/s or more without wheel breakage. In other words, it has good grinding efficiency. Furthermore, the gear grinding wheel 10 of one embodiment can achieve a rotational breakage peripheral speed of 180 m/s or more. Furthermore, the gear grinding wheel 10 of one embodiment can suppress the occurrence of damage to the wheel, even when the operating speed is increased, and can achieve good grinding precision.

The above-mentioned effect of the gear grinding wheel 10 of one embodiment is not the effect of (Condition 1) or (Condition 2) alone, but a synergistic effect of (Condition 1), (Condition 2), and the conditions of the reinforcing portion 2 described below (Conditions 3 to 5).

If the volume ratio of abrasive grain A is less than the lower limit of (Condition 2), the strength of the gear grinding wheel cannot be sufficient, and the grinding efficiency cannot be sufficient, even if all other conditions are met. On the other hand, if the volume ratio of abrasive grain A exceeds the upper limit of (Condition 2), even if all other conditions are met, the wheel will be damaged during gear grinding, and the grinding accuracy will not be sufficient. Also, if the volume ratio of abrasive grain A exceeds the upper limit of (Condition 2), the volume ratio of pores will not be sufficient, and the gear material will be prone to burning during gear grinding, even if all other conditions are met. In addition, it will be difficult to manufacture a normal grinding wheel. This problem during manufacturing can occur significantly when the use part 1 and the reinforcing part 2 are molded as one piece.

In addition, when the volume ratio of the vitrified bond is less than the lower limit of (Condition 2), even if all other conditions are satisfied, the wheel strength of the gear grinding wheel cannot be made sufficient, and the grinding efficiency cannot be made sufficient. On the other hand, when the volume ratio of the vitrified bond exceeds the upper limit of (Condition 2), even if all other conditions are satisfied, the wheel will be dulled during gear grinding, and the grinding accuracy will not be sufficient. In addition, when the volume ratio of the vitrified bond exceeds the upper limit of (Condition 2), even if all other conditions are satisfied, the volume ratio of pores will not be sufficient, and the gear material will be easily burned during gear grinding. In addition, it is difficult to manufacture a normal gear grinding wheel. This problem during manufacturing can occur significantly when the use part 1 and the reinforcing part 2 are molded integrally.
In a preferred embodiment of the use part 1, in the case of (i) of (Condition 2), the volume fraction of the vitrified binder is 11% or more and 16% or less.

Furthermore, if the abrasive grains A satisfying the volume ratio of (Condition 2) are replaced with abrasive grains exceeding the upper limit of the average grain size of (Condition 1), the wheel strength of the gear grinding wheel cannot be made sufficient, and the grinding efficiency cannot be made sufficient, even if all other conditions are satisfied. On the other hand, if the abrasive grains A satisfying the volume ratio of (Condition 2) are replaced with abrasive grains having an average grain size less than the lower limit of (Condition 1), the gear grinding wheel will suffer from dulling during gear grinding, and the grinding accuracy will be insufficient, even if all other conditions are satisfied.
In a preferred embodiment of the use portion 1, the abrasive grains A that satisfy the volume ratio of (Condition 2) are abrasive grains having an average grain size of 50 μm or more and 185 μm or less.

<Reinforcement section>
The reinforcing portion 2 satisfies the following (Condition 3) to (Condition 5). Note that there is no limitation on the height, inner diameter, and outer diameter of the reinforcing portion 2.
(Condition 3): Abrasive grains B having an average grain size of 16 μm or more and 56 μm or less are included. Hereinafter, when referring to abrasive grains B, this means abrasive grains having an average grain size of 16 μm or more and 56 μm or less.
(Condition 4): When the volume of the reinforcing portion 2 is 100%, the volume fraction of the abrasive grains B is 46% or more and 50% or less, the volume fraction of the vitrified binder is 10% or more and 15% or less, and the volume fraction of the pores is 35% or more.
(Condition 5): At least a portion of the pores is impregnated with a thermosetting resin.
The volume ratio of the pores in (Condition 4) means the volume ratio before the thermosetting resin is impregnated.

The gear grinding wheel 10 of one embodiment has a use portion 1 that satisfies (Condition 1) and (Condition 2) and a reinforcing portion 2 that satisfies (Conditions 3) to (Condition 5), and is therefore able to achieve both improved grinding efficiency and improved grinding accuracy, which are in a trade-off relationship.

If the volume ratio of abrasive grains B is less than the lower limit of (Condition 4), the gear grinding wheel will not have sufficient wheel strength and will not have sufficient grinding efficiency, even if all other conditions are met. On the other hand, if the volume ratio of abrasive grains B exceeds the upper limit of (Condition 4), it will be difficult to manufacture a normal gear grinding wheel, even if all other conditions are met. This problem during manufacturing can occur more prominently when the use portion 1 and the reinforcing portion 2 are molded as a single unit.

Furthermore, if the volume fraction of the vitrified bond is less than the lower limit of (Condition 4), the gear grinding wheel will not have sufficient wheel strength and will not have sufficient grinding efficiency, even if all other conditions are met. On the other hand, if the volume fraction of the vitrified bond exceeds the upper limit of (Condition 4), it will be difficult to manufacture a normal gear grinding wheel, even if all other conditions are met. This problem during manufacturing can occur more prominently when the use portion 1 and the reinforcing portion 2 are molded as a single unit.

Furthermore, if the abrasive grains B in (Condition 4) are replaced with abrasive grains exceeding the upper limit of the average grain size in (Condition 3), the gear grinding wheel will not have sufficient strength and will not have sufficient grinding efficiency, even if all other conditions are met. On the other hand, if the abrasive grains B in (Condition 4) are replaced with abrasive grains below the lower limit of the average grain size in (Condition 3), it will be difficult to manufacture a normal gear grinding wheel, even if all other conditions are met. This problem during manufacturing can be particularly noticeable when the use portion 1 and the reinforcing portion 2 are molded as a single unit.

Furthermore, if condition 5 is not met, even if all other conditions are met, the gear grinding wheel will not have sufficient wheel strength and the grinding efficiency will not be sufficient.

The amount of thermosetting resin impregnated into the pores can be adjusted by taking into account the volumetric ratio of the pores. There is no limit to the amount of thermosetting resin impregnated, and regardless of the amount, the strength of the reinforcing part 2 can be made higher than that of a part not impregnated with thermosetting resin.

In a preferred embodiment of the reinforcing portion 2, at least some of the pores located in the vicinity of the surface on the hole 3 side are impregnated with a thermosetting resin so as to fill at least a part of the pores.
In a preferred embodiment of the reinforcing portion 2, at least some of the pores located near the surface on the hole 3 side are impregnated with a thermosetting resin so as to fill 50% or more of the internal volume of the pores.
In a preferred embodiment, the reinforcing part 2 is impregnated with a thermosetting resin so as to fill 50% or more of the internal volume, 75% or more of the internal volume, or 90% or more of the internal volume, when the total internal volume of all pores located near the surface on the hole 3 side is taken as 100%.
In a more preferred embodiment of the reinforcing portion 2, all of the pores located in the vicinity of the surface on the hole 3 side are impregnated with a thermosetting resin so as to completely fill the pores.
The vicinity of the surface on the hole 3 side means a portion that is 10% or less away from the inner peripheral surface when the radial distance from the inner peripheral surface to the outer peripheral surface of the reinforcing portion 2 is taken as 100.
The reinforcing portion 2 of this configuration can increase the strength of the reinforcing portion 2 and improve the efficiency of the grinding process.

(Thermosetting resin)
There is no limitation on the thermosetting resin impregnated in the pores of the reinforcing portion 2, and any conventionally known thermosetting resin may be appropriately selected and used. Examples of the thermosetting resin include phenolic resin, epoxy resin, melamine resin, urea resin, unsaturated polyester, alkyd resin, polyurethane, and polyimide.

There is no limitation on the method of impregnating the thermosetting resin into the pores. For example, the thermosetting resin can be impregnated into the pores by preparing a coating liquid in which the thermosetting resin is dissolved or dispersed in an appropriate solvent, applying this to the reinforcing part 2, and heating (including drying). Heating may be performed at a temperature at which the thermosetting resin can be hardened. Instead of applying the coating liquid, a part or the whole of the reinforcing part 2 may be immersed in the coating liquid. After the reinforcing part 2 and the use part 1 are integrated, the coating liquid of the thermosetting resin may be applied to the inner surface side of the reinforcing part 2. In this form, the thermosetting resin can be impregnated into the pores present near the surface of the hole part 3 of the reinforcing part 2.

Next, the abrasive grains and the vitrified binder contained in the use portion 1 and the reinforcing portion 2 will be described with an example.
The abrasive grains and the vitrified binder contained in the use part 1 and the reinforcing part 2 may be the same or different. When the gear grinding wheel 10 of one embodiment is integrally molded, it is preferable that the abrasive grains and the vitrified binder contained in the use part 1 and the reinforcing part 2 are the same.
Furthermore, as long as the above conditions are met, the abrasive grains contained in the use portion 1 and the reinforcing portion 2 may each be of one type or more than one type. The same applies to the vitrified binder. For example, the abrasive grains A that satisfy (Condition 1) and the abrasive grains B that satisfy (Condition 3) may each be of one type or more than one type. Furthermore, as long as the above conditions are met, the use portion 1 may contain abrasive grains that do not satisfy (Condition 1). Similarly, the reinforcing portion 2 may contain abrasive grains that do not satisfy (Condition 3).

(Abrasive grain)
The abrasive grains can be appropriately selected from those conventionally known in the field of vitrified grinding wheels. Examples of the abrasive grains include alumina-based abrasive grains, silicon carbide-based abrasive grains, CBN (cubic boron nitride) abrasive grains, and diamond abrasive grains. When the gear, which is the workpiece, is made of metal, alumina-based abrasive grains and CBN abrasive grains can be suitably used as the abrasive grains of the use part 1. In particular, the alumina-based abrasive grains can be used to manufacture the gear grinding grinding wheel 10 of one embodiment at low cost. In particular, since the reinforcing part 2 is not used for grinding, it is preferable to use inexpensive alumina-based particles.
In a preferred embodiment of the use portion 1 and the reinforcing portion 2, the abrasive grains A and B are both alumina-based particles.

Examples of alumina-based abrasive grains include white alumina abrasive grains, pink alumina abrasive grains, brown alumina abrasive grains, single crystal alumina abrasive grains, and microcrystalline sintered alumina abrasive grains.

(Vitrified binder)
As the vitrified binder, any of those conventionally known in the field of vitrified grinding wheels can be appropriately selected and used.

<<Method of manufacturing a gear grinding wheel>>
Next, a method for manufacturing the gear grinding wheel 10 according to one embodiment (hereinafter, referred to as the manufacturing method according to the embodiment) will be described. Note that the gear grinding wheel 10 according to the embodiment is not limited to one manufactured by the manufacturing method described below. Note that the manufacturing method according to the embodiment is a manufacturing method in which the use portion 1 and the reinforcing portion 2 are integrally molded using a mold.

First, abrasive grains and a vitrified binder that can satisfy the conditions described in one embodiment of the gear grinding wheel 10 are selected, and the amounts of these to be mixed are determined, and these are mixed to prepare a mixture for the use part and a mixture for the reinforcing part. In other words, a mixture for the use part containing abrasive grains A and a vitrified binder, and a mixture for the reinforcing part containing abrasive grains B and a vitrified binder are prepared. The mixture for the use part and the mixture for the reinforcing part may contain raw materials other than the abrasive grains and the vitrified binder.

In a preferred manufacturing method, the abrasive grains and vitrified binder contained in the mixture for the used portion and the mixture for the reinforcing portion are made of the same type of material. Here, the term "same type of material" refers to materials that have a common basic composition. By using the same type of material, it is easy to set the firing conditions, etc.

The prepared mixture for the use part and the mixture for the reinforcement part are filled into a molding die having an area for the use part and an area for the reinforcement part. The area for the use part and the area for the reinforcement part that constitute the molding die each have a space that can be pressurized to form the desired shapes of the use part 1 and the reinforcement part 2. As an example, the area for the use part and the area for the reinforcement part are separated by a removable partition plate. At this time, it is preferable to fill so that there is no difference in the filling height of the mixture for the use part in the area for the use part and the mixture for the reinforcement part in the area for the reinforcement part.

The gear grinding wheel 10 of one embodiment satisfies (Condition 1) to (Condition 5), and therefore can be easily adjusted so that there is no difference in the filling height of the region for the used part and the region for the reinforcement part. This makes the molding process easier.

After filling the mixture for the use part and the mixture for the reinforcing part, an upper iron plate is placed in the molding die and pressurized to the specified dimensions. At this time, it is preferable to reduce the difference in pressure between the use part area and the reinforcing part area. By applying pressure in this way, it is possible to prevent the material with high molding pressure from pushing through the material with low molding pressure, and to prevent cracks from occurring in the manufactured gear grinding wheel 10.

Once pressure is applied, the formed whetstone is removed from the mold, dried, and then fired.

After firing, the reinforcing portion 2 is impregnated with a thermosetting resin to produce the gear grinding wheel 10.

Although the above description has been given with an example in which the use part 1 and the reinforcement part 2 are integrally molded, the use part 1 and the reinforcement part 2 may be molded separately and then bonded together. In this case, the thermosetting resin may be impregnated before or after bonding. A conventionally known adhesive or the like may be used to bond the use part 1 and the reinforcement part 2. The thermosetting resin impregnated into the reinforcement part 2 may be used as an adhesive. When bonding the use part 1 and the reinforcement part 2 together, the outer peripheral surface of the reinforcement part 2 and the inner peripheral surface of the use part 1 may be surface-treated. An example of the surface treatment is sandblasting.

The present invention will now be described with reference to examples and comparative examples, which are intended to illustrate the feasibility and usefulness of the present invention and are not intended to limit the configuration of the present invention in any way.

(Preparation of abrasive grains)
The following abrasive grains 1 to 9 were prepared. All the abrasive grains used were white alumina abrasive grains.
Abrasive grain 1: #280 (average grain size: 52±3 μm)
Abrasive grain 2: #320 (average grain size: 46±2.5 μm)
Abrasive grain 3: #240 (average grain size: 60±4 μm)
Abrasive grain 4: A mixture of abrasive grain 1 and abrasive grain 2 (mixture ratio 1:1)
Abrasive grain 5: F120 (average grain size: 106 μm)
Abrasive grain 6: F150 (average grain size: 75 μm)
Abrasive grain 7: #400 (average grain size: 34±2 μm)
Abrasive grain 8: A mixture of abrasive grain 5 and abrasive grain 6 (mixture ratio 1:1)
Abrasive grain 9: #800 (average grain size: 18±1 μm)
Abrasive grain 10: F60 (average grain size: 220 μm)
Abrasive grain 11: #1200 (average grain size: 13±1 μm)

(Test wheel 1)
A test grinding wheel 1 having an inner diameter (H): 160 mm, an outer diameter (D): 275 mm, and a thickness (T): 160 mm was prepared. The test grinding wheel 1 was used for measuring the rotational fracture peripheral speed, and the grinding surface processing of the outer peripheral surface was not performed. The test grinding wheel 1 includes abrasive grains 4 and a vitrified bond, and has an abrasive grain volume fraction (Vg): 48%, a vitrified bond volume fraction (Vb): 10.6%, and a pore volume fraction (Vp) of 41.4%. The volume fractions shown in Tables 1 and 2 are calculated values. The pores of the test grinding wheel 1 are impregnated with epoxy resin. The rotational fracture peripheral speed of the test grinding wheel 1 was 190 to 191 (m/s). The test grinding wheel 1 is a grinding wheel that satisfies (Condition 3) to (Condition 5).

(Test wheels 2 to 4)
Test wheels 2 to 4 were prepared by changing abrasive grain 4 to the abrasive grains shown in Table 1 below. The abrasive grain volume fraction (Vg), vitrified bond volume fraction (Vb), pore volume fraction (Vp), and rotational fracture peripheral speed of each test wheel are also shown in Table 1. Test wheel 2 does not satisfy (Condition 3), test wheel 3 does not satisfy the vitrified bond volume fraction of (Condition 4), and test wheel 4 does not satisfy the abrasive grain volume fraction of (Condition 4).

(Test wheel 5)
Test wheel 5 was prepared in the same manner as test wheel 1, except that it was not impregnated with epoxy resin. Test wheel 5 is a wheel that does not satisfy (Condition 5).

As shown in Table 1, only test wheel 1, which satisfies (Conditions 3) to (Conditions 5), has a rotational fracture peripheral speed of 180 (m/s) or more.

Example 1
A gear grinding wheel of Example 1 was produced using a mold in which a use portion 1 and a reinforcing portion 1 were integrally molded. The dimensions of the reinforcing portion 1 were inner diameter (H): 160 mm, outer diameter (D): 190 mm, and thickness (T): 160 mm, and the dimensions of the gear grinding wheel were inner diameter (H): 160 mm, outer diameter (D): 275 mm, and thickness (T): 160 mm. The dimensions of the reinforcing portion 2 were also similar.
The reinforcing part 1 is the same as the test grinding wheel 1 (only the dimensions are changed).
The use portion 1 contains abrasive grains 5 and a vitrified binder, and has an abrasive grain volume fraction (Vg): 46%, a vitrified binder volume fraction (Vb): 11%, and a pore volume fraction (Vp) of 43%.
The rotational fracture peripheral speed of the gear grinding wheel of Example 1 was 180 to 181 (m/s).

(Examples 2 to 6, Comparative Examples 1 to 8)
The gear grinding wheels of Examples 2 to 6 and Comparative Examples 1 to 8 were produced in the same manner as in Example 1, except that the abrasive grains 5, abrasive grain volume fraction (Vg), vitrified bond volume fraction (Vb), and pore volume fraction (Vp) in the use portion 1 were changed to the abrasive grains, abrasive grain volume fraction (Vg), vitrified bond volume fraction (Vb), and pore volume fraction (Vp) shown in Table 2 below and the use portion was molded.
The use parts of Examples 1 to 6 are use parts that satisfy (Condition 1) and (Condition 2).
The use portions of Comparative Examples 1, 3, 4, and 6 do not satisfy the volume ratio of the vitrified binder of (Condition 2).
The use portions of Comparative Examples 2 and 7 do not satisfy the volume ratio of abrasive grains (Condition 2).
The use portions of Comparative Examples 5 and 8 do not satisfy the average grain size of the abrasive grains (Condition 1).
The reinforcing portions of Examples 1 to 6 and Comparative Examples 1 to 8 satisfy (Condition 3) to (Condition 5).
In Comparative Examples 6 to 8, the difference in filling height was large when the use part and the reinforcing part were integrally molded, and a normal gear grinding wheel could not be produced. Even when the abrasive grain 4 in the reinforcing part 1 was changed to the abrasive grain 9, a normal gear grinding wheel could not be produced.

(Comparative Example 9)
A gear grinding wheel of Comparative Example 9 was produced in the same manner as in Example 1, except that reinforcing portion 1 was changed to reinforcing portion 2. Reinforcing portion 2 is the same as in Test Wheel 5 (only the dimensions were changed). The reinforcing portion of Comparative Example 9 is a reinforcing portion that does not satisfy (Condition 5). The used portion of Comparative Example 5 is a used portion that satisfies (Condition 1) and (Condition 2).

(Comparative Examples 10 and 11)
Gear grinding wheels of Comparative Examples 10 and 11 were produced in the same manner as Example 1, except that the abrasive grain volume fraction (Vg), vitrified bond volume fraction (Vb), and pore volume fraction (Vp) in reinforcing portion 1 (test wheel 1) were changed as follows. The reinforcing portions of Comparative Examples 10 and 11 do not satisfy (Condition 4). In Comparative Examples 10 and 11, the difference in filling height became large when the usable portion and the reinforcing portion were integrally molded, and a normal gear grinding wheel could not be produced.
Comparative Example 10: Abrasive grain: Abrasive grain 4, Abrasive grain volume fraction (Vg): 51%, Vitrified bond volume fraction (Vb): 10.5%, Pore volume fraction (Vp): 38.5%
Comparative Example 11: Abrasive grain: Abrasive grain 4, Abrasive grain volume fraction (Vg): 48%, Vitrified bond volume fraction (Vb): 16%, Pore volume fraction (Vp): 36%

Table 2 shows the grain volume fraction (Vg), vitrified bond volume fraction (Vb), pore volume fraction (Vp), and rotational fracture peripheral speed of the gear grinding wheels used in each Example and Comparative Example. Note that no measurements were made for Comparative Examples 6 to 8, 10, and 11, in which normal gear grinding wheels could not be produced (measurement not possible).

1: Use portion 2: Reinforcement portion 3: Hole portion 10: Gear grinding wheel

Claims (4)

A gear grinding wheel, comprising:
The reinforcing member is configured from a cylindrical reinforcing portion and a use portion located on the outer peripheral surface side of the reinforcing portion and fixed to the reinforcing portion ,
The application portion has a grinding surface for grinding a gear,
Both the use portion and the reinforcing portion are vitrified grinding wheels containing abrasive grains and a vitrified binder and having pores therein;
The average particle size of the abrasive grains contained in the use portion is 30 μm or more and 200 μm or less,
The average grain size of the abrasive grains contained in the reinforcing portion is 16 μm or more and 56 μm or less,
In the use portion, the volume fraction of the abrasive grains is (i) 40% or more and less than 47%, or (ii) 47% or more and 50% or less, in the case of (i), the volume fraction of the vitrified binder is 10% or more and 16% or less, and the volume fraction of the pores is greater than 37%, and in the case of (ii), the volume fraction of the vitrified binder is 9% or more and 16% or less, and the volume fraction of the pores is 34% or more,
In the reinforcing portion, the volume ratio of the abrasive grains is 46% or more and 50% or less, the volume ratio of the vitrified binder is 10% or more and 15% or less, and the volume ratio of the pores is 35% or more,
A gear grinding wheel, wherein at least a portion of the pores of the reinforcing portion are impregnated with a thermosetting resin. The gear grinding wheel according to claim 1, wherein the abrasive grains in the use portion and the reinforcing portion are both alumina-based abrasive grains. 3. The gear grinding wheel according to claim 1, wherein the outer peripheral surface of the reinforcing portion is not exposed. 3. The gear grinding wheel according to claim 1, wherein the use portion and the reinforcing portion are directly fixed to each other by integral molding.

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