JP2000326238A - Grinding wheel for low-speed grinding - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a grinding wheel capable of attaining grinding efficiency at relatively low cost and increasing a grinding wheel life or a dressing interval. SOLUTION: Boron carbide abrasive grains included in the grinding wheel structure of a grinding wheel 10 for ball grinding (grinding wheel for low-speed grinding), in spite of their properties of low level of thermostability, present completely no problems in a ball grinding because the ball grinding is low-speed grinding at a relative grinding speed to the material-to-be-ground of 10 m/sec. or less, so that the heat generated at a grinding point is not so high. With their advantageous properties of high hardness next to super-abrasive grains such as diamond and CBN, even if they are used for grinding a ball made of grinding-resistant material such as stainless steel or a ceramic ball of high- hardness, their grinding life or dressing interval can be increased more than conventional grinding wheels for grinding that uses general abrasive grains. Furthermore, boron carbide abrasive grains are roughly one-tenth of super- abrasive grains in price, therefore the grinding wheel that uses boron carbide abrasive grains is relatively more inexpensive than the one that uses super- abrasive grains, thus it is possible to attain grinding at low cost.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a low-speed polishing grindstone having a relative polishing speed of, for example, 10 m / sec or less with a material to be polished.

[0002]

2. Description of the Related Art In a polishing process for finishing the surface of a material to be polished, it is preferable to use a polishing grindstone using superabrasive grains such as diamond or CBN having a higher hardness as the material to be polished becomes harder. However, superabrasives are about 100 times more expensive than ordinary abrasives, and the larger the grindstone, the more difficult it is to manufacture. Since the processing cost becomes high, a polishing grindstone using such superabrasive grains is generally not used.

For this reason, in practice, for example, a resinoid grindstone in which general abrasive grains of about # 60 to # 8000 (fused alumina-based abrasive grains, silicon carbide-based abrasive grains) are combined with a phenol resin or an epoxy resin is often used. I have. This is because such a polishing grindstone, that is, a resinoid grindstone, has a dense grindstone structure, can obtain relatively high strength, and is relatively inexpensive.

[0004]

However, in the polishing process, a difficult-to-cut material such as stainless steel or a ceramic material to be polished having high hardness may be polished. In such a case, if the conventional grinding wheel as described above is used, the polishing performance cannot be obtained, and a reduction in the polishing efficiency, a shortening of the grinding wheel life or a shortening of the dressing interval cannot be avoided.

The present invention has been made in view of the above circumstances, and it is an object of the present invention to provide a polishing machine which can obtain a polishing efficiency relatively inexpensively, prolong the life of a grindstone or prolong a dressing interval. To provide a whetstone.

[0006]

The present inventors have made various studies to achieve the above object, and as a result, the Knoop hardness is the second highest after diamond and CBN, but the heat generated at the grinding point or polishing point is high. Low stability against
In general, a grindstone using boron carbide as abrasive grains, which has not been used as a grindstone, is polished at a relatively low polishing rate of 10 m / sec or less, that is, a relative polishing speed with a material to be polished, that is, a sliding (friction) speed at a polishing point. When it is used for ball polishing or gear honing of difficult-to-cut materials such as stainless steel or high-hardness ceramic polishing materials, the low thermal stability of boron carbide does not become a disadvantage, and general abrasive It has been found that a surprising fact that remarkably good polishing performance can be obtained as compared with the conventional polishing grindstones using. It is presumed that the above-mentioned ball polishing and gear honing have a low polishing rate relative to the material to be polished, so that the polishing point temperature does not become high enough to damage the boron carbide abrasive grains. The present invention has been made based on such findings.

That is, the gist of the present invention is as follows.
A low-speed polishing grindstone for performing low-speed polishing with a relative polishing speed of 10 m / sec or less with a material to be polished, comprising a grindstone structure in which abrasive grains including boron carbide abrasive grains are bound by a binder. Is to be.

[0008]

According to the present invention, the boron carbide abrasive grains contained in the grindstone structure of the grinding wheel for low-speed polishing of the present invention are generated at the polishing point in a low-speed polishing process in which the relative polishing speed with the workpiece is 10 m / sec or less. Since the heat is not so high, the property that its thermal stability is low does not matter at all, and the property that it has the hardness next to superabrasive grains such as diamond and CBN is utilized, so even if it is like stainless steel Even when used for gear honing, which processes ball hardening and hardening materials for hard-to-cut materials and hard ceramic materials, the grinding wheel life is longer than conventional grinding wheels using general abrasive grains. Or the dressing interval becomes longer. In addition, boron carbide abrasive grains are 1
Since the price is about / 10, the grindstone is relatively inexpensive compared to a grindstone for polishing using superabrasive grains, and the polishing process is inexpensive. In addition, since boron carbide abrasive grains have a lower hardness than superabrasive grains, shaping work in dressing and truing is facilitated, and there is an advantage that a high working efficiency is obtained and a dresser life is prolonged.

[0009]

In another preferred embodiment of the present invention, the grinding wheel for low-speed polishing preferably has a polishing surface in which an annular groove for guiding a ball-shaped material to be polished is formed concentrically. A ball grinding wheel for polishing the ball-shaped material to be polished by rolling while sandwiching the ball-shaped material to be polished in the annular groove with another member to be polished. In such ball polishing, the relative polishing rate for the ball-shaped material to be polished is usually about 3 to 4 m / sec or less, and the heat generated at the polishing point does not increase so much, so that the characteristics of the boron carbide abrasive grains are not impaired. Since the property of having the hardness next to super-abrasive grains such as diamond and CBN is utilized, the life of the grindstone becomes longer or the dressing interval becomes longer as compared with conventional grinding wheels using general abrasive grains. Become.

[0010] Preferably, the grinding wheel for low-speed polishing is
An outer peripheral surface of the gear-shaped workpiece is provided with an inner peripheral polishing surface having inner peripheral teeth formed thereon, the outer peripheral tooth of the gear-shaped workpiece being rotated by being rotated around an axis while being engaged with the inner peripheral teeth. This is a gear honing stone that grinds the surface. In such a gear honing, the relative polishing speed between the outer teeth of the gear-shaped material to be polished and the inner teeth to be slid in contact therewith is about 5 m / sec or less, and the heat generated at the polishing point is not so much. As it does not increase, the characteristics of boron carbide abrasive grains are not impaired,
Since the property of having the hardness next to super-abrasive grains such as diamond and CBN is utilized, the life of the grindstone becomes longer or the dressing interval becomes longer as compared with the conventional grinding wheel using general abrasive grains. .

Preferably, the grindstone structure is a resinoid grind structure in which abrasive grains including the boron carbide abrasive grains are bonded by a thermosetting resin binder. In this case, the firing temperature in the firing step in the manufacturing process, that is, the hardening / aging step of the thermosetting resin, that is, the hardening / aging temperature is about 200 ° C. or less, and firing is performed at a temperature exceeding 900 ° C. like a vitrified grindstone. As such, the properties of the boron carbide abrasive grains are not compromised by the temperature of the manufacturing process.

Preferably, the boron carbide abrasive grains and the general abrasive grains are contained in the grindstone structure, and the boron carbide abrasive grains are contained in the abrasive grains in an amount of 5 to 50 to all the abrasive grains contained in the grindstone structures.
% By weight. By doing so, the effect of improving the polishing performance can be obtained, and the polishing grindstone can be inexpensive. When the ratio of the boron carbide abrasive grains to the total abrasive grains is less than 5% by weight, the effect of improving the polishing performance by the boron carbide abrasive grains is hardly recognized, and the ratio of the boron carbide abrasive grains to the total abrasive grains is 5%.
If the content exceeds 0% by weight, the effect of improving the polishing performance by the boron carbide abrasive grains saturates. Therefore, even if it is further mixed, the polishing performance is not increased and the cost becomes high.

Preferably, the boron carbide abrasive grains and the super-abrasive grains are contained in the grinding stone structure, and the boron carbide abrasive grains are 20 to 80 with respect to all the abrasive grains contained in the grinding stone structure.
% By weight. By doing so, the same polishing performance as that of a polishing grindstone using superabrasive grains can be obtained at low cost. When the ratio of the boron carbide abrasive grains to the total abrasive grains is less than 20% by weight, the cost reduction effect due to the mixing of the boron carbide abrasive grains becomes difficult to be recognized, and the ratio of the boron carbide abrasive grains to the total abrasive grains is 80% by weight. If it exceeds, the difference in polishing performance from a polishing grindstone using superabrasives becomes remarkable.

When the relative polishing speed with the material to be polished is not more than 10 m / sec, a characteristic of low-speed polishing can be obtained, but more preferably 0.3 to 5 m.
A value in the range of / s is used. 0.3 relative polishing rate
If it is less than m / sec, the polishing operation efficiency is reduced. On the other hand, if the relative polishing speed exceeds 5 m / sec, it becomes difficult to obtain a characteristic surface state of low-speed polishing. Particularly, in the case of heavy load polishing, the boron carbide abrasive grains may be altered by heat generated at the polishing point.

[0015]

Preferred embodiments of the present invention will be described below in detail with reference to the accompanying drawings.

FIG. 1 shows a grinding wheel 10 for ball polishing according to one embodiment of the present invention. This grinding wheel 10 for ball polishing is
Polished surface 12 which is disk-shaped and is one of the two surfaces
, A plurality of ball guide grooves 14 are formed at equal intervals in the radial direction along a concentric circle. The ball guide groove 14 initially has a V-shaped cross section, and the depth thereof is set to about 3/10 of the diameter of the ball 16 which is the ball-shaped material to be polished. The ball guide groove 14 is used for the ball 1
6/3 of the ball diameter
It is used for polishing after having about 10 cross sections. The ball 16 is made of, for example, martensitic stainless steel such as SUS440C, and has a high chromium content, so that hard metal carbides such as chromium carbide are scattered on its surface to reduce workability. It is said to be a difficult-to-cut material. The backing plate (not shown) adhered to the back surface of the ball-grinding grindstone 10 is fastened to a flange of a rotary drive shaft by a bolt or the like.

The ball grinding wheel 10 is preferably made of abrasive grains including boron carbide (boron carbide B ₄ C, actually B _{12 + x} C _3-x (where 0 ≦ x ≦ 1)). This is a so-called resinoid grindstone composed of a grindstone structure bonded by a known thermosetting resin such as a phenol resin and an epoxy resin.
This grinding wheel for ball polishing 10 is made of B ₄ C / WA4000Z.
It is represented by a grinding wheel symbol of 9B, and is manufactured through a normal resinoid grinding wheel manufacturing process. In the above grindstone symbol, “B ₄ C / WA” means that the abrasive is a mixture of boron carbide abrasive and white alundum (white fused alumina abrasive), and the next “4000” is the abrasive The next "Z" indicates the degree of bonding (hardness) of the grinding stone structure, the next "9" indicates the structure of the grinding stone, and the next "B" indicates the bonding of the abrasive grains. It shows that the agent (bond) is bakelite (phenol resin).

The ball grinding wheel 10 is mounted, for example, to grind the ball 16 at a low speed in a ball grinding apparatus 20 shown in FIG. In the ball polishing device 20, a notch 22 is formed from the outer periphery to the center in the radial direction,
And a fixed polishing plate 24 made of cast iron having a ball guide groove (not shown) similar to the ball guide groove 14 formed on the polishing surface,
A ball-grinding wheel 10 rotatably provided around a common axis with the fixed polishing plate 24 so that the polishing surface 12 faces the polishing surface of the fixed polishing plate 24 at a predetermined interval.
And The ball-grinding grindstone 10 is rotated in a direction indicated by an arrow, for example, by a rotation driving device (not shown), and is continuously supplied with an oil-based polishing liquid. When a large number of the unpolished balls 16 are supplied from the supply gutter 26, the unpolished balls 16 are sandwiched between the ball guide grooves of the fixed polishing disc 24 and the ball guide grooves 14 of the ball grinding wheel 10. In the course of being guided in the circumferential direction, the fixed polishing machine 24
After being polished while being rolled by the relative rotation of the grinding wheel 10 and the ball grinding wheel 10, it is released into the notch 22 and
It is received above and returned to the ball tank 25.
The ball 16 returned to the ball tank 25 is conveyed along the outer circumferential guide groove in the ball tank 25, pushed out onto the supply gutter 26, and polished in the same manner as described above. The surface of the ball 16 is finished by repeating such wet polishing within a predetermined time. At this time, the maximum peripheral speed of the ball polishing grindstone 10, that is, the maximum relative polishing speed with respect to the ball 16, is 3 m / sec or less, preferably 1 m.
/ Sec or less.

In the following, the grinding wheel 10 for ball grinding will be described.
The polishing test conditions and the results of the polishing test performed by the present inventors to clarify the polishing performance of the present invention will be described. In this test, first, a test sample TS provided with a grindstone structure similar to that of the ball-grinding grindstone 10 and a control sample TC using only general abrasive grains similarly to a conventional polishing grindstone were prepared in accordance with the following raw material ratios, respectively. Then, using the polishing test apparatus 30 shown in FIG. 3, ball polishing was performed on the test sample TS and the control sample TC under the following common polishing test conditions. Under these test conditions, preliminary processing of changing the ball guide groove 14 from its initial V-shaped cross section to a semicircular cross section was performed prior to the test polishing. In addition, the test sample TS
In the control sample TC, the volume ratio of the abrasive grains and the phenol resin in the whole grindstone (sample) is 45% by volume and 53% by volume, respectively, and the remaining 2% by volume is pores.
In the test sample TS, “B ₄ C (3 μm)”
The average particle size of the boron carbide abrasive grains is 3 μm, which corresponds to # 3000 to # 4000 on the mesh.

Raw material ratio and dimensions B ₄ C (3 μm) of test sample TS : 14.5% by weight (20% by weight of all abrasive grains) WA (# 4000): 58.1% by weight (80% of all abrasive grains) Phenol resin: 27.4% by weight Specific gravity: 2.21 Ball guide groove: Initial groove depth: 0.6 mm, pitch diameter: 60 mmφ Outer shape: disk, outer diameter: 100 mmφ × thickness: 15 mm

Raw material ratio and dimensions WA (# 4000) of control sample TC : 74.8% by weight (100% by weight of total abrasive grains) Phenol resin: 25.2% by weight Specific gravity: 2.40 Ball guide groove: Initial stage Groove depth 0.6mm, pitch diameter 60mmφ Outer shape: disk, outer diameter 100mmφ x thickness 15mm

Polishing test conditions Circumferential speed: 18.85 m / min (0.32 m / sec) Ball shape: 3.0 mmφ24 Ball material: SUS440C Load: 375 g / piece Polishing oil: Noritake cut EPS-5, 400 cc / h

In the polishing test apparatus 30 shown in FIG.
It is rotatably supported by a frame 32 through a bearing 34 and is driven at 100 rpm by an electric motor 36 with a speed reducer.
pm (peripheral speed of ball groove 18.85m / min, ie 0.3
Rotating shaft 38 driven at a rotational speed of about 2 m / sec)
Is provided. A disk-shaped test sample TS and a control sample TC are detachably fixed to the shaft end of the rotating shaft 38. Further, a fixed plate 40 made of cast iron having the same shape and dimensions as the test sample TS and the control sample TC is placed on the shaft so that the test sample TS or the control sample TC is fixed to the rotating shaft 38 so as to face the test sample TS or the control sample TC. A holding device 42 for holding the shaft so as to be non-rotatable and axially movable.
Is provided so that the test sample TS or the control sample TC can be relatively rotated around the common axis with respect to the fixed platen 40. Test sample TS or control sample T
Ball guide grooves 44 and 46 having the same pitch diameter and width are provided on the opposing surface of C and the opposing surface of the fixed plate 40 made of cast iron, respectively. In a state where 24 balls 16 are arranged in this test, a weight 48 is applied, and a predetermined load (37 in this test example) is applied to the ball 16.
(5 g / piece). In the actual polishing test, the test sample TS or the control sample TC was dropped in the above-mentioned state with the polishing oil (Noritake Cat EPS-5 manufactured by Noritake Company Limited) dropped at a flow rate of 400 cc / h. It is relatively rotated about a common axis with respect to the fixed platen 40, and the polishing amount and the grinding wheel wear amount are measured at predetermined polishing times.

FIGS. 4 and 5 show the results of the above polishing test.
FIG. 4 shows one of the balls 16 with respect to the polishing time.
FIG. 5 shows the change in the polishing amount per unit (reduced weight mg).
Grinding wheel wear (groove depth increase μm) against polishing time
Is shown. 4 and FIG._FourC grinding
The value of the test sample TS containing the grains is shown._FourC abrasive
The value of the control sample TC not containing is shown. In addition, the present invention
According to the measurement of the people, B_FourTest sample TS containing C abrasive grains
Surface roughness of ball 16 in low-speed polishing
(Roughness) Ra was 0.01 μm, whereas B_FourC
In low-speed polishing using a control sample TC containing no abrasive grains
The surface roughness (arithmetic mean roughness) Ra of the ball 16 is 0.02
It was 0 μm. 4 and FIG.
U, B _FourLow-speed polishing using test sample TS containing C abrasive grains
Then B_FourLow speed using control sample TC without C abrasive
Compared to polishing, the polishing amount is large and the amount of grinding wheel wear is small.
Absent. That is, the polishing efficiency is high and the life is long. Only
In the case of low-speed polishing using the test sample TS, the control sample TC was used.
The roughness of the polished surface is about twice that of the slow polishing used.
It has improved every time.

FIG. 6 shows the test sample TS obtained by changing the composition ratio of B ₄ C abrasive grains to all the abrasive grains (B ₄ C abrasive grains + WA abrasive grains), that is, 5 wt%, 20 wt%, 5
Four types of 0% by weight and 80% by weight are prepared, and ball polishing is performed for a predetermined time (4 hours) using the four types of test samples TS under the same conditions as above, and their polishing performances are compared. is there. The polishing performance is represented by a polishing ratio (= abrasion processing amount / abrasion stone wear amount). As is clear from FIG. 6, when the ratio of the B ₄ C abrasive grains to the total abrasive grains is less than 5% by weight, the effect of improving the polishing performance by the B ₄ C abrasive grains is hardly recognized, and the B ₄ C abrasive grains are hardly recognized. When the proportion of the total abrasive grains exceeds 50% by weight, the effect of improving the polishing performance by the boron carbide abrasive grains is saturated. Therefore, the B ₄ C abrasive grains are 5 to 50% by weight based on all the abrasive grains contained in the grindstone structure.
When it is mixed within the range, there is an advantage that the polishing grindstone is inexpensive while the effect of improving the polishing performance is obtained.

FIG. 7 shows the test sample TS obtained by changing the composition ratio of B ₄ C abrasive grains to all the abrasive grains (B ₄ C abrasive grains + CBN abrasive grains), that is, 20% by weight, 50% by weight, Four types of 80% by weight and 100% by weight are prepared, and ball polishing is performed for a predetermined time (4 hours) under the same conditions as above using the four types of test samples TS, and their polishing performances are compared. is there. This test is for recognizing a range in which an inexpensive whetstone is obtained while obtaining performance equivalent to that of a superabrasive polishing whetstone. As apparent from FIG. 7, the B ₄
When the ratio of the C abrasive grains to the total abrasive grains exceeds 70% by weight, the polishing performance starts to decrease, and when it exceeds 80% by weight, the polishing performance decreases significantly, and polishing with a polishing wheel using super abrasive grains. The difference in performance becomes significant. Therefore, when the ratio of the B ₄ C abrasive grains to the total abrasive grains is 80% by weight or less, preferably 70% by weight or less, the same polishing performance as that of the polishing wheel using the CBN abrasive grains is obtained, and the CBN abrasive grains are obtained. The whetstone is inexpensive by the amount of B ₄ C abrasive grains mixed at about 1/10 of the price. If the ratio of the above-mentioned boron carbide abrasive grains to all the abrasive grains is less than 20% by weight, the effect of reducing the cost by mixing the boron carbide abrasive grains is hardly recognized.

As described above, the boron carbide abrasive grains contained in the grindstone structure of the ball-grinding grindstone (low-grinding grindstone) 10 of the present embodiment have a relative polishing rate of 10 m / m with the material to be polished.
In ball polishing, which is a low-speed polishing process in seconds or less, since the heat generated at the polishing point does not increase so much, the property of low thermal stability does not pose any problem at all, and is second only to superabrasive grains such as diamond and CBN. Since the property of having hardness is utilized, even if it is used for polishing a difficult-to-cut material such as a stainless steel ball 16 or a ceramic ball, compared with a conventional grinding wheel using general abrasive grains. In this case, the life of the grinding wheel is prolonged, or the dressing interval is prolonged. In addition, the above-mentioned boron carbide abrasive grains are about 1/10 the price of super-abrasive grains, so that the grindstones are relatively inexpensive as compared with polishing wheels using super-abrasive grains, and inexpensive polishing is performed. Becomes Further, since the hardness of boron carbide abrasive grains is lower than that of superabrasive grains, shaping work in dressing or truing is facilitated, and there is an advantage that a high working efficiency is obtained and a dresser life is prolonged. Furthermore, as compared with a polishing grindstone using superabrasive grains, there is an advantage that the time for preliminary processing in which the ball guide groove 14 having a V-shaped cross section is semicircular in the initial stage is reduced.

Further, the grinding stone structure of the ball grinding wheel 10 of the present embodiment is a resinoid grinding stone structure in which the abrasive grains including the boron carbide abrasive grains are bonded by a thermosetting resin binder, that is, a resinoid grinding stone structure. The firing temperature in the firing step (the curing and aging step of the resinoid resin) is about 200 ° C. or less, and the firing temperature is 900 ° C. like a vitrified whetstone.
Is not calcined at a temperature exceeding the above range, so that there is an advantage that the characteristics of the boron carbide abrasive grains are not impaired by the temperature of the production process.

Next, another embodiment of the present invention will be described. In the following description, the same parts as those in the above-described embodiment are denoted by the same reference numerals, and description thereof will be omitted.

FIG. 8 shows a gear for performing honing, which is a kind of polishing, on the tooth surface of the outer peripheral teeth of the gear 52 using a gear honing grindstone 50, which is a low-speed polishing grindstone according to another embodiment of the present invention. The honing device 54 is shown. The gear honing device 54 is provided with a work holder 56 for centering and rotatably supporting the gear 52 to be honed.
A work driving device 58 that reciprocates the work holding table 56 in the axial direction of the gear 52 by a predetermined stroke,
A grindstone driving device 62 is provided, which holds the gear honing grindstone 50 meshed with the gear 52 via a ring-shaped holder 60 and rotationally drives it around its axis. As shown in FIG. 9, the gear honing grindstone 50 is formed in an annular shape and provided with a large number of inner peripheral teeth 64 on an annular inner peripheral surface, and is disposed in a posture inclined with respect to the axis of the gear 52. Thus, the inner peripheral teeth 64 are meshed with the gear 52. The gear honing grindstone 50 is rotated around the axis by the grindstone driving device 62 to rotate the gear honing grindstone 50 and the gear 52 in mesh with each other. By being moved, honing is performed on the tooth surface of the outer peripheral teeth of the gear 52.

The gear honing grindstone 50 is made of boron carbide [boron carbide B ₄ C, actually B _{12 + x} C
_3-x (where 0 ≦ x ≦ 1)] This is a so-called resinoid grindstone in which abrasive grains are bonded by a well-known thermosetting resin such as a phenol resin or an epoxy resin. The ball grinding wheel 10 is represented by a grinding wheel symbol of B ₄ C / WA100R7Y, and is manufactured through a normal resinoid grinding wheel manufacturing process. In the above grinding wheel symbol, “B ₄ C /
WA "means that the abrasive grains are a mixture of boron carbide abrasive grains and white alundum (white fused alumina abrasive grains)
The next “100” is a number indicating the size (particle size) of the abrasive grain, the next “R” is the hardness of the grindstone, the next “7” is the structure of the grindstone, and the next “Y”. Indicates that the binder is an epoxy resin.

In the following, the gear honing grindstone 5
The polishing test conditions and the results of the polishing test performed by the present inventors to clarify the polishing performance of 0 will be described. In this test, first, the gear honing grindstones 50 were respectively prepared according to the following raw material proportions, and control gear honing grindstones having the same shape but using only general abrasive grains were prepared respectively according to the following raw material proportions. , FIG.
The gear honing was performed with the gear honing stone 50 and the control gear honing stone under the following common gear honing test conditions using the gear honing device 54 shown in FIG. In the gear honing stone 50 and the control gear honing stone, the volume ratios of the abrasive grains and the epoxy resin in the entire grinding stone are both 49% by volume and 33% by volume, and the remaining 18% by volume is voids.
The polishing speed under the gear honing test conditions is a relative sliding speed at which the outer peripheral teeth of the gear 52 and the inner peripheral teeth 64 of the gear honing stone 50 rub against each other during the polishing process due to relative motion. It is calculated based on the abrasive grain motion equation.

Raw material ratio of gear honing stone 50 B ₄ C (130 μm): 14.9% by weight (20% by weight of all abrasive grains) WA (# 100): 59.7% by weight (80% by weight of all abrasive grains) Epoxy resin: 25.4% by weight Specific gravity: 2.34 Inner peripheral teeth: Module m = 2.5, number of teeth Z = 113 Pressure angle P = 15, twist angle = 23.17 Outer shape: Outer diameter 350 mmφ × thickness 27mm x 293.4mm inside diameter

Material ratio of control gear honing wheel WA (# 100): 76.7% by weight Epoxy resin: 23.3% by weight Specific gravity: 2.54 Inner peripheral teeth: Module m = 2.5, number of teeth Z = 113 Pressure angle P = 15, twist angle = 23.17 Outer shape: outer diameter 350 mmφ × thickness 27 mm × inner diameter 293.4 mm

Gear honing test conditions Grinding wheel rotation speed: 950 rpm Work shape: Z = 53, twist angle = 34.5 (RH) Cutting depth 0.05 mm Work material: SCR420H quenching Polishing liquid: NORITAKE CUT SF-20 (Non-water) Polishing speed: 180m / min, ie 3m / sec

According to the above-mentioned gear honing test, when the above-described gear honing grindstone 50 is used, the dress interval, that is, the inner peripheral teeth 6 of the gear honing grindstone 50 are used.
The number of the gears 52 within the standard that can be obtained without truing or dressing No. 4 was 40 pieces / D, whereas according to the control gear honing grindstone, the number was 20 pieces / D. Therefore, according to the gear honing grindstone 50 containing boron carbide abrasive grains, the dress interval and the life of the grindstone are doubled as compared with the control gear honing grindstone that does not include the boron carbide abrasive grains but includes only the general abrasive grains.

The boron carbide abrasive grains contained in the grindstone structure of the gear honing grindstone 50 of this embodiment have a heat generated at the polishing point in a low-speed polishing process in which the relative polishing speed with the material to be polished is 10 m / sec or less. Is not so high, so the property that its thermal stability is low does not matter at all, and the property that it has the hardness next to superabrasives such as diamond and CBN is utilized, so even if it is hardened by quenching, Even when used for a hard gear 52 made of steel such as that described above, the life of the grindstone is longer or the dressing interval is longer than that of a conventional polishing grindstone using general abrasive grains. In addition, the above-mentioned boron carbide abrasive grains are about 1/10 the price of super-abrasive grains, so that the grindstones are relatively inexpensive as compared with polishing wheels using super-abrasive grains, so that inexpensive polishing is possible. Processing. Further, since the hardness of boron carbide abrasive grains is lower than that of superabrasive grains, shaping work in dressing or truing is facilitated, and there is an advantage that a high working efficiency is obtained and a dresser life is prolonged.

Further, the gear honing grindstone 50 of this embodiment is used.
The grinding stone structure also has a baking step (a curing and maturation step of the resinoid resin) in the baking step (resinoid resin hardening maturation step) in the manufacturing process since the abrasive grains including the boron carbide abrasive grains are bonded by a thermosetting resin binder, that is, the grinding stone structure. Is 200
℃ or less, 90% like vitrified whetstone
Since it is not fired at a temperature exceeding 0 ° C., there is an advantage that the characteristics of the boron carbide abrasive grains are not impaired by the temperature of the manufacturing process.

While the embodiment of the present invention has been described with reference to the drawings, the present invention can be applied to other embodiments.

For example, in the above-described ball polishing grindstone 10, a grindstone formed entirely of a mixture of boron carbide abrasive grains and white alundum (white fused alumina abrasive grains) by a thermosetting resin. Although it is composed of tissue, only the part involved in polishing, for example, ball 16
The above-mentioned grindstone structure is used only in a region corresponding to a half of the diameter of the polishing surface 12 in the depth direction from the polishing surface 12, and the other portion is a grindstone structure in which general abrasive grains are bonded by a thermosetting resin. There may be. In this case, the grinding wheel 10 for ball polishing becomes more inexpensive.

In the above embodiment, the ball 16 is made of stainless steel SUS440C. However, the ball 16 may be made of another kind of metal or ceramic having relatively high hardness.

In the above-described embodiment, the ball grinding wheel 10 for grinding the ball 16 and the gear honing wheel 50 for grinding the tooth surface of the gear 52 have been described. The present invention can also be applied to a grinding wheel for polishing.

Further, the grinding wheel 1 for the ball polishing according to the above-described embodiment.
0, the gear honing grindstone 50 was a so-called resinoid grindstone composed of a grindstone structure in which the abrasive grains were bonded by a thermosetting resin, but the abrasive grains were formed by other types of binders such as PVA, rubber, and thermoplastic resin. A bonded whetstone can be used.

Further, the ball grinding wheel 1 of the above embodiment is used.
0, a low-speed polishing wheel to which the present invention is applied, such as the gear honing wheel 50, can obtain a characteristic of a low-speed polishing at a speed of 10 m / sec or less, but more preferably,
A value in the range of 0.3 m to 4 m / sec is used. When the relative polishing speed is less than 0.3 m / sec, the polishing operation efficiency is reduced. On the other hand, if the relative polishing rate exceeds 4 m / sec, especially in the case of heavy load polishing, the boron carbide particles may be altered by heat generated at the polishing point of the abrasive grains, and in particular, in gear honing, It becomes difficult to obtain the characteristic surface state of low-speed polishing.

The above is merely an example of the present invention, and the present invention can be variously modified without departing from the gist thereof.

[Brief description of the drawings]

FIG. 1 is a partially cutaway side view illustrating a configuration of a ball polishing grindstone that is a low-speed polishing grindstone according to one embodiment of the present invention.

FIG. 2 is a schematic diagram briefly explaining a main part configuration of a ball polishing apparatus provided with the ball polishing wheel of FIG. 1;

FIG. 3 is a front view illustrating a main part of a polishing test apparatus in which a polishing test is performed to confirm a polishing effect of the ball polishing grindstone of FIG.

FIG. 4 is a view showing a polishing test result performed by using the polishing test apparatus of FIG. 3;
The case where a ball-grinding grindstone containing boron carbide abrasive grains is used (marked with ○) and the case where a ball-polishing grindstone containing no boron carbide abrasive grains is used (marked with △) are shown to be comparable.

FIG. 5 is a view showing a polishing test result performed using the polishing test apparatus of FIG. 3;
The case where a ball-grinding grindstone containing boron carbide abrasive grains is used (marked with ○) and the case where a ball-polishing grindstone containing no boron carbide abrasive grains is used (marked with △) are shown to be comparable.

6 is a view showing the results of a polishing test performed using the polishing test apparatus of FIG. 3 to confirm a range in which an effect obtained when boron carbide abrasive grains are mixed with general abrasive grains is obtained. It is a figure which shows the grinding | polishing ratio with respect to the ratio of the boron carbide abrasive grain contained in the grindstone for grinding | polishing.

FIG. 7 is a view showing the results of a polishing test performed using the polishing test apparatus of FIG. 3 to confirm a range in which an effect obtained when boron carbide abrasive grains are mixed with CBN abrasive grains is obtained. It is a figure which shows the grinding | polishing ratio with respect to the ratio of the boron carbide abrasive grain contained in the grindstone for grinding | polishing.

FIG. 8 is a front view schematically illustrating the configuration of a gear honing apparatus provided with a gear honing grindstone as a grindstone for low-speed polishing according to another embodiment of the present invention.

9A and 9B are diagrams illustrating a mutual meshing state between a gear honing grindstone and a gear to be polished by the gear honing stone in the gear honing device of FIG. 8, wherein FIG. 9A is a diagram viewed from the front of the gear honing device; (b) is a view from the left side of the gear honing device.

[Explanation of symbols]

 10: Grinding wheel for ball polishing (grinding stone for low-speed polishing) 12: Polishing surface 16: Ball (ball-shaped polishing material) 50: Gear honing wheel (grinding stone for low-speed polishing) 52: Gear (gear-shaped polishing material) 64: Inside Peripheral teeth

 ────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Ao Kusakabe 3-36 Noritakeshinmachi, Nishi-ku, Nagoya-shi, Aichi F-term (reference) Noritake Co., Ltd. 3C063 AA02 AB05 BA24 BB01 BC03 EE03 EE40 FF23

Claims (3)

[Claims] 1. A relative polishing speed with a material to be polished is 10 m.
What is claimed is: 1. A grinding wheel for low-speed polishing for performing low-speed polishing at a rate of not more than 1 / sec, comprising a grinding stone structure in which abrasive grains including boron carbide abrasive grains are bound by a binder. 2. The grinding wheel for low-speed polishing has a polishing surface in which an annular groove for guiding a ball-shaped material to be polished is formed concentrically, and the polishing groove is provided between the polishing surface and another member opposed thereto. 2. The grinding wheel for low-speed polishing according to claim 1, wherein the grinding wheel is a ball grinding wheel for polishing the ball-shaped workpiece by rolling while holding the ball-shaped workpiece in the annular groove. 3. The grinding wheel for low-speed polishing is provided with an inner peripheral polishing surface on which inner peripheral teeth are formed, and is rotated around an axis while meshing with the outer peripheral teeth of the gear-shaped material to be polished and the inner peripheral teeth. 2. The grinding wheel for low-speed grinding according to claim 1, wherein the grinding wheel is a gear honing grindstone which grinds the outer peripheral teeth of the gear-shaped material to be polished.