The present invention relates to an abrasive tool. The present application claims priority based on Japanese Patent Application No. 2016-031032 filed on Feb. 22, 2016. The Japanese patent application is entirely incorporated herein by reference. More specifically, the present invention relates to an abrasive tool comprising a plurality of abrasive grains bonded by a binder.
Conventionally, for example, diamond rotary dressers are disclosed in “New Machining Tool Dictionary,” Kabushiki Kaisya Sangyo Chyosakai, published on Dec. 5, 1991 (NPD 1), and Japanese Patent Laying-open Nos. 5-269666 (PTD 1), 10-058231 (PTD 2) and 2000-246636 (PTD 3).
Conventional diamond rotary dressers for gears have a problem of short lifetime in some cases depending on a condition under which the dresser is used.
Accordingly, what provides a long-life diamond rotary dresser for a gear is disclosed in International Publication No. 2007/000831 (PTD 4).
[PTD 1] Japanese Patent Laying-Open No. 5-269666
[PTD 2] Japanese Patent Laying-Open No. 10-058231
[PTD 3] Japanese Patent Laying-Open No. 2000-246636
[PTD 4] International Publication No. 2007/000831
[NPD 1] “New Machining Tool Dictionary,” Kabushiki Kaisya Sangyo Chyosakai, Dec. 5, 1991, pp. 651-654
According to one aspect of the present invention, an abrasive tool is an abrasive tool having an abrasive grain layer comprising a plurality of hard abrasive grains bonded by a binder, with a plurality of the hard abrasive grains each having a working surface formed to contact a workpiece, a ratio of a total area of a plurality of such working surfaces to an area of an imaginary plane smoothly connecting the plurality of working surfaces being 5% or more and 30% or less.
Conventional rotary dressers may have large variation in sharpness and lifetime, and they were impaired in sharpness at an early stage depending on the production lot and unable to transfer a shape to a grinding wheel accurately, and had reduced lifetime and other problems in some cases. Even the diamond rotary dresser of PTD 4 had a possibility of variation in sharpness and lifetime.
The present invention has been made to solve the above-mentioned problem, and it is an object of the present invention to provide an abrasive tool, such as a diamond rotary dresser, which has a long lifetime and also presents satisfactory sharpness.
The present invention can provide an abrasive tool, such as a diamond rotary dresser, which has a long lifetime and little variation in sharpness and lifetime and hence presents steady performance.
Initially, embodiments of the present invention will be enumerated and described.
An abrasive tool is an abrasive tool having an abrasive grain layer comprising a plurality of hard abrasive grains bonded via a binder, with a plurality of the hard abrasive grains each having a working surface formed to contact a workpiece, a ratio of a total area of a plurality of such working surfaces to an area of an imaginary plane smoothly connecting the plurality of working surfaces being 5% or more and 30% or less.
The area of the working surface of each hard abrasive grain present per unit area of the imaginary plane of a surface of the abrasive grain layer (a total area of working surfaces of hard abrasive grains/the area of the imaginary plane) is calculated as follows: A microscope is used and the abrasive grain layer has the surface exposed to light in the direction of a normal thereto. Light scattered from other than the working surfaces is removed and only a reflection image from the working surfaces in the surface of the abrasive grain layer is analyzed and extracted to calculate the area ratio.
In order to specifically measure the area ratio, an observation is done in the imaginary plane at any three locations each in a field of view of 2 mm×2 mm and working surfaces' areas are measured in the above method, and “a total value of the working surfaces/a total value of the imaginary plane” is presented as the area ratio. The abrasive tool thus configured has optimally controlled an abrasive area acting when processing, and thus has little variation in sharpness and can also have a steady, long lifetime. If the above ratio is less than 5%, the area of working surfaces acting on processing is too small, and the abrasive tool has a reduced lifetime. If the above ratio exceeds 30%, the area of the working surfaces is too large, and sharpness deteriorates.
Preferably, a ratio of a maximum diameter to a minimum diameter (maximum diameter/minimum diameter) of a plurality of hard abrasive grains used for the abrasive tool is 1.2 or more and 10 or less. When the above ratio is 1.2 or more, the grain diameter of the hard abrasive grain can be kept large and hence satisfactory sharpness can be maintained. When the ratio is 10 or less, abrasive grain distribution variation can be kept small. As a result, the tool can be improved in precision. As an example of a method for measuring a grain diameter, there is a method to remove hard abrasive grains from an abrasive tool to determine image data of the hard abrasive grains, and an equivalent circle diameter of the hard abrasive grain is taken as the grain diameter. The maximum and minimum diameters of the hard abrasive grains are measured as follows:
First, the abrasive tool is cut in half, and one half of the abrasive tool has the abrasive grain layer molten to remove hard abrasive grains. Hard abrasive grains of 20% in mass of the removed hard abrasive grains are randomly extracted. Electronic data of an image of the extracted hard abrasive grains is generated using an optical microscope. Based on this image data, an equivalent circle diameter of the hard abrasive grain is measured with a dry-type grain image analyzer, and the equivalent circle diameter is measured as the grain diameter. Note that an equivalent circle diameter is a diameter of a hard abrasive grain measured and analyzed with a dry-type grain image analyzer, based on an image of the hard abrasive grain, and it is a diameter of a circle having the same area as the area of an image of each abrasive grain having a non-circular, deformed shape, and this diameter serves as a grain diameter. A maximum diameter DMAX and a minimum diameter DMIN in the measured grain diameter data are calculated and DMAX/DMIN indicates the maximum diameter/the minimum diameter.
Thus, the hard abrasive grains present in the abrasive grain layer do not have a uniform grain diameter; rather, the hard abrasive grains have a grain diameter varying within some range so that individual hard abrasive grains can be abraded at different speeds in different conditions, and when the abrasive grain layer is seen as a whole, it can have steady sharpness over a long period of time.
Preferably, the plurality of hard abrasive grains are distributed in the abrasive grain layer at a density of 50 to 1500 grains/cm2. The distribution density is measured as follows: The surface of the abrasive grain layer is observed with a microscope. The size of the field of view to be observed is set in magnification such that 20 to 50 hard abrasive grains can be seen in the field of view and the number of hard abrasive grains is counted at each of any three locations. Then, based on the size of the field of view and the number of hard abrasive grains, the density of the hard abrasive grain distribution is calculated.
Preferably, the plurality of hard abrasive grains have a Vickers hardness Hv of 1000 or more and 16000 or less.
Representative examples of a hard abrasive grain having such a Vickers hardness include diamond, cubic boron nitride (cBN), SiC, Al2O3, and the like. The hard abrasive grain may be either a single crystal or a polycrystal.
Preferably, the plurality of hard abrasive grains have a grain size of 91 or more and 1001 or less, as defined in JIS B 4130 (1998), “table 1: types and indications of grain size,” “1. narrow range.” Specifically, see Table 1 below.
dimension of opening of sieve according to JIS Z 8801
The grain size is measured in the following method: initially, as done in the method of measuring the maximum and minimum diameters of the hard abrasive grains, the abrasive tool is cut in half, and one half of the abrasive tool has the abrasive grain layer molten to remove hard abrasive grains. The removed hard abrasive grains are then measured based on a provision of JIS B 4130 (1998).
Preferably, the abrasive grain layer is a single layer.
Preferably, the binder is nickel plating.
Preferably, the abrasive tool is a rotary dresser.
Preferably, the rotary dresser is a disk dresser.
Preferably, it is used for one or both of truing and dressing of a grinding wheel used for processing a gear.
The abrasive tool described below is an abrasive tool that can achieve steady sharpness and a long lifetime by controlling abrasive grains brought into contact with a workpiece to have an optimum state. That is, it is an abrasive tool in which abrasive grains acting when processing have an area, a grain diameter, a grain size distribution and a distribution density controlled to have an optimum state.
Preferably, a ratio of a maximum diameter to a minimum diameter (maximum diameter/minimum diameter) of the plurality of hard abrasive grains 102 is 1.2 or more and 10 or less. Note that hard abrasive grain 102 is limited to what has working surface 119. In
Preferably, the plurality of hard abrasive grains 102 are distributed in abrasive grain layer 123 at a density of 50 to 1500 grains/cm2. Hard abrasive grain 102 is limited to what has working surface 119. Within this range, a superabrasive wheel can present performance with extremely satisfactory sharpness and/or lifetime.
Preferably, the plurality of hard abrasive grains 102 have a Vickers hardness Hv of 1000 or more and 16000 or less. Hard abrasive grains having such hardness allow a wheel to be increased in sharpness and lifetime.
Preferably, hard abrasive grains 102 have a grain size of 91 or more and 1001 or less. A wheel having hard abrasive grains with such a relatively large grain diameter remarkably exhibits an effect of increasing sharpness and lifetime. Working surface 119 is obtained by grinding or polishing a surface of hard abrasive grain 102 (that is, providing hard abrasive grains 102 with a uniform height). The ratio of a maximum area and a minimum area (maximum area/minimum area) of the plurality of working surfaces 119 is preferably 1.5 or more and 10 or less.
(Description of Each Sample)
Various wheels shown in Tables 2-4 were prepared. The wheels are the same in shape and size. The wheels have the shape as shown in
In Tables 2-4, “working surface area ratio” indicates a ratio of a total area of a plurality of working surfaces 119 to an area of imaginary plane 110 smoothly connecting the plurality of working surfaces 119 (in %).
In Tables 2-4, “abrasive grain maximum/minimum diameter ratio” means a ratio of a maximum diameter and a minimum diameter (maximum diameter/minimum diameter) of a plurality of hard abrasive grains 102 (limited to those having working surface 119).
In Tables 2-4, “abrasive grain distribution density” means a distribution density of the plurality of hard abrasive grains 102 (limited to those having working surface 119) (no. of abrasive grains/cm2).
(Method of Controlling Numerical Values in Producing Superabrasive Wheels of Examples)
In producing the various wheels described in Tables 2-4, the time, frequency and the like of grinding or polishing the surfaces of hard abrasive grains were adjusted to control their working surfaces in size to control their area ratio. When increasing the abrasive grains' maximum diameter/minimum diameter value, a plurality of hard abrasive grains having different average diameters mixed as appropriate were used for control, whereas when decreasing the abrasive grains' maximum diameter/minimum diameter value, the abrasive grains to be used were sieved to provide a grain size distribution with a narrower range for control. Abrasive grain distribution density was controlled by adjusting the amount of abrasive grains used for a single wheel.
Tables 2-4 show the thus produced, various wheels' respective working surface area ratios, maximum/minimum abrasive grain diameter ratios, and abrasive grain distribution density values.
These diamond rotary dressers for a gear were used to true and dress a grinding wheel used for processing a gear.
The dressing was done under the following conditions: Target to be dressed: grinding wheel for grinding a gear (material: aluminium oxide grinding wheel)
Dressing Conditions:
Grinding wheel rotation speed: 60 to 80 rpm
Rotary dresser rotation speed: 3000 rpm
Depth of cut: 20 μm/pass (in coarse processing)
Depth of cut: 10 μm/pass (in finishing processing)
The initial dressing is coarse processing and the subsequent dressing is finishing processing.
A result of the dressing was evaluated according to the following criteria:
Comparative Example 2's wheel served as a reference in sharpness and lifetime, and the present invention's wheels were evaluated in performance. With Comparative Example 2's load current value and lifetime being 1.0, evaluation criteria were in three stages of A, B and C, as indicated below.
(Sharpness Evaluation)
Good/bad sharpness was evaluated from a load current value of a dresser driving shaft of a dressing apparatus.
A: The load current value was less than 0.6, and extremely steady dressing was able to be done.
B: The load current value was 0.6 or more and less than 0.8, and steady dressing was able to be done.
C: The load current value was 0.8 or more, and it was difficult to perform steady dressing.
(Lifetime Evaluation)
The precision of a workpiece processed with a dressed grinding wheel was regarded as an accuracy of the dressing, and it was determined that the dresser had reached its end of life when the accuracy of the dressing deteriorated.
A: The accuracy of the dressing substantially unchanged, and the lifetime was 2 or more.
B: The accuracy of the dressing gradually deteriorated and accordingly, the workpiece was slightly burnt, however, the lifetime was 1.2 or more and less than 2.
C: The accuracy of the dressing was poor, and the workpiece was considerably burnt, and the lifetime was less than 1.2.
As is apparent from Tables 2-4, the present invention's examples 1-19 were not evaluated as C in sharpness and lifetime and it has been confirmed that they exhibit satisfactory characteristics. On the other hand, Comparative Examples 1-10 were evaluated as C in either sharpness or lifetime, and it has been confirmed that they present low performance. As shown in Table 2, of the products of the present invention, those having a working surface area ratio of 6 to 25% were evaluated as A in sharpness and lifetime and thus found to be particularly preferable.
As shown in Table 3, of the products of the present invention, those with abrasive grains having maximum/minimum diameter ratio of 1.2-10 were evaluated as A in sharpness and lifetime and thus found to be particularly preferable.
As shown in Table 4, of the products of the present invention, those with abrasive grain distribution density of 100 to 600 grains/cm2 were evaluated as A in sharpness and lifetime and thus found to be particularly preferable.
The present invention is applicable in a field of abrasive tools such as, for example, a superabrasive grinding wheel used to carry out profile grinding on a workpiece, and a diamond rotary dresser used to dress a grinding wheel. In particular, the present invention relates to a diamond rotary, gear dresser used for truing or truing and dressing a grinding wheel used for processing a gear.
It should be understood that the embodiments and examples disclosed herein have been described for the purpose of illustration only and in a non-restrictive manner in any respect. The scope of the present invention is defined by the terms of the claims, rather than the embodiments described above, and is intended to include any modifications within the meaning and scope equivalent to the terms of the claims.
Number | Date | Country | Kind |
---|---|---|---|
2016-031032 | Feb 2016 | JP | national |
Filing Document | Filing Date | Country | Kind |
---|---|---|---|
PCT/JP2016/086372 | 12/7/2016 | WO |
Publishing Document | Publishing Date | Country | Kind |
---|---|---|---|
WO2017/145491 | 8/31/2017 | WO | A |
Number | Name | Date | Kind |
---|---|---|---|
5453312 | Haas et al. | Sep 1995 | A |
5549961 | Haas et al. | Aug 1996 | A |
6012972 | Jankowski | Jan 2000 | A |
6319108 | Adefris | Nov 2001 | B1 |
6368198 | Sung | Apr 2002 | B1 |
6386953 | Wirz | May 2002 | B1 |
6419574 | Takahashi et al. | Jul 2002 | B1 |
20030019570 | Chen et al. | Jan 2003 | A1 |
20080041354 | Imal et al. | Feb 2008 | A1 |
20080271384 | Puthanangady et al. | Nov 2008 | A1 |
20090047877 | Muldowney | Feb 2009 | A1 |
20090053980 | Hwang et al. | Feb 2009 | A1 |
20090215366 | Ishizuka | Aug 2009 | A1 |
20120060426 | Puthanangady et al. | Mar 2012 | A1 |
20150283666 | Nakajima | Oct 2015 | A1 |
20150290771 | Li | Oct 2015 | A1 |
20150291867 | Breder | Oct 2015 | A1 |
20160176018 | Rudolf et al. | Jun 2016 | A1 |
20180043506 | Hoshika | Feb 2018 | A1 |
Number | Date | Country |
---|---|---|
1102800 | May 1995 | CN |
1209471 | Mar 1999 | CN |
1286158 | Mar 2001 | CN |
1400636 | Mar 2003 | CN |
101001720 | Jul 2007 | CN |
101247923 | Aug 2008 | CN |
101367202 | Feb 2009 | CN |
101508087 | Aug 2009 | CN |
101563188 | Oct 2009 | CN |
102825547 | Dec 2012 | CN |
103846817 | Jun 2014 | CN |
104097152 | Oct 2014 | CN |
105612028 | May 2016 | CN |
2326166 | Dec 1998 | GB |
H05-269666 | Oct 1993 | JP |
H06-114739 | Apr 1994 | JP |
H07-237128 | Sep 1995 | JP |
2679178 | Nov 1997 | JP |
H10-058231 | Mar 1998 | JP |
2000-246636 | Sep 2000 | JP |
2002-292570 | Oct 2002 | JP |
2003-089064 | Mar 2003 | JP |
2003-200352 | Jul 2003 | JP |
2003-260663 | Sep 2003 | JP |
2004-130475 | Apr 2004 | JP |
2005-161449 | Jun 2005 | JP |
2005-279842 | Oct 2005 | JP |
2007307701 | Nov 2007 | JP |
4215570 | Jan 2009 | JP |
4354482 | Oct 2009 | JP |
2007000831 | Jan 2007 | WO |
2007119886 | Oct 2007 | WO |
2015018627 | Feb 2015 | WO |
Entry |
---|
Chosakai, New Machining Tool Dictionary (Industrial Research Center of Japan), 1991, pp. 651-654. |
Hirakawa, “Diamond/CBN products-Grain sizes of diamond or cubic boron nitride, JIS B 4130” Japanese Standards Association, 1998, pp. 1-10 [Cited in OA dated Mar. 12, 2018 in corresponding Japanese application]. |
Brochure of “Sysmex, Rapid particle size and shape analysis of suspensions FPIA-3000/FPIA-3000S”, Malvern Instruments Ltd., pp. 2-7 [Cited in OA dated Mar. 12, 2018 in corresponding Japanese application]. |
Measurement result according to FPIA-3000S, Sysmex, 2018 [Cited in OA dated Mar. 12, 2018 in corresponding Japanese application]. |
Measurement result of equivalent circle diameter, 2018 [Cited in OA dated Mar. 12, 2018 in corresponding Japanese application]. |
Inoue, “Optimum Dressing Condition of Vitrified CBN Wheel for Higher Performance in High Efficiency Grinding”, Journal of the Japan Society for Precision Engineering, vol. 58, No. 4. 1992, JSPE-5804 '92-04-586, pp. 20-24 [Cited in OA dated Mar. 12, 2018 in corresponding Japanese application]. |
Zhao et al., “Truing of Resinold-Bonded CBN Wheels” (1st Report, Cutting Edge Shape after Truing), Transactions of the Japan Society of Mechanical Engineers (C edition), vol. 62, No. 601, 1996-9, No. 96-0396, pp. 347-352 [Cited in OA dated Mar. 12, 2018 in corresponding Japanese application]. |
Takashima et al., “High-speed mirror grinding with CBN wheel (7th Report)—Influence of grain size of diamond rotary dresser on ground the surface—”, Proceedings of 2005 JSPE Spring Academic Lecture Meeting, pp. 893-894 [Cited in OA dated Mar. 12, 2018 in corresponding Japanese application]. |
In et al., “Surface Characteristics of the Polyurethane Polisher in Mirror-Polishing Process,—Study on Super-Smooth Polishing Methods (2nd Report)—”, Journal of the Japan Society for Precision Engineering, vol. 65, No. 8, 1999, pp. 1147-1152 [Cited in OA dated Mar. 12, 2018 in corresponding Japanese application]. |
Notification of the Third Office Action issued in counterpart CN Patent Application No. 201680082285.5 dated Dec. 11, 2020. |
Notification to Grant Patent Right for Invention issued in counterpart Chinese Patent Application No. 201680082285.5 dated Mar. 16, 2021. |
Notification of the First Office Action issued in counterpart Chinese Application 201680082285.5 dated Aug. 30, 2019. |
Notification of the Second Office Action issued in counterpart Chinese Patent Application No. 201680082285.5 dated May 20, 2020. |
Extended European Search Report of Application No. EP16891647.6, dated Jul. 16, 2019, 8 pages. |
Number | Date | Country | |
---|---|---|---|
20190054592 A1 | Feb 2019 | US |