JP2004299019A - Segment type super abrasive grinding wheel - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a segment type abrasive grinding wheel capable of further improving grinding speed. <P>SOLUTION: In the super abrasive grinding wheel, because an adhering interface of a segment chip 34 and a base member 36 is inclined by angle θ with respect to an axis of the base member 36, stress in the direction to peel away acting on the adhering interface based on a centrifugal force caused by the rotation of the grinding wheel 30 and a side pressure acting from the work material in grinding, is reduced at the position of the both ends in the axial direction compared to the case where the adhering interface is provided in parallel to the axis. Since the segment chip 34 is suppressed in peeling away from the base member 36 in the adhering interface even if the grinding wheel peripheral speed is increased, and depth of cuts and feed rate are increased, the grinding wheel peripheral speed can be further increased. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a grinding wheel, and more particularly to an improvement of a segment type superabrasive wheel having a plurality of segment chips having a superabrasive layer fixed to a base member.
[0002]
[Prior art]
A plurality of segment chips having a superabrasive layer in which superabrasive grains such as diamond abrasive grains or CBN abrasive grains are combined with a vitreous binder are fixed to the outer peripheral surface of a perforated disk-shaped base member with a synthetic resin or the like. There is known a segment type superabrasive grindstone that performs a grinding process on a surface of a superabrasive layer of a segment chip, that is, a ground surface, by being rotationally driven around an axis of a base member. According to such a grindstone, alumina abrasive grains (Al ₂ O ₃ ) And silicon carbide abrasive grains (SiC), have the advantage that the abrasive layer involved in the grinding has a longer life and therefore has higher processing accuracy as well as a grinding wheel using general abrasive grains such as silicon carbide abrasive grains (SiC). There is. Moreover, since it adopts the form of a segment whetstone, it is possible to dispose relatively expensive superabrasive grains only in a portion contributing to grinding, and centrifugal fracture starting from a mounting hole provided in the shaft center. Since it hardly occurs, there is an advantage that it can be used at a high peripheral speed (for example, see Patent Document 1). For example, a general grindstone composed entirely of an abrasive layer bonded with a vitreous binder is used at a peripheral speed of, for example, about 33 (m / s). m / s). As a result, in the use of such a high peripheral speed, the peel strength at the bonding interface between the base member and the segment chip is an important factor with respect to grinding wheel breakage.
[0003]
By the way, for example, a grinding method of a cylindrical work material is performed by moving the grindstone in a direction perpendicular to the axis of the work material by a moving direction of the grindstone with respect to the work material being rotated around the axis. So-called plunge grinding for moving and so-called traverse grinding for moving the grindstone along a direction parallel to the axis thereof are roughly classified. Further, as an aspect in which these are combined, there is a so-called contouring grinding in which a surface of a work material is ground along a desired contour line in a process of moving a grindstone in one direction (for example, see Patent Document 2).
[0004]
[Patent Document 1]
JP-A-2000-141231
[Patent Document 2]
JP-A-7-266202
[0005]
[Problems to be solved by the invention]
In the above-mentioned plunge grinding, the reaction force received from the work material when the grindstone is pressed against the work material is directed in a direction perpendicular to the axis of the grindstone. The centrifugal force and the reaction force generated along with it work in a direction to decrease each other. That is, in plunge grinding, the problem of grinding wheel destruction hardly occurs. On the other hand, in traverse grinding and contour grinding, the grinding wheel is moved in a direction parallel to its axis while grinding the work material on the side surface of the abrasive layer, as shown in FIG. The reaction force R corresponding to the moving speed and the cutting depth acts on the side surface of the segment chip 14 of the grinding wheel 12 from the work material 10. This reaction force R acts as a compressive stress on an end surface 20 on the rear side in the traveling direction of the grindstone 12 on the fixed interface 18 between the segment chip 14 and the base member 16, but on the end surface 22 on the front side in the traveling direction. Acts as tensile stress. Therefore, the centrifugal force is reduced by the compressive stress on the rear end face 20, but the tensile stress is superimposed on the centrifugal force on the front end face 22, so that the stress in the peeling direction increases.
[0006]
On the other hand, in the high peripheral speed grinding, since the load of each of a large number of abrasive grains contained in the abrasive layer is reduced, by increasing both the cutting depth and the axial feed rate in traverse grinding. It is known that the grinding efficiency can be further increased to increase the production efficiency. However, if the depth of cut or the feed rate is increased in traverse grinding or contour grinding, the above-mentioned reaction force R is further increased, and the stress in the peeling direction on the front end face 22 is further increased. In the case of a grain grindstone, the insufficient peel strength of the fixed interface 18 hinders the improvement of the grinding speed. Note that such a problem is remarkable in traverse grinding or the like involving movement of the grinding wheel in the axial direction, but even in plunge grinding without such movement, the ground surface and the ground surface of the work material are not affected. The same can occur if the inclination is made with respect to the axial direction.
[0007]
The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a segment type superabrasive grinding wheel capable of further improving the grinding speed.
[0008]
[First means for solving the problem]
In order to achieve the above object, the gist of the first invention is that a plurality of segment chips having a ground surface composed of a superabrasive layer in which superabrasive particles are mutually bonded by a vitreous binder are used as a base member. A segment-type super-abrasive grindstone that performs a grinding process on the ground surface by being closely adhered to one another on a circumference centered on the axis, and being driven to rotate around the axis. Based on the centrifugal force and the reaction force acting from the work material, the stress in the direction of peeling them generated at both end positions in the direction parallel to the axis out of the fixed interface between the segment chip and the base member, The bonding interface is inclined with respect to the axis such that the maximum stress generated at both ends of the bonding interface is lower when the bonding interface is parallel to the axis.
[0009]
[Effect of the first invention]
With this configuration, the bonded interface between the segment chip and the base member is inclined with respect to the axis of the base member, so that the centrifugal force generated with the rotation of the grindstone during the grinding process and the work material are reduced. The stress in the peeling direction acting on the fixing interface based on the acting reaction force is reduced at both end positions in the axial direction as compared with the case where the fixing interface is provided parallel to the axis. That is, by inclining the bonding interface, the action direction of the tensile stress in the peeling direction based on the reaction force is tilted with respect to the bonding interface, and the diameter of the base member at the end face of the grindstone where the stress is the largest is set to the other part. On the other hand, if the stress is reduced, the stress acting on the fixed interface due to the rotation is distributed such that the stress decreases on the end face and increases accordingly in other portions. As a result, the stress component acting in the peeling direction based on the rotational stress or the reaction force is reduced in accordance with the degree of the inclination, so that the total stress acting in the peeling direction on the end face of the grindstone decreases. Therefore, even if the peripheral speed of the grindstone is increased and the cutting amount or the feed speed is increased, the separation of the segment chips from the base member at the bonding interface is suppressed, so that the grinding speed can be further increased. In the present application, "the fixed interface is inclined with respect to the axis" refers to a positional relationship in which the generatrix at an arbitrary position of the fixed interface that forms a curved surface is not parallel to the axis.
[0010]
[Second means for solving the problem]
The gist of the second invention for achieving the above object is that a plurality of segment chips having a ground surface comprising a superabrasive layer in which superabrasive particles are mutually bonded by a vitreous binder are used as a base. A segment-type super-type which is closely fixed to one another on a circumference centered on the axis of the member and is driven to rotate around the axis, thereby performing a grinding process on the ground surface forming a cylindrical surface as a whole. An abrasive grain whetstone, wherein the fixed interface between the segment chip and the base member is inclined so as to be located on the outer peripheral side from both end positions in a direction parallel to the axis toward their intermediate position. It is in.
[0011]
[Effect of the second invention]
With this configuration, in the segment type superabrasive grinding wheel having the cylindrical grinding surface, the fixed interface is located on the outer peripheral side as it goes inward in the axial direction (generally, the thickness direction) of the base member. Inclined. In other words, the fixing interface is formed in a V-shape or a U-shape that is inclined in two directions so as to have the largest diameter in the middle part in the thickness direction. Therefore, when the grinding wheel has a cylindrical shape, any of both end faces can be positioned on the front side in the traveling direction at the time of traverse grinding. The directional stress is reduced. That is, when the bonding interface is provided in parallel with the axis of the base member, the total sum of the stress in the peeling direction at the end face on the front side in the traveling direction where the reaction force in the peeling direction acting on the bonding interface from the workpiece can be maximized Lowered. Therefore, even when the peripheral speed of the grindstone is increased and the cutting amount or the feed speed is increased, the separation of the segment chips from the base member at the bonding interface is suppressed, so that the grinding speed can be further increased.
[0012]
[Third Means for Solving the Problems]
The gist of the third invention for achieving the above object is that a plurality of segment chips having a ground surface composed of a superabrasive layer in which superabrasive particles are mutually bonded by a vitreous binder are used as a base. The members are closely fixed to each other on one circumference centered on the axis of the member, and are driven to rotate around the axis, thereby performing the grinding process on the ground surface having a side surface shape of a truncated cone as a whole. A segment-type superabrasive grinding wheel, wherein a fixed interface between the segment tip and the base member is inclined with respect to the axis in the same direction as the ground surface.
[0013]
[Effect of the third invention]
According to this configuration, in the segment type superabrasive grinding wheel having the grinding surface inclined with respect to the axial direction, the fixed interface is located on the outer peripheral side as going in one direction along the axial direction of the base member. Thus, it is inclined in the same direction as the grinding surface with respect to the axis. Therefore, in a grinding wheel for grinding in which the ground surface and the ground surface of the work material are inclined with respect to the axial direction of the base member, when used for plunge grinding in which this is moved in the axial direction. The stress acting in the peeling direction of the bonding interface is reduced on one end face side where the diameter dimension of the ground surface is relatively small. That is, when a bonding interface parallel to the axial direction is provided, the largest stress in the peeling direction is reduced on the side having the smaller diameter. Therefore, even when the peripheral speed of the grindstone is increased and the cutting amount or the feed speed is increased, the separation of the segment chips from the base member at the bonding interface is suppressed, so that the grinding speed can be further increased.
[0014]
Note that, in the above-described embodiment, it is sufficient that the bonding interface is inclined in the same direction as the grinding surface with respect to the axial direction of the base member. Therefore, even if the bonding interface and the grinding surface are parallel to each other, there is no problem. Absent.
[0015]
Other aspects of the invention
Here, preferably, in the first invention, the first grinding surface is provided at one end in the axial direction and is inclined so that the diameter increases toward the other end. And a second grinding surface continuous from the first grinding surface and parallel to the axial direction. According to this configuration, in the segment type superabrasive grinding wheel for traverse grinding designed to perform rough grinding on the first grinding surface and perform finish grinding on the subsequent second grinding surface, the forward direction of the segment type superabrasive wheel is provided. Since the stress in the peeling direction at the bonding interface is reduced on the side of the first ground surface located, the grinding efficiency can be suitably increased.
[0016]
In the case of the above configuration, the fixing interface may be formed as an inclined surface whose diameter increases from the end surface on the first grinding surface side to the other end surface, but may be formed at an intermediate portion thereof. May be inclined in two directions so as to have the largest diameter. In other words, when the orientation at the time of use of the grindstone is determined based on the shape, when the fixing interface is parallel to the axis, the stress in the peeling direction becomes largest on one end surface side, which may be generated. Since it is sufficient to reduce the stress in the peeling direction, the fixed interface may be a surface inclined in two directions such as a V-shape or a U-shape if it is an inclined surface.
[0017]
In the first to third aspects of the present invention, more preferably, the fixing interface has a diameter linearly increased or decreased in relation to an axial position of the base member. In this way, there is an advantage that the shape design and the manufacturing process for securing the required strength are simplified as compared with the case where the diameter dimension can be increased or decreased non-linearly.
[0018]
In the first and second aspects of the present invention, more preferably, the maximum value θmax of the inclination angle θ of the fixing interface with respect to the axial direction is such that the axial thickness of the segment chip is ts, and the radius of the segment chip is When the minimum value of the thickness in the direction is tr, the value is determined by the following expression (1), and the minimum value θmin is a value determined by the following expression (2). That is, the angle θ is preferably determined so that the maximum thickness in the radial direction is at least 1.2 times the minimum thickness, and the angle θ is preferably determined such that the maximum thickness in the radial direction is no more than twice the minimum thickness. preferable. When the fixing interface is formed to be inclined, in addition to the increase in the weight of the segment chip, there is a disadvantage that an additional manufacturing process is required to form such an inclined shape. With this configuration, the inclination angle is kept at a small value within a range in which the stress in the peeling direction acting on the adhesion interface can be sufficiently reduced by inclining the adhesion interface. The increase in the volume of the abrasive layer that does not directly contribute to the growth is suppressed. That is, for example, in a grindstone whose grinding surface is parallel to the axial direction, if the fixing interface is inclined with respect to the axial direction, the volume of the abrasive layer that cannot be used for grinding increases as the inclination angle increases. Therefore, it is preferable that the inclination angle is small as long as the stress in the peeling direction can be sufficiently reduced. On the other hand, if the bonding interface is slightly inclined, the effect of the present invention can be enjoyed.However, since the effect of relaxing the stress in the peeling direction is reduced as the inclination angle becomes smaller, the effect of reducing the stress in the peeling direction is smaller than the above minimum value. The effect of improving the grinding speed is significantly reduced. Therefore, the tilt angle can take any value, but the above range is preferable.
tanθmax = tr / ts (1)
tanθmin = 0.2tr / ts (2)
[0019]
In the case of the shape such as the V-shape or U-shape in which the fixing interface is inclined in two directions so that the diameter dimension is the largest at the intermediate portion in the direction along the axial direction, the radius is the radius. The angle θ at which the maximum thickness in the direction becomes 1.2 times to 2 times the minimum thickness is obtained, for example, by using ts ′ = ts / 2 instead of ts in the above equations (1) and (2). The minimum value of the thickness in the radial direction may be maintained, for example, at the same value as that of the conventional segment chip when the fixing interface is not inclined. That is, the maximum value of the thickness in the radial direction is desirably, for example, twice or less the thickness of the conventional one having the fixed interface.
[0020]
In the first to third aspects of the present invention, preferably, the segment tip integrally includes an underlayer on which general abrasive grains are mutually bonded by a vitreous binder under the superabrasive grain layer. And a base layer fixed to the base member. That is, the fixing interface is formed between the base layer and the base member. In a segment type superabrasive wheel using a segment chip having such an underlayer, it becomes easier to use up the superabrasive layer as compared to a case where the entire segment chip is formed of a superabrasive layer. Although there is an advantage, in the present invention, the shape of the interface between the underlayer and the super-abrasive layer is reduced even if the volume of the unusable portion of the segment chip increases due to the inclination of the bonding interface. By forming the shape into an appropriate shape, for example, a shape (for example, parallel) following the ground surface, there is an advantage that an increase in the amount of waste of the expensive superabrasive layer due to the inclined shape is suppressed.
[0021]
In the case where the underlayer is provided as described above, the maximum inclination angle θmax and the minimum inclination angle θmin in the above equations (1) and (2) are tr and ts in the radial direction of the underlayer. It is a value obtained by substituting the thickness tir with the thickness tis in the axial direction. In addition, the underlayer is generally formed integrally with the superabrasive layer and simultaneously subjected to a firing treatment. For this reason, those interfaces have a sufficiently high peel strength as compared with the bonding interface between the segment chip and the base member, and thus do not substantially affect the strength of the segment type superabrasive grindstone.
[0022]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, an embodiment of the present invention will be described in detail with reference to the drawings.
[0023]
FIG. 2 is a plan view showing the entirety of a segment type superabrasive grindstone (hereinafter, simply referred to as a grindstone) 30 according to one embodiment of the present invention. In the figure, the grindstone 30 has, for example, a mounting hole 32 having an overall diameter of about 400 (mm), a thickness of about 5 (mm), and a diameter of about 25 (mm) at the axis. ing. The whetstone 30 is composed of a segment tip 34 having an arc-shaped and uniform circumferential dimension arranged on the outer peripheral surface of a disc-shaped base member 36 centered on the axis O without any gap in the circumferential direction. In addition to being integrally fixed to the base member 36 with a resin adhesive, the adjacent segment chips 34 are integrally connected with an adhesive with a gap as small as possible.
[0024]
The segment chip 34 has a uniform cross-sectional shape in the axial direction of the grindstone 30 perpendicular to the paper surface, and the inner peripheral surface and the outer peripheral surface are concentric arcs centered on the axis O. ing. The segment chip 34 is composed of two layers stacked in the radial direction of the arc, and includes a base layer 38 fixed to a cylindrical outer peripheral surface (fixed surface) of the base member 36 and a lower layer 38 below the base layer 38. An abrasive layer 40 provided on the outer peripheral side of the base layer 38 and actually performing a grinding process. The dimension of each part of the segment chip 34 is such that the length L on the outer peripheral surface thereof is, for example, about 40 (mm), the thickness t in the radial direction is, for example, about 11.5 (mm), and the axial direction of the grindstone 30 is Is, for example, about 5 (mm).
[0025]
The underlayer 38 is formed by bonding general abrasive grains, for example, mullite powder having a particle size of about # 180 / # 220 with a vitrified binder, and the abrasive grain layer 40 is formed of superabrasive grains, for example, # 80. / Cubic boron nitride (CBN) abrasive grains having a grain size of about # 100 are bonded with a vitrified binder. The abrasive ratio of the underlayer 38 is 50 parts by volume, the vitrified binder is 16 parts by volume, and the porosity is, for example, 34 parts by volume. On the other hand, the abrasive ratio of the abrasive layer 40 is 50 parts by volume, the vitrified binder is 16 parts by volume, and the porosity is 34 parts by volume. That is, the underlayer 38 and the abrasive layer 40 are similarly configured to be porous except that the material and the particle size of the included abrasive grains are different. The grinding wheel 30 has a cylindrical grinding surface (grinding surface) centered on the axis O formed by the outer peripheral surface of the segment chip 34, that is, the outer peripheral surface of the abrasive layer 40. By being rotated around the center O, the work material 10 and the like are ground on the outer peripheral surface.
[0026]
The base member 36 is made of a light alloy material such as an aluminum alloy, for example, and has a diameter of about 390 (mm) and a thickness of about 5 (mm). That is, the segment chip 34 and the base member 36 constituting the grindstone 30 have the same thickness.
[0027]
FIG. 3 is a diagram showing a main part of a cross section of the grinding wheel 30 described above. As described above, in the whetstone 30, the segment chips 34 are fixed to the outer peripheral surface of the base member 36 via the synthetic resin layer 42 having a thickness of, for example, about 0.05 (mm). The fixed interface is not a cylindrical surface parallel to the axis of the grindstone 30. That is, the segment chip 34 has the thickness t (about 11.5 (mm)) on both end surfaces 44 and 46 of the grindstone 30, but goes inward in the axial direction of the grindstone 30. Accordingly, the thickness dimension is linearly reduced according to the following formula, and the thickness dimension is about ti = 9 (mm) at the central position in the thickness direction of the grindstone 30.
[0028]
For this reason, the fixing interface between the segment chip 34 and the base member 36, that is, the fixing surface of the segment chip 34 and the outer peripheral surface of the base member 36 are parallel to the end surfaces 44 and 46 passing through the center position of the base member 36 in the thickness direction. Symmetrically with respect to the direction of the axis of the grinding wheel 30. The inclination angle θ is, for example, about 45 °, and the angle formed by the two inclined surfaces forming the respective pairs of the fixing surface of the segment chip 34 and the outer peripheral surface of the base member 36 is, for example, 90 °. That is, the segment chip 34 has a valley shape (V shape) in which the inner peripheral surface forms a dihedral angle of 90 °, and the base member 36 has a mountain shape (Λ character) in which the outer peripheral surface is inverted. ) Shape. The diameter of the base member 36 is the value at the end faces 44 and 46, that is, the minimum value of the diameter.
[0029]
The interface between the underlayer 38 and the abrasive layer 40 is parallel to the surface and the axial direction of the abrasive layer 40, and the abrasive layer 40 has a uniform thickness of, for example, about tg = 5 (mm). It has dimensions. On the other hand, the underlayer 38 has a shape whose thickness dimension linearly increases and decreases in the direction of the grinding wheel axis. Further, as is clear from the dimensions of the above-described portions, the minimum thickness tir of the underlayer 38 in the radial direction of the grindstone 30 is about ti-tg = 4 (mm), and the maximum thickness tirM is t-tg = 6.5 (mm). ), And the thickness dimension tis of the base layer 38 in the axial direction is about 5 (mm), which is equal to the thickness W of the grindstone. Therefore, the inclination angle θ is such that the maximum thickness tirM is 1.6 times the minimum thickness tir. Degree, that is, an angle having a value of twice or less (that is, an angle smaller than a value given by tan θ = 2tir / tis).
[0030]
FIG. 4 is a diagram showing a state in which traverse grinding of the work material 10 is being performed using the grinding wheel 30 described above. In the figure, the outer peripheral surface of the work material 10 is ground by sending the grindstone 30 in the direction of the arrow S while rotating it around its axis. In this grinding mode, since the work material 10 is mainly scraped off at the end surface 44 on the front side in the traveling direction of the segment chip 34, the segment chip 34 is attached to the side surface of the distal end portion pressed against the work material 10 by an arrow in the figure. It receives a reaction force (side pressure) in the direction indicated by R. The reaction force R acts as a moment on the fixed interface, that is, the synthetic resin layer 42, and a tensile stress F corresponding to the moment acts on a portion of the fixed interface facing the front side in a direction perpendicular to the portion. Will do. Similarly, a compressive stress corresponding to the moment acts on the opposite slope.
[0031]
According to this embodiment, as a result of the fixing interface being inclined with respect to the rotation axis, the stress F generated in the fixing interface due to the lateral pressure in the direction in which the segment chip 34 is peeled off depends on the moment. Since it becomes a component of the stress, the sum of the stresses acting in the peeling direction on the front end face 44 where the stress in the peeling direction is usually highest is reduced. Therefore, there is an advantage that even if the rotation speed and the feed speed in the axial direction of the grindstone 30 are relatively high, the segment chips 34 are not easily separated from the base member 36. For example, even if the peripheral speed of the grindstone is increased to about 160 (m / s) and the load in the grindstone feed direction (axial direction) is increased to about 98 (N) (= 10 (kgf)), the separation of the segment chip 34 is completely lost. Does not occur.
[0032]
FIG. 5 to FIG. 7 are diagrams illustrating the results of the stress analysis during the above-described grinding. In this analysis, in the grinding wheel 30 having the dimensions and shape as described above, the peripheral speed of the grinding wheel is 160 (m / s), the load in the feed direction is 98 (N) (= 10 (kgf)), and the finite element method is used. This was performed using In each of the drawings, "conventional" is described in which the underlayer is formed to have a uniform thickness of about 4 (mm) so that the inner peripheral surface of the segment chip is formed parallel to the outer peripheral surface. A conventional segment-type superabrasive grindstone configured similarly to the grindstone 30, except that the outer peripheral surface of the base member is formed in a cylindrical surface parallel to the axis corresponding thereto, for example, the grindstone shown in FIG. 10 is a diagram illustrating stress in a grindstone having a cross-sectional shape similar to FIG.
[0033]
FIG. 5 shows a stress in a state where the grindstone 30 is rotated at the above peripheral speed but not in contact with the work material 10, that is, a stress acting in a peeling direction on a fixed interface due to rotation such as centrifugal force. Only represents. In the conventional grindstone, the stress caused by the rotation has a substantially uniform value over the entire length in the grindstone thickness direction, that is, the axial direction. On the other hand, by increasing the diameter of the base member 36 in the central part in the thickness direction, the grindstone 30 of the present embodiment, in which the fixing interface is located on the outer peripheral side as compared with the both end faces 44 and 46, is used. The stress is increased by a factor of about 2 at the central portion relatively located on the outer peripheral side, while the stress is reduced by about 1/2 at both end portions located relatively on the inner peripheral side. I have.
[0034]
FIG. 6 shows only the stress in the peeling direction based on the side pressure received from the work material 10 when the grindstone 30 is grinding the work material 10. That is, in this figure, the stress due to rotation is not considered. As is clear from the figure, in the conventional grindstone in which the bonding interface is provided in parallel to the axial direction, an extremely high stress in the peeling direction acts on the front end face 44 pressed against the work material 10, while the thickness direction increases. The stress becomes substantially zero at a position slightly behind the central portion of, and the rear end surface 46 is negative, that is, has a compressive stress. On the other hand, in the whetstone 30 of the embodiment, although the stress tends to decrease from the front end face 44 toward the rear end face 46 as a whole, the stress at the end face 44 is reduced to about 1/2 of the conventional one. At the same time, the stress at the end face 46 is increased to substantially zero.
[0035]
FIG. 7 shows the sum of the above two stresses, which is substantially equal to the stress actually received during the grinding process. As described above, in the conventional grindstone, while the stress due to rotation is substantially uniform, the stress based on the lateral pressure is significantly large at the front end surface 44 and negative at the rear end surface 46. The total stress in the peeling direction is large at the front end surface 44 and small at the rear end surface 46. On the other hand, in the grindstone 30 of the embodiment, the stress due to the rotation is low at both end faces 44 and 46, and the stress based on the lateral pressure is low at the front end face 44 and slightly high at the rear end face 46. Therefore, the total stress in the peeling direction in the peeling direction becomes slightly higher in the vicinity of the center in the thickness direction of the grindstone 30 as compared with the conventional one, but the front side end face 44 is about 1/2 of the conventional one. Value. The stress on the rear end surface 46 is substantially the same as that of the conventional grindstone.
[0036]
Generally, peeling of the segment chip 34 on the grindstone 30 occurs from the end faces 44 and 46 as a base point, and peeling hardly starts from the inside. For this reason, as described above, the stress in the peeling direction at the front end face 44 is reduced, and the stress in the peeling direction at the rear end face 46 is maintained at the same level as in the past, so that the peeling at both end faces 44 and 46 is performed. If the maximum value of the stress in the direction becomes lower than the maximum value of the stress on both end faces of the conventional grindstone, the peel strength of the whole grindstone 30 will be increased. For this reason, even if the grinding process is performed at the high peripheral speed and the high load in the feed direction as described above, the segment chips 34 do not peel off.
[0037]
The grinding wheel 30 is, for example, a segment chip in which the base layer 38 and the abrasive layer 40 are integrated and the inner peripheral surface is parallel to the outer peripheral surface, according to a normal process, that is, through a powder press molding and firing process. Is manufactured by subjecting an inner peripheral surface thereof to V-shaped groove processing. This groove processing is performed, for example, by using a diamond wheel having a mountain-shaped (Λ-shaped) outer peripheral cross section, scraping the inner peripheral surface of the underlayer 38, which is much softer than that, and transferring the mountain-shaped shape. Is done. Since the underlayer 38 and the abrasive layer 40 are integrated by being fired at the same time, the peel strength is extremely high as compared with the bonding interface with the base member 36 fixed by the synthetic resin layer 42. No peeling occurs at the interface between the underlayer 38 and the abrasive layer 40.
[0038]
The grindstone 30 provided with the segment chips 34 in which the abrasive grains are bonded to each other with the vitrified binder, as described above, although the individual segment chips 34 can be integrally manufactured as a whole, but the metal chips are simultaneously formed during firing. It cannot be fixed to the base member 36. Therefore, as described above, the bonding is performed via the synthetic resin layer 42. In such a segment-type superabrasive grindstone 30, the bonding interface formed by the synthetic resin layer 42 has the lowest strength. Therefore, there is an advantage that separation at the interface is suppressed.
[0039]
In short, according to the present embodiment, the fixed interface between the segment chip 34 and the base member 36 is inclined by the angle θ with respect to the axis of the base member 36, so that the grinding wheel 30 rotates during the grinding process. The stress in the peeling direction acting on the bonding interface based on the centrifugal force and the like generated due to and the lateral pressure acting from the work material 10 causes the bonding interface to be parallel to the axis at both end positions in the axial direction. It is reduced compared to the case where it is provided. For this reason, even if the peripheral speed of the grindstone is increased and the cutting depth or the feed speed is increased, the separation of the segment chip 34 from the base member 36 at the fixing interface is suppressed, so that the grinding speed can be further increased.
[0040]
Moreover, according to the present embodiment, in the grindstone 30 having the cylindrical grinding surface, the grindstone 30 is inclined such that the fixed interface is located on the outer peripheral side toward the inside in the axial direction of the base member 36. For this reason, the grindstone 30 has a grinding surface shape capable of performing traverse grinding using either of the both end surfaces 44 and 46, but since the bonding interface is also provided symmetrically in the thickness direction, When used in any direction, there is an advantage that the stress in the peeling direction at the end face on the front side in the traveling direction is reduced.
[0041]
Next, another embodiment of the present invention will be described. In the following description, portions common to the above-described embodiment will be denoted by the same reference numerals, and description thereof will be omitted.
[0042]
FIG. 8 is a diagram illustrating a grinding state in a case where the present invention is applied to the grinding wheel 50 for contouring grinding. The grindstone 50 is used, for example, for grinding along a processing contour line indicated by a dashed line 52 in the drawing. The workpiece is moved toward or away from the workpiece 10.
[0043]
FIG. 9 shows a cross section near the outer peripheral edge of the grindstone 50. As shown in the figure, the segment chip 54 provided on the grindstone 50 also includes an underlayer 38 and an abrasive layer 40, and their interface is provided in parallel with the rotation axis. The interface between the base member 36 and the base member 36 is inclined with respect to the rotation axis. The inclination angle is, for example, about 39 ° with respect to the rotation axis. Therefore, in the contouring grinding using the grindstone 50, similarly to the grindstone 30, the stress in the peeling direction due to the side pressure received from the work material 10 when the workpiece is fed in the direction of the arrow S is relaxed. Also, there is an advantage that the segment chip 54 is hardly peeled off even under high-speed and high-load grinding conditions.
[0044]
In the grinding wheel 50 described above, the outer peripheral surface, that is, the grinding surface, is inclined at an angle of, for example, about 5 ° with respect to the rotation axis in a range from the front end surface 44 to the intermediate position toward the rear end surface 46 in the feed direction. A tapered surface 56 is provided. The tapered surface 56 performs the roughing of the contour grinding, but as a result of such a shape, the grindstone 50 can be used only in a fixed direction shown in the drawing. Therefore, in this whetstone 50, it is sufficient that only the stress in the use mode in which the end face 44 is located on the front side is reduced, and it is not necessary to form the fixing interface 44 in a V-shape inclined in two directions. That is, as shown by a dashed line in the drawing, the diameter of the base member 36 may be an inclined surface 58 that is inclined in one direction such that the diameter gradually decreases from the front end surface 44 to the rear end surface 46.
[0045]
FIG. 10 is a diagram illustrating a cross section of a main part of a grindstone 70 according to still another embodiment in a used state. In the drawing, a grindstone 70 is for grinding a sloped surface of a work material 72 such as a valve having a surface inclined with respect to the rotation axis, that is, a valve face. Therefore, the grinding surface provided on the outer peripheral surface of the grindstone 70, that is, the surface of the segment chip 74, is formed as an inclined surface following the inclined surface, for example, inclined at an angle of about 45 ° in the axial direction. The inner peripheral surface of the segment chip 74, that is, the surface fixed to the base member 36 is parallel to the ground surface. That is, in the present embodiment, the fixed interface between the segment chip 74 and the base member 36 is formed in a direction parallel to the ground surface but inclined with respect to the rotation axis. In the drawing, reference numeral 80 denotes a holder for holding the work material 72 and rotating it around its axis.
[0046]
The grindstone 70 configured as described above, for example, grinds the work material 72 by moving in the direction of the arrow P while rotating about its axis. That is, in the present embodiment, the grindstone 70 is not moved in the axial direction. Even in such a usage mode, since the work surface and the grinding surface are inclined, a part of the reaction force from the work material 72 toward the grindstone 70 has a stress F in a direction parallel to the axis. Therefore, a moment based on the stress F can act on the fixed interface. Therefore, if the bonding interface is provided in parallel with the axis, a large stress in the peeling direction is generated at the end face 76 located on the left side in the figure, that is, the end face on the small diameter side of the grindstone 70, so that the peeling of the segment chip 74 may occur. The grinding wheel peripheral speed and the cutting depth are limited so as not to occur. However, according to the present embodiment, the fixing interface is inclined such that the diameter dimension of the base member 36 increases from the end surface 76 on the small diameter side of the grindstone 70 toward the opposite end surface 78. The stress in the peeling direction is reduced by a corresponding amount, and the stress in the peeling direction based on the centrifugal force is also reduced according to the reduction amount of the diameter dimension.
[0047]
Therefore, as compared with the conventional grindstone in which the bonding interface is parallel to the axial direction, the stress in the peeling direction at the end face 76 is reduced as a whole, so that the peeling of the segment chip 74 is suppressed, and a high peripheral speed and Grinding can be performed with a large cutting depth.
[0048]
That is, according to the present embodiment, in the grindstone 70 having the grinding surface inclined with respect to the axial direction, the fixed interface is located on the outer peripheral side as it goes in one direction along the axial direction of the base member 36. In addition, the valve is tilted with respect to the axis in the same direction as the ground surface, so that the ground surface and the ground surface of the workpiece 72 are tilted with respect to the axial direction of the base member 36. In the face grinding grindstone 70, when it is used for plunge grinding to be moved in the axial direction, the stress acting on the one end surface 76 side where the diameter of the ground surface is relatively small is reduced in the peeling direction of the bonding interface. Can be Therefore, even if the peripheral speed of the grindstone is increased and the cutting amount or the feed speed is increased, the segment chips 74 are prevented from being separated from the base member 36 at the bonding interface, so that the grinding speed can be further increased.
[0049]
As described above, the present invention has been described in detail with reference to the drawings. However, the present invention can be implemented in other embodiments.
[0050]
For example, in the embodiment, a case has been described in which the present invention is applied to the grindstones 30, 50, and 70 provided with the segment chips 34, 54, and 74 in which the base layer 38 and the abrasive layer 40 are integrally provided. The present invention is similarly applied to a grindstone that does not include the base layer 38 but is entirely formed of the abrasive layer 40 such as the segment chips 34 and the like.
[0051]
In the embodiment, the inclination angle of the bonding interface with respect to the axial direction is set to about 45 ° for the grindstone 30, about 39 ° for the grindstone 50, and about 45 ° for the grindstone 70. Is determined by comparing the magnitude of the stress that can be alleviated by the inclination with the complexity of the manufacturing process that increases with the inclination and the wasteful increase in the volume of the underlayer 38, and the like. On the other hand, an appropriate angle is set within a range larger than 0 ° and smaller than 90 °. However, considering the increase in weight of the segment chip 34 and the like due to the inclination, the increase in centrifugal force, the complexity of the process, and the increase in volume that does not directly contribute to grinding, etc., the maximum thickness in the radial direction is the minimum thickness of 1.2. The range of ~ 2 times is most preferred.
[0052]
Further, in the embodiment, the inclination of the fixing interface changes linearly in the cross section, that is, linearly in the thickness direction. However, a non-linear inclined surface having a curve in the cross section may be used.
[0053]
Further, in the embodiment shown in FIG. 10, the bonding interface is formed parallel to the grinding surface, but in this embodiment, the bonding interface is slightly inclined in the same direction as the grinding surface with respect to the axial direction. If so, a stress relaxing effect can be obtained, so that the inclination angle may be larger or smaller than the inclination angle of the ground surface.
[0054]
Further, in the embodiment, the underlying layer 38 is configured as a general abrasive layer containing mullite powder, but the abrasive included in the underlying layer 38 may be alumina, SiC, or the like as long as the abrasive is an inexpensive general abrasive. No problem.
[0055]
Further, in the embodiment, the abrasive layer 40 includes CBN as abrasive particles, but the abrasive layer 40 includes diamond abrasive particles because it is sufficient if the abrasive layer 40 includes superabrasive particles. No problem.
[0056]
Although not specifically exemplified, the present invention can be variously modified without departing from the gist thereof.
[Brief description of the drawings]
FIG. 1 is a diagram illustrating a problem in traverse grinding.
FIG. 2 is a plan view showing the entirety of a segment type superabrasive grinding wheel according to one embodiment of the present invention.
FIG. 3 is a diagram illustrating a cross-sectional structure of the grindstone of FIG. 2;
FIG. 4 is a diagram showing an embodiment of a grinding process using the grindstone of FIG. 2;
FIG. 5 is a view for explaining stress acting on a synthetic resin layer based on centrifugal force in the grindstone of FIG. 2 in the thickness direction of the grindstone.
FIG. 6 is a view for explaining a stress acting on a synthetic resin layer based on a reaction force from a work material in the grindstone of FIG. 2 in a thickness direction of the grindstone.
FIG. 7 is a diagram illustrating a resultant force of a centrifugal force and a reaction force from a work material in a thickness direction of a grindstone.
FIG. 8 is a view for explaining an embodiment of a grinding process using a grindstone according to another embodiment of the present invention.
FIG. 9 is an enlarged view showing a main part of a cross section of the grinding wheel of FIG. 8;
FIG. 10 is a view for explaining an embodiment of a grinding process using a grindstone according to still another embodiment of the present invention.
[Explanation of symbols]
30: Segment type superabrasive grinding wheel
34: Segment chip
36: Base member

Claims (3)

Multiple segment chips with a grinding surface consisting of a superabrasive layer in which superabrasive particles are bonded to each other by a vitreous binder are closely adhered to one another on a circle around the axis of the base member Is a segment type super-abrasive grindstone that performs a grinding process on the grinding surface by being rotationally driven about its axis.
Based on the centrifugal force and the reaction force acting from the work material, the stress in the direction of peeling them generated at both end positions in the direction parallel to the axis out of the fixed interface between the segment chip and the base member, A segment type super-characteristic characterized in that the bonding interface is inclined with respect to the axis so that the maximum stress generated at both end positions when the bonding interface is parallel to the axis is lower. Abrasive whetstone. Multiple segment chips with a grinding surface consisting of a superabrasive layer in which superabrasive particles are bonded to each other by a vitreous binder are closely adhered to one another on a circle around the axis of the base member Is a segment type super-abrasive grindstone that performs a grinding process on the grinding surface that forms a cylindrical surface as a whole by being rotationally driven around its axis.
A segment-type super-type, wherein a fixed interface between the segment chip and the base member is inclined so as to be located on an outer peripheral side from both end positions in a direction parallel to the axis toward an intermediate position between them. Abrasive whetstone. Multiple segment chips with a grinding surface consisting of a superabrasive layer in which superabrasive particles are bonded to each other by a vitreous binder are closely adhered to one another on a circle around the axis of the base member Is a segment type super-abrasive grindstone that performs a grinding process on the grinding surface forming a side surface shape of a truncated cone as a whole by being rotationally driven around the axis thereof,
A segment type superabrasive grinding wheel, wherein a fixed interface between the segment tip and the base member is inclined in the same direction as the ground surface with respect to the axis.

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