JP4682592B2 - Grinding wheel - Google Patents

Description

  The present invention relates to a grinding wheel of a grinding machine that grinds a rotating workpiece, and in particular, even if the rotating grinding wheel is centrifugally expanded by a rotational force, the grinding wheel surface that is a processing surface is simply expanded to be tapered. The present invention relates to a grinding wheel of a grinding machine that can easily perform truing or dressing (hereinafter referred to as truing) at a low rotational speed and is excellent in processing accuracy.

  Conventionally, as a grinding wheel of a grinding machine, a grinding wheel layer is formed on the outer peripheral surface of a disc-shaped grinding wheel core, and a grinding wheel is fixed to a grinding wheel shaft or the like around a mounting hole for the grinding wheel shaft at the center. There is known one in which a fixing hole is formed (for example, Patent Document 1). And this grinding wheel is attached to the mounting hub part or flange part of the said grinding wheel axis | shaft with a fixing bolt etc. from the fixing hole part, or is attached to the grinding wheel axis | shaft via the attachment flange etc. of another member.

Further, a truing device for correcting the grinding wheel shape of a grinding wheel is known (for example, Patent Document 2).
JP 2002-103236 A (FIGS. 1 and 2) Japanese Patent No. 2749154

  However, the truing of the grinding wheel is performed in order to correct the grinding wheel shape before starting the processing and regenerate the sharpness of the grinding wheel, but the cross-sectional shape of the conventional grinding wheel as shown in Patent Document 1 is as follows. Only the case where the grinding wheel is stopped is considered, and the shape change during rotation is not considered.

  That is, a centrifugal force acts on the rotating grinding wheel, and as a result, the grinding wheel core expands due to the centrifugal force. Centrifugal force acting on each part of the grinding wheel core in the axial direction depends on the rotational speed, radius and weight of each part (including the grinding wheel layer, the same applies hereinafter). The grinding wheel is attached to the grinding wheel shaft via a flange or the like, but the restraining regions where the grinding wheel core abuts on the grinding wheel shaft side and restraining force is generated are different on both sides of the grinding wheel core. The expansion of the grindstone core due to the centrifugal force is determined by the relationship between the centrifugal force, the rigidity of each part of the grindstone core, and the restraining force of the grindstone core.

  FIG. 7 is a diagram showing a change in shape when the conventional grinding wheel is stopped and rotated. As shown in FIG. 7A, the conventional grinding wheel does not change its shape when stopped, but when the grinding wheel rotates, the grinding wheel follows the relationship between the centrifugal force acting on each part in the axial direction of the grinding wheel core and the restraining force. A car, that is, a grindstone core, generally centrifugally expands unevenly, and the grindstone outer peripheral surface becomes tapered as shown in FIG. This is because when the grinding wheel rotates, the restraining force differs between the side where the grinding wheel core is restrained by the grinding wheel shaft and the side where it is not restrained by the grinding wheel shaft, and the side that is not restrained is more restrained than the side where it is restrained. This is also because the rigidity related to the elastic deformation of the grindstone core in the radial direction becomes small. As a result, the grindstone core is deformed in the direction in which the restraining force is large, and the grindstone core and the grindstone layer formed on the outer periphery of the grindstone core are unevenly expanded. Since this shape change also depends on the rotational speed of the grinding wheel, truing must be performed at the same rotational speed as when the grinding wheel is processed.

  In recent grinders equipped with a grinding wheel using CBN (Cubic Boron Nitrid) abrasive grains, the grinding wheel is driven at high speed in order to increase the peripheral speed of the grinding wheel and improve the grinding efficiency. Is done. In order to true the grinding wheel sharply, the peripheral speed ratio between the grinding wheel and the truing roll is generally set to 0.75 to 0.8.

  For example, when the peripheral speed of the grinding wheel is set to 120 m / s, the diameter of the truing roll is about 100 mm. Therefore, the rotational speed of the truing roll is 15,000 to 20,000 rpm, and the truing roll can be rotated at a very high speed. It is necessary to attach to the rotating shaft. However, such a truer that can rotate at a high speed is expensive. When a truer that can rotate only at a relatively low speed is used, it is trued under the condition of the rotation speed at the time of machining, and it is machined with the true wheel. As a result, this shape error is transferred to the workpiece, resulting in a decrease in grinding accuracy.

  Therefore, the object of the present invention is that even if a grinding wheel rotating at a predetermined number of revolutions is centrifugally expanded by a rotational force, the grinding wheel surface as a processing surface does not become a taper shape or the like only by expanding uniformly, and truing is prevented. An object of the present invention is to provide a grinding wheel for a grinding machine that can be easily performed at a low rotational speed and has excellent processing accuracy.

In order to achieve the above-mentioned object, the first invention comprises a grindstone core portion and a grindstone layer formed on the outer peripheral portion thereof. The grindstone shaft is rotatably supported and has a flange portion for attachment. In the grinding wheel that is attached to the wheel and rotates at a predetermined rotational speed, the grinding wheel core portion includes a plurality of fixing hole portions for fixing bolts to the flange portion of the grinding wheel shaft, and the plurality of fixing hole portions. And a notch groove provided concentrically with the grindstone shaft on the end surface on the flange portion side of the grindstone shaft, and provided on the flange portion side. An object of the present invention is to provide a grinding wheel for a grinding machine, wherein the rigidity of the end face is smaller than the rigidity of the end face opposite to the flange portion.

  According to the present invention, the grindstone core portion is configured in a shape where the centrifugal expansion force becomes equal at each position in the axial direction at a predetermined rotational speed. Some grindstone surfaces expand almost evenly. As a result, in a grinding wheel of a grinding machine, truing can be easily performed at a low rotational speed, and a highly accurate grinding wheel shape can be obtained during processing.

(First embodiment)
Hereinafter, the overall configuration of the grinding wheel according to the first embodiment of the present invention and the grinding machine on which the grinding wheel is mounted will be described.

(Overall configuration of grinding machine)
FIG. 1 is a plan view schematically showing the overall configuration of the grinding machine. Below, the outline of the whole structure of the grinding machine which concerns on 1st Embodiment is demonstrated.

  The entire driving of the grinding machine 100 is controlled by a computer numerical control device (CNC). A Z-axis rail 11 is provided on the upper surface of the bed 10 constituting the base portion of the grinding machine 100, and the Z-axis moving body 20 is placed on the rear side of the bed 10 via the Z-axis rail 11. Then, it is driven to move in the Z-axis direction (left-right direction). An X-axis rail 21 is provided on the upper surface of the Z-axis moving body 20, and a grindstone table 30 that is an X-axis moving body is placed on the Z-axis moving body 20 via the X-axis rail 21. It is driven to move in the axial direction (front-rear direction). The wheel head 30 includes a wheel head main body 50 on which a wheel driving motor 53 is mounted. In addition, a grindstone shaft unit 51 is mounted on the grindstone base body 50. The grindstone shaft unit 51 is attached to a grindstone shaft 52 that is rotatably supported by the grindstone shaft unit 51, and is rotationally driven by a grindstone drive motor 53 via a drive belt 54. A grinding wheel T is provided. The work table 40 placed on the front side of the bed 10 is provided with a pair of left and right headstocks 41 that support the work W and rotate. The pair of left and right headstocks 41 includes a main shaft 42 that supports the end portion of the workpiece W, and the main workpiece 42 is rotated to rotationally drive the supported workpiece W.

  A disc-shaped tourer 43 is provided concentrically on the spindle 42 of the spindle stock 41. Thus, by providing a truer at a position close to the processing point, truing can be performed in a vibration state close to that at the time of processing. In addition, the number of parts can be reduced and the size can be reduced as compared with the case where a separate truer is installed, and the cost can be reduced. However, since it is rotated by the main shaft 42, the truer rotates at a relatively low speed.

  FIG. 2 is a cross-sectional view of the grinding wheel according to the first embodiment. In the following description, the x-axis is the central axis direction of the grindstone shaft 52 and the y-axis is the radial direction toward the outer periphery, and the origin is on the central axis of the grindstone shaft 52 and on the opposite side of the flange portion 52f of the grindstone core 55. The intersection with the end face 55g. The grinding wheel T includes a disc-shaped grinding wheel core 55, a grinding wheel layer 56 formed on the outer peripheral surface of the grinding wheel core 55, a mounting hole 52h to the grinding wheel shaft 52 in the center, and a grinding stone core 55 around the mounting hole. And a fixing hole 55h for fixing to the grindstone shaft 52 or the like. The grinding wheel T is attached to the mounting hub portion or the flange portion 52f of the grinding wheel shaft 52 by fixing means such as a mounting bolt B from the fixing hole 55h. Or you may attach to the grindstone axis | shaft 52 via the flange for attachment of another member.

  The grindstone core 55 is provided with a notch groove 57 concentrically provided around the mounting hole 52h on the end surface 55f of the grindstone core 55 on the flange 52f side.

(Operation of grinding wheel T)
When the grinding wheel T rotates, centrifugal force works, and as a result, the grinding wheel core 55 expands by centrifugal force. Here, the force acting on the grindstone core 55 is as follows. Centrifugal force acts on each part of the grindstone core 55 in the x-axis direction, and this is determined by the rotational speed, radius and weight. Further, at each part in the x-axis direction of the grindstone core 55, a restraining force is generated by being fixed to the grindstone shaft 52 on the inner diameter side (inner side in the y-axis direction) than the notch groove 57, and is large at the end surface 55f, and the end surface 55g Smaller than Moreover, each part of the x-axis direction of the grindstone core 55 has rigidity, and this is mainly determined by the shape of the grindstone core 55 and the longitudinal elastic modulus. Therefore, the centrifugal expansion amounts of the grindstone core 55 and the grindstone layer 56 are determined by the centrifugal force, the restraining force, and the rigidity in each part in the x-axis direction.

  The notch groove 57 formed in the grindstone core 55 affects the weight and rigidity of each part in the x-axis direction of the grindstone core 55 described above, and the weight is determined by the size of the notch groove 57. Further, the notch groove 57 determines the restraint force of the grindstone core 55 itself on the outer diameter side (y-axis direction outer side), thereby determining the rigidity.

  In the first embodiment, since the notch groove 57 of the grindstone core 55 is provided on the end surface 55f on the flange portion 52f side, the portion of the grindstone core 55 that is located toward the end surface 55f has a smaller weight. On the outer diameter side of the notch groove 57, the restraining force of the grindstone core 55 itself is small and the rigidity is small. On the other hand, on the inner diameter side of the notch groove 57, the grindstone core 55 is connected to the grindstone shaft 52 as shown in FIG. The restraint force is large by fixing. Accordingly, by appropriately providing the notch groove 57, the centrifugal expansion amount that warps to the right in FIG. 2 as shown in FIG. 7B from the mounting hole 52h, and the left in FIG. 2 starting from the notch groove 57. The amount of centrifugal expansion that warps is synthesized. Therefore, the amount or force of centrifugal expansion determined by the centrifugal force, the restraining force, and the rigidity can be made substantially equal in each part in the x-axis direction. Here, the shape of the notch groove 57 is determined by the shape of the grindstone core (grindstone width, grindstone diameter) and the grindstone rotation speed. By changing or analyzing them, the shape of the grindstone core 55 and the notch groove 57 can be changed. Shape optimization can be performed.

(Effects of the first embodiment)
According to the first embodiment described above, when the grinding wheel T is rotated at a predetermined number of rotations, the grinding stone surface, which is the processing surface with the same centrifugal expansion force due to the rotation, is evenly expanded, so the shape accuracy of the grinding wheel is good. Machining accuracy is improved. In addition, the grinding wheel surface expands similar to when stopped due to centrifugal expansion, and does not become tapered, etc., so even if truing is performed at a predetermined rotation speed or less, the effect on the reduction in shape accuracy of the grinding wheel surface is not affected. small. Accordingly, since truing can be performed at a low rotational speed, a truing motor can be reduced in size, and space saving, cost reduction, energy saving, low vibration, and displacement due to heat can be reduced. The effect is particularly great in a high-speed grinder using a CBN grindstone.

(Second Embodiment)
FIG. 3 is a cross-sectional view of the grinding wheel of the second embodiment. The grinding wheel according to the second embodiment of the present invention will be described below. In the following description, parts having the same configuration and function as those of the first embodiment are denoted by the same reference numerals.

  As shown in FIG. 3, the grindstone core 55 has an asymmetric cross-sectional shape with a larger x position on the outer peripheral side of the end surface 55 f and a larger x position on the outer peripheral side of the end surface 55 g. Alternatively, it can be said that the cross-sectional shape is inclined with respect to the y-axis. With such a shape, when considering the x position where the grindstone layer 56 exists in FIG. 3, the binding force of the grindstone core 55 itself in the y direction (radial direction) in the portion where the x position is small, that is, in the vicinity of the end face 55 g. Is large and rigid. On the other hand, in the portion where the x position is large, that is, in the vicinity of the end face 55f, the grindstone core 55 does not exist inside the y direction (radial direction), and the restraining force of the grindstone core 55 itself is small and the rigidity is small. Therefore, the centrifugal expansion amount that warps to the right in FIG. 3 from the mounting hole 52h and the centrifugal expansion amount that warps to the left in FIG. 3 from the inclination start point of the end face 55f are combined. Therefore, it can be set as the cross-sectional shape which makes the centrifugal expansion force in the rotation speed of the predetermined grinding wheel T equal in the vicinity of the end surface 55g and the vicinity of the end surface 55f. Therefore, similarly to the first embodiment, it is possible to make the centrifugal expansion force substantially uniform in each part in the x-axis direction.

(Effect of the second embodiment)
According to the second embodiment described above, in addition to the preferable effects of the first embodiment, since there is no notch groove as in the first embodiment, stress concentration is unlikely to occur, and at high speed rotation The breaking strength is improved.

(Comparative example)
FIG. 4 shows a grinding wheel with a notched groove shown in the first embodiment, an inclined grinding wheel shown in the second embodiment, and a rotation in the case of the straight shape shown in the conventional example. An example of the shape change accompanying this is shown. The analysis conditions were titanium (Ti) as the grinding stone core material, 120 m / s as the grinding wheel peripheral speed, and 160 mm as the grinding stone diameter.

  The left end x = 0 of the graph is the position of the end face 55g, and the right end x = 20 of the graph is the position of the end face 55f. The difference in the grinding wheel centrifugal expansion amount at both ends is 1.42 μm in the case of the straight grinding wheel shown in the conventional example, whereas the difference in the notched groove shape shown in the first embodiment is. In the case of the grinding wheel, it was 0.03 μm, and in the case of the inclined grinding wheel shown in the second embodiment, it was 0.37 μm. From this, the shape accuracy with the notch groove shown in the first embodiment or the inclined grinding wheel shown in the second embodiment is greatly improved. Recognize.

(Third embodiment)
FIG. 5 is a sectional view of the grinding wheel of the third embodiment. The grinding wheel according to the third embodiment of the present invention will be described below.

  As shown in FIG. 5, the grinding stone core 55 is subjected to a hardening process such as induction hardening from the surface of the end face 55 g to a predetermined depth in the hardened layer region S illustrated by shading. Specifically, only the surface layer portion of the end face 55g is heated by irradiating the laser beam, and after the laser beam passes, it is rapidly cooled by self-cooling, and the portion is quenched and modified, and the hardness of the quenched portion is large. That is, the longitudinal elastic modulus of the portion is large. Accordingly, in FIG. 5, the rigidity is large in the portion where the x position is small, that is, in the vicinity of the end face 55g.

  On the other hand, the rigidity is small in the portion where the x position is large, that is, in the vicinity of the end face 55f. Therefore, the centrifugal expansion force at a predetermined rotational speed of the grinding wheel T can be made equal between the vicinity of the end face 55g having a small restraining force and high rigidity and the vicinity of the end face 55f having a large restraining force and low rigidity. Therefore, similarly to the first embodiment, it is possible to make the centrifugal expansion force substantially uniform in each part in the x-axis direction.

(Effect of the third embodiment)
According to the third embodiment described above, in addition to the preferable effects of the first embodiment, since the notched groove 57 as in the first embodiment is not provided, stress concentration is unlikely to occur and high-speed rotation is achieved. In this case, the fracture strength can be improved. Moreover, in addition to the preferable effect by 2nd Embodiment, it is not necessary to make it an asymmetrical shape in a cross section like 2nd Embodiment, and manufacture is easy. Further, fine adjustment can be easily performed by adjusting the quenching depth.

(Fourth embodiment)
FIG. 6 is a sectional view of a grinding wheel according to the fourth embodiment. The grinding wheel according to the fourth embodiment of the present invention will be described below.

  As shown in FIG. 6, the grindstone core 55 is integrally fixed to a reinforcing plate 58 made of a material having a longitudinal elastic modulus larger than that of the grindstone core 55. The reinforcing plate 58 may be fixed together with the grindstone core 55 by the mounting bolt B, or the reinforcing plate 58 may be fixed to the end surface 55g by adhesion or welding. Therefore, in FIG. 6, the rigidity is large in the portion where the x position is small, that is, in the vicinity of the end face 55g. On the other hand, the rigidity is small in the portion where the x position is large, that is, in the vicinity of the end face 55f. Therefore, the centrifugal expansion force at a predetermined rotational speed of the grinding wheel T can be made equal between the vicinity of the end face 55g having a small restraining force and high rigidity and the vicinity of the end face 55f having a large restraining force and low rigidity. Therefore, similarly to the first embodiment, it is possible to make the centrifugal expansion force substantially uniform in each part in the x-axis direction.

(Effect of the fourth embodiment)
According to the fourth embodiment described above, in addition to the preferable effects of the first embodiment, since the notched groove 57 as in the first embodiment is not provided, stress concentration is unlikely to occur and high-speed rotation is achieved. In this case, the fracture strength can be improved. Moreover, in addition to the preferable effect by 2nd Embodiment, it is not necessary to make it an asymmetrical shape in a cross section like 2nd Embodiment, and manufacture is easy. In addition, when the reinforcing plate 58 is attached, it is possible to achieve a static balance or a dynamic balance of the grinding wheel, and it is possible to further reduce vibration associated with the replacement of the grinding wheel.

It is a top view which shows the outline of the whole structure of a grinding machine. It is sectional drawing of the grinding wheel of 1st Embodiment. It is sectional drawing of the grinding wheel of 2nd Embodiment. Shape change associated with rotation in the case of the grinding wheel having the notched groove shape shown in the first embodiment, the grinding wheel having the inclined shape shown in the second embodiment, and the straight shape shown in the conventional example. It is a comparison figure which shows one example of these. It is sectional drawing of the grinding wheel of 3rd Embodiment. It is sectional drawing of the grinding wheel of 4th Embodiment. It is a figure which shows the shape change at the time of the stop of the conventional grinding wheel, and rotation.

Explanation of symbols

10 Bed 11 Z-axis rail 20 Z-axis moving body 21 X-axis rail 30 Grinding wheel base 40 Work table 41 Spindle base 42 Spindle 43 Truer 50 Grinding wheel base body 51 Grinding wheel shaft unit 52f Flange portion 52h Mounting hole 52 Grinding wheel shaft 53 Grinding wheel drive motor 54 Driving belt 55 Grinding wheel core 55h Fixing hole 55f, 55g End face 56 Grinding wheel layer 57 Notch groove 58 Reinforcement plate 100 Grinding machine B Mounting bolt S Hardened layer area T Grinding wheel W Workpiece

Claims (1)

In a grinding wheel that has a grinding wheel core portion and a grinding wheel layer formed on the outer periphery thereof, is rotatably supported and is attached to a grinding wheel shaft having a flange portion for attachment, and rotates at a predetermined rotational speed. ,
The grindstone core portion includes a plurality of fixing hole portions for fixing bolts to the flange portion of the grindstone shaft, and an attachment hole provided inside the plurality of fixing hole portions and penetrating the grindstone shaft. And a notch groove concentrically provided with the grindstone shaft on the end surface on the flange portion side of the grindstone shaft, and the rigidity of the end surface on the flange portion side is that of the end surface opposite to the flange portion. A grinding wheel characterized by being smaller than rigidity.