JP2014113683A - Throw-away type hob - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a throw-away type hob capable of highly accurately gear-cutting a tooth flank of a work object gear, by improving a shape of a throw-away tip.SOLUTION: There is provided a throw-away type bob 1 in which substantially quadrangular plate-like throw-away tips 20 for gear-cutting a left tooth flank WL and a right tooth flank WR of a workpiece W, can be laterally alternately attached to and detached from left-right inclined faces of screw thread parts 11 in a hob body 10 along their twist direction. The throw-away tip 20 is mounted in a state where an outer peripheral rake angle γa becomes negative and a side clearance angle θp becomes positive, and a rake face 21L of the throw-away tip 20 is formed in such a convex shape that a hob radial-direction intermediate part in the rake face 21L, projects toward the front side in the hob rotational direction.

Description

  The present invention relates to a throw-away hob in which a throw-away tip can be attached to and detached from a hob body.

  2. Description of the Related Art Conventionally, a throw-away type hob in which a throw-away tip is detachable has been provided as a tool for cutting gears to be machined. In this throw-away type hob, the throw-away tip is alternately arranged on the right and left along the twist direction in the thread portion of the hob body formed in a screw shape. Such a throwaway hob is disclosed in, for example, Patent Document 1.

JP-A-9-117824

  In addition, some throwaway tips are provided that can cut both the left and right tooth surfaces of the gear to be machined by changing the mounting direction and the mounting direction. For this reason, in such a throw-away tip in which both the left and right tooth surfaces can be cut with one tip, the shape needs to be a rectangular flat plate shape.

  That is, in the above throwaway tip, the angle of the edge portion (outer peripheral cutting edge) formed by the rake face and the flank face must be set to 90 °. Thus, when the throw-away tip is mounted on the hob body, the outer peripheral rake angle of the rake face needs to be positive, so the outer rake angle of the rake face must be negative.

  Thus, the attachment position of the throw-away tip attached in a state where the outer peripheral rake angle is negative is different from the ideal ideal attachment position. As a result, when machining by rotating the hob, the rotation locus of the throw-away tip is also different from the ideal rotation locus due to the influence of the lead angle of the thread. turn into. As a result, an error may occur in the tooth profile of the gear to be processed after processing.

  Accordingly, the present invention solves the above-described problems, and provides a throw-away hob that can cut the tooth surface of a gear to be machined with high accuracy by improving the shape of the throw-away tip. With the goal.

The throw-away hob according to the first invention for solving the above-mentioned problem is
A substantially square flat throw-away tip for cutting both the left and right tooth surfaces of the gear to be machined is applied to the left and right slopes of the threaded portion formed in a screw shape on the outer periphery of the hob body along the twist direction. It is a throw-away hob that can be attached and detached alternately left and right,
The throw-away tip is mounted in a state where the outer peripheral rake angle is negative and the side clearance angle is positive,
The rake face of the throw-away tip has a convex shape such that an intermediate portion in the hob radial direction of the rake face protrudes forward in the hob rotation direction.

The throw-away hob according to the second invention for solving the above-mentioned problem is
The rake face is
It has a flat surface arranged in the hob radial direction intermediate portion in the rake face,
At least one of an inclined surface and a convex curved surface that are inclined and curved toward the front side in the hob rotation direction is provided on both sides in the hob radial direction of the plane.

The throw-away hob according to the third invention for solving the above-mentioned problem is
A substantially square flat throw-away tip for cutting both the left and right tooth surfaces of the gear to be machined is applied to the left and right slopes of the threaded portion formed in a screw shape on the outer periphery of the hob body along the twist direction. It is a throw-away hob that can be attached and detached alternately left and right,
The throw-away tip is mounted in a state where the outer peripheral rake angle is negative and the side clearance angle is positive,
The side flank of the throw-away tip has a convex shape such that an intermediate portion in the hob radial direction on the side flank protrudes outward in the hob rotation axis direction.

A throw-away hob according to a fourth invention for solving the above-described problem is
The side flank is
It has a flat surface arranged in the middle part in the hob radial direction on the side flank,
At least one of an inclined surface and a convex curved surface that are inclined and curved toward the outer side in the hob rotation axis direction is provided on both sides in the hob radial direction of the plane.

A throwaway hob according to a fifth invention for solving the above-described problems is
A substantially square flat throw-away tip for cutting both the left and right tooth surfaces of the gear to be machined is applied to the left and right slopes of the threaded portion formed in a screw shape on the outer periphery of the hob body along the twist direction. It is a throw-away hob that can be attached and detached alternately left and right,
The throw-away tip is mounted in a state where the outer peripheral rake angle is negative and the side clearance angle is positive,
The outer peripheral cutting edge of the throw-away tip has a convex shape such that an intermediate portion in the hob radial direction of the outer peripheral cutting edge protrudes outward in the hob rotation axis direction.

A throw-away hob according to a sixth invention for solving the above-described problem is
The throw-away tip is
A rake face with a negative outer rake angle;
As the outer peripheral rake angle of the rake face becomes negative, an outer peripheral flank face whose outer peripheral flank angle becomes positive,
A side clearance surface having a positive side clearance angle;
Among the inclined surface and the convex curved surface that are inclined and curved toward the hob radial direction, at least one of the surfaces is provided between the rake surface, the outer peripheral flank surface, and the side flank surface,
An edge portion formed by the rake surface, the inclined surface, and the convex curved surface is the outer peripheral cutting edge.

A throw-away hob according to a seventh invention for solving the above-described problem is
The protruding amount of the convex shape is set according to the advance angle of the thread portion.

  Therefore, according to the throw-away hob according to the present invention, the rake face, the side relief face, and the outer peripheral cutting edge of the throw-away tip are formed in a convex shape, so that both the left and right tooth faces of the gear to be machined are highly accurate. Can be chopped.

1 is a perspective view of a throw-away hob according to an embodiment of the present invention. 1 is a front view of a throw-away hob according to an embodiment of the present invention. (A) is a perspective view of the throw-away tip according to Embodiment 1 of the present invention, and (b) is a side view of the throw-away tip according to Embodiment 1 of the present invention. It is the figure which showed the tooth profile shape when gears were cut with the throw away tip which concerns on Example 1 of this invention. (A) is a perspective view of the throw-away tip according to Embodiment 2 of the present invention, and (b) is a side view of the throw-away tip according to Embodiment 2 of the present invention. (A) is a perspective view of the throw-away tip according to Embodiment 3 of the present invention, and (b) is a side view of the throw-away tip according to Embodiment 3 of the present invention. (A) is a perspective view of the throw-away tip according to Embodiment 4 of the present invention, and (b) is a side view of the throw-away tip according to Embodiment 4 of the present invention. (A) is a perspective view of the throw-away tip according to Embodiment 5 of the present invention, and (b) is a front view of the throw-away tip according to Embodiment 5 of the present invention. It is the figure which showed the tooth profile shape when gear cutting was carried out with the throw away tip which concerns on Example 5 of this invention. (A) is a perspective view of the throw-away tip according to Embodiment 6 of the present invention, and (b) is a front view of the throw-away tip according to Embodiment 6 of the present invention. (A) is a perspective view of the throw-away tip according to Embodiment 7 of the present invention, and (b) is a front view of the throw-away tip according to Embodiment 7 of the present invention. (A) is a perspective view of the throw-away tip according to Embodiment 8 of the present invention, and (b) is a front view of the throw-away tip according to Embodiment 8 of the present invention. (A) is a perspective view of the throw-away tip according to Embodiment 9 of the present invention, and (b) is a front view of the throw-away tip according to Embodiment 9 of the present invention. It is the figure which showed the tooth profile shape when gears were cut with the throw away tip which concerns on Example 9 of this invention. (A) is a perspective view of the throw-away tip according to Embodiment 10 of the present invention, and (b) is a front view of the throw-away tip according to Embodiment 10 of the present invention. (A) is a perspective view of the throw-away tip according to Embodiment 11 of the present invention, and (b) is a front view of the throw-away tip according to Embodiment 11 of the present invention.

  Hereinafter, the throw-away hob according to the present invention will be described in detail with reference to the drawings.

  First, the throw-away hob according to the first embodiment of the present invention will be described in detail with reference to FIGS.

  As shown in FIGS. 1 and 2, the throwaway hob 1 is supported so as to be rotatable around the hob rotation axis O, and a plurality of throwaway tips 20 can be attached to and detached from the hob body 10. It is said.

  A screw thread portion 11 having a substantially triangular cross section is formed in a screw shape on the outer peripheral portion of the hob body 10, and the lead angle of the screw thread portion 11 is set to β. ing. In addition, on the left slope and the right slope of the screw thread portion 11, concave chip mounting portions 12 are alternately formed at predetermined intervals along the twist direction (winding axis direction). A throw-away tip 20 is fixed to each tip mounting portion 12 with a bolt B.

  Further, a groove-shaped chip pocket 13 is formed in the thread portion 11 so as to communicate with the tip mounting portion 12 on the front side of the tip mounting portion 12 in the hob rotation direction. That is, by attaching the throw-away tip 20 to the tip mounting portion 12, the tip portion of the throw-away tip 20 faces the chip pocket 13. As a result, the chips generated by the throw-away tip 20 are discharged into the chip pocket 13.

  Although the shape of the throw-away tip 20 will be described later, the throw-away tip 20 is formed in a substantially rectangular flat plate shape. On the other hand, the tip mounting portion 12 is formed so as to be inclined toward the center in the width direction of the screw thread portion 11 (position between the left slope and the right slope) toward the rear side in the hob rotation direction.

  Thereby, when the throw-away tip 20 is attached to the tip mounting portion 12, the side clearance angle θp of the throw-away tip 20 becomes positive. As shown in FIG. 2, when the throwaway tip 20 is fixed with the bolt B, the outer peripheral rake angle γa of the throwaway tip 20 becomes negative. That is, the outer peripheral clearance angle θa of the throw-away tip 20 is positive.

  When the throw-away tip 20 is attached to the tip mounting portion 12 on the left slope, the throw away tip 20 cuts the left tooth surface WL of the workpiece (workpiece gear) W, while being attached to the tip mounting portion 12 on the right slope. If it is done, the right tooth surface WR of the workpiece W is cut (see FIG. 4).

  Therefore, as shown in FIGS. 3 (a), 3 (b) and 4, the throw-away tip 20 includes a rake face 21L for the left tooth surface used when cutting the left tooth surface WL, and a right tooth surface. It has a rake face 21R for the right tooth surface used when cutting WR. These rake faces 21L and 21R are arranged to face each other.

  Further, as shown in FIGS. 3A and 3B, the outer peripheral surface of the throw-away tip 20 includes two outer peripheral flank surfaces 22, a side flank surface 23, and a mounting seat surface 24. Each outer flank 22, each side flank 23, and each mounting seat 24 are arranged to face each other.

  The edge portion formed by the rake face 21L, the outer peripheral flank 22 and the side flank 23 forms an outer peripheral cutting edge 25L for the left tooth surface used when cutting the left tooth surface WL. On the other hand, the edge formed by the rake face 21R, the outer peripheral flank 22 and the side flank 23 forms an outer peripheral cutting edge 25R for the right tooth surface used when cutting the right tooth surface WR.

  That is, the throw-away tip 20 is provided with two outer peripheral cutting edges 25L for the left tooth surface and two outer peripheral cutting edges 25R for the right tooth surface, and is a four-edge type throw-away tip. The installation range of the outer peripheral cutting edge 25L is indicated as C1.

  Further, a bolt hole 26 is formed in the throw-away tip 20 so as to penetrate between the side clearance surfaces 23. Bolts B can be passed through the bolt holes 26.

  Here, the rake face 21L is composed of one plane 21La and two inclined faces 21Lb. The flat surface 21La is disposed at the hob radial direction intermediate portion (chip height direction intermediate portion) of the rake face 21L. In addition, the inclined surface 21Lb is inclined toward the front side in the hob rotation direction, and is disposed on both sides in the hob radial direction (both sides in the chip height direction) of the rake surface 21L.

  That is, on the rake face 21L, the inclined surfaces 21Lb are arranged on both sides in the hob radial direction so that the flat surface 21La protrudes toward the front side in the hob rotation direction. Thus, also in the outer peripheral cutting edge 25L, corresponding to the convex shape of the rake face 21L, the hob radial intermediate portion protrudes forward in the hob rotation direction, and both the hob radial both sides thereof It inclines toward the protruding middle part in the radial direction of the hob.

  Thus, the tooth profile shape of the left tooth surface WL is obtained by making the rake face 21L a convex shape such that the hob radial direction intermediate portion of the rake face 21L protrudes toward the front side in the hob rotation direction. It approximates to the ideal tooth profile shape L mentioned later. The amount of protrusion from one end of the outer peripheral flank 22, the side flank 23, and the mounting seat surface 24 on the plane 21 La, that is, the inclination angle α 1 of the inclined surface 21 Lb with respect to the plane 21 La is set according to the advance angle β. Specifically, it is set to increase as the advance angle β increases.

  On the other hand, the rake face 21R is composed of one plane. That is, the rake face 21L and the rake face 21R have the same shape in plan view, but the rake face 21L has a convex shape that protrudes toward the front side in the hob rotation direction, while the rake face 21R is It has become a single plane.

  From the above, as shown in FIG. 4, when the hob 1 is rotated around the hob rotation axis O, the left tooth surface WL and the right tooth are caused by the throw-away tip 20 mounted on the left slope and the right slope of the thread 11. The tooth surface WR is cut.

  At this time, in the throw-away tip 20 that rotates spirally (screw-shaped) around the hob rotation axis O, the rotation locus deviates from the originally ideal rotation locus due to the influence of the advance angle β. Thereby, tooth profile errors ΔL1 and ΔR1 are advanced between the tooth profile of the left tooth surface WL and right tooth surface WR cut by the outer peripheral cutting edges 25L and 25R and the ideal tooth profile L and R. It occurs depending on the magnitude of β.

  Therefore, in the throw-away tip 20, among the left and right tooth profile errors, corresponding to the left tooth surface WL on the side where the error amount becomes large based on the direction of the twist in the thread portion 11 and the direction of the advance angle β, The rake face 21L has a convex shape. Thereby, the tooth profile shape of the left tooth surface WL and the right tooth surface WR cut by the outer peripheral cutting edges 25L and 25R can be approximated to the ideal tooth profile shapes L and R.

  In FIG. 4, the tooth profile shapes of the left and right tooth surfaces at the time of design are ideal tooth profile shapes L and R, and these ideal tooth profile shapes L and R are indicated by two-dot chain lines. In addition, the tooth profile shapes Lo and Ro when the rake face is not formed in a convex shape (the rake face is a single flat surface) with a conventional throwaway tip are indicated by dotted lines.

  Therefore, the cutting amount of the outer peripheral cutting edge 25L with respect to the left tooth surface WL can be increased by projecting the flat surface 21La of the rake face 21L toward the front side in the hob rotation direction according to the magnitude of the advance angle β. Therefore, the tooth profile error ΔL1 can be reduced.

  Further, although the rake face 21R is not protruded, the tooth profile error ΔR1 becomes small to an acceptable level, and can be used without any problem. As a result, even if the protrusion amount of the rake face 21L and the protrusion amount of the rake face 21R are different, the throw away tip 20 can be used as a throw away tip for left tooth surface tooth cutting and a throw away tip for right tooth surface tooth cutting. And can be used for both.

  Therefore, since the tooth profile shapes of the left tooth surface WR and the right tooth surface WL of the workpiece W after processing can be approximated to the ideal tooth shape L, R, the left tooth surface WR and the right tooth surface WL can be accurately obtained. It can be chopped.

  Here, in the throw-away tip 20 according to Example 1 described above, the rake face 21L is formed in a convex shape by disposing the inclined faces 21Lb one by one on both sides of the flat face 21La in the hob radial direction. Thus, when making the rake face 21L into a convex shape, it is only necessary to arrange the flat surface 21La so as to protrude toward the front side in the hob rotation direction, and the surfaces arranged on both sides of the flat surface 21La in the hob radial direction. The shape may be appropriately changed according to the required gear cutting accuracy.

  For example, the hob radial both sides of the rake face 21L are composed of a plurality of inclined surfaces, one or more convex curved surfaces, or a combination of one or more inclined surfaces and one or more convex curved surfaces. It doesn't matter.

  Therefore, the above-described modifications of the rake face 21L of the throw-away tip 20 are the throw-away tips 20A, 20B, and 20C according to the second to fourth embodiments as shown in FIGS. 5 (a), 5 (b) to 7 (a). , (B) will be specifically described. 5A, 5B to 7A, 7B, members having the same configuration and function as those shown in FIGS. 3A, 3B are shown in FIG. 3 (a) and 3 (b) are denoted by the same reference numerals as those shown in the drawing, and the description thereof is omitted in the following description.

  As shown in FIGS. 5A and 5B, the throw-away tip 20A has a rake face 27L for the left tooth surface used when cutting the left tooth surface WL. The rake face 27L is composed of one flat surface 21La and two inclined surfaces 27La and 27Lb. The inclined surfaces 27La and 27Lb are inclined toward the front side in the hob rotation direction, and are disposed on both sides of the rake surface 27L in the hob radial direction.

  That is, on the rake face 27L, the flat surface 21La, the inclined surface 27La, and the inclined surface 27Lb are continuously arranged from the middle portion in the hob radial direction toward both ends in the hob radial direction. At this time, the protrusion amount of the plane 21La and the inclination angles of the inclined surfaces 27La and 27Lb with respect to the plane 21La are set according to the advance angle β, and the inclination angles of the inclined surfaces 27La and 27Lb are different even at the same angle. An angle is also acceptable.

  As shown in FIGS. 6A and 6B, the throw-away tip 20B has a rake face 28L for the left tooth surface used when cutting the left tooth surface WL. The rake face 28L is composed of one flat surface 21La and two convex curved surfaces 28La and 28Lb. The convex curved surfaces 28La and 28Lb are curved toward the front side in the hob rotation direction, and are disposed on both sides of the rake face 28L in the hob radial direction.

  That is, on the rake face 28L, the flat surface 21La, the convex curved surface 28La, and the convex curved surface 28Lb are continuously arranged from the middle portion in the hob radial direction toward both ends in the hob radial direction. At this time, the protrusion amount of the flat surface 21La and the curvatures of the convex curved surfaces 28La and 28Lb are set according to the advance angle β, and the curvatures of the convex curved surfaces 28La and 28Lb may be the same curvature or different curvatures.

  Further, as shown in FIGS. 7A and 7B, the throw-away tip 20C has a rake face 29L for the left tooth surface used when cutting the left tooth surface WL. The rake face 29L is composed of one flat surface 21La, two inclined surfaces 29La, and two convex curved surfaces 29Lb. The inclined surface 29La and the convex curved surface 29Lb are inclined and curved toward the front side in the hob rotation direction, and are disposed on both sides of the rake surface 29L in the hob radial direction.

  That is, on the rake face 29L, the flat surface 21La, the inclined surface 29La, and the convex curved surface 29Lb are continuously arranged from the intermediate portion in the hob radial direction toward both ends in the hob radial direction. At this time, the protrusion amount of the flat surface 21La, the inclination angle of the inclined surface 29La with respect to the flat surface 21La, and the curvature of the convex curved surface 29Lb are set according to the advance angle β, and the arrangement of the inclined surface 29La and the convex curved surface 29Lb is In the hob radial one end and the hob radial other end, the same arrangement or different arrangements may be used.

  Therefore, the tooth profile shape of the left tooth surface WL can be approximated to the ideal tooth profile shape L by making the rake surfaces 27L, 28L, 29L convex according to the advance angle β.

  Next, a throwaway hob according to a fifth embodiment of the present invention will be described in detail with reference to FIGS. 8 (a), 8 (b), and 9. FIG.

  As shown in FIGS. 8A, 8 </ b> B, and 9, the throw-away tip 30 includes a rake face 31 </ b> L for the left tooth surface used when cutting the left tooth surface WL and a right tooth surface WR. It has a rake face 31R for the right tooth surface used for gear cutting. These rake faces 31L and 31R are arranged to face each other.

  As shown in FIGS. 8A and 8B, the outer peripheral surface of the throw-away tip 30 includes two outer peripheral flank surfaces 32, a side flank surface 33, and a mounting seat surface 34. Each outer peripheral flank 32, each side flank 33, and each mounting seat surface 34 are arranged to face each other.

  The edge formed by the rake face 31L, the outer peripheral flank 32, and the side flank 33 forms an outer peripheral cutting edge 35L for the left tooth surface used when cutting the left tooth surface WL. On the other hand, the edge portion formed by the rake face 31R, the outer peripheral flank 32 and the side flank 33 forms an outer peripheral cutting edge 35R for the right tooth surface used when cutting the right tooth surface WR.

  That is, the throw-away tip 30 is provided with two outer peripheral cutting edges 35L for the left tooth surface and two outer peripheral cutting edges 35R for the right tooth surface, and is a four-edge type throw-away tip. The installation range of the outer peripheral cutting edge 35L is indicated as C2.

  Further, a bolt hole 36 is formed in the throw-away tip 30 so as to penetrate between the side clearance surfaces 33. Bolts B can be passed through the bolt holes 36.

  Here, the left and right side clearance surfaces 33 are composed of one flat surface 33a and two inclined surfaces 33b and 33c. The flat surface 33a is disposed in the intermediate portion in the hob radial direction (intermediate portion in the chip height direction) of the side clearance surface 33. Further, the inclined surfaces 33b and 33c are inclined toward the outer side in the hob rotation axis direction, and are disposed on both side portions in the hob radial direction (both side portions in the chip height direction) of the side clearance surface 33.

  That is, in the side flank 33, the inclined surfaces 33b and 33c are arranged on both sides in the hob radial direction so that the flat surface 33a protrudes outward in the hob rotation axis direction. Thereby, in the outer peripheral cutting edges 35L and 35R, corresponding to the convex shape of the side flank 33, the hob radial direction intermediate portion protrudes outward in the hob rotation axis direction, and both the hob radial direction both sides However, it inclines toward the projecting hob radial direction intermediate part.

  Thus, by making the side flank 33 convex so that the intermediate portion in the hob radial direction of the side flank 33 protrudes outward in the hob rotation axis direction, the left tooth surface WL and the right tooth The tooth profile shape of the surface WR is approximated to ideal tooth profile shapes L and R described later. The amount of protrusion from one end of the outer peripheral flank 32 and the mounting seat surface 34 on the plane 33a, that is, the inclination angle α2 of the inclined surfaces 33b and 33c with respect to the plane 33a is set according to the advance angle β. Is set to increase as the advance angle β increases.

  As described above, as shown in FIG. 9, when the hob 1 is rotated around the hob rotation axis O, the left tooth surface WL and the right tooth are caused by the throwaway tip 30 mounted on the left slope and the right slope of the thread 11. The tooth surface WR is cut.

  At this time, in the throw-away tip 30 that rotates spirally (screw-shaped) around the hob rotation axis O, the rotation locus deviates from the originally ideal rotation locus due to the influence of the advance angle β. As a result, tooth profile errors ΔL2 and ΔR2 are advanced between the tooth profile shapes of the left tooth surface WL and right tooth surface WR cut by the outer peripheral cutting edges 35L and 35R and the ideal tooth profile shapes L and R. It occurs depending on the magnitude of β.

  Therefore, in the throw-away tip 30, among the left and right tooth profile errors, corresponding to the left tooth surface WL on the side where the error amount becomes large based on the direction of the twist in the thread portion 11 and the direction of the advance angle β, The side flank 33 is convex. Thereby, the tooth profile shape of the left tooth surface WL and the right tooth surface WR cut by the outer peripheral cutting edges 35L and 35R can be approximated to the ideal tooth profile shapes L and R.

  In FIG. 9, the tooth profile shapes of the left and right tooth surfaces at the time of design are ideal tooth profile shapes L and R, and these ideal tooth profile shapes L and R are indicated by two-dot chain lines. Further, the tooth profile shapes Lo and Ro when the side flank is not convex (the side flank is a single flat surface) with a conventional throwaway tip are indicated by dotted lines.

  Accordingly, the cutting amount of the outer peripheral cutting edge 35L with respect to the left tooth surface WL is increased by causing the flat surface 33a of the side flank 33 to protrude outward in the hob rotation axis direction according to the magnitude of the advance angle β. Therefore, the tooth profile error ΔL2 can be reduced.

  In addition, although the left flank 33 and the right flank 33 are protruded on both sides, the tooth profile error ΔR2 becomes small to an acceptable level and can be used without any problem. . Thereby, even if each side flank 33 for the left tooth surface and the right tooth surface has the same protruding amount, the throw away tip 30 can be used for the left tooth surface tooth cutting and the right tooth surface tooth cutting. Can be used with both throwaway chips.

  Therefore, since the tooth profile shapes of the left tooth surface WR and the right tooth surface WL of the workpiece W after processing can be approximated to the ideal tooth shape L, R, the left tooth surface WR and the right tooth surface WL can be accurately obtained. It can be chopped.

  Here, in the throw-away tip 30 according to Example 5 described above, the side flank 33 has a convex shape by disposing the inclined surfaces 33b and 33c one by one on both sides of the flat surface 33a in the hob radial direction. As described above, when the side relief surface 33 has a convex shape, the flat surface 33a may be disposed so as to protrude outward in the hob rotation axis direction, and is disposed on both sides of the flat surface 33a in the hob radial direction. The surface shape may be appropriately changed according to the required gear cutting accuracy.

  For example, the hob radial both sides of the side flank 33 are configured from a plurality of inclined surfaces, one or more convex curved surfaces, or a combination of one or more inclined surfaces and one or more convex curved surfaces. It doesn't matter.

  Therefore, the above-described modifications of the side clearance surface 33 in the throw-away tip 30 are the throw-away tips 30A, 30B, and 30C according to the sixth to eighth embodiments, as shown in FIGS. 10 (a), 10 (b) to 12 (a). ) And (b) will be described in detail. 10 (a), 10 (b) to 12 (a), 12 (b), members having the same configuration and function as the members illustrated in FIGS. 8 (a), 8 (b) are shown in FIG. 8 (a) and 8 (b) are denoted by the same reference numerals as those shown in the drawings, and the description thereof is omitted in the following description.

  As shown in FIGS. 10A and 10B, the throw-away tip 30 </ b> A has a pair of left and right side clearance surfaces 37 that face each other. The side clearance surface 37 is composed of one flat surface 33a and four inclined surfaces 37a to 37d. The inclined surfaces 37 a to 37 d are inclined toward the outer side in the hob rotation axis direction, and are disposed on both sides in the hob radial direction of the side clearance surface 37.

  That is, on the side clearance surface 37, the flat surface 33a, the inclined surfaces 37a and 37b, and the inclined surfaces 37c and 37d are continuously arranged from the intermediate portion in the hob radial direction toward both ends in the hob radial direction. At this time, the protrusion amount of the flat surface 33a and the inclination angles of the inclined surfaces 37a to 37d with respect to the flat surface 33a are set according to the advance angle β, and the inclination angles of the inclined surfaces 37a to 37d are different even at the same angle. An angle is also acceptable.

  Further, as shown in FIGS. 11A and 11B, the throw-away tip 30B has a pair of left and right side clearance surfaces 38 facing each other. The side clearance surface 38 is composed of one flat surface 33a and four convex curved surfaces 38a to 38d. The convex curved surfaces 38 a to 38 b are curved toward the outer side in the hob rotation axis direction, and are disposed on both sides in the hob radial direction of the side flank 38.

  That is, on the side clearance surface 38, the flat surface 33a, the convex curved surfaces 38a and 38b, and the convex curved surfaces 38c and 38d are continuously arranged from the middle portion in the hob radial direction toward both ends in the hob radial direction. At this time, the protrusion amount of the flat surface 33a and the curvatures of the convex curved surfaces 38a to 38d are set according to the advance angle β, and the curvatures of the convex curved surfaces 38a to 38d may be the same curvature or different curvatures.

  Furthermore, as shown in FIGS. 12A and 12B, the throw-away tip 30 </ b> C has a pair of left and right side clearance surfaces 39 facing each other. The side relief surface 39 is composed of one flat surface 33a, two inclined surfaces 39a and 39c, and two convex curved surfaces 39b and 39d. The inclined surfaces 39a and 39c and the convex curved surfaces 39b and 39d are inclined and curved toward the outer side in the hob rotation axis direction, and are disposed on both sides of the side relief surface 39 in the hob radial direction.

  That is, on the rake surface 29L, the flat surface 33a, the inclined surfaces 39a and 39c, and the convex curved surfaces 39b and 39d are continuously arranged from the intermediate portion in the hob radial direction toward both end portions in the hob radial direction. At this time, the protrusion amount of the flat surface 33a, the inclination angles of the inclined surfaces 39a and 39c with respect to the flat surface 33a, and the curvature of the convex curved surfaces 39b and 39d are set according to the advance angle β, and the convex surfaces of the inclined surfaces 39a and 39c are convex. The arrangement of the curved surfaces 39b and 39d may be the same or different at one end in the hob radial direction and the other end in the hob radial direction.

  Therefore, the tooth profile shapes of the left tooth surface WL and the right tooth surface WR are approximated to the ideal tooth shapes L and R by making the side clearance surfaces 37, 38, and 39 convex according to the advance angle β. Can do.

  Next, a throw-away hob according to a ninth embodiment of the present invention will be described in detail with reference to FIGS. 13 (a), (b) and FIG.

  As shown in FIGS. 13A, 13B, and 14, the throw-away tip 40 has a rake face 41L for the left tooth surface used when cutting the left tooth surface WL, and a right tooth surface WR. It has a rake face 41R for the right tooth surface used for gear cutting. These rake faces 41L and 41R are arranged to face each other.

  As shown in FIGS. 13A and 13B, the outer peripheral surface of the throw-away tip 40 includes two outer peripheral flank surfaces 42, a side flank surface 43, and a mounting seat surface 44. Each outer flank 42, each side flank 43, and each mounting seat 44 are arranged to face each other.

  A convex curved surface 47 is disposed between the rake face 41L, the outer peripheral flank face 42, and the side flank face 43, respectively. These two convex curved surfaces 47 are formed to be curved in the hob radial direction.

  Thereby, the edge part formed by the rake face 41L, the outer periphery flank 42, and the convex curved surface 47 constitutes the outer peripheral cutting edge 45L for the left tooth surface used when cutting the left tooth surface WL. On the other hand, the edge portion formed by the rake face 41R, the outer peripheral flank 42 and the side flank 43 forms an outer peripheral cutting edge 45R for the right tooth surface used when cutting the right tooth surface WR.

  That is, the throw-away tip 40 is provided with two outer peripheral cutting edges 45L for the left tooth surface and two outer peripheral cutting edges 45R for the right tooth surface, and is a four-edge type throw-away tip. The installation range of the outer peripheral cutting edge 45L is indicated as C3.

  Further, a bolt hole 46 is formed in the throw-away tip 40 so as to communicate between the side clearance surfaces 43, and the bolt B can pass through the bolt hole 46.

  That is, the rake face 41L is formed so that the convex curved surface 47 is adjacent to both sides in the hob rotation axis direction, and the intermediate portion in the hob radial direction protrudes outward in the hob rotation axis direction. Thereby, also in the outer peripheral cutting edge 45L, it corresponds to the convex shape of the rake face 41L, and the hob radial direction intermediate portion is formed to protrude outward in the hob rotation axis direction.

  Thus, the tooth profile shape of the left tooth surface WL is obtained by making the outer peripheral cutting edge 45L convex so that the middle part in the hob radial direction of the outer peripheral cutting edge 45L protrudes outward in the hob rotation axis direction. Is approximated to an ideal tooth profile L described later. The protrusion amount of the outer peripheral cutting edge 45L, that is, the curvature of the convex curved surface 47 is set according to the advance angle β, and specifically, is set so as to increase as the advance angle β increases. Yes.

  As described above, as shown in FIG. 14, when the hob 1 is rotated around the hob rotation axis O, the left tooth surface WL and the right tooth are caused by the throwaway tip 40 mounted on the left slope and the right slope of the thread 11. The tooth surface WR is cut.

  At this time, in the throw-away tip 40 that rotates spirally (threaded) around the hob rotation axis O, the rotation locus deviates from the originally ideal rotation locus due to the influence of the advance angle β. As a result, tooth profile errors ΔL3 and ΔR3 are advanced between the tooth profile of the left tooth surface WL and right tooth surface WR cut by the outer peripheral cutting edges 45L and 45R and the ideal tooth profile L and R. It occurs depending on the magnitude of β.

  Therefore, in the throw-away tip 40, among the left and right tooth profile errors, corresponding to the left tooth surface WL on the side where the error amount becomes large based on the direction of the twist in the thread portion 11 and the direction of the advance angle β, The outer peripheral cutting edge 45L has a convex shape. Thereby, the tooth profile shape of the left tooth surface WL and the right tooth surface WR cut by the outer peripheral cutting edges 45L and 45R can be approximated to the ideal tooth profile shapes L and R.

  In FIG. 14, the tooth profile shapes of the left and right tooth surfaces at the time of design are ideal tooth profile shapes L and R, and these ideal tooth profile shapes L and R are indicated by two-dot chain lines. In addition, the tooth profile shapes Lo and Ro when the outer peripheral cutting edge is cut with a conventional throw-away tip having no convex shape are indicated by dotted lines.

  Therefore, the amount of cutting of the outer peripheral cutting edge 45L with respect to the left tooth surface WL can be increased by causing the outer peripheral cutting edge 45L to protrude outward in the hob rotation axis direction according to the magnitude of the advance angle β. The tooth profile error ΔL3 can be reduced.

  Further, although the outer peripheral cutting edge 41R is not protruded using a convex curved surface, the tooth profile error ΔR3 becomes minute to an acceptable level, and can be used without any problem. As a result, even if the protrusion amount of the outer peripheral cutting edge 45L and the protrusion amount of the outer peripheral cutting edge 45R are different, the throw away tip 40 can be used as the throw away tip for the left tooth surface tooth cutting and the throw for the right tooth surface tooth cutting. Can be used with both away chips.

  Here, in the throw-away tip 40 according to the ninth embodiment described above, the convex curved surfaces 47 are arranged one by one on the left and right sides between the rake face 41L, the outer peripheral flank 42, and the side flank 43, so that The cutting edge 45L has a curved convex shape. Thus, when making the outer peripheral cutting edge 45L into a convex shape, it suffices if the outer peripheral cutting edge 45L has a middle portion in the hob radial direction protruding outward in the hob rotation axis direction. The shape of the entire region in the hob radial direction (linear) and the shape of both ends in the hob radial direction (linear) may be appropriately changed according to the required gear cutting accuracy.

  For example, the shape of the entire outer peripheral cutting edge 45L in the hob radial direction may be configured by one or more straight lines or a plurality of curved lines.

  Therefore, the above-described modified examples of the outer peripheral cutting edge 45L in the throw-away tip 40 are the throw-away tips 40A and 40B according to the tenth and eleventh embodiments, as shown in FIGS. 15 (a), 15 (b) and 16 (a), This will be specifically described with reference to (b). 15 (a), 15 (b) and FIGS. 16 (a), 16 (b), members having the same configuration and function as the members illustrated in FIGS. 13 (a), 13 (b) are shown in FIG. 13 (a) and 13 (b) are denoted by the same reference numerals as those shown in the drawings, and the description thereof is omitted in the following description.

  As shown in FIGS. 15A and 15B, the throw-away tip 40A includes a flat surface 51a and inclined surfaces 51b inclined to the flat surface 51a on the left and right sides of the rake surface 41L in the hob rotation axis direction. 51c. The flat surface 51a is disposed in the middle portion in the hob radial direction of the throw-away tip 40A. Further, the inclined surfaces 51b and 51c are inclined toward the hob radial direction, and are disposed on both sides of the throw-away tip 40A in the hob radial direction.

  Further, the edge formed by the rake face 41L, the outer peripheral flank 42, the flat surface 51a, and the inclined surfaces 51b and 51c is an outer peripheral cutting edge for the left tooth surface used when cutting the left tooth surface WL. 52L. In the installation range C3 of the outer peripheral cutting edge 52L, the edge portions formed by the rake face 41L, the flat surface 51a, and the inclined surfaces 51b and 51c are the outer peripheral cutting edges 52La, 52Lb, and 52Lc. The outer peripheral cutting edges 52La, 52Lb, and 52Lc are linearly formed.

  That is, in the throw-away tip 40A, the outer peripheral cutting edges 52La, 52Lb, and 52Lc are continuously arranged from the intermediate portion in the hob radial direction toward both ends in the hob radial direction. At this time, the protrusion amount of the outer peripheral cutting edge 52La and the inclination angle of the outer peripheral cutting edges 52Lb and 52Lc with respect to the outer peripheral cutting edge 52La are set according to the advance angle β, and the inclination angle of the inclined surfaces 51b and 51c, and The inclination angles of the outer peripheral cutting edges 52Lb and 52Lc may be the same angle or different angles.

  Also, as shown in FIGS. 16A and 16B, the throw-away tip 40B includes a flat surface 53a and a convex curved surface that is inclined with respect to the flat surface 53a on both the left and right sides in the hob rotation axis direction of the rake face 41L. 53b, 53c. The flat surface 53a is disposed in the middle portion in the hob radial direction of the throw-away tip 40B. Further, the convex curved surfaces 53b and 53c are curved toward the hob radial direction and are disposed on both sides of the throw-away tip 40B in the hob radial direction.

  Further, the edge formed by the rake face 41L, the outer peripheral flank 42, the flat surface 53a, and the convex curved surfaces 53b and 53c is an outer peripheral cutting edge for the left tooth surface used when cutting the left tooth surface WL. 54L is made. In the installation range C3 of the outer peripheral cutting edge 54L, the edge portions formed by the rake face 41L, the flat surface 53a, and the convex curved surfaces 53b and 53c are the outer peripheral cutting edges 54La, 54Lb, and 54Lc. The outer peripheral cutting edge 54La is formed in a straight line shape, and the outer peripheral cutting edges 54Lb and 54Lc are formed in a curved line shape.

  That is, in the throw-away tip 40B, the outer peripheral cutting edges 54La, 54Lb, and 54Lc are continuously arranged from the intermediate portion in the hob radial direction toward both ends in the hob radial direction. At this time, the protrusion amount of the outer peripheral cutting edge 54La and the curvatures of the outer peripheral cutting edges 54Lb and 54Lc are set according to the advance angle β, and the curvatures of the outer peripheral cutting edges 54Lb and 54Lc are different even with the same curvature. The curvature may be used.

  Accordingly, the outer peripheral cutting edges 52La, 52Lb, 52Lc and the outer peripheral cutting edges 54La, 54Lb, 54Lc are arranged in accordance with the advance angle β, and the outer peripheral cutting edges 52L, 54L having a convex shape as a whole are left. The tooth profile shape of the tooth surface WL can be approximated to the ideal tooth profile shape L.

  The present invention can be applied to a throw-away hob intended to extend the tip life of the throw-away tip.

DESCRIPTION OF SYMBOLS 1 Hob 10 Hob main body 11 Thread part 20, 20A-20C Throw away tip 21L, 27L-29L Rake face 30, 30A-30C Throw away tip 33, 37-39 Side relief surface 40, 40A, 40B Throw away tip 45L, 52L, 54L Peripheral cutting edge O Hob rotation axis β Advance angle γa Peripheral rake angle θa Peripheral clearance angle θp side clearance angle W Work WL Left tooth surface WR Right tooth surface

Claims (7)

A substantially square flat throw-away tip for cutting both the left and right tooth surfaces of the gear to be machined is applied to the left and right slopes of the threaded portion formed in a screw shape on the outer periphery of the hob body along the twist direction. It is a throw-away hob that can be attached and detached alternately left and right,
The throw-away tip is mounted in a state where the outer peripheral rake angle is negative and the side clearance angle is positive,
The throw-away hob characterized in that the rake face of the throw-away tip has a convex shape such that an intermediate portion in the hob radial direction of the rake face protrudes forward in the hob rotation direction. The throw-away hob according to claim 1,
The rake face is
It has a flat surface arranged in the hob radial direction intermediate portion in the rake face,
A throwaway hob comprising at least one of an inclined surface and a convex curved surface inclined and curved toward the front side in the hob rotation direction on both sides in the hob radial direction of the plane. A substantially square flat throw-away tip for cutting both the left and right tooth surfaces of the gear to be machined is applied to the left and right slopes of the threaded portion formed in a screw shape on the outer periphery of the hob body along the twist direction. It is a throw-away hob that can be attached and detached alternately left and right,
The throw-away tip is mounted in a state where the outer peripheral rake angle is negative and the side clearance angle is positive,
The throw-away type hob is characterized in that the side flank of the throw-away tip has a convex shape such that an intermediate portion in the hob radial direction on the side flank protrudes outward in the hob rotation axis direction. . The throw-away hob according to claim 3,
The side flank is
It has a flat surface arranged in the middle part in the hob radial direction on the side flank,
A throw-away hob comprising at least one of an inclined surface and a convex curved surface inclined and curved outward in the hob rotation axis direction on both sides of the plane in the hob radial direction. A substantially square flat throw-away tip for cutting both the left and right tooth surfaces of the gear to be machined is applied to the left and right slopes of the threaded portion formed in a screw shape on the outer periphery of the hob body along the twist direction. It is a throw-away hob that can be attached and detached alternately left and right,
The throw-away tip is mounted in a state where the outer peripheral rake angle is negative and the side clearance angle is positive,
The throw-away type hob is characterized in that the outer peripheral cutting edge of the throw-away tip has a convex shape such that an intermediate portion in the hob radial direction of the outer peripheral cutting edge protrudes outward in the hob rotation axis direction. . The throw-away hob according to claim 5,
The throw-away tip is
A rake face with a negative outer rake angle;
As the outer peripheral rake angle of the rake face becomes negative, an outer peripheral flank face whose outer peripheral flank angle becomes positive,
A side clearance surface having a positive side clearance angle;
Among the inclined surface and the convex curved surface that are inclined and curved toward the hob radial direction, at least one of the surfaces is provided between the rake surface, the outer peripheral flank surface, and the side flank surface,
An throw-away hob characterized in that an edge portion formed by the rake face, the inclined face and the convex curved face is the outer peripheral cutting edge. The throwaway hob according to any one of claims 1 to 6,
The throw-away hob characterized in that the protruding amount of the convex shape is set according to the advance angle of the thread portion.

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