JP5261154B2 - Hob cutter - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a hob cutter capable of effectively preventing the tooth flank of a gear from being torn near the dedendum by improving cutting-chip processing. <P>SOLUTION: The hob cutter 1 includes a hob body 2 driven into rotation and a plurality of cutting edges 3 arranged on the peripheral surface 2a of the hob body 2 at certain intervals in the circumferential direction, and a workpiece 4 is subjected to tooth cutting by the cutting edges 3 while the hob body 2 is rotated at a high speed, to generate the gear 5. In the hob cutter 1, the cutting edges 3 are designed with dislocation such that the ratio of the dedendum Dd to the overall tooth height h of each tooth 50 of the gear 5 generated (dedendum coefficient &beta;) lies within the prescribed range. <P>COPYRIGHT: (C)2010,JPO&amp;INPIT

Description

  The present invention relates to a hob cutter technique, and more particularly, to a hob cutter technique that creates a gear by cutting a workpiece with a cutting blade by rotating a hob body at a high speed.

  Conventionally, when processing gears (spur gears, helical gears, worm gears, etc.), sprockets, splines, etc., a hob cutter as a cutting tool is used. The hob cutter includes a hob body that is driven to rotate, and a plurality of cutting blades that are disposed on the outer circumferential surface of the hob body with a predetermined spacing along the circumferential direction. When the hob main body is rotated at a high speed while being fixed to the board, the workpiece is cut into a predetermined tooth profile (generated tooth cutting) by the cutting blade.

  In particular, in recent years, a technique (dry cut) has been proposed in which gears and the like are processed without using cutting oil in the gear cutting using the hob cutter. For example, Patent Literature 1 or Patent Literature 2 discloses a configuration of a hob cutter that creates a tooth profile by dry cutting. On the other hand, in such gear cutting by dry cutting, cutting oil is not used as described above, so it is difficult to discharge chips generated during gear cutting (cutting waste) out of the system. It has been pointed out that such a chip enters between the cutting blade of the hob cutter and the tooth surface created on the workpiece, and the tooth surface is peeled off.

Therefore, for example, Patent Document 1 described above proposes a gear processing method for performing gear cutting on a reverse wound conventional cut or the same wound conventional cut in order to prevent the above-described tooth surface flaking. Further, in Patent Document 2, there is a hob cutter formed so that the surface roughness of the back surface of the cutting blade is 10 μm or less in order to prevent the chips between the cutting blades of the hob cutter from becoming clogged with cutting waste. Proposed.
JP 2000-107937 A JP 11-207523 A

  By the way, in recent years, as a result of detailed examination of the generation process of cutting scraps in gear cutting, the tooth surface has a substantially constant size at a predetermined tooth surface, particularly in the vicinity of the tooth base on the trailing side. However, it has been found that the tooth surface properties are deteriorated due to the regular occurrence of the scraps. That is, in the cutting waste generation process, first, cutting waste starts to be generated from the trailing side at the start of cutting of the workpiece. Then, as a result of the cutting chips that have grown greatly pushed by the cutting chips generated from the leading side at the end of cutting and pressed against the trailing side (no cutting chips are generated at the end of cutting), the teeth near the tooth base on the trailing side The chip is pressed on the surface, and the tooth surface is peeled off.

  From this point of view, the above-described conventional hob cutter configuration and processing method can certainly be expected to have a certain effect in terms of preventing the tooth surface of the gears from coming off. From the standpoint, it is not intended to prevent flaking of the tooth surface near the tooth base on the trailing side, and does not propose a special hob cutter for that purpose.

  Accordingly, the present invention relates to a hob cutter that solves the above-mentioned conventional problems, and provides a hob cutter that improves cutting waste processing and effectively prevents tooth surface flaking near the tooth root of a gear. It is intended.

  The problem to be solved by the present invention is as described above. Next, means for solving the problem will be described.

In other words, the present invention includes a hob body that is rotationally driven, and a plurality of cutting blades that are disposed on the outer circumferential surface of the hob body with a predetermined spacing along the circumferential direction. In the hob cutter that creates a gear by cutting a workpiece with the cutting blade by rotating the hob main body at a high speed, the cutting blade has a ratio of dendendum to the total tooth height of each tooth of the gear to be created. It is molded so as to be in the range of 0.50 to 0.53 .

According to a second aspect of the present invention, the cutting blade has a plurality of R surface portions having different convex curved surfaces at the blade tip portion.

In Claim 3 , the said R surface part is continued over the side surface of a cutting blade, respectively.

  By configuring as in the present invention, it is possible to improve the cutting waste treatment and effectively prevent tooth surface flank in the vicinity of the tooth root of the gear.

Next, the best mode for carrying out the invention will be described.
1 is a front view showing an overall configuration of a hob cutter according to an embodiment of the present invention, FIG. 2 is a side view of FIG. 1, FIG. 3 is a front view showing a cutting edge shape, and FIG. FIG. 5 is a front view showing a state where a gear is created by a predetermined cutting blade, FIG. 5 is a front view showing an R surface provided at the blade tip of the cutting blade, and FIG. 6 is a gear when a conventional hob cutter is used. FIG. 7 is a gear generation diagram when the hob cutter of this embodiment is used, and FIG. 8 is a front view showing the shape of the tooth base of the gear.

First, the overall configuration of the hob cutter 1 of this embodiment will be outlined below.
As shown in FIGS. 1 to 3, the hob cutter 1 according to the present embodiment is provided with a hob body 2 that is driven to rotate and an outer peripheral surface 2 a of the hob body 2 with a predetermined spacing along the circumferential direction. Are formed, and the workpiece 4 is toothed by the cutting blades 3, 3 ... by rotating the hob body 2 at a high speed to form a predetermined tooth profile. It is comprised so that the gear 5 which has may be created.

  The hob body 2 is formed in a substantially cylindrical shape, and a through hole 2b is formed along the axial direction. The hob main body 2 is rotatable with respect to the workpiece 4 by inserting the rotating shaft 6 of the hobbing machine through the through hole 2b. On the outer peripheral surface 2a of the hob main body 2, a plurality of cutting blades 3, 3,... Are arranged along the circumferential direction, and a single thread that can twist each of the cutting blades 3, 3,. 30 are arranged with a predetermined spacing along 30.

  The screw 30 is arranged in several turns along the axial direction of the hob body 2 with one turn from the axial center of the hob body 2 toward both ends in the front view of the hob body 2 as one structural unit. Further, the thread 30 is composed of a plurality of cutting blades 3, 3,..., And the cutting blades 3 of the adjacent thread 30 are arranged so as to have a predetermined spacing. Note that the pitch of the thread 30 is determined in accordance with the module of the gear 5.

  When one gear 5 is geared, the teeth 50, 50,... Are created mainly by the cutting blades 3, 3,. In the hob cutter 1 of the present embodiment, when the hob body 2 is provided with several turns of the screw thread 30, the used cutting blades 3, 3. .. Can be used in sequence to extend the replacement cycle of the hob cutter 1.

  The cutting blade 3 has a substantially trapezoidal shape in a front sectional view, and inclined surfaces 31 and 31 as side surfaces are formed on both sides with respect to the screw rod 30. Further, the cutting edge 3 has a rake face 32 formed on one surface (front side in the rotational direction) in the direction along the thread 30 and on the other surface (rear side in the rotational direction) in the direction along the thread 30. A back surface 33 is formed.

  When the hob cutter 1 is used for gear cutting, first, the hob cutter 1 is disposed so that the cutting blades 3, 3... Are orthogonal to the tooth forming surface of the workpiece 4. While the hob body 2 is rotated once in a predetermined direction (arrow direction in FIG. 1), the workpiece 4 is rotated by one pitch of each tooth 50, 50. When the main body 2 is moved in the axial direction of the workpiece 4 (in the direction of the arrow in FIG. 1), a gear 5 having a predetermined tooth shape is created with respect to the workpiece 4. At that time, the teeth 50, 50,... Of the gear 5 are created mainly by the cutting blades 3, 3,. The tooth base 50a of each tooth 50, 50... And the involute curved surface (tooth surface 50b) on both sides of the tooth base are created by the cutting edge formed on the surface 32 (see FIG. 4).

Next, the blade shape design of the cutting blade 3 of the present embodiment will be described in detail below.
As shown in FIGS. 3 and 4, the cutting blade 3 of this embodiment is formed according to the specifications of the gear 5 to be created. Specifically, the tooth profile of the gear 5 to be created, that is, each tooth. Dislocation design is performed such that the ratio of the denden dam Dd to the total tooth height h of 50, 50. Further, as will be described later, a plurality of R surface portions 35, 35... Having different convex curved surfaces are formed on the blade tip portion 34 as the top portion.

  The “dislocation design of the cutting blade 3” in the present embodiment refers to designing the specifications of the cutting blade 3 so as to change the gear cutting pitch circle diameter of the gear 5, and specifically, the purpose. The specifications such as the pressure angle α, the pitch P between the cutting blades 3, the length ha of the blade edge, and the height hf of the blade base are set so as to be different from the reference design corresponding to the tooth profile of the gear 5. Say. The pressure angle α here is the inclination of the inclined surfaces 31, 31, and the blade edge length ha is the distance from the blade tip 34 of the cutting blade 3 to the reference pitch line PL. The length hf refers to the distance from the reference pitch line PL to the blade edge 36.

  The cutting blade 3 of this embodiment is designed so that the gear cutting pitch circle diameter of the tooth 50 is changed so that the Dedendam coefficient β of the tooth 50 becomes a predetermined value. The “Dedendam coefficient β” in the present embodiment is a ratio of the Dedendam Dd to the total tooth height h of each tooth 50, 50... Of the gear 5, and is represented by the following formula (1). It is expressed as a value obtained by dividing Dd by the total tooth height h. The predetermined range of the Dedendam coefficient β of the gear 5 is preferably set so that β is close to 0.50, and more preferably, β is set in the range of 0.53 to 0.50. . Further, “the gear cutting pitch circle diameter” means the diameter of the gear cutting pitch circle C3 (reference pitch circle) of the gear 5, and the gear cutting pitch circle C3 is represented on the gear 5 as a virtual true circle.

  β = Dd / h (1)

  The total tooth height h here refers to the separation between the tip circle C1 and the base circle C2 in the gear 5, and the diameter of the base circle C2 from the diameter of the tip circle C1 (tip circle diameter) (basic circle diameter). ) Minus the value. The denden dam Dd refers to the separation between the gear cutting pitch circle C3 and the base circle C2, and is represented by a value obtained by subtracting the diameter of the base circle C2 from the diameter of the gear cutting pitch circle C3 (tooth cutting pitch circle diameter). The

  As another specification of the tooth profile of the gear 5, the addendum Ad is a separation between the tooth tip circle C1 and the gear cutting pitch circle C3, and the diameter of the gear cutting pitch circle C3 from the diameter of the tooth tip circle C1. Expressed by subtracting. That is, the total tooth height h of each tooth 50, 50... Of the gear 5 in the present embodiment is equal to the sum of the denden dam Dd and the addendum Ad.

  Thus, in the cutting blade 3 of the present embodiment, the dedendam coefficient D of the gear 5 is changed so that the gear cutting pitch circle diameter of the gear 5 becomes a predetermined value, and the dedendam coefficient β of the gear 5 is in a predetermined range. The dislocation is designed so that the blade shape has a predetermined specification. The gear cutting pitch circle diameter of the gear 5 is changed by the shift design of the cutting blade 3, but the tooth profile of the gear 5 (for example, the diameter of the tip circle diameter and the basic circle diameter of the tooth 50) is changed before and after the shift design. does not change.

  Moreover, as shown in FIG.3 and FIG.5, the cutting blade 3 of a present Example has several R surface part 35 * 35 ... which has a different convex curved surface in the blade front-end | tip part 34 as a top part, Specifically, one first R surface portion 35a having a blade tip surface of the blade tip portion 34 formed in a convex shape, and a pair of first R surfaces 35a extending from both ends of the first R surface portion 35a to the inclined surfaces 31 and 31. Two R surface portions 35b and 35b are formed. Each R surface portion 35 (the first R surface portion 35a and the second R surface portion 35b) has a convex curved surface having a different curvature, and the curvature of each convex curved surface is the tooth profile (in particular, the tooth root) of the target gear 5. 50a) (see FIG. 4 and FIG. 8).

  An example of the design of the blade tip 34 will be described. First, the contact height H at which the R surface 35 is formed at the blade tip 34 is determined. The contact height H is set based on a fillet generation diameter that is equal to or less than the fillet generation diameter when the cutting edge 3 is not designed to be dislocated. The fillet generation diameter refers to the diameter of the gear 5 to the contact point between the fillet and the involute tooth surface, where a fillet is created at the tooth root 50a.

  Next, the first R surface portion 35a is calculated as a curvature R having a predetermined strength, and is set as an arc surface of an arc R1 having a circle center P1 on the center line CL of the cutting edge 3. Further, the second R surface portions 35b and 35b are calculated so as to have a curvature R having a predetermined strength, and are offset in a direction not overlapping the center line CL of the cutting blade 3 (left-right direction in FIG. 5). Are set as arc surfaces of the arc R2 having the circle center P2. Then, the end portion of the arc R1 and the end portion of the inclined surface 31 are smoothly continued by the arc R2, so that the R surface portion 35 continuous over the inclined surfaces 31 and 31 of the cutting blade 3 is designed. The

  When the gear 5 is created by using the hob cutter 1 of the present embodiment configured as described above, the reference pitch line PL of the cutting blade 3 that is designed to be displaced comes into contact with the gear cutting pitch circle C3 of the gear 5. In this way, the teeth 50, 50... Are created (see FIG. 4). And by comprising in this way, the cutting waste process in a gear-cutting process can be improved, and the tooth surface 50b near the tooth root of the gearwheel 5 can be prevented effectively.

Here, the gear cutting process of the gear 5 by the hob cutter 1 of the present embodiment will be described in detail below.
With reference to FIGS. 6 and 7, the gear cutting process of the gear 5 by the hob cutter 1 of the present embodiment is performed using a conventional hob cutter in which the cutting edge 3 is not designed to be shifted and the hob cutter 1 of the present embodiment. Compare with the gear generation diagram of the case. As shown in FIG. 6, when the cutting edge 3 is not designed to be shifted (when the cutting edge 3 is designed as a reference), the cutting edge 3 and the tooth surface 50b of the tooth 50 near the tooth base of the tooth 50 on the trailing side. A gap S appears between the two. On the other hand, as shown in FIG. 7, when the hob cutter 1 of this embodiment is used (when the cutting blade 3 is designed to be displaced), the gap S between the cutting blade 3 and the tooth surface 50 b of the tooth 50 is greatly increased. Reduced to

  The trailing side of the gear 5 refers to a flank on the far side of the cutting edge 3 (virtual cutting rack) of the hob cutter 1 in the gear 5, while the leading side of the gear 5 refers to the hob cutter in the gear 5. This means a flank on the near side of one cutting blade 3 (virtual cutting rack).

  In the gear cutting process of the gear 5, the process of generating cutting waste is usually started from the trailing side at the start of cutting the workpiece 4, and the cutting scrap that has grown greatly from the leading side at the end of cutting. It is pressed by the generated cutting waste and pressed against the tooth surface 50b on the trailing side. Therefore, cutting scraps are pressed against the tooth surface 50b in the vicinity of the tooth base 50a on the trailing side by the cutting blade 3, and the biting of the cutting waste occurs between the cutting blade 3 and the tooth surface 50b. As a result, the tooth surface 50b whip occurs.

  As described above, as described above, the cutting blade 3 and the tooth 50 have teeth near the tooth base of the tooth 50 on the trading side, as described above. This is because the gap S appears between the surface 50b (see FIG. 6). That is, when the dislocation design is not performed as in the case of the conventional cutting blade 3 (when the cutting blade 3 is designed as a reference), a gap S is generated between the cutting blade 3 and the tooth surface 50b of the tooth 50. Then, the cutting waste enters the gap S, and the cutting waste bites between the cutting edge 3 and the tooth surface 50b.

  In the hob cutter 1 of the present embodiment, the cutting edge 3 is designed to be displaced so that the ratio of the denden dam Dd to the total tooth height h of each tooth 50, 50. It is possible to reduce the gap S appearing on the tooth surface 50b near the base of the tooth 50 on the trading side with respect to the cutting blade 3. Therefore, there is no room for cutting waste to enter between the cutting edge 3 and the tooth surface 50b (gap S). As a result, the cutting waste is pressure-bonded by the tooth surface 50b in the vicinity of the tooth base on the trailing side. Occurrence of biting between the blade 3 and the tooth surface 50b can be prevented, and flaking of the tooth surface 50b can be effectively prevented.

  In particular, as a result of a confirmation test using the hob cutter 1 in which the cutting blade 3 of the present embodiment is designed to shift and the hob cutter in which the conventional cutting blade is designed as a reference, each tooth 50 and 50 of the gear 5 to be created is obtained. By setting the ratio of the denden dam to the total tooth height h (deden dam coefficient β) in the range of 0.53 to 0.50, it is possible to effectively prevent the tooth surface 50b from peeling. When the dislocation design is not performed as in the case of the conventional cutting blade 3 (when the cutting blade 3 is designed as a reference), the cutting blade 3 is usually designed to be displaced when the Dedendam coefficient β is around 0.60. Thus, the gap S between the cutting edge 3 and the tooth surface 50b of the tooth 50 can be reduced by gradually reducing the Denden dam coefficient β. However, if the Dedendam coefficient β is larger than 0.53, there is still room for cutting chips to enter. On the other hand, if the Dedendam coefficient β is smaller than 0.50, the tooth base 50a of the tooth 50 is cut down by the cutting blade 3. As a result, a gap S appears between the cutting edge 3 and the tooth surface 50b of the tooth 50.

  Further, as shown in FIG. 8, the cutting edge 3 is designed to be displaced in the hob cutter 1 of this embodiment, so that the tooth root 50a is cut down and the tooth edge 50a is cut down in the conventional cutting edge shape (cutting edge R). Therefore, it is necessary to finely adjust the shape of the tooth root 50a of the gear 5 by changing the shape of the blade tip 34. Then, like the cutting blade 3 of the present embodiment, by providing a plurality of R surface portions 35 having different convex curved surfaces at the blade tip portion 34, the shape of the tooth root 50a of the gear 5 is finely adjusted, and the tooth root Strength can be improved. That is, when the R surface portion 35 is provided on the blade tip 34 of the cutting blade 3 (solid line in FIG. 8), the teeth are compared with the case of the blade tip shape of the conventional blade tip 34 (dotted line in FIG. 8). It can be seen that the root 50a is thickened and the tooth root strength is improved.

  In particular, in the present embodiment, the R surface portion 35 is formed so that the first R surface portion 35a and the second R surface portion 35b are respectively continuous over the inclined surface 31 of the cutting blade 3, so that the blade tip portion 34 By smoothing the shape of the tooth base 50a, it is possible to effectively prevent cutting chips from being pressed and the biting between the cutting edge 3 and the tooth surface 50b.

  The hob cutter 1 of the present embodiment is not limited to the above-described embodiment, and various modifications can be made without departing from the object of the present invention.

The front view which showed the whole structure of the hob cutter which concerns on one Example of this invention. The side view of FIG. 1 similarly. The front view which showed the blade shape of the cutting blade. The front view which showed a mode that the gearwheel was created with the predetermined cutting blade. The front view which showed the R surface part provided in the blade front-end | tip part of a cutting blade. The gear creation diagram at the time of using the conventional hob cutter. The gear creation diagram at the time of using the hob cutter of a present Example. The front view which showed the shape of the tooth base of a gearwheel.

DESCRIPTION OF SYMBOLS 1 Hob cutter 2 Hob main body 2a Outer peripheral surface 3 Cutting blade 4 Workpiece 5 Gear 30 Screw thread 31 Inclined surface (side surface)
34 Blade tip portion 35 R surface portion 35a First R surface portion 35b Second R surface portion 50 teeth

Claims (3)

A hob body that is driven to rotate, and a plurality of cutting blades that are disposed on the outer peripheral surface of the hob body with a predetermined spacing along the circumferential direction, and the hob body is rotated at high speed. In the hob cutter that creates a gear by cutting the workpiece with the cutting blade,
The cutting blade is shaped such that the ratio of the denden dam to the total tooth height of each tooth of the gear to be created is in the range of 0.50 to 0.53 .
Hob cutter characterized by that. The hob cutter according to claim 1, wherein the cutting blade has a plurality of R-surface portions having different convex curved surfaces at a blade tip portion . Wherein R surface portion, the hob according to 請 Motomeko 2 you, characterized in that each continuously over the sides of the cutting edge.

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