JP2016034678A - Broach and broach processing method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a broach and a broach processing method capable of broach processing with high accuracy while suppressing a molding error caused in a work-piece.SOLUTION: At a circumference of a broach main body 1 formed in a shaft-like shape, a cutting blade part 4 where a plurality of cutting blades 5 are projected and arranged in a longitudinal direction of the broach main body 1 is formed. The cutting blade part 4 includes: a first external diameter rising part 4A where an external diameter of the cutting blade 5 grows big sequentially from a longitudinal tip side of the broach main body 1 to a rear end side; a tooth thickness rising part 4B where thickness of the cutting blade 5 in a circumferential direction of the broach main body 1 grows big sequentially from the cutting blade 5 at a rear end of the first external diameter rising part 4A to the rear end side; and a second external diameter rising part 4C where the external diameter of the cutting blade 5 grows big sequentially from the cutting blade 5 at a rear end of the tooth thickness rising part 4B to the rear end.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a broach used for broaching of an internal gear or the like, in which a plurality of cutting blades protrude from the outer periphery of a shaft-shaped broach main body to form a cutting blade portion disposed in the longitudinal direction of the broach main body, and the broach It is related with the broaching method by this.

  As such broaching of an internal gear, for example, Patent Document 1 discloses a helical broach composed of a rough blade that roughly forms a tooth profile by cutting the outer diameter and a finishing blade that finishes the tooth profile by cutting the tooth thickness. It describes that a helical gear is machined inside a tooth groove that is frequently used in an automobile transmission or the like.

  That is, in such a helical broach, the rough blade on the front end side of the broach body is formed so that the outer diameter of the cutting edge increases sequentially toward the rear end side, and a tooth groove with a predetermined depth is formed on the workpiece. Next, the finishing blade on the rear end side of the rough blade is formed so that the thickness of the cutting blade in the circumferential direction of the broach body gradually increases toward the rear end side, and the tooth surface of the tooth gap is driven in the circumferential direction. The tooth surface is finished so that the groove width is widened.

JP 2004-306148 A

  By the way, in such a helical broach, the cutting edge of the rough blade and the cutting edge of the finishing blade are arranged along a spiral that is twisted around the axis of the broach body, and the front end of the broach body rotates relative to the workpiece. Of these, the above-mentioned spiral tooth gap is formed, but in the cutting of the outer diameter with a rough blade, the sharp edge of the cutting edge is sharper than the obtuse angle on the opposite side, so the cutting edge cuts. In some cases, the bite bites into the acute angle side more gradually than the position of the power tooth surface.

  Along with this, the tooth surface of the tooth gap formed on the workpiece to a predetermined depth may fall to the acute angle side, and a forming error may occur. Since the tooth thickness is increased and guided so as to drive the entire tooth surface in the circumferential direction, the accuracy of the finish-cut tooth profile may be impaired.

  The present invention has been made under such a background, and an object of the present invention is to provide a broach capable of performing high-precision broaching while suppressing forming errors generated in a workpiece, and a broaching method using the broach.

  In order to solve the above-described problems and achieve such an object, the broach of the present invention has a plurality of cutting blades projecting on the outer periphery of the shaft-shaped broach body and disposed in the longitudinal direction of the broach body. A cutting edge portion is formed, and in this cutting edge portion, a first outer diameter increasing portion in which the outer diameter of the cutting blade sequentially increases from the front end side in the longitudinal direction of the broach body toward the rear end side. And a tooth thickness increasing portion in which the thickness of the cutting blade in the circumferential direction of the broach body gradually increases toward the rear end side from the cutting edge at the rear end of the first outer diameter increasing portion, A second outer diameter increasing portion in which the outer diameter of the cutting edge further increases gradually from the rear end cutting edge toward the rear end side is provided.

  Further, the broaching method of the present invention is a broaching method using such a broach, and by inserting the broach body into the workpiece from the front end side, first the outer edge is cut by the cutting edge of the first outer diameter rising portion. The first tooth gap is formed by cutting the diameter up, and then the tooth surface of the first tooth gap is cut by increasing the tooth thickness so as to drive the tooth surface of the first tooth gap in the circumferential direction of the broach body by the cutting edge of the tooth thickness increasing portion. The second tooth gap is formed, and the cutting edge of the second outer diameter rising portion is guided by the tooth surface of the second tooth groove while cutting the outer diameter to cut the groove depth more than the first tooth groove. A deep third tooth gap is formed.

  In such a broach and broaching method, first, the cutting edge is cut into the workpiece from the first outer diameter rising portion on the front end side in the longitudinal direction of the broach body. On the end side, there is provided a second outer diameter increasing portion in which the outer diameter of the cutting edge gradually increases from the cutting edge at the rear end of the tooth thickness increasing portion toward the rear end side through the tooth thickness increasing portion. Therefore, the depth of the first tooth gap formed on the workpiece by the first outer diameter rising portion is shallower than the depth of the third tooth groove formed by the second outer diameter rising portion. . For this reason, even if a molding error occurs in the tooth surface of the first tooth gap due to the outer diameter increasing cutting by the first outer diameter increasing portion, as described in Patent Document 1, the depth of the third tooth groove is reached. The outer diameter can be reduced compared to the case of cutting at a time.

  Therefore, even when the second tooth gap is formed by cutting the tooth thickness by the tooth thickness increasing portion following the rear end side of the first outer diameter increasing portion, the molding error of the second tooth groove is suppressed to a small level. And a precise tooth surface can be formed. In the outer diameter increasing cutting by the second outer diameter increasing portion following the rear end side of the tooth thickness increasing portion, the cutting blade is guided by the tooth surface of the second tooth gap thus formed with high accuracy. Since the third tooth groove can be formed, according to the broach and broaching method of the above configuration, it is possible to improve the broaching accuracy by suppressing the forming error over the entire tooth groove.

  In addition to the first and second outer diameter increasing portions and the tooth thickness increasing portions located therebetween, the third, fourth,... Outer diameter increasing portions and the second, third. Three or more outer diameter increasing portions including the first outer diameter increasing portion and the second outer diameter increasing portion, and two or more tooth thickness increasing portions including the tooth thickness increasing portion. The tooth gap may be formed by alternately performing cutting with an outer diameter increasing three times or more and cutting with a tooth thickness increasing twice or more alternately in order from the longitudinal tip side of the broach body.

  Moreover, in the broach of this invention, even if the tooth thickness increase part and the 2nd outer diameter increase part are formed in the shell part detachably attached to a broach main body as described in patent document 1, for example Although the first outer diameter increasing portion, the tooth thickness increasing portion, and the second outer diameter increasing portion are integrally formed on the broach body, the space for attaching the shell portion is saved and the broach body The overall length can be shortened. For this reason, it becomes possible to improve the handleability and cost reduction of the broach body, and to promote the space saving of the broaching machine on which the broach is mounted.

  As described above, according to the present invention, it is possible to perform high-precision broaching while suppressing a molding error of a tooth gap of a workpiece.

It is a side view which shows one Embodiment of this invention. It is the figure which piled up the cutting blade along the lead | read | reed which shows the cutting form by the 1st outer diameter raising part of embodiment shown in FIG. It is the figure which piled up the cutting blade along the lead | read | reed which shows the cutting form by the tooth thickness increase part of embodiment shown in FIG. It is the figure which piled up the cutting blade along the lead | read | reed which shows the cutting form by the 2nd outer diameter raising part of embodiment shown in FIG.

  1 to 4 show an embodiment of the broach and broaching method of the present invention. The broach according to the present embodiment is a helical broach for processing an internal helical gear or the like used in the above-described automobile transmission, for example, and is a long shaft centered on the axis O by a hard material such as high-speed tool steel. A front grip portion 2 is formed at the front end portion (left side portion in FIG. 1) of the broach main body 1 formed on the rear portion, and a rear grip portion 3 is formed at the rear end portion (right side portion in FIG. 1). A cutting edge portion 4 is formed between the portions 2 and 3.

  Such a helical broach is supported by the broaching machine by being inserted into the inner periphery of an annular workpiece (not shown) from the front end side, and the front and rear grip portions 2 and 3 are gripped, and is relatively relative to the workpiece. A plurality of spiral tooth grooves are cut on the inner periphery of the workpiece by the cutting blade portion 4 and inserted around the axis O in the direction of the axis O, and rotated around the axis O. A tooth profile such as a helical gear is formed between the grooves.

  A plurality of (many) cutting blades 5 projecting from the outer periphery of the broach main body 1 are disposed in the cutting blade portion 4 at intervals in the circumferential direction with respect to the axis O direction (longitudinal direction) of the broach main body 1. These cutting blades 5 are arranged at equal intervals in the circumferential direction in accordance with the intervals of the above-mentioned tooth grooves formed on the inner periphery of the workpiece, and correspond to the spiral formed by the tooth grooves in the axis O direction. It is arranged so as to form a row of cutting blades spaced along a lead (string winding) L twisted around the axis O.

  And in the cutting blade part 4 in which these cutting blades 5 are arranged, the outer diameter from the axis O of the cutting blade 5 is directed toward the rear end side in order from the front end side to the rear end side in the axis O direction. The first outer diameter increasing portion 4A that gradually increases, and the thickness of the cutting blade 5 in the circumferential direction of the broach body 1 from the rear end cutting edge 5AN of the first outer diameter increasing portion 4A sequentially toward the rear end side. Increased tooth thickness increasing portion 4B, and second outer diameter increase in which the outer diameter from the cutting edge 5BN at the rear end of the tooth thickness increasing portion 4B from the axis O of the cutting blade 5 further increases toward the rear end side. 4C. The cutting edges 5 of the first outer diameter increasing portion 4A, the tooth thickness increasing portion 4B, and the second outer diameter increasing portion 4C are formed integrally with the broach body 1, that is, the broach of the present embodiment is an integral type. Helical brooch.

  Among these, in the first outer diameter increasing portion 4A, the cutting blade 5 extends from the outer peripheral surface of the broach body 1 to the outer peripheral side (the cutting edge side, the upper side in common with FIGS. 2 to 4) as shown by the solid line in FIG. Is formed at a constant pitch in the order of the cutting edge 5A1 at the front end in the direction of the axis O to the cutting edges 5A2, 5A3,... On the rear end side, and the outer diameter from the axis O is increased accordingly. Has been.

  Further, both side portions of the cutting blade 5 in the circumferential direction of the broach main body 1 (in the left-right direction in common with FIGS. 2 to 4) overlap each other when viewed in the direction along the lead L, and the first outer diameter rises. After the cutting edge 5AN at the rearmost end in the portion 4A is increased in outer diameter and cut, the substantially isosceles trapezoidal shape gradually becomes narrower toward the groove bottom side (the cutting edge side of the cutting edge 5) as shown in FIG. The shapes of the cutting edges 5A1 to 5AN are set so that the first tooth gap A having a cross section is formed on the inner periphery of the work.

  However, the groove depth of the first tooth groove A formed in the first outer diameter increasing portion 4A is a tooth groove to be finally formed on the workpiece (a third tooth groove described later in this embodiment). It is set to be shallower than the groove depth of C). Further, the upper and lower bases of the above-mentioned isosceles trapezoidal shape as shown in FIG. From the base of the cutting edge 5 of the first outer diameter rising portion 4A (lower side in common with FIGS. 2 to 4) and the rear end side so that the concave portions extending in a substantially rectangular shape are formed respectively. A convex portion 6 may be formed on the cutting edge portion of the cutting blade 5.

  The cutting edge 5 of the tooth thickness increasing portion 4B following the broach main body 1 rear end side of the first outer diameter increasing portion 4A is located on the rear end side from the cutting edge 5B1 at the front end in the axis O direction as shown by a broken line in FIG. In order of the cutting edges 5B2, 5B3,..., The outer diameter from the axis O is within the range of the outer diameter of the cutting edge 5AN at the rearmost end of the first outer diameter increasing portion 4A, and the thickness in the circumferential direction of the broach body is sequentially increased. It is formed to be large.

  In the present embodiment, the cutting edges 5B1, 5B2,... In the tooth thickness increasing portion 4B are the first tooth gap A in which the side portion in the circumferential direction of the broach body is formed in the first outer diameter increasing portion 4A. 4 is formed so as to be sequentially increased at a substantially constant pitch toward the rearmost cutting edge 5BN while being substantially parallel to the hypotenuse of the isosceles trapezoidal cross section. A second tooth gap B having a groove width wider than that of the first tooth groove A as shown in FIG.

  In this way, in the second tooth gap B formed on the workpiece by the tooth thickness increasing portion 4B, a slope that intersects the tooth surface at an obtuse angle is formed on the groove bottom side of the tooth surface facing the circumferential direction. Further, the chamfered portion 7 overlapped in the order of cutting edges 5B1, 5B2,... 5BN as shown in FIG. May be formed. Moreover, when processing an internal helical gear as described above, the side portion of the cutting edge 5 of the tooth thickness increasing portion 4B may form an involute curve.

  Furthermore, the cutting blade 5 in the second outer diameter rising portion 4C formed on the rear end side in the axis O direction of the tooth thickness increasing portion 4B is formed in an isosceles trapezoid shape that becomes narrower toward the cutting edge side. Then, both side portions of the blade base portion overlap with both side portions of the cutting edge 5BN at the rearmost end of the tooth thickness increasing portion 4B when viewed in the direction along the lead L, and both side portions of the blade edge portion are on the blade base side. It is formed so that it may be located on the extended line of both sides. Therefore, as described above, when the side portion of the cutting edge 5 of the tooth thickness increase portion 4B has an involute curve, the side portion of the cutting edge 5 of the second outer diameter increase portion 4C also forms an involute curve. Become.

  Similarly to the cutting edge 5 of the first outer diameter increasing portion 4A, the cutting edge 5 of the second outer diameter increasing portion 4C protrudes from the outer peripheral surface of the broach main body 1 to the outer peripheral side as indicated by a broken line in FIG. The height increases at a constant pitch in the order of the cutting edge 5C1 at the front end of the axis O direction to the cutting edges 5C2, 5C3,... At the rear end side. The cutting edge 5AN at the rearmost end of 4A is formed so as to gradually increase beyond the outer diameter. The protruding height of the cutting edge 5CN at the rearmost end of the second outer diameter increasing portion 4C is set to be equal to the depth of the tooth groove (third tooth groove C) formed in the workpiece.

  When the work is broached by the broach configured in this way, first, the cutting edges 5A1, 5A2,... 5AN of the first outer diameter increasing portion 4A are sequentially cut into the inner periphery of the work, and the first tooth gap A is formed, but the protruding height of the cutting edge 5AN at the rearmost end of the first outer diameter rising portion 4A is the third tooth finally formed on the workpiece by the second outer diameter rising portion 4C. It becomes smaller than the depth of the groove C. For this reason, even if a molding error occurs as the tooth surface of the first tooth space A falls due to the outer diameter increasing cutting by the first outer diameter increasing portion 4A, the groove depth of the third tooth space C is reached at once. Compared to the case of cutting by increasing the outer diameter, it is possible to suppress a molding error due to such a tooth surface collapse.

  Next, the tooth thickness increasing portion 4B following the rear end side of the first outer diameter increasing portion 4A is cut by the tooth thickness increasing portion to form the second tooth gap B, and the tooth gap to be formed on the workpiece is determined. The part on the inner circumference side of the workpiece is finished. Here, the cutting with increased tooth thickness is performed so that the tooth surface of the first tooth gap A in which the forming error is suppressed as described above is driven in the circumferential direction. The tooth surface of the second tooth gap B on the inner peripheral side can also be finished with high accuracy while suppressing molding errors.

  The third tooth gap C having the final depth is cut by the second outer diameter increasing portion 4C continuing to the rear end side of the tooth thickness increasing portion 4B. The cutting edges 5C1, 5C2,... 5CN of the outer diameter increasing portion 4C are formed so as to overlap with the cutting edge 5BN at the rearmost end of the tooth thickness increasing portion 4B along the lead L. By doing so, cutting is performed with the tooth thickness increased as guided by the tooth surface of the second tooth gap B finished with high accuracy as described above.

  Accordingly, in the workpiece broached to the third tooth gap C having the final depth in this way, it is possible to reduce a molding error due to a fall of the tooth surface. For this reason, according to the broach and broaching method of the said structure, it becomes possible to perform broaching of a helical gear etc. with high precision.

  Further, in the broach of the present embodiment, the first outer diameter increasing portion 4A, the tooth thickness increasing portion 4B, and the second outer diameter increasing portion 4C are integrally formed with the broach body 1. In this respect, for example, the second outer diameter increasing portion 4C at the rearmost end, or the second outer diameter increasing portion 4C and the tooth thickness increasing portion 4B may be formed in the shell portion that is detachable from the broach body 1. In that case, a space for attaching such a shell part itself or a nut for fixing the shell part must be secured in the broach body, and the overall length of the broach body is inevitable. .

  In contrast, by forming the first outer diameter increasing portion 4A, the tooth thickness increasing portion 4B, and the second outer diameter increasing portion 4C integrally with the broach body 1 as in the present embodiment, the broach The main body 1 can be shortened, and the handleability can be improved and cost reduction can be promoted. In addition, it is possible to save space for a broaching machine to which such a broach is attached.

  In the present embodiment, as described above, the case where the present invention is applied to a helical broach for processing a helical gear or the like in which a tooth groove formed on a workpiece is spirally twisted has been described. The broach and broaching method can also be applied to broaches and broaching methods other than the helical broach. In the present embodiment, the second outer diameter increasing portion 4C is formed at the rearmost end of the broach main body 1. However, the second tooth thickness increasing portion and the third outer diameter increasing are arranged on the rear end side. Forming three or more outer diameter increasing portions including the first and second outer diameter increasing portions 4A and 4C, and two or more tooth thickness increasing portions including the tooth thickness increasing portion 4B. Alternatively, the cutting blades 4 may be alternately provided in order from the front end side in the longitudinal direction of the broach main body 1 and the tooth gaps may be formed stepwise.

DESCRIPTION OF SYMBOLS 1 Brooch main body 4 Cutting edge part 4A 1st outer diameter rising part 4B Tooth thickness rising part 4C 2nd outer diameter rising part 5 Cutting blade 5A1, 5A2, ... 5AN Cutting edge 5B1 of the 1st outer diameter rising part 4A, 5B2,... 5BN Cutting edge of tooth thickness increase part 4B 5C1, 5C2,... 5CN Cutting edge of second outer diameter increase part 4C A 1st tooth space B 2nd tooth space C 3rd tooth space O Broach body 1 axis L Lead (string winding) where the row of cutting blades 5 is located

Claims (4)

  A plurality of cutting blades protrude from the outer periphery of the broach main body having an axial shape to form a cutting blade portion disposed in the longitudinal direction of the broach main body. The cutting blade portion has a longitudinal tip of the broach main body. A first outer diameter rising portion in which the outer diameter of the cutting blade increases sequentially from the side toward the rear end side, and a broaching body of the cutting blade from the cutting blade at the rear end of the first outer diameter rising portion The tooth thickness increasing portion where the thickness in the circumferential direction increases gradually toward the rear end side, and the outer diameter of the cutting edge further increases gradually toward the rear end side from the cutting edge at the rear end of the tooth thickness increasing portion. A broach comprising a second outer diameter rising portion.   Three or more outer diameter rising portions including the first outer diameter increasing portion and the second outer diameter increasing portion, and two or more tooth thickness increasing portions including the tooth thickness increasing portion are the broach body. The broach according to claim 1, wherein the broach is alternately provided in order from the front end side in the longitudinal direction.   The first outer diameter increasing portion, the tooth thickness increasing portion, and the second outer diameter increasing portion are integrally formed on the broach body according to claim 1 or 2. Brooch as described.   A broaching method using a broach according to any one of claims 1 to 3, wherein the broach body is first inserted into a workpiece from the front end side, thereby first cutting the first outer diameter rising portion. Cutting with an outer diameter increased by a blade to form a first tooth groove, and then cutting with a tooth thickness increased so that the tooth surface of the first tooth groove is driven in the circumferential direction of the broach body by the cutting blade of the tooth thickness increased portion. Then, the second tooth gap is formed, and further, the outer diameter rising cutting is performed while guiding the cutting edge of the second outer diameter rising portion by the tooth surface of the second tooth gap, and the second tooth gap is cut from the first tooth groove. And forming a third tooth groove having a deep groove depth.

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