JP2007253297A - Helical broach - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To process a broach more precisely by preventing adhesion of foreign matters due to welding when a finishing blade on a rear end of a broach body performs cutting while guiding a cutting blade by a guide blade on an opposite side in a peripheral direction. <P>SOLUTION: A cutting blade 5 on a rear end of a broach body 1 among a plurality of cutting blades 5 helically arranged on an outer periphery of an axial broad body 1 is used as a finishing blade 7. A cutting blade 9 is formed to the finishing blade 7 in a crossing ridgeline part between a rake face 7A directed to a tip side of the broach body 1 and a side face 7B directed to one side in the peripheral direction of the broach body 1. The side face directed to the other side in the peripheral direction is used as a guide face 7C, and a relief part 11 formed to move at least one part on the tip side of the broach body 1 backward relative to an extended face P of the remaining portion. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a helical broach used for cutting a workpiece having a twisted groove on its inner periphery, such as a helical internal gear.

  As such helical internal gears, for example, planetary internal gears have been provided in various ways as gears for automatic transmissions. Recently, as the required quality of automatic transmissions has increased, so has the demand for higher gear quality. It is getting to be. In consideration of economy and accuracy, such gears have conventionally been processed by a single process with a helical broach up to the finishing process, and then quenched and tempered to ensure strength. However, since deterioration in accuracy is unavoidable due to distortion caused by such heat treatment, a method of performing a cutting process with a helical broach on a material subjected to soft nitriding treatment has been adopted as a solution.

Here, as a helical broach used for processing such a helical internal gear, for example, in Patent Document 1, a rough blade group including spline blades in which a required tooth profile is driven in the tooth height direction and the tooth height for cutting is gradually increased. Each of the cutting edges of each spline blade, and a finishing blade group alternately provided in the axial direction with a spline blade and a round blade with a gradually increasing outer diameter for cutting only the crest of the inner tooth to be machined. In a helical broach arranged along a required twist angle, a plurality of blades on the final blade side of the finishing blade group are only spline blades, and the spline blades are configured so that the tooth thickness gradually increases. ing. In such a helical broach, after the tooth profile of the internal gear is formed to the required tooth height by the rough blade group, the crest is formed by the round blade of the finishing blade group and the tooth thickness gradually increases. Therefore, it is said that a tooth profile with extremely high accuracy can be secured because it is finished by cutting in the tooth thickness direction.
JP-A-60-150907

  Incidentally, in recent years, in such a helical broach, among the spline blades of the finishing blade group, that is, the finishing blades, in the plurality of finishing blades on the tip side of the broach body, the rake face facing the tip side and the circumferential direction of the broach body A cutting blade is formed only at the crossing ridge line part with the side facing one side, and the cutting blade is gradually increased to one side in the circumferential direction with these finishing blades toward the rear end side. In a plurality of finishing blades on the rear end side of the broach body, the cutting blade is formed only at the intersection ridge line portion between the rake face and the side face facing the other side in the circumferential direction, and the tooth thickness is set at the rear end. The cutting blade is protruded by gradually increasing toward the other side in the circumferential direction.

  Accordingly, in such a helical broach, after cutting one tooth surface (usually the acute angle side tooth surface) of the internal gear in the tooth thickness direction with the cutting blade of the finishing blade on the front end side, cutting of the finishing blade on the rear end side is performed. The other tooth surface (usually the obtuse angle side tooth surface) of the opposite internal gear to be cut is driven in the tooth thickness direction and cut by the cutting blade. When the tooth surface of the work gear is driven and cut in the thickness direction by these finishing blades, the side surfaces facing the circumferential direction of the finishing blade on the side opposite to the side on which the cutting blade is formed (finishing blade) In the finishing blade on the front end side of the group's inner broach body, the side facing the other side in the circumferential direction (in the finishing blade on the rear end side, the side facing the one side in the circumferential direction) and the rake face are cut. The above-mentioned side surface connected to the guide blade is a guide blade that is slidably brought into contact with the tooth surface of the work gear opposite to the tooth surface and guides the cutting blade in the lead direction of the internal gear and is not used for cutting. Is a guide surface provided with a clearance angle including 0 ° and a negative angle with respect to the guide blade.

  However, if the material subjected to the soft nitriding treatment as described above is cut by such a helical broach, the workability of the material is poor, and therefore, foreign matter is especially present on the cutting blade of the broach body, particularly on the guide blade and the guide surface. Adhesion (welding) is likely to occur, and there is a concern that the machining surface accuracy of the internal gear to be machined as a workpiece may deteriorate. That is, when the cutting blade is guided by the guide blades on the opposite side of the front end side and the rear end side of the broach main body among the finishing blades as described above, the material is applied to the guide blade and the guide surface connected thereto. If foreign matter adheres due to welding, the cutting blade will protrude to the extent that the cutting accuracy will deteriorate, and in particular, the rear end will be finished on the tooth surface that has been finished by the cutting blade of the front end finishing blade. When the guide blade or the guide surface to which the foreign material of the blade adheres is slidably contacted, the tooth surface that has been finished with corners is peeled and damaged, so that the quality of the machined surface is impaired. In addition, when the guide blade is in sliding contact with the tooth surface of the internal gear to be guided to guide the finishing blade in this way, sufficient cutting oil is supplied to the guide blade and the guide surface connected to the rear end side of the broach body. -It is not held, and the generated frictional heat accumulates, making it easier for welding to occur and also reducing the broach life.

  The present invention has been made under such a background. As described above, when cutting is performed while the cutting blade is guided by the guide blade on the opposite side in the circumferential direction in the finishing blade on the rear end side of the broach body, welding is performed. It is an object of the present invention to provide a helical broach that can prevent the adhesion of foreign matters due to the above and can promote more accurate broaching.

  In order to solve the above problems and achieve such an object, according to the present invention, a plurality of cutting blades projecting radially outward of the broach body are provided on the outer periphery of the shaft-shaped broach body. In a helical broach arranged in a spiral shape that twists about the axis of the broach body from the front end side to the rear end side of the main body, the cutting blade on the rear end side of the broach main body among the cutting blades is a finishing blade. In the finishing blade, a cutting blade is formed at the intersection ridge line portion between the rake face facing the tip side of the broach body and the side face facing one side of the circumferential direction of the broach body, and the other side of the circumferential direction is The facing side surface is a guide surface, and the guide surface is provided with a relief portion formed so that at least a part of the front end side of the broach body is retracted with respect to the extension surface of the remaining portion.

  In the helical broach configured as described above, the escape portion is formed so that at least a part of the front end side portion of the broach body of the guide surface is recessed with respect to the extension surface of the remaining portion. The blade itself can be shortened, or the entire cross ridge of the rake face that becomes the guide blade can be retracted, reducing frictional heat generation and clogging and reducing the amount of cutting oil applied to the guide blade and guide surface. Supply and retention can be improved. That is, for example, if the escape portion is formed such that a part of the guide surface in the radial direction of the broach body recedes with respect to the extension surface of the remaining portion in the radial direction, the escape portion becomes the finish blade. By intersecting the rake face, part of the guide blade will be recessed with respect to the other part, and the guide blade will be shortened by that amount. The length is shortened to reduce the generation of frictional heat and fogging, and the cutting fluid can be effectively guided and retained from the recessed part to improve the lubrication and cooling effect. be able to. In this case, the relief portion is continued from the front end side to the rear end side of the broach body of the guide surface, so that the frictional heat is surely dissipated and the cutting oil is supplied to the guide surface more efficiently. can do.

  Further, if the escape portion is formed such that the portion of the guide surface on the front end side of the broach main body is set back with respect to the extension surface to the front end side of the remaining portion on the rear end side of the broach main body, what is a cutting blade? The intersecting ridge line part of the rake face that is the opposite guide blade is itself formed in a negative land shape that is retreated with respect to the extension surface to the front end side of the guide surface on the rear end side of the broach body. The cutting fluid can also be effectively guided to enhance the lubrication / cooling effect. In particular, as described above, when a part of the guide surface in the radial direction of the broach body is retreated to form a relief part, a relief part that is also retreated with respect to the extension surface to the tip side is provided. Even if the sliding contact pressure per unit length is increased by shortening the guide blade, the tooth surface can be prevented from being cut by the guide blade. In this case, the intersection ridge line portion between the negative land portion and the remaining guide surface portion that does not retreat on the rear end side of the broach body functions as a guide blade, so that it matches the position of the intersection ridge line portion. Then, the protruding amount of the cutting blade may be set.

  Thus, according to the helical broach having the above-described configuration, the guide blade is shortened or made into a negative land shape to reduce the generation of frictional heat and fogging, and to efficiently supply and hold the cutting fluid to lubricate / Since the cooling effect can be improved, even if the workpiece material has been subjected to soft nitriding treatment, it is possible to prevent adhesion of foreign matters due to welding to the guide blade or the guide surface. Therefore, it is possible to prevent the processing accuracy from being deteriorated by the foreign matter adhered in this way, and to prevent the processing quality from deteriorating due to the tooth surface of the finished workpiece being peeled and damaged, and extending the broach life. Can be achieved. Therefore, it is possible to provide a helical broach that can sufficiently cope with the advancement of quality for helical internal gears such as planetary internal gears accompanying the advancement of the required quality of recent automatic transmissions. Even when the relief portion is formed on a part of the guide surface in the radial direction as described above or formed on the front end side of the broach body, the remaining portion of the guide surface is an area of the entire guide surface. However, if the area of the remaining part of the guide surface is smaller than this, the guideability by this guide surface may be impaired.

  1 to 3 show a first embodiment of a helical broach according to the present invention that cuts a workpiece having a twisted groove on its inner periphery like a helical internal gear such as the planetary internal gear. In the present embodiment, the broach main body 1 has a long shaft shape with the axis O as the center as shown in FIG. 1, and both end portions thereof are grip portions 2 and 3. The space is a cutting edge portion 4. In the cutting blade portion 4, a plurality of (many) cutting blades 5 projecting radially outward with respect to the axis O are provided on the outer periphery of the broach main body 1 at the front end side (lower side in FIG. 1). ) To the rear end side (upper side in FIG. 1) so as to form a spiral that twists around the axis O, and a plurality of rows of such cutting blades 5 are formed at intervals in the circumferential direction. ing.

  Here, a plurality of cutting blades 5 at the tip side of the broach main body 1 in the cutting blade portion 4 are rough blades 6 for driving the tooth profile of the helical internal gear in the tooth height direction and cutting them. , The tooth height of the cutting blades 5 is sequentially increased along the row of the cutting blades 5 toward the rear end side of the broach body 1. Further, the tooth edge surface (groove wall surface of the torsion groove of the workpiece) of the tooth profile cut to the predetermined tooth height by the rough blade 6 is toothed on the cutting edge portion 4 on the rear end side of the broach body 1 with respect to the rough blade 6. A plurality of finishing blades 7 are provided which are driven into the thickness direction, that is, the circumferential direction of the broach body 1 to form a predetermined tooth thickness. In the present embodiment, the cutting edge 4 on the rear end side of the broach body 1 provided with the finishing blade 7 is formed on the outer periphery of a cylindrical shell 8 that is detachably attached to the broach body 1. Alternatively, it may be formed integrally with the broach body 1 together with the rough blade 6. Moreover, the rounded blade which cuts the tooth top part of a tooth profile may be provided in the part made into the finishing blade 7. FIG.

  Further, the plurality of finishing blades 7 are provided on the front end side of the broach body 1 among the finishing blades 7, and a plurality of finishing blades 7 for driving and cutting one tooth surface of the tooth profile, The finishing blade 7 is provided on the rear end side of the broach main body 1 and is provided with a plurality of finishing blades 7 for driving and cutting the other tooth surface of the tooth profile. Therefore, in these finishing blades 7, there are a rake face 7A facing the tip end side of the broach main body 1 and a side face 7B facing one of the circumferential directions of the broach main body 1 which drives the tooth surface and cuts it. The cutting blade 9 is formed at the intersecting ridge line portion. Normally, the finishing blade 7 on the tip side of the broach main body 1 among the all finishing blades 7 is an acute angle side tooth surface whose tooth surface intersects an acute angle with the end surface on the broach insertion side of the gear. Then, the finishing blade 7 on the rear end side of the broach main body 1 is driven to cut the obtuse angle side tooth surface intersecting with the broach insertion side end surface opposite to the obtuse angle side.

  On the other hand, the tooth on the side opposite to the tooth surface to be cut in the tooth thickness direction at the intersecting ridge line portion of the rake face 7A on the opposite side in the circumferential direction of the broach body 1 from the side on which the cutting blade 9 is formed. A guide blade 10 that slides on the surface and guides the finishing blade 7 is formed, and the other side surface of the finishing blade 7 connected to the guide blade 10 is a guide surface 7C. The other side surface of the guide surface 7C and one side surface 7B of the finishing blade 7 connected to the cutting blade 9 are on the rear end side of the broach body 1 with respect to the guide blade 10 and the cutting blade 9, respectively. The clearance angle is attached to Of these, the guide surface 7C is provided with an escape portion 11 formed so that at least a part of the front end side of the broach body 1 is retracted with respect to the extension surface of the remaining portion. Then, a part of the guide surface 7C in the radial direction is a relief portion 11, and the remaining portion in the radial direction, that is, the guide portion 7D of the guide portion 7C, which is connected to the guide blade 10 in the radial extension surface P in the radial direction. It is formed so as to retreat.

  More specifically, in the present embodiment, as shown in FIG. 2 and FIG. 3, the portion on the radially inner peripheral side of the broach body 1, that is, the outer peripheral side, of the other side surface of the finishing blade 7 that is the guide surface 7 </ b> C. For example, the base portion of the finishing blade 7 that protrudes to the edge is formed so as to be cut out perpendicularly in the tooth thickness direction from the center in the tooth height direction of the finishing blade 7 with respect to the outer peripheral portion in the cross section parallel to the rake face 7A. Thus, the root portion is formed with the relief portion 11 that is retracted in the tooth thickness direction with respect to the extended surface P that extends the remaining portion (guide portion 7D) on the outer peripheral side of the side surface to the inner peripheral side as it is. Has been. Further, in the present embodiment, the relief portion 11 formed in this way is formed in the entire length in the direction of the axis O from the front end side to the rear end side of the broach body 1 of the finishing blade 7. Also at the ridge line portion intersecting with the rake face 7A, the guide blade 10 is formed only on the outer peripheral portion, and the inner peripheral portion is formed on the tooth surface A of the helical internal gear W as shown in FIG. It will be retreated against. In FIG. 3, reference numeral B denotes a tooth surface of the helical internal gear W that is driven and cut in the tooth thickness direction by the cutting blade 9 of the finishing blade 7.

  In the thus configured helical broach, the relief portion 11 is thus formed on the guide surface 7C, whereby the guide blade 10 is shortened and the guide blade 10 is brought into sliding contact with the tooth surface A of the helical internal gear W. Since the length is also shortened, the generation of frictional heat due to the sliding contact of the guide blade 10 can be reduced, and the generated frictional heat can be released from the escape portion 11 and between the guide surface 7C and the tooth surface A. It is possible to prevent frictional heat from being trapped. In addition, the cutting fluid supplied at the time of processing enters between the guide blade 10 and the guide portion 7D of the guide surface 7C and the tooth surface A from the escape portion 11, lubricates and cools both, and heat is also generated by this cooling. Since the removed cutting fluid is discharged from the escape portion 11, it is possible to more reliably suppress the generation of frictional heat and clouding.

  Therefore, according to the helical broach having the above-described configuration, it is possible to prevent a situation in which foreign material adheres due to welding of the material of the helical internal gear W to the guide blade 10 or the guide surface 7C due to such frictional heat. An error occurs in the position of the cutting blade 9 for driving and cutting the tooth surface B due to the adhesion of the foreign matter, so that the processing accuracy is impaired, or the adhered foreign matter is rubbed against the tooth surface A so that the tooth surface A is It is possible to form the tooth surfaces A and B with high accuracy and high quality by preventing them from being damaged. Further, as described above, the guide blade 10 is shortened and the friction is reduced by lubrication with the cutting fluid, so that it is possible to obtain an advantage that cutting resistance during processing by the helical broach can be reduced.

  In the present embodiment, the escape portion 11 is formed so as to penetrate the other side surface, which is the guide surface 7C of the finishing blade 7, from the front end side to the rear end side of the broach body 1, Since the opening is made in the rake face 7A on the front end side of the finishing blade 7 and the rear end face of the finishing blade 7, the frictional heat generated in the guide blade 10 and the guide surface 7C can be more surely dissipated and the cutting fluid can be used. However, the guide blade 10 or the guide portion 7D and the tooth surface A can be efficiently supplied via the relief portion 11.

  In the present embodiment, the relief portion 11 is formed from the approximate center of the tooth height direction of the finishing blade 7 toward the root portion as described above, and is formed from the front end to the rear end of the broach body 1. Therefore, the area of the guide surface 7C is approximately ½ of the entire guide surface 7C. Therefore, the area of the guide portion 7D, which is the remaining portion other than the escape portion 11 of the guide surface 7C, is approximately 1 / of the entire guide surface 7C. However, if the area of the guide portion 7D is too small, the finishing blade 7 may not be reliably guided. For this reason, it is desirable that the area of the remaining guide portion 7D is 1/10 or more with respect to the entire area of the guide surface 7C including the escape portion 11.

  On the other hand, in the present embodiment, of the side surface that is the guide surface 7C of the finishing blade 7, the radially inner peripheral portion of the broach main body 1 is retreated with respect to the extension surface P to form the relief portion 11. Contrary to this, for example, as in the modification shown in FIG. 4, the radially inner peripheral portion of the finishing blade 7 is used as a guide portion 7D, and the outer peripheral portion of the side surface with respect to the extended surface P toward the outer peripheral side. The escape portion 11 may be formed by retreating, and the central portion in the radial direction of the side surface is cut into, for example, a “U” cross section with respect to the inner and outer peripheral side portions as in the modification shown in FIG. It is good also as the escape part 11 by missing. In these cases, since the guide blade 10 is formed at the root portion of the finishing blade 7 having a large width in the tooth thickness direction, the finishing blade 7 can be guided more stably and the cutting blade 9 can perform more accurate follow-up cutting. The effect that it becomes possible is also acquired.

  Further, contrary to the modified example shown in FIG. 5, the radial central portion of the side surface which is the guide surface 7C of the finishing blade 7 is left as a guide part 7D as in the modified example shown in FIG. The outer peripheral side portion and the inner peripheral side portion may be moved backward to form the relief portions 11 respectively. In the modification shown in FIG. 4, the boundary between the relief portion 11 and the guide portion 7 </ b> D is at the center in the radial direction (tooth length direction) of the finishing blade 7, and the relief portion 11 is the broach body of the finishing blade 7. 1 If formed from the front end side to the rear end side, the area of the remaining guide portion 7D is about ½ of the entire area of the guide surface 7C, and the deformation shown in FIGS. In the example, the boundary between the relief portion 11 and the guide portion 7D is at a position that divides the height of the finishing blade 7 in the radial direction, that is, the tooth height, into three equal parts. If formed over the entire area, the remaining guide portion 7D has an area of approximately 2/3 and approximately 1/3 of the entire area of the guide surface 7, respectively.

  In the present embodiment, the finishing blade 7 is formed with the relief portion 11 over the entire length in the direction of the axis O from the rake face 7A to the rear end of the finishing blade 7, but the side surface of the broach body 1 is formed on the side surface as described above. Since the clearance angle is given toward the rear end side, if a sufficient amount of retreat is secured by this clearance angle, a part of the guide surface 7C in the radial direction of the broach body 1 is set as an extension surface P of the remaining portion. 4 and 5 including the modified examples shown in FIG. 4 and FIG. 5, the relief part 11 may be formed only on the tip side of the broach body 1 of the finishing blade 7, that is, only on the rake face 7A side. Good.

  By the way, when the escape portion 11 is formed by retreating a part of the broach body 1 in the radial direction at least on the distal end side of the guide surface 7C as described above, the guide blade 10 is shortened as described above, and frictional heat is generated. On the other hand, since the pressure per unit length when the guide blade 10 is brought into sliding contact with the tooth surface A is increased, the guide blade 10 which is not to be subjected to cutting in some cases is a workpiece. The tooth surface A of the helical internal gear W is cut, which may cause the accuracy and quality of the tooth surface A to be impaired.

  Therefore, in such a case, as in the second embodiment shown in FIGS. 7 and 8, the portion on the tip side of the broach body 1 of the guide surface 7C, that is, the portion on the rake face 7A side, What is necessary is just to form so that it may also recede with respect to the extension surface Q to the front end side of the end part, and to form the escape part 12 also in this front end part. In the second embodiment shown in FIGS. 7 and 8, the same reference numerals are assigned to the same parts as those in the first embodiment shown in FIGS. 1 to 3, and description thereof is omitted.

  That is, in the second embodiment, the portion on the radially inner peripheral side of the broach body 1 is the outer peripheral portion (the guide portion) of the side surface of the finishing blade 7 that is the guide surface 7C as in the first embodiment. 7D portion) is cut out so as to recede with respect to the extended surface P to form the relief portion 11, and at the tip end side of the broach body 1 of the finishing blade 7, a part of the side surface is the remaining portion. The guide surface portion 7D on the rear end side and the extended surface Q of the escape portion 11 toward the front end side are also cut out so as to gradually recede at a constant angle θ toward the front end side, thereby forming the escape portion 12. Yes. Accordingly, the relief portion 12 is formed in a negative land shape with respect to the guide blade 10 of the first embodiment (in this embodiment, a virtual intersecting ridge line portion between the extended surface Q and the rake face 7A). As shown in FIG. 8, the guide surface 7C and the tooth surface A of the helical internal gear W are slid at the intersection ridge line portion between the guide portion 7D and the escape portion 12 left on the rear end side of the broach body 1 of the guide surface 7C. Therefore, the protruding amount of the cutting blade 9 for driving and cutting the tooth surface B may be set based on the position of the intersecting ridge line portion.

  According to the helical broach of the second embodiment as described above, since the guide blade 10 portion is formed in a negative land shape by the escape portion 12 as described above, the tooth surface A is cut by the guide blade 10 as described above, and its accuracy It is possible to prevent the quality and quality from being damaged. Further, in the present embodiment, by forming such a relief portion 12 on the front end side of the finishing blade 7, the guide portion 7D on the rear end side of the broach main body 1 that is in sliding contact with the tooth surface A as described above, The cutting fluid can be guided and reliably supplied to the intersecting ridge line portion with the escape portion 12, and the lubrication / cooling effect can be further improved.

  In the second embodiment, as in the first embodiment, a relief portion 11 is formed on a part of the side surface of the finishing blade 7 that is used as the guide surface 7C in the radial direction of the broach body 1, and then the relief portion 11 is further formed. The escape portion 12 is formed on the front end side of the broach main body 1, but a negative land-like shape is formed on the front end side of the broach main body 1 of the finishing blade 7 without providing the escape portion 11 retracted from the extended surface P in such a radial direction. An escape portion 12 may be provided. Also in this case, since the cutting fluid is supplied to the intersecting ridge line portion between the guide portion 7D and the escape portion 12 which are in sliding contact with the tooth surface A so as to be guided by the escape portion 12, the lubrication / cooling effect is improved. Can be achieved. Further, in the present embodiment, the escape portion 12 is retracted toward the front end side of the broach body 1 so as to form a constant angle θ with respect to the extended surface Q. For example, the finishing blade on which the guide surface 7C is formed The front end side of the broach body 1 on the side surface 7 may be formed so as to recede from the extended surface Q while forming a convex curved surface.

  Furthermore, in the second embodiment shown in FIGS. 7 and 8, the radially inner circumferential relief portion 11 and the outer circumferential guide correspond to the first embodiment shown in FIGS. Although the escape part 12 which recedes with respect to the extension surface Q to the front end side of the part 7D is formed, the second example shown in FIG. 9 corresponds to the modification of the first embodiment shown in FIG. As in the modification of the embodiment, the guide portion 7C may be formed with a relief portion 12 that retreats with respect to the extension surface Q toward the distal end side of the radially outer side relief portion 11 and the inner circumference side guide portion 7D. .

  Corresponding to the modification shown in FIG. 5, as in the modification shown in FIG. 10, the relief portion 11 formed at the center portion in the radial direction (tooth length direction) of the guide surface 7 </ b> C and its radially inner and outer peripheral sides The guide portions 7D formed on the guide portions 7D may be formed on the respective distal end sides with the escape portions 11 and the escape portions 12 that recede in the same shape as the guide portions 7D. As a modification of the second embodiment corresponding to the modification shown in FIG. 5, the front end side of the broach body 1 of the guide surface 7C is cut out by one continuous surface as shown in FIG. The relief part 12 may be formed by retreating. Further, corresponding to the modification shown in FIG. 6, as in the modification shown in FIG. 12, the guide portion 7 </ b> D formed in the center portion of the guide surface 7 </ b> C in the radial direction (tooth height direction) and its radially inner and outer peripheral sides Relief portions 12 may also be formed on the distal end sides of the relief portions 11 formed in the above-described manner, and the retreat portions 12 retreat with the same cross section as the relief portions 11 and the guide portions 7D.

  In the second embodiment and its modifications, the guide portion 7D, which is the remaining portion of the guide surface 7C, has an area of 1/10 or more of the entire guide surface 7C. desirable. For example, assuming that the radial position of the boundary between the relief portion 11 and the guide portion 7D is the same as that of the first embodiment and the modification thereof, the boundary between the relief portion 11 and the guide portion 7D and the relief portion 12 is assumed. When the position is substantially the center of the finishing blade 7 in the direction of the axis O, the area of the guide portion 7D remaining on the guide surface 7C with respect to the retreated escape portions 11 and 12 is relative to the area of the entire guide surface 7C. In the second embodiment shown in FIGS. 7 to 9 and its modification example, it is substantially ¼, in the modification examples shown in FIGS. 10 and 11, it is almost 略, and the modification example shown in FIG. Then it becomes about 1/6.

It is a side view which shows the 1st Embodiment of this invention. It is an expansion perspective view which shows the finishing blade 7 of embodiment shown in FIG. It is the figure which looked at the cutting state of the helical internal gear W by the finishing blade 7 of embodiment shown in FIG. 1 from the direction facing the rake face 7A. It is the figure which looked at the cutting state of the helical internal gear W by the finishing blade 7 of the modification of 1st Embodiment shown in FIG. 1 from the direction facing the rake face 7A. It is the figure which looked at the cutting state of the helical internal gear W by the finishing blade 7 of the other modification of 1st Embodiment shown in FIG. 1 from the direction which opposes the rake face 7A. It is the figure which looked at the cutting state of the helical internal gear W by the finishing blade 7 of the other modification of 1st Embodiment shown in FIG. 1 from the direction which opposes the rake face 7A. It is an expansion perspective view which shows the finishing blade 7 of the 2nd Embodiment of this invention. It is the figure which looked at the cutting state of the helical internal gear W by the finishing blade 7 of embodiment shown in FIG. 7 from the broach main body 1 radial direction outer peripheral side. It is an expansion perspective view which shows the finishing blade 7 of the modification of 2nd Embodiment shown in FIG. 7 corresponding to the modification shown in FIG. It is an expansion perspective view which shows the finishing blade 7 of the modification of 2nd Embodiment shown in FIG. 7 corresponding to the modification shown in FIG. It is an expansion perspective view which shows the finishing blade 7 of the other modification of 2nd Embodiment shown in FIG. 7 corresponding to the modification shown in FIG. It is an expansion perspective view which shows the finishing blade 7 of the other modification of 2nd Embodiment shown in FIG. 7 corresponding to the modification shown in FIG.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Brooch body 4 Cutting edge part 5 Cutting edge 6 Rough edge 7 Finishing edge 7A Rake face 7B Side face of finishing edge 7 connected to cutting edge 9 7C Guide surface 7D Guide part (remaining part of guide surface 7C)
DESCRIPTION OF SYMBOLS 9 Cutting blade 10 Guide blade 11,12 Escape part O Axis line of broach body 1 P Extension surface of broach body 1 radial direction of guide surface 7C Q Extension surface of broach body 1 tip side of guide surface 7C W Helical internal gear (workpiece)
A A tooth surface of the helical internal gear W with which the guide blade 10 is in sliding contact B A tooth surface of the helical internal gear W that is driven and cut by the cutting blade 9

Claims (5)

  A spiral in which a plurality of cutting blades projecting radially outward of the broach body are twisted about the axis of the broach body from the front end side to the rear end side of the broach body on the outer periphery of the shaft-shaped broach body In the helical broach arranged in a shape, the cutting blade on the rear end side of the broach body among the cutting blades is a finishing blade, and in this finishing blade, the rake face facing the front end side of the broaching body and the circumferential direction of the broaching body A cutting blade is formed at a crossing ridge line portion with a side surface facing one side of the above, and a side surface facing the other side of the circumferential direction is a guide surface, and the guide surface has a tip of the broach main body. A helical broach comprising a relief portion formed so that at least a part of the side recedes with respect to an extension surface of the remaining portion.   2. The relief part according to claim 1, wherein a part of the guide surface in the radial direction of the broach body is formed so as to recede from an extension surface of the remaining part in the radial direction. Helical brooch.   The helical broach according to claim 2, wherein the relief portion is continuous from the front end side to the rear end side of the broach body of the guide surface.   The escape portion is formed by retreating a portion of the guide surface on the front end side of the broach main body with respect to an extension surface to the front end side of the remaining portion on the rear end side of the broach main body. The helical broach according to any one of claims 1 to 3. The helical broach according to any one of claims 1 to 4, wherein the remaining portion of the guide surface has an area of 1/10 or more with respect to an area of the entire guide surface.

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