JP2005230937A - Inner surface broaching method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a broaching method causing no chipping at the edge tip of a cutting edge even in the case of broaching a high hardness material of 45-65 HRC at high-speed cutting of 40 m/min. <P>SOLUTION: In this inner surface broaching method for performing predetermined machining to an inner surface 13 of a workpiece, a broaching tool 5 in which a plurality of cutting edges 9 formed with obtuse rake angles are disposed in the axial direction of an outer periphery 8, is used to pass through the axial direction of the workpiece of hollow cylinder shape with a hardness of 45-65 HRC near the surface of a broached part to form chamfered parts 1 at the cutting edge bite parts of the workpiece. The chamfered parts are formed in tapered shape reduced in diameter toward the inner surface of the workpiece. When a chamfer angle of the chamfered part is made α and the rake angle of the cutting edge is made β, the difference γ between the chamfer angle α and the rake angle β is 20°≤γ≤60°. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to an inner surface broaching method for machining the inner surface of a workpiece with a broach tool, and more particularly to an inner surface broaching method for finishing an inner surface of a high hardness material having a workpiece hardness of 45 to 65 HRC.

Conventionally, the thing of patent document 1 is known as a broach tool which carries out broaching of the high hardness material exceeding hardness 45HRC (Rockwell hardness C scale: hereafter the same). This is a broaching tool in which the cutting edge has a twist and is coated with a hard coating, and at least the cutting edge portion is made of powder high-speed tool steel or ultrafine cemented carbide.
Japanese Patent Laid-Open No. 7-195228

  However, since the broach tool of Patent Document 1 has a twist in the cutting edge, it cannot be applied to a general inner surface processing broach except for a helical blade groove broach, and the cutting edge described in Patent Document 1 except for the structure of twist. , Chipping or chipping occurs at the edge of the cutting edge when a hollow cylindrical workpiece is subjected to internal broaching at a cutting speed of 40 m / min or higher, which is normally performed for cutting hard materials with a rod-shaped broach tool. However, there is a problem that the life of the broaching tool is shortened and the machining accuracy of the workpiece cannot be obtained.

  Therefore, an inner surface broach tool shown in FIGS. 3 (a) and 3 (b) is known as a solution to the problem described in Patent Document 1. FIG. This is because the tip of the cutting edge 52 of the cutting edge 51 made of cemented carbide has an obtuse angle and the rake angle β is −30 ° ≦ β ≦ −10 ° (when the cutting edge is an obtuse angle, the rake angle is a minus sign). The inner surface broaching tool 50 is used to finish the inner surface at a cutting speed of 40 to 60 m / min. With the internal broach tool 50 having the rake angle β made obtuse, it is expected that chipping and chipping will not occur at the cutting edge of the cutting edge even when broaching.

  However, even if high-hardness material exceeding 45 HRC is broached at a cutting speed of 40 m / min or more using this inner surface broach tool 50, the number of chips is reduced, but chipping or chipping occurs at the cutting edge of the broach tool. It still occurs, and the above-mentioned problems regarding the work accuracy of the workpiece and the life of the broach tool exist.

  The present invention has been made to solve the problems of the prior art, and even if a high hardness material having a hardness of 45 to 65 HRC is subjected to internal broaching at a high speed cutting of 40 m / min or more, the cutting edge of the broach tool is improved. An object of the present invention is to provide an inner surface broaching method capable of processing without generating chipping or chipping at the cutting edge.

  The inventors have used the broaching tool 5 shown in FIGS. 1 (a), (b), and (c) for the chipping and chipping generated at the cutting edge of the above-described cutting edge, as shown in FIGS. 4 (a) and 4 (b). The work 35 shown in Fig. 2 was broached and studied. The broaching tool 5 had a foam rising edge and a rake angle β of the blade part 3 of −10 °. Here, the rising edge of the foam refers to the shape of the cutting edge that cuts in the same shape as the broaching shape. For the workpiece 35, the hardness is 60HRC by carburizing and quenching, and the involute tooth surface 15 which is the workpiece is pre-processed with another broaching tool, leaving a finishing allowance. Usually used. As a result, at the time of high-speed cutting of broach at 40 m / min or more, a large impact is generated at the moment when the cutting edge 9 that has been raised in the form of the broaching tool 5 first bites the work 35, and the overall vibration during processing is increased. I found out. That is, at the time of high-speed broach cutting of 40 m / min or more, as shown in FIG. 7, the rising edge of the foam 9 whose rake angle is an obtuse angle and the end surface 37 of the involute tooth surface 15 of the workpiece 35 are different in angle. As shown in the vibration waveform diagram of FIG. 5, a large machining vibration of MAX89G occurs during the broaching process, and the cutting edge of the cutting edge 9 of the broaching tool 5 is damaged. I knew that I was giving.

  Based on this knowledge, in the present invention, the surface of the workpiece to be broached using a broach tool in which a plurality of foam rising edges whose rake angles are obtuse angles are arranged in the axial direction of the outer periphery. In an inner surface broaching method in which predetermined processing is performed on the inner surface of a workpiece by passing a broaching tool in the axial direction of a substantially hollow cylindrical workpiece having a hardness of 45 to 65 HRC in the vicinity, the cutting edge biting portion of the workpiece is chamfered. The above-described problem has been solved by providing an inner surface broaching method in which a portion is formed (claim 1).

  In other words, by providing a chamfered part on the part where the cutting edge of the work is bitten, when the cutting edge of the broaching tool comes into contact with the work during broaching, the cutting edge of the broaching tool gradually comes into contact with the part where the chamfering of the work is shallow. To do. Here, the cutting edge biting portion refers to a part of the work that is first cut by the cutting edge of the broach tool when the work is broached. That is, as shown in FIG. 8, in the internal broaching of the work 12 having a hardness of 45 to 65 HRC with the broach tool 5 having the foam rising edge 9 whose rake angle is an obtuse angle as in the conventional example, By forming the cutting edge biting portion like the chamfered portion 1 shown in FIG. 8, the volume of the cutting edge 9 of the broach tool 5 cut into the cutting edge biting portion in a certain time is reduced. As a result, when a high-hardness material having a hardness of 45 to 65 HRC is subjected to high-speed cutting with a broach of 40 m / min or more, the cutting edge of the broaching tool gradually comes into contact with the cutting edge biting portion of the workpiece, so that the cutting edge of the cutting edge is damaged. Generation of such a large impact vibration can be suppressed. The shape of the chamfered portion may be a flat shape or a curved surface shape as long as the cutting edge of the broach tool comes into contact with the cutting edge biting portion of the work so that the area into which the cutting edge simultaneously cuts into the work is reduced.

  The form rising edge here refers to the shape of the cutting edge that cuts in the same shape as the broaching shape, and in the present invention, broaching of various shapes such as involute spline grooves and ball spline grooves is performed. It is processed with this cutting edge.

  Also, when the chamfered portion is tapered to reduce the diameter toward the inner surface of the workpiece, the difference between the chamfered angle α and the rake angle β when the chamfered angle of the chamfered portion is α and the rake angle of the cutting edge is β. The broaching method was such that γ was 20 ° ≦ γ ≦ 60 ° (Claim 2). As a result, the chamfering angle α of the chamfered part of the workpiece and the rake angle β, which is the obtuse angle of the broach tool, do not come into contact with each other with no difference in angle. Here, the difference γ between the chamfer angle α and the rake angle β can be expressed as γ = α − (− β). The chamfering angle here refers to an angle formed between the chamfered portion and the surface perpendicular to the axis of the workpiece when the chamfered portion provided on the cutting edge biting portion of the workpiece is tapered toward the inner surface of the workpiece. Here, the difference γ between the rake angle β of the broach tool and the chamfering angle α of the workpiece is set to 20 ° or more. The difference γ between the rake angle β of the broaching tool and the chamfering angle α of the workpiece is less than 20 °. This is because there is little difference between the chamfering angle α and the rake angle β, and the effect of reducing the impact at the moment when the cutting edge of the broach tool bites into the chamfered part of the work is not sufficient. In addition, the difference γ between the rake angle β of the broach tool and the chamfering angle α of the workpiece is set within 60 ° because the difference γ between the rake angle β of the broaching tool and the chamfering angle α of the workpiece is more than 60 °. This is because the effective cutting length of the machined part of the workpiece is shortened and is not practical.

  Further, the inner surface broaching method is adopted in which the processing part of the workpiece to be processed is an involute tooth surface. That is, as shown in FIG. 2 (c), when machining the involute spline groove 66, the involute tooth surface 15 located on both sides of the large diameter 42 may be machined to the margin 44 shown by the two-dot chain line. When chamfering the involute tooth surface 15 that is a cutting edge biting portion with a broach tool having a cutting edge that is raised in the form as in the present invention, the cutting edge of the broach is applied to the workpiece compared to the case without chamfering. At the same time, the area to be cut can be remarkably reduced, and the effect of reducing the impact vibration when the cutting edge of the broach and the chamfered part of the workpiece come into contact with each other is great.

  As described above, according to the present invention, the surface of a work part to be broached using a broach tool in which a plurality of foam rising edges whose rake angles are obtuse angles are arranged in the axial direction of the outer periphery. In an inner surface broaching method in which predetermined processing is performed on the inner surface of a workpiece by passing a broaching tool in the axial direction of a substantially hollow cylindrical workpiece having a hardness of 45 to 65 HRC in the vicinity, the cutting edge biting portion of the workpiece is chamfered. Since the inner surface broaching method in which the part is formed is employed, it is possible to suppress the occurrence of a large impact vibration when the chamfered part formed on the cutting edge biting part of the work and the cutting edge of the broaching tool contact by broaching. As a result, even if a high hardness material of 45 to 65 HRC was broached at a high speed cutting of 40 m / min or more, the cutting edge of the broaching tool could be machined without chipping or chipping. Item 1).

  Also, when the chamfered portion is tapered to reduce the diameter toward the inner surface of the workpiece, the difference between the chamfered angle α and the rake angle β when the chamfered angle of the chamfered portion is α and the rake angle of the cutting edge is β. Since γ is a broaching method in which 20 ° ≦ γ ≦ 60 °, the rake angle β of the broaching tool and the chamfering angle α of the chamfered part of the workpiece are no longer the same. The impact vibration when the cutting edge biting part and the cutting edge of the broaching tool contacted each other could be more effectively suppressed (claim 2).

  In addition, since the processing part of the workpiece to be processed is an inner broach processing method in which the involute tooth surface is used, a great effect is produced in reducing the impact vibration when the cutting edge of the broach contacts the chamfered part of the workpiece. (Claim 3).

  Embodiments of the present invention will be described below with reference to the drawings. 1A is a side view of a broaching tool used in an embodiment of the present invention, FIG. 1B is an enlarged side view of the cutting edge of FIG. 1A, and FIG. 1C is an AA line enlarged arrow of FIG. 2A is a plan view of a work used in the embodiment of the present invention, FIG. 2B is a cross-sectional view taken along line B-B in FIG. 2A, and FIG. 2C is an involute in FIG. FIG. 8 is a schematic cross-sectional view showing the broaching method of the present invention.

  As shown in FIG. 1 (a), cutting edges 9 provided around and around the outer periphery 8 of the assembly-type inner surface broach tool 5 used in the present invention are made of cemented carbide, and FIG. 2 (a). The shape of the cutting edge 9 for processing the workpiece 12 shown in FIG. 4 is a foamed shape, and the involute tooth surface 15 is processed. The foam rising edge 9 here refers to the shape of the cutting edge that performs cutting with the same shape as the broaching shape. In this embodiment, the involute spline tooth surface 15 is used as the rising edge 9 of the foam rising edge. To process. As for the blade portion 3, as shown in FIG. 1 (b), the rake angle β, which is the angle formed by the perpendicular line 22 drawn from the cutting edge 9 and the rake face 21, is -10 °. The workpiece 12 to be machined is one that has been pre-machined with a normal broach tool leaving a finishing allowance and having a hardness of 60 HRC by carburizing and quenching.

  In particular, the present invention is characterized in that the chamfered portion 1 is formed in the cutting edge biting portion of the work 12 processed by the broach tool 5 as shown in FIG. Here, the cutting edge biting portion refers to a part of the work that is first cut by the cutting edge of the broach tool when the work is broached. In the present embodiment, the tapered chamfered portion 1 extending to the inner surface 13 of the workpiece 12 is formed so as to include the large diameter portion 42. Thereby, since the cutting edge 9 of the broach tool 5 gradually comes into contact with the cutting edge biting portion of the workpiece, it is possible to suppress the occurrence of a large impact vibration that damages the cutting edge of the cutting edge 5 during broaching. A chamfered shape such as the chamfered portion 1 can be easily machined by a lathe. The chamfering angle α, which is an angle formed by the tapered chamfered portion 1 and the axis perpendicular surface 48 of the shaft 26 of the workpiece 12, was 45 °. Accordingly, as shown in FIG. 8, the difference γ between the rake angle β of the blade portion 3 of the broach tool 5 and the chamfering angle α of the workpiece 12 is 45 from the relational expression of γ = α − (− β). ° − (− (− 10 °)) = 35 °, the difference γ between the chamfering angle α and the rake angle β is in the range of 20 ° ≦ γ ≦ 60 °, and the chamfering angle α of the chamfered part of the workpiece and the broach tool There is no contact with the rake angle β in a state where there is no difference in angle. Thereby, the cutting edge 9 of the broach tool 5 gradually bites into the chamfered portion 1 of the work 12, and the shock vibration at the moment when the cutting edge 9 bites is reduced.

  In the above-described embodiment of the present invention, the tapered chamfered portion 1 extending to the inner surface 13 of the workpiece 12 is formed so as to include the involute large diameter 42 which is a cutting edge biting portion, but as shown in FIG. Needless to say, even if the chamfered portion 1 is formed such that the chamfered portion 1 is not chamfered on the involute tooth surface 15 which is a cutting edge biting portion, a certain degree of impact vibration effect can be obtained. In the above-described embodiment of the present invention, the work is fixed and the broaching tool moving broaching is performed by moving the inner surface broaching tool to process the inner surface of the work. Needless to say, the present invention can also be applied to workpiece moving broaching in which a broaching tool is fixed and the workpiece is moved to process the inner surface of the workpiece. In the above-described embodiment of the present invention, a workpiece having a hardness of 60 HRC is used, and in the claims, the broaching method is applied to a so-called high hardness material having a hardness of 45 to 65 HRC. It goes without saying that the processing method is a broaching method that can be similarly applied to workpieces other than the above-described high-hardness material.

  The workpiece 12 shown in FIG. 2 was machined at a cutting speed of 60 m / min using the assembly-type inner surface broach tool 5 shown in FIG. 1 described in the embodiment of the present invention. The chamfering angle α of the workpiece 12 was 60 °, and the rake angle β of the broach tool 5 was 20 °. Thus, the difference γ between the rake angle β of the blade 3 of the broach tool 5 and the chamfering angle α of the workpiece 12 is 60 ° − (− (− 20 °) from the relational expression of γ = α − (− β). ) = 40 °. As a result, as shown in the vibration waveform diagram of FIG. 6, the machining vibration during broaching is smaller than when there is no chamfering (FIG. 5), and the cutting edge 9 of the broaching tool 5 and the cutting edge biting part of the work 12. Even if it comes into contact with a certain involute spline tooth surface 15, a large impact vibration does not occur, and no chipping or chipping occurs in the cutting edge of the cutting edge 9. In addition, the broach life can be machined about twice or more compared to before the work is chamfered.

(A) is a side view of an assembly-type inner surface broach tool showing an embodiment of the present invention, (b) is an enlarged side view of the cutting edge of (a), and (c) is an AA line view of (a). It is an expanded sectional view. (A) is a top view of the workpiece | work used by embodiment of this invention, (b) is BB arrow sectional drawing of (a), (c) is a schematic diagram of the involute groove | channel of (a). . (A) is a side view of the broach tool of a prior art example, (b) is an enlarged side view of the cutting edge of (a). (A) is a top view of the workpiece | work processed with the broach tool of a prior art example, (b) is CC sectional view taken on the line of CC of (a). It is a vibration waveform diagram which shows processing vibration when a workpiece | work is processed by the broaching method of a prior art example. It is a vibration waveform diagram which shows the processing vibration when a workpiece | work is processed by the broaching method of this invention. It is a schematic cross section which shows the broaching method of a prior art example. It is a schematic cross section which shows the broaching method of this invention. The top view of the workpiece | work which shows another example of the broaching method of this invention, (b) is EE arrow sectional drawing of (a).

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Chamfering part 5 Broach tool 8 Outer periphery 9 Cutting edge 12 Work piece 13 Inner surface 15 Cutting edge biting part α Chamfering angle β Rake angle γ Difference between chamfering angle α and rake angle β

Claims (3)

Using a broaching tool in which a plurality of foam rising edges whose rake angles are obtuse angles are arranged in the axial direction of the outer periphery, the hardness in the vicinity of the surface of the part to be broached is 45 to 65 HRC (Rockwell hardness) In the inner surface broaching method in which predetermined processing is performed on the inner surface of the workpiece by passing the broach tool in the axial direction of a substantially hollow cylindrical workpiece that is a C scale), a chamfered portion is formed on the cutting edge biting portion of the workpiece. An inner surface broaching method characterized by comprising: When the shape of the chamfered portion is a tapered shape that decreases in diameter toward the inner surface of the workpiece, the chamfer angle of the chamfered portion is α and the rake angle of the cutting edge is β, the chamfer angle α and the rake angle 2. The inner surface broaching method according to claim 1, wherein a difference γ with respect to β is 20 ° ≦ γ ≦ 60 °. An inner surface broaching method, wherein a processing part of the workpiece processed by the broaching method according to claim 1 or 2 is an involute tooth surface.

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