JP7117825B2 - Helical broach and broaching method - Google Patents

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a helical broach and a broaching method used for cutting a work having twisted grooves on its inner circumference, such as a helical internal gear.

Various types of helical internal gears, such as planetary internal gears, have been provided for use in automatic transmissions. Recently, however, as the quality requirements for automatic transmissions have become more sophisticated, so has the demand for higher quality gears. is becoming
As a helical broach used for machining such a helical internal gear, for example, as shown in FIG. A plurality of cutting edges 101 are arranged in a spiral shape twisted around the axis from the front end side to the rear end side, and the cutting edge on the front end side of the plurality of cutting edges is a rough edge formed integrally with the broach body 102. A cutting edge on the rear end side is a finishing edge (increasing tooth thickness edge) 105 integrally formed with a shell 104 provided separately from the broach body 102 . As shown in FIG. 6, the finishing edge 105A on the tip end side has a cutting edge 105Aa at the intersection ridge between the rake face facing the tip end of the helical broach and the side face facing one of the circumferential directions of the broach body. A guide edge 105Ab is formed at the intersection of the side surface opposite to the cutting edge 105Aa and the rake face. A cutting edge 105Ba is formed at the intersection ridge between the rake face facing the direction of the broach body and the side face facing the other side in the circumferential direction of the broach body, and the intersection of the side face opposite to the cutting edge 105Ba and the rake face It has been proposed that the ridge portion is the guide blade 105Bb.

According to such a helical broach, for example, as shown in FIG. 7, the tooth profile of a helical internal gear, which is a workpiece W, is changed from a small diameter portion to a required groove depth Ha by a rough blade 103 whose tooth height gradually increases. After forming, first, one side surface Sa of the tooth profile is driven and cut in the tooth thickness direction by the tip side finishing edge 105A whose tooth thickness gradually increases, and then the trailing edge side finishing edge 105B whose tooth thickness gradually increases. , the other side surface Sb of the tooth profile is cut in the direction of tooth thickness, thereby finishing the left and right side surfaces into desired shapes.

Further, the following cited document 2 proposes a technique of simultaneously cutting one side surface and the other side surface of the tooth profile of a workpiece with a finishing blade (tooth thickness increasing blade).

JP-A-2007-253298 JP-A-2005-144639

The conventional techniques described above have the following problems.
That is, in the former technique, when the finishing blades 105 (105A, 105B) are used to process the tooth profile of the workpiece so as to gradually increase the tooth thickness, one side face of the tooth profile is cut and the other side face of the tooth profile is machined. Since the process of cutting the side surface is performed separately, the process is complicated and the machining time is lengthened accordingly. This is because the finishing blade 105 is formed integrally with the shell 104 provided separately from the broach body 102, and the tip 102A is gripped by gripping means during processing, and the rotational position is restrained for the broach body 102. Since the finishing blade 105 rattles together with the shell 104 by the amount of the gap when it is fitted into the broach body 102, in order to increase the machining accuracy, one side of the tooth profile is cut and the other side of the tooth profile is cut. This is because it is necessary to have separate processes.

In addition, in the latter technique, when the finishing blade is used to cut the teeth in the tooth thickness direction, one side and the other side of the tooth profile are cut at the same time, so the processing time is shortened. In addition, it was impossible to avoid the rattling caused by the gap during fitting, and for this reason it was not possible to achieve the desired machining accuracy.

SUMMARY OF THE INVENTION It is an object of the present invention to provide a helical broach and a broaching method capable of shortening the machining time and performing high-precision machining.

In order to solve the above-mentioned problems, the helical broach of the present invention has a plurality of cutting edges projecting radially outward from the outer peripheral portion of a shaft-shaped broach body. The blades are arranged in a row, twisted around the axis of the broach body from the front end side to the rear end side of the broach body in a spiral shape, and the rows of the plurality of cutting blades are spaced apart from each other in the circumferential direction. An integrated helical broach in which these cutting edges are arranged to form a helical groove with a predetermined lead on the inner periphery of a machined hole in a work, wherein the plurality of cutting edges on the tip side of the broach body among the plurality of cutting edges are located on the work. It is an outer diameter rising blade that cuts the tooth profile in the tooth height direction, and a plurality of cutting blades on the rear end side of the broach body are tooth thickness rising blades that cut the tooth profile of the workpiece in the tooth thickness direction. The rising edge is formed by a ridgeline portion where the rake face facing the tip side of the broach body intersects with the side face of the broach body on the acute angle side in the circumferential direction, and the rake face and the side face on the obtuse side in the circumferential direction of the broach body. Cutting edges are provided on both of the intersecting ridges, and the blade grooves formed between the rows of the cutting edges extend from the front end side to the rear end side of the broach body. It is characterized by extending spirally so as to be twisted in a direction opposite to the twisting direction, or extending along a reference plane perpendicular to the axis.

Further, the broaching method of the present invention is a broaching method for forming twisted grooves in the inner circumference of a machined hole of a work by the helical broach of the present invention, wherein the broaching method forms twisted grooves in the inner circumference of the machined hole in the work by the helical broach. In the method, the tooth profile of the work is cut in the tooth height direction by the outer diameter rising blade so that the tooth height of the work tooth profile is a predetermined height, and then the sharp angle of the tooth thickness rising blade is cut. It is characterized in that the right and left side surfaces of the tooth profile of the workpiece are processed simultaneously by the cutting edge on the side and the cutting edge on the obtuse angle side, and the tooth thickness of the tooth profile of the workpiece is machined to a predetermined thickness.

According to the helical broach or the broaching method, the cutting edge is formed at the intersection ridge between the rake face facing the tip side of the broach body and the side face of the broach body on the acute angle side in the circumferential direction of the broach body, and Since the cutting edge is also formed on the intersection ridge between the rake face and the side surface on the obtuse side in the circumferential direction of the broach body, it is possible to machine both the left and right side surfaces of the tooth profile of the workpiece at the same time. can save time.
In addition, since there is no need to separately provide a tooth thickness increasing blade having a cutting edge on the acute angle side and a tooth thickness increasing blade having a cutting edge on the obtuse angle side, the space for arranging the tooth thickness increasing blade is reduced, and the broach body accordingly. length is shortened.
In addition, since the helical broach is an integral type in which the increased tooth thickness blade is directly formed on the broach body, the increased tooth thickness blade does not rattle with respect to the broach body whose position is restrained by the gripping means during processing. High-precision machining can be performed.

Furthermore, the blade groove of the cutting edge is twisted in the direction opposite to the twisting direction of the rows of cutting edges from the front end side of the broach body toward the rear end side, or the reference plane perpendicular to the axis of the broach body. Since it is formed so as to extend along the edge, when cutting with the cutting edge, especially cutting with the outer diameter rising edge, it is difficult for the chips generated from the cutting edge to interfere with the cutting edge, so the chip is discharged well. can do

The side clearance angle θa5′≦θa≦45′ of the cutting edge on the acute angle side of the increased tooth thickness edge is set, and the side relief angle θb of the cutting edge on the obtuse angle side of the increased tooth thickness edge is set to 5′≦5′. It is preferable to set θb≦45′.
By setting the side relief angle θa of the cutting edge on the acute angle side of the tooth thickness rising edge and the side relief angle θb of the cutting edge on the obtuse side as described above, both the acute angle side and the obtuse side of the outer diameter rising edge can be obtained. The sharpness of the cutting edge is well balanced.

Incidentally, if the clearance angle θb of the obtuse side surface of the tooth thickness rising edge is smaller than 5′, and if the relief angle θb of the side surface of the tooth thickness rising edge on the obtuse side is smaller than 5′, then the acute angle of the outer diameter rising edge The sharpness of the cutting edge on both the side and the obtuse side deteriorates, and good cutting cannot be performed. Further, when the relief angle θb of the obtuse side surface of the increased tooth thickness edge is greater than 45′, and when the relief angle θb of the obtuse side surface of the increased tooth thickness edge is greater than 45′, The cutting force of both the sharp-angle and obtuse-angle cutting edges increases. As a result, the amount of cutting on the acute angle side becomes large, or the amount of cutting on the obtuse angle side becomes large compared to the amount of cutting on the acute angle side. Moreover, there also arises a problem that the durability of the cutting blade is lowered.

According to the present invention, machining time can be shortened, and high-precision machining can be performed at the same time. Also, the total length of the helical broach can be shortened.

1 is a side view showing an embodiment in which the present invention is applied to an off-normal type helical broach; FIG. FIG. 2 is a schematic view of a row of tooth thickness increasing blades of the helical broach of the embodiment shown in FIG. 1 as viewed from above; FIG. 2 is a perspective view showing a tooth thickness increasing blade of the helical broach of the embodiment shown in FIG. 1; FIG. 2 is an enlarged side view of cutting using the tooth thickness increasing blade of the helical broach of the embodiment shown in FIG. 1 ; FIG. 11 is a side view showing a conventional helical broach; Fig. 10 is a schematic diagram illustrating a finishing blade (tooth thickness increasing blade) of a conventional helical broach; FIG. 11 is an enlarged front view showing an example of processing using a conventional helical broach;

1 to 4 show an embodiment of a helical broach according to the present invention, showing a case where the present invention is applied to an off-normal type helical broach.

The helical broach of the present embodiment is for broaching a work having twisted grooves on its inner periphery, such as a helical internal gear such as the planetary internal gear described above. As shown in FIG. 1, the broach body 1 has a long shaft shape centered on the axis Oa, and both ends thereof are gripping portions 2 and 3, and a cutting edge is provided between the gripping portions 2 and 3. It is called Part 4. A plurality of cutting edges 5 protruding radially outwardly with respect to the axis Oa extend from the front end (left side in FIG. 1) of the broach body 1 to the rear end thereof. They are arranged in a helical row along the lead L twisted about the axis Oa toward the side (right side in FIG. 1). In addition, a plurality of rows of these cutting blades 5 are formed at intervals in the circumferential direction.

In this embodiment, which is an off-normal type helical broach, a blade groove 5A formed between a plurality of cutting blades 5 in the direction of the axis Oa is formed so as to be twisted around the axis Oa.
In this embodiment, the direction in which the blade grooves 5A twist is opposite to the direction in which the row of cutting blades 5 twists from the front end side to the rear end side of the broach body 1. That is, as shown in FIG. 1, the direction of the helix angle α of the blade groove 5A with respect to the axis Oa of the broach body 1 in side view is opposite to the direction of the helix angle β of the row of cutting edges 5 with respect to the axis Oa of the broach body 1. It is In this embodiment, when viewed from the front end side of the broach body 1 along the direction of the axis Oa, the rows of the cutting blades 5 are twisted clockwise toward the rear end side, whereas the blade grooves 5A are twisted clockwise. It is twisted counterclockwise toward the rear end side. The torsion angle β formed by the row of cutting blades 5 with respect to the axis Oa in a side view is set smaller than the torsion angle α formed by the blade groove 5A with respect to the axis Oa.

Here, the plurality of cutting edges 5 of the cutting edge portion 4 on the tip side of the broach body 1 are configured as outer diameter rising edges 6 for cutting the tooth profile of the helical internal gear in the tooth height direction. In the rising edge 6, the tooth height of the cutting edge 5 gradually increases along the row of the cutting edge 5 toward the rear end side of the broach body 1. As shown in FIG. Further, on the cutting edge portion 4 on the rear end side of the broach main body 1 from the outer diameter rising edge 6, there are tooth flanks of the tooth profile cut to a predetermined tooth height by the outer diameter rising edge 6, that is, on both sides of the twisted groove of the workpiece. A plurality of tooth thickness increasing blades 7 are provided for driving and cutting the surface in the tooth thickness direction, that is, in the circumferential direction of the broach body 1 to form a predetermined tooth thickness.

In addition, on the rear end side of the portion of the cutting edge portion 4 where the cutting edge 5 which is the outer diameter rising edge 6 is arranged, a round edge for cutting the small diameter portion of the tooth profile is alternately arranged with the outer diameter rising edge 6. may be provided. Further, this round blade may be provided on the rear end side of the tooth thickness increasing blade 7 . The outer diameter rising edge 6, the tooth thickness rising edge 7, and all of the round cutting edges 5 are formed integrally with the broach body 1 in this embodiment.

FIG. 2 is a schematic view of one row of tooth thickness increasing blades 7 of the helical broach of the embodiment shown in FIG. FIG. 3 is a perspective view showing the tooth thickness increasing blade 7 of the helical broach of the embodiment shown in FIG. FIG. 4 is an enlarged view of the helical broach of the embodiment shown in FIG. , the lower side of the drawing is the front end side of the broach body 1, and the upper side is the rear end side of the broach body 1).
In FIG. 2, the scale of the vertical axis is about 10 times the scale of the horizontal axis, and is exaggerated so that the shape of the increased tooth thickness blade can be easily grasped.

As shown in FIGS. 2 and 3, in the tooth thickness increasing blade 7, a cutting edge 7B is formed on the intersection ridge between the rake face 7A facing the tip side of the broach body 1 and the side face of the broach body 1 on the acute angle side in the circumferential direction of the broach body 1. is formed, and a cutting edge 7C is formed at the intersection ridgeline between the rake face 7A and the side surface of the broach body 1 on the obtuse side in the circumferential direction.
That is, the tooth thickness increasing blade 7 has cutting blades 7B and 7C on both left and right sides, respectively, and does not have a guide blade as described in the background art.
Here, the acute angle side and the obtuse angle side are determined based on the angle formed by the lead L and the blade groove 5A. side, and the right side is defined as the obtuse side.

In addition, the side surface of the tooth thickness increasing blade 7 on the acute angle side connected to the cutting edge 7B is separated from the position of the cutting edge 7B toward the rear end side of the broach body 1 toward one side (obtuse angle side) in the circumferential direction of the broach body. As a result, a predetermined side clearance angle θa is formed with respect to the lead L in which the plurality of cutting edges 5 are arranged. The side clearance angle θa is set within a range of 5'≤θa≤45'. Further, the obtuse side surface of the tooth thickness increasing blade 7 connected to the cutting edge 7C moves away from the position of the cutting edge 7C toward the rear end side of the broach body 1 toward the other side (acute angle side) of the circumferential direction of the broach body. As a result, a predetermined side relief angle θb is formed with respect to the lead L in which the plurality of cutting edges 5 are arranged. This side clearance angle θb is also set within the range of 5′≦θb≦45′. Note that the side clearance angles θa and θb may be equal to or different from each other.

A plurality of tooth thickness increasing blades 7 on the tip side of the broach body 1 are gradually increased in the tooth thickness direction as indicated by symbol Xa in FIG. On the other hand, as the cutting edge 7C on the obtuse angle side moves toward the rear end side along the lead L, it is arranged so as to gradually protrude in the tooth thickness direction as indicated by the symbol Xb in FIG. there is Although the protrusion amount Xa of the cutting edge 7B on the acute angle side and the protrusion amount Xb of the cutting edge 7C on the obtuse angle side are set to be approximately the same, they may be different as necessary.

In addition, for example, the first to fourth tooth thickness increasing blades 7 counted from the rear end of the broach body 1 are set to the same value for the amount of protrusion in the tooth thickness direction of the cutting edge 7B on the acute angle side and the cutting edge 7C on the obtuse angle side. It is That is, even when the several tooth thickness increasing blades 7 positioned at the rear end of the broach body are directed toward the rear end side along the lead L, both the sharp-angle side cutting blade 7B and the obtuse-angle side cutting blade 7C are The cutting blades 7B and 7C are set to have the same protrusion amount without protruding in the tooth thickness direction.

Next, a method of cutting the work W by the helical broach configured as described above will be described.
The broach body 1 is inserted from the tip side into a hole previously formed in the work W, and the broach body 1 is moved relatively forward with respect to the work W along the lead L while gripping the grip portion 2 on the tip side. Rotate while moving. As a result, first, the outer diameter rising edge 6 forms a twisted groove reaching a predetermined depth.

Then, the cutting edge 7B on the acute angle side of the tooth thickness increasing blade 7 is pressed against one side surface of the twist groove to cut the one side surface, and the other side surface of the twist groove is pressed against the other side surface of the twist groove on the obtuse angle side of the tooth thickness increasing blade 7. The cutting edge 7C is pressed to cut the other side surface, thereby finishing the left and right side surfaces of the twisted groove of the work W into a desired shape.
That is, the left and right side surfaces of the twisted groove of the workpiece W are simultaneously cut by the sharp-angle side cutting edge 7B and the obtuse-angle side cutting edge 7C of the tooth thickness increasing edge 7 . As a result, the machining time can be shortened compared to the case where the step of cutting one side surface of the tooth and the step of cutting the other side surface of the tooth are performed separately as described in the background art. can.

In addition, the tooth thickness increasing blade 7 of the helical broach is provided with an acute angle side cutting edge 7B and an obtuse angle side cutting edge 7C. Since there is no need to separately provide the tooth thickness increasing blades, the space for arranging the tooth thickness increasing blades 7 is reduced, and the overall length of the broach body 1 can be shortened accordingly.

In addition, since the helical broach is an integral type in which the tooth thickness increasing blade 7 is directly formed on the broach body 1, the broach body 1 is restrained in its rotational position while the gripping portion 2 on the tip side is gripped by the gripping means during machining. Since the tooth thickness increasing blade 7 does not rattle, the cutting position by the tooth thickness increasing blade 7 is uniquely determined, thereby improving the machining accuracy.

Furthermore, the direction in which the blade groove 5A is twisted about the axis Oa from the front end side of the broach body 1 toward the rear end side is the direction in which the rows of the cutting blades 5 are also twisted around the axis line Oa from the front end side of the broach body 1 toward the rear end side. Since the twisting direction is opposite to the twisting direction, chips generated from the cutting edge 5 are less likely to interfere with the cutting edge 5 during cutting by the cutting edge 5, especially cutting by the outer diameter rising edge 6, so that the chip is discharged. becomes good. Such an effect can also be obtained with a so-called axial type helical broach in which the blade groove 5A extends along the reference plane Ob perpendicular to the axis Oa shown in FIG. Even if the blade groove 5A is twisted in the direction opposite to the direction in which the rows of the cutting blades 5 are twisted in this way, or is formed so as to extend along the reference plane Ob perpendicular to the axis Oa, the cutting blades 5 is formed integrally with the broach body 1, the cutting edge 7B on the acute angle side and the cutting edge 7C on the obtuse angle side of the tooth thickness increasing edge 7 can reliably simultaneously cut the left and right side surfaces of the twisted groove of the workpiece W. can be done.
On the other hand, if the twisting direction of the blade grooves 5A is the same as the twisting direction of the rows of the cutting edges 5, for example, when the work W is cut by the outer diameter rising edge 6, the chips are Since it extends substantially in the direction normal to 5, the chip interferes with the side surface of the workpiece W on the obtuse angle side, and the chip is not discharged well.

In addition, the acute side clearance angle θa of the tooth thickness increasing edge 7 is set to 5′≦θa≦45′, and the obtuse side clearance angle θb of the tooth thickness increasing edge 7 is set to 5′≦θb≦45′. , the sharpness of the cutting edges 7B and 7C on both the acute angle side and the obtuse angle side of the increased thickness edge 7 are well balanced.

The present invention is not limited to the above-described embodiments, and various modifications can be made without departing from the scope of the present invention.
For example, in the present embodiment, an example in which the present invention is applied to an off-normal type integrated helical broach has been described, but the present invention is not limited to this, and may be applied to a normal type or the above-described shaft-straight type helical broach. It is also applicable to

1 broach body 4 cutting edge part 5 cutting edge
6 Outer diameter rising edge 7 Tooth thickness rising edge 7A Rake face 7B Acute angle side cutting edge 7C Obtuse angle side cutting edge θa Side relief angle of acute side cutting edge 7B θb Side side relief angle of obtuse side cutting edge 7C Oa Broach body Axis 1 Ob Reference plane orthogonal to axis Oa of broach body 1 L Lead of row of cutting edge 5

Claims (2)

A plurality of cutting edges protruding radially outward are formed integrally with the outer peripheral portion of the shaft-shaped broach body. A plurality of rows of the cutting blades are arranged in a spiral shape by twisting around the axis of the broach body toward the side and are spaced apart from each other in the circumferential direction. A one-piece helical broach forming a lead twist groove, comprising:
Among the plurality of cutting edges, the plurality of cutting edges on the front end side of the broach body are outer diameter rising edges that cut the tooth profile of the work in the tooth height direction, and the plurality of cutting edges on the rear end side of the broach body are the tooth profile of the work. is a tooth thickness rising blade that cuts in the tooth thickness direction,
Each of the tooth thickness increasing blades has an obtuse angle between the rake face facing the tip of the broach body and the side face of the broach body at an acute angle in the circumferential direction, and the rake face and the broach body at an obtuse angle in the circumferential direction. It has cutting edges on both sides and crossing ridges,
The blade grooves formed between the rows of cutting blades are helical so as to be twisted in the direction opposite to the twisting direction of the rows of cutting blades from the front end side to the rear end side of the broach body. or along a reference plane perpendicular to the axis ,
A side clearance angle θa of the cutting edge on the acute angle side of the increased tooth thickness edge is set to 5′≦θa≦45′, and a side clearance angle θb of the cutting edge on the obtuse angle side of the increased tooth thickness edge is set to 5′≦5′. A helical broach characterized in that θb≦45′ . A broaching method for forming a twisted groove in the inner periphery of a machined hole of a work by the helical broach according to claim 1 ,
cutting the tooth profile of the workpiece in the tooth height direction by the outer diameter rising edge so that the tooth profile of the workpiece has a predetermined height;
Then, the left and right side surfaces of the tooth profile of the workpiece are simultaneously machined by the cutting edge on the acute angle side and the cutting edge on the obtuse angle side of the tooth thickness increasing blade, and the tooth thickness of the tooth profile of the workpiece is machined to a predetermined thickness. A broaching method characterized by:

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