JPH088019Y2 - Helical brooch - Google Patents

Description

[Detailed description of the device] [Industrial applications]

 The present invention relates to an improvement of a helical broach.

[Prior art]

As an example of a conventional helical broach used for processing an internal gear of a helical tooth or a spiral spline groove, FIG. 5 shows a developed state of each tooth row of the finishing blade group. The twist angle β in the tooth trace direction formed by each tooth row with respect to the axial direction is usually about 20 to 30 degrees, and most of them are set to around 25 degrees. And the cutting edge of each tooth 12 between adjacent individual dentitions
The cutting grooves 14 into which the 13 are arranged in a line are formed in a direction substantially perpendicular to the twisting direction of the tooth row. In other words, the cutting edge groove 14 is spirally inserted in a direction inclined at an angle α with respect to the circumferential direction of the broach, and the inclination angle α of the cutting edge groove 14 is
Is approximately equal to the twist angle β of the tooth row. That is, in the conventional helical broach, the inclination angle α is also set to about 25 degrees. When the inclination angle α is set to about 25 degrees, for example, in a helical broach having an outer diameter of about 100 mm, about 10 cutting edge grooves are provided on the periphery. in this way,
The state of the cutting edge 13 formed by inserting the cutting edge groove 14 so as to be substantially perpendicular to the twist direction of the tooth row is called a tooth right angle cutting edge. On the other hand, although not shown, a helical broach is provided with a helix angle β of the tooth row, and for this, the cutting edge groove is formed in an annular shape in the circumferential direction instead of spirally, that is, its inclination angle α is 0. The state of the cutting edge set in degrees is referred to as an axis-perpendicular cutting edge.

[Problems to be solved by the device]

By the way, when actual cutting is performed by the helical broach, the broach is given an axial motion while being twisted along the direction of the twist angle β of the tooth row. At this time, in the helical broach having the right-angled cutting edge, the cutting resistance F ′ acting in the direction orthogonal to the cutting edge 13 is, as shown in FIG. 4, the axial component (thrust component) S ′ and the circumferential direction. It is decomposed into a component (torque component) T '. The magnitude of the circumferential component T'is represented by F'sin α, and when this α is, for example, 25 degrees, about 42% of the force of F'is the circumferential component. If a force of about 42% of the cutting resistance acting on the cutting edge 13 acts as a torque component in the circumferential direction, it is necessary to considerably strongly clamp the work material to regulate the rotation. On the other hand, in a helical broach having a right-angled cutting edge, since the inclination angle α of the cutting edge groove is 0 degree, the torque component of the cutting resistance described above disappears, but in this case, the cutting edge becomes the work material. On the other hand, it acts intermittently, which makes the machining accuracy inferior to that of the right-angled tooth. In this way, in the conventional helical broach with a right-angled tooth cutting edge, it is necessary to clamp the work material fairly firmly in order to regulate the rotation of the work material, but the torque component of the cutting resistance disappears. If a helical broach with a right-angled cutting edge is used, there is a problem in that cutting is intermittently performed and satisfactory processing accuracy cannot be obtained. The present invention has been made in view of the above-mentioned technical problems to effectively solve them. SUMMARY OF THE INVENTION Therefore, an object of the present invention is to provide a helical broach capable of maintaining the machining accuracy and minimizing the circumferential cutting resistance.

[Means for Solving the Problems]

The helical broach according to the present invention has the following constitution in order to solve the above-mentioned conventional technical problems and achieve the object. That is, in a helical broach having a twist angle of at least 20 degrees in the tooth trace direction with respect to the axial direction, it has three twist cutting edges and the inclination angle of the cutting edges with respect to the circumferential direction is set to 10 degrees or less. ing.

[Action and effect of the device]

In a helical broach, when the cutting edge groove is given in a spiral shape, if the number of grooves of the cutting edge groove increases, its inclination angle with respect to the circumferential direction must be increased, and the cutting resistance in the circumferential direction is sufficiently reduced. In particular, the inclination angle is preferably 10 degrees or less. With the helical broach according to the present invention,
Since the number of cutting grooves is three, which is much smaller than the conventional one, the inclination angle of the cutting grooves with respect to the circumferential direction can be made as small as possible, and it should be 10 degrees or less. Will be possible. Third because the inclination angle is 10 degrees or less
As shown in the figure, the direction of the force F acting on the cutting edge at the time of cutting approaches the axial direction, and the cutting resistance (torque) T in the circumferential direction is considerably larger than the cutting resistance (thrust) S in the axial direction. Get smaller. That is, the force acting to rotate the work material in the circumferential direction also becomes small, and the work can be performed without clamping the work material. By the way, when the inclination angle of the cutting edge groove is 10 degrees, the cutting resistance T of the torque component is about 17% of the force F, which is about the same as when the inclination angle is 25 degrees.
Less than half compared to 42%. Furthermore, since the cutting edge groove is formed in a spiral shape, the cutting action by each cutting edge can be performed continuously without discontinuity, and the processing accuracy is maintained at the same level as the conventional helical broach of the right angle tooth cutting edge. It Further, when biting, the three cutting edges bite at the same time, and the posture of the tool is determined most stably, so that the cutting is also performed stably. That is, for example, when the cutting edge is constituted by two cutting edge grooves, only two cutting edges are bited when biting, so that the axial cutting load is received at two points on one line. The posture becomes unstable, and when the cutting edge is configured with four or more cutting edge grooves, there can be multiple surfaces that can receive the axial cutting load, so all of these surfaces are the same. If it is not formed accurately so that it becomes a surface, it will cause the posture of the tool to become unstable, but in the present invention, the three cutting edges form the minimum points (3 points) when defining the plane. That is, it reliably receives the axial cutting load on a single surface.

【Example】

A preferred embodiment of the present invention will be described below with reference to FIGS. 1 and 2. In this embodiment, the present invention is applied to a shell of an assembled helical broach. That is, the shell 1 is assembled in the finishing blade region of the assembled broach body (not shown). FIG. 1 is a half sectional front view of the shell of this embodiment in which the intermediate portion is omitted. The left side of the figure is the bite side, that is, the front end of the shell 1, and the right side is the falling side, that is, the rear end. Further, FIG. 2 is a development view schematically showing each cutting edge formed in the shell of the present embodiment, the lower side of the figure is the eating side of the shell 1, and the upper side is the pull-out side.
Each tooth row is arranged spirally in the circumferential direction along the twist angle β. The twist angle in a normal helical broach is often around 25 degrees, and the twist angle β is set to 25 degrees also in this embodiment. A cutting edge 3 is formed by providing a cutting edge groove 4 to the front edge of each tooth 2. The cutting edge groove 4 is formed by a spiral groove that is inclined at an inclination angle α with respect to the circumferential direction (represented by the lateral direction in FIG. 2), and this inclination angle α is 10 in this embodiment. Is set in degrees. This inclination angle α is the cutting edge groove 4
It is possible to make such a reduction only after the number of is reduced to three, which is far smaller than the conventional one. Further, the cutting edge groove 4 is formed at every position that divides the entire circumference of the shell 12 into three equal parts, and is formed with a total of three threads. The cutting edge groove 4 may be processed by attaching a fixed lead, and is substantially the same as the tooth right angle cutting blade. When the shell 1 thus formed is attached to the finishing blade region of the broach and broaching is performed, three cutting edges 3 are formed on the outer circumference of the shell 1 as shown in the development view of FIG. Simultaneous machining is performed at a position that divides the circumference into three equal parts,
Extremely stable cutting is performed in finish cutting, and high processing accuracy is obtained. In particular, in the cutting, although the cutting edge groove 4 is a weakly twisted groove, a slight inclination angle α with respect to the circumferential direction is obtained.
Since the cutting edge 3 is continuously spirally connected, the cutting edge 3 is always involved in the cutting under the same condition, and does not intermittently act on the work material unlike the cutting edge perpendicular to the axis. Further, since the inclination angle α of the cutting edge groove 4 is made as small as possible, the component force of the circumferential component of the force acting on the cutting edge 3 becomes small enough to be ignored.
Generally, a work loading table of a broaching machine has a large number of needle-like structures called spikes, which are called spikes, on which a work material is placed during machining. According to the present embodiment, the component force of the above-mentioned circumferential component is reduced to such an extent that the work material can be sufficiently held only by the friction between the work material and the spike. It does not rotate during cutting without clamping.

[Brief description of drawings]

FIG. 1 is a front view of a half-section of a shell in which an intermediate portion is omitted in an embodiment of the present invention, and FIG. 2 is each cutting edge in a tooth group of three-row cutting groove formed in the shell in the embodiment of FIG. FIG. 4 is a diagram schematically showing the developed state, FIG. 3 is a diagram for explaining the situation of each component force of the axial component and the circumferential component of the force acting on the cutting edge of the helical broach according to the present invention, FIG. FIG. 5 is a diagram for explaining the situation of each component force of the axial component and the circumferential component of the force acting on the cutting edge of the helical broach in the prior art, and FIG. 5 is the development of each cutting edge of the helical broach in the prior art. FIG. 1 ... Shell, 2 ... Tooth, 3 ... Cutting edge, 4 ... Cutting edge groove,
α: inclination angle of cutting edge groove, β: twist angle of tooth row

Claims (1)

[Scope of utility model registration request] 1. A helical broach having a twist angle (β) in the tooth trace direction with respect to the axial direction of at least 20 degrees or more, having three twist cutting edge grooves (4), and the cutting edge groove in the circumferential direction ( A helical broach characterized in that the inclination angle (α) of 4) is 10 degrees or less.