JPS5940576B2 - shaving cutlet - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a shaving cutter used for precision machining of tooth surfaces of gears.

(Prior art) The meshing ratio between the shaving cutter and the gear to be machined takes an integer value in special cases, but under normal processing conditions it takes a value between 1 and 2, such as 1.8. .

Therefore, in the latter case, one tooth surface (
When looking at the tooth surface on the front or rear side in the direction of rotation,
The contact points of the shaving cutter with the teeth vary over time between two points and one point. That is, in FIG. 2 showing the machining state in the latter case, when machining the vicinity of the pitch circle 3 of the front tooth surface 2A in the rotational direction R of the gear 6 to be machined with the shaving cutter 5, one point in the vicinity of the pitch circle 3 is At this time, the rear tooth surface 2B contacts at two points 31 near the root 10 and near the tip 9.
, 32, making contact at two points.

That is, the shaving cutter 5 and the gear to be processed 6 come into contact at three points in total. Here, 13 in FIG. 2 is the rear gear 2B.
and 14 indicate the line of meshing action of the front tooth surface 2A. Note that Fig. 2 is a diagram viewed from the gear axis direction, and each contact point (meshing point) 30, 31, 32 is shown in the tooth trace direction (
They are located at different positions in the front and back directions of the drawing. For example, the contact point 30 on the pitch circle 3 is located at the center in the tooth trace direction, and the contact point (meshing point) 31 at the root of the tooth and the contact point (meshing point) 32 at the tooth tip are located in the tooth trace direction. are located near the opposite end faces of the When machining the vicinity of the pitch circle 3 on the front tooth surface 2A, the contact point is only one point 30, whereas the contact points on the rear tooth surface 2B are two points 31 and 3.
2, the contact point 30 on the pitch circle 3 receives a large clamping force from the two front and rear contact points 31 and 32, so that the shaving cutter 5 and the gear to be processed at the contact point 30 on the pitch circle 3 The contact pressure between pitch circles 6 and 6 becomes larger than the contact pressure when machining other parts, and the cutting amount near pitch circle 3 becomes larger than that of other parts.

When machining the vicinity of the pitch circle 3 on the rear tooth surface 2B, it is done in exactly the same way. As a result, as shown in Fig. 1, the cutter tooth profile 1
Even if it is a straight line (involute shape) or any other shape, there is a pitch circle 3 on the gear tooth surfaces 2A and 2B.
A dent 4 is created near .

Here, when the straight line 21 in FIG.
A and 2B respectively show the impolite tooth profile, and the cutter tooth profile 1 and tooth surfaces 2A and 2B in this example
uses tooth profiles that are modified by D and e, respectively, compared to the impolite tooth profile. When the dents 4 are formed on the tooth surfaces 2A and 2B of the gears, the shaping cutter 5 lags behind the normal rotational position shown by the solid line and comes to the position shown by the broken line, as shown in FIG. As the dent 4 develops as the machining progresses, parts 33 and 34 of the tooth flanks of the cutter become attached to the tip 9 and part 38 of the root 10 of the workpiece gear 6, which were separated at the start of machining.
, 39. In this state, the dent 4 will no longer develop. After all, in shaping processing, when there is a total of 3 points of contact, 1 point near the pitch circle 3
A dent 4 corresponding to the tooth tip gap a or tooth root gap b relative to the shaving cutter 5 is generated near the pitch circle 3 on the tooth surface that is in contact at the point.

In Figures 1 and 2, 7 is the tooth tip of the cutter, 9 is the tooth tip of the gear, 10 is the tooth root of the gear, and in Figure 2, 11 is the tooth root circle of the gear, and 12 is the gear tooth 2. It is the tip circle. (
Purpose of the Invention) This invention reduces the gap between the tip of the gear or the gap between the teeth of the tooth surface of the tooth surface that is in contact at one point near the pitch circle when a total of three points contact is made in the above-mentioned shaping process. The purpose is to minimize the dents near the pitch circle of the gear to be machined, and to obtain a tooth surface with an accurate shape.

(Structure of the Invention) In order to achieve the above-mentioned object, the present invention aims to reduce the amount of crowning of at least one of the tip and the root of a shearing cutter, that is, the amount of curvature in the direction of the tooth trace.
The amount of crowning is set to be smaller than the amount of crowning in the parts other than the dedendum and the dedendum, thereby reducing the gear tip clearance or dedendum clearance.

(Example) Figure 3 shows the tooth surface that is in contact at one point near the pitch circle 3 (front tooth surface 2A in the state shown in Figure 2) when there is a total of three points of contact shown in Figure 2. Gear tip clearance a and tooth root clearance b
shows an example of a situation that changes as the engagement between the shaping cutter 5 and the gear to be processed 6 progresses.

A solid line indicates a case where the amount of crowning of the shaping cutter 5 is large, and a broken line indicates a case where the amount of crowning is small. The shaping cutter 5 starts from machining the tooth tip of the gear to be processed 6.
As the meshing between the gear 6 and the workpiece gear 6 progresses, the gear tip clearance a increases from zero to X or X', and conversely, the tooth root clearance b increases to Y or Y''. To,
It decreases from a certain value and becomes zero when two points touch again. FIG. 4 shows a situation in which the maximum values of the gaps A and b change depending on the amount of crowning of the shaping cutter 5.

As can be seen from this, by reducing the amount of crowning of the shaping cutter 5, the gaps A and b can be made smaller. FIG. 5 shows an embodiment of the invention. In this example, a general shaping cutter 5 is used in which three or more lands 17 are formed to form a cutting edge, and the amount of crowning at the root portion 18 of the cutter is made smaller than the amount of crowning at other parts. . FIG. 6A shows the cutter tooth profile 1 in this case, and this cutter tooth profile is made by grinding the cutter tooth profile 19, which has a sharp slope at the root part 18 of the cutter, using, for example, the well-known Karl Fruth company method. It can be easily obtained by using a cutter grinder.

That is, it is only necessary to attach the inclined surface 25 to the tooth tip of the grindstone 24 that rotates around the rotation axis 23, and thereby,
The center portion 18a of the tooth root portion 18 of the cutter shown in FIG.
Since the center portion 18a is shaved off by the angle b, the central portion 18a is shaved off to a large degree, and both end portions 18b are shaved down to a small size, so that the amount of crowning of the tooth root portion 18 of the cutter is reduced. FIG. 7 shows a case in which three or more lands 17 are formed and a separate protrusion 20 with a small amount of crowning is attached via a screw 21 to the tooth tip of a shaping cutter 5 with a normal amount of crowning. Indicate the case.

Moreover, FIG. 8 shows a case where a similar protrusion 20 is integrally formed on both the tooth tip and root of the cutter. By the way, in the shoeing cutter 5 shown in FIGS. 5 and 7, if the amount of crowning is reduced over the entire tooth surface from the root to the tooth tip, the lands that come into contact with the tooth surface of the gear during machining will be reduced. As the number of 17 increases, the sharpness of the cutter becomes poor, and problems such as a decrease in machining accuracy and efficiency due to generation of vibration occur.

However, as shown in Figure 5 or Figure 7, if the entire tooth surface of the cutter except for the root and tip is left with large roundings, the desired purpose can be achieved without the above problems. can.

Further, the above-mentioned problem does not occur in a cutter having one (or two) lands as shown in FIG. (Effects of the Invention) As described above, in this invention, when a total of three points contact in shaping processing, the tip gap or root gap of the tooth surface that is in contact at one point near the pitch circle 3 is reduced. , it is possible to suppress the dents near the pitch circle of the gear to a small size, and it is possible to obtain a tooth surface with an accurate shape.

Furthermore, manufacturing of the shaping cutter is extremely easy. In addition, since the above-mentioned indentation becomes smaller, rotational fluctuations of the cutter during machining are reduced, which prevents the occurrence of dents on the tooth tip of the gear tooth surface and uneven patterns and scratches on the tooth root caused by rotational fluctuations of the cutter. can do.

[Brief explanation of the drawing]

Figure 1 is a sectional view showing the relationship between the cutter tooth profile and the gear tooth profile.
Figure 2 shows the meshing diagram between the shaping cutter and the gear to be machined.
Fig. 3 is a diagram of changes in gear tip clearance and root clearance, Fig. 4 is a diagram of changes in crowning amount, Fig. 5 is a perspective view of a shaping cutter according to an embodiment of the present invention, and Fig. 6A. Figure 6B is an illustration of the retouching and grinding of the same cutter, and Figure 6B is the arrow B in Figure 6A.
7 and 8 are perspective views of shaping cutters according to other examples of the present invention. 5... Shaping cutter, 6... Gear to be processed, 7
... Katsu tooth tip, 17... Land, 18... Katsu tooth base, 20... Projection.

Claims (1)

[Claims] 1. A shaving cutter characterized in that the crowning amount of at least one of the tooth tip and the tooth root is smaller than the crowning amount of the other portion.