JPS6121774B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a hobbing method in which gears are cut using a hob, and particularly to a finishing hobbing method.

Currently, carbide skiving hobbing, which only performs finish cutting using a hobbing machine, has already been put into practical use. This carbide skiving hobbing uses a carbide hob, and meshes the cutting edge of the hob with a gear-shaped workpiece that has already been gear-cut to avoid interference (see Figure 1). This is a technique in which a predetermined finishing allowance is then further cut and finished.

As shown in Fig. 1, finishing gear cutting with this carbide skiving hob involves further cutting the already geared workpiece 1, so the workpiece 1 and the hob 2 must be aligned without interfering with each other. is important, but since there is no guideline for tooth alignment at any location, tooth alignment itself is not easy. For this reason, the hob 2 is used by shifting the hob by a specific amount that is easy to determine, such as 1 pitch or 0.5 pitch. However, in finish hobbing, only the side incisors are involved in gear cutting, and the processing area is also fixed. This means that
The smaller the finishing allowance becomes, the more noticeable it becomes, and the gear cutting area of each incisor groove becomes one location that is specified as the creation point moves, as shown in FIG. As mentioned above, it is difficult to shift the hob freely in this point-shaped gear cutting area, that is, the wear point, so it cannot be moved freely, and only a part of the cutting edge (carbide tip) 4 wears out, as shown in Fig. 5. Become.

Therefore, even though only a part of the carbide tip 4 is worn out, the tip must be replaced, which is wasteful. As shown in Fig. 2, the carbide skiving hob is made by brazing a carbide tip 4 to the base metal 3, making it expensive and having a limited number of blades, making it difficult to identify wear points. That is a disadvantage.

When cutting gears from gear material using a hob, the teeth involved in the cutting wear out for each cutting edge, and since they can be shifted arbitrarily, the wear of the hob progresses uniformly as shown in Figure 3. The problem of replacing the cutting edge (chip) due to localized wear could not be considered.

SUMMARY OF THE INVENTION An object of the present invention is to provide a gear hob cutting method that can shorten setup time, extend tool life, and improve finished surface accuracy.

The configuration of the present invention that achieves such an object is such that, in a numerically controlled hobbing machine, the meshing between the hob and the gear-shaped workpiece is released in advance before machining, and then the hob is moved in the axial direction by an arbitrary amount without rotating. and rotating the work table while synchronizing the positional relationship of the shifted hob with the cutting edge,
It is characterized in that the generating gear cutting is performed after the hob and the gear-shaped workpiece are meshed.

The method of the present invention will be explained in detail below based on the drawings.

After releasing the mesh between the hob 2 and the workpiece 1 before processing, the hob 2 is shifted in the direction of the hob axis and the table 18, in other words, the workpiece 1 is rotated accordingly, as shown in FIG. As such, the gear cutting area or wear point B moves to B'. The amount of movement X of this wear point B on the side cutting edge of the hob 2 is as follows: X=A/cosα, where α is the tool pressure angle. Therefore, when hobbing is started in this state, a point B' that is different from the wear point B in the virtual line state (the position before shifting) becomes the wear point, that is, the gear cutting area.
In other words, the movement of the generating point caused by the rotation of the hob 2 (see FIG. 4) is caused to occur on the same cutting edge by shifting the hob 2 in the axial direction. Therefore, even in finish hobbing, by shifting the hob 2 by an arbitrary amount and aligning the teeth, the gear cutting area can be moved one after another on the same cutter, so that only one part of the carbide tip 4 is cut. It never wears out. By appropriately shifting the hob 2 to move the gear cutting area, the carbide tip 4 is uniformly worn, so that the life of the carbide tip 4 is dramatically extended compared to the conventional gear cutting method.

Moreover, the meshing at this arbitrary position is based on the meshing state of the hob 2 and the workpiece 1 at a specific location where meshing is easy, and then the hob 2 is shifted by an arbitrary amount and the workpiece is synchronized with this. This is easy because the work 1 can be moved in accordance with the movement of the hob 2 by rotating the table 18.
That is, it is easy to determine the mounting position of the hob 2 on the hob head (hob mount) 7 at a specific position, and the same is true when mounting the rough-cut work 1 on the work table 18. In every hobbing machine, there is a center of the hob head 7, and it is easy to set the reference position of the hob cutting edge at this point, and once the hob 2 is fixed, the center of the hob head and the cutting edge of the hob 2 are The positional relationship is fixed. On the other hand, an origin is also determined for the table 18, and the roughly cut workpiece 1 is fixed to this in a fixed relationship. For example, the positioning key of the work holder 6 is aligned with the center C of the hobbing machine. Of course, at this time, the origin of the table 18 and the reference position of the hob 2 are in a certain relationship, that is, the hob 2 and the workpiece 1 are in a state where they can mesh without interference. Therefore, after confirming in advance that this positional relationship is correct, before starting the skiving hobbing process, the hob 2 is shifted in the axial direction by an arbitrary amount, and the table 18 is synchronously rotated in accordance with this shift amount. If so, tooth alignment at any hob shift position is automatically achieved. In other words, no time is required for setup.

The above-mentioned shift movement of the hob 2 and synchronized rotation of the table (in other words, the work 1) 18 can be easily carried out using a numerically controlled hobbing machine as shown in FIG. 7. This mechanism enables the hob cutter 2 supported by the hob mount 7 and the hob support 8 to be moved along with the hob mount 7 in the tangential direction of the workpiece 1 on the table 18, and is synchronized with the axial shift of the hob cutter 2. This is to rotate the work table 18. The axial shift of the hob cutter 2 transfers the rotation of the hob shift motor 11 to the hob shift drive transmission gear 10.
The hob shift is transmitted to the hob shift feed screw 9 via the hob shift feed screw 9, and the hob mount 7, which forms a screw pair with the feed screw 9, is moved. The shift amount of the hob 2 is input to the NC control device 14 by the tachometer 12 and the resolver 13, and an equivalent table is input based on the relationship between the hob shift amount and the table rotational movement preprogrammed in the NC control device. An operation command is output to the tachogenerator 12 and resolver 13 of the table drive motor 15 to set the rotation angle. The rotation of this motor 15 is transmitted to the table 18 via a table drive gear 16 and a master worm 17.

The operation of the NC control device can be performed with a specific G code. In this case, the input values are only the size of x·m (module), the hob shift amount, and the number of teeth of the workpiece 1. Alternatively, manual operation may be performed, in which case the hob 2 and the table 18 are individually shifted or rotated based on pre-calculated related quantities.

As described above, according to the present invention, even in finish hobbing, the hob is shifted in the axial direction and the workpiece is rotated and aligned in accordance with the shift amount, thereby moving the gear cutting area on the same cutting edge. This prevents only a portion of the cutting edge from wearing out, dramatically extending tool life. Also,
The setup time for gearing at any position can be shortened because it is only necessary to shift the hob after gearing at a specific position where gearing is easy.

The gear machining method of the present invention is not limited to the carbide skiving hobbing mentioned in the embodiment, but also finishing hobbing with a general high speed steel hob, or processing using another gear cutting machine in advance (e.g. It can be applied to hobbing a workpiece after rough cutting using a gear mill, milling machine, etc., or for finishing hobbing a workpiece that has been machined with an incorrect tooth thickness dimension.

[Brief explanation of the drawing]

Figure 1 is an explanatory diagram showing how to mesh the workpiece and hob cutter when cutting a carbide skiving hob, Figure 2 is a side view showing an example of a brazed carbide skiving hob, and the third is a continuous hob shift. A model diagram showing the state of wear of the side cutting blade, and Figure 4 is an explanatory diagram showing the movement of the creation point of skiving hobbing with the hob in Figure 2, where a is the cutting edge in the direction of the arrow, and b is the direction of the arrow. , c indicates the cutting edge in the arrow view, and d indicates each point of the cutting edge in the arrow view. Fig. 5 is a perspective view showing one cutting edge of a carbide skiving hob, Fig. 6 is an explanatory view showing movement of the working side of the hob cutting blade due to hob shift, and Fig. 7 is a perspective view showing one cutting edge of a carbide skiving hob.
The figure is a schematic explanatory diagram of an NC hobbing machine in which the hob shift and table rotation are synchronized and can be freely aligned. In the drawings, 1 is a workpiece, and 2 is a hob.

Claims (1)

[Claims] 1 In a numerically controlled hobbing machine, after releasing the mesh between the hob and the gear-shaped workpiece before machining,
Without rotating the hob, the hob is shifted in the axial direction by an arbitrary amount, and the positional relationship of the shifted hob with the cutting edge is synchronized, the work table is rotated, and the hob and the gear-shaped workpiece are meshed. A method for machining gears on a hobbing machine, which is characterized in that generating gear cutting is performed after cutting.