JPS6059094B2 - How to polish a shaving cutter - Google Patents

Description

[Detailed description of the invention] The present invention relates to a method for polishing a shaving cutter.

Conventionally, shaving cutters have been widely used as rotary tools for the final cutting of, for example, transmission gears for mass-produced automobiles. In other words, when a gear to be cut is roughly cut with a hob, pinion cutter, etc., a slight cutting allowance is left on the tooth surface of the gear to be cut, and in the next shaving process, the shaving cutter is used as shown in Figure 1. (hereinafter simply referred to as a cutter) 1 and the gear to be cut 2 are engaged, the cutter 1 is driven to rotate, and the table 3 is reciprocated as shown by arrows A and B, thereby removing the slight cutting allowance. This makes it possible to create gears with high dimensional accuracy. However, when cutting, for example, about 50 front gears with one cutter, the grooves 4 formed on the vine tooth surface as shown in Figure 2.
The edges of the blade are worn and deformed, reducing sharpness.

Therefore, the cutter is replaced and the shaving process is continued again, but the cutter tooth surface is polished so that the cutter whose sharpness has deteriorated can be used again. Since such polishing is performed approximately 10 to 20 times with one cutter, such polishing is usually called re-polishing. Note that after re-sharpening 20 times, the cutter teeth become very thin, and the depth of the multi-striped grooves 4 (see Figure 2) on the cutter tooth surface becomes extremely shallow, making it unusable. It disappears. Usually, the gear to be cut is a helical gear or a spur gear, and the cutter that cuts it is also a helical gear or a spur gear, although the helix angle is different from that of the gear to be cut, and the meshing of these two gears is It is handled as a gear with offset shaft. One of the most important things in the design of a shaving cutter is the determination of the helix angle βCo on the cutter's reference pitch value circle, and this is usually calculated using the following formula, as shown in Figure 3 A, C, and C. It is determined.

In addition, FIG. 3 shows a case where both the cutter and the gear to be cut are meshed with each other at the reference pitch circles. Here, βo is the torsion angle on the reference pitch circle of the gear to be cut. Since βo=0, equation (1) holds true.

The shaft intersection angle X affects the sharpness of the cutter, and if it is unavoidable, for example, if interference with the cutter is a problem with stepped gears, it may be determined to be at position 3, but usually it is set at position 10. 1
It is said that 5th place will give the best results. In this way, the helix angle β on the standard pitch circle of the cutter is determined.

Once determined, the number of teeth Zc appropriate for the number of teeth Z of the gear to be cut is determined, and furthermore, the normal module m and the normal tool pressure angle α are determined. Make it common to the gear to be cut, and determine the ivy specifications as shown in the table below. In the past, once these specifications were determined, the cutter tooth surface was polished according to the specifications without changing them from when the cutter was new until it became unusable due to repeated re-polishing.
However, when using a cutter that has been reground a considerable number of times and attaching it to the cutter head 5 (Fig. 1) of a shaving machine to shave a gear, the tooth thickness of the cutter decreases due to the resharpening. As a result, backlash occurs between the cutter and the gear to be cut, and in order to eliminate this backlash, the center distance between the two must be shortened. However, if we reduce the center distance in this way,
Decrease. As the engagement pitch circle diameter decreases, the torsion angles of both also change. Letting the torsion angles that have just changed be βr (gear), β, and c (cutter), respectively, the shaft intersection angle Xr will be as shown in the following equation. Conventionally, this X,
Before serial production shaving processing, in order to find out the
A test cut is made, and the helix angle or lead of the cut gear is measured to determine its quality, and the amount of rotation of the cutter head 5 (arrow F in FIG. 1) is adjusted.

Since this adjustment work must be carried out, this has been a major obstacle to improving work efficiency in the shaving process. This invention eliminates the wasted work time of adjustment work by trial cutting in the conventional shaving processing process mentioned above, and allows shaving processing to be performed with the axis intersection angle x always at a constant value even when using a cutter that has been reground a considerable number of times. The purpose is to provide a method for polishing a cutter such that the helix angle β,c on the meshing pitch circle of the shaving cutter with the workpiece gear is equal to the meshing pitch of the workpiece gear with the shaving cutter. For the torsion angle β1 on the circle, βRc=
β, -Xr or β,.

This can be achieved by polishing the cutter tooth surface so that the relationship becomes =β, +X. An embodiment of the present invention will be described in detail below.

The specifications of the gear to be cut and the cutter are shown in the table below.In the table above, the specifications surrounded by O marks remain unchanged, but the specifications not enclosed by O marks change every time the cutter is polished. The gear to be cut is designed in advance to mesh with the mating gear, so most of its specifications remain unchanged, but the specifications related to its engagement with the cutter change. As shown in Fig. 2, the meshing between the cutter and the gear to be cut during shaving can be thought of as the meshing of shifted gears that roll into contact with each other in the normal cross section at the meshing pitch point P, and the normal meshing pressure The angle α is generally expressed by the following formula. Here, z″ is the virtual number of teeth of the gear to be cut in the cross section perpendicular to the tooth, and is determined by z″.

is the virtual number of teeth of the cutter in the perpendicular cross section, and is determined by . In equation (3), the shift coefficient The shift coefficient Xc changes each time the cutter tooth surface is polished.

Normally, the shift coefficient of a new cutter varies, and even if the cutter tooth surface has been polished to a predetermined shift coefficient value, the shift coefficient X changes each time it is polished. changes. Therefore, for a cutter to be polished, the value of the dislocation coefficient Xc must first be determined. Therefore, the shift coefficient of the cutter is determined by measuring the tooth thickness with a gear caliper, or by measuring the straddle tooth thickness or overball diameter. For example, when using the straddle tooth thickness measurement method, the cutter shift coefficient XCl is expressed by the following formula:
seek. In the above formula, for example, the subscript 1 of XOl means the first polishing (the same applies to other symbols hereinafter). Further, Enl is the measured value of the straddle tooth thickness, and α is determined using the pressure angle perpendicular to the axis.

n represents the number of straddle teeth.

The cutter dislocation coefficient X obtained in this way.

By substituting l for Xc in equation (3), the normal meshing pressure angle α1 between the gear to be cut and the cutter can be determined. From the normal meshing pressure angle α1, the helix angle β,1 on the meshing pitch circle of the gear to be cut and the helix angle βRcl″ on the meshing pitch circle of the cutter are determined by the following equation.

From equation (6), the cutter engagement pitch circle diameters D and Cl are determined by the following equations.

Next, in order to keep the axis crossing angle βRcl is adopted.

That is, next, using equations (7) and (8), the torsion angle β on the new standard pitch circle of the new lead L1 cutter on the cutter tooth surface is calculated.
.

1. New axis-perpendicular pressure angle α5.

1. New standard pitch circle diameter DCl, new base circle diameter Dg
Obtain Ol using the following formulas.

With the above steps, the specifications required for cutter polishing are determined.

In practice, a shaving cutter grinder as shown in Fig. 4A is usually used for cutter polishing, and a suitable diameter D.
Pitch block 7 (including band 8,8″ thickness)
Since the generating grinding work is performed using the grinding wheel 10 as a type of rack-type tool, the helix angle β. ．． 1. Similarly, find the normal pressure angle α, 1. That is, as shown in FIG. 4, the pitch block 7 attached to the tensioned band 8,8''
is fixed to the cutter mounting shaft 9, the inclination angle of the grindstone 10 is set to the normal pressure angle αm1, and the horizontal rotation angle of the grindstone head is set to βm1, and then the cutter mounting shaft 9 is rotated in the directions of arrows G and H. let

Then, the cutter mounting shaft 9 moves in the directions of arrows J and K.
Generative polishing of the tooth surface is performed using a rack-shaped grindstone. In the figure, reference numeral 11 indicates an index plate. Polishing is performed for each tooth using this index plate. When the entire tooth surface on one side has been polished, the cutter is turned over and attached to the cutter mounting shaft, and this time, the other tooth is polished. The polishing work is completed by polishing the tooth surface one by one. By using the cutter polished in this way in the shaving process, the work can be carried out while keeping the axis intersection angle, in fact, the rotation angle indicated by arrow F of the cutter head 5 in Fig. 1 constant. .

Every time a cutter is polished, the cutter polishing setup is performed according to the procedure described above, but normally the decrease in the cutter tooth thickness, that is, the change in the cutter tip shift coefficient, is extremely small (tooth thickness is 20P7TL. (below), so it is not actually necessary to follow the above steps every time polishing. For example, you can predetermine steps with a certain width for the straddle tooth thickness or overball diameter, and then check the actual value. It is preferable to start changing the cutter specifications little by little according to the above procedure only when the value exceeds the lower limit of the stage and becomes smaller.

In addition, if you follow the procedure described above to calculate the time from when it was new until it becomes unusable, and keep this in the form of a list near the cutter grinder, it will be extremely easy to grind the cutter. can. As described above, according to the present invention, it is possible to eliminate trial cuts when changing cutters during shaving processing, and it is possible to finish cutting gears with a constant axis intersection angle at all times, greatly improving work efficiency in the shaving processing process. I can do that.

[Brief explanation of drawings]

Fig. 1 is an explanatory diagram showing an overview of shaving processing, Fig. 2 is an explanatory diagram showing the relationship between the shaving cutter and the gear to be cut, and Fig. 3 is an explanatory diagram of the shaft intersection angle when the reference pitch circles mesh with each other. 4A is a plan view of the shaving cutter grinder, and the opening in FIG. 4 is a sectional view taken along the Rollo line in FIG.

Claims (1)

[Claims] 1. The helix angle β_r_c on the engagement pitch circle of the shaving cutter with respect to the workpiece gear is adjusted so that the axis intersection angle X_r between the shaving cutter and the workpiece gear during shaving processing is always a constant value. For the twist angle β on the pitch circle, β_r_c=β_r−X_r or β_r_c=
A method for polishing a shaving cutter, comprising polishing the tooth surface of the shaving cutter so that the relationship β_r+X_r is established.