JPS6140489B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a hob for generating gears, and particularly to a hob useful for generating helical gears or screw gears with large helix angles.

As shown in FIG. 1, a spur gear is a hob that is commonly used for cutting helical gears or screw gears.

As shown in FIG. 1a, the hob 1 has a plurality of cutting blade rows 5 on the outer periphery of the hob body 2, each of which has a series of ridges 3 and troughs 4 arranged in an easy shape in the direction of the axis P of the hob body 2. There are queues. A groove 6 is formed between these cutting edge rows 5 in the axial direction of the hob 1 or in a direction perpendicular to a helical wire S to be described later. Valley portion 4 and peak portion 3 forming one cutting edge
are arranged along a helical winding S, that is, a spiral. As is well known, as hob 1,
As shown in FIG. 1, in addition to the type in which the cutting blade array 5 and the hob body 2 are integrated, there is also an assembled hob in which the cutting blade array 5 is assembled to the hob body 2.

Fig. 2 is a diagram showing the outer periphery of a hob having six rows of cutting blades arranged in an easy shape in the axial direction.
are positioned shifted in the axial direction by a predetermined dimension. In other words, all the peaks 3 and troughs 4 are arranged along the helical winding S of the tooth trace.

Generating gear cutting is performed on the workpiece gear W using such a hob 1, and a helical gear (helical gear) is formed.
Alternatively, to form a screw gear, the hob axis P is inclined with respect to the rotation center line Q of the gear W to be cut, as shown in FIG. This is done by feeding the hob 1 in the axial direction of the gear W to be cut while rotating the hob 1 relative to each other. Note that FIG. 3 shows a case where a right-handed helical gear is cut using a left-handed hob.

However, as shown in Fig. 4, the torsion angle β
When a helical gear (hereinafter referred to as a helical gear) W with a large helical gear is subjected to generating gear cutting using the conventional hob 1 shown in FIG. The occurrence of this tooth trace error and warping is shown in Figures 5a and 5b, and Figure 5a is an enlarged view showing the end face of the gear at the part indicated by V in Figure 4. 5b is an enlarged front view showing the outer periphery of the gear at the part indicated by V. If the tooth profile shown by the solid line in FIGS. The angle becomes as shown by the broken line A, and a tooth trace error occurs, as well as a large bend in the thin wall as shown in the shaded area C.The reason for this is that as the helix angle β becomes larger, as shown in Figs. As is clear from the above, since the thickness of the tooth at the end of the gear becomes thinner, the part of the gear material W facing the tooth is pressed against the cutting edge of the hob 1 and elastically deforms during generating gear cutting by the hob. Therefore, when generating gear cutting is performed on a helical gear with a large helix angle β using the conventional hob shown in Fig. 1, the above-mentioned tooth trace errors and backlashes are unavoidable. It is.

The existence of such tooth trace errors and return impairs the function of the gear, so after cutting the generating gear,
It is necessary to correct it by means such as grinding, and in the past, there was a problem in that a large amount of man-hours had to be spent on manufacturing the gear.

An object of the present invention is to solve the problems of the prior art described above by cutting off the end portion of the gear where tooth trace errors and backlashes occur at the same time as generating tooth cutting of the gear. In order to achieve this object, the present invention provides a plurality of rows of cutting blades, each of which has a continuous easy-to-shape peak and valley in the axial direction of the hob main body, on the outer periphery of the hob main body, separated by a groove. The gist of the provided hob is that an auxiliary blade for cutting off the gear at the end of the gear to be cut is disposed at at least one end in the axial direction of the hob.

Next, a hob according to an embodiment of the present invention shown in FIGS. 6 to 9 will be described. Similar to the conventional hob shown in FIG. 1, the hob of the present invention shown in FIG. A plurality of rows 5 are provided on the outer periphery of the hob body 2, and between each row of cutting blades 5, a groove 6 is formed that extends in the axial direction of the hob body or in a direction perpendicular to the helical winding to be described later. There is. The valley portions 4 and the peak portions 3 constituting one cutting edge are respectively arranged along the helical winding.

At some ends of the hob in the axial direction, this hob 1
An auxiliary blade 7 for cutting the teeth at the end of the gear W to be cut, on which generating gear cutting is performed, is disposed integrally with the crest 3 so as to eliminate the portion corresponding to the trough 4.

In FIG. 6, the state where the auxiliary blade 7 is not arranged is as shown by the broken line, and the illustrated hob is the part E of the standard blade that performs generating gear cutting on the gear W to be cut.
It is constructed by combining two types of blades: and part D of the auxiliary blade 7, but as shown in FIG. Alternatively, it is possible to form the auxiliary blade 7 in a split form so that it is fixed to the hob.
Further, the auxiliary blades 7 may not be arranged in all of the plurality of cutting blade rows 5, but may be arranged only in some.

FIG. 8 is a diagram showing the expanded state of the outer periphery of the hob 1 having six rows of cutting blades 5. The auxiliary blades 7 are arranged in the part indicated by the broken line, and each of the cutting blade rows 5 is E. It consists of a part for performing the generating gear cutting shown in FIG.

In order to perform generation gear cutting on the gear W to be cut using the hob 1 of the present invention shown in FIG. 6, the helix angle of the thread to be generated on the gear W to be cut and β are as shown in FIG. If the advance angle of the hob (the hob shown in Fig. 7 is a left-handed hob) is γ, the hob is tilted at an angle of β-γ, and the gear W to be cut is rotated around its axis Q. At the same time, while rotating the hob 1 around its axis P so as to have a predetermined rotation speed ratio to the rotation speed, the hob 1 is sent in the axial direction of the gear to be cut as shown by the arrow T. Perform tooth cutting. As a result, only the gear at the end of the gear W to be cut is cut by the auxiliary blade 7.

FIGS. 9a and 9b are views showing the end of the gear W to be cut after generating gear cutting is performed by the hob 1 of the present invention, and correspond to FIGS. 5a and 5b, respectively. Figure 9a,
In b, the shaded portion G indicates the portion cut by the auxiliary blade 7. By cutting this portion G with the auxiliary blade 7, the shape of the tooth portion of the gear W to be cut is changed depending on the shape of the auxiliary blade 7, e.g.
It is possible to take various shapes such as shape G shown by a broken line in the figure.

FIG. 10 is a diagram showing an expanded state of the outer periphery of a hob 1 according to another embodiment of the present invention, in which a gear to be cut W
The auxiliary blade 7 that cuts the teeth at the end of the hob 1 is inserted into the grooves 6 of the hob 1 that are adjacent to each other in the direction along the helical wire.
It is placed between. Auxiliary blade 7 in this case
It may also be formed integrally with the hob 1 or the auxiliary blade 7
It is also good as a split type that can be assembled.

11a and 11b are views showing a part of a hob 1 according to still another embodiment of the present invention, respectively.
Figure a shows a case where the auxiliary blade 7 is arranged so as to eliminate the trough 4 at the end of the hob in the axial direction. The peak portion 3a shown corresponds to the portion scraped off by the auxiliary blades 7, 7, etc. in the next cutting edge row, successive cutting blade row, etc., which are omitted from the figure, and is ultimately involved in generating gear cutting. I don't do that, so I've omitted it.

FIG. 11b shows a case in which the auxiliary blade 7 is arranged between adjacent valleys 4 in the direction along the helical wire in the groove 6, and the size of the auxiliary blade 7 includes the peak 3. 7, the mountain portion 3b adjacent to the helical winding direction is omitted.

In addition, in the above embodiment, an auxiliary blade was provided to cut out the teeth at one end of the gear to be cut, but by arranging the auxiliary blade at both ends in the hob axis direction, It is clear that the teeth at both ends can be cut out.

As described above, according to the present invention, a plurality of rows of cutting blades in which peaks and troughs are arranged in an easy shape in the axial direction of the hob main body are arranged on the outer periphery of the hob main body, with grooves separating them. In the hob, in which the peak portions and the valley portions of the adjacent cutting blade rows are respectively arranged along a helical winding line, an auxiliary blade for cutting a tooth portion at an end of a gear to be cut is provided in the hob. Since it is arranged at at least one end in the axial direction of the gear, even if the gear is a helical gear or a helical gear with a large helix angle, it is possible to cut the teeth at the end where tooth line errors and backlashes occur during generating gear cutting. This eliminates the need to modify the gear by means such as grinding after cutting the generating gear.
Efforts were made to reduce gear manufacturing man-hours.

[Brief explanation of the drawing]

Figures 1a and b are front and side views of a conventional hob, Figure 2 is a developed view of the hob's outer periphery showing the cutting edge of the conventional hob, and Figure 3 shows how a gear to be cut is cut using a conventional hob. A schematic diagram showing a state in which generating gears are being cut. Fig. 4 is a perspective view showing a helical gear with a large helix angle. Fig. 5
Figures a and b are an end view and a front view showing the V section in Figure 4 when the helical gear shown in Figure 4 with a large helix angle is subjected to generating gear cutting using a conventional hob, and Figure 6 is a front view of the helical gear shown in Figure 4 with a large helix angle. A front view showing a hob according to an embodiment, FIG. 7 is a schematic diagram showing a state in which generating gear cutting is performed by the hob of the present invention, and FIG. 8 is a diagram showing the cutting edge of the hob of the present invention. The developed view, FIGS. 9a and 9b, are an end view and a front view corresponding to the V section in FIG. 4 when a helical gear with a large helix angle shown in FIG. 4 is subjected to generating gear cutting using the hob of the present invention, FIG. 10 is a developed view of the outer periphery of a hob according to another embodiment of the present invention, and FIGS. 11a and 11b are front views showing essential parts of the hob according to other embodiments of the present invention, respectively. 1... Hob, 2... Hob body, 3... Yamabe, 4
... Valley part, 5 ... Cutting blade row, 6 ... Groove, 7 ... Auxiliary blade, W ... Gear to be cut.

Claims (1)

[Claims] 1. A hob in which grooves of a plurality of rows of cutting blades are provided in the outer periphery of the hob body in the axial direction of the hob body, in which peaks and troughs are arranged alternately and continuously in a easy shape. A hob characterized in that an auxiliary blade for cutting off teeth at the end is disposed at at least one end in the axial direction of the hob.