JP2000210817A - Gear working method and gear working device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a gear working method and gear working device that can work gears with high precision without causing burr at the end surface of a tooth and reduce working cost and working lead time without requiring deburring facilities, jigs, and the transfer of works. SOLUTION: A first roughing gear hob 3, a second roughing gear hob 4, and a finishing gear hob 5 are installed on a hob shaft. The directions of rotation and movement of the first roughing gear hob 3 and the second roughing gear hob 4 are reserved each other. The cutting is made moving the center of rotation of a gear 6 to be machined from a cut start position A to a retreat position B by the first roughing gear hob 3. Then the cutting is made moving the center of rotation from a cut start position C to a roughing finish position D by the second roughing gear hob 4, and the cutting is made moving the center of rotation from a finishing start position E to a finishing end position F by the finishing gear hob 5.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a gear machining method and a gear machining apparatus for machining a gear by rotating a hob and moving the gear relatively to a gear to be machined.

[0002]

2. Description of the Related Art Conventionally, when machining a gear, hobbing using a high-speed steel hob or a carbide hob is performed on a hobbing machine as a roughing process, and thereafter, removal of burrs generated on a tooth end surface is included. The end face of the tooth is chamfered by a special machine, and shaving is performed by a shaving cutter (made of high-speed steel) as a finishing process to achieve a predetermined accuracy (JIS class 3 to 4).
Have been to get.

[0003] In the chamfering of the tooth end surface, a predetermined accuracy can be efficiently and stably obtained by shaving in a subsequent step.
It is performed for the purpose of suppressing the vibration generated due to the projection on the tooth surface at the time of gear engagement, including the removal of burrs generated on the end face.

[0004] As another gear machining method, a process-intensive method is used in which shaving is abolished and roughing / finishing is performed using only an NC hobbing machine. After that, chamfering is performed.

[0005] By the way, as a deburring equipment for removing burrs generated at the lower end of a tooth during hobbing on a hobbing machine, a cutting edge similar to a cutting edge for turning is set at the lower end of the tooth (a gap between the lower end of the gear and the lower end of the gear). (2 to 0.5 mm), and a burr generated at the lower end portion of the tooth during hobbing is cut and removed by the cutting edge.

[0006]

However, the above-mentioned general gear machining method requires three steps of hobbing, chamfering and shaving.
Each requires equipment, jigs and tools, and work transfer (including desorption), which causes a problem that processing cost and processing lead time increase. On the other hand, in the process intensive method,
Since chamfering is performed after finishing, there is a problem that burrs may occur on the meshing tooth surface side.

[0007] In addition, the above-mentioned burrs have a problem that it is impossible to completely remove burrs generated on the tooth end faces.

SUMMARY OF THE INVENTION The present invention has been made in order to solve such a problem, and does not require burring removal equipment, jigs and tools, and transfer of a work, and a high-precision gear without generating burrs on tooth end faces. It is an object of the present invention to provide a gear machining method and a gear machining apparatus capable of machining a gear and reducing machining cost and machining lead time.

[0009]

Means for Solving the Problems and Action / Effect In order to achieve the above-mentioned object, the gear machining method according to the first aspect of the present invention rotates the gear from one end face to the other end face of the gear to be cut. A gear that performs gear machining by using a first hob having a rake face in a rotation direction and a second hob rotating from the other end face side to the one end face side of the work gear and having a rake face in the rotation direction. In a machining method, the first hob is relatively moved while being rotated from one end face side to the other end face side of the work gear to cut the work gear, and then the other of the work gear is cut. It is characterized in that the second hob is relatively moved while rotating from the end face side to the one end face to cut the gear to be cut.

According to the first aspect of the invention, the gear is machined by cutting one end face of the gear to be machined toward the other end face and the other end face toward the one end face side. Even if burrs are generated, the burrs can be removed without performing a deburring operation, and a gear having a predetermined accuracy (JIS class 3 to 4) can be machined by performing finishing. Since no burrs are generated at the stage of hobbing, the conventional chamfering process can be omitted. Therefore, the process and processing time (processing lead time) can be reduced, and the processing cost can be reduced.

In the first aspect, the first hob is relatively moved from one end face to the other end face while rotating the first hob, and the rotation center position of the first hob is set at the other end face. After retracting the first hob before reaching the extension line, the second hob is arranged so that the phase of the cutting edge matches the teeth formed by the first hob, and the gear to be machined by the second hob Preferably, cutting is performed. Normally, the size of the burr generated on the end face in the gear machining process varies depending on the work material, module, feed, cutting speed, sharpness of the cutting edge, and the like. As described above, the first hob is retreated in a state where the one end surface is cut and the other end surface is not completely cut,
In addition, since the other end face is cut by the second hob, there is an effect that the burr can be more reliably removed even when a larger burr occurs under the above conditions. In this manner, a gear having a predetermined accuracy without burrs on both end surfaces is processed.

In the first invention, the end faces of the gear to be machined are arranged in the vertical direction, the first hob is rotated from the upper end face to the lower end face, and the second hob is moved downward. It is preferable that the trajectory of the rotation center of the first hob is set to be longer than the trajectory of the rotation center of the second hob by rotating from the end face toward the upper end face. By doing so, the rigidity can be improved and the processing efficiency can be improved.

In the first invention, it is preferable that the first hob performs rough machining for cutting the gear to be cut, and the second hob performs rough finishing for cutting the gear to be machined. By doing so, the conventional three steps (hobbing, chamfering, and finishing) can be reduced to one step (hobbing) to process a gear with predetermined accuracy. Therefore,
The processing lead time and the processing cost can be reduced.

In the first invention, after the cutting of the cut gear by the first hob and the second hob is completed, the cut gear rotates from one end to the other end or from the other end to the one end. Then, a third hob having a rake face in the rotation direction is adjusted in phase with the cutting edge of the tooth formed on the gear to be cut by the first and second hobs, and the third hob is rotated while rotating. It is preferable to perform finishing by cutting the gear to be moved by moving from the end face side to the other end face side or from the other end face side to the one end face side. Thus the first
After the teeth are formed by the hob and the second hob, the finishing process is performed by the third hob, so that a step generated on the cutting boundary between the first hob and the second hob can be removed, and the processing accuracy can be improved. There is an effect that it can be improved.

Next, a gear machining apparatus according to a second aspect of the present invention is a gear machining apparatus for machining a gear by rotating a hob and moving the gear relatively to the gear to be machined. A first hob that rotates from the side toward the other end side, has a rake face in the direction of rotation, and moves relatively from the one end side to the other end side; And a second hob which has a rake face in the direction of rotation and moves relatively from the other end face toward the one end face.

In the second invention, one end face of the gear to be cut is cut by the first hob toward the other end face,
The other end face is cut by the second hob toward the one end face, and the gear is processed.

According to the second aspect of the present invention, since the first hob and the second hob cut the one end and the other end of the gear to be cut, respectively, even if a burr occurs on one end or the other end, the deburring operation is performed. It is possible to remove the burrs without any trouble, and it is possible to achieve a predetermined accuracy (J
IS3 to 4) gears are machined. Since no burrs are generated at the stage of hobbing, the conventional chamfering process can be omitted. Therefore, the process and processing time (processing lead time) can be reduced, and the processing cost can be reduced.

In the second invention, it is preferable that the first hob and the second hob are respectively mounted on different hob shafts. After the cutting by the first hob is completed, the first hob is retracted, the second hob is arranged so as to be in phase with the teeth formed on the gear to be cut, and cutting by the second hob is performed. Thus, the gear is processed, and the same effect as that of the first invention is exerted.

In the second invention, it is preferable that the first hob and the second hob are mounted on the same hob shaft. After the end of the cutting by the first hob, the hob shaft is moved in the direction of the hob axis, and the second hob is arranged so as to be in phase with the teeth formed on the gear to be cut. Done. The gear is processed in this way,
An effect similar to that of the first invention is exerted.

In the second invention, it is preferable that a finishing hob for finishing a gear is mounted on a hob shaft on which the first hob and the second hob are mounted.
After teeth are formed by the first hob and the second hob,
By performing the finishing processing using the third hob, a step generated on the cutting boundary between the first hob and the second hob can be removed, and there is an effect that the processing accuracy can be improved.

[0021]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Next, specific embodiments of a gear machining method and a gear machining apparatus according to the present invention will be described with reference to the drawings.

FIG. 1 is a perspective view of a gear processing apparatus 1 according to a first embodiment of the present invention, and FIG. 2 is a schematic view of a hob body mounted on the gear processing apparatus 1. Also,
FIG. 3 is an explanatory diagram for explaining the gear machining method of the first embodiment.

The gear machining apparatus 1 according to the first embodiment includes a hob supporting portion 1 which supports a hob main body 2 and moves up and down in the Z-axis direction in the figure.
a, a processing part 1b movable in the X-axis direction, and a gear support table 1c which is at a position facing the processing part 1b and rotates about the Z-axis as a rotation axis. A motor (not shown) is mounted on the hob support 1a, and the hob main body 2 mounted on the hob support 1a is configured to rotate in the forward and reverse directions around the Y axis as a rotation axis. . In FIG. 1, the hob supporting portion 1a
3 shows a state in which the hob main body 2 is not mounted.

The hob main body 2 has a first roughing hob (corresponding to a first hob in the present invention) 3 and a second roughing hob (corresponding to a second hob in the present invention) on a hob shaft 2a. 4 and a finishing hob (corresponding to a third hob in the present invention) 5 so that the first roughing hob 3 and the second roughing hob 4 rotate in directions opposite to each other. Has been. When the hob body 2 is mounted on the hob support portion 1a, the finishing hob 5, the first rough hob 3, and the second rough hob 4 are sequentially arranged from the rotary drive side (hob machine main metal side). It is configured to be. A gear 6 to be cut is supported on the gear support table 1c.

The first roughing hob 3 moves from the upper end face 6a of the work gear 6 to the lower end face 6b (the gear support table 1c).
(Toward the tooth width direction) (hereinafter referred to as forward rotation), and a rake face 3a is provided in the rotation direction. The second roughing hob 4 is configured to rotate (hereinafter, referred to as reverse rotation) from the lower end surface 6b of the work gear 6 toward the upper end surface 6a (toward the face width direction). A rake face 4a is provided in the rotation direction. Like the first roughing hob 3, the finishing hob 5 rotates forward from the upper end surface 6a of the work gear 6 toward the lower end surface 6b, and the rake face 5a in the rotational direction. Is provided.

In the gear machining apparatus 1 configured as described above, the first rough machining hob 3 is arranged at a position facing the gear 6 to be moved by moving the hob support 1a in the Y-axis direction (hob axis). The hob main body 2 is advanced in the X-axis direction by rapid traverse until the rotation center of the first roughing hob 3 reaches the cutting start position A. The cutting start position A of the first roughing hob 3 is above the upper end surface 6a of the gear 6 to be cut.
The cutting edge of the first roughing hob 3 whose rotation center coincides with that of the cutting gear 6 does not come into contact with the cutting gear 6, and the tip of the cutting edge on the center side of the cutting gear 6 is on the extension line of the preset cutting depth of the gear. It is set so that it is on the outer peripheral side by the allowance for finishing. Next, while the first roughing hob 3 is normally rotated, the hob supporting portion 1a is vertically moved downward by cutting feed (Z-axis direction).
To cut the upper end face 6a of the gear to be machined 6, and the center of rotation of the first roughing hob 3 is positioned at the lower end face 6 of the tooth of the gear to be machined.
When the hob body 2 reaches the retreat position B slightly above
(Processing part 1b) is retracted in the X-axis direction by rapid traverse. Thus, the cutting by the first roughing hob 3 is completed.

Subsequently, the hob supporting portion 1a is moved in the direction of the hob axis so that the phase of the cutting edge of the second rough hob 4 matches the teeth formed on the gear 6 to be cut by the first rough hob 3. (In the Y-axis direction) to dispose the second roughing hob 4 at a position facing the gear 6 to be machined. Then, this hob body 2
Is advanced in the X-axis direction by rapid traverse until the rotation center of the second roughing hob 4 reaches the cutting start position C. The cutting start position C of the second roughing hob 4 is a hanging position of the cutting start position A of the first roughing hob 3 and the lower end surface 6 of the gear 6 to be cut.
The cutting edge of the second rough machining hob 4 which is below b and whose rotation center coincides with the cutting start position C is set so as not to contact the work gear 6. Next, the hob shaft 2 is moved vertically upward (Y-axis direction) by cutting feed while the second rough hob 4 is rotated in the reverse direction, and the lower end face 6b of the gear 6 is cut. 4 is the retracted position B
When the hob body 2 reaches the roughing end position D slightly higher, the hob main body 2 is retracted in the X-axis direction by rapid traverse. Thus, the cutting by the second roughing hob 4 is completed.

After the cutting by the second roughing hob 4 is completed, the phase of the cutting edge of the finishing hob 5 with respect to the teeth formed on the gear 6 by the first and second roughing hobbes 3 and 4. The hob supporting portion 1a is moved in the Y-axis direction so that the finishing hob 5 is opposed to the gear 6 to be machined. The hob main body 2 is advanced at a rapid traverse until the rotation center of the finishing hob 5 reaches the finishing processing start position E. The finishing processing start position E is above the upper end surface 6a of the work gear 6, and the cutting edge of the finishing hob 5 whose rotation center coincides with the finish processing start position E does not contact the work gear 6, and The cutting edge of the cutting gear 6 at the center side is set so as to be on an extension of the cutting depth of the gear set in advance. Next, the hob shaft 2 is moved downward by cutting feed while rotating the finishing hob 5 in the forward direction, and the center of rotation of the finishing hob 5 is lower than the lower end surface 6b of the gear 6 to be finished. When the speed reaches F, the hob main body 2 is moved backward by rapid traverse. Thus, finishing is performed so that the teeth formed by the first roughing hob and the second roughing hob have a preset cutting depth, and gear processing is completed.

According to the first embodiment, the upper end surface 6a and the lower end surface 6b of the machined gear 6 are cut by the first roughing hob 3 and the second roughing hob 4, respectively, from above downward or upward from below. Therefore, it is possible to prevent burrs from being generated on the end surfaces 6a and 6b. Also, the first
Even when a step occurs in the cutting boundary line between the roughing hob 3 and the second roughing hob 4, there is an effect that the finishing hob 5 can correct the cutting and process a high-precision gear.

According to the first embodiment, three or two steps of hobbing, chamfering, and shaving, which have been conventionally performed in a hob only process, can be performed. Equipment, jigs and tools, and the transfer of workpieces are not required, so that machining costs can be reduced and machining lead times can be shortened. The conventional processing lead time is 12.6 in the case of processing in three steps (hobbing, chamfering, shaving).
The machining lead time of this embodiment is 8.4 minutes in the case of machining in two steps (hobbing and chamfering), whereas the first and second roughing hobbs 3, 4 are made of high-speed steel. The time is 5.0 minutes in the case of a hob, and 2.5 minutes in the case of a cemented carbide throwaway hob.

According to the first embodiment, the lower end face 6b of the machined gear 6 is supported by the gear support table 1c, and has a structure resistant to a force applied from above to below. Therefore, the first roughing hob 3 and the finishing hob 5 are moved from the upper end surface 6a toward the lower end surface 6b, and the cutting length of the first roughing hob 3 is changed to the cutting length of the second roughing hob 4. Since the length is made sufficiently longer, the rigidity and the processing efficiency can be improved, and there is an effect that high accuracy can be maintained for a long period of time.

In the first embodiment, the finishing hob 5
Is set so as to cut from the upper end surface 6a of the work gear 6 toward the lower end surface 6b, but is not limited thereto.
It may be set so as to cut from b to the upper end surface 6a. Further, in the first embodiment, the first rough machining hob 3 moves from the upper end face 6a of the work gear 6 to the lower end face 6b, and the second rough work hob 4 moves from the lower end face 6b of the work gear 6 to the upper end face. 6a, but is not limited to this. The first rough machining hob 3 moves from the lower end surface 6b of the gear 6 to the upper end surface 6a, and the second rough machining hob 4 Gear 6
May be cut from the upper end surface 6a toward the lower end surface 6b. Since the first roughing hob 3 and the second roughing hob 4 need only be configured to rotate and move in opposite directions to each other, the first roughing hob 3, the second roughing hob 4, and the finishing There are four types of combinations shown in Table 1 in the rotational movement direction of the processing hob 5.

[Table 1]

A gear machining method according to a modification of the first embodiment is performed by using the gear machining apparatus 1, and an explanatory diagram is shown in FIG. As in the first embodiment, the first
After cutting by the roughing hob 3, the hob support 1
a is moved in the direction of the hob axis so that the second rough machining hob 4 is arranged at a position facing the gear 6 to be machined. The cutting edge of the second roughing hob 4 is adapted to be in phase with the teeth formed by the first roughing hob 3.

The second roughing hob 4 is rotated and moved in the horizontal and vertical directions to perform horizontal cutting (plunge processing).
And vertical cutting is performed. That is, the hob main body 2 is advanced by rapid traverse until the rotation center of the second roughing hob 4 reaches the plunge machining start position G. This plunge machining start position G is on or slightly below the extension of the lower end face 6b of the gear 6 to be cut, and the cutting edge of the second rough machining hob 4 whose rotation center coincides with the plunge machining start position G is covered. The cutting gear 6 is set so as not to be in contact therewith.

Next, while rotating the second roughing hob 4, the hob body 2 is advanced in the horizontal direction by cutting feed,
When the cutting edge of the roughing hob 4 reaches the cutting position of the work gear 6 and reaches the outer position by a margin for finishing, the cutting edge is moved vertically upward, and the rotation center of the second roughing hob 4 is retracted. When reaching the roughing end position D slightly above the position B, the hob main body 2 is retracted by rapid traverse. In this manner, the cutting by the second roughing hob 4 is completed, and then, similarly to the first embodiment, the finishing by the finishing hob 5 is performed to complete the gear machining.

According to this modification, it is not necessary to pull down the second rough machining hob sufficiently below the lower end face 6b of the gear 6 to be machined, so that cutting is performed even if there is no space below the gear 6 to be machined. be able to. Thus, similarly to the first embodiment,
Burrs can be prevented from being formed, and a high-precision gear can be processed, and a processing step and a processing lead time can be reduced, and a processing cost can be reduced. Although the plunge processing of this embodiment has a lower processing speed than vertical cutting, the processing lead time is substantially the same as that of the first embodiment because the processing distance is short. In addition, plunge processing may be performed in the processing of the first roughing hob 3.

Next, the gear machining apparatus according to the second embodiment is
Except for the difference in the configuration of the hob main body 10 mounted on the hob support 1a, there is basically no difference from the configuration of the first embodiment. Note that parts common to the first embodiment will be described using the same reference numerals. FIG. 5 shows the hob body 10 according to the second embodiment.
Is shown. The hob main body 10 rotates on the same hob shaft 11 from the upper end surface of the work gear to the lower end surface thereof, and has a rake face 12a in the rotation direction.
2, and a reversing hob 13 that rotates from the lower end surface to the upper end surface of the work gear and has a rake face 13a in the direction of rotation. The hob body 10
Is mounted on the hob supporting portion 1a, is movable in the hob axial direction, and moves up and down while rotating each hob 12, 13 in each direction.

In the second embodiment, the first embodiment
Similarly to the roughing hob 3, the forward rotation hob 12 cuts the outer peripheral side downward from the upper end surface of the gear to be cut by an amount of finishing machining from a preset cutting depth position, and the lower position from the lower end surface. To end the cutting. Next, the hob shaft 11 is moved in the hob axial direction so that the reverse rotation hob 13 matches the cutting edge phase of the tooth formed by the normal rotation hob 12. The finishing start position is below the lower end face of the gear to be cut, and the cutting edge of the reversing hob 13 whose rotation center coincides with the finishing start position does not come into contact with the gear to be cut. Is set so as to be on an extension of the preset cutting depth of the gear. The reversing hob 13 is rotated and moved upward from the lower end surface to the upper end surface for cutting. Thus, gear processing is completed.
Note that the forward rotation hob 12 may be a finishing process and the reverse rotation hob 13 may be a roughing process.

According to the second embodiment, similarly to the first embodiment, a high-precision gear can be machined without generating burrs on both end faces of the gear. Further, it is possible to shorten the processing steps and the processing lead time, and to reduce the processing cost.

Next, the gear machining apparatus according to the third embodiment is as follows.
Basically, there is no difference from the configuration of the first embodiment except for the configuration of the hob main body 20 mounted on the hob support 1a. Note that parts common to the first embodiment will be described using the same reference numerals. FIGS. 6A and 6B are schematic views of the hob body 20 according to the third embodiment. The hob main body 20 rotates on the two hob shafts 21 and 22 from the upper end surface to the lower end surface of the gear to be machined, respectively, and has the forward rotation hob 23 having a rake face 23a in the rotation direction (FIG. 6A). )When,
The reversing hob 24 (FIG. 6) which rotates from the lower end surface of the work gear toward the upper end surface and has a rake face 24a in the rotational direction.
(B)) is mounted. One hob shaft 21 (22) is mounted on the hob support 1a, and the other hob shaft 22 (21) is mounted after removing the hob shaft 21 (22). The hob support portion 1a is movable in the hob axial direction, and is moved up and down while rotating each hob 12, 13 in each direction, and further moved in the X-axis direction by the processing portion 1b. It is possible. The replacement of the hob shafts 21 and 22 on which the hobbs 23 and 24 are mounted may be manual or automatic.

In the gear machining method configured as described above, similarly to the second embodiment, the forward rotation hob 23 moves from the upper end face of the gear to be cut to a position higher than the lower end face while rotating forward, thereby cutting. After completion, the hob shaft 21 supporting the forward hob 23 is retracted by the processing portion 1b, replaced with the hob shaft 22 supporting the reverse hob 24, and the reverse hob 24 is arranged at a position facing the gear to be machined, The cutting edge phase of the reverse rotation hob 24 is adjusted to the teeth formed by the normal rotation hob 23. Thereafter, the reverse rotation hob 24 moves from the lower end surface to the upper end surface of the work gear while rotating in the reverse direction, and cuts to a preset cutting depth position to complete the gear machining. Thus, the same effects as those of the above embodiment can be obtained.

In the third embodiment, one hob shaft support 1a is provided in the processing portion 1b. However, the present invention is not limited to this, and two hob shaft supports for transmitting rotational driving forces in mutually opposite directions are provided. Provided on the hob shaft support portions, respectively.
You may make it mount | wear with 1 and 22.

Further, in the third embodiment, the gear machining apparatus is constructed by attaching the hob shafts 21 and 22 to the hob support section 1a attached to the machining section 1b movable in the X-axis direction. However, the present invention is not limited to this, and the hob shafts 21 and 22 may be mounted on a multi-tasking machine to which various tools can be attached, so that the gear machining device may be configured.

In the second and third embodiments,
The cutting by the forward hobbs 12 and 23 is completed at a position above the lower end face, and the reverse hobbs 13 and 24 are used to cut from the lower end face to the upper end face. However, the present invention is not limited to this. After cutting from the upper end surface to the lower end surface, the reversing hobs 13 and 24 may cut from the lower end surface 6b to the upper end surface. Alternatively, after cutting from the lower end surface to a position below the upper end surface or to the upper end surface by the reverse rotation hobbes 13 and 24, cutting may be performed from the upper end surface to the lower end surface by the normal rotation hobbes 12 and 23.

In each of the above-described embodiments, the burrs are formed after the gears have been processed as described above by using a deburring apparatus in which the same cutting edges as the turning cutting edges are arranged on the lower end side of the gear to be machined. It is also possible to perform removal processing.

[Brief description of the drawings]

FIG. 1 is a perspective view of a gear machining device according to a first embodiment of the present invention.

FIG. 1 is a schematic view of a hob main body according to a first embodiment.

FIG. 3 is an explanatory diagram for explaining a gear machining method according to the first embodiment.

FIG. 4 is an explanatory view illustrating a gear machining method according to a modification of the first embodiment.

FIG. 5 is a schematic view of a hob main body according to a second embodiment.

FIG. 6 is a schematic diagram (a) of a forward hob according to a third embodiment.
It is a schematic diagram (b) of a reverse hob.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Gear processing apparatus 1a Hob support part 1b Processing part 1c Gear support table 2,10,20 Hob body 2a, 11,21,22 Hob shaft 3 First rough hob 4 Second rough hob 5 Finish hob 6 Machining Gears 12,23 Forward hob 13,24 Reverse hob A, C Cutting start position B Retreat position D Roughing end position E Finishing start position F Finishing end position G Plunge starting position

Claims (9)

[Claims] 1. A first hob which rotates from one end surface side to another end surface side of a gear to be machined and has a rake face in the direction of rotation, and a first hob from the other end surface of the gear to be machined toward one end surface. A gear processing method for performing gear processing using a second hob that rotates and has a rake face in the direction of rotation, wherein the first hob is rotated from one end side to the other end side of the gear to be cut. After the cutting of the gear to be cut, the cutting of the gear to be cut is performed by rotating the second hob relatively from the other end of the cut to the one end thereof. And a gear machining method. 2. The first hob is rotated and relatively moved from one end surface side to the other end surface side of the gear to be machined, and a rotation center position of the first hob reaches an extension of the other end surface. After retreating the first hob before, the second hob is arranged so that the phase of the cutting edge matches the teeth formed by the first hob, and the gear to be machined is cut by the second hob. The gear processing method according to claim 1. 3. An end face of the gear to be machined is arranged in a vertical direction, the first hob is rotated from the upper end face to the lower end face, and the second hob is rotated upward from the lower end face. The gear machining method according to claim 2, wherein the trajectory of the rotation center of the first hob is set to be longer than the trajectory of the rotation center of the second hob by rotating toward the end face. 4. The gear machining according to claim 1, wherein the first hob performs rough machining for cutting the gear to be machined, and the second hob performs finish machining for cutting the gear to be machined. Method. 5. After the cutting of the cut gear by the first hob and the second hob is completed, the cut gear rotates from one end surface to the other end surface or from the other end surface to the one end surface, and rotates. A third hob having a rake face in the direction is aligned with a cutting edge of a tooth formed on a gear to be cut by the first and second hobs, and the third hob is rotated from one end face side while rotating the third hob. The gear machining method according to any one of claims 1 to 3, wherein the finish machining is performed by cutting the gear to be machined by moving toward the end face side or from the other end face side to the one end face side. 6. A gear machining apparatus for machining a gear by rotating a hob and relatively moving the gear with respect to the work gear, wherein the gear is rotated from one end face side to the other end face side of the work gear,
A first hob having a rake face in the rotation direction and relatively moving from the one end face side to the other end face side; and a first hob rotating from the other end face side to the one end face side to rake in the rotation direction. A second hob having a surface and relatively moving from the other end surface toward the one end surface. 7. The gear processing device according to claim 6, wherein the first hob and the second hob are respectively mounted on different hob shafts. 8. The gear processing device according to claim 6, wherein the first hob and the second hob are mounted on a same hob shaft. 9. The gear processing apparatus according to claim 8, wherein a finishing hob for finishing a gear is mounted on a hob shaft on which the first hob and the second hob are mounted.