JP2016047570A - Dry hobbing machining device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a dry hobbing machining device capable of reducing jamming of chips onto a machining surface of gear wheel material, reducing cutting temperature, enhancing machining accuracy, realizing extension of a tool service life, and removing a cutter mark generated on a gear surface of a gear wheel.SOLUTION: Since dry hobbing machining is carried out on a peripheral part of gear wheel material while making a hob finely vibrate in axis direction, friction force generated between a blade surface of hob blades and chips is reduced. Thereby, jamming of chips onto a groove surface of the gear wheel material is reduced, cutting temperature is reduced, machining accuracy is enhanced, and extension of a tool service life is realized. Furthermore, by actuation of micro vibration means, the hob is finely vibrated in a direction orthogonal to a cutting direction of gear wheel material with hob blades, thus finishing effect in grinding is enhanced, the gear surface of the gear wheel is flattened and a cutter mark generated on the gear surface may be removed.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a dry hobbing apparatus, and more particularly, to a dry hobbing apparatus that does not use cutting oil that presses a hob that rotates around the axis line against an outer peripheral surface of a gear material while finely vibrating the hob in the axial direction. .

  In recent years, dry hobbing that does not use cutting oil is known in order to reduce the environmental burden and the physical burden on the worker and to manufacture a high-precision gear at low cost. Conventionally, RGC (Round bar Gear Cutting) processing has been developed as one type of dry hobbing processing (Non-patent Document 1). RGC processing means that gear material (blank) is hardened by quenching by high-frequency heat treatment, and then the gear material is made high without using cutting oil by using an ultra-high hardness hob (hereinafter, carbide hob). By cutting gears with high accuracy, productivity is improved, machining costs are reduced, and the length of gears to be rounded is shortened.

In RGC processing, since the gear material is a super-hard product, a carbide hob is used as the tool. However, the hob blade of the carbide hob is hard and brittle. Therefore, chipping (blade chipping phenomenon) has occurred at the cutting edge due to vibration generated by intermittent cutting in dry hobbing. In addition, since the cutting speed of the carbide hob is high in RGC processing, the hob blade is likely to be thermally cracked, and the temperature rise of the hob shaft and gear material due to the cutting heat is large.
Therefore, as a conventional technique for suppressing this chipping, for example, a technique disclosed in “Carbide Hobbing Machine” of Patent Document 1 is known. This improves dynamic vibration characteristics of the hob shaft by mounting a damper device on the hob shaft, and further reduces vibration on the table shaft side by mounting a clearance removing device on the table shaft of the hobbing machine. Is. As a result, vibrations generated by intermittent cutting during dry hobbing are suppressed, and chipping of the hob blade can be prevented.

  As a countermeasure against heat generation during dry hobbing, Patent Document 1 discloses that cooling air is passed through the hob shaft and cooling air is blown onto the gear material to reduce the cutting heat and increase the temperature of the hob shaft and carbide hob. Techniques for suppression are described. Thereby, generation | occurrence | production of the thermal crack of a cemented carbide hob can be suppressed, and the tool life can be extended. Furthermore, stable machining accuracy can be obtained by suppressing thermal deformation of the machine.

Shingo Fukunaga, Shunji Inoue, Masataka Yonekura, Isao Kashiwagi, straight-cut dry hob machining of high-hardness gear materials, RGC machining, Bulletin of Oita National College of Technology, No. 42 (November 2005), P1-P6 JP-A-8-229738

The “carbide hobbing machine” of Patent Literature 1 suppresses vibrations caused by intermittent cutting in dry hobbing by mounting the damper device on the hob shaft and mounting the play removing device on the table shaft in this way, Prevents chipping of the blade edge.
However, since the dry hobbing disclosed in Patent Document 1 is a gear cutting process that does not use cutting oil, a large amount of chips adhere to the blade surface of the hob blade, and the blade surface of the hob blade and the chip are not separated. The friction force generated between them increased. Therefore, the amount of chips biting into the processed surface (groove surface, tooth surface) of the gear material is increased, and the cutting temperature is increased. As a result, the processing accuracy of the gear is lowered and the tool life is shortened. Further, since this dry hobbing is intermittent cutting of the outer peripheral portion of the gear material by a large number of hob blades, periodic cutting marks called cutter marks are generated on the processed surface of the gear material. This cutter mark is a trace caused by a processing error, and causes wear and abnormal noise generated in the gear.

In addition, as described above, “Carbide hobbing machine” of Patent Document 1 discloses a technique for circulating cooling air in a hob shaft to reduce cutting heat. However, the carbide hobbing machine requires a hob shaft with a flow path along the axis and a cooling device for flowing cooling air through the flow path, and the cost of the apparatus has increased.
Further, Patent Document 1 discloses a technique for reducing the cutting heat by blowing cooling air to the gear material as described above. However, a sufficient temperature drop of the gear material cannot be expected only by blowing the cooling air, and the temperature rise of the hob shaft and the carbide hob cannot be suppressed. Moreover, during dry hobbing, a groove formed by grinding appears on the outer peripheral surface of the gear material, and a large amount of chips stagnate in this groove. Then, even if it tried to blow off the chip in a groove | channel using blowing of cooling air, since the adhesive force to the groove surface of a chip | tip was large, sufficient removal effect was not acquired.

  As a result of intensive studies, the inventor has come up with the idea that the rotating hob is microvibrated in the axial direction by the microvibration means when performing dry hobbing. In this way, the frictional force generated between the blade surface of the hob blade and the chip is reduced, and as a result, the reduction of the bite of the chip into the processed surface (groove surface, tooth surface) of the gear material and The cutting temperature can be reduced, thereby increasing the machining accuracy of the gear and extending the tool life. In addition, the inventors have found that the effect of finishing by cutting can be enhanced by the minute vibration of the hob, and that the smoothing of the cutter marks on the tooth surfaces of the gear can be realized, and the present invention has been completed.

  In other words, the present invention can reduce the biting of chips into the machined surface of the gear material and reduce the cutting temperature, thereby increasing the machining accuracy and extending the tool life. It aims at providing the dry hobbing apparatus which can remove the cutter mark which generate | occur | produces.

  According to the first aspect of the present invention, there is provided a dry hob machining apparatus that performs gear cutting on the outer peripheral surface of the gear material by pressing a hob that rotates about the hob shaft to the outer peripheral surface of the gear material. A dry hobbing device that vibrates the hob in the axial direction by means.

According to the first aspect of the present invention, the dry hob (dry gear cutting) processing is performed on the outer peripheral portion of the gear material while causing the hob to vibrate slightly in the axial direction. The frictional force generated between the blade surface and the chips is reduced. Thereby, the biting of chips into the groove surface of the gear material subjected to dry hobbing is reduced, the cutting temperature is lowered to increase the machining accuracy, and the tool life can be extended. In addition, "chip of chips" occurs when the chips welded to the rake face of the hob blade rotate and cut the gear material again, and the chips are caught in the groove surface of the gear material. .
Also, since the hob vibrates minutely in the direction orthogonal to the cutting direction of the gear material by the hob blade by the operation of the minute vibration means, a finishing effect close to grinding is obtained, and the tooth surface of the gear is smoothed to this tooth surface. The resulting cutter mark can be removed.

The dry hob processing device here is a device for cutting gears by pressing a rotating hob against the outer peripheral surface of a gear material without using grinding oil.
A hob is a tool dedicated to gear cutting in which a large number of hob blades are projected at a constant pitch on the outer peripheral surface of a cylindrical body serving as a main body.
As the type of hob, for example, a standard hob, a topping hob, a worm hob, or the like can be employed according to the type of gear after processing (for example, a spur gear, a helical gear, a bevel gear, or the like). The special hob may be a sprocket hob, a spline hob, a serration hob, or a timing pulley hob. Furthermore, a general high-speed hob may be adopted for classification according to the material, but the carbide hob used for RGC processing has a remarkable effect of the present invention.

“To make the hob vibrate slightly in the axial direction” means to give a fine vibration to the rotating (dry) hob in the axial direction of the rotation axis serving as the center of rotation.
The minute vibration here refers to vibration including an ultrasonic region having a frequency of 500 Hz to 20 kHz and an amplitude of 1 μm to 20 μm, for example.
If the frequency of the micro vibration of the hob is less than 500 Hz, there arises a disadvantage that the hob machine main body part resonates due to vibration. If the frequency of the minute vibration exceeds 20 kHz, the amplitude of the minute vibration becomes small and it becomes difficult to push the hob. A preferable frequency of this minute vibration is 700 Hz to 1 kHz. Within this range, a stable minute vibration can be supplied with little effect on the hobbing machine body.
If the amplitude of the micro vibration of the hob is less than 1 μm, the effect of vibration cutting in which the hob blade is detached from the workpiece cannot be obtained. On the other hand, if the amplitude of the minute vibration exceeds 20 μm, the unevenness of the processed surface increases and the surface roughness deteriorates. A preferable amplitude of the minute vibration is 2 μm to 5 μm. If it is this range, surface roughness will not be deteriorated, reducing cutting temperature by the effect of vibration cutting.
As the minute vibration means, for example, various types of vibration generators including a vibration horn can be employed.
A vibration transmitting member (such as a spindle) made of a highly rigid body may be interposed between the minute vibration means and the hob.

The invention according to claim 2 is the dry hobbing apparatus according to claim 1, wherein an elastic member that stably maintains the minute vibration applied to the hob is connected to the hob.
“Stablely maintains minute vibration” means that vibration having a certain vibration characteristic (natural frequency, amplitude) is continuously applied to the hob during dry hob processing.

  According to the second aspect of the present invention, the minute vibration transmitted from the minute vibration means to the hob during hobbing can change the natural frequency of the minute vibration by the elastic member. Thereby, it is possible to perform processing at an optimal frequency and amplitude.

  The elastic member is provided so as to be elastically deformable in the vibration direction. As the elastic member, for example, a disc spring that elastically deforms in the vibration direction can be employed. A cushion body is formed by superposing one or a plurality of disc springs. Moreover, you may employ | adopt a coil spring, a leaf | plate spring, an air spring, a reinforced rubber etc. as another elastic member. The elastic member generates a flexural vibration by transmitting the vibration amplitude. The natural frequency can be changed by appropriately changing the size and shape of the elastic member.

  According to the first aspect of the present invention, dry hobbing (dry gear cutting) processing is performed on the outer peripheral portion of the gear material while minutely vibrating the hob in the axial direction. The frictional force generated between the blade surface and the chips is reduced. As a result, the biting of chips into the groove surface of the gear material that has undergone dry hobbing is reduced, the cutting temperature is lowered, the machining accuracy is increased, and the tool life is extended. Note that “chip of chips” occurs when the chips welded to the rake face of the hob blade rotate and cut the gear material again to be caught in the groove surface of the gear material.

In addition, since the hob vibrates minutely in the direction orthogonal to the cutting direction of the gear material by the hob blade by the operation of the minute vibration means, the finishing effect in the grinding process is enhanced, and the tooth surface of the gear is smoothed and the cutter generated on this tooth surface The mark can be removed.
Thereby, it is possible to manufacture a gear with high accuracy and high wear resistance. As a result, post-processing such as tooth profile correction by a shaping machine, which is generally performed after dry hobbing, becomes unnecessary, and high-precision gears can be mass-produced at low cost in a short time.

  In particular, according to the second aspect of the present invention, the minute vibration transmitted from the minute vibration means to the hob during hobbing can change the natural frequency of the minute vibration by the elastic member. Thereby, it is possible to perform processing at an optimal frequency and amplitude.

It is a front view of the dry hob processing apparatus which concerns on Example 1 of this invention. It is a principal part expanded side view including the partial cross section figure of the dry hob processing apparatus concerning Example 1 of this invention. It is a principal part expansion perspective view which shows the use condition of the dry hob processing apparatus which concerns on Example 1 of this invention. It is a principal part enlarged side view which shows the tooth surface property of a gearwheel when the presence or absence of a micro vibration is changed during dry hobbing. (A) It is a top view of the chip discharged | emitted at the time of the dry hob process which does not accompany the minute vibration by a conventional apparatus. (B) It is a top view of the chip discharged | emitted at the time of the dry hob process with a minute vibration by the processing apparatus of this invention. (A) It is a graph which shows the cross-sectional curve of the tooth trace direction of the gear tooth surface of the gear obtained by the dry hobbing which does not accompany the micro vibration which concerns on the conventional apparatus. (B) It is a graph which shows the cross-sectional curve of the tooth-tooth direction of the gear tooth surface of the gear obtained by the dry hobbing with a minute vibration by the processing apparatus which concerns on this invention.

  Examples of the present invention will be specifically described below. Here, an example in which the dry hobbing apparatus is applied to dry gear hobbing of a spur gear is shown.

  In FIG. 1, reference numeral 10 denotes a dry hobbing apparatus (hereinafter referred to as a hobbing apparatus) according to Embodiment 1 of the present invention. This hobbing apparatus 10 is centered on a hob shaft (hob arbor) 11 without supplying cutting oil. The gear hobbing is performed by pressing the rotating hob 12 against the outer peripheral surface of the gear material (blank) 13. The gear material 13 that is a cylindrical body is previously hardened by quenching.

As shown in FIG. 1, the hobbing apparatus 10 has a base 14 that is rectangular in plan view and serves as an apparatus base. A column 17 having a hob saddle 16 that can be vertically moved by a hob head longitudinal feed mechanism 15 is erected on one side of the base 14. The hob saddle 16 is provided with a hob rotating portion 19 that rotates the hob 12 for gear processing around a horizontal axis.
A material rotating part 22 is disposed on the other side of the base 14 at a position facing the hob rotating part 19. The material rotating unit 22 has a vertical work arbor 20 to which a gear material 13 that is a cylindrical body is detachably fixed. The work arbor 20 is supported at both ends by a support arm 21. The work arbor 20 of the material rotating unit 22 is rotated by a table 38 driven by a motor (not shown).
At the time of dry hobbing, the hob 12 and the gear material 13 are maintained integrally with the hob saddle 16 by the hob head vertical feed mechanism 15 while maintaining a certain relationship of hobbing and rotating by the corresponding hob rotating part 19 and material rotating part 22. By feeding the hob 12 in the vertical direction, gear teeth are formed on the outer peripheral surface of the gear material 13.

Next, the hob rotating unit 19 will be described in detail with reference to FIGS. 2 and 3.
As shown in FIG. 2, the hob rotating portion 19 extends between the hob shaft tip metal 25 and the hob shaft main metal 24 that extend in the table longitudinal direction (device longitudinal direction) and can be fixed to the front portion of the hob saddle 16. The hob arbor 11 detachably connected via the spindle 26, the hob 12 detachably fixed to the intermediate portion in the longitudinal direction of the hob arbor 11 via the key 27 and the key groove 28, and the hob arbor 11 Three pairs of disc springs (elastic members) 29, which are inserted into the end portion of the hob shaft main metal 24 and are one of the features of the present invention and amplify minute vibrations of the hob 12, and a large diameter of the spindle 26. A thrust bearing 30 attached to the tip, the hob arbor 11 is passed through, and the first cylindrical spacer 31 disposed between the three pairs of disc springs 29 and the hob 12 and the hob arbor 11 are inserted. And a second cylindrical spacer 32 disposed between the hob 12 and the thrust bearing 30 and a spindle 26 which is fitted into a trumpet-shaped spindle mounting hole 25a formed in the hob shaft tip metal 25 and is a round bar. And a frustoconical bush 33 into which the main body portion is inserted.

A tapered connecting hole 24a is formed in the hob shaft main metal 24, and a tapered base portion 11a of the hob arbor 11 is detachably fitted into the connecting hole 24a. At the base of the hob arbor 11, a flange 11 b serving as a contact plate for the disc spring 29 is integrally formed.
In addition, a thin neck portion 11c extending in the axial direction is integrally formed at the center of the tip surface of the hob arbor 11.
The disc spring 29 receives the minute vibration generated by the vibrator 34 and maintains the vibration of the hob 12 in the axial direction in a stable state. The disc spring 29 generates a flexural vibration by the transmission of the vibration amplitude by the adjacent first cylindrical spacer 31. If the type or number of the disc springs 29 is changed, the natural frequency can be changed.
An insertion hole 26a is formed in the center portion of the large-diameter tip surface of the spindle 26, and the narrow neck portion 11c of the hob arbor 11 is rotatably inserted around the axis.

Further, the spindle mounting hole 25a of the hob shaft tip metal 25 is gradually tapered in the forward direction (forward direction). Therefore, the bush 33 has a shape that can be fitted into the spindle mounting hole 25a.
When the hob head rotating shaft inserted in the hob shaft main metal 24 is rotated using a motor (not shown), the hob arbor 11 rotates. At this time, as the hob arbor 11 rotates, the hob 12, the disc springs 29, the first cylindrical spacer 31, and the second cylindrical spacer 32 connected together by the key 27 are rotated together.

Next, with reference to FIG. 2, a description will be given of a vibrator 34 (microvibration means) that microvibrates the hob 12 in the axial direction, which is one of the features of the first embodiment of the present invention together with the disc spring 29. .
The vibration exciter 34 is fixed to a portion in front of the hob shaft tip metal 25 and outputs a minute vibration from the horn 35. The front end of the horn 35 is in contact with the front end surface of the spindle 26 via a hardened steel contact 36.

The vibration exciter 34 is a device that generates minute vibrations by electric or magnetic deformation. An amplifier 37 that individually controls the frequency (for example, 1 kHz) and the amplitude (for example, 12 μm) of the horn 35 is electrically connected to the vibrator 34.
When the vibrator 34 is operated, the knob 37 of the amplifier 37 is operated, and the horn 35 is minutely vibrated at a predetermined frequency and a predetermined amplitude. As a result, this vibration is propagated to the hob 12 through the contact 36, the spindle 26, the thrust bearing 30, and the second cylindrical spacer 32 in this order.
Thus, in the hobbing apparatus 10, the hob arbor 11, the first cylindrical spacer 31, the hob 12, the second cylindrical spacer 32, and the disc spring 29, which are portions on the hob shaft main metal 24 side from the thrust bearing 30, rotate, and the thrust spring 30 rotates. The spindle 26, the contact 36, and the horn 35, which are on the side of the vibrator 34 from the bearing 30, do not rotate.

  A periodic forced external force is applied to the spindle 26 by the vibrator 34. The small displacement of the spindle 26 is ensured by the deformation of the disc spring 29. With this structure, the spindle 26 vibrates minutely in a state close to both ends. It has already been mathematically found that the vibration of the spindle 26 at this time is determined by the following equation of motion:

ρ is the density of the spindle 26, A is the cross-sectional area of the spindle 26, E is the longitudinal elastic modulus of the spindle 26, x is the axial coordinate of the spindle 26, u is the axial displacement of the spindle 26, and t is time.
The natural angular frequency ω _n when the boundary condition is free at both ends is given by Equation 2, and the natural vibration mode is given by Equation 3. L is the length of the spindle 26 and n is the dimension of resonance.

By causing the natural angular frequency ω _n given by Equation 2 to coincide with the frequency f = ω / 2π of the vibrator 34, resonance occurs and large amplitude vibration can be transmitted. By obtaining the length L of the spindle 26 at the time of resonance from Equation 2, the spindle 26 with good vibration transmission efficiency can be designed. The amplitude of the spindle 26 is adjusted by controlling the vibrator 34 by the amplifier 37.

Next, the material rotating unit 22 will be described with reference to FIG.
The material rotating unit 22 includes a table 38 installed on the base 14 and a work arbor 20 vertically stretched between the table 38 and the support arm 21, and the work arbor 20 is the main of the hobbing machine. It is rotated by a motor (not shown). The gear material 13 is detachably fixed to the work arbor 20 via a cylindrical spacer.
At the time of dry hobbing, after the gear material 13 is fixed to the work arbor 20, the work arbor 20 is rotated by the main motor, whereby the gear material 13 is rotated together with the work arbor 20.

Next, with reference to FIGS. 1-3, the dry hobbing method of the gear material 13 for spur gears by the dry hobbing apparatus 10 which concerns on Example 1 of this invention is demonstrated.
As shown in FIGS. 1 to 3, during dry hobbing, the main motor is driven to rotate, and the work arbor 20 to which the gear material 13 is fixed is rotated about a vertical axis. While continuing the rotation of the gear material 13, the hob rotation mechanism (hob head) is driven to rotate, and the hob 12 is integrated with the hob arbor 11 at a higher speed than the gear material 13 around the horizontal axis of the hob arbor 11. Rotate. Such a constant relationship between the hob 12 and the gear material 13 is maintained, and the hob saddle 16 is fed at a low speed in the vertical direction indicated by the arrow X in FIG. Teeth are formed.

  At this time, the amplifier 37 (control device) is operated to cause the horn 35 to vibrate at a predetermined frequency and a predetermined amplitude in the vibrator 34 by an electric or magnetic screen. The minute vibration generated here is transmitted from the tip of the horn 35 to the spindle 26 via the contact 36 and then transmitted to the second cylindrical spacer 32 via the thrust bearing 30. As a result, the hob 12 in contact with the second cylindrical spacer 32 vibrates slightly in the axial direction, for example, at a frequency of 1 kHz and an amplitude of 30 μm while rotating around the axis.

In this way, the dry hobbing process is performed on the outer peripheral portion of the gear material 13 while causing the hob 12 to vibrate slightly in the axial direction, so that the frictional force generated between the blade surface of the hob 12 blade and the chips is reduced. Thereby, cutting temperature falls, the biting of the chip into the groove surface of the gear material 13 subjected to dry hobbing decreases, the machining accuracy is improved, and the tool life can be extended.
Further, since the hob 12 slightly vibrates in the direction orthogonal to the cutting direction of the gear material 13 by the operation of the vibrator 34, the finishing effect in the grinding process is enhanced, and the tooth surface of the gear is smoothed and the cutter generated on the tooth surface. The mark can be removed.

Thereby, it is possible to manufacture a gear with high accuracy and high wear resistance. As a result, post-processing such as tooth profile correction by a shaping machine, which is generally performed after dry hobbing, becomes unnecessary, and high-precision gears can be mass-produced at low cost in a short time.
Further, at the time of hobbing, the minute vibration transmitted from the vibrator 34 to the hob 12 is amplified as the disc spring 29 resonates and vibrates. Thereby, the stable vibration of the hob 12 is maintained, and a uniform machined surface is obtained.
Furthermore, since the frequency of the minute vibration of the hob 12 is set to 20 kHz and the amplitude is set to 30 μm, for example, it is easy to confirm the change of the processed surface due to the vibration.

Next, the test results when the spur gear is actually hobbed using the dry hobbing apparatus of Example 1 will be described.
(Test Example 1)
The vibration hobbing of the present invention was performed on the gear material (material S45C) having a hardness of HRC20 using the dry hobbing apparatus of Example 1 in a dry environment.
First, the hobbing (module 1.75, number of teeth 12, torsion angle 1.39 °) was vibrated in the axial direction to perform vibration hobbing, and the hob vibration was stopped halfway to perform normal hobbing. The processing conditions are a vibration frequency of 20 kHz, a cutting speed of 40.8 m / min, a hob feed speed of 0.5 mm / rev, a cutting depth of 0.34 mm, and a conventional cut. From the measurement using the test indicator, the axial amplitude of the hob when not rotating was about 30 μm.

  FIG. 4 is a photograph of the tooth surface properties of the gears when the hob is processed with vibration and when it is processed without vibration. The white portions in FIG. 4 are due to the reflection of light during photographing. Comparing the state in which the hob vibrates (right side of FIG. 4) and the state in which the hob does not vibrate (left side of FIG. 4) It was found that there was little reflection and the cutter mark was formed on the tooth surface of the gear. On the other hand, when vibration is given to the hob, there are many reflections from the gear tooth surface due to the light given at the time of photographing, the surface is rough, and the cutter mark is not formed on the gear tooth surface. found. From these facts, it was clarified that the state of the tooth surface of the gear was different and the vibration of the hob (hob blade) had an effect on the tooth surface.

(Test Example 2)
The vibration hobbing process of the present invention was performed in a dry environment on a workpiece (material S45C) having hardness HRC55 subjected to induction hardening. The processing conditions are the vibration frequency of the vibrator, 1.034 kHz, the hob amplitude of 2 to 5 μm, and the other conditions are the same as in Test Example 1.

  FIG. 5 shows a photograph of chips obtained during dry hobbing. FIG. 5A shows the case without vibration, and FIG. 5B shows the case with vibration. The chips with vibration are whiter than those without vibration. Usually, the presence of black chips means that the chips were oxidized by heat. That is, the fact that the chips are white means that the chips are not easily oxidized by heat, that is, the chips are not given heat (energy) necessary for oxidation. Therefore, it is considered that the processing temperature is lowered by applying vibration to the hob. This is presumably because the friction between the hob and the gear material is reduced by the minute axial vibration, and the generation of frictional heat is suppressed. From this result, by reducing the processing temperature by vibration, it can be expected that the processing surface is prevented from being deteriorated (enhancement of processing accuracy) due to the biting of chips and the hob life is extended. In addition, cutter marks, which are periodic cutting marks caused by machining errors, can also be removed from the machined surface of the gear material.

  FIG. 6 shows a cross-sectional curve in the tooth line direction of the processed tooth surface. FIG. 6A shows a case where there is no conventional vibration, and FIG. 6B shows a case where there is vibration according to the present invention. In the cross-sectional curve of FIG. 6 (a), periodic peaks every 1 mm indicating that there is a cutter mark on the tooth surface can be confirmed. When there is vibration in FIG. 6B, the cross-sectional curve is aperiodic, and the periodicity of the cutter mark cannot be confirmed. From this result, removal of the cutter mark can be expected according to the present invention. By removing this, the noise reduction and performance improvement of the gear are expected.

  The gear cutting apparatus of the present invention is useful as a dry hobbing technique in which hobbing is performed by pressing a hob rotating around this axis against the outer peripheral surface of the gear material without using cutting oil.

10 Dry hob processing equipment,
11 Hob Arbor (hob shaft),
12 Hob,
13 Gear material,
34 Exciter (microvibration means),
29 Belleville spring.

Claims (2)

In a dry hob machining apparatus that performs gear cutting on the outer peripheral surface of the gear material by pressing a hob that rotates about the hob axis against the outer peripheral surface of the gear material,
A dry hob machining apparatus that microvibrates the hob in the axial direction by means of microvibration means.   The dry hob processing apparatus according to claim 1, wherein an elastic member that stably maintains minute vibration applied to the hob is connected to the hob.