JP2005125419A - Divided hob and gear cutting method of gear - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a divided hob capable of easily and efficiently cutting a bevel gear of continuously changing in a module; and its gear cutting method. <P>SOLUTION: This hob of arranging a plurality of cutting edges 4 along a single-start thread stripe twisted in a double winding on a cylindrical surface 1, is divided into two in the axis direction in the center of the screw stripe 2. The cutting edge 4 running along the screw stripe 2 of a single winding apiece, is arranged in these respective divided hobs 3. The bevel gear of continuously changing in the module, can be easily and efficiently cut by approaching and separating the mutual these hobs 3 in the axis direction by opposing the divided surfaces 6. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a split-type hob capable of gearing spur gears having different modules and bevel gears whose modules continuously change, and a gear gear-cutting method using the split-type hob.

  The hob has a plurality of cutting blades arranged along a thread that twists on the cylindrical surface, and the hob rotates in the direction perpendicular to the tooth length direction of the gear material to be geared. Each time the gear material is rotated by one pitch, the gear material is rotated by one pitch. The gear can be efficiently geared by moving in parallel.

  In the above-described conventional hob, the pitch of the screw thread is set to be constant according to the gear module to be geared, so the module is continuously in the tooth length direction from the small diameter end side to the large diameter end side. The changing bevel gear could not be geared, and was used only for gear cutting of spur gears. For this reason, a Gleason type gear cutting machine is exclusively used for gear cutting of the bevel gear, and there has been a problem that the production efficiency of the bevel gear is low. Further, when gears of the spur gear are cut, it is necessary to prepare another hob having a different screw thread pitch for each gear of different modules.

  In order to cope with these problems, the present inventor has arranged a hob in which a plurality of cutting blades are arranged along a single thread that is twisted by two or more turns on a cylindrical surface, at the center of the thread. The divided hob is divided into two in the direction, and each divided hob can be relatively rotated in an angular direction different from the twist angle of the screw thread, and by the relative rotation, in a rounding range of one round from the dividing position in each divided hob A split type hob in which the number of cutting blades acting on cutting is increased or decreased has been proposed (see Patent Document 1).

  In order to prevent the undercut of the gear tooth root portion in the gear cutting by the hob, the present inventor arranges one winding each arranged along one screw thread and going from the center of the screw thread to both ends. With respect to the above cutting blades, it has also been proposed that the inclined surface on the hob shaft end side is retracted in the inner direction of the cutting blade with respect to the screw thread from a position symmetrical to the inclined surface on the central side of the screw thread (Patent Literature 2).

Japanese Patent No. 2758563 (page 2-5, Fig. 1-2) Japanese Patent No. 3014990 (page 2-3, Fig. 1-4)

  The split-type hob described in Patent Document 1 can gear spur gears of different modules by fixing the relative rotation angle between the divided hobs to a predetermined angle. As the hob moves in the tooth length direction, the bevel gear can also be cut by changing it by a predetermined amount of change in angle. However, it is difficult to accurately change the relative rotation angle between the divided hobs during gear cutting for the gear cutting of the bevel gear whose module continuously changes in the tooth length direction, and has not yet been put into practical use.

  Therefore, an object of the present invention is to provide a split hob that can easily and efficiently gear a bevel gear whose module continuously changes, and a gear cutting method thereof.

  In order to solve the above-described problem, the split type hob according to the present invention includes a hob in which a plurality of cutting blades are arranged along a single thread that is twisted by two turns on a cylindrical surface, at the center of the thread. It is divided into two in the axial direction, and it is assumed that cutting blades are arranged along each screw line in each divided hob, and the divided hobs are opposed to each other with their dividing surfaces facing each other. Adopted a configuration that can move in and away from the direction.

  As a result of repeated investigations to eliminate the difficulty of the split-type hob proposed in Patent Document 1, the present inventor has found that the hob cutting blade that creates the tooth profile for one pitch of the gear sandwiches the tooth profile from both sides. The necessary two turns of the screw thread are sufficient, and the divided hobs obtained by dividing the two screw threads into one turn are simply moved closer to and away from each other in the axial direction without giving a relative rotation angle. Only then, I noticed that each of the divided threads could be moved close to and away from each other. In other words, it has been conceived that the screw threads of each divided winding for sandwiching the tooth profile from both sides do not necessarily have to be connected to each other on the divided extension line, and may be in a parallel relationship with each other.

  Further, unlike the split hob proposed in Patent Document 1, the split hob is arranged on a screw thread with one winding without any increase or decrease in the number of effective cutting edges acting on cutting associated with the relative rotation of each split hob. Since all the cutting blades act on cutting, even if the gear module to be geared is changed, stable and good cutting efficiency can be ensured.

  By forming the material of each divided hob in which the one-turn thread is formed by powder molding, and cutting the plurality of cutting blades by cutting from the thread of each divided hob material formed by the powder molding The split hob can be manufactured efficiently and inexpensively without the need for thread cutting.

  That is, the material of each of the divided hobs has a simple shape with one screw thread, so that the molding pressure in powder molding can be evenly propagated and can be easily released from the mold. In addition, these divided hob materials are point-symmetric with respect to the central axis of the screw thread, and thus can be powder-molded with a common mold. The cutting blades may be cut out after each powdered molded hob is pre-sintered at a low temperature and then sintered at a high temperature to obtain a required hardness.

  By forming each divided hob in which cutting blades along the one-turn thread are arranged by powder molding, cutting of each cutting blade from the thread can be made unnecessary. The divided hob can be sintered at a high temperature as it is. If the powder material is made of a cemented carbide, it is not necessary to attach a cemented carbide blade tip. In addition, these split hobbs have the same cutting edge shape with respect to the central axis of the thread if the rising angle on the rear side of each cutting edge is equal to the rising angle on the front side where the clearance angle is provided. Since it becomes symmetrical, it can be powder-molded with a common mold.

  Prevents undercutting of the gear tooth root by retreating the inclined surface opposite to the divided surface of each cutting blade along each winding thread of each divided hob to the inside of each cutting blade. can do. The inclined surface of the retreated cutting blade also has a point-symmetric shape with respect to the central axis of the screw thread, so that the cutting blade is cut out from the powder-molded material up to the screw thread, and the powder is cut up to the cutting blade. Molded ones having the same rising angle on the front side and the rear side of each cutting blade can be powder-molded with a common mold.

  Further, the gear gear cutting method of the present invention uses any one of the above-described divided type hobs, and the rotary drive shaft thereof is directed in a direction perpendicular to the tooth length direction of the gear material to be geared. The division position of the hob is set to the center of the tooth profile created by the gear material, the interval between the divided hobs is set to a predetermined interval, and the gear material is moved by one pitch of the tooth every time the divided hob rotates once. Each time the gear material rotated by one pitch is rotated, the split hob is moved in parallel with the tooth bottom surface in the tooth length direction of the gear material to be geared, and the gear tooth profile is changed. Adopted the creation method.

  That is, the division position of the divided hob is set to the center of the tooth profile created by the gear material, and the interval between the divided hobs is set according to the gear module to be geared, and the rest is almost the same as a normal hob With the handling method, gears of different modules can be geared efficiently.

  When the gear to be geared is a bevel gear, the split type hob is moved in the length direction of the gear material teeth from the small diameter end side to the large diameter end side of the bevel gear, and the split type hob is moved. Accordingly, the bevel gears can be easily and efficiently geared by separating the divided hobs from each other in the axial direction.

  The split type hob according to the present invention is obtained by dividing a hob in which a plurality of cutting blades are arranged along a single thread that is twisted by two turns on a cylindrical surface into two axially in the center of the thread. Since each of the divided hobbs is arranged with cutting blades along one screw thread, each of the divided hobs can be approached and separated in the axial direction with the divided surfaces facing each other. The spur gear of the module and the bevel gear in which the module continuously changes can be easily and efficiently geared. In addition, since all of the cutting blades arranged on each screw thread act on cutting, this split hob ensures stable and good cutting efficiency even if the gear module to be geared changes. can do.

  By forming the material of each divided hob forming the screw thread of each winding by powder molding, by cutting a plurality of cutting blades by cutting from the thread of each split hob material formed by these powder molding, The split hob can be manufactured efficiently and inexpensively without the need for thread cutting. In addition, these divided hob materials are point-symmetric with respect to the central axis of the screw thread, and therefore can be powder-molded with a common mold.

  By forming each divided hob in which the cutting blades along the one-turn thread are arranged by powder molding, it is not necessary to cut out each cutting blade from the thread, and each powder-formed divided hob is left as it is. Sintering can be performed at a high temperature, and the split hob can be manufactured more efficiently and inexpensively. If the powder material is made of cemented carbide, it is not necessary to install cemented carbide cutting edge tips.

  Undercut of the gear tooth root is prevented by retracting the inclined surface opposite to the divided surface of each cutting blade along the thread of each winding of each divided hob toward the inside of each cutting blade. be able to.

  Further, the gear gear cutting method of the present invention uses the above-described divided hob, and the division drive position of the divided hob is directed so that its rotational drive shaft is oriented in a direction perpendicular to the tooth length direction of the gear material to be geared. Is set to the center of the tooth profile created by the gear material, the interval between the divided hobs is set to a predetermined interval, and the gear material is rotated by one pitch of the tooth every time the divided hob makes one rotation. Each time the gear material that rotates by one pitch rotates one time, the split type hob is moved in parallel with the tooth bottom in the tooth length direction of the gear material to be geared to create the gear tooth profile. The gears of different modules can be efficiently geared with almost the same handling method as a normal hob.

  When the gear to be geared is a bevel gear, the split hob is moved from the small diameter end side to the large diameter end side of the bevel gear in the tooth length direction of the gear material. Thus, the bevel gears can be easily and efficiently geared by separating the divided hobs from each other in the axial direction.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. 1 to 6 show a split hob according to the first embodiment. As shown in FIGS. 1 and 2 (a) and 2 (b), this divided hob is divided into each divided hob 3 divided in the axial direction at the center of a single thread 2 that is twisted on the cylindrical surface 1. A plurality of cutting blades 4 are arrayed along the one screw thread 2 from the center of the thread 2 to both axial ends, and each divided hob 3 is formed by powder molding. Both split hobs 3 are point-symmetrical with a split line 5 extending in the axial direction at an intermediate position between opposing cutting edges 4 at the center of the thread 2 and a spiral split surface 6 at the center of the valley bottom of the thread 2. As will be described later, by using a sliding key or a spline to fix the rotation to the rotary drive shaft 7, the split surface 6 is opposed to approach and separate in the axial direction, so The bevel gear can be geared with a continuously changing module.

  Each cutting edge 4 shown in FIG. 2 (b) is provided with a substantially right clearance angle on the front side, and the rear side rises at an obtuse angle, like a normal hob cutting edge. As shown in the modification of FIG. 2 (c), if the rising angle on the rear surface side of each cutting edge 4 is formed equal to the front surface side provided with a substantially right-angle clearance angle, the retracted inclination described below The shape of each cutting edge 4 of both split hobs 3 including the surface 8b can be point-symmetric with respect to the central axis of the screw 2.

  Moreover, the cutting blade 4 of each said division | segmentation hob 3 has the inclined surfaces 8a and 8b on both sides of the screw thread 2, as shown to the expanded view of FIG. 3 (a), (b), and faces the shaft end side. Each inclined surface 8b is formed so as to recede inward of the cutting edge 4 from a virtual inclined surface 8c that is symmetrical to each inclined surface 8a that faces the central split side with respect to the thread 2 and has a gear tooth root. Undercut is not generated in the part. The developed view of FIG. 3 (a) shows a state in which the distance between the two divided hobs 3 is zero, and if the distance is increased by separating the two divided hobs 3 as shown in FIG. The gear module becomes larger.

  4 and 5 show a mold for powder-molding each of the divided hobs 3 described above. This mold is fitted into the female mold 9 from below, with a female mold 9 provided with a plurality of ridges 9a forming the front and rear surfaces of each cutting blade 4 of the divided hob 3 on a cylindrical inner peripheral surface, A lower mold 10 having an upper surface forming a shaft end side surface including each cutting edge 4 of the divided hob 3, and provided with a protruding line 10 a that fits the protruding line 9 a of the female mold 9 on the outer peripheral surface; 9 has a lower surface that forms a split-side surface including each cutting edge 4 of the split hob 3 and is provided with a ridge 11a that fits the ridge 9a of the female die 9 on the outer peripheral surface. The upper die 11 and a lower die 10 and an upper die 11 which are cylindrical and are fitted in the upper die 11 and form an inner diameter surface of the divided hob 3.

  Although not shown in the drawings, depending on the method of attaching the two divided hobs 3 to the rotary drive shaft 7, key grooves and hole splines are formed on the inner peripheral surface of each divided hob 3 on the outer peripheral surface of the middle mold 12. Concavities and convexities are provided. Key grooves and hole splines are formed point-symmetrically with respect to the central axis of the thread 2, and the rising angle on the rear surface side of each cutting edge 4 is set to a substantially right relief as shown in FIG. If it forms equally with the front side provided with the corner | angular part, both division | segmentation hob 3 can be powder-molded with a common shaping | molding die.

  Below, the procedure which powder-molds the division | segmentation hob 3 using the said shaping | molding die is demonstrated. As shown in FIG. 6, first, a powder material A for cemented carbide or high-speed steel or the like is placed in a state in which a lower mold 10 is fitted into a female mold 9 from below and a middle mold 12 is fitted into the lower mold 10. Fill in the mold. After that, as indicated by the alternate long and short dash line in the figure, the upper die 11 is passed through the middle die 12 from above and fitted into the female die 9 and lowered, and the upper die 11 and the lower die 10 are pressurized from above and below to form powder. Material A is powder-molded. The molded powder material A is extracted from the upper die 11 and the middle die 12, then pushed upward by the lower die 10 and taken out from the female die 9, sintered, and then finished into a divided hob 3 by polishing. In this finishing process, it is possible to omit the polishing of the inclined surface 8b that has retreated toward the axial end side of each of the cutting edges 4.

  7 to 10 show a second embodiment. As shown in FIG. 7, this divided hob is formed by powder molding each divided hob material 13 divided in the axial direction at the center of one thread 2 that is twisted on the cylindrical surface 1. After the divided hob material 13 is pre-sintered, each cutting blade 4 is cut out from the thread 2 to form the divided hob 3 as shown in FIGS. 1, 2 (a) and 2 (b).

  Each of the divided hob materials 13 includes a dividing line 5 extending in the axial direction at the center of the thread 2, and a spiral dividing surface 6 at the center of the valley bottom of the thread 2, similarly to the divided hob 3 in the first embodiment. Each of the inclined surfaces 2b that are divided by 2 and face the axial end side of the screw 2 is closer to the center of the screw 2 than the virtual inclined surface that is symmetrical to each inclined surface 2a that faces the central divided side with respect to the screw 2. It is formed so as to recede inward, and has a symmetrical shape with respect to the central axis of the screw 2. Therefore, each cutting edge 4 cut out from the thread 2 has a slanted surface 8b facing the shaft end side symmetrical to each slanted surface 8a facing the central split side with respect to the thread 2 as shown in FIG. It is formed so as to recede toward the inside of the cutting edge 4 rather than the virtual inclined surface 8c.

  8 and 9 show a common mold for powder-molding each of the divided hob materials 13 described above. The mold includes a cylindrical female mold 14, a lower mold 15 that is fitted into the female mold 14 from below and has an upper surface that forms a shaft end-side surface including the thread 2 of the divided hob material 13, and a female The upper mold 16 is fitted into the mold 14 from above and has a lower surface that forms a divided-side surface including the thread 2 of the divided hob material 13, and is cylindrically fitted into the lower mold 15 and the upper mold 16 to be divided. The divided hob material 13 is powder-molded by a procedure similar to that of the molding die of the first embodiment, comprising an intermediate die 17 that forms the inner diameter surface of the hob material 13.

  10 and 11 show a gear cutting method for a bevel gear according to the first embodiment using the above-described divided hob. In this embodiment, both the divided hobs 3 of the divided hob are fixed to the rotation drive shaft 7 of the servo motor 18 by a sliding key 19 and mounted so as to be able to approach and separate in the axial direction with the divided surface 6 facing each other. ing. The rotary drive shaft 7 is supported at the tip side by a bearing device 20 and is directed in a direction orthogonal to the length direction of the teeth 21a of the gear material 21 to be geared. The servo motor 18 and the bearing device 20 are connected to the gear material 21. Are mounted on each carriage 23 of two linear ways 22 oriented parallel to the tooth bottom surface 21b in the length direction of the teeth 21a.

  First, both the divided hobbs 3 are set at intervals corresponding to the modules of the small-diameter end of the bevel gear that are geared between the divided surfaces 6 by aligning the dividing position with the center of the tooth profile created of the gear material 21. Is set at a standby position corresponding to the small diameter end side of the bevel gear. Thereafter, the servo motor 18 is driven to advance each traveling platform 23, whereby the cutting of each divided hob 3 is started at the position indicated by the one-dot chain line in FIG.

  The gear blank 21 is rotated by one pitch of the teeth 21a for each rotation of the split hob. When the gear blank 21 is rotated once, each carriage 23 is moved forward by a certain distance, as shown by arrows in FIG. Both split hobs 3 are fed to the large diameter end side of the bevel gear by a predetermined feed pitch. In this way, each time the gear blank 21 is rotated, the two divided hobs 3 are moved at a predetermined feed pitch in the length direction of the teeth 21a of the gear blank 21 to the bevel gear large diameter end side in parallel with the tooth bottom surface 21b. Accordingly, the divided hobs 3 are naturally separated in the axial direction following the change of the module in the length direction of the teeth 21a to be cut, that is, the increase in the height and width of the tooth profile, and a solid line in FIG. At the position shown, the interval between the dividing surfaces 6 matches the module at the large-diameter end of the bevel gear, and gear cutting is completed.

  FIG. 12 shows a bevel gear cutting method according to the second embodiment. In this embodiment, both the divided hobs 3 of the divided hob are fixed to the respective rotary drive shafts 7a and 7b of the separate servo motors 18a and 18b that are abutted with each other by the key 24. Each servo motor 18a, 18b is mounted on each carriage 23 of two linear ways 22 having an expansion angle equal to the expansion angle of the bevel gear to be cut from the small diameter end side to the large diameter end side. This is different from the first embodiment. Each servo motor 18a, 18b has a running direction and an inclination of each running table 23 so that each rotary drive shaft 7a, 7b is directed in a direction orthogonal to the length direction of the tooth 21a of the gear material 21 to be cut. Although not shown in the figure, it is configured to move parallel to the tooth bottom surface 21b in the length direction of the teeth 21a of the gear material 21 as in the first embodiment.

  In the gear cutting method of this embodiment, the servo motors 18a and 18b move away from each other as the traveling bases 23 of the two linear ways 22 having the spread angles move forward, and both the divided hobbs 3 are geared. The teeth 21a are forcibly separated to match the change of the module in the length direction of the teeth 21a. The initial setting method for both split hobbs 3 and the method for moving both split hobbs 3 at a predetermined feed pitch for each rotation of the gear blank 21 are the same as in the first embodiment.

  In each of the above-described embodiments, the bevel gear tooth cutting method has been shown. When the spur gear is geared, the distance between the two divided hobs of the split hob is fixed according to the spur gear module to be geared. Then, in the same way as the bevel gear tooth cutting method described above, the rotational drive shaft is oriented in the direction perpendicular to the tooth length direction of the gear material, and the dividing position is aligned with the center of the tooth profile created of the gear material. The split hob may be moved in parallel with the tooth bottom surface at a predetermined feed pitch. The divided hob used in the gear cutting method according to the present invention does not necessarily have to be formed by powder molding, and a divided hob formed by cutting may be used.

The front view which shows the division | segmentation type | mold hob of 1st Embodiment. 1 is a longitudinal sectional view of FIG. 1, b is a side view of a, and c is a side view showing a modification of b. a and b are development views of the hob cutting blade of FIG. 1 is a longitudinal sectional view showing a mold for powder molding the divided hob of FIG. Sectional view along line VV in FIG. FIG. 4 is a longitudinal sectional view showing a procedure for powder-molding a divided hob with the mold shown in FIG. The front view which shows the division | segmentation hob material of the division | segmentation type hob of 2nd Embodiment FIG. 7 is a longitudinal sectional view showing a mold for powder molding the divided hob material of FIG. Sectional view along line IX-IX in FIG. The partially cutaway front view which shows the gear cutting method of the bevel gear of 1st Embodiment Sectional view along line XI-XI in FIG. Partially cutaway front view showing a gear cutting method for a bevel gear according to a second embodiment

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Cylindrical surface 2 Thread 2a, 2b Inclined surface 3 Dividing hob 4 Cutting blade 5 Dividing line 6 Dividing surface 7, 7a, 7b Rotating drive shaft 8a, 8b, 8c Inclined surface 9 Female type 10 Lower type 11 Upper type 9a, 10a 11a ridge 12 medium mold 13 split hob material 14 female mold 15 lower mold 16 upper mold 17 middle mold 18, 18a, 18b servo motor 19 sliding key 20 bearing device 21 gear material 21a tooth 21b tooth bottom 22 linear way 23 carriage 24 key

Claims (6)

  A hob in which a plurality of cutting blades are arranged along a single thread that is twisted by two turns on a cylindrical surface is divided into two in the axial direction at the center of the thread, and each of the divided hobs is divided. A divided hob in which cutting blades are arranged along the thread of each winding, and these divided hobs can be approached and separated in the axial direction with their divided surfaces facing each other.   Claims in which the material of each divided hob formed with one winding thread is formed by powder molding, and the plurality of cutting blades are cut out from the thread of each divided hob material formed by powder molding by cutting. Item 2. The divided hob according to item 1.   2. The split hob according to claim 1, wherein each split hob in which cutting blades along the one-turn thread are arranged is formed by powder molding.   The inclined surface on the opposite side to the said divided surface of each cutting blade along the thread of each winding of each said division hob was made to recede inward of each cutting blade. Split hob.   Using the divided hob according to any one of claims 1 to 4, the rotation drive shaft thereof is directed in a direction perpendicular to the tooth length direction of the gear material to be geared, and the dividing position of the divided hob is changed to a gear. The interval between the divided hobs is set to a predetermined interval in accordance with the center of the tooth profile in which the material is created, and the gear material is rotated by one pitch of the tooth every time the divided hob rotates once. Each time the gear material rotating by pitch is rotated once, the split hob is moved in parallel with the tooth bottom surface in the tooth length direction of the gear material to be geared, thereby creating a gear tooth profile. How to cut teeth.   The gear to be geared is a bevel gear, and the split hob is moved from the small diameter end side to the large diameter end side of the bevel gear in the tooth length direction of the gear material. The gear cutting method according to claim 5, wherein the divided hobs are separated from each other in the axial direction.

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