Apparatus for and method of sizing helical gears

Abstract: A tooth profile sizing apparatus and method for helical gears, capable of shortening the cycle time of the sizing process so as to improve productivity and to reduce equipment cost. The sizing apparatus comprises a lower punch (7) for carrying thereon a gear blank (W), formed with a rotatable first lower punch (7a) and a non-rotatable second lower punch (7b). A sizing die (8) is rotatably and vertically movable with its inner peripheral teeth ( s ) in engagement with outer peripheral teeth ( p ) of the first lower punch. An upper punch (9) for pressing the gear blank into the sizing die is formed with a rotatable first upper punch (9a) and a non-rotatable second upper punch (9b). The upper punch 9 moves in the vertical direction and is provided on its outer circumferential surface with outer peripheral teeth ( q ).

Description: The present invention relates to the art of helical gear sizing and more particularly to an apparatus for and a method of sizing teeth profiles of helical gears made of a sintered powdery material, for example, so as to improve the precision or the like of the teeth profiles of the helical gears. Hitherto, as a tooth profile sizing apparatus for sizing the teeth of helical gears having a non-linear tooth trace, for example, there has been known the technology as disclosed in Japanese patent publication No. HO2-63634. This apparatus comprises an inner lower die on which a gear blank is disposed, an outer lower die adapted to engage or mesh with the teeth of the gear blank to size the gear profile thereof, an upper die for pressing the gear blank inwardly of the outer lower die, and a rotary driving mechanism adapted to rotate the outer lower die in synchronization with the descending movement of the upper die when the gear blank is pressed by the upper die, so that the gear blank is pressed into and sized by the outer lower die in a compressed condition between the upper die and the inner lower die. In order to remove the gear blank from the dies, the upper die is moved upwardly and a piston rod is pushed up to drive the inner lower die upwardly to thereby release the gear blank from the outer lower die. Then, the gear blank is pushed upwardly and released from the inner lower die by a knock-out pin. The tooth profile sizing apparatus as described above, however, requires a long cycle time for the sizing process, and in particular the removal of the sized product is a lengthy process. Further, the structure for removing the product is comparatively complicated and involves a large equipment cost. US 3694127 discloses a powder compacting device for forming a helical gear compact by compacting a powder material in the space defined by a die, an upper and lower punch and a core rod, wherein at least one of said upper and lower punches is divided into at least two parts. WO 97/43067 also discloses a powder compacting device for forming a helical gear compact, comprising a core rod, an upper and lower die, a lower punch formed of two parts and an upper punch. Viewed from one aspect the present invention provides an apparatus for sizing the teeth profiles of helical gears, comprising: a lower punch on which a gear blank having teeth formed thereon is arranged to be placed, an upper punch means which is vertically movable for pressing said gear blank downward, and a sizing die arranged to have inner peripheral teeth thereof engaged with the gear blank pressed by said upper punch to size the teeth profiles of the gear blank; characterized in that said lower punch comprises first and second lower punches, said second lower punch being arranged to non-rotationally carry a said gear blank placed thereon and said first lower punch being axially rotatable around said second lower punch and having outer peripheral teeth thereon, the said sizing die being axially rotatable and vertically movable while the inner peripheral teeth thereof are engaged with the outer peripheral teeth of said first lower punch, and the said upper punch means being axially rotatable and provided with outer peripheral teeth which come into engagement with the inner peripheral teeth of said sizing die. Viewed from another aspect the present invention provides a method of sizing teeth profiles of helical gears, comprising the steps of: non-rotationally positioning a gear blank having teeth formed thereon on a lower punch, sizing the teeth profiles of the gear blank by pressing the gear blank downward with an upper punch means into a sizing die while having the teeth of the gear blank and outer peripheral teeth of said upper punch means engaged with inner peripheral teeth of said sizing die, and upon termination of the sizing step releasing said sizing die from engagement with said upper punch means and the gear blank by rotating and lowering said sizing die, and moving said upper punch means to remove the gear blank. With this arrangement, an interlocking device such as the conventional rotary driving mechanism will not be required, thus making it possible for the equipment to be relatively simple and low-priced in construction and for the time necessary from sizing to removing the product to be shortened, so as_to improve the production cycle. Preferably, said upper punch means comprises a first upper punch arranged axially rotatably around a second non-rotational upper punch, the said first upper punch being provided with said outer peripheral teeth which come into engagement with the inner peripheral teeth of said sizing die. Preferably, said upper punch is rotated during the releasing step. With this arrangement, the upper punch has a rotational first upper punch instead of a non-rotational upper punch as previously described. When the sizing process is conducted with the rotational upper punch according to the method described herein, the removal of the finished gear may be carried out more rapidly. Namely, when the upper punch is constructed to be non-rotational, the upper punch is kept, at the end of the sizing step, in engagement with the inner peripheral teeth of the sizing die. Thus, the upper punch cannot rise up and the gear cannot be removed unless the sizing die is rotated and moved downward so as to release the upper punch from the engagement with the inner peripheral teeth thereof. Therefore, the first upper punch of the upper punch is formed to be rotatable in such a manner that, upon termination of the sizing step, the upper punch may be moved upward substantially at the same time as the downward movement of the sizing die, whereby the time for removing the gear is shortened. Preferably, a phase adjusting device is provided between the first upper punch and the sizing die or between the first upper punch and the first lower punch so as to adjust the relative phase between them when they return to their original positions. When the first upper punch moves downward in accordance with rotation of the first upper punch and the sizing die, it is difficult for a smooth sizing to take place if a phase difference develops between the outer peripheral teeth of the first upper punch and the inner peripheral teeth of the sizing die. Accordingly, the phase adjusting device is provided to angularly realign respective phases of the outer peripheral teeth of the first upper punch and of the inner peripheral teeth of the sizing die to their original positions, thereby adjusting these phases into a relatively aligned relationship at the time of sequential downward movement of the upper punch. Since the inner peripheral teeth of the sizing die are engaged with the outer peripheral teeth of the first lower punch, a similar effect may be obtained if the relative phase between the first lower punch and the first upper punch is adjusted into an aligned relationship. Two embodiments of the invention will now be described by way of example and with reference to the accompanying drawings, in which:- Figure 1 is a cross sectional view of a first embodiment of the present invention, illustrating an initial state of a sizing apparatus in which a gear blank is placed in a set position; Figure 2 is a cross sectional view of the first embodiment, illustrating a state soon after a sizing step is carried out; Figures 3(A) and (B) are explanatory views of a phase adjusting device for a first upper punch; Figures 4(A) and (B) are explanatory views of a phase adjusting device for a sizing die; Figures 5(A), (B), (C) and (D) are operation explanatory views of the sizing apparatus of the first embodiment; and Figures 6(A), (B), (C) and (D) are operation explanatory views of the sizing apparatus of a the second embodiment. Sizing apparatus 1 according to the present invention is constructed as a tooth profile sizing apparatus for improving the precision of teeth profiles, the surface roughness of teeth, or the like, with respect to a gear blank W in the form of sintered powdery material. As shown in Figure 1, the apparatus 1 comprises a base 2, a guide post 3 of the base 2, a lower plate 4 slidably mounted on the lower portion of the guide post 3, a die holder 5 slidably mounted on the intermediate portion of the guide post 3, and an upper plate 6 slidably mounted on the upper portion of the guide post 3. A lower punch 7 is carried on the lower plate 4 or the like. A sizing die 8 is carried on the die holder 5, and an upper punch 9 is mounted on an upper punch plate 6a of the upper plate 6. In the above-described construction, when the upper punch 9 moves downward against the gear blank W to press down the latter into the inside concave portion of the sizing die 8, the profiles of each of plural teeth Wa of the gear blank W is corrected or sized by the inner peripheral teeth s of the sizing die 8 as described hereinafter. The gear blank W is formed having a boss at the center portion thereof which has a through-hole for inserting and passing an axle therethrough. Surrounding this center through-hole, a plurality of openings are formed radially outwardly along the circumferential direction of the gear blank W. The teeth Wa are formed previous to the sizing process on the outer peripheral portion of the gear blank W. The lower punch 7 is provided with a second lower punch 7b fixedly secured to the lower plate 4, and with a first lower punch 7a which is rotatably mounted on the outer circumferential surface of the second lower punch 7b in an axially aligned relationship. Inside of the second lower punch 7b there is provided a work set pin 11 which extends through the center of the second lower punch 7b to slide in the upward and downward directions. Also inside of the second lower punch 7b are a plurality of positioning pins 12, 12 which extend vertically around the work set pin 11 along the circumferential direction of the second lower punch 7b so as to be engageable into and to pass through the openings of the gear blank W. The work set pin 11 is fixed on the tip end of a rod of a cylinder unit 13 which is disposed on the base 2, thereby to move up and down in the vertical direction. The lower end of each of the plural positioning pins 12, 12 is also mounted on the base 2. The outer circumferential surface of the first lower punch 7a is formed with helical outer peripheral teeth p , the pitch of which corresponds to the pitch of the teeth Wa of the gear blank W. The sizing die 8 is rotatably carried on the die holder 5 which is capable of moving up and down through the intermediary of an elevator device (not shown), and has inner peripheral teeth s formed to be engaged with the outer peripheral teeth p of the first lower punch 7a. The inner peripheral teeth 5 serve as reference teeth in the case of sizing the teeth Wa of the gear blank W. The upper punch 9 has a first upper punch 9a and a second upper punch 9b. The second upper punch 9b is fixedly secured to the upper plate 6 and the first upper punch 9a is rotatably engaged with the outer peripheral surface of the second upper punch 9b. At a center portion of the bottom surface of the second upper punch 9b there is provided an engaging hole 14 for permitting the center boss portion of the gear blank W to be engaged therewith. Around the engaging hole 14, a plurality of recessed holes 15 are provided along the circumferential direction to engagingly receive the positioning pins 12, 12 of the lower punch 7. The outer peripheral surface of the first upper punch 9a is formed with helical outer peripheral teeth q the pitch of which corresponds to the pitch of the teeth Wa of the gear blank W. The upper plate 6 is capable of moving up and down through the intermediary of an elevator device (not shown). When the gear blank W is placed on the work set pin 11 of the lower punch 7 in the state seen in Figure 1, the work set pin 11 moves down in a predetermined stroke under the operation of the cylinder unit 13 until the lower surface of the outer periphery of the gear blank W comes to be flush with the upper surface of the sizing die 8. In this condition, when the upper punch 9 moves down to make the lower surface thereof flush with the upper surface of the outer periphery of the gear blank W, the phases are previously adjusted to be registered with each other between the outer peripheral teeth q of the first upper punch 9a, the teeth Wa of the gear blank W, and the inner peripheral teeth s of the sizing die 8. Thereafter, the work set pin 11 further moves down in synchronization with the downward movement of the upper punch 9. In order to register the phase of the outer peripheral teeth q of the first upper punch 9a, the phase of the teeth Wa of the gear blank W, and the phase of the inner peripheral teeth s of the sizing die 8 with each other, at the time the lower surface of the upper punch 9 goes down to the upper surface of the outer periphery of the gear blank W, a first phase adjusting device 16 is provided on the first upper punch 9a and a second phase adjusting device 17 is provided on the sizing die 8. The phasing of the gear blank W is performed when the gear blank W is placed on the work set pin 11, and the positioning pins 12, 12 are engaged with the corresponding openings of the gear blank W, in such a manner that the phase of the teeth Wa of the gear blank W is adjusted in alignment with the phase of the inner peripheral teeth s of the sizing die 8. As seen in Figure 3(A), which is a partial view in enlarged scale of Figure 1, and in Figure 3(B), which is a plan view thereof, the first phase adjusting device 16 comprises an engaging piece 18 mounted on the proximal end of the first upper punch 9a, a spring 20 engaged at an end thereof on the tip end of the engaging piece 18 to bias the latter towards the rotational direction of the first upper punch 9a, and a stopper pin 21 adapted to control the position of the engaging piece 18. The other end of the spring 20 is engaged with a pin 22 anchored to the upper punch plate 6a. The stopper pin 21 is carried on a support member 23 mounted on the upper punch plate 6a. The biasing force of the spring 20 is directed to function in a direction opposite to the direction of rotation of the first upper punch 9a which rotates in engagement with the inner peripheral teeth s of the sizing die 8 at the time of the descending movement of the upper punch 9, so that the spring 20 serves to return the phase of the first upper punch 9a to the initial position thereof when the upper punch 9 returns to its initial position upon termination of the sizing process. As seen in Figure 4(A), which is a partial view in an enlarged scale of Figure 1, and in Figure 4(B), which is a plan view thereof, the second phase adjusting device 17 comprises an engaging piece 24 fixed on the sizing die 8, a spring 25 being engaged at an end thereof on a tip end of the engaging piece 24 to bias the latter towards the rotational direction of the sizing die 8, and a stopper means 26 adapted to control the position of the engaging piece 24. The stopper means 26 is mounted on the die holder 5. The spring 25 is engaged at the other end thereof with a pin 27 anchored to the stopper means 26. The biasing direction of the spring 25 is set in a direction opposite to the direction of rotation of the sizing die 8 when the sizing die 8 moves downwards in order to remove the gear blank W after having finished sizing, in such a manner as described hereunder. Thus, the spring 25 serves to return the phase of the sizing die 8 to the initial position thereof when the sizing die 8 returns to its initial position after the sizing step. The operation of the above-described sizing apparatus 1 will be explained hereunder with reference to drawings not limited to but including Figure 5. As shown in Figures 1 and 5(A), the gear blank W is placed on the work set pin 11 of the second lower punch 7b. The work set pin 11 moves down by a predetermined stroke through the intermediary of the cylinder unit 13 so as to make the lower surface of the outer periphery of the gear blank W flush with the upper surface of the sizing die 8. At the same time, the positioning pins 12, 12 pass through the corresponding openings of the gear blank W to fix the gear blank W in position. Then, the phase of the teeth Wa of the gear blank W is registered to the phase of the inner peripheral teeth s of the sizing die 8. Upon moving the upper plate 6 downward, the upper punch 9 presses at the lower surface thereof the upper surface of the gear blank W so as to force the gear blank W down into the inside concave portion of the sizing die 8. Thus, the tooth profile sizing of the gear blank W takes place due to the inner peripheral teeth s of the sizing die 8. As seen in Figures 2 and 5(B), when the gear blank W is pressed downward into the sizing die 8 up to a position such that the gear blank W is tightly held between the upper punch 9 and the lower punch 7, the sizing step is completed. During the operation as described hereinabove, since the outer peripheral teeth q of the first upper punch 9a are engaged with the inner peripheral teeth s of the sizing die 8, the sizing die 8, or the first upper punch 9a, or both of them, rotate to the accompaniment of the descending movement of the upper punch 9. During the final part of the sizing step, the outer peripheral teeth q of the upper punch 9a are maintained in an engaged relationship with the inner peripheral teeth s of the sizing die 8, as seen in Figure 2. As soon as the sizing step is completed, the upper punch 9 starts moving up, and at the same time the sizing die 8 starts moving down. When the sizing die 8 is rotated in a direction so as to move downward, the first upper punch 9a is rotated simultaneously in the reverse direction to move upward, whereby both members 8 and 9 may be released from the gear blank W. The sized gear blank W is then removed by releasing the gear blank W from the upper punch 9 and the sizing die 8, as seen in Figure 5(B). After removal of the gear blank W, the sizing die 8 moves upwardly to return to the initial position, and the second phase adjusting device 17 allows the phase of the sizing die 8 to be returned to the initial position. By adopting the above described sizing process, the time required for removing the sized and finished gear blank W can be greatly reduced in comparison with the conventional apparatus; thereby improving productivity. Also, the construction of equipment for removing the gear blank W can be made more simple. In this first embodied example, though three components comprising the first upper punch 9a, the sizing die 8, and the first lower punch 7a are formed to be rotatable, it is possible to constitute the first upper punch 9a as a non-rotatable member. Then, a rotatable construction is applied to the sizing die 8 and the first lower punch 7a. An example constructed in such a manner will be explained hereunder by way of a second embodiment. The second embodiment is very similar to the first embodiment, except for provision in rotatable fashion of the first upper punch 9a and for the omission the first phase adjusting device 16. In this embodiment, the gear blank W is disposed on a second lower punch 7b, as seen in Figure 6(A), and is pressed by an upper punch 9 through its downward movement so as to be forced into a sizing die 8, as seen in Figure 6(B). When the gear blank W is pressed down so as to be tightly held between the upper punch 9 and a lower punch 7, the sizing step of the teeth profiles of the gear blank W is carried out by the inner peripheral teeth s of the sizing die 8. During this operation, the outer peripheral teeth q of the first upper punch 9a come into engagement with the inner peripheral teeth s , so that the sizing die 8 rotates to the accompaniment of the descending movement of the upper punch 9. When sizing has been finished, as seen in Figure 6(C), the sizing die 8 moves down as it rotates to be disengaged from the upper punch 9 and the gear blank W. When the sizing die 8 is disengaged from the upper punch 9, the upper punch 9 starts moving up to lie away from the gear blank W, as seen in Figure 6(D). Herein, it can be seen that the reason why the upward movement of the upper punch 9 lags behind is the lack of a rotational mechanism with respect to the upper punch 9 which engages the inner peripheral teeth s of the sizing die 8. The upward movement of the upper punch 9, therefore, is restricted until the upper punch 9 is disengaged from the inner peripheral teeth s of the sizing die 8. As seen in Figure 6(D), upon releasing the gear blank W from the upper punch 9 and the sizing punch 8, the sized gear blank W is removed. In this second embodiment, though a little longer time for removing the gear blank W is required in comparison with the first embodiment, it is shorter than that of the conventional apparatus and a rotational mechanism for the first upper punch 9a is not required, so that equipment costs may be further reduced as compared to the first embodiment. Although certain preferred embodiments of the present invention have been shown and described in detail, the invention is not limited thereto but may be otherwise variously embodied within the scope of the appended claims. It is also to be understood that any sizing art employing substantially the same construction and performing the same function to obtain the same result, therefore, will fall within the same technical scope as the claimed invention. For example, the first and second phase adjusting devices 16, 17 may be of an air pressure control type, a hydraulic pressure control type, or a mechanical control type. The second phase adjusting device 17 may be mounted on the first lower punch 7a in lieu of the sizing die 8. Further, materials, shapes or the like with respect to the work set pin 11, the positioning pins 12 and the gear blank W, may be freely chosen. As described heretofore, according to the present invention, the lower punch on which the gear blank is placed is formed as a rotatable first lower punch and a non-rotatable second lower punch. The gear blank is pressed by the upper punch to be forced into the rotatable sizing die. After the teeth profiles of the gear blank are sized by the inner peripheral teeth of the sizing die, the sizing die rotates and moves down so as to be disengaged from the gear blank, and the upper punch moves upwardly to be disengaged from the gear blank. Then, the gear blank becomes free and can be removed. Accordingly, an interlocking device as employed by the conventional rotary driving mechanism is not required, thereby making construction simple and low-priced, and the time necessary for all steps from the sizing to the removal of the gear blank may be shortened so as to improve productivity. In the case where the upper punch for pressing the gear blank is provided with the rotatable first upper punch as set forth hereinabove, the upward movement of the upper punch and the downward movements of the sizing die may be accomplished at the same time, following the sizing of the teeth profiles of the gear blank by the inner peripheral teeth of the sizing die. The gear blank may be removed or taken out in a short time. Furthermore, the phasing device is provided for adjustment of the relative phase between the first upper punch and the sizing die, or the relative phase between the upper punch and the first lower punch. When each of these components returns to its initial position, the phase may be adjusted to be mutually registered with each other, thereby allowing the sizing operation to be smoothly performed.

Claims: An apparatus for sizing the teeth profiles of helical gears, comprising: a lower punch (7) on which a gear blank (W) having teeth formed thereon is arranged to be placed, an upper punch means (9) which is vertically movable for pressing said gear blank downward, and a sizing die (8) arranged to have inner peripheral teeth ( s ) thereof engaged with the gear blank pressed by said upper punch to size the teeth profiles of the gear blank; characterized in that said lower punch comprises first (7a) and second (7b) lower punches, said second lower punch being arranged to non-rotationally carry a said gear blank placed thereon and said first lower punch being axially rotatable around said second lower punch and having outer peripheral teeth p thereon, the said sizing die being axially rotatable and vertically movable while the inner peripheral teeth thereof are engaged with the outer peripheral teeth of said first lower punch, and the said upper punch means being axially rotatable and provided with outer peripheral teeth ( q ) which come into engagement with the inner peripheral teeth of said sizing die. A method of sizing teeth profiles of helical gears, comprising the steps of: non-rotationally positioning a gear blank (W) having teeth formed thereon on a lower punch (7), sizing the teeth profiles ( W a) of the gear blank by pressing the gear blank downward with an upper punch means (9) into a sizing die (8) while having the teeth of the gear blank and outer peripheral teeth ( q ) of said upper punch means engaged with inner peripheral teeth ( s ) of said sizing die, and upon termination of the sizing step releasing said sizing die from engagement with said upper punch means and the gear blank by rotating and lowering said sizing die, and moving said upper punch means upward to remove the gear blank. Apparatus as claimed in claim 1, wherein said upper punch means (9) comprises a first upper punch (9a) arranged axially rotatably around a second non-rotational upper punch (9b), the first upper punch being provided with said outer peripheral teeth ( q ) which come into engagement with the inner peripheral teeth ( s ) of said sizing die (8). Apparatus as claimed in claim 3, wherein a phase adjusting device (16,17) is provided between said first upper punch (9a) and said sizing die (8) or between said first upper punch and said first lower punch (7a) so as to adjust a phase therebetween when they return to their original positions. A method as claimed in claim 2, wherein said upper punch is rotated during the releasing step.

Inventors: MATSUBARA SADAO, SUGIURA NOBORU, MATSUBARA, SADAO, SUGIURA, NOBORU, Matsubara, Sadao, Honda Giken Kogyo K.K., Sugiura, Noboru, Honda Giken Kogyo K.K.
Applicants: HONDA MOTOR CO LTD, HONDA GIKEN KOGYO KABUSHIKI KAISHA
Application year: 1998
Main classification: B21K1
IPC codes: B22F5, B23F19, B22F3, B21K1, B21J5