Gear, and method and apparatus for manufacturing the same

TECHNICAL FIELD

[0001] This invention relates to a gear having side faces worked by cutting and a method and apparatus for manufacturing the same.

TECHNICAL BACKGROUND

[0002] A gear formed by forging process has pads projecting at least to a pressurized side surface. Cutting process is applied to the side surface in order to cut off the projecting part of the pads.

[0003] A weld flash occurs on an elongation of cut surface of tooth surface on the gear owing to the cutting process. Generally chamfering is carried out to a corner part in order to finish the corner part having the weld flash and this chamfering has been carried out by cutting.

[0004] Cutting process has problems such as attrition of tools, occurrence of chips, difficulty of forming optional form and requiring long machining time. Particularly, chamfering must be carried out one tooth at a time by turns. Therefore, chamfering is inefficient and needs amount of time.

[0005] Furthermore, when chamfering is carried out by cutting process in order to remove a weld flash generated by cutting side surface, new weld flash can occur by the chamfering.

[0006] A process yield is influenced on a large scale by the occurrence of weld flash and a step of screening defective products having weld flash was required.

DISCLOSURE OF THE INVENTION

[0007] The inventor of the present invention has paid attention to that it is avoidable that a weld flash occurred by cutting lies on said tooth part by forming a chamfer part, by a forging process, at least in a portion between tooth part formed on an outer peripheral surface and by keeping a distance between the tooth part and the cut part of the end part in the axial direction, and at the same time that a weld flash occurred on a cut end surface accompanied by cutting was decreased by the advantage for setting angles of the cut part and the chamfer part degrees to obtuse angle,

[0008] The inventors of the present invention also have paid attention to a concept of the invention that in a gear having a part worked by cutting and the other processing, a chamfer part is formed at least in a portion between the tooth part formed on an outer peripheral surface and an end part (side surface) in an axial direction by the forging process.

[0009] Based on these technical concepts, the inventor of the present invention has made further extensive studies and developments, arrived at completion of the present invention.

[0010] It is an object of the present invention to provide a product having high reliability, non-scattering quality, uniform and high accuracy, in order to manufacture a product having no weld flash, to attain lower costs, to avoid influences on process yield by a occurrence of weld flash and to need no step of screening defective products having weld flash.

[0011] A gear of the present invention (the first invention described in claim 1) having a part worked by cutting and the other process, in which a chamfer is formed at least in a portion between a tooth part formed on an outer peripheral surface and an end part thereof in an axial direction by a forging process.

[0012] A gear of the present invention (the second invention described in claim 2) according to the first invention, in which a chamfer is formed by forging process between the tooth part and the axial end part thereof worked by cutting.

[0013] A gear of the present invention (the third invention described in claim 3) according to the second invention, in which the tooth part comprises a tooth form with chamfers formed by forging process.

[0014] A gear of the present invention (the fourth invention described in claim 4) according to the third invention, in which the gear is an idler gear.

[0015] A gear of the present invention (the fifth invention described in claim 5) having a side face worked by cutting, in which a part of a chamfer formed at least in a portion between the tooth part formed on the outer peripheral surface and cutting face by forging process remains therebetween.

[0016] A method for manufacturing a gear of the present invention (the sixth invention described in claim 6) having a part worked by cutting, in which a chamfer is formed at an end part, in tooth trace direction, of the tooth form formed on the outer peripheral surface by forging process, and an end part in axial direction is worked by cutting in order that the chamfer remains between the tooth part and the cut part.

[0017] A method for manufacturing a gear of the present invention (the seventh invention described in claim 7) according to the sixth invention, in which a tooth part having a chamfer is formed at one end thereof is formed on an outer peripheral surface thereof by forging process.

[0018] A method for manufacturing a gear of the present invention (the eighth invention described in claim 8) according to the seventh invention, in which a steped part is formed by forming a chamfer at the other end of said tooth part.

[0019] A method for manufacturing a gear of the present invention (the ninth invention described in claim 9) according to the eighth invention, in which pads, connected with the chamfer formed in a portion of the stepped part, are cut.

[0020] A method for manufacturing a gear of the present invention (the tenth invention described in claim 10) having a side surface worked by cutting, in which a chamfer is formed at an end corner part, in tooth trace direction, of a tooth form by forging process, and the side surface is cut in order that at least a part of the chamfer remains in a portion between the tooth part on the outer peripheral surface and cut face.

[0021] A method for manufacturing a gear of the present invention (the eleventh invention described in claim 11) according to the tenth invention, in which an end of a chamfer formed in order to connect the outer peripheral surface of the tooth part corresponds to the cut face.

[0022] An apparatus for manufacturing a gear of the present invention (the twelfth invention described in claim 12) having a part worked by cutting, in which a forging device for forming a chamfer at an end corner part, in tooth trace direction, of tooth form formed on an outer peripheral surface by forging process, and a cutting device for cutting an end corner part in axial direction in order that the chamfer remains between the tooth part and cutting part.

[0023] An apparatus for manufacturing a gear of the present invention (the thirtieth invention described in claim 13), in which a die including a cavity having an inner peripheral surface formed to a tooth shape in response to a tooth form of a primary formed article, and bottom surface having chamfers forming parts arranged in response to the tooth form of the primary formed article, a die plate for supporting the die, a mandrel projected from the die plate to a center within the cavity, a lower mold comprising a knockout sleeve projectably provided into the cavity by a plurality of ejecter pins, coaxially provided with the mandrel, and an upper mold comprising a cylindrical punch supported by a punch case.

[0024] In a gear of the first invention having a part worked by cutting and the other process, having the above described construction, a chamfer is formed at least in a portion between a tooth part formed on an outer peripheral surface and an end part thereof in an axial direction by a forging process.

[0025] Therefore the present invention has such effects to attain the products having a high reliability, compared with conventional cutting, high degree of freedom of form of a chamfer part, non-scattering quality owing to no weld flash standing between said tooth part, and uniform and high accuracy. The present invention also has such effects to prevent indentation, abnormal noise and vibration of a tooth surface and to improve lifetime.

[0026] In a gear having a side face worked by cutting according to the fifth invention, having the above described construction, a part of a chamfer formed at least in a portion between the tooth part formed on the outer peripheral surface and cutting face by forging process remains therebetween.

[0027] Therefore the present invention has such effects to attain the products having high reliability, compared with conventional cutting, high degree of freedom of form of a chamfer part, non-scattering quality owing to no weld flash standing between the tooth part, and uniform and high accuracy. The present invention also has such effects to prevent indentation, abnormal noise and vibration of a tooth surface and to improve lifetime.

[0028] In a method for manufacturing a gear having a part worked by cutting according to the sixth invention, having the above described construction, a chamfer is formed at an end part, in tooth trace direction, of the tooth form formed on said outer peripheral surface by forging process, and an end part in axial direction is worked by cutting in order that the chamfer remains between the tooth part and the cut part.

[0029] Therefore the present invention has such effects to attain the products having a high reliability compared with conventional cutting process, to provide a product having no weld flash and to enable lower costs owing to no need cutting to form a chamfer part. The present invention also has such effects to avoid influence on process yield by the occurrence of weld flash and to need no step of screening defective products having weld flash.

[0030] In a method for manufacturing a gear of the ninth invention having the above described construction, according to the eighth invention, pads, connected with the chamfer formed in a portion of said stepped part, are cut.

[0031] Accordingly the present invention has such features and effects that a weld flash occurs at an end part of the step part away from the tooth part and the weld flash doesn't stand between the tooth part, so as to prevent indentation, abnormal noise and vibration of a tooth surface and to improve lifetime.

[0032] In a method for manufacturing a gear having a side face worked by cutting according to tenth invention, having the above construction, a chamfer is formed at an end corner part, in tooth trace direction, of a tooth form by forging process, and the side surface is cut in order that at least a part of the chamfer remains in a portion between the tooth part on the outer peripheral surface and cut face.

[0033] Therefore the present invention has such effects to attain products having a high reliability compared with conventional cutting process, to attain a product having no weld flash, to avoid influence on process yield by the occurrence owing to no weld flash standing between the tooth part and to need no step of screening defective products having no weld flash.

[0034] In an apparatus for manufacturing a gear having a part worked by cutting according to the twelfth invention, having the above described construction, the forging device for forms a chamfer part at an end corner part in tooth trace direction of tooth form formed on an outer peripheral surface by forging process, and the cutting device cuts an end part in axial direction in order that the chamfer part remains between the tooth part and the cutting part.

[0035] Therefore the present invention has such effects to attain a product having high reliability compared with conventional cutting, to attain products having no weld flash, to attain lower costs owing to no need cutting to form a chamfer, to prevent influence on process yield by the occurrence owing to no weld flash standing between the tooth part and to need no step of screening defective products having weld flash.

BRIEF DESCRIPTION OF THE DRAWINGS

[0036]
FIG. 1 is a sectional view showing a forging device for forming a gear according to the embodiment and the example of the present invention;

[0037]
FIG. 2 is an illustrative view showing forms of products of each process according to the embodiment and the example of the present invention; and

[0038]
FIG. 3 is a detailed illustrative view of forging process.

BEST MODE FOR CARRYING OUT OF THE INVENTION

[0039] Embodiment of the present invention will now be described with reference to the drawings.

[0040] (Embodiment)

[0041] A gear of the present embodiment having a part worked by cutting and the other process as shown in FIGS. 1-3 wherein a chamfer part is formed at least in a portion between a tooth part formed on an outer peripheral surface and an end part thereof in an axial direction by a forging process.

[0042] A gear of the present embodiment, by way of example, is an idler gear used for automobile transmission according to the techniques of the present invention.

[0043]
FIG. 1 shows a forging device for forming a chamfer part at an end part of tooth form of primary formed article. As shown in FIG. 2(a) a primary formed article 1 comprises tooth form 4 with a chamfer 4a around a gear part 3 formed at an end part of hub part 2, and the chamfer 4a is formed on the side of hub part 2 of tooth part 4. Pads 5 project to the other side. Axial hole 6 is formed at the center.

[0044] The inner circumferential surface of the forging device is formed as a tooth-shaped form corresponding to the tooth shape 4 of the primary formed article 1 in order to set the gear part 3 of the primary formed article 1 as settled the hub or boss part 2 upward.

[0045] The forging device comprises a die 9 constituting a cavity 8 having chamfer forming surface 7 at the bottom portion corresponding to the tooth shape 4 of the primary formed article 1, a die plate 10 for supporting the die 9, a mandrel 11 projected from the die plate to a center in the cavity 8, a lower mold comprising a knockout sleeve 13 projectably provided in the cavity 8 by a plurality of ejector pins 12,12 . . . , coaxially provided with the mandrel 11, and an upper mold comprising a cylindrical punch 15 supported by a punch case 14.

[0046] By setting the primary formed article 1 in the cavity 8 with mandrel 11 inserted into the axial hole 6 (FIG. 3(a)) and operating to send the punch 15 down, the hub part 2 of the primary formed article 1 is inserted into a cylinder of the punch 15, an upper surface of the gear part 3 excepting the tooth shape 4 is pressurized by the cylindrical end surface, the bottom end surface of the tooth shape 4 is pressed into the chamfer forming surface 7, and the stepped part having the chamfer part 16 on the bottom side surface of tooth shape 4 of the primary formed article 1 is formed (FIG. 3b).

[0047] The secondary formed article 17 is ejected from the die by the ejector pins 12,12 . . . through the knockout sleeve 13. Therefore the secondary formed article 17 (FIG. 2(b)) having the chamfer part 16 at the stepped part on the bottom side surface of tooth shape 4 as shown in FIG. 3c is attained.

[0048] The step part of the tooth shape 4′ of the secondary formed article 17 has a slide surface towards the side face intended to be cut, as shown in FIG. 2(b), and the pads 5′ is cut off in one cut along the inclined surface 18 and the side face of the gear part continuing to the slide surface extremely to the end surface of the chamfer part 16 (FIG. 2c).

[0049] The chamfer part formed by the forging process between the whole outer peripheral surface as the end corner part of the finished tooth form and the cut surface remains in the cut products. Therefore, products worked by cutting has no weld flash at least on the tooth surface.

[0050] Thus, it is possible to provide a product of non-scattering in quality, uniform and high accuracy, and to improve productivity dramatically, owing to the chamfer part formed by forging process.

EXAMPLE

[0051] In the Examples of the present invention, the end of the chamfer part formed connected to the whole outer peripheral surface of said tooth part corresponds to the cut surface. By forging technique, whatever form of the chamfer part can be formed in response to a final form easily. Therefore, according to the present examples the chamfer part can remain 100% on the products worked by cutting, weld flash scarcely occur and an effect of forging process function effectively and rationalistically.

[0052] Although, in the present invention, the chamfer part formed by forging process remains 100% in order to avoid the occurrence of weld flash. Therefore, it is enough to obtain the same effect that tooth part and the cut part are at different position each other, the tooth part and the cut part keep a distance each other and the small chamfer part remains.

[0053] In the example the secondary formed article is an article formed the chamfer part at the end corner part on the opposite side of the chamfer forming side of the primary formed article formed the tooth form with chamfers. Although, at the step of the primary formed article, the chamfer part may be formed at the same time in parallel on forming the tooth form without no problem, and the form or profile of a gear such as a gear without a chamfer and a gear with helical tooth should not be restricted by this example.

[0054] By using the form or mold having the chamfer forming surfaces at both the upper part and the lower part, it is possible to form the chamfer parts at the both side of the gear at once. Moreover, the inclined or taper surface towards the side face intended to be cut is daringly or always not necessary, and the cut surface may possibly be a straight line without inclination.

[0055] According to the embodiment and example of the present invention, the chamfer part formed by forging process remains at least in a portion between the outer peripheral whole surface of the tooth part and the cut surface, weld flash can not occur on the tooth surface. In other words, in forging process, because the chamfer part is formed at least in a portion between tooth part formed on the outer peripheral surface and the axial end, a width shorter than the width in axial direction of the chamfer part is cut in order to remain the chamfer part finally, the tooth part and the cut part in the end of axial direction keep a distance each other. Therefore, it is possible to prevent the weld flash from standing between the tooth part when the weld flash occurs by cutting.

[0056] Because the chamfer part is formed by forging process, a degree of freedom of design is higher compared with conventional cutting and the profile of the chamfer part can be in response to whatever. Moreover machining time is shorter than that of the conventional cutting. It has good efficiency and makes it possible to attain the cost down. Furthermore, it has high reliability and it is so suitable to provide products having no weld flash.

[0057] Particularly, the chamfer part is formed between the tooth part on the outer peripheral surface and the cut surface, the angles between the cut surface of the cut part and the chamfer part can be set obtuse angle (for example, from 120° to 150°), and in other words, the angles between an elongation of tooth part on the outer peripheral surface (an axial line of the gear) and the chamfer part can be set from 60′ to 30° Therefore, the occurrence of the weld flash at the cut end surface by cutting can be reduced.

[0058] Moreover, the end of the chamfer part formed connected with the tooth part on the outer peripheral surface corresponds to the cut surface, therefore the whole of the chamfer part is used 100%. When the end part corresponds to the cut surface, the cut surface connects with the surface of the chamfer part by forging process, therefore it is possible to minimize the occurrence of the weld flash.

[0059] The preferred embodiment and example of the present invention, as herein disclosed, are taken as some embodiment and example for explaining the present invention. It is to be understood that the present invention should not be restricted by these embodiment and example and any modifications and additions are possible so far as they are not beyond the technical idea or principle based on descriptions of the scope of the patent claims.

[0060] In preferred embodiments and examples of the present invention, an idler gear as an example of gears is described for explaning the present invention. It is to be understood that the present invention should not be restricted by these embodiment and example, and would be able to be applied to every kind of gears for automobiles or for the other use, in the case that weld flash occurs on gears, a part of which is processed by cutting or by the other process.

[0061] Moreover, it is to be understood that the above described chamfer part should not be restricted as a liner taper form, and a curved line such as an arc-like or a curved surface would be acceptable. Any forms of the chamfer part would be enough to be accepted only when a stepped part is able to be formed between the gear part and the gear face.

[0062] Furthermore, according to the present invention, the chamfer part is formed between the tooth part and the cut surface. Therefore, when the tooth surface is worked by cutting or the other process, it is possible to minimize the occurrence of the weld flash.

Gear, and method and apparatus for manufacturing the same

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