The present invention relates to a method of manufacturing a tooth profile part such as a gear, a sprocket gear, or a spline gear, particularly by cold forging.
A method of manufacturing a gear from a metal material by cold forging is known as shown in Japanese Patent Unexamined Publication No.9-300041.
In
In the conventional method of manufacturing a gear by cold forging, an end face 16 of a form starting part of the tooth profile 12 of the die 11 slopes, while a slope angle B of the end face 16 is 30° or less with respect to a surface orthogonal to a central axis of the die 11. The smaller the slope angle B is, the less the tooth profile is incompletely formed.
Further, although the material 10 is sometimes cold-forged in a single step, it is sometimes finished by cold forging after preforming under a hot or warm condition, annealing, and processing surface lubrication, etc.
In the conventional method of manufacturing the gear by cold forging shown in
In the method shown in
In the conventional method of
On the other hand, as shown in Japanese Patent No.2913522, a method of forging a spur gear is also known, where cold forging is performed in three processing steps. Specifically, the first processing step is to upset a material to form a primary processed gear with a gear shape in which both an addendum and a tooth thickness are set smaller than a tooth contour of the spur gear to be obtained. The second processing step is to press the primary processed gear as freely flowing a material except the tooth profile to form a secondary processed gear. The third processing step is to stretch the secondary processed gear to form a finished product. A method of processing a spur gear by cold forging in each of the steps is also known.
In
In
In
The secondary processed gear 215 is formed by pressing with the punch 213. In the secondary processed gear 215, the material fills in the tooth profile 211, and the underfill on the addendum part is removed. This is because the protuberance 216 is formed by freely flowing the material around except the tooth profile where the material is not bound during processing.
In the method described in Japanese Patent Unexamined Publication No.9-300041, the maximum load during cold forging is often applied on the sloping end surface 16 of the form starting part formed inside the die. Since little effort has been made for lowering the maximum load, a life of the die 11 was short. Consequently, there was a disadvantage of deteriorating the quality of products.
Particularly, when a helical gear is manufactured by cold forging, the load with a tendency to slope the tooth profile 12 of the die 11 to one side is applied. Therefore, an area in the vicinity of the sloping surface 16 has often broken. Such has consequently shortened the life of the die 11.
According to the inventor's knowledge, when processing the helical gear by cold forging, the load is concentratively applied on one surface (front surface) of the tooth profile of the die, not so much on a back surface thereof. Therefore, there is a remarkable difference of the load between the front surface and back surface of the tooth profile, which would cause many defects in the tooth profile.
The method described in Japanese Patent No.2913522 has problems as follows.
As shown in
If the ratio of processing becomes large, plastic-process-hardening of the processed product advances. Further, resistance of deformation becomes large, which makes forming difficult.
Further, a shape coefficient becomes large. A pressure of stretch forming (forming load) becomes large. Distortion of the die becomes large. Therefore, precision of the processed product becomes low. In addition, the die easily breaks if the process speed is raised.
With regard to precision, it is not preferable that the tooth profile formed small in the primary process is enlarged (fatted) in the secondary process as shown in
Particularly, the method described in Japanese Patent No.2913522 is not appropriate for mass-producing gears with high precision.
If the forming load is raised for improving precision, distortion enlarges in the object to be processed, and process distortion enlarges on after-heat processing. As the load enlarges, the die easily breaks.
The object of the present invention is to provide a method of manufacturing a tooth profile part, for example, such as a gear, by cold forging, which can elongate a life of a die for processing and which can manufacture a tooth profile of good quality.
According to the present invention, a method of manufacturing a tooth profile part by cold forging and a tooth profile part manufactured by the same method are as follows:
an initial step of forming a initial tooth profile,
a completing step of forming a completed tooth profile by sizing, and
between the initial step and the completing step, maintaining a tooth thickness of the initial tooth profile substantially identical to a tooth thickness of the initial tooth profile or reducing a tooth thickness within a range of 10% or less compared to a tooth thickness of the initial tooth profile, and at the same time including an intermediate step of ejecting an addendum part beyond the initial tooth profile by cold forging.
According to one mode for carrying out the invention, a preferred example of the tooth profile part is a gear, while a method of manufacturing the gear by cold forging comprises a series of following steps:
During intermediate processing, the tooth thickness is not increased. During intermediate processing, the tooth thickness is set substantially identically or rather decreased (in the range of 10% or below). Thus, it is possible to perform fine forging under the lower load. As a result, it is possible to not only reduce a processing pressure but also raise a processing speed.
Further, it is possible to manufacture the tooth profile part such as a gear or spline gear by cold forging (fine forging) with high precision.
If the intermediate step as described above is included, it is easy to fit the tooth profile of the processed product to the tooth profile of the die in the final step. Even if the helical gear has a large helix angle, much difference of precision does not occur in the products.
Compared to the conventional method of manufacturing a gear made only by drawing, friction under the high face-pressure is no longer applied on the die. Therefore, it is possible to extend the lifetime of the die. The lifetime becomes three to ten times longer than the conventional method of drawing, for example.
It is possible to manufacture a gear having a small face width or a chain sprocket etc. by cold forging. In this case, it is possible to improve the strength and the manufacturing speed compared to the other manufacturing methods.
If the outside area in the radial direction of the metal material is thickened in the axial direction compared to the inside area, the fiber flow is formed along the tooth profile and it is possible to obtain the high strength compared to gear cutting. It does not cause die wearing or second breaking that have occurred in conventional precision shearing.
If a plurality of different dies are used to form the tooth profile step by step, its fiber flow becomes good and no crack will occur.
If the tooth profile is formed step by step as changing the degree of “knocking out” or “stretching” of the intermediate step, an addendum part forms an arc shape or other curved round shape (a curved surface in which the top part thereof positions centrally) and approaches into an addendum part of the complete tooth profile in the die as forming even if the same die is used. Thus the fiber flow becomes good and no crack will occur.
If the following steps are adopted on each cold forging, it is possible to perform forging under a further lower load.
Another mode for carrying out the present invention will be described.
The tooth profile after the intermediate step is slightly larger than the complete tooth profile in outer diameter. Thus, an accurate tooth profile is obtained on sizing (finishing drawing) in the after step.
The processed product after the initial step is set identical to or increased within 10% or below of the finished tooth profile in tooth thickness. Thus, the round shape of the bottom of the first tooth profile is set larger than that of the finished tooth profile. In this case, if the ratio of processing between the initial step and the intermediate step is appropriately determined, it is possible to size in the intermediate process and the completing step to obtain a desirable finished tooth profile, even if the pressure of forming (forming load) is set 10˜50% lower.
In order not to enlarge the processing pressure, it is preferable not to bring it into a full-enclosed condition (in other words, it is preferable to bring it into a non-enclosed condition). For example, in the initial step or the intermediate step, it is processed so that a space will remain between the top of the addendum part of the tooth profile of the die and the top of the addendum part of the tooth profile of the processed product after cold forging.
Further, a part to be the addendum part of the tooth profile of the initial processing die is set substantially identical or smaller compared to the finished tooth profile in tooth thickness. In addition, the round shape of the whole addendum part of the processed product is formed in an arc or other curved surface (a shape in which the top lies at the center) and formed largely. The large and round shape increases the strength against breaking of the processing die.
It is possible to form the finished tooth profile from the coil material in three to seven steps by means of a parts-former. In this case, it is possible to take the best mass production in regard to the cost. In the case of the helical gear, since it is possible to form the helix angle with high accuracy and good precision, it can be used as a reference plane for use in getting precision in the after step.
If the height of ejecting of the addendum part is 60% or more of the finished tooth profile, a considerable effect is obtained.
According to the present invention, since the non-enclosed forging is adopted as described above, it is possible to lower the forming load. Preferably, a forging press (particularly the parts-former) is adopted as a forming machine.
If the following steps are performed, it is possible to process under the lower load in each cold forging.
Further, another preferred mode for carrying out the present invention will be described as follows.
Such a series of the above-stated steps (1)˜(10) is a typical example. The above-stated steps (1)˜(4) are important.
Another mode according to the present invention will be described.
The metal material with a cylindrical outer surface (a circular column, for example) is inserted into a die having a certain female tooth profile. In the die, the metal material is stretched by a punch to form an intermediate tooth profile in cold forging.
The diameter of the circular column material may be smaller than the diameter of an addendum circle of the die or smaller than the minor diameter of the gear.
It is possible to press the circular column material along a central axis direction thereof to circumferentially push it toward the die.
It is possible to push the circular column material to a support member provided at one end of the circular column material in the central axis direction by means of a pushing member provided at the other end thereof. Further, the support member and the pushing member may be formed with a tooth profile corresponding to the tooth profile of the die. The pushing member may be provided at both ends of the circular column material in the central axis direction.
The circular column material may have a bore penetrating in the central axis direction in which a pin is arranged for maintaining the shape of the bore.
By means of a plurality of different dies, the tooth profile may be gradually formed depending on each die. By means of the same die, degrees of ejecting of the addendum part may be varied to gradually form the tooth profile.
After the circular column material is initially formed, internal stress may be removed by softening.
The initial tooth profile may be drawn for forming. The addendum part of the drawn initial tooth profile may be ejected in the die.
Another mode according to the invention will be described.
According to the present invention, a method of manufacturing a gear by cold forging is developed. Particularly, according to the present invention, a distinguished effect is provided on manufacturing a helical gear. It has been understood that the helical gear is very difficult to manufacture by cold forging. However, according to the present invention, it is possible to manufacture the helical gear or gears similar to the same effectively and with high precision.
It is possible to manufacture various kinds of gears following the method according to the present invention. It is possible to form a double gear having large and small gears, a flanged gear, a chamfer bevel gear, a ratchet gear, a gear with serration etc. by cold forging. Furthermore, it is possible to perform cold forging of a straight bevel gear or gears similar to the same.
In the manufacturing method according to the present invention, it is possible to set product-precision of the gear to classes 2 to 5 of Japanese Industrial Standard.
In the manufacturing method according to the present invention, it is possible to process one metal material by cold forging integrally, even in the flanged gear, double gear, or spline gear.
The present invention includes a method of finishing by cold forging after performing in hot or warm condition or a method of additionally grinding etc. before or after or in the middle of forging if the need arises. In other words, the present invention is not limited to the method of manufacturing the final product of the gear only by cold forging from beginning to end.
The material used in the present invention is mainly metal and round bar, ringed material, or preformed product made by cold forging in hot or warm conditions, etc. A preferable metal material is coil material in regard to the cost. Basically, it is possible to use materials usually used for gears.
If the outer circumferential part of the processing material is thickened in advance and processing is then performed, it is advantageous in the following points:
In the present invention, ‘stretching’ of the metal material additionally means expansion of the metal material. Expansion of the metal material can be paraphrased by ‘Harashi’ in Japanese. Since ‘ejection’ means a forming of concentrically protruding the addendum part, it can be said as a special stretching (without increasing the tooth thickness).
It is possible to apply the present invention to various kinds of gears such as a spur gear or a helical gear (it is also called spiral gear or twisted gear).
It is possible to apply the present invention to a small tooth thickness or a large tooth thickness.
According to the present invention, it is possible to combine stretching, drawing, and ejecting of the metal material. If the face width of the gear is relatively large and if it is difficult to obtain cylindricity only by stretching and ejecting, drawing under the appropriate ratio of processing can provide good effect. Even if the material does not have good ductility, it is effective to adopt a drawing method together. The processing ratio is set in consideration of the size and material.
Some materials have no bore, while other materials have bores before forming the tooth profile. If the material has a bore, it is preferable to arrange a mandrel pin in a central part thereof. In this case, the material with the bore is set larger than the material without the bore in length. When initially stretching, it is possible to press both end surfaces to form the tooth profile as the bore is plastic-processed.
A method of forming the helical gear according to the present invention will be described.
In any mode described above, stretching and ejection is preferably performed by compression in which the end surface of the material or the processed product is pressed by means of the punch or the pin.
Various embodiments of the present invention will be described referring to the accompanying drawings.
A die 21 has a bore 21a. The bore 21a penetrates in a direction of a shaft center 26. A female tooth profile 27 is formed on a circumferential surface of the bore 21a. The tooth profile 27 is configured as a normal spur gear. Reference numeral 23 designates a pitch circle. Reference numeral 24 designates an addendum circle of the tooth profile 27. Reference numeral 25 designates a deddendum circle of the tooth profile 27.
When comparing with the conventional example shown in
A pressure pin 28 is provided above the metal material 20 as a pushing member. The pressure pin 28 has an end 28a. The end 28a abuts on the metal material 20. The end 28a is substantially identical to the metal material in diameter.
Under the metal material 20, a support pin 29 is provided as a support member. The support pin 29 supports the metal material 20. The support pin 29 is stationary due to a support means not shown in the figure. A male tooth profile 29a is formed around the support pin 29. The male tooth profile 29a of the support pin 29 corresponds to the female tooth profile 27 of the die 21.
One example of a method of manufacturing the helical gear with the die 21 etc. by cold forging will be described.
First, the metal material 20 is inserted into the die 21. Directly under the metal material 20, the support pin 29 is arranged in advance.
The metal material 20 inserted into the die 21 is pushed by means of the pressure pin 28.
In an initial step of first pushing, the metal material 20 pressed is compressed, shortened between the upper and lower end faces in a vertical direction, stretched outwardly to protrude the side face into the die 21, to form the tooth profile smaller than the tooth profile 27 at the middle of the normal tooth profile 27 of the die 21.
Thus the tooth profile is formed in the first pushing. Furthermore, in the intermediate step, the forming pressure and the forming speed are changed. In the second or third pushing, the normal tooth profile corresponding to the normal tooth profile 27 is formed into the processed product.
In the intermediate step, the tooth thickness is maintained identically. At the same time, the addendum part gradually protrudes in plural times of cold forging as forming the arc to approach the addendum part of the complete tooth profile.
In addition, in the case of the product having the large face width or high precision, it is passed through the sizing die having the tooth profile in the completing step. Thus, high precision is obtained for the tooth profile etc. In this case, it is appropriate to set the amount of sizing around 0.01 to 0.2 mm, for example.
In the initial step, the intermediate step, and the completing step, if the tooth profile of the die is exchanged, it is also possible to form the spur gear in the similar way.
A die 31 has a bore 13a. The bore 13a penetrates in a direction of a shaft center 36. A female tooth profile 37 is formed on a circumferential surface of the bore 31a. The tooth profile 37 is configured as a normal spur gear. Reference numeral 34 designates a deddendum circle of the tooth profile 37. Reference numeral 35 designates an addendum circle of the tooth profile 37. Reference numeral 30a designates an outer diameter of the metal material 30. Reference numeral 31b designates a pitch circle of the die 31.
The metal material 30 is configured as a thin plate with a cylindrical outer circumferential surface and thickened by the same width on both sides of the outer tooth forming part. Although it is preferable to thicken both the sides of the metal material 30 equally, it may be thicken only one of both.
Above the metal material 30, a punch 38 having a tooth is provided. The punch 38 pushes the metal material 30 in the direction of arrow X. The punch 38 has a male tooth profile 38a at a lower part thereof. The male tooth profile 38a corresponds to a female tooth profile 37 of the die 31.
Under the metal material 30, a support pin 39 is provided as a support member. The support pin 29 supports the metal material 30. The support pin 39 is stationary due to a support means not shown in the figure. A male tooth profile 29a is formed around the support pin 39. The male tooth profile 39a of the support pin 39 corresponds to the female tooth profile 37 of the die 31.
One example of a method of manufacturing the helical gear by means of the die 31 etc. by cold forging will be described.
First, the metal material 30 is inserted into the die 31. Directly under the metal material 30, the support pin 39 is arranged in advance.
In a first forging, the metal material 30 inserted into the die 31 is pushed by means of the punch 38. Thereby, the thickened part of the metal material 30 is pushed and stretched outwardly. In a second and the following pushing, the metal material 30 protrudes into the die 30 to form a gear with the same precision as the die 31. Thus, it is possible to obtain the normal gear corresponding to the die 31.
Finally, in the completing step, the tooth profile of the processed product is sized and finished.
Each step will be described in the following.
In the first step, a metal material is inserted into a predetermined die (not shown) and stretched by means of a punch. Thus, an initial tooth profile 41 having an addendum part smaller than that of the normal tooth profile is obtained in the first step. An addendum part 41a of the tooth profile of the first step is designated by reference numeral 41a. The addendum part 41a is configured as a large arc.
In the second step, the initial tooth profile 41 obtained in the first step is further cold-forged by means of a die having a tooth profile several percent smaller in tooth thickness than the die used in the first step and ejected. Thus, a tooth profile 42 of the second step is obtained. An addendum part of the tooth profile of the second step is designated by reference numeral 42a. The addendum part 42a is configured as a non-circular, round, and curved shape.
In the third step, the tooth profile 42 obtained in the second step is ejected by means of a die having a tooth profile several percent smaller in tooth thickness than the die used in the second step. Thus, a tooth profile 43 of the third step is obtained. An addendum part of the tooth profile of the third step is designated by reference numeral 43a. The addendum part 43a is configured as a non-circular, round, and curved shape.
Thus, by means of three types of the dies, the tooth profile having the round addendum part is gradually formed depending on each die, as varying degrees of stretching or ejecting to reduce the tooth thickness.
The tooth profile 43 obtained has a margin for sizing on the normal tooth profile, good fiber flow, and no cracks.
Sizing by drawing for finishing is performed on the tooth profile 43.
FIGS. 7 to 10 illustrate another embodiment of the present invention.
Each step will be described in the following.
In the initial step, the metal material is inserted into a predetermined first die (not shown) and stretched. Thus, an initial tooth profile 51 of the initial step is obtained.
In the intermediate step, the initial tooth profile 51 having a round bottom shape obtained in the initial step is inserted into a predetermined second die (not shown) and ejected. Thus, a tooth profile 52 having a round deddendum shape of the intermediate step shown in
In the intermediate step, the tooth thickness is maintained identically. At the same time the deddendum part gradually protrudes as varying the round shape in plural times of cold forging and approaches the face of tooth of the complete tooth profile.
In the completing step, the tooth profile 52 obtained in the intermediate step is sized (namely drawn) and finished. Thus, the complete tooth profile 53 shown in
The complete tooth profile 53 obtained has a normal tooth profile, good fiber flow, and no cracks.
FIGS. 11 to 14 illustrates another embodiment of the present invention. In the embodiment, stretching and ejecting of the metal material are separated into two steps and a sizing (drawing for finishing) step is further combined. Reference numeral 60 designates a gear. Reference numeral 64 designates a pitch circle.
Each step will be described in the following.
In the initial step, a metal material is inserted into a predetermined die (not shown) and stretched. Thus, an initial tooth profile 61 having an addendum part with an arc shape shown in
In the intermediate step, the initial tooth profile obtained in the initial step is inserted into a die (not shown) different from the die used in the initial step and ejected. Thus, a tooth profile 62 having an addendum part of an arc shape shown in
In the completing step, the tooth profile 62 obtained in the intermediate step is sized. Thus, a tooth profile 63 shown in
Reference numeral 65 schematically illustrates a fiber flow after the second step. The tooth profile 63 obtained has good fiber flow and no cracks.
The embodiment illustrates data with respect to a tooth profile (A) and a tooth trace (B) of a helical gear formed by stretching and ejecting of the metal material. The data were measured by means of a three-dimensional measuring apparatus.
In
TABLE 1 shows tooth number, module, pressure angle, helix angle, addendum modification coefficient, and base circle.
It can be seen that a gear in highest quality can be obtained, even if the gear is formed by stretching and ejecting.
The embodiment illustrates data with respect to a tooth profile (A) and a tooth trace (B) of a helical gear formed by stretching, ejecting, and further drawing of the metal material. The data were measured by means of a three-dimensional measuring apparatus.
In
Tooth number, module, pressure angle, helix angle, addendum modification coefficient, and base circle used in the embodiment of
Although the tooth profiles show classes 0 to 1 of Japanese Industrial Standard, there is a difference of 2 to 5 classes between the left tooth surface and right tooth surface of the tooth trace. Actual value can be estimated to be classes 2 to 4.
A series of manufacturing steps will be described as follows:
(A) illustrates a cylindrical material 70 produced by cutting a solid cylindrical metal material in a predetermined length from a coil material.
(B) illustrates a processed product in which the material 70 is cold-forged under the condition (A) to form a diameter reduction part 71 and a depression 72 at a lower part thereof.
(C) illustrates a condition in which the processed product 70 is cold-forged under the condition (B) to form an upper depression 73 and a lower deep bore 74.
(D) illustrates a condition in which the processed product 70 is cold-forged under the condition (C) to form a diameter expansion part 76 and a lower deep bore 75.
(E) illustrates a condition in which the processed product 70 is stretched under the condition (D) in a die not shown in the figure to form an initial tooth profile 77 larger than the normal tooth profile in tooth thickness and small addendum. A new bore 78 is formed at a lower part thereof.
After the above-described steps, the bore is penetrated to obtain a completed product shown in
FIGS. 18 to 19 illustrate a crank sprocket 79 formed from the processed product. The crank sprocket 79 has a normal tooth profile 87.
The crank sprocket 79 shown in
A tooth thickness is maintained substantially identical to the tooth thickness of the initial tooth profile 77. Or, the tooth profile is reduced in the range of a few % smaller than that of the initial tooth profile 77. At the same time, the addendum part is protruded compared to the initial tooth profile 77. As a result, a completed product having a completed tooth profile 87 (
A die set 81 comprises a die 81a and a die 81b.
A bore 81c passes through in a direction of a central axis 86 of the die 81a. A female tooth profile 87 is formed on a circumferential surface of the bore 81c. The tooth profile 87 is configured as a normal tooth profile. Reference numeral 87a designates an addendum circle of the tooth profile 87. Reference numeral 87b designates a deddendum circle of the tooth profile 87b.
The die 81b is arranged under the die 81a. A bore 81d smaller than the bore 81c in diameter passes through in the direction of the central axis 86 of the die 81b. A circumferential surface of the bore 81d corresponds to a lower outer circumferential surface of the crank sprocket 79. An upper surface of the die 81b supports the tooth profile 87.
A punch 88 as a pushing member is provided above the crank sprocket 79. The punch 88 pushes the crank sprocket 79 in a direction indicated by an arrow X.
A male tooth profile 88a is formed on an outer circumferential surface of the punch 88. The male tooth profile 88a corresponds to the female tooth profile 87 of the die 81a. The punch 88 has an end 88b at a lower part thereof. The end 88b corresponds to an upper surface of the crank sprocket 79 in shape.
A knock out sleeve 89 is provided under the crank sprocket 79 for supporting a lower end of the crank sprocket 79. The knock out sleeve 89 is stationary due to a support means not shown in the figure.
A punch mandrel passes inside the crank sprocket 79.
A method of forming the crank sprocket by cold forging by means of the die 81 etc. of
First, a metal material to be formed with a tooth profile (not shown) is inserted into the die 81. Directly under the metal material, the knock out sleeve 89 is arranged in advance. The punch mandrel 82 is inserted inside the metal material.
The metal material inserted into the die 81 is pushed by means of the punch 88.
The metal material pushed is stretched to have the tooth profile 87 corresponding to the tooth profile of the die 81a.
Thus, it is possible to obtain the crank sprocket 79 by means of the die set 81.
One example of a method of forming a helical gear pinion 90 will be described.
A cylindrical metal material provided with a bore in advance is arranged in a predetermined die (not shown). The metal material is pushed in a direction of a central axis thereof in such a condition that a pin (not shown) corresponding to the bore in shape is inserted in the bore. The metal material pushed is stretched in the circumferential direction. After that, it is ejected so as to have a tooth profile similar to the tooth profile of the corresponding die.
After ejecting, the helical gear pinion 90 is drawn from the die as being rotated along the helix angle.
One example of the helical gear pinion 90 has a helix angle (helix direction) of 25° (left) and precision of class 4 or 5 of Japanese Industrial Standard.
If relative displacement between the die and the product to be processed is reduced, a processed product close to the die in precision is obtained. One example of the method will be described in reference to
A main die for forming a tooth profile is a die 101. For easy understanding, the die 101 is illustrated in a stationary condition in
The die 101 has a bore 101a. The bore 101a penetrates in a direction of a central axis 106. A female tooth profile 107 is formed on a circumferential surface of the bore 101a. The tooth profile 107 is configured as a normal tooth profile. Reference numeral 103 designates a pitch circle. Reference numeral 104 designates an addendum circle of the tooth profile 107. Reference numeral 105 designates a deddendum circle of the tooth profile 107.
An upper extruding pin 108 is provided above the metal material 100 as a pushing member. The upper extruding pin 108 pushes the metal material 100 from the above.
An upper sleeve 102 is provided around the upper extruding pin 108. The upper sleeve 102 supports the metal material 100 and the upper extruding pin 108 from a side thereof.
A lower extruding pin 109 is provided as a pushing member under the metal material 100. The lower extruding pin 109 pushes the metal material 100 from a bottom thereof A lower sleeve 104 is provided around the lower extruding pin 109. The lower sleeve 104 is fixed and supports the metal material 100 and the lower extruding pin 109 from a side thereof.
A method of manufacturing a gear by cold forging by means of the die 101 etc. of
The metal material 100 is inserted into a central part of the die 101. After that, the upper extruding pin 108 and the upper sleeve 102 move downwardly to enclose the metal material 100.
The upper sleeve 102 and the lower sleeve 104 are stopped.
A pressure in a direction indicated by an arrow C is added on the upper extruding pin 108. A pressure in a direction indicated by an arrow D on the lower extruding pin 104. The upper sleeve 102 is stopped in such a condition that it catches the die 101 as a result of an oil pressure or a spring pressure. Thus, the metal material 100 is stretched toward the tooth profile 107 of the die 101 and formed. Thus, the tooth profile 107 is formed on the metal material 100. By means of the same die, forging condition (forming pressure, speed, etc.) is changed on each forming, or, various dies are used on each forming.
An arrow E of
To remove a formed product 110 from the die 101, the upper extruding pin 108 and the upper sleeve 102 are moved upwardly. After that, the lower extruding pin 109 is moved upwardly to let the formed product 110 out of the die 101.
In this way of forming, since a relative displacement between the formed gear and the die is extremely small, it is possible to form the gear in high precision.
A die 111 for drawing has a bore 111a. The bore 111a penetrates in a direction of a central axis 116. A female tooth profile 114 is formed on a circumferential surface of the bore 111a. Reference numeral 117 designates a pitch circle.
The die 111 for drawing comprises a guide part 112 and a drawing part 113.
The guide part 112 is provided for copying at an opening of the die 111 for drawing. It is preferable to set the pitch circle 117 of the guide part 112 slightly larger in diameter than the pitch circle of the ejected product in the before step. It is preferably set 0.05 to 0.2 mm larger, for example. The length in the axial direction of the guide part 112 is preferably five times or more of the tooth module.
The drawing part 113 is provided at a lower end of the guide part 112. A tooth profile 114 of the drawing part 113 is configured as a normal tooth profile.
When forming a completed tooth profile, an initial step is configured as a stretching step of the metal material, and after that, an ejecting step is performed. Thus, a precise tooth trace is formed. Further, the metal material is inserted into the bore 111a. Then, the metal material is drawn by 0.05 to 0.2 mm in the drawing part 113 as the ejected tooth profile is configured as a copying surface. Thus, it is possible to lower deviations of the tooth profile extremely.
In any embodiment described above, it is preferable to take the processed product out of the die on each of the plural steps of cold forging (at least between stretching and ejecting) and to perform lubricant coating or soften, thereby allowing forging under the low load.
In addition, in any embodiment described above, it is preferable not to forge in an enclosed condition except the final step. In other words, on each of the plural steps (plural cold forgings), it is preferable to stop forming before the addendum part of the processed product reaches the deddendum part of the die in order to avoid increasing of the forming load.
FIGS. 25 to 28 illustrate another embodiment of the present invention. In the embodiment, stretching and ejecting of the metal material are separated into two steps and a sizing (drawing for finishing) step is further combined. Reference numeral 120 designates a gear. Reference numeral 124 designates a pitch circle.
Each step will be described as follows:
In the initial step, a metal material is inserted inside a tooth profile 120a of a predetermined die and stretched. Thus, an initial tooth profile 121 having an addendum part with a large arc shape shown in
In the intermediate step, the initial tooth profile 121 obtained in the initial step is inserted into a die 120c and ejected. The die 120c is different from the die used in the initial step. Thus, a tooth profile 122 shown in
In the completing step, the tooth profile 122 obtained in the intermediate step is sized. Thereby a completed tooth profile 123 shown in
Reference numeral 125 designates a schematic fiber flow after the second step. In the tooth profile 123 obtained, the fiber flow 125 is good and has no cracks. In addition, a radius r designated by reference numeral 120e may have wide allowance if it is a plus value.
Each step will be described as follows:
In the initial step, a metal material is inserted into a predetermined die (not shown) and stretched. Thus, an initial tooth profile 131 having an addendum part having a large arc shape is obtained.
In the intermediate step, the initial tooth profile 131 obtained in the initial step is inserted into a die (not shown) different from the die used in the initial step and ejected. Thereby a tooth profile 132 having an addendum part with a large arc shape is obtained.
In the completing step, the tooth profile 132 obtained in the intermediate step is sized. Thereby a tooth profile 133 is obtained. Reference numeral 130d designates a sizing margin.
Reference numerals 131a, 133a designate tooth shapes of processed products. Spaces designated by reference numerals 135a, 135b remain inside the die. A tip part of the addendum part of the tooth profile formed by ejecting is formed so as not to make contact with an addendum part of the tooth profile of the die. Since the tooth profile 133a has no small angle R, strength against rupture (against crack) of the die improves. The shape of the tip part of the addendum part of the tooth profile formed by ejecting is not limited to an arc. It can be a round shape or other free shape.
The present invention is not limited to the embodiments described above. The present invention is not limited to a mode of enclosed forging. The present invention includes a mode of non-enclosed forging.
Filing Document | Filing Date | Country | Kind | 371c Date |
---|---|---|---|---|
PCT/JP04/15672 | 10/15/2004 | WO | 9/12/2006 |