JP2542300C - - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a gear tooth formed integrally by forging and used in a synchromesh type transmission, and a smaller diameter than the gear tooth. The present invention relates to a speed-change gear comprising a reversely tapered outer periphery of a boss portion and spline teeth having a chamfer at its tip. 2. Description of the Related Art Conventionally, a transmission gear with clutch spline teeth used in a synchromesh type transmission is provided with a slack at the base of the spline teeth for machining the spline teeth from a gear blank. The method of shaving and forming integrally with the tooth part, and the gear tooth and the clutch spline tooth part whose tooth form is reverse tapered are manufactured individually by machining or cold forging, and the gear tooth of the gear tooth part finished with high precision There is a method in which a clutch spline tooth portion is fitted to the outer periphery, and the outer surface of this joint portion is integrated by electron beam welding. The former has a drawback that the effective length of the spline is shortened because the root is provided with the spline teeth. The latter has the disadvantage that the metal flow between the spline teeth portion and the transmission tooth portion is cut, the strength is weakened, and machining and welding / assembly are required, resulting in an increase in cost. A method of improving the two-piece system and integrally forming the transmission teeth and the spline teeth in the forging process is proposed in, for example, JP-B-49-11543 and JP-A-52-61162. Have been. However, in the former, the spline teeth are straight, and the spline teeth having an inverted taper shape cannot be formed. In the latter case, it is disclosed that the spline teeth are reversely tapered to the boss portion and are integrally formed by cold forming. No. 1 and FIG. 3). Accordingly, in the latter case, the effective length of the spline teeth is short as in the former case, and cutting is required. SUMMARY OF THE INVENTION An object of the present invention is to provide a transmission gear having a long effective spline tooth length, in which an inversely tapered spline tooth is formed up to the base of a boss portion only in a forging process. And In order to achieve the above object, a transmission gear according to the present invention includes a transmission gear formed integrally by forging and a boss having a smaller diameter than the transmission gear. A transmission gear having a reverse tapered outer periphery of the boss portion and spline teeth having a chamfer at the tip, wherein the reverse tapered spline teeth are formed to the root of the boss portion by forging. After forcibly sliding the die radially arranged with respect to the gear axis between the spline teeth parallel to the gear axis and sliding the die toward the center of the gear in a direction perpendicular to the gear axis, the die is inserted into the gear axis. It is formed up to the root of the boss by forcibly sliding and pulling out from the center of the gear toward the outside in the perpendicular direction, and the shape of the tip of the die is
It is characterized by being formed in a shape according to. FIG. 1 is a front view showing a transmission gear according to the present invention. Reference numeral 1 denotes a gear, reference numeral 2 denotes a transmission gear formed on the outer periphery of the gear, for example, helical teeth, and reference numeral 3 denotes this gear. A boss portion having a diameter slightly smaller than the outer diameter of the gear is provided on one side of the gear 1. The boss portion 3 is formed integrally with the body 1 of the gear, and the outer peripheral surface of the boss portion 3 An inverted tapered spline tooth 4 is formed for stopping. The spline teeth 4 are formed so as to reach the root of the boss portion 3, that is, the connection portion with the gear portion. Next, a manufacturing apparatus and a manufacturing method of the transmission gear of the present invention will be described. Steel materials usable as gears, for example, SC steel, SCM steel, SNC steel, SNCM
In general, a rod-shaped material such as steel, SCR steel or the like is cut so as to be suitable for the size, shape, diameter, etc. of the gear to be manufactured (FIG. 3A). The raw material W cut to the required length is then heated at a heating temperature determined according to the type, size, and weight of the raw material so as to be a temperature suitable for hot forging, that is, plastic working. The heated material W is hot-forged or plastically worked in the upsetting process in accordance with the shape of the gear to be formed, and is upset like the material HW (FIG. 3 (2)). In this case, the upsetting outer diameter is adjusted to the outer diameter of the gear to be manufactured so as to be suitable for the plastic working in the next step. Next, the set-up material HW is placed in a forging die, and is subjected to a single process or a plurality of processes such as a roughing process and a finishing process to form the speed changing tooth portion and the groove-shaped portion serving as the spline teeth into the material FW. (FIG. 3 (3)). The spline teeth 4 formed by this forging die are made slightly smaller than the finished dimensions, and then the teeth are formed to a predetermined size and a predetermined shape in a cold coining step of plastically processing the extra thickness inside the shaft hole side to the outside of the material. Be accurate. Then, as a pretreatment of the cold coining step, a shaft hole 5 is made in the material FW having the outer shape of the gear (FIG. 3D). Also in this case, the diameter of the shaft hole 5 is smaller than the set diameter of the shaft hole, and the shaft hole portion has a surplus portion. After this drilling step, other necessary post-processing steps such as normalizing, shot blasting and the like may be obtained as necessary. [0010] The material FW on which the spline teeth have been formed in advance in this way is then sent to a cold coining step. In this cold coining, the excess thickness inside the shaft hole side is pushed out to the outside of the material so that the spline teeth have a predetermined dimension and a predetermined accuracy (FIG. 3 (5)). The material on which the spline teeth parallel to the gear axis are formed is sent to the step of forming the reverse tapered spline teeth (FIG. 3 (6)). The formation of the reverse tapered spline teeth is performed using the manufacturing apparatus shown in FIG. Next, the manufacturing apparatus will be described. The upper mold 11 is attached to the upper mold mounting base 12 in a state where the spring is lowered, and the lower mold 13 facing the upper mold 11 is fixed to the lower mold mounting base 14.
The punch 15 protruding from the lower die 13 is penetrated through the lower die 13, and a cylindrical knockout cylinder 16 is disposed around the outer periphery of the punch 15.
7 is fixed. When forming a tooth profile in the case 17 in the process of forming the reverse tapered spline teeth, a large number of cam fitting holes 17H corresponding to the inter-tooth angle and the number of teeth of the gear are formed at a constant pitch. The inner surface on the outer peripheral side of the hole 17H is the cam pressing surface 1
7F, the cam pressing surface is a plane that is perpendicular and perpendicular to the longitudinal axis of the die 23, and the cam 21 is fitted into each of the holes 17H. An annular flange 18 supported by a spring 24 attached to the lower die mount 14 is provided on the lower die mount 14, and a cam fitted into the cam fitting hole 17H by the annular flange 18. The cam 21 is bolted to the flange 18 so as to support the bottom of 21. The cam 21 is finished in a planar shape and with high precision so that the back surface thereof is in contact with the cam pressing surface 17F, and the pin 22 is protruded and fixed to the lower inside so that the upper end side is inclined inward. In addition, a die pressing surface 21T having an inclination angle equal to the inclination angle of the pin 22 is formed on the inner surface of the cam and opposed to the pin 22. As shown in FIG. 6 and FIG. 7, a die fitting insertion hole 13H is formed at an upper portion of the lower die 13 at a predetermined angle so as to be aligned with a straight line toward the center of the lower die. At the same time, this die fitting insertion hole 13H has a circular cross section and its top is cut into a flat shape.
Dies 23 each having an open shape and each having a round bar-shaped upper surface cut into a flat shape are fitted into each of the die fitting insertion holes 13H, and the die 23 is radially arranged. , The die 23 does not rotate. The tip 23D of the die 23 can form a predetermined reverse tapered spline tooth on the gear. A pin hole 23H for inserting the pin 22 is formed in the die 23, and a rear end 23T of the die 23 is formed on an inclined surface. After the material FW mounted in the lower mold 13 is formed into reverse tapered spline teeth by the die 23 by lowering the upper mold 11, when the material FW is taken out from the lower mold, the knockout pins 19 are formed. , 20 and the knockout cylinder 16 so as to be easily taken out. After the knockout pin 19 pushes up the flange 18 quickly, the knockout pins 19 and 20 are pushed so that the knockout pin 20 pushes up the knockout cylinder 16.
Determine the length of Thus, after the die 23 is pulled out from the tooth portion of the material FW, the material FW is made to protrude from the lower mold. The raw material FW in which the spline teeth have been formed in the forging process by the manufacturing apparatus configured as described above is set in the lower die 13. Next, when the upper mold base 12 is lowered, the material FW is sandwiched between the upper and lower molds by the upper mold 11 under spring pressure, and the cam 21
Is pressed slightly later than the clamping of the material FW. As a result, the cam 21 and the flange 18 are pushed down, whereby the tapered die pressing surface 21T of the cam 21 pushes the rear end 23T of the die 23, and each die 23 is
3, that is, in the axial direction of the gear,
At D, the spline teeth 4 of the material FW are formed into predetermined reverse tapered spline teeth. Thereafter, the upper die mount 12 is raised and the knockout pin 19 is pushed up. Thereby, the flange 18 also returns. When the flange 18 returns, that is, rises, the cam 21 also rises.
2 is inserted into the pin hole 23H of the die 23, so that the die 23, which can be slid only radially in a state of being inserted into the lower mold 13 in accordance with the rise of the pin 22, is provided with a gear. Forcibly slides and returns in the direction opposite to the axial direction. After the tip 23 D of the die 23 is separated from the teeth of the material FW, the knockout pin 20 is pushed up. As a result, the knockout cylinder 16 is pushed up, and the material FW is pushed up from the lower mold 13 and taken out from the lower mold 13. According to the speed change gear of the present invention, the reverse tapered spline teeth are radially formed with respect to the gear axis between spline teeth formed parallel to the gear axis formed to the root of the boss by forging. After forcibly sliding the arranged die toward the gear center in a direction perpendicular to the gear axis and pushing it in, the die is forced to slide outward from the gear center in a direction perpendicular to the gear axis. Since the spline teeth are formed by pulling out, spline teeth formed on the outer periphery of the boss portion and having a reverse tapered shape and having a chamfer at the tip end thereof have high precision. In addition, since the speed change gear is manufactured only in the forging process, the manufacturing process can be simplified, and since the metal flow is not cut, the strength of the spline teeth increases, and the processing accuracy of the spline teeth increases. In addition to the fact that the effective length of the spline teeth with respect to the length of the boss portion is large, there is an advantage that the speed change gear can be downsized.

[Brief description of the drawings]     FIG.   It is a front view of the gear for speed change of the present invention.     FIG. 2   It is sectional drawing of the gear for speed change of this invention.     FIG. 3   It is explanatory drawing which shows the manufacturing process of a gear for transmission.     FIG. 4   It is a longitudinal cross-sectional view of the manufacturing apparatus of a transmission gear.     FIG. 5   It is a cross-sectional view of the manufacturing apparatus of the gear for transmission.     FIG. 6   It is a top view of the lower type | mold of the manufacturing apparatus of a transmission gear.     FIG. 7   It is a front view which shows a part of lower mold | type of the manufacturing apparatus of a transmission gear.     FIG. 8   It is explanatory drawing of the die of the manufacturing apparatus of a transmission gear.     [Explanation of symbols]   FW material   HW material   W material   1 gear   2 helical teeth   3 Boss   4 spline teeth   11 Upper type   13 Lower mold   17 cases   18 Flange   21 cams   22 pin   23 die

Claims (1)

Claims: 1. A speed change tooth portion integrally formed by forging, and a boss portion having a smaller diameter than the speed change tooth portion. A transmission gear formed with spline teeth having chamfers, wherein the reverse tapered spline teeth are radially formed with respect to the gear axis between spline teeth parallel to the gear axis formed to the root of the boss by forging. After forcedly sliding the die disposed in the direction perpendicular to the gear axis toward the center of the gear and pushing it in, the die is forced to slide outward from the center of the gear in a direction perpendicular to the gear axis. A speed change gear formed so as to be formed up to the root of the boss portion by being pulled out and to conform to the shape of the tip of the die .