JP2009156449A - Integrally molded gear with gear and spline shaft - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a transmission gear in which a transmission tooth part and a clutch tooth part are formed substantially by cold forging, and to provide a transmission gear that maintains strength of the gear by eliminating a machining process to leave a fiber composition called a metal flow inside a tooth profile and simplifies the manufacturing process. <P>SOLUTION: In this transmission gear, a large diameter transmission tooth part and a small diameter stepped spline shaft at a lower part of the transmission tooth part are coaxial with each other and integrally formed. The transmission gear comprises a spar tooth or a helical tooth. A clutch spline tooth is formed at a lower end of the spline shaft, and each of the transmission tooth and the spline tooth is formed by cold forging. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

The present invention relates to a sun gear mainly used for AT vehicles. More specifically, gears for oil pumps other than transmissions such as AT cars, MT cars, CVTs, etc., and the spur teeth or helical teeth for shifting and the spline shaft having the spline teeth for clutch are integrated by cold forging. The present invention relates to a transmission gear formed.

Conventionally, in a transmission, a transmission gear having a transmission gear portion and a clutch tooth portion is formed into a general profile shape by hot forging from a disk-shaped or ring-shaped material, and then has a tooth shape by hot forging. Then, machining such as shaving, broaching or hobbing is performed on the transmission gear portion and the clutch spline gear portion. Alternatively, a transmission gear formed by hot forging is machined to form a transmission gear, and then a clutch spline gear formed by cold forging is applied to the transmission gear by an electron beam. There is a method of integrating by welding. In addition, a method of machining each of the transmission gear portion and the clutch tooth portion integrally formed by hot forging is employed. Regarding the manufacture of this type of transmission gear, there has been proposed a transmission gear that integrates the transmission gear portion and the clutch tooth portion as described above (for example, Patent Documents 1, 2, and 3). reference).

Conventionally, gears used in transmissions include transmission gears in which a spur shaft for clutch is integrated with a spur gear, a dog gear or a helical gear of a transmission gear. As a method for forming such a gear, the following method is employed. That is, the first is a method of forming both the transmission gear portion and the spline shaft by cutting with a tool such as a hob cutter. The second is a method in which one of the transmission gear and the spline shaft is formed by cutting, and the other spline shaft is formed by hot or cold forging. Third, there is a method in which one of the transmission gear portion and the spline shaft is formed by hot forging, and then the spline shaft is formed by cold forging using a rolling die.

An example of a transmission gear in which the above-described transmission teeth and clutch spline teeth are integrated is specifically shown in FIGS. As shown in the product W01 in FIG. 5, the gear for the transmission is subjected to machining by shaving or broaching on the helical teeth formed by twisting the upper large diameter portion in the axial direction by forging. The spline teeth 1 are formed integrally with the lower end portion of the spline shaft 3 by rolling. On the other hand, as shown in the product W02 in FIG. 6, the transmission gear is composed of a helical tooth 2 having a large diameter portion and a spline tooth 1 integrally formed by rolling on the lower end portion of the spline shaft 3. Here, a spline groove 8 is formed on the joint surface between the helical tooth 2 and the spline shaft 3 and meshed, and a snap ring 9 is provided at the upper end of the helical tooth 2 so that the helical tooth 2 is integrally coupled to the spline shaft 3. It has been made. Alternatively, the helical teeth 2 may be integrally coupled to the spline shaft 3 by electron beam welding. The helical tooth 2 shown in FIG. 5 or 6 may be a spur gear whose tooth traces are parallel to the axial direction.

Japanese Patent Publication No.49-11543 Japanese Patent Publication No. 6-73712 JP-A-4-36628

As described above, as represented by patent documents, the conventional transmission gear has the following problems.

In the conventional technology represented by the above publication, the gear portion for transmission and the tooth portion for clutch are integrally formed into a schematic shape by hot or cold forging, and then the tooth portion for clutch is, for example, cold Since sizing is performed and machining is finally performed on the transmission gear portion, the number of processes is large and the cost is inevitably increased. Further, for example, hot forging heated to 1150 to 1200 ° C. has a shorter life due to the severe wear of the mold compared to cold forging at room temperature, which is a factor for increasing the gear manufacturing cost for transmissions.

In machining, the gear part is subjected to shaving, broaching, hobbing, etc., so that the metal flow formed by forging is cut, the gear strength is reduced, and further machining is performed. The manufacturing cost increase due to this cannot be avoided.

In addition, since gears for transmissions and teeth for clutches are formed using machining, hot cooling, or intermediate forging, the material must be moved from the forging device to the cutting device during the formation of the tooth profile. There is a problem that the process becomes complicated.

Accordingly, the transmission gear according to the present invention has been made by paying attention to the above-described problems, and the gear teeth for transmission and the gear teeth for clutch are substantially formed by cold forging. The object is to provide a mechanical gear. Another object of the present invention is to provide a transmission gear that retains the strength of the gear by leaving a fiber structure called metal flow by forging in the tooth profile by omitting machining, and simplifies the manufacturing process. It is to provide.

In recent years, with the advance of forging technology, it has become possible to form gears of all shapes by cold forging and omit machining. Therefore, the inventors of the present invention focused on using the metal flow formed by cold forging as it is, and obtained the knowledge that when the gear was prototyped without machining after cold forging, it was excellent in durability. . The transmission gear of the present invention is embodied based on such knowledge, and the invention of claim 1 is characterized in that a large-diameter gear tooth and a small-diameter stepped spline shaft are coaxially and integrally formed thereunder. The transmission gear is formed of spur teeth or helical teeth, the spline teeth for the clutch are formed at the lower end of the spline shaft, and the transmission teeth and spline teeth are Each of the transmission gears is formed by cold forging. The invention of claim 2 is a transmission gear characterized in that, in addition to the above feature of the invention of claim 1, a flange is formed at the upper end of the gear for speed change.

According to the present invention, the gear portion for transmission and the tooth portion for clutch can be integrally formed by cold forging. Therefore, the generation of a molding defect such as a lack of wall is prevented and the tooth profile accuracy is improved. In addition, the following effects are achieved. By integrally forming the gear portion for transmission and the tooth portion for clutch by cold forging, it is not necessary to perform machining, so the metal flow in the tooth profile is held as it is without being cut, so the strength of the gear As a result, an increase in manufacturing cost due to machining can be avoided, and the manufacturing cost of the transmission gear can be kept low. In other words, a gear for transmission and a gear for clutch can be formed from a cylindrical material by cold forging at a stroke, so the cost can be reduced by drastically reducing processing man-hours. In addition, since the cold forging with less wear of the mold is fundamental, the life of the mold itself is extended, the durability is improved, and the cost reduction effect becomes more remarkable.

Embodiments of the present invention will be specifically described below based on the embodiments of the present invention illustrated in the accompanying drawings.

First, Embodiment 1 of the present invention will be described with reference to FIGS. FIG. 1 shows an embodiment of the present invention and is a process diagram showing a manufacturing process of a transmission gear. FIG. 2 is a front view of the transmission gear. FIG. 3 is an explanatory view showing a preferred embodiment related to the manufacture of the transmission gear. FIG. 4 is an explanatory view showing a metal flow in the cold forging.

The manufacturing process of the spline shaft and gear integrally formed transmission gear according to the present invention will be described with reference to the process diagram of FIG. First, as shown in step (1), a material W1 obtained by cutting a cylindrical material suitable for a transmission gear into a predetermined axial length by a billet shear is obtained. In this case, a steel material suitable for the transmission gear, such as SC steel, SCM steel, SNC steel, SNCM steel, SCR steel, etc., can be used as the material of the material. Next, as shown in step (2), the material W1 is heated to, for example, 1150 ° C. and subjected to hot upset forging to obtain a material W2 that approximates the shape of the final product. The shape of the material W2 has a large-diameter portion D2 that expands in the radial direction of the middle stage, a convex portion that protrudes from the upper portion, a shaft extending downward, and a small-diameter portion D1 at the tip. Next, as shown in step (3), the material W2 is pushed into the die die Q1 having a square tooth-shaped spline tooth die T1 from the tip, and is crushed by cold forging, and spline teeth are formed on the outer periphery of the small diameter portion D1. 1 is formed. Finally, as shown in step (4), the material W3 is crushed by cold forging to form helical teeth 2 on the outer periphery of the large diameter portion D2. For this purpose, the large-diameter portion D2 is pushed into a die mold Q2 having a helical tooth mold T2 on the inside, and is crushed to form the helical teeth 2 on the outer periphery. In this way, a product of the transmission gear W in which the helical teeth 2 are formed on the large diameter portion D2 of the middle step portion and the spline teeth 1 are formed on the small diameter portion D1 of the lower end portion is obtained. The speed change gear W is subjected to finish forming by cold forging on the tooth profile as necessary. The helical teeth 2 and the inner spline teeth 1 are formed by compressing in the axial direction and the radial direction while generating a frictional force on the contact surface portion of the tooth profile finishing die by a cold coining process. The cold forging in the last steps (3) and (4) is not particularly limited, but lubrication with a molybdenum disulfide-based lubricant or the like is performed in order to perform cold forging smoothly. Details of the helical teeth in step (4) will be described later with reference to FIG.

FIG. 2 shows the detailed shape of the transmission gear W that has been subjected to the final finishing process in the processes (3) and (4). A helical tooth 2 is formed in the middle stage, and a spline shaft 3 extends below this to form a spline tooth 1 at the tip. Here, in step (4), when the large-diameter portion D2 is pushed into the die mold Q2 and crushed to form the helical teeth 2 on the outer periphery, the tooth profile is formed at the upper end in the axial direction of the large-diameter portion D2 by the tooth mold T2. An unformed flange 4 remains. This portion of the flange 4 may be removed later by cutting.

Here, the formation of the helical tooth 2 in the step (3) will be described in detail with reference to FIG. From the upper side of the figure, an upper die P1, a material W2 below this, and a die die Q recessed below this are shown. The upper die P1 is positioned directly above the lower die Q and can move up and down in the die Q, and crushes the material W2 in the die die Q. A die type Q2 is formed on the upper stage of the die type Q, and has a female type helical tooth type T2 forming helical teeth on the inside thereof. A die type Q1 is formed below, and a female-type spline tooth type T1 that forms spline teeth is provided inside the die type Q1. The large diameter portion D2 and the small diameter portion D1 of the material W2 are adapted to the inner diameters of the tooth mold T1 and the tooth mold T2 of the die mold Q1 and the die mold Q2, respectively. An ejector P3 is provided below these so as to be able to appear and disappear. Here, a female tooth having the same helical tooth profile as the tooth pattern T2 of the helical tooth 2 on the outer periphery of the ejector P3 and having the same lead amount as the tooth pattern T3, and having the same helical tooth profile on the inner periphery of the die Q opposed thereto. Has type T3. A tooth type T3, which is a helical female type, is provided inside the die type Q at a position corresponding to the tooth type T3. In the step (3) shown in FIG. 1, the pre-tooth 1 is formed by cold forging, and then in the step (4), the helical tooth 2 is also formed by cold forging. After that, when the material W3 is taken out from the die mold Q, in the case of straight teeth, it can be pulled out directly above, but the twisted helical tooth 2 needs to rotate relative to the die Q, so it goes straight up. I can't pull it out. In this embodiment, when the ejector P3 is rotated from below the die Q and moved up and down while moving the screw, and the helical tooth 2 is forcibly rotated, it can be taken out efficiently. Here, the twist angle with respect to the vertical axis of the tooth mold T1 is leftward, for example, about 20 degrees.

The helical tooth 2 formed in the step (4) may be a spar tooth profile parallel to the axis, in addition to a tooth profile in which the above-described tooth profile is twisted with respect to the axis. The cross-sectional shape of the lower spline teeth 1 may be an involute tooth profile as required, in addition to the above-described square tooth profile.

The transmission gear of the present invention is configured as described above, and the operation will be described next. In the present invention, the tooth profile is formed by cold forging. As a result, a metal flow fiber structure flow is continuously formed inside the teeth after cold forging. Since there is no machining after forging, a gear having excellent tooth profile surface durability can be obtained without cutting the metal flow.

Details of the formation of this metal flow will be described with reference to FIG. Forged lines called metal flow are formed in a fiber structure in each tooth profile of the spur gear, the helical gear, and the spline gear formed by cold forging. FIG. 1A schematically shows the distribution of forging lines in the tooth profile in cold forging. A forged stream line F, which is a flow of fiber structure, is formed in multiple layers from the outer periphery toward the inside. On the other hand, for comparison, FIG. (B) schematically shows a case where machine chamfering is performed by hobbing, shaving, cutting, or other mechanical processing after forging. Line F is cut. Since the gear for transmission according to the present invention is still cold forged, the metal flow is not cut and the durability of the tooth profile surface is excellent. That is, since the machining process after forging can be omitted, a tooth profile surface with high productivity and high mechanical strength can be obtained.

Since the tooth profile is formed only by cold forging, the forged surface is not scraped off by machining such as shaving, broaching, or hobbing, and the internal metal flow is maintained and the durability of the gear is maintained. Can be improved. Accordingly, the transmission gear according to the present invention is not limited to the use for automobile transmissions, but can be applied to various machine devices such as machine tools, cargo handling construction machines, and robots.

FIG. 4 is a process diagram illustrating a manufacturing process of a transmission gear according to an embodiment of the present invention. FIG. 3 is a front view of the transmission gear. It is explanatory drawing which shows preferable embodiment which concerns on manufacture of the gearwheel for transmissions same as the above. It is explanatory drawing which shows the metal flow in cold forging same as the above. It is a sectional view of a transmission gear, showing a conventional example. FIG. 6 is a cross-sectional view of another transmission gear.

Explanation of symbols

D1 Small diameter part D2 Large diameter part F Forging line M Machined surface P1 Upper mold, P3 Ejector Q, Q1, Q2 Die mold T1, T2, T3 Tooth mold W, W01, W02 Product W1, W2, W3 Material 1 Spline tooth 2 Helical tooth 3 Spline shaft 4 Flange 8 Spline groove 9 Snap ring

Claims (2)

The large-diameter gear teeth and the small-diameter stepped spline shaft are coaxial
And an integrally formed transmission gear,
The gear for shifting is composed of spur teeth or helical teeth,
Spline teeth for the clutch are formed at the lower end of the spline shaft,
The transmission gear and the spline teeth are formed by cold forging, respectively. The transmission gear according to claim 1, wherein a flange is formed at an upper end portion of the transmission gear.

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