JP5134360B2 - Integrated molded internal gear - Google Patents

Description

The present invention relates to a speed change gear that is integrally formed by cold forging and is mainly used in a transmission of an automobile. More specifically, the outer peripheral gear portion and the inner peripheral transmission gear portion are annular transmission gears integrally formed by cold forging, and the outer peripheral clutch gear portion is composed of a spline gear. The inner peripheral speed change gear portion relates to a speed change gear constituted by a spur gear or a helical gear.

Conventionally, in a transmission, a transmission gear having a transmission gear portion and a clutch gear portion is formed into a general shape by hot forging from a disk-shaped or ring-shaped material, and then a tooth portion is formed by hot forging. Then, machining such as shaving, broaching or hobbing is performed on the gear section for transmission and the clutch spline gear section. Alternatively, the transmission gear portion formed by hot forging is machined to form a transmission gear, and then the clutch spline gear portion formed by cold forging is electron beam welded to the transmission gear portion. There is a way to integrate. In addition, a method of machining each of the transmission gear portion and the clutch gear 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 gear portion as described above (see, for example, Patent Documents 1, 2, and 3).

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

An example of an annular transmission gear in which the aforementioned transmission gear portion and clutch gear portion are integrated is specifically shown in FIGS. In FIG. 6, a spline gear 5 is formed by subjecting a spline gear having an outer peripheral square tooth shape formed by cold forging to machining by shaving or broach, and a spur gear integrally formed by cold forging is formed on the inner side. The spur gear 5 is formed by machining with a broach. Then, a disc-shaped bottom plate 3 having holes 4 is integrally coupled to the annular inner / outer integrated gear from below by electron beam welding. In this way, the gear W for shifting gears W0 having the annular welded portion 9 at the bottom is obtained. Similarly, in FIG. 7, instead of the electron beam welding described above, the disk-shaped bottom plate 3 with the holes 4 drilled is joined from below to a machined annular internal / external integrated gear using a snap ring 10 to change the speed. A gear product W0 is obtained. The inner periphery of the spline gear 5 indicates a helical gear 7 that is twisted in the axial direction. Here, the spline gear 5 on the outer periphery shown in FIG. 6 or FIG. 7 may have an involute tooth profile in addition to a square tooth cross section, and the internal gear may be not only a spur gear parallel to the axis but also a twisted helical gear.

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 speed change gear has the following problems.

In the conventional technology represented by the above publication, the gear portion for transmission and the gear portion for clutch are integrally formed into a schematic shape by hot or cold forging, and then the clutch gear portion is subjected to, for example, cold sizing. In the end, machining is performed on the gear portion for transmission, and the number of processes is large, resulting in an increase in cost. Further, for example, hot forging heated to 1150 to 1200 ° C. has a shorter life due to the severe wear of the mold as compared with cold forging at room temperature, and this is a factor for increasing the manufacturing cost of the transmission gear.

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 speed change and gears for clutch are formed by machining, hot cooling, or intermediate forging, the material must be moved from the forging device to the cutting device in the middle of forming the tooth profile. In other words, there is a problem that the process becomes complicated.

Therefore, the speed change gear of the present invention is made by paying attention to the above-mentioned problems, and it is assumed that a disk-shaped material is used, and only a cold forging process is substantially performed. Thus, an object of the present invention is to provide a transmission gear in which a transmission gear portion and a clutch gear portion are integrated. Another object of the present invention is to provide a speed change gear that keeps 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. There is to do.

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 speed change gear of the present invention is embodied based on such knowledge, and the invention of claim 1 is composed of a disc-shaped bottom plate and an annular gear portion standing and integrated from the bottom plate. The annular gear portion is composed of an outer clutch gear portion and an inner speed gear portion, the clutch gear portion is a spline gear parallel to the axis, and the speed gear portion is The spur gear or the helical gear is formed by cold forging, and the gear portions are integrally erected by cold forging with respect to the disc-shaped bottom plate, and A gear for shifting, in which forged lines are formed in a fiber structure in the tooth profile of the gear , wherein the disk-shaped bottom plate is raised toward the center . According to a second aspect of the present invention, in addition to the above feature of the first aspect of the present invention, a relief portion that is recessed over the entire circumference of the disc-shaped bottom plate is formed at the base of the inner peripheral transmission gear portion. The speed change gear according to claim 1.

According to the present invention, it is possible to integrally form the transmission gear portion and the clutch gear portion by cold forging. Therefore, the occurrence of molding defects such as lacking is prevented, and the tooth profile accuracy is improved. The effect of this is achieved. By integrally forming the gear section for transmission and the clutch gear section by cold forging, it is not necessary to perform machining, so the metal flow in the tooth profile is maintained without being cut, so the strength of the gear is improved. In addition, an increase in manufacturing cost due to machining can be avoided, and the manufacturing cost of the transmission gear can be kept low. That is, since it is possible to form a transmission gear provided with a transmission gear portion and a clutch gear portion from a cylindrical material by cold forging at a stretch, it is possible to reduce costs by greatly reducing the number of processing steps, Further, 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 cross-sectional view of an annular transmission gear. FIG. 3 is an explanatory view showing a preferred embodiment according to the manufacture of the gear portion for transmission. FIG. 4 is a sectional view of an annular transmission gear according to another embodiment. FIG. 5 is an explanatory view showing a metal flow in the cold forging.

A method of forming the transmission gear according to the present invention will be described with reference to the process diagram of FIG. 1 with respect to an embodiment of forming the annular transmission gear shown in FIG. First, from a round bar material suitable for a transmission gear to be manufactured, a saw-shaped material W1 is obtained by performing sawing to a predetermined axial length as shown in the step (1) by a saw. In this case, the steel material suitable for the gear for gear change, for example, SC steel, SCM steel, SNC steel, SNCM steel, SCR steel, etc. can be used.

In the subsequent processes, the clutch gear part and the transmission gear part are integrated by forming a spline gear parallel to the axis in the clutch gear part and a spur gear parallel to the axis in the transmission gear part. Get. In all the cold forging processes in the process, although not particularly limited, a lubrication treatment with a molybdenum disulfide-based lubricant or the like is performed in order to perform cold forging smoothly. As shown in step (2), a bowl-shaped material W2 having a circular recess 2 and a bottom plate 3 recessed by cold forging is obtained. Next, as shown in step (3), the center portion of the bottom plate 3 is A material W3 is obtained in which the through-hole 4 is drilled by cold forging. Next, as shown in step (4), a notched portion E that is recessed over the entire circumference is formed by cold forging the lower portion of the outer circumference in the direction of the arrow with the annular lower die P1. Here, by forming the notch portion E, it becomes easy to perform gear cutting of the outer peripheral portion described later, and thus the material W4 is obtained. Through the above process, a material before molding the clutch gear part and the transmission gear part is obtained.

Hereinafter, the process proceeds to a process of forming the clutch gear portion and the transmission gear portion by cold forging. As shown in step (5), by raising the lower die P2 having spline teeth from the lower side of the material, the spline gear 5 having a square tooth cross-sectional shape as the clutch gear portion is parallel to the axis over the entire outer periphery. The material W5 is obtained. Here, the annular lower mold P2 includes a tooth mold T2 having a square tooth profile corresponding to the spline gear 5 on the inner peripheral surface. Next, as shown in step (6), a normalizing heat treatment N is performed at a temperature suitable for softening the material W5. Next, the heat-treated bowl-shaped material is set upside down to form a transmission gear portion on the inner peripheral surface of the annular portion. As shown in step (7), by raising the lower mold P3, a spur gear 6 parallel to the axis is formed as a transmission gear over the entire inner circumference of the recess 2. Here, the lower mold P3 includes a spur tooth pattern T3 corresponding to the spur gear 6 on the outer periphery. Through this process, a product W is obtained in which the clutch gear portion and the transmission gear portion are integrally formed by cold forging. In addition, about process (4), (5), and (7), the description of the upper type | mold or die type | mold which supports a raw material from the upper direction and the periphery was abbreviate | omitted for simplicity.

The internal gear formed in the step (7) may be a helical gear twisted in addition to the spur gear whose tooth profile is parallel to the axis. A preferred embodiment for forming a helical gear in FIG. 3 will be described in detail. A helical gear is formed on the inner periphery of the annular portion by turning the heat-treated bowl-shaped material upside down. As an apparatus for forming a tooth profile, a mandrel P4 is provided on the inner side of a die-type Q supported from the periphery, and the mandrel P4 is raised toward the recess 2 of the bowl-shaped material, whereby the axis line extends over the entire inner periphery of the recess 2. A helical gear that is twisted with respect to is formed. Through this process, a product W is obtained in which a helical gear is formed on the inner peripheral gear section. Here, a helical tooth profile T4 is provided on the outer peripheral surface of the mandrel P4. In forming the helical gear, since the helical gear 7 is twisted with respect to the axis, the relative rotation between the mandrel P4 and the product W is allowed when the product W is taken out. It is efficient to provide a helical tooth profile T5 that meshes with the ejector P5 so that the ejector P5 rotates and moves up and down along the helical tooth profile T4, and the tooth-shaped product W is forcibly rotated. Can be taken out well. In this way, as shown in FIG. 4, an annular transmission gear product W having a helical gear 7 on the inner periphery is obtained. If necessary, the bottom plate 3 is raised toward the center hole 4 and deformed. In the root of the helical gear 7 constituting the internal gear, a relief portion 8 that is recessed in the bottom plate 3 is formed over the entire circumference. By having the recessed relief portion 8, in the step (7) of FIG. 1, when the lower die P3 is pushed up from below and the internal gear is formed on the inner periphery, the tooth profile T3 is formed, so the tooth profile can be easily formed. become. Similarly, in the case of forming a spur gear parallel to the axis, a relief portion 8 that is recessed in the bottom plate 3 is formed at the base over the entire circumference.

The cross-sectional shape of the outer spline gear 5 may be an involute tooth profile as required, in addition to the above-described square tooth profile.

The speed change 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 shifting 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. Therefore, the gear of the present invention can be applied not only to the use of automobile transmissions but also 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 cross-sectional view of the transmission gear. It is explanatory drawing which shows preferable embodiment which concerns on manufacture of the gearwheel part for transmission same as the above. FIG. 6 is a cross-sectional view of a transmission gear according to another embodiment. It is explanatory drawing which shows the metal flow in cold forging same as the above. FIG. 9 is a cross-sectional view of a transmission gear, showing a conventional example. FIG. 5 is a cross-sectional view of another speed change gear.

Explanation of symbols

E Notch N Normalizing heat treatment F Forging line M Machined surface P1, P2, P3 Lower mold P4 Mandrel P5 Ejector Q Die mold T2, T3, T4, T5 Tooth mold W, W0 Product W1, W2, W3, W4 , W5 Material 1 Gear body 2 Recess 3 Bottom plate 4 Hole 5 Spline gear 6 Spur gear 7 Helical gear 8 Escape portion 9 Welded portion 10 Snap ring

Claims (2)

Consists of a disc-shaped bottom plate and an annular gear unit that is erected and integrated from the bottom plate ,
This annular gear portion is composed of an outer clutch gear portion and an inner transmission gear portion,
The clutch gear is a spline gear parallel to the axis,
And, the gear portion for transmission consists of a spur gear or a helical gear,
Each of the gear portions is formed by cold forging,
The gear part is erected integrally with the disk-shaped bottom plate by cold forging,
And, a gear for shifting, in which a forged line is formed in a fiber structure in the tooth profile of each gear ,
The speed change gear, wherein the disk-shaped bottom plate is raised toward the center . At the root of the inner peripheral gear section,
The speed change gear according to claim 1, wherein a relief portion that is recessed over the entire circumference of the disk-shaped bottom plate is provided.

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