JP2005342779A - Method for forming gear - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for forming a gear with which the formation of the gear can be performed by a simple process and in good precision. <P>SOLUTION: The processes for forming an internal gear 2, are as the followings, in which firstly, a material is cut off (B1); an outer shape forming process is performed with hot-forging (B2); successively, oxidized film formed on a product surface with the hot-forging is removed by applying shot-blasting (B3); successively, lubricating treatment is performed (a lubricating treatment process B4); a die and the material are irradiated with near infrared rays and heated to 50-200°C (a heating process B5); and an extrusion-formation is performed with cold-forging (an extrusion-working process B6). <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a gear forming method, and more particularly to a method of forming a gear by cold forging.

  Conventionally, the gear is formed by hot forging to adjust the shape as an intermediate product, followed by shot blasting to remove the oxide film formed on the product surface, lubrication, and cold at room temperature. A method of forging was known.

For example, in the molding method disclosed in Japanese Patent Application Laid-Open No. 10-99937 (Patent Document 1), as shown in FIG. 3B, first, the material is cut (B11), and then by hot forging. A gear material was formed into a gear by cold forging at room temperature after molding into a predetermined shape including a tooth portion (B12), shot blasting (B13) and lubrication (B14) (B15). According to the gear forming method disclosed in Patent Document 1, in cold forging, the tooth profile accuracy is obtained by ironing the tooth portion of the gear material formed by hot forging. In particular, it is said that the occurrence of galling of the mold with respect to the tooth bottom, which has been conventionally observed, can be prevented by making the amount of ironing of the tooth bottom surface smaller than the amount of ironing on the tooth tip surface and the tooth surface.
JP-A-10-99937

  However, in the forming method disclosed in Patent Document 1, ironing is performed in cold forging, and in particular, the ironing amount of the tooth bottom surface is made smaller than the ironing amount of the tooth tip surface and the tooth surface. Since the hot forging is formed in a state close to the completed dimensions, the hot forging has a problem that it is necessary to sufficiently control the heating temperature.

  Further, when cold forging is performed at room temperature, there is a problem that the dimension of the molded product changes as the number of processes increases (see FIG. 6). Further, when cold forging is performed at room temperature, there is a problem that the load for forming is large when the number of processing is small and decreases as the number of processing increases (see FIG. 7). That is, when the number of processing exceeds a predetermined number, a small pressing device may be used, but there is a problem that a large pressing device is necessary because the load is large when the number of processing is small.

  In the case of an internal gear (internal gear), if the tooth bottom length BL (see FIG. 2) is short, galling is likely to occur when the number of machining is small. This is particularly noticeable when the root length BL is 0.3 mm or less.

  The present invention solves the above-described problems, and an object of the present invention is to provide a gear forming method capable of forming a gear with high accuracy by a simple process.

  In order to achieve this object, the gear forming method according to claim 1 includes: an outer shape forming step in which a gear material is hot forged to form an outer shape of the gear; and a gear material formed by the outer shape forming step is lubricated. A lubrication treatment step for performing the treatment, a heating step for heating the gear material or mold lubricated by the lubrication treatment step from 50 ° C. (hereinafter referred to as C) to 200 ° C., and A gear material or a mold heated from 50 ° C. to 200 ° C. by a temperature process is extruded in cold forging to form a gear tooth profile.

  A gear forming method according to a second aspect is the gear forming method according to the first aspect, wherein the heating step heats only the mold out of the gear material and the mold.

  According to a third aspect of the present invention, there is provided a method of forming a gear according to the first aspect of the present invention, wherein the heating step heats at least the gear material out of the gear material and the mold.

  A gear forming method according to a fourth aspect is the gear forming method according to any one of the first to third aspects, wherein the heating step is performed by irradiating near infrared rays.

  The gear forming method according to claim 5 is the gear forming method according to any one of claims 1 to 4, wherein the gear is an internal gear.

  A gear forming method according to a sixth aspect is the gear forming method according to the fifth aspect, wherein the gear is a helical internal gear.

  According to the method for forming a gear according to claim 1, in the outer shape forming process in which the gear material is hot forged to shape the outer shape of the gear, since a tooth shape is not formed, a highly accurate mold is not required, There is an effect that temperature control at the time of forging is easy. Further, since the mold or the gear material is heated by the heating process of heating the gear material or the mold from 50 degrees C to 200 degrees C, it is possible to prevent galling in the extrusion process. In particular, it is possible to prevent galling even in an internal gear having a short root length. In addition, since the forming load can be reduced at the initial stage where the number of processing when manufacturing a large number of gears is small, the press device can be downsized. In addition, when manufacturing a large number of gears, there is little variation between the dimensions of the gears formed at the initial stage where the number of processing is small and the dimensions of the gears formed at the stage where the number of processing is large. It can be performed. In addition, since the heating temperature is set within a range not exceeding 200 ° C., the coating applied to the gear material by the lubrication process does not deteriorate, and seizure and galling do not occur between the mold and the gear material. The life of the mold is not shortened.

  According to the method for forming a gear according to claim 2, in addition to the effect produced by the method for forming a gear according to claim 1, the heating step only heats the mold. If the mold is first heated and continuously processed, the temperature of the mold is maintained by the heat generated by the processing, and thus it is not necessary to heat the subsequent processes. Therefore, since there is little fluctuation | variation with the dimension of the gearwheel shape | molded in the initial stage with few numbers of processes, and the dimension of the gearwheel shape | molded in the stage with many numbers of processes, it can shape | mold highly accurately.

  According to the method for forming a gear according to claim 3, in addition to the effect produced by the method for forming a gear according to claim 1, the heating step heats at least the gear material out of the gear material and the mold. Therefore, when processing a large number of gears, the molding load can be reduced at the initial stage of processing and the number of processes increased compared to when processing at normal temperature, and the press device can be downsized. effective.

  According to the method for forming a gear according to claim 4, in addition to the effect exhibited by the method for forming a gear according to any one of claims 1 to 3, the heating step is performed by irradiating near infrared rays. When heating is performed using infrared rays or mid-infrared rays, it takes a long time to warm to a predetermined temperature, and there is an effect that the heating can be efficiently performed in a short time.

  According to the method for forming a gear according to claim 5, in addition to the effect produced by the method for forming a gear according to any one of claims 1 to 4, the gear is an internal gear and the tooth bottom length of the internal gear is When it is short (the root diameter is large), it is possible to prevent galling.

  According to the method for forming a gear according to claim 6, in addition to the effect produced by the method for forming a gear according to claim 5, the gear is a helical internal gear, and when the inclination angle of the helical tooth is large, the forming is performed. Although the load increases, there is an effect that the molding load can be more significantly reduced by heating.

  Hereinafter, preferred embodiments of the present invention will be described with reference to the accompanying drawings. FIG. 1 is a diagram showing a planetary gear device which is an example of a gear device manufactured according to the present invention. The sun gear 3 is coaxially fitted to the axial center portion of the ring-shaped internal gear 2, and three planetary gears 4 are arranged at equal intervals between the internal gear 2 and the sun gear 3. Meshes with the internal gear 2 and the sun gear 3. The three planetary gears 4 are connected to each other by a planet carrier 5. The teeth 2a, 3a, 4a of the internal gear 2, the sun gear 3, and the planetary gear 4 are helical teeth that are inclined at a predetermined angle with respect to the axis.

  FIG. 2 is an enlarged perspective view of a tooth portion of the internal gear 2 formed according to the present invention. The tooth 2a of the internal gear 2 is a helical tooth that is inclined at a predetermined angle with respect to the axial center line, and the tooth thickness T is the same thickness over the entire length of the tooth. Are formed at an equal pitch. The root length BL needs to be formed short in order to transmit a large torque. When the root length BL is short, galling tends to occur in cold forging. Similarly, the teeth of the sun gear 3 and the planetary gear 4 are formed into helical teeth.

  FIG. 3 (A) shows the process of molding the internal gear 2 of the present invention. First, the material is cut (B1), the outer shape is formed by hot forging (B2), and then shot blasting is performed. The oxide film formed on the surface of the product by hot forging is removed (B3), and then a lubrication process is performed (lubricating process, B4), and near infrared rays are irradiated to the mold and the material at 50 to 200 degrees. C is heated (warming process, B5), and extrusion molding is performed by cold forging (extrusion process, B6).

  In the outer shape forming step B2, the outer shape is formed along the tooth tip diameter of the gear, and the tooth surface and the tooth bottom which are tooth shapes are not formed. In the lubrication treatment step B4, a method of forming a zinc phosphate coating on the surface of the gear material called bonderite treatment is used. The film formed by this bonderite treatment becomes cocoon-shaped when the temperature exceeds 200 ° C., and the lubricating ability decreases. When the lubrication capability is lowered, seizure or galling occurs between the mold and the material, and the life of the mold may be shortened or the processing itself may be impossible. Therefore, in the present invention, the temperature to be heated is set in a range not exceeding 200 degrees C.

  As a method of the heating step B5, a method of irradiating a mold or a gear material with near infrared rays is used. According to this method, it is possible to heat to a predetermined temperature in a short time. As another method, there is a method in which a liquid such as water or oil is heated and immersed in the liquid, and in the case of a mold, there is a method in which it is heated in an electric furnace.

  The details of the extrusion process by cold forging will be described later. After the extrusion process, the gear material is subjected to sizing. This sizing process is cold forging that improves dimensional accuracy. Then, if necessary, machining such as turning is performed to remove burrs and improve dimensional accuracy, and finally quenching is performed.

  FIG. 4 is a diagram illustrating the operation of the mold apparatus 9 that performs cold forging using the mold and the material heated to 50 to 200 degrees C as described above. The mold apparatus 9 is mounted on a press apparatus (not shown) to perform molding processing. A mandrel 10 is disposed at the axial center of the container 6, the container 6 is fitted and held by a clamp 7 and is rotatably mounted on the lower plate 8, and is mounted on the lower plate 8 by a cylinder of a pressing device (not shown). It is formed to be movable up and down by a predetermined amount.

  The container 6 has a circular along-hole 6a through which a ring-shaped material W passes at the axial center thereof, and an annular molding space (a) in which the mandrel 10 is fitted concentrically is formed in the insertion hole 6a. . The mandrel 10 is rotatably mounted on the lower plate 8, and molding teeth 11 are formed on the outer periphery of the lower plate 8 at a predetermined pitch in the circumferential direction.

  This forming tooth 11 is a helical forming tooth inclined at a predetermined angle with respect to the axial center line of the mandrel 10, and the upstream side to which the material W is supplied as shown in FIG. The downstream side from which the air is discharged is referred to as finish molding tooth 11b. The pre-formed tooth 11a is formed in a tooth profile that is negatively displaced with respect to the tooth 2a of the target internal gear 2, and covers the diameter D3 of the root circle, the diameter D5 of the tip circle, and the tooth thickness T. The tooth tip portion of the upstream side 11a-1 is raised at a gentle angle with an inclination angle α of about 15 degrees, and the raised portion 11a-2 is directed to the downstream side. Extend the specified length.

  The finish molding teeth 11b are formed in a tooth profile that is substantially equal to the teeth 2a of the target internal gear 2. That is, the diameter D3 of the root circle, the diameter D5 of the tooth tip circle, and the tooth thickness T are made substantially equal to those of the internal gear 2 and the tooth tip portion is formed from the downstream end 11a-2 of the preformed tooth 11a. The tilt angle β is raised at a gentle angle of about 15 degrees. The tooth bottom portion on the downstream side 11-b is raised from a downstream end of the tooth bottom portion on the upstream side 11-a by a gentle arc having a radius R of about 45 mm, and the raised portion is extended by a predetermined length.

  A cylindrical punch 13 is disposed above the container 6 and the mandrel 10, and the punch 13 is moved up and down by a ram so that its lower end can be fitted into an annular molding space (a) and moved downward. When done, the material W fitted in the molding space (a) is pressed and moved downward. In the molding space (A), for example, three materials W1, W2, and W3 are sequentially stacked and fitted, and each time the punch 13 moves downward, one portion of the material W is 11 parts of the first molding tooth. And helical teeth are formed on the inner peripheral surface of the material W.

  When the punch 13 is moved downward, as shown in the left half of FIG. 4, the container 6 and the mandrel 10 are moved downward to come into contact with the lower plate 8, and the lowermost material W1 is formed into 11 molded teeth. And helical teeth are formed on the inner peripheral surface of the material W1, and the helical internal gear 2 having the helical teeth 14a on the inner periphery is obtained. When the punch 13 is moved upward, as shown in the right half of FIG. 4, the container 6 is moved upward by a predetermined amount by the cylinder, and accordingly, the mandrel 10 is interposed in the molding space (a). It is moved upward by a predetermined amount via the material W. Thereby, an extraction space (A) is formed in the upper part of the lower plate 8, and the internal gear 2 (the material W1 in which helical teeth are formed) that has dropped onto the lower plate 8 can be taken out. After that, the punch 13 moves further upward as shown by the phantom line in FIG. 1 to move away from the container 6 and the mandrel 10 so that a new material W can be fitted into the molding space (a) from above. Yes.

  FIG. 6 is a graph showing the B.B. of the formed gear with respect to the number of processed cases of forming at normal temperature and forming by heating. B. D. It is a figure which shows the change of. Here, B.I. B. D. Is an acronym for Between Balls Diameter, which is a measurement method in which a hard ball (Ball) is sandwiched between the tooth surfaces of the teeth sandwiching the diameter of the gear and the length between the hard balls is measured. In this figure, both the mold and the material are molded at room temperature, the mold and the material are heated to 100 degrees C, the mold alone is heated to 100 degrees C, and only the material is 100 In the case of heating to degree C, the horizontal axis is the machining number, and the vertical axis is B.P. B. D. It is displayed together with the upper and lower limits of the finished product.

  As is apparent from this figure, in the initial stage of processing up to 20, the case of normal temperature and the case of heating only the material are B. D. It is recognized that the value of increases gradually. On the other hand, when only the mold is heated and when both the mold and the material are heated, the B.V. B. D. The value is obtained. When the number of processing exceeds 30, the variation is reduced in any case, and a stable dimension can be obtained.

  Therefore, if only the mold is heated, or if the mold and the material are heated, a gear having a stable dimension can be manufactured without being affected by the number of processes.

  Similarly, FIG. 7 is a diagram showing a change in load required for molding with respect to the number of processing in the case of molding at normal temperature and in the case of molding by heating. The horizontal axis is the number of processes, the vertical axis is the forming load, and the unit of the load is represented by KN (kilonewton).

  As is apparent from this figure, in the initial stage of processing up to 20, the molding load gradually decreases, but compared to the case at room temperature, the material or the mold, both the material and the mold are added. In the case of warming, the molding load becomes small at the initial stage of processing up to 20 pieces. In particular, it can be seen that when only the material is heated and when both the material and the mold are heated, the molding load is smaller than the normal temperature when the number of processing exceeds 20.

  Therefore, by heating the material or the material and the mold, the molding load can be reduced, so that the press device can be reduced in size.

  As described above, according to the method for forming a gear according to the present invention, the outer shape of the gear is formed by hot forging and lubrication is performed, and then the mold or the gear material, or the mold and the gear element material are used. Since the tooth profile is extruded by cold forging and heated to 50 to 200 ° C., the gear tooth profile is not formed in hot forging, and rough molding is possible. There is no need to control the temperature, and the temperature control is relatively rough. Also, in this cold forging, by heating the mold or gear material, it is possible to suppress variations in the gear dimensions at the initial stage when the number of processing is small when manufacturing a large number of gears. A good product can be manufactured. In particular, when the tooth profile of an internal gear or a helical internal gear with a short root length is formed by extrusion, galling can be prevented and the molding can be efficiently performed with fewer steps. Further, at least when the gear material is heated, that is, when the gear material is heated and when the gear material and the mold are heated, the molding load can be reduced.

  The present invention has been described above based on the above embodiments, but the present invention is not limited to the above embodiments, and various improvements and modifications can be made without departing from the spirit of the present invention. It can be easily guessed.

  For example, in the above embodiment, only the outer shape is formed in the hot forging B2, but the tooth profile may be formed a little. In particular, when the size of the gear is large, the smaller the amount of ironing formed in cold forging, the more the generation of galling can be prevented, and the molding load may be small. Therefore, in cold working, the amount of ironing is small, and by heating the mold or gear material, galling can be better prevented, and gears with good dimensional accuracy can be molded with a small molding load. Can do.

  In the above embodiment, the formation of the helical internal gear has been described. However, the present invention may be applied to the formation of other gears such as a spur gear.

It is a figure which shows a planetary gear apparatus. It is a figure which shows the helical tooth of an internal gear. (A) is a figure which shows the conventional shaping | molding process of the shaping | molding process (b) of this invention. It is sectional drawing of the metal mold | die apparatus which shape | molds an internal gear. It is an enlarged view of the part for shape | molding the tooth | gear of a metal mold | die. It is a figure which shows the change of the dimension (BBD) of the shape | molded gearwheel with respect to the number of processes at the time of normal temperature and heating. It is a figure which shows the change of the shaping | molding load with respect to the number of processes at the time of normal temperature and heating.

Explanation of symbols

1 planetary gear device 2 helical internal gear 2a tooth (helical tooth)
6 Container 9 Helical internal gear mold device 10 Mandrel 13 Punch W Gear material

Claims (6)

In the gear forming method,
An outer shape forming process in which the gear material is hot forged to shape the outer shape of the gear;
A lubrication treatment step for subjecting the gear material formed by the outer shape formation step to a lubrication treatment;
A heating step of heating the gear material or the mold lubricated by the lubrication treatment step from 50 degrees C to 200 degrees C;
A gear material or mold heated from 50 ° C. to 200 ° C. in the warming step is extruded in cold forging to form a gear tooth shape. Gear molding method.   The gear forming method according to claim 1, wherein the heating step is to heat only the mold among the gear material and the mold.   The gear forming method according to claim 1, wherein the heating step heats at least the gear material out of the gear material and the mold.   The gear forming method according to any one of claims 1 to 3, wherein the heating step is performed by irradiating near infrared rays.   The gear forming method according to claim 1, wherein the gear is an internal gear. The gear forming method according to claim 5, wherein the gear is a helical internal gear.

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