JP2006281264A - Method for manufacturing gear - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a technique for manufacturing a gear, which technique can keep an appropriate temperature, and can make the gear compact by reducing its porosity. <P>SOLUTION: A sintered gear material 1 processed by sintering is heated by heating devices 2, 3, and is rolled by the warm-rolling process. The heating devices 2, 3 are coaxially arranged with the sintered gear material 1 rotatably mounted so as to surround and cover tooth flank portions. The sintered gear material 1 is heated by moving the heating devices 2, 3 in the direction parallel with the axis of the sintered gear material 1. Dies 6a, 6b of a rolling apparatus advance and are pushed into the sintered gear material 1 to roll the gear in the state that the sintered gear material 1 is heated and the heated temperature is kept. By this rolling process, the sintered gear material 1 becomes a compact gear product having a small porosity. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a technique for producing a product gear by rolling a sintered material gear. More specifically, the present invention relates to a manufacturing technique for manufacturing a product gear in which a sintered material gear is heated and rolled to densify a tooth surface.

  When rolling a sintered material gear at the raw material stage, the tooth surface is hardened and the density is improved by improving the forming density from the conventional cold forming technology that forms at room temperature or at high temperature. A hot forming technique for forming is known. Recently, a warm molding technique is known as molding at an intermediate temperature. Rolling molding of a gear is performed by performing rolling processing with a rolling die that meshes with a tooth portion.

  Various methods are also known for this rolling process. As an example, there is a plunger cutting process in which two dies are opposed to each other and pushed into a material gear for rolling. This method is applied to cold forming, hot forming, or warm forming, and is a general forming method that is versatile and efficient. In general, rolling and densifying a material gear to be rolled, particularly in the case of a sintered gear, reduces the porosity and increases the strength of the tooth surface. Reducing the porosity also depends on the rolling method.

  Conventionally, for example, in a technology for densifying a sintered gear, the rolling speed of the densification is controlled by correlating the rotational speed of the die and the axial feed of the sintered gear (for example, see Patent Document 1). The technology is known. However, conventional manufacturing results have demonstrated that in the case of sintered gears, warm forming can lower the porosity than cold forming or the like. In the sintered gear, reducing the porosity increases the density and improves the surface fatigue strength and bending fatigue strength.

For these reasons, various manufacturing techniques for this purpose have recently been proposed. As an example thereof, a technique (for example, see Patent Documents 2 and 3) for densifying a sintered gear by high-frequency heating of the tooth surface is known. However, there is a demand for a technology for manufacturing a sintered gear that is more efficient and can be densely rolled in a short time, and that is low-cost and accurate.
Japanese Patent Laid-Open No. 2000-129312 JP 2003-13111 A Japanese Patent No. 3278262

  As described above, in order to improve densification, various measures in gear rolling are solved and appropriate measures are taken. Recently, however, high precision and high efficiency are required in various fields, and gear rolling technology is no exception. In particular, when analyzing the conventional rolling technology for hot forming or warm forming, the manufacturing process is not necessarily efficient, and the process is not necessarily efficient, and is a process of heating uniformly and uniformly to make the temperature constant. It's hard to say.

  For example, the technique of Patent Document 2 is disclosed as a warm forming technique, but the heating method for the material gear is to heat an induction current through the surface layer of the gear by a high-frequency heating device. The heating itself uses known means, but the coil of the high-frequency heating device is raised and lowered from the standby position with respect to the heating position of the gear installed in a horizontal state.

  That is, the coil is partially moved close to or away from a specific position of the gear, and the entire tooth surface is heated by rotating the gear. During the rolling process, the coil is lowered to the standby position and separated from the gear. This method is hard to say that the temperature of the gear is kept uniform.

  The technique of Patent Document 3 uses a high-frequency heating device as described above for the gear heating device, but has a configuration in which an auxiliary induction coil is provided in addition to the induction coil. The manufacturing technology is a configuration in which a gear to be rolled is heated by an induction coil, then the gear is detached from the chuck, reattached, and heated by an auxiliary coil for rolling. According to this method, the heating temperature is 1000 ° C. or more, and the gear is moved. This manufacturing technique is also not efficient, and is a method subject to restrictions when applied to warm forming.

  Generally, sintered gears are inherently porous after sintering and have a high porosity. For this reason, this is pressed and densified by rolling, and the porosity is reduced to strengthen the gear. In order to stably roll this into a high quality product gear, temperature control, in other words, proper temperature control is required. The success or failure of improving the densification of the gear depends on this temperature control. There is a demand for a low-cost manufacturing technique that can be rolled in a short time while keeping the temperature constant and that can be rolled densely with a reduced porosity.

The present invention has solved these conventional problems and has been developed as a manufacturing method by warm forming, and has achieved the following object.
An object of the present invention is to provide a gear manufacturing method in which a sintered material gear is rolled while maintaining an appropriate temperature, the porosity is reduced, and the gear is densified. Another object of the present invention is to provide a gear manufacturing method that achieves low cost by simplifying the structure.

  The present invention takes the following means in order to achieve the object.

  The gear manufacturing method according to the first aspect of the present invention is a method of manufacturing a product gear by heating a sintered material gear that has been subjected to sintering treatment with a heating device and rolling it with a rolling device, wherein the heating device is rotatably attached. The sintered material gear is coaxially surrounded and disposed so as to cover the tooth surface, and this heating device is moved to the heating position of the sintered material gear in parallel with the axial direction of the sintered material gear and heated. And when the heating device is positioned at the heating position and the sintered material gear is in a heated state, the rolling device advances to the sintered material gear and pushes and rolls.

The gear manufacturing method of the second aspect of the present invention is the first aspect of the present invention.
The heating device is a high frequency heating device, a first heating device that is positioned and heated by the sintered material gear, and a second heating device that moves after heating by the first heating device and heats the sintered material gear. It is comprised from these.

The gear manufacturing method of the third aspect of the present invention is the first aspect of the present invention.
The heating temperature by the heating device is in the range of 200 ° C to 500 ° C.

The gear manufacturing method according to the fourth aspect of the present invention is the first aspect of the present invention.
The first heating device and the second heating device are integrally formed and moved simultaneously.

  As described above, during rolling, the sintered material gear is heated by two heating devices. These two heating devices can be shifted in the axial direction simultaneously. Thus, the sintered material gear heated by the first heating device can be heated and held by the next second heating device so as not to lower the temperature, and the rolling process can be performed in this state. As a result, the rolled product gear has a low porosity and can be manufactured as a densified gear. In addition, it can be manufactured at a low cost with a simple configuration.

  Hereinafter, the details of the gear manufacturing method according to the present invention will be described. 1 and 2 are external views showing the configuration of a rolling process of a sintered material gear (hereinafter referred to as “material gear”) 1 that has been subjected to a sintering process. FIG. 1 is an external view showing a state in which a material gear 1 is heated by a first heating device 2 of a high-frequency heating device having an induction coil. FIG. 2 is an external view showing a state where the material gear 1 is heated by the second heating device 3 of the high-frequency heating device having the auxiliary induction coil.

  3 and 4 are explanatory views schematically showing the above-described configuration. 3 corresponds to FIG. 1, and FIG. 4 corresponds to FIG. In the drawing, the material gear 1 is rotatably attached to a chuck 5 via a support 4. Two dies 6a and 6b are provided in the radial direction of the material gear 1 with the material gear 1 interposed therebetween, and the two dies 6a and 6b move forward toward the material gear 1 and are pushed into the material gear. Perform rolling process.

  FIG. 3 and FIG. 4 are explanatory diagrams as development views, and the heating device and the die are simply shown as one configuration diagram, but the actual configuration is shown in FIG. 1 and FIG. The configuration of this rolling device is a plunge type rolling method and is the same configuration as a publicly known one that is generally applied. The heating device is provided in this rolling device. In this rolling apparatus, a material gear 1 sintered on a base body 7 is supported on the center 8 side via a support 4 and is rotatably attached to a chuck 5.

  The base body 7 is provided with two dice 6a and 6b so as to be opposed to each other with the material gear 1 interposed therebetween as described above. The dies 6a and 6b have a shape similar to that of the material gear 1, and are driven by a driving device (not shown) with respect to the material gear 1, and are pushed and rolled while rotating. The material gear 1 rotates by following the dies 6a and 6b by pushing the two dies 6a and 6b.

  On the other hand, the heating device is provided so as to cover the material gear 1. In the present embodiment, the heating device has two heating portions along the axial direction of the material gear 1. One is the 1st heating apparatus 2 which enables the state which the coil part coaxially surrounds the raw material gearwheel 1 and the tooth surface part is covered substantially coaxially. That is, the material gear 1 is provided facing the inner circumference of the first heating device. The other of the heating devices is arranged parallel to the axial direction with respect to the first heating device 2, and the coil portion coaxially surrounds a part of the material gear 1 and enables a state of covering the tooth surface portion. Device 3.

  The second heating device 3 is provided with an auxiliary induction coil in order to maintain the heating temperature of the material gear 1 heated by the first heating device 2. Both the first heating device 2 and the second heating device 3 can be moved in the axial direction of the material gear 1 by a driving device (not shown). In this movement, the first heating device 2 and the second heating device 3 may be moved independently of each other, but in the present embodiment, they are configured to move together at the same time.

  When heating with the 1st heating apparatus 2, as shown in FIG. 3, the 1st heating apparatus 2 is shifted and moved like an arrow, and it heats so that the tooth surface of the raw material gear 1 may be covered. At this time, the dies 6a and 6b are retracted as shown by arrows. After the heating by the first heating device 2, the heating device shifts as shown by the arrow shown in FIG. 4, and the second heating device 3 leaves part of the material gear 1, that is, the intrusion area of the dies 6a and 6b. Enclose the range.

  Therefore, the second heating device does not surround the entire circumference of the material gear 1 but is actually provided in a state of being divided into vertical positions. In this state, the second heating device 3 supplementarily heats the tooth surface temperature of the material gear 1 so as to maintain a constant temperature. In this state, the two dies 6a and 6b are advanced to the material gear 1 side while avoiding interference with the second heating device 3 as indicated by arrows, and the material gear 1 is rolled by performing a pushing operation. As described above, the material gear 1 is heated by high-frequency heating in which an electric current is passed through the induction coil and heated by induction heat. Since this heating method is well-known, detailed description is abbreviate | omitted.

  Since the heating temperature is premised on warm forming, it is a relatively low temperature range of about 200 ° C. to 500 ° C. below the recrystallization temperature. Since the 1st heating apparatus 2 and the 2nd heating apparatus 3 are comprised integrally as a heating apparatus, when the 1st heating apparatus 2 moves, the 2nd heating apparatus 3 also moves and retracts simultaneously, and similarly When the second heating device 3 moves, the first heating device 2 also moves and retracts at the same time. Since the mutual movement is performed in a short time, the temperature of the tooth surface portion of the material gear 1 is not lowered.

  The two dies 6a and 6b roll the material gear 1 while maintaining a predetermined temperature. Therefore, the material gear 1 can uniformly reduce the porosity in any tooth surface by pressing the dies 6a and 6b, and as a result, the density is greatly improved. In the present embodiment, it is premised on warm forming with a low heating temperature. Therefore, the heating device may be a device having a small capacity and a small scale.

  Further, the movement of the heating device is simple because the two heating devices of the first heating device 2 and the second heating device 3 are integrally and simultaneously performed parallel to the axial direction of the material gear 1. Compared to the conventional method of partially heating the material gear 1, the tooth surface can be maintained at a uniform and stable temperature. In addition, the configuration is simple and can be realized at a low cost as compared with the configuration in which the heating device is fixedly installed and the material gear 1 is moved and installed. Thus, according to the present invention, as explained in the present embodiment, the porosity of the sintered material gear can be reduced and the density can be greatly increased, and the surface pressure fatigue strength and the bending fatigue strength are increased. be able to.

  Next, an example of a material gear manufacturing method implemented according to the embodiment described above will be described. In describing this embodiment, the relationship between the material gear and the tool is defined by the configuration shown in FIG. That is, the tooth surface side of the material gear in the machining progress direction of the tool (die) and the material gear is driven, and the tooth surface side of the material gear opposite to the tool (die) and the material gear in the machining progress direction is the follower. The results of this example are shown in FIGS.

In this example, compression molding pressure: 686 Mpa (7 ton / cm ² ), sintering condition: 1150 ° C., 20 minutes, composition in nitrogen gas atmosphere, the composition is Fe (Bal.) + 0.06% C + 0. 55% Ni + 1.03% Mo + 0.2% Mn, average density after sintering: 700 g / cm ³ (1P1S material, which is a sintered material formed by one-time compression once sintered by Kobe Steel) Using. The porosity of the material is about 10%. An empty tooth surface layer after rolling of a gear m of module m = 3 using this material under the conditions of cold forming (by room temperature) and warm forming (by high frequency heating). It is the result of having compared the porosity distribution. In the figure, the horizontal axis is the distance (mm) (dense depth) from the tooth surface, the vertical axis is the porosity (%), and the distribution is plotted for the driven side and the follower side.

  FIG. 6 is a distribution diagram showing the tooth surface porosity distribution of the sintered alloy gear when cold rolled. The amount of pressing on one side in the radial direction of the tool was set to 0.45 mm and 0.60 mm. FIG. 7 is a distribution diagram showing the tooth surface porosity distribution of the sintered alloy gear in the case of warm rolling. As in the case of FIG. 6, the pressing amount in the radial direction of the tool was set to 0.45 mm and 0.60 mm.

  From a comparison between the two, for example, in comparison with a porosity of 1% or less, in the case of FIG. 6, when the push amount is 0.45 mm, it can be slightly scattered on the follower side, and is 0.60 mm. In the amount of indentation, the surface layer is only scattered in a range up to about 0.4 mm. On the other hand, in the case of FIG. 7, when the push amount is 0.45 mm, the surface layer is 0.5% or less on both the driven side and the follower side, and when the push amount is 0.60 mm, the driven side and the follower side. In both cases, a surface layer of up to 1.3 mm achieves 1% or less.

  Compared to cold rolling, warm rolling achieves a high degree of achievement in terms of reducing the porosity, and as a result, densification is concentrated on the surface layer, resulting in an ideal rolling result. . Therefore, it is the result which confirmed the effect of the present invention by warm forming.

FIG. 1 is an external view of a rolling device showing a state of heating with a first heating device. FIG. 2 is an external view of the rolling device showing a state of being heated by the second heating device. FIG. 3 is an explanatory diagram of an embodiment corresponding to FIG. FIG. 4 is an explanatory diagram of an embodiment corresponding to FIG. FIG. 5 is an explanatory diagram showing the positional relationship between driven and follower in the tooth profile. FIG. 6 is a data diagram showing a tooth surface layer porosity distribution of a sintered alloy gear in the case of cold rolling. FIG. 7 is a data diagram showing a tooth surface layer porosity distribution of a sintered alloy gear in the case of warm rolling.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Raw material gear 2 ... 1st heating apparatus 3 ... 2nd heating apparatus 4 ... Supporting tool 5 ... Chuck 6a, 6b ... Dice 7 ... Base | substrate 8 ... Center

Claims (4)

In a method of manufacturing a product gear by heating a sintered material gear that has been subjected to a sintering process by a heating device and rolling by a rolling device,
The heating device is coaxially surrounded by the sintered material gear that is rotatably attached and is disposed so as to cover the tooth surface portion. The heating device is disposed at the heating position of the sintered material gear in the axial direction of the sintered material gear. And moving in parallel with the heating,
A method of manufacturing a gear comprising: a step in which the rolling device moves forward and pushes into the sintered material gear when the heating device is located at the heating position and the sintered material gear is in a heated state. In the manufacturing method of the gear according to claim 1,
The heating device is a high frequency heating device, a first heating device that is positioned and heated by the sintered material gear, and a second heating device that moves after heating by the first heating device and heats the sintered material gear. A gear manufacturing method characterized by comprising the following. In the manufacturing method of the gear according to claim 1,
The heating temperature by the heating device is in a range of 200 ° C to 500 ° C. In the manufacturing method of the gear of Claim 2,
The gear manufacturing method, wherein the first heating device and the second heating device are configured integrally and moved simultaneously.

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