JPH10305344A - Form rolling of sintered gear - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for form rolling of a sintered gear advantageous in the improvement of an accuracy of teeth of a sintered gear by making the surface layer thereof. SOLUTION: The sintered gear 1 is formed by using a sintered material and a form rolling dies 2, 3, with working teeth, of a pair of gear forms. The form of the working teeth of the form rolling dies 2, 3 is compensated based on the form data of the sintered gear after the form rolling and the sintered gear 1 is form rolled by using the dies 2, 3 correction. At the compensation, the teeth is indented more than a regular involute curve at the pitch circle and the vicinity area in the teeth form profile.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a method for rolling a sintered gear.

[0002]

2. Description of the Related Art Conventionally, Japanese Patent Application Laid-Open No. Sho 50-66461 discloses a method of rolling a gear sintered material on the outer periphery using a gear sintered material and a rolling die having a gear shape having machined teeth. A technique of forming a sintered gear by performing processing is disclosed. According to this, pores remaining in the outer peripheral portion of the gear sintered material disappear, and the teeth of the sintered gear can be densified, which can contribute to the enhancement of the strength of the sintered gear.

[0003]

Since the above-described method for rolling a sintered gear aims at densification by eliminating voids remaining on the surface layer of the gear sintered material, it is compared with a forged gear or the like. Therefore, there is a situation that the processing cost, that is, the rolling cost, is considerably large. As described above, since the rolling allowance is considerably large, the surface layer of the sintered gear can be densified, but the gear accuracy of the sintered gear is likely to deteriorate.

SUMMARY OF THE INVENTION The present invention has been made in view of the above circumstances, and is a sintered gear which is advantageous for improving the precision of the teeth of the sintered gear while densifying the surface layer of the teeth of the sintered gear. An object of the present invention is to provide a method of rolling.

[0005]

According to a first aspect of the present invention, there is provided a method for rolling a sintered gear, comprising the steps of: using a gear sintered material and a rolling die having a gear shape having machined teeth; In the method of rolling a sintered gear for forming a sintered gear by forming, the shape of the machined tooth of the rolling die is corrected based on the shape data of the sintered gear after the rolling, and the rolling after the shape correction is performed. The method is characterized by rolling a sintered gear with a forming die.

According to the method for rolling a sintered gear according to the second aspect, in the first aspect, the correction is performed such that a region near the pitch circle in the profile of the tooth profile of the processing tooth of the rolling die is smaller than a normal involute curve. It is characterized by being dented.

[0007]

BEST MODE FOR CARRYING OUT THE INVENTION In order to densify the surface layer of the tooth portion of a sintered gear, the rolling allowance is set to be considerably larger than when a forged material is rolled. The rolling allowance can be, for example, about 0.1 to 0.2 mm in one side tooth thickness. The material of the sintered gear can be, for example, alloy steel or carbon steel. In the method of the present invention, when correcting the shape of the processing tooth of the rolling die, after rolling the sintered gear, the sintered gear is rolled based on the shape data of the rolled sintered gear. The form which corrects the processing tooth of the formed rolling die itself can be adopted. Alternatively, after rolling the sintered gear with a rolling die, a form may be adopted in which another rolling die is manufactured based on the shape data of the rolled sintered gear, taking into account the corrected shape.

[0008]

Embodiments of the present invention will be described below. 1A and 1B show a sintered gear 1 to be manufactured. The sintered gear 1 is a helical gear having helical teeth, and can be defined, for example, in the following gear introduction. That is, the pressure angle is 16.5 °, the torsion angle is 20 °, the module is 1.9, the tooth width is 18 mm,
The pitch circle diameter is 80.9 mm. The sintered gear 1 is made of an alloy steel, and its basic composition is Fe-2% Ni by weight.
-0.5% Mo-0.2% C. The virtual line S1 shown in FIG. 1 indicates a pitch circle. A shaft hole 10 is provided at the center of the sintered gear 1.
Are formed.

FIG. 2 is a plan view of the rolling device. As can be understood from FIG. 2, a fixed die 2 as a rolling die rotatable in the direction of arrow P1 having a helical processing tooth 20X on the outer peripheral portion, and an arrow having a helical processing tooth 30X on the outer peripheral portion. A feed die 3 as a rolling die rotatable in the P2 direction and a mechanism 24 for rotating the fixed die 2
A mechanism 34 for rotating the feed die 3; a feed adjusting mechanism 36 for adjusting the feed amount of the feed die 3;
With

Before the correction, the processing teeth 20X of the fixed die 2
The machining tooth 30X of the feed die 3 has an involute tooth profile, and is defined by a regular involute curve. In the present embodiment, a gear sintered material 5 having coarse teeth 50 arranged in advance at predetermined intervals on the outer peripheral portion is used. The gear sintered material 5 is obtained by sintering a compact formed by compression molding of a partial diffusion alloy powder in a sintering temperature range.

Using the unfixed fixed die 2 and feed die 3 defined by the regular involute curve as described above, the rough teeth 50 of the gear sintered material 5 are rolled. At this time, the gear sintered material 5 rotates in the direction of arrow P3. The rolling process is performed in a normal temperature state, that is, in a cold state. Thus, the above-described sintered gear 1 is manufactured. The target value of the surface density of the surface layer of the tooth portion of the sintered gear 1 is about 7.5 to 7.6 g / cm ³ . As described above, in order to densify the surface layer of the sintered gear 1,
The rolling allowance was set as large as 0.12 mm in one side tooth thickness.

When the sintered gear 1 is rolled by the fixed die 2 and the feed die 3 defined by the regular involute curve as described above, the tooth profile error and the tooth line error of the sintered gear 1 are deteriorated. It is presumed that the reason for this is that, as described above, the rolling allowance is large in order to achieve densification. FIG. 8 schematically shows a main part in the process of rolling, taking the processed tooth 20X of the fixed die 2 as an example. Each term described below will be described based on FIG. As can be understood from FIG. 8, when the fixed die 2 provided with the processing teeth 20X rotates in the direction of the arrow P1, the rough teeth 50 on the outer peripheral portion of the gear sintered material 5 are finish-rolled. Of the processing teeth 20X protruding from the fixed die 2, a tooth surface that directly presses the rough teeth 50 of the gear sintered material 5 as a work is referred to as a drive-side tooth surface 20d. Of the processed teeth 20X of the fixed die 2, the tooth surface that sandwiches the coarse tooth 50 together with the drive-side tooth surface 20d is referred to as a coast-side tooth surface 20c.

Further, the coarse teeth 5 of the gear sintered material 5 which is a work.
Of 0, the tooth surface to be pressurized by the drive side tooth surfaces 20 _d of the forming teeth 20X of the driven-side tooth surface 50d. Among the protruding coarse teeth 50 of the gear sintered material 5, a surface facing the driven tooth surface 50 d of the coarse teeth 50 and facing the coast tooth surface 20 c is referred to as a follower tooth surface 50 f. FIG. 3 shows a sintered gear 1 using a fixed die 2 and a feed die 3 defined by a regular involute curve.
5 shows a profile curve of a tooth portion of the sintered gear 1 in the case of manufacturing the same. (A1) of FIG. 3 shows a profile curve of the tooth profile of the follower-side tooth surface 50f of the sintered gear 1. (A2) of FIG. 3 shows the profile curve of the tooth profile of the driven-side tooth surface 50d of the sintered gear 1.

FIG. 3 (B1) shows the profile curve of the tooth trace of the follower-side tooth surface 50f of the sintered gear 1. FIG.
(B2) shows the profile curve of the tooth trace on the driven-side tooth surface 50d of the sintered gear 1. In this example, a profile curve was measured for one tooth portion of the sintered gear 1 in the circumferential direction. FIG. 3 is based on the form of magnifying 500 times in the Y direction and 4 times in the X direction.

In FIG. 3, A _A means the tip side of the sintered gear 1. A _C denotes the tooth bottom side of the sintered gear 1. B
_X means one end side in the tooth trace direction. _BY means the other end side in the tooth trace direction. The hatched area in FIG. 3 means the thickness of the teeth of the sintered gear 1. As can be understood from FIG. 3 (A1), in the follower-side tooth surface 50f of the sintered gear 1, the sintered gear 1
And the flesh of the sintered gear 1 tends to bulge in the tooth bottom side region 12. In the area 11 near the pitch circle corresponding to the central area in the gear setting direction, the thickness of the sintered gear 1 tends to be concave.

Similarly, as can be understood from FIG. 3 (A2), on the driven-side tooth surface 50d of the sintered gear 1,
The flesh of the sintered gear 1 tends to bulge in the tooth tip side region 20 and the flesh of the sintered gear 1 bulges in the tooth bottom side region 22. In the area 21 near the pitch circle, which is the central area in the gear setting direction, the thickness of the sintered gear 1 tends to be concave. Next, the profile of the sintered gear 1 in the direction of the tooth trace will be described. That is, as can be understood from (B1) of FIG. 3, in the tooth trace of the follower-side tooth surface 50d of the sintered gear 1, the one end region 50 to the other end region 5d.
In the case of 2, the teeth tend to swell, that is, have a slightly crowning shape, and both ends in the direction of the tooth line tend to sag.

As can be understood from FIG. 3 (B2), the tooth streaks of the driven-side tooth surface 50d of the sintered gear 1 tend to swell from the one end region 60 to the other end region 62, that is, have a slightly crowning shape. Both ends in the direction of the tooth line tend to sag. (After Correction) In the present embodiment, correction is performed on the profile of the machined tooth 20X of the fixed die 2. In the present embodiment, the same correction is performed on the profile of the machining tooth 30X of the feed die 3. The correction is performed based on the shape data (profile data according to FIG. 3) of the sintered gear 1 after being rolled by the dies 2 and 3 defined by a regular involute curve.

FIG. 4 shows the profile of the processed tooth 20X after the correction. That is, the profile of one tooth profile is measured,
Show the profile. The profile of the tooth trace of the machined tooth 20X was also measured for one machined tooth 20X, and the profiles are shown in (B1) and (B2) of FIG. That is, (A1) of FIG. 4 shows the coast-side tooth surface 2 of the machining tooth 20X.
8 shows the profile curve of the tooth profile 0c. (A2) in FIG.
Shows the profile curve of the tooth profile of the drive-side tooth surface 20d of the machined tooth 20X. (B1) of FIG. 4 shows a profile curve of the tooth trace on the coast side tooth surface 20c of the processed tooth 20X. (B2) of FIG. 4 is the drive-side tooth surface 2 of the machining tooth 20X.
3 shows the profile curve of the tooth trace of 0d.

4 (A1) and (A2) show 50 in the Y direction.
Based on the form of magnifying 0 times and magnifying 4 times in the X direction
Follow. (B1) and (B2) in FIG.
It is based on a form that is enlarged and doubled in the X direction.
In FIG. 4, A_AMeans the tip side of the machined tooth 20X
You. A_CMeans the root side of the machined tooth 20X. B_XIs
It means one end side in the tooth streak direction of the artificial tooth 20X. B _YIs
It means the other end side in the tooth streak direction of the artificial tooth 20X. In FIG.
The hatched area means the meat constituting the processed tooth 20X.
To taste.

The dashed line M shown in (A1) and (A2) of FIG. 4 shows the profile of the normal involute curve of the processed tooth 20X before correction. As can be understood from (A1) of FIG.
In the coast-side tooth surface 20c, the flesh of the machined tooth 20X tends to swell in the tooth tip side region 10W while being depressed with respect to the regular involute curve M, and the flesh of the machined tooth 20X is normal in the tooth bottom side region 12W. The profile of the machined tooth 20X is corrected so that the involute curve M of FIG.

Further, the profile of the machining tooth 20X is corrected so that the flesh of the machining tooth 20X is depressed with respect to the regular involute curve M in the area 11W near the pitch circle, which is the central area of the machining tooth 20X in the tooth setting direction. . In the case of the coast-side tooth surface 20c of the machined tooth 20X of the fixed die 2 of the present embodiment, the tip side region 10 with respect to the regular involute curve M
The dent amount of W can be appropriately set in the range of 10 to 30 μm,
The dent amount of the tooth bottom side region 12W with respect to the regular involute curve M can be appropriately set in the range of 10 to 30 μm, and the pitch circle vicinity region 11W with respect to the regular involute curve M.
Can be appropriately set in the range of 10 to 30 μm.
The dent amount in the area 11W near the pitch circle is 10W in the tip side area.
Or larger than the tooth bottom side region 12W.

In this embodiment, as shown in FIG. 4 (C), when the total tooth length of the machined tooth 20X of the fixed die 2 is H, the position of the tooth tip side region 10W is the tooth bottom. means near [(5/6) × H] from the outer diameter end R _m of radius R _K. Processing position of the tooth bottom region 12W of the tooth 20X means from a radially outer end R _m near [(1/6) × H] root radius R _K.

Further, as can be understood from FIG. 4 (A2), in the profile of the tooth profile on the drive side tooth surface 20d of the machined tooth 20X, in the tooth tip side region 20W, it is depressed and expanded with respect to the regular involute curve M. The profile of the processed tooth 20X is corrected so that the tooth becomes slightly bulged while the meat is dented with respect to the regular involute curve M in the tooth bottom side region 22W. In the area 21W near the pitch circle, which is the central area in the direction in which the machined tooth 20X extends, the profile of the machined tooth 20X is corrected so that the meat of the machined tooth 20X is depressed with respect to the regular involute curve M.

The processing tooth 20 of the fixed die 2 according to this embodiment
In the case of the drive-side tooth surface 20d of X, the dent amount of the tooth tip side region 20W with respect to the normal involute curve M is 10
The indentation amount of the tooth bottom side region 22W with respect to the normal involute curve M is 10 to 3 μm.
It can be set appropriately within the range of 0 μm. With respect to the regular involute curve M, the dent amount in the area 21W near the pitch circle is 10
It can be set as appropriate within the range of 30 μm. Note that the amount of depression in the area 21W near the pitch circle is 20 W on the tooth tip side and 22 W on the tooth bottom side.
Greater than.

Similarly, as shown in FIG. 4C, the processing tooth 2X is also formed on the drive-side tooth surface 20d of the processing tooth 20X.
When all tooth depth dimension of 0X was H, the position of the tip side region 20W from radially outer end R _m of root radius R _K [(5/6) ×
H]. Position of the tooth bottom side area 22W means near [(1/6) × H] from the outer diameter end R _m of root radius R _K.

As can be understood from FIG. 4 (B1),
In the profile in the tooth lead direction of the coast side tooth surface 20c of the machined tooth 20X, the central area 51W functioning as the central area in the tooth lead direction is slightly concaved from the one end area 50W to the other end area 52W so as to be slightly concave. . (B in FIG. 4)
As can be understood from 2), in the profile of the drive side tooth surface 20d of the machined tooth 20X in the tooth trace direction, a slightly arcuate shape is formed from the one end region 60W to the other end region 62W so that the central region 61W in the tooth trace direction is slightly depressed. To be corrected.

Although the above description is directed to the processing teeth 20X of the fixed die 2, the processing teeth 30X of the feed die 3
Similar profile correction is performed for X. In the present embodiment, carburizing, quenching and tempering are performed on the teeth of the sintered gear 1 after finish rolling using both the corrected solid die 2 and the corrected feed die 3. (Test Results) FIG. 5 shows the relationship between the size of the rolling allowance and the difference before and after the rolling process when the rolling process is performed with the fixed die and the feed die before correction. "0" on the horizontal axis in FIG. 5 indicates the tooth profile error and the tooth trace error of the sintered gear 1 before the rolling process. Further FIG.
In the formula, Δ (black square) means a tooth profile error of the sintered gear 1 and ▲ (black triangle) means a tooth trace error of the sintered gear 1. As can be understood from FIG. 5, as the rolling allowance increases, the tooth profile error and the tooth line error tend to increase. In particular, as the rolling allowance increases, the rate of increase in the tooth profile error increases. In this specification, the definition of the tooth profile error and the tooth line error is based on JIS-B1702.

FIG. 6 shows tooth profile errors before and after correction before, after, and after heat treatment. In FIG. 6, ● (black circle) means the average value of the tooth profile errors when using a die corrected to have the profile shown in FIG.
In FIG. 6, ▲ (black triangle) indicates the positive value of the tooth profile error when using a die corrected to have the profile shown in FIG.
3σ (variation). 6 indicates the average value of the tooth profile error when using the uncorrected dice.
Is +3 of the tooth profile error when using the die before correction
means σ (variation).

As can be understood from the marks △ in FIG. 6, when rolling is performed with the die before correction, the tooth profile error after rolling is greatly increased as compared with before rolling. This is because the rolling allowance is large. However, as can be understood from the marks ● (solid circle) and ▲ (solid triangle) in FIG. 6, if the roll is rolled with a die corrected to have the profile shown in FIG. 4, the tooth profile error after rolling is 10 μm ( It is considerably lower than JIS class 3). Therefore, when the corrected dice are used, J
IS3 class accuracy was easily obtained.

FIG. 7 shows tooth lead errors before and after correction before, after, and after heat treatment. In FIG. 7, ●
(Solid circle) means the average value of the tooth streak error when using the dice corrected to have the profile shown in FIG. 4, and ▲ (solid triangle) means the dice corrected to have the profile shown in FIG. It means + 3σ (variation) of the tooth lead error when used.は means the average value of the tooth line error when using the die before correction, and △ means +3 of the tooth line error when using the die before correction.
means σ (variation).

As can be understood from the marks △ in FIG. 7, if the roll is formed with the die before the correction, the tooth lead error after the rolling is large. However, as can be understood from the marks of ● (black circle) ▲ (black triangle) in FIG. 7, when rolling is performed with the corrected dies, the tooth lead error after rolling is considerably lower than 10 μm (JIS class 3). . In the tests shown in FIGS. 6 and 7, the rolling allowance was 0.12 mm on one side in order to densify the surface layer of the sintered gear 1.

Table 1 shows the errors when rolling with a die without correction and the errors when rolling with a die after having been corrected to have the profile shown in FIG. As can be understood from Table 1, if the correction is made, both the tooth profile error and the tooth lead error become smaller. When the dies are corrected as described above, the tooth profile error is class 2 and the tooth lead error is class 0 based on the average value of the dimensions of the sintered gear 1, and as a rolled sintered gear, it is considerably large. High accuracy.

[0033]

[Table 1] (Table 1: Reading with average value: JIS-B1702)

[0034]

According to the method of the present invention, it is advantageous to obtain a high-accuracy sintered gear in which the tooth surface is densified and the tooth profile error and the tooth lead error are reduced. According to the method of the second aspect, the correction is performed such that the area near the pitch circle is depressed from the regular involute curve in the tooth profile of the machining tooth of the rolling die. Therefore, as can be understood from the test results described above, it is advantageous for reducing the tooth profile error and the tooth trace error.

[Brief description of the drawings]

FIG. 1 is a configuration diagram of a sintered gear.

FIG. 2 is a process diagram of rolling a sintered gear by rolling.

FIG. 3 is a diagram showing a profile curve of a tooth portion of a sintered gear rolled by a die before correction.

FIG. 4 is a view showing a profile curve of a processed tooth of a die after correction.

FIG. 5 is a graph showing a relationship between a size of a rolling allowance, a tooth profile error and a tooth lead error.

FIG. 6 is a graph showing a relationship between a process and a tooth profile error.

FIG. 7 is a graph showing a relationship between a process and a tooth streak error.

FIG. 8 is a configuration diagram schematically showing a main part in the process of rolling.

[Explanation of symbols]

In the figure, 1 is a sintered gear, 2 is a fixed die, 20X is a machined tooth, 3 is a feed die, and 30X is a machined tooth.

Continuation of the front page (72) Inventor Haruo Otsuka 1-1-1 Fujikoshi Honcho, Toyama City, Toyama Prefecture Fujiuchi Co., Ltd. (72) Inventor Shunichi Asakura 1-1-1, Fujikoshi Honmachi, Toyama City, Toyama Prefecture Fujikoshi Co., Ltd.

Claims (2)

[Claims] 1. A method for rolling a sintered gear by forming a sintered gear by rolling the gear sintered material using a gear sintered material and a rolling die having a gear shape having machined teeth. In the method, the shape of the processing tooth of the rolling die is corrected based on the shape data of the sintered gear after the rolling, and the sintered gear is rolled by the rolling die after the shape correction. Construction method. 2. The rolling method for a sintered gear according to claim 1, wherein the correction is performed by depressing a region near a pitch circle from a regular involute curve in a tooth profile of a processing tooth of the rolling die. Method.