JPS6220963A - Power transmission gear coupling large/small gears - Google Patents

Abstract

PURPOSE:To eliminate internal residual stress by forming a groove in the innercircumferential face of an inner hole of large gear while forming a containing chamber between said groove and the outercircumferential face of the shaft section of small gear then welding the spigot joint while containing a ring in said chamber. CONSTITUTION:A groove 7 having the inner bottom face 7a of smaller diameter D2 than the diameter D1 of tooth bottom circle of small gear 2 is formed in the innercircumferential face of an inner hole 4 of large gear 1 while containing chamber 9 -is formed between said groove 7 and the outercircumferential face of the shaft section 3 of small gear 2 to apply electron beam welding onto the spigot joint F between the containing chamber 9 and the outer endface 1b of large gear 1 while containing a ring 11 in said chamber 9. Consequently, micro porosity will occur at the fused portion of ring 11 to enable taking out of fusing member from the ring 11 without sacrifice of the strength of large and small gears thus to eliminate forced shrinkage and high internal residual stress.

Description

[Detailed Description of the Invention] Purpose of the Invention (Field of Industrial Application) This invention provides a power transmission gear in which a large-diameter external gear and a small-diameter external gear are integrally joined by welding at their spigot parts. In particular, the present invention relates to two-stage gears for industrial drive systems that require high torque transmission.

(Prior Art) Conventionally, as shown in FIG. 7, there is a two-stage gear of this type in which a large gear 1 and a small gear 2 are integrally formed. In this two-stage gear, the large gear 1 can be hobbed, but the small gear 2 cannot be hobbed because the large gear 1 forms a wall, and is therefore hobbed using a pinion cutter or the like.

This two-stage gear was finished by shaving using a plunger cut method, then carburized, and then heat treated. However, when gear cutting is performed using a pinion cutter, the accuracy of the small teeth 12 is generally inferior to that of hobbing, resulting in noise and vibration.

Therefore, a two-stage gear shown in FIGS. 8 and 9 was developed. In this two-stage gear, the large gear 1 and small gear 2 are formed separately, and the shaft portion 3 protruding from the inner end surface 2a of the small tooth TJ2 is fitted into the inner hole 4 of the large gear 1. The inner end surface 2a side of the tooth portion 5 of the small gear 2 is brought into contact with the inner end surface 1a of the large gear 1 to constitute the spigot part F, and - the outer end surface 1b of the large tooth I11
Electron beam welding is performed on this spigot part F, and the large and small gears 1.2 are connected to each other at this welded part 6. Since the large gear 1 and the small gear 2 are formed separately from each other in this way, they can be hobbed before welding, and the accuracy of the tooth parts can be ensured.

(Problems to be Solved by the Invention) However, the inner cusp #6a of the electron beam welded part 6 tends to have rough parts or microporosity due to volume change, and the large gear 1 is prone to become rough due to welding distortion of the electron beam welded part 6. There is a risk of deformation as shown by the imaginary line in FIG. 8, and as a result, when a deformed two-stage gear is used, there is a problem of increased noise.

The present invention has been made to solve the above-mentioned problems, and an object of the present invention is to provide a power transmission gear in which both large and small gears are combined without reducing the strength of both the large and small gears.

Structure of the Invention (Means for Solving Problems) The power transmission gear of the present invention has a groove on the inner circumferential surface of the inner hole of the large gear, the inner surface having an inner bottom diameter smaller than the bottom diameter of the small gear. At the same time, a storage chamber is formed between this groove and the outer circumferential surface of the shaft portion of the small gear, and with the ring stored in this storage chamber, the ring is welded to the pilot part between the outer end surface of the large gear. It has been subjected to

(Function) With the above configuration, when welding, welding is performed from the outer end surface of the large gear to the spigot part, but at this time, a part of the ring in the storage chamber is melted. When welding is completed, the welded part begins to cool from the part that protrudes from the outer end surface of the large gear.
Cooling gradually shifts to the inside, but the melted part of the ring is the innermost part and cools last, so the melted part of the ring gradually supplies the melted material to the melted part of the song. It has a structure that solidifies while being cooled.

(Example) Hereinafter, an example of the present invention will be described with a focus on improvements based on a comparison with the above-mentioned prior art.

First, regarding the first embodiment shown in FIGS. 1 and 2,
The inner circumferential surface of the inner hole 4 of the large gear 1 has a diameter D of the tooth bottom of the small gear 2.
A groove 7 having an inner bottom surface 7a with a diameter D2 smaller than 1 is formed so as to open toward the inner end surface 1a side of the canine medium 1, and a groove 7 is formed on the outer circumferential surface of the shaft portion 3 of the small float 2 to oppose this groove 7. A groove 8 is formed therebetween, and a storage chamber 9 is formed between these grooves 7 and 8. A chamfered portion 10 is formed at the open end edge of the inner bottom surface 7a of the groove 7. Incidentally, a radiused portion 13 is formed at each corner of the above-mentioned 7.8 in order to avoid stress concentration.

In the shaft portion 3, a ring 11 having a square cross section is provided in the groove 8.
is fitted onto the outside and stored in the storage chamber 9. Note that the ring 11 is formed with a diagonal cut 11a, and the shaft 3
The diameter can be expanded when fitting into the groove 8 via the .

Electron beam welding is performed on the spigot part F between the storage chamber 9 and the outer end surface 1b of the large gear 1, and this welded part 6
As a result, not only a bead 14 formed on the outer end surface 1b of the large gear 1 but also a back bead 15 is formed in the storage chamber 9, and the ring 11 is welded to the back bead 15.

Now, when the power transmission gear configured as described above is welded, welding is performed from the outer end surface of the large gear 1 to the spigot part F. At this time, a part of the ring 11 in the storage chamber 9 is melted. When welding is completed, cooling of the welded part starts from the part that protrudes from the outer end surface of the large gear 1, and cooling gradually moves to the inside, but the part where the ring 11 is melted is the innermost part, so it is cooled. will be the last. Therefore, ring 1
The melted part 1 cools and solidifies while gradually supplying the melted material to the other melted parts. Therefore, since the microporosity at the tip of the welded portion 6 occurs in the melted portion of the ring 11, the strength of both the large and small gears 1.degree.2 does not deteriorate. Furthermore, since the molten material is drawn out from the ring 11, there is little deformation of the large gear 1, and since there is no unreasonable contraction, there is no high internal residual stress.

Note that even if the ring 11 and the tip of the welded portion 6 are separated from each other during welding as shown in FIG. 4, the ring 1-
1 is not involved in the connection between the large and small gears 1 and 2, so the strength of the connection between the two gears 1 and 2 does not weaken, and the detached ring 11 remains stored and held in the storage chamber 9. Therefore, they do not run outside.

Next, a second embodiment will be explained with reference to FIGS. 5 and 6.

In addition, the same reference numerals are attached to the same or corresponding configurations as those of the first embodiment, and the explanation thereof will be omitted.

In this embodiment, the rounded portions 13 of the grooves 7 and 8 constituting the storage chamber 9 are connected to each other, and the cross section as a whole is approximately circular in the structure of the first embodiment. The difference is that a ring 11 having a circular cross section is fitted into the storage chamber 9.

Therefore, in this embodiment, since the grooves 7 and 8 are both arcuate, stress concentration during force transmission can be further alleviated than in the first embodiment.

Other operations are similar to those in the first embodiment.

It should be noted that the present invention is not limited to the above-mentioned embodiments, and may be arbitrarily modified without departing from the spirit of the present invention.

Effects of the Invention As detailed above, in this invention, the microporosity is generated in the melted part of the ring, so the strength of both the large and small gears does not decrease, and since the molten material is drawn out from the ring, the strength of the large gear is improved. Since there is little deformation and no unreasonable contraction, there is no high internal residual stress. Furthermore, even if the ring and the tip of the welded part are separated from each other after welding, the ring is not involved in the connection between the large and small gears, so the strength of the connection between the two gears will not be weakened, and the detached ring Since it remains stored in the storage chamber, it does not fly out and is safe, making it an excellent invention for industrial use.

[Brief explanation of the drawing]

FIG. 1 is a sectional view showing a two-stage gear according to the first embodiment of the present invention;
Fig. 2 is a partially enlarged sectional view of Fig. 1, Fig. 3 is a perspective view of the ring, Fig. 4 is a partially enlarged sectional view of the ring and the electron beam welded part separated from each other, and Fig. 5 is a partial enlarged sectional view of the second embodiment. FIG. 6 is a front view of the ring, FIG. 7 is a front view of a conventional two-stage gear, and FIG. 8 is the same. FIG. 9 is a cross-sectional view of the conventional two-stage gear. is a partially enlarged sectional view of FIG. 8; 1 is a large gear, 2 is a small gear, 3 is a shaft portion, 4 is an inner hole, 5 is a tooth portion, 6 is a welded portion, 7 is a groove, 8 is a groove, 9 is a storage chamber, 11.
is the ring, F is the spigot part, and Dl is the root diameter of the small diameter gear. Patent Applicant Toyota Industries Corporation Representative
Person Patent Attorney On 1) Hironobu Figure 5 Drawing No. 3 Figure 6

Claims (1)

[Claims] 1. A large gear and a small gear are formed separately from each other, and a shaft portion protruding from the inner end surface of the small gear is fitted into an inner hole of the large gear, and the teeth of the small gear are fitted. In a power transmission gear in which both large and small gears are connected by connecting the inner end surface side to the inner end surface of the large gear to form a spigot part and welding this spigot part to the outer end surface of the large gear, the inner periphery of the inner hole of the large gear A groove having an inner bottom surface having a diameter smaller than the diameter of the tooth bottom of the pinion is formed on the surface, and a storage chamber is formed between the groove and the outer circumferential surface of the shaft portion of the pinion,
A power transmission gear combining both a large gear and a small gear, characterized in that the spigot part between the ring and the outer end surface of the large gear is welded with the ring stored in the storage chamber.