JP3512608B2 - Gear pair - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a gear pair.

[0002]

2. Description of the Related Art Conventionally, there are two types of tooth surface finishes for power transmission gears represented by transmissions, such as grinding finish and shaving finish. Gears produced by grinding finish (hereinafter referred to as grinding finish gears) Is a carburized and quenched carburized and hardened gear material, and a shaving-finished gear (hereinafter referred to as a shaving-finished gear) is carburized and hardened after shaving the carved gear material. It was finished by doing.

Here, carburizing and quenching refers to a heat treatment for diffusing and permeating carbon into the surface of a steel material forming a gear and then quenching to harden the surface including tooth surfaces. If such heat treatment is performed, It is possible to manufacture a gear having a tooth surface having high wear resistance and a core portion having high toughness.

The carburizing method includes a solid carburizing method in which a steel product is carburized using a solid carburizing agent, and a gas for carburizing a steel product using a modified RX gas such as hydrocarbon-based methane or propane as a carburizing agent. A carburizing method and a liquid carburizing method of carburizing a steel product in a molten salt bath containing NaCN as a main component are known, but in general, thermal efficiency is high, continuous carburization is possible, and a uniform carburizing is possible. A gas carburizing method is used which results in a carburized layer having a carbon content.

[0005]

However, in the former grinding finish gear, since the surface of the gear material is hardened by carburizing and quenching, the tooth surface is ground and finished in the final step. Although it is possible to obtain a gear having the above, there is a problem that the manufacturing cost is high because it takes a lot of time and labor to grind the hardened gear material.

On the other hand, in the latter shaving finish gear, since the shaving process is performed at a relatively soft stage before the surface of the gear material is hardened by carburizing and quenching, the shaving process is relatively easy and takes a short time. Although it has the advantage that it can be carried out with, there is a drawback that distortion occurs due to carburizing and quenching in the final process, the accuracy is worse than that of a ground finish gear, and there is a large stress on the tooth root during use. Will cause the breakage strength to decrease, the tooth surface will hit one side and a large tooth surface pressure locally will cause the tooth surface strength to decrease, and the meshing noise will increase. However, there is a problem in that it is difficult to manufacture high-performance gears due to such problems.

Generally, in a power transmission gear, a drive gear and a driven gear are used in a combination having the same tooth surface finish, and a grinding finish gear is used between grinding finish gears. , Shaving finish gears are usually used between shaving finishing gears, but the reason is that even if one is a high precision grinding finish gear and the other is a poor precision shaving finish gear, it will mesh. This is because it is impossible to secure the relative accuracy in the event of an emergency.

The present invention has been made in view of the above circumstances, and a grinding finish gear and a shaving finish gear can be used in combination, so that the breakage strength and the tooth surface strength are high and the meshing noise is small. The purpose is to realize a high performance gear pair at low cost.

[0009]

DISCLOSURE OF THE INVENTION The present invention comprises a grinding finish gear obtained by carburizing and quenching a gear-cut gear material, and a shaving finish gear obtained by carburizing and quenching the gear-cut gear material. It is composed of a combination, and the tooth surface of the shaving finish gear is
So that the tooth profile on the side of the finished gear is transferred
The present invention relates to a gear pair characterized by intentionally forming an abnormal carburizing layer .

When the grinding finish gear and the shaving finish gear are used in mesh with each other, the tooth surface of the grinding finish gear is hardened with high precision by removing the carburizing abnormal layer caused by carburizing and quenching by grinding. On the other hand, on the tooth surface of the shaving finish gear, a soft carburized abnormal layer is formed with a substantially uniform thickness by carburizing and quenching in the final process, so at the beginning of operation the shaving finish gear The tooth surface of No. 3 is rapidly and reasonably abraded, and the highly accurate tooth profile on the side of the grinding finished gear is transferred to the tooth surface of the shaving finished gear to obtain good tooth contact.

Further, in the present invention, the gear material forming the shaving finish gear has a chemical composition of 0.
10 to 0.30% by weight C, 0.01 to 0.50% by weight Si, 0.60 to 2.00% by weight Mn,
025 wt% or less P and 0.040 wt% or less S
And not more than 2.00 wt% Cr and 0.020 to 0.0
80 wt% Nb, 0.0010 to 0.0100 wt% B, 0.010 wt% or less N, 0.100 wt% or less Ti, and the balance Fe, and Si. M
The total content of n and Cr is preferably 1.90 to 4.50% by weight.

When such a gear material is carburized and quenched, the presence of a gas containing oxygen such as H ₂ O, CO ₂ and CO in the carburizing atmosphere causes the carbon in the vicinity of the surface during the process of carbon penetration into the steel. Elements such as Si, Mn, and Cr that are more easily oxidized at high temperature than Fe combine with oxygen to precipitate oxides (grain boundary oxidation) at the crystal grain boundaries, and solid solution elements Si, Mn, and C near the grain boundaries.
Since r is locally reduced and hardenability deteriorates, a soft carburized abnormal layer, which is an incompletely hardened structure, is satisfactorily formed with a substantially uniform thickness on the surface after carburizing and quenching, and is substantially uniform on the tooth surface. It is possible to easily obtain a shaving-finished gear in which an abnormal carburizing layer having a different thickness is formed. In addition, a soft carburized abnormal layer
20 to 30 for good production with a substantially uniform thickness
It is preferable to form it relatively deep as a thickness of μm.

[0013]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described below with reference to the drawings.

FIGS. 1 and 2 show an example of an embodiment for carrying out the present invention. A gear pair 1 of this embodiment shown in FIG. 1 is a ground finish gear obtained by carburizing and quenching a gear material of which gear cutting has been performed. 2 and shaving finish gear 3 which is carburized and quenched after shaving the gear material that has been geared
The tooth surface of the shaving finish gear 3 is worn on the tooth surface of the shaving finish gear 3 at the initial stage of operation and is on the side of the grinding finish gear 2.
The abnormal carburizing layer 4 (see FIG. 2) having a substantially uniform thickness is intentionally formed so that the shape is transferred .

That is, in carburizing and quenching by the gas carburizing method,
Industrial gases such as methane, propane and butane used as carburizing agents are not pure, and oxygen-containing gases such as H ₂ O, CO ₂ and CO are present in the carburizing atmosphere. Elements such as Si, Mn, and Cr near the surface, which are more easily oxidized at high temperature than Fe, combine with oxygen to precipitate oxides at the grain boundaries (grain boundary oxidation), and solid solution elements S near the grain boundaries.
It is known that since i, Mn, and Cr are locally reduced and the hardenability is deteriorated, a soft carburized abnormal layer 4 having an incompletely hardened structure is formed on the surface after carburizing and quenching.

Therefore, in the present embodiment, by appropriately adjusting the chemical composition of the gear material forming the shaving finish gear 3, the carburizing abnormality of the tooth surface of the shaving finish gear 3 is intentionally approximately uniform. The layer 4 is formed and used in combination with the grinding finish gear 2.

More specifically, the gear material forming the shaving finish gear 3 has a chemical composition of 0.10 to 0.10.
0.30 wt% C and 0.01 to 0.50 wt% S
i, 0.60 to 2.00 wt% Mn, 0.025
1. P by weight or less, S by 0.040 weight% or less, 2.
00 wt% or less Cr, 0.020 to 0.080 wt% Nb, and 0.0010 to 0.0100 wt% B
And 0.010% by weight or less of N, 0.100% by weight or less of Ti, and the balance of Fe.
The total content of r may be set to 1.90 to 4.50% by weight, and the gear material having such a chemical composition may be carburized and quenched.

For example, the chemical composition of the gear material forming the shaving finish gear 3 is 0.18% by weight of C,
0.28 wt% Si, 1.19 wt% Mn,
0.023 wt% P, 0.017 wt% S,
0.58 wt% Cr, 0.028 wt% Nb,
0.0023 wt% B, 0.006 wt% N,
Assuming that 0.015 wt% Ti and the balance Fe are included, 0.04% CH ₄ , 30.4% H ₂ , and 23.
9% CO ₂ , 0.4% H ₂ O and the balance N ₂ butane-modified RX gas having a composition of N ₂ were used for carburizing in a carburizing atmosphere at 930 ° C. for 3.5 hours for carburizing, Then 13
Immerse it in oil at 0 ° C and cool it down to 90 ° C in the air.
When the shaving finish gear 3 is manufactured by holding for a minute and tempering and then air cooling, the tooth surface of the shaving finish gear 3 has a thickness L ₁ of 20 to 20 as shown in FIG. The uniform carburization anomalous layer 4 having a thickness of 30 μm is formed relatively deep and has a fine appearance so as to cover the grain boundary oxidized portion. The carburization depth of the carburization layer 5 immediately below the carburization anomalous layer 4 is 0.7. It is formed to be about 1.3 mm.

When the grinding finish gear 2 and the shaving finish gear 3 are used in mesh with each other, the tooth surface of the grinding finish gear 2 is hard (Vickers) because the carburizing abnormal layer 4 due to carburizing and quenching is removed by grinding. Hardness is about 700 Hv
However, the tooth surface of the shaving finish gear 3 is soft (Vickers hardness is about 400H) by carburizing and quenching in the final process.
Since the abnormal carburization layer 4 is formed with a substantially uniform thickness, the tooth surface of the shaving finish gear 3 is quickly and reasonably abraded in the initial stage of operation, and the tooth surface of the shaving finish gear 3 is ground and finished. The highly accurate tooth profile on the gear 2 side is transferred, and good tooth contact can be obtained.

Here, in transferring the highly accurate tooth profile of the grinding finish gear 2 side to the tooth surface of the shaving finish gear 3, 1/4 of the capability (allowable torque) of the gear pair 1 is transferred.
Transfer is possible if a load of about ½ is applied.

When the composition ratio of each of the chemical components of the gear material forming the shaving finish gear 3 deviates from the range of the composition ratio defined above, the tooth surface of the shaving finish gear 3 is substantially covered. It becomes difficult to form the abnormal carburizing layer 4 having a uniform thickness. For example, the chemical composition of the gear material forming the shaving finish gear 3 is 0.22 wt% C and 0.32 wt% Si. , 0.80% by weight
Mn, 0.022 wt% P, 0.015 wt%
S, 1.14% by weight Cr, 0.001% by weight Nb, 0.0003% by weight B, 0.008% by weight
N, 0.002 wt% Ti, and the balance Fe, and when the composition ratio of B and Nb is not within the specified range, even if carburizing and quenching is performed under the same conditions as described above, The tooth surface of the manufactured shaving finish gear 3 has a rough texture that surrounds only the periphery of the grain boundary oxidized portion and has a thickness L ₂ as shown in FIG. Only a shallow and uneven carburizing anomalous layer 4 is formed.

If the abnormal carburizing layer 4 formed with a non-uniform thickness in the shallow area of the tooth surface of the shaving finish gear 3 is schematically shown, it is considered that the abnormal state is as shown in FIG. Even if the shaving finish gear 3 having the uneven carburizing abnormal layer 4 is used as the gear pair 1 in combination with the grinding finish gear 2, the aspect is thick in the upper layer portion and in the lower layer portion. Due to the sharp and rough texture, brittle fracture is likely to occur, and as shown in FIG. 5, when the wear of the contact portion progresses, the thickness of the abnormal carburized layer 4 becomes uneven. Therefore, the hard carburized layer 5 is mixed and exposed between the soft carburized abnormal layers 4 in a patchy manner, and the tooth surface is likely to be damaged due to local stress concentration.

In short, even if the conventional shaving finish gear 3 as in the past is simply combined with the grinding finish gear 2, the highly precise tooth profile of the grinding finish gear 2 is transferred to the tooth surface of the shaving finish gear 3. This is impossible, and the tooth surface of the shaving finish gear 3 is first formed on the tooth surface of the shaving finish gear 3 by intentionally forming the abnormal carburizing layer 4 on the tooth surface of the shaving finish gear 3 as in this embodiment. It is possible to transfer the highly accurate tooth profile on the side of the grinding finish gear 2.

Reference numeral 6 in FIGS. 4 and 5 indicates a grain boundary oxidized portion.

Therefore, according to the above embodiment, it is possible to transfer the highly accurate tooth profile on the side of the grinding finish gear 2 to the tooth surface of the shaving finish gear 3 in the initial stage of operation, and to achieve good tooth contact between both gears 2 and 3. Since it can be obtained, the contact pressure of the tooth flanks can be reduced to improve the tooth flank strength, and the stress applied to the roots of both gears 2 and 3 can be reduced to significantly improve the breakage strength. At the same time, the interference portion due to the meshing of the teeth can be removed by reasonably quick wear, and the meshing noise of both gears 2 and 3 can be remarkably reduced. Pair 1
One of the gear pair 1 can be inexpensively realized as the shaving finish gear 3.

The gear pair of the present invention is not limited to the above-mentioned embodiment, and a spur gear is shown in the drawing, but various shapes such as helical gears and bevel gears are used. It is needless to say that the present invention can be applied to gears and that various changes can be made without departing from the scope of the present invention.

[0027]

According to the above-described gear pair of the present invention, it is possible to transfer the highly accurate tooth profile on the side of the finish grinding gear to the tooth surface of the shaving finish gear at the initial stage of operation, so that good tooth contact between both gears can be achieved. As a result, the contact pressure on the tooth flanks can be reduced to improve the tooth flank strength, the stress on the tooth roots of both gears can be reduced, and the breakage strength can be greatly improved. The interference part due to the meshing of the gears can be removed by reasonably quick wear, and the meshing noise of both gears can be significantly reduced. An excellent effect that one of them can be realized as a shaving finish gear at low cost can be obtained.

[Brief description of drawings]

FIG. 1 is a sectional view showing an example of an embodiment for carrying out the present invention.

2 is a micrograph showing a microstructure of a cross section of the shaving-finished gear of FIG. 1. FIG.

FIG. 3 is a micrograph showing a comparative example in which an abnormal carburizing layer having a nonuniform thickness is formed.

FIG. 4 is an explanatory view schematically showing a generation state of an abnormal carburization layer in the micrograph of FIG.

FIG. 5 is an explanatory view showing a state where wear of the contact portion of FIG. 4 has progressed.

[Explanation of symbols]

1 gear pair 2 Ground finish gear 3 Shaving finish gear 4 Carburized abnormal layer

Claims (3)

(57) [Claims] 1. A combination of a grinding finish gear, which is obtained by carburizing and quenching a gear-cut gear material, and a shaving finish gear, which is obtained by subjecting a gear-cut gear material to shaving and then carburizing and quenching. The tooth surface of the gear is worn and grinded in the initial stage of operation.
By intentionally forming an abnormal carburizing layer so that the tooth profile on the side is transferred
A pair of gears characterized by that. 2. A gear material forming a shaving finish gear has, as chemical components, 0.10 to 0.30% by weight of C, 0.01 to 0.50% by weight of Si, and 0.60 to 0.60.
2.00 wt% Mn and 0.025 wt% or less P
And 0.040 wt% or less of S, 2.00 wt% or less of Cr, and 0.020 to 0.080 wt% of Nb,
0.0010 to 0.0100 wt% B and 0.010
% N or less, 0.100% or less Ti, and the balance Fe, and the total content of Si, Mn, and Cr is 1.90 to 4.50% by weight. The gear pair according to claim 1. 3. The abnormal carburizing layer has a thickness of 20 to 30 μm.
The gear pair according to claim 1 or 2, characterized in that: