JPS62188854A - Transmission housing - Google Patents

Abstract

PURPOSE:To prevent a noise, by forming a sleeve by materials having a high vibration damping performance, and absorbing the vibration of a gear and a shaft by the sleeve. CONSTITUTION:A transmission housing 1 is formed of a flake graphite cast iron containing carbon and graphite and having a composition containing C, Si, Mn, P, S and a substantial residue of Fe. The cast iron is treated by austenitizing and isothermal transformation. The base structure of the cast iron is formed by a mixture of bainite, retained austenite and if required, martensite. As the transmission housing 1 absorbs the vibration of a shaft 4 by a sleeve 3, a high vibration damping performance is obtained, thus absorbing the vibration generated in the housing and suppressing a vibration noise.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a transmission housing, and more particularly to a transmission housing having a sleeve with excellent damping performance.

(Prior Art) In automobile transmissions, vibrations of gears and shafts, or vibrations of gears and shafts.
+ The quadrangle transmission transmits to the transmission housing and resonates, producing a fairly loud sound, which causes noise in the environment inside and outside the vehicle. Conventionally, a sleeve has been provided between a transmission housing and a bearing that supports a gear or shaft, but this sleeve is designed to solve problems in terms of strength. #j1 iron or the like is used as the material for this sleeve.

(Problems to be Solved by the Invention) However, the damping ability of materials conventionally used for sleeves, such as cast iron, is not sufficient to achieve the objective of Noise Prevention II:. Flake graphite cast iron has traditionally been considered as a material with high damping ability, and in particular,
Heat-treated flake graphite cast iron as described in No. 9 and JP-A No. 52-5618 has a high damping ability and is also excellent in strength, but it does not reduce the vibration noise of gears and shafts. In order to suppress this, materials with even better damping ability are desired. Therefore, an object of the present invention is to provide a transmission housing that can effectively suppress the generation of vibration noise by forming the sleeve from a material with higher damping ability.

(Means for Solving the Problems) In order to achieve the above object, the transmission housing of the present invention contains C: 3 to 4% by weight, Si: 1.
8 to 3.51%%, Mn: 0.8% by weight or less, P: 0.
1% by weight or less, S: 0.15% by weight or less,
The remainder is substantially Fe, and the carbon equivalent is 4.3 to 5.0
% by weight, and flake graphite cast iron containing 8 to 22% graphite in area ratio is subjected to austenitization treatment at 850 to 1000°C for 30 minutes or more and isothermal transformation treatment at 200 to 400°C for 10 minutes or more, It is characterized in that it is formed by casting or press-fitting a sleeve formed of flake graphite cast iron whose base structure is a mixed structure of bainite, retained austenite, and optionally martensite.

The transmission housing of the present invention is manufactured by die casting in which a sleeve formed from austempered flake graphite cast iron as shown in L is cast into the transmission housing body, or the sleeve is
It is manufactured by press-fitting into a molded body of a transmigration housing.

The transmission housing body can be made of materials commonly used for transmission housings, such as aluminum.

Next, the reasons for limiting the heat treatment conditions for each component of the flake graphite cast iron forming the sleeve will be described.

C: If it is less than 3%, the necessary area ratio of graphite cannot be obtained, and therefore the desired attenuation ability cannot be obtained.

Also, if it is higher than 4%, it will cause significant embrittlement of the material.
It is necessary to set it to 3-4%.

If Si: less than 1.8%, the necessary area ratio of graphite cannot be obtained, and therefore the desired attenuation ability cannot be obtained. Also 3.5%
1.8~ because higher values result in significant embrittlement of the material.
It needs to be 3.5%.

Mn: If it is higher than 0.8%, it will segregate and cause embrittlement, so it needs to be 0.8% or less.

P: If it is higher than 0.1%, the material becomes brittle, so 0.1%
It is necessary to do the following.

S: If it is higher than 0.15%, the material becomes brittle, so 0.
It is necessary to keep it below 15%.

) Father element equivalent: If it is other than 4.3 to 5.0%, the necessary surface jA ratio of graphite cannot be obtained, and therefore the desired attenuation ability cannot be obtained, so it is necessary to set it to 4.3 to 5.0%. There is.

Since high damping ability cannot be obtained with a graphite area ratio other than 28% to 22%, it is necessary to set the area ratio to 8% to 22%.

If the austenitization treatment is lower than 2850℃, the amount of C in the base will be small and high damping capacity will not be obtained, and if it is higher than 2850℃, it will be difficult in terms of production technology.

Further, if the heating time is shorter than 30 minutes, sufficient austenitization cannot be achieved, so it is necessary to carry out the heating at 850°C to 1000°C for 30 minutes or more.

Isothermal transformation treatment = If the temperature is lower than 200°C, heat treatment distortion will increase and quench cracking will occur, if it is higher than 400°C, sufficient damping capacity will not be obtained, and if it is shorter than 10 minutes, sufficient bainite formation will not occur.

It is necessary to carry out the heating at 200°C to 400°C for 10 minutes or more.

(Function) In the transmission housing of the present invention, since the sleeve is made of the material limited above, it has a high vibration damping ability and can suppress vibrations by absorbing vibrations generated within the housing.

(Example) Hereinafter, the present invention will be explained in more detail with reference to Examples.

Example: C: 3.7%, Si: 2.5%, Mn: 0.5
%, P: 0.04%, S: 0.07%, the carbon equivalent is 4.5%, and the graphite area ratio is 15%. The obtained austempered flaky graphite cast iron is subjected to an austempering process consisting of isothermal transformation treatment at 300°C for 2 hours, as shown in Fig. 1.
A sleeve 3 is attached to the transmission housing body 2 at a position corresponding to the circumference of the bearing 7 of the pillion differential drive 6, a position corresponding to the circumference of the bearing 7 of the pillion differential drive 6, and a position corresponding to the circumference of the gear bearing 7 of the intermizoite shaft 4. I made an aluminum transmission blind housing 1 cast in the aluminum alloy using Guicast.

Test Example 2 The vibration characteristics of the transmission housing of the above embodiment and the conventional transmission housing were investigated. In the conventional transmission housing, the material of the sleeve in the above embodiment is JIS FC.
A product manufactured in place of D45 spheroidal graphite cast iron was used. The results are shown in the graph of FIG. 2. In the graph, the broken line a shows the vibration characteristics of the transmission housing according to this example, and the solid line shows the vibration characteristics of the transmission housing of the conventional example. From the graph, it can be seen that the transmission of this example It is clear that the effect of the sleeve on the housing is superior compared to that of the prior art.

Since it is made of a material with high vibration damping ability, the vibrations of the gear and shaft are well absorbed by the sleeve, and the noise generated by the vibrations can be significantly suppressed compared to the past.

[Brief explanation of drawings]

FIG. 1 is a cross-sectional view showing a transmission housing according to an embodiment of the present invention and a transmission 7/john member built therein, and FIG. 2 shows vibration characteristics of the transmission housing of FIG. 1 and a conventional transmission housing. This is a graph showing. l...Transmission housing 2...Transmission housing body 3...Sleeve 4...Intermizoite shaft 5...Gear counter driven 6...Pillion differential drive Patent applicant Toyota Motor Corporation ( 1 other person) Age 1

Claims (1)

[Claims] C: 3-4% by weight, Si: 1.8-3.5% by weight, Mn
: 0.8% by weight or less, P: 0.1% by weight or less, S: 0.
Containing 15% by weight or less, the remainder being substantially Fe,
Flaky graphite cast iron having a carbon equivalent of 4.3 to 5.0% by weight and containing 8 to 22% of graphite in terms of area ratio is subjected to austenitization treatment at 850 to 1000°C for 30 minutes or more and 200 to 400°C.
It is made by casting or press-fitting a sleeve made of flake graphite cast iron that has been subjected to isothermal transformation treatment at 10 degrees Celsius and whose base structure is a mixed structure of bainite, residual austenite, and in some cases martensite. transmission housing.