JP3260099B2 - Aluminum cast-in member excellent in damping ability and method of manufacturing the same - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an aluminum alloy die-casting component having a through hole for supporting a bearing such as a transmission case rear cover of an automobile, and more particularly to an aluminum alloy casting having excellent vibration damping ability and low noise generation. It relates to a wrapping member.

[0002]

2. Description of the Related Art Recently, automobiles have been reduced in weight from the viewpoint of resource saving and energy saving. In order to reduce the weight of automobiles, structural changes and materials of various components that make up automobiles are being actively performed.Especially because the weight can be easily reduced, the material is changed from heavy iron to aluminum. Changing to light alloys such as alloys is under way. Changing the material from iron to aluminum alloy requires approximately 2% of the vehicle weight.
It starts with engine parts, which account for about a percentage, and extends to drive trains and underbody parts.

[0003]

For example, the transmission case has conventionally been made of iron, but for the above-mentioned reason, the formation of a light alloy has been studied. This transmission case covers the outside of a transmission portion having a number of gears for transmitting the output from the engine to the drive shaft while changing the rotation speed, and the rear cover has a bearing holding portion for supporting the drive shaft. Although it is necessary to have holes, it is not necessary to increase the mechanical strength of the main body so much that the main body is formed to be thin.

[0004] In recent years, however, there has been an increasing demand for lower vibration and lower noise as automobiles become more sophisticated and sophisticated. Therefore, when a transmission case including a large number of high-speed rotating gears and its rear cover are formed of an aluminum alloy, noise caused by vibration becomes a problem. That is, in the case of the conventional iron transmission case, the damping capacity of the material itself is high, and this is not a problem. On the other hand, with the change of the material to the aluminum alloy, the damping capacity of the material itself is low ( (Attenuation coefficient = 0.3%). An object of the present invention is to provide a member cast with an aluminum alloy that does not generate much noise due to vibration as described above.

[0005]

Means for Solving the Problems In order to solve the above problems, the present inventors have conducted various studies on a transmission case. First, it is conventionally known that the noise is caused by vibration of the engine being transmitted to a transmission case from a bearing for supporting a drive shaft and a holding hole thereof. Thus, the present inventors
This problem can be solved by casting a steel member with excellent damping ability into the bearing holding hole, including reinforcement of the bearing holding hole, and found that cast iron with an appropriate structure has particularly excellent damping ability. The present invention has been reached.

That is, the present invention relates to an aluminum cast-in member excellent in damping performance , wherein an austempered graphite cast iron member is cast in an aluminum alloy member having a main part having a thickness of 6 mm or less. If the member is heavy
2.5% to 4.0% C, 2.0% to 3.5% Si, 0.1% to 0.8%
Mn, or even 0.1-2.0% Cu, 0.1-2.0% Ni and 0.
One or more of Mo of 0.5 to 0.5%
Part Fe and unavoidable impurities, and said aluminum
After the molten alloy is poured, the graphite cast iron
It is characterized by being cooled down . When the graphite cast iron member is flaky graphite cast iron, the damping ability is further improved. Further, it is preferred graphite morphology is predominantly (JIS) A type austempering flake graphite cast iron, more preferably the tissue of the graphite cast iron member comprises 5.0 to 14.0% of residual austenite, and the balance bainite.

In the present invention, the aluminum alloy member may contain 2.0 to 4.0% by weight of Cu, 7 to 12% of Si,
It is preferable that it is made of 0.3% or less of Mg and the balance is aluminum. High pressure casting such as die casting or squeeze casting is a good method for manufacturing aluminum cast-in members .
Particularly, a die casting method is preferable. Particularly, when the aluminum cast-in member is an automobile part such as a transmission case rear cover, excellent characteristics can be exhibited.

The reasons for limiting each component of the present invention are as follows. When the thickness of the main part of the aluminum alloy member is greater than 6 mm, the damping capacity of the aluminum alloy member is increased by the influence of the thickness, so that it is not particularly necessary to apply the present invention. The thickness of the main part of the aluminum alloy member is a general thickness (thickness of a part shaping the shape of the product). In a thin member, a thin part other than the boss portion and the rib portion is used. Say the thickness. The graphite cast iron member needs to have a certain level of mechanical strength in order to hold a bearing that supports the drive shaft, and a structure composed of residual austenite and residual bainite by austempering as in the present invention (hereinafter referred to as “bainite”). It is preferable that the toughness and the fatigue resistance are further improved by adopting a “BA structure”). Further, by using such a structure containing bainite, the damping ability is further increased as compared with the structure containing only graphite.

In particular, when the graphite cast iron is flaky graphite cast iron,
It has excellent damping ability as compared with spheroidal graphite cast iron, and can be expected to have an even greater noise prevention effect. Further, the reason for limiting the composition of the graphite cast iron member is that C is an important component in cast iron together with Si, and if it is less than 2.5%, chill tends to occur, and if it exceeds 4.0%, dross tends to occur. Therefore, C is 2.
5 to 4.0%. Si is an important component in cast iron together with C. If it is less than 2.0%, the flow of the molten metal during pouring is poor, and if it exceeds 3.5%, the toughness is reduced. For this reason, Si is set to 2.0 to 3.5%. Mn is an element necessary for increasing the hardenability, and if its content is less than 0.1%, its effect is small, and if it exceeds 0.8%, toughness is reduced.
Therefore, Mn is set to 0.1 to 0.8%. Cu is an effective element having a bainite-promoting effect. If it is less than 0.1%, its effect is small, and if it exceeds 2.0%, toughness is reduced. Therefore, Cu is set to 0.1 to 2.0%.
Ni is an effective element having a bainite promoting effect,
If it is less than 0.1%, the effect is small, and if it exceeds 2.0%, the toughness is reduced. Therefore, Ni is 0.1 to 2.0.
%. Mo is an effective element having a bainite-promoting effect. When the content is less than 0.05%, the effect is small.
If it exceeds 5%, the toughness is reduced. Therefore, Mo is set to 0.05 to 0.5%. Among the above elements, Cu, N
i and Mo may contain two or more kinds. In addition, as the heat treatment of the graphite cast iron, the cast product is kept at 820 to 950 ° C. for 0.5 to 5 hours to austenitize, and immediately
It is preferable to carry out an austempering treatment at 80 ° C. or more for 0.5 hours or more.

The structure of the graphite cast iron member preferably has a residual austenite amount of 5.0 to 14.0% and a residual bainite structure. When the amount of retained austenite is less than 5.0%, the workability such as machinability is remarkably reduced, and 14.0.
%, The vibration damping ability decreases. Further, the aluminum alloy contains 2.0 to 4.0% by weight of Cu,
It is preferable that the material consist of 2% of Si, 0.3% or less of Mg and the balance aluminum. Cu is added to improve the strength of the product. If the content is less than 2.0%, the effect is small, and if it is more than 4.0%, the elongation is greatly reduced, and the cracking sensitivity is increased. Si improves the flow of hot water and improves the shrinkage, but if less than 7%, the effect is small,
If it is more than 12%, primary crystal Si increases, and strength, workability, molten metal flow, and shrinkage decrease. Mg is added for the purpose of improving the strength, but if it exceeds 0.3%, the toughness decreases.

In general, graphite cast iron members subjected to austempering have a problem in that when the temperature rises near the transformation point during casting or the like, bainite transforms to pearlite, and the bent BA structure is broken. The present inventors have conducted intensive studies and found that the temperature of the graphite cast iron member was 400 ° C.
It was found that the bainite structure hardly changed to the pearlite structure if it could be cooled to 400 ° C. or less within 10 seconds even if the temperature rose to not less than 10 ° C. Therefore, as a result of studying a casting method in which the temperature of the graphite cast iron member can be cooled to 400 ° C. within 10 seconds during casting, a high-pressure casting method such as a die casting method or a squeeze casting method is preferable as the casting method, and particularly, die casting is preferred. It has been found that casting methods are preferred.

[0012]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of the present invention will be described with reference to the following experimental examples. (Experimental Example 1) First, it was examined whether or not the structure of the BA material was transformed by increasing the temperature. 3.04% C, 2.27% by weight
% Si, 0.76% Mn, 0.31% Mo, 0.
A molten metal having a composition of 51% Cu and the balance of Fe was poured into a sand mold at a pouring temperature of 1380 ° C. to obtain a flake graphite cast iron member.
After heating this member to a temperature of 850 ° C. and holding it for 2 hours, it was immediately immersed in a salt bath held at 390 ° C. to have a structure of flaky graphite and 8.6% of retained austenite. The rest consists of bainite 10
A specimen of BA material of mm × 10 mm × 20 mm was obtained. The test pieces were then 2.3% by weight Cu, 10.5% Si, 0.11% Mg, 0.8% Fe, 0.71%
5 seconds, 10 seconds, 30 seconds, and 60 seconds in a 580 ° C. alloy melt containing Zn, 0.23% Mn and the balance aluminum.
After soaking half of the test piece for 2 seconds, it was allowed to cool in air and examined for changes in the structure. Each organization photo (400
1 and 2 for 10 seconds, FIGS. 3 and 4 for 10 seconds, FIGS. 5 and 6 for 30 seconds, and FIGS. 7 and 8 for 60 seconds. 1, 3, 5, and 7 are the parts that are not immersed, and FIGS. 2, 4, 6, and 8 are the parts that are immersed, and (a) is 100 times the metal and (b) is 400 times the metal. It is an organization photograph. Further illustrating the relationship between the immersion time and the Rockwell hardness of the test strip (H _R C) in FIG. According to the above results, no change in the bainite structure was observed after immersion for up to 10 seconds (see FIGS. 2 and 4), but part of the bainite structure changed to a pearlite structure after immersion for 30 seconds and 60 seconds. (See FIGS. 6 and 8). Also from FIG. 9, although immersion until time 10 seconds maintains a hardness of H _R C32~35, the immersion time of 30 _seconds, H R C2
It can be seen that it drops sharply to 5. From the above results,
Under the immersion condition of about 10 seconds, which is the condition of the actual die casting, neither the bainite structure nor the hardness change was observed.
It can be seen that the function as the material A can be maintained.

(Experimental Example 2) FIG. 10 shows a sectional shape of a transmission. As shown in FIG. 10, the power of the engine is transmitted from the driving force transmission unit 4 through the output shaft 5 to the transmission unit 6. Further, a bearing support member 3 is cast in the transmission case rear cover 2 to hold a bearing 8 that supports the output shaft 7 to which power is transmitted from the transmission unit 6. The transmission section 6 is entirely covered by the transmission case 1. FIG. 11 shows a detailed view of the bearing support member 3 and the transmission case rear cover 2. The transmission case rear cover 2 was prepared by casting the bearing support member 3 with an aluminum alloy. First, in weight percent,
04% C, 2.27% Si, 0.76% Mn,
An outer diameter 80 of graphite cast iron consisting of 0.307% Mo, 0.51% Cu and balance Fe, having a structure of flaky graphite and retained austenite 8.6%, and balance bainite.
A bearing holding member 3 having a diameter of 70 mm, an inner diameter of 70 mm and a thickness of 5 mm was prepared, fitted into a die casting mold, and surrounded by 2.3% by weight of Cu, 10.5% of Si, 0.11% by weight.
% Of Mg and the balance of aluminum at 690 ° C. by injection at an injection pressure of 700 kg / cm 2, whereby the thickness of the main part in the aluminum alloy part is 4 m.
m transmission case rear cover (B) was prepared. For a comparative example, a transmission case rear cover (A) was prepared by die-casting the entire body with only an aluminum alloy without disposing a bearing holding member made of graphite cast iron in a die-casting die. Using the transmission case rear covers A and B, an engine-driven bench test was actually performed, and the radiation sound at each vehicle speed corresponding to the case where the transmission case was incorporated into an automobile was measured.
It is shown in FIG. From FIG. 12, it can be seen that the rear cover B according to the example of the present invention emits lower radiated sound than the rear cover A of the comparative example, and that the radiated sound of the rear cover of the present invention is lower especially in the 85 Km / h range and the 95 Km / h range. Is evident.

[0014]

According to the present invention, even when an aluminum alloy which is lightweight but has a low damping ability is used, die-casting of a thin automobile part such as a transmission case and the like, which is excellent in mass productivity, in particular, generates little noise due to vibration. It can be manufactured using a method.

[Brief description of the drawings]

FIG. 1 is an optical micrograph of a metal structure of a BA material according to an example.

FIG. 2 is an optical micrograph of a metal structure of a BA material according to an example.

FIG. 3 is an optical micrograph of a metal structure of a BA material according to an example.

FIG. 4 is an optical micrograph of a metal structure of a BA material according to an example.

FIG. 5 is an optical micrograph of a metal structure of a BA material according to a comparative example.

FIG. 6 is an optical micrograph of a metal structure of a BA material according to a comparative example.

FIG. 7 is an optical micrograph of a metal structure of a BA material according to a comparative example.

FIG. 8 is an optical micrograph of a metal structure of a BA material according to a comparative example.

9 is a diagram showing the relationship between the immersion time and the H _R C of the molten aluminum of the BA material of the test piece.

FIG. 10 is a sectional view of a transmission according to one embodiment of the present invention.

FIG. 11 is a sectional view of a transmission case rear cover according to one embodiment of the present invention.

FIG. 12 is a diagram showing a relationship between a vehicle speed of a transmission case rear bar and a radiation sound.

[Explanation of symbols]

1 transmission case, 2 transmission case rear cover, 3 bearing support member, 4
Driving force transmission unit, 5 output shaft, 6 transmission unit, 7 output shaft, 8 bearing unit

──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Etsuro Tamura 5200 Mikajiri, Kumagaya City, Saitama Prefecture Inside the Kumagaya Plant of Hitachi Metals Co., Ltd. (72) Mitsuteru Sugano 1-7-2 Nishishinjuku, Shinjuku-ku, Tokyo Fuji Heavy Industries Incorporated (72) Inventor Takato Aoki 1-7-2 Nishi-Shinjuku, Shinjuku-ku, Tokyo Fuji Heavy Industries, Ltd. (72) Inventor Terushige Sato 1-7-1, Nishi-Shinjuku, Shinjuku-ku, Tokyo Fuji Heavy Industries (56) References JP-A-62-188854 (JP, A) JP-A-61-19753 (JP, A) JP-A-62-188852 (JP, A) JP-A-3-138068 (JP, A A) JP-A-8-134577 (JP, A) JP-A-7-259966 (JP, A) JP-A-9-257119 (JP, A) JP-A-7-207332 (JP, A) JP-A-3 -234351 (JP, A) 123020 (JP, A) JP Akira 57-1845 (JP, A) JP flat 9-262657 (JP, A) (58 ) investigated the field (Int.Cl. ^7, DB name) B22D 19/00 C22C 21 / 02 C22C 37/10 C21D 5/00 F16H 57/02 F16F 15/02

Claims (9)

(57) [Claims] 1. An aluminum cast-in member having excellent damping performance , wherein an austempered graphite cast iron member is cast in an aluminum alloy member having a main part having a thickness of 6 mm or less , wherein the graphite cast iron member comprises: 2.5-4.0% by weight
C, 2.0-3.5% Si, 0.1-0.8% Mn, or even 0.1%.
1-2.0% Cu, 0.1-2.0% Ni and 0.05-0.5% Mo
Contains one or more of these, with the balance being Fe and inevitable
Before the aluminum alloy pouring, consisting of impurities
The graphite cast iron member is cooled to 400 ° C or less within 10 seconds.
An aluminum cast-in member characterized by the following . 2. The aluminum cast-in member having excellent damping ability according to claim 1, wherein said graphite cast iron member is flaky graphite cast iron. 3. A graphite structure forms mainly (JIS) A type aluminum cast member having excellent damping capacity as claimed in claim 2, characterized in that the austempering flake graphite cast iron. 4. The structure of the graphite cast iron member is 5.0 to 14.0%.
Aluminum cast member having excellent damping capacity according to any one of claims 1 to 3, characterized in that it consists of residual austenite, and the balance bainite. 5. The method according to claim 1, wherein the aluminum alloy member is
2.0 to 4.0% of Cu, 7 to 12 percent of Si, claim 1-4, characterized in that it consists of 0.3% Mg and the balance aluminum
An aluminum cast-in member excellent in damping ability according to any one of the above. 6. The bearing member according to claim 6, wherein the graphite cast iron member is a bearing support member.
Wherein the aluminum cast-in member is
2. A case cover, comprising:
Aluminum casting having excellent damping ability according to any one of claims 1 to 5,
Wrapping member. When 7. austempering graphitic cast iron member the thickness of the main portion is wrapped casting cast by the following aluminum alloy 6 mm, below 400 ° C. in temperature Note within 10 seconds after the hot water of the graphite cast iron member A method for producing an aluminum cast-in member having excellent damping ability, characterized in that the member is cooled so as to be cooled. 8. The bearing member according to claim 1, wherein the graphite cast iron member is a bearing support member.
Wherein the aluminum cast-in member is
8. A case rear cover.
Manufacturing method of aluminum cast-in member with excellent damping ability described
Law. 9. The method for producing an aluminum cast-in member having excellent damping ability according to claim 7, wherein the cast-in casting is die casting.