JPS638340B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a cast case with a vibration-proof structure suitable for a transmission case, an engine body, or the like.

In recent years, noise from automobiles has become a major social problem, and the sound radiated from a cast case caused by internal noise or vibration of an engine or transmission accounts for a fairly large proportion of automobile noise.

In order to reduce the sound radiated from this type of case,
Conventionally, methods have been used to increase the rigidity of the entire case by increasing the thickness of the casting case itself, reinforcing it with ribs inside and outside the casting case, or covering the outer periphery of the casting case with sound-absorbing material. There is.

However, the former method significantly increases the weight, and the latter method has disadvantages such as poor maintainability and an increase in oil temperature within the case, and is not necessarily satisfactory.

As shown in Japanese Utility Model Application Publication No. 53-50345, in the vibration isolation structure of a sheet metal oil pan, etc., a plate-shaped vibration isolation member is fixed to the part corresponding to the vibration antinode position of the oil pan, etc. There are some devices that are configured so that at least a part of the periphery of the oil pan is in elastic contact with an oil pan, etc. Since the center of the oil pan is fixed so that it comes into elastic contact with other objects, it is troublesome to process the oil pan and other vibration-proofing members.Moreover, even if the oil pan is made entirely of anti-vibration steel plate, the radiated sound will be reduced by -1dB. Judging from the fact that it is common knowledge that the effect is only about (decibels), the contact between the vibration isolating member and the oil pan, etc. is limited to the periphery of the member and does not come in contact with the center. , no greater effect than that using the above-mentioned anti-vibration steel plate can be expected.

In view of the above points, the present invention was devised to provide a cast case with an easy-to-manufacture vibration-proof structure that suppresses increase in weight and deterioration of maintainability, and has a large effect of reducing radiated sound. The gist of this is that a damping member made of a thin steel plate, which is formed in substantially the same shape as the inner surface of a cast case, is partially welded by casting at locations distributed over the entire inner surface of the case.

The following description will be made based on the illustrated embodiment.

The figure shows an example in which the present invention is implemented in a cast case of a transmission, in which damping members 21 and 22 made of thin steel plates press-formed into substantially the same shape as the inner surface are provided on the inner surface of the transmission case 1. Welded parts 211a, 221a and non-welded parts 211b,
221b is distributed and dispersed to form welded parts 211a, 22.
1a, which is welded to the cast case 1 during casting.

The thin steel plates used for the damping members 21 and 22 have a thickness of about 1.6 to 2.0 mm,
In this example, members 21 and 22 are
Although it is divided into two parts, depending on the vibration isolation area, it may be made into one piece instead of being divided. Further, the ends of the damping members 21 and 22 are bent inward as shown in FIG.
2b is formed.

When welding such damping members 21 and 22 to the inner surface of the transmission case 1, first, the damping members 21 and 22 formed as shown in FIG. 2A are placed inside the core molds 31 and 32 as shown in FIG. The core pieces 41 and 42 are manufactured by setting each mold in a mold and filling the mold with core sand. At this time, the damping members 21 and 22 are formed with locking parts 21a and 21b and 22a and 22b, respectively, so that the core sand is embedded in the damping members 21 and 22, and the damping members are separated from the core due to the heat during pouring, and the thin steel plate is This prevents melting and, in turn, destruction of the core.

Next, the core pieces 41 and 42 are placed in the core mold 31,
32 and bonded together using, for example, an epoxy adhesive, a core 40 having damping members 21 and 22 on the outer periphery is manufactured as shown in FIG. 2C.

After the core 40 is manufactured in this way, the surfaces of the damping members 21 and 22 attached to the outer periphery are coated with an aqueous solution of an alumina-based or graphite-based welding prevention agent, such as Suncoat (trade name). Disperse and apply locally. That is, as shown in FIG. 2C, welding preventive agents 51 and 52 are applied at appropriate intervals (for example, 30 to 50 mm) to areas where welding is not desired. Note that an aqueous solution of borax or the like may be applied as a flux to the part to be welded.

The transmission case 1 is formed by setting such a core 40 in a mold (not shown) and pouring the metal.
At this time, the surfaces of the damping members 21 and 22 to which no anti-welding agent is applied or to which flux is applied are melted by the temperature of the hot water and welded to the cast case 1. On the other hand, the part coated with the anti-welding agent is not welded and is attached in close contact with the inner surface of the case 1.

The cast transmission case 1 formed as described above generates vibrations and noise when operating as a transmission with gears etc. installed inside, but the radiated sound due to this is emitted from the inner surface of the case 1 and the damping member. 21,2
The friction damping effect is significantly reduced by the planar friction damping effect caused by the surface contact between the welded portions and the non-welded portions formed between the welded portions dispersed over the entire surface of the Damping member 2
It is only necessary to disperse and weld the damping members 21 and 22, and because the damping members 21 and 22 are in surface contact, no special processing is required, and productivity can be improved.

According to experiments conducted by the present inventors, in a transmission case equipped with the damping members 21 and 22 as described above, the sound pressure with respect to the rotational speed of the input shaft when operating as a transmission with gears incorporated therein is The level is as shown by line A in Figure 3,
Sound pressure level B of the same type transmission case without any countermeasures
As is clear from the comparison with the line, it was confirmed that the radiated sound was significantly reduced (more than 3 dB).

As described above, in the cast case according to the present invention, the damping member made of thin steel plate formed in substantially the same shape as the inner surface of the case is partially welded by casting at dispersed locations over the entire inner surface of the case. A large damping effect can be achieved over the whole of the cast case, especially regarding radiated sound, and there is little increase in weight, and since the damping member is attached to the inner surface of the case, maintainability will not be deteriorated.

In addition, since the damping member is attached to the inner surface of the casting case, it can be incorporated into the process when manufacturing the male core of the casting case and casting the case, making it easy to manufacture and cost-effective. can also be lowered.

Note that the above embodiment takes a transmission case as an example,
Although the damping member is attached to the inner surface of the damping member, it is also possible to apply this to an engine body, for example.

[Brief explanation of the drawing]

FIG. 1 is a sectional view of a cast case according to the present invention;
FIGS. 2A to 2D are diagrams showing an example of the manufacturing process of a damping member and a core to which it is attached, and FIG. 3 is a diagram showing an experimental example of sound pressure level using a transmission as an example. 1; Casting case, 21, 22; Damping member, 40; Core.

Claims (1)

[Claims] 1. A cast case with a vibration isolation structure, in which damping members made of thin steel plates, which are formed in substantially the same shape as the inner surface of the cast case, are partially welded by casting at locations distributed over the entire inner surface of the case. .