JPS62135647A - Silencing cover for engine - Google Patents

Abstract

PURPOSE:To improve a noise shielding characteristic, by coating an engine or its peripheral vibration source with a cover and providing a metallic plate to be arranged in at least a part of the cover facing to the outside so that the whole unit of the cover is formed by synthetic resin. CONSTITUTION:In a two-cycle engine, which secures a crankcase 2 to the bottom part of a cylinder block 1 and mounts a bowl-shaped crankcase cover 3 to the side part of said case 2, the crankcase cover 3 is formed as a whole by synthetic resin. Further this cover 3, in which corresponding to its external wall part (bottom part of bowl) a metallic plate 13 of good noise shielding characteristic is built by insert forming, forms the external wall part 3a into integrally molded construction interposing one sheet of the metallic plate 13 in a sandwich shape by two synthetic resin layers. In this way, a noise around the engine can be reduced.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Application] The present invention relates to a soundproofing technique for an internal combustion engine, and relates to a technique that is effective when used, for example, in a soundproofing structure of a crankcase of an engine.

[Prior Art and Problems] In the crankcase of an engine such as a motorcycle, a transmission, a generator, etc. are arranged along with a crankshaft. Therefore, the sound of gears meshing that occurs inside the crankcase may leak to the outside of the crankcase.
There is a problem in that vibrations in the transmission and cylinder vibrations associated with engine explosions are transmitted through the crankcase, causing the crankcase cover to resonate and generate noise.

Therefore, there is a recess (recess) on the outer wall of the crankcase cover.
By attaching an outer wall plate to this receiver via an elastic member such as rubber, and keeping this outer wall plate away from the cover wall, the noise generated from the crankcase is reduced. An invention has been proposed (Japanese Unexamined Patent Application Publication No. 57-8319).

In the crankcase to which this prior invention was applied,
The elastic member makes it difficult for vibrations caused by the explosion of the transmission or engine to be transmitted to the outer wall plate, thereby reducing noise caused by resonance of the outer wall of the crankcase cover. Furthermore, since the crankcase cover has a double-walled structure, there is an advantage that the meshing noise of the gears in the crankcase is less likely to leak to the outside compared to when the outer wall is one piece.

However, in the prior invention, when the inner wall of the crankcase force bar vibrates, the air between the inner wall and the outer wall plate vibrates, causing the outer wall plate to vibrate.

In other words, like a drum, when one side vibrates, the other side also vibrates, so it was found that the sound reduction effect was not as large as expected.

[Object of the Invention] An object of the present invention is to provide a sound reduction cover that can effectively reduce vibrations and noise generated in the engine and its surrounding operating mechanisms.

[Structure of the Invention] This invention provides a case cover provided to cover the crankcase and other vibration sources in the engine and its surroundings, which is made of synthetic resin. is an integrally molded structure in which the metal plate is integrally incorporated. This makes it difficult for vibrations from the engine, transmission, etc. to be transmitted to the cover by using the damping properties of the synthetic resin, and also prevents the noise generated inside the case from leaking outside by using the sound insulation effect of the metal plate. , which aims to reduce noise around the engine.

[Embodiment] FIG. 1 shows an embodiment in which the present invention is applied to a crank case cover for a two-cycle motorcycle.

A crankcase 2 is fixed to the lower part of a cylinder block 1 constituting a two-stroke engine, and a bowl-shaped crankcase cover 3 is attached to the side of the crankcase 2.
This provides the crankcase 2 with a sealed structure. A crankshaft 5 supported by a pair of ball bearings 4 is disposed within the crankcase 2, and a crank arm 6 integrated with the crankshaft 5 has a connecting rod connected to a piston 7 within the cylinder block 1. The lower ends of 8 are connected by a crank pin (not shown).

In this embodiment, a crankcase cover 3 attached to the side of the crankcase 2 so as to cover a generator 9 attached to one end of the crankshaft 5 is made of synthetic resin. Moreover, the crankcase cover 3 is formed by incorporating a metal plate 13 with good sound insulation properties into the outer wall (bottom of the bowl) to form an insert.
A has an integral mold structure in which one metal plate 13 is sandwiched between two synthetic resin layers. The peripheral wall portion 3b of the crankcase cover 3 is made of only synthetic resin material.

Therefore, the crankcase cover 3 of this embodiment prevents the vibration of the cylinder block 1 caused by engine explosion, the clutch installed on the opposite side (right side in China) of the crankshaft 5, and the transmission (not shown) at the bottom of the crankcase.
Even if vibrations are transmitted through the crankcase 2, the peripheral wall portion 3b made of synthetic resin with good damping characteristics damps the vibrations.

Therefore, due to the vibration of the crankcase 2, the outer wall portion 3a
will not resonate and generate large noise.

Moreover, since the metal plate 13 with a good sound insulation effect is incorporated in the outer wall 3a, noise such as gear meshing noise in the transmission generated inside the crankcase 2 is prevented from leaking to the outside through the outer wall 3a. be able to.

In other words, the crankcase cover 3 of this embodiment has a structure in which the outer wall portion 3a is unlikely to resonate even if the crankcase itself vibrates or the internal air vibrates.

Note that the crankcase cover attached to cover the opposite side of the crankcase 2, that is, the clutch side, is generally formed of a metal plate such as aluminum in order to avoid thermal distortion due to lubricating oil in the clutch. Therefore, in this embodiment as well, the crankcase cover on the side opposite to the generator may be made of aluminum. Alternatively, when the crankcase cover is formed using a synthetic resin with excellent heat resistance, it may have an integral mold structure with metal plates 13 on the outer wall portions 3a on both sides as shown in FIG.

FIG. 2 shows a second embodiment of the sound reduction cover according to the invention.

In this embodiment, the outer wall 3a of the crankcase cover 3
Instead of using a sandwich structure in which the metal plate 13 is sandwiched between synthetic resin layers from both sides, the metal plate 13 is joined to the inside of the outer wall 3a of the crankcase cover 3 made of synthetic resin, and the locking piece 14 is used to connect the metal plate 13 to the inside of the outer wall 3a of the crankcase cover 3 made of synthetic resin. It is designed to be installed by locking the plate 13. The locking piece 14 is formed integrally with the crank cover. The cover of this embodiment also has substantially the same sound reduction effect as the cover of the above embodiment due to the same function, and since the metal plate 13 is locked with the locking piece 14, the metal plate 13 can be attached to the outer wall with adhesive. There is less risk of it falling off than when it is glued to the inner surface of the portion 3a. In other words, since there is lubricating oil inside the crankcase and the temperature is quite high, if the metal plate 13 is attached using adhesive, there is a risk that the adhesive surface will peel off and the metal plate 13 will fall off. In the cover of the above embodiment, the metal plate 1 is
There is no such thing because we are suppressing 3.

The metal plate 13 has a locking piece 14 as in the first embodiment.
When forming the crank cover 3 having the above, it can be installed by incorporating it as an insert and integrally forming it. Alternatively, after the cover is formed, the outer wall portion 3a or the locking piece 14 may be deformed and the metal plate 13 may be fitted therein.

15 is a protection plate integrally formed with the cover 3 so as to cover the chain sprocket that drives the rear wheels.

Note that since a panel is provided in which a synthetic resin layer is sandwiched between two metal plates, it is also possible to use this panel to form a case cover as in the above embodiment by press working. However, such panels are quite difficult to deep draw, so they are difficult to apply to deep objects such as crankcase covers.

Furthermore, in areas that are bent at right angles due to deep drawing, the intermediate synthetic resin layer may be cut, which may reduce the sound reduction effect by half. In other words, if the intermediate synthetic resin layer is cut, the outer and inner metal plates will come into contact with each other, and the vibrations of the inner metal plate will be transmitted to the outer metal plate, eliminating the vibration damping effect of the synthetic resin layer.

Although the present invention has been described above as applied to a crank case cover, the present invention is not limited thereto, and can be applied to general case covers provided to cover engine head covers and other vibration sources in the engine or its surroundings. I can do it.

[Function/Effect] The cover of the crankcase and other cases provided to cover the engine and surrounding vibration sources is made of synthetic resin, and the parts facing the outside where a greater sound insulation effect is desired are made of metal plates. The damping properties of the synthetic resin make it difficult for vibrations from the engine, transmission, etc. to be transmitted to the case cover, and the sound insulation effect of the metal plate reduces noise generated inside the case. By preventing leakage to the outside, noise around the engine can be reduced.

[Brief explanation of drawings]

FIG. 1 is a sectional front view showing one embodiment of the present invention applied to an engine crankcase cover, and FIG. 2 is a sectional view showing another embodiment of the crankcase cover. 2...Crankcase, 3...Crankcase cover, 3a...Outer wall part, 5...Crankshaft,
9... Generator, 13... Metal plate. 1st page Figure 2

Claims (1)

[Claims] (1) A cover provided to cover the vibration source of the engine or its surroundings, characterized in that it is entirely made of synthetic resin, with a metal plate disposed at least on the outwardly facing part. engine noise reduction cover.