JPH053709Y2 - - Google Patents

Description

[Detailed description of the invention] A. Purpose of the invention (1) Industrial application field The present invention is a cover device for an exhaust manifold for an internal combustion engine, in which the exhaust manifold itself is covered with a heat shielding cover fixed to the exhaust manifold. Regarding.

(2) Prior art In the exhaust manifold of an internal combustion engine, the exhaust manifold is covered with a heat shielding cover to prevent heat damage to parts near the manifold and to keep the manifold itself warm, thereby minimizing heat from the manifold. Things that have been made to block it are already known.
Furthermore, in order to especially enhance the heat shielding effect of the heat shielding cover, the cover is formed from two sheets of plate material that are overlapped with each other, and the cover is fixed to a boss portion protruding from the outer surface of the exhaust manifold main body. A device in which a gap is formed over a wide range between the cover and the outer surface of the manifold body is also known (for example, see Japanese Utility Model Application No. 50-150618).

(3) Problems to be solved by the invention However, if a gap is formed over a wide range between the heat shielding cover and the outer surface of the manifold body as described above, there will be fewer restraints on the cover, and the cover will become looser. itself becomes more likely to vibrate.
In particular, the heat shield cover is made of approximately the same material and has the same thickness.
If the cover is constructed by overlapping two plates, the natural frequencies of each plate will be approximately the same, making it easier for the plates to resonate with each other. Generates relatively large vibration noise due to the vibration of the main unit.
There are problems specific to this type of heat shield cover.

The present invention was proposed in view of the above circumstances, and an object of the present invention is to provide a cover device for an exhaust manifold for an internal combustion engine that can solve the above problems with a simple structure.

B. Structure of the invention (1) Means for solving the problem In order to achieve the above object, the present invention fixes a heat shielding cover to the boss protruding from the outer surface of the manifold body of the exhaust manifold. In the cover device for an exhaust manifold for an internal combustion engine, the cover device for an exhaust manifold for an internal combustion engine is configured to cover the manifold main body with a gap, and the heat shielding cover is composed of at least two plates of substantially the same material that are overlapped with each other, and It is characterized in that the thickness of at least one of the plates is different from the thickness of the other plates.

(2) Effects According to the above configuration, the heat insulation performance of the cover itself is improved due to the mutual polymerization effect of at least two plates forming the heat shield cover. In addition, even if these plates are made of approximately the same material, the natural frequencies of each plate can be easily made to differ simply by a difference in plate thickness, so the plates exert a vibration damping effect on each other, and as a result, the cover Even when vibrations from the engine body are transmitted through the exhaust manifold, the vibration noise generated by the cover itself is kept low.

(3) Embodiment An embodiment of the present invention will be described below with reference to the drawings. In FIG. 1, four exhaust ports (not shown) are located on one side of the cylinder head portion 1 of a multi-cylinder internal combustion engine E in the crankshaft direction ( The upstream ends of a plurality of branch pipes constituting the manifold body 2 of the exhaust manifold M are respectively connected to these exhaust ports, and the downstream ends of the branch pipes are connected to the exhaust ports. The ends are gathered together and connected to an exhaust pipe 3, and a catalytic converter and a muffler (not shown) are interposed in the middle of the exhaust pipe 3.

The outer surface of the exhaust manifold M is covered with a heat shielding cover C of the present invention. This cover C is constructed by press-forming two plates 4 and 5 made of the same material (for example, rolled steel), which are overlapped with each other, in a shape that follows the outer shape of the exhaust manifold M. Those two plates 4 and 5 remain in a polymerized state,
It is fixed by a bolt B to a boss portion 2a that is integrally provided on the outer surface of some branch pipes in the manifold main body 2, and in this fixed state, between the cover C and the outer surface of the manifold main body 2, there is a part of the cover C. Gaps S are formed over a wide range to enhance the heat shielding effect. Moreover, since the cover C is formed from the two plate materials 4 and 5 that overlap each other, an air layer is formed between the plate materials 4 and 5 to some extent, and the cover C
The insulation performance of

Also, the outer plate 4 of the two plates 4 and 5
The plate thickness t ₁ of the inner plate material 5 and the plate thickness t ₂ of the inner plate material 5 are set to be different from each other, thereby significantly reducing the vibration noise of the cover C.
This was confirmed by the experiment described below.

That is, the plate thicknesses t ₁ and t ₂ are respectively 0.6 mm and 0.4 mm.
(Example 1), 0.8 mm; 0.4 mm (Example 2), 0.5 mm; 0.5 mm (Comparative example), and cover C removed (Reference example). The loudness of the sound was measured at measurement points near the exhaust manifold M during engine operation. Figure 3 shows the change in the sound pressure level with respect to the engine speed, and Figure 4 shows the frequency distribution of the measured sound when the engine speed is 1200 rpm.In particular, according to Figure 3, the plate thickness t ₁ ; It is clear that the sound pressure level is lower in the samples with different t ₂ (Examples 1 and 2) than on the samples with the same t 2 (Comparative Examples), and
It is also clear that the sound pressure level is lower when the difference between t ₁ and t ₂ is larger (Example 2) than when it is smaller (Example 1). On the other hand, according to Fig. 4, at frequencies above 1KHz, which is a particular problem in terms of noise countermeasures for internal combustion engines,
It is clear that the sound pressure level is much lower in Examples 1 and 2 than in Comparative Example in the high frequency range. The reason for this effect is that the natural frequencies of the plates 4 and 5 differ greatly due to the difference in plate thickness, and the plates 4 and 5 exert a vibration damping effect on each other, reducing the vibration noise of the cover C. This is thought to be due to the fact that it can be kept low.

Incidentally, the same effect can be obtained even if the cover C is composed of three or more plates that are overlapped with each other, and the thickness of at least one of the plates is made different from the thickness of the other plates. It has been confirmed through experiments that this can be obtained.

C. Effects of the invention As described above, according to the invention, the heat shielding cover is fixed to the boss portion protruding from the outer surface of the exhaust manifold body and covers the manifold body with a gap, and is made of at least two layers overlapping each other. The heat shield cover is made of at least two plates made of substantially the same material, and the thickness of at least one of the plates is different from that of the other plates. Due to the mutual polymerization effect, the heat insulation performance of the heat shield cover itself becomes good, and even if the plates are made of almost the same material, the natural frequencies of each plate can be easily made to differ simply by a difference in plate thickness. Therefore, even if a wide gap is formed between the outer surface of the manifold body and the heat shielding cover due to the special installation of the boss part, the vibrations will be damped during engine operation. As a result, the vibration noise generated by the cover itself can be suppressed to a low level, and as a result, an extremely useful heat shielding cover device that satisfies both requirements for heat insulation and quietness can be obtained.

[Brief explanation of the drawing]

The drawings show one embodiment of the device of the present invention, and FIG. 1 is a partially cutaway front view of an internal combustion engine, and FIG.
FIG. 3 is a graph showing the magnitude of sound near the intake manifold with respect to the engine speed, and FIG. 4 is a graph showing the frequency distribution of sound near the intake manifold. C...Cover, E...Internal combustion engine, M...Exhaust manifold as exhaust system, 2...Manifold body, 2a...Boss part, _t1 , _t2 ...Plate thickness, 4,5
...Plate material.

Claims (1)

[Scope of utility model registration request] A heat shielding cover C is fixed to a boss portion 2a protruding from the outer surface of the manifold body 2 of the exhaust manifold M, and the heat shielding cover C covers the manifold body 2 with a gap S. In the cover device for an engine exhaust manifold, the heat shielding cover C is composed of at least two overlapping plates 4 and 5 made of substantially the same material, and at least one of the plates 4 and 5 is made of substantially the same material. A cover device for an exhaust manifold for an internal combustion engine, characterized in that a plate thickness t ₁ of a plate material 4 is different from a plate thickness t ₂ of another plate material 5.