JPH0641727B2 - Silencer for internal combustion engine - Google Patents

Description

TECHNICAL FIELD The present invention relates to a silencer provided in an exhaust pipe of an internal combustion engine.

[Prior Art] As a conventional silencer for a general internal combustion engine, a cylindrical sound-deadening layer made of a sound-absorbing material is provided in a part of the exhaust pipe by penetrating a large number of ventilation holes. And a structure in which an outer tube is covered on the outer periphery of the sound deadening layer. As this sound absorbing material, glass wool containing each component shown in Table 1 below (the content in the table is the content considered excluding the binder adhering to the surface of the glass wool) is needle punched. By so doing, the fibers are entangled with each other to form a felt, and this glass wool mat is most commonly formed by winding the glass wool mat around the exhaust pipe in a tubular shape. Since this glass wool has a high sound absorbing property and is inexpensive, it is used as an indispensable silencer for most internal combustion engines today.

[Problems to be Solved by the Invention] In the muffler having the above-described configuration, since the high-temperature and high-pressure exhaust gas flowing through the exhaust pipe is blown out from the ventilation hole to the sound absorbing material, the sound absorbing material has low sound absorbing property and low cost. In addition to the properties, high temperature heat resistance, fiber strength, and a large number of entangled fibers are required.

However, the glass wool containing each component shown in Table 1 is
The fiber strength was not sufficient, and the number of needles was suppressed to about 20 / cm ^{2 in} order to avoid pulverization by needle punching, so there was little entanglement between the fibers. Also,
Since the high-temperature heat resistance was not necessarily sufficient, there were cases where high-temperature exhaust gas gradually deteriorated and became brittle. In this way, the fiber strength is insufficient, there is little entanglement of the fibers, and the glass wool that has become brittle due to heat deterioration gradually breaks into powder by high-pressure exhaust gas and is sucked into the exhaust pipe from the ventilation hole to the atmosphere. Since it scatters, there is a problem that the muffling effect of the muffler is gradually reduced and pollutes the atmosphere.

Particularly in the field of automobiles, the temperature and pressure of exhaust gas are rising with the recent trend toward higher output of internal combustion engines for automobiles and the addition of exhaust gas treatment devices. The problem of (1) is becoming more prominent, and sometimes glass wool is even melted into glass fragments. Further, since the number of automobiles is very large, and the total amount of the glass wool scattered into the atmosphere is considerably large, it is necessary to solve the problem as soon as the exhaust glass regulation problem.

In order to solve the above problems, it is necessary to use, as the sound absorbing material, a material that has excellent high temperature heat resistance and is difficult to be powdered. Therefore, it has been attempted to use ceramic fibers, silica glass fibers, alumina fibers, acid-treated glass mats, mixed products of these, and mixed products of these with the glass wool as the sound absorbing material. ,
Each material had the following advantages and disadvantages, and it was difficult to apply.

(1) Ceramic fiber High temperature heat resistance is sufficient. However, since the fiber length is as short as about 10 mm, there is little entanglement between the fibers, and it is difficult to form a felt by needle punching. Further, since it is brittle, it is easily broken during needle punching and powdered.

(2) Silica glass fiber and alumina fiber High temperature heat resistance and fiber length are sufficient. However, since it is still fragile, it has the same problem as (1) above. Further, since the cost is 100 to several hundred times higher than that of the conventional glass wool, it is generally not even a target for practical application.

(3) Mixing mat of ceramic fiber and conventional glass wool In the test by the present inventor, the disadvantages of the ceramic fiber of (1) appear, breakage during needle punching or powder, or the defects of the glass wool appear, It has been found to scatter when using the silencer.

(4) Acid-treated mat (The above-mentioned conventional glass wool was soaked in hydrochloric acid to elute impurities to increase the SiO ₂ content, and its components are shown in Table 2.) High temperature heat resistance is comparable to that of the above glass wool. And the higher the SiO ₂ content, the higher. However, since the fiber surface of glass wool is attacked by hydrochloric acid and becomes brittle, there is the same problem as in (1) above. Further, since the corrosive holes due to hydrochloric acid are vacant in the fibers of the glass wool to form cavities, when the hydrochloric acid is washed away with water, the hydrochloric acid that has entered the corrosive holes remains and causes corrosion of the exhaust pipe and outer pipe of the metal product. Become.

The object of the present invention is to solve the above problems, to obtain a good quality sound deadening layer in which many fibers are entangled with each other and less powder is formed, and when the muffler is used, thermal deterioration of the sound deadening layer and scattering due to powdering occur. It is an object of the present invention to provide a novel silencer for an internal combustion engine, which is small in number and whose cost is not so much increased as compared with the conventional one.

[Means for Solving the Problems] In order to achieve the above object, a silencer for an internal combustion engine according to the present invention has a large number of vent holes penetrating a part of an exhaust pipe of the internal combustion engine. The outer periphery of the part contains the components shown in the following Table 3 (the content in the table is the content taken into consideration excluding the binder adhering to the surface of the glass wool), and by needle punching The structure was provided with a cylindrical sound deadening layer using a felted glass wool mat.

The CaO content, which was contained in a large amount in the conventional glass wool in Table 1, may or may not be contained, and when it is contained, 1 wt% or less is suitable. The average fiber diameter of the glass wool is 7-1.
2 μm is common.

Compared with the conventional glass wool of Table 1, this glass wool has a high temperature heat resistance (specifically, for example, a transition point or a softening point) and a fiber strength because of a higher content of SiO ₂ and Al ₂ O ₃ It also has some flexibility.

Further, the needle punching is, for example, 24 # to 32 #.
The needle can be used, and the number of needles to be driven can be appropriately selected within the range of 5 to 70 needles / cm ² .

The tubular sound deadening layer using the glass wool mat is formed by winding the glass wool mat around the exhaust pipe in a tubular shape, and the glass wool mat is molded into a tubular shape with a resin to form an exhaust pipe. Two modes, one fitted to the outer circumference, can be exemplified.

[Operation] The silencer for an internal combustion engine according to the present invention has a cylindrical silencing layer formed by using a glass wool mat having needle punched glass wool having high temperature heat resistance, high fiber strength and appropriate flexibility as described above. Therefore, it has the following effects.

Since glass wool has a sufficiently long fiber length, many fibers are entangled with each other, and it is easy to make felt by needle punching. Furthermore, since the present glass wool has both fiber strength and flexibility, it is hard to break during needle punching and hard to be powdered. Therefore, compared to conventional glass wool, even if the number of needles is the same, the entanglement of fibers will increase, and if the number of needles is increased, the entanglement of fibers will be further increased without powdering too much. You can do a lot. Therefore, a high-quality sound deadening layer having many entanglements of fibers and less breakage can be obtained.

Since this sound deadening layer is made of glass wool having high temperature heat resistance and high fiber strength as described above, it is less likely to be thermally deteriorated by the exhaust gas blown out from the vent hole of the exhaust pipe during use of the muffler, and is not easily powdered. . Therefore, scattering of the sound deadening layer during use is reduced.

[Embodiment] An embodiment of a silencer for an internal combustion engine embodying the present invention will be described below with reference to the drawings.

As shown in FIG. 1 and FIG. 2, a large number of vent holes 2 are provided so as to be distributed over the entire circumference in a predetermined length portion in the middle of the exhaust pipe 1 of the internal combustion engine. On the outer periphery of the predetermined length portion of the exhaust pipe 1, glass wool containing the components shown in the following Table 4 (the content in the table is the content considered except for the binder attached to the surface of the glass wool) The cylindrical sound deadening layer 3 is provided.

The glass wool used in this example is manufactured by a continuous melt spinning method, and has excellent high-temperature heat resistance with a transition point of 780 ° C. or higher and a softening point of 950 ° C. or higher, and a tensile strength of 400 kg / mm ² or more. Has excellent fiber illuminance. The fiber diameter of this glass wool is 9 μm on average.

This glass wool uses 32 # needles and the number of needles is 2
By needle-punching at 0 to 70 fibers / cm ² , the glass wool mat 3a is formed into a felt and has many entangled fibers. The sound absorbing layer 3 is formed by winding the glass wool mat 3a around the exhaust pipe 1 in a tubular shape.

Then, the outer circumference of the sound deadening layer 3 is covered with an outer pipe 4 that covers the outer circumference surface and both end surfaces of the sound deadening layer 3, and the diameter-reduced ends of the outer pipe 4 are the outer circumference of the exhaust pipe 1. It is fixed by welding or crimping.

On the basis of the above-described operation, the silencer of the present embodiment configured as described above has a high-quality silencer layer 3 in which many fibers are entangled with each other and less powder is formed, and the cost is lower than that of the conventional one. It does not increase so much, and when the muffler is used, thermal deterioration and powdering of the muffling layer 3 are less likely to occur, so that an excellent effect of less scattering is achieved.

In order to confirm the above effect, the glass wool mat 3a
Each of the following tests was conducted. Further, for comparison, a glass wool mat obtained by converting the conventional glass wool of Table 1 into a felt by needle punching (referred to as Comparative Example 1).
Then, the same test was performed on the above-mentioned acid-treated mat (referred to as Comparative Example 2).

(1) Pulverization test Continuous glass fiber (raw yarn), which is the raw material for glass wool mat, is carefully cut into a fiber length of 75 mm ± 2 mm using a cutting machine, and this fiber is sieved to remove powder. It was This fiber is put into a needle punching machine, and the number of needles is 20 using 32 # needle,
Various glass wool mats were made by needle punching in place of 50 and 70. Then, while measuring the thickness and density of each glass wool mat,
In order to know the powdering rate by needle punching, the component having a fiber length of less than 10 mm, the component of 10 to 30 mm, the component of 30
The abundance of each of the components of -50 mm and the components of 50-75 mm was examined. The test results are shown in Table 5.

From this result, the glass wool of the present example has more entanglement between fibers even if the number of needles is the same as in the conventional glass wool, and if the number of needles is increased, the powdered wool is pulverized too much. It was confirmed that the entanglement between the fibers can be further increased without the need.

(2) Heat shrinkability test As a sample, a wool mat having a thickness of 6 mm, a density of 100 kg / m ³ , and 20 needles / cm ² is 120 mm × 7.
It was cut to a size of 0 mm. Marks were provided on the surface at appropriate intervals, and the intervals between the marks were measured with a caliper or the like to give l ₁ . After this glass wool mat was put in an oven at 850 ° C. for 4 hours and taken out, the distance between the marks was measured again with a caliper to be ₁₂ and the heat shrinkage rate was calculated by the following formula. The test results are shown in Table 6.

Heat shrinkage rate (%) = (l ₁ −l ₂ ) / l ₁ × 100 (3) Tensile test As a sample, 15 same glass wool mat as in (2) above was used.
Cut into a size of 0 mm x 50 mm so that the longitudinal direction of the material is 150 mm, gripping interval 100 mm, pulling speed 2
Tensile tests were performed 10 times at 8 mm / min, and the average value was obtained.
The test results are shown in Table 7.

(4) Weight change test As a sample, the same glass wool mat as in (2) above was used.
It was cut into a size of 0 mm × 150 mm, put in an oven at 100 ° C. for 1 hour and taken out, and then weighed to obtain W ₁ . Then, after putting this glass wool mat in a furnace at 850 ° C. for 4 hours and taking it out, the weight was measured to obtain W ₂ ,
The weight change rate was calculated by the following formula. The test results are shown in Table 8.

Weight change rate (%) = (W ₁ −W ₂ ) / W ₁ × 100 (5) Sound absorption performance test Using a glass wool mat having a thickness of 10 mm, a density of 100 kg / m ³ , and a needle count of 20 needles / cm ^{2 as} a sample, according to JIS-A1405 “in-pipe method”, a vertical incident sound absorption meter was used. The sound absorption coefficient was measured. The thickness of the air layer behind the sample was 0 mm. The test results are shown in Table 9.

(6) Scattering resistance test Regarding this test, two types of preliminary tests were performed on a conventional glass wool mat before carrying out this example.

The first preliminary test is a test for investigating the progress of the scattering of fibers. The glass wool mat 33a of Comparative Example 1 having a thickness of 10 mm, a density of 100 kg / m ³ , and a needle driving number of 20 / cm ² is 50 mm. The sample was cut into a size of × 50 m and sandwiched between a flat plate punching metal 5 (punch hole 5a diameter 3 mm, interval 5 mm) and iron plate 6 (interval 9 mm) as shown in FIG. . Then, as shown in FIG. 3, a nozzle 8 having a diameter of 12 mm of the hot air generator 7 is positioned 2 mm immediately in front of the punching metal 5, and hot air of 650 ° C. and a wind speed of 340 m / sec is applied to the glass wool mat 33a from the nozzle 8. It was jetted for 20 hours so as to hit at a right angle. At this time, the motor 9 moves the sample backward by the amplitude 4
The wind pressure was changed by reciprocating at 60 mm / cycle and 60 cycles / second. At this time, the progress of the scattering of the glass wool mat 33a was as follows.

First, as shown in FIG. 5, the glass wool mat 3
The fibers attached to the surface of 3a were scattered.

Subsequently, as shown in FIG. 6, a dent 34 was formed on the surface of the glass wool mat 33a at a portion corresponding to the punching hole 5a.

Subsequently, as shown in FIG. 7, hot air enters the inside of the glass wool mat 33a, and there is little entanglement between the fibers inside the mat (for example, a short fiber that is broken).
Was scattered.

Finally, as shown in FIG. 8, short fibers and powdered fibers are scattered and the depressions 34 of the glass wool mat 33a are connected to each other inside the mat, and the fiber length is long and entangled with other fibers. Only the existing fibers have crosslinked and remain.

Also, when the same test was conducted from the beginning by raising the temperature of the hot air to 750 ° C. (high temperature), the progress of the above scattering
However, at the end, the fibers that should remain above became brittle due to high temperature, were pulverized by wind pressure, and grew into large depressions 34 as shown in FIG.

Next, the second preliminary test is a test for investigating the relationship between the density and the scattering of the glass wool mat.
/ M ³ of the glass wool mat 33a of Comparative Example 1 and the density of 130 kg / m ³ of the glass wool mat 33 of Comparative Example 1
Similarly to the first preliminary test, a was sandwiched between the punching metal 5 and the iron plate 6 to form a sample, and the temperature was 500 ° C. (medium / low temperature).
Hot air having a wind speed of 340 m / sec was jetted for 20 hours. Then, assuming that the weight of the sample before applying the hot air was W ₁ and the weight of the sample after applying the hot air was W ₂ , the scattering rate was calculated by the following formula.
The test results are shown in Table 10.

Scattering rate (%) = (W ₁ −W ₂ ) / W ₁ × 100 From the results of the above two types of preliminary tests, the conditions suitable for the scattering resistance are that the heat resistance of the glass fiber is high, the existence ratio of the glass fiber with a long fiber length is high, there are many entanglements between the fibers, and the glass wool mat It was found that the product had a high density (however, the powdering rate was small).

Now, the scattering resistance test for this example is 10 m in thickness.
m, density 100 kg / m ³ , 20 needles / cm
^Using the glass wool mat 3a of No. ² as in the first preliminary test, hot air having a wind speed of 340 m / sec and 750 ° C. was jetted for 20 hours. The test results are shown in Table 11. From this result, the effectiveness of this example was confirmed.

The present invention is not limited to the configurations of the above-described embodiments, but may be embodied by being arbitrarily modified within the scope of the gist of the invention as follows, for example.

(1) Implementation in a mode in which the outer tube 4 is not used.

(2) A felter layer made of metal fibers is provided between the exhaust pipe 1 and the sound deadening layer 3 to further reduce scattering of the sound deadening layer.

[Effects of the Invention] Since the silencer for an internal combustion engine of the present invention is configured as described above, a high-quality silencer layer in which many fibers are entangled with each other and less powder is obtained, and the silencer is used when the silencer is used. It has an excellent effect that there is little scattering of layers and the cost does not increase so much as compared with the conventional case.

[Brief description of drawings]

FIG. 1 is a partially cutaway perspective view showing an embodiment of a muffler for an internal combustion engine embodying the present invention, FIG. 2 is a sectional view of the same embodiment, and FIG. 3 shows a method of a scattering resistance test. FIG. 4 is a side view, FIG. 4 is a perspective view showing a sample used in the same test, and FIGS. 5 to 9 are cross-sectional views showing the progress of scattering in a scattering resistance test conducted on a conventional comparative example. 1 ... Exhaust pipe, 2 ... Vent hole, 3 ... Sound deadening layer, 3a ... Glass wool mat.

Claims (1)

[Claims] 1. A large number of vent holes (2) are formed through a part of an exhaust pipe (1) of an internal combustion engine, and a part of the exhaust pipe has an S-shaped outer periphery.
iO ₂ from 58 to 70 _{wt%, Al} 2 O 3 _20~28 wt%, MgO7～12 wt% tubular silencer layer using glass wool mat (3a) comprising been felt by needle punching wherein each component of ( A silencer for an internal combustion engine provided with 3).