JP7605465B2 - Sound suppressor - Google Patents

Description

The present invention relates to a silencer that is inserted into the refrigerant pipes, exhaust pipes, etc. of vehicle air conditioners.

In vehicle air conditioners, mechanical noise from the compressor and noise caused by cavitation of the refrigerant are transmitted to the evaporator via the piping and then transmitted to the driver from the air outlet, or transmitted to the driver via the vehicle body through the space in the engine compartment midway through the piping. For this reason, muffler-type silencers or internal insertion-type silencers are installed in the piping of vehicle air conditioners. Muffler-type silencers are large and heavy, and brazing increases costs, so internal insertion-type silencers have been widely adopted in recent years.

For example, Patent Document 1 describes a device in which a spiral fin is provided on the outer surface of an inner tube. This creates a phase difference due to the difference in the inner and outer flow paths, which causes sound interference and has a sound-deadening effect, but it is difficult to mold and adjust the length of the flow paths.

Patent document 2 describes a silencer that is inserted into a tubular body, in which a resonator chamber is provided between the silencer and the body, and the flow path of the body is connected to the resonator chamber via a connecting channel. Patent document 3 describes a sound absorbing device in which the outer member surrounding the inner member is a bellows, a cavity is formed between the inner member and the outer member, and the opening of the inner member is open to the cavity. Both of these are of the resonance type, and the resonance frequency is determined by the shape of the resonator, so the frequency range in which the sound absorbing effect is achieved is narrow.

European Patent Publication EP2138750A1 Patent No. 5785173 specification JP 2005-84693 A

The present invention was made in consideration of the above-mentioned problems of the conventional technology, and aims to provide a noise suppression device that has a large transmission loss, is easy to mold and adjust according to frequency, and has a wide range of frequencies for which it produces a noise suppression effect.

As a means for solving the above problems, the present invention provides
(1) A silencer to be inserted into a main pipe through which a fluid flows, the silencer including an inner pipe and a side branch chamber formed between the main pipe and the inner pipe,
The inner surface of the inner tube has a port that communicates with the side branch chamber.

(2) The side branch chamber is
The main pipe;
The inner tube;
an upstream side partition plate and a downstream side partition plate formed on an outer surface of the inner pipe;
a rib plate formed on an outer surface of the inner tube and extending in an axial direction;
It is preferable that the .lambda.

(3) It is preferable that the inner surface of the upstream end of the inner pipe is formed as a tapered surface whose diameter decreases toward the downstream side.
(4) It is also preferable that the inner surface of the downstream end of the inner pipe is formed as a tapered surface whose diameter increases toward the downstream side.

(5) A resonance chamber is provided between the main pipe and the inner pipe,
The inner surface of the inner tube is preferably provided with an opening communicating with the resonating chamber.

(6) It is preferable that the inner tube is provided with an outer cylinder that seals the side branch chamber.

(7) It is preferable that the silencer is configured with a plurality of modules divided in the circumferential direction.
(8) The silencer may be configured with a plurality of modules divided in the axial direction.
(9) Alternatively, the noise absorbing device may be configured with a plurality of modules divided in the circumferential and axial directions.

According to the invention of claim 1, sound waves that enter the side branch from an inlet on the inner surface of the inner pipe and are reflected back interfere with the sound waves in the inner pipe in an opposite phase, resulting in silencing. In addition, an inlet that communicates with the side branch chamber is provided on the inner surface of the inner pipe, and the side branch chamber branches off from the inner pipe, which has a smaller cross-sectional area than the main pipe. Therefore, compared to when the side branch chamber branches off from the main pipe, the cross-sectional area ratio before and after the branch can be made larger, which increases the transmission loss and improves the silencing effect.

The side branch chamber of the silencer of the present invention is open to the outside air before being inserted into the main pipe, making it easy to mold.

In addition, the frequency at which the noise reduction effect occurs can be adjusted by changing the length of the side branch chamber along the axial direction of the inner tube.

Furthermore, by forming multiple side branch chambers of different lengths between the main pipe and the inner pipe, the frequency range in which the sound deadening effect is produced can be widened.

According to the invention of claim 2, the side branch chamber is surrounded by the inner surface of the main pipe, the partition plate, and the rib plate, simplifying the length and cross-sectional area from the entrance/exit of the side branch chamber to the inner end, and achieving a noise reduction effect at frequencies close to the target frequency.

According to the inventions of claims 3 and 4, the upstream or downstream end of the inner tube is formed with a tapered surface, which reduces the pressure loss (hereinafter referred to as pressure loss) when the fluid flows into and out of the inner tube.

According to the invention of claim 5, the energy of the sound waves that enter the resonating chamber from the opening on the inner surface of the inner tube is absorbed in the resonating chamber and silenced. This provides a combined sound silencing effect that combines the sound silencing effect of the side branch chamber in a wide frequency range with the sound silencing effect of the resonating chamber in a specific frequency range. In particular, by compensating for the frequency range in which it is difficult to obtain a sound silencing effect from the side branch chamber with the sound silencing effect of the resonating chamber, it is possible to obtain a sound silencing effect in a wider frequency range.

According to the invention of claim 6, the outer tube seals the side branch chamber, preventing leakage from the side branch chamber due to bending or vibration of the main pipe, and maintaining the sound deadening effect.

According to claims 7 to 9, the modules can be combined to provide the optimal noise reduction effect depending on the frequency of the sound source.

1 is a perspective view of a noise suppressor according to a first embodiment of the present invention, in which a part of a main pipe is cut away. FIG. 2 is a perspective view of a silencer inserted into the main pipe of FIG. 1 . 3A and 3B are a front view and a left side view of the silencer of FIG. 2 . IVa-IVa line cross-sectional view (a) and IVb-IVb line cross-sectional view (b) of FIG. Cross-sectional view taken along line V-V in FIG. FIG. 1 is a perspective view of a conventional side branch type silencer. FIG. 3 is a cross-sectional view showing a first modified example of the silencer of FIG. 2 . FIG. 3 is a cross-sectional view showing a second modified example of the silencer of FIG. 2 . FIG. 3 is a cross-sectional view showing a third modified example of the silencer of FIG. 2 . FIG. 4 is a cross-sectional view showing a fourth modified example of the silencer of FIG. 2 . FIG. 11 is a cross-sectional view showing a fifth modified example of the silencer of FIG. 2 . FIG. 4 is a cross-sectional view showing an example of the invention and a comparative example used in an analysis of the sound deadening effect. Graph showing analysis results of transmission loss for the comparative example (base), invention example (A), invention example (B), and invention example (Z). 14 is a graph showing the analysis results of the transmission loss of the comparative example (base), invention example (A), invention example (B), and invention example (Z) of FIG. 13, expressed as average values in the low frequency range, high frequency range, and entire frequency range. FIG. 5 is a perspective view of a silencer according to a second embodiment of the present invention. FIG. 11 is a perspective view of a silencer according to a third embodiment of the present invention. FIG. 17 is a cross-sectional view of the silencer of FIG. 16 . FIG. 17 is a cross-sectional view showing a modification of the sound deadening device of FIG. 16 . FIG. 13 is a perspective view of a noise suppressor according to a fourth embodiment of the present invention. FIG. 4 is a cross-sectional view showing an example of the invention and a comparative example used in an analysis of the sound deadening effect. 1 is a graph showing analysis results of transmission loss for a comparative example (base), an example of the invention (refine 1), and an example of the invention (refine 2). 22 is a graph superimposing the analysis results of the transmission loss of the comparative example (base), the invention example (refine 1), and the invention example (refine 2) in FIG. 21 . 22 is a graph showing the analysis results of the transmission loss of the comparative example (base), invention example (refine 1), and invention example (refine 2) in FIG. 21 as average values in the low frequency range, high frequency range, and entire frequency range. FIG. 13 is a perspective view of a noise suppressor according to a fifth embodiment of the present invention, with a portion of a main pipe cut away. FIG. 13 is a perspective view showing an assembled state and a divided state of a circumferentially divided type noise suppressor according to a sixth embodiment. FIG. 13 is a perspective view showing an assembled state and a divided state of an axially split type noise suppressor according to a seventh embodiment. FIG. 13 is a perspective view showing a state in which one module of a noise suppressor according to an eighth embodiment of a mixed type divided in the circumferential direction and the axial direction is separated.

An embodiment of the present invention will be described below with reference to the attached drawings.

First Embodiment
FIG. 1 shows a silencer 1 according to a first embodiment of the present invention. The silencer 1 is provided in a pipe through which a refrigerant flows in an air conditioner for a vehicle. Specifically, the silencer is inserted into a pipe (hereinafter referred to as a "main pipe") 2 on the outlet side of an evaporator or a compressor in an air conditioner for a vehicle, the air conditioner including a compressor, a condenser, an expansion valve, and an evaporator (not shown). The main pipe 2 is made of a material having elasticity and flexibility, such as rubber or synthetic resin, but is not limited thereto, and a material having no flexibility, such as aluminum, may also be used. In the main pipe 2, a fluid (hereinafter referred to as a "refrigerant") flows from the upstream on the left side to the downstream on the right side in FIG. 1.

As shown in Figures 2 and 3, the silencer 1 comprises an inner pipe 3, end partition plates 4 formed at the upstream and downstream ends of the inner pipe 3, a number of intermediate partition plates 5 formed on the outer surface of the inner pipe 3 in the axial middle part near the upstream end, and a number of rib plates 6 formed at predetermined intervals around the circumference of the inner pipe 3, and is integrally formed from synthetic resin.

The silencer 1 is fixed inside the main pipe 2 by fastening either the upstream or downstream end partition plate 4 from the outside of the main pipe 2 with a fixing member (not shown). To ensure fixation by the fixing member, the thickness of the end partition plate 4 may be increased so that the contact area with the fixing member is increased.

The inner pipe 3 has an outer diameter smaller than the inner diameter of the main pipe 2. The end partition plate 4 is annular with an outer diameter approximately the same as the inner diameter of the main pipe 2. The intermediate partition plate 5 is sector-shaped with an outer diameter approximately the same as the inner diameter of the main pipe 2, and the four intermediate partition plates 5 are formed at the same axial position, resulting in an overall annular shape. Four rib plates 6 are provided in the circumferential direction, protruding radially at four equally spaced positions around the outer circumferential surface of the inner pipe 3 and extending in the axial direction. The number of rib plates 6 is arbitrary, and may be one or more. In addition, the rib plates 6 do not have to be equally spaced in the circumferential direction. The outer circumferential surfaces of the end partition plates 4, the outer circumferential surface of the intermediate partition plate 5, and the outer end surfaces of the rib plates 6 are in close contact with the inner surface of the main pipe 2 when the silencer 1 is inserted into the main pipe 2, so that the side branch chambers 7a, 7b, 7c, 7d and 7e, 7f, 7g, 7h described later are sealed by the main pipe 2. As an alternative to a fixing member, the silencer 1 can be pressed into the main pipe 2 or a sealing material can be used.

As shown in FIG. 4(a), four side branch chambers 7a, 7b, 7c, and 7d are formed between the main pipe 2 and the inner pipe 3 and on the upstream side of the intermediate partition plate 5. Also, as shown in FIG. 4(b), four side branch chambers 7e, 7f, 7g, and 7h are formed between the main pipe 2 and the inner pipe 3 and on the downstream side of the intermediate partition plate 5. On the inner surface of the inner pipe 3, four inlets 8a, 8b, 8c, and 8d that communicate with the side branch chambers 7a, 7b, 7c, and 7d, and four inlets 8e, 8f, 8g, and 8h that communicate with the side branch chambers 7e, 7f, 7g, and 7h are formed.

As shown in Figures 3 and 4(a), the side branch chambers 7a, 7b, 7c, and 7d are formed in a space surrounded by the inner surface of the main pipe 2, the outer surface of the inner pipe 3, the upstream end partition plate 4, the intermediate partition plate 5, and a pair of rib plates 6. The inlets and outlets 8a, 8b, 8c, and 8d that communicate with the side branch chambers 7a, 7b, 7c, and 7d are formed upstream of the intermediate partition plate 5 and close to the intermediate partition plate 5, penetrating the wall of the inner pipe 3.

As shown in Figures 3 and 4(b), the side branch chambers 7e, 7f, 7g, and 7h are formed in a space surrounded by the inner surface of the main pipe 2, the outer surface of the inner pipe 3, the downstream end partition plate 4, the intermediate partition plate 5, and a pair of rib plates 6. The inlets and outlets 8e, 8f, 8g, and 8h that communicate with the side branch chambers 7e, 7f, 7g, and 7h are formed downstream of and close to the intermediate partition plate 5, penetrating the wall of the inner pipe 3.

Next, the operation of the silencer 1 of this embodiment will be described.

As shown in FIG. 5, the refrigerant flowing through the main pipe 2 flows into the inner pipe 3 at the upstream end of the silencer 1 and flows out of the inner pipe 3 at the downstream end. Sound generated from a sound source (not shown) on the upstream side of the silencer 1 (mechanical noise of the compressor and noise caused by cavitation of the refrigerant) propagates downstream along with the refrigerant and enters the inner pipe 3 of the silencer 1. Note that the sound source may be on the downstream side, in which case the silencing effect will be generated on the upstream side.

The sound waves propagating through the inner tube 3 enter the four side branch chambers 7a, 7b, 7c, 7d through the inlets 8a, 8b, 8c, 8d on the inner surface of the inner tube 3, and also enter the four side branch chambers 7e, 7f, 7g, 7h through the inlets 8e, 8f, 8g, 8h. They are reflected at the inner ends of the side branch chambers 7a, 7b, 7c, 7d and 7e, 7f, 7g, 7h, and return to the inlets 8a, 8b, 8c, 8d and 8e, 8f, 8g, 8h, where they interfere with the sound waves in the inner tube 3 in the opposite phase and are silenced.

Here, if the cross-sectional area of the inner pipe is S, the cross-sectional area of the side branch chamber is Ss, the length of the side branch chamber is l, the frequency of the sound wave is f, and the sound speed is c, then the transmission loss TL in the silencer 1 is expressed by Equation 1. The length l of the side branch chamber is the axial distance from the intermediate partition plate 5 to the end partition plate 4, as shown in Fig. 5.

In the silencer 1 of this embodiment, the inner surface of the inner pipe 3 is provided with inlets 8a, 8b, 8c, 8d, 8e, 8f, 8g, 8h that communicate with the side branch chambers 7a, 7b, 7c, 7d, 7e, 7f, 7g, 7h, and the side branch chambers 7a, 7b, 7c, 7d, 7e, 7f, 7g, 7h branch out from the inner pipe 3, which has a smaller cross-sectional area than the main pipe 2.

Figure 6 shows a silencer 10 of a conventional structure for comparison with the present invention. The conventional silencer 10 in Figure 6 has an intermediate partition plate 5 provided in the middle of the inner pipe 3, tubular side branch chambers 17a, 17b formed between the main pipe 2 and the inner pipe 3, and inlets 18a, 18b for each side branch chamber 17a, 17b provided at the upstream and downstream ends of the inner pipe 3. The transmission loss TL of the silencer 10 can be calculated by applying Equation 1, with the cross-sectional area of the main pipe 2 being S instead of the cross-sectional area of the inner pipe 3.

"
In the silencer 1 of this embodiment shown in Fig. 5, the side branch chambers 7a, 7b, 7c, 7d and 7e, 7f, 7g, 7h branch off from the inner pipe 3. Therefore, compared to the conventional silencer 10 shown in Fig. 6, in which the side branch chambers 17a, 17b branch off from the main pipe 2, the cross-sectional area ratio Ss/S before and after the branching can be made larger, the transmission loss TL becomes larger, and the sound absorbing effect can be improved.

The first to fourth side branch chambers 7a, 7b, 7c, 7d and 7e, 7f, 7g, 7h of the silencer 1 of this embodiment are open to the outside air before being inserted into the main pipe 2, making them easy to mold.

In addition, the length of each side branch chamber 7a, 7b, 7c, 7d and 7e, 7f, 7g, 7h can be adjusted along the axial direction of the inner tube 3 to suit the frequency of the sound source.

Furthermore, by forming multiple side branch chambers 7a, 7b, 7c, 7d and 7e, 7f, 7g, 7h of different lengths between the main pipe 2 and the inner pipe 3, the frequency range in which the sound deadening effect is produced can be widened.

In the first embodiment of the silencer 1, the inlets 8a, 8b, 8c, 8d and 8e, 8f, 8g, 8h of the side branch chambers 7a, 7b, 7c, 7d and 7e, 7f, 7g, 7h are arranged close to the upstream and downstream sides of the intermediate partition plate 5, but as shown in Figure 7, the inlets 8a, 8b, 8c, 8d of the side branch chambers 7a, 7b, 7c, 7d may be arranged close to the upstream end partition plate 4, or as shown in Figure 8, the inlets 8e, 8f, 8g, 8h of the side branch chambers 7e, 7f, 7g, 7h may be arranged close to the downstream end partition plate 4. Also, as shown in FIG. 9, the inlets 8a, 8b, 8c, and 8d of 7a, 7b, 7c, and 7d may be provided close to the upstream end partition plate 4, and the inlets 8e, 8f, 8g, and 8h of 7e, 7f, 7g, and 7h may be provided close to the downstream end partition plate 4. The size of the inlets may be the same for all side branch chambers, or may be different for each side branch chamber.

In the silencer 1 of the first embodiment, as shown in FIG. 10, the inner surface of the upstream end of the inner tube 3 may be formed with a tapered surface 9a that narrows toward the downstream side. Similarly, the inner surface of the downstream end of the inner tube 3 may be formed with a tapered surface 9b that widens toward the downstream side. This can reduce the pressure loss of the refrigerant flowing from the main tube 2 through the inner tube 3 to the main tube 2.

In the silencer 1 of the first embodiment, the side branch chambers 7a, 7b, 7c, 7d and 7e, 7f, 7g, 7h are provided on the upstream and downstream sides of the intermediate partition plate 5, but as shown in FIG. 11, two intermediate partition plates, a first and a second, 5a, 5b may be provided on the outer surface of the inner tube 3, and the side branch chambers 7a, 7b, 7c, 7d may be provided between the first intermediate partition plate 5a and the second intermediate partition plate 5b. In this case, the upstream side of the first intermediate partition plate 5a and the downstream side of the second intermediate partition plate 5b form conventional side branch chambers 17a, 17b.

To confirm the sound deadening effect of the silencer 1 of the first embodiment, the inventors performed acoustic analysis by computer simulation for the four analysis models shown in FIG. 12.

In Fig. 12, the comparative example (base) is a silencer 10 with a conventional structure shown in Fig. 6, in which the side branch chambers 17a and 17b branch off from the main pipe. In contrast, the invention examples (A), (B) and (Z) are similar to the silencer 1 of the first embodiment shown in Fig. 2, and among them, the invention example (A) has the inlets 8a, 8b, 8c, 8d and 8e, 8f, 8g and 8h of 4 mm (close to the thickness of the inner pipe), the invention example (B) has the inlets 8a, 8b, 8c, 8d and 8e, 8f, 8g and 8h of 10 mm (close to the cross-sectional area of the side branch chamber), and the invention example (Z) has tapered surfaces 9a and 9b with a gradient of 20° at the upstream end and downstream end of the invention example (A). Each analytical model has an outer diameter of 20 mm and a total length of 100 mm. For each analysis model, the inner diameter of the inner tube 3 was changed and the frequency of the sound source was changed to determine the transmission loss.

Figure 13 shows the transmission loss when the frequency is changed from 0 to 8000 Hz in each analytical model in which the inner diameter p of the inner tube 3 is 8 mm. From Figure 13, it was confirmed that analytical models (A), (B), and (Z) of the invention examples have a larger transmission loss and a larger sound deadening effect than the comparative example (base) at 3500 to 7000 Hz. In particular, it was confirmed that analytical model (B) has a larger transmission loss and a larger sound deadening effect than the other analytical models at 4000 Hz and above.

Figure 14 shows the average transmission loss at low frequencies from 0 to 4000 Hz, the average transmission loss at high frequencies from 4000 to 8000 Hz, and the average transmission loss at all frequencies for each analysis model in which the inner diameter p of the inner tube 3 is 6 mm, 8 mm, and 10 mm. From Figure 14, it was confirmed that in the analysis model in which the inner diameter of the inner tube 3 is the same (p = 8), the transmission loss is larger and the sound deadening effect is greater in all of the invention examples (A), (B), and (Z) compared to the comparative example (base). It was also confirmed that the smaller the inner diameter p of the inner tube 3, the larger the transmission loss and the greater the sound deadening effect.

For each analysis model, the fluid pressure loss was 11.0 kPa for the comparative example (base), 11.4 kPa for invention example (A), 11.8 kPa for (B), and 6.9 kPa for (Z). It was confirmed that invention example (Z), which has tapered surfaces 9a and 9b to reduce pressure loss, was highly effective in reducing pressure loss.

Second Embodiment
FIG. 15 shows a noise suppressor 20 according to a second embodiment of the present invention.

In the second embodiment of the silencer 20, two rib plates 6 are protruded at two equally spaced positions around the outer circumferential surface of the inner tube 3, so that two side branch chambers 7a, 7b are formed on the upstream side of the intermediate partition plate 5, and two side branch chambers 7c, 7d are formed on the downstream side of the intermediate partition plate 5. In addition, the thickness of the intermediate partition plate 5 separating the side branch chambers 7a and 7c is made thicker than the thickness of the intermediate partition plate 5 separating the side branch chambers 7b and 7d, so that the lengths of the four side branch chambers 7a, 7b, 7c, and 7d are different. In this way, the length of the four side branch chambers 7a, 7b, 7c, and 7d can be adjusted according to the frequency of the sound source, thereby widening the range of frequencies that produce a sound silencing effect.

Third Embodiment
16 and 17 show a noise suppressor 30 according to a third embodiment of the present invention.

The silencer 30 of the third embodiment has two intermediate partition plates 5a and 5b on the outer surface of the inner tube 3, four side branch chambers 7a, 7b, 7c, and 7d formed between the upstream end partition plate 4 and the first intermediate partition plate 5a, four side branch chambers 7e, 7f, 7g, and 7h formed between the downstream end partition plate 4 and the second intermediate partition plate 5b, and four resonance chambers 31a, 31b, 31c, and 31d formed between the first intermediate partition plate 5a and the second intermediate partition plate 5b. The configurations of the side branch chambers 7a, 7b, 7c, and 7d and 7e, 7f, 7g, and 7h are the same as those of the first embodiment except for the length dimensions, so they are denoted by the same reference numerals and will not be described.

The resonance chambers 31a, 31b, 31c, and 31d are formed by spaces surrounded by the inner surface of the main pipe 2, the outer surface of the inner pipe 3, the first intermediate partition plate 5a, the second intermediate partition plate 5b, and a pair of rib plates 6. The openings 32a, 32b, 32c, and 32d that communicate with the resonance chambers 31a, 31b, 31c, and 31d are formed to penetrate the wall of the inner pipe 3 between the first intermediate partition plate 5a and the second intermediate partition plate 5b.

In the third embodiment of the silencer 30, in addition to the sound absorbing effect of the side branch chambers 7a, 7b, 7c, 7d and 7e, 7f, 7g, 7h, the resonance chambers 31a, 31b, 31c, 31d also provide a sound absorbing effect. That is, the energy of the sound waves that enter the inner tube 3 is absorbed and silenced by the resonance chambers 31a, 31b, 31c, 31d.

Here, if the volume of the resonance chambers 31a, 31b, 31c, and 31d is V, the cross-sectional area of the openings 32a, 32b, 32c, and 32d is Sr, the length of the openings 32a, 32b, 32c, and 32d is l, and the sound speed is c, the resonance frequency ωr is expressed by Equation 2.

Therefore, by matching the resonant frequency of the resonating chambers 31a, 31b, 31c, and 31d with the frequency of the incident sound, a sound deadening effect can be achieved for a specific frequency range, and in combination with the sound deadening effect of the side branch chambers 7a, 7b, 7c, 7d and 7e, 7f, 7g, and 7h, the range of frequencies over which the sound deadening effect can be achieved can be widened.

The third embodiment of the sound deadening device has resonance chambers 31a, 31b, 31c, and 31d between the first intermediate partition plate 5a and the second intermediate partition plate 5b, side branch chambers 7a, 7b, 7c, and 7d between the end partition plate 4 and the first intermediate partition plate 5a, and side branch chambers 7e, 7f, 7g, and 7h between the second intermediate partition plate 5b and the end partition plate 4. However, as shown in FIG. 18, side branch chambers 7a, 7b, 7c, and 7d may be provided between the first intermediate partition plate 5a and the second intermediate partition plate 5b, resonance chambers 31a, 31b, 31c, and 31d may be provided between the end partition plate 4 and the first intermediate partition plate 5a, and resonance chambers 31e, 31f, 31g, and 31h may be provided between the second intermediate partition plate 5b and the end partition plate 4.

Fourth Embodiment
FIG. 19 shows a noise suppressor 40 according to a fourth embodiment of the present invention.

In the third embodiment of the silencer 30 shown in FIG. 16, the four sector-shaped intermediate partition plates 5 are positioned at the same axial position to form the first and second annular intermediate partition plates 5a and 5b, whereas in the fourth embodiment of the silencer 40 shown in FIG. 19, the sector-shaped intermediate partition plates 5 are formed offset in the axial direction, so that the sizes and positions of the resonance chambers 31a, 31b, 31c, and 31d are all different, and the lengths of the side branch chambers 7a, 7b, 7c, and 7d and 7e, 7f, and 7h are also different.

Specifically, the resonance chamber 31a is formed in the axial center of the inner tube 3. The resonance chamber 31b is formed in the axial center of the inner tube 3 and is larger than the resonance chamber 31a. The resonance chamber 31c is formed closer to the downstream end partition plate 4 of the inner tube 3 and is smaller than the resonance chamber 31a. There is no intermediate partition plate downstream of the resonance chamber 31c, and the downstream end partition plate 4 is used as this as well. Therefore, there is no side branch chamber 7g adjacent to the downstream side of the resonance chamber 31c. As a result, seven side branch chambers 7a, 7b, 7c, 7d, and 7e, 7f, and 7h are formed. The resonance chamber 31d is formed in the axial center of the inner tube 3 and is smaller than the resonance chamber 31a.

By matching the resonant frequency of the resonating chambers 31a, 31b, 31c, and 31d with the frequency of the incident sound, a sound deadening effect can be achieved for a specific frequency range, and in combination with the sound deadening effect of the side branch chambers 7a, 7b, 7c, 7d and 7e, 7f, and 7h, the range of frequencies over which the sound deadening effect can be achieved can be expanded.

To confirm the sound deadening effect of the silencer 20 of the second embodiment and the silencer 40 of the fourth embodiment, the inventors performed acoustic analysis by computer simulation for the three analysis models shown in FIG. 20.

In this acoustic analysis, the medium was air with a temperature of 25°C, a pressure of 0.101325 MPa (standard atmospheric pressure), a density of 1.184 kg/ ^m3 , and a sound speed of 346.25 m/s. The target frequency range for obtaining a noise reduction effect was 0 to 4000 Hz. If the length of the side branch is l and the sound speed is c, the theoretical value of the target frequency f was calculated using Equation 3.

In Figure 20, the comparative example (base) is a silencer 10 with the conventional structure shown in Figure 6, in which the side branch chambers 17a and 17b branch off from the main pipe 2. The lengths of the side branch chambers 17a and 17b are 22 mm and 72 mm, respectively, and the theoretical values of the frequencies aimed at achieving a noise reduction effect are 3935 Hz, 1202 Hz, and odd multiples of these.

The invention example (refine 1) is the same as the silencer 20 of the second embodiment shown in Figure 15, and has a structure in which four side branch chambers 7a, 7b, 7c, and 7d branch off from the inner tube 3. The lengths of the side branch chambers 7a, 7b, 7c, and 7d are 26 mm, 32 mm, 48 mm, and 62 mm, respectively, and the theoretical values of the target frequencies for obtaining the noise reduction effect are 3329 Hz, 2705 Hz, 1803 Hz, and 1396 Hz, or odd multiples of these.

The example of the invention (refine 2) is the same as the silencer 40 of the fourth embodiment shown in Fig. 19, and has a structure in which seven side branch chambers 7a, 7b, 7c, 7d and 7e, 7f, 7h branch off from the inner tube 3, and four resonance chambers 31a, 31b, 31c, 31d are provided. The lengths of the side branch chambers 7a, 7b, 7c, 7d and 7e, 7f, 7h are, in order from longest to shortest, 87 mm x 1, 43 mm x 2, 29 mm x 2, and 22 mm x 2, and the theoretical values of the frequencies that provide the noise reduction effect are 995 Hz, 2013 Hz, 2985 Hz, 3935 Hz, and odd multiples of these. The resonance volumes of the resonance chambers 31a, 31b, 31c, 31d, from largest to smallest, are 2027.7 mm ³ , 1436.3 mm ³ , 295.7 mm ³ , 253.5 mm ³ , and the theoretical values of the target frequencies for obtaining the noise reduction effect are 1159 Hz, 1378 Hz, 3036 Hz, 3279 Hz.

Each analytical model had an outer diameter of 20 mm, a total length of 100 mm, and an inlet/outlet width of 4 mm. For each analytical model, the transmission loss was calculated by changing the frequency of the sound source.

Figures 21 (a), (b), and (c) show the change in transmission loss when the frequency is changed from 0 to 10,000 Hz in the comparative example (base), invention example (refine 1), and invention example (refine 2). In all of the comparative example (base), invention example (refine 1), and invention example (refine 2), it was confirmed that the transmission loss was large at frequencies close to the target frequency, and that a sound deadening effect was obtained.

The example of the invention (refine 1) has a greater number of side branches than the comparative example (base), and each side branch is a different length, so noise reduction is achieved over many frequencies. Also, the example of the invention (refine 1) has a greater transmission loss across the entire frequency range than the comparative example (base), in which each side branch branches off from the main pipe, and so has a greater overall noise reduction effect.

The example of the invention (refine 2) exhibits the sound-absorbing effect of the four resonant chambers in addition to the sound-absorbing effect of the seven side branch chambers, and at some specific frequencies, it has a larger transmission loss and a higher sound-absorbing effect than the example of the invention (refine 1).

Figure 22 is a superimposition of the graphs of the comparative example (base), invention example (refine 1), and invention example (refine 2) in Figure 21. This graph shows that the invention example (refine 1) and invention example (refine 2) have greater overall transmission loss and greater sound deadening effect than the comparative example (base).

Figure 23 shows the average transmission loss in the low frequency range of 0 to 4000 Hz, the average transmission loss in the high frequency range of 4000 to 8000 Hz, and the average transmission loss in the entire frequency range of 0 to 8000 Hz for each of the comparative example (base), invention example (refine 1), and invention example (refine 2). This shows that the invention example (refine 1) has the same sound deadening effect in both the low and high frequency ranges, while the invention example (refine 2) has a higher sound deadening effect in the low frequency range than in the high frequency range, and also has a higher sound deadening effect than the invention example (refine 1) across the entire frequency range.

Fifth Embodiment
FIG. 24 shows a noise suppressor 50 according to a fifth embodiment of the present invention.

The silencer 50 according to the fifth embodiment is formed by pressing the silencer 40 according to the fourth embodiment shown in FIG. 19 into an outer cylinder 51 whose length is equal to or greater than the distance between the end partition plates 4 or the intermediate partition plate 5 at both ends, so that the outer cylinder 51 seals each side branch chamber and the resonating chamber.

The outer tube 51 is made of a synthetic resin such as nylon. The outer tube 51 may be made of a metal such as aluminum, but it is preferable to use a sealant or adhesive so that when the silencer 40 is inserted into the outer tube 51, the outer surfaces of the end partition plate 4, the middle partition plate 5, and the rib plate 6 of the silencer 40 are in close contact with the inner surface of the outer tube 51.

The silencer 50 according to the fifth embodiment is inserted into the main pipe 2 that forms the refrigerant flow path with the outer tube 51 attached. In the silencer 50 according to the fifth embodiment, even if the main pipe 2 is bent when piping in the engine room, the outer tube 51 seals each side branch chamber, preventing leakage from the side branch chambers due to bending or vibration of the main pipe 2, and maintaining the sound absorbing effect.

<Embodiments of a split type sound absorbing device>
The silencers 1, 20, 30, 40, and 50 in the above-described embodiments are of an integrated type, but as will be described below, they may be of a split type.

25 shows a sixth embodiment of the silencer 60, which is obtained by equally dividing the silencer 40 of the fourth embodiment shown in FIG. 19 in the circumferential direction. That is, the silencer 60 is composed of four modules M1, M2, M3, and M4, in which the inner tube 3 and the rib plate 6 are equally divided in the circumferential direction by dividing planes S1 and S2 including the axis C. The first module M1 has a side branch chamber 7a, a resonating chamber 31a, and a side branch chamber 7e. The second module M2 has a side branch chamber 7b, a resonating chamber 31b, and a side branch chamber 7f. The third module M3 has a side branch chamber 7c and a resonating chamber 31c. The fourth module has a side branch chamber 7d, a resonating chamber 31d, and a side branch chamber 7h. The modules M1, M2, M3, and M4 are combined so that the rib plates 6 overlap, and are inserted into the main tube 2 (see FIG. 1). The modules M1, M2, M3, and M4 may be bonded to each other, or the dividing surfaces S1 and S2 may have recesses and protrusions so that they can fit together. Also, the dividing surfaces S1 and S2 may or may not include the rib plate 6.

Figure 26 shows a silencer 70 according to the seventh embodiment, which is divided in the axial direction. That is, the silencer 70 is composed of three modules M11, M12, and M13, in which the inner tube 3 and the intermediate partition plate 5 are divided in the axial direction at the dividing planes S11 and S12 perpendicular to the axis C. The first module M11 has four side branch chambers 7a to 7d in the circumferential direction, the second module M12 has four side branch chambers 7e to 7h in the circumferential direction, and the third module M13 has four side branch chambers 7i to 7l in the circumferential direction. The modules M11, M12, and M13 are assembled so that the intermediate partition plates 5 overlap, and are inserted into the main tube 2 (see Figure 1). The modules M11, M12, and M13 may be bonded to each other, or the dividing planes S may be provided with recesses and protrusions so that they fit together. In FIG. 26, each module M11 to M13 has a side branch chamber 7a to 7l, but it may be composed of one with a resonance chamber and one with a side branch chamber. Also, the division surfaces S11 and S12 may or may not include the intermediate partition plate 5.

Figure 27 shows a silencer 80 according to the eighth embodiment, which is divided in the circumferential and axial directions. That is, the silencer 80 is configured with a total of eight modules M21 to M28, in which the inner tube 3 and the rib plate 6 are equally divided in the circumferential direction by the dividing planes S21 and S22 including the axis C, and the inner tube 3 and the intermediate partition plate 5 are divided in the axial direction by the dividing plane S23 perpendicular to the axis C. Each of the modules M21 to M28 has a resonance chamber 31a to 31h. The modules M21 to M28 may be bonded to each other, or the dividing planes S21, S22, and S23 may have recesses and protrusions so that they fit together. In FIG. 27, each of the modules M21 to M28 has a resonance chamber 31a to 31h, but it may also be configured with one having a resonance chamber and one having a side branch chamber. In addition, the dividing planes S21 and S22 may or may not include the rib plate 6. Furthermore, the dividing surface S23 may or may not include the intermediate partition plate 5.

In this way, by preparing multiple side branch type modules, resonance type modules, or mixed type modules that combine side branch and resonance types, all with the same outer diameter and different sound deadening effects, and combining each module according to the frequency of the sound source, it is possible to achieve the optimal sound deadening effect.

The present invention is not limited to the above-described embodiment, and can be modified and changed within the scope of the invention as defined in the claims.
For example, the number of side branch chambers is not limited to four as in the above embodiment, and the length of the side branch chambers can also be changed as appropriate.

1...Silencer (first embodiment)
Reference Signs List 2: Main pipe 3: Inner pipe 4: End partition plate 5, 5a, 5b: Intermediate partition plate 6: Rib plate 7a, 7b, 7c, 7d, 7e, 7f, 7g, 7h: Side branch chamber 8a, 8b, 8c, 8d, 8e, 8f, 8g, 8h: Inlet/outlet of side branch chamber 9a, 9b: Tapered surface 10: Silencer (conventional structure for comparison)
17a, 17b...Side branch chamber (conventional structure for comparison)
18a, 18b... Inlet and outlet of side branch chamber (conventional structure for comparison)
20... Silencer (second embodiment)
30... Silencer (third embodiment)
31a, 31b, 31c, 31d... Resonance chamber 32a, 32b, 32c, 32d... Opening of resonance chamber 40... Silencer (fourth embodiment)
50... silencer (fifth embodiment)
51: Outer cylinder 52: Small diameter portion 60: Silencer (sixth embodiment)
70... Silencer (seventh embodiment)
80... Silencer (eighth embodiment)

Claims (7)

A silencer to be inserted into a main pipe through which a fluid flows, the silencer comprising an inner pipe and a side branch chamber formed between the main pipe and the inner pipe,
an inner surface of the inner tube is provided with an inlet/outlet port communicating with the side branch chamber ;
the side branch chamber is surrounded by the main pipe, the inner pipe, upstream and downstream partition plates formed on an outer surface of the inner pipe, and an axially extending rib plate formed on the outer surface of the inner pipe,
a noise suppressor further comprising an outer cylinder for sealing the side branch chamber and for closely contacting outer surfaces of the partition plate and the rib plate . 2. The silencer according to claim 1 , wherein the inner surface of the upstream end of the inner pipe is formed as a tapered surface whose diameter decreases toward the downstream side. 3. The silencer according to claim 1, wherein the inner surface of the downstream end of the inner pipe is formed as a tapered surface whose diameter increases toward the downstream side. a resonance chamber between the main pipe and the inner pipe;
4. The silencer according to claim 1, wherein an opening is provided on the inner surface of the inner tube so as to communicate with the resonance chamber. 5. The noise suppressor according to claim 1 , wherein the noise suppressor is composed of a plurality of modules divided in a circumferential direction. 5. The noise suppressor according to claim 1 , wherein the noise suppressor is composed of a plurality of modules divided in the axial direction. 5. The noise suppressor according to claim 1 , wherein the noise suppressor is composed of a plurality of modules divided in the circumferential and axial directions.

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