JP2002174108A - Exhaust pipe structure of work vehicle - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an exhaust pipe structure of a work vehicle with excellent muffling effect. SOLUTION: The end part of an outlet pipe 25 of a muffler 23 is fitted in the inside of a tail pipe 20 fixed at an engine cover 10A. Its fit-in length L2 is set as follows by using an overall length L1 of a tail pipe 20, a sectional area S1 of a tail pipe 20, and a gap area S2 between the tail pipe 20 and the outlet pipe 25.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an exhaust pipe structure of a working vehicle which reduces noise of an exhaust system.

[0002]

2. Description of the Related Art Exhaust system noise includes pressure pulsation noise due to combustion explosion in an engine, in-pipe air column resonance, airflow noise, and radiation noise. Among them, the pressure pulsation noise is low noise such as a baud having a primary component at 80 Hz to 100 Hz in a construction machine, and becomes a muffled sound in a cab. For such pressure pulsation noise, it is necessary to provide a tail pipe (tail pipe) on the cover that constitutes the engine compartment and fit the end of the exhaust pipe with a gap inside the tail pipe to reduce noise. It is said to be effective. According to this configuration, the pressure pulsation sound (sound power) from the engine is emitted from the opening end of the tail pipe to the outside of the engine room via the exhaust pipe, and is also emitted to the engine room from the gap between the tail pipe and the exhaust pipe. You.

[0003]

According to the above configuration, the magnitude of the acoustic power emitted from the open end to the outside of the engine compartment is determined by the shape of the fitting portion at the end of the exhaust pipe. Therefore, if the shape of the fitting portion is incorrectly designed, a sufficient noise reduction effect cannot be obtained.

[0004] It is an object of the present invention to provide an exhaust pipe structure of a working vehicle having an excellent noise reduction effect.

[0005]

The present invention will be described with reference to the drawings of the embodiments. (1) The invention according to claim 1 is an exhaust pipe 26, 27, 24, 23, 25 including a silencer 23 for exhaust gas from the engine 11, and a tail pipe connected to the exhaust pipe 26, 27, 24, 23, 25. The present invention is applied to an exhaust pipe structure of a working vehicle that is guided to the outside of the engine room 5 through the engine 20. The tailpipe 20 is fitted with a gap 20b around the outer circumference of an outlet pipe 25 provided at the end of the exhaust pipe, and at least the acoustic power W01 emitted from the open end 20a of the tailpipe 20 to the outside of the engine compartment is reduced. The above-described object is achieved by determining the shape of the fitting portion between the outlet pipe 25 and the tail pipe 20 so as to be smaller than the acoustic power W02 emitted from the engine 20b into the engine room. (2) The invention according to claim 2 provides an exhaust pipe 26, 27, 24, 23, 25 including a muffler 23 for exhaust from the engine 11, and a tail pipe connected to the exhaust pipe 26, 27, 24, 23, 25. The present invention is applied to an exhaust pipe structure of a working vehicle that is guided to the outside of the engine room 5 through the engine 20. The tail pipe 20 is fitted with a gap 20b around the outer circumference of an outlet pipe 25 provided at the end of the exhaust pipe, and at least the insertion loss IL1 from the engine 11 to the open end 20a of the tail pipe 20 is reduced by the engine 11 from the engine 11. The above-described object is achieved by determining the shape of the fitting portion between the outlet pipe 25 and the tail pipe 20 so as to be larger than the insertion loss IL2 over the gap 20b. (3) According to a third aspect of the present invention, in the exhaust pipe structure for a working vehicle according to the second aspect, the fitting length L between the exhaust pipe 25 and the tail pipe 20 is set.
2, the total length L1 of the tail tube 20 and the cross-sectional area S1 of the tail tube 20;
It is determined at least in the following range based on the gap area S2.

(Equation 1) 0 <S2 <S1 k: wave number = 2π / λ λ: wavelength = c / fc c: sound velocity f: frequency (4) The invention according to claim 4 is the exhaust pipe structure for a working vehicle according to claim 3. The ratio of the sectional area S1 of the tailpipe 20 to the gap area S2 is determined at least in the following range based on the total length L1 of the tailpipe 20 and the fitting length L2 of the tailpipe 20 and the exhaust pipe 25.

(Equation 2) Where 0 <L2 <L1 <λ / 2 k: wave number = 2π / λ λ: wavelength = c / fc c: sound velocity f: frequency

[0006] In the section of the means for solving the above-mentioned problems, which explains the configuration of the present invention, the drawings of the embodiments are used to make the present invention easier to understand. However, the present invention is not limited to this.

[0007]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An exhaust pipe structure of a working vehicle according to an embodiment of the present invention will be described below with reference to the drawings. FIG. 1 is a side view of a hydraulic shovel to which the present invention is applied. As shown in FIG. 1, the excavator includes a traveling body 1,
A revolving body 2 rotatably provided on a traveling body 1, a boom 4a and an arm 4 rotatably mounted on the revolving body 2.
b, a working device 4 comprising a bucket 4c. A driver's cab 3 is mounted on the revolving superstructure 2, and an engine room 5 and a counterweight 6 are arranged behind the driver's cab 3.

FIG. 2 is a cross-sectional view of the engine room 5 in the vehicle width direction (a view as viewed from the rear of the vehicle). As shown in FIG. 2, an engine 11 is disposed substantially at the center of the engine room 5 whose periphery is covered by covers 10A to 10D. A hydraulic pump 12 is provided on the side of the engine 11 in the vehicle width direction, and a fan 15 that is driven to rotate via a pulley 13 and a V-belt 14 is provided on the opposite side. Fan 15
A radiator 16 and an oil cooler 17 are provided on a side of the fan 15, and a shroud 18 is formed from the radiator 16 to the outer peripheral portion of the fan 15. When the fan 15 rotates, as shown by the arrow in the figure, the side cover 10B
Cooling air is sucked into the engine compartment 10 through a suction port 10a opened to the inside. The cooling air passes through an oil cooler 17 and a radiator 16 and is heat-exchanged. Then, the cooling air passes around the engine 11 and covers upper, side and lower covers 10.
The air is discharged out of the engine room through discharge ports 10b opened to A, 10C, and 10D, respectively. The upper cover 1
0A is provided so as to be rotatable about a hinge 19 as a fulcrum.

FIG. 3 is an enlarged view of the upper part of the engine compartment 5 shown in FIG. 2, and FIG. 4 is a sectional view taken along the line IV-IV of FIG. As shown in FIG.
A muffler 23 is fixed to the bracket 21 via a U-bolt 22. A tail pipe 20 is erected substantially vertically on the upper surface of the cover 10A.
A circular hole 10 </ b> E having substantially the same shape as the inner diameter of the tail pipe 20 is opened in a mounting portion of the tail pipe 20 of 0A. The exhaust from the engine 11 is supplied to the muffler 23 by the muffler 2.
3 is connected to an outlet pipe 25 that guides exhaust gas that has passed through the muffler 23 to the outside of the engine room 5. The outlet pipe 25 is erected substantially vertically upward from the main body of the muffler 23, and the tip of the outlet pipe 25 passes through the circular hole 10 </ b> E of the cover 10 </ b> A and is accommodated in the tail pipe 20 with a gap. As shown in FIG. 4, the tip of the tail pipe 20 is directed rearward of the hydraulic shovel, and the opening 20a at the tip is directed slightly obliquely downward. As a result, the exhaust gas from the engine 11 is discharged toward the rear of the vehicle via the outlet pipe 25 and the tail pipe 20.

As shown by the arrows in FIG. 4, the pressure pulsation noise from the engine 11 is emitted from the open end 20a to the outside of the engine room through the outlet pipe 25 and the tail pipe 20, and the outer periphery of the outlet pipe 25 It is discharged toward the engine compartment from between the surface and the circular hole 10E of the cover 10A (gap 20b). As described above, when the sound powers distributed outside the engine room and inside the engine room are represented by W01 and W02, it is necessary to reduce the sound power W01 emitted from the opening end 20a in order to reduce noise. Therefore, in the following, in order to reduce the sound power W01, W01 <
The condition W02 is set, and the shape of the fitting portion between the tail pipe 20 and the outlet pipe 25 is set so as to satisfy this condition.

FIG. 5 is a diagram schematically showing an exhaust pipe structure for guiding exhaust gas from the engine 11 to the outside. In FIG. 5, the end of the outlet pipe 25 and the end of the tail pipe 20 are joined. First, basic acoustic transfer characteristics of the exhaust pipe will be described using this model. As shown in FIG. 5, pressure pulsation sound (sound power W
s) passes through an exhaust manifold 26, an exhaust pipe 27, an inlet pipe 24, a muffler 23, an outlet pipe 25, and a tail pipe 20, and is emitted outside as sound power W0. Each component constituting the exhaust pipe has its own unique sound transmission characteristics, and a combination of these characteristics becomes the sound transmission characteristics of the entire exhaust pipe from the exhaust manifold 26 to the tail pipe 20.

In general, the four-terminal theory is used for handling the sound transfer characteristics. This represents the sound transfer characteristic by a four-terminal transfer matrix, as shown in the following equation (3).

(Equation 3) Here, P: sound pressure Q: volume velocity (value obtained by dividing the vibration velocity (particle velocity) of the opening end face by area) Subscript s: sound source 0: output destination (opening end of tail pipe 20) 1, 2,. : Each component such as exhaust manifold, muffler, etc. In the above equation (3), the four-terminal component is given by the structural factor (tube length, tube diameter, etc.), medium density, and sound speed of each component. Combining the components of equation (3) gives the following equation (4)
As shown in (1), the transfer matrix of the exhaust pipe from the exhaust manifold 26 to the tail pipe 20 is obtained.

(Equation 4) By expanding the above equation (4), the following equation (5) is obtained.

(Equation 5) The relative ratio of the sound power Ws generated at the sound source to the sound power W0 emitted at the opening end, that is, the exhaust pipes 26, 27, 24,
The insertion loss IL due to the insertion of the tail pipes 23 and 25 and the tail pipe 20 is expressed by the following equation (6).

(Equation 6) In this case, the sound power W is represented by the following equation (7).

(Equation 7) Where ρ: medium density ω: angular frequency (= 2πf) C: sound velocity The larger the value of the insertion loss IL, the greater the acoustic power W0 on the opening end side.
Is small, that is, the sound is small. The acoustic impedance Z = P / Q at the opening end is approximately set to 0, and the sound pressure P0 at the opening end is set to 0. Thereby, P0 = 0 is substituted into the above equation (5), and the following equation (8) is established.

(Equation 8) Then, from Expressions (7) and (8), Expression (6) is expressed by the following Expression (9).

(Equation 9) Thus, the insertion loss IL can be approximately obtained by grasping the d component of the transfer matrix.

Assuming the above, the exhaust pipe 2 when the tail pipe 20 and the outlet pipe 25 are fitted together as shown in FIG.
The transfer matrices of 6, 27, 24, 23, 25 and the tail pipe 20 are obtained. Since the sound powers W01 and W02 are emitted from the opening end 20a and the gap 20b of the tail pipe 20 as described above, the transfer matrices are divided according to these, as shown in the following equations (10) and (11). Become.

(Equation 10)

[Equation 11] However, the subscript a: the transfer matrix from the exhaust manifold 26 to the outlet pipe 25 01: the open end 20a side of the tail pipe 20 02: the gap 20b side of the tail pipe 20 TP01: the transfer matrix TP02 from the outlet pipe 25 to the open end 20a Transfer matrix from the outlet pipe 25 to the gap 20b From this, the insertion loss IL1 when the sound power W01 is emitted from the open end 20a and the sound power W0 from the gap 20b
The insertion loss IL2 when 2 is emitted is expressed by the following equations (12) and (13), respectively.

(Equation 12)

(Equation 13) Here, the larger the insertion loss IL, the smaller the sound power W0. Therefore, in order to satisfy the above-described relationship of the sound power W01 <W02, it is necessary to satisfy the relationship of the insertion loss IL1 <IL2, and the equations (12) and (13) are used. Therefore, the d component needs to satisfy the following expression (14).

[Equation 14]

As shown in FIG. 4, when the length (total length) of the tail pipe 20 is L1, the fitting length of the outlet pipe 25 is L2, the sectional area of the tail pipe 20 is S1, and the area of the gap 20b is S2. At least 0 <L2 <L1 and 0 <S
2 <S1. At this time, the transfer matrices from the outlet pipe 25 to the opening end 20a and the transfer matrices from the outlet pipe 25 to the gap 20b shown in the equations (10) and (11) are expressed by the following equations (15) and (16), respectively. Is done.

(Equation 15)

(Equation 16) Here, k: wave number (= 2πf / C) j: imaginary number By substituting these equations (15) and (16) into the above equations (10) and (11), the following equations (17) and (18) are obtained.

[Equation 17]

(Equation 18) Here, the matrix components ca, da, d01, and d02 are treated as complex numbers as in the following equations (19) to (22).

[Equation 19]

(Equation 20)

(Equation 21)

(Equation 22) However, subscript r: real term i: imaginary term By this, the above equations (17) and (18) are
It is rewritten as (26).

(Equation 23)

(Equation 24)

(Equation 25)

(Equation 26) Here, the variables of the above equations (23) to (26) are replaced by the following equation (27).
As shown in (30), α1, α2, β1, β2 are substituted, and the variable y is set by the following equation (31).

[Equation 27]

[Equation 28]

(Equation 29)

[Equation 30]

(Equation 31) By substituting the above equations (21) to (30) into the equation (31), the following equation (32) is established.

(Equation 32) Here, the variable p is set by the following equation (33).

[Equation 33] From Expression (33) and Expressions (27) to (30), the following Expression (3) is obtained.
4) and (35) hold, and the following formula (36) holds from formulas (34) and (35).

(Equation 34)

(Equation 35)

[Equation 36] From the equations (34) to (36), the above equation (32) can be rewritten as the following equation (37).

(37) From the above equation, p> 1 or the following equation (38) must be satisfied in order to satisfy y> 0.

(38) The following equation (39) is obtained from the equation (38).

[Equation 39]

The equation (39) is expanded to the following equation (40).

(Equation 40) Further, the following equation (41) is obtained by dividing both sides of the above equation (40) by cos (kL2) and multiplying both sides by S2.

[Equation 41] Rearranging the above equation (41) gives the following equation (42).
Thereby, the condition of the length L2 of the fitting portion is obtained.

(Equation 42) Note that the above equation (39) can be modified as the following equation (43), whereby the pipeline loss IL1> IL2
The condition of the area ratio S1 / S2 is obtained.

[Equation 43]

If the left side of the equation (42) is f1 as in the following equation (44), it is necessary to satisfy at least f1> 0 from L2> 0.

[Equation 44] In the equation (44), the denominator in the parentheses of the arc tangent always takes a positive value under the condition of 0 <S2 <S1, whereas the numerator is switched between positive and negative according to the value of kL1. As a result, the value of f1 changes as in the following equations (45) to (47).

[Equation 45]

[Equation 46]

[Equation 47] Therefore, in order to satisfy f1> 0, kL1 needs to satisfy Expression (45). By substituting 2π / λ for k in equation (45), the following equation (48) is obtained.

[Equation 48]

Here, for example, the primary component 80 of the pressure pulsation sound
Substituting into the above equation (48) as Hz and sound speed of 513 m / s (equivalent to the exhaust temperature of 380 ° C.), the total length L1 of the tail pipe 20 is calculated as follows. 0 mm <L1 <λ / 2 = 3206 mm (n = 0) λ = 6413 mm <L1 <3λ / 2 = 9619 mm (n
= 1) Normally, the total length L1 of the tail pipe 20 is at most 1000 m
m, and n = 0 is appropriate. Further, the variables L1, S
1, S2 is, for example, L1 = 600 mm, S1 = 36305 mm2,
FIG. 6A shows the relationship (calculated value) between the fitting length L2 and the insertion loss IL1, IL2 when S2 = 18159 mm2. As a result, the insertion loss IL2 increases (the noise decreases) and the insertion loss IL1 decreases (the noise increases) as the fitting length L2 increases.
There is a tendency, and IL1> IL2 is satisfied in the range of L2 <197 mm. Here, the set values of L1, S1, and S2 are calculated by the above equations (4
Substituting into 2), the range of the fitting length L2 is 0 <L2 <197
mm, which is consistent with FIG. in this way,
By determining the fitting length L2 so as to satisfy Expression (42), IL1> IL2, and the noise is appropriately reduced.

Next, under the condition that the primary component of the pressure pulsation sound is 80 Hz and the sound speed is 513 m / s, for example, the total length L1 of the tail pipe
FIG. 6B shows the relationship (calculated value) between the area ratio S1 / S2 and the insertion loss IL1, IL2 when the fitting length L2 = 100 mm and the fitting length L2 = 100 mm. From this, the insertion loss IL2 tends to increase (noise reduction) and the insertion loss IL1 tends to decrease (noise increase) as the area ratio S1 / S2 increases, and the area ratio S1 / S2 increases.
IL1> IL2 is satisfied in the range of 2 <4.81. Here, when the set values of L1 and L2 are substituted into the above equation (43),
The range of the area ratio S1 / S2 is 1 <S1 / S2 <4.81, which corresponds to FIG. 6B. If the cross-sectional area of the outlet pipe 25 is Smo (= S1−S2), 0 <1.26S
mo <S1. Thus, if the cross-sectional area S1 of the tail pipe 20 is 1.26 times or more the cross-sectional area of the outlet pipe 25, the insertion loss IL1> IL2 is satisfied, and the noise is appropriately reduced.

As described above, according to the present embodiment, the end of the outlet pipe 25 of the muffler is fitted to the tail pipe 20, and the pressure pulsation noise from the engine 11 is transmitted to the open end 20a of the tail pipe 20 and the tail pipe 20. 20b between the outlet pipe 25
From each other. And then,
Sound power W01 emitted from at least the open end 20a
The shape of the fitting portion is determined so that the sound power is smaller than the sound power W02 emitted from the gap 20b (W01 <W02). As a result, the engine noise emitted to the outside of the engine room is significantly reduced, and a sufficient noise reduction effect can be obtained.

Further, an insertion loss IL1 when the acoustic power W01 is emitted from the opening end 20a of the tail pipe 20, and
Since the shape of the fitting portion is determined so that IL1> IL2 using the insertion loss IL2 when the sound power W02 is emitted from the gap 20b, the total length L1, the fitting length L2, and the tail pipe of the tail pipe 20 are determined. Conditional expressions of equations (42) and (43) can be calculated from parameters such as the cross-sectional area S1 of 20 and the gap area S2 between the tail pipe 20 and the outlet pipe 25. Then, the fitting length L2 is calculated using equation (42),
By calculating the area ratio S1 / S2 using equation (43),
The shape of the fitting portion with sufficiently reduced engine noise can be obtained without performing extensive analysis or the like, which is very useful when designing an exhaust pipe.

Although the exhaust pipe structure according to the above embodiment is applied to a hydraulic excavator, it may be applied to other work vehicles (for example, agricultural machines). Further, in the above embodiment, the outlet of the muffler 23 may be cooled to reduce the airflow noise (ejector effect). Further, in the above embodiment, the lower limit of the area ratio S1 / S2 is set to be larger than 1 (1 <S1 / S2), but the lower limit of the area ratio S1 / S2 is set in consideration of the ejector effect. You may make it. Furthermore, in the above embodiment, the engine 1
Although the exhaust gas from the engine cover 1 is discharged from the upper portion of the engine cover 10, the exhaust gas may be discharged from the side portion or the rear portion of the engine cover 10.

[0022]

As described above, according to the present invention, the following effects can be obtained. (1) According to the first aspect of the present invention, at least the sound power emitted from the open end of the tailpipe to the outside of the engine room is smaller than the sound power emitted into the engine room from the gap between the outlet pipe and the tailpipe. In addition, since the shape of the fitting portion between the outlet pipe and the tail pipe is determined, the acoustic power emitted to the outside of the engine room is greatly reduced, and an excellent noise reduction effect is obtained. (2) According to the second aspect of the present invention, the insertion loss of the outlet pipe and the tail pipe is set so that the insertion loss from the engine to the open end of the tail pipe is larger than the insertion loss from the engine to the gap between the outlet pipe and the tail pipe. Since the shape of the fitting portion is determined, it is possible to calculate a conditional expression for making the acoustic power emitted from the opening end of the tailpipe out of the engine room smaller than the acoustic power emitted into the engine room from the gap. (3) According to the third and fourth aspects of the present invention, a conditional expression for reducing noise using parameters such as the total length and fitting length of the tailpipe, the cross-sectional area of the tailpipe, and the gap area is provided. Therefore, the optimum shape of the fitting portion can be easily obtained, which is very useful in designing the exhaust pipe.

[Brief description of the drawings]

FIG. 1 is a side view of a hydraulic shovel to which the present invention is applied.

FIG. 2 is a cross-sectional view in the vehicle width direction of an engine room of the hydraulic shovel of FIG. 1;

FIG. 3 is an enlarged view of a main part of FIG. 2;

FIG. 4 is a sectional view taken along line IV-IV of FIG. 3;

FIG. 5 is a view schematically showing an exhaust pipe structure for guiding exhaust gas from an engine to the outside.

FIG. 6 is a diagram showing a calculation result of insertion loss by the exhaust pipe structure according to the present embodiment.

[Explanation of symbols]

5 Engine room 11 Engine 20 Tail pipe 23 Muffler 24 Inlet pipe 25 Outlet pipe 26 Exhaust manifold 27 Exhaust pipe W01, W02 Sound power IL1, IL2 Insertion loss

Claims (4)

[Claims] 1. An exhaust pipe structure of a working vehicle in which exhaust gas from an engine is guided to an outside of an engine room through an exhaust pipe including a muffler and a tail pipe connected to the exhaust pipe, wherein the tail pipe is At least a sound power emitted from the open end of the tail pipe to the outside of the engine room is fitted to an outer peripheral side of an outlet pipe provided at an end of the exhaust pipe, and at least an acoustic power emitted to the engine room from the gap. An exhaust pipe structure for a working vehicle, wherein a shape of a fitting portion between the outlet pipe and the tail pipe is determined so as to be smaller than the above. 2. An exhaust pipe structure of a working vehicle in which exhaust gas from an engine is guided to the outside of an engine room through an exhaust pipe including a muffler and a tail pipe connected to the exhaust pipe, wherein the tail pipe is It is fitted with a gap to the outer peripheral side of the outlet pipe provided at the end of the exhaust pipe, and the insertion loss from at least the engine to the open end of the tail pipe is larger than the insertion loss from the engine to the gap. The exhaust pipe structure for a working vehicle, wherein the shape of the fitting portion between the outlet pipe and the tail pipe is determined as described above. 3. The exhaust pipe structure for a working vehicle according to claim 2, wherein the fitting length L2 between the outlet pipe and the tail pipe is the total length L1 of the tail pipe, and the cross-sectional area S1 of the tail pipe. An exhaust pipe structure for a working vehicle, wherein the exhaust pipe structure is determined at least in the following range based on the gap area S2. (Equation 1) Where 0 <S2 <S1 k: wave number = 2π / λ λ: wavelength = c / fc c: sound velocity f: frequency 4. The exhaust pipe structure of a work vehicle according to claim 3, wherein a ratio of a cross-sectional area S1 of the tail pipe to the gap area S2 is determined by a total length L1 of the tail pipe, the tail pipe, and the outlet. An exhaust pipe structure for a working vehicle, wherein the exhaust pipe structure is determined at least in the following range according to the fitting length L2 of the pipe. (Equation 2) Where 0 <L2 <L1 <λ / 2 k: wave number = 2π / λ λ: wavelength = c / fc c: sound velocity f: frequency