WO2008018821A1

WO2008018821A1 - A device for attenuating and/or directing sound, and a work machine

Info

Publication number: WO2008018821A1
Application number: PCT/SE2006/000944
Authority: WO
Inventors: Nicklas Frenne
Original assignee: Volvo Construction Equipment Ab
Priority date: 2006-08-11
Filing date: 2006-08-11
Publication date: 2008-02-14

Abstract

The invention relates to a device for attenuating and/or directing sound, wherein it comprises a tubular element (122) delimiting an inner space (201) for conveying a gas flow. A wall (301) defining an envelope surface of the tubular element comprises a plurality of silencing through-holes (302,303) and the tubular element is adapted for direct communication between the internal gas flow and the atmosphere through said silencing through-holes.

Description

A device for attenuating and/or directing sound/ and a work machine

FIELD OF THE INVENTION AND PRIOR ART

The present invention relates to a device for attenuating and/or directing sound, wherein it comprises a tubular element delimiting an inner space for conveying a gas flow. The device is particularly designed for a vehicle, and especially for a work machine, but may also be used in other applications, such as for stationary machines, where there is a need for attenuating and/or directing sound/noise. The device is particularly adapted for being applied in an exhaust system forming part of an exhaust piping for conveying exhaust gases from a vehicle engine.

The term "work machine" comprises different types of material handling vehicles like construction machines, such as a wheel loader, a backhoe loader and an articulated hauler. Further terms frequently used for work machines are "earth-moving machinery" and "off- road work machines". The invention will be described below in a case in which it is applied in a frame- steered work machine constituting a wheel loader. This is to be regarded only as an example of a preferred application.

The invention relates particularly to machines with a substantially closed engine compartment in which the temperature can be very high and in which there is a need for ventilating the compartment. A tailpipe is arranged through an opening in the hood defining the engine compartment. An exhaust pipe from the engine extends so that it is in fluid communication with the tailpipe. Preferably, the exhaust pipe is arranged for forcing the heated air from the compartment via an ejector effect.

The tailpipe of a wheel loader extends out of an engine compartment in a vertical, upwards direction from an opening in the engine hood. That is to say, a first end of the tailpipe opens into the engine compartment, whilst the other end opens into the atmosphere. The last portion of the exhaust pipe comprising the outlet end is normally bent rearwards.

SUMMARY OF THE INVENTION

One purpose of the invention is to achieve a device capable of attenuating and/or directing sound, in particular for a vehicle, so that a driver/operator will be less exposed to noise during operation of the vehicle. More particularly, it is desired to achieve a device that creates conditions for reducing the noise emitted from the vehicle engine exhaust system in the direction of the driver of the vehicle.

This purpose is achieved by a device according to claim 1. Thus, the purpose is achieved in that a wall defining an envelope surface of the tubular element comprises a plurality of silencing through-holes and that the tubular element is adapted for direct communication between the internal gas flow and the atmosphere through said silencing through-holes . In this way, a compact, cost-efficient and lightweight silencer may be achieved with positive sound direction characteristics .

It has turned out that a sufficient sound attenuating and direction effect may be achieved with the tubular element forming a sole pipe in the atmosphere. Thus, the pipe is free from co-operation with any surrounding parts .

According to one embodiment of the invention, the tubular element comprises a closed end wall in its axial direction and an opposite open end in the axial direction. By the arrangement of the closed end, the gas/air is forced through the radial through-holes, which leads to a sound/noise attenuating effect.

According to a further embodiment of the invention, a portion of the tubular element comprising the through- holes is straight all the way to the end wall. The straight pipe with closed end wall will direct the sound in the extension direction of the pipe, which creates conditions for directing the sound/noise.

According to a further embodiment of the invention, the silencing through-holes are arranged in rows, and that each row comprises a plurality of through-holes. By adapting the mutual distance between the rows in correspondence to the sound waves to be directed, a stronger direction effect may be achieved. The rows of silencing through-holes are preferably arranged substantially at right angles with regard to an axial direction of the tubular element. A further purpose of the invention is to achieve a work machine adapted for attenuating and/or directing sound, so that a driver will be less exposed to noise during operation of the vehicle.

This purpose is achieved by the work machine according to claim 15. Thus, it is achieved by a work machine comprising a hood defining an engine compartment, and a tubular element in fluid connection with an exhaust outlet of an engine, wherein the tubular element extends upwards from the hood, wherein the tubular element delimits an inner space for conveying an exhaust gas flow, characterized in that a wall defining an envelope surface of the tubular element comprises a plurality of silencing through-holes for outlet of the exhaust gas and that the tubular element is adapted for direct communication between the internal exhaust gas flow and the atmosphere through said silencing through-holes for attenuating and directing sound.

Further advantageous embodiments and advantages of the invention will be apparent from the following description, drawings and claims.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention will be explained below, with reference to the embodiments shown on the appended drawings, wherein FIG 1 schematically shows a wheel loader in a side view, FIG 2 shows an exhaust device for attenuating and directing sound in an enlarged side view,

FIG 3 shows a tubular element with a plurality of through-holes according to a first embodiment in a perspective view, FIG 4 schematically shows a sound wave propagation in the tubular element in figure 3, FIG 5 shows an enlarged view of the through holes in the tubular element in figure 3, FIG 6 shows a second embodiment of a through-hole configuration, FIG 7 shows alternative positions of a device for attenuating and/or directing sound in a wheel loader, and FIG 8 shows alternative positions of a device for attenuating and/or directing sound in a truck.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS OF THE INVENTION Figure 1 shows a wheel loader 101. The body of the wheel loader 101 comprises a front body section 102 with a front frame, and a rear body section 103 with a rear frame. The rear body section 103 comprises a cab 114. The body sections 102,103 are connected to each other via an articulation joint in such a way that they can pivot in relation to each other around a vertical axis . The pivoting motion is achieved by means of two first actuators in the form of hydraulic cylinders 104,105 arranged between the two sections. Thus, the wheel loader is an articulated work vehicle. The hydraulic cylinders 104,105 are thus arranged one on each side of a horizontal centerline of the vehicle in a vehicle traveling direction in order to turn the wheel loader 101.

The wheel loader 101 comprises an equipment 111 for handling objects or material. The equipment 111 comprises a load-arm unit 106, or boom, and an implement 107 in the form of a bucket fitted on the load-arm unit. A first end of the load-arm unit 106 is pivotally connected to the front vehicle section 102. The bucket 107 is pivotally connected to a second end of the load-arm unit 106.

The load-arm unit 106 can be raised and lowered relative to the front section 102 of the vehicle by means of two second actuators in the form of two hydraulic cylinders 108,109, each of which is connected at one end to the front vehicle section 102 and at the other end to the load-arm unit 106. The bucket 107 can be tilted relative to the load-arm unit 106 by means of a third actuator in the form of a hydraulic cylinder 110, which is connected at one end to the front vehicle section 102 and at the other end to the bucket 107 via a link mechanism.

The wheel loader 101 comprises an engine compartment 116, an internal combustion engine 117, in particular a diesel engine, arranged in the engine compartment, and an engine hood or casing 118, which separates the engine compartment 116 from the surrounding atmosphere. The wheel loader 101 further comprises an exhaust system 119, via which exhaust gases are conveyed from the engine 117 to the atmosphere via a silencer 124. The exhaust system 119 comprises an exhaust pipe 120, which is connected to an exhaust outlet of the engine 117.

A device 121 for attenuating and directing noise is in operational contact with the exhaust pipe 120 for directing the exhaust gases from the engine. The device 121 comprises a tubular element 122 delimiting an inner space 201 for conveying an exhaust gas flow. Thus, the tubular element 122 forms a tailpipe. The exhaust pipe

120 extends from the engine 117 up to the tubular element 122. The tubular element 122 is sealingly arranged in an opening 123 in said hood 118 and projects out of the opening. The tubular element 122 is vertically directed upwards from the hood 118.

Figure 2 shows the device 121 for attenuating and directing sound, which is coupled to the exhaust gas pipe 120, in a side view. The exhaust pipe 120 opens into a chamber 202, which is formed by an essentially cylindrical side wall 203, an annular top end wall 204 and an annular bottom end wall 205. The tubular element 122 extends down into the chamber 202 through an opening 206 in the top end wall 204. The tubular element 122 is somewhat widened at its lower end. The opening 206 in the top end wall 204 coincide with the opening 123 in the hood 118.

The bottom end wall 205 has an opening 207, from which a pipe- and funnel-shaped air baffle element 208 extends upward through the chamber 202 far enough to overlap and to extend radially inside a part of the tubular element 122. A gap 209, through which the exhaust gases are led from the chamber 202 into the tubular element 122, exists between the tubular element 122 and the air baffle element 208. The gap 209 is so narrow that a pressure build-up, and preferably also an acceleration of the rate of flow of the exhaust gases occurs therein. In this way, an ejector effect is achieved in that the exhaust gases forces air from the engine compartment out to the atmosphere via the tubular element 122. The chamber 202, or more specifically the walls

203,204,205 forming the chamber are arranged on the inside of the engine hood 118, that is to say in the engine compartment 116. It is advantageously arranged directly opposite, for example directly above, some particularly heat-affected or heat-sensitive component in the engine compartment. Examples of such typically heat-affected components are a manifold or a turbo unit

(not shown) .

Figure 3 shows the tubular element 122 in a perspective view. A wall 301 defining an envelope surface of the tubular element 122 comprises a plurality of silencing through-holes 302,303. The tubular element 122 is adapted for direct communication between the internal gas flow and the atmosphere through said silencing through-holes 302,303. In other words, the through-holes form outlet passages for communicating acoustically treated exhaust gas to the atmosphere.

The tubular element 122 is upright, i.e. vertically directed upwards from the hood 118, serving to direct noise upwardly from the hood 118 and away from the cab 114 and a driver.

The tubular element 122 has a cylindrical shape forming a sleeve structure. It is delimited by two parallel planes 304,305 and the wall 301 forms an intermediate surface with circular cross sectional shape. The top plane 305 is closed by a top end wall 306. The top end wall extends at right angles relative to an axial direction 307 of the tubular element 122. The bottom plane 304 is open, forming an inlet for the exhaust gas flow. Thus, the tubular element 122 forms a sole pipe with a closed top end. In other words, the device comprises a single-wall structure. The tubular element 122 has a circular cross section and a uniform tubular diameter along its length (except for the widened end portion) . More specifically, a portion of the tubular element 122 comprising the through-holes 302,303 is straight all the way to the top end wall 306.

In operation, the exhaust gas flow enters the inlet end 304 of the tube 122, flows towards the closed end 305 and is forced to make a 90° change of direction to exit the tube 122 through the multiplicity of through-holes

302,303. The silencing action is similar to an ordinary silencer. That is, the gas passes out of the radial holes 302,303 and is blown out into the atmosphere.

The silencing through-holes 302,303 are arranged in parallel rows, wherein each row comprises a plurality of through-holes. In the showed exemplary embodiment, the rows of silencing through-holes 302,303 are linearly arranged at right angles with regard to the axial direction 307 of the tubular element 122. Further, the rows are arranged on equal mutual distances in the axial direction 307 of the tubular element 122. However, it may be advantageous to arrange the rows in a different manner for various reasons, for example in order to achieve a proper gas flow. For example a set of rows may be arranged at a relatively small internal mutual distance followed by another set of rows arranged at a larger mutual distance. The specific through-hole pattern, especially with regard to the axial distance between the rows, may vary for different applications in order to achieve an optimum/desired direction and attenuation characteristic. The through-holes are preferably evenly distributed around the tube circumference. Increasing number of distributed through-holes around the circumference improves directional properties but reduce attenuation properties. In other words, the tube 122 has many radial ports 302,303 perforated therein.

The through-holes 302,303 may be of various sizes, shapes, patterns and total area. The selection is ordinarily made on the basis of sound, noise and backpressure characteristics desired.

According to a first embodiment, the silencing through- holes 302,303 have a circular shape, see also figure 5. There are at least four rows of silencing through-holes, and preferably, at least eight rows of silencing through-holes. Further, there are at least four silencing through-holes in each row and preferably at least eight silencing through-holes in each row.

More specifically, the through-hole configuration is designed for an optimum sound attenuation without the exhaust gas flow therefrom being restricted to such an extent that it interferes with engine operation. Figure 4 schematically shows a sound wave propagation in the tube 122 during operation of the engine. The distance between adjacent rows 302,303 of through-holes are arranged in order to coincide with sound waves so that it at least substantially equals a propagation distance in the axial direction of the tube between a positive wave amplitude (wave top) and a negative wave amplitude

(wave bottom) . The invention is however not limited to that the distance between adjacent rows exactly matches the propagation distance. Instead, a very similar effect is achieved with other wave lengths . The showed example in figure 4 should be regarded as an illustrative case, disclosing the physical phenomena.

The through-hole configuration is preferably determined by the exhaust gas pressure which the engine imparts and the back-pressure generated by other components of the exhaust system.

Figure 5 shows an enlarged view of the through holes 302 in the wall 301 of the tubular element 122 in figure 3. The through-holes 302 are circular in cross section. The through-hole height (h) or diameter, i.e. its extension in the axial direction 307, is substantially larger than a wall thickness (t) . The height is preferably more than twice the wall thickness and preferably, h=10*t. Circular through-holes give specifically good attenuating characteristics at low frequencies.

Figure 6 shows a second embodiment of a through-hole configuration in a wall of a tubular element. The silencing through-holes 602 have an elongated shape, forming slots extending in the direction of said row. The through-hole height (h) , i.e. its extension in the axial direction, is substantially larger than a wall thickness (t) . The height is preferably more than twice the wall thickness and preferably, h=10*t. This embodiment improves directional characteristics at high frequencies .

Figure 7 shows alternative positions of a device for attenuating and/or directing sound in the wheel loader 101. First, the above described first embodiment of the device 121 is schematically shown again, wherein the tubular element extends vertically upwards from the hood. A large arrow 701 indicates the exhaust gas flow from the engine compartment and a smaller arrow 702 indicates a direction of sound waves with the arrow pointing from stronger to weaker sound pressure level.

Further, according to a second embodiment, the device is arranged for directing an airflow into the engine compartment or engine. Two tubular elements 703,704 are directed in opposite directions in a substantially horizontal direction and along the vehicle longitudinal direction. Thus, each tubular element is arranged in parallel with a vehicle traveling direction. Further, the tubular element is arranged beneath the engine compartment. The device comprises means (not shown) for directing the air flow into the engine compartment or engine .

The silencing through-holes form air inlets and the open end of the tubular element forms an air outlet in the second embodiment. A first closed end wall of the tubular element is pointing rearwards and a second closed end wall is pointing forwards in the second embodiment. A large arrow 705 indicates the air flow to the engine compartment and the smaller arrows 706,707 indicates a direction of sound waves with the arrow pointing from stronger to weaker sound pressure level.

A larger total length of the device is achieved by using two tubular elements in opposite directions . Such a long tubular device with distributed rows of through- holes creates conditions for sound waves with a longer wave length to coincide with the sound waves in the tubes, wherein lower frequencies may be better directed along the tube.

Thus, the device may be applied in an air inlet arrangement for suction of air to the engine for combustion and for taking in air for cooling of the engine.

Further, according to a third and fourth embodiment, the device is arranged for directing an airflow out of and into, respectively, the operator compartment (cab 114) . The tubular element 708 is directed in a substantially vertical direction. The open end of the tubular element forms an air inlet in the cab and the silencing through-holes form air outlets outside the cab in the third embodiment. Further, the closed end wall of the tubular element is pointing upwards in the third embodiment .

The silencing through-holes form air inlets outside the cab and the open end of the tubular element forms an air outlet inside the cab in the fourth embodiment. Further, the closed end wall of the tubular element is pointing upwards in the fourth embodiment .

The devices according to the third and fourth embodiments are arranged at a mutual distance in the transverse direction of the vehicle. A large arrow 709 indicates the air flow to and from, respectively, the engine compartment and the smaller arrow 710 indicates a direction of sound waves with the arrow pointing from stronger to weaker sound pressure level. Figure 8 shows alternative positions of a device for attenuating and/or directing sound in a truck 801.

According to a fifth embodiment of the invention, the tubular element 802 forms an extension of an engine exhaust pipe. It may be formed in a separate unit fitted to the exhaust pipe or the tubular element may form an integral part of the exhaust pipe. The tubular element 802 is directed in a substantially horizontal direction and along the vehicle longitudinal direction. Thus, the tubular element is arranged in parallel with a vehicle traveling direction. The silencing through-holes form air outlets and the open end of the tubular element forms an air inlet. The closed end wall of the tubular element is pointing rearwards. A large arrow 803 indicates the air flow to the engine compartment and a smaller arrow 804 indicates a direction of sound waves with the arrow pointing from stronger to weaker sound pressure level.

By arranging the tubular element in the exhaust system pointing rearwards enhances the characteristics of giving warning to other vehicles and pedestrians in the traffic. Further, the noise created when a vehicle is passing may be reduced.

Further, one embodiment 805,806 for directing air flow into the engine compartment or engine, respectively, is shown in figure 8. This embodiment corresponds to the second embodiment described above for the wheel loader and will not be further explained here.

Further, also two embodiments 807 for directing an airflow out of and into, respectively, the operator compartment are shown in figure 8. These two embodiments correspond to the third and fourth emdodiment described above for the wheel loader and will not be further explained here.

In accordance with the description above, the requirements for proper sound attenuating effect and proper directional effect are somewhat conflicting in that a totally smaller number of through-holes gives a better attenuation effect, while a larger number of rows gives a better directional effect.

The invention is not in any way limited to the above described embodiments, instead a number of alternatives and modifications are possible without departing from the scope of the following claims.

According to one alternative to the exhaust system shown in figure 2, an exhaust pipe from the engine extends into the center of the tailpipe (tubular element) in order to carry the exhaust gases into the tailpipe and via this out to the atmosphere. The outer circumference of the exhaust pipe is smaller than the inner circumference of the tailpipe so that an annular gap is formed between these pipes. In this way, hot air in the engine compartment is forced out of the engine compartment via said tailpipe through an ejector effect.

According to one alternative, the through-holes are only located on one side of the tube circumference.

Claims

1. A device (121) for attenuating and/or directing sound, wherein it comprises a tubular element (122) delimiting an inner space (201) for conveying a gas flow, c h a r a c t e r i z e d in that a wall (301) defining an envelope surface of the tubular element (122) comprises a plurality of silencing through-holes (302,303) and that the tubular element is adapted for direct communication between the internal gas flow and the atmosphere through said silencing through-holes .

2. A device according to claim 1 , c h a r a c t e r i z e d in that the tubular element (122) comprises a closed end wall (306) in its axial direction and an opposite open end (304) in the axial direction.

3. A device according to any preceding claim, c h a r a c t e r i z e d in that a portion of the tubular element (122) comprising the through-holes (302,303) is straight all the way to the end wall (306).

4. A device according to any preceding claim, c h a r a c t e r i z e d in that the silencing through- holes (302,303) are arranged in rows, and that each row comprises a plurality of through-holes.

5. A device according to claim 4, c h a r a c t e r i z e d in that the rows of silencing through-holes (302,303) are arranged substantially at right angles with regard to an axial direction (307) of the tubular element (122) .

6. A device according to claim 4 or 5, c h a r a c t e r i z e d in that at least some of the silencing through-holes (602) have an elongated shape extending in the direction of said row.

7. A device according to any preceding claim, c h a r a c t e r i z e d in that at least some of the silencing through-holes (302,303) have a substantially circular shape.

8. A vehicle comprising a casing (118) with an opening (123) for a gas through-flow, c h a r a c t e r i z e d in that it comprises the device according to any preceding claim, wherein the tubular element (122) is arranged at said opening for conveying said gas flow and projects outwards from the casing.

9. A vehicle according to claim 8, c h a r a c t e r i z e d in that said casing forms a hood (118) defining an engine compartment .

10. A vehicle according to claim 8, c h a r a c t e r i z e d in that said casing forms a cab wall defining an operator compartment .

11. A vehicle according to any of claims 8-10, c h a r a c t e r i z e d in that the tubular element (122) is vertically directed upwards from the casing (118) .

12. A vehicle according to any of claims 8-11, c h a r a c t e r i z e d in that the tubular element is horizontally directed.

13. A vehicle according to any of claims 8-12, c h a r a c t e r i z e d in that the vehicle forms a work machine.

14. A work machine (101) comprising a hood (118) defining an engine compartment (116) , and a tubular element (122) in fluid connection with an exhaust outlet of an engine (117), wherein the tubular element (122) extends upwards from the hood, wherein the tubular element (122) delimits an inner space for conveying an exhaust gas flow, c h a r a c t e r i z e d in that a wall (301) defining an envelope surface of the tubular element (122) comprises a plurality of silencing through-holes (302,303) for outlet of the exhaust gas and that the tubular element (122) is adapted for direct communication between the internal exhaust gas flow and the atmosphere through said silencing through-holes for attenuating and directing sound.

15. A work machine according to claim 14, c h a r a c t e r i z e d in that the tubular element (122) comprises one open end (304) in communication with the engine and one closed end (305) in its axial direction.

16. A work machine according to claim 14 or 15, c h a r a c t e r i z e d in that the silencing through- holes (302,303) are arranged in rows, and that each row comprises a plurality of through-holes.

17. A work machine according to claim 16, c h a r a c t e r i z e d in that the rows of silencing through-holes (302,303,602) are arranged substantially at right angles with regard to an axial direction (307) of the tubular element (122) .

18. A work machine according to any of claims 14-17, c h a r a c t e r i z e d in that a portion of the tubular element (122) comprising the through-holes (302,303) is straight all the way to the end wall (306) .