Patent Description:
Documents <CIT> (<CIT>) and <CIT> (<CIT>) each disclose an exhaust gas diffusing device including, at an end portion of an exhaust pipe, a cylindrical member for diffusing exhaust gas.

Document <CIT> discloses a unit ("muffler cutter") including an attachment pipe and a mixing/discharging pipe attached to the attachment pipe. The mixing/discharging pipe has a diameter larger than that of the exhaust pipe. The mixing/discharging pipe has, at an end portion thereof on the exhaust pipe side, a plurality of introduction openings for introducing outside air. The mixing/discharging pipe contains a freely rotatable fan.

Attaching the attachment pipe to the back end of the exhaust pipe results in the mixing/discharging pipe overlapping with the back end of the exhaust pipe. The mixing/discharging pipe receives exhaust gas as well as outside air, diffuses the exhaust gas by means of rotation of the fan at an intermediate portion of the mixing/discharging pipe to reduce the concentration of the exhaust gas, and then discharges the exhaust gas.

Document <CIT> discloses a unit ("diffuser") including a cylinder having an elliptical cross section and an exhaust pipe connection fitting attached to an end portion of the cylinder. The cylinder has first outside air introduction openings, and contains a pair of guide vanes facing each other.

The pair of guide vanes define a nozzle therebetween. The cylinder has second outside air introduction openings in the vicinity of the nozzle. Connecting the exhaust pipe connection fitting to the exhaust pipe allows exhaust gas from the exhaust pipe to be introduced into the cylinder. The exhaust gas thus introduced increases its flow speed at the nozzle. The cylinder introduces outside air through the second outside air introduction openings as well as the first outside air introduction openings to cool the exhaust gas before discharging it.

Document <CIT> pertains to an exhaust gas control system havin a guiding pipe with a proximal inlet end for connecting to a distal end of an engine exhaust pipe. An expanding portion of the guiding pipe has a central rearward expanding cone and spiraling blades extending between the cone and the walls of the expanding portion. The expanding portion is followed by an axially decreasing chamber and then an axially increasing chamber to the distal opening. A duct is supported on radial vanes around the latter chambers. The duct has a forward opening slightly rearward of a maximum cross-sectional dimension of the guiding pipe and has an outlet positioned rearward of the distal opening of the guiding pipe.

Document <CIT> discloses a booster consisting of a convergent pipe situated at a distance from a circuit intake so that the flow of air or gas passing through the pipe is first compressed and allowed to expand, creating a supplementary flow of outside air which is drawn into the intake. The convergent pipe forms a truncated cone set at a variable distance from the circuit intake.

In document <CIT>, an exhaust gas cooling apparatus and method for cooling an exhaust gas is disclosed. The exhaust cooling apparatus has a first fluid conduit and a variable nozzle extending from the first fluid conduit. The variable nozzle is disposed in an inlet end of a second fluid conduit, wherein the variable nozzle has at least two dissimilar materials adjacent to each other and a fluid inlet opening is located between an outer periphery of the variable nozzle and an inner surface of the inlet end of the second fluid conduit.

Document <CIT> relates to an exhaust flow rate increasing device for a vehicle, in which air outside the front end of an exhaust pipe is induced by the flow of gas exhausted through the exhaust pipe as the vehicle progresses and the outside air is faster than the flow of the exhaust gas.

In document <CIT>, a diffuser assembly for cooling a hot exhaust gas comprises an exhaust gas feeder unit and a tubular exhaust gas discharge unit having an upstream end mounted on the feeder unit such that there is a clearance space between the inner surface of said upstream end and the outer surface of a body portion of the feeder unit.

Document <CIT> discloses a tailpipe of an automotive vehicle comprising a front tube coupled to a muffler, the front tube including two flared ends and a neck having a plurality of apertures, a rear tube having a flared end, an outer venturi tube surrounding a rear portion of the front tube and the whole rear tube, the outer tube including a flared front end, a cylindrical section, an enlarged section, and a rear section having an inward extending rim at an opening thereof, and a plurality of twisted blades equally spaced apart around the rear tube and connected to the front, the rear, and the outer tubes, each blade having a plurality of apertures. Stream of exhaust from the muffler entering into the neck is divided into a number of components prior to forming whirlwind after leaving the tailpipe.

A work vehicle such as a tractor including a diesel engine, for example, may include a diesel particulate filter (DPF) to clean exhaust gas. Including a DPF as such, however, involves the concern that exhaust gas discharged from the engine may be heated up as a result of heat generation through the cleaning process and be discharged without being cooled sufficiently.

Such high-temperature exhaust gas may be cooled with use of, for example, the diffusion technique disclosed in documents <CIT> or <CIT>. The technique of document <CIT>, however, mixes exhaust gas with outside air at an intermediate portion of the mixing/discharging pipe before discharging the exhaust gas. The mixing/discharging pipe is long as a result. The technique of document <CIT> uses a pair of guide vanes to define a throttle nozzle. The pair of guide vanes thus partially block the flow of exhaust gas.

The above circumstances have led to a demand for an exhaust gas diffusing device that cools exhaust gas from an exhaust pipe, that does not block the flow of exhaust gas, and that does not require an increased distance for exhaust gas and outside air to be mixed with each other.

A work vehicle with an exhaust gas diffusing device according to claim <NUM> is provided.

The above configuration allows exhaust gas from the exhaust pipe to enter the outside air mixing cylinder together with outside air, and causes the exhaust gas and the outside air to flow as guided by the air director. This promotes mixing of exhaust gas with outside air. Further, the air director is disposed either in the exhaust pipe or at a position on the outside air mixing cylinder which position is upstream in the direction in which exhaust gas flows. This makes it possible to not only mix exhaust gas with outside air but also dissipate heat without the need to increase the distance over which exhaust gas and outside air flow through the space inside the outside air mixing cylinder from its upstream portion to its downstream portion.

The above configuration thereby provides an exhaust gas diffusing device that cools exhaust gas from an exhaust pipe, that does not block the flow of exhaust gas, and that does not require an increased distance for exhaust gas and outside air to be mixed with each other.

The exhaust gas diffusing device is arranged such that the at least one air director is disposed only in the exhaust pipe.

With the above configuration, the air director is disposed in the exhaust pipe only. This simple configuration allows exhaust gas to be guided into the outside air mixing cylinder.

The exhaust gas diffusing device is arranged such that the at least one air director is disposed at the discharge-side end portion of the exhaust pipe.

With the above configuration, the air director is disposed at the discharge-side end portion of the exhaust pipe. This allows exhaust gas flowing in a direction defined by the air director to directly enter the outside air mixing cylinder past the air director.

The exhaust gas diffusing device may further be arranged such that the exhaust gas diffusing device has a gap between the discharge-side end portion and an end portion of the outside air mixing cylinder which end portion is upstream in the direction in which the exhaust gas flows.

The above configuration causes a negative pressure when exhaust gas flows from the exhaust pipe into the outside air mixing cylinder. The negative pressure in turn draws in outside air through the gap into the outside air mixing cylinder.

The exhaust gas diffusing device is arranged such that the at least one air director does not coincide with the outside air mixing cylinder as viewed in a direction orthogonal to the direction in which the exhaust gas flows.

The above configuration involves a gap between the air director on the exhaust pipe and the outside air mixing cylinder which gap allows outside air to pass therethrough. The air director thus does not prevent outside air from being drawn in.

The exhaust gas diffusing device may further be arranged such that the at least one air director is oriented to guide the exhaust gas in such a direction that the exhaust gas comes into contact with an inner surface of the outside air mixing cylinder.

With the above configuration, the air director guides exhaust gas toward the inner surface of the outside air mixing cylinder. This allows exhaust gas to come into contact with the inner surface of the outside air mixing cylinder for efficient heat dissipation. In particular, guiding exhaust gas toward the inner surface of the outside air mixing cylinder causes the exhaust gas to whirl along the inner surface, thereby promoting the mixing of exhaust gas with outside air.

The exhaust gas diffusing device may further be arranged such that the at least one air director includes a plurality of air directors arranged in point symmetry to each other as viewed in the direction in which the exhaust gas flows.

With the above configuration, the plurality of air directors guide exhaust gas uniformly and cause the exhaust gas to whirl, thereby efficiently mixing exhaust gas with outside air.

The description below deals with an embodiment of the present invention with reference to drawings.

<FIG> illustrates a tractor T as a work vehicle. The tractor T includes a hood <NUM> at a front portion thereof, and also includes inside the hood <NUM> a diesel engine <NUM>, a radiator <NUM>, an air cleaner <NUM>, and a diesel particulate filter (DPF) cleaning device <NUM> for cleaning exhaust gas.

The tractor T also includes an exhaust pipe <NUM>, a body frame <NUM>, and an exhaust gas diffusing device A. The exhaust gas diffusing device A includes an outside air mixing cylinder <NUM> at such a position on a side of the body frame <NUM> as to receive exhaust gas from the exhaust pipe <NUM>. The exhaust gas diffusing device A allows exhaust gas of the engine <NUM> cleaned by the cleaning device <NUM> and thereby heated to be mixed with outside air to be cooled.

The exhaust pipe <NUM> is positioned at a front portion of the vehicle body and so oriented as to discharge exhaust gas in an obliquely downward direction. The outside air mixing cylinder <NUM> is so oriented as to send out exhaust gas in the direction of the exhaust pipe <NUM>.

As illustrated in <FIG>, the exhaust gas diffusing device A includes an outside air mixing cylinder <NUM>, an intermediate cylinder <NUM>, and air directors <NUM> supported by the intermediate cylinder <NUM>. The outside air mixing cylinder <NUM>, the intermediate cylinder <NUM>, and the air directors <NUM> are each made of, for example, a heat-resistant steel material or a stainless steel material.

The exhaust pipe <NUM> has a cylindrical axis X virtually extending through the center of the pipe. The outside air mixing cylinder <NUM> has its center extending coaxially with the cylindrical axis X. The intermediate cylinder <NUM> is fitted around the exhaust pipe <NUM> and fixed thereto with use of a plurality of bolts <NUM>. The intermediate cylinder <NUM> is provided with a pair of support frames <NUM> fixed thereto. The air directors <NUM> are integral with one of the support frames <NUM> (detailed later).

With the above configuration, the air directors <NUM> are at a discharge-side end portion 6E of the exhaust pipe <NUM>. The air directors <NUM> are, in other words, provided for the exhaust pipe <NUM> only.

As illustrated in <FIG>, the outside air mixing cylinder <NUM> is a cylindrical member having an inner diameter D2 larger than the outer diameter D1 of the discharge-side end portion 6E of the exhaust pipe <NUM>. The outside air mixing cylinder <NUM> is held in place by the body frame <NUM> of the tractor T. The intermediate cylinder <NUM> is fitted around and fixed to the discharge-side end portion 6E of the exhaust pipe <NUM>, and holds the air directors <NUM> in place.

The outside air mixing cylinder <NUM> may alternatively be held in place by (i) the exhaust pipe <NUM> with, for example, a bracket in-between or (ii) the intermediate cylinder <NUM> fitted around and fixed to the exhaust pipe <NUM>.

As illustrated in <FIG>, placing the exhaust pipe <NUM> and the outside air mixing cylinder <NUM> in position results in a gap G being formed between the discharge-side end portion 6E of the exhaust pipe <NUM> and the upstream end portion 11E of the outside air mixing cylinder <NUM>. The present embodiment is arranged such that the air directors <NUM> are in a space inside the discharge-side end portion 6E of the exhaust pipe <NUM> and that the air directors <NUM> and the outside air mixing cylinder <NUM> are so positioned as not to coincide with each other as viewed in the direction orthogonal to the direction in which exhaust gas flows (that is, in the direction in which <FIG> is viewed).

<FIG> illustrates a case of the discharge-side end portion 6E and the corresponding end portion of the intermediate cylinder <NUM> coinciding with each other. In a case where, for instance, the intermediate cylinder <NUM> protrudes from the discharge-side end portion 6E of the exhaust pipe <NUM>, the gap G is formed between the end portion of the intermediate cylinder <NUM> and the upstream end portion 11E of the outside air mixing cylinder <NUM>.

As illustrated in <FIG>, the two air directors <NUM> are, for example, press-worked to be integral with a first one of the pair of support frames <NUM>, and are inclined in respective directions opposite to each other. The two air directors <NUM> are, as illustrated in <FIG>, in point symmetry to each other as viewed in the direction in which exhaust gas flows from the exhaust pipe <NUM> (that is, in the direction of the cylindrical axis X).

As illustrated in <FIG>, a second one of the pair of support frames <NUM> has a depression 14b at a central position in its length direction (that is, in the radial direction of the intermediate cylinder <NUM>). Engaging the first support frame <NUM> with the depression 14b and welding the first support frame <NUM> to the second support frame <NUM> for fixation results in the pair of support frames <NUM> being orthogonal to each other and radially crossing the intermediate cylinder <NUM> as viewed in the direction of the cylindrical axis X.

The support frames <NUM> each include, at respective opposite ends thereof, engagement sections 14a each in the form of a bend in the direction of the cylindrical axis X. The support frames <NUM> are welded and fixed to the outer surface of the intermediate cylinder <NUM> with the engagement sections 14a in contact with an outer edge of the intermediate cylinder <NUM>.

The above configuration involves a gap between the radially outer end of each of the pair of air directors <NUM> on the first support frame <NUM> and the inner surface of the intermediate cylinder <NUM>. The gap receives the discharge-side end portion 6E of the exhaust pipe <NUM> when the intermediate cylinder <NUM> is fitted around the exhaust pipe <NUM>. This allows the air directors <NUM> to be inside the exhaust pipe <NUM> as viewed in the direction orthogonal to the direction in which exhaust gas flows (that is, in the direction orthogonal to the cylindrical axis X).

The above configuration causes exhaust gas from the exhaust pipe <NUM> to come into contact with the pair of air directors <NUM> immediately before being discharged from the discharge-side end portion 6E of the exhaust pipe <NUM> and then be sent out toward the inner surface of the outside air mixing cylinder <NUM> as illustrated in <FIG>. Orienting the pair of air directors <NUM> in a particular manner causes exhaust gas to, after coming into contact with the air directors <NUM>, be sent out toward the inner surface of the outside air mixing cylinder <NUM> such that the exhaust gas whirls along the inner surface of the outside air mixing cylinder <NUM> (that is, about the cylindrical axis X as the center). The air directors <NUM> configured as above do not block the flow of exhaust gas, and allow exhaust gas to flow with a reduced pressure loss.

As described above, the gap G is between the exhaust pipe <NUM> and the outside air mixing cylinder <NUM>. The gap G causes a negative pressure when exhaust gas flowing along the cylindrical axis X passes through the gap G. The negative pressure in turn causes outside air to enter the outside air mixing cylinder <NUM> through an outside air introducing section F. The air directors <NUM>, which guide exhaust gas toward the inner surface of the outside air mixing cylinder <NUM>, promote mixing of exhaust gas with outside air introduced through the outside air introducing section F.

The above configuration allows exhaust gas to be diffused to promote mixing of exhaust gas with outside air without requiring an increased distance for exhaust gas and outside air to be mixed with each other inside the outside air mixing cylinder <NUM>. This makes it possible to reduce the length of the outside air mixing cylinder <NUM> (that is, the dimension thereof along the cylindrical axis X) and discharge cooled exhaust gas from the discharge-side end portion. The above configuration, which does not require the outside air mixing cylinder <NUM> to be long as such, does not require the exhaust gas diffusing device A to be large-sized.

The outside air mixing cylinder <NUM> has an outer surface in constant contact with outside air. Further, exhaust gas mixed with outside air as described above flows through the outside air mixing cylinder <NUM> while in contact with its inner surface in such a manner as to whirl along the inner surface. This further promotes heat dissipation, thereby allowing suitable heat dissipation.

The present invention may alternatively be arranged as below other than the embodiment described above. Any member below that is identical in function to a particular member described for the above embodiment has the same reference sign as that particular member.

Claim 1:
A work vehicle, comprising:
- an exhaust pipe (<NUM>) configured to send out exhaust gas of an engine (<NUM>) of the work vehicle,
- an intermediate cylinder (<NUM>) is fitted around the exhaust pipe (<NUM>) and fixed to a discharge-side end portion (6E) of the exhaust pipe (<NUM>) with use of a plurality of bolts (<NUM>), and
- an exhaust gas diffusing device (A) configured to receive outside air and mix the outside air with the exhaust gas,
the exhaust gas diffusing device (A) including:
- an outside air mixing cylinder (<NUM>) having an inner diameter (D2) larger than the outer diameter (D1) of the discharge-side end portion (6E) of the exhaust pipe (<NUM>), positioned to receive the exhaust gas from the exhaust pipe (<NUM>), and configured to receive outside air and
- at least one air director (<NUM>) supported by the intermediate cylinder (<NUM>) and disposed only in the exhaust pipe (<NUM>) at the discharge-side end portion (6E) of the exhaust pipe (<NUM>) to promote the mixing of the exhaust gas with the outside air,
wherein the at least one air director (<NUM>) does not coincide with the outside air mixing cylinder (<NUM>) as viewed in a direction orthogonal to the direction in which the exhaust gas flows.