Air cleaner for portable engine

An air cleaner for a portable engine, includes an air cleaner case attached to an upper part of an engine body of the engine. Preferably, the air cleaner case is supported on an upper wall of a shroud covering the engine. Preferably, the air cleaner case is formed integrally with the shroud. Preferably, the air cleaner further includes an air intake structure divided into a plurality of intake passages having inlets displaced relative to each other with respect to an air flow direction in which an intake air flows.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to an air cleaner for a portable engine and, more particularly, to an air cleaner suitable for a portable engine for driving a backpack blower, a backpack power applicator or a hand held bush cutter.

2. Description of the Related Art

FIG. 10shows a known portable engine E disclosed in JP-A No. 2002-303148 by way of example. This engine is used for driving a backpack blower A as shown inFIG. 9. The backpack blower A includes an engine E, a blower1, a back frame15holding the engine E and the blower1, a flexible pipe16connected to the discharge pipe of the blower1, a duct17, and a nozzle18. An operator supports the back frame15holding the engine E and the blower1on the operator's shoulders by straps19connected to the back frame15. Air is blown through the nozzle18to blow and collect dead leaves M and trash.

Referring toFIG. 10, an exhaust muffler11is joined to one of the opposite sides of a cylinder8, and an intake pipe (insulator)7, a carburetor12and an air cleaner13are connected in that order to the other side of the cylinder8. The cylinder8and the exhaust muffler11are covered with a shroud21. The air cleaner13has an intake duct100opening downward.

In the prior constitution shown inFIG. 10, since the air cleaner13is arranged in the lateral of the carburetor12and is joined to the carburetor12connected to the intake pipe7, the air cleaner13juts out greatly laterally and increases the width of the engine E. When the engine E is used for driving the backpack blower1as shown inFIG. 9, the greatly laterally jutting air cleaner13obstructs the cleaning work.

When the volume of the air cleaner13is increased to enhance the output of the engine, to reduce the noise of the intake air of the engine, or to extend the useful life of the air cleaner element, the air cleaner13needs to be formed of a high-strength material or to be provided with reinforcing members to make the air cleaner13sufficiently durable, because the air cleaner13juts out laterally from the carburetor12connected to the intake pipe7as shown inFIG. 10. As a result, the cost and the weight of the air cleaner13increase.

Since the intake duct100of the air cleaner13opens simply downward, it is possible that blown dead leaves and trash stick to the open lower end of the intake duct100to reduce the flow of intake air suddenly.

SUMMARY OF THE INVENTION

Accordingly, it is an object of the present invention to provide an air cleaner for a portable engine which is able to solve the foregoing problems.

According to the present invention, an air cleaner for a portable engine comprises an air cleaner case attached to an upper part of an engine body of the engine.

Preferably, the air cleaner case is supported on an upper wall of a shroud covering the engine.

Preferably, the air cleaner case is formed integrally with the shroud.

Preferably, the air cleaner case is supported by the upper part of the engine body and a carburetor connected to an intake port formed in the engine body.

Preferably, a carburetor cover is formed integrally with the air cleaner case, and an access hole through which an idle adjusting screw of a carburetor of the engine is operated is formed in the carburetor cover in a part corresponding to the idle adjusting screw.

The air cleaner for a portable engine further comprises an air intake structure divided into a plurality of intake passages, the intake passages having inlets displaced relative to each other with respect to an air flow direction in which an intake air flows.

Preferably, the plurality of intake passages includes an inner passage and an outer passage enclosing the inner passage, the inner passage having an inlet positioned behind an inlet of the outer passage with respect to the air flow direction.

Preferably, a recess is formed in an edge defining the inlet of the outer passage.

The air cleaner for a portable engine further comprises a plurality of sets of the inner passage and the outer passage, the plurality of sets being arranged contiguously with each other.

Preferably, the plurality of intake passages are contiguous with and parallel to each other, and inlets of adjacent intake passages are displaced relative to each other with respect to the air flow direction.

Since the air cleaner case is attached to the upper part of the engine body, the engine for, for example, a backpack blower can be formed in a narrow width. The backpack blower driven by the engine provided with the air cleaner of the present invention can be easily carried on the operator's back and facilitates cleaning work. The air cleaner case has necessary rigidity and strength even if the air cleaner is designed so as to have large volume to extend the useful life of the air cleaner element, for example, and the air cleaner case is not formed of a particular strong material.

Supporting the air cleaner case by both the upper part of the engine body and the carburetor increases the rigidity of the air cleaner.

Formation of the air cleaner case integrally with the shroud is effective in reducing manufacturing and assembling costs.

When the air cleaner case is formed integrally with the carburetor cover and the access hole is formed in the carburetor cover, the carburetor does not need to be protected by a carburetor protecting member, and a screw driver can be easily engaged with the idle adjusting screw to facilitate idling speed adjustment.

The division of the intake structure into the plurality of intake passages is effective in attenuating unpleasant intake noise of frequencies in an undesirable frequency range. Displacement of the inlets of the intake passages relative to each other with respect to an air flow direction in which intake air flows is effective in preventing the inlets of all the intake passages from being shut when the inlets of some of the intake passages are covered with dead leaves or the like. Thus, the complete shutting of intake passages can be prevented.

When the intake passages includes the inner passage and the outer passage enclosing the inner passage, and the inlet of the inner passage is positioned behind the inlet of the outer passage with respect to the air flow direction, the resistance of passages against the flow of intake air increases and intake noise of the engine can be suppressed. The inner and the outer passages respectively having different sectional areas reduce noises of different frequencies, respectively.

The recess formed in the edge defining the inlet of the outer passage can secure a gap through which intake air is introduced into the intake passages even when dead leaves and the like stick to the inlet of the outer passage.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

An air cleaner according to an embodiment of the present invention will be described with reference to the drawings as applied to an engine E included in a backpack blower as shown inFIG. 9.

Blower and Engine

Referring toFIG. 1, a blower1includes a fan2and a fan casing3, and an engine E for driving the fan2is joined to a back part of the fan casing3. The engine E includes an engine body10having a cylinder8. An exhaust muffler11is connected to the right side of the cylinder8, and an intake pipe7serving as an insulator is connected to the left side of the cylinder8. A carburetor12is connected to the intake pipe7. The cylinder8and the exhaust muffler11of the engine E are covered with an engine cover20formed by processing a metal plate. The engine cover20is covered with a shroud21of a resin. These constructions are basically the same as those shown inFIG. 10.

Referring toFIG. 2showing the engine E in a rear view, the shroud21has an upper wall21a,a back wall21b,a right wall21c,a left wall21dand a lower wall21eextending under the exhaust muffler11, which are formed integrally. The shroud21is fastened together with a recoil starter to the engine E with bolts22, and to the blower1with bolts23.

The air cleaner13has an air cleaner case25, an air cleaner cover26put on the air cleaner case25and fastened to the air cleaner case25with bolts30, an air cleaner element27held in the air cleaner case25, and a duct28extending downward from a left part of the air cleaner case25substantially perpendicularly to the bottom wall of the air cleaner case25. The air cleaner case25is formed of a resin by molding. A right part of the air cleaner case25is supported in a horizontal position on the upper wall21aof the shroud21, and a left part of the air cleaner case25juts out horizontally to the left from the shroud21above the carburetor12. The duct28is formed integrally with the air cleaner case25. A lower end part of the right wall of the duct28is connected to the left side surface of the carburetor12.

A triangular extension duct28aserving also as a reinforcing member is formed integrally with the duct28between an upper half part of the duct28and a left half part of the air cleaner case25. A carburetor cover29disposed behind the carburetor12is formed integrally with the extension duct28a.As shown inFIG. 3, the carburetor cover29is provided in a part corresponding to the head of an idle adjusting screw24included in the carburetor12with an access hole29a.

Referring toFIG. 4, an air cleaner mount31is formed integrally with the upper wall21aof the shroud21so as to protrude upward. A boss32formed near the right end of the bottom wall of the air cleaner case25is seated on the air cleaner mount31. A right part of the air cleaner case25is fastened to the upper wall21aof the shroud21with a bolt33and a nut34.

A lower end part of the duct28is fastened together with the carburetor12to the intake pipe7with a lateral bolt36. A side lid28ais fastened to a lower part of the left side wall of the duct28with a bolt38with an O ring28cheld between the side lid28aand the left side wall of the duct28.

An air intake structure40is formed in a right part of the upper wall of the air cleaner cover26. The air intake structure40includes three parallel intake ducts (intake passages)41having a rectangular cross section. Tubular walls42having an elliptic cross section are extended in the intake duct41to define an outer passage41aand an inner passage41bin each of the intake duct41. The tubular walls42are connected to the intake duct41with right and left horizontal ribs44. Thus each of the outer passages41ais divided into an upper passage and a lower passage by the ribs44.

Referring toFIG. 5, an inlet41cof the inner passage41bis disposed at a predetermined distance behind an inlet41dof the outer passage41awith respect to a direction in which intake air flows.

Referring toFIG. 6, arc-shaped segmental recesses51and52are formed in the end edges of the upper and the side walls of the intake ducts41.

Mounting of Air Cleaner

Referring toFIG. 4, the air cleaner cover26, the air cleaner element27and the side lid28aare separated from the air cleaner case25. The boss32of the air cleaner case25is mounted on the air cleaner mount31of the upper wall21aof the shroud21, the boss32(the right end part of the air cleaner case25) is fastened to the air cleaner mount31(the upper wall21aof the shroud21) with the bolt33and the nut34, and the lower part of the duct28is fastened together with the carburetor12to the intake pipe7with the lateral bolt36.

Then, the air cleaner element27is placed in the air cleaner case25, the air cleaner cover26is fastened to the air cleaner case25, and the side lid28ais fastened to the left side wall of the duct28.

Operation

Referring toFIG. 3, while the engine E is in operation, atmospheric air is sucked through the inlets41dof the intake ducts41, and as shown inFIG. 5, the sucked air flows through the outer passages41aand the inner passages41binto the dirty side13aof the air cleaner13.

Thus, air sucked into the three intake ducts41is distributed to the outer passages41aand the inner passages41b.Consequently, unpleasant intake noise of frequencies in a specific frequency range can be suppressed, and sounds of different frequencies can be efficiently suppressed by the outer passages41aand the inner passages41brespectively having different sectional areas.

Even if dead leaves and the like stick to the inlets41dof the intake ducts41while air is being sucked through the intake ducts41, gaps can be surely formed between the dead leaves and the inlet ends of the intake ducts41because the segmental recesses51and52are formed in the end edges of the upper and the side walls of the intake ducts41. Consequently, air can be sucked into the intake ducts41without being impeded.

Referring toFIG. 4, intake air taken into the dirty side13ais filtered by the air cleaner element27and the filtered clean intake air flown into the clean side13bflows through the duct28into the carburetor12. Part of the clean intake air is mixed with fuel to produce an air-fuel mixture, the air-fuel mixture flows through a lower passage55for the air-fuel mixture passage in the intake pipe7into the cylinder8, and the rest of the clean intake air flows through an upper passage56for intake air into the cylinder8.

Adjustment of Idling

When idling speed needs to be adjusted, a screw driver is inserted through the access hole29aof the carburetor cover29in the space inside the carburetor cover29, and the idle adjusting screw24is turned with the screw driver.

An air cleaner in a second embodiment according to the present invention will be described with reference toFIG. 7, in which parts like or corresponding to those of the air cleaner in the first embodiment shown inFIG. 4are denoted by the same reference characters. As shown inFIG. 7, the air cleaner in the second embodiment has an air cleaner case25formed integrally with a shroud21. Namely, the cleaner case25and the shroud21are formed as a single unit by molding. Walls are raised from a left part of the upper wall21aof the shroud21to form the air cleaner case25, and an air cleaner cover26is fastened to the open upper end of the air cleaner case25.

Since the air cleaner case25is formed integrally with the shroud21, the air cleaner in the second embodiment has less parts, needs less assembling steps and less weight than the air cleaner in the first embodiment.

FIG. 8shows an intake structure140in a modification of the foregoing intake structure. This intake structure140includes a plurality of parallel intake ducts (intake passages)141having the shape of a round tube. The intake ducts141have inlets141adisplaced relative to each other with respect to a direction in which intake air flows. The division of the intake structure140into the plurality of intake ducts141is effective in attenuating unpleasant intake noise of frequencies in an undesirable frequency range. Displacement of the inlets141aof the intake ducts141relative to each other with respect to a direction in which intake air flows is effective in preventing the inlets141aof all the intake ducts141from being shut when the inlets141aof some of the intake ducts141are covered with dead leaves or the like. Thus the complete shutting of the intake passages can be prevented.

Although the air cleaner in the foregoing embodiments have the L-shaped air cleaner cases, an air cleaner may be disposed on top of the engine, and the air cleaner may be connected to the carburetor by a flexible duct.

The present invention is applicable not only to portable engines for the backpack blower, but also to portable engines for other purposes.

Although the invention has been described in its preferred embodiments with a certain degree of particularity, obviously many changes and variations are possible therein. It is therefore to be understood that the present invention may be practiced otherwise than as specifically described herein without departing from the scope and spirit thereof.