JP2007046586A - Portable working machine - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a portable working machine capable of maintaining efficiency of cooling by cooling air satisfactorily and promoting its miniaturization. <P>SOLUTION: A cut-off saw being the portable working machine is constituted in such a way that a first volute 26 is provided around a fan 23 rotated and driven by an engine, a second volute 27 is provided on an inner side of the first volute 26, a first fin 24 corresponding to the first volute 26 is provided on a surface of the fan 23, a second fin 25 corresponding to the second volute 27 is provided on a rear surface of the fan 23, cooling air is generated in the first fin 24 to jet it around the engine from the first volute 26, and the air from which dust is separated in the second volute 27 among the air generated in the second fin 25 is fed into a cleaner box 21 for use as intake air. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a portable work machine, and more particularly to a hand-held portable work machine such as a cut-off saw or a chain saw.

  2. Description of the Related Art Conventionally, an engine-driven hand-held cut-off saw is known as a portable work machine for cutting a concrete lump (for example, Patent Document 1). The cut-off saw is sometimes referred to as an engine cutter or a handy cutter. In an operation using such a cut-off saw, a large amount of concrete dust is generated when a concrete block is cut. For this reason, the engine air cleaner for collecting dust is clogged at an early stage, and it is necessary to frequently clean and replace the air cleaner.

  Therefore, in recent cut-off saws, a device has been devised to prevent dust from being sucked into the engine cylinder, and even with long-term use of the air cleaner or the same maintenance frequency, it can be handled with a smaller air cleaner. It is like that. For example, the cut-off saw of Patent Document 1 is provided with a cooling fan that sends sucked air around the engine as cooling air. This cooling fan is a volute (vortex) formed in a part of a cover that covers the engine. The cooling air is efficiently sent to the engine side. And the countermeasure which prevents the suction | inhalation of the dust in a cylinder by using this volute is taken.

  In other words, the air sucked into the cooling fan contains a large amount of dust as described above, but if this mixed air is blown out through the volute by the cooling fan, dust is generated by the centrifugal separation function of the volute. The air in which the dust is separated is sent to the air cleaner, and the air containing the dust is used for engine cooling, thereby reducing the burden on the air cleaner. As a specific structure, paying attention to the fact that dust is separated from the air flowing inside (center side) in the volute, this area and the cleaner box where the air cleaner is placed are connected with a dedicated flow path. Therefore, air with less dust is sent to the air cleaner side.

Swedish Patent Publication No. 422232 Specification

  However, in the technique of Patent Document 1, since a part of the cooling air sent from the cooling fan is sent to the cleaner box for intake of the engine, the air volume for cooling the engine is reduced accordingly, and the cooling efficiency is lowered. There is a problem. Therefore, it is conceivable to increase the fin portion of the cooling fan and increase the air volume. However, this increases the size of the cooling fan, which causes a problem that the size reduction of the entire cut-off saw is hindered.

  The objective of this invention is providing the portable working machine which can maintain the cooling efficiency by cooling air favorably, and can accelerate | stimulate size reduction.

A portable work machine according to claim 1 of the present invention includes a fan that is rotationally driven by an engine,
A first volute provided around the fan and a second volute provided inside or outside the first volute, one of the front and back surfaces of the fan corresponding to the first volute A first fin is provided, and a second fin corresponding to the second volute is provided on the other surface, and the first volute uses air sucked by the first fin as cooling air for cooling the engine. The region near the inner periphery of the second volute communicates with the intake air flow path of the engine, and the region near the outer periphery is open to the periphery of the engine.

  A portable work machine according to a second aspect of the present invention is the portable work machine according to the first aspect, wherein a cyclone-type centrifugal separator is provided in the middle of the intake flow path downstream of the second volute. It is characterized by.

  In the above, according to the first aspect of the present invention, the air sent as the intake air of the engine is generated by the second fins and the dust is centrifuged by the second volute, and is used as cooling air for cooling the engine. Since it is not produced | generated, the flow volume of the cooling air produced | generated by the 1st fin is not reduced, and an engine can be cooled efficiently. In addition, since the fin on the back side of the fan is provided using the space on the back side of the fan that originally existed as a dead space, it is not necessary to secure a dedicated space for the fin. As compared with the case where the same air volume is obtained by increasing the size, the fan overhang can be reduced and the working machine can be downsized.

  According to the second aspect of the present invention, the first-stage centrifugation is performed by the second volute, and the second-stage centrifugation is performed by the downstream centrifugal separation unit. It can be further cleaned and the burden on the air cleaner can be greatly reduced.

Hereinafter, an embodiment of the present invention will be described with reference to the drawings.
FIG. 1 is a side view showing a structure around an engine 2 mounted on a cut-off saw (portable work machine) 1 of the present embodiment. FIG. 2 is a bottom sectional view showing the periphery of the engine 2. 3 is a side view showing a main part around the engine 2, FIG. 4 is a plan view of the main part, and FIG. 5 is a cross-sectional view taken along the line VV in FIG.

  1 and 2, a cut-off saw 1 is a hand-held portable work machine that cuts a concrete lump, a roadbed material, and the like, and includes a work machine body 11 on which an engine 2 is mounted, and a front side from the work machine body 11. A guide member (not shown) provided toward the side, a cutter head attached to the tip of the guide member, and a cutter blade 12 attached to the cutter head are provided. A clutch housing 14 for a centrifugal clutch is provided on one end side of the crankshaft 13 of the engine 2, and a belt is wound around the clutch housing 14 and a pulley provided on the cutter head. The blade mounting portion connected to the pulley is driven by the engine 2 via the belt, and the cutter blade 12 rotates.

  As shown in FIGS. 3 to 5, a cleaner box 21 made of a synthetic resin and formed in a box shape is provided on the rear side of the engine 2, that is, on the handle 15 side. The cleaner box 21 is fixed to a carburetor 22 disposed on the intake port side of the engine 2 with a screw or the like, and can accommodate an air filter (not shown) inside. On the other hand, the other end side of the crankshaft 13 (the side opposite to the side where the clutch housing 14 is provided) is provided with a fan 23 for sending cooling air for cooling the engine 2 and air for intake into the cleaner box 21. Further, a recoil starter 16 is provided outside the fan 23 via a ratchet mechanism.

  Here, the fan 23 includes first fins 24 formed on the front surface (surface on the recoil starter 16 side) and second fins 25 formed on the back surface (surface on the engine 2 side). The first fin 24 is larger than the second fin 25, and the amount of air blown out is large. Such a fan 23 is accommodated in the 1st, 2nd volutes 26 and 27 formed in the circumference | surroundings. The first and second volutes 26 and 27 are formed by one case member 28 constituting the crankcase 17 having a half structure of the engine 2.

  Specifically, the case member 28 is formed via a case main body 31 screwed to the other case member 29, and a plurality of support ribs 32 and the widening wall 33 to the case main body 31. The housing portion 34 also functions as a frame, and first and second volutes 26 and 27 are formed in the housing portion 34. As shown in FIGS. 2 and 5, between the plurality of support ribs 32 is an opening portion 32 </ b> A that allows the engine 2 side and the fan 23 side to communicate with each other, and the air that enters through the opening portion 32 </ b> A is the second fin of the fan 23. Suctioned at 25 and flows in the second volute 27. Of course, the air sucked by the first fin 24 is sucked from an air suction slit or the like provided in a cover that covers the work machine body 11 and flows in the first volute 26 as in the prior art.

  That is, the first volute 26 is formed corresponding to the first fin 24 of the fan 23, and the second volute 27 is formed corresponding to the second fin 25. Further, the second fin 27 protrudes using a space that is inevitably formed between the back surface of the fan 23 and the case body 31, and is dedicated for projecting the second fin 27. The space is not specially formed.

  Each of the first and second volutes 26 and 27 as described above has a centrifugal separation function for separating dust from the air to be sucked. In the present embodiment, in particular, the second volute 27 is centrifuged. Separation function is important. Rather than separating the dust, the first volute 26 is provided to generate and jet a sufficient amount of cooling air.

  That is, the cooling air passing through the first volute 26 on the outer peripheral side is ejected from the outlet 26A provided on the tip side of the first volute 26 (downstream side in the air flow direction) to cool the engine 2 with a sufficient air volume. . At this time, the cooling air contains concrete dust generated at the time of cutting work. As shown in FIG. 5, the cooling air is indicated by white arrows (flow of air) and black arrows (flow of dust). Since it does not enter the cleaner box 21, there is no fear that a large amount of dust will clog the air cleaner in the cleaner box 21 at an early stage.

  On the other hand, a part of the air passing through the second volute 27 is made relatively clean from which the dust is separated by the centrifugal separation function and is sent into the cleaner box 21, and the remaining part including the separated dust is sent. Air is jetted around the engine 2. Below, the structure of the 2nd volute 27 for producing such an air flow is explained in full detail.

  The second volute 27 is formed including a boundary wall portion 35 provided as a boundary with the first volute 26. The protruding end of the boundary wall portion 35 is close to the back surface of the fan 23, and this back surface serves as a wall surface to shield the second volute 27 and the first volute 26 from each other. A pipe-shaped communication member 36 that connects the second volute 27 and the cleaner box 21 is attached to the distal end side of the second volute 27. The flow path from the communication member 36 to the engine 2 is the intake flow path 37 according to the present invention.

  According to the communication member 36, the inflow port 38 provided at one end thereof is located in a region on the inner peripheral side of the second volute 27. Therefore, in the air passing through the second volute 27 while swirling in a spiral shape, dust having a large specific gravity contained in the air is drawn to the boundary wall portion 35 by centrifugal force and flows through the outer peripheral side region. It spouts from the spout 27A opened around the engine 2 together with the flowing air. Then, relatively clean air containing almost no dust flows inside the second volute 27 and passes through the communication member 36 toward the cleaner box 21 side.

  As described above, according to the cut-off saw 1 of the present embodiment, the fan 23 generates the first fin 24 that generates the cooling air for cooling the engine 2 and the first air that generates the air to be sent into the cleaner box 21. Two fins 25 are provided. Around the fan 23, a first volute 26 that blows cooling air generated by the first fins 24 around the engine 2 and air generated by the second fins 25 are provided. A second volute 27 is provided for sending a part of the intake air to the cleaner box 21 side and ejecting the remaining air to the engine 2 side.

  Accordingly, the air sent to the cleaner box 21 is not generated as cooling air for cooling the engine 2, so that the flow rate of the cooling air does not decrease unlike the conventional case, and the engine 2 It can be cooled efficiently. Further, since dust is removed from the air sent into the cleaner box 21, the air cleaner in the cleaner box 21 is not clogged at an early stage, and the maintainability is good. In addition, since the second fin 25 protrudes using the space on the back side of the fan 23 that originally existed as a dead space, it is not necessary to newly secure a space dedicated to the second fin 25. For this reason, compared with the case where the 1st fin 24 is enlarged and the same air volume is obtained, the overhang | projection amount of the fan 23 can be made small and the cut-off saw 1 can be reduced in size.

  By the way, in this embodiment, the other end side of the communication member 36 is connected to the air introduction part 42 of the cyclone centrifugal separation part 41 provided integrally with the cleaner box 21. The centrifuge unit 41 includes a plurality (three in this embodiment) of cyclone chambers 43 communicating with the air introduction unit 42. Since the internal structure of the cyclone chamber 43 is substantially the same as that of a general cyclone type centrifuge, the detailed illustration and description thereof will be omitted here.

  That is, the air that has passed through the air introduction part 42 first becomes a vortex in the vortex generator 44 provided at the inlet of the cyclone chamber 43, and the dust in the air is attracted to the inner peripheral surface of the cyclone chamber 43. The air is discharged together with a part of the air from the discharge port 45 having a reduced diameter at the tip. Further, cleaner air in which dust is separated from the air exists on the center side of the vortex flow in the cyclone chamber 43. This clean air is introduced into the cleaner box 21 by the negative pressure at the time of suction by the engine 2 through the pull-in tube 46 drawn into the center of the cyclone chamber 43, and is filtered by the air cleaner. It is sent to the carburetor 22.

  As described above, according to the present embodiment, the first-stage centrifugation is performed by the second volute 27 described above, and the second-stage centrifugation is performed by the centrifugal separator 41, so that it flows into the cleaner box 21. The concrete dust can be more reliably removed from the air to be generated, the air cleaner can be more easily clogged, and the maintainability can be remarkably improved. In addition, if the maintenance period is set to be the same as the conventional one, the air cleaner can be greatly reduced in size.

In addition, this invention is not limited to the said embodiment, Including other structures etc. which can achieve the objective of this invention, the deformation | transformation etc. which are shown below are also contained in this invention.
For example, in the above-described embodiment, the cyclone-type centrifuge unit 41 is provided in the cleaner box 21. However, such a centrifuge unit may be provided as necessary, and the first-stage centrifuge by the second volute 27 may be provided. If the dust can be sufficiently removed by the separation, it can be omitted.

  In the above embodiment, the first volute 26 through which the cooling air is passed is provided outside the second volute 27. However, the second volute may be provided outside the first volute. It is necessary to provide the first fin for generating air on the back side of the fan and the second fin on the front side.

  Further, in the embodiment, the first and second volutes 26 and 27 are both formed in the housing portion 34 of the case member 29. However, with respect to the volute corresponding to the fin on the surface side of the fan, the exterior covering the fan is provided. You may form in the back surface side of a cover.

  The present invention can be used not only for cut-off saws but also for chain saws. In particular, when cutting dry wood, a large amount of wood flour is generated. The present invention is also effective in preventing the wood flour from being sucked into the cleaner box as dust. In addition, the present invention can be used for any portable work machine used while dust is generated.

The side view which shows the structure around the engine mounted in the portable working machine which concerns on one Embodiment of this invention. The bottom sectional view showing the engine circumference. The side view which shows the principal part around an engine. The top view of the said principal part. VV sectional view taken on the line of FIG.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 ... Cut-off saw which is a portable working machine, 2 ... Engine, 23 ... Fan, 24 ... 1st fin, 25 ... 2nd fin, 26 ... 1st volute, 27 ... 2nd volute, 37 ... Intake flow path 41 ... Centrifugation part.

Claims (2)

In portable work machines,
A fan driven by an engine,
A first volute provided around the fan;
A second volute provided inside or outside the first volute,
A first fin corresponding to the first volute is provided on one of the front and back surfaces of the fan, and a second fin corresponding to the second volute is provided on the other surface,
The first volute is provided such that air sucked by the first fin can be ejected as cooling air for cooling the engine,
A portable working machine characterized in that a region near the inner periphery of the second volute communicates with the intake air flow path of the engine, and a region near the outer periphery opens to the periphery of the engine. The portable work machine according to claim 1, wherein
A portable working machine, wherein a cyclone-type centrifugal separator is provided in the middle of the intake flow path downstream of the second volute.

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