JP2008075558A - Flywheel for air cooled engine - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a flywheel for an air cooled engine not causing remarkable cooling performance drop even in an operation under a condition where a cooling air suction port can be easily blocked. <P>SOLUTION: This engine is constructed to keep an outer diameter of a roughly disk shape bulkhead 31c on which crank case side cooling blades 31a and fan cover side cooling blades 31b are arranged, at least smaller than either of an outer end diameter of the crank case side cooling blades 31a and an outer end diameter of the fan cover side cooling blades 31b, and to make cooling air circulated in a flywheel 31 axial center side of the cooling blade outer tip. Consequently, the cooling blades in a blocked side generate vacuum, cooling air can be sucked through an outside of the flywheel 31 from an opposite side and sent to the cylinder 11, even when either of the crank case side cooling air suction port 21a and the fan cover side cooling air suction port 41a is blocked. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention mainly relates to an air-cooled engine mounted on a small portable work machine, and more particularly to a technique for increasing the circulation efficiency of cooling air in the air-cooled engine.

Small portable work machines equipped with air-cooled engines are often used for cutting vegetation outdoors, such as brush cutters and chainsaws. The surrounding area starts with cut grass, wood chips, and dust and dead leaves are scattered around the engine. There is a case. For this reason, when the cooling air intake port is blocked by the grass, wood chips, dead leaves, etc., there is a possibility that the engine cooling performance will be lowered. The following methods are known as engine cooling methods using a flywheel for preventing such a situation (see, for example, “Patent Document 1”, “Patent Document 2”, and “Patent Document 3”).
(1) A cooling air inlet is provided in either the crankcase or the fan cover, and a cooling blade is provided on one side of the flywheel on the same side as the cooling air inlet, and intake air from the cooling air inlet is A method of cooling by blowing air to the cylinder by rotating the cooling blade.
(2) Cooling air inlets are provided in both the crankcase and the fan cover, and cooling blades are provided on both sides of the flywheel, and the intake air from the cooling air inlets is blown to the cylinder by the rotation of the cooling blades. How to cool.
JP 2000-192815 A Japanese Utility Model Publication No. 58-181985 JP 2001-355446 A

However, in the prior art of (1) and the like, for example, if the crankcase is provided with a cooling air intake port, the cooling air intake port is mostly covered with an engine exterior such as a fuel tank or an air cleaner. For this reason, obstruction due to vegetation or the like is relatively unlikely to occur, but the operator's visibility is poor, and if the occlusion occurs once, it is easily left unattended. In addition, it may take time to remove clogged vegetation and the like, and the operation in the state where the suction port is closed may be continued.
On the other hand, if the fan cover is provided with a cooling air intake port, the cooling air intake port is provided on the exterior surface of the engine, so the visibility from the operator is high, and removal of clogged plants and the like is easy, Since it is provided on the exterior surface, there is a problem that it is likely to cause blockage due to plants and the like.
That is, in the case of the configuration in which the air is blown and cooled on one side of the flywheel as in Patent Document 1, when the cooling air inlet is blocked as described above, there is a possibility that the engine cooling performance is remarkably lowered.

  Further, even in the case where the air is blown on both sides of the flywheel as in the prior arts (2) and (3), the cooling air intake port on either the crankcase side or the fan cover side is not provided. When closed, the blowing capacity of the cooling blade on the closed side is remarkably reduced, and blowing is mainly performed on the opposite side of the closing. When the flywheel crankcase side and the fan cover side are separated by the partition wall on which the cooling blades are arranged, the amount of air blown when one of the cooling air inlets is closed is 50% before closing. End up.

  In order to solve the above problems, the present invention provides a flywheel for an air-cooled engine that does not cause a significant decrease in cooling performance even when it is operated in a situation where the cooling air inlet is likely to be blocked as described above. Is.

  The problems to be solved by the present invention are as described above. Next, means for solving the problems will be described.

  That is, in claim 1, the centrifugal crankcase side cooling blade for blowing the intake air from the cooling air intake port provided in the crankcase to the cylinder, and the intake air from the cooling air intake port provided in the fan cover. In the air-cooled engine provided on the flywheel with the centrifugal fan cover side cooling blades that blow air to the cylinder, the outer diameter of the substantially disk-shaped partition wall in which the crankcase side cooling blades and the fan cover side cooling blades are arranged , At least the outer end diameter of the crankcase side cooling blade or the outer end diameter of the fan cover side cooling blade is smaller.

  According to a second aspect of the present invention, in the flywheel, the crankcase-side cooling blade and the fan cover-side cooling blade are in the same phase (arrangement of overlapping) at least in a portion protruding outward from the partition wall.

  As effects of the present invention, the following effects can be obtained.

The outer diameter of the substantially disk-shaped partition wall in which the crankcase side cooling blades and the fan cover side cooling blades are arranged is at least the outer end diameter of the crankcase side cooling blades or the outer end of the fan cover side cooling blades. The cooling air is smaller than any one of the diameters, so that the cooling air can flow on the flywheel axial center side from the outer end of the cooling blade. As a result, even when either the cooling air intake port on the crankcase side or the fan cover side is blocked, the cooling blade on the closed side generates a negative pressure, and the cooling air is blown from the opposite side of the blocking through the outside of the flywheel bulkhead. The air can be sucked and blown to the cylinder via the cooling blade on the side where the cooling air is closed.
In the embodiment, the cooling air volume in the closed state of the cooling air inlet on one side at the same engine speed is secured to 75% before the blocking. This is because, as shown in the prior art (2), in the configuration in which the crankcase side and the fan cover side of the flywheel are separated by the partition wall on which the cooling blades are arranged, either one of the cooling air intake ports is blocked. It can be said that the deterioration of the cooling performance is suppressed even when compared with the fact that the blown air amount is 50% before closing. That is, even when one side of the cooling air intake port is closed due to disturbance in the working environment, it is possible to prevent a significant decrease in engine cooling performance.
Further, since the partition wall is smaller than the outer diameter of the cooling blade, the amount of material used can be reduced and the weight can be reduced as compared with the prior art, and the manufacturing cost can be suppressed.

  In claim 2, by setting the crankcase side cooling blade and the fan cover side cooling blade in the same phase (overlapping arrangement), the area where the cooling air can flow is maximized, and the cooling air intake port on one side has When closed, it is possible to minimize a decrease in the air flow rate of the closed cooling blade. Further, since the bending moment due to the centrifugal force generated in the cooling blade is substantially balanced on both sides of the partition wall, the partition wall can be made thin, and the weight can be reduced.

Next, embodiments of the invention will be described. It should be noted that the technical scope of the present invention is not limited to the embodiments, but extends to the entire scope of the technical idea that the present invention truly intends, as will be apparent from the matters described in the present specification and drawings. It is.
FIG. 1 is a longitudinal side view of an air-cooled engine showing a flow of cooling air in a steady state.
FIG. 2 is a longitudinal side view of the air-cooled engine showing the flow of cooling air in a state where the crankcase-side cooling air intake port is closed.
FIG. 3 is a perspective view of the flywheel crankcase side.
FIG. 4 is a perspective view of the flywheel on the fan cover side.
FIG. 5 is an external side view of the air-cooled engine showing the intake / exhaust state of the cooling air.
FIG. 6 is a three-dimensional perspective view of the crankcase.

[overall structure]
First, an overall configuration of a small portable air-cooled engine 10 according to an embodiment of the present invention will be described with reference to a longitudinal side view of the air-cooled engine shown in FIG. In FIG. 1, the left side is the front.
In this embodiment, the entire structure of the air-cooled engine 10, the flywheel 31, and the centrifugal clutch 42 is covered with a cover (cylinder case 24, fan cover 41, lower cover, etc.) so that the operator cannot directly touch the high-temperature part of the engine. Yes. A flywheel 31 is disposed on one side (front side) of the crankshaft 13 of the air-cooled engine 10, a recoil starter is disposed on the other side (rear side), and power connection means such as a centrifugal clutch 42 is connected to the flywheel 31. In this embodiment, a rotary blade is attached to the other end of the power transmission shaft to constitute a brush cutter. In this brush cutter, an operator grips a support pipe covering a power transmission shaft in front of the air-cooled engine 10 or a handle extended from the support pipe.
The drive unit of the air-cooled engine 10 includes a cylinder 11 disposed in a cylinder case 24, a piston 12 disposed so as to be slidable in the cylinder 11, and a crankshaft 13 disposed below the piston 12. The connecting rod 14 is connected to the piston 12 and the crankshaft 13. Cooling fins 11a, 11a,... Are provided on the outer periphery of the cylinder 11 so that cooling is promoted by increasing the surface area of the cylinder 11. The crankshaft 13 is pivotally supported in the crankcase 21 so as to be rotatable with its axis line oriented in a direction orthogonal to the vertical sliding direction of the piston 12. On one side of the cylinder case 24, slits are opened as cooling air outlets 24a, 24a,.

  One end of the crankshaft 13 is connected to a flywheel 31, which will be described later, and a centrifugal clutch 42 is connected to the flywheel 31 on the opposite side of the crankshaft 13 so as to cover the centrifugal clutch 42. A clutch drum 43 is disposed. Here, the centrifugal clutch 42 includes a main body fixed to the flywheel 31, a centrifugal body 42a pivotally supported by the main body, and the centrifugal body 42a interposed between the main body and the centrifugal body 42a. It is comprised from the spring 42b pulled in the direction. A plurality of the centrifugal bodies 42a are arranged at appropriate intervals on the outer peripheral portion of the main body. A drive shaft 44 is coupled to the clutch drum 43 so as to be rotatable coaxially with the rotation shaft of the clutch drum 43, and a bearing 45 is disposed at a rotation base portion of the drive shaft 44 so as to be attached to the fan cover 41. It is supported rotatably. In FIGS. 1 and 2, only the rotation base of the drive shaft 44 is shown, and the middle part is omitted.

  The energy generated by the combustion of fuel in the cylinder 11 is a reciprocating motion of the piston 12 and is transmitted to the crankshaft 13 via the connecting rod 14 and converted into a rotational motion of the crankshaft 13. The rotation of the crankshaft 13 is transmitted to the centrifugal clutch 42 via the flywheel 31. Here, when the rotational speed of the centrifugal clutch 42 increases, the spring 42 b is extended by the centrifugal force of the centrifugal body 42 a, and the centrifugal body 42 a that is one end of the centrifugal clutch 42 is joined to the clutch drum 43. Thus, the clutch drum 43 is rotated, and the rotation of the clutch drum 43 is transmitted to the drive shaft 44 and is transmitted to a working unit (not shown).

[Cooling structure in steady state]
Next, the cooling structure of the air cooling engine 10 by the flywheel 31 at the time of steady state is demonstrated. The arrows in FIG. 1 indicate the flow of cooling air in a steady state. 3 is a perspective view of the flywheel 31 on the crankcase 21 side, FIG. 4 is a perspective view of the flywheel 31 on the fan cover 41 side, FIG. 5 is an external side view of the air-cooled engine 10, and FIG. is there. 3 and 4 indicates the direction of rotation of the flywheel 31 during operation.
When the air-cooled engine 10 is in operation, the inside of the air-cooled engine 10 is cooled by the cooling air drawn in by the flywheel 31. The flywheel 31 is coupled to one end of the crankshaft 13 as described above, and is disposed between the crankcase 21 and the fan cover 41. As shown in FIG. 3 and FIG. 4, centrifugal crankcase side cooling blades 31a, 31a,... A plurality of fan cover-side cooling blades 31b, 31b,... Are provided on one surface of the fan cover 41 at the outer edge of the flywheel 31 so as to stand in the rotation axis direction. Is formed in a substantially disk shape as a partition wall 31c between the cooling blades 31a and 31b. That is, the cooling blades 31a and 31b are provided on the outer peripheral edges of the front and back surfaces of the flywheel 31 configured in a disk shape with appropriate intervals.
Here, the outer diameter of the partition wall 31c is at least from either the outer end diameter of the crankcase side cooling blade 31a (A in FIG. 3) or the outer end diameter of the fan cover side cooling blade 31b (B in FIG. 4). Is also made smaller. In this embodiment, the outer end diameter of the crankcase side cooling blade 31a and the outer end diameter of the fan cover side cooling blade 31b are substantially the same size, and the outer diameter of the partition wall 31c is the outer end diameter of the crankcase side cooling blade 31a. And it is set as the structure smaller than both the outer end diameters of the fan cover side cooling blade 31b. In the present embodiment, the crankcase side cooling blades 31a and the fan cover side cooling blades 31b are both composed of 14 pieces and are curved toward the turning direction. As long as the flywheel 31 is rotated to generate cooling air, the number and shape of the flywheel 31 are not limited to those of the present embodiment.

Here, the cooling air is sucked from two places: a crankcase side cooling air inlet 21 a opened in the crankcase 21 and a fan cover side cooling air inlet 41 a opened in the fan cover 41.
As shown in FIGS. 1, 5 and 6, the crankcase is divided into two parts in the front and rear, and the flywheel 31 is housed in front of the front crankcase 21 and the balance weight part of the crankshaft is housed in the rear. Yes. The flywheel 31 side (front side) of the front crankcase 21 spreads out in a bowl shape, and a flange portion is formed at the peripheral edge so that the fan cover 41 can be fixed. A hole 21 b that penetrates through 13 is opened. Further, a plurality of crankcase-side cooling air inlets 21a, 21a,... Are opened from the periphery of the hole 21b to the side and the outer peripheral direction. In the longitudinal side view of the air-cooled engine 10 in FIG. 1, only a part of the crankcase side cooling air inlet 21a is shown below.
As shown in FIGS. 1 and 5, at the regular time, cooling air is sucked from the crankcase side cooling air inlet 21 a by the rotation of the flywheel 31, and the paths C1 to C3 indicated by the arrows in FIG. It passes through to the upper cylinder 11. At this time, when the air is sucked from the crankcase-side cooling air intake port 21a, the blown air simultaneously cools the components on the crankcase 21 side such as the crankshaft 13 and the fuel tank 22. The fuel tank 22 is covered with a lower cover.

On the other hand, the fan cover 41 is formed in a bowl shape that expands in a funnel shape, and houses a centrifugal clutch 42, a clutch drum 43, and the like. The sharp side (front shaft center portion) of the fan cover 41 is connected to an operating rod (not shown), and the rotation base portion of the drive shaft 44 is disposed therein. Further, slits are opened as fan cover side cooling air inlets 41a, 41a,... On the side surface of the fan cover 41 from the side to the lower side.
As shown in FIGS. 1 and 5, the cooling air is sucked from the fan cover side cooling air inlet 41a by the rotation of the flywheel 31, and the paths D1 to D3 indicated by the arrows in FIG. It passes through to the upper cylinder 11. At this time, the air is sucked from the fan cover side cooling air inlet 41a and blown, and at the same time, the components on the fan cover 41 side such as the centrifugal clutch 42, the clutch drum 43 and the bearing 45 are cooled.
When the air-cooled engine 10 is driven in this manner, the rotation of the cooling blades 31a and 31b provided on the flywheel 31 causes the crankcase-side cooling air intake port 21a and the fan cover-side cooling air intake port 41a disposed on both lower sides of the flywheel 31. The outside air is sucked in, the cooling air is sent upward, cools after passing through both side surfaces of the cylinder 11, and then passes through a path E indicated by an arrow in FIG. It is discharged to the rear on the opposite side.

[Cooling structure when the crankcase cooling air inlet is closed]
Next, the cooling structure of the air-cooled engine 10 by the flywheel 31 when either the crankcase side cooling air inlet 21a or the fan cover side cooling air inlet 41a is blocked by vegetation or the like will be described with reference to FIG. To do. Here, a case where the crankcase side cooling air inlet 21a is closed will be described as an example, but substantially the same effect can be obtained even when the fan cover side cooling air inlet 41a is closed. The arrows in FIG. 2 indicate the flow of cooling air when the crankcase side cooling air inlet 21a is closed. The same parts and configurations as those used for the description of the cooling structure in the steady state are denoted by the same reference numerals and description thereof is omitted.

When the crankcase side cooling air inlet 21a is closed, the flow of cooling air indicated by C1 in FIG. 1 is cut off, and the amount of cooling air flowing through the crankcase 21 of the flywheel 31 is reduced. Here, in the flywheel 31 according to the present invention, the outer diameter of the substantially disc-shaped partition wall 31c in which the crankcase side cooling blade 31a and the fan cover side cooling blade 31b are arranged is at least the outer end diameter of the crankcase side cooling blade 31a. (A in FIG. 3) or the outer end diameter of the fan cover side cooling blade 31b (B in FIG. 4). That is, the crankcase 21 side and the fan cover 41 side of the flywheel 31 communicate with each other on the inner side from the outer ends of the cooling blades 31a and 31b so that the cooling air can be easily circulated.
Thereby, when the crankcase side cooling air inlet 21 a is closed, the crankcase side cooling blade 31 a generates a negative pressure by the rotation of the flywheel 31. Then, cooling air flows from the fan cover 41 side to the crankcase 21 side through the outside of the flywheel 31 (path F1 indicated by the arrow in FIG. 2), and blows the cooling air to the cylinder 11 via paths F2 and F3. It becomes possible to do. That is, even if the crankcase side cooling air inlet 21a is closed, the cooling air can be circulated through the crankcase 21 side of the flywheel 31.

In the form of the present embodiment, the cooling air amount in the closed state of the cooling air intake port on one side at the rotational speed of the same engine is secured at 75% before the closing. In the configuration in which the crankcase 21 side and the fan cover 41 side of the flywheel 31 are separated by the partition wall 31c in which the cooling blades 31a and 31b are arranged, the feed when the cooling air inlets 21a and 41a are blocked is used. Compared to the fact that the air volume is 50% before the blockage, it can be said that the decrease in cooling performance is suppressed. In other words, even when one of the cooling air inlets 21a and 41a is closed due to disturbance in the working environment, it is possible to prevent a significant decrease in engine cooling performance.
Further, since the partition wall 31c is smaller than the outer diameter of the cooling blade (A in FIG. 3, B in FIG. 4), the amount of material used can be reduced and the weight can be reduced as compared with the prior art, and the manufacturing cost can be suppressed. .

Further, the crankcase side cooling blade 31a and the fan cover side cooling blade 31b are configured in the same phase (arrangement of overlapping) and are configured to maximize the area through which the cooling air can flow. Even when the side cooling air intake port 21a is closed, it is possible to minimize a decrease in the air flow rate of the crankcase side cooling blade 31a. In addition, since the bending moment due to the centrifugal force generated in the cooling blades 31a and 31b is substantially balanced on both sides of the partition wall 31c, the partition wall 31c can be configured to be thin, and the weight can be reduced.
With the above-described configuration, even when working in a situation where the crankcase side cooling air inlet 21a or the fan cover side cooling air inlet 41a is likely to be blocked, the operation can be performed without causing a significant decrease in cooling performance. You can continue.
In the present embodiment, the outer diameter of the partition wall 31c is configured to be smaller than the outer end diameters of the crankcase side cooling blade 31a and the fan cover side cooling blade 31b. If the 41 side is the structure connected so that cooling air can distribute | circulate, there exists the same effect. That is, the outer diameter of the partition wall 31c may be the same as the outer end diameter of the cooling blades 31a and 31b, and a communication hole or a notch may be provided in the partition wall 31c so that the cooling air can flow.

FIG. 2 is a longitudinal side view of an air-cooled engine showing a flow of cooling air at a constant time. The longitudinal side view of the air-cooled engine which showed the flow of the cooling air in the state where the crankcase side cooling air inlet is closed. The crankcase side perspective view of a flywheel. The fan cover side perspective view of a flywheel. FIG. 2 is an external side view of an air-cooled engine showing a cooling air intake / discharge state. The three-dimensional perspective view of a crankcase.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Air-cooled engine 11 Cylinder 12 Piston 13 Crankshaft 21 Crankcase 21a Crankcase side cooling air inlet 31 Flywheel 31a Crankcase side cooling blade 31b Fan cover side cooling blade 31c Bulkhead 41 Fan cover 41a Fan cover side cooling air inlet 42 Centrifugal clutch 44 Drive shaft

Claims (2)

A centrifugal crankcase side cooling blade that blows intake air from a cooling air inlet provided in the crankcase to the cylinder;
The centrifugal fan cover side cooling blades that blow the intake air from the cooling air intake port provided in the fan cover to the cylinder,
In the air-cooled engine installed on the flywheel,
The outer diameter of the substantially disk-shaped partition wall in which the crankcase side cooling blade and the fan cover side cooling blade are arranged,
A flywheel for an air-cooled engine, characterized in that it is at least smaller than either the outer end diameter of the crankcase side cooling blade or the outer end diameter of the fan cover side cooling blade. In the flywheel, the crankcase side cooling blades and the fan cover side cooling blades,
At least in the part protruding outward from the bulkhead,
The flywheel of the air-cooled engine according to claim 1, wherein the flywheel has the same phase (superposition arrangement).

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