JP2013189949A - Engine and engine working machine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve the cooling efficiency of an engine to be mounted on a portable type engine working machine such as a chain saw and a power cutter.SOLUTION: An engine 11 which rotationally drives a saw chain serving as a rotating tool, has an engine body 11a provided with a crankcase and a cylinder 16. An insulator 33 is arranged between an intake port 31 formed in the cylinder 16 and a carburetor 34 for generating a fuel/air mixture to be supplied to the intake port 31. A cutout part 53 as an air flow guide part for guiding the ascending air current is formed in an intake side fin 52a which is a section of a heat radiation fin 52 of the cylinder 16 facing the insulator 33.

Description

  The present invention relates to an engine and an engine work machine mounted on a portable engine work machine such as a chain saw or a power cutter.

  There are a chain saw, a power cutter, and the like as a hand-held or portable engine working machine using an engine as a drive source. The chain saw is provided with a saw chain, which is a chain-shaped saw blade for cutting a work object such as wood, in the working machine body. In the power cutter, a disk cutter for scoring and cutting stone or concrete is provided in the work machine body. An engine mounted on such an engine working machine has an engine body including a crankcase in which a crankshaft is rotatably mounted and a cylinder in which a piston is incorporated so as to be linearly reciprocable. A cooling fan is attached to one of the projecting end portions of the, thereby forming a forced air cooling engine. The cooling air generated by the cooling fan is blown along the engine toward the opposite side of the engine with respect to the cooling fan, and the engine is forcibly cooled. Since the cooling fan stops when the engine is stopped, the engine is cooled by natural air cooling after the engine is stopped.

  In order to supply a mixture of fuel and air to the engine, the engine is equipped with a carburetor via an insulator. When the engine is stopped, the flow of the mixture within the carburetor and the insulator is also stopped. For this reason, since the cooling effect of the vaporizer and the insulator by the air-fuel mixture is lost, heat conduction occurs from the cylinder to the vaporizer through the insulator, and the temperature of the vaporizer rises. If the temperature rise of the carburetor becomes too large, gasoline, that is, much of the fuel will evaporate, so that sufficient fuel cannot be supplied from the carburetor to the engine, making it difficult to restart the engine. In particular, an engine used for a portable engine working machine has a strong demand for miniaturization, and is required to make the insulator as short as possible. For this reason, in a portable engine work machine, it is necessary not only to efficiently perform forced air cooling during engine operation, but also to reduce the temperature of the carburetor without increasing the insulator length, It is an important technical issue to reduce the temperature rise of the vaporizer by promoting the above.

  In Patent Document 1, a carburetor is incorporated in a casing, that is, a casing, and air intakes for supplying external air to the carburetor are provided on the upstream side and the downstream side of the engine cooling air in the casing, respectively. An engine of an engine working machine such as a chain saw is described.

Japanese Utility Model Publication No.59-192664

  In this engine, in order to efficiently perform forced cooling, the radiating fins of the cylinder are extended in four directions, that is, the direction of the crankshaft that is perpendicular to the intake side and the exhaust side. As described above, it is advantageous to increase the area of the radiating fins in order to cool the cylinder in forced air cooling, and in general, in the case of a chain saw, a power cutter or the like that requires a high output, it is common to make the radiating fins as long as possible. Is.

  However, if the portion on the intake side of the radiating fin is extended so as to cover the upper part of the insulator attached to the intake port, the rising air flow of natural heat generated from the periphery of the insulator is interrupted by the radiating fin when the engine is stopped. The For this reason, there is a problem that heat is locally trapped in the vicinity of the insulator and the temperature rise of the insulator is increased. Since the heat dissipating fins are heated by the residual heat of the engine, there is a problem that the temperature of the insulator is further increased by the radiant heat. Therefore, in order to increase the efficiency of forced air cooling, it is preferable to enlarge the portion on the intake side of the radiating fin, but if this portion is increased, the heat dissipation of the insulator will be hindered, and the temperature of the insulator and the vaporizer will rise. The problem that it becomes easy occurs. As described above, in the conventional air-cooled engine for engine working machines, the shape of the radiating fins is set mainly for the purpose of efficiently performing forced air cooling, and sufficient effectiveness is achieved for natural air cooling when the engine is stopped. The engine cooling efficiency cannot be increased.

  An object of the present invention is to improve engine cooling efficiency.

  An engine according to the present invention is an engine including an engine body having a crankcase in which a crankshaft is rotatably incorporated, and a cylinder in which a piston coupled to the crankshaft via a connecting rod is reciprocally incorporated. An insulator disposed between an intake port provided in the cylinder and a carburetor that generates an air-fuel mixture supplied to the intake port, and a portion of the radiating fin of the cylinder facing the insulator, It has an airflow guide part which guides an updraft.

  The engine according to the present invention is characterized in that an exhaust opening is formed in a cylinder cover that covers the top of the cylinder so as to face the insulator. The engine of the present invention has a cooling fan attached to the projecting end portion of the crankshaft and generating forced cooling air along the cylinder from the projecting end portion side toward the opposite side. An air guide plate is provided upstream of the forced cooling air from the opening. The engine of the present invention is characterized in that the airflow guide portion is formed by a notch portion provided in the radiating fin. The engine of the present invention is characterized in that the airflow guide portion is formed by a through-hole provided in the radiating fin. The engine of the present invention is characterized in that a recess is provided in a carburetor chamber that accommodates the carburetor, and a protrusion that enters the recess is provided in the radiating fin.

  The engine work machine of the present invention has a work machine main body to which a rotary tool rotated by the crankshaft is mounted, and the rotary tool is driven by the engine described above.

  Since the airflow guide part is provided in the part of the radiating fin of the cylinder facing the insulator, the rising airflow of natural convection generated around the insulator when the engine is stopped is not disturbed by the radiating fin, and the cylinder cooling chamber can be smoothly Released upwards. Thereby, it is possible to prevent heat from being locally accumulated around the insulator, and to promote natural air cooling of the insulator. By providing the airflow guide portion on the heat dissipating fin, the heat dissipating fin can be greatly extended from the intake side, so that the efficiency of forced air cooling can be improved. Thus, both the efficiency of forced air cooling and natural air cooling can be improved, and the cooling efficiency of the engine can be improved.

It is a top view which shows a part of chain saw as an engine working machine. It is the sectional view on the AA line in FIG. FIG. 2 is a partially cutaway plan view of FIG. 1 illustrating a heat dissipating fin of a cylinder by cutting a cylinder cover. FIG. 3 is an enlarged sectional view taken along line BB in FIG. 2. It is a perspective view which shows the outer surface of the cylinder cover with which an engine is mounted | worn. It is a perspective view which shows the inner surface of a cylinder cover. FIG. 7 is a plan view of FIG. 6. It is a top view which shows a part of chain saw carrying the engine of the modification.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. As shown in FIG. 2, the chain saw 10 as an engine working machine has a working machine body 12 in which the engine 11 is incorporated. The engine 11 has an engine body 11a having a crankcase 14 in which a drive shaft, that is, a crankshaft 13 is rotatably incorporated, and a cylinder 16 in which a piston 15 is incorporated so as to be linearly reciprocally movable. Each 16 is made of an aluminum alloy. The piston 15 is connected to the crankshaft 13 by a connecting rod 17, and the reciprocating motion of the piston 15 is converted into the rotational motion of the crankshaft 13.

  As shown in FIG. 1, a cooling fan 18 is attached to one protruding end 13 a of the crankshaft 13, and the cooling fan 18 is accommodated in a volute case (not shown) attached to the work machine body 12. A fan cover 19 is attached to the work machine body 12 so as to cover the case. A starter (not shown), that is, a recoil starter, is provided inside the fan cover 19, and the engine 11 is started by operating the operation knob 20. A sprocket is connected to the other protruding end 13 b of the crankshaft 13 via a centrifugal clutch (not shown), and the sprocket is rotatably attached to the crankshaft 13. A guide bar 23 is attached to the work machine main body 12 as shown by a two-dot chain line in FIG. 1, and a saw chain 24 as a rotary tool provided around the guide bar 23 is stretched around a sprocket. The saw chain 24 is rotationally driven by the engine 11 via a centrifugal clutch. Thus, the one protruding end 13a side of the crankshaft 13 is a fan driving side end, and the opposite protruding end 13b is a tool driving side end.

  The engine main body 11 a is attached to the work machine main body 12 with the crankshaft 13 extending laterally with respect to the work machine main body 12. A rear handle 25 is provided at the rear of the work machine main body 12 so as to protrude rearward. The work machine main body 12 spans the engine 11 from the one projecting end 13a side of the crankshaft 13 to the other projecting end 13b side. A front handle 26 is disposed as an operation handle. One end portion of the front handle 26, that is, the fan-side leg portion 26 a is fixed to one front end portion of the work machine body 12, and the other end portion, that is, the tool drive-side leg portion 26 b is fixed to the rear handle 25. The distance between the tool drive side leg 26b of the front handle 26 and the cylinder 16 is set to be shorter than the distance between the fan side leg 26a and the cylinder 16, and the operator holds the rear handle 25 with the right hand, In the state where the side portion of the front handle 26 is gripped, the work such as wood is cut by the chain saw 10. A side cover 28 that covers the centrifugal clutch and the sprocket is attached to the tool drive side of the work machine main body 12 so that the operator can attach the leg 26b on the rotary tool side where the saw chain 24 is arranged as a rotary tool that rotates at high speed. Without gripping, the side of the front handle 26, that is, the cooling fan 18 side is gripped to perform the work. The work machine body 12 is provided with a hand guard 29 that protrudes forward from the front handle 26.

  As shown in FIG. 2, an intake port 31 is opened in the cylinder 16 in a direction perpendicular to the crankshaft 13 toward the rear side of the work machine body 12, and an exhaust port 32 is formed on the opposite side of the intake port 31. It opens toward the front of the work machine body 12. An insulator 33 provided with a flow path communicating with the intake port 31 is attached to the cylinder 16, and a vaporizer 34 is attached to the insulator 33. In order to seal between the insulator 33 and the intake port 31, the insulator 33 is provided with a gasket 33a. The insulator 33 has heat resistance and is made of a polymer resin having a much lower thermal conductivity than the cylinder 16, and prevents the heat of the cylinder 16 from being transmitted to the vaporizer 34. A support portion 35 is provided on the inlet side of the vaporizer 34, and a filter element 36 is attached to the support portion 35. The carburetor 34 is supplied with external air cleaned by the filter element 36 and fuel from a fuel tank (not shown), and the carburetor 34 generates a mixture of air and fuel. It is supplied into the main body 11a. The supplied air-fuel mixture is ignited by a spark plug 37. A muffler 38 is attached to the cylinder 16 by a bolt 39 so as to communicate with the exhaust port 32, and combustion gas discharged from the exhaust port 32 is discharged to the outside through the muffler 38.

  The engine body 11 a is covered with an engine cover 41. A gap is provided between the engine cover 41 and the front handle 26, and the front handle 26 is provided across the engine cover 41 via the gap. The engine cover 41 includes a cover main body 42 and a cylinder cover 43 attached to the cover main body 42, and the cylinder cover 43 covers the top of the cylinder 16. A cleaner cover 44 is integrated with the cylinder cover 43, and an engagement protrusion 47 that engages with the cover main body 42 is provided at the tip of the cylinder cover 43 as shown in FIGS. 6 and 7. Yes. The filter element 36 is covered with the cleaner cover portion 44, a heat shield plate 45 is provided between the insulator 33 and the vaporizer 34, and the vaporizer chamber 46 is formed by the heat shield plate 45 and the cleaner cover portion 44. The vaporizer 34 is accommodated in the vaporizer chamber 46. By incorporating the carburetor 34 into the carburetor chamber 46, it is possible to prevent wood chips, dust and the like from flowing into the carburetor 34, and to prevent the carburetor 34 and the filter element 36 from being contaminated. The cylinder cover 43 is attached to the engine 11 by a set screw 48 disposed on the cleaner cover portion 44.

  As shown in FIG. 1, the cooling air discharge port 18 a of the cooling fan 18 opens toward the cylinder cover 43, and the forced cooling air generated by the cooling fan 18 is discharged toward the cylinder cover 43. A heat radiating plate 49 is attached to the exhaust port 32 side of the cylinder 16 as shown in FIG. 2, and the forced cooling air generated by the cooling fan 18 is discharged from the cooling air outlet as shown by an arrow in FIG. 18a passes through a cylinder cooling chamber 50 formed by a heat shield plate 45, a heat radiating plate 49, and a cylinder 16, and is discharged to the outside from a discharge port 51 provided on the tool drive end side of the engine cover 41. When the flow direction of the forced cooling air flowing along the inner surface of the cylinder cover 43 is shown, the direction is indicated by an arrow in FIG.

  As shown in FIG. 2, the cylinder 16 is provided with a large number of radiating fins 52, and among the radiating fins 52, the intake side fins 52 a on the intake side are closer to the carburetor 34 than the insulator mounting surface T of the cylinder 16. It extends to. As shown in FIGS. 2 to 4, a notch portion 53 is provided as an airflow guide portion for guiding an ascending airflow from the insulator 33 at a portion facing the insulator 33 in the intake fin 52 a of the radiating fin 52. Is provided. The notch 53 opens the top of the insulator 33 so as not to overlap with the insulator outline V in plan view. The notch 53 has a substantially U-shape that is recessed from the outline of the cylinder 16 in plan view, and is formed across a number of intake-side fins 52 a above the insulator 33. The cylinder cover 43 is provided with an exhaust opening 54 so as to face the notch 53 and the insulator 33. As shown in FIGS. 4 and 5, four openings 54 are provided in the cylinder cover 43. Each of the openings 54 has a longitudinal direction perpendicular to the crankshaft 13 as shown in FIG. If the direction line is S, it is a long hole in a direction inclined with respect to the longitudinal direction line S. This inclination direction is a direction in which the tip end side of the engine cover 41 of the opening 54 is the downstream side of the forced cooling air. An air guide plate 55 is provided on the inner surface of the cylinder cover 43 for deflecting the direction of the forced cooling air so that the forced cooling air does not leak from the opening 54. As shown in FIGS. 6 and 7, the air guide plate 55 includes a deflecting portion 55a extending in a direction crossing the forced cooling air on the uppermost stream side of the opening 54, and the forced cooling air integrated with the deflecting portion 55a. And a guide portion 55b extending in the flow direction. Between the front end of the air guide plate 55 and the cylinder 16, a flow path 56 for allowing forced cooling air to pass is formed.

  When the engine 11 is driven, an air flow is generated by the rotation of the cooling fan 18. The air flow is guided to the cooling air discharge port 18a, and the forced cooling air discharged from the cooling air discharge port 18a is guided to the cylinder 16 by the engine cover 41 and into the cylinder cooling chamber 50 as shown by an arrow in FIG. Inflow. In the cylinder cooling chamber 50, the forced cooling air is divided into the engine rear side, that is, the intake side, and the engine front side, that is, the exhaust side, via the spark plug 37, and then discharged to the outside from the discharge port 51 on the side cover 28 side. . The forced cooling air flowing on the intake side is guided along the cylinder 16 by the air guide plate 55 while cooling the intake side fins 52a. As a result, the cooling air does not flow in the vicinity of the opening 54 by the air guide plate 55, and the forced cooling air is prevented from leaking outside from the opening 54, thereby preventing the efficiency of forced cooling from being lowered.

  On the other hand, when the drive of the engine is stopped, the rotation of the cooling fan 18 is stopped and the flow of forced cooling air is stopped. When the engine drive is stopped, the residual heat of the engine 11 is radiated by natural air cooling by natural convection. At this time, heat conduction from the air inlet 31 to the carburetor 34 through the insulator 33 occurs, but the airflow guide portion formed by the notch portion 53 is provided in the air intake side fin 52a of the heat radiating fin 52. Therefore, the natural convection ascending airflow generated around the insulator 33 is not obstructed by the radiating fins 52. As a result, heat is not locally stored in the insulator 33. Therefore, the natural convection ascending airflow generated from the periphery of the insulator 33 is smoothly discharged to the upper side of the cylinder cooling chamber 50, and the natural air cooling of the insulator 33 can be promoted. Since the heat dissipation effect of the insulator 33 is improved, the temperature of the insulator 33 can be lowered, so that the temperature rise of the vaporizer 34 can be suppressed. Further, since the opening 54 is provided above the notch 53, the rising airflow that has reached the upper part of the cylinder cooling chamber 50 smoothly flows from the opening 54 to the outside as shown by the arrows in FIG. Discharged. Thereby, heat does not accumulate in the cylinder cooling chamber 50, and natural air cooling of the insulator 33 and the engine 11 can be performed more effectively.

  FIG. 8 is a plan view showing a part of a chain saw on which the engine of the modified example is mounted. In FIG. 8, members that are the same as those described above are denoted by the same reference numerals.

  As shown in FIG. 8, the opening 54 formed in the cylinder cover 43 is a long hole in which the dimension in the width direction of the cylinder cover 43 is longer than the dimension in the longitudinal direction. The cylinder cover 43 described above is provided with four openings 54, whereas the cylinder cover 43 shown in FIG. 8 is provided with one opening 54, which is the insulator 33. It is provided close to the cylinder 16 that is hotter. As a result, the natural convection ascending airflow generated in the high temperature portion of the insulator 33 can be discharged to the upper side of the cylinder cooling chamber 50, so that the natural air cooling of the insulator 33 can be further promoted. The opening 54 can be provided as shown in FIG. 8 only by performing additional processing on the existing engine.

  As shown in FIG. 8, a recess 61 is formed at the corner on the entire surface side of the carburetor chamber 46, and the intake fin 52 a of the radiating fin 52 protrudes into the recess 61 along the recess 61. A part 62 is provided. As described above, the intake fin 52a of the radiating fin 52 is provided with the convex portion 62 along the concave portion 61 provided in the carburetor chamber 46, so that the area of the fin is enlarged by the amount of the convex portion 62, The efficiency of forced air cooling can be increased.

  As described above, in the engine 11 having the cylinder cover 43 covering the top of the cylinder 16 and having the carburetor 34 attached to the intake port 31 of the cylinder 16 via the insulator 33, the radiator fins 52 of the cylinder 16 are connected to the insulator 33. Even if the cooling efficiency by forced cooling air is increased by making it protrude toward the carburetor 34 side more than the mounting surface, the airflow guide portion is provided in the intake side fin 52a of the radiating fin 52 by the notch portion 53. Thus, when the engine is stopped, the natural convection ascending airflow generated from the periphery of the insulator 33 can be smoothly guided to the upper side of the cylinder cooling chamber 50, and heat is locally trapped around the insulator 33. There is no such thing. Thereby, the natural air cooling of the insulator 33 can be accelerated | stimulated and the temperature rise of the vaporizer | carburetor 34 can be reduced.

  As shown in FIG. 3, the airflow guide portion is formed by providing a notch 53 at the center in the width direction of the intake side fin 52a. However, even if the notch 53 is formed by shifting in the width direction. good. Moreover, a through hole may be formed in the intake side fin 52a, and the air flow guide portion may be formed by a penetration plan. Further, a flow path 56 through which forced cooling air passes is formed between the front end portion of the air guide plate 55 and the cylinder 16, and the front end portion of the air guide plate 55 extends to the vicinity of the insulator 33. The natural convection ascending airflow generated around the insulator 33 may be separated from the ascending airflow generated around the engine body 11a and released to the atmosphere. Furthermore, you may arrange | position so that the opening part 54 can be combined with the attachment hole for attaching the ignition plug 37. FIG.

  The present invention is not limited to the above-described embodiment, and various modifications can be made without departing from the scope of the invention. For example, although the illustrated engine 11 is mounted on a chain saw 10 as an engine working machine, the illustrated engine can be applied as a power cutter engine, and other engine operations such as a brush cutter and a mower. It can also be applied as a machine engine. In the engine 11 mounted on the chain saw 10, when the chain saw 10 is disposed on the base, the crankshaft 13 is horizontal, and the engine body 11a is directed in the vertical direction. On the other hand, in an engine working machine in which the engine body is inclined and mounted on the work machine main body, and in an engine working machine in which the crankshaft is mounted in the work machine main body with the vertical axis directed vertically, the cylinder covering the top of the cylinder When the engine working machine is disposed on the base, the cover is provided with an opening and a wind guide rib at a position above the top of the cylinder.

DESCRIPTION OF SYMBOLS 10 ... Chain saw, 11 ... Engine, 11a ... Engine main body, 12 ... Work machine main body, 13 ... Crankshaft, 13a ... Projection end part, 13b ... Projection end part, 14 ... Crankcase, 15 ... Piston, 16 ... Cylinder, 17 ... Connecting rod, 18 ... Cooling fan, 18a ... Cooling air outlet, 19 ... Fan cover, 20 ... Operation knob, 23 ... Guide bar, 24 ... Saw chain, 25 ... Rear handle, 26 ... Front handle, 28 ... Side cover , 29 ... Hand guard, 31 ... Inlet, 32 ... Exhaust, 33 ... Insulator, 33a ... Gasket, 34 ... Vaporizer, 35 ... Support, 36 ... Filter element, 37 ... Spark plug, 38 ... Muffler, 39 ... Bolt 41 ... Engine cover 42 ... Cover body 43 ... Cylinder cover 44 ... Cleaner cover part 45 ... Heat insulation 46 ... Vaporizer chamber, 48 ... Set screw, 49 ... Heat radiation plate, 50 ... Cylinder cooling chamber, 51 ... Exhaust port, 52 ... Heat radiation fin, 52a ... Suction side fin, 53 ... Notch, 54 ... Opening portion, 55 ... Air guide plate, 55a ... Deflection part, 55b ... Guide part, 56 ... Flow path, 61 ... Concave part, 62 ... Convex part.

Claims (7)

An engine comprising an engine body having a crankcase in which a crankshaft is rotatably incorporated, and a cylinder in which a piston coupled to the crankshaft via a connecting rod is reciprocally incorporated;
An insulator disposed between an air inlet provided in the cylinder and a vaporizer that generates an air-fuel mixture supplied to the air inlet;
An engine having an airflow guide portion that is provided in a portion of the radiating fin of the cylinder facing the insulator and guides an upward airflow.   The engine according to claim 1, wherein an exhaust opening is formed in a cylinder cover that covers a top portion of the cylinder so as to face the insulator.   A cooling fan is attached to the projecting end of the crankshaft and generates forced cooling air from the projecting end toward the opposite side along the cylinder, and the cylinder cover is forced to cool than the opening. The engine according to claim 2, wherein a wind guide plate is provided on the upstream side of the wind.   The engine according to any one of claims 1 to 3, wherein the airflow guide portion is formed by a notch portion provided in the heat radiating fin.   The engine according to any one of claims 1 to 3, wherein the airflow guide portion is formed by a through hole provided in the heat radiating fin.   The engine according to any one of claims 1 to 5, wherein a concave portion is provided in a vaporizer chamber that houses the vaporizer, and a convex portion that enters the concave portion is provided in the radiating fin.   An engine working machine having a working machine main body to which a rotary tool rotated by the crankshaft is mounted, and driving the rotary tool by the engine according to any one of claims 1 to 6. .

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