JP2012072710A - Engine, and engine working machine with the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an engine or the like that does not degrade the efficiency of cooling a cylinder block by a simple structure, and has improved heat resistance.SOLUTION: A wind introduction passage 17 in which part of an air flow generated by a cooling fan flows is formed between an insulator 8 of the engine 1 and the cylinder block 3, and a cylinder block-side opening 27 opened at the wind introduction passage 17, an external opening formed apart from the cylinder block 3 rather than the cylinder block-side opening 27 and a cooling passage 28 for connecting the cylinder block-side opening 27 and the external opening are formed at the insulator 8 of the engine 1.

Description

  The present invention relates to an engine that connects a carburetor to a cylinder block via an insulator and an engine work machine including the engine.

  For example, as shown in Patent Document 1, in order to reduce the heat transmitted from a cylinder block of an engine, there is one in which an insulator for introducing cooling air generated by a cooling fan is provided between a cylinder block and a carburetor.

Japanese Utility Model Publication No. 61-1646

  By the way, the engine of Patent Document 1 requires a configuration for introducing a part of the cooling air into the insulator, the structure is complicated, and a part of the cooling air is not used for cooling the cylinder block. There exists a subject that cooling efficiency falls.

  The present invention has been made in view of the above problems, and has an engine including an insulator with a simple structure and improved heat insulation without reducing cylinder block cooling efficiency, and an engine work machine including the engine. The purpose is to provide.

In order to achieve the above object, an engine according to the first aspect of the present invention provides:
A cylinder block in which an intake port is formed;
A crankcase attached to the cylinder block and rotatably supporting a crankshaft;
A cooling fan that is driven by rotation of the crankshaft to generate an air flow toward the cylinder block;
An insulator provided between the cylinder block and a carburetor for supplying an air-fuel mixture, and having an air-fuel mixture passage communicating the intake port and the carburetor;
Between the insulator and the cylinder block, an air guide path through which a part of the air flow generated in the cooling fan flows is formed,
The insulator is provided with an outlet opening that opens into the air guide passage, an inlet opening that is spaced apart from the cylinder block from the outlet opening, and a cooling passage that connects the outlet opening and the inlet opening. Be
It is characterized by that.

  Moreover, it is preferable that the cross-sectional area of the flow path in the vicinity of the outlet opening of the air guide path is smaller than the cross-sectional area of the flow path before and after the flow path in the vicinity of the outlet opening.

  Further, the inlet opening may be provided on a side surface between the cylinder block and the carburetor of the insulator.

  The inlet opening may be provided on an outer wall of the insulator facing the carburetor.

  Furthermore, the cooling passage may be formed in a substantially straight tube shape along the mixture passage.

Further, a guide wall is provided between the insulator and the cylinder block for flowing an air flow generated by the cooling fan along the cylinder block.
The guide wall may have a through hole at a position corresponding to the outlet opening.

  An engine working machine according to a second aspect of the present invention includes the above-described engine.

  According to the present invention, since the insulator has a cooling passage that opens to the air guide path between the cylinder block, air is introduced into the insulator from the outside by using the negative pressure due to the air flow by the cooling fan. It is possible to improve the heat insulation of the insulator without reducing the cooling efficiency of the cylinder block with a simple structure.

The perspective view of the brush cutter carrying the engine which concerns on this invention. Sectional drawing of the engine which concerns on this invention. III-III sectional view taken on the line of FIG. The expanded sectional view of the insulator part of FIG. The exploded perspective view of an insulator. The front view of the insulator of the modification of this invention. VII-VII line sectional drawing of FIG. The front view of the insulator of another modification of the present invention. IX-IX sectional view taken on the line of FIG.

  Embodiments of the present invention will be described below with reference to FIGS. As shown in FIG. 1, the brush cutter 1001 equipped with the engine 1 has a rotary blade 1003 attached to the tip of the operating rod 1002 and the engine 1 attached to the rear end of the operating rod 1002. The output of the engine 1 is supplied to the rotary blade 1003 through a drive shaft that is inserted into the operation rod 1002. The operator operates the brush cutter 1001 by holding the handle 1004 attached to the operation rod 1002.

  As shown in FIG. 2, an OHV type four-cycle engine (engine) 1 is capable of rotating a crankshaft 4 and a cylinder block 3 that accommodates a piston 2 so as to reciprocate between a top dead center and a bottom dead center. A crankcase 5 attached to the cylinder block 3 accommodated in the cylinder block 3, a muffler 6 attached to an exhaust port (not shown) of the cylinder block 3, and a carburetor 9 attached to the intake port 7 of the cylinder block 3 via an insulator 8. A fuel tank 10 is provided below the crankcase 5. The piston 2 is connected to the crankshaft 4 via a piston pin 11 and a connecting rod 12. A crank weight 13 is attached to the crankshaft 4. FIG. 2 shows a state in which the piston 5 is at the top dead center, and a spark plug 15 is attached to the top of the cylinder bore 14.

  As shown in FIG. 3, an air guide path 17 is formed between the cylinder block 3 and the insulator 8 to form an air guide path 17 for guiding the cooling air generated by the cooling fan 16 attached to the crankshaft 4 around the cylinder block 3. A wind plate (guide wall) 18 is provided. The air guide plate 18 is provided so as to cover the heat radiating fins 19 formed on the side surface of the cylinder block 3 on the insulator 8 side. The air guide plate 18 extends linearly on the cooling fan 16 side beyond the side surface on the insulator 8 side in a top view (state shown in FIG. 3), and has a cylinder bore on the side away from the cooling fan 16. And bent along the side surface of the cylinder block 3 away from the cooling fan 16.

  As shown in FIGS. 2 and 4, the insulator 8 includes a carburetor-side insulator 20 located on the carburetor 9 side, a cylinder block-side insulator 21 located on the cylinder block 3 side, a carburetor-side insulator 20, and a cylinder block-side insulator 21. And a seal member 22 provided therebetween. An air guide plate 18 sandwiched between two gaskets 23 is provided between the cylinder block side insulator 21 and the cylinder block 3. The insulator 8 is provided with an air-fuel mixture passage 25 that connects the main bore 24 of the carburetor 9 and the intake port 7 and guides the air-fuel mixture supplied by the carburetor 9 to the intake port 7. The cylinder block 3 side of the cylinder block-side insulator 21 is formed to be substantially flat, and faces the space that forms the air guide path 17 between the intake port 7 and the heat radiation fin 19 of the cylinder block 3 and is opposed to the cylinder block 3. It has a facing portion 26. A cylinder block side opening (exit opening) 27 is opened in the facing portion 26, and a cooling passage 28 that passes through the cylinder block side insulator 21 from the cylinder block side opening 27 substantially parallel to the air-fuel mixture passage 25 from the cylinder block side opening 27. Is provided. The cooling passage 28 bends upward in the figure (in the direction from the bottom dead center to the top dead center) at the connecting portion between the carburetor-side insulator 20 and the cylinder block-side insulator 21 of the insulator 8, and bypasses the air-fuel mixture passage 25. Then, it is connected to an external opening (inlet opening) 30 opened in the outer peripheral surface 29 above the insulator 8. As shown in FIG. 3, in the vicinity of the cylinder block side opening 27 of the facing portion 26, the cylinder block 3 is formed with a protruding portion 31 that protrudes toward the cylinder block side opening 27. The cross-sectional area decreases in the vicinity of the side opening 27, and the cross-sectional area increases as the distance from the cylinder block side opening 27 increases. Further, the air guide plate 18 is provided with a mixture passage through hole 32 at a position corresponding to the mixture passage 25, and a cooling passage through hole at a position corresponding to the cylinder block side opening 27 of the cooling passage 28. (Through hole) 33 is provided.

  As shown in FIG. 5, the insulator 8 is provided with two first mounting holes 34 and two second mounting holes 35 extending substantially parallel to the air-fuel mixture passage 25. An attachment screw (not shown) for attaching the insulator 8 to the cylinder block 3 is inserted into the first attachment hole 34, and an attachment screw (not shown) for attaching the carburetor 9 to the insulator 8 is inserted into the second attachment hole 35. ) Is inserted. The mating surface 36 of the carburetor-side insulator 20 and the cylinder block-side insulator 21 is connected to the mating surface-side opening 37 and the external opening 30 that open to the mating surface 36 side of the cooling passage 28 extending from the cylinder block-side opening 27. A circular passage 38 is provided along the mating surface 36 so as to bypass the air-fuel mixture passage 25, and the circular passage 38 constitutes a part of the cooling passage 28. Further, the seal member 22 is provided with a through hole 39 in a portion corresponding to the mating surface side opening 37 and a groove portion 40 in the vicinity of the external opening 30. The flow of air flowing in the cooling passage 28 between the carburetor-side insulator 20 and the cylinder block-side insulator 21 is performed in the through hole 39 and the groove 40 portion.

  According to the engine 1 configured as described above, the engine 1 starts, the crankshaft 4 rotates, and the cooling fan 16 connected to the crankshaft 4 rotates. The cooling air generated by the rotation of the cooling fan 16 flows around the cylinder block 3 as indicated by arrows in FIG. In the air guide path 17 surrounded between the cylinder block 3 and the air guide plate 18, the cross-sectional area of the flow path is suddenly increased in the vicinity of the cylinder block side opening 27 of the insulator 8 by the protrusion 31 of the cylinder block 3. Since it is throttled (decreased), the flow velocity of the cooling air flowing through the air guide path 17 increases in the vicinity of the cylinder block side opening 27. For this reason, negative pressure is generated in the cylinder block side opening 27 of the cooling passage 28, and air is drawn into the insulator 8 from the external opening 30 due to a pressure difference with the external opening 30 opened to the atmosphere. The drawn air is exhausted from the cylinder block side opening 27 to the air guide passage 17 via the circular air passage 38 in the cooling passage 28, and is released to the atmosphere after cooling the cylinder block 3 as a part of the cooling air. Is done.

  The engine 1 includes a cylinder block side opening 27 that opens to the facing portion 26 facing the air guide path 17, an external opening 30 provided on the outer peripheral surface 29, and a cooling passage that connects the cylinder block side opening 27 and the external opening 30. And an insulator having 28. For this reason, using the negative pressure due to the air flow of the cooling fan 16 flowing in the vicinity of the cylinder block side opening 27 of the air guide path 17, air is introduced into the insulator 8 from the external opening 30 opening to the outside through the cooling passage 28. It becomes possible to introduce. Therefore, the heat insulating property of the insulator 8 can be improved without decreasing the cooling efficiency of the cylinder block 3 with a simple structure. Moreover, since the air introduced into the insulator 8 is exhausted to the air guide path 17 and cools the cylinder block 3 as a part of the cooling air, the cooling performance of the engine 1 can be improved. Furthermore, a protruding portion 31 that protrudes toward the cylinder block side opening 27 of the facing portion 26 is formed at a portion facing the facing portion 26 of the cylinder block 3 that constitutes the air guide path 17. For this reason, the cross-sectional area in the flow path direction of the air guide path 17 is reduced, that is, narrowed in the vicinity of the cylinder block side opening 27 compared to the cross-sectional area of the flow path in the vicinity of the cylinder block side opening 27 in the flow direction. Yes. Therefore, the flow velocity of the cooling air flowing through the air guide path 17 can be further increased to increase the negative pressure, air can be introduced from the outside into the insulator 8 more efficiently, and the heat insulation of the insulator 8 can be further improved. In addition, the cooling performance of the engine 1 can be further improved. Furthermore, since the air guide plate 18 is provided between the cylinder block 3 and the insulator 8, the air flow generated by the cooling fan 16 is efficiently guided into the air guide path 17, and the cylinder block side opening is efficiently performed. It is possible to generate a negative pressure near 27. Therefore, air can be effectively introduced into the insulator 8 from the outside, the heat insulating property of the insulator 8 can be improved, and the cooling performance of the engine 1 can be improved.

  In the above-described embodiment, the insulator 8 includes the carburetor-side insulator 20, the cylinder block-side insulator 21, and the seal member 22, and the cooling passage 28 is a connecting portion between the carburetor-side insulator 20 and the cylinder block-side insulator 21. However, the present invention is not necessarily limited to this configuration. For example, as shown in FIGS. 6 and 7, the insulator 108 may be a one-piece configuration and a straight tubular cooling passage 128 may be provided. In addition, in the following description, the same code | symbol is attached | subjected to the component similar to the above-mentioned, and the detailed description is abbreviate | omitted. In this case, the cooling passage 128 is separated from the carburetor 9 (not shown) substantially parallel to the air-fuel mixture passage 25 from the cylinder block side opening 27, and to the external opening 130 that opens to the carburetor 9 (not shown) facing surface 141. It extends straight in the direction of the tube. Also in this case, similarly to the above-described insulator 8, cooling of the inside of the insulator 108 from the external opening 130 is performed using negative pressure due to the air flow of the cooling fan 16 flowing in the vicinity of the cylinder block side opening 27 of the air guide path 17. Air can be introduced into the passage 128. Therefore, the heat insulating property of the insulator 108 can be improved without reducing the cooling efficiency of the cylinder block 3 with a simple structure. Further, since the air introduced into the insulator 108 is exhausted to the air guide path 17 and the cylinder block 3 is cooled as a part of the cooling air, the cooling performance of the engine 1 can be improved. Furthermore, since the insulator 108 is a one-part structure and the cooling passage 128 is a straight tube, manufacturing is facilitated and the cost of the product can be reduced.

  Further, the number of cooling passages 128 is not limited to one, and a plurality of cooling passages 128 may be provided as shown in FIGS. In this case, the cooling passages 128 are provided at six locations so as to surround the mixture passage 25, and the respective external openings 130 are provided separately from the carburetor 9 (not shown). In this case, since there are a plurality of cooling passages 128, the amount of air introduced into the insulator 108 is increased, the heat insulation of the insulator 108 can be further improved, and the cooling passages are connected to the cylinder block 3 of the engine 1. Since the amount of air introduced through 128 increases, the cooling performance of the engine 1 can be further improved.

  In addition, this invention is not limited to the above-mentioned embodiment, A various deformation | transformation and improvement are possible in the range described in the claim. For example, the engine 1 according to the present invention is not limited to a four-cycle engine, and may be a two-cycle engine. In addition to the brush cutter 1001, the engine 1 can be applied to various working machines such as a chain saw, a hedge trimmer, and a generator. In addition, the air guide path 17 does not necessarily have a configuration in which the protruding portion 31 is provided in the cylinder block 3 to reduce the cross-sectional area of the flow path, and the protruding portion 31 may not be provided. Further, instead of the projecting portion 31, the space between the heat dissipating fins 19 in the axial direction of the cylinder bore 14 may be narrowed in the vicinity of the cylinder block side opening 27 to reduce the cross-sectional area of the air guide path 17.

DESCRIPTION OF SYMBOLS 1 Engine 3 Cylinder block 4 Crankshaft 5 Crankcase 7 Intake port 8 Insulator 9 Carburetor 16 Cooling fan 17 Air guide path 18 Air guide plate 19 Radiation fin 20 Carburetor side insulator 21 Cylinder block side insulator 22 Seal member 25 Air mixture path 26 Opposite Part 27 Cylinder block side opening 28 Cooling passage 30 External opening 31 Projection

Claims (7)

A cylinder block in which an intake port is formed;
A crankcase attached to the cylinder block and rotatably supporting a crankshaft;
A cooling fan that is driven by rotation of the crankshaft to generate an air flow toward the cylinder block;
An insulator provided between the cylinder block and a carburetor for supplying an air-fuel mixture, and having an air-fuel mixture passage communicating the intake port and the carburetor;
Between the insulator and the cylinder block, an air guide path through which a part of the air flow generated in the cooling fan flows is formed,
The insulator is provided with an outlet opening that opens into the air guide passage, an inlet opening that is spaced apart from the cylinder block from the outlet opening, and a cooling passage that connects the outlet opening and the inlet opening. Be
An engine characterized by that. The cross-sectional area of the flow path in the vicinity of the outlet opening of the air guide path is reduced compared to the cross-sectional area of the flow path in the flow direction in the vicinity of the outlet opening
The engine according to claim 1. The inlet opening is provided on a side surface of the insulator between the cylinder block and the carburetor;
The engine according to claim 1 or 2, wherein The inlet opening is provided on an outer wall of the insulator facing the carburetor.
The engine according to claim 1 or 2, wherein The cooling passage is formed in a substantially straight tube shape along the mixture passage.
The engine according to claim 4. Between the insulator and the cylinder block, a guide wall for flowing an air flow generated by the cooling fan along the cylinder block is provided,
The guide wall has a through hole at a position corresponding to the outlet opening.
The engine according to any one of claims 1 to 5, characterized in that:   An engine working machine comprising the engine according to any one of claims 1 to 6.

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