JP6193713B2 - Air-cooled engine - Google Patents

Description

  The present invention relates to an air-cooled engine used as a drive source for a working machine such as a brush cutter.

  Conventionally, in this type of air-cooled engine, there is a type in which a cover body that prevents foreign matter from entering the air suction port of a cooling fan is fixed to a crankcase with a screw body (for example, Patent Documents 1 and 2).

Japanese Patent No. 4112892 JP 2003-314280 A

  However, in the cover body fixing structure shown in Patent Documents 1 and 2, since the long cover body is cantilevered by the engine, the cover body shakes and is uncomfortable due to the influence of engine vibration during engine operation. In addition to generating excessive noise, a load is applied to the screw body fixing portion, which is a support portion of the cover body in the crankcase, and durability is reduced.

  SUMMARY OF THE INVENTION An object of the present invention is to provide an air-cooled engine that can support a cover body on the engine without the occurrence of noise due to the vibration of the cover body for preventing foreign matter entry even under the influence of the vibration of the engine.

  In order to achieve the above object, an air-cooled engine according to the present invention includes a crankshaft supported by a crankcase, and a cylinder block and a muffler that cool air that is attached to one end of the crankshaft and is sucked from an air suction port. An air-cooled engine having a cooling fan that is fed to a fuel tank and a fuel tank disposed below the crankcase, wherein the crankcase has the air intake port that opens toward the other end of the crankshaft. And a cover body that extends from the outer periphery of the air suction port toward the other end along the outer peripheral surface of the crankcase, and is attached to the cover body for preventing foreign matter from entering the air suction port. And the cover body is supported between the fuel tank and the crankcase in a state where the elastic body is in pressure contact with the fuel tank.

  According to this configuration, the cover body is supported between the fuel tank and the crankcase in a state where the elastic body is in pressure contact with the fuel tank, so that the vibration of the cover body is absorbed and relaxed by the elastic body. Therefore, the generation of noise due to the vibration of the cover body is suppressed, and the durability of the support portion of the cover body is improved.

  In the air-cooled engine of the present invention, it is preferable that the elastic body is mounted in a mounting hole formed in the cover body. According to this configuration, since the elastic body can be mounted using a mounting hole formed in advance in the cover body, a separate mounting means is not required, and the structure can be simplified.

  In the air-cooled engine according to the present invention, the cover body has an end wall whose proximal end portion is close to the outer peripheral portion of the air intake port in the crankcase and which extends toward the outer peripheral surface of the crankcase at the distal end portion and is close to the outer peripheral surface. Is preferably provided. According to this configuration, since the volume space of the cover body, that is, the inner space of the cover body can be increased, an increase in suction resistance by the cover body can be suppressed.

  In the air-cooled engine of the present invention, it is preferable that the cover body has a plurality of through holes. According to this configuration, it is possible to take in only the cooling air and prevent the entry of foreign matter through the plurality of small holes. Moreover, the plurality of small holes can be easily formed by punching.

  In the air-cooled engine of the present invention, it is preferable that the cover body is detachably attached to the crankcase by a screw body. According to this configuration, the cover body can be easily removed and attached by the screw body during maintenance.

  In the air-cooled engine of the present invention, it is preferable that the cover body is fastened together with the crankcase by a first screw body that attaches the muffler to the crankcase. According to this configuration, a dedicated screw body for screwing the cover body to the crankcase becomes unnecessary, and the number of parts can be reduced.

  In the air-cooled engine of the present invention, it is preferable that the cover body is attached to a fan housing that covers the cooling fan or a cover bracket supported by a crankcase by a second screw body. According to this configuration, the cover body is attached by the second screw body using the cover bracket supported by the fan housing or the crankcase, so that the second screw body is attached to the fan housing or the crankcase. No special mounting part is required.

  In the air-cooled engine of the present invention, the crankcase has the air intake port and a large crankcase half located on one end side of the crankshaft and a small crankcase located on the other end side of the crankshaft. Preferably, the cover body extends from the vicinity of the outer periphery of the air intake port of the large crankcase half to the axial center of the small crankcase half. According to this structure, since the cover body becomes longer in the axial direction and the volume of the inner space can be increased, the increase in the cooling air suction resistance can be further suppressed.

  According to the present invention, the cover body is supported in a state where the elastic body is in pressure contact with the fuel tank, so that vibration of the cover body can be suppressed. Therefore, the generation of noise due to the vibration of the cover body is suppressed, and the durability of the support portion of the cover body is improved.

It is a partial cross section side view of the small air-cooled engine which shows preferable embodiment of this invention. It is a front view of the small air-cooled engine. It is the rear view which looked at the large crankcase half of the same small air-cooled engine from the engine back. It is the rear view which looked at the fan housing of the small air-cooled engine from the engine back. It is a perspective view of the cover body of the same small air cooling engine. It is a rear view of the cover body. It is a left view of the cover body. It is a right view of the cover body. It is a bottom view of the cover body. It is a perspective view of an elastic body. It is a perspective view of the bracket for covers which attaches the cover body. It is an attachment section to the crankcase of the cover body, and is an enlarged sectional view showing an attachment part on the muffler side. It is an attachment section to the crankcase of the cover body, and is an enlarged sectional view showing an attachment portion on the air cleaner side.

  A preferred embodiment of the present invention will be described below with reference to FIGS. A small air-cooled engine 1 shown in FIG. 1 is a small two-cycle engine used as a drive source for a working machine such as a brush cutter.

  In this small air-cooled engine 1, a cylinder block 2 in which a combustion chamber (not shown) is formed is connected to an upper portion of a crankcase 3 that forms a crank chamber (not shown). The cylinder block 2 and the crankcase 3 are each made of a metal such as an aluminum alloy. The crankcase 3 supports a crankshaft 4 to which a piston (not shown) is connected. A work machine is connected to the front part of the small air-cooled engine 1, and a recoil starter 5 is provided at the rear part.

  As shown in FIG. 2, a carburetor 6 and an air cleaner 7 constituting an intake system are connected to one side of the cylinder block 2 (left side of FIG. 2), and the other side (right side of FIG. 2) A muffler 8 constituting an exhaust system is connected. A fuel tank 9 is attached to the lower part of the crankcase 3, and a cap 19 for opening and closing the fuel filler opening is attached to the upper part of the fuel tank 9.

  The cylinder block 2 and the muffler 8 are covered with a resin shroud 10. A spark plug P is provided on the upper part of the cylinder block 2 and is covered and protected by a plug cap 11.

  The crankcase 3 shown in FIG. 1 includes a large crankcase half 3A that forms the front half and a small crankcase half 3B that forms the rear half. A cooling fan 12 is attached to one end, which is the front end of the crankshaft 4, so as to rotate integrally. The large crankcase half 3A opens toward the other end, which is the rear end of the crankshaft 4. The air inlet 13 is formed. The cooling fan 12 is covered by a fan housing 15 connected to the large crankcase half 3A.

The cooling air CA sucked from the air suction port 13 by the rotation of the cooling fan 12 is supplied to the cylinder block 2 and the muffler 8 of FIG. The cooling air CA supplied from the cooling fan 12 cools the cylinder block 2, and then is discharged to the outside from the main discharge port 16 </ b> A formed in the shroud 10. After cooling the muffler 8, the exhaust gas discharge port 18. And it is discharged | emitted from the sub discharge port 16B outside .

Recoil starter 5 rotates the crank shaft 4 via the starter pulley (not shown) disposed on the axis C and concentric crankshaft 4. The starter pulley is rotated by the starter handle 5a to start the engine 1.

  Between the fuel tank 9 and the crankcase 3 shown in FIG. 1, it extends from the vicinity of the outer peripheral side of the air suction port 13 toward the rear end portion (the other end portion) along the outer peripheral surface 3 a of the crankcase 3. A cover body 20 that prevents foreign matter from entering the suction port 13 is provided. The cover body 20 is provided with a plurality of elastic bodies 24 at predetermined intervals, and the elastic bodies 24 are supported between the fuel tank 9 and the crankcase 3 in a state of being pressed against the fuel tank 9. . The cover body 20 is attached to the crankcase 3 by first and second screw bodies 31 and 42 as will be described later.

  The large crankcase half 3A has a large-diameter portion 3Aa that houses a part of the cooling fan 12 and a small-diameter portion 3Ab, and a step portion 3Ac that connects both 3Aa and 3Ab is provided therebetween. FIG. 3 is a rear view of the large crankcase half 3A as viewed from the rear of the engine. Three air suction ports 13 defined by ribs 17 are formed in the step portion 3Ac of the large crankcase half 3A. As described above, the cover body 20 is disposed in the vicinity of the outer peripheral side of the air suction port 13, and the boss 21 and the first flange 22 used for attaching the cover body 20 to the large crankcase half 3 </ b> A include the large crankcase half. It is provided on both sides of the body 3A. The first flange 22 is formed with a screw hole 22a and a knock pin hole 22b.

As shown in FIG. 4, the fan housing 15 is provided with a second flange 23, which is superposed on the first flange 22 of 3A in FIG. used. The second flange 23, the insertion hole 23 a and the knock pin hole 23 b is formed.

  FIG. 5 is a perspective view of the cover body. As shown in the figure, the cover body 20 is provided with a plurality of small holes 20a by punching over the entire surface of a substantially U-shaped plate material, and the first and second sides of the base end portion (front end portion) are first and second. Second brackets 27A and 27B are provided, respectively. As shown in FIG. 6, the first bracket 27 </ b> A is provided at an intermediate portion in the vertical direction of the base end portion, and the second bracket 27 </ b> B is provided at an upper portion. The bottom surface of the cover body 20 has a shape that substantially conforms to the shape of the upper surface of the fuel tank 9 (FIG. 2). An end wall 20b that extends toward the outer peripheral surface 3a (FIG. 1) of the crankcase 3 and is close to the outer peripheral surface 3a is formed at the tip of the cover body 20.

  As shown in FIG. 7, the first bracket 27 </ b> A is attached to a predetermined position of the cover body 20 by spot welding 28. Further, as shown in FIG. 8, the second bracket 27 </ b> B is attached to a predetermined position of the cover body 20 by spot welding 28.

  As shown in the bottom view of FIG. 9, a plurality of mounting holes 26 are formed on the bottom surface of the cover body 20. In the illustrated example, four mounting holes 26 are provided, but there may be two, three, five or more. An elastic body 24 such as a synthetic rubber shown in FIG. 10 is attached to the mounting hole 26. The elastic body 24 is provided with a protrusion 24b at the center of the disk portion 24a, and a constricted portion 24c is formed between the disk portion 24a and the protrusion 24b. As shown in FIG. 1, the elastic body 24 is attached to the cover body 20 with the constricted portion 24 c entering the mounting hole 26, the disc portion 24 a is pressed against the upper surface of the fuel tank 9, and the protrusion 24 b is connected to the crankcase 3. Facing the side.

  Next, the attachment portion of the cover body 20 to the crankcase 3 will be described. The stay 30 of the muffler 8 of FIG. 2 is attached to the boss 21 shown in FIG. 3 by the first screw body 31. At this time, the first bracket 27A is also fastened together. That is, as shown in FIG. 12, the stay 30 and the first bracket 27 </ b> A are superposed on the boss 21 of the fan housing 15, and the first screw body 31 is inserted into the insertion holes of the first bracket 27 </ b> A and the stay 30. The first bracket 27A and the stay 30 are attached to the fan housing 15 by being screwed into the screw holes 21a. Thus, one side portion of the cover body 20 is supported by the fan housing 15.

On the other hand, as shown in FIG. 13, the second bracket 27B of the cover body 20 is attached to the first flange 22 of the large crankcase half 3A and the second flange 23 of the fan housing 15 via the cover bracket 33. ing. As shown in FIG. 11, the cover bracket 33 is formed in a U shape, and a screw insertion hole 34 is formed in an end wall of the front portion (left side in FIG. 11).
And a knock pin hole 35, and a welding nut 36 is provided inside the end wall of the rear portion (right side in FIG. 11 ).

The first flange 22 of the large crankcase half 3A shown in FIG. 13 and the second flange 23 of the fan housing 15 are overlapped, and the knock pin 41 is the cover bracket 33 and the knock pin holes 35 of the first and second flanges 22 and 23. , 22b and 23b, the cover bracket 33 and the first and second flanges 22 and 23 are positioned. The third screw body 43 is inserted into the cover bracket 33 and the insertion holes 34 and 23a of the second flange 23, and is screwed into the screw hole 22a of the first flange 22, so that the cover bracket 33 is a large crankcase half body. 3A and the fan housing 15 are attached.

  Here, the harness clamp 45 is also attached to the cover bracket 33 by the third screw body 43. A harness 46 is held by the harness clamp 45. The second bracket 27B is attached to the cover bracket 33 by screwing the second screw body 42 into the welding nut 36 through the insertion hole of the second bracket 27B of the cover body 20. Thus, the other side portion of the cover body 20 is supported by the crankcase 3 and the fan housing 15.

  One of the first flange 22 of the large crankcase half 3A and the second flange 23 of the fan housing 15 may be omitted. As a result, the other side of the cover body 20 is directly supported only by the crankcase 3 or the fan housing 15.

  Next, the operation of the small air-cooled engine having the above configuration will be described. An elastic body 24 is attached to the cover body 20 shown in FIG. 1, and the cover body 20 is supported between the fuel tank 9 and the crankcase 3 in a state where the elastic body 24 is pressed against the fuel tank 9. The vibration of the cover body is absorbed and relaxed by the elastic body 24. Therefore, since the cover body 20 does not vibrate, the generation of noise due to the vibration of the cover body 20 is suppressed, and the durability of the first and second brackets 27A and 27B that are the support portions of the cover body 20 is improved.

  As shown in FIG. 9, since the elastic body 24 is mounted in the mounting hole 26 formed in advance in the cover body 20, no separate mounting means is required, and the structure is simplified.

  As shown in FIG. 1, the cover body 20 has a proximal end portion close to the outer peripheral portion of the air inlet 13 in the crankcase 3, an end portion extending toward the crankcase 3 and close to the outer peripheral surface 3 a. Since the wall 20b is provided, since the volume space between the cover body 20 and the crankcase 3, that is, the inner space S of the cover body 20, can be increased, an increase in suction resistance by the cover body 20 can be suppressed.

  As shown in FIG. 5, since the plurality of small holes 20a penetrating the cover body 20 are formed, only the cooling air CA is taken in by the plurality of small holes 20a, and the entry of foreign matter can be blocked by the small holes 20a. Moreover, the plurality of small holes 20a can be easily formed by punching.

  As shown in FIG. 2, since the cover body 20 is detachably attached to the crankcase 3 by the first and second screw bodies 31, 42, the first and second screw bodies 31, The cover body 20 can be easily removed by 42.

  Since one side portion of the cover body 20 is fastened to the crankcase 3 by the first screw body 31 that attaches the muffler 8 to the crankcase 3, a dedicated screw body for screwing the cover body 20 to the crankcase 3 is unnecessary. Thus, the number of parts can be reduced.

  As shown in FIG. 1, the cover body 20 is attached by the second screw body 42 using the cover bracket 33 supported by the fan housing 15 and the crankcase 3. 3, a special mounting portion for attaching the second screw body 42 to the third member is not necessary, and the attachment structure of the cover body 20 can be simplified.

  Since the cover body 20 extends long from the vicinity of the outer peripheral side of the air inlet 13 of the large crankcase half 3A to the axial center of the small crankcase half 3B, the inner volume S of the cover body 20 can be increased. The suction resistance of the cooling air CA passing through the cover body 20 does not increase. Since this inhalation resistance can be kept low, the inhalation sound is reduced, and the vibration of the cover body 20 can be restrained. Also from this, the influence on the screw mounting portion of the cover body 20 can be further reduced.

  As described above, the preferred embodiments have been described with reference to the drawings, but various additions, changes, or deletions can be made without departing from the spirit of the present invention. For example, instead of the first and second screw bodies 31 and 42 in FIG. 2, both upper side portions of the cover body 20 are pressed against the outer peripheral surface 3a of the crankcase 3 via a vibration isolating material such as rubber. It may be. Further, instead of the cover bracket 33 in FIG. 1, a boss having a screw hole is formed in the fan housing 15, and the second bracket 27 </ b> B is attached to the fan housing 15 by the second screw body 42 using this screw hole. It may be screwed. In the above-described embodiment, a small two-cycle air-cooled engine has been described. However, the present invention can be similarly applied to a small four-cycle air-cooled engine.

DESCRIPTION OF SYMBOLS 1 ... Small air-cooled engine 2 ... Cylinder block 3 ... Crankcase 3a ... Outer peripheral surface 3A ... Large crankcase half 3B ... Small crankcase half 4 ... Crankshaft 8 ... Muffler 9 ... Fuel tank 12 ... Cooling fan 13 ... Air suction Port 15 ... Fan housing 20 ... Cover body 20a ... Small hole 20b ... End wall 24 ... Elastic body 26 ... Mounting hole 31 ... First screw body 33 ... Cover bracket 42 ... Second screw body 43 ... Third screw Body CA ... Cooling air S ... Inside space

Claims (5)

A crankshaft supported by the crankcase, a cooling fan that is attached to one end of the crankshaft and that feeds cooling air drawn from the air intake port to the cylinder block and the muffler , and a lower part of the crankcase An air-cooled engine with a fuel tank,
The crankcase has the air inlet opening toward the other end of the crankshaft;
Furthermore, a cover body that extends from the outer periphery of the air suction port toward the other end along the outer peripheral surface of the crankcase, and prevents entry of foreign matter into the air suction port;
An elastic body mounted on the cover body,
The cover body is detachably attached to the crankcase by a first screw body, with a base end portion close to the outer peripheral portion of the air suction port in the crankcase,
The cover body is supported between the fuel tank and the crankcase in a state where the elastic body is pressed against the fuel tank,
An air-cooled engine in which a mounting hole is formed in a bottom surface having a plurality of small holes penetrating the cover body, and the elastic body is mounted in the mounting hole . The air-cooled engine according to claim 1 , wherein an end wall that extends toward an outer peripheral surface of the crankcase and is close to the outer surface is provided at a tip portion of the cover body . A crankshaft supported by the crankcase, a cooling fan that is attached to one end of the crankshaft and that feeds cooling air drawn from the air intake port to the cylinder block and the muffler, and a lower part of the crankcase An air-cooled engine with a fuel tank,
The crankcase has the air inlet opening toward the other end of the crankshaft;
Furthermore, a cover body that extends from the outer periphery of the air suction port toward the other end along the outer peripheral surface of the crankcase, and prevents entry of foreign matter into the air suction port;
An elastic body mounted on the cover body,
The cover body is supported between the fuel tank and the crankcase in a state where the elastic body is pressed against the fuel tank,
The cover body is an air-cooled engine that is fastened to the crankcase together with a first screw body that attaches the muffler to the crankcase. The air-cooled engine according to any one of claims 1 to 3 , wherein the cover body is attached to a fan housing that covers the cooling fan or a cover bracket supported by the crankcase by a second screw body. Air-cooled engine. The air-cooled engine according to any one of claims 1 to 4 , wherein the crankcase has a large crankcase half body that has the air intake port and is positioned on one end side of the crankshaft, and the crankshaft. A small crankcase half located on the other end side, and the cover body extends from the vicinity of the outer periphery of the air intake port of the large crankcase half to the axial center of the small crankcase half. Air-cooled engine.

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