JP2007262953A - Engine - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To stably support a decompression shaft of a decompression mechanism by a simple support structure. <P>SOLUTION: In an engine provided with the decompression mechanism on a bonnet 25 covering a valve gear provided with valve arms 27, 28 opening and closing a suction valve 21 and an exhaust valve respectively on an cylinder head 3 of an engine, a decompression shaft 41 of the decompression mechanism is arranged in a direction crossing with valve arms 27, 28 at right angles, and both sides of the decompression shaft 41 are rotatably supported by the bonnet 25. An end part of an exhaust valve 22 side of the decompression shaft 41 is supported inside of the bonnet 25, an end part of a suction valve 21 side is supported by the bonnet 25 and projects out of the bonnet 25, and a decompression lever 42 is provided on an end part of the suction valve 21 side. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to an engine having a decompression mechanism on a bonnet that covers a valve operating mechanism in which a valve arm for opening and closing an intake valve and an exhaust valve is provided on each cylinder head of the engine.

Conventionally, a valve arm chamber is formed by attaching a bonnet to a cylinder head, and the valve arm chamber is opened and closed by pushing an intake valve and an exhaust valve with the valve arm, and the valve arm of the valve mechanism is pushed to intake air. An engine having a decompression mechanism that forcibly opens a valve or an exhaust valve to release a compression pressure in a cylinder is known (for example, see Patent Document 1). In such an engine, the decompression mechanism is operated when the engine is started, so that the intake valve or the exhaust valve is opened to release the compression pressure in the cylinder, and the crankshaft is easily rotated.
JP 2004-278372 A

  A conventional engine has a decompression mechanism that includes a decompression shaft that pushes an intake valve or an exhaust valve, and a decompression shaft that is connected to the decompression shaft outside the hood. However, the decompression shaft is located on one side of the hood. Since it was cantilevered, it could not be supported stably with a simple structure. Further, when the exhaust valve arm is pushed by the decompression shaft, the decompressor may be located near the exhaust muffler, making it difficult to operate the decompressor.

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

  That is, according to the first aspect of the present invention, in an engine having a decompression mechanism on a bonnet that covers a valve operating mechanism in which a valve arm for opening and closing an intake valve and an exhaust valve is respectively opened and closed on a cylinder head of the engine. The decompression shaft is arranged in a direction perpendicular to the valve arm, and both sides of the decompression shaft are rotatably supported by the bonnet. The exhaust valve side end of the decompression shaft is supported inside the hood, and the intake valve side Is supported by a bonnet, protrudes outward from the bonnet, and a decompressor is provided at the end on the intake valve side.

  According to a second aspect of the present invention, a cam that forcibly pushes the valve arm for the exhaust valve in the valve opening direction is formed in a portion of the decompression shaft that is located on the extension of the exhaust valve.

  According to a third aspect of the present invention, the decompression shaft is formed such that the diameter of the portion located on the extension of the intake valve is smaller than the diameter of the cam formed on the portion located on the extension of the exhaust valve; These are arranged outside the operating locus of the valve arm for the intake valve.

  According to a fourth aspect of the present invention, the diameter of the cam formed on the decompression shaft at a portion located on the extension of the exhaust valve is smaller than the diameter of the boss formed at the end on the intake side so as to be supported by the bonnet. It is formed as follows.

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

  According to the first aspect of the present invention, the decompression shaft can be stably supported on both ends of the bonnet, and the support structure for the decompression shaft can be simplified. In addition, since the intake side of the engine can be used as the operation side of the decompression mechanism, there is no exhaust muffler in the vicinity of the decompression lever, so that the decompressor can be easily operated.

  According to the second aspect, even when the decompressor is operated by operating the decompressor during engine operation, the engine can be stopped without causing backfire or the like. Further, since the cam is integrally formed on the decompression shaft, the decompression mechanism can be manufactured at low cost.

  In claim 3, interference between the valve arm for the intake valve and the decompression shaft can be avoided. For this reason, the intake valve arm can be made of the same member as the exhaust valve arm, and the number of parts can be reduced to reduce the manufacturing cost. Further, since the decompression shaft is configured to abut on the valve arm by changing its diameter, the decompression mechanism can have a simple structure without using a gap adjusting screw or the like.

  According to the fourth aspect of the present invention, the decompression shaft can be inserted and assembled to the bonnet from one side, and the manufacturing cost can be reduced.

  Next, embodiments of the invention will be described.

  1 is a front view showing an overall configuration of an engine according to an embodiment of the present invention, FIG. 2 is a partially sectional front view, FIG. 3 is a partially sectional side view of a bonnet, and FIG. AA arrow sectional drawing, FIG. 5 is BB arrow sectional drawing in FIG.

  As shown in FIGS. 1 and 2, when the engine according to the present invention is a horizontal engine, a cylinder head 3 is provided on one side of a cylinder block 2 provided with a crankcase 1 in the engine. An oil pan 4 is provided below the cylinder block 2, and a fuel tank 5 and a cooling water tank 6 are provided above the cylinder block 2. An air cleaner 7 and an exhaust muffler 8 are arranged side by side on the side of the cooling water tank 6 and above the cylinder head 3. In this embodiment, the engine is a horizontal engine, but it can also be a vertical engine.

  A cylinder 10 is formed in the cylinder block 2 in the lateral direction, and a piston 11 is accommodated in the cylinder 10. A crankshaft 12 is pivotally supported on the crankcase 1 attached to the cylinder block 2, the crankshaft 12 and the piston 11 in the cylinder 10 are connected via a connecting rod 13, and the piston 11 is connected to the crankshaft 12. The cylinder 10 can be reciprocated along with the rotation.

  The cylinder block 2 is also provided with a gear case 19 that houses various gears such as a crank gear 15 fixed to the crankshaft 12 and a start gear 18 that meshes with the crank gear 15. A start handle (not shown) is provided outside the gear case 19. Can be arranged. The start handle is attached to a shaft that rotatably supports the start gear 18 by a mounting portion 19a formed on the gear case 19, and is manually operated at the time of start. The crankshaft 12 is rotated by the operation, and the cylinder 10 The piston 11 can be reciprocated inside.

  The cylinder head 3 is formed with an intake port communicating with the air cleaner 7 and an exhaust port communicating with the exhaust muffler 8, and is provided with an intake valve 21, an exhaust valve 22, and a fuel injection valve 23. A bonnet 25 is attached to the side of the cylinder head 3 opposite to the cylinder block 2 to form a valve arm chamber 26.

  As shown in FIGS. 3 to 5, the valve arm chamber 26 is provided with a valve operating mechanism having valve arms 27 and 28 for opening and closing the intake valve 21 and the exhaust valve 22, respectively. That is, in the valve arm chamber 26, the valve arm shaft 27 for the intake valve and the valve arm 28 for the exhaust valve are swingably supported by the valve arm shaft 29 pivotally supported by the cylinder head 3. One end of each of the valve arms 27 and 28 is in contact with one end of each of the valve rods 21a and 22a of the intake valve 21 and the exhaust valve 22 protruding from the cylinder head 3 side. In the present embodiment, push rods 31 and 32 projecting from the crankcase 1 through the cylinder head 3 are connected to the right end of the lower end).

  The other ends of the push rods 31 and 32 connected to the lower ends of the valve arms 27 and 28 are brought into contact with cams provided on the camshaft 33 that is rotated as the crankshaft 12 is rotated. The push rods 31 and 32 can be reciprocated in the lateral direction by the rotation of the cam shaft 33. Further, springs 35 and 36 are fitted on the valve rods 21a and 22a of the intake valve 21 and the exhaust valve 22 which are in contact with the upper end side surfaces of the valve arms 27 and 28, respectively. The exhaust valve 22 is urged in the valve closing direction.

  In this way, the valve operating mechanism is configured and can be operated by the reciprocating motion of the push rods 31 and 32 by the cam shaft 33. When the valve mechanism is operated, the valve arms 27 and 28 are pushed by the push rods 31 and 32 to swing around the valve arm shaft 29, and the intake valve 21 and the exhaust valve 22 are moved by the springs 35 and 36. Pushing and opening in the valve-opening direction against the urging force, and conversely, when the valve mechanism is inactive, the push rods 31 and 32 are released, and the intake valve 21 and the exhaust valve 22 are connected to the springs 35 and 36, respectively. Due to the urging force, the valve arms 27 and 28 are returned to their original positions.

  The valve arm chamber 26 is provided with a decompression mechanism for releasing the compression pressure in the cylinder 10. As shown in FIG. 3, the decompression mechanism includes a decompression shaft 41 having a cam 41 a that forcibly pushes the valve arm 27 in the valve opening direction, a decompression shaft 42 that rotates the decompression shaft 41, and the decompression shaft 42. And a spring 43 that holds the valve in a predetermined operation position.

  The decompression shaft 41 is provided in the valve arm chamber 26 on the side opposite to the valve rods 21 a and 22 a of the intake valve 21 and the exhaust valve 22 with respect to the valve arms 27 and 28. It arrange | positions in the direction orthogonal to a direction, and both sides are rotatably supported by the bonnet 25. As shown in FIG. An end portion of the decompression shaft 41 on the intake valve 21 side has a boss portion 41b having a larger shaft diameter than other portions, and a support portion 25a formed on a side surface of the bonnet 25 on the intake valve 21 side from the through hole. The boss portion 41b is fitted into the shaft hole to be rotatably supported. On the other hand, the end of the decompression shaft 41 on the exhaust valve 22 side has the same shaft diameter as most other parts, and is fitted into the shaft hole by a concave support portion 25b formed on the side surface of the bonnet 25 on the exhaust valve 22 side. Combined and supported rotatably.

  As shown in FIG. 4, the decompression shaft 41 is camped on the exhaust side portion that is opposed to the upper end portion of the exhaust valve valve arm 28 and is located on the extension in the axial direction of the valve rod 22 a of the exhaust valve 22. 41 a is formed, and a part of the cam 41 a can be brought into contact with the exhaust valve arm 28 as the decompression shaft 41 rotates. The cam 41a is formed in an approximately 2/3 circular shape in sectional view centering on the axis of the decompression shaft 41. That is, the cam 41a is partially cut out in a half moon shape in sectional view, and the valve arm for the exhaust valve A seat portion 28a formed so as to protrude toward the decompression shaft 41 at the upper end portion of the cam 28 abuts on an arc portion (circumferential portion) of the cam 41a, and a straight portion (plane portion) of the cam 41a is used for an exhaust valve. The seat 28a of the valve arm 28 is configured not to contact with a predetermined distance.

  The decompression shaft 41 faces the upper end portion of the valve arm 27 for the intake valve, and the diameter of the intake side portion located on the extension in the axial direction of the valve rod 21a of the intake valve 21 is larger than the extension of the exhaust valve 22. It is formed so as to be smaller than the diameter of the exhaust side portion located at the position, that is, the diameter of the cam 41a. As shown in FIG. 5, the decompression shaft 41 is arranged outside the operating locus so that the intake side portion of the decompression shaft 41 is located outside the swingable range of the intake valve valve arm 27. Is configured not to contact the intake valve side valve arm 27 at a predetermined interval.

  Here, the decompression shaft 41 can be used for the intake valve even when the intake valve arm 27 is the same as the exhaust valve arm 28 and has a seat portion 27a at its upper end as in the present embodiment. The seat 27a of the valve arm 27 is configured not to contact the intake side portion. Thus, the decompression shaft 41 can be adapted to a valve operating mechanism in which the intake valve arm 27 and the exhaust valve arm 28 are shared.

  Further, the decompression shaft 41 is formed so that the diameter of the cam 41a formed at the exhaust side portion thereof is smaller than the diameter of the boss portion 41b formed at the intake side end portion. That is, the diameter of the cam 41a is set smaller than the diameter of the shaft hole formed in the intake side support portion 25a of the bonnet 25 that supports the boss portion 41b, and the cam 41a passes through the shaft hole of the intake side support portion 25a. It is possible. As a result, the decompression shaft 41 can be inserted into the valve arm chamber 26 from the intake side of the bonnet 25 and assembled to the bonnet 25.

  Further, in the decompression shaft 41, the end portion on the intake side excluding the boss portion 41b is located outside so as to be positioned on the intake side from the bonnet 25 to the engine body, in other words, on the side where the air cleaner 7 and the intake manifold are located. One end of the decompressor 42 is fixed to the end of the decompression shaft 41 on the intake side. In this way, the operation part of the decompression mechanism is not heated by the exhaust muffler 8 on the engine operation side where the operation part such as the start handle insertion part, the fuel cock or the regulator lever is positioned, and the intake side, and the operation is easy to perform. The decompression shaft 41 is rotated by the rotation operation of the decompressor 42 at the operation section, and the cam 41a is pressed against the exhaust valve arm 28, and the exhaust valve arm 28 is rotated to exhaust the exhaust valve. It can be opened by pressing 22.

  Then, a spring 43 is externally fitted to the end portion of the intake side projecting outside the decompression shaft 41 and is interposed between the decompression bar 42 and the bonnet 25. The decompression force of the spring 43 causes the decompression bar 42 to move. It is held in a non-operation position. This non-operation position is a rotation position where the cam 41a of the decompression shaft 41 does not contact the exhaust valve arm 28, and the exhaust valve arm 28 is not pushed by the cam 41a on the decompression shaft 41, and the exhaust The valve 22 is not pressed.

  By configuring in this way, in the decompression mechanism, the decompression shaft 41 is rotated with the rotation of the decompressor 42 by rotating the decompressor 42 against the biasing force of the spring 43. The cam 41a on the decompression shaft 41 rotates in a direction in contact with the seat portion 28a of the exhaust valve valve arm 28, and gradually presses against the seat portion 28a of the exhaust valve valve arm 28 so that the exhaust valve valve arm 28 is moved. Push. At this time, by pushing the cam 41a, the exhaust valve valve arm 28 swings about the valve arm shaft 29, and the valve rod 22a of the exhaust valve 22 is moved in the valve opening direction against the urging force of the spring 36. By pushing, the exhaust valve 22 is opened and the decompression mechanism is activated. On the other hand, when the decompressor 42 is released, that is, when the operating force is released, the original operating position is returned to the original operating position by the biasing force of the spring 43, and the cam 41a on the decompressing shaft 41 moves away from the exhaust valve arm 28 and presses the two Is released, the exhaust valve 22 is closed, and the decompression mechanism is deactivated.

  Therefore, in the engine of the present invention, the compression pressure in the cylinder 10 can be released by operating the decompression mechanism described above to forcibly open the exhaust valve 22. Thereby, when the engine is started by rotating the crankshaft 12 with the start handle, even if the piston 11 reciprocates in the cylinder 10 as the crankshaft 12 rotates, the compression pressure in the cylinder 10 increases. Therefore, the crankshaft 12 can easily rotate, and the starting handle can be rotated without requiring a large force. When starting the engine, when the crankshaft 12 reaches an appropriate rotational speed, the decompression mechanism is deactivated and the exhaust valve 22 is closed, whereby the compression pressure in the cylinder 10 rises and the engine can be started. it can.

  As described above, in an engine provided with a decompression mechanism on a bonnet 25 that covers a valve operating mechanism provided with valve arms 27 and 28 for opening and closing the intake valve 21 and the exhaust valve 22 in the cylinder head 3 of the engine, The decompression shaft 41 of the decompression mechanism is arranged in a direction orthogonal to the valve arms 27 and 28, and both sides of the decompression shaft 41 are rotatably supported by the bonnet 25. The decompression shaft 41 is disposed on the exhaust valve 22 side. The end is supported inside the bonnet 25, the end on the intake valve 21 side is supported by the bonnet 25, and the decompression is provided outside the bonnet 25 and the decompressor 42 is provided at the end on the intake valve 21 side. The decompression shaft 41 can be stably supported on both ends of the bonnet 25, and the support structure of the decompression shaft 41 can be simplified. In addition, since the intake side of the engine can be used as the operation side of the decompression mechanism, there is no exhaust muffler or the like in the vicinity of the decompression bar 42, and the decompressor 42 is easy to operate.

  Further, in the engine, the cam 41a that forcibly pushes the exhaust valve arm 28 in the valve opening direction is formed in a portion of the decompression shaft 41 that is located on the extension of the exhaust valve 22, so that the decompressor 42 is operated during engine operation. Even if the decompression mechanism is operated by operating, the engine can be stopped without causing backfire or the like. Further, since the cam 41a is integrally formed on the decompression shaft 41, the decompression mechanism can be manufactured at low cost.

  In the engine, the decompression shaft 41 is formed such that the diameter of the portion located on the extension of the intake valve 21 is smaller than the diameter of the cam 41a formed on the portion located on the extension of the exhaust valve 22, and Since the intake valve arm 27 is disposed outside the operating locus, interference between the intake valve arm 27 and the decompression shaft 41 can be avoided. Therefore, the intake valve arm 27 can be made of the same member as the exhaust valve arm 28, and the number of parts can be reduced to reduce the manufacturing cost. In addition, since the decompression shaft 41 is configured to abut on the valve arm 27 by changing its diameter, the decompression mechanism can have a simple structure without using a gap adjusting screw or the like.

  Further, in the engine, the diameter of the cam 41a formed on the portion of the decompression shaft 41 positioned on the extension of the exhaust valve 22 is larger than the diameter of the boss portion 41b formed on the end portion on the intake side in order to support the bonnet 25. Since it formed so that it might become small, it becomes possible to insert the decompression axis | shaft 41 in the bonnet 25 from the one side, and to assemble | attach, and can reduce manufacturing cost.

1 is a front view showing an overall configuration of an engine according to an embodiment of the present invention. Similarly a partial cross-sectional front view. The partial cross section side view of a bonnet. AA arrow sectional drawing in FIG. BB sectional drawing in FIG.

Explanation of symbols

3 Cylinder Head 21 Intake Valve 22 Exhaust Valve 25 Bonnet 27 Valve Arm 28 Valve Arm 41 Decompression Shaft 41a Cam 41b Boss Part 42 Decompressor

Claims (4)

  In an engine equipped with a decompression mechanism on a bonnet that covers a valve mechanism for opening and closing an intake valve and an exhaust valve on the cylinder head of the engine, the decompression shaft of the decompression mechanism is orthogonal to the valve arm. It is arranged in the direction, and both sides of the decompression shaft are rotatably supported by the bonnet, the exhaust valve side end of the decompression shaft is supported inside the bonnet, and the intake valve side end is supported by the bonnet. In addition, the engine is characterized in that a decompressor is provided at an end on the intake valve side so as to protrude outward from the bonnet.   The engine according to claim 1, wherein a cam for forcibly pushing the valve arm for the exhaust valve in a valve opening direction is formed in a portion of the decompression shaft positioned on the extension of the exhaust valve.   The decompression shaft is formed such that the diameter of the portion located on the extension of the intake valve is smaller than the diameter of the cam formed on the portion located on the extension of the exhaust valve, and the valve arm for the intake valve The engine according to claim 2, wherein the engine is disposed outside the operating locus of the engine. The decompression shaft is formed so that the diameter of the cam formed in the portion located on the extension of the exhaust valve is smaller than the diameter of the boss formed at the end on the intake side in order to support the bonnet. The engine according to claim 2 or 3, wherein the engine is characterized by the following.

Images