KR101036533B1 - Decompression device for engine - Google Patents

Abstract

An exhaust cam is provided on a cam shaft rotatably supported by a cylinder head, and a base of the exhaust cam is provided on a decompression weight rotatably supported by a cam shaft through a decompression pin having an axis parallel to the cam shaft. In the decompression device of an engine to which a decompression cam which can protrude from the original part is connected, the decompression device is made compact so that the cylinder head can be miniaturized.

The decompression pin 55 is disposed inside the outer circumference of the upper portion 40b of the exhaust cam 40 in the axial direction of the cam shaft 30.

Description

Decompression unit for engines {DECOMPRESSION DEVICE FOR ENGINE}

The present invention relates to a camshaft rotatably supported by a cylinder head, which has an arc-shaped base portion centered on the axis of the camshaft, protrudes outward from the base portion, and is continuous at both ends in the circumferential direction of the base portion. An exhaust cam having a high portion is provided to openly drive the exhaust valve at the high portion, and a decompression weight supported by the exhaust cam so as to be rotatable to the cam shaft through a pressure reducing pin having an axis parallel to the cam shaft. The present invention relates to a decompression device for an engine to which a decompression cam that can protrude from the base portion is connected.

Such a pressure reduction device is already known by patent document 1, for example.

[Patent Document 1] Japanese Patent No. 3435951

By the way, in the decompression device disclosed in Patent Document 1, although the decompression weight is rotatably supported by the decompression holder fastened to the camshaft through the decompression pin, a part of the decompression pin is located at the axial direction of the camshaft. It is arrange | positioned outside the high part, and the decompression device is enlarged in the radial direction of a camshaft, resulting in the enlargement of the cylinder head.

This invention is made | formed in view of such a situation, and an object of this invention is to provide the decompression device of the engine compactized so that a cylinder head can be miniaturized.

In order to achieve the above object, the invention described in claim 1 includes an arc-shaped base portion centered on an axis of the camshaft and a projecting outward from the base portion, on a cam shaft rotatably supported by a cylinder head. And an exhaust cam having a high portion continuous at both ends in the circumferential direction of the base circular portion, the exhaust cam being installed to openly drive the exhaust valve at the high portion, and through the pressure reducing pin having an axis parallel to the cam shaft, In the decompression device of an engine in which a decompression cam that can protrude from the base portion is connected to a decompression weight supported by the exhaust cam so that the rotation is possible, the decompression pin is located at the upper portion of the cam shaft in an axial direction of the camshaft. It is arrange | positioned inside an outer periphery, It is characterized by the above-mentioned.

In addition, the invention described in claim 2, in addition to the configuration of the invention described in claim 1, one end of the camshaft is rotatably supported by the cylinder head via a support bearing, and the decompression weight itself and the support The decompression weight with a washer interposed between the bearings is disposed between the support bearing and the exhaust cam and cantilevered to the exhaust cam.

In addition, the invention described in claim 3 is characterized in that, in addition to the configuration of the invention described in claim 2, a plurality of protrusions in contact with the washer are formed to protrude on the surface of the pressure reducing weight that faces the washer. .

Further, the first ball bearing 37 of the embodiment corresponds to the support bearing of the present invention.

According to the invention as set forth in claim 1, since the decompression pin is disposed inside the outer periphery of the high portion of the exhaust cam in the axial direction of the cam shaft, the decompression device can be made closer to the axis of the cam shaft and more compact, As a result, the cylinder head can be miniaturized.

Further, according to the invention described in claim 2, since the decompression weight is cantilevered to the exhaust cam, the decompression device can be made compact in the direction along the axis of the camshaft to further reduce the cylinder head, and the decompression weight is exhausted. By being sandwiched between the cam and the washer, it is possible to prevent rattling of the cantilever-supported pressure-reducing weight, so that the operability of the pressure-reducing device can be made good.

In addition, according to the invention as set forth in claim 3, since only a plurality of protrusions formed on the decompression weight contacts the washer, the contact area of the decompression weight with respect to the washer is reduced, thereby reducing the frictional force generated between the decompression weight and the washer, Can improve the operability of the.

EMBODIMENT OF THE INVENTION Hereinafter, embodiment of this invention is described based on one Example of this invention shown in an accompanying drawing.

1 to 6 show one embodiment of the present invention, FIG. 1 is a longitudinal sectional view of an essential part of the engine, FIG. 2 is a sectional view taken along the line 2-2 of FIG. 1, and FIG. 2 is an enlarged cross-sectional view taken along line 3-3 of FIG. 2, FIG. 4 is an enlarged cross-sectional view taken along line 4-4 of FIG. 2 in a decompression off state, FIG. 5 is an exploded perspective view of the decompression device, and FIG. It is sectional drawing corresponding to FIG.

1, the engine main body 11 of this engine is mounted in a motorcycle, for example, and the engine main body 11 has the cylinder which has the cylinder bore 16 which fits the piston 15 so that sliding is possible. A cylinder head 13 coupled to the cylinder block 12 so as to form a combustion chamber 17 between the block 12 and the upper end of the piston 15 and the cylinder block 12; 13 is provided with a head cover 14 coupled to the opposite side to the cylinder block 12, and a crankcase (not shown) coupled to the cylinder block 12 from the opposite side to the cylinder head 13. .

The cylinder head 13 is provided with an intake port 18 opening on one side thereof and an exhaust port 19 opening on the other side of the cylinder head 13, and intake air passing through the intake port 18. An intake pipe 21 forming a passage 20 is connected to the cylinder head 13, and a fuel injection valve 22 is attached to the intake pipe 21.

In addition, the cylinder head 13 includes an intake valve 24 for switching communication between the intake port 18 and the combustion chamber 17, and an interruption between the exhaust port 19 and the combustion chamber 17. The exhaust valve 25 which switches communication and interruption is provided so that opening and closing operation is possible, and the intake valve 24 and the exhaust valve 25 are deflected to the closed valve direction by the valve springs 26 and 27.

Referring to FIG. 2 together, the intake valve 24 and the exhaust valve 25 are valve actuated in a valve operation chamber 28 formed between the cylinder head 13 and the head cover 14. Opened and closed driven by the device 29, the valve actuating device 29 includes a cam shaft 30 disposed between the intake valve 24 and the exhaust valve 25, and rotation of the cam shaft 30. Intake rocker arm 31 that swings in accordance with the rotation of the camshaft 30 and swings in accordance with rotation of the camshaft 30, and the exhaust rocker arm 32 that opens and closes the exhaust valve 25. It is provided.

The cylinder head 13 has a first support part 33 having a first bearing hole 35 and a second support part 34 having a second bearing hole 36 coaxial with the first bearing hole 35. Is provided integrally. One end of the cam shaft 30 is rotatably supported by the first support part 33 via a first ball bearing 37 which is a support bearing between the inner circumference of the first bearing hole 35, A portion near the other end of the cam shaft 30 rotatably penetrates the second bearing hole 36, and a second ball bearing 38 between the inner circumference of the second bearing hole 36 and the cam shaft 30. ) Is interposed. In this way, the cam shaft 30 is press-fitted into the inner rings of the first and second ball bearings 37 and 38.

An intake cam 39 is integrally provided between the first and second support parts 33 and 34 near the second support part 34 of the cam shaft 30, and the first support part of the cam shaft 30 ( Near the 33), the exhaust cam 40 is provided integrally. The intake cam 39 and the exhaust cam 40 project outwardly from the arc-shaped base portions 39a and 40a centered on the axis of the camshaft 30 and the base portions 39a and 40a, and the base portions It is formed so as to have the high parts 39b and 40b which are continuous at both ends of the circumferential direction of 39a and 40a, respectively.

The intake side rocker arm 31 is pivotably supported by the intake side rocker shaft 41 supported by the cylinder head 13 with an axis parallel to the cam shaft 30, and the intake side rocker A roller 43 pivotally supported at one end of the arm 31 makes a rolling contact with the intake cam 39, and a tappet screw 45 is screwed to adjust the retreat position to the other end of the intake side rocker arm 31. ) Contacts the stem end 24a of the intake valve 24. In addition, the exhaust rocker arm 32 is swingable by the exhaust rocker shaft 42 supported by the cylinder head 13 with an axis parallel to the cam shaft 30 and the intake rocker shaft 41. Roller 44 pivotally supported at one end of the exhaust side rocker arm 32 is brought into contact with the exhaust cam 40, and the retracted position is set at the other end of the exhaust side rocker arm 32. An adjustable screwed tappet screw 46 contacts the stem end 25a of the exhaust valve 25.

A driven sprocket 47 is fixed to the other end of the cam shaft 30 protruding from the second support portion 34. This driven sprocket 47 constitutes a part of the timing transmission means 48 which transmits rotational power from the crankshaft (not shown) rotatably supported by the crankcase to the camshaft 30, and the crank A cam chain 49 that transfers power from the shaft is wound around the driven sprocket 47. In addition, a chain travel passage 50 for driving the cam chain (circuit) 49 is formed in the cylinder block 12 and the cylinder head 13 of the engine main body 11.

By the way, the cam shaft 30 to which the 1st and 2nd ball bearings 37 and 38 are mounted has the 2nd bearing hole 36 from the one end part, ie, the end side of the side in which the exhaust cam 40 is provided. It is assembled to the cylinder head 13 so as to penetrate through, the second bearing hole 36 of the second support portion 34 is inserted through the intake cam 39 and the exhaust cam 40 provided in the cam shaft 30. It is formed with a larger diameter than the first bearing hole 35 so as to allow. In addition, the cylinder head 13 and the head cover 14 are coupled to each other such that the gasket 51 is interposed between the cylinder head 13 and the head cover 14 at positions substantially corresponding to the axis of the cam shaft 30, and the side wall of the cylinder head 13 is connected. In the portion facing the second support portion 34, the recess 52 recessed away from the head cover 14 to allow the cam shaft 30 to be inserted through the second bearing hole 36. ) Is provided, and a lid 51a for closing the recess 52 is integrally formed with the gasket 51.

3 to 5 together, the valve operating device 29 has a relatively low engine speed, that is, a rotation speed of the camshaft 30, in order to lower the exhaust pressure during engine start and to facilitate starting. The pressure reduction device 54 which opened the valve slightly at the timing which originally closed the exhaust valve 25 in the state is provided, and this pressure reduction device 54 has the pressure reduction which has an axis line parallel to the camshaft 30. The decompression weight 56 which is rotatably supported by the camshaft 30 via the pin 55, and is installed between the exhaust cam 40 and the 1st ball bearing 37, and an exhaust cam in the state with low engine speed Protruding from the base portion 40a of the 40 and contacting the exhaust side rocker arm 32, but by the action of centrifugal force generated as the camshaft 30 rotates in the direction indicated by the arrow 53 in Figs. When the decompression weight 56 is rotated, the exhaust side A decompression cam 57 is connected to the decompression weight 56 so as not to contact the rocker arm 32.

The pressure reduction weight 56 is formed in an arc shape so as to cover the cam shaft 30 from the side, and the first ball bearing 37 of the upper portion 40b of the exhaust cam 40 of the cam shaft 30. On the side surface, the support protrusion 58 which extends along the radial direction of the cam shaft 30 protrudes integrally. Thus, the surface of the side of the second ball bearing 38 of the decompression weight 56 is formed flat along the plane orthogonal to the axis of the cam shaft 30 except for a portion thereof, and the decompression weight 56 One end side of the camshaft, that is, the downstream side along the rotational direction 53 of the camshaft 30, is provided with the thinned portion 56a by cutting the exhaust cam 40 side, and the other end side of the decompression weight 56. An accommodating recess 59 is formed by cutting the exhaust cam 40 side and exiting the exhaust cam 40. The accommodating recess 59 of the thin portion 56a and the accommodating recess 59 facing the exhaust cam 40 are provided. The surface is formed flat along the same plane orthogonal to the axis of the cam shaft 30.

A support hole 60 is provided in the thin portion 56a, and a ring-shaped contact protrusion 61 surrounding the support hole 60 is placed on the support protrusion 58 of the cam shaft 30. The other end side of the pressure-reduction pin 55 is integrally formed so as to be in sliding contact, and one end of the pressure-reducing pin 55 is inserted into the support hole 60 is pressed into the outer end of the support protrusion 58. Accordingly, the decompression weight 56 provided between the first ball bearing 37 and the exhaust cam 40 passes through the exhaust cam 40 through the decompression pin 55 having an axis parallel to the cam shaft 30. On cantilevered support. In addition, the outer end of the support protrusion 58 is in the upper portion 40b of the exhaust cam 40 as viewed in the axial direction of the cam shaft 30, and the pressure reducing pin 55 is formed of the cam shaft 30. Viewed from the axial direction, it is arrange | positioned inside the outer periphery of the said high part 40b.

In addition, a semicircular hydraulic pressure part 56b is provided at one end of the pressure reduction weight 56, and one side of the cam shaft 30 provided at the position corresponding to the hydraulic pressure pressure part 56b is blocked. A cylindrical blockage lifter 63 having one end with an end wall 63a in contact with the hydraulic pressure section 56b is fitted in the movement hole 62 so as to be slidable, and the sliding hole 62 A coiled spring 64 is compressed between the closed end and the end wall 63a of the lifter 63. The spring force of this spring 64 acts on the hydraulic pressure section 56b via the lifter 63, and the decompression weight 56 is in the middle of the decompression weight 56 by the spring force of the spring 64. The part is deflected toward the side that comes close to the outer circumferential surface of the cam shaft 30. In addition, the end wall 63a of the lifter 63 has air for avoiding pressurization and depressurization of the space formed between the lifter 63 and the camshaft 30 to ensure smooth operation of the lifter 63. The hole 65 is provided.

The decompression cam 57 is disposed between the other end side of the decompression weight 56 and the exhaust cam 40 at a position corresponding to the base circular portion 40a of the exhaust cam 40, and a part of the decompression cam 57 is decompressed. The decompression camshaft 66 accommodated in the accommodation recess 59 of the weight 56 and integrally connected to the decompression cam 57 is rotated by the shaft hole 67 provided in the exhaust cam 40. Possibly fitted. Thus, the decompression camshaft 66 and the shaft hole 67 have an axis parallel to the axis of the camshaft 30, and the decompression cam 57 can rotate around an axis parallel to the axis of the camshaft 30. Is supported on the cam shaft 30.

The decompression cam 57 is basically formed in a cylinder coaxial with the decompression camshaft 66, but a part of the decompression cam 57 side of the decompression cam 57 is an axis of the decompression cam 57. It is cut to form a planar portion 68 parallel to the. That is, the outer periphery of the exhaust cam 40 side of the decompression cam 57 connects between the arc part 69 which centers on the axis line of the decompression cam shaft 66, and the both ends of the circumferential direction of this arc part 69. It is formed so that the said flat part 68, and this decompression cam 57 is the said flat part 68 located inward of the base part 40a of the said exhaust cam 40, as shown to FIG. 3 and FIG. 6) the pressure-reduced off state with the outward facing, and a reduced pressure-on state in which a part of the arc portion 69 protrudes outward from the base circular portion 40a of the exhaust cam 40 as shown in FIG. 6. Can be rotated from

On the other hand, at one end of the exhaust-side rocker arm 32, a contact portion 70 capable of contacting the circular arc portion 69 of the decompression cam 57 is provided adjacent to the roller 44, and the roller ( Even when 44 is in contact with the base circular portion 40a of the exhaust cam 40, when the circular arc portion 69 of the pressure reducing cam 57 protrudes outward from the base circular portion 40a, As the contact portion 70 comes into contact, the exhaust rocker arm 32 rotates to open the exhaust valve 25 slightly.

A connecting pin 72 having an axis parallel to the cam shaft 30 is press-fitted into a portion corresponding to the accommodation recess 59 of the pressure-sensitive weight 56, and the pressure-reducing weight of the press-fit pin 72 is press-fitted. The guide groove 71 into which the protrusion from 56 is fitted is provided in the portion on the pressure reduction weight 56 side of the pressure reduction cam 57 so as to extend along the radial direction of the pressure reduction cam 57. In this way, the rotation speed of the camshaft 30 is relatively large, and the centrifugal force acting on the decompression weight 56 is large, and the decompression weight 56 resists the biasing force of the spring 64 so that an intermediate portion of the decompression weight 56 can be obtained. In the decompression off state in which the decompression weight 56 is rotated to be spaced apart from the outer circumference of the cam shaft 30, as shown in FIGS. 3 and 4, the connecting pin 72 fitted to the guide groove 71 is provided. It rotates with the decompression weight 56, and in this state, the decompression cam 57 is in the rotation position which made the flat part 68 facing inside outward from the base circular part 40a of the said exhaust cam 40, The contact portion 70 of the exhaust rocker arm 32 does not contact the decompression cam 57, and the exhaust rocker arm 32 swings in accordance with the cam profile of the exhaust cam 40, and the exhaust valve 25 ) Also opens and closes at a timing corresponding to the cam profile of the exhaust cam 40. In addition, since the rotation speed of the cam shaft 30 is relatively small, the centrifugal force acting on the pressure reduction weight 56 is small, and the pressure reduction weight 56 cams the intermediate portion of the pressure reduction weight 56 by the biasing force of the spring 64. In the decompression-on state rotated to approach the outer periphery of the shaft 30, as shown in FIG. 6, the connecting pin 72 fitted to the guide groove 71 rotates with the decompression cam 56, and this In the state, the decompression cam 57 is in a rotational position where a part of the arc portion 69 protrudes outward from the base circle portion 40a of the exhaust cam 40, and the contact portion 70 of the exhaust side rocker arm 32 is located. () Is in contact with the arc portion 69 of the decompression cam 57, the exhaust-side rocker arm 32 is the decompression cam at the timing that the roller 44 is in contact with the base circle portion 40a of the exhaust cam 40. Slightly swinged by 57, and the exhaust valve 25 also slightly valves at the closing timing, regardless of the cam profile of the exhaust cam 40. It is to open the.

A ring washer 73 (see FIG. 2) is interposed between the decompression weight 56 and the inner ring of the first ball bearing 37, and the surface of the decompression weight 56 facing the washer 73 is disposed. In contact with the washer 73, a plurality of, for example, a pair of protrusions 74 and 75 are integrally in contact with each other. One of the protrusions 74 and 75 is formed in a ring shape so as to surround the opening end of the first ball bearing 37 side of the support hole 60, and the other protrusion 75 is a circle. It is formed in a plate shape and protrudes from the other end of the pressure reduction weight 56.

Next, the operation of this embodiment will be described. The decompression weight 56 of the decompression device 54 is rotated to the camshaft 30 through the decompression pin 55 having an axis parallel to the camshaft 30. It is supported by the said exhaust cam 40 so that the said decompression pin 55 may be inward of the outer periphery of the high part 40b in the exhaust cam 40 in the axial direction of the said camshaft 30. Since it is arrange | positioned, the decompression device 54 can be made closer to the axis line of the camshaft 30, and can be made more compact, and the cylinder head 13 can also be miniaturized by this.

Moreover, one end of the cam shaft 30 is rotatably supported by the 1st support part 33 of the cylinder head 13 via the 1st ball bearing 37, and is between the inner ring of the 1st ball bearing 37. FIG. Since the pressure reducing weight 56 with the washer 73 interposed therebetween is disposed between the first ball bearing 37 and the exhaust cam 40 and cantilevered to the exhaust cam 40, the cam shaft 30 The pressure reduction device 54 can be made compact in the direction along the axis, so that the cylinder head 13 can be further miniaturized, and the pressure reduction weight 56 is sandwiched between the exhaust cam 40 and the washer 73, thereby allowing the cantilever beam to be reduced. Rattle of the supported pressure reduction weight 56 can be prevented, and the operability of the pressure reduction apparatus 54 can be made favorable.

Further, since a plurality of, for example, a pair of protrusions 74 and 75 in contact with the washer 73 protrude from the surface of the pressure reducing weight 56 facing the washer 73, the washer of the pressure reducing weight 56 is provided. By reducing the contact area with respect to 73, the friction force which arises between the pressure reduction weight 56 and the washer 73 can be reduced, and the operability of the pressure reduction weight 56 can be improved more.

As mentioned above, although the Example of this invention was described, this invention is not limited to the said Example, A various design change is possible without deviating from this invention described in a claim.

1 is a longitudinal sectional view of an essential part of an engine;

2 is a cross-sectional view taken along the line 2-2 of FIG.

3 is an enlarged cross-sectional view taken along the line 3-3 of FIG. 2 in a decompression off state;

4 is an enlarged sectional view taken along line 4-4 of FIG. 2 in a decompression off state;

5 is an exploded perspective view of the decompression device.

6 is a cross-sectional view corresponding to FIG. 4 in a reduced pressure on state.

<Explanation of symbols for the main parts of the drawings>

13: cylinder head

30: camshaft

37: first ball bearing as a support bearing

40: exhaust cam

40a: base portion

40b: senior

54: decompression device

55: decompression pin

56: decompression weight

57: decompression cam

73: washer

74, 75: protrusions

Claims (3)

The cam shaft 30 rotatably supported by the cylinder head 13 protrudes outward from the arc-shaped base circle portion 40a centered on the axis of the cam shaft 30 and the base circle portion 40a. And an exhaust cam 40 having a high portion 40b continuous at both ends of the base circle portion 40a in the circumferential direction, and is installed to openly drive the exhaust valve 25 at the high portion 40b. The base circular portion (1) is attached to the decompression weight 56 supported by the exhaust cam 40 so as to be rotatable to the cam shaft 30 through a decompression pin 55 having an axis parallel to the cam shaft 30. A decompression device of an engine to which a decompression cam 57 that can protrude from 40a is connected, The decompression device of the engine, wherein the decompression pin (55) is disposed inside the outer circumference of the upper portion (40b) as seen in the axial direction of the camshaft (30). The method of claim 1, wherein one end of the cam shaft 30 is rotatably supported by the cylinder head 13 via a support bearing 37, The decompression weight 56 with the washer 73 interposed between the decompression weight itself and the support bearing 37 is disposed between the support bearing 37 and the exhaust cam 40, and the exhaust cam ( 40) cantilever support of the engine, characterized in that the decompression device. The decompression of the engine according to claim 2, wherein a plurality of protrusions (74, 75) in contact with the washer (73) is formed on the surface of the pressure reducing weight (56) opposite the washer (73). Device.

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