JP2923842B2 - Engine decompression device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a camshaft which rotates in conjunction with the rotation of a crankshaft, and which is provided with a valve cam.
The present invention relates to a decompression device for an engine that opens and closes an intake valve and / or an exhaust valve via a cam follower that abuts on a valve cam surface of the valve cam.

[0002]

2. Description of the Related Art Smooth cranking is enabled by providing a decompression lift to an intake valve and an exhaust valve which are in a closed position when the engine is started to temporarily open the intake valve and the exhaust valve. A decompression device for improving the startability of a vehicle is known, for example, from Japanese Utility Model Publication No. 2-41290.

In this decompression device, a weight lever is pivotally supported on a cam gear that rotates together with a camshaft, and an engagement pin provided on the weight lever is engaged with a U-shaped engagement portion provided on the decompression pin. By doing so, the decomp pin is driven to rotate by swinging of the weight lever due to centrifugal force.

[0004]

However, in the above-mentioned conventional apparatus, a fulcrum member for supporting the weight lever in the cam gear is required, so that not only the number of parts is increased, but also the engagement pin and the U-shaped Since the engaging portion and the engaging portion slide with each other, the sliding portion may be caught, which may hinder the smooth rotation of the decomp pin.

The present invention has been made in view of the above circumstances, and has as its object to provide a decompression device having a simple structure and a reliable operation.

[0006]

According to a first aspect of the present invention, there is provided a decompression device for an engine, wherein a valve operating cam is provided on a camshaft that rotates in conjunction with rotation of a crankshaft. In an engine that opens and closes an intake valve and / or an exhaust valve through a cam follower that abuts on a valve cam surface of the valve cam, the engine is rotatably supported by the valve cam, and rotates in one direction from the valve cam surface. A decompression pin having a decompression cam surface that protrudes and retracts from the valve cam surface by rotation in the other direction, an arm that extends in a radial direction from the rotation axis of the decompression pin, and is bent substantially in an L shape and one end is connected to the arm The other end is connected to a camshaft or a member that rotates integrally with the camshaft, and a decompression spring for urging the decompression pin in the one direction. , Provided in the bent portion of the decompression spring, characterized by comprising a centrifugal weight to rotate the decompression pin to deform the decompression spring by a centrifugal force accompanying the rotation of the cam shaft in the other direction.

According to a second aspect of the present invention, there is provided a decompression device for an engine, wherein a driven member for transmitting rotation of a crankshaft to a camshaft is provided integrally with a valve operating cam. The decompression spring is housed in a recess formed on the side surface on the side of the reaction valve cam.

[0008]

According to the first aspect of the present invention, when the engine having a low rotational speed of the crankshaft is started, the decompression pin is urged in one direction by the resilient force of the decompression spring, and the decompression cam surface is moved by the valve operating cam. Project from the surface. As a result, a decompression lift is provided to the intake valve and / or the exhaust valve, so that cranking of the crankshaft is facilitated and the startability of the engine is improved. During operation of the engine, the decompression spring is deformed by the centrifugal force acting on the centrifugal weight, the decompression pin rotates in the other direction, and the decompression cam surface is retracted from the valve cam surface of the valve cam.

According to the second aspect of the present invention, since the decompression spring is housed in the recess formed in the driven member integral with the valve cam, the decompression mechanism can be made compact.

[0010]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Preferred embodiments of the present invention will be described below with reference to the drawings.

FIGS. 1 to 9 show an embodiment of the present invention. FIG. 1 is a cross-sectional view (along line 1-1 in FIG. 2) taken along a crank axis of an OHC engine. 1 of FIG.
3 is an enlarged sectional view taken along line 3-3 of FIG. 1; FIG.
3 is a sectional view taken along line 4-4 of FIG. 3, FIG. 5 is an enlarged sectional view taken along line 5-5 of FIG. 1, FIG. 6 is a sectional view taken along line 6-6 of FIG. 5, FIG. FIG. 8 is a perspective view of the decompression mechanism, and FIG. 9 is an explanatory view of the operation.

As shown in FIGS. 1 and 2, the engine E is an air-cooled single cylinder whose main part is Fe or A.
It is made of a light alloy such as a 1 alloy, and is formed by integrally molding a cylinder block 1, a cylinder head 2, and a crankcase half 3. The crankcase half 3 is integrally formed with another crankcase half 4 separately formed of the same material as the crankcase half 3 to form a crankcase 5. That is, one of the crankcase halves 3 and the other half of the crankcase 4 are respectively provided with the cylinder axis L _1.
-L ₁ and the bonding surface 3 ₁ which is cut diagonally so the crankshaft axis L ₂ -L ₂ across both 4 ₁ are formed, abuts these joint surfaces 3 _1, 4 _1, they more Are integrally connected by the connecting bolts 6.
Journal shaft portions 9 ₁ and 9 ₂ of a crank shaft 9 are directly rotatably supported in bearing holes 7 ₁ and 8 ₁ of crank bearing portions 7 and 8 formed in the crank case halves 3 and 4, respectively. A flywheel 10 is fixed to one end of the crankshaft 9 as usual.

The crankshaft bearings 7, 8 may of course support a crankshaft via a surface bearing or a rolling bearing.

Cylinder barrel 1 of cylinder block 1
_On the outer periphery of ₁ , as usual, a plurality of cooling fins 11 ₁
… Are protruded integrally, and the cylinder barrel 1
_A piston 12 is slidably fitted in the cylinder bore 11 in ₁ . And the top surface of this piston 12,
The combustion chamber 15 is formed by the wall surface of the cylinder head 2 facing the combustion chamber. The piston 12 has a piston pin 1
A small end of the connecting rod 14 is rotatably connected to the connecting rod 14 via a crankshaft _{3, and} a crank pin 93 of the crankshaft 9 is rotatably connected to a large end of the connecting rod 14.

[0015] As shown in FIG.
Includes the cylinder axis L of the engine E ₁-L₁Sandwich it
An intake port 17 and an exhaust port 18 are formed on both sides of the
These ports 17 and 18 are connected to the combustion chamber 15.
The valve seats 19 and 20 are press-fit into the open ends, respectively.
Is done. The intake port 17 is one side inside the cylinder head 2
The outer end is extended to one side outer surface of the cylinder head 2.
And is connected to the carburetor 21.
G is extended inside the cylinder head 2 to the other side,
The outer end opens on the other outer surface of the cylinder head 2. Also
The cylinder head L has a cylinder axis L₁-L₁Across
Valve guide holes 23 and 24 are formed substantially in parallel with this.
In the valve guide hole 23, the intake port 17 can be opened and closed.
The stem portion of the intake valve 25 is slidably inserted, and
In the valve guide hole 24, the exhaust port 18 can be opened and closed.
The stem portion of the exhaust valve 26 is slidably inserted. Intake
Engaging the upper ends of the stems of the valve 25 and the exhaust valve 26, respectively.
Spring seats 27 and 28 and suction and exhaust ports of cylinder head 2
Spring seat surfaces 29, 30 formed on the upper surfaces of the seats 17, 18
Between the valve springs 31 and 32 each formed of a coil spring,
And these valve springs 31 and 32 are
The intake and exhaust valves 25 and 26 are urged in the valve closing direction,
The valve parts of the valves 25 and 26 are seated on the valve seats 19 and 20.
You. At one side of the intake and exhaust valves 25 and 26, combustion
A spark plug 34 is screwed onto the upper wall of the chamber 15 (see FIG. 1).
See).

As shown in FIG. 1, a cam shaft 35 is mounted on the cylinder head 2 in parallel with the crankshaft 9 on the cylinder axis L ₁ -L ₁ . A valve actuating cam 36 is rotatably supported, and a timed driven cog pulley 37 is formed integrally with the valve actuating cam 36. On the other hand, a timing drive cog pulley 38 is fitted and fixed to the crankshaft 9 corresponding to the timing driven cog pulley 37, and an endless timing cog belt 39 is suspended between these cog pulleys 37, 38. ing.

The governor drive gear 55 formed integrally with the timing drive cog pulley 38 is provided with a boss 4 of the crankcase half 4.
The governor driven gear 57 of the governor 56 supported by ₂ meshes. The oil dippers 58 formed in the lower half of the governor driven gear 57 are immersed in the oil stored in the bottom of the crankcase 5, so that when the governor 56 rotates, the oil dippers 58 splash oil splashes. This oil adheres to the endless adjustment cog belt 39 and is carried into the cylinder head 2 to lubricate the valve train.

The valve cam 36 and the cam shaft 35
May be formed integrally with the camshaft 35 in this case.
Is rotatably supported by the cylinder head 2.

As shown in FIGS. 3 and 4, cam follower shafts 41 and 42 are symmetrically supported on the upper side on both sides of the single cam shaft 35 with the cylinder head 2 therebetween. Cam follower shaft 41,
At 42, intermediate portions of intake and exhaust cam followers 43 and 44 are rotatably supported. The intake and exhaust cam followers 43 and 44 are disposed symmetrically with the valve cam 36 interposed therebetween, and are formed in a bifurcated shape having substantially the same shape. Arms 43 ₁ , 4 extending substantially horizontally in a direction approaching each other
4 ₁ and extends obliquely downward toward each other toward the bottom of the valve operating cam 36, the other arm portion 43 _2, 44
Has _two . The lower end of the first arm portion 43 _1, 44 ₁ of the tip has been screwed is adjusting screw 47 which is screwed a lock nut 45 and 46 respectively, their adjusting screw 47 and 48, the intake, The upper ends of the exhaust valves 25 and 26 are pressed by the resilient forces of the valve springs 31 and 32. The other arm portions 43 ₂ , 44
The _second end portion, the sliding surface 49, 50 are respectively formed, these sliding surface 49 and 50, the valve operating cam surfaces 36 ₁ of the animal valve cam 36 in the lower than the rotation center of the valve cam 36 They are pressed obliquely upward.

[0020] Incidentally, the sliding surface 49 and 50 they may be joined together may be formed on the other arm portion 43 _2, 44 ₂ integral with, or separately formed.

A head cover 52 is attached to the open upper surface of the cylinder head 2, an air cleaner 53 is connected upstream of the carburetor 21, and an exhaust port 18 is provided.
An exhaust chamber 54 is connected downstream (see FIG. 2).

Next, the structure of the decompression mechanism will be described with reference to FIGS.

The pair of bearing holes 2 ₁ provided in the cylinder head 2, 2 ₂ the camshaft 35 supported on is fixed by split pin 61 passing through the cylinder head 2. O-ring 62 held in a circumferential groove of camshaft 35
The contact surface of the bearing hole 2 ₁ a camshaft 35 and the cylinder head 2 is sealed. The valve cam 36 and the timing driven cog pulley 37 are formed integrally, and a thrust washer 63 is interposed between the timing driven cog pulley 37 and the inner wall surface of the cylinder head 2.

The support hole 37 ₁ schematically cylindrical decompression pin 64 which passes through the timing driven Kogupuri 37 is rotatably supported. One end of the decompression pin 64 is fitted into the support hole 36 ₂ facing the valve operating cam surfaces 36 ₁ of the valve operating cam 36, the other end is retained in contact with the thrust washer 63. At one end of the decompression pin 64, a valve operating cam surfaces 36 ₁ and the decompression cam surface 64 ₁ to be projectable radially outward notches capable Shisabotsu radially inward from the valve-operating cam surfaces 36 ₁ 64 ₂
Are formed.

Reaction valve cam 36 of timed driven cog pulley 37
The side surface of the side a recess 37 ₂ is formed, the recess 3
7 ₂ arms 65 provided integrally on the other end of the decompression pin 64 is accommodated in. In order to regulate the rotation limit of the arm 65, a pair of stopper surfaces 3
7 _3, 37 ₄ are formed. Between the tip of the pin 37 ₅ and the arm 65 extending integrally in the recess 37 in _2, both ends of the decompression spring 66 formed in a substantially L shape is locked. The bent portion of the decompression spring 66 is wound in a loop shape, and the centrifugal weight 67 is locked there. Decompression spring 66 and centrifugal weights 67 are housed when in the recess 37 in the _second driven Kogupuri 37 tone.

Timing driven cog pulley 37 and valve operating cam 3
The number of parts can be reduced by integrating 6, also the decompression mechanism is made compact by placing the decompression spring 66 the timing recesses 37 ₂ formed with the driven Kogupuri 37.

When the centrifugal force is not acting on the centrifugal weight 67 or when the centrifugal force acts on the centrifugal weight 67, the arm 65 is moved by the decompression spring 66 to which the set load is applied in the direction in which the bending angle increases in FIG. on one of the stop faces 37 ₃ abuts, the decompression cam surface 64 ₁ at this time the decompression pin 64 projects from the valve operating cam surfaces 36 ₁ of the valve operating cam 36 (see FIG. 9 (a)). When the centrifugal force acting on the centrifugal weight 67 increases, the decompression spring 66 is deformed, and the arm 65 is moved to the other stopper surface 3.
Rotates to a position abutting the 7 _4, the valve operating cam surface 36 of the decompression cam surface 64 ₁ is the valve operating cam 36 of the decompression pin 64 ₁
(See FIG. 9B).

Next, the operation of this embodiment will be described.

When the crankshaft 9 is rotated by the start of the engine E, the single valve cam 36 rotates with a reduction ratio of 1/2 of the crankshaft 9. Intake which is connected to the valve operating cam surfaces 36 ₁ of the valve operating cam 36, the exhaust cam followers 43 and 44 are respectively swung at a predetermined timing, thereby intake, exhaust valves 25 and 26 and valve spring 31, 32 Opening / closing driving is performed at a predetermined timing in cooperation with each other, and the operation of the engine E is performed as usual.

When the camshaft 35 rotates in the direction of arrow a in FIG. 3 due to cranking when the engine E is started, the centrifugal weight 67 is rotated because the rotation speed of the camshaft 35 is lower than during normal operation of the engine E. centrifugal forces acting on is small, the decompression cam surface 64 ₁ is the valve operating cam 36 of the decompression pin 64 by the elastic force of the decompression spring 66
Projecting from the valve-operating cam surfaces 36 ₁ (see FIG. 9 (a)).

In FIG. 3, when the valve cam 36 rotates in the direction of arrow a, the exhaust cam follower 44 is driven to open the exhaust valve 26, and then the intake cam follower 43 is driven to open the intake valve 25. . Since the decompression cam surfaces 64 ₁ of the decompression pin 64 in the rotational direction delayed side of the most protruding portion of the valve operating cam surfaces 36 ₁ projects, after the exhaust valve 26 is once opened is closed (ie in the intake stroke), the exhaust valve 26 Is given a decompression lift. However,
At this time, since the intake valve 25 has already been opened, the decompression lift of the exhaust valve 26 does not substantially function. Subsequently, after the intake valve 25 is once opened and closed (that is, in a compression stroke), a decompression lift is given to the intake valve 25. Thus, in the compression stroke in which a large load is applied when cranking the engine E, a decompression lift is given to the intake valve 25, so that smooth cranking is possible and the startability is improved.

[0032] When the rotational speed of the camshaft 35 with the engine E is started to increase, since the decompression cam surfaces 64 _1, as shown in FIG. 9 (b) is submerged retreat from the valve-operating cam surfaces 36 _1, the intake valve 25 and exhaust The decompression lift is no longer applied to the valve 26, and the engine E shifts to normal operation.

As described above, since the centrifugal weight 67 is supported by using the decompression spring 66, a special member for supporting the centrifugal weight 67 is not required, and the number of parts is reduced. Further, since the decompression mechanism does not have a sliding portion, there is no possibility that a malfunction may occur due to the catch of the sliding portion. Furthermore, by simply adjusting the weight of the centrifugal weight 67, or that can be easily adjusted to haunt timing of the decompression cam surfaces 64 _1, has been described an embodiment of the present invention, the present invention is limited to that embodiment Without departing from the invention, various embodiments are possible within the scope of the invention.

For example, in the embodiment, the decompression lift is given to both the intake valve 25 and the exhaust valve 26, but the decompression lift may be given to only one of them. Furthermore, are provided on the pin 37 at ₅ temper driven Kogupuri 37 supporting the decompression spring 66 in the embodiment can be provided it to the valve cam 36 and the cam shaft 35.

[0035]

As described above, according to the first aspect of the present invention, the member rotating integrally with the camshaft and the arm provided on the decompression pin are connected to each other by the decompression spring having the centrifugal weight. The decompression spring is deformed by the centrifugal force acting on the weight to rotate the decompression pin, so that the decompression pin is urged in one direction by the elastic force of the decompression spring when the engine starts, and the decompression pin is reliably decompressed to the intake valve and / or exhaust valve. Can give a lift. In addition, since the centrifugal weight is supported by using the decompression spring, a special member for supporting the centrifugal weight is not required, so that not only the number of parts is reduced but also the decompression pin has no sliding portion in the drive section. Therefore, there is no possibility that an operation failure due to the catch of the sliding portion or the like occurs.

According to the second aspect of the present invention,
A driven member for transmitting the rotation of the crankshaft to the camshaft is provided integrally with the valve operating cam, and the decompression spring is housed in a recess formed on the side surface of the driven member on the side of the reaction valve cam. Can be.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view (a cross-sectional view taken along line 1-1 in FIG. 2) of an OHC engine that is longitudinally cut along a crank axis.

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

FIG. 3 is an enlarged sectional view taken along line 3-3 in FIG. 1;

FIG. 4 is a sectional view taken along line 4-4 in FIG. 3;

FIG. 5 is an enlarged sectional view taken along line 5-5 of FIG. 1;

FIG. 6 is a sectional view taken along line 6-6 in FIG. 5;

FIG. 7 is a view in the direction of arrows in FIG. 6;

FIG. 8 is a perspective view of a decompression mechanism.

FIG. 9 is an explanatory diagram of an operation.

[Explanation of symbols]

9 Crankshaft 25 Intake valve 26 Exhaust valve 35 Camshaft 36 Valve-operated cam 36 ₁ Valve-operated cam surface 37 Timed driven cog pulley (driven member) 37 ₂ concave portion 43 Intake cam follower (cam follower) 44 Exhaust cam follower (cam follower) 64 Decomp pin 64 ₁ Decompression cam surface 65 Arm 66 Decompression spring 67 Centrifugal weight

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-2-157412 (JP, A) JP-A-2-87912 (JP, U) JP-A-3-1206 (JP, U) JP-A-2-107 83314 (JP, U) JP-A-2-41290 (JP, U) JP-A 4-75117 (JP, U) (58) Fields investigated (Int. Cl. ⁶ , DB name) F01L 13/08

Claims (2)

(57) [Claims] 1. A valve cam (36) is provided on a camshaft (35) that rotates in conjunction with the rotation of a crankshaft (9), and a valve cam surface (36 ₁ ) of the valve cam (36) is provided. In an engine that opens and closes an intake valve (25) and / or an exhaust valve (26) via contacting cam followers (43, 44), the engine is rotatably supported by a valve actuating cam (36). the decompression pin with the valve operating cam surface (36 ₁₎ valve operating cam surfaces by the rotation in the other direction as well as projecting from (36 ₁₎ from the submerged withdrawal decompression cam surface (64 ₁₎ (6
4), an arm (65) extending in the radial direction from the rotation axis of the decompression pin (64), a substantially L-shaped bent end connected to the arm (65) and the other end connected to the camshaft (35) or cam. A decompression spring (66) connected to a member (37) that rotates integrally with the shaft (35) and biasing the decompression pin (64) in the one direction; and a camshaft provided at a bent portion of the decompression spring (66). A decompression device for an engine, comprising: a centrifugal weight (67) for rotating the decompression pin (64) in the other direction by deforming the decompression spring (66) by centrifugal force accompanying the rotation of (35). 2. A driven member (37) for transmitting rotation of the crankshaft (9) to the camshaft (35) is provided integrally with the valve cam (36), and a reaction valve cam (36) of the driven member (37). Characterized in that the decompression spring (66) is housed in a concave portion (37 ₂ ) formed on the side surface on the side.
A decompression device for an engine according to claim 1.