JP2827426B2 - Valve system for 4-cycle engine - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Object of the Invention] (Industrial application field) The present invention relates to a four-cycle engine capable of changing a lift amount and a valve opening timing of an intake / exhaust valve in accordance with an operating condition. The present invention relates to a valve gear, and more particularly to a lubricating device for suitably lubricating a rocker arm and a cam.

(Prior Art) Generally, in a four-stroke engine mounted on a vehicle such as an automobile and a motorcycle, intake and exhaust valves are disposed above a combustion chamber, and these valves are driven by a valve train. That is, the valve train includes a camshaft linked to the crankshaft of the engine, and the cam formed on the camshaft moves the intake and exhaust valves up and down at a predetermined timing.

(Problems to be Solved by the Invention) By the way, the above-mentioned four-stroke engine is required to obtain a high output in a wide rotation speed range from a low rotation speed range to a middle and high rotation speed range, that is, to have a wide power band. Is desirable.

However, in the conventional valve gear, since the valve opening / closing timing and the lift amount are fixed, only an output characteristic having a peak value in a specific engine speed range is obtained.
Therefore, a choice must be made between emphasizing the output characteristics in the low rotational speed region and emphasizing the output characteristics in the middle and high rotational speed regions.

The present invention has been made in view of the above-described circumstances, and provides a valve train for a four-cycle engine capable of improving output within a wide rotation speed range and efficiently performing lubrication of a rocker shaft and a cam. The purpose is to provide.

[Configuration of the invention]

(Means for Solving the Problems) According to the present invention, a rocker shaft rotatably supported by a cylinder head and having an eccentric large-diameter portion is formed, and a branch tip portion is formed by being directly inserted into the rocker shaft. A low-speed rocker arm, a medium-high speed rocker arm disposed on both sides of the low-speed rocker arm and inserted into the eccentric large-diameter portion, and rotatably supported by the cylinder head and the bearing housing. A low-speed cam and a medium-high speed cam for driving the medium-high speed rocker arm, respectively, and the tip of the middle-high speed rocker arm and the branch tip of the low-speed rocker arm are vertically overlapped, The cam profile of the middle / high speed cam is formed differently from the cam profile of the low speed cam, In the bearing housing, a low-speed lubricating oil passage and a medium-high-speed lubricating oil passage are juxtaposed in parallel with a camshaft in which the low-speed and middle-high speed cams are formed coaxially. A low-speed lubrication port is provided for lubricating oil to the cam and low-speed rocker arm, and a medium-high speed lubrication port for lubricating the medium-high speed cam and medium-high speed rocker arm to the medium-high speed lubricating oil passage. In addition, the lubricating oil is supplied to the middle / high speed lubricating oil passage when the middle / high speed cam and the middle / high speed rocker arm are operated.

(Effects) Therefore, according to the valve gear of a four-cycle engine according to the present invention, the cam floor surface of the medium-high speed rocker arm is lowered by rotating the rocker shaft by a predetermined angle to rotate the eccentric large diameter portion. Of the cam floor surface in the vertical direction. When the cam floor surface of the medium / high speed rocker arm is moved downward with respect to the cam floor surface of the low speed rocker arm, the contact between the medium / high speed rocker arm and the medium / high speed cam is released, and the low speed rocker arm and the low speed cam are disengaged. In contact therewith, the valve of the four-stroke engine is driven by this low speed cam.

Also, when the cam floor surface of the medium-high speed rocker arm is changed to a position substantially above or at the same position with respect to the cam floor surface of the low speed rocker arm, the contact between the low speed rocker arm and the low speed cam is released, and the medium high speed rocker arm is released. The medium and high speed cams respectively contact each other, and the valve of the four-stroke engine is operated by the medium and high speed cams.

Thus, by selecting the cam by rotating the rocker shaft, the engine output can be improved over a wide rotation speed range.

Further, the lubricating oil is supplied to the medium- and high-speed lubricating oil passages formed in the bearing housing when the medium- and high-speed cams and the medium-high-speed rocker arm operate, and the lubricating oil is not guided when the low-speed cam and the low-speed rocker arm operate. Therefore, the lubricating oil may be supplied only to the low-speed lubricating oil passage when the low-speed cam and the low-speed rocker arm are operated. For this reason, the capacity of the oil pump for supplying the lubricating oil can be reduced, and therefore, the melocanical loss of the engine can be reduced.

Hereinafter, an embodiment of the present invention will be described with reference to the drawings.

FIG. 11 is a perspective view showing one embodiment of a valve train of a four-stroke engine according to the present invention.

The valve train is disposed on the intake side and the exhaust side of one cylinder of the engine. Therefore,
Valves 1 and 2 shown in FIG. 11 are arranged for intake or exhaust.

This embodiment includes a camshaft 6 having a low-speed cam 3 and medium-high speed cams 4 and 5 disposed on one side and the other side of the low-speed cam 3, respectively.
Rocker arm 7 and medium-high speed rocker arms 8 and 9 which are positioned below the respective rocker arms 5 and 5, and support portions 7 a, 8 a and 9 a of these rocker arms 7, 8 and 9 are inserted and rocker shafts to be described later Bearing part 22 (10th
Rocker shaft 11 rotatably supported by (Fig.)
And is provided.

The tip of the low-speed rocker arm 7 branches in two directions, and these two branched ends 7b abut the stem heads of the valves 1 and 2 for opening and closing the combustion chamber of the engine (not shown). Further, the support portion 7a of the low-speed rocker arm 7 is directly inserted into the rocker shaft 11, and is rotatably provided.

The support portion 8a of the medium / high speed rocker arm 8 is rotatably fitted to the rocker shaft 11 via an eccentric bush 12 having a larger diameter than the rocker shaft 11. This eccentric bush
The shaft 12 is eccentric from the center of the rocker shaft 11 as shown in FIG. 13, and is detachably fixed to the rocker shaft 11 by the retaining pin 10. Therefore, the eccentric bush 12 functions as an eccentric large diameter portion in the rocker shaft 11.

As shown in FIG. 12, the support portion 9a of the medium / high speed rocker shaft 9 also rotates with respect to the rocker shaft 11 via the eccentric bush 13 having the same shape as the eccentric bush 12 and eccentric in the same direction. It is inserted as much as possible. This eccentric bush
13 is also detachably fixed to the rocker shaft 11 by the retaining pin 10 and functions as an eccentric large diameter portion.

In addition, each tip 8b of the rocker arms 8 and 9 for medium and high speeds
And 9b are in contact with one and the other branch tip 7b of low-speed rocker arm 7 via shim 14a. The contact points between the branch portions 7b of the low-speed rocker arms 7 and the tip portions 8b and 9b of the medium- and high-speed rocker arms 8 and 9 are set substantially on the axis of the valves 1 and 2.

Therefore, as shown in FIG. 13, when the low-speed cam 3 presses down on the cam floor surface 7c of the low-speed rocker arm 7 and lowers its tip portion 7b, the rocker arms 8 and 9 move.
Each of the tip portions 8b and 9b descends following the branch portion 7b by gravity. On the other hand, as shown in FIG. 14, when the middle and high speed cams 4 and 5 depress the cam floor surfaces 8c and 9c of the middle and high speed rocker arms 8 and 9, respectively, the tip portions 8b and Since 9b presses each tip 7b of the low-speed rocker arm 7,
The tip 7b is forcibly lowered.

The shim 14a is a shim having a T-shaped vertical section, and is fitted to both branch portions 7b of the low-speed rocker arm 7 from above. A cylindrical shim 14b with a cover is covered on the valve stem heads of the valves 1 and 2, and the lower surface of the branch tip 7b of the low-speed rocker arm 17 abuts on the shim 14b. These shims 14a and 14b are used for adjusting the tappet clearance of the valve.

Also, of the cams 3, 4 and 5, the medium-high speed cam 4
And 5 have the same cam profile, and the low speed cam 3 has a different cam profile from those of these medium and high speed cams 4 and 5. That is,
The cam profile of the low-speed cam 3 is set such that an appropriate valve lift and opening / closing timing are obtained when the engine is operated in a low rotation speed range. Also,
The cam profiles of the middle and high speed cams 4 and 5 are set such that a suitable valve lift and opening / closing timing are obtained when the engine is operated in a middle / high speed range.

The valve lift amount is the stroke length of the valves 1 and 2, and coincides with the cam lift amount. In FIG. 15, the cam profile of the low-speed cam 3 is indicated by a solid line A (cam lift amount).
la), and the cam profiles of the middle and high speed cams 4 and 5 are indicated by a broken line B (cam lift lb). As is apparent from FIG. 15, the cams 4 and 5 for medium and high speeds are used.
The cam profile is set so that a larger valve lift than the low speed cam 3 can be obtained.

The two-dot chain line C in FIG. 15 indicates the thick tops 12a and 13a of the eccentric bushes 12 and 13 by rotating the rocker shaft 11.
13 shows the cam profiles of the middle and high speed cams 4 and 5 when the cam is positioned obliquely inward (FIG. 13).

By the way, as shown in FIGS. 10 and 11, the rocker shaft 11 is rotated by a hydraulic cylinder 15 operated by hydraulic pressure from the engine. A rack 16 is connected to a piston (not shown) of the hydraulic cylinder 15, and the rack 16 is engaged with a pinion 17 formed at one end of the rocker shaft 11. These hydraulic cylinders 15,
The rack 16 and the pinion 17 constitute a drive mechanism. Further, the hydraulic cylinder 15 is provided with a low-speed hydraulic port 18 and a high-speed hydraulic port 19, and hydraulic pressure from the engine is selectively guided to the respective ports 18,19.

When the engine speed is in the low speed range, hydraulic pressure is supplied to the low-speed hydraulic port 18, the rack 16 is pulled back, and the pinion 17 is rotated in the direction of arrow M (FIG. 11).
As shown in FIG. 13, the eccentric bushes 12 and 13 rotate so that their thick tops 12a and 13a are positioned obliquely inward. Also, when the engine speed is in the middle / high speed range, hydraulic pressure is supplied to
The pinion 17 is pushed out, the pinion 17 is turned in the direction of the arrow N (FIG. 11), and the eccentric bushes 12 and 13 have their thick tops 12a and 13a obliquely outward as shown in FIG. To rotate.

Thus, the rocker shaft 11 is provided with the hydraulic cylinder 15,
The eccentric bushing is activated by the operation of the rack 16 and the pinion 17.
The axes of 12 and 13 are configured to always move in the upper half range of the rocker shaft 11.

Rocker shaft 11 and hydraulic cylinder 15 as described above
Are arranged on the cylinder head 21 shown in FIG. A total of four rocker shafts 11 are arranged, one each at the front and rear and left and right of the cylinder head 21 in the vehicle, and are arranged to extend in the vehicle left and right direction. Each rocker shaft 11 is rotatably supported by a rocker shaft bearing 22. The camshaft 6 is arranged above these rocker shafts 11. The camshaft 6 is rotatably supported by an upper half bearing portion 24 formed above the camshaft and a lower half bearing portion 25 formed above the rocker shaft bearing portion 22. .

Further, two sets of the low-speed rocker arm 7 and the medium- and high-speed rocker arms 8 and 9 are installed on one rocker shaft 11. The positions of the low-speed rocker arm 7 and the medium- and high-speed rocker arms 8 and 9 of each set are regulated together with the rocker shaft 11 by a positioning spring 26 interposed in the rocker shaft 11.

Further, a stopper groove 27 is formed on the outer periphery of the other end of the rocker shaft 11 having the pinion 17 formed at one end.
This stopper groove 27 extends along the circumferential direction of the rocker shaft 11,
The rocker shaft 11 includes a stopper formed over the range of the rotation angle of the rocker shaft 11 and a slide portion extending in the axial direction of the rocker shaft 11 from one or both ends of the stopper. When the tip of the stopper screw 28 screwed into the cylinder head 21 abuts on both ends of the stopper portion when the rocker shaft 11 is rotated by the operation of the hydraulic cylinder 15, the rotation of the rocker shaft 11 is restricted, The rocker shaft 11 stops.

Note that the slide portion of the stopper groove 27 is
It functions when adjusting the tappet clearance by exchanging the shim 14b installed on the stem head. That is, Shim 14
When replacing b, it is necessary to slide the rocker shaft 11 to the outside of the cylinder head 21 against the urging force of the positioning spring 26 and move the low-speed rocker arm 7 and the medium-high speed rocker arms 8 and 9 in the same direction. However, at this time, the tip of the stopper screw 28 moves in the slide portion. Reference numeral 29 in FIG. 10 denotes a head cover.

Now, the bearing housing 23 is provided with a lubricating device as shown in FIGS. That is, the bearing housing
23 has a medium-to-high speed lubricating oil passage 30 parallel to the camshaft 6.
And a low-speed lubricating oil passage 31 are juxtaposed. These medium and high speed lubricating oil passages 30 and low speed lubricating oil passages 31
An oil seal 32 is formed over the entire length of the lubricating oil passage 23 at each end of the lubricating oil passages 30 and 31.

A low-speed lubricating oil supply passage 33 is formed in the bearing housing 23 at a substantially central position in the longitudinal direction thereof so as to communicate with the low-speed lubricating passage 31 (FIG. 3). It is guided into the low-speed lubrication path 31. A low-speed lubrication port 34 is formed in the bearing housing 23 at a position directly above the low-speed cam 3 so as to communicate with the low-speed lubricating oil passage 31. From the low-speed lubrication port 34, the lubricating oil in the low-speed lubricating oil passage 31
During operation of the engine, oil is constantly supplied to the low-speed cam 3 and the low-speed rocker arm 7. Further, the bearing housing 23 includes:
A low-speed lubricating oil return path 35 is formed at both ends of the low-speed lubricating oil path 31, and the lubricating oil in the low-speed lubricating path 31 is guided to the camshaft 6.

As shown in FIGS. 2 and 7, the bearing housing 23 is further provided with a medium- and high-speed lubricating oil supply passage 36 communicating with a substantially central position in the longitudinal direction of the medium and high-speed lubricating oil passage 30. The lubricating oil from the engine oil pressure source is provided to be able to be introduced into the lubricating oil passage 30 for the medium and high speeds through the lubricating oil supply passage 36 for the medium and high speed. The bearing housing 23 has a lubricating oil passage for
A medium / high speed lubrication port 37 communicating with 30 is formed. The middle / high speed lubrication port 37 is formed directly above the middle / high speed cams 4 and 5 to supply the lubricating oil in the middle / high speed lubricating oil passage 30 to the middle / high speed cam 4, the middle / high speed rocker arm 8, and the middle / high speed rocker arm 8. Lubricate the high-speed cam 5 and the medium-high speed rocker arm 9 respectively.

Meanwhile, a check valve 38 shown in FIG. The check valve 38 is a valve using a steel ball 40 urged by a valve spring 39.
When it comes into contact with the ball stopper 41 against the urging force of
It is configured to allow the flow of the lubricating oil in the direction of the arrow and not allow the flow in the opposite direction. This check valve 38 is used for the low speed cam 3.
Of the low-speed rocker arm 7 to the medium-high speed cam 4
The engine speed (about 9000 rp) when the drive is switched to driving of the medium and high speed rocker arms 8 and 9 by
m), the set pressure, ie, the valve spring, so that the valve opens at a hydraulic pressure slightly lower than the hydraulic pressure of the lubricating oil (for example, the hydraulic pressure of the lubricating oil at an engine speed of about 7000 rpm).
39 spring constants are determined.

Therefore, due to the presence of the check valve 38, the lubrication for medium and high speeds is performed only in the engine speed range slightly higher than the engine speed when the drive from the low speed cam is switched to the high speed cam drive. Lubricating oil is supplied from the oil supply passage 36 into the medium-to-high speed lubricating oil passage 30,
It is provided that lubricating oil is injected from 37.

 Next, the function and effect will be described.

When the rocker shaft 11 is rotated in the direction of arrow M in FIG. 2 by the operation of the hydraulic cylinder 15 when the engine is at a low rotational speed, the thick tops 12a and 13a of the eccentric bushes 12 and 13 are slanted inward. (Fig. 13). Thus, the cam floor surfaces 8c and 9c of the medium and high speed rocker arms 8 and 9 become the cam floor surfaces of the low speed rocker arm 7 respectively.
Moves downward relative to 7c. Therefore, a gap is formed between the peripheral surfaces of the middle and high speed cams 4 and 5 and the cam floor surfaces 8c and 9c of the middle and high speed rocker arms 8 and 9, and as a result, the middle and high speed cams 4 and 5 Idle.

At this time, since the low-speed rocker arm 7 is constantly pushed upward about the axis of the rocker shaft 11 by the urging force of the valve spring 20, its cam floor surface 7c is in contact with the peripheral surface of the low-speed cam 3. Touch Therefore, when the camshaft 6 rotates, the valves 1 and 2
Moves up and down based on the lift characteristic A of the low-speed cam 3 shown in FIG. That is, the valves 1 and 2 open and close the combustion chamber while ensuring a valve lift appropriate for a low engine speed range.

On the other hand, when the rocker shaft 11 is rotated in the direction of arrow N in FIG. 11 by the operation of the hydraulic cylinder 15 when the engine is in the middle / high rotation range, the thick tops 12a and 13a of the eccentric bushes 12 and 13 are inclined. Located outside (No. 14
Figure). As a result, the cam floor surfaces 8c and 9c of the medium and high speed rocker arms 8 and 9 move relatively upward or to the same position with respect to the cam floor surface 7c of the low speed rocker arm 7, and the cam floor surfaces 8c and 9c respectively move Abut against the peripheral surfaces of the cams 4 and 5.

As shown in FIG. 15, the cams 4 and 5 for medium and high speeds are formed with a larger cam lift than the cams 3 for low speed, so that the rocker shaft 6 under the condition shown in FIG.
Is rotated, the low-speed cam 3 idles, while the medium-high speed cams 4 and 5 are respectively driven by the medium-high speed rocker arms 8.
Via valves 9 and 9, valves 1 and 2 are driven based on the lift characteristic B in FIG. As a result, valves 1 and 2
Opens and closes the combustion chamber while ensuring a valve lift suitable for the middle and high engine speed ranges of the engine.

According to the above embodiment, a cam profile suitable for the low speed range of the engine is formed on the low speed cam 3, and a cam profile suitable for the middle / high speed range of the engine is formed on the middle and high speed cams 4 and 5. Further, the medium and high speed rocker arms 8 and 9 are rotatably fitted into the eccentric bushes 12 and 13 of the rocker shaft 11, respectively, and the low speed rocker arm 7 is directly fitted into the rocker shaft 11 to form the rocker shaft 11.
The rotation of the cam 11 and the low-speed rocker arm 7
Contact between the medium and high speed cams 4 and 5 and the medium and high speed rocker arms 8 and 9 can be selected.
Valves 1 and 2 with low-speed cam 3 or medium-high speed cam
4 and 5 can be selectively driven. Therefore, the output of the four-stroke engine can be improved in a wide rotation speed range from the low rotation speed range to the middle and high rotation speed ranges of the engine.

Further, since the selection of the low speed cam 3 and the middle and high speed cams 4 and 5 is performed by the rotation of the eccentric bushes 12 and 13, no great stress is generated in each part when the cams 3, 4 and 5 are selected. Therefore, the cams 3, 4, and 5 can be smoothly selected.

Further, lubricating oil is constantly supplied to the low-speed lubricating oil passage 31 formed in the bearing housing 23 during operation of the engine, and lubricating oil is supplied from the low-speed lubrication port 34 to the low-speed cam 3 and the low-speed rocker arm 7. Is done. On the other hand, due to the action of the check valve 38, the rotation speed of the lubrication passage 31 formed in the bearing housing 23 is slightly lower than the engine rotation speed (approximately lower than the engine rotation speed at which the rocker arm and the cam are switched from the low speed side to the medium high speed side). (7000 rpm), the lubricating oil is supplied for the first time, and the lubricating oil is supplied from the lubrication port 37 for middle and high speed.

Thus, the low-speed rocker arm 7 is
Lubricating oil passage 30 for medium and high speeds
Since the lubricating oil is not supplied into the inside, the capacity of the oil pump (not shown) for supplying the lubricating oil can be reduced accordingly. As a result, mechanical loss of the engine can be reduced.

In addition, a check valve 38 is provided in the medium-to-high speed lubricating oil supply passage 36 to selectively supply or stop the lubricating oil to the medium-to-high speed lubricating passage 30. Since the lubricating oil is supplied in the entire rotation speed range of the engine, the structure of the lubricating device provided in the bearing housing 23 can be simplified, and the cost does not increase.

Further, in this lubricating device, the middle and high speed lubricating oil passage 30 and the low speed lubricating oil passage 31
Although the lubricating oil is supplied to both, the pump capacity of the oil pump is improved at the time of high engine rotation,
Does not cause any trouble. In the above embodiment, the case where the cam profiles of the middle and high speed cams 4 and 5 are shown by the broken line B in FIG. 15 has been described. The lift of the valves 1 and 2 may be changed when the engine is running at a medium or high speed as indicated by a broken line B 'in FIG. 17 or a broken line B "in FIG.

Further, in the above embodiment, the case where the hydraulic cylinder 15 is used as the rotational drive source of the rocker shaft 11 has been described. However, a motor is used as the rotational drive source, and the rocker shaft 11 is rotationally driven by power transmission means such as a pulley and a belt. You may make it do.

〔The invention's effect〕

As described above, according to the valve train of the four-stroke engine according to the present invention, the eccentric large-diameter portion is formed on the rocker shaft rotatably supported, and the medium-high speed rocker arm is fitted to the eccentric large-diameter portion. Since the low-speed rocker arm was inserted between the medium- and high-speed rocker arms and directly inserted into the rocker shaft, the selection of the cam by the rotation of the rocker shaft enabled the engine output over a wide rotation speed range. Can be improved.

A low-speed lubricating oil passage and a medium-high-speed lubricating oil passage are provided side by side in a bearing housing located above a camshaft forming the low-speed and medium-high-speed cams. Since the lubricating oil is supplied via the high-speed lubrication port when the medium- and high-speed cams and the medium- and high-speed rocker arms are operated, the lubricating oil is almost always supplied during the operation of the low-speed cam and the low-speed rocker arms. It is not supplied from the above-mentioned medium / high speed lubrication port. As a result, the capacity of the oil pump that supplies the lubricating oil can be reduced, and the mechanical loss of the engine can be reduced.

[Brief description of the drawings]

1 is an enlarged plan view showing the bearing housing of FIG. 10, and FIGS. 2, 3, 5, 7, and 8 are lines II-II and III-III of FIG. FIG. 4 is a sectional view taken along lines V-V, V-V, VII-VII and VIII-VIII, respectively.
FIG. 6 is a rear view of the bearing housing shown in FIG.
9 is an enlarged sectional view showing the check valve of FIG. 7 in an enlarged manner, FIG. 10 is a longitudinal sectional view of a cylinder head or the like to which the valve train of FIG. 2 is applied, FIG. 11 is a perspective view showing one embodiment of the valve train of the four-stroke engine according to the present invention, FIG. 12 is a plan view of the valve train of FIG. 11, FIG. 13 and FIG. FIG. 3 is an operation state diagram showing the operation of the valve train,
FIG. 15 is a diagram showing a cam profile of the cam shown in FIGS. 10 and 11, and FIGS. 16 and 17 are diagrams showing modifications of the cam profile shown in FIG. 1,2 valve, 3 low speed cam, 4,5 medium speed cam, 6 rocker shaft, 7 low speed rocker arm, 8,9 medium speed rocker arm, 11 Rocker shaft, 12, 13 eccentric bush, 21 cylinder head, 15 hydraulic cylinder, 16 rack, 17 pinion, 30 rocker shaft bearing, 31 positioning spring, 24 Stopper groove, 25 ... Stopper part, 27 ...
Stopper screw, 30 ... Lubricating oil passage for medium and high speed, 31 ...
Low-speed lubricating oil passage, 34 Low-speed lubrication port, 37 Medium-high speed lubrication port, 38 Check valve, A Low-speed cam profile, B Medium-high-speed cam profile .

Continuation of the front page (58) Field surveyed (Int.Cl. ⁶ , DB name) F01L 13/00 301 F01L 13/00 302 F01M 9/10

Claims (1)

(57) [Claims] A rocker shaft rotatably supported by a cylinder head and having an eccentric large-diameter portion; a low-speed rocker arm directly inserted into the rocker shaft and having a branch tip; A medium-high speed rocker arm disposed on both sides of the rocker arm and fitted into the eccentric large diameter portion, rotatably supported by the cylinder head and the bearing housing,
A low-speed cam and a medium-high speed cam for driving the low-speed and medium-high speed rocker arms, respectively, and a tip of the middle-high speed rocker arm and a branch tip of the low-speed rocker arm are vertically overlapped. In addition, the cam profile of the middle / high speed cam is formed differently from the cam profile of the low speed cam, and the bearing housing is parallel to a cam shaft on which the low speed and middle / high speed cams are formed coaxially. A low-speed lubricating oil passage and a medium-high-speed lubricating oil passage are provided side by side. The low-speed lubricating oil passage is provided with a low-speed lubrication port for supplying lubricating oil to the low-speed cam and the low-speed rocker arm. A lubricating oil passage is formed in the lubricating oil passage for lubricating the lubricating oil to the cam for medium speed and the rocker arm for medium and high speed. Valve operating device of four-stroke engine, wherein the lubricating oil is supplied during serial in the high-speed cam and the high speed rocker arm actuated.