JPH0565814A - Valve system for four-cycle engine - Google Patents

Abstract

PURPOSE:To improve engine output over a wide range of engine speeds by forming an eccentric large diameter part on a rocker shaft, fitting intermediate- high speed rocker arms on the eccentric large diameter part, and fitting a low speed rocker arm directly on the rocker shaft. CONSTITUTION:The supporting part 7a of a low speed rocker arm 7 is directly and turnably fitted on a rocker shaft. The respective supporting parts 8a, 9a of intermediate-high speed rocker arms 8, 9 are turnably fitted on the rocker shaft 11 through an eccentric bush 12 larger in diameter than the rocker shaft 11. The eccentric bush 12 functions similarly to the eccentric large diameter part on the rocker shaft 11. Engine output can thus be improved over a wide range of engine speeds, since a low speed. cam 3 and intermediate-high speed cams 4, 5 are selected by turning the rocker shaft 11.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a valve operating system for a four-cycle engine capable of changing the valve lift amount and valve timing of intake / exhaust valves in accordance with operating conditions, and particularly to a low speed cam and an intermediate valve. The present invention relates to a valve operating system for a four-cycle engine that smoothly changes engine output due to switching of operation with a high-speed cam.

[0002]

2. Description of the Related Art Generally, in a four-cycle engine mounted on a vehicle such as an automobile and a motorcycle, intake / exhaust valves are arranged above a combustion chamber, and these valves are driven by a valve train. That is, the valve operating device includes a cam shaft that interlocks with the crankshaft of the engine, and a cam formed on the cam shaft moves the intake / exhaust valve up and down at a predetermined timing.

[0003]

By the way, the above-mentioned four-cycle engine is capable of obtaining a high output in a wide rotational speed range from a low rotational speed range to a medium / high rotational speed range, that is, having a wide power band. Is desirable.

However, in the conventional valve operating system, since the valve opening / closing timing and the lift amount are fixed, only output characteristics having a peak value in a specific engine speed range can be obtained, and therefore, in a low speed range. There is no choice but to focus on the output characteristics or the output characteristics in the middle and high rpm ranges.

The present invention has been made in consideration of the above circumstances, and it is possible to improve the engine output in a wide rotational speed range and to change the operation of the low speed cam and the medium and high speed cam. It is an object of the present invention to provide a valve train for a four-cycle engine that can smoothly implement changes in the above.

[0006]

According to the present invention, a low speed rocker arm rotatably fitted to a rocker shaft and operated by a low speed cam, and a eccentric large diameter portion formed on the rocker shaft are rotatably supported. A medium-high speed rocker arm that is fitted and operated by a medium-high speed cam,
A hydraulic actuator that is operatively connected to the rocker shaft and that rotates the rocker shaft in the forward and reverse directions by the hydraulic pressure of the working oil to selectively switch the operation of the low speed cam and the middle and high speed cam. In the valve train of a 4-cycle engine, the rocker shaft is
The exhaust side rocker shaft with which the exhaust side low speed rocker arm that operates the exhaust valve and the exhaust side medium and high speed rocker arm that engages the intake valve, and the intake side low speed rocker arm and the intake side medium and high speed rocker arm that operate the intake valve have been fitted. An intake side rocker shaft is provided, and the hydraulic actuator is operatively connected to each of the exhaust side rocker shaft and the intake side rocker shaft to separate the exhaust side rocker shaft and the intake side rocker shaft from each other. It is provided so that the exhaust side rocker shaft and the intake side rocker shaft start to rotate with a time lag when the operation switching between the low speed cam and the medium and high speed cam is performed. is there.

[0007]

Therefore, according to the valve operating system for a four-cycle engine of the present invention, the rocker shaft is rotated by a predetermined angle to rotate the eccentric large-diameter portion, so that the cam floor surface of the middle-high speed rocker arm is rotated at a low speed. The position of the rocker arm is changed relative to 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 middle-high speed rocker arm and the middle-high speed cam is released, and the low-speed rocker arm and the low-speed cam are separated. Upon contact, the valve of the 4-cycle engine is driven by this low speed cam.

Further, when the cam floor surface of the medium-high speed rocker arm is moved to a position substantially above or at the same position as 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 rocker arm for high speed and the cam for middle and high speed contact each other, and 4
The valves of the cycle engine are operated by this medium-speed cam. By thus selecting the cam by rotating the rocker shaft, it is possible to improve the engine output over a wide rotation speed range.

Further, since the hydraulic actuator is configured to start the rotation of the exhaust side rocker shaft and the intake side rocker shaft with a time lag, for example, when switching the operation from the low speed cam to the medium high speed cam, the exhaust gas is exhausted. Either the side rocker shaft or the intake side rocker shaft is rotated first, and the other of the rocker shafts is rotated after a predetermined time has elapsed after the rotation. Therefore, as compared with the case where the exhaust side rocker shaft and the intake side rocker shaft are simultaneously rotated to switch from the low speed cam to the operation of the medium and high speed cams, the change of the engine output due to the switching of the cams can be smoothly performed.

[0010]

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

FIG. 2 is a perspective view showing an embodiment of a valve train for a 4-cycle engine according to the present invention. This valve operating device is provided on each of the intake side and the exhaust side of one cylinder of the engine. Therefore, the valves 1 and 2 shown in FIGS. 2 to 4 are arranged to perform intake or exhaust.

In this embodiment, a camshaft 6 having a low speed cam 3 and medium and high speed cams 4 and 5 respectively arranged on one side and the other side of the low speed cam 3 (FIG. 3). 4), the low-speed rocker arm 7, the medium-high speed rocker arms 8 and 9 located below the cams 3, 4 and 5, respectively, and the supporting portions 7a, 8a and 9a of these rocker arms 7, 8 and 9 respectively. And a rocker shaft 11 rotatably supported by a rocker shaft bearing portion of a cylinder head.
2, and a hydraulic actuator 13 for rotating 1 in the P direction or the O direction in FIG.

The tip of the low speed rocker arm 7 is branched into two directions, and both branch tip portions 7b are in contact with the stem heads of the valves 1 and 2 for opening and closing the combustion chamber of the engine (not shown). Also, low-speed rocker arm 7
The support portion 7a is directly inserted into the rocker shaft 11 and is rotatably provided.

The respective support portions 8a and 9a of the medium- and high-speed rocker arms 8 and 9 are provided with an eccentric bush 12 having a diameter larger than that of the rocker shaft 11, and the rocker shaft 1.
1 is rotatably inserted. This eccentric bush 12
As shown in FIG. 3, the shaft center is eccentric from the center of the rocker shaft 11, and is removably fixed to the rocker shaft 11 by the positioning fixing pin 10. Therefore,
The eccentric bush 12 functions as an eccentric large-diameter portion of the rocker shaft 11.

The lower surfaces of the tip portions 8a and 9a of the medium and high speed rocker arms 8 and 9 are brought into contact with one and the other branch tip portions 7b of the low speed rocker arm 7 through shims 14a, respectively. Therefore, as shown in FIG. 3, when the low speed cam 3 pushes down the cam floor surface 7c of the low speed rocker arm 7 and lowers the respective tip portions 7b thereof (when the low speed cam 3 is in operation), The tips 8b and 9b of 8 and 9 are not pushed down together with the branch tips 7b. On the other hand, as shown in FIG. 4, the middle and high speed cams 4 and 5 are connected to the middle and high speed rocker arm 8
When the cam floor surfaces 8c and 9c of the rocker arms 9 and 9 are pushed down (when the middle and high speed cams 8 and 9 are operating), the tip portions 8b and 9b of the rocker arms 8 and 9 are
Presses each branch tip portion 7b of the low speed rocker arm 7, the branch tip portion 7b is forcibly lowered.

The valve stem heads of the valves 1 and 2 are capped with a cylindrical shim 14b having a lid, and the lower surface of the branch tip 7b of the low speed rocker arm 7 abuts on the shim 14b. These shims 14a and 14b are used for adjusting the tappet clearance of the valves 1 and 2.

Of the cams 3, 4 and 5, the middle and high speed cams 4 and 5 have the same cam profile, and the low speed cam 3 is different from the cam profile of these middle and high speed cams 4 and 5. Has a cam profile. That is, the cam profile of the low speed cam 3 is set so that the valve lift amount and the opening / closing timing suitable for the engine operating in the low speed range can be obtained. Also, the middle and high speed cams 4 and 5 are
The cam profile is set so that an appropriate valve lift amount and opening / closing timing can be obtained when operating in a high rotation speed range.

Here, as described above, the valves 1 and 2 represent exhaust valves or intake valves. Therefore, when the valves 1 and 2 are exhaust valves, the low-speed rocker arm 7 and the medium-high speed rocker arms 8 and 9 indicate low-speed and medium-high speed rocker arms on the exhaust side, and the rocker shaft indicates the exhaust side shown in FIG. Rocker shafts 11a, 11b
Indicates. Further, when the valves 1 and 2 in FIG. 2 are intake valves, a low speed rocker arm 7 and a medium and high speed rocker arm 8 are provided.
Reference numerals 9 and 9 respectively indicate low-speed and middle-high speed rocker arms on the intake side, and rocker shaft 11 indicates intake-side rocker shafts 11c and 11d shown in FIG.

As shown in FIGS. 1, 2 and 5, the hydraulic actuator 13 uses engine oil as working oil and has an actuator body 15. Exhaust side cylinders 16a and 16b and intake side cylinders 16c and 16d are formed in a square shape in the actuator body 15. The exhaust side pistons 17a and 17b and the intake side pistons 17c and 17d are provided in the cylinders 16a, 16b, 16c and 16d, respectively. Are housed respectively. A rack 18 is formed at the tip of each of the exhaust side pistons 17a and 17b and the intake side pistons 17c and 17d.
The pinions 19 formed on the exhaust side rocker shafts 11a and 11b and the intake side rocker shafts 11c and 11d mesh with each other.

The exhaust side pistons 17a and 17b or the intake side pistons 17c and 17d reciprocate due to the hydraulic pressure of the working oil introduced to the exhaust side cylinders 16a and 16b or the intake side cylinders 16c and 16d,
By this reciprocating motion, the exhaust side rocker shafts 11a and 11b or the intake side rocker shafts 11c and 11d rotate in the arrow P direction or the O direction via the rack and pinion.

In the actuator body 15, the exhaust side low speed oil groove 20a and the exhaust side medium and high speed oil groove 2 for guiding the working oil to the exhaust side cylinders 16a and 16b are provided.
0b is formed, and working oil is further supplied to the intake side cylinder 1
An intake side low speed oil groove 20c and an intake side low speed oil groove 20d leading to 6c and 16d are formed. Further, in the actuator body 15, an exhaust side low speed port 21a is formed in communication with the exhaust side low speed oil groove 20a, and an exhaust side medium high speed port 21b is formed in communication with the exhaust side medium / high speed oil groove 20b. .. Further, in the actuator body 15, an intake side low speed port 21c is formed in communication with the intake side low speed oil groove 20c, and an intake side medium high speed port 21d is formed in communication with the intake side medium high speed oil groove 20d. ..

The exhaust side low speed oil groove 20a communicates with the tips of the exhaust side cylinders 16a and 16b, and the exhaust side medium high speed oil groove 20b communicates with the exhaust side cylinders 16a and 1b.
The base end of 6b communicates. Therefore, the exhaust side pistons 17a and 17b synchronously reciprocate due to the inflow of the working oil from the exhaust side low speed port 21a or the exhaust side medium and high speed port 21b, and the exhaust side rocker shaft 1
1a and 11b are synchronously rotated in the same direction. Also,
The intake-side low-speed oil groove 20c communicates with the leading ends of the intake-side cylinders 16c and 16d, and the intake-side medium-high speed oil groove 20d communicates with the proximal ends of the intake-side cylinders 16c and 16d. Therefore, the intake side pistons 17c and 17d synchronously reciprocate due to the inflow of operating oil from the intake side low speed port 21c or the intake side medium and high speed port 21d, and the intake side rocker shafts 11c and 1d.
1d is synchronously rotated in the same direction. In this way, the exhaust side rocker shafts 11a and 11b and the intake side rocker shafts 11c and 11d are provided so as to be independently rotatable.

The exhaust side low speed port 21a and the exhaust side medium high speed port 21b are connected to the exhaust side oil switching solenoid valve 22 shown in FIG. 2, and the flow of the oil is switched so that the working oil flows to either one. Further, the intake side low speed port 21c and the intake side medium high speed port 21d are connected to the intake side oil switching solenoid valve 23, and the flow of oil is switched so that the working oil flows to either one. The exhaust side and intake side oil solenoid valves 22 and 23 are controlled by a controller 24 based on the engine speed and the like.

That is, the controller 24 demagnetizes the electromagnets of the exhaust-side oil switching solenoid valve 22 and the intake-side oil switching solenoid valve 23 when the engine is in the low engine speed range (for example, about 8500 rpm or less) to exhaust the exhaust side. The working oil is pressure-fed to the low speed port 21a and the intake side low speed port 21c. As a result, the exhaust side pistons 17a and 17b and the intake side pistons 17c and 17d of the hydraulic actuator 13 are pushed back in the direction of arrow M in FIG. 5, and the exhaust side rocker shafts 11a and 11b and the intake side rocker shaft 11c.
And 11d both rotate in the direction of arrow O. As a result,
As shown in FIG. 3, the eccentric bush 1 of the exhaust side and intake side rocker shafts 11a, 11b, 11c and 11d.
The thick top part 12a of 2 moves diagonally forward, and the low speed cam 3 on the exhaust side and the intake side operates the low speed rocker arm 7 on the exhaust side and the intake side to drive the exhaust / intake valves 1 and 2. Therefore, the engine output at this time is as shown in FIG.
As indicated by the alternate long and short dash line A.

In addition, the controller 24 of FIG. 2 is arranged in the engine speed range (for example, about 8500 to about 10500 rp).
In m), either one of the electromagnets of the exhaust side oil switching solenoid valve 22 or the intake side oil switching solenoid valve 23, for example, the electromagnet of the exhaust side oil switching solenoid valve 22 is excited to turn on the electromagnet of the intake side oil switching solenoid valve 23. In the demagnetized state, the working oil is pressure-fed to the exhaust side medium high speed port 21b and the intake side low speed port 21c. As a result, only the exhaust side pistons 17a and 17b of FIG. 5 are retained while the intake side pistons 17c and 17d of the hydraulic actuator 13 are pushed back.
Of the intake side rocker shaft 11
With c and 11d rotated and held in the direction of arrow O,
Only the exhaust side rocker shafts 11a and 11b have an arrow P.
Is rotated in the direction. As a result, the exhaust side rocker shaft 1
Only the thick-walled top portion 12a of the eccentric bush 12 provided on 1a and 11b moves diagonally rearward as shown in FIG.
The exhaust side medium and high speed cams 4 and 5 actuate the exhaust side rocker arms 8 and 9 to drive the exhaust valves 1 and 2.
At this time, the thick-walled top portion 12a of the eccentric bush 12 provided on the intake-side rocker shafts 11c and 11d corresponds to that shown in FIG.
Since the oblique front state shown in (3) is maintained, the intake side holds the state in which the low speed cam 3 operates the low speed rocker arm 7 to drive the intake valves 1 and 2. Therefore, the engine output at this time is as shown by the broken line B in FIG.

The controller 24 of FIG. 2 further excites the electromagnets of the exhaust side oil switching solenoid valve 22 and the intake side oil switching solenoid valve 23 together in the high engine speed region (for example, about 10500 rpm or more) to exhaust the exhaust side. The working oil is pressure-fed to the medium / high speed port 21b and the intake side medium / high speed port 21d. As a result, the exhaust side pistons 17a and 17b and the intake side pistons 17c and 17d of the hydraulic actuator 13 are pushed out in the direction of the arrow N in FIG. 5, and the exhaust side rocker shafts 11a and 11b and the intake side rocker shaft 11c.
And 11d both rotate in the direction of arrow P. As a result,
As shown in FIG. 4, on the exhaust side and the intake side, the middle and high speed cams 4 and 5 actuate the middle and high speed rocker arms 8 and 9 to drive the intake and exhaust valves 1 and 2. Therefore, the engine output at this time is as shown by the solid line C in FIG.

It has been described that the controller 24 pressure-feeds the working oil to the exhaust side medium / high speed port 21b and the intake side low speed port 21c in the engine middle speed range. The working oil may be fed under pressure to the high speed port 21d to push out the intake side pistons 17c and 17d of the hydraulic actuator 13 and hold the exhaust side pistons 17a and 17b in the pushed back state. In this case, the intake side medium / high speed cams 4 and 5 actuate the intake side medium / high speed rocker arms 8 and 9 to drive the intake valves 1 and 2, and the exhaust side low speed cam 3 moves to the exhaust side low speed. The rocker arm 7 is operated to drive the exhaust valves 1 and 2. At this time also, the engine output becomes as shown by the broken line B in FIG.

As described above, the controller 24 controls the exhaust side rocker shafts 11a and 11 when switching the operation of the cam.
b and the intake side rocker shafts 11c and 11d are controlled to rotate with a time lag. Therefore, for example, when the engine is raised, first, the low speed cams 3 on the exhaust side and the intake side are both actuated, and then either the medium speed cams 4 and 5 on the exhaust side or the intake side are actuated,
The other low speed cam 3 on either the exhaust side or the intake side is actuated, and then both the exhaust side and intake side medium and high speed cams 4 and 5 are actuated. In this way, the operation switching of the cam in three stages can be performed.

According to the above embodiment, the low speed cam 3 is formed with a cam profile suitable for a low engine speed range, and the medium and high speed cams 4 and 5 are provided with a cam profile suitable for a high engine speed range. Further, the eccentric bushes 12 and 13 of the rocker shaft 11 are rotatably fitted to the medium-high speed rocker arms 8 and 9, respectively, and the low-speed rocker arm 7 is directly fitted to the rocker shaft 11, so that the rocker shaft 11 By the rotation, the contact between the low speed cam 3 and the low speed rocker arm 7 and the contact between the middle and high speed cams 4 and 5 and the middle and high speed rocker arms 8 and 9 can be selected. Cam 3
Alternatively, it can be selectively driven by the medium and high speed cams 4, 5. Therefore, it is possible to improve the output of the four-cycle engine in a wide range of engine speeds from a low engine speed range to a medium to high engine speed range.

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

Further, in the controller 24, the hydraulic actuator 13 has the exhaust side rocker shafts 11a and 11a.
Since b and the intake side rocker shafts 11c and 11d are configured to rotate with a time lag, the operation switching of the cam can be performed in three stages. As shown in FIG. 6, the output change of the engine in this case is a dashed line A in the low engine speed range, a broken line B in the middle engine speed range, and a solid line C in the high engine speed range, showing a smooth output change. .. On the other hand, when the exhaust side rocker shafts 11a and 11b and the intake side rocker shafts 11c and 11d are simultaneously rotated to switch the operation of the cam in two stages, in the engine low rotation range (for example, about 9500 rpm or less). The engine output is indicated by a one-dot chain line A and a solid line C in the middle and high engine speed range (for example, about 9500 rpm or higher). Therefore, in this embodiment, the change of the engine output due to the switching of the operation of the cam can be carried out smoothly as compared with the case of the above two-stage switching.

[0032]

As described above, according to the valve operating system for a 4-cycle engine of the present invention, the eccentric large-diameter portion is formed on the rocker shaft rotatably supported.
The medium-high speed rocker arm is fitted to this eccentric large diameter part, and the low-speed rocker arm is placed between the medium-high speed rocker arms and fitted directly to the rocker shaft. By selecting, it is possible to improve the engine output over a wide rotational speed range.

A hydraulic actuator is operatively connected to each of the exhaust side rocker shaft and the intake side rocker shaft so that the exhaust side rocker shaft and the intake side rocker shaft can be independently rotated. When switching the operation between the low speed cam and the medium and high speed cam,
Since the rocker shaft on the exhaust side and the rocker shaft on the intake side are configured to start rotating with a time lag, the engine output can be smoothly changed by switching the operation of the cam.

[Brief description of drawings]

FIG. 1 is a horizontal sectional view taken along the line II of FIG. 5, showing a hydraulic actuator in an embodiment of a valve operating system for a 4-cycle engine according to the present invention.

FIG. 2 is a perspective view showing a valve train in the embodiment of FIG.

3 is a side view showing an operating state of a low speed cam in the valve train of FIG.

FIG. 4 is a side view showing an operating state of a middle / high speed cam in the valve operating system of FIG.

5 is a vertical cross-sectional view taken along the line VV of FIG.

FIG. 6 is a graph showing engine output based on the operation of the hydraulic actuator of FIG.

[Explanation of symbols]

 1, 2 Valves 3 Low speed cam 4, 5 Medium and high speed cam 7 Low speed rocker arm 8, 9 Medium and high speed rocker arm 11 Rocker shaft 11a, 11b Exhaust side rocker shaft 11c, 11d Intake side rocker shaft 12 Eccentric bush 13 Hydraulic actuator 16a , 16b Exhaust side cylinder 16c, 16d Intake side cylinder 17a, 17b Exhaust side piston 17c, 17d Intake side piston 18 Rack 19 Pinion

Claims (1)

[Claims] 1. A low-speed rocker arm rotatably fitted to a rocker shaft and operated by a low-speed cam, and a medium-high speed cam rotatably fitted to an eccentric large-diameter portion formed on the rocker shaft. And a rocker shaft for medium and high speeds, which is operated by the above, and is operatively connected to the rocker shaft, and the hydraulic pressure of the working oil rotates the rocker shaft in the forward and reverse directions to operate the low speed cam and the middle and high speed cams. In a valve train of a 4-cycle engine having a hydraulic actuator for selectively switching, the rocker shaft is an exhaust side rocker shaft fitted with an exhaust side low speed rocker arm and an exhaust side medium high speed rocker arm for operating an exhaust valve. And the intake side low-speed rocker arm that operates the intake valve and the intake side medium-high speed rocker arm are fitted. The intake side rocker shaft, and the hydraulic actuator is operatively connected to each of the exhaust side rocker shaft and the intake side rocker shaft to form the exhaust side rocker shaft and the intake side rocker shaft. Is configured to be independently rotatable, and is configured to start the rotation of the exhaust side rocker shaft and the intake side rocker shaft with a time lag when the operation switching between the low speed cam and the medium and high speed cam is performed. A valve train for a 4-cycle engine, which is characterized in that