JPH0559923A - Valve system of four cycle engine - Google Patents

Abstract

PURPOSE:To switch operation of a cam surely by arranging an pressure increasing device for increasing oil pressure of operation oil in an intermediate and high speed oil passage, and arranging an one way valve for allowing flow of operation oil which flows from an oil switching valve toward a hydraulic actuator. CONSTITUTION:A pressure increasing device 35 for increasing oil pressure of operation oil is arranged in an intermediate and high speed oil passage 30 for connecting a hydraulic actuator 15 to an oil switching valve 16. A one way valve 36 is arranged so as to allow flow of operation oil which flows from the oil switching valve 16 toward the hydraulic actuator 15 bypassing the pressure increasing device 35. Operation oil of high pressure is generated by the pressure increasing device 35, and rocker shaft turning effort which exceeds a rocker shaft turning demand torque is generated by operation oil of high pressure when the hydraulic actuator 15 passes the change point of an excentric large diameter part.

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, which can change the valve lift of the intake / exhaust valve, the valve opening timing, etc. according to the operating conditions.
In particular, the present invention relates to a valve operating system for a four-cycle engine that surely switches the operation from a low speed cam to a medium / high speed cam without increasing the size of an oil pump or a hydraulic actuator.

[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 rotation speed range, and at the same time, increase the size of the oil pump or the hydraulic actuator without increasing the size of the oil pump or the hydraulic actuator. It is an object of the present invention to provide a valve operating system for a 4-cycle engine capable of reliably switching the operation from a cam to a medium-high speed cam.

[0006]

SUMMARY OF THE INVENTION According to the present invention, there is provided a low speed rocker arm which is directly fitted to a rocker shaft and operated by a low speed cam, and a medium and high speed cam which is fitted to an eccentric large diameter portion of the rocker shaft. A medium-to-high speed rocker arm, a hydraulic actuator operatively connected to the rocker shaft to rotate the rocker shaft in the forward and reverse directions by the hydraulic pressure of the working oil, and a low-speed oil passage and an intermediate actuator to the hydraulic actuator. An oil switching valve that is connected through a high-speed oil passage and selectively switches the flow of the working oil to one of these oil passages, and both tip ends of the low-speed and middle-high speed rocker arms. Are stacked on the extension of the intake / exhaust valve axis, and the operating valve is installed in the middle / high speed oil passage. And a one-way valve that allows the flow of the working oil from the oil switching valve to the hydraulic actuator by bypassing the pressure increasing device. It is what

[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 pressure booster is arranged in the medium-high speed oil passage, when the oil switching valve for switching the operation of the cam from the low-speed cam to the medium-high speed cam is operated, a high pressure is increased by the pressure booster. The hydraulic oil can be supplied to the hydraulic actuator, and the rocker shaft can rotate normally. In general,
When the rocker shaft is rotated in the forward direction to switch the operation of the cam from the low speed cam to the medium and high speed cam, it passes the eccentric large-diameter point, so the required torque for the rocker shaft requires a large value when passing through it. And According to the present invention, when the operation is switched from the low-speed cam to the medium-high speed cam, the pressure booster supplies high-pressure operating oil to the hydraulic actuator. Therefore, the high-pressure operating oil causes the hydraulic actuator to rotate the rocker shaft with a large value. A rocking force that satisfies the required torque is generated, and the rocker shaft can be reliably rotated in the forward direction. As a result, the operation switching from the low speed cam to the medium high speed cam can be reliably performed without increasing the size of the oil pump or the hydraulic actuator.

[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 operating system for a 4-cycle engine according to the first 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 cam shaft 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.
1, a hydraulic actuator 15 for rotating 1 and an oil switching solenoid valve 16 (FIG. 1) for switching the flow of operating oil supplied to the hydraulic actuator 15.

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 capped cylindrical shim 14b, 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. In other words, the cam profile of the low speed cam 3 is set so that the valve lift amount and the opening / closing valve timing suitable for when the engine is operating in the low rotation speed range are obtained.
Further, the cam profiles of the medium- and high-speed cams 4 and 5 are set so that a suitable valve lift amount and opening / closing valve timing can be obtained when the engine is operated in the medium / high speed range.

As shown in FIGS. 2 and 1, the hydraulic actuator 15 uses engine oil as working oil and has an actuator body 17. This actuator body 17 has 2
One cylinder 18 is provided side by side, and each of these cylinders 18
The piston 19 is arranged opposite to the. Further, in the actuator body 17, a medium / high speed oil groove 21 is formed in communication with the center of each cylinder 18 in the axial direction, and low speed oil grooves 20 are formed in communication with both ends of each cylinder 18. Further, a rack 22 is integrally formed at the tip of the piston 19, and the rack 22 meshes with a pinion 23 formed at the end of the rocker shaft 11. Such a hydraulic actuator 15 guides the working oil into the cylinder 18 through the low speed oil groove 20 or the medium and high speed oil groove 21 and reciprocates the piston 19, thereby moving the rocker shaft 1 through the rack 22 and the pinion 23.
1 is rotated in the P direction (forward direction) or the O direction (reverse direction).

On the other hand, the oil switching solenoid valve 1
6 is a low speed hydraulic pipe 28 as a low speed oil passage.
And, it is connected to the hydraulic actuator 15 through a medium-high speed hydraulic pipe 30 serving as a medium-high speed oil passage.
The oil switching solenoid valve 16 has a valve body 24.
A spool valve 25 is disposed inside, and the spool valve 25 is slid by exciting and demagnetizing an electromagnet 26. In the valve body 24, an oil supply port 27 into which engine oil flows, a low speed oil supply port 29 communicating with the low speed oil groove 20 of the hydraulic actuator 15 via a low speed hydraulic pipe 28, and a medium / high speed pipe 30.
After passing through the hydraulic actuator 15, the medium speed oil groove 21
And a relief port 32 that communicates with an oil pan (not shown) and the like. Further, the excitation and demagnetization of the electromagnet 26 is controlled by the controller 33 interrupting the current flowing to the solenoid 34 of the electromagnet 26 based on the engine speed or the like.

The middle-high speed oil pipe 30 is branched into two first middle-high speed oil pipes 30a and second middle-high speed oil pipes 30b on the way. The first medium speed oil pipe 30a has a medium speed oil pipe 3
Pressure increasing device 35 for increasing the oil pressure of the working oil flowing in 0
And a one-way valve 36 is provided in the second medium-high speed oil pipe 30b. This one way valve 3
Reference numeral 6 allows the flow of the working oil from the medium / high speed oil supply port 31 of the oil switching solenoid valve 16 to the medium / high speed oil groove 21 of the hydraulic actuator 15, and blocks the flow in the opposite direction.

The pressure boosting device 35, as shown in FIG.
A large diameter cylinder 38 and a small diameter cylinder 3 are attached to the device body 37.
9 are formed in communication with each other, a large diameter piston 40 is accommodated in the large diameter cylinder 38, and a small diameter piston 41 is accommodated in the small diameter cylinder 39. The device body 37 further includes an oil inflow port 42 and an oil return port 4
3 is formed in communication with the large diameter cylinder 38, and the oil discharge port 44 is formed in communication with the small diameter cylinder 39. Here, the large-diameter piston 40 and the small-diameter piston 41
Are integrally formed. A return spring 45 is interposed between the large diameter piston 40 and the side wall of the large diameter cylinder 38.

The area of the large-diameter piston 40 is A ₁ , the area of the small-diameter piston 41 is A _2, and the working oil of hydraulic pressure P ₁ flows from the oil inflow port 42 into the large-diameter cylinder 38.
It is assumed that hydraulic oil having a hydraulic pressure P ₂ is discharged from the oil discharge port 44. Large diameter piston 40 and small diameter piston 4
If the force acting on 1 is F, then F = P ₁ A ₁ = P ₂ A ₂ and therefore P ₂ = (A ₁ / A ₂ ) P ₁ . Here, since A ₁ > A ₂ , the hydraulic pressure of the working oil is increased by the pressure increasing device 35.

Generally, when the rocker shaft 11 is rotated to switch the operation of the low speed cam 3 to the operation of the middle and high speed cams 4 and 5, when the eccentric bush 12 passes through the thought point, As indicated by the solid line A in FIG. 6, the rocker shaft rotation request torque is significantly increased. On the other hand, after switching to the medium- and high-speed cams 4 and 5, the rocker shaft rotation required torque for the rocker shaft 11 to hold the operating position of the medium- and high-speed cams 4 and 5 becomes small. Here, the solid line A in FIG. 6 is the rocker shaft rotation request torque at the time of cam switching from the low speed cam to the medium high speed cam, and the solid line B is at the time of cam switching from the medium high speed cam to the low speed cam. The required rocker shaft rotation torque is shown. Further, in FIG. 6, the rocker shaft rotation angle 0 ° indicates the rocker shaft rotation angle when the low speed cam 3 is operating, and the rocker shaft rotation angle 140 ° is the rocker shaft rotation angle when the middle and high speed cams 4 and 5 are operating. Indicates.

In the pressure booster 35 shown in FIG. 1, the oil switching solenoid valve 16 controls the flow of working oil to the oil supply port 2.
It operates immediately after switching from 7 to the middle- and high-speed oil supply port 31, and the large-diameter piston 40 and the small-diameter piston 41 are operated.
Slides to generate high pressure. At this time, the one-way valve 36 is closed. By the operation of the pressure booster 35 and the one-way valve 36, the hydraulic actuator 15 generates a rotational force in the P direction that overcomes the rocker shaft rotation request torque required when the eccentric bush 12 passes through the ideal point.

After the switching to the medium- and high-speed cams 4 and 5, the hydraulic oil in the hydraulic oil from the pressure increasing device 35 decreases due to leakage of the hydraulic oil in the hydraulic actuator 15 and the pressure increasing device 35, and the one-way valve. The valve 36 is opened. Therefore, after the switching to the medium and high speed cams 4 and 5 is completed, the working oil flows from the medium and high speed oil supply port 31 of the oil switching solenoid valve 16 through the one-way valve 36 into the medium and high speed oil groove 21 of the hydraulic actuator 15. The hydraulic actuator 15 holds the rotation stop position of the rocker shaft 11 in which the operating state of the middle and high speed cams 4 and 5 is ensured by the supplied and supplied normal oil pressure by an oil pump (not shown).

Next, the operation will be described.

When the controller 33 turns off the solenoid 34 of the electromagnet 26 and demagnetizes the electromagnet 26, the spool valve 25 is moved from the position shown in FIG. And the low speed oil supply port 29 communicate with each other, and the middle and high speed oil supply port 31 is the relief port 32.
Communicate with. Further, since the large-diameter piston 40 and the small-diameter piston 41 of the pressure booster 35 are in the stored state by the action of the return spring 45, the oil return port 43 and the oil discharge port 44 communicate with each other. Therefore, the working oil is supplied from the oil supply port 27 to the low speed oil supply port 29,
At the same time as being introduced into the low speed oil groove 20 of the hydraulic actuator 15 via the low speed hydraulic pipe 28, the working oil in the cylinder 18 of the hydraulic actuator 15 passes through the medium / high speed oil groove 21 and then the oil of the pressure booster 35. From the discharge port 44 to the oil return port 43, the oil is returned to the oil pan. Therefore, the piston 19 of the hydraulic actuator 15 is pushed back in the direction of the arrow M shown in FIG. 1, and the pinion 23 rotates in the direction of the arrow O, which causes the thick top 12a of the eccentric bush 12 to move, as shown in FIG. When moving diagonally forward, the low speed cam 3 moves to the low speed rocker arm 7
Is operated to drive the valves 1 and 2.

When the controller 33 turns on the solenoid 34 of the electromagnet 26 to excite the electromagnet 26,
The spool valve 25 moves to the position shown in FIG. 1, and as a result, the refueling port 27 and the medium / high speed refueling port 31 communicate with each other, and the low speed refueling port 29 and the relief port 32 communicate with each other. At this time, the working oil in the medium-high speed oil pipe 30 flows to the pressure increasing device 35 through the first middle-high speed oil pipe 30a, and the pressure increasing device 35 operates to generate high-pressure working oil. 35 is discharged from the discharge port 44. At the same time as the one-way valve 36 is closed by the hydraulic pressure of this hydraulic oil, high-pressure hydraulic oil is supplied to the medium- and high-speed oil groove 21 of the hydraulic actuator 15. Further, the working oil in the cylinder 18 of the hydraulic actuator 15 is returned to the oil pan from the relief port 32 via the low speed oil pipe 28, the low speed oil supply port 29. For these reasons, the piston 19 of the hydraulic actuator 15 is pushed out in the direction of arrow N shown in FIG. 1, the pinion 23 rotates in the direction of arrow P, and the rocker shaft 11 rotates when the rocker shaft 11 passes through the eccentric bush 12. Rotate by overcoming the required torque. As a result, as shown in FIG. 4, the thick-walled top portion 12a of the eccentric bush 12 moves obliquely rearward, and the middle and high speed cams 4 and 5 actuate the middle and high speed rocker arms 8 and 9 to operate the valves 1 and 2. To drive.

After switching the operation to the medium- and high-speed rocker arms 4 and 5, the hydraulic actuator 15 and the pressure increasing device 35.
The hydraulic pressure of the working oil discharged from the pressure booster 35 is reduced due to leakage of the working oil from the valve, and the one-way valve 36 is opened. Therefore, the working oil flowing to the medium / high speed oil supply port 31 is guided to the medium / high speed oil groove 21 of the hydraulic actuator 15 via the one-way valve 36,
The rocker shaft 11 is held in the operating position of the middle and high speed cams 4 and 5 via the rack 22 and the pinion 23. As a result, the valves 1 and 2 are continuously operated by the medium and high speed cams 4 and 5.

According to the above embodiment, the low speed cam 3 is formed with a cam profile suitable for the low engine speed range, and the middle and high speed cams 4 and 5 are provided with the cam profile suitable for the medium and high engine speed range. The rocker arms 8 and 9 for medium and high speed are rotatably fitted to the eccentric bushes 12 and 13 of the rocker shaft 11, respectively.
The rocker shaft 11 is directly fitted with the low-speed rocker arm 7, and when the rocker shaft 11 rotates, the low-speed cam 3 and the low-speed rocker arm 7 come into contact with each other, and the medium-high speed cams 4 and 5 and the medium-high speed rocker arm 8 Since it is possible to select the contact with each of the valves 9 and 9, the valves 1 and 2 can be selectively driven by the low speed cam 3 or the medium and high speed cams 4 and 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.

Since the low speed cam 3 and the medium and high speed cams 4 and 5 are selected by the rotation of the eccentric bush 12, no great stress is generated in each part when the cams 3, 4 and 5 are selected. .. Therefore, the cams 3, 4, 5 can be smoothly selected.

In general, the rocker shaft 11 is shown in FIG.
When the cam operation is switched from the low speed cam 3 to the middle and high speed cams 4 and 5 by rotating in the direction of arrow P in FIG. It requires a large value when passing through. In the present invention, the first medium-speed oil pipe 30
Since the pressure booster 35 is disposed in a, when the oil switching solenoid valve 16 that switches the operation of the cam from the low speed cam 3 to the middle and high speed cams 4 and 5, is operated by the pressure booster 35. Oil can be supplied to the hydraulic actuator 15. Therefore, this high-pressure hydraulic oil causes the hydraulic actuator to generate a rotational force that satisfies the above-described large value of the rocker shaft rotation request torque, so that the rocker shaft 11 can be reliably rotated in the forward direction. As a result, the oil pump (not shown) and the hydraulic actuator 1
The operation switching from the low speed cam 3 to the medium and high speed cams 4 and 5 can be reliably performed without increasing the size of the cam 5.

Further, since it is not necessary for the pressure booster 35 to instantaneously supply high-pressure working oil to increase the size of the oil pump or the hydraulic actuator 15, mechanical loss is reduced as compared with the case where the oil pump is increased in size. Since the hydraulic actuator 15 can be reduced in size and the size thereof can be reduced, the degree of freedom in the mounting position of the hydraulic actuator can be increased.

[0035]

As described above, according to the valve operating system for a four-cycle engine of the present invention, the medium- and high-speed oil passages connecting the hydraulic actuator and the oil switching valve are provided with:
Since the pressure increasing device for increasing the hydraulic pressure of the working oil is provided, and the one-way valve that bypasses the pressure increasing device and allows the flow of the working oil from the oil switching valve to the hydraulic actuator is installed. , The pressure booster generates high-pressure working oil, and the high-pressure working oil causes the hydraulic actuator to generate a rocker shaft rotation force that exceeds the rocker shaft rotation required torque when the eccentric large-diameter portion passes through the consideration point.
It is possible to reliably switch the operation from the low speed cam to the medium and high speed cam without increasing the size of the oil pump or the hydraulic actuator.

[Brief description of drawings]

FIG. 1 is a cross-sectional view showing an oil switching valve, a hydraulic actuator, a pressure increasing device, and the like 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 of 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 an enlarged sectional view showing the pressure booster of FIG. 1. FIG.

FIG. 6 is a graph showing a relationship between a rocker shaft rotation request torque and a rocker shaft rotation angle.

[Explanation of symbols]

 1, 2 valve 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 12 eccentric bush 15 hydraulic actuator 16 oil switching solenoid valve 28 low speed oil pipe 30 medium and high speed oil Pipe 35 Pressure booster 36 One way valve

Claims (1)

[Claims] 1. A low-speed rocker arm directly fitted to a rocker shaft and operated by a low-speed cam, and a medium-high speed rocker arm fitted to an eccentric large-diameter portion of the rocker shaft and operated by a medium-high speed cam. And a hydraulic actuator that is operatively connected to the rocker shaft and rotates the rocker shaft in the forward and reverse directions by the hydraulic pressure of the working oil, and is connected to the hydraulic actuator through a low speed oil passage and a medium and high speed oil passage. And an oil switching valve that selectively switches the flow of the working oil to one of these oil passages, and both tip portions of the low-speed and middle-high speed rocker arms are sucked and sucked.
A pressure booster for increasing the hydraulic pressure of the working oil is arranged in the middle and high speed oil passages so as to be superposed on the extension of the axis of the exhaust valve, and bypasses the pressure booster. And a one-way valve that allows the flow of working oil from the oil switching valve to the hydraulic actuator.