JPH0755284Y2 - 4-cycle engine valve drive - Google Patents

Description

[Detailed Description of the Invention] [Object of the Invention] (Industrial field of application) The present invention relates to a four-cycle engine capable of changing the lift amount of the intake / exhaust valve, the valve opening / closing timing, etc. according to the operating conditions. The present invention relates to a valve train, and more particularly to a valve train for a four-cycle engine that can efficiently replace a shim interposed between the tip ends of the first, second, and third rocker arms.

(Prior 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 operating device. That is, the valve operating device includes a camshaft that interlocks with the crankshaft of the engine, and a cam formed on the camshaft moves the intake / exhaust valve up and down at a predetermined timing.

(Problems to be solved by the invention) By the way, in the above-mentioned four-cycle engine, a high engine output can be obtained in a wide rotation speed range from a low rotation speed range to a high rotation speed range, that is, a power band is wide band. desirable.

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

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 it is interposed between the tip ends of the first, second and third rocker arms. It is an object of the present invention to provide a valve train for a four-cycle engine that can efficiently replace a shim for adjusting tappet clearance.

[Constitution of device]

(Means for Solving the Problem) In order to solve the above-mentioned problems, a valve operating system for a four-cycle engine according to the present invention includes a rocker shaft that includes an eccentric large-diameter portion and is rotatably supported. A first rocker arm directly inserted into the rocker shaft,
Second and third rocker arms arranged on both sides of the first rocker arm and fitted into the eccentric large-diameter portion, and first and second rocker arms for driving the first, second, and third rocker arms, respectively. And a third cam, wherein the second and third cams are formed to have the same cam profile and the cam profile of the first cam is formed to be different from the cam profile, and the rotation of the rocker shaft is performed. By driving, the supporting portions of the second and third rocker arms are moved and displaced to select the first cam and the second and third cams, while the rocker arms of at least one of the second and third rocker arms are selected. The support part has a hooking part formed in the upper half thereof, and the tip of the rocker arm and the hooking part are used to move in the axial direction of the rocker shaft. It is those configured to function.

(Operation) According to the valve operating system for a 4-cycle engine according to the present invention, the rocker shaft is rotated by a predetermined angle to rotate the eccentric large-diameter portion, thereby moving and displacing the support portions of the second and third rocker arms. , The cam floor surfaces of the second and third rocker arms are vertically moved relative to the cam floor surfaces of the first rocker arm.
When the cam floor surfaces of the first and third rocker arms are moved downward relative to the cam floor surfaces of the first rocker arm, the second and third rocker arms and the second and third rocker arms are moved.
The contact with the cam is released, the first rocker arm and the first cam contact, and the valve of the 4-cycle engine is
The cam adjusts the valve lift amount and the valve opening / closing timing to drive the valve.

In addition, when the cam floor surfaces of the second and third rocker arms are moved substantially upward or at the same position with respect to the cam floor surfaces of the first rocker arm, the contact between the first rocker arm and the first cam is released, and the second rocker arm is released. And the third rocker arm and the second and third cams contact each other, and
The valve of the cycle engine is operated by adjusting the valve lift amount and the valve opening / closing timing by the second and third cams. By thus selecting the cam by rotating the rocker shaft, the engine output can be improved over a wide range of rotation speeds.

Further, since the hook portion is formed in the upper half portion of the support portion on the support portion of at least one of the second and third rocker arms, the tip portions of the second and third rocker arms and the tip portion of the first rocker arm are In order to replace the shim for adjusting the tappet clearance interposed between the two, it is possible to apply a force in the axial direction of the rocker shaft to both the tip portion of the second or third rocker arm and the support portion. The second or third rocker arm can be smoothly moved in parallel with the rocker shaft.
As a result, when the second or third rocker arm is slid, the second or third rocker arm and the rocker shaft can be smoothly slid, and the shim, which is a consumable item, can be replaced efficiently. Can be carried out.

(Embodiment) An embodiment of the present invention will be described below with reference to the drawings.

FIG. 3 is a perspective view showing an embodiment of a valve operating system for a four-cycle engine according to the present invention, FIG. 1 is a partial plan view of a cylinder head to which the valve operating system of FIG. 3 is applied, and FIG. Is a cross-sectional view taken along the line I-I of FIG. 1, FIG. 4 is a plan view of the valve operating system of FIG. 3, and FIGS. 5 and 6 are operating states showing the operation of the valve operating system of FIG. It is a figure.

This valve operating device is provided on each of the intake side and the exhaust side of one cylinder of the engine. Therefore, the third
The valves 1 and 2 shown in FIGS. 6 and 2 are arranged for intake or exhaust.

In this embodiment, a low speed cam 3 as a first cam, and a middle and high speed cam 4 and a third cam as second cams respectively arranged on one side and the other side of the low speed cam 3 are used. 6 also includes a camshaft 6 (FIGS. 5, 6, and 2) having a medium-high speed cam 5, and a low-speed rocker arm as a first rocker arm located below each of the cams 3, 4, and 5. 7, medium and high speed rocker arm 8 as the second rocker arm and the same medium and high speed rocker arm 9 as the third rocker arm, and these rocker arms
Supporting portions 7a, 8a and 9a of 7, 8 and 9 are fitted and inserted, and a rocker shaft 11 rotatably supported by a bearing portion 33 (Fig. 2) is provided.

The tip of the low-speed rocker arm 7 is bifurcated, and both bifurcated tips 7b are in contact with the stem heads of the valves 1 and 2 for opening and closing the combustion chamber 27 (Fig. 2) of the engine. . Also, the supporting portion 7a of the low-speed rocker arm 7
Is rotatably provided by being directly fitted into the rocker shaft 11.

The support part 8a of the rocker arm 8 for medium and high speed is a rocker shaft.
It is rotatably fitted into the rocker shaft 11 via an eccentric bush 12 having a diameter larger than 11. This eccentric bush 12
As shown in FIG. 5, the shaft center is eccentric from the center of the rocker shaft 11 and is detachably fixed to the rocker shaft 11 by a retaining pin 10. Therefore, the eccentric bush 12 functions as an eccentric large-diameter portion of the rocker shaft 11.

As shown in FIG. 4, the supporting portion 9a of the rocker arm 9 for medium and high speeds
Is also rotatably fitted into the rocker shaft 11 via an eccentric bush 13 having the same shape as the eccentric bush 12 and eccentric in the same direction. The 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 of the rocker shaft 11.

The lower surfaces of the tip portions 8b and 9b 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 via shims 14, respectively. This shim 14 is a consumable part having a T-shaped vertical section,
The low-speed rocker arm 7 is fitted onto both branching tips 7b from above. Further, the contact points between the branch tip portion 7b of the low speed rocker arm 7 and the tip portions 8b and 9b of the medium and high speed rocker arms 8 and 9 are set substantially on the axes of the valves 1 and 2.

Therefore, as shown in FIGS. 5 and 2, 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, the tip ends of the rocker arms 8 and 9 are lowered. The parts 8b and 9b follow the branch tip part 7b by gravity and descend.

On the other hand, as shown in FIG. 6, the middle and high speed cams 4 and 5 are the cam floor surfaces 8c and 8c of the middle and high speed rocker arms 8 and 9, respectively.
When the 9c is pushed down, the tips 8b and 9b of these rocker arms 8 and 9 are moved to the low speed rocker arm 7 respectively.
By pushing down each tip branching portion 7b, the tip portion 7b is forcibly lowered.

Among the cams 3, 4, and 5, the middle-high speed cams 4,5 have the same cam profile, and the low-speed cam 3 has a cam profile different from the cam profile of the middle-high speed cams 4,5. That is, the cam profile of the low speed cam 3 is set so that the valve lift amount and the valve opening / closing timing suitable for the operation of the engine in the low speed rotation range can be obtained. Further, the cam profiles of the medium and high speed cams 4 and 5 are set so that the valve lift amount and the valve opening / closing timing suitable for the engine being operated in the medium / high speed rotation range (high speed rotation range) can be obtained. It

The valve lift amount is the stroke length of the valves 1 and 2, and matches the cam lift amount. In FIG. 7, the cam profile of the low speed cam 3 is shown by the solid line A (cam lift amount l
a), and the cam profiles of the middle and high speed cams 4 and 5 are shown by a broken line B (cam lift amount lb). As is apparent from FIG. 7, the medium speed cams 4 and 5
Has a cam profile set so that a valve lift amount larger than that of the low speed cam 3 can be obtained.

It should be noted that the chain double-dashed line C in FIG. 7 indicates that the rocker shaft 11 is rotated to position the bush thick portions 12a and 13a of the eccentric bushes 12 and 13 diagonally forward (see FIGS. 5 and 2).
The figure shows the cam profiles of the middle and high speed cams 4 and 5.

By the way, as shown in FIGS. 1 and 3, the rocker shaft 11 is rotated by a hydraulic actuator 15 which is operated by hydraulic pressure from the engine. A rack 16 is connected to a piston (not shown) of the hydraulic actuator 15, and the rack 16 is meshed with a pinion 17 formed at one end of the rocker shaft 11. Further, the hydraulic actuator 15 is provided with a low speed hydraulic port 18 and a high speed hydraulic port 19, respectively.
The hydraulic pressure from the engine is selectively led to 9.

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,
The pinion 17 is rotated in the direction of arrow O, and the eccentric bush 12
As shown in FIG. 5 and FIG. 2, the bushes 13 and 13 rotate so that the bush thick portions 12a and 13a are located diagonally forward. When the engine speed is in the middle / high speed range, the hydraulic pressure is supplied to the medium / high speed hydraulic port 19, the rack 16 is pushed out, the pinion 17 is rotated in the direction of arrow P, and the eccentric bush 12 and As shown in FIG. 6, 13 rotates so that its bush thick portions 12a and 13a are positioned diagonally rearward.

As described above, the rocker shaft 11 is configured such that the bush thick portions 12a and 13a of the eccentric bushes 12 and 13 are constantly moved from diagonally forward to diagonally rearward on the upper half side of the rocker shaft 11 by the operation of the hydraulic actuators 15, 16 and 17. It is configured to rotate the range. By the rotation of the rocker shaft 11, the supporting portions of the high speed rocker arms 8 and 9 are moved and displaced relative to the low speed rocker arm 7.

The rocker shaft 11, the hydraulic actuator 15 and the like as described above are provided in the cylinder head 21 shown in FIGS. 1 and 2.
Is located in. Rocker shaft 11 is cylinder head 21
The front and rear and right and left of the vehicle are provided with a total of four and extend in the left and right direction of the vehicle. These rocker shafts
A lower half bearing hole 22 that supports the camshaft 6 is formed above the portion 11. Further, a valve guide 23 is arranged near the lower half bearing hole 22 and a stud bolt insertion hole 24 is formed. Further, a mating surface 25 with the head cover is formed at the upper part of the cylinder head 21, and a cam chain chamber 26 is formed at the center position of the cylinder head 21 in the vehicle left-right direction.

A combustion chamber 27 is formed under the cylinder head 21 as shown in FIG. 2, and an intake port 28 and an exhaust port 29 are formed in communication with the combustion chamber 27. The valve faces of the valves 1 and 2 are arranged at the boundary between the combustion chamber 27 and the intake port 28 and the exhaust port 29. The intake port 28 and the exhaust port 29 are opened and closed by the action of the valve spring 20, the low speed rocker arm 7, and the medium and high speed rocker arms 8 and 9.

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 as shown in FIG. 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 30 interposed in the rocker shaft 11.

Now, of the rocker arms 7, 8 and 9 of each set, the support portions 8a and 9a of the rocker arms 8 and 9 for medium and high speeds which come into contact with the positioning spring 30 have hook holes 31 as hook portions in the upper half thereof. Is drilled. In addition, the mating surface 25 of the cylinder head 21
A groove 32 is formed at a position facing the hook hole 31. The hook hole 31 is a portion where the tip of the needle-shaped tool 33 is hooked when the low speed rocker arm 7 and the medium and high speed rocker arms 8 and 9 are slid along the rocker shaft 11. Further, at this time, the groove portion 32 functions as a fulcrum that supports an arbitrary portion in the longitudinal direction of the slide tool 33 in order to apply the lever principle.

Next, the function and effect will be described.

When the rocker shaft 11 is rotated in the direction of arrow O by the operation of the hydraulic cylinder 15 when the engine is in the low speed range, the bush thick portions 12a and 13a of the eccentric bushes 12 and 13 are located diagonally forward. (FIG. 5, FIG. 1 and FIG. 2). As a result, the rocker arm 8 for medium and high speed
The cam floor surfaces 8c and 9c of 9 and 9 move downward relative to the cam floor surface 7c of the low speed rocker arm 7.
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 are Spins idle.

At this time, the low-speed rocker arm 7 is constantly pushed upward by the urging force of the valve spring 20 about the axis of the rocker shaft 11, so that the cam floor surface 7c of the low-speed rocker arm 7 contacts the peripheral surface of the low-speed cam 3. Contact. Therefore, when the camshaft 6 rotates, the valves 1 and 2 move 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 fuel chamber while ensuring the valve lift amount and the valve opening / closing timing suitable for the low engine speed range.

On the other hand, when the engine is in the middle / high speed range, the rocker shaft 11 is moved by the operation of the hydraulic actuator 15 so that the arrow P
When rotated in the direction, the bush thick portions 12a and 13a of the eccentric bushes 12 and 13 are located diagonally rearward (Fig. 6). As a result, medium and high speed rocker arms 8 and 9
Cam floor surfaces 8c and 9c of the low-speed rocker arm 7 move relatively upward or to the same position relative to the cam floor surface 7c of the low-speed rocker arm 7, and the cam floor surfaces 8c and 9c respectively contact the peripheral surfaces of the middle- and high-speed cams 4 and 5. Contact.

Here, as shown in FIG. 7, since the cam lift amount of the medium speed cams 4 and 5 is larger than that of the low speed cam 3, the cam shaft 6 is rotated under the condition shown in FIG. In this case, the low speed cam 3 runs idle, while the medium and high speed cams 4 and 5 are driven by the medium and high speed rocker arms 8 and 9, respectively, based on the lift characteristic B of FIG.
And 2 are driven. As a result, valves 1 and 2 are
The combustion chamber is opened and closed while ensuring the valve lift amount and valve opening / closing timing that are suitable for the medium / high engine speed range.

According to the above-mentioned embodiment, the cam profile suitable for the low engine speed range of the engine 3 is formed on the low speed cam 3, and the cam profile suitable for the medium and high engine speed ranges 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.
The rotation of can select contact between the low speed cam 3 and the low speed rocker arm 7 and contact between the middle and high speed cams 4 and 5 and the middle and high speed rocker arms 8 and 9, respectively. Low speed cam 3 or medium and high speed cam 4,
It can be driven selectively with 5. Therefore,
It is possible to improve the output of the 4-cycle engine in a wide range of engine speeds from a low engine speed range to a high engine speed range.

Further, the low speed cam 3 and the medium and high speed cams 4 and 5 are selected with the eccentric bushes 12 and 13 which are eccentric large diameter parts.
Since the relative movement displacement of the middle and high speed cams 4 and 5 is caused by the rotation of, the selection of the cams is smoothly performed when the cams 3 and 4 are selected, and a large stress does not occur in each part. Therefore, the cams 3, 4, 5 can be smoothly selected.

Further, since the shim 14 interposed between the tip portions 8b and 9b of the medium- and high-speed rocker arms 8 and 9 and the tip branch portion 7b of the low-speed rocker arm 7 is a consumable part, the shim 14 is replaced. When adjusting the tappet clearance by exchanging, first grip the tip portions 8b, 9b of the rocker arms for medium and high speeds 8 and 9 in which the hook holes 31 are formed with pliers (not shown), and, on the other hand, The tip of the slide tool 33 is fitted into the hook hole 31. Next, in this state, the pliers and the slide tool 33 are used to slide the medium and high speed rocker arms 8 and 9 parallel to the axial direction of the rocker shaft 11. At this time, slide the slide tool 33 to the cylinder head at any one position in the longitudinal direction.
It is also possible to support the groove portions 32 of 21 and to use the lever portion 32 as a fulcrum to generate a large force using the slide tool 33 to slide the medium and high speed rocker arms 8 and 9. In this way, the middle and high speed rocker arms 8 and 9 are slid in the axial direction of the rocker shaft 11 to be separated from the low speed rocker arm 7, and the shim 14 mounted on the branch tip 7b of the low speed rocker arm 7 is smoothly exposed. The shim 14 can be replaced smoothly and smoothly.

In this way, when replacing the shim 14, rocker arms for medium and high speed 8,
Since force can be applied to both the support parts 8a, 9a and the tip parts 8b, 9b of 9, the rocker arms 8 and 9 for medium and high speed are connected to the rocker shaft 1
It can be slid smoothly in the axial direction of 1. As a result, when the medium- and high-speed rocker arms 8 and 9 are slid, no tightness occurs between the medium- and high-speed rocker arms 8 and 9 and the rocker shaft 11, and the shim 14 can be replaced efficiently and efficiently.

Further, since the groove 32 is formed on the mating surface 25 of the cylinder head 21 and the groove 32 functions as a fulcrum of the lever, the slide tool 33 supports the supporting portions 8a of the rocker arms 8 and 9 for medium and high speeds.
You can exert great power on 9a. Therefore, the medium- and high-speed rocker arms 8 and 9 can be quickly slid, and the replacement work of the shim 14 can be performed in a short time.

Further, when the hook holes 31 of the medium- and high-speed rocker arms 8 and 9 are used as through holes, the lubricating oil that has flowed down from above the rocker arms 8 and 9 passes through the hook holes 31 and the rocker arms 8 and 9 for medium and high speed rockers. Since it flows into the space between the shaft 11 and the shaft 11, the lubricating performance of the rocker arms 8 and 9 for medium and high speeds can be improved.

In the embodiment described above, the cam profile of the middle and high speed cams 4 and 5 is shown by the broken line B in FIG. 7, but the cam profile of the middle and high speed cams 4 and 5 is shown in FIG. Broken line B'or broken line B "in FIG.
As shown in (1), the lift of the valves 1 and 2 may be changed at the time of middle and high rotation of the engine.

In the above embodiment, the case where the hydraulic cylinder 15 is used as the rotation drive source of the rocker shaft 11 has been described.
A motor may be used as the rotational drive source, and the rocker shaft 11 may be rotationally driven by a power transmission means such as a pulley and a belt.

Although it has been described that the supporting holes 8a and 9a of the medium- and high-speed rocker arms 8 and 9 have the locking holes 31 as the locking portions, these may be used as the locking projections.

[Effect of device]

As described above, according to the four-cycle engine valve operating system of the present invention, the eccentric large-diameter portion is formed on the rocker shaft rotatably supported.
The rocker arm is fitted into the eccentric large-diameter portion, and the first rocker arm is disposed between the second and third rocker arms and directly fitted into the rocker shaft. The support portion of the third rocker arm can be moved and displaced relative to the support portion of the first rocker arm, and the first cam and the second and third cams can be selected.
By selecting this cam, it is possible to improve the engine output over a wide rotational speed range.

Further, since the upper half of the supporting portion of at least one of the second and third rocker arms has the hooking portion, the slide tool is fitted into the hooking portion when the shim is replaced, and the second portion is formed. Also, a force can be applied to the support portion of the third rocker arm, and the second and third rocker arms can be smoothly slid in the axial direction of the rocker shaft by operating both the support portion and the tip portion. Since the shim attached to the branch tip of the first rocker arm can be exposed, the shim replacement work can be performed in a short time.

[Brief description of drawings]

1 is a partial plan view of a cylinder head to which the valve operating system of FIG. 3 is applied, FIG. 2 is a sectional view taken along line II-II of FIG. 1, and FIG. 3 is a four-cycle engine according to the present invention. FIG. 4 is a perspective view showing an embodiment of the valve operating system of FIG. 4, FIG. 4 is a plan view of the valve operating system of FIG. 3, and FIGS. 5 and 6 are operation state diagrams showing the operation of the valve operating system of FIG. FIG. 7 is a diagram showing a cam profile of the cam shown in FIG. 3, and FIGS. 8 and 9 are diagrams showing respective modified examples of the cam profile shown in FIG. 7. 1,2 …… Valve, 3 …… Low speed cam, 4,5 …… Medium and high speed cam, 7 …… Low speed rocker arm, 7a …… Low speed rocker arm support, 8,9 …… Medium and high speed rocker arm , 11 ……
Rocker shaft, 12,13 ... Eccentric bush, 21 ... Cylinder head, 25 ... Cylinder head mating surface, 30 ... Positioning spring, 31 ... Latching part (latching hole), 32 ... Groove part, A …… Cam profile for low speed cam, B …… Cam profile for medium and high speed cam.

Claims (1)

[Scope of utility model registration request] 1. A rocker shaft rotatably supported by an eccentric large-diameter portion, a first rocker arm directly inserted into the rocker shaft, and arranged on both sides of the first rocker arm. The second and third rocker arms fitted and inserted into the eccentric large diameter portion, and the first, second and third cams for driving the first, second and third rocker arms, respectively. The second and third cams are formed in the same cam profile, and the cam profile of the first cam is formed so as to be different from the above-mentioned cam profile, and the rotation of the rocker shaft causes the supporting portions of the second and third rocker arms to move. While moving and displacing, the cam selection between the first cam and the second and third cams is performed, while at least the second and third rocker arms are selected. The supporting portion of the other rocker arm is formed with a hooking portion in the upper half portion thereof, and the tip end portion and the hooking portion of the rocker arm are configured to be movable in the axial direction of the rocker shaft. Valve drive for 4-cycle engine.