JP3446418B2 - Engine valve gear - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an improvement in a valve operating system for an engine.

[0002]

2. Description of the Related Art When an engine rotates at 6000 rpm, intake / exhaust valves open and close 50 times per second, so deformation of parts such as rocker arms that reciprocate following a cam is avoided. As the deformation of the rocker arm is large, the intake / exhaust valve cannot perform an accurate opening / closing operation according to the shape of the cam surface.

As a conventional engine valve operating device, for example, as disclosed in Japanese Patent Laid-Open No. 59-103907, a rocker arm driven by rotation of a cam swings around a pivot as a fulcrum to expand and contract a valve spring. There is a structure that opens and closes the intake / exhaust valve while doing so.

The valve lift characteristic of the cam used in this type of valve operating device is set to have a symmetrical shape at the start of the valve lift and at the end of the valve lift.

When the valve opens and closes via the rocker arm that follows the rotation of the cam, positive acceleration that accelerates in the valve opening direction acts at the beginning of the valve lift and at the end of the valve lift. When the contrast valve lift characteristic is set at the end of the valve lift, the maximum value of the positive acceleration at the start of the valve lift is equal to the maximum value of the positive acceleration at the end of the valve lift.

[0006]

With the rotation of the cam, the force point at which the cam surface is in contact with the rocker arm moves on the rocker arm, but this force point and the point of action at which the rocker arm swings or contacts the valve of the rocker arm. The greater the distance is, the less rigid the rocker arm.

The rocker arm is deformed according to the positive acceleration acting on the valve, but the amount of deformation of the rocker arm by the cam is
The force point of the cam surface in contact with the rocker arm increases as the distance from the rocking fulcrum of the rocker arm or the point of action in contact with the valve of the rocker arm increases.

However, in the conventional cam in which the maximum value of the positive acceleration at the start of the valve lift and the maximum value of the positive acceleration at the end of the valve lift are set to be equal, the force point contacting the rocker arm on the cam surface is set. When the rocker arm moves from a portion with low rigidity to a portion with high rigidity, the amount of deformation of the rocker arm by the cam is larger at the start of the valve lift than at the end of the valve lift. As a result, the rocker arm and the exhaust valve cannot follow the movement of the cam due to the deformation of the rocker arm that occurs when the valve lift starts.
Illegal movements such as so-called jumps occur. As shown by the broken line in FIG. 5, this jump amount sharply increases in the high speed range, and therefore the maximum engine speed may be restricted by the improper movement occurring at the start of the valve lift.

SUMMARY OF THE INVENTION It is an object of the present invention to solve the above-mentioned problems and achieve both accurate opening / closing operation of the intake / exhaust valve and expansion of the valve lift time area.

[0010]

According to a first aspect of the present invention, there is provided a valve operating system for an engine, wherein a cam that rotates in synchronization with engine rotation, a valve spring that biases the valve in a valve closing direction, and a cam follow the cam. In an engine including a rocker arm that opens and closes to open and close the valve against the valve spring by swinging, the maximum value Amax of the valve positive acceleration that occurs at the beginning of valve lift and the positive acceleration of the valve that occurs at the end of valve lift. Among the maximum values Bmax, the one that minimizes the distance to the rocking arm fulcrum of the rocker arm or the point of action of the rocker arm that contacts the valve at the time of occurrence is set to be large.

A valve operating system for an engine according to a second aspect is
It rotates in synchronism with the engine rotation, and has low and high profile cams with different sizes. A main rocker arm that opens and closes the valve against the valve spring by swinging following the low speed cam is in contact with the valve. no site, and sub-rocker arm that swings with respect to the main rocker arm by following a high-speed cam having a larger profile than the low-speed cam, menu according to the engine operating condition
And a prop for locking the relative displacement of the sub-rocker arm with respect to the in-locker arm, the maximum value Ama of the positive acceleration of the valve generated at the start of the valve lift Ama.
x and the maximum value Bmax of the positive acceleration of the valve that occurs at the end of the valve lift, the distance from the swing point of the sub-rocker arm to the point of contact with the sub-rocker arm of the cam surface when that occurs or the point of action that touches the prop of the sub-rocker arm Set the smallest one to a large value.

[0012]

In the engine valve operating system according to the first aspect of the present invention, the rocker arm swings following the rotation of the cam when the engine is operating, and the rocker arm absorbs air while expanding and contracting the valve spring.
Open and close the exhaust valve.

When the valve opens and closes via the rocker arm that follows the rotation of the cam, positive acceleration that accelerates the valve opening direction acts at the beginning of the valve lift and at the end of the valve lift to maximize the valve lift. Negative acceleration that accelerates in the direction of closing the valve works in the vicinity.

The rocker arm can be considered as a beam supported at two points, that is, its swinging fulcrum and the point of action in contact with the valve.
Therefore, as the cam rotates, the force point at which the cam surface contacts the rocker arm moves on the rocker arm, and the rigidity of the rocker arm decreases as the force point moves away from the swing fulcrum or the action point.

According to the present invention, the maximum value of the positive acceleration generated when the cam surface slides on a portion of the rocker arm having low rigidity is set to a relatively small value, thereby reducing the deformation of the rocker arm and causing a jump or bounce of the valve. It suppresses the illegal movement of the engine and suppresses the limitation of the maximum engine speed by the irregular movement.

Further, by setting the maximum value of the positive acceleration generated when the cam surface is brought into sliding contact with the highly rigid portion of the rocker arm to a relatively large value, the time area in which the valve is open is increased, and the intake / exhaust efficiency is increased. Can be improved.

In a valve operating system for an engine according to a second aspect of the present invention, the valve is a low speed cam during the operation in which the prop does not lock the swing of the sub-rocker arm with respect to the rocker arm, and the main rocker and the sub-rocker arm swing independently. The opening angle or the lift amount of the valve is reduced by opening / closing according to the profile. At this time, although the sub-rocker arm is swung by the high speed cam, the prop is held in the non-locking position where it does not engage with the sub-rocker arm, so that the movement of the main rocker arm is not hindered. Rocking of the rocker arm is engaged via a prop for the main lock <br/> Kaamu, the main rocker arm and rocker arm during the operation of swing together, the valve is driven to open and close according to profile of the high-speed cam, The valve opening angle or lift amount becomes large. When the valve opens and closes via the sub-rocker arm that follows the rotation of the high-speed cam, a positive acceleration that accelerates in the valve opening direction at the beginning of the valve lift and at the end of the valve lift acts, and the valve lift becomes the maximum. Negative acceleration acts to accelerate the valve in the direction of closing.

With the rotation of the high-speed cam, the force point at which the cam surface contacts the sub-rocker arm moves on the sub-rocker arm, but the distance from this power point to the swing fulcrum of the sub-rocker arm or the point of action in contact with the valve of the sub-rocker arm. The shorter the rocker arm, the higher the rigidity.

According to the present invention, the maximum value of the positive acceleration generated when the cam surface slides on the low-rigidity portion of the sub-rocker arm is set to be relatively small, so that the deformation of the sub-rocker arm is reduced and the valve jump or It suppresses the occurrence of illegal movement such as bounce, and suppresses the limitation of the maximum engine speed by this irregular movement.

Further, by reducing the deformation of the sub-rocker arm at the start of the valve lift or at the end of the valve lift, the prop is evenly contacted with the sub-rocker arm, and the wear of both can be suppressed.

Further, by setting the maximum value of the positive acceleration generated when the cam surface of the high-speed cam slides on the highly rigid portion of the sub-rocker arm to a relatively large value, the time area in which the valve is open can be increased, The intake / exhaust efficiency can be improved.

[0022]

Embodiments of the present invention will be described below with reference to the accompanying drawings.

As shown in FIG. 3, the cylinder head 61 has an intake port 62 for introducing intake air into the combustion chamber 79 and the combustion chamber 7.
It has an exhaust port 63 and the like for exhausting exhaust gas from 9.

An intake valve 72 for opening and closing the intake port 62,
Exhaust valves 73 for opening and closing the exhaust ports 63 are provided respectively. The intake / exhaust valves 72, 73 are slidably supported on the cylinder head 61 via a valve guide 65.

A retainer 66 is fitted on the stem portions of the intake / exhaust valves 72 and 73, and the retainer 66 and the cylinder head 6 are attached.
A coiled valve spring 67 is interposed between the two. The intake / exhaust valve 7 is driven by the urging force of the valve spring 67.
2, 73 are pulled up and seated on the respective valve seats 68.

Two cam shafts 80 are provided on the cylinder head 61. Intake / exhaust cams 82, 83 for opening / closing the intake / exhaust valves 72, 73 via the rocker arm 71 are formed on the camshafts 80, respectively.

The rotation of a crankshaft (not shown) is transmitted to each camshaft 80 through a chain and a sprocket, and they rotate in the same direction as indicated by an arrow in the figure.

Intake / exhaust cams 82 and 83 and intake / exhaust valve 7
Each rocker arm 71 is interposed between 2 and 73. Each rocker arm 71 has its base end swingably supported via a pivot 70, and a cam follower portion 8 for slidingly contacting intake / exhaust cams 82, 83 in the middle thereof.
5 and the respective tips are in sliding contact with the stem tops of the intake / exhaust valves 72, 73 via shims.

Each pivot 70 is supported by the cylinder head 61 via a hydraulic lash adjuster 84. The hydraulic lash adjuster 84 receives the hydraulic pressure sent from an oil pump (not shown) via an oil gallery 87, and sucks / exhausts the cam follower portion 85 of the rocker arm 71.
It is pressed against No. 2,83 and keeps the valve clearance at zero.

The intake / exhaust cams 82, 83 are brought into sliding contact with each other so that the intake / exhaust valves 72, 73 are connected to the respective valve seats 8.
The base circle portion 87 to be seated on the valve seat 68 and the intake / exhaust valves 72, 73 are slidably brought into contact with the respective valve seats 68.
It has a cam mountain portion 82 that lifts from.

The force point where the cam surfaces of the intake / exhaust cams 82, 83 contact the cam follower portion 85 of each rocker arm 71 is displaced in the rotational direction of the intake / exhaust cams 82, 83, and moves from right to left in FIG. .

That is, the force point at which the cam surface of the intake cam 82 contacts the cam follower portion 85 is displaced from the tip end side in contact with the intake valve 72 to the base end side in sliding contact with the pivot 70.

As shown in FIG. 1, the valve lift characteristic of the intake valve 72 is that the intake valve 72 is seated on the valve seat 68 and stopped while the base circle portion 87 of the intake cam 82 is in sliding contact with the rocker arm 71. is doing. As the cam surface of the intake cam 82 begins to come into sliding contact with the rocker arm 71, the intake valve 72 separates from the valve seat 68, and the lift speed increases. The acceleration when the speed at which the intake valve 72 lifts increases is defined as positive acceleration.

Then, as the intake valve 72 lifts, its speed decreases and it stops momentarily at the maximum lift position. During this period, it is decelerating, so negative acceleration is working.

Subsequently, the intake valve 72 starts to close from the maximum lift position, and the closing speed increases. Here, too, negative acceleration acts on the intake valve 72.

Subsequently, when the intake valve 72 is closed, the intake valve 72 is decelerated and the valve seat 68 is seated. Here, a positive acceleration acts as when opening the intake valve 72.

In the schematic diagram of the valve operating system shown in FIG. 4, the point PAi on the cam follower portion 85 is the intake cam 82 when the positive acceleration at the start of the valve lift reaches the maximum value Amax.
Is the point of contact. Further, at the point PBi on the cam follower portion 85, the positive acceleration at the end of the valve lift is the maximum value Bm.
This is a force point with which the intake cam 82 comes into contact when it becomes ax.

In FIG. 4, a point Pb is a rocker arm 71.
Is the point of contact with the intake valve 72. Also, the point Pp
Is a rocking fulcrum of the rocker arm 71 by the pivot 70.

In this embodiment, the cam follower portion 85 is provided closer to the action point Pb than the swing fulcrum Pp. Therefore, the positive acceleration at the start of the valve lift is the maximum value Amax.
The distance Lb from the force point PAi with which the intake cam 82 comes into contact with the point of action Pb close to this is close to the point PBi with which the intake cam 82 comes into contact when the positive acceleration at the end of the valve lift reaches the maximum value Bmax. Swing fulcrum P
It is shorter than the distance Lp to p.

Since the rocker arm 71 is considered as a double-supported beam supported by two points, the swing fulcrum Pp and the action point Pb, the force point of the load acting from the intake cam 82 to the cam follower portion 85 is the swing fulcrum Pp or the action. As the distance from the point Pb increases, the rigidity of the rocker arm 71 decreases and the deformation amount of the rocker arm 71 increases.

That is, in the case of the conventional device in which equal loads from the intake cam 82 act on the force points PBi and PAi, the deformation amount of the rocker arm 71 is such that the load acts on the force point PBi where the distance Lp to the swing fulcrum Pp is relatively large. In this case, the distance Lb to the action point Pb is larger than that of the force point PAi which is relatively small. As a result, the rocker arm 71 and the intake valve 72 are deformed due to the deformation of the rocker arm 71 at the end of the valve lift.
Can no longer follow the movement of the intake cam 82, so that an illegal motion such as a so-called jump occurs, and this illegal motion may limit the maximum engine speed.

In response to this, the present invention shows the valve lift characteristic of the intake cam 82 as shown in FIG. 1, in which the maximum value Amax of the positive acceleration at the start of the valve lift is the maximum positive acceleration at the end of the valve lift. The value is set to be larger than the value Bmax by a predetermined value C.

In FIG. 1, the valve lift characteristic shown by a thin line is a conventional one, and is set so that the maximum value of the positive acceleration at the start of the valve lift is equal to the maximum value of the positive acceleration at the end of the valve lift. , Has a symmetrical shape. In contrast to this conventional valve lift characteristic, in the valve lift characteristic of the present invention, the valve lift at the end of the valve lift is set small and the valve lift at the start of the valve lift is set large.

As described above, the force point at which the cam surface of the intake cam 82 contacts the cam follower portion 85 moves from the high rigidity portion of the rocker arm 71 to the low rigidity portion of the rocker arm 71. By setting the maximum value Bmax of the positive acceleration at the end of the valve lift, which occurs when sliding on a portion with low
The deformation of the rocker arm 71 that occurs at the end of the valve lift is reduced, and the maximum engine speed is prevented from being restricted by an improper movement such as bounce of the intake valve 72 that occurs at the end of the valve lift.

Further, by setting the maximum value Amax of the positive acceleration at the start of the valve lift, which occurs when the intake cam 82 slides on the portion of the rocker arm 71 having high rigidity, to be relatively large, it is surrounded by the line segment of the valve lift characteristic. The increased area, that is, the time area in which the intake valve 72 is open, is increased to improve intake efficiency.

On the other hand, since the exhaust cam 83 rotates in the direction shown by the arrow in FIG. 3, the force point at which its cam surface contacts the cam follower portion 85 has a low rigidity of the rocker arm 71 as the exhaust cam 83 rotates. It will move from the part to the higher part.

In the present invention, as shown in FIG. 2, the valve lift characteristic of the exhaust cam 83 is such that the maximum value Amax of the positive acceleration at the start of the valve lift is a predetermined value from the maximum value Bmax of the positive acceleration at the end of the valve lift. Set so that it becomes smaller by C.

In FIG. 2, the valve lift characteristic shown by a thin line is a conventional one, and is set so that the maximum value of the positive acceleration at the start of the valve lift is equal to the maximum value of the positive acceleration at the end of the valve lift. , Has a symmetrical shape. In contrast to this conventional valve lift characteristic, the valve lift characteristic of the exhaust valve 73 according to the present invention is such that the valve lift at the start of the valve lift is set small and the valve lift at the end of the valve lift is set large.

As described above, the force point at which the cam surface of the exhaust cam 83 contacts the cam follower portion 85 moves from the low rigidity portion of the rocker arm 71 to the high rigidity portion of the rocker arm 71. By setting the maximum value Amax of the positive acceleration at the start of the valve lift, which occurs when sliding on a portion with low
The deformation of the rocker arm 71 that occurs at the start of the valve lift is reduced, and improper movement such as a jump of the exhaust valve 73 that occurs at the start of the valve lift is suppressed. This allows the exhaust valve 73
As shown by the solid line in FIG. 5, the jump amount of 1 is prevented from rapidly increasing in the high speed range, so that it is possible to prevent the maximum engine speed from being restricted by the improper movement occurring at the start of the valve lift.

Further, by setting the maximum value Bmax of the positive acceleration at the end of the valve lift, which occurs when the exhaust cam 83 is in sliding contact with the portion of the rocker arm 71 having high rigidity, to a relatively large value, the time during which the exhaust valve 73 is open is set. By expanding the area, the exhaust efficiency can be improved.

Next, another embodiment shown in FIG. 6 will be described. It should be noted that the same reference numerals are used for parts corresponding to those in FIG.

In this embodiment, the cam follower portion 85 is provided closer to the swing fulcrum Pp than the point of action Pb. Since the intake cam 82 rotates in the direction indicated by the arrow in the figure, when the positive acceleration at the start of the valve lift reaches the maximum value Amax, the distance Lb from the force point PAi with which the intake cam 82 contacts to the action point Pb adjacent thereto is: When the positive acceleration at the end of the valve lift reaches the maximum value Bmax, it is longer than the distance Lp from the force point PBi with which the intake cam 82 is in contact to the swing fulcrum Pp adjacent thereto.

An equal load is applied from the intake cam 82 to the power point PBi.
In the case of the conventional device which acts on PAi and PAi, the rocker arm 71
When the load acts on the force point PAi where the distance Lb to the action point Pb is relatively large, the deformation amount of is larger than the force point PBi where the distance Lp to the swing fulcrum Pp is relatively small. As a result, the rocker arm 71 that occurs when the valve lift starts
Due to the deformation, the rocker arm 71 and the intake valve 72 cannot follow the movement of the intake cam 82, and an irregular motion such as a so-called jump occurs, which may limit the maximum engine speed.

In response to this, according to the present invention, as shown in FIG. 2, the valve lift characteristic of the intake cam 82 is such that the maximum value Amax of the positive acceleration at the start of the valve lift is the maximum positive acceleration at the end of the valve lift. The value is set to be smaller than the value Bmax by a predetermined value C.

As described above, the force point at which the cam surface of the intake cam 82 contacts the cam follower portion 85 moves from the low rigidity portion of the rocker arm 71 to the high rigidity portion thereof. By setting the maximum value Amax of the positive acceleration at the start of the valve lift, which occurs when sliding on a portion with low
The deformation of the rocker arm 71 that occurs at the start of the valve lift is reduced, and the maximum rotation speed of the engine is prevented from being restricted by an improper movement such as bounce of the intake valve 72 that occurs at the start of the valve lift.

Further, by setting the maximum value Bmax of the positive acceleration at the end of the valve lift, which occurs when the intake cam 82 slides on the portion of the rocker arm 71 having high rigidity, to be relatively large, the valve lift characteristic is surrounded by a line segment. The increased area, that is, the time area in which the intake valve 72 is open, is increased to improve intake efficiency.

Next, another embodiment shown in FIG. 7 will be described. It should be noted that the same reference numerals are used for the portions corresponding to those in FIG.

In this embodiment, the rocker arm 91 is provided with the cam follower portion 85 and the action point Pb with the rocking fulcrum Pp interposed therebetween. Since the intake cam 82 rotates in the direction shown by the arrow in the figure, the positive acceleration at the start of the valve lift is the maximum value Ama.
The distance LpA from the force point PAi with which the intake cam 82 comes into contact when it reaches x to the swing fulcrum Pp close to this point is from the point PBi with which the intake cam 82 comes into contact when the positive acceleration at the end of the valve lift reaches the maximum value Bmax. Is longer than the distance LpB to the rocking fulcrum Pp close to.

An equal load is applied from the intake cam 82 to the power point PBi.
In the case of the conventional device that acts on PAi and PAi, the rocker arm 91
When the load acts on the force point PAi having a relatively large distance LpA to the swing fulcrum Pp, the amount of deformation becomes larger than the force point PBi having a relatively small distance LpB to the swing fulcrum Pp. As a result, the rocker arm 91 or the intake valve 72 cannot follow the movement of the intake cam 82 due to the deformation of the rocker arm 91 that occurs at the time of starting the valve lift, so that an irregular motion such as a so-called jump occurs, and the maximum rotational speed of the engine is restricted by the irregular motion. May be done.

In response to this, according to the present invention, as shown in FIG. 2, the valve lift characteristic of the intake cam 82 is such that the maximum value Amax of the positive acceleration at the start of the valve lift is the maximum positive acceleration at the end of the valve lift. The value is set to be smaller than the value Bmax by a predetermined value C.

As described above, the force point at which the cam surface of the intake cam 82 contacts the cam follower portion 85 moves from the low rigidity portion of the rocker arm 91 to the high rigidity portion of the rocker arm 91. By setting the maximum value Amax of the positive acceleration at the start of the valve lift, which occurs when sliding on a portion with low
The deformation of the rocker arm 91 that occurs at the start of the valve lift is made small, and the maximum engine speed is prevented from being restricted by an improper movement such as bounce of the intake valve 72 that occurs at the start of the valve lift.

Further, by setting the maximum value Bmax of the positive acceleration at the end of the valve lift, which occurs when the intake cam 82 slides on the portion of the rocker arm 91 having high rigidity, to be relatively large, it is surrounded by the line segment of the valve lift characteristic. The increased area, that is, the time area in which the intake valve 72 is open, is increased to improve intake efficiency.

Next, another embodiment shown in FIGS. 8 to 11 will be described.

The intake camshaft 20 is a pair of low speed cams 2.
1 and a high speed cam 22 located between each low speed cam 21. The low speed cam 21 and the high speed cam 22 adjacent to the low speed cam 21 are integrally formed on a common cam shaft 20. The high-speed cam 22 has a profile in which both the valve lift amount and the valve opening period are larger than those of the low-speed cam 21 so that the valve lift characteristics required at low engine speed and high engine speed are satisfied. .

As shown in FIG. 9, each cylinder is provided with a single main rocker arm 1 corresponding to two intake valves 9. A base end of the main rocker arm 1 is swingably supported by a cylinder head via a rocker shaft 3 common to each cylinder. The main rocker arm 1 has two arm portions 8. The tip 8a of each arm 8 is in sliding contact with the stem top of each intake valve 9 via a shim 7. As the main rocker arm 1 swings, the intake valves 9 are opened and closed while expanding and contracting a valve spring (not shown).

The main rocker arm 1 is fixedly provided with a pair of cam follower portions 14 slidably contacting the pair of low speed cams 21, and a single sub-rocker arm 2 is swingably provided between the cam follower portions 14.

The base end of the sub-rocker arm 2 is connected to the main rocker arm 1 via the sub-rocker shaft 16 so as to be relatively rotatable.

As shown in FIG. 11, the sub-rocker arm 2
Has no portion that comes into contact with the intake valve 9, and a cam follower portion 23 that slidably contacts the high speed cam 22 is formed at the tip of the portion so as to project in an arc shape.

A lifter 41 slidably accommodated in the hole 26 of the sub-rocker arm 2 is provided as a lost motion mechanism for causing the sub-rocker arm 2 to follow the high speed cam 22. The tip of the lifter 41 contacts the follower portion 27 of the main rocker arm 1. A lost motion spring 25 for pressing the sub-rocker arm 2 against the high speed cam 22 is interposed in the hole 26 via a lifter 41.

Between the main rocker arm 1 and the sub rocker arm 2, the relative rotation of both is locked, and the cams involved in the opening / closing operation of each intake valve 9 are the low speed cam 21 to the high speed cam 22.
A cam switching mechanism for switching to is provided.

As this cam switching mechanism, a prop 31 is rotatably connected to the main rocker arm 1 via a shaft 32. The prop 31 has one end 31
As shown in the drawing, a is rotated relative to a locking position where it engages with the stepped portion 2a of the sub-rocker arm 2 and a non-locking position where one end 31a thereof is disengaged from the stepped portion 2a formed on the sub-rocker arm 2. Has become.

The prop 31 has its one end 31a engaged with the step portion 2a of the sub-rocker arm 2 to lock the relative rotation of the sub-rocker arm 2 with respect to the main rocker arm 1.

In order to switch the prop 31 between the non-locking position and the locking position, the prop 31 and the main rocker arm 1 are
A spring (not shown) for biasing the prop 31 to the non-locking position is interposed between the holes 48 formed in the main rocker arm 1 and locks the sub-rocker arm 2 against the spring. Hydraulic piston 3 to rotate to position
0 is provided.

The hydraulic piston 30 contacts the lever portion 46 protruding from the prop 31. A hole 36 into which the hydraulic piston 30 is slidably fitted is formed in the main rocker arm 1, and a hydraulic chamber 37 is formed behind the hydraulic piston 30.

Hydraulic passage 38 for guiding the operating hydraulic pressure to the hydraulic chamber 37
Are provided through the inside of the main rocker arm 1 and the rocker shaft 3.

The discharge hydraulic pressure of the oil pump is introduced into the hydraulic chamber 37 via a switching valve (not shown) during a predetermined high speed operation. A control unit (not shown) that electronically controls the operation of the switching valve outputs an engine speed signal, a cooling water temperature signal, a lubricating oil temperature signal, a supercharging intake pressure signal, and a throttle valve opening signal. It is designed to smoothly switch between the low speed cam 21 and the high speed cam 22 while inputting and suppressing rapid changes in engine torque based on these detected values.

When the switching valve is opened during high-speed operation of the engine and the discharge pressure of the oil pump is introduced into the hydraulic chamber 37 through the hydraulic passage 38, the hydraulic piston 30 opens the prop 31 as shown in FIG. Move to locking position, prop 3
By engaging one end 31a of 1 with the stepped portion 2a of the main rocker arm 1, the main rocker arm 1 and the sub rocker arm 2 swing integrally. The high-speed cam 22 is formed so that both the valve opening angle and the lift amount are larger than the low-speed cam 21. Therefore, the low-speed cam 21 when swinging together with the main rocker arm 1 and the sub-rocker arm 2 is integrated. Is lifted from the cam follower portion 14 of the main rocker arm 1, and each intake valve 9 is driven to open and close according to the profile of the high speed cam 22, so that both the opening angle and the lift amount of the valve increase. The high speed cam 22 rotates in the direction shown by the arrow in FIG. In FIG. 11, the cam follower unit 23
The upper point PAi is a force point with which the high speed cam 22 contacts when the positive acceleration at the start of the valve lift reaches the maximum value Amax. Further, the point PBi on the cam follower portion 23 is a force point with which the high speed cam 22 comes into contact when the positive acceleration at the end of the valve lift reaches the maximum value Bmax.

In FIG. 11, the point Pm is the point of contact with the prop 31 of the sub-rocker arm 2. Also, point P
s is a swing fulcrum of the sub-rocker shaft 16 of the sub-rocker arm 2.

In this embodiment, the cam follower portion 23 is provided closer to the action point Pm than the swing fulcrum Ps. Therefore, the positive acceleration at the start of the valve lift is the maximum value Amax.
The distance Lm from the force point PAi with which the high speed cam 22 comes into contact with the point of action Pm close to this is close to the point PBi with which the high speed cam 22 comes into contact when the positive acceleration at the end of the valve lift reaches the maximum value Bmax. Swing fulcrum P
It is shorter than the distance Ls to s.

Since the sub-rocker arm 2 is considered as a doubly supported beam supported at two points, the swing fulcrum Ps and the action point Pm, the force point of the load acting from the high speed cam 22 to the cam follower portion 23 is the swing fulcrum Ps. Alternatively, as the distance from the point of action Pm increases, the rigidity of the sub-rocker arm 2 decreases and the amount of deformation increases.

That is, in the case of the conventional device in which equal loads from the intake cam 82 act on the force points PBi and PAi, the deformation amount of the sub-rocker arm 2 is determined by the distance Ls to the swing fulcrum Ps.
When the load acts on the relatively large force point PBi, the distance Lm to the point of action Pm is larger than the relatively small force point PAi. As a result, the amount of deformation of the sub-rocker arm 2 increases at the end of the valve lift, as shown in FIG.
There is a possibility that one end 31a of the prop 31 partially abuts against the stepped portion 2a of the sub-rocker arm 2, causing partial contact, and wear of both ends may progress. Further, when the amount of deformation of the sub-rocker arm 2 becomes large, the intake valve 9 is moved to the high-speed cam 22 due to the deformation of the sub-rocker arm 2 that occurs when the valve lift is started.
The improper movement such as so-called jump may occur, which makes it impossible to follow the movement of the engine, and the improper movement may limit the maximum engine speed.

In response to this, the present invention shows the valve lift characteristic of the high speed cam 22 as shown in FIG. 1, in which the maximum value Amax of the positive acceleration at the start of the valve lift is the maximum positive acceleration at the end of the valve lift. The value is set to be larger than the value Bmax by a predetermined value C.

As described above, the force point at which the cam surface of the high speed cam 22 contacts the cam follower portion 23 moves from the high rigidity portion of the sub rocker arm 2 to the low rigidity portion of the sub rocker arm 2, and the high speed cam 22 moves. By setting the maximum value Bmax of the positive acceleration at the end of the valve lift, which occurs when sliding in contact with a portion having low rigidity, to make the deformation of the sub-rocker arm 2 at the end of the valve lift small, and at the end of the valve lift. Intake valve 9
It avoids that the maximum engine speed is restricted by illegal movement such as bounce.

As shown in FIG. 12, by reducing the deformation of the sub-rocker arm 2 that occurs at the start of valve lift, one end 31a of the prop 31 uniformly contacts the stepped portion 2a of the sub-rocker arm 2 and wear of both is suppressed. To be

Further, the high speed cam 22 is the sub rocker arm 2
Is set to a relatively large maximum value Amax of the positive acceleration at the start of valve lift that occurs when slidingly contacting a portion having high rigidity, the area surrounded by the line segment of the valve lift characteristic, that is, the intake valve 9 opens. By expanding the time area in which it is present, the intake efficiency can be improved.

On the other hand, when the engine shifts from the high speed region to the low speed region again, the switching valve is closed, the hydraulic pressure introduced into the hydraulic chamber 37 via the hydraulic passage 38 is lowered, and the propeller is propelled by the elastic restoring force of the spring. 31 rotates to the unlocked position,
The restraint of the sub rocker arm 2 is released.

During low speed operation of the engine, the main rocker arm 1 swings in accordance with the profile of the low speed cam 21 to open / close each intake valve 9 against the valve spring 8.
At this time, although the sub-rocker arm 2 is swung by the high speed cam 22, the prop 31 does not move.
By being held in the non-locking position where the main rocker arm 1 is not engaged with the main rocker arm 1, the movement of the main rocker arm 1 is not hindered.

[0088]

As described above, the engine valve operating system according to the present invention is an engine equipped with a rocker arm that opens and closes a valve against a valve spring by swinging following a cam. Of the maximum value Amax of the valve positive acceleration generated at the start of the valve lift and the maximum value Bmax of the valve positive acceleration generated at the end of the valve lift,
When this occurs, the rocker arm is deformed at the start and end of the valve lift because the distance to the rocker arm swing fulcrum or the point of action of the rocker arm that contacts the valve is set to a minimum value with respect to the force point on the cam surface that contacts the rocker arm. Both of them are suppressed to be small, thereby suppressing improper movements such as valve jumps and bounces, and it is possible to prevent the improper movements from limiting the maximum engine speed. As a result, both the accurate opening / closing operation of the intake / exhaust valve and the expansion of the valve lift time area can be achieved, and the engine output and fuel consumption can be improved.

A valve operating system for an engine according to claim 2 is:
The sub-rocker arm that swings with respect to the main rocker arm by following a high-speed cam that has a larger profile than the low-speed cam and does not have a part that contacts the valve, and the relative displacement of the sub-rocker arm with respect to the main rocker arm depending on engine operating conditions In an engine including a locking prop, the maximum value Amax of the valve positive acceleration that occurs at the start of the valve lift and the maximum value Bmax of the valve positive acceleration that occurs at the end of the valve lift are set to the sub-rocker arm on the cam surface at the time of occurrence. Since the minimum distance to the rocking fulcrum of the sub-rocker arm or the point of action of the sub-rocker arm that contacts the prop of the sub-rocker arm is set to a large value, the deformation of the sub-rocker arm that occurs at the beginning of the valve lift and at the end of the valve lift is both kept small. By sub Exactly performed that the opening and closing of the intake and exhaust valves through the Kkaamu, and both to expand the valve lift time area, it is possible to improve the output and fuel efficiency of the engine. Further, the props evenly hit the sub-rocker arm, the wear of both is suppressed, and the durability is improved.

[Brief description of drawings]

FIG. 1 is a characteristic diagram of valve lift and valve acceleration of an exhaust valve with respect to a cam angle showing an embodiment of the present invention.

FIG. 2 is a characteristic diagram of valve lift and valve acceleration of the intake valve with respect to the cam angle.

FIG. 3 is a sectional view of the engine.

FIG. 4 is a schematic diagram of a valve train of the same.

FIG. 5 is a characteristic diagram of jump amount with respect to engine rotation speed.

FIG. 6 is a schematic diagram of a valve operating system showing another embodiment.

FIG. 7 is a schematic diagram of a valve operating system showing still another embodiment.

FIG. 8 is a side view of a valve operating system showing still another embodiment.

FIG. 9 is a plan view of the valve operating device.

FIG. 10 is a perspective view of the main rocker arm.

FIG. 11 is a sectional view of the valve train, which is also taken along the line AA of FIG. 9.

FIG. 12 is a front view of the sub-rocker arm, the prop, and the like at the time of deformation.

FIG. 13 is a front view of a sub-rocker arm, a prop and the like when not deformed, showing a conventional example.

[Explanation of symbols]

1 Main rocker arm 2 Sablocka arm 3 rocker shaft 9 intake valve 16 Sub rocker shaft 20 camshaft 22 high speed cam 23 Cam follower section 31 Prop 61 cylinder head 62 intake port 63 Exhaust port 70 pivot 71 rocker arm 72 Intake valve 73 Exhaust valve 80 camshaft 82 Intake cam 83 Exhaust cam 85 Cam follower

─────────────────────────────────────────────────── ─── Continuation of front page (72) Inventor Shunji Yamada 2 Takaracho, Kanagawa-ku, Yokohama, Kanagawa Nissan Motor Co., Ltd. (56) References JP-A-63-295811 (JP, A) JP-A-6- 221123 (JP, A) JP 5-163914 (JP, A) JP 5-163915 (JP, A) JP 5-171909 (JP, A) JP 8-4505 (JP, A) Fukui Sho 59-182601 (JP, U) Fukui Hei 6-73301 (JP, U) Fukui 14-998 (JP, Y1) (58) Fields investigated (Int.Cl. ⁷ , DB name) F01L 1/18 F01L 13/00 301

Claims (2)

(57) [Claims] 1. A cam that rotates in synchronization with engine rotation, a valve spring that biases the valve in a valve closing direction, and a valve spring that opens and closes against the valve spring by swinging following the cam. In an engine equipped with a rocker arm, the maximum value of the positive acceleration of the valve that occurs at the start of valve lift Am
Of ax and the maximum value Bmax of the positive acceleration of the valve that occurs at the end of the valve lift, the distance between the rocking arm fulcrum of the cam surface and the point of action of the rocker arm that contacts the valve becomes the minimum with respect to the force point of the cam surface that contacts the rocker arm. A valve operating system for an engine, which is characterized by a large size. 2. A low-speed cam and a high-speed cam that rotate in synchronism with the engine rotation and have different profiles, and a main rocker arm that opens and closes the valve against a valve spring by swinging following the low-speed cam. , A sub-rocker arm that swings with respect to the main rocker arm by following a high-speed cam that has a profile larger than the low-speed cam and that has no part in contact with the valve, and the relative displacement of the sub-rocker arm with respect to the main rocker arm according to engine operating conditions. In a engine equipped with a prop that locks the
Of ax and the maximum value Bmax of the positive acceleration of the valve generated at the end of valve lift, the distance from the point of contact of the cam surface to the sub-rocker arm to the rocking fulcrum of the sub-rocker arm or the point of action of the sub-rocker arm prop that contacts the prop surface of the sub-rocker arm The engine valve operating system is characterized in that the smallest one is set large.