JPH089963B2 - Valve train for internal combustion engine - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION A. Object of the Invention (1) Field of Industrial Application The present invention relates to a valve spring for urging an engine valve in a valve closing direction, a lift portion for opening the engine valve, and an engine valve. The present invention relates to an improvement in a valve operating system of an internal combustion engine including a cam having a base portion that allows valve closing and a hydraulic tappet that eliminates a valve head clearance by being interposed in a force transmission system from the cam to an engine valve.

(2) Related Art Conventionally, in such a valve operating device, in order to prevent the valve failure of the engine valve from being caused by the vibration of the cam due to the center runout or bending of the cam shaft, the valve is closed at the base portion of the cam. A certain downward gradient is applied from the valve point to the valve opening point, and the drop between the two points is set to a lift amount equivalent to the play of the hydraulic tappet or a lift amount slightly smaller than that, and the engine valve It is known to offset the swing in the lift direction of the base portion with the downward slope of the base portion without disturbing the valve opening timing (see Japanese Patent Laid-Open No. 59-43911).

(3) Problems to be Solved by the Invention However, during the operation of the base part, the deflection in the lift direction may locally occur rather than occur gently over the entire section of the valve closing point and the valve opening point. It was investigated by the inventor. In order to absorb such a local runout of the base portion by the above-mentioned conventional device, it is necessary to increase the play of the hydraulic tappet to set a large down slope between the valve closing point and the valve opening point. In this case, the play of the hydraulic tappet increases, which causes an adverse effect that the valve opening characteristic of the engine valve changes.

The present invention has been made in view of such circumstances, and an internal combustion engine in which the influence of a local large swing in the lift direction of the base portion is not exerted on the engine valve without particularly increasing the play of the hydraulic tappet. It is an object of the present invention to provide a valve operating device of the above.

B. Configuration of the Invention (1) Means for Solving the Problems In order to achieve the above object, the present invention provides a hydraulic tappet from a valve closing point at which a base portion of a cam starts to an opening point at which the base portion ends. Let A be the head converted into the amount of expansion and contraction and A be the play of the hydraulic tappet, and let A ≤ Lo, and at the same time descend at a steep slope from the valve closing point side toward the valve opening point side to the base of the cam. The first feature is that one steep slope portion and a zero slope flat portion that is continuous at the beginning or end of this steep slope portion are provided, and the base portion is the same from the valve closing point where the base portion starts. When the drop in terms of the expansion / contraction amount of the hydraulic tappet is A and the play of the hydraulic tappet is Lo up to the valve opening point where A ends, the condition is A ≦ Lo and the base of the cam opens from the valve closing point side. At least one steep descent section that descends steeply toward the point side, In that a from steep descending slope portion beginning or sequentially and closing point side at the end of the slow descending slope portion descending at a gentle gradient towards the valve open point side is set to the second feature.

(2) Operation According to the above configuration, since the steeply descending slope portion and the flat portion or the gradually descending slope portion are provided side by side with the base portion, within the range of the limited drop A between the valve closing point and the valve opening point. A large gradient and a large amount of downhill can be given to the steep downhill portion. And
If this steep slope part is matched with the local swing timing in the lift direction of the base part, even if the shake is large, it can be offset by the slope of the steep slope part, and cannot be offset. The runout can be absorbed by the play of the hydraulic tappet.

(3) Examples Hereinafter, examples of the present invention will be described with reference to the drawings.

First, referring to FIG. 1 showing a first embodiment of the present invention, a combustion chamber 2 is provided in a cylinder head 1 of an internal combustion engine, and the combustion chamber 2
And a port 3 that is open to the outside are formed, and the port is opened and closed by an engine valve 4 such as an intake and exhaust valve.

The engine valve 4 is supported by the cylinder head 1 via a valve guide 5 so as to be able to move up and down, and is opened and closed by a valve operating device 6 according to the present invention.

The valve gear 6 is a retainer fixed to the head of the engine valve 4.
A valve spring 7 that is compressed between the cylinder head 1 and the cylinder head 1 and urges the engine valve 4 in the closing direction, a hydraulic tappet 9 that is mounted in the support hole 8 of the cylinder head 1, and a swinging motion of the hydraulic tappet 9. A cam follower 10 that is movably supported and has its tip end engaged with the head portion of the engine valve 4, and a slipper surface 10a formed on the upper side of the cam follower 10 that is supported by the cylinder head 1 and is rotationally driven by a crank shaft (not shown). And a cam shaft 11 for engaging the cam C.

As shown in FIGS. 1 and 2, the cam C has a lift portion Cl for opening the engine valve 4 and a base portion Cb for allowing the valve 4 to be closed. One of the boundary points of Cb (that is, the starting end of the base portion Cb) is the valve closing point Pc, and the other (that is, the base portion).
The end point of Cb) becomes the valve opening point Po. The base portion Cb has a valve closing point Pc.
A steeply descending slope part that descends steeply toward a predetermined intermediate point P ₁ from
It is composed of d ₁ and a flat portion f ₁ which reaches the valve opening point P ₀ from the intermediate point P ₁ with a zero gradient.

Next, the hydraulic tappet 9 will be described with reference to FIG. The hydraulic tappet 9 has a bottomed cylinder 20 and a plunger 22 slidably fitted in a cylinder hole 20a of the cylinder 20 and defining a hydraulic chamber 21 therein, as main constituent elements. Are fitted into the support holes 8.
The plunger 22 has a spherical end 22a at the outer end thereof which is a cam follower 1
0 It is engaged with the spherical recess 10b at the base end.

The plunger 22 is provided with an oil reservoir chamber 23 and a valve hole 24 that connects the oil reservoir chamber 23 to the hydraulic chamber 21.
Is an oil supply passage 32 formed in the cylinder head 1 through an oil hole 25 in the side wall of the plunger 22, an annular oil passage 27 between the sliding surfaces of the cylinder 20 and the plunger 22, and an oil hole 26 in the side wall of the cylinder 20. The oil supply passage 32 is connected to the discharge port of an oil pump (not shown). Therefore, during the operation of the engine, the oil sump 23 is constantly filled with the oil sent from the oil pump.

A flange portion 28a of a hat-shaped valve cage 28 is fitted to the lower end of the plunger 22 and fixed by a caulking ring 33. The valve cage 28 accommodates a free-ball type check valve 29 which opens and closes the valve hole 24 with an opening / closing stroke defined therein. That is, the check valve
The valve 29 is not spring-biased in the valve closing direction, and the valve hole 24 is closed only by increasing the pressure in the hydraulic chamber 21.

Further, the hydraulic chamber 21 accommodates an extension spring 31 that urges the plunger 22 to project above the cylinder 20.

When the lift portion Cl applies a pressing force to the slipper surface 10a of the cam follower 10 as the cam C rotates, the plunger 22 of the hydraulic tappet 9 is pressed to the hydraulic chamber 21 side, so that the hydraulic chamber 21 is pressurized. And a small amount of oil flows out of the chamber 21 through the valve hole 24 into the oil reservoir chamber 23.
After the initial sinking, the check valve 29 closes the valve hole 24 to maintain the hydraulic pressure in the hydraulic chamber 21, and subsequently the entire plunger 22 is compressed due to compression of bubbles mixed in the oil in the hydraulic chamber 21. After the elastic sinking, the hydraulic pressure in the hydraulic chamber 21 suddenly rises, and as a result, the pedal tension is exerted on the plunger 22, so that the cam follower 10 moves downward by the lift Cl with the spherical end 22a of the plunger 22 as a fulcrum. The engine valve 4 is swung and resists the force of the valve spring 7 to open the engine valve 4.

While the engine valve 4 is open, high pressure oil in the hydraulic chamber 21
Also, the plunger 22 slightly leaks to the sliding gap of the plunger 22, so that the plunger 22 leaks and sinks.

Next, when the base portion Cb of the cam C reaches the cam follower 10, the valve spring 7 pushes up the engine valve 4 together with the cam follower 10 to return it to the closed position. On the other hand, in the hydraulic tappet 9, the extension spring 31 extends and returns the plunger 22 to bring the slipper surface 10a of the cam follower 10 into contact with the cam 11a, thereby eliminating the valve head gap.

When the expansion chamber 31 expands the plunger 22 to reduce the pressure in the hydraulic chamber 21, the check valve 29 opens, so that the oil in the oil reservoir 23 is supplied to the hydraulic chamber 21 through the valve hole 24. The oil spill from the tank is replenished.

Here, L ₀ ... hydraulic tappet play l _1A ... hydraulic tappet 9 required for check valve 29 to close
Initial sinking amount l _1B・ ・ ・ Elastic sinking amount of tappet 9 due to compression of bubbles in oil in hydraulic chamber 21 L …… During closing of engine valve 4, hydraulic tappet 9 is caused by hydraulic leak from hydraulic chamber 21. When the amount of sinking is set, the drop A converted from the valve closing point Pc of the cam C to the valve opening point Po of the hydraulic tappet 9 is set so that the following equation is satisfied.

A ≦ Lo (1) L ₀ = l _1A + l _1B + L (2) In this embodiment, since the latter half of the base portion Cb is the flat portion f ₁ , the valve closing point Pc and the valve opening point The drop A between Pos is spent on the steep slope d ₁ in the first half.

 Next, the operation of this embodiment will be described.

FIG. 4 shows displacements of the hydraulic tappet 9 and the engine valve 4 as the cam C rotates. In the figure, the plunger 22 starts to sink due to the operation of the lift portion Cl at the point a, the check valve 29 closes at the point b, and the hydraulic tappet 9 is closed between the points b and c.
Occurs at the point d, the opening of the engine valve 4 is started,
At the point e, the engine valve 4 is closed (seated on the valve seat), and the plunger 22 extends due to the repulsive force of the elastic depression between the points f and g, and the point h
Then, the plunger 22 completely returns to eliminate the valve head gap.

After passing the point h, the plunger 22 extends along the steep descent portion d in the base portion Cb of the cam C with the check valve 29 opened until the point i is reached. In particular, the steeply descending slope portion d has a drop A between the valve closing point Pc and the valve opening point Po, so that the slope and the descending amount are large as compared with the conventional one that descends over the entire section of the base portion Cb. Therefore, even if the cam C swings greatly in the lift direction immediately after the engine valve 4 is closed, the swing is offset by the large descending slope and the descending amount of the steep descending slope portion d, and the check valve 29 of the hydraulic tappet 9 is canceled. It can prevent valve closing. As a result, the engine valve 4 receives no unnecessary valve opening force and can maintain a normal valve closed state.

In this case, if the shake of the cam C is so large that it cannot be canceled by the steep descending slope portion d, the remaining shake is absorbed by the play L ₀ of the hydraulic tappet 9 itself.

Particularly, in the present embodiment in which the hydraulic tappet 9 is configured as a free check valve type, the play L ₀ is the initial sink amount l _1A + the elastic sink amount l _1B + the leak sink amount L, and among them, L _1A is the hydraulic tappet 9 Since it is possible to freely set a large value by selecting the opening / closing stroke of the check valve 29, it is possible to take a large amount of play L ₀ without damaging the stepping function of the hydraulic tappet 9 after the check valve 29 is closed. It is possible to increase the absorption amplitude of the hydraulic tappet 9 and reliably absorb the residual shake of the cam C.

After passing point i, the plunger 22 is reached until point a is reached again.
Follows the flat portion f ₁ of the base portion Cb. During this time, cam C
If the valve swings slightly in the lift direction, the swing is absorbed by the play Lo of the hydraulic tappet 9, and the check valve 29 can be prevented from closing.

Thus, a large swing in the lift direction immediately after the closing of the engine valve 4 is effectively absorbed within the limited drop A at both ends of the base portion Cb, and when the lift portion Cl of the cam C operates again. Since the check valve 29 can be closed at a predetermined time, the opening start timing of the engine valve 4 can be stabilized.

FIG. 5 shows the second embodiment of the present invention.
The Cb, first descending from the closed point Pc, and drop of approximately A / 2 to the first intermediate point P ₂ in the valve closing point Pc closer than the base portion Cb central steeply
The steep descent portion d ₂ , the flat portion f ₂ that reaches a predetermined second intermediate point P ₃ with a zero gradient from the first intermediate point P ₂ , and the remaining head from the second intermediate point P ₃ to the valve opening point Po Second steep descent section d ₃
And the other configurations are the same as those in the previous embodiment.

According to this embodiment, it is possible to cope with a large swing in the lift direction of the base portion Cb immediately after the engine valve 4 is closed and immediately before the valve is opened.

FIG. 6 shows a third embodiment of the present invention.
In Cb, from the valve closing point Pc to the intermediate point P ₄ which is relatively close to the valve opening point Po, there is a gentle downward slope e ₁ that descends approximately A / 3 of the head, and from the intermediate point P ₄ to the valve opening point Po. Up to and including the steeply descending slope portion d ₄ which steeply descends the remaining head, other configurations are similar to those of the first embodiment.

According to this embodiment, it is possible to cope with a weak shake in the lift direction of the base portion Cb after the engine valve 4 is closed and a strong shake immediately before the valve is opened.

FIG. 7 shows a fourth embodiment of the present invention.
At Cb, a first steep descent section d ₅ that steeply drops a head of approximately A / 3 from the valve closing point Pc to a first intermediate point P ₅ that is relatively close to it, and a valve opening point from the first intermediate point P ₅ A gentle downward slope e ₂ that descends approximately A / 3 of the head to the second intermediate point P ₆ that is relatively close to Po, and a steep downward slope that remains from the second intermediate point P ₆ to the valve closing point Po. The second steep slope portion d ₆ is provided.

According to this embodiment, it is possible to cope with the strong shake in the lift direction of the base portion Cb immediately after the closing of the engine valve 4 and immediately before the opening of the engine valve 4 and the weak shake in the middle portion of the closed valve engine.

FIG. 8 shows a fifth embodiment of the present invention.
Cb is approximately 2A from the valve closing point Pc to the intermediate point P ₇ which is relatively close to it.
A steep descending slope part d ₇ that descends the head of / 3, and the second intermediate point
A gentle descending slope portion e ₃ that descends the remaining head from P ₇ to the valve opening point Po with a gentle slope is provided, and the other configurations are the same as in the first embodiment.

According to this embodiment, it is possible to cope with the strong shake in the lift direction of the base portion Cb immediately after the engine valve 4 is closed and the weak shake thereafter.

FIG. 9 shows a sixth embodiment of the present invention.
At Cb, the first intermediate point P ₈ near the center of the base Cb from the valve closing point Pc
To the first flat part f ₃ which reaches the second intermediate point P ₉ from the first intermediate point P ₈ to the second flat point P ₉ at a steep slope d
₈ and the second intermediate point P ₉ reaching the valve opening point Po with zero gradient
The flat portion f ₄ is provided, and other configurations are similar to those of the first embodiment.

According to this embodiment, it is possible to cope with a strong swing in the lift direction of the base portion Cb in the middle portion of the valve closing period of the engine valve 4.

FIG. 10 shows a seventh embodiment of the present invention, in which the base portion is
At Cb, a flat portion f ₅ that reaches the intermediate point P ₁₀ relatively close to the valve opening point Po from the valve closing point Pc with a zero slope, and from the intermediate point P ₁₀ to the valve opening point P ₁₀
A steeply descending slope portion d ₉ that steeply descends the head A to o is provided, and other configurations are similar to those of the first embodiment.

According to this embodiment, it is possible to cope with a large swing in the lift direction of the base portion Cb immediately before the opening of the engine valve 4.

Further, FIG. 11 shows an eighth embodiment of the present invention, in which a hydraulic tappet 9 is attached to a swinging end portion of a cam follower 10 pivotally supported by a fixed rocker shaft 35, and its tip is attached to an engine valve 4 The structure is the same as that of the first embodiment except that it is brought into contact with the head.

In FIGS. 5 to 11, parts corresponding to those in the first embodiment are designated by the same reference numerals.

C. Effects of the Invention As described above, according to the present invention, the head difference between the valve closing point at which the base portion of the cam starts and the valve opening point at which the base portion ends is converted into the expansion / contraction amount of the hydraulic tappet, A, the hydraulic tappet. When the play is Lo, A ≦ Lo, and at the same time, the cam base has at least one steep slope and a flat or gentle slope that is continuous with the start or end of the steep slope. Since it is installed side-by-side, compared to the conventional structure in which the cam base has a constant downward slope over the entire section, the range of the limited drop between the valve closing point and the valve opening point is limited. It is possible to give a large downward slope to the steep downward slope portion within, and to secure a sufficient amount of the downward slope,
Therefore, if this steep slope portion is matched with the local swing timing in the lift direction of the base portion, even if the swing is large, it can be effectively offset by the slope of the steep slope portion, and it can also be offset. Unstable runout can be absorbed by the play of the hydraulic tappet, so that in the valve-closed region of the engine valve, the normal valve-closed state can be maintained even by runout of the base portion in the lift direction. Moreover, since it is not necessary to set the play of the hydraulic tappet to be particularly large in order to absorb the vibration, there is no fear that the valve opening characteristic of the engine valve is disturbed when the lift portion is operated.

[Brief description of drawings]

1 to 4 show a first embodiment of the present invention. FIG. 1 is a general view, FIG. 2 is a profile development view of a cam, and FIG. 3 is a vertical sectional view of a hydraulic tappet. The figures are displacement characteristic diagrams of hydraulic tappets and engine valves due to cam rotation, FIGS. 5 to 10 are cam profile development diagrams showing second to seventh embodiments of the present invention, and FIG. 11 is the present invention. 8 is an overall view corresponding to FIG. 1, showing an eighth embodiment of FIG. A: head, C: cam, Cl: lift, Cb: base, d _{1 to} d ₉ ... steep descent, e _{1 to} e ₃ ... gentle descent, f _{1 to} f _5: Flat part, Pc: Valve closing point, Po: Valve opening point 4: Engine valve, 6 ... Valve operating device, 9 ... Hydraulic tappet

 ─────────────────────────────────────────────────── ─── Continuation of front page (72) Inventor Masahiko Matsumoto 1-4-1 Chuo, Wako-shi, Saitama, Ltd. Inside Honda R & D Co., Ltd. (56) Reference JP-A-61-49112 (JP, A) Patent 31033 (JP, C1)

Claims (2)

[Claims] 1. A valve spring (7) for urging the engine valve (4) in a closing direction, a lift portion (Cl) for opening the engine valve (4) and closing of the engine valve (4) are allowed. A cam (C) having a base portion (Cb) that operates and a hydraulic tappet (9) that is interposed in a force transmission system from the cam (C) to the engine valve (4) and eliminates a valve head gap. In the valve operating system of the internal combustion engine, the hydraulic tappet (9) from the valve closing point (Pc) at which the base portion (Cb) of the cam (C) starts to the valve opening point (Po) at which the base portion (Cb) ends. Let A be the drop calculated in terms of the amount of expansion and contraction, and Lo be the play of the hydraulic tappet (9), and set A ≤ Lo and at the base (Cb) of the cam (C) from the valve closing point (Pc) side. At least one steep slope (d _{1 to} d ₃ , d ₈ , d ₉ ) descending steeply toward the valve opening point (Po) side, and this steep slope (d _{1 to} d ₃ , d _8). , the beginning of the d ₉₎ also Flat portion of zero gradient consecutive to the end (f ₁ ~f ₅₎ and is characterized in that the provided valve operating system for an internal combustion engine. 2. A valve spring (7) for urging the engine valve (4) in a valve closing direction, a lift portion (Cl) for opening the engine valve (4) and closing of the engine valve (4). A cam (C) having a base portion (Cb) that operates and a hydraulic tappet (9) that is interposed in a force transmission system from the cam (C) to the engine valve (4) and eliminates a valve head gap. In the valve operating system of the internal combustion engine, the hydraulic tappet (9) from the valve closing point (Pc) at which the base portion (Cb) of the cam (C) starts to the valve opening point (Po) at which the base portion (Cb) ends. Let A be the drop calculated in terms of the amount of expansion and contraction, and Lo be the play of the hydraulic tappet (9), and set A ≤ Lo and at the base (Cb) of the cam (C) from the valve closing point (Pc) side. At least one steep slope (d _{4 to} d ₇ ) that descends steeply toward the valve opening point (Po) side, and the start or end of this steep slope (d _{4 to} d ₇ ) is continuous. And the valve closing point (P
From c) side, characterized in that a and gentle descending slope portion descending at a gentle gradient towards the valve open point (Po) side (e ₁ ~e _3), a valve gear of an internal combustion engine.