JPH0625524B2 - Valve drive for internal combustion engine - Google Patents

Description

Detailed Description of the Invention A. OBJECT OF THE INVENTION (1) Industrial field of use The present invention relates to a valve operating system for an internal combustion engine, and more particularly to a plurality of valve springs for urging a plurality of engine valves in a valve closing direction and a corresponding engine valve opening valve. A cam shaft having a plurality of cams including a lift portion and a base portion that allows the engine valve to be closed, and a plurality of cam shafts that are interposed in a force transmission system from each cam to a corresponding engine valve to eliminate a valve head gap. The improvement with the hydraulic tappet of

(2) Conventional technology Conventionally, in a valve train of an internal combustion engine, in order to prevent a valve closing failure in an engine valve due to cam vibration caused by center runout or bending of a cam shaft, a base portion of the cam is prevented. A constant downward gradient is applied from the valve closing point to the valve opening point, and the drop between these 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 base It is known to offset the runout in the lift direction of the base part with the downward slope of the base part (JP-A-59-4).
3911 gazette).

(3) Problems to be Solved by the Invention However, in the case of an internal combustion engine equipped with a plurality of similar engine valves,
The inventor has determined that the swinging degree of the base portion of each cam in the lift direction is not uniform even on the same cam shaft, and varies depending on the position of the cam. Therefore, in order to absorb the runout of all the base parts by the above-mentioned conventional device, it is necessary to increase the play of the full 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 a delay in the opening timing of all engine valves and a decrease in the opening stroke.

The present invention has been made in view of such circumstances, and it is possible to prevent different swings in the lift direction of each base portion from affecting the corresponding engine valve without increasing the play of each hydraulic tappet. An object of the present invention is to provide a valve operating device for an internal combustion engine.

B. Configuration of the Invention (1) Means for Solving the Problems In order to achieve the above object, according to the present invention, the base portion of each cam is configured by connecting a plurality of gradient portions having different gradients and , At least one of the gradient portions is a downward gradient portion that descends from the valve closing point side to the valve opening point side, and the gradient change position of the base portion between the plurality of cams is a swing mode in the lift direction of each base portion. It is set differently depending on.

(2) Operation When the base parts of multiple cams swing in different directions in the lift direction, each swing can be efficiently performed by the unique shape of the corresponding base part that includes at least the downslope portion and has different slope changing positions. Can be offset.

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

First, in FIG. 1 showing a first embodiment of the present invention, reference numeral 1 is a cylinder head of a four-cylinder internal combustion engine, and therefore four combustion chambers 2 and four intake (opening in these combustion chambers 2 are An exhaust (exhaust) air port 3 is formed, and the intake (exhaust) air port 3 is opened and closed by an intake (exhaust) air valve, that is, an engine valve 4.

Each engine valve 4 is movably supported by the cylinder head 1 via a valve guide 5, and is opened / closed by a valve train 6 according to the present invention.

The valve operating device 6 is provided between the retainer 4a fixed to the head of each engine valve 4 and the cylinder head 1, and a valve spring 7 for urging the engine valve 4 in the closing direction. Corresponding to the hydraulic tappet 9 mounted in the support hole 8 of the cylinder head 1, and a cam follower 10 which is swingably supported by each hydraulic tappet 9 and whose tip is engaged with the head of the corresponding engine valve 4. , The first to fourth cams C ₁ to C on the slipper surface 10a on the upper side of each cam follower 10 are driven to rotate by the crankshaft.
₄ and a cam shaft 11 that engages with each other.

As shown in FIG. 2, the cam shaft 11 is a toothed pulley 12 that is decelerated from a crank shaft via a timing belt.
And first to fifth journals J _{1 to} J ₅ arranged in order from the toothed pulley 12 side, and the first to fourth cams C ₁ to
C ₄ is sequentially arranged between the journals J _{1 to} J ₅ so as to be arranged from the toothed pulley 12 side.

The first to fifth journals J _{1 to} J ₅ are lower bearing half bodies 13 _{1 to} 13 ₅ formed integrally with the cylinder head 1, and
The bearing halves 13 _{1 to} 13 ₅ are supported by the upper bearing halves 14 _{1 to} 14 ₅ which are bonded to each other.

As shown in FIG. _1, each of the cams C _{1 to} C ₄ has a lift portion Cl that opens the corresponding engine valve 4 and a base portion Cb that allows the valve 4 to be closed. One of the boundary points of Cl and Cb is the valve closing point Pc and the other is the valve opening point Po, and a predetermined drop A is given to the valve opening point Po based on the valve closing point Pc.

Figure 3 is a cam shaft during rotation of 11, the amount upper bearing half 14 ₁ first to fifth journal _J 1 through J ₅ swings downward
Shows the results of measurement on the basis of the inner surface of ~ 14 _5, this result based shake estimates of the first to fourth lifting direction of the base portion Cb of the cam C ₁ -C _4, deflection thereof Symmetrically with each of the base portions Cb of the _first to fourth cams C _{1 to} C _4.
The shape of is determined.

That is, as shown in FIG. 4, the first and fourth cams C ₁ , C
Each base portion Cb of _4, first close to the closing point Pc
A first slow descending slope portion _{e 1} down the drop of approximately (1/5) A in the gradually to an intermediate point _{P 1,} the valve open point from the first intermediate point _{P 1} Po
To a second intermediate point P ₂ relatively close to the steep descent slope portion d that steeply descends a head of approximately (3/5) A, and a remaining steep slope from the second intermediate point P ₂ to the valve opening point Po. It is composed of a second gentle descending slope portion e ₂ .

Also, as shown in FIG. 5, the second and third cams C ₂ , C ₃
Each of the base portions Cb has a gentle descending slope portion e that gradually descends a head of approximately (1/5) A from the valve closing point Pc to an intermediate point P ₃ near the center of the base portion Cb, and an intermediate point P ₃ To a valve-opening point Po at a steep slope.

Thus, the first and second intermediate points P ₁ and P _{2 at the} base portions Cb of the first and fourth cams C ₁ and C _{4 and} the base portions of the second and third cams C ₂ and C ₃ are provided. the said intermediate point P ₃ in Cb is true slope change position of the present invention. And as is clear from FIGS. 4 and 5, the first and fourth cams C
The first and second intermediate points P ₁ and P ₂ (that is, the gradient change position) and the second and third intermediate points C ₁ and C ₄ of the base portion Cb.
The intermediate point P in each base portion Cb of the cams C ₂ and C _3
3 (that is, the gradient change position) means that each base portion Cb of
It is set to be different depending on the swing mode in the lift direction shown in FIG.

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 22 at its outer end.
The spherical recess 10b at the base end of the cam follower 10 corresponding to a
Engage with.

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.
The oil sump chamber 23 includes an oil hole 25 on a side wall of the plunger 22, an annular oil passage 27 between sliding surfaces of the cylinder 20 and the plunger 22.
Also, through the oil hole 26 on the side wall of the cylinder 20, it communicates with the oil supply passage 32 bored in the cylinder head 1, and this oil supply passage 32 communicates with the discharge port of an oil pump (not shown). Therefore, during operation of the engine, the oil sump 23 is constantly filled with oil sent from the oil pump.

The lower end of the plunger 22 has a hat-shaped valve cage 28.
Flange portion 28a of the caulking ring 3
It is fixed by 3. The valve cage 28 accommodates a free-ball type check valve 29 which has an opening / closing stroke defined therein and opens / closes the valve hole 24. That is, the check valve 29 is not biased by the spring 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.

Then, when the lift portion Cl of each of the cams C _{1 to} C ₄ applies a pressing force to the slipper surface 10 a of the cam follower 10 as the cam shaft 11 rotates, the hydraulic tappet 9 causes the plunger 22 to move.
Is pushed toward the hydraulic chamber 21 side, the hydraulic chamber 21 starts to increase in pressure, and a small amount of oil flows from the chamber 21 through the valve hole 24 into the oil reservoir 23, causing the plunger 22 to initially sink, The check valve 29 closes the valve hole 24 to maintain the oil pressure in the hydraulic chamber 21, and subsequently, the entire plunger 22 elastically sinks due to the compression of bubbles mixed in the oil in the hydraulic chamber 21. As a result of the hydraulic pressure of the chamber 21 suddenly rising and the plunger 22 exerting a pedaling tension due to the hydraulic pressure, the corresponding cam follower 10 has the spherical end portion 2 of the plunger 22.
2a is used as a fulcrum to swing downward by the lift portion Cl, and the corresponding engine valve 4 is opened against the force of the valve spring 7.

While the engine valve 4 is open, the high pressure oil in the hydraulic chamber 21 is transferred to the cylinder 2
0 and a slight leak into the sliding gap of the plunger 22, causing the plunger 22 to leak and sink.

Next, when the base portion Cb of each of the cams C _{1 to} C ₄ arrives at 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.

If the hydraulic chamber 21 is decompressed by the expansion action of the expansion spring 31 on the plunger 22, 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.

Lo ... Hydraulic tappet play _1A ... Hydraulic tappet 9 required to close the check valve 29.
Initial sink amount _1B ... Elastic sink amount of tappet 9 due to compression of bubbles in oil in hydraulic chamber 21 L ... Leak sink that hydraulic tappet 9 sinks due to hydraulic leak from hydraulic chamber 21 during opening of engine valve 4. When the amount is expressed as follows, the drop A converted from the valve closing point Pc of each of the cams C _{1 to} C _{4 to} the valve opening point Po in terms of the expansion / contraction amount of the hydraulic tappet 9 is set so that the following equation is satisfied.

A ≦ Lo ………… (1) Lo = _1A + _1B + L …… (2) Next, the operation of this embodiment will be described.
When each base portion Cb of the cams C _{1 to} C ₄ is operated, the plunger 22 of the corresponding hydraulic tappet 9 follows the shape of each base portion Cb with the check valve 29 opened.

By the way, the base portions C of the first and fourth cams C ₁ and C ₄
Since b is configured by sequentially connecting the first gently descending slope portion e ₁ , the steeply descending slope portion d, and the second gradually descending slope portion e ₂ from the valve closing point Pc side, the plunger 22 that engages with the above is described above. Since the slope portions e ₁ , d, e ₂ are sequentially extended downward, the first and fourth cams C ₁ , C ₄ are closed during the closing of the corresponding engine valve _4.
When each of the base portions Cb of the hydraulic swing wing swings symmetrically with the downward slope portions e ₁ , d, e ₂ in the lift direction, the swing is offset by the downward slope portions e ₁ , d, e ₂ and the check of the hydraulic tappet 9 is cancelled. The closing of the valve 29 can be prevented.

Since the base portion Cb of the second and third cam C _2, C ₃ is constituted from the closed point Pc side lined with gentle slope portion e and steep part d, it plunger 22 to engage the Since the slope portions e and d extend downward, the base portions Cb of the second and third cams C ₂ and C ₃ are connected to the descending slope portions e and d while the corresponding engine valve 4 is closed. When it swings symmetrically in the lift direction, the swing is offset by the gradient portions e and d, and the check valve 29 of the hydraulic tappet 9 can be prevented from opening.

In any of the above cases, if the shake of the cams C _{1 to} C ₄ is large enough to be absorbed by each base portion Cb, the remaining shake is absorbed by the play Lo of the corresponding hydraulic tappet 9 itself.

Thus, all engine valves 4 receive no unnecessary opening force,
A normal valve closed state can be maintained. Moreover, it is not necessary to set the play Lo of each hydraulic tappet 9 to be particularly large.

FIG. 7 shows a second embodiment of the present invention, in which each hydraulic tappet 9 is attached to the swinging end portion of a cam follower 10 pivotally supported by a fixed rocker shaft 35, and the tip end portion thereof corresponds. The structure is the same as that of the previous embodiment except that it is brought into contact with the head portion of the engine valve 4, and in the figure, parts corresponding to those of the previous embodiment are designated by the same reference numerals.

The present invention can be applied to a single-cylinder internal combustion engine as long as it has a plurality of engine valves of the same type, such as a two-intake valve type and a two-exhaust valve type.

C. As described above, according to the present invention, the base portion of each cam is configured by connecting a plurality of gradient portions having different gradients, and at least one of the gradient portions is opened from the valve closing point side. It is a downward slope portion that descends to the valve point side, and the gradient change position of the base portion between the plurality of cams is set to differ depending on the swing mode of each base portion in the lift direction. When the base portions of the above swing in different directions in the lift direction, the respective swings can be efficiently canceled by the unique shape of the corresponding base portion that includes at least the downslope portion and has a different slope changing position, and thus, Even if the base parts of a plurality of cams swing in different directions in the lift direction, it is not necessary to set the play of all hydraulic tappets to a particularly large value. You can avoid it.

[Brief description of drawings]

1 to 6 show a first embodiment of the present invention,
FIG. 1 is a vertical sectional side view of a main part of a four-cylinder internal combustion engine equipped with a valve operating system of the present invention, FIG. 2 is a vertical sectional front view showing a cam shaft and its supporting structure, and FIG. FIG. 4 is a diagram showing the deflection of each journal, FIG. 4 is a profile development view of the first and fourth cams on the cam shaft, FIG. 5 is a profile development view of the second and third cams on the cam shaft, and FIG. FIG. 7 is a vertical sectional view of the hydraulic tappet, and FIG. 7 is an overall view corresponding to FIG. 1, showing a second embodiment of the present invention. C ₁ ~C ₄ ...... cam, Cl ...... lift portion, Cb ...... base portion, Pc ...... closing point, Po ...... valve open _{point, P 1;} P _2;
P ₃ ... First intermediate point as gradient change position; second intermediate point; intermediate point, e ₁ ; d; e ₂ ... first slow downhill gradient section; steep downhill gradient section; second slow down gradient section Downhill section, e; d
...... Slowly descending slope part as slope part; steeply descending slope part 4 ...... engine valve, 6 ...... valve device, 7 ...... valve spring, 9 ......
Hydraulic tappet, 11 ... Cam shaft

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Toshiaki Hiro, 1-4-1 Chuo, Wako-shi, Saitama, Honda R & D Co., Ltd. (56) Reference JP-A-61-49112 (JP, A) JP Sho 58-51204 (JP, A)

Claims (1)

[Claims] 1. A plurality of valve springs (7) for urging a plurality of engine valves (4) in a closing direction, and corresponding engine valves (4).
(C ₁ -C) consisting of a lift portion (Cl) that opens the valve and a base portion (Cb) that allows the engine valve (4) to close.
₄ ) a plurality of cam shafts (11) and the respective cams (C ₁ to C _1
4 ) and a plurality of hydraulic tappets (9) which are interposed in a force transmission system from the corresponding engine valve (4) to eliminate the valve head clearance, each cam (C ₁ ,
The base portion (Cb) of C ₄ ; C ₂ , C ₃ ) is configured by connecting a plurality of gradient portions (e ₁ , d, e ₂ ; e, d) having different gradients, and at least one of them. Two slopes (e
₁ , d, e ₂ ; e, d) is a descending slope portion that descends from the valve closing point (Pc) side to the valve opening point (Po) side, and a plurality of cams (C ₁ , C ₄ ; C ₂ , C ₃ ) Base part (Cb) between each other
Valve positions of the internal combustion engine are set so that the gradient change positions (P ₁ , P ₂ ; P ₃ ) of the bases (C ₁ , P ₂ ; apparatus.