JPH09228808A - Valve gear for internal combustion engine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To suppress abrasion of a cam and a valve lifter by reducing Hertz stress in the low rotating range of an engine, and to prevent generation of a phenomenon such as jumping and bounce by increasing the set load of a valve spring in a high rotating range. SOLUTION: In the valve gear of an internal combustion engine or opening/ closing valves (an intake valve and an exhaust valve) 1 at a suitable timing, one end of a valve spring 5 is received by a movable spring seat 10, and also the spring seat 10 is vertically moved by oil pressure, and thereby the installing length of the valve spring 5 is changed so as to change a set load thereof. The set load of the valve spring 5 is reduced in the low rotating range of the engine, and thereby it is possible to suppress Hertz stress of the nose part of a cam 18a, and also it is possible to suppress abrasion of the cam 18a and a valve lifter 16. The set load of the valve spring 5 is increased in the high rotating range of the engine, and thereby, it is possible to prevent generation of jumping and bounce of the valve spring 5.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a valve operating system for an internal combustion engine that opens and closes intake and exhaust valves at appropriate timings.

[0002]

2. Description of the Related Art Generally, in a four-cycle internal combustion engine, an intake / exhaust valve is opened / closed by a valve operating device at an appropriate timing to exchange gas in a cylinder. In particular, an OHC (overhead camshaft) type operation is performed. The valve device integrally includes an intake / exhaust valve urged to the closing side by a valve spring, a valve lifter held at the top of each stem of the intake / exhaust valve, and a cam slidably contacting the valve lifter. The intake / exhaust valve is opened and closed at an appropriate timing by rotationally driving the cam shaft with a part of engine power.

By the way, in such a valve train, since the Hertz stress of the cam nose portion at the time of engine stop or idling operation and the minimum margin load of the valve spring at the time of maximum rotation are determined, the angular area (intake / exhaust) When the valve lift amount is increased to increase the integral value ∫fdθ) of the variation of the gas passage area f of each valve with respect to the crank angle θ while the valve is open, the Hertzian stress becomes excessive and the cam or valve lifter becomes too large. Wear and abrasion loss increase.

Therefore, it is possible to reduce the Hertzian stress by reducing the set load of the valve spring.
When the set load of the valve spring is reduced, the margin load of the valve spring becomes small in a high engine speed region, and problems such as jumping and bounce of the valve spring occur.

The present invention has been made in view of the above problems. An object of the present invention is to reduce the Hertz stress in a low engine speed region to suppress wear of cams and valve lifters.
An object of the present invention is to provide a valve operating device for an internal combustion engine, which can increase the set load of the valve spring in a high rotation range to prevent occurrence of phenomena such as jumping and bounce.

[0006]

In order to achieve the above object, the invention according to claim 1 operates an internal combustion engine which opens and closes an intake valve and an exhaust valve biased in a closing direction by a valve spring at appropriate timings. In the valve device, one end of the valve spring is received by a movable spring seat, and by moving the spring seat up and down by hydraulic pressure, a mounting length of the valve spring is changed to change a set load thereof. .

According to a second aspect of the present invention, in the first aspect of the present invention, the moving amount of the valve seat is controlled according to the engine speed, and the valve spring mounting length is increased in a low speed range. It is characterized by lowering the set load and increasing the set load by shortening the mounting length of the valve spring in the high rotation range.

According to a third aspect of the present invention, in the first or second aspect of the invention, the oil chambers defined by the spring seats are provided in the intake valve and the exhaust valve, respectively, and the oil chamber on the intake valve side and the exhaust side are provided. The pressure oil supply line to the oil chamber is formed as a separate system, and an orifice is provided on the outlet side of each supply line.

According to a fourth aspect of the invention, in the invention of the third aspect, the diameter of the orifice is made different between the intake side and the exhaust side, and the orifice diameter on the side where the valve weight is large is larger than the orifice diameter on the other side. It is characterized by being set small.

Therefore, according to the first or second aspect of the present invention, in the low engine speed range, the mounting length of the valve spring is lengthened to reduce the set load, so that the Hertz stress in the cam nose portion is suppressed to a small value. The wear of the cam and valve lifter is suppressed, the wear loss is suppressed to a small value, and the set length is increased by shortening the valve spring mounting length in the high engine speed range, so the valve spring margin is increased. The load is increased to prevent jumping, bounce, etc., stable operation of the intake and exhaust valves is ensured, and the engine speed is increased.

According to the invention of claim 3 or 4,
Since a high hydraulic pressure acts on the oil chamber on the side of the large valve weight, a required set load can be applied to the valve spring of the valve on the high weight side, which is functionally required to have a high set load.

[0012]

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

<First Embodiment> FIG. 1 is a longitudinal sectional view of a valve train according to a first embodiment of the present invention, and FIG. 2 is a view showing a change in valve spring force with respect to a valve lift amount using an engine speed as a parameter. Is.

The OHC type valve operating device shown in FIG. 1 is a device provided in a four-cycle engine. This valve is opened and closed at an appropriate timing by opening and closing a valve (intake valve or exhaust valve) 1 in a cylinder 2. It is a gas exchange.

The valve 1 is composed of an umbrella portion 1a and a stem portion 1b. By inserting the stem portion 1b into a cylindrical valve guide 4 press-fitted and held in a cylinder head 3 made of an aluminum alloy casting. , Is held so that it can slide up and down. The valve 1 is constantly urged toward the closing side (upward in FIG. 1) by a valve spring 5, and the umbrella portion 1a has a cylinder of a port (intake port or exhaust port) 6 formed in the cylinder head 3. The seat 6 is intermittently seated on the ring-shaped valve seat 7 fitted around the peripheral edge of the opening to open the port 6 at an appropriate timing.

By the way, in the valve gear according to the present embodiment, the mounting length of the valve spring 5 is variable, and its set load is adjusted according to the engine speed. The configuration of will be described.

That is, the valve spring 5 includes a retainer 9 fixed to the top of the stem portion 1b of the valve 1 via a cotter 8 and a spring seat 1 movably supported in the vertical direction.
It is disguised between 0 and.

The spring seat 10 has a recess 3 formed around the valve guide 4 of the cylinder head 3.
It is vertically movably fitted and retained in a, and its outer peripheral surface and the recess 3a are sealed by an oil sheet 11 provided on the cylinder head 3 side. The inner peripheral side of the spring seat 10 is in sliding contact with the outer periphery of the valve guide 4 via an oil seal 12 held by the spring seat 10, and the spring seat 10 and the valve guide 4 are separated by the oil seal 12. It is sealed.
In FIG. 1, 13 is a seal ring attached to the outer circumference of the upper end portion of the valve guide 4, which is in sliding contact with the outer circumference of the stem portion 1b of the valve 1.

Thus, as shown in FIG. 1, an oil chamber S defined by the spring seat 10 is formed in the recess 3a of the cylinder head 3, and the oil chamber S is oiled via the oil passage 14. It communicates with the road 15. The oil passage 15 is formed in the cylinder head 3 to be long in the direction perpendicular to the paper surface of FIG. 1, and is connected to a hydraulic pump (not shown).

On the other hand, on the top of the stem portion 1b of the valve 1, a cap-shaped valve lifter 16 having an opening at the bottom is held via a shim 17 for adjustment, and the valve lifter 16 is formed on the cylinder head 3. It is fitted and held in the formed circular hole-shaped guide portion 3b so as to be vertically slidable.

A cam shaft 18 which is long in the direction perpendicular to the paper surface of FIG. 1 is rotatably disposed above the cylinder head 3, and the cam shaft 18 is integrally formed with a cam 18a having a predetermined shape. . The upper surface (crown surface) of the valve lifter 16 is brought into contact with the cam 18a at a predetermined pressure by the urging force of the valve spring 5. The hydraulic pump is rotationally driven by the cam shaft 18.

Next, the operation of the valve operating system according to this embodiment will be described.

When the engine is operated and the rotation of the crankshaft (not shown) is transmitted to the camshaft 18 through a power transmission system (not shown) such as a chain transmission mechanism, the camshaft 18 is half the crankshaft. The nose portion (top portion) of the cam 18a, which is rotationally driven at a speed and is integrally formed with the cam 18a, is the valve lifter 16.
Abut and push it down. Then, the valve 1 in the closed state is opened as shown in FIG.

After that, when the nose portion of the cam 18a is released from the contact with the valve lifter 16, the valve 1 is closed again by the urging force of the valve spring 5 as shown in FIG. Is opened and closed at an appropriate timing, and the required gas exchange is performed in the cylinder 2.

By the way, as described above, the hydraulic pump (not shown) is driven by the cam shaft 18, and pressure oil having a pressure corresponding to the engine speed (rotation speed of the cam shaft 18) is supplied to the oil passages 15, 1.
The oil is supplied to the oil chamber S via No. 4.

Thus, the pressure of the pressure oil supplied to the oil chamber S depends on the engine speed n, and the pressure of the pressure oil is low in the low rotation range, so the spring seat 10 is at a low position, and therefore, The distance between the retainer 9 and the valve seat 10 is lengthened, the mounting length of the valve spring 5 is lengthened, and the set load of the valve spring 5 is suppressed low.

On the contrary, in a high engine speed range where the engine speed n is high, the pressure of the pressure oil supplied to the oil chamber S becomes high, so that the spring seat 10 receives a high oil pressure on its lower surface and moves upward. As a result, the distance between the retainer 9 and the valve seat 10 becomes shorter, the mounting length of the valve spring 5 becomes longer, and the set load of the valve spring 5 is increased.

Here, in FIG. 2, the valve spring 5 with respect to the lift amount of the valve 1 when the engine speed n is n ₁ , n ₂ , ..., N ₅ (n ₁ <n ₂ <... <n ₅ ) respectively. The change in the urging force (valve spring force) of the valve spring increases as the engine speed n increases.

As described above, in the present embodiment,
In the low engine speed range where the engine speed n is low, the set length of the valve spring 5 is increased to reduce the set load, so that the Hertz stress at the nose portion of the cam 18a is suppressed to a small level, and the cam 18a and the valve lifter 16 are suppressed. Wear of the engine is suppressed and wear loss is suppressed to be small, and the fuel efficiency of the engine is improved.

Further, in the high engine speed range where the engine speed n is high, the mounting length of the valve spring 5 is shortened and the set load thereof is increased. Therefore, the margin load of the valve spring 5 is increased and jumping, bounce, etc. Is prevented, stable operation of the valve 1 is ensured in a high rotation range, and the engine speed is increased.

<Second Embodiment> Next, a second embodiment of the present invention will be described with reference to FIGS. 3. FIG. 3 is a circuit diagram showing a pressure oil supply system to a valve operating system of a multi-cylinder engine, and FIG. 4 is a diagram showing changes in hydraulic pressure with respect to a camshaft rotation speed with an orifice diameter as a parameter.

In this embodiment, the valve operating system according to the present invention is applied to a multi-cylinder engine, and the basic structure of the valve operating system is the same as that of the first embodiment.

Thus, in the present embodiment, in order to supply the pressure oil to the plurality of oil chambers (similar to the oil chamber S shown in FIG. 1) S1 and S2 provided for the intake valve and the exhaust valve, respectively. The supply lines of the intake side and the intake side are separate systems.

That is, the supply line L connected to the discharge side of the hydraulic pump (not shown) is branched into two systems, an intake side supply line L ₁₁ and an exhaust side supply line L ₂₁ , and the intake side supply line L.
Each of the plurality of oil passages 19 branching from ₁₁ is connected to the oil chamber S1 of the intake side, a plurality of oil passages 20 branching from the exhaust-side supply line L ₂₁ is connected to the oil chamber S2 of the exhaust-side .

The oil passage 21 extending from each intake-side oil chamber S1 merges with the intake-side discharge line L _12, and the oil passage 22 extending from each exhaust-side oil chamber S2 merges with the exhaust-side discharge line L ₂₂ . I am joining. Then, the discharge lines L on the intake side and the exhaust side
Orifices 23 and 24 are provided at ₁₂ and L ₂₂ , respectively, and an intake side orifice 2 having a heavy intake valve is provided.
The diameter of 3 is set smaller than the diameter of the exhaust-side orifice 24 having an exhaust valve lighter than the intake valve.

The pressure oil discharged from the hydraulic pump (not shown) driven by the camshaft is supplied from the supply line L to the intake side and exhaust side supply lines L ₁₁ , L ₂₁ and the oil passage 19,
It is supplied to the oil chambers S1 and S2 via 20 and the set load of the valve spring of the intake / exhaust valve is adjusted according to the engine speed (camshaft speed) as in the first embodiment.

By the way, in the present embodiment, the orifices 23 and 24 are provided in the discharge lines L ₁₂ and L ₂₂ on the intake side and the exhaust side, respectively, and the diameter of the orifice 23 on the intake side is smaller than the diameter of the orifice 24 on the exhaust side. Since the pressure is set, the pressure (hydraulic pressure) in the oil chamber S1 on the intake side becomes higher than the pressure (hydraulic pressure) in the oil chamber S2 on the exhaust side, and a high weight that requires a high set load is functionally required. A required set load can be applied to the valve spring of the intake valve.

Here, FIG. 4 shows changes in the respective hydraulic pressures on the intake side and the exhaust side with respect to the camshaft rotational speed, with the orifice diameter as a parameter.

[0039]

As is apparent from the above description, claim 1
According to the invention described in claim 2, since the set length of the valve spring is increased by lowering the set length of the valve spring in the low engine speed range, the Hertz stress of the cam nose portion is suppressed to a small level, and the wear of the cam and the valve lifter is reduced. In addition, the wear loss is kept small, and the set length of the valve spring is shortened to increase the set load in the high engine speed range, increasing the margin load of the valve spring and jumping or bouncing. It is possible to obtain the effect that the occurrence of the above is prevented, stable operation of the intake and exhaust valves is secured, and the engine speed is increased.

According to the invention of claim 3 or 4,
The high hydraulic pressure acts on the oil chamber on the side with a large valve weight, so the required set load can be applied to the valve spring of the valve on the high weight side, which requires a high set load from the functional viewpoint. Is obtained.

[Brief description of drawings]

FIG. 1 is a vertical sectional view of a valve train according to a first embodiment of the present invention.

FIG. 2 is a diagram showing a change in valve spring force with respect to a valve lift amount in the valve operating system according to the first embodiment of the present invention, with an engine speed as a parameter.

FIG. 3 is a circuit diagram showing a pressure oil supply system to a valve train of a multi-cylinder engine according to a second embodiment of the present invention.

FIG. 4 is a diagram showing a change in hydraulic pressure with respect to a camshaft rotation speed, using an orifice diameter as a parameter.

[Explanation of symbols]

1 Valve (intake valve, exhaust valve) 5 Valve spring 10 Valve seat 23, 24 Orifice L ₁₁ , L ₂₁ Pressure oil supply line L ₁₂ , L ₂₂ Pressure oil discharge line S, S 1, S 2 Oil chamber

Claims (4)

[Claims] 1. A valve operating system for an internal combustion engine, which opens and closes an intake valve and an exhaust valve biased in a closing direction by a valve spring at appropriate timings, wherein one end of the valve spring is received by a movable spring seat, and A valve operating system for an internal combustion engine, wherein the spring seat is moved up and down by hydraulic pressure to change the mounting length of the valve spring to change the set load. 2. The amount of movement of the valve seat is controlled in accordance with the engine speed, the mounting length of the valve spring is lengthened to lower the set load in the low speed range, and the mounting length of the valve spring is controlled in the high speed range. The valve operating system for an internal combustion engine according to claim 1, wherein the set load is increased by shortening the height. 3. An oil chamber partitioned by the spring seat is provided in each of the intake valve and the exhaust valve, and a pressure oil supply line to the intake valve side oil chamber and the exhaust side oil chamber is provided as a separate system. The valve operating system for an internal combustion engine according to claim 1 or 2, wherein an orifice is provided on the outlet side of each supply line. 4. The internal combustion engine according to claim 3, wherein the diameter of the orifice is made different between the intake side and the exhaust side, and the orifice diameter on the side having a larger valve weight is set smaller than the orifice diameter on the other side. Engine valve system.