JPS6233045Y2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to improvements in intake and exhaust valve springs for internal combustion engines.

Air supply valve attached to the cylinder lid of an internal combustion engine,
The structure of the exhaust valve is shown in Figure 1. In the figure, the valve stem 1 is placed in a state where it receives an upward spring load via the spring receiver 6 by the valve holders 4 and 5 attached to the upper part of the valve holder 2 incorporated in the cylinder lid 3. There is. The valve stem 1 has a structure in which its upper end is pushed downward by a tappet 7 to open the valve.

During the opening/closing operation, a helical spring is usually provided to prevent asymmetric movements such as jumping of the valve mechanism due to inertial force.

As the performance of internal combustion engines improves and the number of revolutions increases,
The need to open the valve rapidly requires an increase in the force of the valve spring to counteract the increased inertial force. In the design of valve springs,
In order to increase the spring force while ensuring the strength of the spring material, the coil diameter and spring height of the valve spring must be increased, which poses a major hindrance to securing space above the cylinder lid and designing component placement. Become. In addition, high-speed rotation and rapid opening of the valve cause a high-order excitation effect on the valve spring, causing a surging phenomenon of the spring, which is likely to cause noise and spring damage. Further, the large spring mounting force makes it difficult to disassemble and assemble the valve spring portion, which may cause handling problems.

The purpose of this invention is to focus on the above points and use an air spring instead of a helical spring.The main feature of this invention is that the valve valves of the intake valve and exhaust valve are attached to the cylinder lid. In the installed internal combustion engine, a piston is connected to the valve stems of supply and exhaust valves and is slidably fitted in a cylinder provided in the valve chamber, and is partitioned by the lower surface of the piston and the inner surface of the cylinder. The device is equipped with a sealed air chamber and an air supply valve that controls the amount of air supplied to the air chamber.

In this case, the valve spring portion can be made more compact, problems caused by the surging phenomenon peculiar to helical springs can be prevented, and handling is also improved.

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

FIG. 2 is a sectional view showing the structure of an air spring type valve according to an embodiment of the present invention.

In the figure, reference numerals 1, 2, 3 and 7 indicate the same members as in FIG.

The upper part of the valve holder 2 is formed into a cylinder whose end is open upward.

A piston 9 is connected to the end of the valve stem 1 and is slidably housed in the cylinder, forming an air chamber 8 with the cylinder.

The air chamber 8 is sealed by a seal ring 10 of the piston 9 and a seal ring 12 of the valve stem bush 11.

Each air chamber 8 has an air supply valve 1 with a check valve.
4. An air safety valve 15 and a drain tank 16 are provided.

FIG. 3 is a sectional view showing the structure of another embodiment of the air spring type valve according to the present invention.

In this case, the air chambers 8 of a large number of valves are connected to the air communication passage 13 having a sufficient passage area through respective branch passages, and the air supply valve 1
4. Only one air safety valve 15 and one drain tank 16 are provided in the air communication path 13.

The operation in the case of the above configuration will be described.

Generally, the opening/closing timing and lift of the intake and exhaust valves of an internal combustion engine are determined by cams, and the valves are pushed open by a tappet 7 of the valve mechanism. During this operating period, as shown in Figure 4, positive and negative inertial forces F _I based on the acceleration of the cam act on the valve train, and when negative inertia is applied, the valve train moves away from the cam. This will result in a phenomenon of cluttering. In order to suppress this, in the conventional valve part, helical springs 4 and 5 are provided, and the spring force F _S is set to exceed the negative inertial force F _I . In FIG. 4, it is designed to maintain the relationships F _SA > F _IA and F _SB > F _IB .

In the present invention, a sealed air chamber 8 is provided in the upper part of the valve valve 2 by applying an appropriate pressure, and a piston 9 is attached to the upper part of the valve stem, so that the force due to air pressure is constantly applied to the valve mechanism via the tappet 7. This counteracts the negative inertia force applied to the valve train during operation.

As shown in FIG. 2, when an air chamber is provided for each valve, the air is compressed as the valve lifts, and its air pressure increases. As shown in FIG. 5, it has almost the same load characteristics as the valve spring. In the figure, the solid line indicates the valve spring force F _S and the broken line A ₁ indicates the air spring force of the individual valve.

As shown in Figure 3, when the air chambers of multiple valves are connected by an air communication path with sufficient passage area and capacity, the operation of each _valve causes , although some pulsations occur in the air pressure, the air spring force is almost constant. In either case, it serves to suppress the negative inertia force applied to the valve train, allowing smooth operation.

The operation of the air spring type valve will be explained in more detail with reference to FIGS. 4 to 6.

The inertial force F _I acting on the valve train is calculated from the moving part weight W, cam acceleration α, and gravitational acceleration g using the following equation.

F _I = W/g・α (i) Also, in Fig. 6, v is the cam speed, S is the cam lift, area C is the rapid valve opening area, and area D is the area where the cam speed is gradual following area C. Region E is a region where the cam lift is constant. When the acceleration α changes as shown in FIG. 6, the inertial force F _I changes as shown in FIG. 4 according to equation (i) in accordance with the change in the acceleration α.

On the other hand, in the conventional device shown in _FIG.
is expressed by the following formula.

F _S = F _O +K・S (ii) In formula (ii), F _O is the mounting load of the helical springs 4 and 5, K is the composite spring constant of the helical springs 4 and 5, and S is the combined spring constant of the helical springs 4 and 5. This is the cam lift shown in the figure. Therefore, when the cam lift S changes as shown in FIG. 6, the spring force F _S changes in proportion to the cam lift S as shown in FIG. 4.

Generally, the air spring force A is expressed by the following equation, where A _P is the pressure receiving area of the piston 9, P _O is the initial pressure of the air spring, and P is the pressure increase based on the displacement of the piston 9.

A=A _P (P _O +P) (iii) Furthermore, if the specific heat ratio of air is k and the compression ratio is ε, the pressure increase is P=P _O (ε ^k −1) (iv) And the maximum valve lift The volume of air chamber 8 at the time is V
_C and the stroke volume of the piston 9 as V _S , the compression ratio is expressed by the following equation.

ε=V _C +V _S /V _C =1+V _S /V _C (v) Note that V _S =A _P ·S(vi).

As shown in Figure 2, each valve has its own air chamber 8.
, the cam lift S and the increase in air pressure P
The relationship is shown by equations (iv), (v), and (vi), and when the cam lift S changes as shown in Figure 6, the air spring force A is as shown in _A1 in Figure 5. Change.

Furthermore, when the air chambers 8 of multiple valves are connected by air communication passages having sufficient passage area and capacity as shown in FIG. 3, the air chamber volume V _C at maximum valve lift in equation (v) includes the volume of the air communication passage 13, so it can be considered to be sufficiently large compared to the volume V _S of the higher piston 9, and the increase in air pressure becomes zero, regardless of the cam lift S. In this case the spring force A changes as shown by _A2 in FIG.

In the case of the single air chamber shown in Figure 2, the air temperature rise at the maximum lift of the valve is several times higher, even if adiabatic compression is assumed.
This temperature rise will be limited to about 10°C and will not cause any problems. In the case of the air chamber connected type shown in Figure 3, this type of temperature rise will not occur.

On the other hand, if the temperature of the air chamber rises due to heat transfer from around the valve during engine operation, the increase in air pressure will be
For example, an increase in temperature of 50°C will approximately double the pressure. If the pressure increases, the spring load becomes excessive and unnecessary overload is applied to the valve train, so the air safety valve 15 regulates the maximum pressure.

The piston 9 and the valve stem bush 11 are provided with seal rings 10 and 12, respectively,
The compressed air in the air chamber is prevented from leaking, but if air leaks for some reason and the pressure drops, air is automatically supplied from the air source by the air supply valve 14 with a check valve and the air is supplied as needed. It is designed to ensure the minimum air pressure.

When the engine is stopped for a long time and the air supply from the air source is stopped, the valve stem opens due to its weight, but the valve closes to prevent foreign matter and moisture from entering the cylinder from the supply and exhaust side. It's better to keep it. One relatively weak spring 17, which slightly exceeds the weight of the valve stem and piston and the frictional force of each part, is provided at the bottom of the air chamber piston to push the valve stem upward when the engine is stopped.

Note that instead of the air supply valve 14, a valve having a function of automatically controlling the amount of supplied air may be provided. In this case, the air safety valve 15 is unnecessary.

The effects of the present invention as described above will be described.

Generally, the supply and exhaust valves of internal combustion engines are equipped with valve springs in order to suppress the negative inertial force generated during the operation of the valve train, but when the air spring according to the present invention is used, the following advantages are achieved. be.

(1) Compared to the valve spring method, the valve valve upper structure is more compact, making it easier to arrange the upper part of the cylinder lid in terms of space.

(2) There is no need to worry about noise or spring breakage due to the surging phenomenon unique to valve springs.

(3) Inspection and maintenance are easy because there is no need to disassemble or assemble the valve spring, which requires a strong installation load.

[Brief explanation of the drawing]

Fig. 1 is a sectional view showing the structure of a conventional intake valve and exhaust valve of an internal combustion engine, Fig. 2 is a sectional view showing the structure of an air spring type valve according to an embodiment of the present invention, and Fig. 3 is a sectional view showing the structure of an air spring type valve according to the present invention. FIG. 4 is a diagram showing changes in valve spring force and inertia force, and FIG. 5 is a diagram showing changes in valve spring force and air spring force. A diagram showing the state, FIG. 6 is a diagram showing changes in cam lift, cam speed, and cam acceleration. 1... Valve stem, 2... Valve fan, 3... Cylinder lid, 8
...Air chamber, 9...Piston, 13...Air communication path, 1
4...Air supply valve with check valve, 15...Air safety valve.

Claims (1)

[Scope of utility model registration request] In an internal combustion engine in which the intake and exhaust valves are mounted on the cylinder lid, the valve is connected to the valve stems of the intake and exhaust valves and is slidably fitted into the cylinder provided on the valve. An air supply/exhaust valve for an internal combustion engine, comprising: a piston, a sealed air chamber defined by the lower surface of the piston and an inner surface of a cylinder, and an air supply valve that controls the amount of air supplied to the air chamber. Spring.