JPH0517366Y2 - - Google Patents

Description

[Detailed explanation of the idea] (Industrial application field) The present invention relates to a valve device for an internal combustion engine.

(Prior art) In the case of internal combustion engines for automobiles, multiple exhaust valves and intake valves provided in one cylinder are operated independently of each other for the purpose of improving combustibility in high-speed, high-load ranges. is proposed.

As this type of valve device, for example,
What was disclosed in Publication No. 17967 is the valve timing of two exhaust valves in the same cylinder in a 4-stroke, 4-valve internal combustion engine, as shown in Figure 7.
Valve timing of E ₁ , E ₂ and two intake valves
I ₁ and I ₂ each have a predetermined phase difference, and near top dead center from the exhaust stroke to the intake stroke, one set of exhaust valves and intake valves closes and the other set of exhaust valves and intake valves opens. This increases the flow rate of fresh air in the cylinder to improve scavenging efficiency. In addition, only one intake valve opens near the bottom dead center from the intake stroke to the compression stroke, creating an intake swirl in the cylinder.
It is designed to improve combustibility mainly in high-speed, high-load ranges.

(Problem to be solved by the invention) By the way, in such a valve device, since the two exhaust valves have a phase difference in the timing of full closing, valve overlap occurs when the intake and exhaust valves open at the same time. When the actual valve opening area of the exhaust valve becomes smaller,
In order to obtain sufficient intake inertia supercharging effect in high-speed, high-load ranges, it was necessary to extend the valve overlap period.

However, if the valve overlap period is long, in the engine's low speed and low load range, even if the valve opening area is small, the exhaust gas will flow back into the cylinder from the downstream of the exhaust valve due to the large suction load, so the fuel There was a problem that in the reduced low load range where much gas was not supplied, the proportion of residual gas increased and combustibility was significantly impaired.

The purpose of the present invention is to solve these conventional problems and improve performance in the entire engine speed range.

(Means for Solving the Problems) In order to achieve the above object, the present invention provides a valve device for an internal combustion engine having a plurality of exhaust valves in one cylinder, in which the plurality of exhaust valves have the same valve diameter and stem diameter. and the shapes of the backs of the valve umbrellas are different.

(Function) Pressure waves are generated in the exhaust passage as the exhaust valve opens, and scavenging is promoted in the rotation speed range where the immediate downstream side of the exhaust valve becomes negative pressure when the exhaust valve is fully closed. In the rotation speed range where engine pressure is high, the pumping loss used to discharge exhaust gas increases, causing a drop in the torque generated by the engine, and a so-called torque trough occurs in this rotation speed range.

In this invention, by making the shapes of the backs of bubble umbrellas different, when multiple exhaust valves in the same cylinder open, the speed at which the area of the opening defined by each exhaust valve increases is different. Since the pressures that are input into the exhaust passage when each exhaust valve is opened are also input with a phase difference from each other, the amplitude of the pressure wave generated in the exhaust passage becomes small, and as a result, when the exhaust valve is fully closed, the exhaust Pumping loss is reduced in the rotation speed range where the pressure immediately downstream of the valve is positive, and the exhaust inertia effect promotes scavenging to reduce residual gas and increase volumetric efficiency, reducing torque drop in this rotation speed range. can do.

In addition, by synchronizing the closing timings of multiple exhaust valves in the same cylinder, the effective opening area of the exhaust passage that each exhaust valve opens when valves overlap becomes larger. It is no longer necessary to set the overlap timing so large, and as a result, it is possible to reduce backflow of exhaust gas in the low speed and low load range, improve combustibility, and ensure idle stability.

(Example) Hereinafter, an example of the present invention will be described based on the accompanying drawings.

As shown in Figure 1, two
The exhaust valves 1 and 2 have right cylindrical stems 11 and 21.
and umbrella portions 12 and 22 that close each exhaust port 4.

The stems 11, 21 of each exhaust valve 1, 2 are slidably supported via a guide 3 fixed to the cylinder head 7, and during engine operation, each umbrella portion 12 is supported by a cam that slides into the upper end of the stem (not shown). , 22 are lifted at predetermined timings synchronized with each other.

As shown in FIG. 2, in each of the exhaust valves 1 and 2, the outer diameter of the umbrella portions 12 and 22, that is, the valve diameter, is set to be the same as D, and the outer diameter of the stems 11 and 21 is set to be the same as d, respectively. The umbrella back 13 of one of the exhaust valves 1, which expands in the shape of a bulge, is curved with a large curvature relative to the umbrella back 23 of the other exhaust valve 2, so that the shapes thereof are different from each other. In other words, the seat surface 1 that seats on the valve seat 5
The umbrella backs 13, 23 curve from 4, 24 toward the stems 11, 21 and the inclination angle (the angle between the line perpendicular to the valve center line and the tangent above the starting point of the umbrella backs 12, 22) θ ₁ , Differentiate θ ₂ .

The cylinder head 7 forms each exhaust port 4 and valve seat 5 in the same cylinder into the same shape.

In this way, the exhaust valves 1 and 2 are connected to the respective umbrella backs 13 and 2.
3 have different shapes, when the exhaust valves 1 and 2 are opened, the cross-sectional areas of the openings defined between each exhaust port 4 and each umbrella back 13 and 23 are the same even when the lift is the same. On the other hand, when the exhaust valves 1 and 2 open, the blowdown pressures that enter the exhaust port 4 have a phase difference.

In Fig. 3, the pressure waves generated in the downstream exhaust passages of the exhaust valves 1 and 2 are shown by broken lines, and the blowdown pressure (dotted chain line) that is incident when the exhaust valve 2 opens
On the other hand, the blowdown pressure (double-dashed line) that is injected when the exhaust valve 1 opens is delayed by a certain phase difference, so the pressure wave (dashed line) created by combining these pressure waves has an amplitude of This can be kept smaller than in the case of a conventional device in which the two exhaust valves open in the same phase (solid line).

Figure 4 shows the results of actually measuring pressure fluctuations under operating conditions at a rotational speed of 3600 rpm, where the pressure wave generated 120 mm downstream of exhaust valves 1 and 2 becomes positive pressure when exhaust valves 1 and 2 are fully closed. The characteristic shown by the broken line and the solid line in the figure shows the case of a conventional device in which the two exhaust valves have the same shape. As can be seen from this experimental result, in this example, blowdown (section A in the figure)
As this decreases, the amplitude of the reflected wave (section B in the figure) can also be suppressed to a small level.

As mentioned above, around 3600rpm, exhaust valves 1 and 2
When the exhaust valves 1 and 2 are fully closed, the pressure immediately downstream of the exhaust valves 1 and 2 becomes positive, causing a torque valley. However, in this embodiment, the blowdown pressure that is input when the exhaust valves 1 and 2 are opened is also equal to each other. Due to the phase difference, the amplitude of the pressure wave generated in the exhaust passage becomes smaller, which reduces the pumping loss used to discharge exhaust gas, reduces residual gas, and increases the volumetric efficiency of intake air. It is possible to reduce the drop in torque in several ranges.

In addition, by completely closing the exhaust valves 1 and 2 in synchronization with each other, the actual opening area of the exhaust passage that each exhaust valve 1 and 2 opens when there is valve overlap with the intake valves 3 and 4 increases. There is no need to set the valve overlap period so large. As a result, while volumetric efficiency is secured by utilizing the inertia of the intake air in the high-speed, high-load range, exhaust gas flows into the cylinder from downstream of the exhaust valves 1 and 2 due to the large intake load in the low-speed, low-load range. It suppresses backflow, prevents deterioration of combustibility due to residual gas, and improves idle stability.

Next, in another embodiment shown in FIGS. 5A and 5B, in an engine provided with two exhaust valves 8 and 9 per cylinder, the inclination angle θ ₈ of the seat surfaces 16 and 26 of each exhaust valve 8 and 9 is , θ ₉ are different.

Corresponding to the inclination angle of the seat surfaces 16, 26, the seat surfaces 17, 27 on the cylinder head 7 side and the chamfered portion 1
8 and 28 are formed with different inclination angles.

With this structure, when the exhaust valves 8 and 9 are opened, the respective seating surfaces 16 and 26
The cross-sectional areas of the openings defined between the seat surfaces 17, 27 and the chamfered portions 18, 28 are different, and the blowdown that enters the exhaust port 4 when the exhaust valves 8, 9 are opened is different. A phase difference occurs between the pressures, and the amplitude of pressure waves generated in the exhaust passage can be reduced.

(Effects of the invention) As described above, according to the invention, a plurality of exhaust valves provided in the same cylinder have the same valve diameter and stem diameter, and the shapes of the backs of the valve caps are different, so that each exhaust valve has the same valve diameter and stem diameter. The blowdown pressure that is injected into the exhaust port when the valve opens is injected with a phase difference between each other, weakening the pressure wave generated in the exhaust passage and reducing pumping loss in the rotation speed range where torque troughs occur. It is possible to improve output by reducing
Furthermore, this can be easily implemented by changing the shape of the exhaust valve.

[Brief explanation of drawings]

Fig. 1 is a sectional view showing one embodiment of the present invention;
The figure is a side view of the exhaust valve, Figure 3 is a diagram showing the action,
FIG. 4 is a diagram showing the experimental results. Figure 5A,
B is a side view of an exhaust valve showing another embodiment, and FIG. 6 is a diagram showing the relationship between bubble opening area and crank angle. FIG. 7 is an explanatory diagram of the operation of an intake and exhaust valve showing a conventional example. 1, 2... Exhaust valve, 11, 21... Stem, 1
2, 22... Umbrella part, 13, 23... Umbrella back part.

Claims (1)

[Scope of utility model registration request] A valve for an internal combustion engine comprising a plurality of exhaust valves for one cylinder, wherein the plurality of exhaust valves have the same valve diameter and stem diameter, and different shapes of the backs of the valve caps. Device.