JPS6034727Y2 - Internal combustion engine valve train - Google Patents

Description

[Detailed explanation of the idea] This invention relates to a valve train for an internal combustion engine.

Generally, in internal combustion engines, there is a period from the exhaust stroke to the intake stroke in which the intake and exhaust valves are open at the same time (valve overlap period) to increase exhaust efficiency and fresh air filling efficiency, especially in the engine high speed range. Efforts are being made to improve engine output.

However, due to this valve overlap, there is a problem in that in a low engine load range where the suction negative pressure is strong, the amount of residual gas in the cylinder increases, making the engine operating performance unstable.

For this reason, conventionally, the overlap period has been appropriately determined based on these considerations.

However, what is most desirable is to make the valve timing of the intake and exhaust valves variable in accordance with the operating conditions, and to maintain an optimum amount of overlap in accordance with the engine load condition.

For this reason, various engines that change the valve timing of intake and exhaust valves have been proposed, such as Japanese Patent Application Laid-Open No. 53-12972.
The system disclosed in the Mine Gazette moves a control ring that functions as a valve seat up and down depending on the operating condition, but when the intake and exhaust valves collide with this, noise is generated, and the control ring collides with the control ring. Its operation is unreliable, as it jumps up at every turn, and its structure is complicated.

In order to solve this problem, this invention has two intake and exhaust valves.
As a heavy structure, the first valve and the second valve are installed depending on the engine operating condition.
An object of the present invention is to provide a valve operating system for an internal combustion engine in which substantial valve timing can be varied by controlling the relative positions of valves.

This idea will be explained below based on the drawings.

As shown in FIGS. 1 to 3, a second valve 2 is disposed coaxially and superimposed on the outside of a first valve driven by a cam, and these first valve 1 and second valve 2 are capable of relative displacement in the axial direction.

The valve head 1b of the first valve 1 can freely move toward and away from the valve seat 13, thereby opening and closing the intake (exhaust) port 16.

On the other hand, the valve head 2b of the second valve 2 is formed to have a small diameter so as to come into sliding contact with the inner circumferential surface of the valve seat 13.

The first valve 1 has a threaded portion 1a on the valve stem 1c, and the second valve 2 has a threaded portion 2a on the inner circumference of the valve stem cylinder 2c. A pinion 3 is fitted in the valve shaft cylinder 2c of the second valve 2, which is displaced in the axial direction by relative rotation, and is prevented from rotating by a notch 2d.

In this case, the pinion 3 is held in a gap 4a provided at the bottom of the valve spring seat 4, and the rack 5 is also held in this gap 4a.
The sheet 4 is held by a horizontal groove 4b provided at a portion thereof passing through the sheet 4.

The rack 5 is connected to a piston 7 in a hydraulic cylinder 6 which communicates with an oil gear rally 10 via an oil passage 9, and is biased by a spring 8 in the direction of contraction of the cylinder 6.

The valve end of the first valve 1 is formed in an oval-shaped notch 1d, and is attached to the rocker arm 12 in a non-rotating state via a cap 11 fitted into the notch 1d.

Next, the operation of this invention will be explained.

As shown in FIG. 6, the oil pressure C supplied from the oil pump to the gear rally 10 changes depending on the engine speed.

Therefore, as shown in FIG. 7, when the engine speed is low, the oil pressure is low at E, so the piston 7 is pushed back by the spring 8, and the rack 5 moves backward, causing the pinion 3 to rotate clockwise.

On the other hand, since the first valve 1 is prevented from rotating by the cap 11, the valve head 2b of the second valve 2 is prevented from rotating by the threaded parts 1a and 2a.
moves away from the valve head 1b of the first valve 1.

Therefore, when both the first valve 1 and the second valve 2 start lifting, the time when the valves actually open is when the second valve 2 leaves the valve seat 13, that is, as shown in FIG. 7A.

On the other hand, the time when the valve closes is also earlier, which corresponds to the timing of the mouth.

In this way, when the engine speed is low, E has a shorter valve opening time.
Intake valve lift L also becomes smaller.

Also, when the engine is running at high speed, F means that the oil pressure increases, contrary to the above.
Since the piston 7 is pushed out and rotates the pinion 3 counterclockwise, the first valve 1 and the second valve are connected by the threaded parts 1a and 2a.
The valve heads 1b and 2b of the valve 2 are brought closer together as shown in FIG.

As a result, the valve opening period is substantially controlled in accordance with the operation of the first valve 1, and as shown in FIG. 7, the valve opening period is expanded as shown in FIG. be.

In this way, the valve opening time and valve opening degree (lift) can be controlled by the oil pressure that changes depending on the engine speed, so when this device is applied to the intake valve as shown in Figure 7, there is no overlap at low engine speed E. Since it becomes smaller as shown in B, it is possible to suppress the increase in residual gas due to exhaust gas blowing into the intake pipe during overlap, which has been a problem in the past.

Therefore, the low engine speed E can improve combustion efficiency by reducing the proportion of residual gas in the cylinder, especially during idling.

On the other hand, at engine high speed F, contrary to the above, the overlap becomes large as shown in A, and the exhaust efficiency and fresh air filling efficiency in the cylinders can be increased.

As described above, this invention provides a threaded part for the valve stem of the first valve and the valve stem cylinder of the second valve to engage with each other, and the second valve is rotated by a rack connected to a hydraulic cylinder. Since the overlap of the intake and exhaust valves can be optimally controlled according to the speed, it is possible to increase output by improving combustion at low speeds and improving fresh air charging efficiency at high speeds, while also reducing the weight of the moving parts of the valves. This makes it possible to operate at high speeds, and in the case of multi-cylinder engines, it has the effect of eliminating variations in control between cylinders and increasing accuracy.

[Brief explanation of the drawing]

FIG. 1 is a longitudinal sectional view showing a valve train for an internal combustion engine according to this invention, FIG. 2 is a side view and a partial plan view of part A in FIG. 1,
Figure 3 is a plan view showing the arrangement of the rack and hydraulic cylinder of the same device, Figure 4 is a partial view showing how the valve opens when the oil pressure is low, and Figure 5 shows how the valve opens when the oil pressure is high. FIG. 6 is an explanatory diagram showing the relative relationship between oil pressure and engine speed, and FIG. 7 is an explanatory diagram showing the valve opening degree at low and high speeds of the engine. 1...First valve, la, 2a...Threaded part, lb. 2b... Valve head, 3... Zenion, 4.
... Valve spring seat, 5 ... Rack, 6 ... Hydraulic cylinder, 7 ...
Piston, death...spring.

Claims (1)

[Scope of utility model registration request] A first valve is provided which is driven via a cam and moves into and out of contact with a valve seat, and a second valve which is disposed coaxially overlapping the first valve and slides into contact with the inner periphery of the valve seat. While the valve stem of the valve and the valve stem cylinder of the second valve are engaged through the threaded portion,
A driving means for rotating the valve according to the operating state is provided, and the first
A valve operating system for an internal combustion engine, characterized in that the distance between a valve and a valve head of a second valve is controlled.