JPS6123627Y2 - - Google Patents

Description

[Detailed explanation of the idea] The present invention relates to a variable compression ratio internal combustion engine.

If compression is increased in order to increase combustion efficiency in the low load range of an internal combustion engine, fuel efficiency can be improved as intended in the low load range. On the other hand, knocking occurs in the high load range. As a countermeasure to this, the ignition advance angle has to be retarded compared to before the high compression ratio was achieved. the result,
This will lead to a decrease in engine output and deterioration of fuel efficiency characteristics.

On the other hand, there have been proposals in the past to change the compression ratio of the engine depending on the load state of the engine or the pressure state in the combustion chamber. However, in these conventionally proposed variable compression ratio engines, the volume of the combustion chamber is changed by, for example, bending a spring depending on the pressure within the combustion chamber. For this reason, even when the load is low, if the compression pressure exceeds the set value of the spring, the volume of the combustion chamber changes, causing problems such as not being able to achieve a high compression ratio, making it impossible to put it into practical use.

This invention aims to improve fuel efficiency by combusting the intake air-fuel mixture at an unprecedentedly high compression ratio at low loads, increasing combustion efficiency, and at the same time switching to a compression ratio similar to that of conventional engines at high loads, where knocking is likely to occur. An object of the present invention is to provide a variable compression ratio internal combustion engine that takes countermeasures against knocking.

The present invention achieves this purpose by communicating the combustion chamber of an internal combustion engine with an auxiliary combustion chamber via a third valve, and a valve drive mechanism for driving the third valve closes the third valve in a low engine load region. This is achieved by using a variable compression ratio internal combustion engine that is configured to open the engine from the middle of the compression stroke to the latter half of the exhaust stroke in high engine load ranges.

Embodiments of the present invention will be described below with reference to the accompanying drawings. In FIG. 1, a cylinder bore 1a is formed in a cylinder block 1, and a piston 3 is hermetically fitted therein so as to be able to reciprocate. An auxiliary combustion chamber 5b consisting of a combustion chamber wall 5a and a circumferential recess communicating with the combustion chamber wall 5a is formed in the cylinder head 5, and the cylinder head 5 is mounted and fixed on the cylinder block 1. A combustion chamber 7 is formed as a space surrounded by the upper surface of the piston 3, the cylinder bore 1a, and the combustion chamber wall 5a.

An intake valve 9 controls the inflow of air-fuel mixture from an intake port 5c formed in the cylinder head 5 and open to the combustion chamber 7. Similarly, as shown in FIG. 2, an exhaust valve 11 controls the outflow of the combusted exhaust gas to an exhaust port 5d formed in the cylinder head 5 and open to the combustion chamber 7. 13 is a spark plug. The intake valve 9 and the exhaust valve 11 are opened and closed by a conventional valve mechanism, but the structure is obvious to those skilled in the art and will not be described further.

As described above, the combustion chamber 7 and the sub-combustion chamber 5b communicate with each other, and the third valve 15 is provided at a portion where the sub-combustion chamber 5b opens into the combustion chamber 7.

This third valve 15 can be opened toward the combustion chamber 7 side.

A valve retainer 17 is fixed to the valve rod 15a of the third valve 15, and a valve spring 19 is installed between the valve retainer 17 and the upper surface of the cylinder head 5 to urge the third valve upward and seat it on the valve seat 21. let Here, the third valve 15 is made of a material with high heat resistance. A swing arm 25 is provided between the hydraulic lifter 23 and the valve rod 15a, and the swing arm 25 collides with a cam 27 to press the valve rod 15a.

Next, the valve timing mechanism for driving the third valve will be explained. A camshaft 31 that rotates in synchronization with the rotation of a crankshaft (not shown) of the engine is provided, and the camshaft 31
A linear slide bearing 33 (fourth
(Figure). That is, the camshaft 3
An axial groove 31a is bored in the groove 31a, and a ball 33a of a slide bearing 33 is fitted into the groove 31a, and the circumferential position of the ball 33a is held by a retainer 33b. More specifically, in a four-cylinder internal combustion engine, four sets of grooves are formed on the camshaft 31 at 90° as shown in Fig. 4.
They are evenly spaced and are shifted by 1. Therefore, four cams 27 manufactured in the same shape, namely cams 27-1, 27-2, 27 for cylinders No. 1 to No. 4
-3 and 27-4 as shown in FIG. 4 and simply attach them, making manufacturing and assembly easy.

The cam 27 for opening and closing the third valve 15 includes a low load cam 27a and a high load cam 27b, as shown in FIG.
Contains. Here, the low load cam 27a consists of only a base circle, and therefore the low load cam 27a consists of only a base circle.
While the third valve 7a is in contact with the swing arm 25, the third valve 15 remains closed as shown by line A in FIG. On the other hand, the high load cam 27b has a predetermined lift and opens the third valve as shown by line B in FIG.
As shown in FIG. 3, a semicircular stopper 27c made of spring steel is provided at the lifting area between the low-load and high-load cams 27a and 27b for driving the third valve 15, and the high-load cam 27b is provided with a semicircular stopper 27c. Circular tsuba 2 on the side
7d.

A fork 43 engaged with the collar 27d is loosely fitted onto a cam moving shaft 41 installed parallel to the cam shaft 31, and connecting springs 49, 51 are installed between the plates 45, 47 fixed to the cam moving shaft 41 and the fork 43. ing.

When the cam movement shaft 41 is moved, the connecting spring 49 or 51 is compressed and movement energy is stored. Low load cam 27a and high load cam 2
When the common base circle part 7b is located on the swing arm 25, the cam 2 is moved by the accumulated movement energy.
7 is moved at high speed along the camshaft 31. Note that when the cams 27a and 27b are at the stopper 27c position, the movement of the cam 27 is blocked by the stopper 27c, and when the lift portions of the cams 27a and 27b are in contact with the swing arm 25, the frictional force acting between them causes the cams to move. 27 movement is obstructed.

Note that the variable valve timing mechanism for driving the third valve of the present invention may have other known embodiments.

With the above configuration, when the engine is in a low load state, the low load cam 27a consisting only of a base circle collides with the swing arm 25 to keep the third valve 15 closed. This causes the engine to operate at a high compression ratio. The compression ratio in this case can be set much higher than the normal compression ratio to increase combustion efficiency and improve fuel efficiency. Next, when the engine is in a high load state, the low load cam 27a is changed to the high load cam 2.
7b to open and close the third valve 15. In this case, the opening timing V _T of the third valve 15 is set from the middle of the compression stroke to the latter half of the exhaust stroke (see FIG. 6). However, the optimum timing can be determined through experiments, taking into consideration the combustion improvement effect and the knocking suppression effect. In addition, V _I and V _E in Fig. 6 indicate the intake valve 9.
and the opening timing of the exhaust valve 11.

By opening the third valve 5 as described above, the combustion chamber volume increases to the sum of the main combustion chamber 7 and the auxiliary combustion chamber 5b. By setting the compression ratio of the engine at this time to the same level as that of conventional engines, a healthy thermal cycle is created without knocking. Also third valve 15
The combustion gas from the previous cycle enters the sub-combustion chamber 5 by opening and closing.
b is added to the top, and this goes into the suction mixture in the next cycle. Therefore, the proportion of burned gas in the cylinder air-fuel mixture increases, and the so-called internal EGR effect reduces the generation of _NOx and suppresses the occurrence of abnormal combustion.
Furthermore, by opening and closing the third valve and seating it on the valve seat, there is also the effect of cooling the third valve, which has been exposed to high temperatures due to combustion.

Additionally, depending on how the valve timing of the third valve is selected, turbulence can be imparted to the burned gas stored in the auxiliary combustion chamber when it is mixed into the air-fuel mixture, and the turbulence improves combustion. .

[Brief explanation of the drawing]

Fig. 1 is a sectional front view of an embodiment of the present invention, Fig. 2 is a bottom view of the cylinder head of Fig. 1, Fig. 3 is a plan view of the valve timing switching mechanism of the third valve of Fig. 1, and Fig. 4 is a plan view of the valve timing switching mechanism of the third valve of Fig. 1. The figure is a partial front view, FIG. 5 is a valve lift diagram of the third valve, and FIG. 6 is a valve timing diagram of the embodiment shown in FIG. 7...Combustion chamber, 5a...Sub-combustion chamber, 9...Intake valve, 11...Exhaust valve, 15...Third valve, 2
7...Cam, 27a...Low load cam, 27b...
...High load cam.

Claims (1)

[Scope of utility model registration request] The combustion chamber of the internal combustion engine is communicated with the auxiliary combustion chamber via a third valve, and a valve drive mechanism for driving the third valve keeps the third valve closed in a low engine load range and in a high engine load range. A variable compression ratio internal combustion engine characterized by being configured to open the engine from the middle of the compression stroke to the latter half of the exhaust stroke.