JPH1150866A - Internal combustion engine variable compression ratio mechanism - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an internal combustion engine variable compression ratio mechanism capable of improving output performance together with antiknock performance. SOLUTION: The interior of a cylinder head 11 of a vehicular engine 10 is arranged with a valve system 12 as well as a combustion chamber 32. The valve system 12 is composed by equipping it with a valve 13, a valve lifter 14, a coil spring 15 and the like. A recessed part 20 is provided on the corresponding place on the cylinder head 11 to a valve face 13a of the valve 13, and a valve seat 18 is arranged in the recessed part 20 so that it can make a vertical motion. A disc spring 21 for energizing the valve seat 18 to the combustion chamber 32 side is arranged above the valve seat 18. The disc spring 21 allows the valve seat 18 to move upwards by making an elastic deformation when specific combustion pressure corresponding to high load operation of the engine 10 is applied.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a variable compression ratio mechanism for an internal combustion engine.

[0002]

2. Description of the Related Art Generally, in an internal combustion engine, when the compression ratio in a combustion chamber is increased, the combustion pressure is increased, the thermal efficiency is increased, and the output is improved. However, on the other hand, if the compression ratio is excessively increased, the combustion pressure becomes too high, which causes knocking. The combustion pressure generated in the combustion chamber differs between the low-load and medium-load operation states and the high-load operation state, and the combustion pressure in the high-load operation state is higher than the combustion pressure in the low-load and medium-load operation states. Therefore, conventionally,
The compression ratio in the combustion chamber has been set to a compression ratio at which the combustion pressure does not cause knocking at a high engine load.

[0003]

However, if the compression ratio in the combustion chamber is set in accordance with the operating condition at high engine load, the output performance at low and medium loads will inevitably decrease. become.

As described above, since the improvement of the knocking resistance and the improvement of the output performance are incompatible with each other, it has been desired to develop an internal combustion engine capable of improving the performance of both by varying the compression ratio. It is rare.

The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a variable compression ratio mechanism for an internal combustion engine that can improve output performance and knock resistance. It is in.

[0006]

To achieve the above object, according to the first aspect of the present invention, a face of a valve provided in a combustion chamber of an internal combustion engine is provided so as to be movable in an axial direction. A valve seat against which a portion abuts, and urges the valve seat toward the combustion chamber, and elastically deforms when the combustion pressure in the combustion chamber reaches a predetermined combustion pressure corresponding to a high-load operation of the engine. The gist of the invention is to provide an elastic body that allows the valve seat to move in the valve axial direction.

According to such a structure, the compression ratio in the fuel chamber is maintained high during low load and medium load operation of the internal combustion engine in which the combustion pressure in the combustion chamber does not reach the predetermined combustion pressure, so that the thermal efficiency increases. The output is thus improved. Further, during a high-load operation of the internal combustion engine in which the combustion pressure in the combustion chamber reaches the predetermined combustion pressure, the elastic body is deformed and the valve seat moves to the outside of the combustion chamber. This allows
Since the compression ratio in the fuel chamber is reduced and the combustion pressure is reduced, the occurrence of knocking is suitably reduced.

According to a second aspect of the present invention, in the variable compression ratio mechanism for an internal combustion engine according to the first aspect, the elastic body is a disc spring whose entire periphery of a tip side abuts on the valve seat. The gist is that there is.

According to such a structure, a sealing function is added to the elastic body itself, and the outflow of combustion gas in the combustion chamber is prevented. As a result, a decrease in the output efficiency of the internal combustion engine is also suitably prevented.

[0010]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment in which the present invention is applied to a vehicle engine will be described below with reference to FIGS.

FIG. 1 is a sectional view of a vehicle engine schematically showing a variable compression ratio mechanism according to the present embodiment. FIG. 1
As shown in FIG.
1, a ventilation path 31 as an intake path or an exhaust path;
A combustion chamber 32 communicating with the ventilation path 31 is provided. In the cylinder head 11, the valve train 1
2 are provided. The valve system 12 includes a valve 13 having a valve face portion 13a and a valve stem portion 13b, a valve lifter 14 for lifting the valve 13 downward in FIG.
4 is provided with a coil spring 15 and the like for urging the member 4 upward in the figure. That is, in the valve train 12, the valve 13 and the valve lifter 14
6 and the coil spring 15 move the cylinder head 11 up and down, and the air passage 31 and the combustion chamber 32
Opening / closing the communication part (port) 17 with the port.

On the other hand, a recess 20 is provided at a position corresponding to the valve face portion 13a in the cylinder head 11.
The valve seat 18 is disposed in the recess 20 so as to be vertically movable in the recess 20. At this time, a slight clearance is provided between the valve seat 18 and the inner wall of the recess 20 to allow the valve seat 18 to move up and down. A disc spring 21 for urging the valve seat toward the combustion chamber 32 is provided above the valve seat 18.
Are disposed in close contact with the inner wall of the concave portion 20 and the valve seat 18, that is, in a state where at least the entire periphery of the distal end side is in contact with the valve seat 18. Therefore, the valve seat 18 is restricted from moving up and down by the disc spring 21, and the confidentiality in the combustion chamber 32 when the valve 13 is closed is suitably maintained. Further, a valve guide 19 is provided at a location corresponding to the valve stem 13b. The above-mentioned disc spring 2
When the combustion pressure in the combustion chamber 32 reaches a predetermined combustion pressure corresponding to a high-load operation of the engine 10, the elastic deformation occurs to allow the valve seat 18 to move upward in the drawing. An elastic coefficient (biasing force) is set.

Next, the operation of the variable compression ratio mechanism configured as described above will be described with reference to FIG. In addition, FIG.
And (b) is an enlarged view showing the operation of the variable compression ratio mechanism.

When the vehicle engine 10 starts operating, that is, when fuel is burned in the combustion chamber 32, a combustion pressure is generated in the combustion chamber 32. In the low-load and medium-load operation states of the engine 10, FIG.
A combustion pressure indicated by an arrow P in (a) is generated in the combustion chamber 32. At this time, the disc spring 2 shown by the arrow SP in FIG.
1 is set to be stronger than the combustion pressure P. That is, even if the combustion pressure P is generated in the combustion chamber 32, the valve seat 18 does not move upward. Therefore, in the normal operation state of the engine 10, the combustion chamber 3
The compression ratio within 2 is kept high.

On the other hand, when the vehicle engine 10 is in a high-load operation state, for example, during a high acceleration operation or a high-hill operation, the combustion pressure generated in the combustion chamber 32 due to a sudden increase in the intake air amount. May be abnormally high. Then, as shown in FIG. 2 (b), when the combustion pressure reaches the combustion pressure Pmax exceeding the urging force SP of the disc spring 21 against the valve seat 18, the valve seat 18 is lifted upward by the combustion pressure Pmax. . That is, in this case, when the valve seat 18 is lifted, the volume in the combustion chamber 32 is increased by the volume of the lift, and the compression ratio is lowered. Thereby, occurrence of knocking during high-load operation is reduced.

Since a slight clearance is provided between the valve seat 18 and the inner wall of the recess 20, the combustion gas in the combustion chamber 32 flows out to the ventilation path 31 through the clearance. It is possible.
However, as described above, since the disc spring 21 is disposed in close contact with the valve seat 18 and the inner wall of the recess 20, the outflow of combustion gas is suitably prevented by the disc spring 21, and the output of the engine 10 is reduced. There is no loss in efficiency.

As described above, according to the present embodiment, the following effects can be obtained. -At the time of low load and medium load operation of the vehicle engine 10,
Since the inside of the combustion chamber 32 can be maintained at a high compression ratio, the output performance of the engine 10 can be improved. In addition, during high load operation of the engine 10, the compression ratio in the combustion chamber 32 can be reduced to lower the combustion pressure, so that the anti-knock performance can be improved. In other words, the compression ratio in the combustion chamber 32 is usually
By setting it high, the output performance at the time of low load and medium load operation can be improved, and at the time of high load operation, the compression ratio in the combustion chamber 32 is reduced by using the combustion pressure to withstand. Knocking performance can be improved.

The disc spring 21 prevents the combustion gas in the combustion chamber 32 from flowing out of the clearance between the valve seat 18 and the inner wall of the recess 20. Therefore, there is no need to provide a seal member such as a packing in the clearance, and the number of components can be reduced, and a decrease in the output efficiency of the vehicle engine 10 can be prevented.

Since the compression ratio in the combustion chamber 32 can be varied with a simple structure, the production cost and the production TA
T (Turn Around Time) and the number of parts can be reduced.

The above embodiment may be modified as follows, and the same operation and effect can be obtained in such a case. In the above embodiment, the compression ratio in the combustion chamber 32 is made variable by the disc spring 21. However, the disc spring 21 may be changed to a bellows-like spring (bellows spring) 41 as shown in FIG. Also in this case, the bellows spring 41 elastically deforms when the combustion pressure in the combustion chamber 32 reaches a predetermined combustion pressure corresponding to the high load operation of the engine 10,
The elastic coefficient (biasing force) is set so as to allow the valve seat 18 to move upward in the drawing.

In the above embodiment, the compression ratio in the combustion chamber 32 is made variable by the disc spring 21.
May be changed to a coil spring 42 as shown in FIG. However, in this case, it is desirable to provide a seal member 43 on the peripheral surface of the valve seat 18 in contact with the inner wall of the concave portion 20 to prevent the outflow of the combustion gas. Also in this case, the coil spring 42 is connected to the combustion chamber 3.
When the combustion pressure in the engine 2 reaches a predetermined combustion pressure corresponding to the high-load operation of the engine 10, it is elastically deformed and its elastic coefficient (biasing force) so as to allow the valve seat 18 to move upward in the drawing. Is set.

By the way, in this specification, the elastic body includes not only a disc spring, a coil spring and a bellows spring but also a leaf spring and other various elastic bodies.

[0023]

According to the first aspect of the present invention, the compression ratio in the fuel chamber is kept high during low load and medium load operation of the internal combustion engine in which the combustion pressure in the combustion chamber does not reach the predetermined combustion pressure. Therefore, the output can be improved by increasing the thermal efficiency. Further, during a high-load operation of the internal combustion engine in which the combustion pressure in the combustion chamber reaches the predetermined combustion pressure, the elastic body is deformed and the valve seat moves to the outside of the combustion chamber. This makes it possible to lower the combustion pressure by lowering the compression ratio in the fuel chamber, so that the occurrence of knocking can be suitably reduced.

According to the second aspect of the present invention, the sealing function is added to the elastic body itself, so that the outflow of the combustion gas in the combustion chamber can be prevented. As a result, a decrease in the output efficiency of the internal combustion engine can be suitably prevented.

[Brief description of the drawings]

FIG. 1 is a sectional view schematically showing a variable compression ratio mechanism according to an embodiment.

FIG. 2 is an enlarged view showing the operation of the variable compression ratio mechanism of the embodiment.

FIG. 3 is an enlarged view schematically showing a variable compression ratio mechanism according to another embodiment.

FIG. 4 is an enlarged view schematically showing a variable compression ratio mechanism according to another embodiment.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 10 ... vehicle engine, 13 ... valve, 18 ... valve seat, 20 ... recessed part, 21 ... disc spring (elastic body), 32 ... combustion chamber, 41 ... bellows spring (elastic body), 42 ... coil spring (elastic body).

Claims (2)

[Claims] 1. A valve seat provided in a combustion chamber of an internal combustion engine so as to be movable in an axial direction of a valve, and a face portion of the valve is in contact with the valve seat, and the valve seat is biased toward the combustion chamber. And an elastic body that elastically deforms when the combustion pressure in the combustion chamber reaches a predetermined combustion pressure corresponding to a high-load operation of the engine and allows the valve seat to move in the valve axial direction. A variable compression ratio mechanism for an internal combustion engine. 2. The variable compression ratio mechanism for an internal combustion engine according to claim 1, wherein the elastic body is a disc spring whose entire periphery of a tip side abuts on the valve seat. Variable compression ratio mechanism of the engine.