JP2000204963A - Internal combustion engine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve the combustion efficiency and startability of internal combustion engine in low load area in a combustion engine for transmitting combustion pressure from a piston to a crankshaft through a connecting rod by attaching a variable means of compression ratio that is the ratio of cylinder internal capacity to the connecting rod. SOLUTION: In the combustion chamber 2 of a cylinder 1, the combustion pressure generated by explosion stroke is transmitted from a piston 5 to a crankshaft 7 through a connecting rod 6'. The connecting rod 6 is curved orthogonally to the sliding direction of the piston 5. The deflection of the connecting rod 6 is changed by the combustion pressure to reduce the compression ratio, whereby the rise of combustion pressure in high load is minimized. Namely, a variable means is imparted to the connecting rod 6 itself. According to this, in a low load area having a low cylinder pressure, the deflection is minimized to increase the compression ratio, whereby the combustion efficiency is improved, and the startability of the internal combustion engine is also improved.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] The present invention relates to an internal combustion engine.

[0002]

2. Description of the Related Art In a general engine configuration which is currently widely used, a connecting rod connecting a small end portion of a piston and a large end portion of a crankshaft is formed to be bilaterally symmetrical and has an H-shaped cross section. Alternatively, it has a shape such as an I-shaped cross section.

The connecting rod receives alternately or simultaneously a compressive force due to gas pressure, a compressive and tensile force due to inertial force, and a bending force due to whirling. Therefore, sufficient rigidity, strength and weight reduction are required.

[0004] One of the factors affecting the engine performance is the compression ratio. The compression ratio is the ratio of the cylinder internal volume when the piston is at bottom dead center and when it is at top dead center.

[0005] By setting the compression ratio to an appropriate value, combustion efficiency, startability, or engine performance can be improved. However, at present, there is no means for controlling the compression ratio to an appropriate value, and this is a subject to be solved in the future.

[0006]

When the supercharging pressure or the like is increased in order to improve the engine performance, the combustion pressure increases, and a problem occurs in the strength of the engine.

[0007] At this time, if the compression ratio is reduced, the combustion pressure is reduced, which is effective. However, when the compression ratio is reduced, problems such as combustion in a low load region and deterioration of engine startability have occurred.

[0008] In order to solve this problem, some means for changing the compression ratio is required. SUMMARY OF THE INVENTION Accordingly, the present invention has been made to solve the above-described problem, and an object of the present invention is to provide an internal combustion engine that varies the compression ratio to improve the combustion efficiency in a low load range, the startability of the engine, and the like.

[0009]

In order to solve the above problems, according to the present invention, a combustion chamber is provided in a cylinder, and the cylinder is slid by receiving a combustion pressure generated by burning an air-fuel mixture in the combustion chamber. And a piston, and a connecting rod is connected to the piston, and the combustion pressure is transmitted to a crankshaft as a driving force through the connecting rod. It is characterized by having variable means for varying the compression ratio, which is the ratio of the volume in the cylinder at the top dead center.

It is also preferable that the variable means maintains the in-cylinder pressure in a predetermined range according to the combustion pressure generated in the combustion chamber. It is also preferable that the connecting rod is bent to be the variable means.

[0011] It is also preferable that the connecting rod is made of a material having a spring constant. It is also preferable that the variable means increases the compression ratio as the combustion pressure increases.

It is also preferable that the variable means lowers the compression ratio as the combustion pressure increases. It is also preferable to control the in-cylinder pressure by a method other than the combustion pressure described above.

[0013]

(First Embodiment) First, FIG. 5 shows a schematic configuration diagram of an internal combustion engine (hereinafter, referred to as an engine).

As shown in FIG. 5, the engine comprises a cylinder 1, a combustion chamber 2 inside the cylinder, a suction valve 3 for sucking vaporized fuel such as gasoline from the outside, and a combustion gas burned in the combustion chamber 2. An exhaust valve 4 for exhausting, a piston 5 that slides by receiving a combustion pressure generated by an explosion stroke in the combustion chamber 2, and a connecting rod (hereinafter, referred to as a connecting rod) connected to the piston 5 and transmitting the combustion pressure to the crankshaft 7 as a driving force. , A connecting rod) 6.

Next, the relationship among intake pressure and engine performance, in-cylinder pressure, and compression ratio will be described with reference to FIGS. 1, 2, 3 and 4. In general, as shown in FIG. 1, the relationship between the intake pressure and the performance is such that when the intake pressure is increased, the in-cylinder pressure increases and the performance is improved. (FIG. 2) At this time, by reducing the compression ratio, as shown in FIG.
The cylinder pressure decreases at the same output.

Therefore, as shown in FIG. 4, if the compression ratio is lowered and the intake pressure is increased so that the in-cylinder pressure becomes the same, the engine performance can be greatly improved. As described above, by varying the compression ratio in accordance with the combustion pressure, the in-cylinder pressure can be kept constant, and the engine performance can be greatly increased.

In the present invention, an internal combustion engine capable of changing a compression ratio by providing a connecting rod with a variable means to maintain a constant in-cylinder pressure will be described below. First, FIG. 5 shows a schematic configuration diagram of an internal combustion engine (hereinafter referred to as an engine).

In a normal engine configuration as shown in FIG. 5, a connecting rod 6 connecting the small end of the piston 5 and the large end of the crankshaft 7 is compressed by gas pressure, compressed and pulled by inertial force. The force and the bending force due to whirling are alternately or simultaneously received.

Therefore, the design is designed to withstand these forces. However, in the present invention, the connecting rod 6 itself is provided with a variable means in a completely opposite concept to the above-described configuration of the connecting rod 6, and an increase in the combustion pressure is minimized by changing a compression ratio in accordance with the combustion pressure. It has a configuration.

Next, a first embodiment of the present invention will be described with reference to FIG. In the engine configuration shown in FIG. 6, those having the same functions as those of the engine configuration shown in FIG. 5 are denoted by the same reference numerals, and description thereof will be omitted.

In FIG. 6, the connecting rod 6 'is provided so as to be curved perpendicularly to the sliding direction of the piston 5. This is different from the conventional concept of the connecting rod, in which the connecting rod is bent in advance, the amount of deflection of the connecting rod 6 ′ is changed by the combustion pressure generated in the combustion chamber 2, and the compression ratio is lowered, so that the combustion under a high load is performed. This is to minimize the rise in pressure.

Therefore, the connecting rod 6 'itself has a structure having a variable means. Here, the combustion pressure P
The relationship between the deflection amount X and the deflection amount X will be described. The combustion pressure is P,
Assuming that the piston area is A and the amount of deflection of the connecting rod X is represented by the following equation.

P · A = kX (k is a spring constant) Therefore, P = kX / A. Therefore, by setting the spring constant k to an arbitrary value, it becomes possible to control the combustion pressure P.

FIG. 7 is a diagram showing the relationship between the amount of deflection X of the connecting rod and the combustion pressure P. As shown in FIG. 7, the combustion pressure is reduced by increasing the deflection amount X of the connecting rod from the reference point, and the combustion pressure can be increased by decreasing the deflection amount X from the reference point.

Further, as shown in FIG. 8, it is possible to keep the maximum value of the combustion pressure P below the limit value. Thus, by changing the amount of deflection X of the connecting rod, it is possible to keep the maximum combustion pressure below the limit value while maintaining the compression ratio.

Next, the engine performance according to the change in the amount of deflection X of the connecting rod 6 'will be described. First, the engine performance under a low load will be described.

As described above, the relationship between the combustion pressure P and the deflection X of the connecting rod is proportional. When the in-cylinder pressure decreases, the deflection amount X decreases, and as a result, the compression ratio increases.

That is, when the in-cylinder pressure is low and the load is low, the amount of deflection X is reduced and the compression ratio is improved. As the deflection amount X decreases, the compression ratio increases, so that deterioration of combustion at low load can be prevented, and deterioration of engine performance can also be prevented.

At the same time, the startability can be improved. Next, the engine performance under a high load will be described. As described above, increasing the intake pressure increases the in-cylinder pressure and improves the engine performance.

However, the cylinder pressure has an engine strength upper limit value. In such a case, if the intake pressure is increased so that the in-cylinder pressure becomes constant by lowering the compression ratio, it is possible to greatly improve the engine performance.

As described above, by varying the compression ratio in accordance with the combustion pressure, it is possible to maintain or improve the engine performance. (Embodiment 2) Next, Embodiment 2 will be described.

In the first embodiment described above, the structure in which the connecting rod itself is curved to vary the compression ratio in accordance with the change in the combustion pressure has been described. In the second embodiment, an example will be described in which the compression ratio is increased as the combustion pressure increases, and the engine performance is improved.

The configuration of the engine is a normal configuration as shown in FIG. In the second embodiment, as shown in FIG. 6, the connecting rod 6 'is not curved, but has a known shape as shown in FIG. 5, and a means for increasing the compression ratio of the connecting rod as the combustion pressure increases. The connecting rod has it.

As this means, a material whose shape can be changed by temperature or pressure, such as shape memory metal, is used. The operation will be described below with reference to FIG.

As shown in FIG. 9, when the compression ratio increases, the air-fuel mixture is strongly compressed, the temperature of the air-fuel mixture increases, and the air-fuel mixture burns in a short time and the combustion pressure increases. Become.

Further, since the volume of expansion of the combustion gas in the combustion stroke is increased by the amount corresponding to the compression, the exhaust gas temperature is not too high and the fuel efficiency is improved. However, there is a limit to increasing the compression ratio. Above this limit value, abnormal combustion occurs and knocking or the like occurs.

Therefore, it is sufficient to determine the maximum value of the compression ratio so as to be less than the limit value. By increasing the compression ratio as described above, it is possible to improve engine performance.

In particular, it is effective for a supercharged engine. Third Embodiment Next, a third embodiment will be described.

In the third embodiment, the connecting rod is provided with means for reducing the compression ratio as the combustion pressure increases.
As this means, as described in the second embodiment,
For example, a material whose shape can be changed by temperature or pressure, such as shape memory metal, is used.

The operation will be described below with reference to FIG. As described above, the engine performance can be improved by lowering the compression ratio and increasing the intake pressure.

In general, as a method of increasing the suction pressure, there are a turbocharger and a supercharger, which are superchargers. Further, as the suction pressure is increased by the supercharger, the amount of air sucked into the cylinder increases, and the combustion pressure also increases, thereby improving the engine performance.

However, since the compression ratio increases in proportion to the supercharging pressure, it is necessary to lower the compression ratio. In general, 1
If the air pressure is supercharged, the amount of intake air is doubled. For this reason, the compression ratio also becomes about twice.

Further, as described in the second embodiment, when the compression ratio is increased, abnormal combustion occurs, so that there is a limit value. Therefore, as shown in FIG. 10, from the relationship between the suction pressure and the compression ratio, by lowering the compression ratio in consideration of this limit value, the suction pressure can be increased and the engine performance can be improved.

(Fourth Embodiment) Next, a fourth embodiment will be described. In a fourth embodiment, a method for controlling the in-cylinder pressure will be described.

In the first embodiment, the connecting rod is curved to vary the compression ratio. In the second and third embodiments,
The example in which the engine performance is improved by using a material that can expand and contract by temperature or pressure, such as a shape memory metal, for the connecting rod has been described. The engine having such a variable means detects the engine speed and the like, and further improves the engine performance by controlling the supercharging pressure, fuel injection amount, intake air amount, and the like based on information based on the detection result. Can be planned.

The compression ratio is controlled by the above method,
The in-cylinder pressure can be kept constant, and the engine performance can be improved.

[0047]

According to the present invention, it is possible to minimize the rise in cylinder pressure by slightly changing the basic compression ratio, thereby improving engine performance and ensuring engine durability. is there.

That is, when the load is low, by increasing the compression ratio, deterioration of combustion can be prevented, and deterioration of engine performance can be prevented. At high load, lowering the compression ratio makes it possible to keep the in-cylinder pressure constant, and increasing the intake pressure makes it possible to significantly improve engine performance.

When the basic compression ratio is reduced, the startability of the engine is deteriorated. However, by using the present invention, the compression ratio can be increased even when the engine is started.
Startability can be improved.

Further, the number of engine components does not change.
The simple shape does not increase the cost and contributes to the improvement of engine performance. Further, by using a material such as a shape memory metal or the like that can change the shape by temperature or pressure for the connecting rod, the compression ratio can be varied, and the engine performance can be improved.

Further, the engine performance can be further improved by detecting the engine speed and the like, and controlling the supercharging pressure, fuel injection amount, intake air amount and the like based on information based on the detection result.

[Brief description of the drawings]

FIG. 1 is a diagram showing a relationship between engine performance and intake pressure.

FIG. 2 is a diagram showing a relationship between an in-cylinder pressure and an intake pressure.

FIG. 3 is a diagram illustrating a relationship between an in-cylinder pressure and a compression ratio.

FIG. 4 is a diagram showing the relationship between engine performance and suction pressure and maximum combustion pressure when the compression ratio changes.

FIG. 5 is a schematic diagram showing a configuration of a conventional engine.

FIG. 6 is a schematic diagram showing a configuration of an engine according to the embodiment of the present invention.

FIG. 7 is a diagram showing a change in combustion pressure with a change in the amount of deflection of a connecting rod.

FIG. 8 is a diagram showing a relationship between stress and combustion pressure.

FIG. 9 is a diagram illustrating a relationship between a compression ratio and engine performance.

FIG. 10 is a diagram showing a relationship between a compression ratio, a suction pressure, and engine performance.

[Explanation of symbols]

 Reference Signs List 1 cylinder block 2 combustion chamber 3 intake valve 4 exhaust valve 5 piston 6 connecting rod 6 'connecting rod 7 crankshaft P combustion pressure A piston area k spring constant X deflection amount

Claims (6)

[Claims] 1. A combustion chamber in a cylinder, and a piston that slides by receiving a combustion pressure generated by burning an air-fuel mixture in the combustion chamber, and a connecting rod is connected to the piston to connect the piston. In the internal combustion engine that transmits the combustion pressure to a crankshaft as a driving force via a rod, the connecting rod varies a compression ratio that is a ratio of a cylinder internal volume when the piston is at a bottom dead center and a top dead center. An internal combustion engine comprising a variable means for causing the internal combustion engine to perform the operation. 2. The internal combustion engine according to claim 1, wherein the variable means maintains the in-cylinder pressure in a predetermined range according to the combustion pressure generated in the combustion chamber. 3. The internal combustion engine according to claim 1, wherein said variable means is formed by curving the connecting rod. 4. The internal combustion engine according to claim 3, wherein the connecting rod is made of a material having a spring constant. 5. The internal combustion engine according to claim 1, wherein the variable means increases the compression ratio as the combustion pressure decreases. 6. The internal combustion engine according to claim 1, wherein the variable means decreases the compression ratio as the combustion pressure increases.