JP2013174218A - Compression ignition type internal combustion engine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To achieving suitable ignition timing in a compression ignition type internal combustion engine using gasoline as fuel.SOLUTION: A spark plug 6 is mounted on a cylinder head 2 as a shock wave generating means. A termination of a compression stroke, the first-time spark is performed when a piston 3 is at a distance E1 and further when the piston 3 has risen to a distance E2 near a top dead center, the second-time spark is performed. The first shock wave 12 generated by the first spark comes into collision with an inner surface of a combustion chamber and reflects therefrom to thereby generate a first reflected wave 13, so that the second shock wave 14 generated by the second spark collides with the first reflected wave 13. An interfacial boundary 15 where the second shock wave 14 has collided with the first reflected wave 13 becomes partially high in pressure to allow fuel particles 16 located at the interfacial boundary 15 to become easy to combust. Hence, the fuel particles combust when the piston 3 reaches the top dead center, thereby triggering the explosive combustion of the whole of an air-fuel mixture.

Description

  The present invention relates to a compression ignition type internal combustion engine having excellent combustion stability.

  Compression ignition internal combustion engines are widely used as diesel engines using light oil or heavy oil as fuel. A compression ignition type internal combustion engine has an advantage that a high output can be obtained because of a high compression ratio, and therefore, an internal combustion engine using gasoline as fuel has been studied to be a compression ignition type (auto ignition type), or Some have been put to practical use. For example, Patent Document 1 discloses an internal combustion engine capable of switching between spark ignition and compression ignition.

JP 2012-7504 A

  In the case of the spark ignition method, the ignition timing can be controlled relatively easily by controlling the timing of energization to the spark plug. However, in the case of the compression ignition method, the ignition timing can vary depending on various factors such as the engine temperature and the air-fuel ratio. Since it depends on the influence, there is a problem that it is difficult to control the ignition timing. In addition, problems such as a decrease in output are caused regardless of whether the ignition is early or delayed.

  The present invention has been made in view of the present situation as described above, and an object thereof is to provide a compression ignition type internal combustion engine capable of controlling the ignition timing.

  In order to achieve the above object, in the present invention, in an internal combustion engine in which the air-fuel mixture sucked into the combustion chamber is compressed by a piston and ignited, at least a part of the air-fuel mixture sucked into the combustion chamber is pressurized or elevated. Shock wave generating means for heating is provided. Here, as the shock wave generating means, for example, a spark bragg, an ultrasonic vibrator, a high frequency vibrator, or the like can be used.

  According to the present invention, since the fuel particles of the air-fuel mixture sucked into the combustion chamber are pressurized or (/ and) heated by a shock wave, at least a part of the fuel can be made extremely easy to burn. It becomes easy to burn and pre-ignition the fuel, and this can be used as a trigger to explode the entire mixture. Since the shock wave generation timing can be electrically controlled, the fuel preliminary ignition timing can also be controlled. Therefore, the fuel can be burned at an optimal timing while being of the compression ignition type. As a result, a high output can be obtained, and the concentration of harmful components of the exhaust gas can be reduced by complete combustion.

It is a principal part sectional view of an embodiment, (A) is a figure in the state where the first spark was performed, and (B) is a figure in the state where the second spark was performed. (A) is a schematic diagram which shows the state in which the fuel particle is receiving energy, (B) is principal part sectional drawing in a combustion state.

(1). Structure Next, an embodiment of the present invention will be described with reference to the drawings. First, the structure will be described. The internal combustion engine of the present embodiment is a four-cycle system, and has a cylinder block 1 and a cylinder head 2 that overlaps the cylinder block 1 as in the prior art. A cylinder bore 4 in which the piston 3 slides is formed in the cylinder block 1, and a combustion recess 5 corresponding to the cylinder bore 4 is formed in the cylinder head 2. The combustion recess 5 has a roof-type structure, and a spark brag 6 faces the center.

  The cylinder head 2 is formed with an intake port 8 that is opened and closed by the intake valve 7 and an exhaust port 10 that is opened and closed by the exhaust valve 9 in a state of being distributed to both sides of the cylinder bore 4 with the shaft center therebetween. Yes. A fuel injection nozzle 11 faces the intake port 8.

  In the present embodiment, two intake ports 8 and two exhaust ports 10 are arranged in a direction perpendicular to the paper surface. Therefore, in the cross-sectional view of the center portion displaying the spark brag 6, the intake port 8 and the exhaust port 10 are not originally shown as cross sections, but the spark brag 6 and the intake / exhaust ports 8 and 10 are displayed together for convenience. Yes.

(2). Control Mode In this embodiment, the spark brag 6 constitutes the shock wave generating means described in the claims, and the spark brag 6 is an engine control unit (ECU: not shown) as the control means. It is controlled as follows.

  That is, as shown in FIG. 1A, when the piston 3 reaches a distance E1 to the top dead center at the end of the compression process, first, the spark plug 6 is first energized. Then, the first shock wave 12 is generated around the spark location due to air bursting or the like due to the spark, and the first shock wave 12 propagates in the radial direction. The first shock wave 12 is transmitted to the cylinder bore 4 or the cylinder head 2. The first reflected wave 13 is radiated toward the inside of the combustion chamber by colliding with the inner surface of the member constituting the combustion chamber.

  Therefore, next, as shown in FIG. 5B, when the piston 3 further approaches the top dead center and reaches the distance E2 to the top dead center, the spark plug 6 is energized a second time. Then, a second shock wave 14 is generated in the combustion chamber by the second spark, and the second shock wave 14 and the first reflected wave 13 collide with each other, as shown in FIG. A high pressure region is generated at the boundary surface 15 between the shock wave 14 and the first reflected wave 13, whereby the fuel particles 15 positioned on the boundary surface 15 are pressurized to a high pressure.

  Since the group of fuel particles 16 located at the boundary surface 15 between the second shock wave 14 and the first reflected wave 13 is in a state in which it is easily burned by being pressurized to a high pressure, the piston further When 3 shifts to the top dead center, compression ignition is performed and preliminary combustion is performed, and the flame of this preliminary combustion propagates to the entire combustion chamber at a stretch, whereby the entire mixture is burned (exploded) at a stretch. Explosive combustion preferably occurs when the piston 3 slightly exceeds the top dead center. Therefore, it can be said that the combustion of the fuel pressurized by the shock wave preferably occurs when the piston 3 is located at the top dead center.

  While the first shock wave 12 and the second shock 14 spread in the radial direction around the spark spot, the first reflected wave 13 returns from the entire combustion chamber, so that the first shock wave 14 and the first reflected wave 13 are It is assumed that the colliding boundary surface 15 has a planar spread. For this reason, it is presumed that the pre-combustion in which the fuel pre-pressurized by the shock wave burns also has a wide area, and therefore, the air-fuel mixture filled in the combustion chamber can be combusted in a short time.

  It should be noted that a plurality of boundary surfaces 15 where the first shock wave 14 and the first reflected wave 13 collide are expected to be generated in a layered manner. It can be said that the explosive combustion due to is even more certain.

  The combustibility of the air-fuel mixture in the combustion chamber differs depending on various factors such as the type of fuel, the engine temperature, the air-fuel mixture temperature, the rotational speed, the air-fuel mixture concentration, and the presence (or concentration) of EGR gas. Therefore, an optimal combustion state can be realized by adjusting the timing of the first spark and the second spark using these elements as variables. For example, when it is related to the engine temperature, it is preferable to delay the timing of the first spark and the second spark because combustion becomes easier when the engine temperature becomes higher.

  In the case of control using the spark brag 6, the piston 3 is in the compression stroke in the sparking state, so it is important not to ignite by the first spark. It is possible to perform compression ignition and ignition by spark at the same time by performing the second spark near the top dead center. It is also possible to pressurize the fuel particles by causing the combustion chamber to easily reflect shock waves and causing the reflected waves to collide with each other by a single shock wave.

(3). Variations When using the spark brag 6 as in the present embodiment, the spark voltage (in other words, the strength of the shock wave) can be increased by making the high voltage generator energized to the spark brag 6 variable. It is also possible to change. It is also possible to change the intensity of the first shock wave 12 and the intensity of the second shock wave 14 by changing the voltage between the first spark and the second spark (the reflected wave 13 is attenuated, so the first shock wave is attenuated). If 12 is made stronger than the second shock wave 14, the collision boundary surface 15 between the first reflected wave 13 and the second shock wave 14 can be strongly pressurized.

  Further, when stable combustion is realized in a steady state, the control using the spark brag 6 is not performed, and the control using the spark brag 6 is performed when the combustion becomes unstable. It is also possible to switch between running and unused driving. Moreover, when using the spark brag 6, it is also possible to pressurize the air-fuel mixture stepwise by energizing it three or more times.

  It is also possible to arrange a plurality of spark brags 6 in one combustion chamber. In this case, it is possible to energize a plurality of spark brags 6 a plurality of times at the same time, or it is possible to energize a plurality of spark brags 6 in order, and a plurality of spark brags 6 are simultaneously generated. It is also possible to dispose the shock waves so that they collide with each other and energize them simultaneously.

  As the shock wave generating means, it is also possible to use an ultrasonic generator, a high frequency generator, or a vibrating hand device such as a magnetron. When using an ultrasonic generator, irradiate ultrasonic waves from multiple parts to make it collide, give kinetic energy to the fuel particles located at the impacted boundary surface, increase the temperature and pressure, or slightly before top dead center By irradiating the top surface of the piston 3 positioned with ultrasonic waves, it is possible to rub the fuel particles in contact with the top surface of the piston 3 against the top surface of the piston 3 to increase the temperature and pressure.

  The arrangement position of the shock wave generating means is not limited to the cylinder head, and may be provided on the cylinder block or the piston. When the piston is provided, power may be supplied by wireless power supply using high frequency. In addition, by using a gasket sandwiched between the cylinder block and the cylinder head 2 as a shock wave excitation unit, a pressure / heating region for the air-fuel mixture is formed on the surface along the inner periphery of the gasket. Is also possible. Needless to say, the present invention can also be applied to a diesel engine using light oil or heavy oil as fuel.

  The present invention can be embodied in an internal combustion engine such as a compression ignition gasoline engine. Therefore, it can be used industrially.

DESCRIPTION OF SYMBOLS 1 Cylinder block 2 Cylinder head 3 Piston 4 Cylinder bore 6 Spark bragg as an example of shock wave generation means 7 Intake valve 9 Exhaust valve 12 First shock wave 13 First reflected wave 14 Second shock wave 15 First reflected wave and second shock wave Boundary interface 16 Fuel particles

Claims (1)

This is a method of igniting the air-fuel mixture sucked into the combustion chamber by compressing it with a piston.
Shock wave generating means for pressurizing or heating at least a part of the air-fuel mixture sucked into the combustion chamber is provided,
Compression ignition internal combustion engine.

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