JPH0681654A - Combustion chamber structure of direct cylinder injection type engine - Google Patents

Abstract

PURPOSE:To attain a wide range with low fuel consumption and high output by providing an injector for stratified combustion, a spark plug with a spark gap installed in a specific position, and an injector for uniform combustion. CONSTITUTION:A combustion chamber 6 is a pot type long in the distance to the top part 6a from the deck face 1a of a cylinder block 1. During the low-medium load operation of an engine, fuel is injected from a first injector 8 toward the center part of the combustion chamber 6. When the injected fuel engulfs air to generate a cloud of rich mixture near the spark gap 10b of a spark plug 10, stratified combustion leading to fire propagation is performed. During high load operation, fuel is injected from a second injector 9 toward the center part in a cylinder bore 4, and mixture of uniform concentration is formed to perform uniform combustion. A wide range with low fuel consumption and high output can be thus attained.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a combustion chamber structure of a direct injection type internal combustion engine equipped with an injector for directly injecting fuel into a combustion chamber, and more specifically, to stable stratified combustion at low load and high load. The present invention relates to a combustion chamber structure of a direct injection engine for a cylinder, which is improved so as to achieve a wide range of low fuel consumption and high output while achieving both good and uniform combustion.

[0002]

2. Description of the Related Art As a combustion chamber structure of a direct injection type cylinder engine having an injector for directly injecting fuel into a combustion chamber,
It is known that a spark plug is installed in front of the injector in the fuel injection direction (see Japanese Patent Laid-Open No. 62-58013). In this type of in-cylinder direct injection engine, the combustion method can be switched between stratified combustion and uniform combustion by appropriately controlling the fuel injection timing and ignition timing.

In the stratified charge combustion, the fuel injection timing of the injector is controlled immediately before the ignition timing, and when a cloud, which is a rich air-fuel mixture, is generated near the spark gap of the spark plug, it is ignited and the flame is propagated. Since it is a combustion method and stable combustion without misfire can be obtained, it is suitable as a combustion method in the low and medium load operating regions of the engine. Further, the uniform combustion is a combustion method in which the fuel injection timing is advanced relatively larger than the ignition timing to generate a mixture having a uniform concentration in the combustion chamber and ignite the mixture. It is suitable as a combustion method in the load operation region.

[0004]

By the way, in the cylinder direct injection type engine in which the combustion system is switched between the stratified combustion and the uniform combustion, the injector must inject a required amount of fuel within an extremely short time. In addition, a large injection amount per unit time and a high injection rate are required.
Moreover, since the fuel injection amount is small at the time of stratified combustion at low load and the fuel injection amount is large at the time of uniform combustion at high load, the injector is required to have a large dynamic range, which is the ratio of the minimum flow rate to the maximum flow rate. To be done.

However, at present, the dynamic range of the injector has a certain limit, and it is quite difficult to realize a dynamic range of 10 or more. For this reason, there is a certain limit in achieving both stable stratified combustion at low load and good uniform combustion at high load to achieve wide range of low fuel consumption and high output.

As a means for exceeding this limit, it is conceivable to use two injectors, one for stratified charge combustion and one for uniform combustion, but in this case, two injectors and one ignition are used. The problem is how to arrange the plug with respect to the combustion chamber, and if the arrangement or the shape of the combustion chamber is inappropriate, the following problems occur. That is, if the distance between the injection port of the injector for stratified charge combustion and the deck surface of the cylinder block cannot be sufficiently secured, the injected fuel collides with the piston top surface and H
The generation of C (hydrocarbon) is increased or the fuel efficiency is deteriorated. Further, in a V-type engine in which the cylinder axis is largely inclined, if the spark plug is installed so as to be largely inclined with respect to the cylinder axis, the electrode portion may be in a slightly upward posture. Is easily accumulated, and smoldering occurs at the time of ignition, or fuel fogging occurs and reliable ignition cannot be obtained. Furthermore, when the injector for uniform combustion is installed with a large inclination with respect to the cylinder axis, the injected fuel adheres to the cylinder wall surface, increasing the generation of HC (hydrocarbons), or deteriorating fuel efficiency and reducing output. Come on.

Therefore, the present invention can be applied to a V-type engine, and achieves both stable stratified combustion at low load and good uniform combustion at high load to achieve wide range of low fuel consumption and high output. It is an object of the present invention to provide a combustion chamber structure for a direct injection type engine that can achieve the above.

[0008]

To this end, a combustion chamber structure for a direct injection type internal combustion engine according to the present invention comprises a jar-shaped or conical combustion chamber having a long distance from the deck surface to the top of a cylinder block. A squish area that is continuous around the bottom of the combustion chamber, and a first injector for stratified combustion that is installed with the injection port facing the top of the combustion chamber so as to inject fuel toward the center of the combustion chamber. And a spark plug installed with the electrode portion positioned obliquely below and facing the spark gap forward of the first injector in the fuel injection direction, and the fuel is injected toward the center of the cylinder bore. It is provided with a second injector for uniform combustion installed with the injection port facing the squish area.

[0009]

According to the combustion chamber structure of the direct injection type internal combustion engine which employs such means, the fuel is injected from the first injector toward the central portion of the combustion chamber immediately before the ignition timing during low and medium load operation. Is jetted. When the injected fuel entrains air to generate a cloud of a rich mixture in the vicinity of the spark gap of the spark plug, the spark plug is ignited, whereby stratified combustion accompanied by flame propagation is performed. Also,
During high-load operation, fuel is injected from the second injector toward the center of the cylinder bore at a timing that is relatively advanced relative to the ignition timing. When this injected fuel is sufficiently premixed with air to generate a mixture having a uniform concentration, the ignition plug is ignited to perform uniform combustion.

Here, the combustion chamber is a pot type or a conical type in which the distance from the deck surface of the cylinder block to the top is long, and the first injector for stratified combustion has its injection port facing the top of the combustion chamber. Therefore, the injected fuel does not adhere to the top surface of the piston during the stratified combustion, and the situation that the generation of HC (hydrocarbon) increases or the fuel consumption deteriorates is avoided in advance.

Further, since the second injector for uniform combustion has the injection port facing the squish area so as to inject the fuel toward the central portion in the cylinder bore, the injected fuel is allowed to reach the cylinder wall surface during uniform combustion. It is possible to prevent the occurrence of the situation in which HC (hydrocarbon) is increased, the fuel consumption is deteriorated, and the output is decreased without adhering.

Further, since the spark plug is installed such that the electrode portion thereof is located obliquely below, it is difficult for the droplet fuel to accumulate, and there is no smoldering or fuel fogging during ignition, and it is possible to ensure that Ignite.

[0013]

Embodiments of the present invention will now be described in detail with reference to the accompanying drawings. FIG. 1 shows a schematic structure of a direct injection type cylinder engine having a combustion chamber structure according to the first embodiment. This engine is a two-cycle gasoline engine that is forcibly scavenged by a scavenging pump (not shown), and a cylinder block 1 is formed with a cylinder bore 4 in which a scavenging port 2 and an exhaust port 3 are opened.
A piston 5 is reciprocally slidably fitted in the piston.

A cylinder head 7 forming a combustion chamber 6 is joined to the cylinder block 1, and a first injector 8 for stratified combustion for injecting fuel into the combustion chamber 6 is connected to the cylinder head 7. A second injector 9 for uniform combustion that injects fuel into the cylinder bore 4 and a spark plug 10 are installed. A fuel injection signal and an ignition signal from the control unit 11 are input to the first injector 8, the second injector 9, and the spark plug 10.

Here, the combustion chamber 6 is a pot type having a long distance A from the deck surface 1a of the cylinder block 1 to the top portion 6a, and is arranged eccentrically to one side from the center of the cylinder bore 4. A squish area 6b is continuously formed around the bottom of the combustion chamber 6, and the width of the squish area 6b is narrow on one side where the combustion chamber 6 is eccentrically arranged and wide on the opposite side.

The first injector 8 has a weak penetration and produces a cloud in the vicinity of the injection port 8a. The first injector 8 is installed on the axis of the combustion chamber 6 and the injection port 8a is installed in the combustion chamber 6. The fuel is injected in the shape of a hollow cone toward the center of the combustion chamber 6, facing the center of the top portion 6a of the fuel cell 6. On the other hand, the second injector 9 has a high injection rate, a narrow injection angle, and a slightly strong penetration, and is installed on the line B in FIG. 2 connecting the center of the cylinder bore 4 and the center of the combustion chamber 6. The injection port 9a faces the widest part of the squish area 6b, and the fuel is injected toward the center of the cylinder bore 4.

Further, the spark plug 10 has an electrode portion 10
It is installed around the combustion chamber 6 in a posture in which a is located diagonally below, and its spark gap 10b is exposed to the front of the first injector 8 in the fuel injection direction.

Here, even when the axis of the cylinder bore 4 is inclined by about 45 degrees in the direction in which the second injector 9 is located downward along the line B, as in the V-type engine, the spark plug 10 has electrodes. The spark plug 10 is installed within the range shown by the diagonal lines in FIG. 2 so that the posture in which the portion 10a is inclined downward can be maintained. That is, when a line passing through the center O of the combustion chamber 6 and orthogonal to the line B in FIG.
The spark plug 10 is installed within the angle range of about 45 degrees from the C line on the arrangement side of the second injector 9 with respect to the center.

Next, the first aspect of the present invention thus constructed
The operation of the embodiment will be described. During low and medium load operation of the engine, only the first injector 8 injects fuel toward the center of the combustion chamber 6 immediately before the ignition timing by the fuel injection signal from the control unit 11. When this injected fuel entrains air and a cloud of a rich mixture is generated in the vicinity of the spark gap 10b of the spark plug 10, the spark plug 10 receiving an ignition signal from the control unit 11 ignites this cloud. Stratified combustion is performed with flame propagation.

Here, the combustion chamber 6 is a pot type in which the distance A from the deck surface 1a of the cylinder block 1 to the top portion 6a is long, and the first injector 8 has an injection port 8a at the top portion 6a.
Since the injected fuel does not adhere to the top surface of the piston 5 during the stratified charge combustion, it is possible to prevent the generation of HC (hydrocarbon) from increasing and the fuel consumption to deteriorate. Further, the spark plug 10 is installed in a posture in which the electrode portion 10a is located obliquely below, and the direction in which the axis of the cylinder bore 4 is located along the line B and the second injector 9 is located below, as in the V-type engine. Since the posture is maintained even when it is tilted at about 45 degrees, it is difficult for the droplet fuel to accumulate in the spark plug 10. Therefore, the ignition plug 10 does not cause smoldering or fuel fogging during ignition and reliably ignites the cloud, and stable stratified combustion is performed.

When the engine is operating under a high load, the fuel injection signal from the control unit 11 causes the fuel to be injected into the central portion of the cylinder bore 4 at a timing when only the second injector 9 is advanced relatively larger than the ignition timing. Jet toward. Then, when this injected fuel is sufficiently premixed with air to generate an air-fuel mixture having a uniform concentration in the combustion chamber 6, the spark plug 10 which receives an ignition signal from the control unit 11 ignites this air-fuel mixture having a uniform concentration. By doing so, uniform combustion is performed.

Here, since the second injector 9 for uniform combustion has its injection port 9a facing the squish area 6b so as to inject fuel toward the central portion in the cylinder bore 4, injection is performed during uniform combustion. Since the fuel does not adhere to the inner wall surface of the cylinder bore 4 and the occurrence of HC (hydrocarbon) increases, the deterioration of fuel consumption and the reduction of output are avoided, good uniform combustion is achieved. Is obtained.

Therefore, according to the first embodiment, even when applied to a V-type engine, stable stratified combustion at low load and good uniform combustion at high load are both achieved, resulting in low fuel consumption and high output. Wide range can be achieved.

FIG. 3 shows a schematic structure of a direct injection type cylinder engine having a combustion chamber structure according to a second embodiment of the present invention. In the second embodiment, the jar-shaped combustion chamber 6 is changed to a conical-shaped combustion chamber 12, and the arrangements of the second injector 9 and the ignition plug 10 are changed accordingly, and the like. Since there is no change in the structure, the parts corresponding to those in the first embodiment are designated by the same reference numerals and detailed description thereof will be omitted.

Here, the spark plug 10 is on the opposite side of the combustion chamber 12 from the eccentric direction of the combustion chamber 12 and connects the center of the cylinder bore 4 and the center of the combustion chamber 12 with B in FIG.
It is arranged on the line. And this spark plug 10
The spark gap 10b of the electrode portion 10a, which is installed at an inclination angle of 45 degrees or less with respect to the axis of the combustion chamber 12 and is located obliquely below, faces the front of the first injector 8 in the fuel injection direction.

Further, the second injector 9 is installed within the range shown by the diagonal lines in FIG. 4, that is, within the angle range of about 60 degrees from the C line with the center of O on the side where the spark plug 10 is disposed. The injection port 9a faces a relatively wide portion of the squish area 6b, and the fuel is injected toward the center of the cylinder bore 4.

Also in the second embodiment constructed as described above, the spark plug 10 is installed in a posture in which the electrode portion 10a thereof is located obliquely downward, and in this posture, the axis of the cylinder bore 4 is B as in the V-type engine. Even if the spark plug 10 is inclined by about 45 degrees in the direction in which the spark plug 10 is located along the line, the spark plug 10 is maintained, so that the droplet fuel is less likely to accumulate in the spark plug 10. In addition, the first injector 8 and the second injector 9
Respectively injects fuel in the optimum state as in the case of the first embodiment. Therefore, also in the second embodiment, substantially the same operational effects as the first embodiment can be obtained.

The present invention is not limited to a two-cycle gasoline engine, but can be applied to a four-cycle engine or an engine using alcohol as fuel.

[0029]

As described above, according to the present invention,
During low and medium load operation, fuel is injected from the first injector toward the center of the combustion chamber immediately before the ignition timing. When the injected fuel entrains air to generate a cloud of a rich mixture in the vicinity of the spark gap of the spark plug, the spark plug is ignited, whereby stratified combustion accompanied by flame propagation is performed. Further, during the high load operation, the fuel is injected from the second injector toward the central portion in the cylinder bore at the timing when the advance angle is relatively larger than the ignition timing. When this injected fuel is sufficiently premixed with air to generate a mixture having a uniform concentration, the ignition plug is ignited to perform uniform combustion.

Here, the combustion chamber is a pot type or a conical type in which the distance from the deck surface of the cylinder block to the top is long, and the first injector for stratified combustion has its injection port facing the top of the combustion chamber. Therefore, the injected fuel does not adhere to the top surface of the piston during the stratified combustion, and the situation that the generation of HC (hydrocarbon) increases or the fuel consumption deteriorates is avoided in advance.

Further, since the second injector for uniform combustion has the injection port facing the squish area so as to inject the fuel toward the central portion in the cylinder bore, the injected fuel is allowed to reach the cylinder wall surface during uniform combustion. It is possible to prevent the occurrence of the situation in which HC (hydrocarbon) is increased, the fuel consumption is deteriorated, and the output is decreased without adhering.

Furthermore, since the spark plug is installed with its electrode portion positioned obliquely below, it is difficult for the droplet fuel to accumulate, and there is no smoldering or fuel fogging during ignition, and it is possible to ensure Ignite.

Therefore, according to the present invention, even when applied to a V-type engine, both stable stratified combustion under low load and good uniform combustion under high load are achieved to achieve wide range of low fuel consumption and high output. Can be achieved.

[Brief description of drawings]

FIG. 1 is a vertical cross-sectional view showing a first embodiment of the present invention.

FIG. 2 is a sectional view taken along the line II-II of FIG.

FIG. 3 is a vertical sectional view showing a second embodiment of the present invention.

4 is a sectional view taken along the line IV-IV of FIG.

[Explanation of symbols]

 1 Cylinder Block 1a Deck Surface 2 Scavenging Port 3 Exhaust Port 4 Cylinder Bore 5 Piston 6 Combustion Chamber 6a Top 6b Squish Area 7 Cylinder Head 8 First Injector 8a Injector 9 Second Injector 9a Injector 10 Spark Plug 10a Electrode 10b Spark gap 11 Control unit 12 Combustion chamber

Claims (1)

[Claims] 1. A pot-type or conical-type combustion chamber having a long distance from the deck surface to the top of a cylinder block, a squish area continuous around the bottom of the combustion chamber, and a fuel toward the center of the combustion chamber. Fuel injection of the first injector, which is installed with the injection port facing the top of the combustion chamber so as to inject fuel, and the spark gap in a posture in which the electrode portion is positioned obliquely below. The spark plug installed facing the front in the direction, and the second injector for uniform combustion installed with the injection port facing the squish area so as to inject fuel toward the central portion in the cylinder bore. The combustion chamber structure of the direct injection type internal combustion engine characterized by being equipped.