Auxiliary chamber type internal combustion engine

Auxiliary chamber type internal combustion engine has a main combustion chamber and an auxiliary chamber having an injection port through which the main combustion chamber communicates. The auxiliary chamber has a passage sectional area which is smoothly decreased toward the injection port. Further, the engine has a fuel injector injecting a fuel into the auxiliary chamber; an ignition plug igniting the fuel in the auxiliary chamber; and a swirl generating portion swirling a gas in the auxiliary chamber. The swirl generating portion swirls only the gas flowing into the auxiliary chamber from the main combustion chamber.

CROSS-REFERENCE TO RELATED APPLICATION

This application is based on Japanese Patent Application No. 2013-234626 filed on Nov. 13, 2013, the disclosure of which is incorporated herein by reference.

TECHNICAL FIELD

The present disclosure relates to an auxiliary chamber type internal combustion engine having a main combustion chamber and an auxiliary chamber.

BACKGROUND

JP-2011-38465A shows an internal combustion engine having a main combustion chamber and an auxiliary chamber. A spring member is disposed in the auxiliary chamber to generate a swirl flow. An air flowing into the auxiliary chamber from the main combustion chamber and a fuel supplied to the auxiliary chamber are homogeneously mixed, whereby an ignitability of the fuel in the auxiliary chamber can be stabilized.

However, it is still necessary to improve a spread of a flame jet which is injected from the auxiliary chamber to the main combustion chamber.

SUMMARY

It is an object of the present disclosure to provide an auxiliary chamber type internal combustion engine which can spread a flame jet promptly in a main combustion chamber.

According to the present disclosure, an auxiliary chamber type internal combustion engine has a main combustion chamber, and an auxiliary chamber having an injection port through which the main combustion chamber communicates. The auxiliary chamber has a passage sectional area which is smoothly decreased toward the injection port. The auxiliary chamber type internal combustion engine further has a fuel injector injecting a fuel into the auxiliary chamber; an ignition plug igniting the fuel in the auxiliary chamber; and a swirl generating portion swirling a gas in the auxiliary chamber.

According to the above configuration, a fuel is supplied into the auxiliary chamber, and is ignited by the ignition plug. Since the air in the auxiliary chamber is swirled by the swirl generating portion, the fuel ignited in the auxiliary chamber becomes the swirling flame jet. The passage sectional area of the auxiliary chamber is smoothly decreased toward the injection port. Thus, the flow direction of the flame jet does not change rapidly in the auxiliary chamber. A flow velocity of the flame jet is increased at the injection port. Therefore, the swirling flame jet is injected from the injection port to the main combustion chamber without causing a vortex breakdown. Then, the flow velocity of the swirling flame jet is decreased in the main combustion chamber, so that a vortex breakdown is generated and the flame jet is rapidly spread in the main combustion chamber. As a result, the fuel combustion in the main combustion chamber can be improved.

DETAILED DESCRIPTION

First Embodiment

A first embodiment of the present invention will now be described with reference to the accompanying drawings.FIG. 1is a schematic chart illustrating an auxiliary chamber type internal combustion engine10which uses gas fuel.

The internal combustion engine10has a cylinder block12, a piston14, a cylinder head20, an intake valve41, an exhaust valve42, a main fuel injector51, a second sub fuel injector52, an ignition plug54, and an Electric Control Unit (ECU)50.

The cylinder block12, the piston14and the cylinder head20define a main combustion chamber15. The cylinder head20is provided with an intake port21and an exhaust port22. The air is intaken into the main combustion chamber15from an intake port21through an intake valve41. The exhaust gas is discharged from the main combustion chamber15to an exhaust port22through an exhaust valve42. The intake valve41and the exhaust valve42are driven by a cam shaft (not shown).

The fuel pressurized by a fuel pump (not shown) is supplied to the main fuel injector51. The main fuel injector51is provided to the cylinder head20in such a manner as to confront a center of the main combustion chamber15. During a compression stroke, the main fuel injector51injects the gas fuel toward a head of the piston14. The main fuel injector51is controlled by the ECU50.

An auxiliary chamber23is defined in the cylinder head20above the main combustion chamber15. A volume of the auxiliary chamber23is smaller than that of the main combustion chamber15. The main combustion chamber15and the auxiliary chamber23communicate with each other through an injection port24which has a circular cross section. The second sub fuel injector52and the ignition plug54are provided to the cylinder head20adjacent to the auxiliary chamber23. The second sub fuel injector52supplies the fuel into the auxiliary chamber23through an injection nozzle52a. The ignition plug54ignites the air-fuel mixture in the auxiliary chamber23.

Although the fuel supplied to the auxiliary chamber23may be the same as the gas fuel supplied to the main combustion chamber15, it is preferable that the fuel supplied to the auxiliary chamber23has higher combustion velocity than that of the gas fuel supplied to the main combustion chamber15. Specifically, a high octane value liquid fuel which is rich in an aromatic compound or a gas fuel which is rich in hydrogen is preferable.

A cavity14ais formed on a top surface of the piston14. The cavity14aconfronts the injection port24. The cavity14ais formed cylindrically and its axis line agrees with an axis line of the injection port24. A diameter and a depth of the cavity14aare determined based on a compression ratio of the internal combustion engine10.

The ECU50is a microcomputer having a CPU, a ROM, a RAM and an input/output interface. The ECU50receives output signals from various sensors, such as a crank angle sensor, a coolant temperature sensor, and an accelerator position sensor. Then, the ECU50controls the main fuel injector51, the second sub fuel injector52, and ignition-plug54based on the output signals.

Next, with reference toFIGS. 2 and 3, a configuration of the auxiliary chamber23will be explained in detail.FIG. 2is a schematic chart showing the auxiliary chamber23and its vicinity.FIG. 3is a schematic chart showing the auxiliary chamber23and vanes30. It should be noted that the vanes30are not illustrated inFIG. 2.

The auxiliary chamber23is comprised of a cylindrical portion25and a circular cone portion26.

An axis line of the cylindrical portion25agrees with the axis line of the injection port24. The second sub fuel injector52and the ignition plug54are provided to the cylinder head20in such a manner as to confront the cylindrical portion25of the auxiliary chamber23. The ignition plug54has a grounding electrode54bwhich extends from a specified position54ato a center of the ignition plug54. The ignition plug54is arranged in such a manner that a distance between the injection nozzle52aand the specified position54abecomes longest. The cylindrical portion25is connected to the circular cone portion26.

An axis line of the circular cone portion26agrees with the axis line of the injection port24and the axis line of the cylindrical portion25. A top part of the circular cone portion26is connected to the injection port24.

An inner diameter of the circular cone portion26is gradually decreased from a connecting portion with the cylindrical portion25to the connecting portion with the injection port24. That is, a passage sectional area of the auxiliary chamber23is smoothly decreased from the cylindrical portion25to the injection port24. An inner surface of the injection port24and an inner surface of the circular cone portion26, which are shown by dashed lines inFIG. 2, cross at an angle θ. The angle θ is defined in such a manner that the air flowing into the auxiliary chamber23from the main combustion chamber15separates from the inner surface of the circular cone portion26during a compression stroke of the engine10. Specifically, the angle θ is 12°˜60°.

As shown inFIG. 3, a plurality of vanes30is provided on the inner surface of the circular cone portion26. Each of the vanes30is a blade spirally extending from the bottom of the circular cone portion26to the top of the circular cone portion26. Each of vanes30protrudes from an inner surface of the circular cone portion26inwardly. Each of the vanes30swirls the air flowing to the injection port24along the inner surface of the auxiliary chamber23.

A combustion of the internal combustion engine10will be described hereinafter.

In an intake stroke, the intake valve41is opened and the air is intaken into the main combustion chamber15through the intake port21.

Then, in a compression stroke, the intake valve41is closed and the air is compressed by the piston14. The fuel is injected towards the cavity14aof the piston14from the main fuel injector51. At this time, as shown by arrows inFIG. 2, the air is introduced into the auxiliary chamber23through an injection port24from the main combustion chamber15.

When the air swirls from the main combustion chamber15to the auxiliary chamber23, it is likely that the flame jet may not swirl from the auxiliary chamber23to the main combustion chamber15due to the vanes30. According to the present embodiment, as shownFIG. 3, the vanes30are formed on the circular cone portion26from which the air separates. Thus, the air flowing into the auxiliary chamber23from the main combustion chamber15is not swirled.

Then, the second sub fuel injector52injects the fuel into the auxiliary chamber23. The injected fuel is mixed with the air which flows into the auxiliary chamber23from the main combustion chamber15. At this time, the air flow shown by arrows inFIG. 2accelerates the mixture of air and fuel.

Then, the ignition plug54ignites the air-fuel mixture. The air-fuel mixture is combusted to generate a flame jet to the injection port24. Since the ignition plug54is arranged in such a manner that the distance between the injection nozzle52aand the specified position54abecomes longest, the air-fuel mixture can be combusted near the center of the auxiliary chamber23relative to the specified position54a. The flame jet flowing along an inner surface of the auxiliary chamber23is swirled by the vanes30. At this time, since the air flowing into the auxiliary chamber23from the main combustion chamber15is not swirled, the flame jet is swirled by the vanes30without any trouble. If the air flowing into the auxiliary chamber23from the main combustion chamber15is swirled by the vanes30, the swirling directions are opposite between the air and the flame jet.

The passage sectional area of the circular cone portion26is smoothly decreased toward the injection port24. Thus, the flow direction of the flame jet does not change rapidly in the auxiliary chamber23. Since the passage sectional area of the circular cone portion26is smoothly decreased, the flow velocity of the flame jet is increased at the injection port24. Therefore, the swirling flame jet is injected from the injection port24to the main combustion chamber15without causing a vortex breakdown. Generally, since the pressure is relatively low at a center of a swirling flow, the vortex breakdown is easily caused when the flow velocity is decreased.

Then, the flow velocity of the swirling flame jet is decreased in the main combustion chamber15, so that a vortex breakdown is generated and the flame jet is rapidly spread in the main combustion chamber15. The cavity14aconfronting the injection port24is formed on a top surface of the piston14. For this reason, it can be restricted that the flame jet injected into the main combustion chamber15from the auxiliary chamber23collides with the piston14.

As described above, the flame jet injected into the main combustion chamber15from the auxiliary chamber23can be promptly spread in the main combustion chamber15by using of its vortex breakdown. As a result, without depending on flame propagation, the air-fuel mixture injected by the main fuel injector51can be combusted promptly. The fuel combustion in the main combustion chamber15is improved and a heat efficiency of the internal combustion engine10is enhanced. Furthermore, even when a premixing of the air and the fuel injected by the main fuel injector51is insufficient, the air-fuel mixture is ignited by the flame jet. As a result, the fuel consumption performance of the internal combustion engine10can be raised, and a discharge of nitrogen oxides can be suppressed.

According to the above embodiment, following advantages can be obtained.

Since the air in the auxiliary chamber23is swirled by the vanes30, the fuel ignited in the auxiliary chamber23becomes the swirling flame jet. The passage sectional area of the circular cone portion26is smoothly decreased toward the injection port24. Therefore, the swirling flame jet is injected from the injection port24to the main combustion chamber15without causing a vortex breakdown. Then, the flow velocity of the swirling flame jet is decreased in the main combustion chamber15, so that a vortex breakdown is generated and the flame jet is rapidly spread in the main combustion chamber15. As a result, the fuel combustion in the main combustion chamber15can be improved.

The air flowing into the auxiliary chamber23from the main combustion chamber15is not swirled. Thus, the swirling flame jet is surely generated.

The vanes30are formed on the circular cone portion26from which the air separates. Thus, the air flowing into the auxiliary chamber23from the main combustion chamber15is separated from the inner surface of the circular cone portion26, so that the air is not swirled. Meanwhile, the vanes30swirl the flame jet flowing into the injection port24along an inner surface of the auxiliary chamber23. Therefore, the flame jet flowing into the main combustion chamber15from the auxiliary chamber23is surely swirled by the vanes30.

The cavity14aconfronting the injection port24is formed on a top surface of the piston14. For this reason, it can be restricted that the flame jet injected into the main combustion chamber15from the auxiliary chamber23collides with the piston14. It is expedited that the flame jet is spread in the main combustion chamber15due to the vortex breakdown.

The above-mentioned embodiment may be modified as follows.

As shown inFIG. 4, instead of vanes, a plurality of grooves130may be formed on the inner surface of the circular cone portion26of the auxiliary chamber23. InFIG. 4, the grooves are indicated with hatching for explaining easily. Each of the grooves130is spirally extending from the bottom of the circular cone portion26to the top of the circular cone portion26. Each of the grooves130swirls the air flowing to the injection port24along the inner surface of the auxiliary chamber23. The air flowing into the auxiliary chamber23from the main combustion chamber15is not swirled. Also in the above configuration, the same advantages as those in first embodiment can be obtained.

Second Embodiment

Hereafter, a second embodiment will be described. In the second embodiment, a first sub fuel injector152injects a swirling fuel into the auxiliary chamber23. In the second embodiment, the same parts and components as those in the first embodiment are indicated with the same reference numerals and the same descriptions will not be reiterated.

FIG. 5is a schematic chart showing the auxiliary chamber23and its vicinity.

The cylinder head20has two injection passages57,58and a confluent portion56at an upper end of the cylindrical portion25. Each of the injection passages57,58communicates with the cylindrical portion25at its opening end57a,58a. The ignition plug54is arranged in such a manner that a distance between the opening end58aand the specified position54abecomes longest. The injection passages57,58are fluidly connected with each other at the confluent portion56. The first sub fuel injector152is provided to the cylinder head20in such a manner as to confront the confluent portion56. The first sub fuel injector152(first fuel supply valve) has the same configuration as the above second sub fuel injector52in the first embodiment.

FIG. 6is a perspective chart schematically showing the injection passages57,58and the confluent portion56.

The confluent portion56is positioned above the auxiliary chamber23. The injection passages57,58extend from the confluent portion56spirally relative to the cylindrical portion25, and are fluidly connected to the cylindrical portion25. The fuel is swirled by the first sub fuel injector152, the confluent portion56and the injection passages57,58.

Next, the combustion cycle of the internal combustion engine10in present embodiment will be explained.

In a compression stroke, the air is introduced into the auxiliary chamber23through an injection port24from the main combustion chamber15.

Then, the first sub fuel injector152injects the fuel into the confluent portion56. The injected fuel in the confluent portion56flows into the injection passages57,58. The fuel is injected into the cylindrical portion25spirally from the opening ends57a,58a. Thus, the air in the auxiliary chamber23is swirled by the injected fuel.

The first sub fuel injector152may inject the fuel before or after the main fuel injector51injects the fuel. In the case that the first sub fuel injector152injects the fuel before the main fuel injector51injects the fuel, the air in the auxiliary chamber23is swirled and then introduced into the auxiliary chamber23from the main combustion chamber15. Since the air flowing into the auxiliary chamber23from the main combustion chamber15is not swirled, the swirl of the air in the auxiliary chamber23is not weaken. In the case that the first sub fuel injector152injects the fuel after the main fuel injector51injects the fuel, the air is introduced into the auxiliary chamber23from the main combustion chamber15, and then swirled in the auxiliary chamber23. At this case, the air flow shown by arrows inFIG. 2accelerates the mixture of air and fuel.

Then, the ignition plug54ignites the air-fuel mixture in the auxiliary chamber23. Since the ignition plug54is arranged in such a manner that the distance between the opening ends57a,58aand the specified position54abecomes longest, the air-fuel mixture can be combusted near the center of the auxiliary chamber23relative to the specified position54a. The air-fuel mixture is combusted to generate a flame jet to the injection port24. The passage sectional area of the circular cone portion26is smoothly decreased toward the injection port24. Thus, the flow direction of the flame jet does not change rapidly in the auxiliary chamber23. Since the passage sectional area of the circular cone portion26is smoothly decreased, the flow velocity of the flame jet is increased at the injection port24. Therefore, the swirling flame jet is injected from the injection port24to the main combustion chamber15without causing a vortex breakdown.

According to the above embodiment, following advantages can be obtained.

The air in the auxiliary chamber23is swirled by the first sub fuel injector152, the confluent portion56, and the injection passages57,58. Thus, the air in the auxiliary chamber23can be swirled without providing vanes or grooves.

The above-mentioned embodiment may be modified as follows. The same parts and components as those in the second embodiment are indicated with the same reference numerals and the same descriptions will not be reiterated.

As shown inFIG. 7, the auxiliary chamber23can be defined only by the circular cone portion26without the cylindrical portion. Since no vane is formed on the circular cone portion26, the gas flowing into the auxiliary chamber23from the main combustion chamber15is not swirled. Therefore, the angle θ between the inner surface of the injection port24and the inner surface of the circular cone portion26may be about 12° or less. The angle θ is defined in such a manner that the air flowing into the auxiliary chamber23from the main combustion chamber15does not separate from the inner surface of the circular cone portion26during a compression stroke of the engine10.

InFIG. 5, a plurality of vanes may be provided on the circular cone portion26. The flame jet flowing into the main combustion chamber15from the auxiliary chamber23is surely swirled by the first sub fuel injector152, the confluent portion56, the injection passages57and58and the vanes.

Third Embodiment

Hereafter, a third embodiment will be described. In the third embodiment, the same parts and components as those in the first embodiment are indicated with the same reference numerals and the same descriptions will not be reiterated.

FIG. 8is a schematic chart showing the auxiliary chamber23and its vicinity.FIG. 9is a schematic chart showing an injection passage59.

The cylinder head20has an injection passage59at a side of the cylindrical portion25. The injection passage59communicates with the cylindrical portion25tangentially at its opening end59a. The ignition plug54is arranged in such a manner that a distance between the injection nozzle52aand the opening end59abecomes longest. The first sub fuel injector152is provided to the cylinder head20in such a manner as to confront the injection passage59. The first sub fuel injector152(first fuel supply valve) has the same configuration as the above second sub fuel injector52in the first embodiment. The first sub fuel injector152injects the fuel into the injection passage59.

Moreover, the injection nozzle52aof the second sub fuel injector52(second fuel supply valve) confronts the cylindrical portion25. The second sub fuel injector52supplies the fuel into the auxiliary chamber23, as shown by arrows inFIGS. 8 and 9. The ECU50controls a fuel-injection rate between the first sub fuel injector152and the second sub fuel injector52based on the operational state of the internal combustion engine10. The fuel is swirled by the first sub fuel injector152, the injection passage59and the ECU50.

Next, the combustion cycle of the internal combustion engine10in present embodiment will be explained.

In a compression stroke, the air is introduced into the auxiliary chamber23through an injection port24from the main combustion chamber15. Since no vane is formed on the circular cone portion26, the air flowing into the auxiliary chamber23from the main combustion chamber15is not swirled.

Then, the first sub fuel injector152injects the fuel into the injection passage59. The injected fuel in the injection passage59flows through the injection passage59. The fuel is injected from the opening end59ain a tangential direction of a cylindrical portion25, as shown by the arrow. Since the injected fuel flows along the inner circumferential surface of the cylindrical portion25, the air in the auxiliary chamber23is swirled by the injected fuel. Meanwhile, the fuel injected by the second sub fuel injector52does not swirl the air in the auxiliary chamber23. The ECU50controls a fuel-injection rate between the first sub fuel injector152and the second sub fuel injector52, whereby a swirl intensity of the air in the auxiliary chamber23is adjusted. The sub fuel injectors152,52may inject the fuel before or after the main fuel injector51injects the fuel.

Then, the ignition plug54ignites the air-fuel mixture in the auxiliary chamber23. Since the ignition plug54is arranged in such a manner that the distance between the injection nozzle52aand the opening end59abecomes longest, the air-fuel mixture can be combusted near the center of the auxiliary chamber23relative to the specified position54a. The air-fuel mixture is combusted to generate a flame jet to the injection port24. The passage sectional area of the circular cone portion26is smoothly decreased toward the injection port24. Therefore, the swirling flame jet is injected from the injection port24to the main combustion chamber15without causing a vortex breakdown.

According to the above embodiment, following advantages can be obtained.

The air in the auxiliary chamber23is swirled by the first sub fuel injector152and the injection passage59. Thus, the air in the auxiliary chamber23can be swirled without providing vanes or grooves.

The first sub fuel injector152injects the fuel into the auxiliary chamber23, whereby the air in the auxiliary chamber23is swirled. Meanwhile, when it is unnecessary to swirl the air in the auxiliary chamber23, the second sub fuel injector52injects the fuel into the auxiliary chamber23.

The ECU50controls a fuel-injection rate between the first sub fuel injector152and the second sub fuel injector52, whereby a swirl intensity of the air in the auxiliary chamber23is adjusted. Therefore, according to the operational state of the internal combustion engine10, the vortex breakdown of the flame jet and a spread velocity of the flame jet in the main combustion chamber15can be controlled.

The above-mentioned embodiment may be modified as follows. The same parts and components as those in the above embodiment are indicated with the same reference numerals and the same descriptions will not be reiterated.

As shown inFIG. 10, the auxiliary chamber23can be defined only by the circular cone portion126without the cylindrical portion. The passage sectional area of the circular cone portion126is gradually decreased toward the injection port24. Since no vane is formed on the circular cone portion126, the gas flowing into the auxiliary chamber23from the main combustion chamber15is not swirled. Therefore, the angle θ between the inner surface of the injection port24and the inner surface of the circular cone portion26may be about 12° or less. The angle θ is defined in such a manner that the air flowing into the auxiliary chamber23from the main combustion chamber15does not separate from the inner surface of the circular cone portion126during a compression stroke of the engine10.

InFIG. 8, a plurality of vanes may be provided on the circular cone portion26. Therefore, the flame jet flowing into the main combustion chamber15from the auxiliary chamber23is surely swirled by the vanes, the first sub fuel injector152and the injection passage59.

The fuel-injection rate between the first sub fuel injector152and the second sub fuel injector52can also be set constant. Even in this case, the air in the auxiliary chamber23is swirled by the fuel injected by the first sub fuel injector152.

The above-mentioned embodiments may be modified as follows. The same parts and components as those in the above embodiments are indicated with the same reference numerals and the same descriptions will not be reiterated.

A sectional shape of the injection port24can also be changed into an ellipse form. However, it is preferable that the sectional shape of the injection port24is circular so that the swirl of the flame jet is not weakened. Moreover, the passage sectional area of an injection port24can be set in a range in which the swirl of the flame jet is not weakened.

As shown inFIG. 11, the piston14may have no cavity on its top surface. Moreover, the main fuel injector51may be provided to the cylinder head20in such a manner as to confront an outer periphery of the main combustion chamber15. That is, the main fuel injector51injects the fuel into a side portion of the main combustion chamber15. It should be noted that the volume of the main combustion chamber15inFIG. 1and the volume of the main combustion chamber15inFIG. 11are substantially equal to each other.

As shown by a dashed line inFIG. 11, the main fuel injector51may be provided to the cylinder head20to inject the fuel into the intake port21.

Above embodiments can be applied not only the auxiliary chamber type internal combustion engine using fuel gas but also an auxiliary chamber type diesel engine and an auxiliary chamber type gasoline engine.