JP4134708B2 - Combustion assist device for internal combustion engine - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a combustion control device that injects gas into a combustion chamber of an internal combustion engine.
[0002]
[Prior art]
A technique is known in which high-pressure air is injected into a cylinder of a diesel engine to quickly complete diffusion combustion in the latter half of combustion under high load (see, for example, Patent Document 1). Further, in a direct injection diesel engine, an air injection valve is provided in the combustion chamber, and high pressure air is injected toward the swirl flow downstream side in the fuel injection direction during the expansion stroke, thereby disturbing the dense fuel. Technology (for example, see Patent Document 2), the cylinder bore wall is provided with one or more air injection holes in the fuel injection valve direction or the combustion chamber tangential direction, and the compressed fuel is injected at the bottom dead center of the piston. In a technique for controlling penetration, preventing diffusion, and promoting fuel atomization (see, for example, Patent Document 3), an in-cylinder direct injection engine, an air injection valve is provided in the combustion chamber, and high-pressure air is injected during fuel injection. Thus, the dispersion of the injected fuel is suppressed and a combustible air-fuel mixture is formed in the vicinity of the spark plug (see, for example, Patent Document 4), and compression is performed from another cylinder at a pressure higher than the pressure in the cylinder in which the fuel is injected. Air Supplied as Shisutoea art (e.g., see Patent Document 5) are known.
[0003]
[Patent Document 1]
JP-A-8-319837 (page 3, FIG. 1)
[Patent Document 2]
JP 62-267519 A (2nd and 3rd pages, FIG. 1)
[Patent Document 3]
Japanese Utility Model Publication No. 1-74323 (page 3-7, FIG. 1)
[Patent Document 4]
JP 2001-248443 A (3rd and 4th pages, FIGS. 1 and 2)
[Patent Document 5]
Japanese Unexamined Patent Publication No. 2-115569 (page 2-4, FIG. 1)
[0004]
[Problems to be solved by the invention]
The effect of preventing knocking according to the above-described conventional technique acts on both initial combustion in the combustion chamber (0 to 10% combustion period) and late combustion in which knocking mainly occurs (10 to 90% combustion period). However, it is not possible to improve only the lowering of the burning rate in the late combustion, and it does not improve the root cause for preventing knocking.
[0005]
Further, in the problem that the fuel injected by the direct injection type internal combustion engine adheres to the combustion chamber, there is a method of promoting the vaporization of the injected fuel by increasing the temperature of the combustion chamber in the compression ignition type internal combustion engine. In the spark ignition type internal combustion engine, problems such as knocking due to an increase in the temperature in the combustion chamber occur.
[0006]
In view of the circumstances as described above, it is an object of the present invention to suppress knocking by increasing the combustion rate in the later stage of the combustion process and to prevent fuel from adhering to the side wall surface of the combustion chamber.
[0007]
[Means for Solving the Problems]
In order to solve the above-described problems, the present invention provides a plurality of high-pressure gas injection holes that are provided on a side wall surface of a combustion chamber of an internal combustion engine and injects gas into the combustion chamber, and injects gas into the combustion chamber from the high-pressure gas injection holes. A combustion auxiliary device for an internal combustion engine comprising a high-pressure gas injection valve and high-pressure gas supply means for supplying high-pressure gas injected from the high-pressure gas injection hole was used.
[0008]
The internal combustion engine has turbulent flow generating means for generating turbulent flow in the combustion chamber, and the turbulent flow generating means allows gas to flow toward the combustion chamber side wall surface from a nozzle hole provided in the combustion chamber side wall surface. The jetting means for jetting was used.
[0009]
The cause of knocking is that the air-fuel mixture spontaneously ignites from the vicinity of the side wall surface of the combustion chamber and rapidly burns before the flame surface propagating from the ignition device as the fire source reaches the end of the combustion chamber. . Therefore, the propagation speed of the flame surface generated from the ignition device is increased, and the flame surface reaches the combustion chamber end before firing from the combustion chamber end. In addition, the temperature of the gas around the side wall surface of the combustion chamber is made uniform by stirring the heated air-fuel mixture on the side wall surface of the combustion chamber. Due to this homogenization, there are no places where the temperature is higher than in other parts. As a result, the gas around the side wall surface of the combustion chamber does not spontaneously ignite. In order to reduce these knocks, a plurality of injection holes are provided on the side wall surface of the combustion chamber, and gas is injected into the combustion chamber from these injection holes.
[0010]
The injected gas is mainly air, and the air taken in from the outside is pressurized to high pressure by a high-pressure gas supply means such as a high-pressure pump. Further, since it is difficult to structurally provide a valve in the nozzle hole, it is preferable to provide an injection valve in a passage between the high-pressure pump and the nozzle hole and perform air injection control using this valve.
[0011]
When the air injected from the nozzle hole comes into contact with the wall surface of the combustion chamber or the flow of air injected from another nozzle hole, the flow is disturbed and a turbulent flow is generated. Also, the timing of injection is preferably immediately before the piston is raised and the air-fuel mixture is sufficiently compressed and ignited by the ignition device. Therefore, the nozzle hole is attached at a position where the side wall surface of the combustion chamber is formed even when the piston is raised, that is, near the joint surface between the cylinder block and the cylinder head, which is the upper portion of the combustion chamber. Good. It is desirable that the injection positions of the injection holes are attached so that turbulent flow is uniformly generated.
[0012]
When the turbulent flow is generated at the end of the combustion chamber, the air-fuel mixture stagnating at the end of the combustion chamber is agitated, and the combustion speed can be increased.
[0013]
Next, using the form of the combustion assist device, the internal combustion engine has a wall flow generating means for generating a wall flow flowing along the side wall surface of the combustion chamber in the combustion chamber, and the wall flow generating means is a combustion The nozzle is an injection means for injecting gas along the combustion chamber side wall surface from the nozzle hole provided in the chamber side wall surface.
[0014]
In a direct injection type internal combustion engine in which fuel is directly injected into a combustion chamber, liquid fuel is atomized and injected into the combustion chamber. Generally, since the temperature in the combustion chamber is high, the injected fuel is vaporized, but part of the fuel reaches the side wall surface of the combustion chamber before vaporization and adheres to the side wall surface of the combustion chamber.
[0015]
The combustion chamber has a cooling water passage for cooling the internal combustion engine inside the side wall thereof. Therefore, the side wall surface of the combustion chamber is cooled by the cooling water flowing through the cooling water channel, and the fuel that is injected and adheres to the side wall surface of the combustion chamber becomes more difficult to vaporize. And the fuel which is not vaporized tends to cause incomplete combustion in the combustion stroke of the internal combustion engine. As a result, pollutants such as soot and HC are generated.
[0016]
Therefore, in order to prevent fuel from adhering to the side wall surface of the combustion chamber, an injection hole for injecting gas is provided on the side wall surface of the combustion chamber, and gas is injected from the injection hole along the side wall surface of the combustion chamber. Form a wall. The finely divided fuel approaching the combustion chamber wall surface is taken into the airflow and drifts in the combustion chamber due to the formed airflow wall, and does not adhere to the wall surface. In addition, the finely divided fuel may be vaporized while drifting in the combustion chamber.
[0017]
In order to form this wall flow, the nozzle hole is provided so as to inject gas into a shape along the side wall surface of the combustion chamber. The nozzle holes are provided on the side wall surface of the combustion chamber so as to be arranged at equal intervals at the same position.
[0018]
The time of injection from the injection hole is before fuel is injected into the combustion chamber and the injected fuel reaches the side wall surface of the combustion chamber. The nozzle hole is provided above the piston position at the time when the fuel is injected.
[0019]
Gas injection control means for injecting gas into the combustion chamber according to the operating state of the internal combustion engine is provided.
[0020]
In the spark ignition internal combustion engine, the combustion assist device is used to prevent knocking. Therefore, there is no need to use the combustion assist device when the internal combustion engine is operating under conditions where knocking does not occur. In the in-cylinder direct injection internal combustion engine, the combustion assist device is used to prevent the injected fuel from adhering to the combustion chamber side wall. Therefore, it is not necessary to use the combustion assisting device if the fuel is not attached. Therefore, whether to perform gas injection of the combustion assisting device is determined according to various conditions of the internal combustion engine.
[0021]
In the present invention, the gas injection control means can stop the gas injection before the flame injected by the combustion of the internal combustion engine reaches the gas injected from the nozzle hole.
[0022]
When a flame due to combustion of the internal combustion engine reaches the gas injected from the nozzle hole, the flame is cooled by this air, and the combustion speed may be reduced. As the combustion speed decreases, knocking is likely to occur. Therefore, the injection of gas is stopped before reaching the flame to suppress the occurrence of knocking.
[0023]
In the present invention, ignition means for changing the ignition timing of the air-fuel mixture according to the operating state of the internal combustion engine is further provided, and the gas injection control means makes the interval between the gas injection stop and the ignition timing constant. I was able to
[0024]
In general, the ignition timing is advanced when the internal combustion engine reaches a high speed. Here, the interval between the gas injection stop timing and the ignition timing can be kept constant by advancing the gas injection stop timing in conjunction with this. Thereby, it becomes possible to suppress the fall of flame temperature.
[0025]
DETAILED DESCRIPTION OF THE INVENTION
<First Embodiment>
An embodiment in which a combustion assist device for an internal combustion engine according to the present invention is applied to a gasoline engine system which is a spark ignition type internal combustion engine will be described.
[0026]
In FIG. 1, an internal combustion engine (hereinafter referred to as an engine) 1 is an in-line four-cylinder gasoline engine system having a fuel supply system 10, a combustion chamber 20, an intake system 30, an exhaust system 40, and the like as main parts. Hereinafter, the configuration of the gasoline engine system will be described.
[0027]
The fuel supply system 10 includes a supply pump 11, a pressure accumulation chamber (common rail) 12, a fuel injection valve 13, an engine fuel passage P1, and the like.
[0028]
The supply pump 11 increases the pressure of the fuel pumped up from the fuel tank (not shown) and supplies it to the common rail 12 through the engine fuel passage P1. The common rail 12 has a function of holding (accumulating) the high-pressure fuel supplied from the supply pump 11 at a predetermined pressure, and distributes the accumulated fuel to each fuel injection valve 13 provided in the intake port. The fuel injection valve 13 is an electromagnetic valve provided with an electromagnetic solenoid (not shown) therein, and is appropriately opened to supply and inject fuel into the intake port.
[0029]
The intake system 30 forms a passage (intake passage) for intake air supplied into each combustion chamber 20. On the other hand, the exhaust system 40 forms a passage (exhaust passage) for exhaust gas discharged from each combustion chamber 20.
[0030]
In the intake system 30, the intake air taken from the atmosphere is filtered by the air cleaner 31. The throttle valve 32 provided downstream of the air cleaner 31 is an electronically controlled on-off valve whose opening degree can be adjusted in a stepless manner. It has a function of adjusting (reducing) the supply amount of intake air. Then, the air whose supply amount has been adjusted is sent to the intake port of the engine 1, where it is mixed with the fuel injected from the fuel injection valve 13 to become an air-fuel mixture.
[0031]
In the exhaust system 40, an exhaust passage 40 b is connected to the downstream side of the exhaust collecting pipe 40 connected from the combustion chamber along the exhaust gas flow path, the catalyst casing 42 is connected downstream thereof, and the exhaust passage 40 c is further connected downstream. Yes. The catalyst casing 42 accommodates a three-way catalyst that purifies harmful components such as NOx contained in the exhaust gas, or an NOx storage reduction catalyst.
[0032]
Further, various sensors are attached to each part of the engine 1, and signals related to the environmental conditions of the part and the operating state of the engine 1 are output.
[0033]
That is, the rail pressure sensor 70 outputs a detection signal corresponding to the fuel pressure stored in the common rail 12. The air flow meter 72 outputs a detection signal corresponding to the flow rate (intake amount) of intake air upstream of the throttle valve 32 in the intake system 30. The oxygen concentration (A / F) sensor 73 outputs a detection signal that continuously changes in accordance with the oxygen concentration in the exhaust gas upstream of the catalyst casing 42 of the exhaust system 40. Similarly, the catalyst outflow exhaust temperature sensor 74 outputs a detection signal corresponding to the temperature of exhaust gas (exhaust temperature) downstream of the catalyst casing 42 of the exhaust system 40.
[0034]
Further, the accelerator opening sensor 76 is attached to an accelerator pedal (not shown), and outputs a detection signal that is a basis of a work amount required in the engine 1 according to the depression amount of the pedal. The crank angle sensor 77 outputs a detection signal (pulse) every time the output shaft (crankshaft) of the engine 1 rotates by a certain angle. Each of these sensors 70 to 79 is electrically connected to an electronic control unit (ECU) 80.
[0035]
The ECU 80 includes a central processing unit (CPU), a read only memory (ROM), a random access memory (RAM), a backup RAM in which stored information is not erased even after the operation is stopped, a timer counter, etc., and an input including an A / D converter A logic operation circuit including a port and an output port connected by a bidirectional bus is provided.
[0036]
The ECU 80 inputs the detection signals of the various sensors through the input port, and performs basic control on the fuel injection and the like of the engine 1 from the program stored in the ROM in the CPU included in the ECU 80 based on these signals. In addition, various controls related to the operating state of the engine 1 are performed.
[0037]
As shown in FIG. 2, the combustion chamber 20 is formed by a cylinder block 21 on a side wall and a cylinder head 22 on an upper wall, and a piston 23 is inserted into the cylinder block 21 from below. A cylinder liner 24 is inserted into the cylinder block 21 that forms the side wall of the combustion chamber 20, and the inner surface of the cylinder liner 24 becomes the inner wall surface of the combustion chamber 20, and the cylinder liner 24 and the cylinder block 21 are joined to each other. A cooling water passage 25 is provided on the surface so as to circulate on the side surface of the cylinder liner 24 of each cylinder.
[0038]
The cylinder head 22 forming the upper wall of the combustion chamber 20 is provided with an intake port 33 connected to the intake system 30 and an exhaust port 38 connected to the exhaust system 40. The intake valve 27a and the exhaust valve 27b are attached so as to be the valves of the intake port 33 and the exhaust port 38, respectively. A spark plug 28 serving as an ignition device is attached to the center of the combustion chamber 20 of the cylinder head 21.
[0039]
A piston 23 provided below the combustion chamber 20 is connected to one end of a connecting rod (not shown) at the lower portion thereof, and the other end of the connecting rod is connected to a crankshaft (not shown). Then, the reciprocating motion of the piston is changed to the rotational motion of the crankshaft.
[0040]
A spacer 52 is sandwiched between the cylinder head 22 and the cylinder block 21, and a ring 53 with an injection hole is sandwiched at a connection portion with the combustion chamber 20. The ring 53 with nozzle holes is formed obliquely with respect to the normal line of the combustion chamber 20 having a circular cross section, and a plurality of nozzle holes 54 for injecting high-pressure air into the combustion chamber 20, and the plurality of nozzle holes 54. An annular passage 55 that is annularly connected to the nozzle hole 54 is provided.
[0041]
The spacer 52 is provided with a high-pressure air passage 56 that continues to the annular passage 55 and continues to the side of the cylinder block 21. A high-pressure air injection valve 51 serving as a valve for injecting high-pressure air is provided upstream of the high-pressure air passage 56. A high-pressure pump 50 is provided upstream of the high-pressure air injection valve 51 to pressurize and send air to the high-pressure air injection valve 51. Then, the air purified by the air cleaner 31 flows into the high-pressure pump 50 from the intake system 30.
[0042]
Hereinafter, a method of suppressing knocking by high-pressure air injected from the injection hole 54 will be described. In the normal combustion process, the air-fuel mixture flows into the combustion chamber 20 from the intake port 33, and the air-fuel mixture is compressed by the piston 23, ignited by the spark plug 28, combusted and volume expanded, and the piston 23 is pushed back downward. . On the other hand, in the knocking, the air-fuel mixture compressed by the piston 23 is burned before the flame surface ignited by the spark plug 28 reaches the end of the combustion chamber due to the self-heating by the compression and the combustion chamber temperature. It is a phenomenon that spontaneously ignites from the end of the room and spreads rapidly. Therefore, in order to suppress knocking, a method of causing the flame surface to reach the end of the combustion chamber before spontaneous ignition from the end of the combustion chamber, or a mixture that is locally overheated is mixed with another non-superheated mixture. And the temperature is lowered.
[0043]
As a specific method, the air-fuel mixture is compressed by the piston 23, and the air-fuel mixture is ignited by the spark plug 28. The flame surface of the ignited flame spreads from the position of the spark plug 28 provided at the center of the combustion chamber 20 to the end of the combustion chamber. At this time, the high-pressure air injection valve 51 is opened, and compressed air is injected from a plurality of injection holes 54 provided in a ring 53 sandwiched between the cylinder head 22 and the cylinder block 21 to turbulently flow near the side wall of the combustion chamber 20. Is generated.
[0044]
The injection timing of the high-pressure air injection valve 51 is controlled by the ECU 80. More specifically, the ECU 80 determines the ignition timing of the spark plug 28 and the fuel injection amount injected from the combustion injection valve 13 based on signals detected by the crank angle sensor 77, the accelerator opening sensor 76, and the like. The high-pressure air injection timing of the high-pressure air injection valve 51 is controlled from the determined addition timing, fuel injection amount, and piston position obtained from the crank angle sensor 77. Further, the high-pressure pump 50 is interlocked with the crankshaft, and pressurizes the air to be injected as the crankshaft rotates.
[0045]
As shown in FIG. 3, the nozzle holes 54 are provided at the same angle with respect to the normal line, and the compressed air flow injected from the nozzle holes 54 is compressed air flow emitted from the adjacent nozzle holes 54. Turbulence is generated by this interference. By generating the turbulent flow, the air-fuel mixture stagnating around the side wall surface of the combustion chamber is agitated. Therefore, when the flame surface reaches the turbulent flow region, the flame surface propagation speed is accelerated, and the flame surface can reach the combustion chamber side wall surface before knocking starts. In addition, turbulent flow is generated and the mixture is agitated, so that the mixture heated on the side wall surface of the combustion chamber is evenly agitated, and the partial temperature rise is moderated, making it difficult to cause spontaneous ignition. .
[0046]
In performing the knocking suppression method, if the operating state of the engine 1 is not a state that induces knocking, it is not particularly necessary to perform the knocking suppression method. As shown in FIG. 4, knocking occurs at high speed and occurs only at high load (at high output). Therefore, the knocking occurrence region is measured in a state where high-pressure air injection is not performed in advance, and the knocking occurrence region is mapped by the rotation speed and the load based on the measurement result. If the operating state of the engine 1 is within this mapping region, the combustion assist device by high-pressure air injection in the first embodiment is operated. If it is outside the region, it is not necessary to suppress knocking. Is not activated.
[0047]
The knocking suppression method will be described based on the chart of FIG. First, in S501, it is determined whether or not the operating state of the engine 1 is a state that induces knocking. If knocking occurs, the process proceeds to S502, and if knocking does not occur, the process proceeds to S507 to end the chart.
[0048]
Next, immediately before the ignition plug 28 is ignited in S <b> 502, the high-pressure air injection valve 51 is opened, and high-pressure air is emitted from the injection hole 54.
[0049]
Next, the high-pressure air injected from the plurality of injection holes 54 in S503 interferes with the high-pressure air injected from the other injection holes 54, and generates turbulent flow around the side wall surface of the combustion chamber to form a high turbulent flow region. . By forming a high turbulent flow region with this high-pressure air, the air-fuel mixture around the side wall surface of the combustion chamber does not stagnate, so that only the air-fuel mixture around the side wall surface of the combustion chamber is not heated.
[0050]
Next, in S504, the flame surface of the flame ignited by the spark plug 28 at S502 reaches the high turbulent flow region. In the high turbulent flow region, the flow of the airflow is fast, and in S505, the propagation of the flame surface is accelerated by the flow of the airflow, thereby preventing a decrease in the combustion speed.
[0051]
Then, after suppressing the occurrence of knocking in S506, the process proceeds to S507 and this chart is finished.
[0052]
In the first embodiment, the combustion speed is increased by generating the turbulent flow, and the stirring of the air-fuel mixture by generating the turbulent flow is advanced, so that the combustion efficiency can be further improved.
<Second Embodiment>
Next, an embodiment applied to a diesel engine system, which is an in-cylinder direct injection internal combustion engine that directly injects fuel into a combustion chamber, will be described for the second embodiment according to the present invention.
[0053]
In FIG. 6, an engine 101 is an in-line four-cylinder diesel engine system that includes a fuel supply system 110, a combustion chamber 120, an intake system 130, an exhaust system 140, and the like as main parts. Hereinafter, the configuration of the diesel engine system will be described.
[0054]
The fuel supply system 110 includes a supply pump 111, a pressure accumulation chamber (common rail) 112, a fuel injection valve 113, an engine fuel passage P1, and the like.
[0055]
The supply pump 111 raises the fuel pumped up from the fuel tank (not shown) and supplies it to the common rail 112 through the engine fuel passage P1. The common rail 112 has a function of holding (accumulating) the high-pressure fuel supplied from the supply pump 111 at a predetermined pressure, and distributes the accumulated fuel to each fuel injection valve 113. The fuel injection valve 113 is an electromagnetic valve provided with an electromagnetic solenoid (not shown) therein, and is appropriately opened to supply and inject fuel into the combustion chamber 120.
[0056]
The intake system 130 forms a passage (intake passage) for intake air supplied into each combustion chamber 120. On the other hand, the exhaust system 140 forms a passage (exhaust passage) for exhaust gas discharged from each combustion chamber 120.
[0057]
The engine 101 is provided with a known supercharger (turbocharger) 145. The turbocharger 145 includes a turbine wheel 147 and a compressor 148 connected via a shaft 146. One compressor 148 is exposed to intake air in the intake system 130, and the other turbine wheel 147 is exposed to exhaust gas in the exhaust system 140. The turbocharger 145 having such a configuration has an effect of increasing the intake pressure (supercharging effect) by rotating the compressor 148 using the exhaust flow (exhaust pressure) received by the turbine wheel 147.
[0058]
In the intake system 130, an intercooler 131 provided downstream of the turbocharger 145 forcibly cools intake air whose temperature has been increased by supercharging. The throttle valve 132 provided further downstream than the intercooler 131 is an electronically controlled on-off valve whose opening degree can be adjusted in a stepless manner, and restricts the flow passage area of the intake passage under predetermined conditions. The function of adjusting (reducing) the supply amount of the intake air is provided.
[0059]
Further, an exhaust gas circulation passage (EGR passage) 160 that bypasses the upstream (intake system 130) and the downstream (exhaust system 140) of the combustion chamber 120 is formed in the engine 101. Specifically, the EGR passage 160 communicates the exhaust manifold 140 a upstream of the turbocharger 145 in the exhaust system 140 and the downstream side of the throttle valve 132 in the intake system 130. The EGR passage 160 has a function of returning a part of the exhaust gas to the intake system 130 as appropriate. The EGR passage 160 is opened and closed steplessly by electronic control, and the exhaust gas flowing through the EGR passage 160 (circulating) is cooled by an EGR valve 161 that can freely adjust the exhaust flow rate flowing through the passage. EGR cooler 162 is provided.
[0060]
Further, in the exhaust system 140, on the downstream side of the portion where the exhaust collecting pipe 140a connected from the combustion chamber and the turbine wheel 147 are provided, an exhaust passage 140b along the exhaust gas flow path, and downstream of the catalyst casing 142, Further, the exhaust passage 140c is sequentially connected downstream. The catalyst casing 142 accommodates an NOx storage reduction catalyst that purifies harmful components such as NOx contained in the exhaust gas.
[0061]
Further, various sensors are attached to each part of the engine 101, and signals related to the environmental conditions of the part and the operating state of the engine 101 are output.
[0062]
In other words, the rail pressure sensor 170 outputs a detection signal corresponding to the fuel pressure stored in the common rail 112. The air flow meter 172 outputs a detection signal corresponding to the flow rate (intake amount) of intake air upstream of the throttle valve 132 in the intake system 130. The oxygen concentration (A / F) sensor 173 outputs a detection signal that continuously changes in accordance with the oxygen concentration in the exhaust gas upstream of the catalyst casing 142 of the exhaust system 140. Similarly, the catalyst outflow exhaust temperature sensor 174 outputs a detection signal corresponding to the exhaust gas temperature (exhaust temperature) downstream of the catalyst casing 142 of the exhaust system 140.
[0063]
Further, the accelerator opening sensor 176 is attached to an accelerator pedal (not shown), and outputs a detection signal that is a basis of a work amount required in the engine 101 according to the depression amount of the pedal. The crank angle sensor 177 outputs a detection signal (pulse) every time the output shaft (crankshaft) of the engine 101 rotates by a certain angle. Each of these sensors 170 to 177 is electrically connected to an electronic control unit (ECU) 180.
[0064]
The ECU 180 includes a central processing unit (CPU), a read-only memory (ROM), a random access memory (RAM), a backup RAM in which stored information is not erased even after operation is stopped, a timer counter, etc., and an input including an A / D converter A logic operation circuit including a port and an output port connected by a bidirectional bus is provided.
[0065]
The ECU 180 inputs detection signals of the various sensors through the input port, and based on these signals, the CPU included in the ECU 180 performs basic control on the fuel injection of the engine 101 from the program stored in the ROM. In addition, various controls related to the operating state of the engine 101 are performed.
[0066]
The combustion chamber 120 shown in FIG. 7 is formed by a cylinder block 121 having a side wall and a cylinder head 122 having an upper wall, and a piston 123 is inserted into the cylinder block 121 from below. A cylinder liner 124 is inserted into the cylinder block 121 that forms the side wall of the combustion chamber 120, and the inner surface of the cylinder liner 124 becomes the inner wall surface of the combustion chamber 120, and the cylinder liner 124 and the cylinder block 121 are joined to each other. A cooling water passage 125 is provided on the surface so as to circulate on the side surface of the cylinder liner 124 of each cylinder.
[0067]
The cylinder head 122 that forms the upper wall of the combustion chamber 120 is provided with an intake port 133 that continues from the intake system 130 and an exhaust port 138 that continues to the exhaust system 140. The intake valve 127a and the exhaust valve 127b are attached to be the valves of the intake port 133 and the exhaust port 138, respectively. A fuel injection device 113 that directly injects fuel into the combustion chamber 120 is attached to the center of the combustion chamber 120 of the cylinder head 122.
[0068]
A spacer 152 is sandwiched between the cylinder head 122 and the cylinder block 121, and a ring 153 is sandwiched between the connecting portion with the combustion chamber 120. The ring 153 has a plurality of injection holes 154 that are formed obliquely with respect to the normal line toward the combustion chamber 120 having a circular cross-sectional shape and that injects high-pressure air into the combustion chamber 120. An annular passage 155 that is annularly connected to the hole 154 is provided. The spacer 152 is provided with a high-pressure air passage 156 that continues to the annular passage 155 and continues to the side of the cylinder block 121.
[0069]
A high-pressure air injection valve 151 serving as a valve for injecting high-pressure air is provided upstream of the high-pressure air passage 156. A high pressure pump 150 is provided upstream of the high pressure air injection valve 151 to pressurize the air and send it to the high pressure air injection valve 151. Air purified by an air cleaner flows into the high-pressure pump 150 from the intake system 130.
[0070]
A concave portion is provided at the top of the piston 123. This recess corresponds to the ejection hole of the fuel injection device 113, and fuel from the ejection hole is injected toward this recess. And by injecting fuel into this recessed part, the fuel injected around this recessed part will stagnate.
[0071]
As described above, the fuel injected into the fuel chamber 120 is injected into the concave portion of the piston 123, so that the fuel stays almost in the center of the combustion chamber 120. However, when a part of the fuel is injected, Adhering to the cylinder liner 124 which is the side wall surface of the combustion chamber. Since the cylinder liner 124 is cooled with cooling water, the surface temperature of the cylinder liner 124 becomes lower than the temperature of the combustion chamber. Therefore, the fuel adhering to the cylinder liner 124 is less likely to evaporate than the fuel that is injected and floated in the combustion chamber. The fuel that adheres and does not vaporize causes incomplete combustion when combustion occurs in the combustion chamber, resulting in an increase in HC, soot, etc. in the exhaust.
[0072]
Hereinafter, a method for suppressing the adhesion of fuel to the side wall of the combustion chamber by the high-pressure air injected from the nozzle hole 154 will be described. In a normal combustion process, first, the piston 123 ascends to compress the air taken into the combustion chamber 120. Then, fuel is injected in a compressed state, that is, in a state where the piston 123 is moved upward. Thereafter, the piston 123 further rises, and the fuel is ignited by self-heating of the compressed air near the top dead center, and combustion starts.
[0073]
Therefore, in order to prevent the fuel from adhering to the side wall surface of the combustion chamber, it is only necessary to prevent the injected fuel from adhering to the side wall surface of the combustion chamber during the period after the fuel is injected and ignited until the flame spreads. . For this reason, as shown in FIG. 8, air is injected from the nozzle hole 154 to form an air curtain, and the fuel injected by the air curtain is prevented from adhering to the side wall surface of the combustion chamber.
[0074]
As a specific procedure, the high-pressure air injection valve 151 is opened at the same time or just before fuel is injected into the combustion chamber 120, and high-pressure air is injected from a plurality of nozzle holes 154. The nozzle hole 154 is provided so that air can be injected along the side wall surface of the combustion chamber. By ejecting air from each nozzle hole 154 along the side wall surface of the combustion chamber, an annular air flow is generated along the side surface of the combustion chamber. The generated annular airflow is used as an air curtain to prevent the injected fuel from adhering to the side wall surface of the combustion chamber.
[0075]
The purpose of the second embodiment is to prevent the fuel injected into the combustion chamber from adhering to the side wall surface of the combustion chamber. Therefore, under the condition that the injected fuel does not adhere to the side wall surface of the combustion chamber, for example, when the engine 101 is in a high temperature state and the amount of injected fuel is small, the fuel remains in the combustion chamber without performing the second embodiment. It does not adhere to the inner wall surface. Therefore, by determining whether or not the second embodiment is performed according to each condition, it becomes possible to reduce the power loss of the engine 1 when the pressure of the air is increased.
[0076]
In the second embodiment, the diesel engine system is used as the direct injection internal combustion engine. However, if the internal combustion engine directly injects fuel into the combustion chamber, a spark ignition internal combustion engine such as a gasoline engine is used. The second embodiment can also be applied to the above.
[0077]
In the second embodiment, a wall flow is formed by a gas flow to reduce the fuel adhering to the side wall surface of the combustion chamber, thereby increasing the rate of complete combustion of the fuel injected into the combustion chamber. Can do. That is, the combustion efficiency of the fuel injected into the combustion chamber is increased.
[0078]
In the first embodiment and the second embodiment, by injecting high-pressure air into the combustion chamber, the air is taken into the combustion chamber separately from the air taken in from the intake port. However, in the present embodiment, the amount of air taken in as the high-pressure air to be injected is, for example, at the nozzle hole area of about 0.1 mm ^ 2, the injection time of about 0.5 milliseconds, and the injection pressure of 10 MPa. As a result, the change in the air-fuel ratio (A / F) is about 0.2 to 0.1. This value is not a value that causes a particular problem in the present embodiment. Therefore, the air-fuel ratio is not particularly reset, but in another embodiment, a method of injecting high-pressure air in the same manner as in the present embodiment is also considered in consideration of the air-fuel ratio.
[0079]
In the first embodiment and the second embodiment, a high pressure pump is used to create high pressure air, and high pressure air is directly injected from the high pressure pump from the high pressure air injection valve. In addition to this, a pressure accumulating chamber may be provided in advance to accumulate high pressure air, and high pressure air may be sent from the pressure accumulating chamber to the high pressure air injection valve for injection. By providing this pressure accumulating chamber, it is possible to store high-pressure air with a high-pressure pump in advance when the engine is at a low load, and stop the high-pressure pump at a high load. This makes it possible to carry out the present embodiment without causing power loss due to operating the high-pressure pump at the time of a high load that requires the most power.
<Third Embodiment>
In the present embodiment, the injection of high-pressure air is stopped before reaching the high-pressure air into which the flame when the air-fuel mixture burns in the combustion chamber is injected. In order to realize this, in the present embodiment, the injection timing of the high-pressure air is changed in conjunction with the ignition timing of the air-fuel mixture.
[0080]
In the present embodiment, an embodiment applied to a gasoline engine system which is a spark ignition type internal combustion engine will be described. In the diesel engine system, the ignition timing by the spark plug is replaced with the fuel injection timing by the fuel injection valve. Can be applied.
[0081]
In the present embodiment, although the injection control of high-pressure air is different, the basic configuration of the engine and other hardware to be applied is the same as that of the first embodiment, and the description thereof is omitted.
[0082]
Here, since the temperature of the high-pressure air injected into the combustion chamber 20 is lower than that of the flame in the combustion chamber 20, when the flame contacts the high-pressure air immediately after injection, the temperature of the flame decreases. As a result, when the flame propagation speed becomes slow, the air-fuel mixture spontaneously ignites before the flame surface reaches the end of the combustion chamber and knocking occurs. Therefore, in order to suppress the occurrence of knocking, before the flame surface reaches high pressure air, stop the injection of high pressure air, suppress the decrease in the combustion speed in the late stage of combustion, and before spontaneous ignition from the end of the combustion chamber It is effective to make the flame surface reach the end of the combustion chamber.
[0083]
In the present embodiment, the injection start timing and injection stop timing of the high-pressure air are changed in conjunction with the ignition timing of the spark plug 28. In the present embodiment, since the period during which high-pressure air is injected is made constant, the amount of change in the injection start timing and the injection stop timing becomes equal.
[0084]
FIG. 9 is a time chart showing the relationship between the ignition timing of the spark plug 28 and the high-pressure air injection period. FIG. 9A shows a state before advance, and FIG. 9B shows a state after advance. The ignition timing is advanced when the engine 1 reaches a high speed. Thereby, the high-pressure air injection start timing is also advanced by the same angle. As a result, the high-pressure injection stop timing is also advanced by the same angle, and a constant interval can be maintained from the ignition timing. The fixed interval is obtained in advance by experiments or the like so that there is no possibility of occurrence of knocking.
[0085]
As described above, according to the present embodiment, it is possible to suppress a decrease in flame temperature and a flame propagation speed due to the high-pressure air by linking the injection timing of the high-pressure air with the ignition timing of the air-fuel mixture. Thus, knocking can be suppressed.
[0086]
【The invention's effect】
By using the combustion assist device for an internal combustion engine according to the present invention, it becomes possible to suppress knocking by increasing the combustion speed in the later stage of the combustion process and to prevent fuel from adhering to the side wall surface of the combustion chamber.
[Brief description of the drawings]
FIG. 1 is a schematic configuration diagram showing a spark ignition internal combustion engine according to a first embodiment.
FIG. 2 is a schematic cross-sectional view around a combustion chamber according to the first embodiment.
FIG. 3 is a schematic view around a nozzle hole according to the first embodiment.
FIG. 4 is a graph showing the relationship between the operating state of the internal combustion engine according to the first embodiment and high-pressure air injection.
FIG. 5 is a flowchart when performing high-pressure air injection according to the first embodiment.
FIG. 6 is a schematic configuration diagram showing a direct injection type internal combustion engine according to the second embodiment.
FIG. 7 is a schematic cross-sectional view around a combustion chamber according to a second embodiment.
FIG. 8 is a schematic view around a nozzle hole according to the second embodiment.
FIG. 9 is a time chart showing the relationship between the ignition timing of the ignition plug and the high-pressure air injection period according to the third embodiment. FIG. 9A shows a state before advance, and FIG. 9B shows a state after advance.
[Explanation of symbols]
1 engine
10 Fuel supply system
11 Supply pump
12 Common rail
13 Fuel injection valve
20 Combustion chamber
21 Cylinder block
22 Cylinder head
23 piston
24 Cylinder liner
25 Cooling channel
27a Intake valve
27b Exhaust valve
28 Spark plug
30 Intake system
31 Air cleaner
32 Throttle valve
33 Intake port
38 Exhaust port
40 Exhaust system
40a Exhaust collecting pipe
40b Exhaust passage
40c Exhaust passage
42 Catalyst casing
50 High pressure pump
51 High-pressure air injection valve
52 Spacer
53 rings
54 injection hole
55 Annular passage
56 High pressure air passage
70 Rail pressure sensor
72 Air Flow Meter
73 Oxygen concentration sensor
74 Exhaust temperature sensor for catalyst outflow
76 Accelerator position sensor
77 Crank angle sensor
101 engine
110 Fuel supply system
111 Supply pump
112 common rail
113 Fuel injection valve
120 Combustion chamber
121 cylinder block
122 Cylinder head
123 piston
124 cylinder liner
125 Cooling channel
127a Intake valve
127b Exhaust valve
130 Intake system
131 Intercooler
132 Throttle valve
133 Intake port
138 Exhaust port
140 Exhaust system
140a Exhaust collecting pipe
140b Exhaust passage
140c Exhaust passage
142 Catalyst casing
145 Turbocharger
146 shaft
147 Turbine wheel
148 Compressor
150 High pressure pump
151 High-pressure air injection valve
152 Spacer
153 ring
154 nozzle hole
155 Annular passage
156 High pressure air passage
160 EGR passage
161 EGR valve
162 EGR cooler
170 Rail pressure sensor
172 Air flow meter
173 oxygen concentration sensor
174 Catalyst exhaust temperature sensor
176 Accelerator opening sensor
177 Crank angle sensor
P1 Engine fuel passage

Claims (4)

A plurality of high-pressure gas injection holes provided on the combustion chamber side wall surface of the internal combustion engine for injecting gas into the combustion chamber;
A high-pressure gas injection valve that injects gas into the combustion chamber from the high-pressure gas injection hole;
High-pressure gas supply means for supplying a high-pressure gas to be injected from the high-pressure gas nozzle;
Turbulent flow generating means for injecting high-pressure gas and generating turbulent flow in the vicinity of the combustion chamber side wall when the air-fuel mixture is ignited and the flame surface spreads toward the combustion chamber end;
Gas injection control means for injecting gas into the combustion chamber according to the operating state of the internal combustion engine,
The combustion assisting device for an internal combustion engine, wherein the gas injection control means stops the gas injection before a flame caused by combustion of the internal combustion engine reaches the gas injected from the nozzle hole .   2. The combustion of the internal combustion engine according to claim 1, wherein the turbulent flow generating means is an injection means that injects gas toward a side wall surface of the combustion chamber from an injection hole provided on a side wall surface of the combustion chamber. Auxiliary device.   The internal combustion engine has a wall flow generating means for generating a wall flow flowing along the side wall surface of the combustion chamber in the combustion chamber, and the wall flow generation means is combusted from an injection hole provided on the side wall surface of the combustion chamber. 2. The combustion assisting device for an internal combustion engine according to claim 1, wherein the combustion assisting device is an injection means for injecting gas along the indoor side wall surface. An ignition means for changing an ignition timing for the air-fuel mixture according to an operating state of the internal combustion engine is further provided, and the gas injection control means makes the interval between the gas injection stop and the ignition timing constant. Item 4. The combustion auxiliary device for an internal combustion engine according to any one of Items 1 to 3 .

Images