JPH04259640A - Internal combustion engine with spark ignition for lean combustion - Google Patents

Abstract

PURPOSE:To provide an internal combustion engine with speak ignition for lean combustion introducing the aux. chamber fuel system. in which the fuel supply rate to the aux. chamber is controllable as any desired so that the nitrogen oxide concentration in the exhaust gas does not rise even with varying operating condition of the engine. CONSTITUTION:A spark ignition type internal combustion engine which comp[rises an aux. chamber 24 which is fed with the fuel gas and leads to a main combustion chamber 19, an ignition plug 25 whose foremost confronts the aux. chamber 24 while situated in it and which is to ignite the fuel gas, a nitrogen oxide concentration sensor 32 which is installed on the way of exhaust pipe 21 and which is to sense the nitrogen oxide concentration in the exhaust gas from combustion, a fuel distributing means 33 which can change the fuel gas supplying rate to the aux. chamber 24, and a control means 34 which controls the supplying rate of fuel gas by the fuel distributing means 33 on the basis of the nitrogen oxide concentration in the exhaust gas.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a pre-chamber combustion type lean burn spark ignition internal combustion engine which is capable of suppressing nitrogen oxide concentration to a low level.

0002

[Prior Art] In recent years, efforts have been made to suppress the amount of carbon monoxide, hydrocarbons, or nitrogen oxides contained in the combustion exhaust gas of spark-ignited internal combustion engines that use gasoline as the main fuel.
Lean combustion, in which the mixture ratio of air and fuel (hereinafter referred to as air-fuel ratio) is set larger than the stoichiometric air-fuel ratio, in other words, the ratio of fuel amount to air amount is set to be lower, with the aim of improving fuel efficiency. A device has been developed to do this.

[0003] When carrying out this lean combustion, there are problems such as the ignitability of the fuel being worse than in the case of normal combustion using the stoichiometric air-fuel ratio, and the combustion being more likely to become unstable.These problems need to be solved. There is a need.

One of the known spark ignition internal combustion engines for lean combustion is a pre-chamber combustion type engine as shown in FIG.

That is, as shown in FIG. 2, which shows the concept of this pre-chamber combustion type lean burn spark ignition internal combustion engine, a piston 104 connected to a crankshaft 103 of an engine 102 via a connecting rod 101 is slidably connected to a crankshaft 103 of an engine 102. A cylinder head 108 that slidably holds an intake valve 106 and an exhaust valve 107 is attached to a cylinder block 105 housed in the cylinder block 105 . The main combustion chamber 109 surrounded by the cylinder head 108, the cylinder block 105, and the piston 104 has the intake valves 10 facing the main combustion chamber 109, respectively.
6 and the intake pipe 110 and the exhaust pipe 1 via the exhaust valve 107.
11 are connected to each other. Further, a throttle valve 112 is installed in the middle of the intake pipe 110, and a fuel passageway for fuel from a fuel supply device (not shown) is installed in the middle of the intake pipe 110 between the throttle valve 112 and the main combustion chamber 109. A supply pipe 113 is in communication.

On the other hand, a subchamber 114 facing the main combustion chamber 109 is formed in the center of the cylinder head 108 . The auxiliary chamber 114 facing the tip of the spark plug 115 has a auxiliary chamber fuel supply branched from the fuel supply pipe 113 on the downstream side of the fuel pressure regulator 116 provided in the middle of the fuel supply pipe 113. A pipe 117 communicates with the sub-chamber fuel supply pipe 117, and a piston 104 in FIG.
A check valve 118 is interposed to prevent backflow of fuel during the compression stroke in which the fuel increases. Further, a fuel supply valve 119 is interposed in the middle of the fuel supply pipe 113 between the pressure regulator 116 and the intake pipe 110, and the amount of fuel supplied to the intake pipe 110 side can be adjusted by changing the opening period. has been done. The fuel supply valve 119 is connected to the crankshaft 1.
03 (hereinafter referred to as engine speed) and the opening degree of the throttle valve 112, and set the corresponding opening period to the fuel supply valve 119.
A controller 120 is connected thereto.

In other words, the pressure of fuel supplied to the intake pipe 110 and the auxiliary chamber 114 is kept constant by the pressure regulator 116, and the amount of fuel supplied to the main combustion chamber 109 depends on the engine speed and the opening degree of the throttle valve 112. Based on the command from the controller 120, the fuel supply valve 119 appropriately adjusts the ratio of fuel to a so-called lean air-fuel ratio, in which the proportion of fuel is smaller than the stoichiometric air-fuel ratio. On the other hand, the sub-room 114
As shown in FIG. 2, fuel is sucked into the side via a check valve 118 during the intake stroke when the piston 104 descends, and the air-fuel ratio in this subchamber 114 is naturally equal to the stoichiometric air-fuel ratio. This results in a so-called rich state, where the proportion of fuel is higher than that of the fuel.

[0008] Reference numeral 121 in the figure is a shutoff valve that can be opened and closed for stopping the supply of fuel to the engine 102.

By the way, as shown in FIG. 3, which shows the relationship between the air-fuel ratio and the nitrogen oxide concentration, the nitrogen oxide concentration is maximum near the stoichiometric air-fuel ratio, but when the main combustion chamber 109 is set at a lean air-fuel ratio, On the lean side, the nitrogen oxide concentration decreases, while on the side of the auxiliary chamber 114, which is set to a rich air-fuel ratio, the nitrogen oxide concentration tends to decrease as the rich side. Therefore, in the pre-chamber combustion type lean burn spark ignition internal combustion engine shown in FIG. 2, the concentration of nitrogen oxides in the exhaust gas in both the main combustion chamber 109 and the pre-chamber 114 is lower than in the case of the stoichiometric air-fuel ratio. This results in clean exhaust gas.

0010

[Problems to be Solved by the Invention] In the conventional pre-chamber combustion system lean burn spark ignition internal combustion engine shown in FIG.
The amount of fuel supplied to the auxiliary chamber 114 side is uniquely determined by the difference between the fuel supply pressure based on the pressure regulator 116 and the pressure in the auxiliary chamber 114 based on the opening degree of the throttle valve 112, and cannot be controlled arbitrarily. I can't.

Generally, the amount of nitrogen oxides produced is controlled by the air-fuel ratio in the main combustion chamber 109 and the air-fuel ratio in the auxiliary chamber 114 if the ignition timing is constant. As a result of the fact that the amount of fuel supplied into the chamber 114 varies depending on the operating state of the engine 102, it is extremely difficult to maintain the nitrogen oxide concentration below a predetermined value under all operating states of the engine 102. In particular, when the engine 102 is operated under high load, the pressure in the main combustion chamber 109 increases as the load increases, and the pressure in the subchamber 114 also increases, so the amount of fuel supplied to the subchamber 114 decreases. The air-fuel ratio in the subchamber 114 approaches the stoichiometric air-fuel ratio from the rich side. Along with this, the amount of fuel supplied to the main combustion chamber 109 side through the intake pipe 110 in a negative pressure state increases relatively, and the air-fuel ratio on the main combustion chamber 109 side changes from the lean side to the stoichiometric air-fuel ratio side. As a result, as is clear from FIG. 3, the nitrogen oxide concentration tends to be relatively higher in both the main combustion chamber 109 and the auxiliary chamber 114 than when the engine 102 is in a low load state.

0012

[Object of the Invention] The present invention aims to prevent the concentration of nitrogen oxides in exhaust gas from increasing even if the operating conditions of the engine change, and in particular to prevent the concentration of nitrogen oxides in exhaust gas from increasing as the engine load increases. Another object of the present invention is to provide a lean combustion spark ignition internal combustion engine of a pre-chamber combustion type in which the fuel supply ratio into the pre-chamber can be arbitrarily controlled.

[0013]

[Means for Solving the Problems] A lean burn spark ignition internal combustion engine according to the present invention has an intake pipe for introducing a mixed gas of air and fuel, a main combustion chamber communicating with the intake pipe, and a main combustion chamber connected to the main combustion chamber. In a spark-ignition internal combustion engine having an exhaust pipe communicating with the combustion exhaust gas, the engine has a sub-chamber to which fuel gas is supplied and communicates with the main combustion chamber, and a distal end facing into the sub-chamber and igniting the fuel gas. a spark plug, a nitrogen oxide concentration sensor provided in the middle of the exhaust pipe for detecting the nitrogen oxide concentration in the combustion exhaust gas, and a fuel capable of changing the supply ratio of the fuel gas to the subchamber. The apparatus includes a distribution means and a control means for controlling the supply rate of the fuel gas by the fuel distribution means based on the concentration of nitrogen oxides in the combustion exhaust gas.

[0014]

[Operation] The nitrogen oxide sensor detects the nitrogen oxide concentration in the exhaust gas flowing in the exhaust pipe, and the control means controls the air-fuel ratio of the pre-chamber to a preset value based on the output signal from the nitrogen oxide concentration sensor. The supply ratio of fuel gas by the fuel distribution means is controlled so that: Thereby, the fuel supply ratio to the pre-chamber side is adjusted regardless of the operating state of the engine.

For example, when the load on the engine increases, the pressure in the main combustion chamber increases and the pressure in the pre-chamber also increases. For this reason, in the past, since the supply pressure of fuel into the pre-chamber is constant, the amount of fuel supplied to the pre-chamber decreases and the air-fuel ratio in the pre-chamber approaches the stoichiometric air-fuel ratio from the rich side. The amount of fuel supplied to the main combustion chamber through the intake pipe increases relatively, and the air-fuel ratio in the main combustion chamber approaches the stoichiometric air-fuel ratio from the lean side. Therefore, nitrogen oxides in the exhaust gas tend to increase in both the main combustion chamber and the sub-chamber.

In contrast, in the present invention, the concentration of nitrogen oxides in the exhaust gas is detected by a nitrogen oxide sensor, and the proportion of fuel supplied to the pre-chamber is increased by the fuel distribution means via the control means, so that the air in the pre-chamber is increased. By correcting the fuel ratio to the rich side, the air-fuel ratio on the main combustion chamber side is relatively corrected to the lean side, thereby suppressing an increase in the nitrogen oxide concentration.

[0017]

[Embodiment] As shown in FIG. 1, which shows the concept of an embodiment of a pre-chamber combustion type lean burn spark ignition internal combustion engine according to the present invention, a piston is connected to a crankshaft 13 of an engine 12 via a connecting rod 11. A cylinder head 18 that slidably holds an intake valve 16 and an exhaust valve 17 is attached to a cylinder block 15 that slidably houses the intake valve 14 . An intake pipe 20 and an exhaust pipe 21 are connected to the main combustion chamber 19 surrounded by the cylinder head 18, cylinder block 15, and piston 14 via the intake valve 16 and exhaust valve 17, which face the main combustion chamber 19, respectively. They are connected to each other. Further, a throttle valve 22 is installed in the middle of the intake pipe 20, and a fuel passageway for fuel from a fuel supply device (not shown) is installed in the middle of the intake pipe 20 between the throttle valve 22 and the main combustion chamber 19. A supply pipe 23 is in communication.

On the other hand, an auxiliary chamber 24 facing the main combustion chamber 19 is formed in the center of the cylinder head 18 . The auxiliary chamber 24, which the tip of the spark plug 25 faces, contains auxiliary chamber fuel that branches from the fuel supply pipe 23 downstream of the fuel pressure regulator 26 provided midway through the main fuel supply pipe 23. A supply pipe 27 is in communication with the sub-chamber fuel supply pipe 27.
In FIG. 2, a check valve 28 is interposed in the middle of the piston 14 to prevent backflow of fuel during the compression stroke in which the piston 14 moves upward. Further, a fuel supply valve 29 is interposed in the middle of the fuel supply pipe 23 between the pressure regulator 26 and the intake pipe 20, and the amount of fuel supplied to the intake pipe 20 side can be adjusted by changing the opening period. A controller 30 is connected to this fuel supply valve 29, which sets the amount of fuel supplied based on the engine speed and the opening degree of the throttle valve 22, and gives the fuel supply valve 29 a corresponding opening period. ing.

Reference numeral 31 in the drawing designates a shutoff valve that can be opened and closed for stopping the supply of fuel to the engine 12.

A nitrogen oxide concentration sensor 32 is incorporated in the exhaust pipe 21 to detect the concentration of nitrogen oxides in the exhaust gas flowing through the exhaust pipe 21. Further, a booster pump 33 is provided in the middle of the sub-chamber fuel supply pipe 27 on the upstream side of the check valve 28, and is capable of increasing the fuel supply pressure in the sub-chamber fuel supply pipe 27. The booster pump 33 as a fuel distribution means according to the present invention includes:
A controller 3 that controls the operation of the booster pump 33 based on a detection signal from the nitrogen oxide concentration sensor 32
4 is connected. That is, although the pressure of fuel supplied to the intake pipe 20 is kept constant by the pressure regulator 26, the pressure of fuel supplied to the subchamber 24 can be further increased by the booster pump 32.

Therefore, the ratio of fuel supplied to the main combustion chamber 29 is adjusted to a lean air-fuel ratio preset by the fuel supply valve 29 based on a command from the controller 30 based on the engine speed and the opening degree of the throttle valve 22. be adjusted appropriately. On the other hand, the piston 1 in FIG.
During the intake stroke in which the engine 4 descends, fuel is sucked in through the check valve 28, but the air-fuel ratio in the auxiliary chamber 24 naturally becomes rich.

Here, when the load on the engine 12 increases, the booster pump 33 is activated by the controller 33 as a control means of the present invention based on the output signal from the nitrogen oxide concentration sensor 31 installed in the middle of the exhaust pipe 21.
increases the supply pressure of fuel flowing in the sub-chamber fuel supply pipe 27. This prevents a reduction in the supply of fuel sucked into the auxiliary chamber 24 through the check valve 28 during the intake stroke when the piston 14 descends in FIG. The increase in nitrogen oxide concentration is suppressed by correcting the lean fuel ratio toward the stoichiometric air-fuel ratio and maintaining a predetermined rich state. At this time, the constant pressure fuel flowing through the fuel supply pipe 23 regulated by the pressure regulator 26 is maintained during the opening period of the fuel supply valve 29 determined by the controller 30 based on the engine speed and the opening degree of the throttle valve 22. is supplied into the main combustion chamber 19 through the intake pipe 20,
The air-fuel ratio on the main combustion chamber 19 side is maintained at a predetermined lean state.

Therefore, even if the load on the engine 12 changes, the pre-chamber 24 and the main combustion chamber 19 are maintained at a predetermined air-fuel ratio, and as a result, the nitrogen oxide concentration in the exhaust gas is always maintained below a predetermined value. be able to.

[0024]

According to the lean burn spark ignition internal combustion engine of the present invention, the auxiliary chamber to which fuel gas is supplied is communicated with the main combustion chamber, and the nitrogen oxide sensor detects the concentration of nitrogen oxides in the exhaust gas flowing in the exhaust pipe. and based on the output signal from the nitrogen oxide concentration sensor, the control means controls the proportion of fuel gas supplied by the fuel distribution means so that the air-fuel ratio in the subchamber becomes a preset value. Therefore, it is possible to provide a lean burn spark ignition internal combustion engine in which the fuel supply ratio to the pre-chamber side can be adjusted regardless of the operating state of the engine.

For example, even if the load on the engine increases, the nitrogen oxide concentration in the exhaust gas is detected by the nitrogen oxide sensor in the present invention, and the proportion of fuel supplied to the subchamber is controlled by the fuel distribution means via the control means. By increasing the air-fuel ratio in the pre-combustion chamber to the rich side, the air-fuel ratio in the main combustion chamber is relatively leaner, and the nitrogen oxide concentration is always kept below a certain value, resulting in clean exhaust gas. can do.

[Brief explanation of the drawing]

FIG. 1 is a conceptual diagram showing an embodiment of a pre-chamber combustion type lean burn spark ignition internal combustion engine according to the present invention.

FIG. 2 is a conceptual diagram showing an example of a conventional pre-chamber combustion type lean burn spark ignition internal combustion engine.

FIG. 3 is a graph showing the relationship between air-fuel ratio and nitrogen oxide concentration.

[Explanation of symbols]

12 is the engine, 19 is the main combustion chamber, 22 is the throttle valve, 2
3 is a fuel supply pipe, 24 is a subchamber, 25 is a spark plug, 26
27 is a pressure regulator, 27 is a subchamber fuel supply pipe, 28 is a check valve, 29 is a fuel supply valve, 30 and 34 are controllers, 3
2 is a nitrogen oxide concentration sensor, and 33 is a booster pump.

Claims (1)

[Claims] Claim 1: A spark-ignition internal combustion engine having an intake pipe that guides a mixed gas of air and fuel, a main combustion chamber that communicates with the intake pipe, and an exhaust pipe that communicates with the main combustion chamber and guides combustion exhaust gas. , an auxiliary chamber to which fuel gas is supplied and communicates with the main combustion chamber; a spark plug whose tip portion faces into the auxiliary chamber and ignites the fuel gas; and a spark plug provided in the middle of the exhaust pipe to ignite the combustion exhaust gas. a nitrogen oxide concentration sensor for detecting the concentration of nitrogen oxides occupied in the subchamber, a fuel distribution means capable of changing the supply ratio of the fuel gas to the subchamber, and a fuel distribution means capable of changing the supply ratio of the fuel gas to the subchamber; A lean burn spark ignition internal combustion engine, comprising a control means for controlling based on the concentration of nitrogen oxides in the combustion exhaust gas.