JP3736670B2 - Operation control method of premixed compression self-ignition engine - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an operation control method for a premixed compression self-ignition engine that operates by compressing self-ignition, for example, by sucking a mixture of gaseous fuel and air.
[0002]
[Prior art]
FIG. 4 schematically shows a conventional intake / exhaust device for a premixed compression self-ignition engine using gaseous fuel.
In FIG. 4, the intake air A is heated by the intake air heater 5, the gaseous fuel G is mixed, and the premixed gas is sucked into the cylinder 1 through the intake valve 4 through the intake valve, and after combustion by compression ignition The exhaust gas E is discharged from the exhaust passage 7 through the exhaust valve.
[0003]
In such a premixed compression auto-ignition engine, the operating range and auto-ignition combustion vary greatly depending on the temperature of the supplied pre-mixed gas and the fuel concentration. The higher the supply temperature and the higher the fuel concentration, the more self-ignition occurs. Is prone to occur.
However, in order to control these parameters as control factors for engine operation, the responsiveness is very poor and it is difficult to perform highly accurate control.
[0004]
Further, when the engine is started, if a fuel-rich mixture is supplied, the ignitability is high and the startability is improved. However, a slight difference in fuel concentration causes knock-like combustion. In other words, the method of improving the startability by supplying a fuel mixture with a high fuel concentration in the initial unstable combustion state may cause engine damage due to knock-like combustion, shortening the life by damaging the engine. There is a disadvantage that it ends up.
[0005]
[Problems to be solved by the invention]
The present invention has been proposed to cope with the above-mentioned problems, and in a premixed compression auto-ignition engine, it is possible to improve startability and to quickly respond to abnormal combustion based on fuel concentration and the like. An object of the present invention is to provide a method for controlling the operation of a premixed compression self-ignition engine.
[0006]
[Means for Solving the Problems]
As a result of various researches and developments, the inventor has paid attention to the phenomenon that when the exhaust pressure is increased in such a premixed compression auto-ignition engine, compression auto-ignition tends to occur as shown in FIG. This is presumed to be due to the so-called “internal EGR” when the exhaust pressure becomes high, and the high temperature of the EGR gas or components contained in the EGR gas cause self-ignition.
The premixed compression self-ignition engine of the present invention based on such knowledge is provided in the premixed compression self-ignition engine by providing a throttle valve whose opening degree can be adjusted in the exhaust passage, and provided with a combustion detection means. Is configured to control.
[0007]
According to the present invention, the intake air (A) is heated by the intake air heater (5), the gaseous fuel (G) is mixed, and the premixed gas is introduced into the cylinder (1) from the intake passage (4) through the intake valve. In the operation control method of the premixed compression self-ignition engine in which the exhaust gas (E) is discharged from the exhaust passage (7) through the exhaust valve after combustion by compression ignition, the exhaust passage (7) is opened. A throttle valve (8) adjustable in degree is interposed, a combustion detection means (11) is attached to the cylinder (1), and the throttle valve (8) is opened by a signal from the combustion detection means (11). controller for degree control comprises a (10), a control system is an optimal opening during startup the throttle valve during start-up (8), and after start completion, throttle valve (8) to the opening of the normal operation, the target determines whether the output or not, the combustion detecting means whether abnormal combustion or not if the target output ( Determined in 1), spread the opening of abnormality when the combustion throttle valve (8), if than the target output of the low output, increasing the fuel supply amount, the opening of if abnormal combustion throttle valve (8) If the output is higher than the target output, the fuel supply amount is decreased, and if abnormal combustion, the opening of the throttle valve (8) is narrowed.
[0008]
As the combustion detecting means, it is preferable to use a pressure sensor for measuring the combustion pressure in the cylinder, an ion probe for detecting the ionic current of the flame during combustion, an O ₂ sensor provided in the exhaust passage, or the like.
[0009]
For a multi-cylinder engine having a plurality of cylinders, it is preferable that the combustion detecting means and the throttle valve are provided for each cylinder.
Further, regarding the throttle valve, one throttle valve may be provided in the wake after the exhaust pipes of the cylinders are gathered.
[0010]
In the present invention, it is preferable that a second passage that is branched from the exhaust passage and arranged in parallel is provided, and the throttle valve is provided in the second passage.
Furthermore, when carrying out the present invention, a bypass passage that bypasses the throttle valve may be provided in the exhaust passage.
[0014]
That is, according to the present invention, the combustion state is monitored by the combustion detection means, and if knock-like abnormal combustion is detected during stable operation, the throttle valve is widened to respond quickly to abnormal combustion.
The throttle valve opening is increased for knock-like abnormal combustion that occurs when the output increases, and the throttle valve opening is reduced for unstable output combustion that occurs when the output decreases. Rapid and highly accurate combustion control can be performed.
[0015]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments of the present invention will be described with reference to FIGS.
It should be noted that the same components as those in the description of the prior art in FIG.
In FIG. 1, a throttle valve 8 whose opening degree can be adjusted is interposed in the exhaust passage 7, and a pressure sensor 11 for detecting a combustion pressure is attached to the cylinder 1. The signal from the pressure sensor 11 is sent to the control device 10, and the control device 10 controls the opening degree of the throttle valve 8.
[0016]
In FIG. 2, a branch pipe 9A (second passage) branches from the exhaust pipe 7, and is arranged in parallel to join with the exhaust pipe 7 (9). The opening of the branch pipe 9A can be adjusted. A narrow throttle valve 8 is interposed, and a pressure sensor 11 for detecting the combustion pressure is attached to the cylinder 1. And the signal of the pressure sensor 11 is sent to the control apparatus 10, and the control apparatus 10 performs the opening degree control of the throttle valve 8 interposed in the branch pipe 9A.
In FIG. 2, a region parallel to the branch pipe 9 </ b> A in the exhaust pipe 7 is expressed with a reference numeral 9.
[0017]
Next, the operation control method will be described with reference to FIG.
First, in step S1, it is determined whether or not the engine is starting. If No, the process proceeds to step S4. If Yes, the throttle valve 8 is set to an optimum opening degree at the start in step S2. Then, in step S3, it is determined whether or not the start is finished. If No, the process returns to step S2, and if Yes, the process proceeds to step S4.
[0018]
In step S4, the throttle valve 8 is set to the opening during normal operation, and the process proceeds to step S5. In step S5, it is determined whether or not the output is a predetermined output (for example, detected by a torque meter, output voltage or current). If Yes, the process proceeds to step S6. If the output is lower than the predetermined output, the process proceeds to step S8. If it is an output, it will progress to step S11.
[0019]
In step S6, whether or not the abnormal combustion (knocking) has occurred is detected and determined by the combustion detection means 11. If Yes, the opening of the throttle valve 8 is widened in step S7 and the process returns to step S5. If No, it is determined whether or not the operation is ended in Step S14. If Yes, the operation ends. If No, the process returns to Step S5.
[0020]
In step S8, in which it is determined that the output is lower than the predetermined output, the fuel supply amount is increased. In step S9, it is determined whether the combustion detection means is not abnormal combustion (knocking). If there is, the opening of the throttle valve 8 is widened in step S10 and the process returns to step S5.
[0021]
Further, in step S11 where it is determined that the output is higher than the predetermined output, the fuel supply amount is decreased, and in step S12, it is determined whether or not the combustion detection means 11 is abnormal combustion (output unstable combustion). Returning to S5, if Yes, the opening of the throttle valve 8 is narrowed in Step S13, and the process returns to Step S5.
[0022]
That is, the control device 10 controls the opening degree of the throttle valve 8, and at the time of start-up, the exhaust pressure is increased as the opening degree at the time of start-up to make the start-up easier, and if it starts, it is expanded to the normal opening degree. .
[0023]
In FIG. 5, the characteristic curve in the case where the exhaust pressure is higher by 0.2 bar than the intake pressure is clearly higher than the characteristic curve in the case where the exhaust pressure is 1.0 bar. When the exhaust pressure is high, both the in-cylinder pressure and the heat generation rate are improved as compared with the case where the exhaust pressure is low.
Therefore, if the exhaust pressure is increased, a condition that allows easy start-up is formed.
[0024]
When the stable operation returns to the control flow of FIG. 3 again, the combustion state is monitored by the combustion detecting means 11, and when knocking-like combustion is detected, the throttle valve 8 is opened to reduce the exhaust pressure and the normal combustion state (stable combustion) Quickly return to the state.
[0025]
If knocking combustion is detected when the output increases, the throttle valve 8 is opened to reduce the exhaust pressure and increase the fuel.
On the other hand, if output unstable combustion is detected when the output is reduced, the throttle valve 8 is narrowed to increase the exhaust pressure, thereby shifting to a state where self-ignition tends to occur.
[0026]
As described above, according to the illustrated embodiment, combustion control is performed with high accuracy even when the output is changed.
[0027]
【The invention's effect】
The effects of the present invention are listed below.
(1) Increasing the exhaust pressure facilitates self-ignition combustion and improves startability. Therefore, the starting time for stable operation is shortened, and the amount of heat supplied to the intake air heater can be reduced.
(2) Even in the output control during stable operation, when knock-like abnormal combustion occurs, the control of the throttle valve can quickly and accurately control the combustion, and the risk of engine damage is reduced. Highly accurate combustion control improves thermal efficiency.
[Brief description of the drawings]
FIG. 1 is a schematic diagram showing an embodiment of an intake / exhaust device for a premixed compression self-ignition engine of the present invention.
FIG. 2 is a schematic view showing another embodiment of the exhaust system of the premixed compression self-ignition engine of the present invention.
FIG. 3 is a flowchart showing an operation control method of the present invention.
FIG. 4 is a conventional premixed compression auto-ignition engine. FIG. 5 is a characteristic diagram for proving the validity of the knowledge in the present invention.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 ... Cylinder 4 ... Intake passage 5 ... Intake heater 7 ... Exhaust passage 8 ... Throttle valve 10 ... Control apparatus 11 ... Pressure sensor

Claims (1)

The intake air (A) is heated by the intake air heater (5), gaseous fuel (G) is mixed, and the premixed air is sucked into the cylinder (1) from the intake passage (4) through the intake valve, and compression ignition is performed. In the operation control method of the premixed compression auto-ignition engine in which the exhaust gas (E) is discharged from the exhaust passage (7) through the exhaust valve after combustion by the exhaust valve, the throttle passage in the exhaust passage (7) can be adjusted. (8) is installed, a combustion detection means (11) is attached to the cylinder (1), and the opening degree of the throttle valve (8) is controlled by a signal from the combustion detection means (11). (10), and the control device sets the throttle valve (8) to an optimum opening degree at the time of starting, and sets the throttle valve (8) to the opening degree of the normal operation after the starting and determines whether or not the target output is obtained. and, whether abnormal combustion or not if the target output is determined by the combustion detection means (11), Spread the opening of the normal combustion case of the throttle valve (8), in the case of low output from the target output to increase the fuel supply amount, spread the opening of if abnormal combustion throttle valve (8), the target output An operation control method for a premixed compression self-ignition engine, characterized in that if the output is higher, the amount of fuel supply is reduced, and if the abnormal combustion occurs, the opening of the throttle valve (8) is reduced.

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