JPH01219338A - Combustion controller for diesel engine - Google Patents

Abstract

PURPOSE:To prevent the worsening of a combustion state and a shortage of output from occurring by reducing the extent of exhaust gas reducing gradually at the time of acceleration detection, while retarding it gradually after fuel injection timing is once advanced as long as the specified timing. CONSTITUTION:When an engine's accelerating state is detected by an accelerating state detecting means 54 from a variation in engine speed, valve opening quantity of an EGR valve 16 is controlled by an EGR valve control part 50 and the extent of exhaust gas quantity being put back to the intake side is gradually reduced. Then, a timer control part 27 is controlled by a fuel injection timing control part 40 and, after fuel injection timing is once advanced in synchronization with an accelerating start and thereby combustion speed is improved, it is gradually retarded. With this constitution, exhaust emission at the time of stopping a supply of exhaust gas is prevented from worsening, while the worsening of a combustion state with a substantial increase in the extent of exhaust gas reducing quantity can be effectively compensated by advancement of the fuel injection timing and the retard control afterward.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a combustion control device for a diesel engine.

(Prior art) In general, in diesel engines, as in the case of spark ignition engines, exhaust gas recirculation is performed by returning the optimum amount of exhaust gas to the intake side according to the engine load and rotational speed at that time. , improves real fuel efficiency by effectively contributing to the combustion of the air-fuel mixture in the exhaust gas, and improves exhaust emissions such as reducing NOx by lowering the oxygen concentration in the intake air and lowering the maximum combustion temperature. effect can be obtained.

Furthermore, when a fuel with a low cetane number, such as alcohol (methanol), is used as fuel for the diesel engine, the heat of the exhaust gas returned to the intake side warms the intake air, increases the intake air temperature, and reduces ignitability. and combustion performance is also improved.

This is generally called the hot EGR effect, and is one of the important functions of the EGR system in diesel engines (see Japanese Patent Laid-Open No. 139960/1982).

(Problems to be Solved by the Invention) However, the above-mentioned functions and effects cause the following problems depending on the relationship with the exhaust gas temperature.

In other words, if exhaust gas whose temperature is lower than the required exhaust gas temperature THGO (see Figure 4), which is sufficient to obtain the hot EGR effect as described above, is supplied into the intake air, the original hot EGR effect cannot be obtained. If this is not possible, the intake air temperature (Fig. 4 d) will drop, resulting in poor ignition and misfire, which will actually worsen fuel efficiency and exhaust emissions.

Therefore, in a state where the fuel injection amount is particularly increased as the engine load increases, such as during acceleration (see Figure 4C), and the exhaust gas temperature decreases, it is not possible to substantially reduce the exhaust gas. Therefore, EGR control must be stopped (see Figure 4C).

However, as a result, the intake air temperature further decreases and the combustion performance further deteriorates.

(Means for Solving the Problems) The present invention was made with the aim of solving the above problems, and in order to solve the problems,
An EGR passage that returns part of the exhaust gas to the intake side, and the EGR
In a diesel engine equipped with an EGR valve installed in the middle of a passage to adjust the amount of exhaust gas returned to the intake side, and an electronically controlled fuel injection device that injects fuel into the engine, an acceleration state of the engine is detected. an acceleration state detection means for controlling the EGR valve; and an E for controlling the amount of exhaust gas returned by arbitrarily controlling the opening degree of the EGR valve
GR valve control means and fuel injection timing control means for controlling fuel injection timing of the electronically controlled fuel injection device are provided, and when the acceleration state of the engine is detected by the acceleration state detection means, the EGR valve is The EGR valve is controlled by the control means to gradually reduce the amount of exhaust gas returned to the intake side, and the fuel injection timing of the fuel injection device is once advanced by a predetermined period at the start of the acceleration, and then gradually retarded. This is what happens.

(Function) According to the problem-solving means of the present invention, first, there is an EGR passage that returns part of the exhaust gas to the intake side, and an EG passage provided in the middle of the EGRa passage that adjusts the amount of exhaust gas returned to the intake side.
In a diesel engine configured with an R valve and an electronically controlled fuel injection device that injects fuel into the engine, an acceleration state detection means for detecting an acceleration state of the engine, and a valve opening degree of the EGR valve are provided. EG that adjusts the amount of exhaust gas returned by arbitrarily controlling it.
R valve control means and fuel injection timing control means for controlling fuel injection timing of the electronically controlled fuel injection device are provided, and when the acceleration state of the engine is detected by the acceleration state detection means, the EGR valve The control means controls the opening amount of the EGR valve to gradually reduce the amount of exhaust gas returned to the intake side, and the fuel injection timing of the fuel injection device is once advanced by a predetermined advance angle in synchronization with the start of acceleration. After improving the combustion speed, the fuel injection timing is gradually retarded to prevent deterioration of exhaust emissions when the exhaust gas supply is stopped. This is effectively compensated by stepwise retard control based on the advance angle amount.

(Example) FIGS. 1 and 2 show a combustion control device for a diesel engine according to an example of the present invention.

First of all, FIG. 2 shows a schematic configuration of the combustion control system of the apparatus according to the embodiment, and the reference numeral l in the figure indicates alcohol (for example).
This is the main body of a diesel engine that uses methanol as fuel. The engine body of the diesel engine (
Intake boat 2 of l (hereinafter simply referred to as engine body)
is connected to an air cleaner 4 via an intake passage 3 having a predetermined pipe diameter and a predetermined length. Further, a surge tank 5 is provided in the middle of the intake passage 3, and an intake air temperature sensor 6 is installed in one corner of the surge tank 5 to detect the intake air temperature. Therefore, the intake air taken in through the air cleaner 4 is transferred to the surge tank 5.
After the intake air temperature TA is detected by the intake air temperature sensor 6 in the section, the intake air is supplied and charged into the engine combustion chamber 8 via the intake boat 2. The temperature T^ of the intake air during the intake process, which is detected by the intake air temperature sensor 6 at the same time as the intake air is filled, is determined by the engine control unit (
(hereinafter abbreviated as ECU) 7 and is stored in memory.

On the other hand, reference numeral 10 denotes an exhaust passage having a predetermined pipe diameter and a predetermined length connected to the exhaust boat 9 of the engine main body l, and an exhaust gas temperature sensor 12 for detecting the temperature T11G of the exhaust gas is installed on the downstream side of the exhaust passage. is set up. The exhaust gas temperature sensor 12 detects the temperature of the exhaust gas during the exhaust stroke of the engine and inputs the detected temperature to the ECU 7.

Further, reference numeral 15 connects the exhaust passage 10 and the intake passage 3 so that they are in communication with each other, and the exhaust passage lO
Part of the exhaust gas from the engine flowing along the side is returned to the intake passage 3 upstream of the intake boat 2, and the heat of the exhaust gas increases the temperature of the intake air to produce alcohol fuel with a low cetane number. In addition to improving ignitability during combustion, the unburned air-fuel mixture in the exhaust gas effectively contributes to combustion, improving fuel efficiency, and reducing the oxygen concentration of the air-fuel mixture in the combustion chamber to reduce NOx. EG made
The R passage (exhaust gas recirculation passage) is shown. And the E
On the downstream side of the GR passage I5 (closer to the intake passage), there is a map showing the operating status of the engine (the area is divided by a map).
An EGR valve 16 is installed to control the amount of exhaust gas returned according to the above-mentioned conditions. The opening/closing state (ON, 0FF) of this EGR valve 16 and the opening degree θε of the EGR valve 16
The GR is controlled by the EGR control signal Te supplied from the ECU 7 (described in detail later with reference to FIG. 1).

Further, reference numeral 21 denotes a direct injection type fuel injector fixed to the cylinder head portion of the engine main body 1 with its nozzle portion facing into the engine combustion chamber 8. For example, it is connected to a distribution type electronically controlled fuel injection pump 23 via.

The electronically controlled fuel injection pump 23 includes a spill control section (for example, as shown in FIG. 1, mainly a spill ring 26a, a spill control solenoid 26b1, a spill ring position sensor 26C for forming a feedback signal, etc.) for controlling the fuel injection amount. configured)26
．． ! : Timer control unit for fuel injection timing control (as shown in FIG. 1, mainly timing control valve 27a1 timer piston 27b)
1 Timer position sensor 27 for feedback signal formation
c) 27, each of which operates with a feedback control function according to the fuel injection amount control signal Tpo and fuel injection timing control signal TFto supplied from the ECU 7. It has become.

By the way, the ECU 7 is, for example, a microprocessor (C
It is mainly composed of a memory (ROM and RAM) and an interface (Ilo) circuit. In addition to the above-mentioned detection signals, the interface circuit of the ECU 7 also receives, for example, an engine starting signal (ECU trigger) from a starter switch (not shown), an engine rotation speed detection signal Ne from the engine rotation speed detection means, and an engine rotation speed detection signal Ne from the engine rotation speed detection means. Cooling water temperature Tw of the engine body l detected by the water temperature thermistor, accelerator opening θAC detected by the accelerator opening sensor, fuel injection ff1Tp
At the same time, the engine load detection signal TR determined by o is also manually input.

Then, the ECU 7 has its microprocessor section 70
For example, as shown in FIG. 1, the controller is configured to have at least three types of mutually related control functions.

That is, first, reference numeral 30 is a fuel injection amount control section for controlling the spill control section 26 of the electronically controlled fuel injection pump 23, and reference numeral 40 is a fuel injection amount control section for controlling the timer control section 27 of the electronically controlled fuel injection pump 23. The injection timing control section and the reference numeral 50 are an EGr (valve control section) that controls the valve opening degree θEGR of the EGR valve 16.

First, the fuel injection amount control section 30 includes a basic fuel injection amount setting means 31, a basic fuel injection amount correction means 32 for correcting the basic fuel injection amount Tpa set by the basic fuel injection amount setting means 31, and a fuel injection amount correction means 32 for correcting the basic fuel injection amount Tpa set by the basic fuel injection amount setting means 31. The output of the fuel injection amount feedback correction means 33 is used as the final fuel injection amount control signal Tpo to the spill control section 26 on the electronically controlled fuel injection pump 23 side. is applied to the spill control solenoid 26b, and the magnetic attraction force at that time operates the moving coil 26d of the solenoid in the direction of the arrow in the figure, presses the spill ring 26a in the direction of the arrow in the figure, and moves the plunger pump (not shown) to a predetermined stroke. It operates and injects a set amount of fuel.

The amount of movement of the moving coil 26d is accurately detected by a spill ring position sensor 26c on the other end side,
The actual fuel injection amount is detected from the amount of movement. This fuel injection amount detection signal is transmitted to the rectifier amplifier circuit (power amplifier) 34.
is fed back to the fuel injection amount correction feedback means 33 as a fuel injection amount feedback control signal.

Therefore, the basic fuel injection amount setting means 31 determines the basic amount based on, for example, the accelerator opening θAC representing the engine load amount and the engine rotation speed Ne, and the next basic fuel injection amount correction means 32 determines, for example, the engine water temperature Tw. The target fuel injection amount corrected in an open-loop manner according to the operating state parameters at that time, such as intake air temperature TA, intake pressure PR, starting signal 1g0N, etc., is finally fed back with high precision by the fuel injection amount feedback correction means 33. After being corrected, the voltage is applied to the spill control solenoid 26b.

Next, the fuel injection timing control section 40 first includes a basic fuel injection timing setting means 41 that determines a basic fuel injection timing 'l'FTB from the engine rotation speed Ne and the accelerator opening degree θ^C at that time; The basic fuel injection timing TFTB set by the basic fuel injection timing setting means 41 is set to the intake pressure Pa.
, a basic fuel injection amount correction means 42 that performs open-loop correction according to engine operating state parameters such as engine water temperature Tw and starting signal 1g0N; The fuel injection timing feedback correction means 43 adds a fuel injection timing feedback detection signal from the timer position sensor 27c of the side timer control section 27, performs feedback correction, and applies the signal to the timing control valve 27a. As described above, the fuel injection timing control signal TFTo of a predetermined duty is applied to the timing control valve 27a,
When a corresponding current flows, the moving core 27
d moves in the direction of the arrow shown (to the right), and the fuel passage '27
Open the aperture 27r of e. On the other hand, the timer piston 27b
moves in the direction of the arrow accordingly, and the roller ring 27h
is rotated to control the advance angle, and the timer position sensor 27c directly connected to the other end via the core 27g also moves in the same way. Then, the actual fuel injection timing expressed in accordance with the amount of movement is fed back to the fuel injection timing feedback correction means 43 via the rectification amplifier circuit (power amplifier) 44.

Further, the EGR control unit 50 includes a basic reduction amount setting means for determining a basic exhaust gas reduction amount TGB based on the engine rotational speed Ne of the engine and the engine load amount (to which the basic fuel injection amount TPB corresponds) at that time TR. 51 and
A basic reduction amount correction means 52 that corrects the basic reduction ff1TGB determined by the basic reduction amount setting means 51 in accordance with the engine water temperature Tw and an acceleration detection signal from an acceleration state detection means 54 described later, and the engine rotation speed. The acceleration state detection means 54 detects the acceleration state of the engine from a change in Ne, and the acceleration state detection means 54 detects the acceleration state of the engine, and also detects the exhaust gas temperature THG.
Exhaust gas reduction amount correction means corrects the basic exhaust gas reduction amount TeB so as to gradually reduce it as shown in FIG. It consists of 53.

That is, the exhaust gas return amount is normally calculated ((
For example, when the engine load and engine speed Ne suddenly increase (Fig. 3a), the amount of fuel injection increases accordingly. The temperature of the exhaust gas itself is hot EGR effect.

(required temperature to obtain the desired result) IGO (Figure 3b) If the temperature is considerably lower than that of IGO (Fig. 3b), the intake temperature will decrease even if exhaust gas is reduced and the above ignition compensation will be required. It becomes impossible to obtain the original hot EGR effect, and combustion performance deteriorates, resulting in engine malfunction, deterioration in fuel efficiency, and deterioration in exhaust emissions.

Therefore, in the above configuration, in the above case, the EGR
By gradually closing the opening of the valve 16 (see Fig. 3C) and gradually reducing the amount of exhaust gas returned, the intake temperature is ensured as high as possible, while fuel injection is performed at the start of acceleration. The timing (Fig. 3 d) is greatly advanced by a predetermined advance angle to improve the combustion state and prevent deterioration of fuel efficiency and exhaust emissions due to excessive amount of exhaust gas reduction. ) by gradually retarding the fuel injection timing TFT which is advanced by a predetermined angle ΔTFT in response to the stabilization of the intake air temperature TA (see Fig. 3C) by the gradual reduction control of the exhaust gas reduction ff1 (EGR amount). The aim is to continuously maintain stable combustion conditions.

(Effects of the Invention) As explained above, the present invention includes an EGR passage that returns part of the exhaust gas to the intake side, and an EGR passage that is provided in the middle of the EGR passage to adjust the amount of exhaust gas returned to the intake side. In a diesel engine comprising an EGR valve and an electronically controlled fuel injection device for injecting fuel into the engine, an acceleration state detection means for detecting an acceleration state of the engine, and a valve opening degree of the EGR valve can be arbitrarily controlled. EGR valve control means for controlling the amount of exhaust gas returned by adjusting the amount of exhaust gas returned; and fuel injection timing control means for controlling the fuel injection timing of the electronically controlled fuel injection device; is detected, the EGR valve is controlled by the EGR valve control means to gradually reduce the amount of exhaust gas returned to the intake side, and the fuel injection timing of the fuel injection device is once set to a predetermined value at the start of the acceleration. This is characterized in that the timing is advanced and then gradually retarded.

That is, in the configuration of the present invention, first, there is an EGR passage that returns part of the exhaust gas to the intake side, an EGR valve that is provided in the middle of the EGR passage and adjusts the amount of exhaust gas returned to the intake side, and an EGR passage that returns part of the exhaust gas to the intake side. In a diesel engine configured with an electronically controlled fuel injection device that injects fuel, an acceleration state detection means for detecting an acceleration state of the engine and an opening degree of the EGR valve are arbitrarily controlled. An EGR valve control means for adjusting the amount of exhaust gas returned and a fuel injection timing control means for controlling the fuel injection timing of the electronically controlled fuel injection device are provided, and the acceleration state of the engine is detected by the acceleration state detection means. In this case, the EGR valve control means controls the opening amount of the EGR valve to gradually reduce the amount of exhaust gas returned to the intake side, and also starts the acceleration of the fuel injection timing of the fuel injection device. The combustion speed is improved by advancing the advance angle by a predetermined value in synchronization with the combustion speed, and then gradually retarding it. This prevents deterioration of exhaust emissions when the exhaust gas supply is stopped, and also prevents the exhaust gas from deteriorating due to the substantial increase in the amount of exhaust gas returned. This deterioration in the combustion state is effectively compensated for by advancing the fuel injection timing and performing stepwise retard control based on the amount of advance.

Therefore, according to the above configuration of the present invention, the deterioration of the combustion state and the lack of output due to the deterioration of ignition performance due to the decrease in intake temperature peculiar to diesel engines, which conventionally generally occurred during acceleration, are significantly improved, and the driving performance is improved. It will also be possible to contribute to

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing the configuration of a control section of a combustion control device for a diesel engine according to an embodiment of the present invention, FIG. 2 is a control system diagram showing the overall system configuration of the control device, and FIG. This figure is a time chart showing the operational states of the main parts of the block circuit of FIG. 2 in correlation with each other, and FIG. 4 is a time chart of the same conventional example. l...Engine body 3...Intake passage 6...Intake air temperature sensor 7...Engine control unit 8...
... Engine combustion chamber 10 ... Exhaust passage 15 ... EGR passage 16 ... EGR valve 21 ... Fuel injector 23 ...
Electronically controlled fuel injection pump 26... Spill control section 27... Timer control section 30...
Fuel injection amount control section 40... Fuel injection timing control section 50... EGR valve control section 51... Basic reduction amount setting means 52... Basic reduction amount correction means 53. ... Final EGR amount correction means 54 ... Acceleration state detection means 9 Load rise due to acceleration Fig. 3 Fig. 4

Claims (1)

[Claims] 1. An EGR passage that returns part of the exhaust gas to the intake side;
In a diesel engine equipped with an EGR valve installed in the middle of the GR passage to adjust the amount of exhaust gas returned to the intake side, and an electronically controlled fuel injection device that injects fuel into the engine, the acceleration state of the engine is controlled. an acceleration state detection means for detecting; an EGR valve control means for controlling the amount of exhaust gas returned by arbitrarily controlling a valve opening degree of the EGR valve; and a fuel injection timing of the electronically controlled fuel injection device. fuel injection timing control means, and when the acceleration state detection means detects an acceleration state of the engine, the EGR valve control means controls the EGR valve to gradually reduce the amount of exhaust gas returned to the intake side. 2. A diesel engine combustion control device, characterized in that the fuel injection timing of the fuel injection device is once advanced by a predetermined period at the start of the acceleration, and then gradually retarded.