JPS58165567A - Fuel control device for diesel engine - Google Patents

Abstract

PURPOSE:To improve operability, emissivity, thermal efficiency and the like by controlling operation of a subsidiary fuel supply device so as to reduce or lower supply of said fuel when the output of an exhaust density sensor detecting CO2 density is below a predetermined value. CONSTITUTION:Besides supplying fuel directly from a fuel injection nozzle 10 into a combustion chamber 6, subsidiary fuel, which turned to particles due to operation of an oscillator 17 in a subsidiary fuel supply device 13, is mixed with air in a mixing chamber 14 and supplied into an intake passage 5. In such a Diesel engine, the oscillator 17 is controlled by means of a control device 20. This control device 20 inputs a signal of CO2 density prepared by an exhaust density sensor 19 provided in an exhaust passage 7 and a signal of an engine speed prepared by a rotation sensor 21, while it sends out a driving signal to the oscillator 17 to supply subsidiary fuel when CO2 density (d) exceeds a predetermined value do. On the other hand, in case of d<do, the signal of driving is not given to the oscillator 17 and supply of the subsidiary fuel is stopped.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an improvement in a fuel control device for a diesel engine.

Conventionally, in diesel engines, for example, Japanese Patent Application Laid-Open No. 6.2-1. As shown in Japanese Patent Application No. 1.412, a fuel injection nozzle is provided to directly supply fuel into the combustion chamber, and an auxiliary fuel supply device is provided in the intake passage to supply auxiliary fuel in addition to the main fuel supplied from the fuel injection nozzle. Techniques for supplying fuel together with intake air are known.

Although the supply of the above-mentioned auxiliary fuel has advantages such as improving ignition delay and improving air utilization efficiency, this auxiliary fuel supply also has the advantage of improving ignition delay and improving air utilization efficiency, but even under light loads when the amount of fuel supplied from the fuel injection nozzle is decreasing, this auxiliary fuel is When fuel is supplied, a premature ignition phenomenon occurs in which the ignition timing of the fuel becomes too early, causing the combustion pressure to rise quickly in response to the movement of the piston, which adversely affects thermal efficiency.

Therefore, it is necessary to adjust the supply of the auxiliary fuel according to the magnitude of the engine load, that is, the increase or decrease in the amount of fuel supplied. In this case, it is not possible to accurately detect the amount of fuel supplied, and therefore, the supply control of the auxiliary fuel is also inaccurate, resulting in a problem that the auxiliary fuel supply effect is not sufficiently exhibited.

In view of this, the present invention has a correlation between the carbon dioxide concentration in the exhaust gas and the excess air ratio λ, and by detecting the carbon dioxide concentration with the exhaust gas concentration sensor, the fuel supplied to the combustion chamber is Since the amount can be detected accurately, the output of the exhaust gas concentration sensor is used to control the operation of the auxiliary fuel supply device so as to reduce or stop the supply of auxiliary fuel when the concentration of carbon dioxide in the exhaust gas is below a predetermined value. We provide a diesel engine fuel control device equipped with a device that accurately controls the supply timing of auxiliary fuel according to the operating condition, improving drivability,
The purpose is to improve emissions, heat resistance, thermal efficiency, etc.

Embodiments of the present invention will be described below with reference to the drawings.

In the diesel engine 1 shown in Fig. 7, 2 is a cylinder block equipped with a piston 6, 4 is a nozzle to the cylinder, 5 is an intake passage that supplies intake air to combustion *6, and 7 is a cylinder block that is equipped with a piston 6. 1° exhaust passage, 8 is an intake valve, and 9 is an exhaust valve.

Further, 10 is a fuel injection nozzle that is disposed in the cylinder head 4 and supplies fuel directly to the combustion chamber B, 11 is a fuel injection pump that supplies fuel from the fuel tank 12 to the fuel injection nozzle 10, and 13 is an intake passage 5. The intake passage 5 is arranged in
This is an auxiliary fuel supply device that supplies auxiliary fuel to.

In the auxiliary fuel supply device 13, 14 is a mixing chamber for mixing intake air and auxiliary fuel, and 15 is a fuel tank 1 in the mixing chamber 14.
2 is a float for storing the auxiliary fuel supplied via the pump 16 at a constant level; 17 is a vibrator (nepizer) disposed at the bottom of the mixing chamber 14 to atomize the auxiliary fuel; The auxiliary fuel atomized in step 17 is mixed with the air that has flowed into the mixing chamber 14 from the intake passage 5 and is supplied to the intake passage 5, and by adjusting the current supply to the vibrator 17,
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4. During acceleration, etc., a large amount of auxiliary fuel enters the intake passage 5 at once □
Prevent it from being supplied.

':・1° On the other hand, 19 is an exhaust gas concentration sensor disposed in the exhaust passage 7, and the exhaust gas concentration sensor 9 detects the carbon dioxide concentration in the exhaust gas. For example, carbon dioxide is detected at a specific wavelength. Since the infrared rays of used.

Furthermore, 20 receives the detection output of the exhaust gas concentration sensor 19, and when the carbon dioxide concentration in the exhaust gas is below a predetermined value, the auxiliary fuel supply device 13 reduces or stops the supply of the auxiliary fuel.
This control device 20 controls the operation of the vibrator 17, that is, the energization of the vibrator 17.
In addition to the signal, there is also a rotation sensor 2 that detects the engine rotation speed.
A signal from 1 is input.

The value of the carbon dioxide concentration d in the exhaust gas detected by the exhaust gas concentration sensor 19 is, as shown in the graph of FIG. It has a correlation with excess rate λ. That is, in a high load state where the excess air ratio λ is small and the fuel supply amount is increased, the carbon dioxide concentration d increases, while the excess air ratio λ
In a low load state where the fuel supply amount is large and the fuel supply amount is reduced, the carbon dioxide concentration d becomes small.

Therefore, the control device 20 sets the excess air ratio λ to the set value λ
. At the above light engine load, that is, the carbon dioxide concentration d in the exhaust gas detected by the exhaust gas concentration sensor 19 is the set excess air ratio λ. When the voltage is below a predetermined value do corresponding to be. Further, the control device 20 increases the supply amount (absolute amount) of the auxiliary fuel according to the magnitude of the engine rotation speed detected by the rotation sensor 21, since as the engine rotation speed increases, the amount of intake air per hour increases. This is how it is controlled.

Next, FIG. 3 shows a block diagram when the control device 20 is an analog control system, in which the auxiliary fuel supply device 13 is controlled on and off according to the carbon dioxide concentration d, and
An example of control will be described in which the amount of secondary fuel is increased in response to an increase in the engine speed during supply of secondary fuel. The detection signal of the exhaust gas concentration sensor 9 is input to a comparator 22 and compared with a reference signal from a reference signal generation circuit 26. The reference signal of the reference signal generation circuit 23 is a set excess air ratio λ0 (when the excess air ratio λ is smaller than this value, the sub-fuel supply device 13
operate. (λo=1.5) (the auxiliary fuel supply device 13 is activated when the carbon dioxide concentration d is greater than this value) is set in advance. When the detected carbon dioxide concentration d from the exhaust gas concentration sensor 9 exceeds a predetermined value do, a signal is output from the comparator 22 to the drive circuit 24, and the drive circuit 24 outputs a predetermined control signal via the correction circuit 25. When the detected carbon dioxide concentration is below the fixed value do, the drive line 24 outputs a control signal. No supplementary fuel supply! j ,'stopped.

On the other hand, the engine rotation speed signal of the rotation sensor 21 is D-
The signal is input to the correction circuit 25 via the A converter 26.

In this correction circuit 25, the control signal from the drive circuit 24 is corrected by the signal from the D-A converter 26, and as the engine speed increases, the control signal is increased to increase the supply of auxiliary fuel. It is configured.

Further, FIG. 3 illustrates a flowchart when the control device 20 is of a digital control type, and a control example similar to that of FIG. 3 will be explained with reference to this flowchart. First, in step A, the control device 20 inputs and stores the output signal of the exhaust gas concentration sensor 19, that is, the carbon dioxide concentration signal d in the exhaust gas, and in step B, the detected carbon dioxide concentration d is set to a predetermined value do. If the determination in step B is YES, that is, if the detected carbon dioxide concentration d exceeds the predetermined value do, the engine rotation speed signal from the rotation sensor 21 is input in step C. Then, in step D, calculate the control signal according to the engine speed by 1.111°.
In step E, a control signal is output to the vibrator 17 of the auxiliary fuel supply device 16 to supply a predetermined amount of auxiliary fuel. Also,
If the determination in step B is NO, that is, if the detected carbon dioxide concentration d is below the predetermined value dO, the process returns to step A without operating the auxiliary fuel supply device 16, and the next carbon dioxide concentration signal is sent from the exhaust gas concentration sensor 19. is input, and after operating the auxiliary fuel supply device 13 in step E, the process returns to step A in the same way.

Note that in the control examples shown in FIGS. 3 and 3 above.

Based on the carbon dioxide concentration signal from the exhaust gas concentration sensor 19,
The auxiliary fuel supply device 13 is controlled on and off to stop the auxiliary fuel supply device 13 when the detected carbon dioxide concentration d is below a predetermined value do. Also in the following cases, the auxiliary fuel supply device 1
3 may be operated, and the supply amount of the auxiliary fuel may be controlled to be reduced. Furthermore, the amount of supplementary fuel supplied when the load increases may be increased or decreased depending on the carbon dioxide concentration d. In addition, as the supplementary fuel supply device 13, in addition to the one using the vibrator 17 as in the embodiment, An injection nozzle may be disposed in the intake passage 5, a part of the fuel of the fuel injection pump 11 may be supplied from this injection nozzle as auxiliary fuel, and the supply of this auxiliary fuel may be controlled according to the carbon dioxide concentration. (In this case, since the supply amount of the auxiliary fuel changes according to the engine speed, rotation correction based on detection by the rotation sensor 21 is not necessary.

Furthermore, a different type of fuel from that supplied from the fuel injection nozzle 10 may be used as the auxiliary fuel.

As explained above, according to the present invention, an exhaust gas concentration sensor for detecting the carbon dioxide concentration in the exhaust gas is disposed in the exhaust passage, and the control device receives the output of the exhaust gas concentration sensor to determine the carbon dioxide concentration in the exhaust gas. Since the supply of auxiliary fuel is controlled to be reduced or stopped when the amount is below a predetermined value, it is possible to accurately detect the engine load, that is, the amount of fuel supplied, and the supply of auxiliary fuel can be adjusted accurately according to the operating condition. It has the advantage of being able to fully exhibit the effects of improving driveability, emission performance, etc. by supplying the auxiliary fuel without causing a decrease in thermal efficiency or the like.

[Brief explanation of the drawing]

The drawings illustrate embodiments of the present invention, in which Fig. 1 is a schematic diagram of a diesel engine, Fig. 2 is a graph showing the relationship between carbon dioxide concentration in exhaust gas and excess air ratio, and Fig. 3 is an analog control system. FIG. 7 is a block diagram illustrating an example of a control device using a digital control system. FIG.

Claims (1)

[Claims] (1) In a diesel engine equipped with a fuel injection nozzle that directly supplies fuel into the combustion chamber and an auxiliary fuel supply device that supplies auxiliary fuel to the intake passage, disposed in the exhaust passage,
an exhaust concentration sensor that detects the carbon dioxide concentration in the exhaust;
and a control device that controls the operation of the auxiliary fuel supply device to reduce or stop the supply of auxiliary fuel when the carbon dioxide concentration in the exhaust gas is below a predetermined value in accordance with the output from the exhaust gas concentration sensor. Features of diesel engine fuel control device.