JPS6364629B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an intake system for a diesel engine, which is equipped with a fuel atomizer in the intake system that atomizes fuel into particles of about several microns and supplies the fine particles as auxiliary fuel.

Traditionally, in diesel engines, in addition to the main fuel that is injected directly into the combustion chamber from the fuel injection pump, atomized fuel is supplied as auxiliary fuel along with intake air to improve the ignitability and combustibility of the fuel. It is known that this increases the utilization of intake air, improves thermal efficiency and output, and also makes exhaust smoke cleaner and reduces vibration and noise.

For example, Japanese Patent Publication No. 44-6655 describes a technology to atomize fuel using a blower.
Publication No. 112018 discloses a technology for atomizing fuel by using an ultrasonic oscillation element in a gasoline engine. Conventional fuel atomization devices use ultrasonic waves to apply ultrasonic waves to fuel flowing down the intake passage wall. A type of fuel atomizer that applies vibration to atomize fuel is known. However, conventional fuel atomizers of this kind have a structure that directly applies ultrasonic vibrations to the fuel flowing through the intake passage, so it is difficult to equalize the particle size of the atomized fuel and stabilize the supply amount. There are some drawbacks.

As a solution to this difficulty, a structure can be considered in which an ultrasonic vibrator is disposed within a casing that forms a chamber, and ultrasonic vibrations are applied to the fuel stored in the chamber to atomize the fuel. In such a chamber type, since the stored fuel is atomized, it is considered that the particle size of the atomized fuel can be made uniform and the amount of fuel produced can be stabilized.

On the other hand, even in diesel engines, the exhaust gas recirculation system, which prevents the generation of nitrogen oxides (NOx) by recirculating part of the exhaust gas to the intake system, is an effective method for suppressing NOx. It has been adopted.

However, in a diesel engine equipped with a chamber type fuel atomization device as described above,
When adopting an exhaust gas recirculation system, if carbon particles contained in the recirculated exhaust gas enter the atomization device, the carbon particles will be adsorbed by the fuel, and the fuel will be atomized and exit with the intake air. However, the adsorbed carbon remains in the chamber, and the viscosity of the fuel in the chamber increases due to carbon deposition, making it difficult to atomize using ultrasonic vibration, which only worsens the atomization efficiency. First, there is a problem that the device itself is contaminated by carbon particles.

The present invention has been made to solve this problem, and when adopting an exhaust gas recirculation system, the recirculated exhaust gas is of the chamber type while maintaining the advantages of using the chamber type as the fuel atomizer. An object of the present invention is to provide an intake device for a diesel engine having a structure that does not adversely affect the fuel atomization device of the diesel engine.

For this reason, the present invention provides a diesel engine equipped with a nozzle for directly injecting fuel into the combustion chamber and an auxiliary fuel supply means in the intake system, in which the auxiliary fuel supply means atomizes the fuel using an ultrasonic vibrator. The fuel atomizer comprises a casing for storing fuel and an ultrasonic vibrator for atomizing the fuel in the casing,
The casing of the fuel atomizer communicates with an intake passage downstream of the air cleaner through an air inlet, and also communicates with the intake passage for atomized fuel generated in the casing of the fuel atomizer and air flowing in from the air inlet. A supply passage for the air-fuel mixture to the intake passage communicates downstream of the air inlet, while an exhaust gas recirculation passage whose one end communicates with the exhaust passage opens into the intake passage downstream of the air inlet. This product provides an intake system for a diesel engine.

Hereinafter, the present invention will be specifically explained based on illustrated embodiments.

In Fig. 1, 1 is the diesel engine body with the fuel injection nozzle 2 facing into the combustion chamber 3, 4 is the intake passage with the air cleaner 5 installed upstream, 6 is the exhaust passage, and 7 is the middle of the intake passage 4. This is a chamber type fuel atomization device (fuel atomization device) installed in the

This atomization device 7 constitutes an auxiliary fuel supply system for a main fuel supply system that pressurizes fuel from a fuel tank 8 with a fuel injection pump 9 and injects the fuel from a fuel injection nozzle 2 at a predetermined timing. A piezoelectric or magnetostrictive ultrasonic vibrator 13 is installed at the bottom of a rectangular parallelepiped casing 12 separated from the horizontal intake passage 4 by a partition wall 11.
It is equipped with

The casing 12 accommodates fuel fed from the fuel tank 8 by the fuel feed pump 14 so that it is always kept at a constant depth by a float 16 in a float chamber 15 provided on the side wall of the casing 12. Then, this fuel is atomized into particles of approximately several microns by vibration of the ultrasonic vibrator 16 and suspended in the mixing chamber 17 above the casing 12.

The mixing chamber 17 communicates with the intake passage 4 through an air inlet 18 provided on the upstream side of the partition wall 11 so that a portion of the intake air that has passed through the air cleaner 5 is introduced into the mixing chamber 17. A mixture supply port 20 is provided on the downstream side of the intake passage 4, which opens exactly at a portion of the bench lily 19 formed on the downstream side of the intake passage 4. can be led out to the intake passage 4.

On the other hand, 21 is an exhaust gas recirculation passage whose one end 21a is opened to the exhaust passage 6, and a recirculation control valve 22 for controlling the recirculation of exhaust gas according to the operating condition of the engine is interposed in the middle of the passage. end 21b
is opened downstream from the vent lily 19 of the intake passage 4 to prevent the recirculated exhaust gas from entering the fuel atomization device 7 during exhaust gas recirculation. This exhaust gas recirculation passage 21 may open into the intake passage 4 upstream from the vent lily 19 as long as it is downstream from the air inlet 18 of the fuel atomizer 7, as shown by the dotted line 21' in FIG. . In this case as well, the recirculated exhaust gas can be prevented from flowing into the fuel atomizer 7, and the vent lily 1 of the intake passage 4 can be prevented from flowing into the fuel atomizer 7.
In the 9th section, the air-fuel mixture led out from the air-fuel mixture supply port 20 and the recirculated exhaust gas can be mixed, so that good mixing performance can be achieved. In addition, in Figure 1, 4
Reference numerals 0 and 41 indicate intake and exhaust valves that respectively open and close the intake passage 4 and the exhaust passage 6 with respect to the combustion chamber 3 at predetermined timings.

A high frequency voltage is applied to the ultrasonic vibrator 13 of the atomization device 7 by a control circuit 23, and the amount of atomized fuel generated is controlled by controlling the applied high frequency voltage. In this case, the amount of auxiliary fuel supplied by the atomizer 7 is
As shown in the figure, it is preferable to make it proportional to the injection amount Q _I per unit time injected by the fuel injection nozzle 2 at a constant ratio. On the other hand, since the power energy supplied to the ultrasonic transducer 13 is approximately proportional to the electric energy supplied to the ultrasonic transducer 13, the control circuit 23
The high frequency voltage applied to the injection amount per unit above
Control so that Q is proportional to _I.

As shown in FIG. 3, for this reason, the control circuit 23
In this step, the position of the control sleeve 26, which determines the stroke amount of the plunger 25 of the fuel injection pump 9 and therefore the amount of fuel injection per injection, is set to the first position.
A fuel injection detection device 28 detects the detection signal by a pick-up 27 and outputs an output signal V _Q1 corresponding to the fuel injection amount based on the detection signal, and
The second pickup 31 detects the rotation of the gear 30 for operating the governor fixed to the drive shaft 29 which rotates at the rotation speed of the engine, and outputs an output signal N corresponding to the engine rotation speed per unit time. A device 32 is provided, and these output signals V _Q1
By multiplying by and N by the multiplication circuit 33, the fuel injection amount _VQ per unit time is calculated.

This fuel injection amount V _Q per unit time is applied to an adder circuit 34, and the adder circuit 34 receives an output signal V _W output from an engine temperature detection device 35.
is added to the output signal V _Q from the multiplier circuit 33, and this is inputted to the amplifier circuit 36 as the final control signal V _I , and the amplifier circuit 36 outputs the output signal from the high frequency oscillation circuit 37 in proportion to the control signal V _I. The wave height of the high frequency wave is amplified, and the ultrasonic transducer 13 is driven to oscillate by the amplified high frequency wave. As a result, the electric energy supplied to the ultrasonic vibrator 13 is proportional to the main fuel injection amount V _I per unit time,
The amount of auxiliary fuel supplied to the intake passage 4 by the fuel atomizer 7 is proportional to the amount of main fuel.

The engine temperature detection device 35 is formed as a voltage dividing circuit in which a thermistor TH immersed in engine cooling water is connected to a fixed resistor R connected to a reference power source Vcc., and the resistance value of the thermistor TH is determined by the engine cooling water temperature. Utilizing the characteristic that the partial pressure V W decreases in inverse proportion to the rise in temperature of the engine, a partial pressure V _W that is inversely proportional to the rise in engine cooling water temperature is output to the adding circuit 34 . Therefore, when the engine is cold and the engine temperature is low, the amount of auxiliary fuel is increased from the amount after the engine is warmed up, as shown by the dotted line in Figure 2, and it is possible to compensate for poor combustibility when the engine is warmed up. .

As is clear from the above description, the present invention provides a diesel engine equipped with a nozzle for directly injecting fuel into a combustion chamber and an auxiliary fuel supply means in the intake system, in which the auxiliary fuel supply means is supplied by an ultrasonic vibrator. The fuel atomizer includes a casing for storing fuel and an ultrasonic vibrator for atomizing the fuel in the casing. It communicates with the intake passage downstream of the air cleaner through the air inlet, and also connects the atomized fuel generated in the casing of the fuel atomizer and the air flowing in from the air inlet to the intake passage. To provide an intake device for a diesel engine, characterized in that a supply path is communicated downstream of the air inlet, and an exhaust gas recirculation passage whose one end communicates with an exhaust passage is opened to an intake passage downstream of the air inlet. It is something.

According to the present invention, since the recirculated exhaust gas does not enter the chamber type fuel atomizer equipped with an ultrasonic vibrator, the fuel atomizer is contaminated by the accumulation of carbon particles in the exhaust gas. Since the ultrasonic vibrator can be operated stably without being damaged, it is possible to stably supply auxiliary fuel with good atomization, and therefore to effectively promote the combustion of the main fuel. On the other hand, the recirculated exhaust gas can effectively prevent the generation of NOx.

[Brief explanation of drawings]

FIG. 1 is an overall schematic explanatory diagram showing the intake system of a diesel engine according to an embodiment of the present invention, FIG. 2 is a graph showing the ratio of the auxiliary fuel amount to the main fuel amount Q _I , and FIG. 3 is the same as the one shown in FIG. FIG. 2 is a block circuit diagram showing the configuration of a control circuit of FIG. 1...Engine body, 2...Fuel injection nozzle,
4...Intake passage, 5...Air cleaner, 6...Exhaust passage, 7...Fuel atomization device, 13...Ultrasonic vibrator, 18...Air inlet, 20...Fuel supply port, 21... Exhaust gas recirculation passage.

Claims (1)

[Claims] 1. In a diesel engine equipped with a nozzle for direct fuel injection into a combustion chamber and an auxiliary fuel supply means in the intake system, the auxiliary fuel supply means atomizes fuel using an ultrasonic vibrator. The fuel atomizer includes a casing that stores fuel and an ultrasonic vibrator that atomizes the fuel in the casing. It communicates with the intake passage downstream of the air cleaner, and also connects the intake passage of the atomized fuel generated in the casing of the fuel atomizer and the air flowing in from the air inlet to the intake passage of the mixture. An intake system for a diesel engine, characterized in that an exhaust gas recirculation passage communicating downstream of the air inlet and communicating with an exhaust passage at one end opens into an intake passage downstream of the air inlet.