JPH03107546A - Combustion controller of diesel engine - Google Patents

Abstract

PURPOSE:To improve ignitability and shorten a time for complete explosion by actuating a start assisting means at a start-up of an engine, opening an exhaust shutter valve and closing the exhaust shutter valve at the OFF time of a startor. CONSTITUTION:At an exhaust passage 4 of an engine 1, an exhaust shutter valve 5 for sucking exhaust air is provided, and it is closely and openly driven by an actuator 6 controlled by a negative pressure control valve 10. At a cylinder of the engine 1, a glow plug 7 is provided, and intake heater 8 is provided at an intake passage 8 so as to compose a start means. The negative pressure control valve 10, the glow plug 7 and the intake heater 8 are controlled by a control unit 12. In this case, at the start-up of the engine 1, start assisting means 7, 8 are actuated, and the exhaust shutter valve 5 is opened. At the OFF time of a startor 16, the exhaust shutter 5 is closed.

Description

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

(Prior Art) Conventionally, many starting aid means have been proposed in order to promote ignition of injected fuel when starting a diesel engine. Typical examples include glow plugs and intake heaters. In addition, a variable valve timing mechanism is used to increase the intake kinetics by opening the intake valve late, thereby raising the intake air temperature and improving ignition performance.

On the other hand, as disclosed in, for example, Japanese Patent Application Laid-Open No. 51-51142, an air shutter valve is provided in the exhaust passage of the engine, and this exhaust shutter valve is closed for a predetermined period of time when the engine is started, thereby restricting the exhaust gas. By doing this, the engine is loaded and the fuel injection amount is increased, and the internal EGR effect increases the hot water temperature in the cylinder.
Some devices are known that promote warm-up during cold periods.

However, even though the above-mentioned individual technologies are known, it has not yet been known how these technologies can be combined to improve engine starting performance, revving performance, etc.

(Objective of the Invention) Therefore, the object of the present invention is to improve the ignition performance at the time of starting and to improve the ignition performance from ignition to complete explosion (stable ignition) by effectively controlling the above-mentioned starting aid means and exhaust shutter valve in combination. An object of the present invention is to provide a combustion control device for a diesel engine that is time-saving.

(Structure of the Invention) The present invention provides a diesel engine equipped with a starting assist means, which includes an exhaust shutter valve provided in the exhaust system so as to be openable and closable, a starter sensor that detects a starter on/off signal, and a starter sensor that detects a starter on/off signal. control means for activating the starting assist means and for opening the exhaust shutter valve and for closing the exhaust shutter valve when the starter sensor detects the starter off signal; It is characterized by

(Effects of the Invention) In the present invention, the exhaust shutter valve is opened to allow intake air and exhaust gas to flow smoothly until ignition occurs, and then the start operation means is operated, so that ignition performance is improved. By using the starter off signal as the ignition signal, the exhaust shutter valve is closed after ignition without using any other special sensor, and the internal EGR effect increases the temperature inside the cylinder, thereby increasing the time required to reach complete explosion. Can be shortened.

(Example) Hereinafter, an example of the present invention will be described with reference to the drawings.

FIG. 1 is a schematic configuration diagram showing an embodiment of the present invention. An engine 1 includes an intake passage 3 that supplies intake air that has passed through an air cleaner 2 to the combustion chamber of each cylinder, and an intake passage 3 that supplies exhaust gas generated by combustion. An exhaust passage 4 for discharging the air to the outside is provided.

The exhaust passage 4 includes an exhaust shutter valve 5 for restricting the exhaust gas.
is provided. Further, a negative pressure diaphragm type actuator 6 for opening and closing the exhaust shutter valve 5 is provided.
In addition, a duty-controlled negative pressure control valve 10 is provided in the negative pressure introduction passage 9 that introduces negative pressure from the vacuum pump 18 to the actuator 6 . and,
By controlling the negative pressure in the actuator 6 according to the opening/closing time ratio (duty ratio) of the negative pressure control valve 10, the opening degree of the exhaust shutter valve 5 is changed.

A glow plug 7 is arranged in each cylinder of the engine 1 to heat the combustion chamber to facilitate starting, and an intake heater 8 is provided in the intake passage 3 to heat intake air to facilitate starting. It is arranged.

Reference numeral 11 denotes a filling control means consisting of an intake valve late closing mechanism, which increases the kinetic energy of the intake air by delaying the filling of the intake air into the combustion chamber using, for example, a known variable/variable valve timing mechanism. This is a means of increasing the intake air temperature to facilitate starting. Also, by opening the intake valve late, the pumping loss increases and the amount of fuel injection increases, which increases the combustion temperature and improves ignition performance.

The negative pressure control valve 10, glow plug 7, intake heater 8, and intake valve late closing mechanism 11 are connected to a control unit 12.
controlled by The control unit 12 includes
The engine speed signal from the engine speed sensor 14 provided on the fuel injection pump 13 and the fuel injection pump 13
An accelerator opening signal from an accelerator opening sensor 15 that detects the depression amount of the accelerator pedal in conjunction with the position of the control lever at , and a starter on/off signal from the starter 16 are input, and the control unit 12 receives these signals. Based on the input, a control signal is output to the glow plug 7 or the intake heater 8, the negative pressure control valve 10, and the intake valve late closing mechanism 11.

FIG. 2 is a flowchart of the combustion control routine executed by the control unit 12.

In FIG. 2, initialization is first performed in step s1, and the engine key switch is turned on in the next step si. In step s3, the exhaust shutter valve 5 is opened, and in the next step S4, the glow plug 7, intake heater 8, intake slow closing mechanism 11, etc. are activated, and the starter 16 is turned on. Detects on/off signals from the starter 16.

Then, it is determined from this signal whether or not ignition has occurred in step S6, and if the scooter off signal cannot be detected, step S6 is performed.
Returning to step 5, if the starter off signal is detected, the exhaust shutter valve 5 is closed in step S7.

In the next step S8, the engine rotational speed is detected, and based on this rotational speed signal, it is determined in step S9 whether or not a complete explosion has occurred.If the complete explosion has not been achieved, the process returns to step S7.
Exhaust shack - Hold valve 5 closed. If it is determined that a complete explosion has occurred, the exhaust shutter valve 5 is opened in step SIO, and normal control is performed in step Sll. The exhaust shutter valve 5 may be controlled to gradually open before the complete explosion occurs, instead of being closed and opened only when the complete explosion occurs.

The above is the configuration of one embodiment of the diesel engine according to the present invention. By controlling the starting assist means and the exhaust shutter valve 5 in this way, the ignition performance is improved.
Moreover, the time from ignition to complete explosion can be significantly shortened.

FIG. 3 is a graph showing the effects of the present invention. This data is for a diesel engine with a swirl chamber with a displacement of 2000 cc and a compression ratio of 21.1 at an engine speed of 750
rpm and an outside temperature of 29°C. In the figure,
Curve A shown as a solid line shows that when only slow intake closing is performed,
Curve B shown by a broken line is the case when neither intake late closing nor exhaust throttling is performed, and curve C shown by a dashed dotted line is when only exhaust throttling is performed.In both cases, the glow plug is used as a temperature sensor without igniting the engine. The intake air temperature was measured. As is clear from FIG. 3, when starting (during cranking), opening the exhaust shutter valve 5 and not restricting the exhaust air, but operating only the intake slow closing mechanism 11, increases the intake air temperature. Improves ignitability.

In the above embodiment, one exhaust shutter valve 5 is provided in the exhaust passage 4, but the exhaust shutter valve 5 and the ignition sensor 16 are provided for each cylinder, and the above-mentioned control is performed for each cylinder. You can.

Further, in the above embodiment, the exhaust shutter valve 5 is driven by the negative pressure diaphragm type actuator 6, but it goes without saying that this actuator may be replaced with an electric motor.

Furthermore, in the above embodiment, the intake valve late closing mechanism 11 is used as a means for delaying the filling of intake air into the combustion chamber.
Instead of this mechanism, a control valve is installed in the intake passage that closes the original intake passage and opens when the negative pressure generated during the downward stroke of the engine piston exceeds a predetermined value. may be delayed.

[Brief explanation of drawings]

FIG. 1 is a schematic diagram of a fuel control system for a diesel engine according to the present invention, FIG. 2 is a flowchart of a fuel control routine, and FIG. 3 is a graph showing the effects of the present invention. 1-Engine 3 4-Exhaust passage 5 6-Actuator 7 8-Intake heater 1゜11-Intake valve slow closing mechanism 12-Control unit 13-Fuel injection pump 14-Engine speed sensor 15-Accelerator opening sensor 16- Starter intake passage exhaust shutoff valve glow plug negative pressure control valve

Claims (1)

[Scope of Claims] A diesel engine equipped with a starting assist means for promoting ignition of injected fuel at the time of starting, comprising: an exhaust shutter valve which is provided in the exhaust system so as to be openable and closeable and throttles the exhaust gas by closing the shutter valve; a starter sensor that detects an off signal, and when starting, activates the starting aid means and opens the exhaust shutter valve, and when the starter sensor detects the off signal of the starter, opens the exhaust shutter valve. 1. A combustion control device for a diesel engine, comprising: control means for bringing the engine into a closed operating state.