JPH0417792Y2 - - Google Patents

Description

[Detailed Description of the Invention] [Industrial Application Field] This invention relates to a starting improvement device for a diesel engine that delays fuel injection timing in order to suppress the amount of NOx (nitrogen oxides) generated.

[Prior art] In order to suppress the amount of NOx generated, diesel engines that delay the fuel injection timing (decreasing the amount of advance of the fuel injection timing from the top dead center of the compression stroke) slightly reduce the generated torque. Therefore, deterioration of startability especially when the engine temperature is low may become a problem.

As a conventional countermeasure against this problem, for example, the fuel injection timing is advanced only at the time of starting (during the period when the starter is operating).

[Problems to be Solved by the Invention] The purpose of the invention is to provide a starting improvement device for a diesel engine that can improve startability at low temperatures.

[Means for solving the problem] According to this invention, in a diesel engine that aims to suppress the amount of nitrogen oxides generated by delaying the fuel injection timing, a reference engine speed is determined as a function of engine temperature, and a low temperature start is achieved. Air is blown into the combustion chamber through an air nozzle after the actual engine rotational speed becomes equal to or higher than the reference engine rotational speed.

[Function] Immediately after cranking, the actual engine speed has not reached the standard engine speed, so
No air is blown into the combustion chamber from the air nozzle. Therefore, the increase in the rotational speed of the diesel engine at the initial stage of cranking is prevented from being hindered due to the air blowing into the combustion chamber.

As time passes from the start of cranking, the actual engine rotation speed increases and becomes equal to or higher than the reference engine rotation speed. Along with this, air is started to be blown into the combustion chamber from the air nozzle. In this way, the compression pressure in the combustion chamber increases and the compression temperature rises, so that the combustion state of the fuel becomes better.

[Example] Hereinafter, this invention will be described with reference to an example of the drawings.

In FIG. 1, a diesel engine 10 consists of a plurality of cylinders (six in this embodiment),
An air nozzle 12 is attached to the top of each cylinder. In this diesel engine 10, the fuel injection timing is delayed in order to suppress the amount of NOx generated. The air tank 14 stores high-pressure air therein and supplies the air to each air nozzle 12 via piping 16.
connected to. The electromagnetic on-off valve 18 is connected to the piping 16
is provided in the middle of each branch branching to each air nozzle 12, and opens and closes each branch in response to a control signal from the computer 20. computer 20
is the engine coolant temperature as the engine temperature,
Actual engine speed, crank angle signal, starter signal, and other data are input, and each electromagnetic on-off valve 18 is independently controlled based on these data. From the engine coolant temperature and actual engine speed, it is determined whether or not the air is in the air blowing range. From the crank angle signal, the opening timing of each electromagnetic on-off valve 18 is calculated, and the starter signal (starter is activated) is determined. It is detected whether or not it is the starting period from the signal indicating whether or not the engine is running.

FIG. 2 shows the air blown and no air blown regions as a function of actual engine speed and engine coolant temperature. Air injection into the fuel chamber is recommended when the engine coolant temperature is below 10°C, when deterioration of startability due to delayed fuel injection timing to suppress the amount of NOx generated is a particular problem. It is carried out only during cold start. The boundary between the air injection region and the non-air injection region is the reference engine rotation speed, and the reference engine rotation speed is an increasing function of the engine coolant temperature. This is because the lower the engine temperature, the more desirable it is to improve startability by blowing air.

The operation of the embodiment will be explained.

Immediately after starting cranking, the actual engine rotation speed is less than the reference engine rotation speed, so the electromagnetic on-off valve 18 is kept closed and air is not blown into the combustion chamber of the diesel engine 10. Therefore, the engine rotation speed increases smoothly without hindering the increase in engine rotation speed at the initial stage of cranking due to air blowing.

When time has passed since the start of cranking and the actual engine speed increases and becomes equal to or higher than the reference engine speed defined as shown in FIG. At the angle (crank angle during the intake stroke or compression stroke), an opening signal is sent to each electromagnetic on-off valve 18. As a result, the electromagnetic on-off valve 18 opens and high pressure air is injected from each air nozzle 12 into the combustion chamber. As a result, the compression pressure in the combustion chamber increases, the compression temperature increases, and the combustion of the fuel improves.
Improves starting performance.

[Effect of the invention] As described above, according to this invention, during a cold start, as soon as the actual engine rotation speed becomes equal to or higher than the reference engine rotation speed, air injection from the air nozzle to the combustion chamber is started, and the air in the combustion chamber is Since the compression pressure increases and the compression temperature rises, fuel combustion is improved and starting performance can be improved.

In addition, air is not blown from the initial stage of cranking, and only after the actual engine speed increases appropriately and reaches the reference engine speed or higher.
Since air injection is started, the actual engine speed during cold start increases smoothly despite air injection.

[Brief explanation of the drawing]

FIG. 1 is a block diagram of an embodiment of the invention, and FIG. 2 is a graph showing the air blowing area and the no air blowing area as a function of the actual engine speed and engine cooling water temperature. 10... Diesel engine, 12... Air nozzle, 14... Air tank, 20... Computer.

Claims (1)

[Scope of Claim for Utility Model Registration] (1) In a diesel engine that attempts to suppress the amount of nitrogen oxides generated by delaying the fuel injection timing, the reference engine speed is determined as a function of engine temperature, and the actual engine rotation speed is determined as a function of engine temperature. A starting improvement device for a diesel engine, characterized in that air is blown into the combustion chamber through an air nozzle after the rotational speed reaches the reference engine rotational speed or higher. (2) The starting improvement device for a diesel engine according to claim 1, wherein the reference engine speed is an increasing function of the engine temperature. (3) The diesel engine starting improvement device according to claim 1 or 2, wherein the engine temperature is detected from engine cooling water.