JPS63302126A - Direct injection type engine - Google Patents

Abstract

PURPOSE:To enhance the sealing ability of a combustion chamber so as to improve the starting ability of an engine in which fuel is injected into a recess formed in the upper section of a piston, by carrying out fuel injection in such a way that fuel sticks on the inner peripheral surface of a cylinder bore in a predetermined period during starting. CONSTITUTION:During cold start of a Diesel-engine 1, a control unit 4 greatly retards the injection timing of a fuel injection nozzle 5 in a period of initial few cycles from the start of cranking during cold start of the engine 1. Accordingly, a piston 6 is positioned lower than the height H of jet spray from the fuel injection nozzle 5 in the period of initial few cycles from the start of cranking during cold start of the engine so as to feed jetted fuel onto the inner peripheral surface of a cylinder liner 7 so that the fuel sticks thereon. This sticking fuel is spread over the inner peripheral surface of the cylinder liner 7 by piston rings 13a through 13c so as to enhance the seal ability, thereby a temperature sufficient for compression is obtained during start of the engine, thereby it is possible to enhance the starting ability of the engine.

Description

[Detailed description of the invention] (Industrial application field) The present invention relates to direct injection engines.

(Prior Art) Generally, a direct injection diesel engine is known in which a recess as a combustion chamber is formed in the upper part of a piston that slides in a cylinder bore, and fuel is injected into the recess (for example, (Refer to Publication No.-67930).

In such a diesel engine, there is a problem in startability because the intake air temperature is low and the compression temperature does not rise during cold starting.

Therefore, as a method for improving startability, it is known to advance the fuel injection timing to improve ignition performance (see, for example, Japanese Patent Publication No. 61-42087).

(Problem to be solved by the invention) By the way, the reason why the compression temperature does not become high enough when starting the engine is because there is not enough lubricating oil adhering to the cylinder liner that forms the inner peripheral surface of the cylinder bore, and the sealing between the piston and the cylinder liner is insufficient. It is known that this is partly due to the deterioration of gas flow and the resulting gas blow-through.

As described in the above-mentioned Japanese Patent Publication No. 61-42087, in order to improve ignitability, the fuel injection timing is simply advanced under the condition that the fuel is injected into the recess formed in the upper part of the piston. Depending on the method of squaring, it is not possible to prevent the compression temperature from decreasing due to gas blow-through due to a decrease in sealing performance.

The present invention has been made in view of the above problems, and an object of the present invention is to provide a direct injection engine that improves the sealing performance of the combustion chamber, obtains a sufficient compression temperature at the time of starting, and improves startability.

(Means for Solving the Problems) In order to achieve the above object, the present invention includes an injection control means that injects fuel so that fuel adheres to the inner circumferential surface of the cylinder bore for a predetermined period at the time of startup.

(Operation) At the time of startup, fuel is injected so that it adheres to the inner circumferential surface of the cylinder bore, so as the piston slides against the inner circumferential surface of the cylinder bore, there is a gap between the piston and the inner circumferential surface of the cylinder bore (inner circumferential surface of the cylinder liner). Fuel enters and the sealing performance improves.

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

In FIG. 1 showing the overall configuration of a direct injection diesel engine, l is a four-cylinder diesel engine equipped with an electronically controlled fuel injection pump 2. As shown in FIG.

The fuel injection pump 2 has a fuel injection timing controlled by an electronically controlled timer 3, and the electronically controlled timer 3 is electrically controlled by a control unit 4.

This control unit 4 generates an intake air temperature signal.

It receives various signals such as water temperature signal, engine speed signal, rack position signal, etc., and greatly retards the fuel injection timing during the first few cycles from the start of cranking during cold start. (See range A in Figure 2)
.

As a result, during the first few cycles from the start of cranking during a cold start, the piston 6 is positioned below the spray height H from the fuel injection nozzle 5, as shown in FIG. , the fuel injected from the fuel injection nozzle 5 enters the recess 6a in the upper part of the piston 6 as usual.
Instead of being supplied into the cylinder liner 7, it is supplied to the inner circumferential surface of the cylinder liner 7, adheres to it, and is stretched over the inner circumferential surface of the cylinder liner 7 by the piston rings 13a, 13b, 13c of the piston 6. Reference numeral 8 denotes an intake manifold, and an intake throttle valve 10 is disposed in a gathering portion 9 of the intake manifold so as to be openable and closable. This intake throttle valve 10
are opened and closed by a diaphragm device 11.

This intake throttle valve IO is closed during the first few cycles from the start of cranking when the electronically controlled timer 3 retards the fuel injection timing during a cold start. That is, during the above several cycles, the control unit 4 controls the switching of the electromagnetic three-way valve 12 to operate the diaphragm device 11.
The intake throttle valve lO is closed (see Fig. 4).

As a result, the air density in the cylinder bore decreases, the penetration force of the sprayed fuel increases, and more of the sprayed fuel reaches and adheres to the inner peripheral surface of the cylinder liner 7, so that the piston 6
Due to this sliding movement, a sufficient amount of fuel enters between the piston 6 and the cylinder liner 7, thereby further improving the sealing performance between them.

Next, the flow of processing by the control unit 4 will be explained with reference to FIG.

First, turn on the ignition key (Step S4)
Then, it is determined whether the engine cooling water temperature is higher than a set temperature based on the output of the water temperature sensor, for example (step S2).

When the engine coolant temperature is above the set temperature,
Since there will be no problem with startability, start cranking immediately (step S3), and determine whether the engine has started (step S4). If the engine has started, the process will end; if it has not started, start the engine. The cranking is continued until it is completed (step Ss).

On the other hand, when the engine coolant temperature is lower than the set temperature, the electromagnetic three-way valve 12 is controlled to close the intake throttle valve lO (step S6), and as described above, the air density is lowered and the penetration force of the injected fuel is reduced. Throttle the intake air to increase the intake.

Thereafter, the electronic control timer 3 is controlled to significantly retard the fuel injection timing (step S7), and cranking is started (step Ss).

After starting cranking, the number of cranking times is set to N
It is determined whether or not the rotation speed N is reached (step S9), and the process is continued until the set rotation speed N is reached.

When the set rotation speed N is reached, it is determined that the sealing performance has improved, and the intake throttle valve IO is opened to release the intake throttle (step 5lo), and the retard control of the fuel injection timing is released (
Step 511).

Then, it is determined whether the engine has started or not (step S4). If the engine has started, the cranking is finished, and if it has not started, cranking is continued until the engine starts (step S4).
s).

In the above embodiment, the fuel injection timing is significantly retarded so that fuel adheres to the inner circumferential surface of the cylinder bore, but it may also be significantly advanced (range B in Figure 2). reference).

The above embodiment is an example in which the engine is applied to a diesel engine having a fuel injection pump 2 equipped with an electronically controlled timer 3, but as shown in FIG. can also be applied. That is, in that case, the rotating shaft 23 of the pump 22 is connected to the rotating shaft 24 of the mechanical timer 21 via the sleeve 25. At startup, the electromagnetic three-way valve 26 is switched by a signal from a control unit (not shown), the diaphragm device 27 is activated, and when the sleeve 25 moves in the X direction via the lever 28, the sleeve 25 and the mechanical timer 21 Since the rotating shaft 24 is helically spline-fitted, the angle can be changed significantly in the advance direction.

(Advantageous Effects) As described above, the present invention allows fuel to adhere to the inner circumferential surface of the cylinder bore during startup, so the sealing performance of the combustion chamber is improved, and sufficient compression temperature can be obtained even during cranking. Improves starting performance.

[Brief explanation of drawings]

The drawings show an embodiment of the present invention, with Fig. 1 showing the overall configuration of a direct injection engine, Fig. 2 showing the relationship between the crank angle and the position of the piston, and Fig. 3 showing the relationship between the sprayed fuel jet height and the piston. Figure 4 is a diagram showing the relationship between opening and closing of the intake throttle valve and injection timing, Figure 5 is a flowchart showing the process flow of the control unit, and Figure 6 is a modification example. It is a main part configuration diagram. 1...Diesel engine, 2.22...
・Fuel injection pump, 3...Electronic control timer,
4... Control unit, 7...
Cylinder liner, 21... Mechanical timer. Figure 1, crank angle 2nd

Claims (1)

[Claims] (l) An engine in which a recess is formed in the upper part of a piston that slides in a cylinder bore, and fuel is injected into the recess,
1. A direct injection type engine, comprising injection control means for injecting fuel so that fuel adheres to the inner circumferential surface of the cylinder bore for a predetermined period of time at the time of startup.