JPH09222038A - Method and device for starting cylinder injection engine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To save a time required for starting by effecting injection before an injection pressure is increased to a proper value. SOLUTION: A starting device for a cylinder injection engine feeds fuel to an injector 9, injecting fuel directly to the interior of a combustion chamber 11, through a piping 102. The starting device comprises a pressure sensor 20 to measure a pressure in a piping fed to a fuel; an accumulator 8 to absorb or feed a pressure in a piping; and an engine control unit 16 to calculate an injection time so that a fuel injection amount is kept at a value equivalent to a proper injection amount during injection of a proper pressure. The engine control unit 16 detects the preload of the accumulator, and calculates an injection period so that an injection amount of fuel during a pressure higher than the preload is kept at a value equal to a proper injection amount during a proper injection pressure, and starts an engine through injection at a pressure lower than the injection proper pressure.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a spark ignition internal combustion engine, and more particularly, to a method of supplying fuel at the time of starting an internal combustion engine spark ignition internal combustion engine in which fuel is directly injected into a combustion chamber, a control method therefor, and a control method therefor. Regarding the device.

[0002]

2. Description of the Related Art Among internal combustion engines, in a cylinder fuel injection engine in which fuel is directly injected into a combustion chamber, as a condition for starting the engine, the fuel pressure in the injection pipe reaches a proper injection pressure due to atomization of fuel. Are listed. Conventionally,
The time required for the pressure in the injection pipe to reach the proper injection pressure from the start signal to the actual start is required to be relatively long due to the influence of the volume of the injection pipe and the like.

[0003]

As described above, in the direct injection type spark ignition internal combustion engine, the internal combustion engine is not started until the pressure in the injection pipe reaches the set pressure of the regulator which is the proper injection pressure. Took a long time.

An object of the present invention is to provide a method for reducing such a dead time at the time of starting.

[0005]

In order to solve the above problems, the injection is started at the stage where the preload of the accumulator is reached before the fuel pressure in the high pressure pipe reaches the injection proper pressure. At this time, the pressure inside the pipe is measured by installing a pressure sensor in the high-pressure pipe. The shortage of the injection amount due to injection at a pressure lower than the proper pressure is compensated by extending the injection period. This is an engine control unit (hereinafter referred to as ECU)
The injection amount is accurately compensated by giving a relationship between the pressure and the injection period that keeps the injection amount constant.

There is also a method of assuming an approximately intermediate pressure between the preload and the proper pressure, determining an injection period suitable for this assumed pressure, and performing injection under this condition without using a pressure sensor.

By adopting the above means,
The present invention can have the following functions.

When the start signal is received from the start switch, the pump is activated and the fuel pressure in the high pressure pipe starts to rise. When the fuel pressure reaches the preload of the accumulator,
The ECU sends an injection start signal to the injector. At this time, at the same time, the ECU calculates an injection period for ensuring an appropriate injection amount and sends it to the injector. Based on these signals, the injector injects fuel into the combustion chamber. As described above, according to the present method, since the starting can be performed at a lower pressure than the conventional method, the time from start to starting can be shortened.

[0009]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 shows an embodiment of a fuel supply system in a direct injection type spark ignition internal combustion engine of the present invention. Here, 1 is an engine, 2 is a fuel tank,
3 is a feed pump, 4 is a motor, 5 is a low pressure regulator
, 6 is a high pressure pump, 7 is a camshaft, 8 is an accumulator, 9 is an injector, 10 is a spark plug, 11 is a combustion chamber, 12 is a high pressure regulator, 13 is a piston, 1
4 is an intake pipe, 15 is a throttle, 16 is an engine control unit (ECU), 17 is a start switch,
18 is an exhaust pipe, 20 is a pressure sensor, 101 is low-pressure piping,
Reference numeral 102 represents a high pressure pipe, and 103 represents a return pipe.

When the start switch 17 is turned on, the signal is transmitted to the ECU 16 and the motor 4. The motor 4 starts its operation at the same time when it receives a start signal from the ECU 16, and the feed pump 3 driven by the motor 4 pumps up and pressurizes the fuel from the fuel tank 2.

The pressurized fuel is sent to the high pressure pump 6 through the low pressure pipe 101. At this time, if the fuel pressure in the low pressure pipe 101 is equal to or higher than the preset pressure of the low pressure regulator 5, the fuel for the differential pressure is returned to the fuel tank 2 and the pressure in the low pressure pipe 101 is constant. Kept in.
Next, the fuel pressurized to the set pressure of the low pressure regulator 5 is sent to the high pressure pipe 102 by the high pressure pump 6. The high pressure pump 6 is driven by a cam shaft 7 in the engine 1.

Here, the fuel pressure in the high-pressure pipe 102 is
When the pressure exceeds the set pressure of accumulator 8, accumulator
The excessive pressure is absorbed by the controller 8 and, on the contrary, when the pressure becomes equal to or lower than the set pressure, the insufficient pressure is supplied to the high-pressure pipe 102 by the accumulator 8. The accumulator 8 damps the fuel pressure pulsation in the high-pressure pipe 102. The fuel is directly injected from the injector 9 into the combustion chamber 11 by an injection command signal sent from the ECU 16 described later.

Since the injection is sequentially performed in the other combustion chambers in response to the signal from the ECU 16, pressure pulsation is generated in the high pressure pipe 102, but this pulsation is absorbed by the accumulator 8 described above. Finally, the fuel in the high-pressure pipe 102 is kept at a constant pressure by the high-pressure regulator 12. The high-pressure regulator 12 regulates the pressure inside the high-pressure pipe.
It has a mechanism for discharging excess fuel to the return pipe 103 when the pressure becomes equal to or higher than the set pressure of the tank. The fuel discharged to the return pipe 103 and having a reduced pressure is returned to the low pressure pipe 101 and recirculated.

The throttle 15 is opened by a signal from the ECU 16, and the air whose flow rate has been adjusted passes through the intake pipe 14,
It flows into the combustion chamber 11. The air and the injected fuel are mixed in the combustion chamber 11 and compressed as the piston 13 rises. The compressed air-fuel mixture is spark-ignited by the spark plug 10 controlled by a signal from the ECU 16, and burns and explodes.

As a result, the pressure in the combustion chamber 11 rises,
It acts on the piston 13 and the engine 1 rotates. Also,
Exhaust gas is discharged from the exhaust port 18. In this way, the fuel sucked up from the fuel tank 2 is transferred to the injector 9
The engine is started by being further injected, mixed with air, compressed, and exploded.

Next, the function of the ECU 16 will be described. FIG. 2 shows an example of the main function of the ECU. When the ECU 16 receives a start signal from the start switch 17, the ECU 16 receives signals such as water temperature, intake temperature, throttle position, exhaust temperature, and air flow rate from sensors arranged in various places of the engine.

By appropriately judging them, an appropriate injection amount,
The signals of the injection timing and the injection period are sent to the injector, the signal of the ignition timing is sent to the spark plug, the signal of the throttle opening is sent to the throttle, and so on. These signals allow the engine to operate normally.

Next, the first embodiment will be described. The feature of this embodiment is that the high-pressure pipe 102 in the apparatus shown in FIG.
In addition, the pressure sensor 20 having high responsiveness is provided, and the ECU 16 is wired so as to send this data.

The pressure in the high-pressure pipe 102 at the time of starting is shown in FIG.
Changes as shown in FIG. In FIG. 3, a is a preload of the accumulator 8 and b is a set pressure of the regulator 12, that is, a proper injection pressure. As described above, the pressure does not reach b immediately after the start, but after the pressure rises to the preload a of the accumulator 8 relatively quickly, the proper injection pressure b is gradually increased.
Transition to

The reason for this is that the accumulator 8 absorbs the pressure when the fuel pressure exceeds the preload a. Conventionally, it was not started unless the pressure reached b,
In the present invention, it is an object to effectively use the period in which the pressure from a to b gradually increases and to shorten the starting time.

The operation of this embodiment will be described. High pressure piping 1
The pressure sensor 20 on 02 measures the fuel pressure in the high-pressure pipe and sends the data to the ECU 16. ECU16
When the sent pressure reaches the preload a of the accumulator 8, the injection start signal is sent to the injector 9 with this precondition. However, for example, the preload of the accumulator 8 is 4 MPa and the set pressure of the regulator 12 is 5.5.
In the case of MPa, when injection is performed with a preload of 4 MPa of the accumulator 8, the appropriate injection pressure of 5.5 MPa is 1.
There is a shortage of 5 MPa.

In this state, if the same amount of air enters the combustion chamber as in the steady state, the fuel injection amount becomes insufficient due to insufficient pressure,
The air-fuel mixture that is formed may become lean and normal combustion may not occur. Therefore, in this embodiment, the shortage of the injection amount is compensated by extending the injection period. For example, it is assumed that the injection period required to keep the injection amount constant when the injection pressure is changed is as shown in FIG. From FIG. 4, it is understood that when the injection pressure is insufficient by d, the injection amount necessary for normal combustion can be obtained by extending the injection period by e and performing injection.

That is, as shown in FIG. 5, assuming that the injection amount when the injection is performed at the proper injection pressure is the region F, the pressure is low by d and the injection amount when the injection period is extended is represented by the region G. It Therefore, the injection period is set so that the area representing this injection amount does not change in accordance with the change in pressure.

After reaching the preload a, the injection timing is determined at an appropriate pressure between the preload a and the proper pressure b by taking into consideration signals from other engine sensors. .

By incorporating this mechanism in the ECU, it becomes possible to start when the fuel pressure in the high-pressure pipe reaches the preload of the accumulator 8. This indicates that the engine can be started earlier than before by only c in FIG.

Next, a second embodiment of the present invention will be described.
The feature of the second embodiment is that, without using the pressure sensor as in the first embodiment, an approximate injection pressure between the preload a and the appropriate pressure b is assumed, and an injection period suitable for this assumed pressure is determined. However, the fuel is injected under this condition. At this time, the injection timing can correspond to the timing at which the substantially intermediate pressure is reached by detecting the crank angle, for example.

In the above-described embodiment, the control of the injection period until reaching the injection proper pressure is represented by a diagram that decreases with time as shown in FIG. In the second embodiment, FIG.
As shown in, the injection period is fixed at a certain value, and when the injection proper pressure b is reached, the injection period is returned to an appropriate injection period.

When the preload a of the accumulator 8 is 4 MPa and the proper injection pressure b is 5.5 MPa as in the above example,
The difference between the flow rates when the two pressures are injected is about 10%. Therefore, until the fuel pressure in the high-pressure pipe rises from 4 MPa to 5.5 MPa, even if the injection period is fixed at a value that is an appropriate value at about the intermediate value, for example, 4.75 MPa, It can be seen that the error is only 5%. That is, by setting the error of about 5% within the allowable range, the injection amount at the time of low pressure starting can be secured by a simpler method, and normal combustion can be started earlier than before.

[0029]

According to the present invention, by controlling the injection period by the ECU, it is possible to form an appropriate air-fuel mixture even if the injection pressure at the start is low. As a result, what was conventionally started after waiting for the pressure in the injection pipe to reach the injection proper pressure, it is possible to start at the same time as the pressure becomes the preload of the accumulator.

As described above, the time from the input of the start signal to the start can be shortened and the waiting time can be shortened.

[Brief description of drawings]

FIG. 1 is a schematic diagram of a fuel supply system of a direct injection type internal combustion engine according to the present invention.

FIG. 2 is an explanatory diagram showing a main function of an engine control unit.

FIG. 3 is an explanatory diagram showing how the pressure in the high-pressure pipe rises when the engine is started.

FIG. 4 is a relationship diagram between pressure and injection period when the injection amount is constant.

FIG. 5 is an explanatory diagram showing a change in injection amount by area.

FIG. 6 is an explanatory diagram showing changes in the injection period in the control method of the first embodiment.

FIG. 7 is an explanatory diagram showing changes in the injection period in the control method of the second embodiment.

[Explanation of symbols]

 1 Engine 2 Fuel Tank 3 Feed Pump 4 Motor 5 Low Pressure Regulator 6 High Pressure Pump 7 Camshaft 8 Accumulator 9 Injector 10 Spark Plug 11 Combustion Chamber 12 High Pressure Regulator 13 Piston 14 Intake Pipe 15 Throttle 16 Engine Control unit (ECU) 17 Start switch 18 Exhaust pipe 20 Pressure sensor 101 Low-pressure pipe 102 High-pressure pipe 103 Return pipe

Front page continuation (72) Inventor Mamoru Fujieda 7-1-1 Omika-cho, Hitachi-shi, Ibaraki Hitachi Ltd. Hitachi Research Laboratory

Claims (5)

[Claims] 1. A method of starting a cylinder injection engine, wherein fuel is injected through at least one injector for directly injecting fuel into at least one combustion chamber provided in an internal combustion engine through respective pipes, wherein the pressure in the pipe is Has reached the pre-pressure of the accumulator, and based on the relationship between the fuel pressure and the injection period, the fuel injection amount at the pressure above the pre-pressure is made equal to the proper injection amount at the injection proper pressure. A method for starting an in-cylinder injection engine, characterized in that the injection period is calculated so as to maintain it, and injection is performed at a pressure lower than the appropriate injection pressure to start the engine. 2. A fuel injection pipe for supplying a fuel to at least one injector for directly injecting fuel into at least one combustion chamber provided in an internal combustion engine, in which the fuel is supplied through respective pipes. Based on the relationship between the fuel pressure and the injection period, the pressure sensor that measures the pressure inside the pipe, the accumulator that absorbs or supplies the pressure inside the pipe, and the injection amount of fuel is determined as the proper injection amount at the proper injection pressure. An engine control unit that calculates the injection period so as to keep the same, and the engine control unit detects the preload of the accumulator by the pressure sensor, and injects the fuel injection amount when the pressure is equal to or higher than the preload. The injection period is calculated so as to maintain the same amount as the proper injection amount at the time of pressure, and injection is performed at a pressure lower than the proper injection pressure Starting device for a direct injection engine, characterized in that to start the engine Te. 3. A method of starting an in-cylinder injection engine, wherein fuel is injected through at least one injector for injecting fuel directly into at least one combustion chamber provided in an internal combustion engine through respective pipes, and a preload of an accumulator is provided. The injection period is calculated and the fuel injection timing is controlled based on the detection of the crank angle so that the injection amount at an intermediate pressure between the injection and the injection appropriate pressure is kept the same as the injection amount at the injection appropriate pressure. A method for starting an in-cylinder injection engine, comprising injecting fuel for the calculated injection period to start the engine. 4. The method for starting an in-cylinder injection engine according to claim 1, wherein an injection period at the time of preload of the accumulator is calculated, and the engine is started when the preload is reached. 5. The in-cylinder injection engine starting device according to claim 2, wherein the injection period during preload of the accumulator is calculated and the engine is started when the preload is reached.