JPS6011652A - Engine fuel injection device - Google Patents

Abstract

PURPOSE:To make it possible to carry out combustion of lean mixture due to stratified burning in a wide range, by providing such an arrangement that the initiation timing of fuel injection by a fuel injection valve is set in a substantially later half of the intake-air stroke and the termination timing thereof is set at the termination of the intake-air stroke, in a predetermined engine operation range. CONSTITUTION:Upon engine operation, a CPU 10 determines whether the basic fuel injection amount which has been computed in accordance with the outputs of an intake-air pressure sensor 12 and a crank angle sensor 22, is greater than a set injection amount or not, and when it is less, controls the pressure of fuel. That is, a duty ratio is read out from a map in a memory in accordance with the basic fuel injection, and an ON-OFF valve 9 is controlled in accordance with the duty ratio by means of a fuel pressure control circuit 21. After an injection time period, as a fixed time period, is set to an injection timing control circuit 19, the value which is obtained by subtracting this fixed time from a required time for intake-air stroke, is set as the injection initiating timing. When this injection initiating timing is detected, fuel injection is made from injectors 5.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a fuel injection device for an engine that supplies fuel to the engine by injection from a fuel injection valve.

(Prior art) The above-mentioned fuel injection device injects
Effective atomization and combustibility were achieved by spraying fuel onto the intake valve, vaporizing it using the heat of the intake valve, and inhaling the already vaporized air-fuel mixture in the next intake stroke.

However, in recent years, emphasis has been placed on fuel efficiency and lean burn has been desired, and when performing lean burn when the engine is under low load, the above-mentioned method of vaporizing air through the intake valve and then inhaling the air is not suitable in terms of combustibility. There is a limit to lean combustion with Nozu-2-, and satisfactory lean combustion could not be obtained.

In other words, by being vaporized by the heat of the intake valve, the intake air-fuel mixture has a uniform fuel distribution throughout, and lean combustion can only be achieved up to an air-fuel ratio at which this air-fuel mixture can be ignited.
- Conventionally, as a means of promoting lean combustion even further than the lean combustion in the above-mentioned system, fuel is injected at the end of the intake stroke when the engine is under low load, and the mixture is deposited in the upper part of the cylinder, that is, near the plug. Stratified combustion has been developed in which air is concentrated in the lower layer and only air is burned (for example, Japanese Patent Application Laid-open No. 57-108428@).

In this case, the air-fuel mixture in the upper layer has only to have an air-fuel ratio that can be ignited, and the lower layer contains only air, so it is possible to promote lean combustion as a whole.

However, even within the engine's low-load zone, there are zones where power can be increased. For example, if idling and low-speed driving are low-load zones, a larger amount of air mixture is required in the low-speed driving zone compared to idling. Therefore, as the amount of air mixture increases,
If the fuel injection time is increased, the stratification of the air-fuel mixture within the cylinder collapses, resulting in a state in which the air-fuel mixture is dispersed throughout the cylinder, making stratified combustion impossible.

As a result, there is a problem that the possible range of lean combustion by stratified combustion is narrow.

(Object of the Invention) An object of the present invention is to provide a fuel injection device for an engine that has a wide range of possible lean combustion that can be achieved by stratified combustion when the engine is under low load.

(Structure of the Invention) When the operating region is in a predetermined operating region including at least a low load, the start timing of fuel injection by the fuel injector is set to almost the latter half of the intake stroke, and the end timing of the intake stroke is set at the end timing of the intake stroke. The present invention is characterized in that the engine fuel injection device increases the fuel pressure for fuel injection as the amount of intake air increases.

(Effects of the Invention) According to the present invention, since the fuel injection timing is from almost the latter half of the intake stroke to its end, this range is the range in which the stratification of the air-fuel mixture within the cylinder can be maintained. By injecting fuel while changing the fuel pressure, lean combustion can be achieved by stratified combustion.This lean combustion results in a range in which the fuel pressure can be varied, and lean combustion can be achieved by stratified combustion over a wide range.

(Example) An embodiment of the present invention will be described in detail below based on the drawings.

The drawing shows a fuel injection system for an engine. In Fig. 1, an engine 1 is formed with four cylinders, and an air cleaner 3 and a throttle valve 4 are installed at the part where the intake pipe 2 gathers, and an air cleaner 3 and a throttle valve 4 are installed at the part where the intake pipe 2 branches out to the cylinders. Injector 5 that injects fuel
An injector 5 is provided for each cylinder.

The above-mentioned injectors 5... are connected to a fuel tank (not shown) via a pressure regulator 6,
The pressure regulator 6 is connected to the intake pipe 2 via the back pressure pipe 7 on its back pressure side, so that the injector 5
Control is performed so that the differential pressure between the fuel pressure applied to ... and the intake pressure in the intake air = 5 - pipe 2 is always constant.

Passage 8 bypassing the pressure regulator 6 mentioned above
An ON/OFF valve 9 for opening and closing this passage 8 is interposed, and this valve 9 is composed of, for example, an electromagnetic solenoid valve, and is controlled ON and OFF by the CPU 10, and when turned ON and the passage 8 is opened, the pressure regulator is activated. By returning the fuel from 6 to the injectors 5..., the fuel pressure of the injectors 5... is lowered, and this fuel pressure becomes lower as the time that the valve 9 is open is longer.

The fuel injection time and timing of the injectors 5 are controlled by the CPU 10.

The throttle opening sensor 11 detects the throttle opening and outputs a throttle opening signal to the cpuio, and the intake pressure sensor 12 detects the intake pressure in the intake pipe 2, which changes depending on the operating condition, and responds to the intake pressure. The intake pressure signal is output to the CPU 10, and the water temperature sensor 13 detects the temperature of the cooling water of the engine 1 and outputs a water humidity signal to the CPLllo.

-〇- The distributor 14 has a built-in crank angle sensor, and outputs a crank angle signal that detects the crank angle from the crank angle sensor and a TDC signal that detects the top dead center of the first cylinder to the CPU 10.

In the figure, 15 is an ignition switch, and 16 is a starter motor. When the ignition switch 15 is turned on, the starter motor 16 is driven and the engine 1 is started. 17 is an exhaust pipe.

FIG. 2 shows a control circuit, and the CPU 10 includes a basic injection amount circuit 18, one injection timing control circuit, a correction circuit 20, and a fuel pressure control circuit 21, and stores program memory and data for controlling each circuit. It also has memory.

The basic jet mentioned above! l)1 The ffi circuit 18 receives the crank angle signal from the crank angle sensor 22 and the intake pressure sensor 12.
The basic injection amount of fuel is calculated based on the intake pressure signal from the water temperature sensor 13 and the water temperature signal from the water temperature sensor 13.

In this calculation, the intake air amount is detected based on the engine rotational speed calculated based on the crank angle signal and the aforementioned intake pressure signal, and the injection amount is calculated according to the next intake air amount. Furthermore, when the water temperature signal indicates a set temperature, for example 60°C or less, a correction amount corresponding to the temperature difference below is calculated, and this correction amount is added to the above-mentioned injection amount to calculate the basic injection amount. Ru.

Note that when the water temperature signal indicates the set temperature, that is, 60° C. or higher, the correction amount is zero, and the injection amount is not corrected.

The correction circuit 20 corrects the basic injection amount (acceleration correction) when acceleration is detected based on the throttle opening signal from the throttle opening sensor 11, and also corrects the basic injection amount at the time of start based on the start signal from the ignition switch 15. The basic injection amount set as the injection amount is corrected.

At the start, the amount of intake air cannot be measured, so the above setting is used.

The injection timing control circuit 19 receives the crank angle signal from the crank angle sensor 22, the intake pressure signal from the intake pressure sensor 12, the water temperature signal from the water temperature sensor 13, and the throttle opening signal from the throttle opening sensor 11. Based on this, as will be described later, when the basic injection (2) becomes equal to or greater than the set injection amount α, each injector 5 . . . is drive-controlled at the fuel injection timing.

If the basic injection amount is less than or equal to the set injection amount α, the fuel pressure control circuit 21 controls the ON/OFF valves 9 to set the injection time to a predetermined period β and control the injectors 5 . . . by the fuel pressure.

As shown in FIG. 4, the drive control of the injectors 5 based on the fuel injection time and the drive control based on the fuel pressure described above are based on the boundary between the low load and low rotation of the engine 1 and the high load and high rotation of the engine 1. The fuel injection amount at this boundary position is set to the above-mentioned setting fJJuα, and when the load is low, the injection time is set to a constant time β and the fuel pressure is set, and when the load is high, the fuel pressure is set to a constant high pressure and the injection amount is set to the injection time. is controlled.

In addition, as shown in Figure 3, the injection timing is set so that when the load is low, injection starts from the latter half of the intake stroke, and the period during which the end of injection coincides with the end of the intake stroke is a certain period β. , when the load is high, it is lengthened to accelerate the start of injection.

The operation of the engine fuel injection system configured as described above will be explained based on FIG. 5.

In a first step 31, the CPU 10 reads the TDC signal of the top dead center of the crankshaft from the crank angle sensor 22, and uses this as a reference signal for processing operations.In a second step 32, the CPU 10 determines whether it is time to start.

This determination is made based on the start signal from the ignition switch 15 being input to the correction circuit 2o, and when it is determined that it is time to start, the intake air amount cannot be measured, so the preset injection At the third step 33, the basic injection amount circuit 18 executes a correction process so that the injection amount is set, and the engine 1 is started with this set injection amount.

When the determination is No in the second step 32, in the fourth step 34, CPtJlo is the rank angle signal of the crank angle sensor 22, the intake pressure signal of the intake pressure sensor 12, the water temperature signal of the water temperature sensor 13, and the slot 10-torque. The throttle opening signal of the gap sensor 11 is read, and in the fifth step 35, the correction circuit 20 calculates the acceleration correction amount based on the detected acceleration, and the Komoto injection DA amount circuit 18 calculates the engine correction amount based on the crank angle signal. The number of revolutions is calculated, and the amount of intake air is calculated based on this number of revolutions and the intake pressure signal, and the amount of intake air at that time is calculated by taking into account the correction amount from the correction circuit 20 and the correction based on the water temperature signal. Calculate the basic injection amount according to the amount.

In the sixth step 36, the CPU 10 determines whether the calculated basic injection amount is fuel pressure control or injection timing control.
It is determined whether the fuel pressure is larger or smaller than the basic injection amount, and when it is determined that the fuel pressure is smaller, the fuel pressure is controlled and turned on in accordance with this basic injection amount in a seventh step 37.

The duty ratio of the OFF valve 9 is read from the map stored in the memory, and in an eighth step 38, a signal is output to the fuel pressure control circuit 21 based on this duty ratio, and the ON/OFF valve is turned on.
Controls the OFF valve 9.

In the ninth step 39, the CPU 10 controls the injection timing control circuit 1.
In step 9, set the injection time as a fixed time β -11-.

In a tenth step 40, the CPU 10 determines the start timing of the injection timing, and this start timing is the time obtained by subtracting the above-mentioned fixed time β from the required time of the intake stroke. One injection timing control circuit outputs an injection signal to each injector 5, and each injector 5 injects fuel.

Note that this fuel slope injection was turned on and off in the eighth step 38.
Since the FF valve 9 is controlled with a duty ratio according to the injection amount, the fuel pressure is controlled.

Then, in a twelfth step 42, the CPU 10 reads the next crank angle signal to determine the end of the intake stroke, that is, the end timing of the injection, and the injection timing control circuit 19 stops driving each injector 5.

As a result, the control of the fuel injection amount based on the processing in steps 37 to 39 of steps 7 to 9 is performed at low load and low rotation as shown in FIG. 3, and when the injection amount is below the set injection amount α shown in FIG. In this fuel pressure control, lean combustion is performed by stratified-12-combustion, and its range is wide up to the set injection amount α.

Then, in a thirteenth step 43, the CPU 10 determines whether the ignition switch 15 is OFF, that is, whether the engine is stopped. If YES, the process ends, but if NO, the process returns to the fourth step 34.

In the aforementioned sixth step 36, the CPU 10 determines the basic injection mm.
When it is determined that the injection timing is equal to or larger than the set injection IA value α, the injection timing is controlled, and in the 14th step 44, the fuel pressure control circuit 21 is turned on and the OFF valve 9 is turned off, and the pressure regulator 6 is turned on. The injection timing control circuit 19 reads the injection time corresponding to the basic injection amount from the map stored in the memory in a fifteenth step 45, and sets each injector 5 to the first injection time according to the above-mentioned injection time. The 10th to 12th steps 40 to 42 are driven and controlled.

As a result, the control of the fuel injection amount based on the 14th and 15th steps 44.45 is performed during the high load-13-high rotation shown in FIG. With this injection timing control, the stratification of the air-fuel mixture is broken and dispersed, improving the air utilization rate and achieving high output.

In the configuration of this invention, the fuel injection valve corresponds to the injector 5, the fuel pressure adjustment device corresponds to the pressure regulator 6 and the ON/OFF valve 9, and the intake air amount detection means corresponds to the intake pressure sensor 12 and the crank angle sensor 22.
The fifth step 3 is calculated by the CPU 10 based on the signal of
5, the operating state detecting means corresponds to the basic injection gA color circuit 18, and the operating region discriminating means corresponds to the sixth step 36.
Corresponding to the process of CPtJlo for determining
corresponds to the processing of

[Brief explanation of the drawing]

The drawings show an embodiment of the present invention, and FIG. 1 is a configuration diagram of a fuel injection device for an engine. FIG. 2 is a control circuit block diagram. FIG. 3 is an explanatory diagram showing the intake stroke of each cylinder. -14- Fig. 4 is a diagram showing the relationship among fuel pressure, injection time, and injection amount. FIG. 5 is a flowchart of fuel injection control. 1... Engine 5... Injector 6... Pressure regulator 9, ON, OFF bar/L, 7 1o... CPU 12... Intake pressure sensor 18...
Basic injection amount circuit 19...Injection timing control circuit 21...Fuel pressure control circuit 22...Crank angle sensor 15 - Figure 2 Figure 3 Figure 5 Quantity chart positive 31 TDC number reading 2 A trout? 433 Grand 7fAa Dawn Talk Signal σ^ Body 1 quantity Resolute lK' 1 Government number 5

Claims (1)

[Claims] 1. A fuel injection valve provided for each cylinder of the engine, a fuel pressure adjustment device that adjusts the fuel pressure of fuel sent to these fuel injection valves, and an intake air amount that detects the intake air amount of the engine. a detection means; an operating state detecting means for detecting the operating state of the engine; an operating region determining means for receiving the output of the operating state detecting means and determining a predetermined operating region including at least a low load; When the output is received and the operation is in a predetermined operating range, the fuel injection timing by the fuel injection valve is controlled so that the start timing of the fuel injection is approximately in the latter half of the intake stroke, and the end timing is controlled to be the end timing of the intake stroke. 1- A fuel injection device for an engine, comprising injection air mass control means that controls the fuel pressure adjustment device to increase the fuel pressure as the amount of intake air increases based on the output of the air mass detection means.