JPH07238849A - Fuel injection control device - Google Patents

Abstract

PURPOSE:To make the fuel particle diameter smaller, as well as to reduce the wall surface attaching amount of the fuel, in a high load operation. CONSTITUTION:When the suction amount detected by. a throttle opening sensor 224 is large, the operating amount of a VVT 233 is increased, the valve opening timing of a suction valve 23 is advanced, and the overlapping amount of the valve opening timing is increased. And by setting the valve closing timing of a fuel injection valve 225 within the overlapping period by a control device 26, the atomization of the fuel injected at the latter phase of the fuel injection period is expedited by a reversely flowing exhaust gas.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a fuel injection control device for an internal combustion engine, and more particularly to a fuel injection control device for an internal combustion engine capable of promoting atomization of fuel.

[0002]

2. Description of the Related Art In an internal combustion engine equipped with a fuel injection valve for each cylinder, fuel injection is performed while the intake valve of the corresponding cylinder is closed (for example, Japanese Patent Laid-Open No. 1-29094).
No. 4), the assist air or the pressure in the intake pipe is a negative pressure, and the particles are atomized by decompression boiling.

By promoting the atomization of the fuel, combustion of the fuel in the cylinder becomes stable, and good emission is secured.

Therefore, the lower the load of the internal combustion engine, the more The amount of fuel injection itself is small, and the energy required for atomization is small. 2. Since the pressure in the intake pipe is lower, the amount of assist air should increase. 3. Since the pressure in the intake pipe is lower, the depressurization boiling effect is increased. Due to the above reasons, the atomization is promoted.

Further, the earlier the fuel injection timing is, the more
It becomes possible to secure a sufficient time for atomization. However, if the fuel injection timing is advanced, it is inevitable that the amount of fuel adhering to the wall surface of the intake pipe increases. FIG. 1 is a graph showing fuel atomization characteristics. (A) is the vertical axis, the particle size of the fuel, the horizontal axis is the fuel injection end timing, and (b) is the vertical axis, the amount of fuel adhering to the wall surface, the horizontal axis. The fuel injection end timing is set.

That is, if the load is low, the fuel particle size can be kept small regardless of the fuel injection timing, and the amount of fuel adhering to the wall surface of the intake pipe can be reduced.

[0007]

However, when the load becomes high, the adhering amount increases when the fuel injection timing is advanced in order to reduce the fuel particle size, the air-fuel ratio fluctuates transiently, and the wall adhering amount decreases. Therefore, if the fuel injection timing is delayed, it is impossible to avoid the instability of combustion due to the large fuel particle size.

The present invention has been made in view of the above problems.
An object of the present invention is to provide a fuel injection control device for an internal combustion engine, which is capable of reducing the amount of adhered wall surfaces and reducing the particle size of fuel particles under a high load.

[0009]

A fuel injection control apparatus according to a first aspect of the present invention is applied to an internal combustion engine having an overlap period in which both an intake valve and an exhaust valve are open. In the controller, the fuel injection valve is closed during the overlap period during the high load operation. A fuel injection control device according to a second aspect of the present invention is a fuel injection control device that performs fuel injection by an air assist fuel injection valve, and is at least 1 installed in an air assist pipe connecting an intake pipe upstream and a fuel injection valve. The two assist air flow rate control valves and the assist air flow rate control valve are opened according to the fuel injection timing from the fuel injection valve, and the opening degree of the assist air flow rate control valve is increased as the fuel injection time elapses.

[0010]

In the fuel injection control device according to the first aspect of the present invention, the fuel injection is ended during the overlap period when the fuel injection amount is large during the high load operation. In the fuel injection control device according to the second aspect of the present invention, the assist air amount is increased toward the latter stage of fuel injection.

[0011]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 2 is a block diagram of a valve timing control device according to the first invention, which is one cylinder 21 of an internal combustion engine.
A piston 211 is vertically slidable in the combustion chamber 22, and the upper portion of the piston 211 serves as a combustion chamber 22. Piston 21
1 is connected to a crankshaft 213 via a connecting rod 212.

A magnetic body 214 is attached to the crankshaft 213.
Is embedded and a reference pulse is output from the first magnetic sensor 215 arranged close to the crankshaft 213. A timing pulley 216 is installed at the tip of the crankshaft 213. An intake pipe 221 and an exhaust pipe 222 are connected to the combustion chamber 22,
A throttle valve 223 for adjusting the amount of intake air is installed upstream of the intake pipe 221. The opening of the throttle valve 223 is detected by the opening sensor 224.

An intake valve 23 is provided at a connection port between the combustion chamber 22 and the intake pipe 221, and a fuel injection valve 22 is provided immediately upstream of the intake valve 23.
5 is installed. An exhaust valve 24 is installed at the connection port between the combustion chamber 22 and the exhaust pipe 222. The intake valve 23 and the exhaust valve 24 are driven by cams (not shown) attached to the cam shafts 231 and 241.

Timing pulleys 232 and 242 are installed at the tips of the camshafts 231 and 241, and are driven via a timing pulley 216 and a timing belt 217 installed on the crankshaft. Further, a variable valve timing actuator (hereinafter referred to as VV) is provided between the intake valve cam shaft 231 and the timing pulley 232.
Write T. ) 233 is installed and the crankshaft 21
It is possible to change the rotation phase of the intake valve cam shaft 231 with respect to the No. 3 ratio.

The VVT 233 is driven by hydraulic pressure supplied from a hydraulic pressure source (not shown), and the rotational phase is controlled by controlling the opening degree of the control valve 234. A magnetic material 235 is embedded in the intake valve camshaft 231, and a pulse is output from the second magnetic sensor 236 arranged in proximity to the intake valve camshaft 231 every one rotation.

A distributor 25 is attached to the internal combustion engine 2 so that one pulse is generated by the first rotation speed sensor 251 every two rotations of the internal combustion engine, and the second rotation speed sensor 252 causes a 30 ° cam angle of the internal combustion engine. One pulse is output for each. The valve timing controller 26 is a microcomputer system, and the bus 26
1, the CPU 262, the memory 263, the input interface 264, and the output interface 265.
Composed of.

A first magnetic sensor 215, an opening sensor 224, a second magnetic sensor 236, a first rotation speed sensor 251, and a second rotation speed sensor 252 are connected to the input interface 264, and their respective detection signals are detected. Are taken into the valve timing controller 26. The output interface 265 includes a fuel injection valve 225 and a control valve 23.
4 are connected and controlled based on the calculation result of the valve timing control device 26.

FIG. 3 is a flow chart of a fuel injection timing control routine executed by the control unit 26, which is executed every fixed cam angle. Step 30 In the first open period t _TAU speed sensor 251 based on the throttle valve opening TA detected by the engine speed N _e and the throttle valve opening sensor 224 is detected by the fuel injection valve 225
Is determined.

In step 31, it is judged whether or not the overlap amount α is equal to or larger than a predetermined threshold value α _TH (for example, 30 ° cam angle). The overlap amount α is determined by an overlap control routine (not shown) according to the operating state of the internal combustion engine, and is controlled by the VVT 233. If an affirmative decision is made in step 31, the valve opening timing t _open is set to t _TAU in order to determine the fuel injection valve opening cam angle with reference to top dead center in step 321, and step 32
At 2, the flag XVVT indicating that the overlap amount α is equal to or larger than the predetermined threshold value α _TH is set to "1", and the routine proceeds to step 34.

When a negative determination is made in step 32, fuel flight until the lump of fuel injected from the fuel injection valve 225 during the valve opening period t _TAU determined in step 331 reaches the intake valve 23 in step 331. Time t _FLY
(For example, 5 milliseconds) is added to determine the valve opening timing t _open , the flag XVVT is reset in step 332, and the process proceeds to step 34.

In step 34, the valve opening timing t _open is converted into the fuel injection valve opening cam angle A by the following equation based on the internal combustion engine speed N _e . A = (t _open · 360 ° · 60) / (N _e · 100)
0) The internal combustion engine speed N _e is rpm and the valve opening timing t
_open shall be expressed in milliseconds.

In step 35, it is judged whether or not the flag XVVT is "1", and if a positive judgment is made, the routine proceeds to step 36, where the fuel injection valve is opened so that the fuel injection valve is closed within the overlap period. Set the valve timing. For example, when the overlap threshold value α _TH is 30 ° cam angle, the valve closing cam angle of the fuel injection valve is set to 15 ° before top dead center and the valve opening cam angle of the fuel injection valve is further set to A Set the cam angle advanced.

FIG. 4 is an explanatory view of the valve timing when the overlap is large. It is assumed that the internal combustion engine rotates clockwise, and thereafter, the cam angle is taken clockwise with reference to the top dead center. . Therefore, the valve opening cam angle C of the fuel injection valve
Determine O as follows and proceed to step 38.

CO = − (A ° + 15 °) That is, when the overlap is large, that is, when the internal combustion engine is operating at a high load, the fuel injection valve is closed during the overlap period, and the exhaust gas that flows back into the intake pipe is exhausted. The gas promotes atomization of the fuel. When a negative determination is made in step 35, the process proceeds to step 37, and the valve opening cam angle CO of the fuel injection valve is set as follows so that the timing when the tail of the injected fuel mass reaches the intake valve is the top dead center. Decided to
Go to step 38.

CO = -A ° That is, FIG. 5 is an explanatory view of the valve timing when the overlap is small. When the internal combustion engine is operated at a light load, the fuel injection is completed before the overlap and the fuel is the intake valve. Atomization is sufficiently made during the flight time to reach. In step 38, the fuel injection valve opening cam angle CO is output and this routine is ended.

FIG. 6 is a block diagram of a valve timing control device according to the second invention, showing a case where a three-valve idling speed control valve (hereinafter referred to as an ISC valve) is applied to a V-type internal combustion engine. A bypass pipe 226 opens upstream of the throttle valve, and the bypass pipe 226 is an IS valve.
It is connected to the air assist pipe 228 via the C valve 227.

The fuel injection valves 225R and 225L are so-called air-assist type fuel injection valves.
Air assist pipes 228R and 228L that are branched into two are connected to the air ports of 25R and 225L.
That is, when the ISC valve 227 opens, a part of the intake air flows into the bypass pipe 226, the ISC valve 227 and the air assist pipe 22.
8R and 228L to flow into the fuel injection valves 225R and 225L to promote atomization of fuel.

FIG. 7 is a flowchart of the ISC control routine executed in the second invention, which is executed at regular time intervals. In step 701, it is determined whether or not the engine is in idle operation. If it is in idle operation, step 70
Go to 2. In step 702, it is determined whether or not the intake air amount Ga is equal to or more than a predetermined threshold value (for example, 10 grams / second). If the determination is affirmative, that is, if the engine is operating under high load, the process proceeds to step 703.

In step 703, it is determined whether the fuel injection valves 225R and 225L are energized, that is, whether fuel is being injected. If an affirmative decision is made at step 703, then the processing advances to step 704, at which it is decided whether or not the flag XTAU indicating the open / closed state of the fuel injection valve is "0". If an affirmative decision is made in step 704, it is assumed that the fuel injection valve has changed from the closed state to the open state, the flag XTAU is set to "1" in step 705, and the ISC valve 227 driven by the stepping motor in step 706. The opening command D is determined as a value obtained by adding the skip amount F to the idle opening command E, and the process proceeds to step 708.

If a negative determination is made in step 704, it is determined that the fuel injection valve remains open.
7, the opening command D of the ISC valve 227 is increased by a minute amount d, and the process proceeds to step 708. That is, the opening of the ISC valve 227 is rapidly increased at the same time when the fuel injection valve is opened, and thereafter the opening is increased at a constant rate.

In step 708, it is determined whether or not the opening command D is greater than or equal to a predetermined maximum value D _max (for example, 100). If a negative determination is made in step 708, the process directly proceeds to step 710. Step 710
Then, the opening degree command D is set as the stepping motor drive command ISCS, the drive command ISCS is output in step 711, and this routine ends.

If it is determined in step 701 that the engine is idling, the process proceeds to step 712, the opening command E during idling is determined, and the process proceeds to step 713. Step 7
In step 13, the opening command E during idle operation is set as the stepping motor drive command ISCS, and step 711
Proceed to. When a negative determination is made in step 702, that is, when the vehicle is operating under a light load, the process directly proceeds to step 713.

If a negative determination is made in step 703, that is, if the fuel injection valve is in the closed state, step 714.
After resetting the flag XTAU, the process proceeds to step 713. FIG. 8 is a detailed flowchart of the idle opening command processing executed in step 712 of the ISC control routine. In step 7121, it is determined whether or not the feedback control of the idle speed is allowed, and if the determination is affirmative. In step 7122, it is determined whether the rotation speed N _e is equal to or higher than a predetermined threshold rotation speed N _th (eg 700 rpm).

If an affirmative decision is made in step 7122, the operation proceeds to step 7123, in which the idle opening command E is decreased by a predetermined amount e, and this routine is ended. If a negative determination is made in step 7122, the process proceeds to step 7124, the idle opening command E is increased by a predetermined amount e, and this routine is ended. If a negative decision is made in step 7121, this routine is directly ended.

FIG. 9 is a timing chart for explaining the operation of the second invention, in which the vertical axis is the fuel injection valve 225R or 2
The energization state of 25 L, the drive command ISCS, the intake air amount Ga, and the rotation speed N _e are shown, and the horizontal axis shows time. Before time t ₄ , the engine is idling, and the intake air amount Ga decreases at time t ₁ , so that the drive command ISC decreases when the rotation speed N _e decreases.
The idle opening command value E of S is increased by a predetermined amount e.

When the rotation speed N _e starts to increase above the threshold rotation speed N _th (700 rpm) at time t ₂ , the idle opening command value E of the drive command ISCS decreases by a predetermined amount e. When the rotation speed N _e returns to the threshold rotation speed N _th (700 rpm) at time t ₃ , the idle opening command value E of the drive command ISCS maintains a constant value.

After time t ₄ , the engine is in a normal operation state, and when the fuel injection valve is opened at time t ₅ , the drive command ISCS increases from the idle opening command value E by a skip amount F steps, and then a small amount d. It increases by one. Therefore, the amount of assist air increases in the latter stage of fuel injection. The fuel injection valve is closed and the drive command ISCS at time t ₆ returns to the idle opening command value E.

Similarly, when the fuel injection valve is opened at time t ₇ , the drive command ISCS increases from the idle opening command value E in skip steps F steps, and thereafter, increases by a minute amount d. But drive command ISCS the intake air amount Ga is reduced below a predetermined threshold value at time t ₈ returns to the idle opening command value E.

[0039]

According to the fuel injection control device of the first aspect of the present invention, when the fuel injection amount is large during the high load operation, the fuel injection is ended in the overlap period, so that the fuel injected in the latter period is The atomization is promoted by the exhaust gas flowing back into the intake pipe. According to the fuel injection control device of the second aspect of the present invention, it is possible to promote atomization of the fuel injected in the latter period by increasing the assist air amount in the latter period of the fuel injection.

[Brief description of drawings]

FIG. 1 is a graph showing fuel atomization characteristics.

FIG. 2 is a configuration diagram of a valve timing control device according to a first invention.

FIG. 3 is a flowchart of a fuel injection timing control routine.

FIG. 4 is an explanatory diagram of valve timing when the overlap is large.

FIG. 5 is an explanatory diagram of valve timing when the overlap is small.

FIG. 6 is a configuration diagram of a valve timing control device according to a second invention.

FIG. 7 is a flowchart of an ISC control routine.

FIG. 8 is a detailed flowchart of idle opening command processing.

FIG. 9 is a timing diagram illustrating the operation of the second invention.

[Explanation of symbols]

 21 ... Cylinder 22 ... Combustion chamber 223 ... Throttle valve 224 ... Throttle opening sensor 225 ... Fuel injection valve 23 ... Intake valve 233 ... VVT 234 ... Control valve 25 ... Distributor 251 ... First rotation speed sensor 252 ... Second rotation Number sensor 26 ... Control device

Claims (2)

[Claims] 1. A fuel injection control device applied to an internal combustion engine having an overlap period in which both an intake valve and an exhaust valve are open, wherein the fuel injection valve is used during high load operation. A fuel injection control device that closes during the overlap period. 2. A fuel injection control device for injecting fuel with an air assist fuel injection valve, comprising: at least one assist air flow control valve installed in an air assist pipe connecting an intake pipe upstream and the fuel injection valve. A fuel injection control device that opens the assist air flow rate control valve at a timing of fuel injection from the fuel injection valve, and increases the opening degree of the assist air flow rate control valve as the fuel injection time elapses.