JPH073206B2 - Fuel injection control device for internal combustion engine - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a fuel injection control device for controlling an air-fuel ratio during a fuel pressure increase control at a high temperature start of an internal combustion engine.

Conventional technology In general, when the engine that has been operating under high load for a long time is stopped, the temperature of the engine becomes high and vapor may be generated in the fuel pipe of the fuel injection device. In an engine that supplies a fuel amount proportional to the injection time of the injection device, the fuel supply amount is reduced by the vapor amount even at the same fuel injection time, and the air-fuel ratio becomes over lean because the sufficient fuel amount is not supplied. In many cases, the engine cannot be started, or even if the engine is completed, the idle operation state becomes unstable after starting and the engine stalls.

Such a fuel injection device has a pressure regulator in order to keep the amount of fuel injected from the fuel injection valve per fixed time constant, but normally, by introducing negative pressure in the intake pipe to the diaphragm chamber of this pressure regulator. The fuel pressure is controlled so that the differential pressure between the fuel pressure and the intake pipe negative pressure is constant (Japanese Patent Laid-Open No. 59-96439).

On the other hand, at the time of high temperature restart, the intake pipe negative pressure introduced into the diaphragm chamber of the pressure regulator is switched to atmospheric pressure by the VSV (vacuum switching valve) as a negative pressure control valve, so that the intake pipe is kept for a predetermined time after the high temperature start. The fuel pressure applied to the fuel injection valve is increased by the amount of the negative pressure to avoid the over lean of the air-fuel ratio due to the vapor generation.

However, according to the conventional fuel injection control device, when restarting immediately after stopping the engine in a state where the engine temperature is sufficiently high, the temperature of the exhaust system is sufficiently high and the activity is high. The feedback control of the air-fuel ratio based on the converted oxygen sensor may be started immediately, but at this time, if the operation of the pressure regulator is stopped by the engine cooling water temperature and the timer, the learning control is performed because the fuel injection amount is large. As a result, the learning correction coefficient value decreases.

Therefore, when the idle operation is continued, the oxygen sensor is deactivated due to the decrease in the combustion temperature and the air-fuel ratio feedback is stopped.If the pressure regulator starts operating in this state, the low learning correction coefficient value For example, while learning control by 0.95 is being executed, the fuel pressure increase is released, so at the time of release of the fuel pressure increase the air-fuel ratio becomes over lean, engine stalls occur, and the idle operation state becomes unstable. is there.

Means for Solving the Problems In order to solve the above problems, a fuel injection control device for an internal combustion engine according to the present invention has a basic structure as shown in FIG. The engine temperature determination means for determining whether or not, the engine start detection means for detecting the start of the engine, the air-fuel ratio sensor for detecting the air-fuel ratio from the concentration of specific components in the exhaust gas, the output of the air-fuel ratio sensor An air-fuel ratio feedback control coefficient for correcting the fuel injection amount by using the air-fuel ratio feedback correction coefficient obtained based on the air-fuel ratio feedback control coefficient, and controlling the air-fuel ratio of the air-fuel mixture to the target air-fuel ratio; Control means for controlling the fuel injection pressure of the fuel injection valve, a pressure regulator connected to the intake passage for controlling the fuel injection pressure of the fuel injection valve, an engine temperature determination means, and an engine start detection hand. Based on the stage, when the engine is restarted at high temperature, the pressure regulator is started to the atmosphere, and the stop control means for stopping the learning control of the air-fuel ratio by the learning control means is provided.

Operation According to the present invention, the pressure regulator is opened to the atmosphere by the stop control means and the learning control of the air-fuel ratio is stopped for a predetermined period after the high temperature start based on the engine determination means and the start time detection means. . The enrichment of the air-fuel ratio based on the increase in the fuel injection amount due to opening of the pressure regulator to the atmosphere is controlled near the logical air-fuel ratio while the air-fuel ratio feedback control means is operating. However, when the idle operation continues, the exhaust system temperature decreases due to the decrease in the combustion temperature, and the air-fuel ratio sensor becomes inactive, the air-fuel ratio feedback control by the air-fuel ratio feedback control means is stopped, but the learning control is stopped. Therefore, the air-fuel ratio becomes rich again.

Therefore, in that state, even if the operation of the stopped pressure regulator is started and the fuel pressure falls to a predetermined value determined based on the intake pipe negative pressure during normal operation, the air-fuel ratio does not become over lean. To be done.

EXAMPLES Examples of the present invention will be described with reference to the drawings.

FIG. 2 shows an example of a schematic configuration of an internal combustion engine to which the fuel injection control device of the present invention is applied.

In the figure, 1 is an internal combustion engine body, 2 is a cylinder block, 3 is a cylinder head, 4 is a piston, 5 is a combustion chamber, 6 is a spark plug, 7 is an intake valve, 8 is an exhaust valve, and 9 is an exhaust manifold 10. An oxygen sensor for detecting the oxygen concentration in the exhaust gas, 15 a water temperature sensor for measuring the cooling water temperature, 16 an ignition switch, and 21 a battery power source.

In the intake system, the intake amount of intake air taken in from the air cleaner 24 is measured by the air flow meter 25, the intake temperature is measured by the intake temperature sensor 26, and the intake is performed by the throttle valve 28 that opens and closes according to the stroke of the accelerator pedal 27. A predetermined amount of air is sent to the intake manifold 30. The throttle body 31 is provided with a throttle sensor 32 for detecting the opening degree and the fully closed position of the throttle valve 28 interposed therein.

In the fuel system, a fuel injection valve 38 for injecting and supplying a predetermined amount of fuel pumped by the fuel pump 37 from the fuel tank 35 through the normal 36 is mounted in the vicinity of the intake valve 7 and is applied to the fuel injection valve 38. The fuel pressure is adjusted by the pressure regulator 39. That is, during normal operation, the negative pressure control valve (VSV) 45 introduces an intake pipe negative pressure into the diaphragm chamber of the pressure regulator 39, and the fuel pressure applied to the fuel injection valve 38 is always higher than the intake pipe pressure by a predetermined value, for example, 2.55 kg / cm ² It is set so as to be higher, and excess fuel is returned to the fuel tank 35 through the passage 46. At the time of high-temperature start-up operation, atmospheric pressure is introduced into the diaphragm chamber of the pressure regulator 39 by the negative pressure control valve (VSV) 45, and the fuel pressure applied to the fuel injection valve 38 is increased regardless of the intake pipe pressure.

Then, in the ignition system, the high voltage generated in the ignition coil 40 is supplied to the distributor 41, and the high voltage is distributed and supplied to the ignition plugs 6 of the respective cylinders at a predetermined timing while performing a predetermined ignition timing control by the distributor 41. I have to. The distributor 41 is provided with a rotation speed sensor 43 that detects a rotation angle and a rotation speed from a rotation position of a distributor shaft 42 that rotates in synchronization with a crankshaft (not shown). Thus, the pulse signal is output 24 times every two revolutions of the crankshaft, and the pulse signal is output once at a predetermined angle every one revolution of the crankshaft.

The control device 50 is a microcomputer operated by a battery power source 21, and in this microcomputer, as shown in FIG. 3, a central processing unit (CPU) 51 is provided.
A read only memory (ROM) 52, a random access memory (RAM) 53, and a backup random access memory (RAM) 54 that retains memory even when the ignition switch 16 is off. Of these, the ROM 52 stores programs such as a main routine, a fuel injection amount control routine, an ignition timing control routine, and various fixed data and constants necessary for these processes. In addition, the microcomputer has an A /
A D converter 55 and an I / O device 56 having a buffer memory are incorporated, and these 55 and 56 are connected to each other by 51 to 54 and a common bus 57.

In the A / D converter 55, the output signals of each sensor such as the air flow meter 25 and the intake air temperature sensor 26 are input to the multiplexer via the buffer, and these data are A / D converted to the CPU.
CPU 51 and RAM 53 or 54 at a predetermined time according to the command of 51
I am trying to output to. As a result, the latest detection data such as the intake air amount, the intake air temperature, the water temperature, etc. are fetched into the RAM 53, and these data are stored in the predetermined area. I / O device 56
In this case, the detection signals of the sensors such as the throttle sensor 32 and the rotation speed sensor 43 are input, and these data are stored in the CPU 51.
Is output to the CPU 51 and the RAM 53 or 54 at a predetermined time.

The CPU 51 calculates the fuel injection amount based on the data detected by each sensor according to the program stored in the ROM 52, and outputs a pulse signal based on the calculated fuel injection amount to the fuel injection valve 38 via the I / O device 56. That is, basically, the basic fuel amount is calculated from the intake air amount detected by the air flow meter 25 and the engine speed detected by the rotation speed sensor 43, and this is corrected according to the detected intake air temperature and the cooling water temperature. A pulse signal corresponding to the corrected fuel amount is sent from the drive circuit (not shown) in the I / O device 56 to the fuel injection valve 38.

That is, the fuel injection amount TAU is determined based on the equation TAU = TP × FAF × FG + α. Here, TP is the basic injection amount that is determined from the intake air amount Q / engine speed N, FAF is the air-fuel ratio feedback correction coefficient that is determined based on the output of the oxygen sensor,
FG is a learning correction coefficient at the time of idling, and α is another correction coefficient.

The learning correction coefficient FG of these is set to a value of 1.0 when the operation of the pressure regulator 39 is stopped after the high temperature start and before the elapse of a predetermined time. That is, if the operation of the pressure regulator 39 is stopped for a certain period after the high temperature start, the learning control of the air-fuel ratio is prohibited during the operation stop of the pressure regulator.

Next, the learning control prohibiting routine of the fuel injection control will be described based on the flowcharts shown in FIGS. 4 and 5.

In the first step 401, the engine cooling water temperature THW is a predetermined value A ° C.
If THW ≧ A ° C., it is determined whether or not it is the above, the process proceeds to step 402, and it is determined by the timer whether or not the predetermined time Bsec has elapsed after the high temperature start. If it is within Bsec after the high temperature start, the process proceeds to 403. The operation of the pressure regulator 39 is stopped. That is, the atmospheric pressure is introduced into the diaphragm chamber of the pressure regulator 39 by the VSV 45 to increase the fuel pressure applied to the fuel injection valve. Next, at step 404, the learning control inhibition flag XGKS for setting the learning correction coefficient FG during the idle operation to 1.0 is set (XGKS is set to 1), and this routine is ended.

In step 401, the engine cooling water temperature THW is lower than a predetermined value A ° C, or in step 402 a predetermined time Bse after high temperature startup.
When it is detected by the timer that the value exceeds c, the routine proceeds to step 405, where the pressure regulator 39 is operated, that is, the intake pipe negative pressure is introduced into the diaphragm chamber of the pressure regulator 39, and the fuel pressure applied to the fuel injection valve 38 is increased. A predetermined value than the intake pipe pressure at that time, for example 2.55 kg
/ cm ² is set to a higher value, then proceeds to step 406 lower the learning control prohibition flag XGKS (a XGKS to 0), the routine is terminated.

In the learning control prohibition execution routine shown in FIG. 5, first, at step 507, it is judged if the learning control prohibition flag XGKS is set. If XGKS is down, the routine proceeds to step 508 to execute the learning control. If XGKS is standing, the learning correction coefficient FG is set to 1.0 without executing learning control, and this routine is finished.

Next, FIG. 6 shows an air-fuel ratio feedback waveform, a learning correction coefficient, an air-fuel ratio and an engine speed when the engine is restarted immediately after it is stopped in a state where the engine temperature is sufficiently high.

Explaining this graph, at the time of restarting immediately after the engine is stopped at high temperature (between A and B in FIG. 6), the temperature of the fuel system does not rise so much, so the operation of the pressure regulator 39 is stopped. Cranking is performed with the fuel pressure increased and the air-fuel ratio becoming rich due to the increased fuel. When the cranking is completed, the air-fuel ratio feedback control is started. If the idle operation is continued in this state, the oxygen sensor 9 is subsequently deactivated and the air-fuel ratio feedback control is stopped (B point).

According to the present embodiment, since the learning correction control is stopped immediately after the feedback control is stopped until the operation of the pressure regulator 39 is started (between B and C), the air-fuel ratio becomes slightly rich, and the engine Idle speed is increased.

After that, when the timer measures a predetermined time from the start point of time, the fuel control by the pressure regulator 39 is started and the fuel pressure increase is released, but at the same time, the fuel amount increase by the learning correction control is started, so the engine speed is The normal idle speed is maintained without any depression.

According to the present invention, since the learning control of the air-fuel ratio is stopped after the high temperature restart, when the feedback control of the air-fuel ratio is stopped and the fuel pressure increase by the pressure regulator is released, the air-fuel ratio at that time is released. Since the learning control is started, it is possible to avoid over lean of the air-fuel ratio, thereby reliably preventing the engine stall without lowering the idle speed, and stably maintaining the idle speed thereafter. The effect is obtained.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a block diagram showing the basic configuration of the present invention, FIG. 2 is a schematic configuration diagram showing an embodiment of an internal combustion engine and its peripheral devices to which the present invention is applied, and FIG. Is a block diagram showing an embodiment of the control circuit of the present invention, FIGS. 4 and 5 are flowcharts showing an embodiment of the present invention, and FIG. 6 is a feedback waveform and learning correction coefficient in the embodiment of the present invention. 5 is a graph showing the relationship between the air-fuel ratio, the engine speed, and time. 1 ... Internal combustion engine body, 6 ... Spark plug, 9 ... Oxygen sensor (air-fuel ratio sensor), 15 ... Water temperature sensor, 21 ... Battery power supply, 28 ... Throttle valve, 38 ... Fuel injection valve, 39 ...... Pressure regulator, 45 …… VSV (negative pressure control valve) 50 …… Control device, 51 …… Central processing unit (CPU), 52 …… Read only memory (ROM), 53, 54 …… Random access memory ( RAM), 55 …… A / D converter, 56 …… I / O device.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Chika Kato 1 Toyota-cho, Toyota-shi, Aichi Prefecture Toyota Motor Corporation (56) Reference JP-A-59-206651 (JP, A)

Claims (1)

[Claims] 1. An engine temperature determination means for determining whether or not an engine is at a predetermined temperature or higher, an engine startup detection means for detecting the startup of the engine, and an air-fuel ratio from the concentration of a specific component in exhaust gas. Air-fuel ratio feedback control that corrects the fuel injection amount by using the air-fuel ratio sensor that operates and the air-fuel ratio feedback correction coefficient obtained based on the output of the air-fuel ratio sensor to control the air-fuel ratio of the air-fuel mixture to the target air-fuel ratio. Means, learning control means for controlling the air-fuel ratio feedback correction coefficient to approach a predetermined value, a pressure regulator connected to an intake passage for controlling the fuel injection pressure of a fuel injection valve, and the engine temperature determination means. And, based on the engine start detection means, at the time of high temperature restart, the pressure regulator is started to the atmosphere, and the learning control means learns the air-fuel ratio. The fuel injection control device for an internal combustion engine, characterized in that it has a stop control means for stopping the control.