JPH01300032A - Start controller for electronically controlled fuel injection type internal combustion engine - Google Patents

Abstract

PURPOSE:To facilitate the shortness of starting time and the sureness of starting by variably setting the time from the start of engine to the point, where decrease compensation of injection amount for starting is started, and the maximum decrease rate by the decrease compensation, according to the temperature of engine. CONSTITUTION:An injection amount setting means A at the start time sets the fuel injection amount for starting according to the operation conditions at the time of engine start. An injection amount decrease compensating means B compensates the fuel injection amount for starting and decreases same gradually when a specified time passes from the start of engine. According to the engine temp. detected by an engine temp. detecting means C, a decrease transition time setting means D sets a specified time in the means B according to the engine temp. A decrease rate control means E controls the maximum decrease rate of fuel injection amount according to the engine temp. detected.

Description

DETAILED DESCRIPTION OF THE INVENTION <Industrial Application Field> The present invention relates to a start control device for an electronically controlled fuel injection type internal combustion engine.

<Prior art> In an electronically controlled fuel injection type internal combustion engine, during normal operation, the fuel injection amount is set in accordance with the intake air flow rate per unit revolution of the engine, but the fuel injection amount at the time of starting is determined mainly by the engine temperature. I'm trying to set it up. (Jitsugan 1986-
015569 etc.).

The fuel injection amount Tc for starting (expressed as the opening time of the fuel injection valve) has been set, for example, by the following formula.

Tc = TstX KNsy Set. K9 and 7 are rotational speed correction coefficients, which are set to decrease as the rotational speed increases. In addition, KTST is an elapsed time correction coefficient, and is set to 1 and does not function until a predetermined time has elapsed from the start of the engine, but when the elapsed time from the start of the engine exceeds the predetermined time, this coefficient The starting injection amount T is gradually reduced, thereby preventing the ignition plug from getting wet and becoming unable to start even if the starting time becomes long.

<Problems to be Solved by the Invention> By the way, the fuel injection amount Tc for starting, which is set according to the above formula, is obtained so that the time from starting to complete explosion is short. The air-fuel ratio of the intake air-fuel mixture is set to be richer than the stoichiometric air-fuel ratio, and the elapsed time correction coefficient is K?
3? The settings were such that the injection amount reduction correction would not work for about 10 seconds after starting the engine.

For this reason, at temperatures other than extremely low temperatures, if a complete explosion is not achieved within the standard cranking time at the initial stage of startup due to insufficient cranking speed due to a drop in battery voltage or a decline in ignition ability, the subsequent air-fuel mixture condition will be too rich and will not result in a complete explosion. First, since the elapsed time correction coefficient A and A have been used to reduce the injection amount at startup, the air-fuel ratio has reached an ignition-enabled air-fuel ratio state and the start can be performed, and the elapsed time correction There is a risk that the ignition plug may become wet before the start-up injection amount reduction correction control using the coefficient KTST starts, making it impossible to start the engine.

In other words, in order to ensure startability at extremely low temperatures, the time required to shift to the reduction correction by the elapsed time correction coefficient K T S T is set long, so the elapsed time correction coefficients K T and T are effective at room temperature. However, it was not possible to prevent the air-fuel ratio from becoming richer when starting failed in the initial stage and the starting time was prolonged.

The present invention has been developed in view of the above problems, and provides good starting performance even when starting time is prolonged at room temperature while ensuring starting performance at extremely low temperatures that require a rich mixture for a long time. The purpose is to make it possible to obtain.

<Means for Solving the Problems> Therefore, in the present invention, as shown in FIG. In the electronically controlled fuel injection internal combustion engine configured, a starting injection amount setting means sets a fuel injection amount for starting according to operating conditions when starting the engine, and when a predetermined time has elapsed from the start of engine starting, the starting injection amount setting means sets the starting fuel injection amount according to the operating conditions. an injection amount reduction correction means for correcting and gradually decreasing the fuel injection amount for starting set by the injection amount setting means; an engine temperature detection means for detecting the engine temperature; and an engine temperature detection means for detecting the engine temperature; The starting control device is configured to include a reduction transition time setting means for setting, and a reduction rate regulating means for regulating the maximum reduction rate of the fuel injection amount by the injection amount reduction correction means according to the engine temperature.

<Operation> According to this starting control device, in the starting operation state of the engine, the starting fuel injection amount setting means sets the fuel injection amount for starting according to the operating conditions, and the fuel injection valve is adjusted based on this fuel injection amount. However, when a predetermined period of time set according to the engine temperature detected by the engine temperature detection means has elapsed from the start of the engine start, the injection amount reduction correction means reduces the amount of fuel for starting. The injection amount is gradually corrected to decrease, and the fuel injection amount of the engine gradually decreases.

Further, the maximum reduction rate in the reduction correction of the fuel injection amount for starting is also regulated according to the engine temperature detected by the engine temperature detection means.

In other words, instead of shifting to the reduction correction of the injection amount after a certain period of time from the start of engine operation, regardless of the engine temperature, the time until the injection quantity reduction correction is changed according to the engine temperature, and at the same time, the maximum reduction The fuel injection rate is also regulated based on the engine temperature to prevent the injection amount from being corrected to decrease more than necessary in response to the engine temperature.

<Example> The present invention will be explained in detail below.

In FIG. 2, an engine 1 is connected to an air cleaner 2 through an intake duct 3. Air is taken in via the throttle valve 4 and the intake manifold 5. A fuel injection valve 6 is provided in a branch portion of the intake manifold 5 for each cylinder. The fuel injection valve 6 is an electromagnetic fuel injection valve that opens when the solenoid is energized and closes when the energization is stopped. The fuel that is pressure-fed from the intake manifold 5 and adjusted to a predetermined pressure by a pressure regulator is injected and supplied into the intake manifold 5.

Each combustion chamber of the engineer is provided with a spark plug 7, which ignites a spark to ignite and burn the air-fuel mixture.

From engine 1, exhaust manifold 8° exhaust duct 9. Exhaust gas is discharged via a three-way catalyst 10 and a muffler 11.

The control unit 12 includes a CPU and a ROM.

It is equipped with a microcomputer including a RAM, an A/D converter, and an input/output interface, and receives input signals from various sensors to control the operation of the fuel injection valve 6 and spark plug 7.

As the various sensors mentioned above, a hot wire type or flap type air flow meter 13 is provided in the intake duct 3, and outputs a voltage signal according to the intake air flow rate Q. In addition, a crank angle sensor 14 is provided, and in the case of a 4-cylinder engine, a reference signal every 180" of crank angle and a crank angle sensor 14 of 1° of crank angle are provided.
Or output a unit signal every 2 degrees. Here, the engine rotation speed N can be calculated by measuring the cycle of the reference signal or the number of unit signals generated within a predetermined time.

Also, the cooling water temperature Tw in the water jacket of the engine 1
A water temperature sensor 15 is provided to detect the water temperature. In this embodiment, since the cooling water temperature Tw is treated as representing the engine temperature, the water temperature sensor 15 corresponds to engine temperature detection means.

Further, a 0□ sensor 16 is provided at the gathering part of the exhaust manifold 8, and detects the air-fuel ratio of the air-fuel mixture taken into the engine 1 via the 0□ concentration in the exhaust gas. The control unit 12, which receives detection signals from the various sensors described above, is configured to receive on/off signals from a starter switch 17.

Here, the CPU of the microcomputer built in the control unit 12 calculates the basic fuel injection amount Tp (valve opening time of the fuel injection valve 6) based on the intake air flow rate Q and the engine speed N detected by the various sensors. ) is calculated, and the basic fuel injection amount Tp
is corrected based on the cooling water temperature Tw and the air-fuel ratio detected by the 02 sensor 16 to determine the final fuel injection amount Tf.
Calculate. Then, a driving pulse signal having a pulse width corresponding to the fuel injection amount Ti is sequentially outputted to the fuel injection valve 6 of each cylinder in synchronization with the intake stroke of each cylinder, and fuel is injected and supplied to each cylinder.

Further, when the starting state of the engine 1 is detected based on the signal from the starter switch 17, the fuel injection amount Ti is not set based on the basic fuel injection amount Tp as described above,
The basic injection amount TsT is set based on the cooling water temperature Tw detected by the water temperature sensor 15, and this is set at the engine speed (
The engine is configured to correct the starting fuel injection amount T based on the cranking rotation speed) and the elapsed starting time. That is, in this embodiment, the control unit 1
2 is an injection amount setting means for starting and an injection amount reduction correction means.

This function also serves as a reduction transition time setting means and a reduction rate regulating means.

The setting control of the starting fuel injection amount Tc will be explained according to the routine shown in the flowchart of FIG.

This routine is executed in response to an ON signal from the starter switch 17, and first, in step 1 (indicated by S in the figure, the same applies hereinafter), the water temperature sensor 15
Read the cooling water temperature Tw detected by .

Then, in the next step 2, based on the cooling water temperature Tw read in step 1, the basic injection amount T at starting is determined from the map.
, T by searching. As shown in the graph in the flowchart, this basic injection amount T, a at startup becomes much larger when the engine is cold, when the atomization of the fuel deteriorates and the liquid fuel flowing along the inner wall of the intake passage (wall flow) increases. This is to prevent the air-fuel ratio from becoming lean when the engine is cold.

In step 3, the engine speed N calculated as described above based on the detection signal from the crank angle sensor 14 is read.

Then, in the next step 4, the rotation speed correction coefficient KNS is calculated from the map based on the engine rotation speed N read in step 3.
, search for. The rotational speed correction coefficient KNST is set to decrease as the rotational speed increases, so as to cope with a decrease in filling efficiency due to an increase in intake pipe negative pressure as the rotational speed increases.

In step 5, the basic injection time LsA is searched and determined based on the cooling water temperature Tw detected by the water temperature sensor 15. This basic injection time tsr indicates a period after starting the engine 1 in which the injection amount determined by the starting basic injection amount TST and the rotation speed correction coefficient 1T is supplied to the engine 1 as is, and is shown in the flowchart. As shown in the graph, the cooling water temperature T that requires a rich mixture for a long time
A longer time is set when w is low, and a shorter time is set when the cooling water temperature Tw is high, so that correction to reduce the starting fuel injection amount Tc is started early.

That is, in this embodiment, when a predetermined period of time elapses after starting, the elapsed time correction coefficient, which will be described later, changes to ! The starting fuel injection amount Tc is gradually reduced by A, but the time until the start of this reduction correction is variably set according to the cooling water temperature Tw.
If the time until the start of reduction correction is set longer as w is lower, the injection amount will not be reduced in the middle of startup during extremely low temperature startup that requires long-term rich mixture supply, thereby preventing deterioration of startability ( In addition, at times other than extremely low temperatures, when starting fails, reduction correction is performed early to avoid deterioration in startability due to continuous supply of excessively rich air-fuel mixture.

In step 6, the elapsed time t after starting the engine is read, and in the next step 7, this elapsed time t is compared with the basic injection time txt searched in step 5, and the basic injection is started after starting. It is determined whether the time tsy has elapsed.

Here, if t, a≧t, and it is determined that it is not time to start the reduction correction of the injection amount after starting the engine, the process proceeds to step 8, and T is set as the elapsed time correction coefficient. The time tK for setting is set to zero, and the elapsed time correction coefficient Kt! ? Prevent the reduction correction of the injection amount from being performed. On the other hand, if tst<t, and it is determined that the elapsed time t from the start of startup exceeds the basic injection time tst, the process proceeds to step 9, where Lst is set to time tx, and time L1 is set to the basic injection time tst. The elapsed time correction coefficient K TST is set in the next step 10 based on this time tK.

In step 10, the elapsed time correction coefficient K Tst is searched from the map based on the time 1K set as described above. As shown in the graph in the flowchart, the elapsed time correction coefficients are set to 1 when time t and K are zero, and gradually become smaller and approach zero as time tK increases. be. Ding to such elapsed time correction factor.

By multiplying the starting basic injection amount T, a by the starting basic injection amount T, the starting fuel injection amount Tc is set to gradually decrease after the basic injection time tsT has passed. In this way, if the starting fuel injection amount Tc is gradually reduced after the basic injection time 11T corresponding to the cooling water temperature Tw has passed, starting failure can be prevented while ensuring the supply of the necessary rich mixture. In some cases, more fuel than necessary is injected and supplied, causing the air-fuel ratio to become overrich, which can prevent startability from worsening.

In the next step 11, based on the cooling water temperature Tw detected by the water temperature sensor 15, the elapsed time correction coefficient KT,
? Find the minimum 4fiKtttxrw from the map. As shown in the graph in the flowchart, this minimum value KTSA, 4.2 is set to a smaller value when the cooling water temperature Tw is low. When the cooling water temperature Tw is low, at which the proportion of fuel (effective injection amount) supplied to the engine 1 as atomized fuel decreases, a larger reduction correction is performed, and the fuel flows along the inner wall of the intake passage and is supplied to the engine 1. While avoiding enrichment of air-fuel ratio due to liquid fuel, cooling water temperature T
When w is relatively high, the ratio of effective injection amount is high, and the amount of liquid fuel (wall flow) is small, the reduction correction factor is lowered to prevent the air-fuel ratio from becoming leaner due to short-term reduction correction and deteriorating startability. did.

In step 12, the elapsed time correction coefficient K r s t set based on the time tx in step 10 is compared with the minimum value KTSTMIN of the elapsed time correction coefficient (tst) set in step 11, and the starting elapsed time is determined. It is determined whether the elapsed time correction coefficient KT!+7 set based on the cooling water temperature Tw is less than or equal to the minimum value Ktsys+,4. □
If it is determined that the elapsed time correction coefficient (txt) is 9, the elapsed time correction coefficient (txt) is set smaller than necessary in step 10, so proceed to step 13 and set the minimum value KTSTi1 to the elapsed time correction coefficient. A. By setting T, the elapsed time correction coefficient K ysT that is smaller than the minimum value KTST□8 is prevented from being set.

In this way, the basic injection amount at startup T ST and the rotation speed correction coefficient KN! When the T I elapsed time correction coefficient is set to □7, the starting fuel injection amount T is calculated according to the following equation.

T (+-T 3t X K sst X K T3T
When the starting fuel injection amount Tc is calculated according to the above formula, a drive pulse signal with a pulse width corresponding to the starting fuel injection amount Tc is output to the fuel injection valve 6.
Fuel is injected from the

As described above, according to the present embodiment, in the starting operation state of the engine 1, the time t corresponding to the cooling water temperature Tw representing the engine temperature after the start of the engine is used without performing the reduction correction by A. The fuel injection amount tT is set, and after the time tsr has elapsed, the starting fuel injection amount 'rc is gradually reduced, and the rate of this reduction is also changed in accordance with the cooling water temperature Tw.

This makes it possible to supply a rich air-fuel mixture for a longer period of time during low-temperature start-up to ensure startability, and to quickly reduce the injection amount when the start-up time is prolonged to prevent starting failures due to over-richness. In addition, when starting at a high temperature, the system shifts to the reduction correction in a short period of time to avoid over-riching when the starting time is prolonged.
By reducing the rate of decrease compared to when the temperature is low, it is possible to prevent the air-fuel ratio from becoming lean due to excessive decrease correction.

Therefore, reliable startability can be ensured while shortening the starting time.

<Effects of the Invention> As explained above, according to the present invention, the time from starting to starting the reduction correction of the starting injection amount;
Since the maximum reduction rate due to this reduction correction is variably set according to the engine temperature, it is possible to ensure a rich mixture supply for a long time during a cryogenic start, while quickly shifting to the reduction correction during a high temperature start. It is possible to avoid enriching the air-fuel ratio when starting fails, and the maximum reduction rate is made larger at low-temperature starts with a lot of wall flow than at high temperatures, and excessive reduction correction is made at high temperatures with little wall flow, resulting in a lean air-fuel ratio. This has the effect of reducing the starting time and ensuring reliable starting.

[Brief explanation of the drawing]

Fig. 1 is a block diagram showing the configuration of the present invention, Fig. 2 is a system schematic diagram of an internal combustion engine showing an embodiment of the invention, and Fig. 3 is a flowchart showing fuel injection amount setting control at startup in the above embodiment. It is. ■...Engine 6...Fuel injection valve 12...Control unit 14...Crank angle sensor 1
5...Water temperature sensor 17...Starter switch patent applicant Fujio Sasashima, agent of Japan Electronics Co., Ltd., patent attorney

Claims (1)

[Scope of Claims] In an electronically controlled fuel injection internal combustion engine configured to drive and control a fuel injection valve on and off according to a fuel injection amount set according to engine operating conditions, the engine is operated at the time of engine startup. a starting injection amount setting means for setting a starting fuel injection amount according to conditions; and a starting fuel injection amount setting means for setting the starting fuel injection amount set by the starting injection amount setting means when a predetermined time has elapsed from the start of engine startup. an injection amount reduction correction means for correcting and gradually decreasing the injection amount; an engine temperature detection means for detecting the engine temperature; a reduction transition time setting means for setting the predetermined time according to the engine temperature; 1. A start control device for an electronically controlled fuel injection internal combustion engine, comprising: a reduction rate regulating means for regulating the maximum reduction rate of the fuel injection amount by the quantity reduction correction means.