JP2013209913A - Fuel injection control device of internal combustion engine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a fuel injection control device of an internal combustion engine, the device capable of optimizing an increased amount injection time upon restarting the internal combustion engine after an idling stop, based on the activation of an O2 sensor and thereby, reducing fuel consumption.SOLUTION: A fuel injection control device of an internal combustion engine includes: a means (53) for estimating a restart time O2 sensor temperature, which estimates a restart time O2 sensor temperature (Y) that is an element temperature of an O2 sensor (61) upon restarting the internal combustion engine after an idling stop operation, based on a pre-IS operation state that is an operation state of the internal combustion engine just before the idling stop operation, and based on an idling stop duration time (xe) in an idling stop region (Re); and a means (54) for setting an increased amount injection time, which sets a fuel increased amount injection time (Tr) based on the restart time O2 sensor temperature (Y) estimated by the means (53) for estimating a restart time O2 sensor temperature. The control device controls a fuel injection device (60) to open only during the fuel increased amount injection time (Tr) set by the means (54) for setting the increased amount injection time from a restart time point of the internal combustion engine.

Description

  The present invention relates to a fuel injection control device for an internal combustion engine in a vehicle that performs idle stop control.

  Conventionally, a fuel efficiency improvement technique at the time of restart of an internal combustion engine after an idle stop has been proposed (see, for example, Patent Document 1).

JP 2010-223174 A

  The fuel injection device according to Patent Document 1 optimizes the air-fuel ratio by feeding back the air-fuel ratio detected by the oxygen concentration detected by the heaterless O2 sensor provided in the exhaust system of the internal combustion engine to the fuel injection amount. Feedback control is performed, and the fuel injection amount is determined using an O2 feedback coefficient based on a detection value of the O2 sensor as one parameter.

A method is disclosed in which the value immediately before the idling stop is stored as the O2 feedback coefficient, and the injection amount control is performed with the stored O2 feedback coefficient after performing the increase injection for a predetermined time when the internal combustion engine is restarted. .
According to such control, when the internal combustion engine is restarted, it is possible to return to the O2 feedback coefficient stored in advance, so that it is possible to further reduce fuel consumption.

However, although it has been described that the increase injection time immediately after the restart of the internal combustion engine is set according to the engine water temperature, a specific method is not disclosed.
Although there is a correlation between the engine water temperature (or oil temperature) and the element temperature of the O2 sensor, it does not always correspond one-on-one.

  Therefore, in actuality, rather than setting the boost injection time according to the temperature of the internal combustion engine, the O2 sensor is surely considered in consideration of the possibility that the element temperature of the O2 sensor is inactive during the idle stop. Incremental injection for a certain time (for example, 5 seconds) with a margin to reach the activation temperature has been performed.

This increased injection time is assumed to be a condition in which the actually considered O2 sensor cools down considerably, such as when the idle stop time is very long, and is therefore often too long to be applied during normal idle stop.
Therefore, the control for setting the increased injection time to a certain time is a problem from the viewpoint of reducing fuel consumption.

  The present invention has been made in view of this point, and the object of the present invention is to optimize fuel injection by restarting the internal combustion engine after idling stop based on the activation of the O2 sensor, thereby reducing fuel consumption. The present invention provides a fuel injection control device for an internal combustion engine.

In order to achieve the above object, the invention according to claim 1
A fuel injection device (60) for injecting fuel into an intake system of an internal combustion engine mounted on a vehicle;
An O2 sensor (61) provided in the exhaust system of the internal combustion engine;
Fuel for the internal combustion engine comprising idle stop control means (51) for entering the idle stop control when the predetermined idle stop control condition is satisfied, leading the engine to stop, and restarting the internal combustion engine when the predetermined restart condition is satisfied In the injection control device,
The O2 sensor temperature (Y) at restart, which is the element temperature of the O2 sensor (61) at the time of restart of the internal combustion engine after the idle stop, is the operation state immediately before the IS that is the operation state of the internal combustion engine immediately before entering the idle stop. And a restart O2 sensor temperature estimating means (53) for estimating from the idle stop elapsed time (xe) in the idle stop region (Re),
An increase injection time setting means (54) for setting a fuel increase injection time (Tr) based on the restart O2 sensor temperature (Y) estimated by the restart O2 sensor temperature estimation means (53);
The fuel injection device (60) is controlled to open for the fuel increase injection time (Tr) set by the increase injection time setting means (54) from the restart point of the internal combustion engine to increase the amount of fuel, and then the O2 is injected. A fuel injection control device for an internal combustion engine, which enters O2 feedback control based on an oxygen concentration detected by a sensor (61).

The invention according to claim 2
The fuel injection control device for an internal combustion engine according to claim 1,
The idle stop control means (51)
In the operation state immediately before the IS, by setting the accelerator throttle valve (35v) to the fully closed state from the engine speed higher than the idle speed, a throttle fully closed region (Rbc) for shifting to the idle speed is set.
The restart O2 sensor temperature estimation means (53) estimates the initial O2 sensor initial temperature (a) in the throttle fully closed region from the engine speed immediately before the accelerator throttle valve (35v) is fully closed. The O2 sensor initial temperature (a) is used as an initial temperature, and the O2 sensor temperature (Y) at the time of restart is estimated.

The invention described in claim 3
The fuel injection control device for an internal combustion engine according to claim 1 or 2,
The idle stop control means (51)
A fuel cut region (Rb) in which fuel injection is not performed is set in the throttle fully closed region,
The restart O2 sensor temperature estimation means is:
A temperature drop amount (b · xb) of the O 2 sensor temperature in the fuel cut region (Rb) is estimated from a time width (xb) of the fuel cut region (Rb).

The invention according to claim 4
The fuel injection control device for an internal combustion engine according to claim 3,
The idle stop control means (51)
In the throttle fully closed region (Rbc), a reduction region (Rc) in which the engine speed decreases to an idle speed after the fuel cut is set,
The restart O2 sensor temperature estimation means (53)
The temperature between the FC end temperature, which is the temperature at the end of the fuel cut region (Rb) obtained from the temperature drop (b · xb), and the predetermined idle temperature, which is the convergence temperature at the idle speed of the O2 sensor (61) The decrease temperature gradient (c) of the O2 sensor (61) in the decrease region (Rc) is obtained from the difference (ΔY),
A temperature drop amount (c · xc) of the drop region (Rc) is estimated from a time width (xc) of the drop region (Rc) and the drop temperature gradient (c).

The invention according to claim 5
The fuel injection control device for an internal combustion engine according to claim 4,
The idle stop control means (51)
In the operation state immediately before the IS, after the throttle fully closed region, an idle region (Rd) for a predetermined time and an engine deceleration stop region (Rd ′) in which the engine speed after the idle region (Rd) drops to 0 are set. And
The restart O2 sensor temperature estimation means (53)
A temperature drop amount (d) of the O2 sensor (61) in the idle region (Rd) and the engine deceleration stop region (Rd ′) is estimated.

The invention described in claim 6
The fuel injection control device for an internal combustion engine according to any one of claims 1 to 5, wherein a temperature drop amount of the O2 sensor (61) in the idle stop region (Re) from the idle stop elapsed time (xe). (e · xe) is estimated.

As a result of research, the applicant has found that the heater-less O2 sensor temperature (the element temperature of the O2 sensor) has a one-to-one correspondence with the operating state of the internal combustion engine, except for the peak engine speed range and the idle speed range. I found it in a relationship.
Therefore, according to the fuel injection control device for an internal combustion engine according to claim 1, the temperature of the O2 sensor immediately before entering the idle stop can be estimated from the operation state immediately before the IS that is the operation state of the internal combustion engine immediately before entering the idle stop. If the idle stop elapsed time is taken into consideration from the estimated O2 sensor temperature, the restart O2 sensor temperature (Y) can be estimated with relatively high accuracy.

  By setting the fuel increase injection time (Tr) based on the O2 sensor temperature (Y) at the time of restart, the fuel injection device is controlled to open for the fuel increase injection time (Tr), and the fuel is increased and injected. Since the increase correction until the sensor reaches the activation temperature can be minimized, it is possible to simultaneously return to the O2 feedback control and improve the fuel efficiency.

  According to the fuel injection control device for an internal combustion engine according to claim 2, the engine speed, which is a parameter indicating how many cycles the O2 sensor (61) has been exposed to the exhaust gas per unit time, particularly the accelerator throttle valve (35v) The initial O2 sensor temperature (a) in the throttle fully closed region (Rbc) can be estimated from the engine speed immediately before the engine is fully closed, and the O2 sensor temperature (Y ) Can be guessed.

According to the fuel injection control device for an internal combustion engine according to the third aspect, the idle stop control means (51) sets the fuel cut region (Rb) in which fuel injection is not performed in the throttle fully closed region (Rbc).
In the fuel cut region (Rb), the O2 sensor (61) is exposed to intake air having a temperature substantially equal to the outside air temperature.
Since the temperature of the intake air is much lower than the exhaust gas temperature, the O2 sensor temperature will drop at a stretch in the fuel cut region (Rb).
Therefore, if the temperature drop gradient (b) of the O2 sensor temperature in the fuel cut region (Rb) is obtained through experiments or the like, by measuring the time width (xb) of the fuel cut region (Rb), the fuel cut region (Rb) The amount of temperature decrease (b · xb) of the O2 sensor temperature in the region (Rb) can be accurately estimated.

According to the fuel injection control device for an internal combustion engine according to claim 4, the idle stop control means (51) is provided in the fully closed region of the throttle, in which the engine speed decreases to the idle speed after the fuel cut (Rc ) Is set.
In this decrease region (Rc), the O2 sensor temperature decreases with a gentle gradient, and this gradient changes depending on the temperature difference (ΔY) between the FC end temperature and the idle temperature, which is the O2 sensor temperature immediately after the end of the fuel cut.
Therefore, if the temperature decrease gradient (c) in the decrease region is obtained through experiments, the temperature of the O2 sensor temperature in the decrease region (Rc) is measured by measuring the time width (xc) of the decrease region (Rc). The amount of decrease (c · xc) can be estimated with high accuracy.

According to the fuel injection control device for an internal combustion engine according to claim 5, the idle stop control means (51) has an idle region (Rd) for a predetermined time after the throttle fully closed region and an engine speed after the idle region. The engine deceleration stop area (Rd ') that falls to 0 is set.
The idle region (Rd) and the engine deceleration stop region (Rd ') are not easily affected by the operating state, and the decrease in the O2 sensor temperature is treated as one region. The temperature decrease amount (d) of the O2 sensor temperature in the deceleration stop region (Rd ′) can be obtained, and the temperature decrease amount (d) of the O2 sensor temperature in the idle region (Rd) and the engine deceleration stop region (Rd ′). Can be accurately estimated.

  According to the fuel injection control device for an internal combustion engine according to claim 6, the idle stop elapsed time (xe) is measured if the decrease gradient (e) of the O2 sensor temperature in the idle stop region (Re) is obtained by experiments or the like. By doing so, it is possible to accurately estimate the temperature drop amount (e · xe) of the O2 sensor temperature in the idle stop region (Re).

1 is an overall side view of a motorcycle according to an embodiment of the present invention. It is a simplified system diagram of a fuel injection control device. It is a graph which shows the correspondence of O2 sensor temperature Y at the time of restart, and fuel increase injection time Tr. It is a graph which shows the change of O2 sensor temperature and an engine speed when it enters into an idle stop from one driving state of an internal combustion engine, and is restarted. It is a graph which shows the change of O2 sensor temperature and an engine speed when it enters into an idle stop and restarts from another driving | running state of an internal combustion engine. It is a graph which shows the change of O2 sensor temperature and an engine speed when it enters into an idle stop and restarts from another driving | running state of an internal combustion engine. It is a graph which shows the change of O2 sensor temperature and an engine speed when it enters into an idling stop and restarts from another driving | running state of an internal combustion engine.

Hereinafter, an embodiment according to the present invention will be described with reference to FIGS.
FIG. 1 is a side view of a scooter type motorcycle 1 according to an embodiment to which the present invention is applied.
The vehicle body front portion 2 and the vehicle body rear portion 3 are connected via a low floor portion 4, and the vehicle body frame forming the skeleton of the vehicle body is generally composed of a down tube 6 and a main pipe 7.

  That is, the down tube 6 extends downward from the head pipe 5 at the vehicle body front portion 2, the down tube 6 is bent horizontally at the lower end and extends rearward below the floor portion 4, and a pair of left and right main pipes 7 at the rear end. The main pipe 7 rises diagonally rearward from the connecting portion, bends horizontally at a predetermined height, and extends rearward.

A fuel tank and a storage box are supported by the main pipe 7, and a seat 8 is disposed above the fuel tank and the storage box.
On the other hand, in the vehicle body front portion 2, a steering handle 11 is provided on the upper side and supported by the head pipe 5, a front fork 12 extends downward, and a front wheel 13 is supported on the lower end thereof.
A bracket 15 protrudes near the center of the obliquely inclined portion of the main pipe 7, and the power unit 20 is connected and supported in a swingable manner via a link member 16 pivotally supported by the bracket 15.

  The power unit 20 includes an internal combustion engine 30 at a front portion of a unit case 21, a belt-type continuously variable transmission is disposed from the internal combustion engine 30 to the rear, and a reduction gear mechanism is integrally provided at a rear portion thereof. The output shaft of the gear mechanism is the rear axle, and the rear wheel 17 is attached.

  The power unit 20 has a pair of left and right power unit hangers 21h and 21h projecting forward at the front upper portion of the unit case 21 and connected to the lower end of the link member 16 via a pivot shaft 19. On the other hand, a rear cushion 18 is interposed between the bracket 27 at the rear end of the unit case 21 and the main pipe 7 at the swingable rear portion (see FIG. 1).

  The internal combustion engine 30 is a single-cylinder four-stroke cycle internal combustion engine that protrudes from the front surface of the unit case 21 with the cylinder block 31, the cylinder head 32, and the cylinder head cover 33 stacked substantially forward to a nearly horizontal state. ing.

A throttle body 35 containing an accelerator throttle valve 35v is connected to an intake pipe 34 that extends upward from the upper intake port of the cylinder head 32 and bends backward, and a connecting pipe 36 that extends rearward from the throttle body 35 is a unit. The rear half of the case 21 is connected to an air cleaner 37 disposed along the left side of the rear wheel 17.
Further, an exhaust pipe 38 extending downward from the lower exhaust port of the cylinder head 32 and bent rearward is biased to the right and extends rearward and is connected to a muffler 39 (see FIG. 2) on the right side of the rear wheel 17.

A fuel injection valve 60 is provided in the intake pipe 34 of the internal combustion engine 30 so as to inject fuel into the intake port.
Further, the exhaust port or the exhaust pipe 38 of the internal combustion engine 30 is provided with an O2 sensor 61 that detects the oxygen concentration in the exhaust gas.
The internal combustion engine 30 is controlled by an ECU (engine control unit) 50.
The fuel injection control by the fuel injection valve 60 is also performed by the ECU 50, and a simplified system diagram of this fuel injection control device is shown in FIG.

The ECU 50 enters idle stop control when a predetermined idle stop control condition is satisfied, leads the engine to stop, and restarts the internal combustion engine when a predetermined restart condition is satisfied, and a fuel injection valve 60. Fuel injection control means 52 for driving control is provided.
The fuel injection control means 52 includes a restart O2 sensor temperature estimation means 53 for estimating the restart O2 sensor temperature Y, which is the element temperature of the O2 sensor 61 when the internal combustion engine is restarted after an idle stop, and a fuel increase injection time. Increase injection time setting means 54 for setting Tr is included.

  The ECU 50 includes an oxygen concentration detected from the O2 sensor 61, an engine speed from the engine speed sensor 62, a throttle opening from the throttle opening sensor 63, an intake air temperature from the intake air temperature sensor 64, an engine temperature from the water / oil temperature sensor 65, etc. Is input, the operating state of the internal combustion engine 30 is monitored, and the fuel injection control means 52 performs fuel injection control of the fuel injection valve 60 according to the operating state.

The O2 sensor temperature (the element temperature of the O2 sensor) has a substantially one-to-one correspondence with the operating state of the internal combustion engine, except for the peak engine speed range and the idle range.
The O2 sensor temperature immediately before entering the idling stop can be estimated from the operating state immediately before the IS that is the operating state of the internal combustion engine immediately before entering the idling stop, and if the elapsed idling stop time is considered from the estimated O2 sensor temperature, The restart O2 sensor temperature Y can be estimated with relatively high accuracy.

  If the O2 sensor temperature Y at the time of restart is high, the increased fuel injection amount at the time of restart can be reduced, that is, the fuel increase injection time Tr can be shortened to return to the O2 feedback control at an early stage. If the O2 sensor temperature Y is low, the fuel increase injection time Tr can be lengthened to promote activation of the O2 sensor 61 and return to the O2 feedback control as soon as possible.

Therefore, a correspondence relationship between the restart O2 sensor temperature Y and the fuel increase injection time Tr is obtained in advance by experiments or the like, and a graph of the correspondence relationship is shown in FIG.
The fuel increase injection time Tr changes linearly downward with respect to the restart O2 sensor temperature Y, and the fuel increase injection time Tr decreases as the restart O2 sensor temperature Y increases.
The fuel increase injection time Tr is 5 seconds at the maximum, and when the restart O2 sensor temperature Y exceeds about 320 ° C., the fuel increase injection time Tr is 0 second and the fuel increase injection is not performed at the restart. Immediately, O2 feedback control is entered.

In the following, changes in the O2 sensor temperature and the engine speed when the engine is idled and restarted from various operating states will be described with reference to FIGS.
FIG. 4 shows changes in the O2 sensor temperature and the engine speed when the internal combustion engine is decelerated from when it was operated at a high engine speed and stopped.
In FIG. 4, the change in the O2 sensor temperature is indicated by a solid line, and the change in the engine speed is indicated by a broken line.

The region between t5 and t6 where the engine speed is 0 rpm is the idle stop region Re, and the time point t6 is when the internal combustion engine is restarted.
In the state immediately before the IS, which is the state of operation of the internal combustion engine immediately before entering the idle stop region Re, a throttle fully closed region Rbc that shifts to the idle speed is set by fully closing the accelerator throttle valve 35v.
In FIG. 4, the throttle fully closed region Rbc is between t1 and t3.

The engine speed of the internal combustion engine is a parameter indicating how many cycles the O2 sensor 61 has been exposed to the exhaust gas per unit time. Therefore, the engine speed immediately before the accelerator throttle valve 35v is fully closed (near the time t1). From the number, the O2 sensor initial temperature a that is the O2 sensor temperature in the initial stage (near the time t1) of the throttle fully closed region Rbc can be estimated.
The O2 sensor initial temperature a is the initial temperature when the O2 sensor temperature Y is estimated at restart.
The O2 sensor initial temperature a can be corrected by the intake air temperature. The lower the intake air temperature, the lower the O2 sensor initial temperature a.
The intake air temperature can be detected by an intake air temperature sensor 64 provided in the fuel injection system.

  Note that as the throttle opening increases, the fuel consumption increases and the heat quantity of the exhaust gas also increases. Therefore, the O2 sensor initial temperature a is set to the throttle immediately before the accelerator throttle valve 35v is fully closed (near the time t1). You may make it estimate from an opening degree.

A fuel cut region Rb in which fuel injection is not performed is set in the throttle fully closed region Rbc.
In FIG. 4, the fuel cut region Rb is between t1 and t2.
In the fuel cut region Rb, the O2 sensor (61) is exposed to intake air having a temperature substantially equal to the outside air temperature.
Since the temperature of the intake air is much lower than the exhaust gas temperature, the O2 sensor temperature is lowered at a stretch in the fuel cut region Rb.

Therefore, if the temperature decrease gradient b of the O2 sensor temperature in the fuel cut region Rb is obtained through experiments, the temperature of the O2 sensor temperature in the fuel cut region Rb is measured by measuring the time width xb of the fuel cut region Rb. The amount of decrease can be accurately estimated as b · xb obtained by multiplying the temperature decrease gradient b by the time width xb.
The temperature decrease gradient b can be corrected by the intake air temperature, and the temperature decrease gradient b increases as the intake air temperature decreases.

  Therefore, the FC end temperature, which is the O2 sensor temperature immediately after the end of the fuel cut region Rb, is ab · xb obtained by subtracting the temperature decrease amount b · xb of the O2 sensor temperature in the fuel cut region Rb from the O2 sensor initial temperature a. Can be calculated.

Within the throttle fully closed region Rbc, a reduction region Rc is set in which the engine speed decreases to the idle speed after the fuel cut region Rb.
In FIG. 4, the decrease region Rc is between t2 and t3.

  In this decrease region Rc, the O2 sensor temperature decreases with a gentle gradient, and this gradient c is determined by the FC end temperature ab · xb, which is the O2 sensor temperature immediately after the end of the fuel cut, and the idle temperature Yi (about approximately in the embodiment). It varies depending on the temperature difference ΔY (= ab−xb−Yi).

Therefore, if the temperature decrease gradient c in the decrease region Rc is obtained by experiments or the like, the temperature decrease amount of the O2 sensor temperature in the decrease region Rc can be obtained by measuring the time width xc of the decrease region Rc. It can be accurately estimated as c · xc obtained by multiplying c by the time width xc.
Therefore, the O2 sensor temperature at the end of the decrease region Rc (time point t3) can be calculated as ab · xb−c · xc obtained by subtracting the temperature decrease amount c · xc from the FC end temperature ab · xb.
The temperature decrease gradient c varies depending on the specifications of the internal combustion engine and the complete vehicle.

After the throttle fully closed region Rbc, an idle region Rd for a predetermined time and an engine deceleration stop region Rd ′ where the engine speed after the idle region Rd falls to 0 and enters idle stop are set.
In FIG. 4, the period between t3 and t4 is the idle area Rd, which is determined at a fixed time, and the period between t4 and t5 is the engine deceleration stop area Rd ′.

The engine speed slightly increases in the idle region Rd and decreases to 0 in the engine deceleration stop region Rd ′.
On the other hand, the O2 sensor temperature is substantially maintained in the idle region Rd, and gradually decreases slightly at the end of the idle region Rd and then gradually decreases in the engine deceleration stop region Rd ′. The engine deceleration stop region Rd ′ is a region that is not easily affected by the operating state of the internal combustion engine. Therefore, the idle region Rd and the engine deceleration stop region Rd ′ are treated as one region, and the idle region Rd is experimentally determined for each vehicle. And the temperature drop amount d of the O2 sensor temperature in the engine deceleration stop region Rd ′ can be obtained.

The temperature decrease amount d can be corrected by the intake air temperature, and the temperature decrease gradient b is larger as the intake air temperature is lower.
This temperature drop amount d is an accurate estimated value.
Therefore, the O2 sensor temperature at the end of the engine deceleration stop region Rd ′ (time t5) is obtained by subtracting the temperature decrease amount d from the O2 sensor temperatures ab, xb-c, xc at the end of the decrease region Rc (time t3). It can be calculated as subtracted ab, xb-c, xc-d.

In the idle stop region Re starting from the end of the engine deceleration stop region Rd ′ (at time t5), the O2 sensor temperature decreases with time. Therefore, a decrease e of the O2 sensor temperature in the idle stop region Re is obtained in advance by experiments or the like. Then, by measuring the idle stop elapsed time xe, the temperature decrease amount of the O2 sensor temperature in the idle stop region Re is accurately estimated as e · xe obtained by multiplying the temperature decrease gradient e by the idle stop elapsed time xe. be able to.
The decrease gradient e can be corrected by the intake air temperature. The lower the intake air temperature, the larger the temperature decrease gradient b.

Therefore, the O2 sensor temperature at the end of the idle stop region Re, that is, at the restart of the internal combustion engine (time t6), that is, the O2 sensor temperature Y at the time of restart is the O2 sensor at the end of the engine deceleration stop region Rd ′ (time t5). It can be calculated as ab, xb-c, xc-d-e, xe obtained by subtracting the temperature drop amount e, xe from the temperature ab, xb-c, xc-d.
In other words, the restart O2 sensor temperature Y is calculated as Y = ab, xb-c, xc-d-e, xe, and can be estimated with relatively high accuracy.

In the example shown in FIG. 4, the restart O2 sensor temperature Y is about 360 ° C., which is lower than the idle temperature Yi (about 400 ° C.) but higher than the O2 sensor activation temperature Ya (about 300 ° C.). In light of the graph showing the correspondence relationship between the O2 sensor temperature Y at the time of restart and the fuel increase injection time Tr in FIG. 3, the fuel increase injection time Tr is 0 second. Therefore, when the internal combustion engine is restarted, the fuel increase injection is Without executing, the O2 feedback control is entered immediately.
The restart of the internal combustion engine is executed by the driver performing a throttle operation during idle stop.

FIG. 5 shows changes in the O2 sensor temperature and the engine speed when the internal combustion engine is decelerated from when it was operated at a relatively low engine speed and stopped.
Also at this time, since the idle stop elapsed time xe is short, the restart O2 sensor temperature Y is 390 ° C., which is slightly lower than the idle temperature Yi.
Therefore, in view of the graph of FIG. 3, the fuel increase injection time Tr is 0 second, and the fuel increase injection is not executed when the internal combustion engine is restarted, and the O2 feedback control is immediately started.

FIG. 6 shows changes in the O2 sensor temperature and the engine speed when the internal combustion engine is decelerated and stopped when the internal combustion engine is operated at a relatively low engine speed, as in the case shown in FIG. However, the idle stop elapsed time xe is longer.
Therefore, the O2 sensor temperature Y at the time of restart is further lowered to about 320 ° C.
The restart O2 sensor temperature Y is slightly higher than the O2 sensor activation temperature Ya, and the fuel increase injection time Tr is approximately 0 seconds in light of the graph of FIG. If the sensor temperature is Y, a fuel increase injection time Tr that is not 0 seconds is set.

FIG. 7 shows the example shown in FIG. 6 in which only the idle stop elapsed time xe is extended.
At a certain point in time, the O2 sensor temperature is lower than the O2 sensor activation temperature Ya. For example, if the throttle operation is performed at time t6 shown in FIG. If it is about 200 ° C. and the restart O2 sensor temperature Y is 200 ° C., the fuel increase injection time Tr is set to about 2 seconds in view of the graph of FIG.

Therefore, when the internal combustion engine is restarted, the fuel injection valve 60 is controlled to open for about 2 seconds, which is the fuel increase injection time Tr, and the fuel is increased and injected to promote the activation of the O2 sensor 61. Will enter O2 feedback control based on the oxygen concentration detected.
As described above, since the increase correction until the O2 sensor reaches the activation temperature can be suppressed to the minimum necessary, it is possible to simultaneously return to the O2 feedback control and improve the fuel efficiency.

The decrease gradient e of the O2 sensor temperature in the idle stop region Re is a decrease gradient e1 for each of a case where the length of the idle stop elapsed time xe is a span of several seconds to several tens of seconds, a short case, a medium case, and a long case. , E2, e3 may be obtained.
Note that the relationship is e1>e2> e3.
By using such decreasing gradients e1, e2, and e3, it becomes possible to predict the restarting O2 sensor temperature Y with higher accuracy.

Further, the restart O2 sensor temperature Y may be corrected by the engine temperature.
The engine temperature can be detected by a water temperature / oil temperature sensor 65 provided in the internal combustion engine.

Y ... O2 sensor temperature at restart, Tr ... Fuel increase injection time,
Rbc: Throttle fully closed region, Rb ... Fuel cut region, Rc ... Decrease region, Rd ... Idle region, Rd '... Engine deceleration stop region, Re ... Idle stop region,
30 ... Internal combustion engine, 35 ... Throttle body, 35v ... Accelerator throttle valve,
50 ... ECU, 51 ... Idle stop control means, 52 ... Fuel injection control means, 53 ... Restart O2 sensor temperature estimation means, 54 ... Increase injection time setting means,
60 ... fuel injection valve, 61 ... O2 sensor, 62 ... engine speed sensor, 63 ... throttle opening sensor, 64 ... intake air temperature sensor, 65 ... water temperature / oil temperature sensor.

Claims (6)

A fuel injection device (60) for injecting fuel into an intake system of an internal combustion engine mounted on a vehicle;
An O2 sensor (61) provided in the exhaust system of the internal combustion engine;
Fuel for the internal combustion engine comprising idle stop control means (51) for entering the idle stop control when the predetermined idle stop control condition is satisfied, leading the engine to stop, and restarting the internal combustion engine when the predetermined restart condition is satisfied In the injection control device,
The O2 sensor temperature (Y) at restart, which is the element temperature of the O2 sensor (61) at the time of restart of the internal combustion engine after the idle stop, is the operation state immediately before the IS that is the operation state of the internal combustion engine immediately before entering the idle stop. And a restart O2 sensor temperature estimating means (53) for estimating from the idle stop elapsed time (xe) in the idle stop region (Re),
An increase injection time setting means (54) for setting a fuel increase injection time (Tr) based on the restart O2 sensor temperature (Y) estimated by the restart O2 sensor temperature estimation means (53);
The fuel injection device (60) is controlled to open for the fuel increase injection time (Tr) set by the increase injection time setting means (54) from the restart point of the internal combustion engine to increase the amount of fuel, and then the O2 is injected. A fuel injection control device for an internal combustion engine, which enters O2 feedback control based on an oxygen concentration detected by a sensor (61). The idle stop control means (51)
In the operation state immediately before the IS, by setting the accelerator throttle valve (35v) to the fully closed state from the engine speed higher than the idle speed, a throttle fully closed region (Rbc) for shifting to the idle speed is set.
The restart O2 sensor temperature estimation means (53) estimates the initial O2 sensor initial temperature (a) in the throttle fully closed region from the engine speed immediately before the accelerator throttle valve (35v) is fully closed. The fuel injection control apparatus for an internal combustion engine according to claim 1, wherein the O2 sensor initial temperature (a) is used as an initial temperature to estimate the restart O2 sensor temperature (Y). The idle stop control means (51)
A fuel cut region (Rb) in which fuel injection is not performed is set in the throttle fully closed region,
The restart O2 sensor temperature estimation means is:
The temperature drop amount (b · xb) of the O2 sensor temperature in the fuel cut region (Rb) is estimated from the time width (xb) of the fuel cut region (Rb). Fuel injection control device for internal combustion engine. The idle stop control means (51)
In the throttle fully closed region (Rbc), a reduction region (Rc) in which the engine speed decreases to an idle speed after the fuel cut is set,
The restart O2 sensor temperature estimation means (53)
The temperature between the FC end temperature, which is the temperature at the end of the fuel cut region (Rb) obtained from the temperature drop (b · xb), and the predetermined idle temperature, which is the convergence temperature at the idle speed of the O2 sensor (61) The decrease temperature gradient (c) of the O2 sensor (61) in the decrease region (Rc) is obtained from the difference (ΔY),
The internal combustion engine according to claim 3, wherein the temperature reduction amount (c · xc) of the reduction region (Rc) is estimated from the time width (xc) of the reduction region (Rc) and the decrease temperature gradient (c). Engine fuel injection control device. The idle stop control means (51)
In the operation state immediately before the IS, after the throttle fully closed region, an idle region (Rd) for a predetermined time and an engine deceleration stop region (Rd ′) in which the engine speed after the idle region (Rd) drops to 0 are set. And
The restart O2 sensor temperature estimation means (53)
The fuel injection control device for an internal combustion engine according to claim 4, wherein a temperature drop amount (d) of the O2 sensor (61) in the idle region (Rd) and the engine deceleration stop region (Rd ') is estimated. .   The temperature drop amount (e · xe) of the O2 sensor (61) in the idle stop region (Re) is estimated from the idle stop elapsed time (xe). A fuel injection control device for an internal combustion engine according to claim 1.

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