JP2002242737A - Engine control device and engine starting method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To swiftly stabilize an idling speed at an engine start, to reduce harmful exhaust gas components, and to reduce a load of a starter during cranking. SOLUTION: An engine control device is provided with a throttle valve 2a adjusting an intake flow rate, an air flow sensor 1 measuring the intake flow rate, an electronic controlled throttle 2 supplying fuel to an engine 7, and an engine control unit 6 taking in a result measured by the air flow sensor 1 and controlling an opening of the throttle valve 2a and a fuel injection quantity from the electronic controlled throttle 2. The engine control unit 6 enlarges the opening of the throttle valve 2a at the engine start wider than an opening during an idle rotation, and when the intake flow rate reaches what is necessary for the idle rotation, it starts to supply the fuel by the electronic controlled throttle 2.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an engine control device and an engine start method with improved engine start.

[0002]

2. Description of the Related Art Japanese Patent Laid-Open No. 10-103128 discloses a first conventional example of starting an engine. In this first conventional example, fuel injection is not performed during the first 1.5 revolutions at the time of starting cranking, and the cylinder that injects fuel as a transition measure is changed according to the number of reference signals up to the first cylinder discrimination signal thereafter. It has been proposed to make a decision and then to transition to normal sequential injection when a reference signal allowing cylinder discrimination is input.

A second prior art example of starting an engine is disclosed in Japanese Patent Application Laid-Open No. H11-182286.
In the second conventional example, the current position is accurately known by satellite communication such as GPS to obtain the altitude of the vehicle, and the fuel injection width and the throttle opening at the time of starting are corrected in accordance with the altitude. Has been proposed.

[0004]

However, in the first prior art of the above prior art, although the fuel injection is performed by determining the intake stroke for each cylinder, the fuel injection is started at the start cranking start. After 1.5 revolutions later, fuel adheres to the intake pipe wall to form a liquid film, and the liquid film is formed as the intake air flow increases with the rapid increase in engine speed after the start of combustion. The fuel that has flowed into the engine causes air-fuel ratio fluctuations. When the air-fuel ratio fluctuates, the engine speed becomes unstable after the start of combustion, that is, the idle speed does not stabilize, causing not only discomfort, but also in the worst case, fuel adheres to the spark plug, causing misfire or engine stop. May lead to

More importantly, the inflow of the liquid film causes the air-fuel ratio to become rich (excessive fuel), and the unburned fuel components such as HC (hydrocarbon), which is a harmful exhaust gas component, may increase. Especially at the time of start, it is considered that the exhaust gas purifying catalyst mounted on the exhaust system has not reached the operating temperature,
There is concern about an increase in HC emissions.

In the second conventional example, the throttle opening is corrected at the time of starting so as to obtain the same air flow rate as at low altitude even at high altitude by obtaining altitude information. The problem of air-fuel ratio fluctuation due to liquid film formation has not been sufficiently studied.

Further, in both of the above conventional examples, the throttle valve opening is fixed at a position corresponding to idle, so that intake resistance (pressure loss) at the time of cranking occurs, and the load on the starter increases. There is a disadvantage that the cranking time becomes longer.

SUMMARY OF THE INVENTION It is an object of the present invention to stabilize the idle speed quickly when starting the engine and to reduce harmful exhaust gas components. Another object of the present invention is to reduce the load on the starter during cranking.

[0009]

In order to solve the above-mentioned problems, an engine control device according to the present invention comprises an adjusting means for adjusting an intake air flow rate of an engine, a measuring means for measuring an intake air flow rate, and supplying fuel to the engine. Fuel supply means, and control means for taking in the result measured by the measurement means and controlling the adjustment means and the fuel supply means.The control means, when starting the engine, when the intake flow rate required for idle rotation is reached. The fuel supply is started by the fuel supply means.

According to the above configuration, the fuel supply is not started from the fuel supply means until the intake air flow required for idling is reached, so that a fuel liquid film is not formed on the wall of the intake pipe, and the combustion is prevented. Air-fuel ratio fluctuations after the start can be suppressed. As a result, it is possible to quickly stabilize the idle speed and reduce the harmful exhaust gas component.

Further, the control means may be so constructed that when the engine is started, when the rotation speed of the engine driven by the starter reaches the idling rotation speed, the fuel supply means starts fuel supply.

Further, the engine control device of the present invention includes a throttle valve for adjusting the intake air flow rate of the engine, a measuring means for measuring the intake air flow rate, a fuel supply means for supplying fuel to the engine, and a result measured by the measuring means. Control means for controlling the opening of the throttle valve and the amount of fuel supplied from the fuel supply means by taking in the throttle valve, when the engine is started, the opening of the throttle valve is made larger than the opening during idle rotation, When the intake air flow required for idle rotation is reached, fuel supply is started by the fuel supply means, and the opening of the throttle valve is reduced to an opening at which the intake air flow required for idle rotation is secured. I have.

According to the above construction, the fuel supply is started by the fuel supply means after the intake air flow required for idling is secured, so that the liquid film of the fuel is formed on the intake pipe wall surface in the same manner as described above. Therefore, fluctuations in the air-fuel ratio after the start of combustion can be suppressed. As a result, it is possible to quickly stabilize the idle speed and reduce the harmful exhaust gas component. Further, in the case of the above configuration, since the opening of the throttle valve is once larger than the opening during idling, the intake resistance can be reduced, and the load on the starter during cranking can be reduced. It is possible.

Further, according to the engine start method of the present invention, when starting the engine, the intake air flow rate of the engine is adjusted,
The fuel supply is started when the intake flow rate reaches an intake flow rate required for idling rotation.

Further, according to the engine starting method of the present invention, when the engine is started, the opening of the throttle valve is made larger than the opening at the time of idling, and the fuel is supplied when the intake air flow required for idling is reached. And the opening degree of the throttle valve is reduced to an opening degree at which an intake air flow required for idling is secured.

[0016]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 shows the overall configuration of an engine control device according to the present invention. As shown in FIG. 1, the engine control device includes an air flow sensor 1 as a means for measuring an intake flow rate, an electronic control throttle 2 as a means for adjusting the intake flow rate, and an injector 3 as a means for supplying fuel to the engine. A starter 4 for driving the engine to rotate, a crank angle sensor 5 for detecting the number of revolutions and the crank angle of the engine 7, receiving signals from the sensors, performing calculations, and outputting signals to the actuator based on the calculation results. An engine control unit 6 for controlling the operating state of the engine 7 and a spark plug 8 for igniting fuel.

The electronic control throttle 2 includes a throttle valve 2a provided in the intake pipe 10, a motor 2b for rotating the throttle valve 2a, and a throttle valve 2a.
A throttle position sensor 2d for detecting the opening of
A throttle controller 2c drives the motor 2b so that the signal from the throttle position sensor 2d is taken in and the opening of the throttle valve 2a becomes the command opening from the control unit 6.

Although not shown, an input section for reading signals from the air flow sensor 1 and the crank angle sensor 5, a ROM in which a calculation method is programmed in advance, and a ROM required for calculation are provided inside the engine control unit 6. A RAM for storing information, a CPU for performing the calculation, and an output unit for outputting a result of the calculation are provided. In the figure,
11 is an exhaust pipe, 12 is a cylinder body, and 13 is a piston.

In the conventional starting method, when the engine is started, the opening of the throttle valve is kept constant, the engine is cranked by a starter, and after reaching a predetermined number of revolutions, fuel is supplied from an injector to spark plug. To start combustion. The predetermined number of revolutions is, for example, about 300 rpm, and is, for example, a number of revolutions lower than the idle speed of about 800 rpm. In such a method, when the fuel injection is started at the time of starting, the air flow does not reach the air flow during idle rotation (less than the intake air flow during idle rotation) because the throttle valve is at a fixed open position, and the air flow is reduced. Because the fuel particles do not follow the fuel, the fuel adheres to the wall surface of the intake pipe and forms a liquid film or a liquid pool. Then, as the number of revolutions increases rapidly after the initial explosion, the intake air flow rate increases, the fuel liquid film flows into the engine, the air-fuel ratio becomes rich, and the unburned gas is discharged as harmful HC.

This will be described in detail with reference to FIGS. 9 and 10. 9 and 10, A is a throttle valve opening, B is an engine speed, C is an intake flow rate, D is a fuel injection amount, E is an air-fuel ratio, and F is a plot of a time course of the exhaust HC amount. It is. During the cranking period (the period is indicated at the top of the figure), the opening of the throttle valve is constant as shown in A. During cranking, the engine speed (B) and the intake flow rate (C) also gradually increase. The fuel starts to be injected from during the cranking, but the fuel flow rate (D) is larger than the required idling amount in consideration of the fuel attached to the intake pipe. The air-fuel ratio (E) is initially lean because the rotation speed is low and fuel does not evaporate and it takes time to form a liquid film, and gradually transitions to rich as evaporation proceeds. Since combustion has not been started, unburned gas is discharged, and therefore the HC amount (F) increases. Thereafter, when the combustion starts, the engine generates torque, so that the engine speed rapidly increases (during B), and the intake air flow rate also increases (during C). Then, the fuel liquid flows into the cylinder from the fuel liquid film due to an increase in the fluid force of the intake air, and the fuel supplied to the engine cylinder increases due to an increase in fuel particles transported by the intake flow and an empty space. The fuel ratio temporarily becomes excessively rich (during E). Therefore, the fuel that has not been consumed in the combustion is discharged as HC (in F). In an extreme case, the spark plug may get wet due to the inflow of the liquid film, causing a misfire without generating a spark and discharging HC.

When the liquid film flows in, the rich engine generates more torque than intended. Therefore, an attempt is made to reach an engine speed higher than the idling speed, and the control works to reduce the fuel amount. At the same time, the excess fuel inflow from the liquid film is reduced, so that the engine speed is lower than the idle speed (for example, a drop of about 100 rpm). Similarly, when the spark plug gets wet or misfires, the rotation speed also decreases. If the adaptation of the engine control device is inappropriate or the change over time is large, hunting such as injecting excessive fuel in order to recover the dropped rotation speed and increasing the rotation speed above the idle speed again May occur.

In any case, HC after the start of combustion
Since the amount is very large and the exhaust gas purifying catalyst has not reached the operating temperature at the time of starting, HC is released to the atmosphere as it is, which adversely affects the environment. Further, it takes a long time to reach a stable idle speed, which gives the vehicle user discomfort. In the worst case, the engine stalls due to misfire.

Therefore, in the present embodiment, the intake flow rate is monitored during cranking at the time of starting, and an operation is performed so as to obtain an intake flow rate corresponding to idle before fuel injection is started. The valve is operated so as to have an idle-equivalent air flow rate. In other words, when the rotation speed during cranking is low, the throttle valve is opened more than the idle opening, and the throttle valve is gradually closed as the cranking rotation speed increases, so that the intake flow rate corresponding to idle is set. And then start fuel injection. As a result, it is possible to prevent a rapid flow of the liquid film of the fuel into the engine, and it is possible to purify the exhaust gas and stabilize the idle speed at an early stage. Further, by opening the throttle valve during cranking, the pressure loss is reduced, the load torque of the starter is reduced, and the cranking rotation speed can be increased and the cranking time can be shortened. At the same time, since the pressure loss of the throttle valve is small, an increase in the intake flow rate can be realized in a short time, and the starting time can be reduced. Note that the electronic control throttle is used here because the opening of the throttle valve can be operated from fully closed to fully open.This is compared to a valve for idle speed control used for idle control.
This is because when opened, the pressure loss can be significantly reduced and the intake flow rate can be freely adjusted.

The above features of the present embodiment will be described in detail with reference to FIGS. After starting cranking,
The intake flow rate (C) increases as the rotation speed (B) increases. This intake flow rate is detected by an air flow sensor.
When the detected intake flow rate is smaller than the idle intake flow rate predicted in advance, the opening of the throttle valve is opened. When the cranking speed increases, the intake flow rate increases, but the opening of the throttle valve is controlled based on the signal of the air flow sensor so that the idle intake flow rate is obtained.
Therefore, the throttle valve performs an operation of gradually closing from an open state after the start of cranking. A shows a state in which the throttle valve is opened at the same time as cranking starts. After the intake flow reaches idle,
Fuel injection is started (D), and combustion is started. At the start of fuel injection, the intake air flow is already large enough, and as a result, the amount of liquid film formed decreases as fuel is carried into the airflow,
The fuel increase correction amount at the time of starting can be reduced. Even if a liquid film is formed, the liquid film is stable because there is no rapid increase in the intake air flow rate after the start of combustion, and it is possible to prevent an excessive liquid film from flowing into the engine. As a result, the variation in the air-fuel ratio is extremely small (E), the amount of HC emission can be reduced (F), and the variation in the number of revolutions after starting is also reduced.

FIG. 2 shows a control block of an engine starting method in the engine control device of the present invention. The engine control device of the present invention, as shown in FIG.
Start determination means A, intake flow rate determination means B, intake flow rate measurement means C, intake flow rate adjustment means D, intake flow rate control means E, fuel supply amount determination means F, fuel supply means G.

The start determination means A determines the start of the start from the driver's operation of the accelerator pedal or the like in a vehicle that performs a start signal of an ignition key or idling stop. The intake air flow determining means B determines an intake air flow required for idling. The intake air flow rate measuring means C includes an air flow sensor or the like, and measures the intake air flow rate. The intake flow rate adjusting means D comprises an electronically controlled throttle or the like, and adjusts the intake flow rate.

The intake air flow control means E is provided in the control unit, and controls the control signal based on information from the intake air flow rate measuring means C and information from the intake air flow rate determining means B. Send to D. The fuel supply amount determining means F is also provided in the control unit, and when the result of the intake flow rate measuring means C becomes equal to the determined value of the intake flow rate determining means B, the start of fuel supply is determined and the fuel supply amount is determined. To determine. The fuel supply means G includes an injector or the like, and actually supplies the fuel.

In the conventional control at the time of starting, the fuel injection is started as short as possible after the intake flow rate is not measured and the signal of the crank angle sensor can be discriminated from the cylinder. Therefore, the amount of fuel is increased more than necessary for idling combustion so that combustion is reliably started with an unknown intake air flow rate, resulting in an increase in HC emission and an increase in fuel consumption.

On the other hand, in the present embodiment, since the air flow rate is detected before the fuel injection and the control is performed so that the required idle air flow rate is attained, the start-up fuel amount is smaller than in the conventional case. Thus, it is possible to prevent deterioration of exhaust gas and reduce fuel consumption. Further, since there is little change in the intake air flow rate before and after the start of combustion, it is possible to shift to smooth and stable idle rotation after cranking.

FIG. 3 shows a control flow from the start of the engine control to the fuel injection in the engine control device of the present invention. First, in this flowchart, in step S1, in a vehicle in which ignition key start or idle stop is performed, the presence or absence of an accelerator pedal operation signal is determined. If the vehicle is starting, the process proceeds to step S2 to determine an idle intake flow rate. If there is no start signal, the process proceeds to the last stage and waits for the start signal again. After determining the idle intake flow rate in step S2, the process proceeds to step S3, where the current intake flow rate is determined. And step S4
Then, the current intake flow rate obtained in step S3 is compared with the idle intake flow rate determined in step S2. If the current intake flow rate is equal to or greater than the idle intake flow rate, the process proceeds to step S5, and the fuel injection amount is reduced. Decide and start fuel injection. If the current intake flow rate is equal to or less than the idle intake flow rate in step S4, the process directly proceeds to step S6. In step S6, a target throttle valve opening is calculated in order to obtain an idle intake flow rate, and based on the result, step S7 is performed.
To actually control the throttle valve.

The idle intake flow rate is determined in advance, the throttle valve opening is operated with the idle intake flow rate as a target value, and fuel injection is started after the idle intake flow rate is reached, whereby fuel adhesion to the intake pipe wall is achieved. The amount can be reduced, and the HC emission can be reduced. In addition, since the throttle valve opening is operated with the idle intake flow rate as a target value, the throttle valve operates from an open position corresponding to the idle intake flow rate to an open position, thereby reducing intake resistance and reducing the load on the starter, Reduction of cranking time,
Higher cranking speed is possible.

FIG. 4 shows a flow for determining the idle intake flow rate. In step S11, the idle speed is determined based on the temperature information from the cooling water temperature sensor and the intake air temperature information from the air flow sensor. Next, proceed to step S12,
The intake flow rate during idling is calculated by multiplying the idling speed by the charging efficiency. The charging efficiency is related to the intake air temperature, and this is shown in FIG. 5 as the relationship between the intake air temperature and the charging efficiency. Although it is best to correct the intake air flow rate for the idle intake air flow rate, the cooling water temperature may be used when information on the intake air temperature cannot be obtained. In such a case, the accuracy decreases due to an increase in the water temperature due to the combustion. Therefore, it is necessary to filter the temperature signal with a low-pass filter or the like.

In the above routine, when calculating the intake flow rate at that time from the idle speed, the charging efficiency of the cylinder is taken into consideration. Therefore, a more accurate idle intake air flow rate can be obtained as compared with a case where the intake air flow rate is simply calculated from the idle speed.

In this case, when obtaining the intake flow rate corresponding to the idle speed, the intake flow rate is calculated from the specified idle speed. However, the intake flow rate is set to about 80% of the specified idle speed. Also, it is possible to reduce the HC and make a transition to a smooth idle.

FIG. 6 shows a processing flow for determining the current intake air flow rate. The output of the air flow sensor using a hot wire or the like to determine the current intake air flow is combined with the response compensation (high-pass), smoothing (low-pass) filter, output of the air flow sensor, and flow characteristics in step S13. It is determined by performing the filtering process.

FIG. 7 shows the contents of the filtering process. First, in step S14, the delay of the airflow sensor is corrected using a phase advance filter. In step S15, the static flow rate output characteristics that have been verified in advance are stored in a map or a function expression, and the flow rate is obtained. However, at the time of starting, fluctuations in the intake air flow are large, so that pulsation is reduced by a low-pass filter in the next step S16.

FIG. 8 shows a flow for determining a target throttle valve opening. In step S17, information on the current intake flow rate and the target idle intake flow rate is obtained, and a target throttle valve opening is determined from the deviation using PID control. Each constant of the PID changes depending on the deviation amount, and is determined from a map of the current opening amount and the deviation.

In this manner, the target value of the throttle valve can be set to a value equal to or larger than the throttle opening required for the actual idling, and if the flow rate increases, the flow rate can be reduced to a value corresponding to the idling. Even after the initial explosion after the initial explosion, the change in the intake air flow rate is small, and it is possible to realize smooth idle, low HC emission, and quick cranking.

In the above embodiment, as shown in FIG. 3, when the current intake flow rate is equal to or more than the idle intake flow rate,
Although the fuel injection amount was determined and the fuel injection was started, when the rotation speed of the engine driven by the starter reached the idle rotation speed, the fuel injection amount was determined and the fuel injection was started. Is also good.

[0040]

As described above, according to the present invention,
Since the intake flow rate and the supplied fuel amount at the time of starting the engine are appropriately controlled, it is possible to reduce the harmful HC component discharged, stabilize the idling speed at an early stage, and improve the fuel efficiency.

[Brief description of the drawings]

FIG. 1 is an overall configuration diagram of an engine control device of the present invention.

FIG. 2 is a control block diagram of an engine starting method in the engine control device of the present invention.

FIG. 3 is a flowchart showing a process from the start of starting to the fuel injection in the engine control device of the present invention.

FIG. 4 is a flowchart for determining an idle intake flow rate.

FIG. 5 is a diagram showing a relationship between intake air temperature and charging efficiency.

FIG. 6 is a flowchart showing a method for calculating a current intake air flow rate.

FIG. 7 is a flowchart illustrating a filtering process.

FIG. 8 is a flowchart for determining a throttle valve opening.

FIG. 9 is a diagram showing a characteristic portion of the engine control device of the present invention in comparison with a conventional example.

FIG. 10 is a view showing a continuation of FIG. 9;

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Air flow sensor 2 Electronically controlled throttle 2a Throttle valve 2b Motor 2c Throttle controller 2d Throttle position sensor 3 Injector 4 Starter 5 Crank angle sensor 6 Engine control unit 7 Engine 8 Spark plug

 ────────────────────────────────────────────────── ─── Continuing from the front page (72) Inventor Masami Nagano 2520 Ojitakaba, Hitachinaka-shi, Ibaraki F-term within the Hitachi, Ltd. Automotive Equipment Group (reference) 3G301 HA01 JA00 JA03 JA07 JA21 JA26 JA34 KA01 KA05 LA01 LB01 MA01 MA12 NA01 NA04 NB07 NC02 ND02 PA04Z PA10Z PA11A PA11Z PB03Z PE03Z

Claims (5)

[Claims] An adjusting means for adjusting an intake air flow rate of an engine; a measuring means for measuring the intake air flow rate; a fuel supply means for supplying fuel to the engine; and the adjusting means taking in a result measured by the measuring means. And control means for controlling the fuel supply means, wherein the control means causes the fuel supply means to start fuel supply when an intake air flow required for idle rotation is reached at the time of engine start. Engine control device. 2. An adjusting means for adjusting an intake air flow rate of an engine, a measuring means for measuring the intake air flow rate, a fuel supply means for supplying fuel to the engine, and the adjusting means taking in a result measured by the measuring means. And a control means for controlling the fuel supply means, wherein the control means supplies fuel from the fuel supply means when the engine starts rotating when the rotation speed of the engine driven by the starter reaches an idle rotation speed. An engine control device characterized by being started. 3. A throttle valve for adjusting an intake air flow rate of an engine, a measuring means for measuring the intake air flow rate, a fuel supply means for supplying fuel to the engine, and a throttle valve for receiving a result measured by the measuring means. Control means for controlling the opening of the throttle valve and the amount of fuel supplied from the fuel supply means, wherein the control means makes the opening of the throttle valve larger than the opening during idle rotation when the engine is started, When the required intake flow rate is reached, fuel supply is started by the fuel supply means, and the opening degree of the throttle valve is reduced to an opening degree at which the intake flow rate required for idle rotation is secured. Engine control device. 4. An engine starting method, comprising: adjusting an intake flow rate of an engine when starting the engine; and starting fuel supply when the intake flow rate reaches an intake flow rate required for idling. . 5. When starting the engine, the opening of the throttle valve is made larger than the opening during idling, fuel supply is started when the intake flow rate required for idling is reached, and An engine starting method, wherein the opening of the throttle valve is reduced to an opening at which a required intake air flow is secured.