JPH09264178A - Rotating speed control device for engine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To solve the instability by individual difference of an air supplying system just after starting, and quickly perform the blowing-up of an engine by feedback controlling the engine rotating speed just after the start of the engine, and limiting the feedback control after air increase correction is started. SOLUTION: When an ignition switch is on, whether the engine rotating speed exceeds, for example, 500rmp or not is checked in an ISC control device 8, and when it is 500rpm or less just after starting, an opening control signal is calculated on the basis of a correction variable for ISC feedback control and a correction variable for air increase correction to control an ISC valve 7. Thereafter, when the engine rotating speed rises and exceeds 500rpm, ISC feedback control is stopped, and air increase correction is started. When the engine rotating speed once exceeds 500rmp and reaches self-excited rotating state, the air increase correction is performed as the feedback control is stopped to ensure the blowing-up.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a control device for controlling an engine rotation speed when starting an engine, and more particularly to improving stability of engine rotation at an initial stage of starting the engine.

[0002]

2. Description of the Related Art Generally, when the engine is idling, the rotation of the engine becomes unstable, which makes it difficult to control the throttle valve. , "ISC valve") is provided, and the number of revolutions during idling is controlled by controlling the opening of this valve.

When the engine is idling when starting,
Rotation tends to be more unstable than normal idling. In order to eliminate this instability, the amount of air supplied should be increased when starting the engine (hereinafter referred to as "air increase correction").
This is done by gradually decreasing this amount of increase over time.

On the other hand, the control of the idle speed during engine start is usually performed by feedback correction based on the deviation of the speed from the target speed or the deviation of the air amount from the target air amount for obtaining the target speed. ing. Since the engine rotation is particularly unstable during idling when starting the engine as described above, the idling speed feedback control (hereinafter referred to as "ISC
It is normal not to perform "feedback control").

In a conventional engine control device for performing air amount increase correction and ISC feedback control, such as Japanese Patent Laid-Open No. 1-318738, for example, ISC feedback control and post-start air amount increase correction are harmonized to reduce engine rotation. For the purpose of preventing it, the ISC feedback control is limited until the air increase correction is started after the start. Specifically, the valve opening degree of the ISC until the air amount increase correction is started is the air amount determined by the low engine water temperature at the start.

[0006]

However, although the air amount increase correction is effective during the period in which the engine speed is rising at the time of idling, in actual engines, there are variations in the flow passages and valves, and therefore, especially during start-up. The inventors found that in the early stage, the rotation cannot be stabilized by limiting the ISC feedback control and simply performing the air amount increase correction.

Therefore, the present invention has been made in view of the above problems of the prior art, and an object thereof is to provide an engine rotational speed control device which achieves both stability at the time of starting and improvement of the starting property. It is a thing.

[0008]

In order to achieve the above object, a rotation speed control device of the present invention for controlling an engine rotation speed in a starting period includes a feedback means for feedback controlling an engine rotation speed, and the feedback means. The feedback control means is executed in a first period from the start of cranking until a predetermined engine speed is reached and the engine is in a self-excited rotation state, and thereafter the engine is controlled. And a control means for limiting the feedback control by the feedback means in the second period in which the rotation speed is high.

During the period immediately after the engine is started, the engine speed is controlled by feedback control, so instability due to individual differences in the air supply system and the like is eliminated. Further, in particular, the increase correction effect of the feedback control promotes the increase in rotation, so that the engine is quickly blown up and warming up is performed in a short period of time. Further, when the feedback control is limited, the reduction correction of the feedback control is limited, which contributes to the stability of rotation.

In order to achieve the same object, an engine rotational speed control device of another structure of the present invention, which performs air amount increase correction after complete explosion of the engine, starts the air amount increase correction control during a starting period. Until then, the idle speed of the engine is feedback-controlled, and the feedback control of the idle speed of the engine is limited after the air increase correction control is started.

According to the control device having this structure, the engine speed is controlled by the feedback control during the period immediately after the starting, so that the instability due to the individual difference of the air supply system is eliminated and the air amount increase correction is started. After that, feedback control is limited, so the engine blows up quickly and warm-up is performed in a short period of time. According to a preferred aspect of the present invention, the engine rotation speed at which the engine is in the self-excited rotation state is set to be lower than the feedback target rotation speed and higher than the cranking rotation speed.

According to a preferred aspect of the present invention, the engine speed in the self-excited rotation state is set to a speed near the feedback target speed. According to a preferred aspect of the present invention, the feedback control is stopped and the air increase correction control is started substantially at the same time. According to a preferred aspect of the present invention, the air increase correction control is started before the feedback control is stopped, and then the feedback control is stopped, thereby providing a period in which the both controls are overlapped. .

According to a preferred aspect of the present invention, the feedback control is restarted after the end of the air increase correction control. According to a preferred aspect of the present invention, fuel correction control is performed corresponding to the feedback control of the engine speed. This is to eliminate an unexpected air lean state associated with the feedback control.

[0014]

Embodiments of the present invention will be described below in detail with reference to the accompanying drawings. FIG. 1 is a diagram showing a configuration of an engine and an air supply system according to one embodiment to which the present invention is applied. A throttle valve 3 is provided in an air supply passage 2 of the engine 1, and an air flow meter 4 for detecting an intake air amount is provided upstream of the throttle valve 3. The upstream side of the meter 4 is connected to the air cleaner 5. Throttle valve 3
Is provided with a bypass air supply passage 6 communicating between the upstream side and the downstream side, and the ISC valve 7 for adjusting the amount of bypass air and controlling the idle speed is provided in the bypass air supply passage 6. There is. The ISC valve 7 is an ISC control device (hereinafter,
(Hereinafter referred to as "CU") 8 control signal. C
U8 includes an intake air amount signal, an idle switch signal from an idle switch 9 attached to the throttle valve 3, an output signal of a rotation sensor 10 for detecting the engine speed, and a water temperature sensor for detecting the temperature of engine cooling water. 11 output signals and the like are input.

The CU 8 calculates the opening control signal C according to the following equation in order to control the opening of the control valve 7. C _B = 1 + C _efb + C _esw (1) Here, C _efb is a correction variable for ISC feedback control, and C _esw is a correction variable for air increase correction. The feedback correction variable C _efb is forcibly set to 0 when the engine speed N _e is N _e ≧ 500 rpm and the correction variable C _esw is not zero (that is, when the air increase correction is being performed). At other times, it is calculated by C _efb = k ₁ × (N _T −N _e ) ... (2). Here, k ₁ is a predetermined constant and N _T is an idle target rotation speed.

Further, a correction variable C for correcting the air amount increase
_esw is the value when it is determined that the engine has completed starting, that is, when N _e exceeds 500 rpm, or N _e ≧ N _T
Is set to an initial value C ₀ (T _W ) determined according to the engine water temperature T _W , and thereafter, is _{gradually reduced} by C _esw = C _esw −Δ (Δ is a positive constant) (3). It When the correction variable is determined according to the equation 1, the CU 8 converts this C _B into the opening ratio of the control valve 7,
The control valve 7 is opened at this opening ratio. When the control valve 7 is opened at this opening ratio, air corresponding to the opening ratio flows into the combustion chamber of the engine through the flow passage 6. This air amount is detected by the meter, and the CU 8 calculates the fuel injection amount. Injection amount τ
Is calculated as the valve opening time of the fuel injection valve, and τ = k × (Q / N _e ) × (1 + C _W ) ... (4) Here, C _W is a correction coefficient based on the water temperature or the like. In this way, fuel injection matching the opening degree of the control valve 7 is performed and the idle rotation speed is controlled.

An outline of control by the CU 8 of this embodiment will be described with reference to FIG. In FIG. 2, from the top, the idle switch signal, the ignition start signal, the actual engine speed signal N _e , the air increase correction variable C _esw , the feedback correction variable C _efb , and the opening of the control valve 7. When the start key is pressed, the start signal is turned on for a fixed time T ₁ . During this period, the engine is rotated by the starter motor, so the engine speed N _e cannot rise to the motor rotation speed. As described above, the CU 8 performs the ISC feedback control and does not perform the air amount increase correction before the engine is in the start completion state. Therefore, the period T ₁
Then, C _efb is calculated according to Equation 2, while C _esw = 0 ... (5).

When the start signal is turned off, the engine tries to blow up by itself (period T ₂ ). As described above, the engine start completion state is determined, for example, when the engine speed reaches 500 rpm.
This time is t ₁ . Then, during the period T ₁ + T ₂ , the feedback control is performed with respect to the engine speed. Therefore, during that period, it is guaranteed that the most suitable air amount is supplied to the engine, and The rotation state is also stabilized. As a result, a stable rotation state can be obtained even if there are variations in the air supply system of the engine.

In the present embodiment, when the engine is in the start-up completed state, the engine is capable of self-excited rotation. Therefore, in order to improve the blowing, feedback control is stopped after time t ₁ and variable C _Perform air amount increase correction according to _esw . As described in Equation 3, the variable C _esw gradually decreases. This is because the engine gradually warms up. Variable C
_When the value of _esw becomes zero (time t ₂ ), the air increase correction is stopped and the feedback control is restarted. Time t ₂
After that, the feedback toward the target rotational speed N _T is performed according to the equation 2.

The control procedure of the embodiment will be described in detail below. The flowchart of FIG. 3 shows the control procedure of the CU 8. In step S2, it is detected that the ignition switch is changed from OFF to ON. If this change is made, the variables C _efb and C _{e sw} are initialized in step S4. Also in step S6, a "correction flag" indicating that the air increase correction at the time of engine start is being executed.
In addition, a "restart flag" indicating that the feedback control has been restarted is initialized.

At step S8, the idle switch is turned on.
After confirming the N state, the so-called ISC control of steps S10 to S14 is performed. That is, step S1
0, the correction coefficient C is calculated according to Equation 1, and step S
This coefficient C is converted into a duty ratio in 12 and output to the valve 7 in step S14. The CU 8 also executes the control procedure of FIG. 4 independently of the control procedure of FIG.

That is, in step S20, it is confirmed that the idle switch is turned on, and in step S22 it is checked whether the engine speed N _e exceeds 500 rpm. Since it is 500 rpm or less immediately after the start, the process proceeds to step S24, and after confirming that the correction flag is reset to confirm that the air increase correction is not performed, the variable C is calculated according to the equation 2 in step S26. _{Calculate efb} . The value of the variable C _efb calculated in step S26 is reflected in step S10 of FIG. 3 to calculate the correction coefficient C. Since the air increase correction variable C _esw is reset in step S4, C _esw = 0 as long as the engine speed N _e is 500 rpm or less, and therefore the valve 7 in steps S10 to S14 is set.
The control of is a control according to the feedback, and the air increase correction is not performed.

When the engine speed increases and exceeds 500 rpm, the determination in step S22 becomes YES and the process proceeds to step S30. In step S30, it is confirmed that the flag "restart flag" indicating that the feedback control is restarted is not set, and the process proceeds to step S32. In step S32, after confirming that the correction flag is reset, the process proceeds to step S34, and the "correction flag" is set to 1 in order to store that the air amount increase correction at the time of engine start is started. In step S36, the engine water temperature T _W is detected, a constant C ₀ suitable for the temperature is obtained, and in step S38 this C ₀ is _{set as} the initial value of the variable C _esw . In step S40, the feedback variable C _efb is reset.

Thus, the ISC feedback control was stopped and the air amount increase correction was started. Once the engine speed exceeds 500 rpm and reaches the self-excited rotation state, it is better to perform the air amount increase correction and secure the blow-up after that, while the feedback control is stopped. Therefore, after the "correction flag" is set, while the engine speed N _ep exceeds 500 rpm, the process proceeds to step S30 → step S32 → step S50 → step S52, and at step S52, the air increase correction variable is set. C
_Esw is gradually _reduced according to Equation 3. Alternatively, as long as the “correction flag” is set (NO determination in step S24) even if it is temporarily reduced to less than 500 rpm, step S
50 → Proceeds to step S52, and increases air amount correction variable C
_Esw is gradually _reduced according to Equation 3.

Thus, the air increase correction is continuously performed until the value of the variable C _esw becomes zero (determination of C _YES = 0 in step S50). When it is detected in step S50 that the value of the variable C _esw has become zero, the “correction flag” is reset in step S54 in order to store that the air increase correction has been completed, and instead, the feedback control is restarted. A "resume flag" is set in step S56 to store what should be done.

As long as the "correction flag" is reset and the "restart flag" is set, step S24 → step S26 or step S30 → step S2.
6, the feedback control according to the equation 2 is restarted. Immediately after the engine is started, the ISC control device of the embodiment described above performs rotation speed feedback control to ensure rotation stability, and if the engine is in the self-excited rotation state, that is, the completion of start is confirmed. , Air increase correction (C
_esw ) is performed to ensure good blow-up, and when the warm-up state is reached (C _esw = 0), feedback control is restarted to ensure stability of engine speed.

A modification of the above embodiment will be proposed below. If the ISC feedback control is performed immediately after the start as in the above embodiment, the air-fuel ratio may shift to the lean side. This is because it takes time for the air flow sensor to normally measure the amount of air. That is, if the ISC feedback control controls the control valve 7 in the direction to increase the air amount, the actually increased air amount is measured by the sensor as the air amount Q which is smaller than the actual air amount. The small signal Q is input to the CU 8 and the small fuel injection amount is determined according to the equation 4.

In order to solve this problem, equation 4 is modified as follows. τ = k × (Q / N _e ) × (1 + C _W + K × C _efb ) (6) That is, the constant K that corrects the fuel injection amount based on the feedback correction variable C _efb is a positive constant. Therefore, in this fuel correction, if the correction variable C _efb is positive (the feedback correction is increasing), the fuel injection amount is increased,
Correction variable C _efb is negative (feedback correction is decreasing)
If so, the fuel injection amount is reduced, and an excessive lean state or rich state is eliminated.

The second modification is to eliminate the control discontinuity that may occur when the ISC feedback control is stopped and the air increase correction control is started at the same time. That is, in FIG. 2, time t ₁
Then, the stop of the ISC feedback control and the start of the air amount increase correction control occur at the same time. This simultaneous occurrence serves as a basis for causing the actual opening of the ISC control valve 7 to lose smoothness.
Therefore, as shown in FIG. 5, the stop of the ISC feedback control is delayed. If the stop of the feedback control is delayed, there is a period in which the ISC feedback control and the air amount increase correction control coexist, and this coexistence produces smoothness.

Further, in the above embodiment, the ISC feedback control is explained by setting the feedback to the target rotation speed, but it goes without saying that it can be applied to the rotation speed control by the feedback control to the target air amount.

[0031]

As described above, according to the engine rotational speed control device of the present invention, it is possible to achieve both stability of rotation and warm-up for a short period of time when the engine is started.

[Brief description of drawings]

FIG. 1 is a diagram showing an ISC system configuration of a preferred embodiment to which the present invention is applied.

FIG. 2 is a timing chart showing the operation of this embodiment.

FIG. 3 is a flowchart showing a control procedure of the embodiment.

FIG. 4 is a flowchart showing a control procedure of the embodiment.

FIG. 5 is a diagram illustrating control according to a modified example.

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification code Office reference number FI technical display location F02D 45/00 322 F02D 45/00 322F

Claims (8)

[Claims] 1. A rotation speed control device for controlling an engine speed during a starting period, comprising feedback means for feedback-controlling an engine rotation speed, and control means for controlling the feedback means,
The feedback control means is executed in the first period from the start of cranking until the engine reaches the self-excited rotation state after reaching the predetermined engine speed, and thereafter in the second period when the engine speed is high. And a control unit for limiting feedback control by the feedback unit. 2. A rotation speed control device for an engine, which performs an air amount increase correction after a complete explosion of the engine, wherein an idle speed of the engine is feedback controlled until a start of the air amount increase correction control. An engine speed control device for an engine, wherein the feedback control of the engine idle speed is limited after the air increase correction control is started. 3. The engine speed when the engine is in the self-excited rotation state is set to be lower than the feedback target rotation speed in the first period and higher than the cranking rotation speed. The engine rotation speed control device according to. 4. The engine speed control device according to claim 1, wherein the engine speed reaches a speed near a feedback target speed in the self-excited rotation state. 5. The engine rotation speed control device according to claim 4, wherein the limitation of the feedback control and the start of the air increase correction control are performed substantially at the same time. 6. The engine rotation speed control device according to claim 4, wherein the air amount increase correction control is started before the limitation of the feedback control and the feedback control is stopped after that. 7. The feedback control is restarted after the end of the air amount increase correction control.
7. The engine rotation speed control device according to any one of 1 to 6. 8. The engine rotation speed control device according to claim 1, wherein fuel correction control is performed corresponding to the feedback control of the engine speed.