JPH0792014B2 - Idle speed control device for internal combustion engine - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to an idle speed control device for an internal combustion engine,
For example, the present invention relates to an idle speed control device for an internal combustion engine of a prospective control system that increases an intake air amount by a predetermined amount when an electric load or the like is applied in a vehicle internal combustion engine or the like.

[Prior Art] In an idle speed control device for an internal combustion engine for a vehicle, which adjusts an intake air amount by a control amount and feedback-controls an idle speed to a target value, electrically detects and detects the input of an electric load or the like. There is known an idle speed control device for an internal combustion engine of a predictive control system which corrects a drop in idle speed due to load application by increasing a control amount by a predetermined amount from the time of load application to increase an intake air amount.

In this type of idle speed control device for an internal combustion engine, for example, if one or more electric loads are frequently interrupted or turned on, the control amount, that is, the intake air amount increases, and the idle speed becomes excessively large. In order to solve this problem, Japanese Unexamined Patent Publication (Kokai) No. 1-187332 provides an upper limit card for the intake air amount when an electric load is applied.

[Problems to be Solved by the Invention] However, in the idle speed control device for an internal combustion engine of the prospective control system that adopts the upper limit guard, it is possible to prevent an excessive increase in the rotation speed above the upper limit guard value, but Excessive rotation speed cannot be prevented. Further, if the upper limit guard value is compressed, a drop in rotation becomes noticeable when a large load is applied. Furthermore, it is not preferable to set the upper limit guard during warm-up operation by setting the upper limit guard value, even though the control amount fluctuates greatly during warm-up operation and the control amount may exceed the upper limit guard value. .

It should be noted that when the load is cut off, the control amount may be simply subtracted by a predetermined amount to reduce the intake air amount to prevent the cumulative increase, but in this case, if the load input time becomes long,
Since the engine speed normally converges to the target speed by the above feedback control, a temporary engine speed drop occurs.

The present invention has been made in view of the above problems, and avoids the above-mentioned drawbacks, and is an idle of an internal combustion engine of a prospective control system capable of preventing a cumulative increase of a control amount despite frequent input of a load input signal. The problem to be solved is to provide a rotation speed control device.

[Means for Solving the Problem] As shown in the claim correspondence diagram of FIG. 5, an idle speed control device for an internal combustion engine of the present invention adjusts the intake air amount by a control amount to set the idle speed to a target value. Feedback control means for feedback control, load applying detection means for electrically detecting load application, control amount incrementing means for increasing the control amount by a predetermined amount at the time of detected load application, and load application time detection Load-on-time detecting means, and load-off-time control amount correcting means having different control amount change characteristics at the time of load cutoff when the load input time is less than or equal to a predetermined characteristic change time and when it exceeds the characteristic change time. It is characterized by having.

In a preferred aspect of the present invention, the control amount correcting means at the time of load cutoff subtracts the control amount by a predetermined decrease amount at the time of load cutoff when the load closing time is equal to or shorter than the characteristic change time. In carrying out this aspect, the control amount correcting means at the time of load shedding is
The control amount value at the time of immediately preceding load application can be stored, and the subtraction can be carried out within a range not lower than the control amount value at the time of immediately preceding load application.

In another preferred aspect of the present invention, the control amount correcting means during load shedding speeds up the responsiveness of the feedback control for a predetermined period from the time point of load application or the time point of load application.

[Operation] The feedback control means adjusts the intake air amount according to the control amount and feedback-controls the idle speed to the target value. The load input detection means electrically detects the load input. The control amount increment means increases the control amount by a predetermined amount at the time when the detected load is applied to increase the intake air amount and correct the drop of the idle speed.

Here, the characteristic operation of the idle speed control device for an internal combustion engine of the present invention is that the load applying time is detected by the load applying time detecting means, and the detected load applying time exceeds or exceeds a predetermined characteristic change time. Based on the above, the control amount correcting means at load shedding changes the control amount changing characteristics at the time of load shedding.

That is, the inventors can prevent the above cumulative increase by reducing the intake air amount by subtracting the control amount by a predetermined amount when the load is cut off. However, in this case, a temporary engine rotation drop occurs when the load input time becomes long. I paid attention to the point that I do. To solve this problem, the load application time is determined, the load application time is compared with a predetermined threshold time (the characteristic change time described above), and the load application time is less than or equal to the predetermined threshold time. Only in this case, it has been noticed that if the control amount when the load is cut off is subtracted by a predetermined amount, the excessive increase in the rotation speed due to the decrease in the intake air amount does not occur.

Therefore, it is preferable that the threshold time is set to be equal to or less than the time when the convergence of the rotation speed by the feedback control is almost completed.

This prevents the control amount at the time of load cutoff from being subtracted by a predetermined amount even if the load application time is long (the rotation speed convergence by the feedback control is almost completed), and the temporary There is no noticeable drop in rotation.

[Embodiment] An embodiment of an idle speed control device for an internal combustion engine of the present invention applied to an internal combustion engine for a vehicle will be described with reference to the drawings.

(Device Configuration) FIG. 1 shows a device configuration of an idle speed control device for an internal combustion engine of this embodiment.

An internal combustion engine (hereinafter referred to as an engine) 1 is a spark ignition type gasoline engine, and an intake pipe 20 thereof is provided with a throttle valve 2 for adjusting an engine torque by adjusting an amount of air taken into the engine 1. There is. Throttle valve 2
A fully closed sensor 2a for detecting the fully closed position is provided.

The intake pipe 20 is a bypass passage that bypasses the throttle valve 2.
A bypass valve 3 having a solenoid valve 21 for idle correction is provided in the bypass passage 21. An air flow meter 4 for detecting the amount of intake air is provided upstream of the throttle valve 2 inside the intake pipe 20. The intake pipe 20 serves as a branch portion 22 (only one is shown) that branches for each cylinder on the downstream side, and each of these branch portions is provided with an electromagnetic injection valve 5 for fuel injection.

On the other hand, the engine 1 is provided with an engine speed sensor 6 that detects an engine speed Ne and a water temperature sensor 7 that detects a cooling water temperature THW of the engine.

Each of these sensors and actuators is connected to an engine control unit (ECU) 8 which is an electronic control unit including a microcomputer and constitutes feedback means in the present invention.

Furthermore, a logical sum signal (hereinafter referred to as an electric load connection / disconnection signal) Se of each connection / disconnection signal indicating the connection / disconnection of various devices (hereinafter, collectively referred to as an electric load) that becomes a load of the alternator such as a headlamp, a defogger, and various electric fans, An OR circuit 9 for synthesizing is provided, and the OR circuit 9 outputs this electric load connection / disconnection signal Se to the ECU 8.

(Operation) The operation of the idle speed control device for the internal combustion engine will be described with reference to the flowcharts of FIGS. 2 and 3.

First, the idle speed control (ISC control) will be described with reference to the flowchart of FIG.

This ISC control is performed as a subroutine of an engine control routine executed by the ECU 8 for a predetermined time (here, 100 m
every sec).

First, in step 100, sensor signals from the various sensors described above are read. In step 110, it is detected from the sensor signals from the fully closed sensor 2a, the engine speed sensor 6 and the like whether or not the engine is idling. Here, if it is not in the idling state, this routine is ended.

On the other hand, if the engine is idling in step 110, the process proceeds to step 120, and the target speed NT
To set. In step 130, prospective control by the electric load is performed. The prospective control in step 130 will be described with reference to the flowchart shown in FIG. Step 13
1 detects whether the electric load is ON. Here, when the electric load is ON, the routine proceeds to step 132, where it is detected whether or not the ON is being recognized. If it is being recognized ON, the prospective control routine is ended.

On the other hand, if it is not recognized to be ON in step 132, that is, if the electric load changes from OFF to ON at this control timing, the process proceeds to step 133. At step 133, the current control amount D is stored as the ON control amount D _ON . In step 134, the control amount D is estimated and controlled. Specifically, in order to prevent the engine speed Ne from decreasing due to the input of the electric load, the expected ON amount D _EON is added to the control amount D so as to increase the intake air amount (D ← + D _EON ). In the following step 135, the predetermined time T is set and the prospective control routine is ended.

On the other hand, if the electric load is OFF in step 131, step 13
Go to 6. In step 136, it is detected whether OFF recognition is in progress.
Here, if OFF recognition is in progress, the prospective control routine ends. If OFF recognition is not being performed in step 136, the process proceeds to step 137. In step 137, it is detected whether or not it is within the time T. If it is not within the time T, the process proceeds to step 13B.

On the other hand, if it is within the time T in step 137, step 138
Go to. A routine for setting the control amount D so that the control amount D (value _obtained by subtracting the OFF expected amount D _EOFF from the control amount D) by the prospective control does not become less than or equal to the stored ON control amount D _{ON in} steps 138 to 13A Is. Specifically, it is detected whether or not the ON control amount D _ON stored in step 138 is larger than the control amount D (= D−D _EOFF ) by the prospective control. Here, the ON control amount D _ON is the control amount D by the prospective control.
In the following cases, the process proceeds to step 139. In step 139, the control amount D is set to a value _obtained by subtracting the expected OFF amount D _EOFF from the control amount D (D ← D−D _EOFF ) and the process proceeds to step 13B.

On the other hand, when the ON control amount D _ON is larger than the control amount D by the prospective control in step 138, the process proceeds to step 13A. In step 13A, set the control amount D to ON and the control amount D _ON (D ← D _ON ),
Go to step 13B. In step 13B, the time T is set and the prospective control routine ends.

Returning to FIG. 2 again, at step 140, the engine speed Ne
Is greater than the target speed NT. If the engine speed Ne is higher than the target speed NT, step 150
Go to. In step 150, it is detected whether or not it is within the time T. Here, if it is not within the time T, the routine proceeds to step 160, where the control amount D is subtracted by the integral amount ΔD (D ← D−Δ
D). If it is within the time T in step 150, the process proceeds to step 170, and a value obtained by multiplying the integrated amount ΔD by a predetermined value (4 in this embodiment) is subtracted from the control amount D (D ← D-4 × Δ).
D).

On the other hand, in step 140, the engine speed Ne is set to the target speed NT.
If smaller, proceed to step 180. In step 180, it is detected whether or not it is within the time T. Here, if it is not within the time T, the routine proceeds to step 190, where the control amount D is the integral amount ΔD.
Only (D ← D + ΔD). If it is within the time T at step 180, the routine proceeds to step 200, where a value obtained by multiplying the control amount D by the predetermined amount (4 in this embodiment) of the integral amount ΔD is added (D ← D + 4 × ΔD).

This completes the ISC control.

In the above flow chart, step 131 constitutes load applying detection means, step 134 constitutes control amount incrementing means, step 137 constitutes load applying time detection time,
Steps 138, 139, and 13A constitute a control amount correction means during load shedding.

As described above, in this embodiment, since the subtraction at the electric load cutoff time is performed only during the electric load ON time within the predetermined time T, the temporary rotation increase at the electric load cutoff time is performed as shown in FIG. Can be suppressed.

Further, by providing the lower limit guard (step 13A), it is possible to prevent the excessive subtraction and the rotation drop due to the excessive subtraction when the ISC control amount is in a decreasing direction such as during engine warm-up.

Further, in this embodiment, the subtraction is performed only within the predetermined time T of the electric load ON time, and the integral constant is set to be large for the predetermined time T after the electric load is turned on and the electric load is cut off. Even if the addition or subtraction of the quantities is a slightly inappropriate value, there is an advantage that the engine speed can be converged to the target idle speed in a short time.

It should be noted that in the present embodiment, the one in which the bypass valve 3 is used for the idle control is disclosed, but it is needless to say that the present invention can be applied to the case where the idle control is performed by the throttle valve 2. Also,
It is also possible to use an intake pressure sensor instead of the air flow meter to detect the intake air amount.

[Effects of the Invention] As described above, according to the present invention, in the idle speed control device for an internal combustion engine of the prospective control method, the load application time is detected by the load application time detection means, and the detected load application time is predetermined. Since the control amount correcting means at load shedding changes the control amount changing characteristics at the time of load shedding, based on whether the characteristic change time is less than or exceeds the characteristic change time, the following effects can be obtained.

That is, when the load application time is short, a predetermined amount of the control amount at the time of the load cutoff is subtracted to prevent a temporary increase in the idle speed, which is an excellent effect.

[Brief description of drawings]

FIG. 1 is a block diagram showing an embodiment of an idle speed control device for an internal combustion engine of the present invention, FIG. 2 is a flow chart showing idle control operation, FIG. 3 is a flow chart showing prospective control, and FIG. A signal waveform (not shown) showing the relationship among the electric load connection / disconnection signal Se, the control amount D, and the engine speed NE in the case of performing the prospective control, FIG. 5 is a claim correspondence diagram. 3 ... Bypass valve (feedback control means) 4 ... Air flow meter (feedback control means) 6 ... Engine speed sensor (feedback control means) 7 ... Water temperature sensor (feedback control means) 8 ... ECU (engine control unit) ) (Feedback control means) (Control amount incrementing means) (Load closing time detecting means) (Load cutoff control amount correcting means) 9 ... OR circuit (load closing detecting means)

Claims (4)

[Claims] 1. A feedback control means for adjusting the intake air amount by a control amount to perform feedback control of an idle speed to a target value, a load closing detection means for electrically detecting a load application, and a load application detection means for detecting a load application. A control amount increment means for increasing the control amount by a predetermined amount; a load closing time detecting means for detecting a load closing time; a case where the load closing time is a predetermined characteristic change time or less and a case where the characteristic change time is exceeded. 2. An idle speed control device for an internal combustion engine, comprising: a load-displacement control amount correction means having different control amount change characteristics at load-disconnection. 2. The control amount correcting means at the time of load cutoff subtracts the control amount by a predetermined reduction amount at the time of load cutoff when the load application time is equal to or less than the characteristic change time. Idle speed control device for internal combustion engine. 3. The control amount correcting means at load cutoff stores the control amount value at the time of immediately preceding load application, and carries out the subtraction within a range not lower than the control amount value at the time of immediately preceding load application. The idle speed control device for an internal combustion engine according to claim 2. 4. The control amount correcting means at the time of load cutoff is for a predetermined high-speed follow-up period from the load application time or the load application time.
The idle speed control device for an internal combustion engine according to claim 1, wherein the response of the feedback control is speeded up.