JP3178878B2 - Idle speed control method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an idle speed control method for an engine, and more particularly to a method for improving the convergence of the engine speed to a target idle speed when the engine speed is increased by idle-up control. ,
The present invention relates to an idle speed control method.

[0002]

2. Description of the Related Art Conventionally, when there is a load fluctuation on an engine such as when an air conditioner (A / C) changes from off to on, for example, in order to prevent engine stall due to the load fluctuation and the like, a certain amount of idle rotation Prospective control (idle-up control) for increasing the number is performed. In this way, for example, when the air conditioner (A / C) changes from off to on, etc., other load conditions at that time (for example, the state of a neutral switch in an automatic vehicle (differs depending on the neutral state or the drive state) or A certain amount of DAC according to the current state of the electric load) and the current bypass opening (the opening of the ISC valve provided to bypass the throttle valve) DU
After the idle-up control is performed, the absolute value | NE-NT of the difference between the engine speed NE and the theoretical target idle speed NT at that time is performed. | According to the DUT
So-called feedback control for calculating Y is performed.

However, when the air conditioner or the like is turned on, for example, a valve switching valve VSV (a bypass valve for idling up) provided in the air conditioner is used.
And the like, the engine speed NE rises considerably, and the convergence to the target idle speed NT becomes considerably poor. FIG. 5 is a timing chart showing the convergence state of the engine speed NE in the case of the above-mentioned prior art, and shows the bypass opening (ISC valve opening) when the air conditioner (A / C) is switched from off to on. When the fixed amount DAC is added to DUTY, the engine speed NE significantly increases from the target idle speed NT at that time, and the engine speed NE converges to the target speed NT only by the feedback control. It has been shown that it takes a considerable amount of time to complete the operation, and there have been problems in terms of fuel efficiency and feeling for the driver.

[0004]

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned problem, and it is possible to prevent an unnecessary increase in idle speed from continuing more than a required time during the idle-up control. This not only improves fuel efficiency, but also eliminates discomfort to the driver.

[0005]

According to the present invention, there is provided an engine for controlling an engine idle speed.
, In the idle speed control method to be plus a constant amount DAC bypass opening of the throttle valve when the load change for the engine is detected, the slot
By adding a fixed amount to the bypass opening of the valve
Difference between increased engine speed and target idle speed |
NE-NT | when the was continued at and fixed time above a certain value, then until the difference both said speed becomes smaller than the predetermined value, the not a predetermined attenuation amount ΔDTY the bypass opening DUTY <br / The present invention provides an idle speed control method characterized in that the idle speed is reduced stepwise.

The amount of attenuation may be changed according to the temperature of the cooling water or the temperature of the intake air of the engine, and the amount of attenuation may be increased as the temperature of the cooling water or the temperature of the intake air is lower.

[0007]

According to the above configuration, after a certain period of time has elapsed after a load change has occurred (for example, after the air conditioner has been turned on), it is considered that there is no risk of engine stall. If | NE-NT | is a predetermined value or more, the attenuation of the bypass opening is increased (that is, the bypass opening DUTY is reduced stepwise by a predetermined attenuation (a fixed opening) ΔDTY). The target idle speed NT of the engine speed NE.
(I.e., converge to the target rotational speed NT in a shorter time).

The damping amount is changed in accordance with the cooling water temperature or the intake air temperature of the engine, and the lower the cooling water temperature or the intake air temperature, the greater the damping amount.
A constant convergence speed can be realized irrespective of the cooling water temperature or the intake air temperature.

[0009]

FIG. 1 is a flowchart showing a processing procedure of an idle speed control method according to one embodiment of the present invention. First, in step 1, it is determined whether or not the above-described load fluctuation on the engine has occurred. . If the answer is yes (that is, if the load of the air conditioner or the like is turned on from off), in step 2, CLOAD (a counter that is reset when the load is turned on and that is automatically incremented every fixed time thereafter) is reset. Is done.
At this time, as described above, the bypass opening DUTY
Is increased by a constant amount (so-called idle-up control is performed), and the engine speed NE rises considerably from the theoretical target idle speed NT at that time, as in the above-described conventional case.

Next, in step 3, the CLOAD
Based on the value, whether when a said load change has passed a predetermined time above T ₁ from (i.e. CLOAD is when reset) is determined. If the answer is YES, the engine speed NE and the target speed NT after the lapse of the predetermined time T ₁ or more in step 4.
NE-NT | | is whether a certain value N ₁ or more is determined difference between. And if yes, that is, when the difference between the both rotation speed becomes a constant value N ₁ or more, predetermined attenuation amount from the current of the bypass opening (ISC valve opening degree) DUTY proceeds to step 5 DerutaDTY Is set as a new bypass opening DUTY. If the determination in step 3 is a know-how (the above-mentioned fixed time T ₁
If the elapsed before) or the determination in step 4 of a know (that is, when the difference between the rotational speed is smaller than a predetermined value N _1), the normal feedback control described above it is made the routine proceeds to step 6.

According to an embodiment of the way the present invention, as shown in FIG. 4, after a predetermined time T ₁ from a load variation has elapsed, even the engine rotational speed NE and該理Theory target The difference from the idle speed NT is the above-mentioned constant value N ₁
When it is equal to or more than the above, the difference between the two rotation speeds is
From ₁ until the small (i.e. during the period T ₂ of the FIG. 4),
At each operation timing, the bypass opening DUTY is reduced stepwise by a predetermined amount of attenuation ΔDTY sequentially (that is, the bypass opening is reduced stepwise by a constant opening ΔDTY to reduce the attenuation of the difference value). Hasten). As a result, as shown in FIG. 4, the period T during which the attenuation amount ΔDTY is added as an amount of decrease in the bypass opening degree.
_{In 2} , the descending gradient of the bypass opening DUTY is increased compared to the other periods (that is, the period during which the normal feedback control is performed) (actually, the value of the bypass opening during this period is , At each operation timing, the above-mentioned ΔDTY is gradually lowered.)

As a result, as shown in FIG. 4, the engine speed NE converges to the target idle speed NT in a shorter time than in the case of the prior art shown in FIG. The convergence can be improved. Incidentally perform plus from the predetermined time T ₁ from the load change occurs elapsed attenuation as described above, after the said time has elapsed as described above, performed plus such attenuation also because is deemed to no longer a risk of engine stall, the time T ₁ is set in consideration of this fact.

In the above embodiment, a constant value is set as the attenuation amount ΔDTY. Instead, the attenuation amount ΔDTY is changed according to the temperature of the engine coolant or the temperature of the intake air of the engine. Is also good. That is, the amount of overshoot and the convergence speed of the engine speed at the time of idling-up differ depending on the cooling water temperature and the intake air temperature. As the cooling water temperature and the intake air temperature are lower, the target idle speed NT (Usually, after the warm-up, the target idle speed is set to, for example, 700 rpm. However, when the cooling water temperature or the intake air temperature is low, that is, before the warm-up, the target idle speed NT is increased. Higher than the value after warm-up)
During such a cold period, the amount of increase in the engine speed NE during the idle-up is also increased.

Therefore, as exemplified in the map of FIG. 2, by setting the attenuation amount ΔDTY in step 5 of FIG. 1 to be larger as the coolant temperature of the engine becomes lower, The convergence speed is increased, so that the engine speed NE can converge to the target speed NT at a constant convergence speed regardless of the level of the cooling water temperature.

Further, as illustrated in the map of FIG. 3, as the intake air temperature of the engine decreases, the attenuation ΔDTY in step 5 of FIG. The convergence speed at that time is increased, so that the engine speed NE can converge to the target speed NT at a constant convergence speed regardless of the level of the intake air temperature.

[0016]

According to the present invention, when the idle speed is increased by a certain amount at the time of a load change, the increase of the idle speed is prevented from continuing more than a required time.
By improving the convergence to the target idle speed, fuel efficiency can be improved and discomfort to the driver can be eliminated.

[Brief description of the drawings]

FIG. 1 is a flowchart showing a processing procedure as one embodiment of the present invention.

FIG. 2 is a diagram showing an example of a map used in the processing procedure shown in FIG.

FIG. 3 is a diagram showing another example of a map used in the processing procedure shown in FIG. 1;

FIG. 4 is a timing chart showing a convergence state of the engine speed in the case of the present invention.

FIG. 5 is a timing chart showing a convergence state of the engine speed in the case of the related art.

[Explanation of symbols]

 NE: engine speed NT: theoretical target idle speed DUTY: bypass opening (opening of ISC valve) ΔDTY: attenuation of bypass opening A / C: air conditioner

Claims (3)

(57) [Claims] An idle speed control method for increasing the bypass opening of a throttle valve by a fixed amount when a load variation on the engine is detected during the idle speed control of the engine. The throttle valve
If the difference between the engine rotation speed and the target idle rotation speed increased by adding the path opening by a certain amount is equal to or more than a certain value and continues for more than a certain time, then the difference between the rotation speeds There until less than said predetermined value, and decreases the bypass opening predetermined attenuation amount not a One stepwise,
Idle speed control method. 2. The idle speed control method according to claim 1, wherein the lower the cooling water temperature of the engine, the greater the attenuation. 3. The idle speed control method according to claim 1, wherein the lower the intake air temperature of the engine, the greater the attenuation.