JP2660623B2 - Idle speed control device for internal combustion engine - 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 device for an internal combustion engine, and more particularly, to the response of a device for controlling an idle speed to a target speed by adjusting an intake air amount during idle operation. Regarding technology to improve.

[0002]

2. Description of the Related Art As an idle rotation speed control device for an internal combustion engine, an auxiliary air control valve is provided in an auxiliary air passage that bypasses a throttle valve, and the opening of the auxiliary air control valve is controlled during idling operation. There is one in which the idle rotation speed is controlled by controlling the amount of auxiliary air supplied to the engine through an air passage (actually-open flat 1-1).
No. 79148).

The auxiliary air control valve is of an electromagnetic type and has a duty (a duty ratio of a pulse width to a cycle when controlling the opening degree by controlling the pulse width of a valve opening drive pulse signal given at a constant cycle). %) Is controlled in accordance with the opening degree. The duty ISC _ON (%) for the auxiliary air control valve is calculated by, for example, the following equation.

ISC _ON = ISC _Tw + ISC _CL where ISC _Tw is a basic control value, and the engine cooling water temperature Tw
Is set with reference to the map on the ROM based on the I
SC _CL is a feedback correction value. The engine speed is compared with the target idle speed under the feedback control condition of the idle speed, and based on the comparison result, for example, proportional integral control is performed so that the actual speed approaches the target. Is set using.

More specifically, the target idle speed N _SET
And the actual engine speed Ne, for example, when it is lower than the target idle speed, the duty IS
C _CL was gradually increased by the integral operation amount, also so as to increase correct the duty ISC _CL according to the proportional operation amount corresponding to the deviation between the target and the actual rotation.

[0006]

In the idle speed control as described above, the target idle speed _NSET is changed in accordance with the state of the auxiliary load such as an air conditioner, so that the load of the auxiliary load is reduced. The required amount of work has been corrected. However, in the conventional apparatus, the responsiveness of the auxiliary air amount control is poor because the auxiliary air amount is gradually changed over time by the proportional / integral control while monitoring the actual engine speed, and the target idle rotation speed is reduced when the load is applied. Even if the speed is increased, there is a problem that the target change cannot be followed satisfactorily and a large drop in rotation occurs at the initial stage of load application.

In particular, when the response of the auxiliary air control valve is poor, the rotation drop at the initial stage of the load application becomes large (see FIGS. 5 and 6). The problem of rotation drop at the time of load application as described above can be solved to some extent by setting a large manipulated variable of the proportional control in the proportional / integral control.However, when the manipulated variable of the proportional control is increased, hunting in a steady state increases. Problem. In addition, if the operation amount of proportional control can be set to an optimal value finely for each condition, it is possible to achieve both prevention of rotation drop at load application and prevention of hunting at steady state, but the operation amount is optimized It is difficult to set it to a value, and a great number of matching steps are required.

SUMMARY OF THE INVENTION The present invention has been made in view of the above problems, and provides an idle rotation speed control apparatus having a simple configuration capable of following a change in a target idle rotation speed with good responsiveness and suppressing occurrence of hunting in a steady state. The purpose is to provide.

[0009]

SUMMARY OF THE INVENTION Therefore, an internal combustion engine idle speed control apparatus according to the present invention includes an auxiliary air control valve in an auxiliary air passage that bypasses a throttle valve.
The idle rotation speed is controlled by controlling the opening of the auxiliary air control valve during idle operation to control the amount of auxiliary air, and is configured as shown in FIG.

In FIG. 1, a target setting means sets a target idle speed based on engine operating conditions. Further, the model rotation setting means sets a model rotation speed which is actually a tracking target based on the target idle rotation speed set by the target setting means. The model torque setting means sets a model output torque necessary for causing the actual engine rotation speed to follow the model rotation speed based on the model rotation speed set by the model rotation setting means.

The required auxiliary air amount setting means sets an amount corresponding to the required auxiliary air amount based on the model output torque set by the model torque setting means and the model rotation speed. The opening degree of the auxiliary air control valve is controlled according to the amount corresponding to the required auxiliary air amount.

[0012]

According to this configuration, the target idle speed set based on the engine operating conditions is not set as the direct follow target, but the model idle speed, which is the actual target rotational speed, is set from the target idle speed. I do. Then, a model output torque necessary for causing the actual engine speed to follow the model speed is obtained, and the amount of auxiliary air is controlled so that the model output torque is actually obtained.

That is, while the target rotational speed (model rotational speed) is determined in accordance with the actual response of the auxiliary air control valve, the output torque required to follow the target is determined, and the auxiliary air amount corresponding to the output torque is determined. By controlling, the actual rotation speed follows the model rotation speed.

[0014]

Embodiments of the present invention will be described below. In FIG. 2 showing the system configuration of the present embodiment, air from an air cleaner 1 passes through a throttle valve 3, which is linked to an accelerator pedal (not shown), and an auxiliary air passage 4 that bypasses the throttle valve 3 in a throttle chamber 2. Under the control of the mounted auxiliary air control valve 5, it is sucked. Then, the fuel is mixed with the fuel injected from the fuel injection valve 7 in the branch portion of the intake manifold 6 and is sucked into the cylinder of the engine 8.

The opening of the auxiliary air control valve 5 is controlled by a control signal ISC _ON from the control unit 9, and signals from various sensors are input to the control unit 9 for such control. As the various sensors, a crank angle sensor 10 is provided, and the engine speed Ne can be calculated based on a cycle T _ref of a reference signal REF output at every predetermined crank angle. Further, a water temperature sensor 11 is provided to detect an engine cooling water temperature Tw. In addition, the idle switch 1 which is turned on when the throttle valve 3 is fully closed.
2. A neutral switch 13 which is turned on when the transmission is in a neutral position, and a vehicle speed sensor 14 for detecting a vehicle speed VSP are provided.

Here, the microcomputer in the control unit 9 performs arithmetic processing according to the flowchart of FIG. 3 to control the opening of the auxiliary air control valve 5 when the idle speed feedback control condition is satisfied. . The feedback control condition is detected when the idle switch 12 is ON (throttle valve 3 is fully closed) and the neutral switch 13 is ON (neutral state), or when the idle switch 12 is ON and the vehicle speed sensor 14 detects. The vehicle speed VSP is a predetermined value (for example, 8 km
/ h) Provided that:

The functions of the target setting means, the model rotation setting means, the model torque setting means, the necessary auxiliary air amount setting means and the control means in this embodiment are performed by the control unit 9 as shown in the flowchart of FIG. Provided as software. In the flowchart of FIG. 3, first, in step 1 (referred to as S1 in the figure, the same applies hereinafter), the cooling water temperature Tw, the presence or absence of the auxiliary equipment load,
Referring to a map storing a previously target idle speed N _SET according to the engine operating conditions of the gear position, etc. in A / T, determining the target idle speed N _SET corresponding to the current engine operating conditions. Step 1 corresponds to the target setting means.

In the next step 2, the model rotational speed Nmodel (initial value = 0) as the actual follow-up target is set to the latest model rotational speed Nmodel- ₁ and the latest model rotational speed in step 1 as shown in the following equation. Target idle speed N _SET
Update setting with the weighted average value of The step 2 corresponds to a model rotation setting unit. _{Nmodel ← Nmodel -1 × r + (} 100 -r) × N SET the model rotational speed Nmodel is to vary with a predetermined response delay with respect to the target idle speed N _SET set in step 1 (FIG. 4 The weighting constant r for determining the response delay characteristic is set in accordance with the response of the auxiliary air control valve 5.

That is, the weighted average by the weighting constant r
The target idle speed N _SETActually follow
Is converted to a rotation speed that can be
Step mode compared to using an actuator as an actuator
The response is generally poor when using a
When using a promoter, the weighting constant r is
Set larger.

In the next step 3, a model output torque Tmodel, which is an output torque necessary for following the change in the model rotation speed Nmodel, is converted into a conversion constant GAINM.
Is calculated according to the following equation. Step 3 corresponds to model torque setting means. _{Tmodel ← GAINM (Nmodel -Nmodel -1)} / T ref that is, changing the actual engine speed Ne by variation of the model rotational speed Nmodel the model output torque Tmo
It is good to change the actual output by del.
Incidentally, division by the period T _ref of the reference signal REF are those needed when the model rotational speed Nmodel is updated every reference signal REF.

[0021] In step 4, the change in T _ENG the actual engine output torque is calculated according to the following equation using the conversion constant GAINM '. T _ENG ← GAINM 'The _{(Ne-Ne -1) / T} ref embodiment, since the calculated engine speed Ne based on the period T _{re f} of the reference signal REF outputted from the crank angle sensor 10, the period T _By dividing by _ref , the change rate of the rotation speed per unit time can be obtained.

In the next step 5, when there is a difference between the model rotational speed Nmodel and the actual engine rotational speed Ne in a no-load state, the output torque Tpump required to return to the actual rotational speed Ne is obtained. Is calculated according to the following equation using the conversion constant GAINP. Tpump ← GAINP × (Nmodel / Ne−1) In step 6, the auxiliary air amount Q required to make the actual engine speed Ne follow the model speed Nmodel in accordance with the following equation. This step 6 corresponds to a necessary auxiliary air amount setting means.

Q ← K · Nmodel ｛Tmodel + (Tmodel− ₃₋ T _ENG ) + Tpump｝ −Q _{BASE The} above equation is set based on the basic equation of intake air amount Q = output torque × rotation speed Ne. is there. Here, the coefficient K is a correction coefficient corresponding to a change in the charging efficiency, and
For example, it is set separately according to the cooling water temperature Tw. Also,
Q _BASE is the amount of leaked air that is sucked into the engine through another passage other than the auxiliary air control valve 5, that is, the throttle valve 3 and the like in the idle operation state.

Further, even if the auxiliary air amount is controlled in accordance with the model output torque Tmodel set so as to be able to follow the change in the model rotation speed Nmodel, (Tmodel- _3- T _ENG ) actually means the model due to engine variation. because it may be impossible to obtain an output torque tModel, the difference between the actual torque T _ENG with respect to the torque Tmodel- ₃ requirements, is corrected as excess or deficiency by the engine variation.

Here, Tmodel- ₃ is ₃ when the model output torque Tmodel is updated and set for each reference signal REF.
Shows data from previous times. That is, from the time when the opening degree of the auxiliary air control valve 5 is controlled to change the auxiliary air amount Q to the time when this actually appears as a change in the engine output torque, 1/2 cycle (360 ° CA ), It is only after 360 ° CA that it can be determined whether or not the latest model output torque Tmodel has actually been satisfied. Therefore, the latest detected actual torque change T
_ENG should accurately determine whether or not the model output torque Tmodel- ₃ set before 360 ° CA is satisfied.

If the engine 8 of this embodiment is a six-cylinder engine and the reference signal REF is output every 120 ° CA, the model output torque Tmode set before 360 ° CA
l is the set value T three times before the reference signal REF.
model- ₃ . Therefore, rather than model output torque Tmodel is calculated on the date as described above, it reads the three previous data, by comparing the the actual torque variation T _ENG This model output torque Tmodel the engine variation To be obtained without being affected by

In the next step 7, a control signal corresponding to the auxiliary air amount Q required in advance to control the auxiliary air control valve 5 to an opening corresponding to the required auxiliary air amount Q obtained in step 6 The control signal ISC corresponding to the currently required auxiliary air amount Q is referred to by referring to the map storing the ISC _ON.
Search for and ask for _ON . Here, by performing a first order delay correction to the set control signal ISC _ON or required amount of auxiliary air Q, it may be adapted to compensate the control delay due to the air charge for the collector portion of the intake manifold.

[0028] Then, in step 8, and outputs the set control amount ISC _ON the auxiliary air control valve 5, is actually auxiliary air amount set in Step 6 through the auxiliary air control valve 5 is obtained To do. The steps 7 and 8 correspond to control means. Thus, according to this embodiment, with respect to the change of the target idle speed N _SET, set the model rotational speed Nmodel as a target that can actually follow, it is required in response to a change in the model rotational speed Nmodel The auxiliary air amount Q is controlled so as to obtain a model output torque Tmodel which is an output torque of the type. Therefore, it is possible to follow the target idle rotation speed N _SET with maximum responsiveness while suppressing the occurrence of hunting.
Target idle rotation speed N _SET by loading auxiliary equipment
Is set to increase, it is possible to prevent a large rotation drop due to poor response.

In particular, when an actuator having poor response is used as the actuator of the auxiliary air control valve 5, if the above control is performed, a remarkable effect can be obtained with respect to reduction of rotation drop and suppression of occurrence of hunting. . In the above embodiment, the feedback correction (Tmodel- _3- T _ENG ) is set so that the model output torque Tmodel can be obtained reliably. However, the setting of the feedback correction may be omitted. the, when the target idle speed N _sET is changed, by setting the model output torque Tmodel corresponding to the change of the target idle rotational speed N model rotational speed Nmodel set from _sET, required auxiliary air quantity Q so Any configuration that controls the opening of the auxiliary air control valve 5 may be used.

[0030]

As described above, according to the present invention, the actual engine speed can be changed with the maximum response characteristic corresponding to the response of the auxiliary air control valve to be used with respect to the change of the target idle speed. For example, it is possible to prevent the occurrence of a large drop in rotation when the target idle rotation speed is set to increase with load application, and to suppress the occurrence of hunting.

[Brief description of the drawings]

FIG. 1 is a block diagram showing a basic configuration of the present invention.

FIG. 2 is a system schematic diagram showing one embodiment of the present invention.

FIG. 3 is a flowchart showing an embodiment of idle rotation control.

FIG. 4 is a time chart showing a relationship between a target idle rotation speed and a model rotation speed.

FIG. 5 is a time chart showing response characteristics of idle control when an actuator having a fast response is used.

FIG. 6 is a time chart showing response characteristics of idle control when an actuator having a slow response is used.

[Explanation of symbols]

 3 Throttle valve 4 Auxiliary air passage 5 Auxiliary air control valve 8 Engine 9 Control unit 10 Crank angle sensor 11 Water temperature sensor 12 Idle switch 13 Neutral switch 14 Vehicle speed sensor

Claims (1)

(57) [Claims] An auxiliary air control valve is provided in an auxiliary air passage that bypasses a throttle valve, and an idle air speed is controlled by controlling an opening degree of the auxiliary air control valve during idle operation to control an amount of auxiliary air. In an idle speed control device for an internal combustion engine, a target setting means for setting a target idle speed based on engine operating conditions, and a model for actually following a target based on the target idle speed set by the target setting means Model rotation setting means for setting a rotation speed; and a model torque for setting a model output torque necessary for causing an actual engine rotation speed to follow the model rotation speed based on the model rotation speed set by the model setting means. Setting means, which is required based on the model output torque set by the model torque setting means and the model rotational speed. A necessary auxiliary air amount setting means for setting an amount corresponding to the auxiliary air amount; and controlling an opening degree of the auxiliary air control valve according to the amount corresponding to the required auxiliary air amount set by the necessary auxiliary air amount setting means. An idle speed control device for an internal combustion engine, comprising: