JP2502380B2 - Idle speed control device for internal combustion engine - Google Patents

Description

Description: Outline When an internal combustion engine is idling and a state in which a rotation speed is lower than a target rotation speed by a predetermined value or more is detected, a relatively large change rate is provided in a bypass side passage for idling. The control amount of the flow control valve is rapidly increased. As a result, when the time rate of change of the rotational speed becomes close to zero, the control amount corresponding to the target value (α) of the intake air amount corresponding to the product value of the intake pipe pressure and the target rotational speed at that time is reached. The control amount is sharply reduced.

Therefore, in a state where the rotation speed is lower than the target rotation speed by a predetermined value or more and the engine is very stalled, the intake air flow rate is rapidly increased. Further, when the time change rate of the rotational speed starts to rise after reaching the minimum value, the intake air flow rate is sharply reduced to a value at which the torque at that time can be maintained, and so-called upward blowing due to overcontrol is prevented. . In this way, engine stall is reliably prevented.

FIELD OF THE INVENTION The present invention relates to a device for controlling the idle speed of an internal combustion engine.

2. Description of the Related Art In an internal combustion engine, the rotational speed fluctuates due to a slight load fluctuation during idling when a small torque is generated. For example, the rotation speed decreases when the power load of an audio device or the like, the use of an air conditioner or the like is started, and the power steering is stationary or the D range of the automatic transmission is turned on.

On the other hand, in recent years, the idle rotation speed has been kept relatively low in order to improve fuel economy, and therefore, if the factors causing the load fluctuation as described above are duplicated, there is a risk of engine stall.

In a typical conventional technique, a control device that controls a flow control valve provided in a bypass side passage for idling incorporates outputs of various devices that cause load fluctuations, detection results of sensors, and the like, for example, a cooling machine. When is used, the idle speed is controlled by increasing the idle speed by 250 rpm. Further, integral control is performed with a small control gain for suppressing overcontrol so that the rotation speed thus set is obtained.

Problems to be Solved by the Invention In the above-described conventional techniques, the control device needs to take in outputs from various devices and detection results of sensors, which complicates the configuration and increases the cost. .

Further, since the control gain is low, the response is poor, the rotation speed is lower than the target rotation speed, and even when the engine stalls easily, the increase control of the rotation speed is performed by the gentle integration control. Therefore, as described above, the state in which the engine is easily stalled by a slight disturbance continues for a long time.

On the other hand, if the control gain is increased, the response is improved but the stability is deteriorated. In other words, over-control occurs, resulting in over-control, resulting in an undesired situation such as so-called hunting or blowing.

An object of the present invention is to provide an idle speed control device for an internal combustion engine, which can have a simplified structure, improved stalling resistance, and both responsiveness and stability.

Means for Solving the Problems According to the present invention, the upstream side and the downstream side of a throttle valve are communicated with each other by a bypass bypass passage for idling, and a control amount of a flow control valve provided in the bypass passage is changed. In the idle rotation speed control device for an internal combustion engine that maintains the rotation speed of the internal combustion engine at a predetermined target rotation speed, when the rotation speed is lower than the predetermined rotation speed lower than the target rotation speed, the engine is It is determined that it is just before the stop, a predetermined relatively large predetermined amount is added to the control amount of the flow control valve to rapidly increase the control amount, and the rotation speed is increased by the sudden increase of the control amount. When the speed returns to the predetermined value, the control amount is rapidly increased to a predetermined control amount corresponding to the target value (α) of the intake air amount corresponding to the product value of the intake pipe pressure and the target rotation speed at that time. A idle speed control apparatus for an internal combustion engine, characterized by reduced.

Further, the present invention is characterized in that the intake pipe pressure is obtained in consideration of a response delay of the torque generated by the internal combustion engine with respect to a change in the control amount of the flow control valve.

Operation According to the present invention, when the state where the rotation speed is lower than the target rotation speed by a predetermined value or more is detected during idling of the internal combustion engine, the flow rate provided in the bypass bypass passage at a relatively large rate of change is detected. Increase the control amount of the control valve. As a result, when the time rate of change of the rotation speed becomes close to zero, at that time, the control amount corresponding to the target value (α) of the intake air amount corresponding to the product value of the intake pipe pressure and the target rotation speed. Until the control amount of the flow control valve is rapidly reduced.

Therefore, in the state where the rotation speed is lower than the target rotation speed by a predetermined value or more and the engine is stalled very easily, the intake air flow rate is rapidly increased to prevent the engine stalling. Further, when the time rate of change of the rotational speed starts to rise after passing zero, the intake air flow rate is rapidly reduced to a value at which the torque at that time can be maintained, and so-called upward blowing due to overcontrol is prevented. . In this way,
(EN) Idle rotation speed control with improved stalling resistance, high control gain, and good stability is performed.

First Embodiment FIG. 1 is a control device 1 for an internal combustion engine according to a first embodiment of the present invention.
It is a block diagram which shows the structure relevant to it. The combustion air introduced from the intake port 2 is purified by the air cleaner 3, and the flow rate of the combustion air is adjusted by the throttle valve 5 interposed in the intake pipe 4 through the intake pipe 4, and then the surge air is supplied to the surge tank 6. Inflow. Combustion air flowing out of the surge tank 6 is mixed with fuel injected from a fuel injection valve 8 interposed in an intake pipe 7 and supplied to a combustion chamber 11 of an internal combustion engine 10 via an intake valve 9. A spark plug 12 is provided in the combustion chamber 11, and exhaust gas from the combustion chamber 11 is discharged through an exhaust valve 13 and is discharged from the exhaust pipe 14 into the atmosphere through a three-way catalyst 15.

The intake pipe 4 is provided with an intake air temperature detector 21 for detecting the temperature of intake air, a throttle valve opening detector 22 is provided in association with the throttle valve 5, and the surge tank 6 is provided with an intake pipe 7 An intake pressure detector 23 for detecting pressure is provided. A cooling water temperature detector 24 is provided near the combustion chamber 11, an oxygen concentration detector 25 is provided upstream of the three-way catalyst 15 in the exhaust pipe 14, and a downstream side of the three-way catalyst 15. An exhaust temperature detector 26 is provided. The rotation speed of the internal combustion engine 10, that is, the number of rotations per unit time is determined by the crank angle detector.
Detected by 27.

The controller 1 includes the detectors 21 to 27, a vehicle speed detector 28, and a starter motor 33 for starting the internal combustion engine 10.
Start detector 29 to detect whether or not is activated
When an automobile equipped with the internal combustion engine 10 is equipped with an automatic transmission, an air conditioner detector 30 for detecting the use of an air conditioner, etc., and whether or not the shift stage of the automatic transmission is in the neutral position The detection result from the neutral detector 31 for detecting is input.

Furthermore, the control device 1 is energized by a battery 34, and the control device 1 controls the detectors 21-31.
The fuel injection amount, the ignition timing, etc. are calculated on the basis of the detection result of the above, the power supply voltage of the battery 34 detected by the voltage detector 20, and the like, and the fuel injection valve 8 and the spark plug are calculated.
Control 12 and so on.

A side passage 35 that bypasses the upstream side and the downstream side of the throttle valve 5 is formed in the intake pipe 4, and a flow control valve 36 is provided in the side passage 35. Flow control valve 36
Is duty-controlled by the control device 1, and adjusts and controls the flow rate of combustion air at the time of idling when the throttle valve 5 is almost fully closed. The control device 1 also drives the fuel pump 32 when the internal combustion engine 10 is operating.

FIG. 2 is a block diagram showing a specific configuration of the control device 1. The detection results of the detectors 20 to 25 are given from the input interface circuit 41 to the processing circuit 43 via the analog / digital converter 42. Also, the detectors 22, 27 to 3
The detection result of 1 is given to the processing circuit 43 via the input interface circuit 44. The processing circuit 43 is provided with a memory 45 for storing various control maps and learning values, and the processing circuit 43 receives a constant voltage circuit 46 from the power from the battery 34. Supplied through.

The control output from the processing circuit 43 is derived via the output interface circuit 47, is applied to the fuel injection valve 8 to control the fuel injection amount, and is also applied to the ignition plug 12 via the igniter 48 to ignite. The timing is controlled, and further, the flow rate control valve 36 is applied to control the amount of inflowing air through the side passage 35 at the time of idling, and the fuel pump 32 is driven.

The detection result of the exhaust temperature detector 26 is given to the exhaust temperature detection circuit 49 in the control device 1, and when the detection result is abnormally high, the warning lamp 51 is turned on via the drive circuit 50.

FIG. 3 is a timing chart for explaining the operation of the control device 1 configured as described above. It is assumed that the air-fuel ratio control is being performed based on the output from the oxygen concentration detector 25 and the like. Time t1 in FIG. 3 (2)
As shown previously, when the rotational speed NE of the internal combustion engine 10 is relatively stable, the control duty of the flow control valve 36 is predicted and obtained as follows based on the actual rotational speed NE. From the difference between the advanced rotation speed NEADV and the target rotation speed NT, as shown in FIG. 4 (2), integral control is performed in increments of a relatively small increment ΔD1.

In performing the integration control, as shown in FIG. 4 (1), the target rotation speed NT is used as a center, for example, ±
A dead zone W1 of 15 rpm is provided, and the integral control is stopped when the advance rotational speed NEADV is within the dead zone W1, and is executed when it goes out of W1. During steady operation of the internal combustion engine 10, the rotational speed NE is stable within this dead zone W1.

The prediction calculation of the advance rotational speed NEADV is performed as follows. First, the rotational speed NE, which is the number of revolutions per unit time, is calculated based on the first equation from the time T180 required for the crankshaft to rotate 180 ° CA.

Next, the rotation speed NEO at the previous calculation timing
And from the rotational speed NE at the current calculation timing, 18
The change amount ΔNEa of the rotational speed NE between 0 ° CA is calculated. That is, ΔNEa = NE−NEO (2) The change rate ΔNE per unit time (32 msec) is obtained from the change amount ΔNEa thus obtained using the third equation.

Further, the advance time TADV based on the change rate ΔNE and the difference between the rotation speed NE and the target rotation speed NT shown in FIG.
From this, the advance rotational speed NEADV is obtained according to the fourth equation.

By using the advance rotational speed NEADV obtained in this way, it is possible to prevent overshoot due to overcontrol, and to increase the gain during integral control, that is, to increase the increment ΔD1 relatively. It is possible to improve stability.

Further, the increment ΔD1 of the integral control is, as shown in FIG. 6, when the difference between the advance rotational speed NEADV and the target rotational speed NT is within the dead zone W1 of NT ± 15 rpm as described above. It is set to zero, and outside the dead zone W1, the difference is set to a value corresponding to NEADV-NT. In this way, in the steady state, the rotation speed NE is controlled so as to be within the dead zone W1.

The target rotation speed NT is, for example, 700 rpm when there is no load.
Is set to 950 rpm when the air conditioner is used.
Is set to

As shown in FIG. 3 (1) at time t1, when the gear position of the automatic transmission is switched from the neutral position to the drive position by the neutral detector 31, the load on the internal combustion engine 10 increases and the rotational speed NE Starts to drop as shown in FIG. 3 (2).

Due to this drop, the change rate ΔNE becomes less than or equal to a predetermined threshold L2 as shown in FIG. 3 (3),
When the rotation speed NE is less than the threshold value L4 higher than the target rotation speed NT by 100 rpm, for example, as shown in FIG. 3 (4) at the time t2, the calculated value of the control duty of the flow rate control valve 36 is: A relatively large increment ΔD2 corresponding to the rate of change ΔNE is added, whereby the intake pressure P _M of the surge tank 6 rises sharply and the intake air flow rate increases, as shown in FIG. 3 (5). Increase.

As shown in FIG. 7, the relationship between the rate of change ΔNE and the increment ΔD2 is such that when it is greater than one threshold L2 smaller than zero and less than the other threshold L1 larger than zero, Δ
It is set to the dead zone W2 of D2 = 0. The rate of change ΔNE
Is less than the threshold value L2 and more than L1, the increment ΔD2 is set corresponding to the rate of change ΔNE.
The graph shown in FIG. 7 and the graphs shown in FIGS.
The graph shown in the figure is stored as a map in the memory 45 in advance.

The decrease of the rotational speed NE is suppressed by the increase of the intake air flow rate, and the change rate ΔNE goes through the minimum state at the time t3,
As shown in FIG. 3 (3) at time t4, when the change rate ΔNE exceeds the threshold value L2 and enters the dead zone W2 again, that is, when the change rate ΔNE becomes almost zero, the parameter related to the intake air flow rate is changed. , The calculated value of the control duty is repeatedly subtracted by a predetermined value ΔD3 as shown in FIG. 3 (4) until it becomes substantially equal to a target value α described later (time t4a), and is rapidly reduced. . As a result, excessive control is suppressed due to the delay in the response of the torque generated by the internal combustion engine 10 to the change in the control duty.

Further, when a parameter described later becomes substantially equal to the target value α, at that time, the control duty set in advance is set to 2
After the increment ΔD4 of about 3% is added, the integral control corresponding to the difference between the actual rotation speed NE and the target rotation speed NT is performed.

However, even with this control, when the rotation speed NE does not stabilize well and shows an increase, the change rate ΔNE becomes equal to or greater than the threshold value L1 as shown at time t5, and the rotation speed NE
NE is a threshold value L3 lower than the target rotation speed NT by, for example, 50 rpm.
When it exceeds, the control duty is subtracted by the increment ΔD2 corresponding to the change rate ΔNE as shown in FIG. When the rate of change ΔNE enters the dead zone W2 in this way, the control duty is repeatedly increased by the increment ΔD3 at the time t6, and when the parameter to be described later becomes substantially equal to the target value α, at that time, the control duty is determined to be 2 to a predetermined value. After the increment ΔD4 of about 3% is added, the integral control corresponding to the difference between the actual rotation speed NE and the target rotation speed NT is performed. In this way, the intake pressure P _M becomes stable as shown in FIG. 3 (5).

In the present embodiment, the value of the increment ΔD2 is set according to the value of the rate of change ΔNE. However, when the capacity of the flow control valve 36 is small or when the capacity of the surge tank 6 is large, the value of the increment ΔD2 is changed. There is no problem even if the value is fixed. That is, the same performance can be obtained even if the flow control valve 36 is controlled to be almost fully opened when the drop in the rotation speed NE is detected, and is almost completely closed if the increase in the rotation speed NE is detected.

Further, as shown from time t7 onward, when the shift stage of the automatic transmission is switched to the neutral position, the rotation speed NE increases and is quickly stabilized by the same operation.

The threshold value L2, which is the determination level, is a value obtained by subtracting the correction value h1 shown in FIG. 9 from the value KDPC obtained corresponding to the rotation speed NE shown in FIG. 8, that is, KDPC-h1.
And the larger value of the value KDPCa updated according to the change rate ΔNE. Therefore, L2 = max (KDPC-h1, KDPCa) (5) The value KDPC is set such that when the rotational speed NE is 600 rpm or less, the change rate ΔNE per 32 msec is set to 9.375 rpm, and the rotational speed NE is 21.875 rpm when above 800 rpm
When the rotation speed NE is 600 to 800 rpm, the rotation speed NE is set between 9.375 and 21.875 rpm in proportion to the rotation speed NE.

Further, the correction value h1 is set to zero when the difference between the target rotation speed NT and the actual rotation speed N2 is 50 rpm or less, and becomes a value of 3 to 10 in proportion to the difference between 50 and 200 rpm. It is set, and is set to 10 when it is 200 rpm or more. Therefore, for example, when the target rotation speed NT is 650 rpm and the actual rotation speed NE is 600 rpm, the rate of change ΔNE is 9.375-3 = 6.375 (rpm / 32 msec) or more and the rotation speed NE is decreasing. , The time
An abrupt increase in control duty, indicated by t2, is made.

Also, for example, when the target rotation speed NT is 800 rpm and the actual rotation speed NE is 600 rpm, the change rate ΔNE is 9.375−10 = −0.625 (rpm / 32 msec), so the rotation speed NE is in a substantially steady state. Even so, the control duty is rapidly increased. That is, the farther the rotational speed NE is from the target rotational speed NT, the easier it is to execute the sudden increase control of the control duty.

On the other hand, by using the value KDPCa, for example, when the rotational speed NE is pulsating as shown in FIG.
Is changed from positive to negative, the value KDPC updated during the period W21 in which the rate of change ΔNE is positive, that is, the period in which the rotational speed NE is equal to or more than the threshold value L5 (NT-150 rpm) and equal to or less than L4 (NT + 100 rpm)
In contrast to a, when the change rate in the period W22 is small when the change rate ΔNE is negative, the abrupt control by the increment ΔD2 is abandoned. This corresponds to the fluctuation of the rotational speed NE shown in FIG. 11 (1) and corresponds to the flow control valve 36 as shown in FIG. 11 (2).
Control duty is changed, the generated torque of the internal combustion engine 10 and the load are balanced, and the rotation speed NE pulsates due to vibration or the like, even though the control duty is near the value at which the control duty should be stabilized. This is to prevent unnecessary fluctuations in the control duty as indicated by the broken line in FIG.

Further, the threshold value L1 which is another determination level is obtained by subtracting a correction value h2 determined corresponding to the difference between the actual rotation speed NE and the target rotation speed NT shown in FIG. 12 from a predetermined constant value. Will be asked for. That is, L1 = 9.375−h2 (6) The correction value h2 is the same as the correction value h1 and is the actual rotation speed.
When the difference between NE and the target rotation speed NT is 50 rpm or less, it is set to zero, when it is 50 to 200 rpm, it is changed in the range of 3 to 10 according to the difference, and when it is 200 rpm or more, it is set to 10. To be done.

That is, for example, the target rotation speed NT is 700 rpm,
When the actual rotation speed NE is 750 rpm, the threshold value L1 is 6.
375 (rpm / 32 msec), and when the rate of change ΔNE of the rotational speed NE is greater than or equal to this threshold value L1, the control duty abrupt decrease control is performed after the time t7.

In this way, the target rotation speed NT and the actual rotation speed NE
The thresholds L1 and L2 are changed in accordance with the difference between the two, and the conditions for executing the sudden increase / decrease control of the control duty are changed accordingly, so that the target rotation speed NT can be quickly converged.

On the other hand, the detection output of the intake pressure detector 23 used for the control calculation of the idle rotation speed and the fuel injection amount is changed by the opening / closing operation of the intake valve 9 as shown in FIG. 13 (1). The fluctuation range is 50 at 4000 rpm, for example.
It is a large value of about 100 mmHg. In order to absorb this fluctuation and detect an accurate intake pressure, the detection output of the intake pressure detector 23 is subjected to filter processing in the control device 1.

Therefore, even if the flow control valve 36 is suddenly opened as shown in FIG. 13 (2) due to the delay due to the filter processing, the pressure waveform after the filter processing is
It appears as shown by reference numeral l2 after a delay of time Δt2 with respect to the change of the actual pressure waveform of the intake pressure shown by reference numeral 1 in FIG. 13 (3).

Therefore, in Fig. 13 (3), the calculation timing t1
When the control duty is calculated based on the intake pressure in 1, the intake pressure that should originally be used for calculating the control duty is reduced by the pressure difference ΔP2 corresponding to the filter processing time Δt2. Therefore, the pressure difference ΔP2 corresponding to the delay of the time Δt2 is predicted and calculated, and the calculation timing t1
Intake pressure in 1 needs to be corrected.

As shown in FIG. 13 (3), the pressure waveform l2 after the filtering process is almost equal to the pressure waveform 1 of the actual intake pressure, and therefore the time change rate dP / dt of the intake pressure P is accurately obtained. Therefore, it is possible to accurately correct such a delay.

The time change rate dP / dt is obtained as follows. That is, the intake air flow rate to the surge tank 6
And when the outflow air amount from the surge tank 6 is Qout, However, ΔQ is the amount of change in the intake air flow rate, and K1 is a constant. When the control duty of the flow rate control valve 36 is DUTY and the rotation speed of the internal combustion engine 10 is N, Qout = K3 · η · N · P (9) where K2, K3 are constants, η is the intake efficiency, P
₀ is atmospheric pressure. Therefore, from the first equation, the intake pressure P after delay correction is However, Pi is the intake pressure at the above calculation timing, and K1
a = 1 / K1.

On the other hand, if the time between 180 ° CA is T, Becomes In this 11th formula, Δt2 is constant with respect to the time axis, and if this is set to B, That is, with respect to the delay due to the filter processing, by accurately obtaining ΔQ, these corrections can be accurately obtained with a generally positive value.

Next, a method of calculating ΔQ / N will be described. The change in the intake air flow rate Qin when the flow rate control valve 36 opens suddenly is
It becomes as indicated by the reference numeral l3 in FIG. On the other hand, due to the influence of the surge tank 6 and the like, the outflow air flow rate Qout from the surge tank 6 is indicated by reference numeral l4. These flow rates Qin and Qout are shown by the above-mentioned formula 8 and formula 9, respectively.

During steady operation of the internal combustion engine 10, Qin = Qout and the flow rate Q
In is determined in advance by actually measuring the steady-state flow rate Qout using the control duty DUTY of the flow rate control valve 36 and the intake pressure P as parameters. That is, as shown in FIG. 15, the values corresponding to N · P in the equation 9 are N and P in each control duty DUTY when the intake pressure P is changed while keeping the control duty DUTY constant. Let us use the product value MAP of and. As a result, the flow rate Qin can be expressed as in Expression 13. The graph shown in FIG. 15 is stored in the memory 45 as a map.

Qin ＝ K3 ・ η ・ MAP (13) Therefore, It can be expressed as.

However, in this Equation 14, MAP / N and P _M are
Due to variations in manufacturing of the internal combustion engine 10 and changes over time, in actual control, there is a case where they do not match in the steady state.Therefore, in the present embodiment, the intake pressure P _M obtained by calculation Pc Replace with and use. Even if the intake pressure P _M deviates due to such variations as described above, the time change rate dP / dt thereof is substantially the same, and therefore, similar to the above-described delay correction shown by the tenth equation, It can be expressed as. However, P _ci is the calculated value of this time, and P _ci-1 is the calculated value of the previous time. Therefore, MAP / N
, And the calculated value Pc always coincides with the steady state, and during the transition, the MAP / N changes abruptly with the change of the control duty DUTY, and the value Pc changes following so as to coincide with it. Therefore, the value Pc is successively calculated based on the 16th equation, for example, every 4 msec.

However, K5 = K1a · K3 · η.

As described above, the correction value Pc was obtained in consideration of the delay due to the filter process and the variation of the internal combustion engine 10. However, when the delay is small or when the control is desired to be simpler, the value Pc is used instead. It is also possible to control using the actual intake pressure P _M. It was but connexion, what is described in Pc in the following description, the case of substitute P _M is assumed to replace the P _M.

Further, in the internal combustion engine 10, when the calculated value Pc of the intake pressure obtained as described above is used, for example, when the control duty of the flow control valve 36 is increased, the value Pc increases corresponding to the increase. Therefore, there is a considerable response delay until the generated torque actually increases and the rotation speed NE increases.

Therefore, in the present embodiment, in response to the response delay, the value Pc obtained as described above is further subjected to the delay processing shown in the seventeenth equation to correspond to the actual response characteristic of the internal combustion engine 10. Obtain the calculated value PcFa of the intake pressure.

However, PcFO is the calculated value of the previous PcFa, and h3 is a constant and is selected to be 4, for example.

The smaller value of this value PcFa and the value Pc is the delayed inspiratory pressure Pc.
F, the control duty calculation of the flow control valve 36 is performed using the delayed intake pressure PcF. That is, when the values Pc and PcFa are indicated by reference signs l5 and l6 in FIG. 16, respectively, the delayed intake pressure PcF is a value indicated by reference sign l7. This delayed inspiratory pressure P
By using cF, the control duty can be stably converged after the abrupt control shown at the times t2 and t5 is performed.

17 to 20 are flow charts for explaining the above-described idle rotation speed control operation. FIG. 17 shows the operation for obtaining the rotational speed NE of the internal combustion engine 10. This operation is performed at a timing with a small error due to the stroke difference between the cylinders of the internal combustion engine 10, for example, every 180 ° CA when there are four cylinders. Be seen. In step s1, the rotational speed NE is measured by the crank angle detector 27, and in step S2, the time change rate ΔNE is calculated from the measurement result in step s1 and the previous measurement result, and then another operation is performed. Move.

FIG. 18 shows an operation for obtaining the intake pressure P _{M. In} step s11, the measurement result of the intake pressure detector 23 is digitally converted by the analog / digital converter 42 and read into the processing circuit 43. This operation is performed, for example, every time a conversion operation is performed every 2 msec.

FIG. 19 is a flow chart for explaining the correction calculation shown in the above-mentioned Expression 16, for example, an analog signal of the throttle valve opening θ detected by the throttle valve opening detector 22 every 4 msec. It is performed for each digital conversion operation. At step s21, the throttle valve opening degree θ is read, and at step s22, the throttle valve opening degree θ obtained at the above-mentioned step s21 and the value Pc obtained at step s30 described later.
Therefore, the map value MAP is read out based on the graph shown in FIG.

The value MAP and the rotational speed NE are divided in step s23, and the value Pc is subtracted from the division result in step s24. At step s25, the sign for the approximation operation of the value Pc at step s30 described later is set according to whether the result of the subtraction at step s24 is positive or negative. In step s26, it is determined whether or not the set sign is positive, and if not, in step s27, the absolute value of the subtraction result in step s24 is calculated, and then the process proceeds to step s28, and if so, Go directly to step s28.

At step s28, the subtraction result at step s24 is multiplied by the rotation speed NE. In step s29, the above value K
5 is multiplied by the calculation result obtained in step s28, and the value Pc is updated based on the code set in step s25 in step s30 using this multiplication result. In this way, the approximate calculation of the value Pc shown in the 16th equation is performed. As described above, when the actual intake pressure P _M is used instead of the value Pc, the operation shown in FIG. 19 is unnecessary.

FIG. 20 is a flow chart for explaining the duty control operation of the flow rate control valve 36 for controlling the idle rotation speed. At step n1, it is judged whether the internal combustion engine 10 is stopped, and if so, the step n1 is executed.
At n2, the control duty DUTY of the flow control valve 36 is set to 0%, and at step n2a, the actual intake pressure P _M is set as the initial value of the value PcFa.
If is being driven, the process proceeds to step n3.

At step n3, whether or not a change in the rotational speed NE between 180 ° CA can be detected, that is, the step s
It is determined whether or not the operation timing of 1s2 has ended and the predetermined operation timing has come. If not, the process proceeds to step n41, and if so, the process proceeds to step n4.

At step n4, the arithmetic processing shown by the first equation is performed on the basis of the time T180 required for the internal combustion engine 10 to rotate 180 ° CA. At steps n5, n6, and n7, the arithmetic processings shown by the second, third, and fourth equations are performed, respectively, and thus the advance rotational speed NEADV is obtained at steps n4 to n7.

Further, in step n7a, the value PcFa is calculated from the value Pc obtained in step s30 based on the equation (17). At step n8, the increment NTADD1 of the idle rotation speed determined corresponding to the cooling water temperature detected by the cooling water temperature detector 24 is obtained.

At step n9, it is judged whether or not a predetermined time, for example, 2 seconds has elapsed since the internal combustion engine 10 was started by the starter motor 33 and started, and if not, at step n10, the idling speed is changed. Incremental NTADD2,
For example, after setting to 300 rpm, the process proceeds to step n11, and if so, the process directly proceeds to step n11. This increment NTA
DD2 is a value for promptly supplying the lubricating oil to each part of the internal combustion engine 10. As shown in steps n42 to n44 to be described later, DD2 decreases with the passage of time after the passage of 2 seconds. Being done.

At step n11, the basic idle rotation speed NTBASE is obtained according to the detection results of the air conditioning detector 30 and the neutral detector 31, and the usage status of the electric load. At step n12, the increments NTADD1 and NTADD2 are added to the basic idle rotation speed NTBASE to obtain the target rotation speed NT. However, at this time, the maximum value of the target rotation speed NT is 12
Set to 50 rpm.

At step n13, it is judged based on the output of the start detector 29 whether or not the starter motor 33 is being started, and if so, at step n14,
The control duty DUTY is set to the control duty DSTART at the time of start, which is determined corresponding to the cooling water temperature, and then the process proceeds to step n15. When it is not the time of starting at step n13, the routine proceeds to step n16, where it is judged whether or not the throttle valve 5 is in the idle state, which is the fully closed state. If not, at step n15, the sudden control flag FPC described later is set. After being reset to zero, go to step n41, and if so go to step n17.

In step n17, it is determined whether the value Pc obtained in steps s21 to s30 and the value PcFa obtained based on the equation (17) in step n7a using the value Pc are larger, and steps n18 or n19 are determined. The smaller value is set as the delayed inspiratory pressure PcF and the process proceeds to step n21.

In step n21, it is judged whether or not the time change rate ΔNE obtained in the step s2 is less than or equal to the threshold value L2 shown in the equation 5, and if so, that is, the rotation speed.
When NE is decreasing, the process proceeds to step n22, where it is determined whether or not the rotation speed NE is equal to or more than the threshold value L4, and when it is not, that is, a rapid increase control of the control duty DUTY shown at the time t2. When it is necessary to do so, move to step n23. In step n23, the sudden control flag is set.
The flag FPSML, which is provided corresponding to the FPCS and indicates whether the increase control or the decrease control needs to be performed, is set to 1 to indicate that the increase control needs to be performed, and the process proceeds to step n31.

When the rate of change ΔNE is larger than the threshold value L2 in the step n21, and when the rotation speed N is in the step n22.
When E is higher than the above-mentioned threshold value L4, that is, when it is not necessary to control the sudden increase of the control duty, step n2
Go to 5. In step n25, it is judged whether or not the change rate ΔNE is equal to or more than the threshold value L1 shown in the above equation 6, and if so, that is, when the rotational speed NE is increasing, in step n26 the rotational speed NE is It is determined whether or not the threshold value is less than or equal to the threshold value L3. If not, that is, when it is necessary to perform the rapid decrease control, the process proceeds to step n27. In step n27, the flag FPSML is reset to 0 and the process proceeds to step n31.

At step n31, the abrupt control flag FPCS is set to 1 to indicate that the control duty is being abruptly increased or decreased.

In step n32, the control duty until then is DUTY
Based on the time change rate ΔNE of the rotation speed NE,
The control duty is increased by adding the increment ΔD2 obtained from the figure.
DUTY is updated. At step n33, this updated control duty DUTY is limited to within the range of 10-90%. This operation changes the control duty duty to the flow control valve 36
To correspond exactly to the control duty DUTY, that is, within a range in which the correct operation of the flow control valve 36 can be guaranteed.

In step n34, it is determined whether or not the rotation speed NE is increasing, and if so, it is determined in step n35 whether or not the rotation speed NE is equal to or more than the threshold value L5 and less than or equal to L4. At some point, move to step n36. At step n36, the value KDPCa is updated by the rate of change ΔNE, as shown by the period W21 in FIG.
Go to 41. Further, in step n34, the rotation speed NE
Is not rising, and when the rotation speed NE is out of the range of the threshold value L5 or more and L4 or less in step n35, the process directly proceeds to step n41.

In step n41, the control duty for the rapid increase / decrease control obtained in steps n32 and 33, or the control duty in the integral control obtained in steps n55 and n33 described below, or in steps n62 to n64 described later Flow control valve based on the control duty during return control
36 is duty controlled.

In step n42, it is determined whether or not a predetermined time, for example, 1 second has elapsed. If not, the operation is ended, and if so, the process proceeds to step n43. In step n43, it is judged whether or not the increment NTADD2 is 0, and if so, the operation is ended. Otherwise, in step n44, the increment NTADD2 is subtracted by 10 rpm and updated, and then the operation is performed. finish.

When the change rate ΔNE is less than the threshold value L1 in step n25 and when the rotation speed NE is higher than the threshold value L3 in step n26, that is, when the abrupt control as described above is not performed, the process proceeds to step n50. In step n50,
The rotational speed NE is a predetermined value from the target rotational speed NT.
It is determined whether or not the threshold value is equal to or lower than the threshold value L6 lower by 200 rpm, and if so, that is, if the engine is in a very stalled state, the process proceeds to step n51, and if not, the process proceeds to step n52.

In step n51, it is judged whether or not the sudden control flag FPCS is 1, and if so, that is, the control duty
Immediately after the abrupt increase / decrease control of DUTY is performed, the process proceeds to step n61. At step n61, the target value α of the intake air flow rate, which is a parameter related to the torque of the internal combustion engine 10, is calculated from the product value of the target rotational speed NT and the delayed intake pressure PcF.
Is set. In step n62, control duty
The predetermined increment ΔD3 is added or subtracted. That is, when the flag FPSML is 0, the increment ΔD3 is added,
When it is 1, the increment ΔD3 is subtracted.

In step n63, based on the control duty DUTY updated in step n62 and the delayed intake pressure PcF, the fifteenth
The value MAP is read from the graph shown in the figure, and it is judged whether or not the value MAP is substantially equal to the target value α set in the step n61. If not, these steps n62,
When n63 is repeated and the target value α is almost equalized in this way, the process proceeds to step n64.

At step n64, the control duty at the time of the return control obtained as described above is updated by adding the increment ΔD4. In step n65, the sudden control flag FPCS is
Is reset to 0, and then step n34 is entered.

The flag FPSML is set to 1 at step n52, and the sudden control flag EPCS is set to 1 at step n53. After the increment ΔD2 is set to 50% in step n54, the operation after step n32 is started, and the control duty D
A sudden increase control of UTY is performed, thus preventing stalling.

When the abrupt control flag FPCS is not 1 in step n51, that is, after the return control shown in steps n61 to n65 has been performed, the process moves to step n55,
Leading angle rotational speed NEADV obtained in steps n4 to n7
Then, in accordance with the difference from the target rotation speed NT, the increment ΔD1 is read out based on the graph shown in FIG. 6 and the control duty DUTY is updated. Then, the process proceeds to step n33, where the integral control is performed. .

As described above, in the control device 1 according to the present invention, when a sudden drop in the rotation speed NE due to a load change is detected,
The control duty DUTY of the flow rate control valve 36 is changed by an increment ΔD2 corresponding to the rate of change ΔNE of the rotational speed NE to quickly suppress the drop. When the drop in the rotation speed NE has subsided, the control duty DUTY corresponding to the target value α of the intake air flow rate at that time is rapidly reduced by a predetermined integral ΔD3, and then the increment ΔD4 is added. Therefore, it is possible to secure good stability with a large control gain and without excessive control that causes a blow-up, and also to reliably prevent engine stall during return control by the increment ΔD3. You can

Also, when the rotational speed NE increases due to load fluctuation, similarly, it is possible to quickly suppress blow-up, etc. and reliably prevent engine stall due to overcontrol, thus providing both responsiveness and stability. Idle rotation speed control can be performed.

Furthermore, thresholds L3 and L4 are provided near the target rotation speed NT, and the abrupt control by the increment ΔD2 is performed at the measured rotation speed.
If the NE is higher than the threshold L3 during rising, the threshold is falling during falling
Since it is executed when it is less than L4, unnecessary control can be prevented, and thereby stability can be further improved.

Further, by the step n52, when the rotational speed NE drops below the threshold value L6 and it is very easy to stall, and when the rotational speed further decreases, the control duty is unconditionally changed at steps n54, n32, n33. Since the increase is made by 50%, the engine stall can be surely prevented by this.

Furthermore, since the thresholds L1 and L2, which are the determination levels for executing the sudden control, are changed corresponding to the rotation speed NE and the difference between the rotation speed NE and the target rotation speed NT, the difference is large. At the same time, it is possible to quickly converge to the target rotation speed NT, prevent unnecessary control at high rotation speed where the rotation speed NE is stable, and reduce slightly when the rotation speed NE is not stable at low rotation speed. It is possible to detect various fluctuations sensitively and prevent engine stall reliably.

Further, by improving the responsiveness to load fluctuations in this way, it is possible to minimize the output of various devices to be taken into the control device 1, the measurement results of the sensors, etc. Can be simplified.

In the above-described embodiment, the case where the control amount of the flow control valve is increased when the time rate of change of the rotation speed is equal to or less than the predetermined value L2 has been described, but the rotation speed is simply equal to or less than the predetermined value. At times, the control amount of the flow control valve may be increased.

That is, when it is detected that the rotation speed is lower than a predetermined value (a rotation speed at which engine stall is likely to stall) that is lower than the target rotation speed, that is, when it is determined that the engine is about to stop, the predetermined value is set. A relatively large predetermined amount (ΔD2 = 50%) is added to the control amount to increase the control amount, and the time rate of change of the rotation speed becomes zero or almost zero due to the increase of the control amount. Then, the control amount is rapidly reduced to a predetermined control amount corresponding to the target value (α) of the intake air amount corresponding to the product value of the intake pipe pressure and the target rotation speed at that time.

As a result, it is possible to prevent blow-up due to engine stall and excessive control, improve responsiveness and stability, and control the rotation speed.

As described above, according to the present invention, when the internal combustion engine is idle, the rotational speed is lower than the target rotational speed by a predetermined value or more, and when a very easy engine stall is detected,
Since the control amount of the idle flow control valve is rapidly increased at a relatively large change rate, the intake air flow rate is increased at a relatively large time change rate, and engine stall can be reliably prevented.

Further, when the time rate of change of the rotation speed becomes near zero,
Since the control amount of the flow control valve is suddenly reduced to a value at which the torque of the internal combustion engine at that time can be maintained, the over-control can prevent the engine from blowing up.

In this way, with a high control gain, the responsiveness can be improved, the engine stalling resistance can be improved, and the stability can be improved at the same time. In addition, the number of outputs from various devices and sensors that are loads can be reduced, and the configuration can be simplified.

[Brief description of drawings]

FIG. 1 is a block diagram showing a control device 1 of an internal combustion engine according to an embodiment of the present invention and a configuration related thereto, FIG. 2 is a block diagram showing a concrete configuration of the control device 1, and FIG. 4 is a timing chart for explaining the idle rotation speed control operation, FIG. 4 is a timing chart for explaining the integral control operation, and FIG. 5 is a rotation speed NE and a target rotation speed.
Graph showing the change in advance time TADV corresponding to the difference with NT,
FIG. 6 is a graph showing changes in the increment ΔD1 during integral control, FIG. 7 is a graph showing changes in the increment ΔD2 during sudden control, and FIG. 8 is a graph showing changes in the value KDPC with respect to the rotational speed NE. Fig. 10 is a graph showing changes in the correction value h1 corresponding to the difference between the target rotation speed NT and the rotation speed NE. Fig. 10 shows the value KDPC.
FIG. 11 is a graph showing the change of the rotational speed NE for explaining the updating operation of a, FIG. 11 is a timing chart for explaining the erroneous control prevention operation for the vibration of the internal combustion engine 10, and FIG. 12 is the rotational speed NE and the target. Fig. 13 is a graph showing the change of the correction value h2 with respect to the difference from the rotation speed NT, Fig. 13 is a timing chart for explaining the operation during the transition when the control duty DUTY is changed, and Fig. 14 is the intake air to the surge tank 6. Flow rate Qi
Fig. 15 is a graph showing the relationship between n and the outflow air flow rate Qout, Fig. 15 is a graph showing changes in the value MAP with respect to changes in the intake pressures P, Pc, PcF in each control duty DUTY, and Fig. 16 is the internal combustion engine 10
FIG. 17 to FIG. 20 are graphs showing changes in the delayed intake pressure PcF in consideration of the response delay of the torque generated by the engine, and FIGS. 17 to 20 are flow charts for explaining the idle speed control operation. 1 ... Control device, 4, 7 ... Intake pipe, 5 ... Slot valve, 6 ...
Surge tank, 8 ... Fuel injection valve, 10 ... Internal combustion engine, 14 ... Exhaust pipe, 20-31 ... Detector, 35 ... Bypass, 36 ... Flow control valve, 43
… Processing circuit, 45… Memory

Claims (2)

(57) [Claims] 1. A rotational speed of an internal combustion engine is provided by connecting an upstream side and a downstream side of a throttle valve with an bypass bypass passage for idling, and changing a control amount of a flow control valve provided in the bypass passage. In an idle speed control device for an internal combustion engine that maintains a predetermined target rotation speed, when it is detected that the rotation speed is lower than a predetermined rotation speed lower than the target rotation speed, it is determined that the engine is immediately before stopping. Then, a predetermined relatively large predetermined amount is added to the control amount of the flow control valve to rapidly increase the control amount, and the rotation speed is increased to the predetermined value by the rapid increase of the control amount. When the temperature is restored, the control amount is rapidly reduced to a predetermined control amount corresponding to a target value (α) of the intake air amount corresponding to the product value of the intake pipe pressure and the target rotation speed at that time. When Idle speed control device for internal combustion engine. 2. The idle speed of the internal combustion engine according to claim 1, wherein the intake pipe pressure is determined in consideration of a response delay of the torque generated by the internal combustion engine with respect to a change in the control amount of the flow control valve. Control device.