JPH09228877A - Idle speed control device for internal combustion engine - Google Patents

Abstract

(57) An object of the present invention is to provide an idle speed control device for an internal combustion engine, which converges to a target speed without causing a drop in speed or a rise. A second target rotation speed is generated from a first target rotation speed before the change so as to approach a new first target rotation speed, and the second target rotation speed is converged to the second target rotation speed. Since the supply air amount, ignition timing, and fuel injection amount are adjusted, the second target rotation speed gradually changes even if the first target rotation speed changes, and excessively accumulates or releases the control amount in integral control. Can be prevented. Further, thereby, it is possible to prevent the engine rotation speed from further dropping or rising after reaching the new first target rotation speed.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to an idle speed control device for an internal combustion engine.

[0002]

2. Description of the Related Art A conventional idle speed control device for an internal combustion engine bypasses a throttle valve provided in an intake system of the engine as disclosed in, for example, Japanese Patent Application Laid-Open No. 57-83665. By providing an auxiliary air passage and an auxiliary air valve in this auxiliary air passage, and setting the auxiliary air valve opening and ignition timing so that the actual rotation speed approaches the target rotation speed, the actual rotation speed is changed to the target rotation speed. Control devices that provide feedback to speed are known.

There is also known an idle rotation speed control device that changes the target rotation speed in accordance with changes in operating conditions, and feed-forwards the amount of air required to cause the change in the target rotation speed. .

For example, when the auxiliary load such as an air conditioner is turned on, the target rotation speed is changed, and the load equivalent amount and the target rotation speed change amount are combined to correct the supply air amount in a feedforward manner. It has been known.

[0005]

However, in such a conventional idle rotation speed control device for an internal combustion engine, as shown in FIG. 8, the target rotation speed is changed and the changed target rotation speed is changed. In the case of increasing or decreasing the supply air amount that is constantly balanced with, even if the supply air amount is increased or decreased, the intake system including the collector has a delay element. It takes time to converge to the rotation speed. Therefore, during this period, the deviation between the target rotation speed and the engine rotation speed remains. In the meantime, if the feedback control having an integral action is simultaneously performed, the supply air amount is further increased or decreased according to the deviation, so that the feedback control and the feedforward control interfere with each other. Therefore, after the engine speed reaches the target speed, the air amount increased by the integral feedback control supplies an air amount that exceeds the air amount that would normally be in equilibrium. There was a problem that the shot was taken and the rotation and fall were further increased.

[0006] In order to prevent this, reducing the gain of the feedback control causes deterioration of the control performance in the first place, which departs from the essential purpose of the idle speed control.

The present invention has been made in view of such a conventional situation, and when the target rotation speed is changed, the supply is constantly balanced with the target rotation speed changed in a feedforward manner accordingly. The second target rotation speed that smoothly connects the target rotation speed before the change and the target rotation speed after the change is generated while the air amount is increased / decreased, and is converged to the second target rotation speed. By adjusting the supply air amount and the ignition timing or the fuel injection amount, the deviation between the rotation speed change caused by the supply air amount by the feedforward control and the second target rotation speed which is the target of the feedback is reduced. As a result, the feedback control and the feedforward control reduce the interference, and after the engine rotation speed reaches the target rotation speed,
It is another object of the present invention to provide an idle speed control device for an internal combustion engine that converges to a target speed without causing a drop in speed or a rise in speed.

[0008]

Means for Solving the Problems For this reason, the present invention provides
In the idle speed control device for an internal combustion engine according to claim 1, the amount of air supplied to the internal combustion engine is adjusted according to the deviation between the target speed and the actual speed so that the speed of the internal combustion engine converges to the target speed. In an idle rotation speed control device for adjusting the ignition timing or the fuel injection amount, first target rotation speed setting means for setting a predetermined target rotation speed, and when the first target rotation speed is changed, Rotation speed correction air amount calculation means for calculating the amount of supply air to be corrected corresponding to generation of this rotation speed difference, and supply air according to the correction amount determined by the rotation speed correction air amount calculation means A second eye that has a supply air amount increasing / decreasing means for increasing / decreasing the amount and continuously connects the first target rotation speed before and after the change with a predetermined characteristic to generate a second target rotation speed. The idle rotation speed control device has a rotation speed generation means, and the idle rotation speed control device supplies the amount of air supplied to the internal combustion engine and the ignition timing or the fuel so as to converge to the second target rotation speed generated by the second target rotation speed generation means. The configuration is such that the injection amount is adjusted.

According to another aspect of the present invention, in the idle speed control device for an internal combustion engine, the second target rotation speed generation means changes the first target rotation speed before the change with a first-order lag or a second-order lag. 2nd so as to approach the target rotation speed of 1
The target rotation speed is generated.

Further, in the idle speed control device for an internal combustion engine according to a third aspect, the first-order or second-order delay according to the second aspect is a response of the engine speed which is expected to change due to the injection of the correction air amount. It is configured to have a first-order or second-order lag with a time constant of the waveform.

Further, in the idle speed control device for an internal combustion engine according to a fourth aspect, the first target rotation speed setting means according to the first to third aspects changes when changing the first target rotation speed. It has a rate of change limiter that limits the rate,
The first target rotation speed is gradually brought closer to the desired target rotation speed based on the limitation of the change rate limiting means.

According to another aspect of the present invention, in the idle speed control device for an internal combustion engine, the limit of the change rate is set based on at least one of the time constant of the primary or secondary delay or the characteristic of the auxiliary air valve. It has a configuration.

According to a sixth aspect of the present invention, in the idle speed control device for an internal combustion engine, in the change rate limiting means according to the fourth aspect, the automatic transmission is changed from the D range to the N range or from the N range to the D range. In this case, the change rate limit value is changed to a larger value.

[0014]

According to the first aspect of the present invention, when the first target rotation speed is changed and the supply air amount corresponding to the auxiliary machine load at the new first target rotation speed is increased / decreased,
Second target rotation speed is generated so as to approach the new first target rotation speed from the target rotation speed, and the supply air amount, ignition timing, or fuel injection is performed so as to converge to the second target rotation speed. Since the amount is adjusted, the second target rotation speed gradually changes even if the first target rotation speed changes, so it is possible to prevent excessive accumulation or release of the control amount in the integral control. . Further, thereby, it is possible to prevent the engine rotation speed from further dropping or rising after reaching the new first target rotation speed.

In the present invention, the second rotation speed is generated with a first-order or second-order delay with respect to the first target rotation speed, and the delay of the intake system and the delay from the generated torque to the increase of the rotation speed are simulated. As a result, the deviation between the actual rotation speed and the target rotation speed becomes smaller. The above-mentioned delay can be approximated by a second-order delay, and even if it is further approximated by a first-order delay, a similar effect can be obtained, and a first-order or second-order delay is used.

In the third aspect, the time constant of the first-order or second-order lag is a time constant of the response waveform of the engine rotation speed when the supply air amount is changed stepwise by the correction of the supply air amount required for changing the rotation speed. By doing so, the change in the engine rotation speed and the change in the second target rotation speed are almost the same, so that the deviation between the actual rotation speed and the target rotation speed becomes small. Therefore, it is possible to prevent jamming and discharging due to an unnecessary control amount by the feedback control.

In the present invention, when the first target rotation speed is changed, the first target rotation speed is gradually changed by limiting the rate of change of the change, so that the low-pass characteristic is changed. Will have. Therefore, even if the engine load state changes, it is possible to prevent the engine speed from changing significantly.

In the fifth aspect, when the change rate limit is set, if the value is increased, it becomes higher than the response speed of the engine rotation speed and greatly deviates from the second target rotation speed. there is a possibility. When that happens,
Since the deviation between the actual rotation speed and the target rotation speed becomes large, an unnecessary control amount due to the feedback control results in the inclusion and release. On the contrary, if it is too small, it takes a long time to reach the required rotation speed in the first place, and it takes too much time until the requirement to change the rotation is satisfied. Also, if the rate of change is too small, an unrealizable target rotation speed may be given when the resolution of the auxiliary air valve is rough, and conversely the convergence to the target rotation speed deteriorates. there's a possibility that. Therefore, it is possible to prevent the actual rotation speed from deviating significantly from the second target rotation speed by limiting the rate of change based on the time constant based on the response from the supplied air amount to the engine rotation speed.

In the sixth aspect, the first target rotation speed is usually set higher in the N range than in the D range. This is in consideration of the ease of driving in the D range (drivability). In this case, in the D range, the amount of supplied air is usually larger than in the N range due to the load of the torque converter and the like, and the D range has a strong characteristic against disturbance. Therefore, in this case, there is no problem even if the priority of the driveability request is raised, and the priority of increasing the limit of the change rate and accelerating the convergence to the target rotation speed is high.

[0020]

Embodiments of the present invention will be described below with reference to the drawings. The configuration of the present application is shown in FIG. FIG.
An embodiment of a configuration for specifically realizing the present application is shown in FIG. Reference numeral 1 denotes a hot wire type air flow rate sensor, which measures the amount of air supplied to the intake pipe. Reference numeral 2 is a bypass passage for bypassing the throttle valve to supply air to the engine, and the auxiliary air valve 3 adjusts the supply air amount.
Reference numeral 4 is a throttle valve which opens and closes in conjunction with an accelerator pedal (not shown). 5 is the intake manifold,
6 is an intake pipe, 7 is an exhaust pipe, 8 is a cylinder block, 9 is a cylinder head, 10 is a combustion chamber, 11 is a piston, 12
Is a connecting rod. Reference numerals 13 and 14 denote an intake valve and an exhaust valve, respectively, which are opened and closed in synchronization with the rotation of a crank shaft (not shown). Reference numeral 15 is an injector, which injects fuel in an amount commanded by the ECU. 16 is a spark plug,
The fuel in the combustion chamber is ignited at the timing commanded by the ECU. An O ₂ sensor 17 detects the presence or absence of oxygen in the exhaust gas. A water temperature sensor 19 detects the water temperature of the engine cooling water. An engine control unit (ECU) 20 performs time measurement, arithmetic processing, storage, and instructions to the actuator.

First, the sensors and actuators used in the present application will be described. The rotation speed of the internal combustion engine is measured in the ECU on the basis of a reference signal generated by a generally known cam type crank angle sensor. The throttle opening sensor is a potentiometer type and outputs a signal corresponding to the depression amount of the accelerator pedal. The signal is input to the ECU. The auxiliary air valve is driven by a step motor, and its opening is adjusted by a command value from the ECU. The spark plug ignites the fuel at the command ignition timing from the ECU. EC is the injector
A command quantity of fuel from U is supplied to the engine. The ECU measures engine speed, calculates target speed, determines idle speed, calculates auxiliary air valve opening, calculates ignition timing, etc. within 10 ms.
Perform every ec.

The engine rotational speed NE [rpm] is a measured value of the output interval of a reference signal issued by the camshaft type crank angle sensor for each combustion (crank angle is 180 ° for 4 cylinders, 120 ° for 6 cylinders). It is calculated by TREF (s). The following formula is for four cylinders. NE = 30 / TREF The target rotation speed is set according to the operating condition of the internal combustion engine. For example, the following settings are made according to the state of the transmission and the state of the air conditioner switch.

[Table 1] Feedback determining means is used for vehicle speed, engine speed,
It is determined according to the situation such as accelerator opening. There are many examples of idle determination methods. For example,
The feedback determination is turned on when the state in which both the conditions (a) and (b) below are satisfied continues for a delay determined by the engine rotation speed when the conditions (a) and (b) are both satisfied. When the feedback judgment is ON, the idle rotation speed control is performed, and when it is OFF, the idle rotation speed control is not performed. (A) Accelerator opening is fully closed (b) Neutral state or vehicle speed is 0 As an example of idle rotation speed control, when feedback determination is ON, the ignition timing is the deviation between the target rotation speed and the actual rotation speed. The proportional (P) control is performed in accordance with. The basic ignition timing is determined according to the conditions such as the water temperature, the engine rotation speed, and the idle determination. For example, when the idle state is in the neutral state, 15 [degBTDC] is set, and when the idle state is not in the neutral state, 10 [deg]
BTDC].

Further, the supply air amount is subjected to, for example, integral (I) control with respect to the deviation between the target rotation speed and the actual rotation speed. Further, regarding the control characteristic of the present application, the one to which claim 2 is applied (hereinafter, referred to as the first embodiment), the one to which claim 4 is applied (hereinafter, referred to as the second embodiment) and the claim 6 are described. The applied one (hereinafter referred to as the third embodiment) will be sequentially described.

Hereinafter, the EC of the second target rotation speed generating means
The procedure in U will be described based on the flowchart shown in FIG. Here, a method of generating the second target rotation speed with a first-order lag with respect to the first target rotation speed will be described.

First, NESET in the flowchart
Is the first target rotation speed. NETARGET is
This is the second target rotation speed. The CNQ is a coefficient of the first-order lag filter for generating the second target rotation speed, and
Is set by After each variable name (o1d)
The ones with means the previous calculated value.
In S101, the first target rotation speed NESET is read. In S102, the second target rotation speed NETA of the last time
Read RGET (o1d). In S103, the first-order lag filter coefficient CNQ is read. In S104, a new NETARGET is calculated by the following formula. NETAEGET = CNQ x NETAEGET (old) + (l-CNQ) x NESET Due to this, when NESET is changed, it approaches NESET after being changed with a first-order delay.

First, when the first embodiment is carried out, N
The operation when the air conditioner load is turned on in the range will be described. When the air conditioner is turned on, first, the first target rotation speed is changed from 650 rpm to 750 rpm, and at the same time, the engine rotation speed is constantly 750 rpm, and the amount of air enough to balance the air conditioner load is increased and corrected. Further, in order to increase the rotation speed, which is the main object of the present application, the amount of air required to increase the rotation speed from 650 rpm to 750 rpm is also increased and corrected. Here, because the load is constantly balanced and the amount of air required to increase the rotation is corrected,
It will eventually converge to the first target rotation speed. The trajectory of the engine rotation speed at that time is approximated by a first-order lag,
The first target rotation speed (7) which is the changed target rotation speed
Since it converges to 50 rpm), by setting CNQ from the time constant, as shown in FIG. 5, the trajectory of the second target rotation speed and the actual rotation speed does not deviate significantly. Therefore, even if the feedback control is executed for the disturbance, the problem as shown in FIG. 8 does not occur,
The engine rotation speed converges on the first target rotation speed.

Next, the operation when the air conditioner load is turned on in the N range when the second embodiment is carried out will be described.
As shown in FIG. 4A, when the air conditioner is turned on, first, the first target rotation speed is changed from 650 rpm to 750 rpm.
Change to rpm, but change speed is 1 every 1 sec
Limit to change by 2.5 rpm. Further, the amount of air such that the engine rotation speed constantly reaches the limited first target rotation speed and the amount of air enough to balance the air conditioner load are increased and corrected. Since the engine speed is once converged every 12.5 rpm, the second
Since the deviation from the target rotation speed is smaller than that in the first embodiment, the engine rotation speed converges more stably to the first target rotation speed. This is shown in FIG.

Next, the operation when the N range is switched to the D range when the third embodiment is carried out will be described.
The first target rotation speed in the N range is 650 rpm, while the first target rotation speed in the D range is 600 rpm. As described above, the D range is generally set to be lower in order to improve fuel efficiency and reduce creep force. So N
If the first target rotation speed is still high when the range is changed from the range to the D range, the creep force becomes strong, so the drivability is prioritized and the change rate limit is increased. For example, FIG.
As shown in, the limit is changed so as to be changed by 12.5 rpm every 0.25 sec, and the first target rotation speed is changed quickly. As a result, the drivability is secured while the engine rotation speed converges to the first target rotation speed. This is shown in FIG.

Although the embodiment of the present invention has been described in detail with reference to the drawings, the specific configuration is not limited to this embodiment, and a design change or the like may be made without departing from the gist of the present invention. If so, they are included in the present invention. For example, when setting the time constant, it may be set experimentally in advance.
It is also possible to have a model in the CU and determine it based on the operating state, for example, engine cooling water temperature or addition.

[0030]

As described above, according to the present invention, in claim 1, even if the first target rotation speed is changed, the engine rotation speed is made to converge to the second target rotation speed. By adjusting the supply air amount, the ignition timing, or the fuel injection amount individually or in combination, it becomes possible to provide an idle rotation speed control device having good convergence to the first target rotation speed. Claims 2 and 3
In the above, there is a characteristic of the engine by generating the second target rotation speed with a first-order or second-order lag so as to approach the first target rotation speed after the change from the first target rotation speed before the change. The second target rotation speed can be generated, and the idle rotation speed control device having good convergence with the first target rotation speed can be provided. In Claims 4 and 5, when the first target rotation speed is changed, by limiting the rate of change, a low-pass characteristic is provided, so there is a load fluctuation during the change of the target rotation speed. Even if it occurs, it is possible to provide an idle rotation speed control device that is resistant to load fluctuations without causing a sudden rotation speed fluctuation. In claim 6, when the N range is switched to the D range,
Since it is possible to quickly reduce the first target rotation speed to the target rotation speed of the D range, it is possible to provide an idle rotation speed control device that realizes good drivability even when starting at the moment of entering the D range. I can do it now.

[Brief description of drawings]

FIG. 1 is a configuration diagram of the present invention.

FIG. 2 is a diagram showing an embodiment to which the present invention is applied.

FIG. 3 is a flowchart of control of second target rotation speed generation means in the ECU.

FIG. 4A is a diagram showing how the first target rotation speed changes when a change rate limit is applied in the second embodiment, and FIG. 4B shows a change rate in the third embodiment. It is a figure which shows the mode of change of the 1st target rotation speed when a limit is added.

FIG. 5 is a diagram showing effects of the first embodiment.

FIG. 6 is a diagram showing the effect of the second embodiment.

FIG. 7 is a diagram showing the effect of the third embodiment.

FIG. 8 is a diagram showing an increase in engine rotation speed due to interference between feedforward control and feedback control by conventional control.

Claims (6)

[Claims] 1. A first target rotation speed setting means for setting a predetermined rotation speed of an internal combustion engine, and the first target rotation speed and an actual rotation so as to converge to the predetermined first target rotation speed. In an idle rotation speed control device that adjusts the supply air amount, ignition timing, or fuel injection amount of an internal combustion engine individually or in combination according to the deviation from the speed, when the first target rotation speed is changed, , The rotation speed correction air amount calculation means for calculating the supply air amount to be corrected corresponding to the change in the target rotation speed, and the rotation speed correction air amount calculation means. Has a supply air amount increasing / decreasing means for increasing / decreasing the supply air amount according to the correction amount, and continuously connects the first target rotation speed before and after the change with a predetermined characteristic to obtain the second target rotation speed. Living And a second target rotation speed generating means, wherein the idle rotation speed control device supplies the amount of supply air and ignition so as to converge to the second target rotation speed generated by the second target rotation speed generating means. An idle speed control device for an internal combustion engine, characterized in that the timing or the fuel injection amount is adjusted individually or in combination. 2. The second target rotation speed generating means is configured to bring the second target rotation speed closer to the changed first target rotation speed with a first-order or second-order delay from the first target rotation speed before the change. The idle speed control device for an internal combustion engine according to claim 1, wherein the speed is generated. 3. The first-order or second-order lag according to claim 2 is a first-order or second-order lag having a time constant of a response waveform of an engine rotation speed, which is expected to change due to the injection of the corrected air amount. The idle speed control device for an internal combustion engine according to claim 2, characterized in that. 4. The first target rotation speed setting means according to claim 1 has change rate limiting means for limiting the change rate when changing the first target rotation speed, and the change rate limiting means. 4. The idle rotation speed control device for an internal combustion engine according to claim 1, wherein the first target rotation speed is gradually approached to a desired target rotation speed based on the limitation of 1. 5. The internal combustion engine according to claim 4, wherein the restriction by the change rate restricting means is set based on at least one of the time constant of the primary or secondary delay and the characteristic of the auxiliary air valve. Idle speed controller. 6. The change rate limiting means according to claim 4, wherein the automatic transmission has a D range to N range or an N range to D range.
5. The idle speed control device for an internal combustion engine according to claim 4, wherein the limit value of the rate of change is changed to a large value when the range is changed.