JP2006177301A - Idle rotation speed controller for internal combustion engine - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To accurately compensate intake density of ISC compensation amount in a cold condition and avoid unnecessary compensation of intake density and erroneous learning of an ISC learned value in a warm condition. <P>SOLUTION: When the engine 1 is warm, the ISC learned value qg obtained after completing learning becomes a value corresponding to deviation from a proper value of intake air amount based on difference in intake density. The deviation is compensated by adjusting the ISC compensation amount Qcal based on the ISC learned value qg. When the engine 1 is cold, intake density compensation based on intake density compensation amount H is performed for only cold compensation item A of the ISC compensation amount Qcal to compensate the deviation. The intake density compensation amount H is set to such a value that increases the cold compensation item A as intake density is reduced to compensate the deviation from the proper value of intake air amount based on difference in intake density when the engine is cold and is set to "zero" when the engine is warm. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

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

  In an internal combustion engine such as an automobile engine, fuel injection corresponding to the intake air amount is performed. Therefore, as the intake air amount increases, the amount of air-fuel mixture burned increases and the engine output increases. For this reason, at the time of idling operation of the internal combustion engine, idling rotation speed control for controlling the engine rotation speed through adjustment of the intake air amount is performed. The adjustment of the intake air amount in the idle rotation speed control is performed based on the ISC correction amount. For example, the intake air amount increases as the ISC correction amount increases.

  The ISC correction amount includes a feedback term that increases or decreases the engine speed to approach the target value during idle operation, an ISC learning value that increases or decreases to converge the feedback term within a predetermined range when the internal combustion engine is warm, It is a value provided with a cold correction term that increases or decreases in the meantime, and a cold / warm correction term that increases or decreases from the cold to the warm of the engine.

  Here, the ISC learning value is for compensating for a steady deviation from an appropriate value of the intake air amount due to a change over time of the intake system, such as deposit adhesion in the intake system in an internal combustion engine. That is, the ISC learning value (hereinafter referred to as the learned ISC learning value) in a state where the feedback term is converged within the predetermined range during the warm period is a value corresponding to the steady deviation, and the ISC learning at this time The steady deviation is compensated by adjusting the amount of intake air corresponding to the value.

  Further, the intake air amount of the internal combustion engine changes according to the density of the intake air (intake air density). For example, in high altitudes where the atmospheric pressure is low, the intake air density decreases and the intake air amount of the engine decreases. Sometimes, the deviation of the intake air amount from the appropriate value based on the difference in intake air density can also be compensated by the ISC learning value learned during the warm period. That is, when the learning of the ISC learning value is completed in the warm state, the ISC learning value becomes a value corresponding to the intake air density, and the difference in the intake air density is adjusted by adjusting the cold / warm correction term corresponding to the ISC learning value at this time. The deviation from the appropriate value of the intake air amount based on the above is compensated. For this reason, the amount of intake air can be maintained at a necessary value (appropriate value) even in a situation where the intake density is low, such as at high altitudes, during warm weather.

  However, the increase / decrease of the ISC learning value is not performed during cold weather when engine operation is difficult to stabilize. For this reason, it is possible to adjust the cold / warm correction term to a value corresponding to the intake air density based on the learned ISC learned value during the warm period, but the learned ISC learned value is adjusted during the cold period. Therefore, the cold correction term cannot be adjusted to a value corresponding to the intake air density. This is because a large amount of intake air is required for stable engine operation in the cold state, and even if the cold correction term is adjusted with the ISC learning value learned in the warm state, the cold correction term after the adjustment is adjusted. This is because is less than the value suitable for the intake density. Therefore, for example, when the engine is cold at a high altitude where the intake air density is low, a shortage of the intake air amount becomes remarkable, which may lead to a stall of the internal combustion engine.

In order to cope with such a problem, it is conceivable to apply the technique of Patent Document 1, that is, the intake density correction in which the ISC correction amount is increased as the atmospheric pressure is lower and the intake density is smaller. In this case, at the time of cold, the shortage of the cold correction term that cannot be compensated only by adjusting the cold correction term based on the ISC learning value is compensated by the intake density correction of Patent Document 1 for the ISC correction amount (cold correction term). Thus, the cold correction term can be set to a value suitable for the intake air density. Therefore, it is possible to suppress the occurrence of stall due to a shortage of intake air amount when cold at high altitude as described above.
JP-A-6-294337

  As described above, by applying the intake air density correction of Patent Document 1, it is possible to adjust the ISC correction amount (cold correction term) to a value corresponding to the intake air density when cold. However, by simply applying the intake air density correction of Patent Document 1, the intake air density correction for the ISC correction amount (cold / warm correction term) is not only cold, but also cold. This is done in a similar manner. Since the adjustment of the cold / warm correction term based on the learned ISC learning value is performed during the warm period, even if the intake air density correction of Patent Document 1 is further performed, the adjustment is useless. It will be a thing. Further, when the intake density correction of Patent Document 1 is performed, if the ISC learning value is learned, the ISC learning value includes the amount of the intake density correction, and the ISC learning value is erroneously learned. Will also be invited.

  The present invention has been made in view of such circumstances, and its purpose is to accurately perform the intake density correction of the ISC correction amount when cold, and to perform unnecessary intake density correction and ISC learning when warm. An object of the present invention is to provide an idle speed control device for an internal combustion engine that can avoid erroneous learning of values.

In the following, means for achieving the above object and its effects are described.
In order to achieve the above object, according to the first aspect of the present invention, in the idle rotational speed control device for an internal combustion engine that controls the engine rotational speed during idle operation through adjustment of the intake air amount based on the ISC correction amount, the ISC correction amount. Is a feedback term that increases or decreases the engine rotational speed to approach the target value, an ISC learning value that increases or decreases to converge the feedback term within a predetermined range when the internal combustion engine is warm, and a cooler that increases or decreases when the engine is cold. And a cold / warm correction term that increases or decreases from the cold to the warm of the engine, and only when the internal combustion engine is cold and only for the cold correction term The gist of the invention is to perform the intake air density correction to increase the cold correction term as the intake air density decreases.

  When the internal combustion engine is warm, the ISC learning value is increased or decreased so that the feedback term converges within a predetermined range. The learning of the ISC learning value is completed when the feedback term converges within a predetermined range. When the internal combustion engine is warm, the learned ISC value is a value corresponding to the intake air density (intake density), and the cold / warm correction term is a value corresponding to the intake density based on the ISC learned value. Adjusted to By this adjustment, a deviation from an appropriate value of the intake air amount based on the difference in intake density is compensated. On the other hand, when the internal combustion engine is cold, intake density correction is performed so that the cold correction term becomes larger as the intake density becomes smaller than the cold correction term. The deviation from the appropriate value can be compensated. Further, such an intake air density correction is not performed for the cold / warm correction term during the warm period. For this reason, during the warm period, unnecessary correction of the intake air density with respect to the cold / warm correction term, and the erroneous learning of the ISC learning value associated with the learning of the ISC learning value simultaneously with the correction of the intake air density. Can be avoided.

  According to a second aspect of the present invention, in the idle rotation speed control device for an internal combustion engine that controls the idle rotation speed by adjusting the intake air amount based on the ISC correction amount, the ISC correction amount is set so that the engine rotation speed approaches the target value. A feedback term that increases or decreases, an ISC learning value that increases or decreases to converge the feedback term within a predetermined range when the internal combustion engine is warm, a cold correction term that increases or decreases when the internal combustion engine is cold, and a cold state of the engine And a cold / warm correction term that increases and decreases over the temperature, and only when the internal combustion engine is cold, the density of the intake air is higher than the cold correction term and the cold / warm correction term. The gist of the invention is that the intake density correction is performed so that both correction terms become larger as the value becomes smaller, and the intake density correction for the cold / warm correction term is made smaller than the intake density correction for the cold correction term.

  When the internal combustion engine is warm, the ISC learning value is increased or decreased so that the feedback term converges within a predetermined range. The learning of the ISC learning value is completed when the feedback term converges within a predetermined range. When the internal combustion engine is warm, the learned ISC value is a value corresponding to the intake air density (intake density), and the cold / warm correction term is a value corresponding to the intake density based on the ISC learned value. Adjusted to By this adjustment, a deviation from an appropriate value of the intake air amount based on the difference in intake density is compensated. On the other hand, when the internal combustion engine is cold, the intake air density correction is performed so that the smaller the intake air density is, the smaller the intake air density is with respect to the cold correction term and the cold / warm correction term. Here, the cold / warm correction term is adjusted based on the ISC learning value learned during the warm time, thereby reducing the need for the intake air density correction. In consideration of this, the intake air density correction for the cold / warm correction term is performed smaller than the intake air density correction for the cold correction term. By the above intake density correction, it is possible to compensate for the deviation of the intake air amount from the appropriate value based on the difference in intake density. Further, such an intake air density correction is not performed for the cold / warm correction term during the warm period. For this reason, during the warm period, unnecessary correction of the intake air density with respect to the cold / warm correction term, and the erroneous learning of the ISC learning value associated with the learning of the ISC learning value simultaneously with the correction of the intake air density. Can be avoided.

According to a third aspect of the invention, in the first or second aspect of the invention, the intake air density correction is not performed when the cold correction term is a value for reducing the intake air amount.
During cranking during cold start of the internal combustion engine, the cold correction term may be a value that reduces the intake air amount to reduce the intake air amount. In such a case, the cold correction term is further adjusted to reduce the intake air amount through the intake air density correction, and the startability of the internal combustion engine may be deteriorated due to excessive reduction of the intake air amount. However, according to the above configuration, when the cold correction term becomes a value on the side of reducing the intake air amount by the intake density correction, the intake air density correction is not performed. Deterioration of startability of the internal combustion engine due to excessive reduction of the amount can be suppressed.

  In the invention according to claim 4, in the invention according to any one of claims 1 to 3, the correction corresponding to the intake density in the high altitude is erroneously performed in the low altitude. When performed, it was performed in a manner that would not cause an excessive increase in engine speed.

  According to the above configuration, even if the intake air density correction at the high altitude is mistakenly performed at the low altitude for the cold correction term, the engine rotation is excessively increased accordingly, which affects the drivability of the internal combustion engine. Can be suppressed.

  According to a fifth aspect of the invention, in the invention according to any one of the first to fourth aspects, the intake air density correction in the cold correction term is performed using an intake air density correction coefficient calculated based on the intake air density. The intake air density correction coefficient is guarded on the side that increases the intake air amount based on a guard value that is set according to the engine speed in the idle state. .

  According to the above configuration, when the intake air density correction at a high altitude is mistakenly performed at a low altitude with respect to the cold correction term, even if the engine rotation increases accordingly, it is set according to the engine rotation speed at that time The intake density correction coefficient is guarded on the side that increases the intake air amount based on the guard value that is set. Through this guard process, it is possible to suppress an excessive increase in the engine rotational speed, and to suppress the excessive increase in the engine rotational speed from affecting the drivability of the internal combustion engine.

According to a sixth aspect of the present invention, in the fifth aspect of the present invention, updating of the guard value based on the engine rotational speed is permitted only to update the guard value to the intake air amount reduction side.
If the engine speed decreases through the intake density correction coefficient guard process, and if the guard value is updated to the intake air amount increase side as the engine speed decreases, the intake density correction coefficient is greater than the guard value. It becomes a value on the amount reduction side, the guard of the intake density correction coefficient is released, and the engine speed increases again. Then, when the guard value is updated to a value on the intake air amount decrease side with respect to the intake density correction coefficient as the engine rotational speed increases, the intake density correction coefficient again increases the intake air amount using the card value. Is guarded about. As described above, when the update of the guard value to the intake air amount increase side is permitted, hunting that the guard execution / guard release of the intake density correction coefficient is repeated occurs. However, according to the above configuration, only updating of the guard value to the intake air amount decreasing side is permitted, and updating of the guard value to the intake air amount increasing side is prohibited, so that hunting as described above occurs. Can be avoided.

Hereinafter, an embodiment in which the present invention is applied to an in-cylinder injection engine for an automobile will be described with reference to FIGS.
In the engine 1 shown in FIG. 1, air is sucked into the combustion chamber 3 from the intake passage 4, and an amount of fuel corresponding to the amount of this air (intake air amount) passes from the fuel injection valve 2 into the combustion chamber 3. Is injected into. For this reason, the larger the intake air amount through the adjustment of the opening degree of the throttle valve 12 provided in the intake passage 4, the greater the amount of air-fuel mixture combusted in the combustion chamber and the higher the engine output. During idle operation of the engine 1, idle rotation speed control is performed in which the intake air amount is adjusted based on the opening degree adjustment of the throttle valve 12 to control the engine rotation speed.

  Such idle rotation speed control is executed through an electronic control device 20 mounted on the automobile to control the operation of the engine 1. The electronic control unit 20 controls the drive of the fuel injection valve 2 and the throttle valve 12 and inputs detection signals from various sensors described below.

An accelerator position sensor 15 that detects the amount of depression (accelerator depression amount) of the accelerator pedal 14 that is depressed by the driver of the automobile.
A throttle position sensor 16 that detects the opening of the throttle valve 12 (throttle opening).

An air flow meter 13 that detects the flow rate of air taken into the combustion chamber 3 via the intake passage 4 (intake air flow rate).
A crank position sensor 10 that outputs a signal corresponding to the rotation of the crankshaft 9 that is the output shaft of the engine 1.

A water temperature sensor 11 that detects the cooling water temperature of the engine 1.
Here, throttle opening degree control performed by driving the throttle valve 12 by the electronic control unit 20 will be described.

  The opening degree of the throttle valve 12 is controlled based on the throttle opening degree command value TAt through the electronic control unit 20. This throttle opening command value TAt is calculated using the following equation (1).

TAt = TAbase + Qcal · kt (1)
TAbase: Basic throttle opening
Qcal: ISC correction amount
kt: Conversion coefficient In the above equation (1), the basic throttle opening degree TAbase is the engine rotation amount obtained based on the accelerator depression amount obtained from the detection signal from the accelerator position sensor 15 and the detection signal from the crank position sensor 10. It is a value calculated based on the speed or the like.

  The basic throttle opening degree TAbase is set to “0”, for example, when the engine 1 is idling. Therefore, the throttle opening command value TAt during idle operation is determined by the term “Qcal · kt” in the equation (1). In the term “Qcal · kt”, the ISC correction amount Qcal is a dimensionless parameter that increases or decreases in order to adjust the engine rotation speed in the idle rotation speed control, and the conversion coefficient kt indicates the throttle opening of the ISC correction amount Qcal. It is for converting into a parameter of degree.

  During the idle rotation speed control, as the ISC correction amount Qcal increases, the opening of the throttle valve 12 increases and the engine rotation speed increases. Conversely, the smaller the ISC correction amount Qcal, the smaller the opening of the throttle valve 12 and the lower the engine speed.

Next, the procedure for calculating the ISC correction amount Qcal used for idle rotation speed control will be described.
The ISC correction amount Qcal is obtained under the condition that the engine 1 is idling in the warm-up completion state, and the feedback term qi, the ISC learning value qg, the cold correction term A, the cold / warm correction term B, and Based on the intake air density correction amount H, it is calculated using the following equation (2).

Qcal = qi + qg + A + B + H (2)
Qcal: ISC correction amount
qi: feedback term
qg: ISC learning value
A: Cold correction term
B: Cold / warm correction term
H: Intake density correction amount Hereinafter, the feedback term qi, the ISC learning value qg, the cold correction term A, the cold / warm correction term B, and the intake density correction amount H will be described individually.

[Feedback term qi]
The feedback term qi is a value that is increased or decreased to bring the engine rotation speed closer to a preset target value according to the load state when the engine 1 is idling. That is, when the engine speed is lower than the target value, the feedback term qi is increased and the ISC correction amount Qcal is increased. As a result, the throttle opening command value TAt becomes large and the throttle valve 12 is controlled to the open side, so that the engine rotation speed increases and approaches the target value. When the engine speed is higher than the target value, the feedback term qi is reduced and the ISC correction amount Qcal is reduced. As a result, the throttle opening command value TAt becomes small, and the throttle valve 12 is controlled to the closed side, so that the engine speed decreases and approaches the target value.

[ISC learning value qg]
The ISC learning value qg is a value for compensating for a steady deviation from an appropriate value of the intake air amount due to a change with time of the intake system such as deposit adhesion in the intake system of the engine 1. The ISC learning value qg is increased or decreased so that the feedback term qi converges within a predetermined range when the engine 1 is in a stable state where the engine operating state is stable, for example, when the cooling water temperature detected by the water temperature sensor 11 is 70 ° C. or higher. Is done.

  More specifically, when the feedback term qi is out of the predetermined range, the ISC learning value qg is increased and the ISC correction amount Qcal is increased. As a result, the feedback term qi that has previously increased the ISC correction amount Qcal is reduced toward the predetermined range. Further, when the feedback term qi deviates from the predetermined range, the ISC learning value qg is reduced and the ISC correction amount Qcal is reduced. As a result, the feedback term qi that had previously reduced the ISC correction amount Qcal is increased toward the predetermined range.

  Then, the ISC learning value qg (hereinafter referred to as the learned ISC learning value qg) in a state where the feedback term qi is converged within the predetermined range during the warm period is a value corresponding to the steady deviation. The steady deviation is compensated by adjusting the throttle opening (intake air amount) corresponding to the ISC learning value qg. The ISC learning value qg that has been learned as described above is stored in a non-volatile memory provided in the electronic control unit 20, and is used to calculate the ISC correction amount Qcal at the time of idle speed control in the next engine operation. Used.

[Cold correction term A]
The cold correction term A is a correction term that increases or decreases when the engine 1 is cold, that is, when the cooling water temperature is less than 70 ° C. when the ISC learning value qg is not increased or decreased. Such cold correction term A includes a start-up raising term qsta, a water temperature correction term qthw, a target rotational speed correction term qdlnt, a cranking correction term qcrnk, and the like.

  The start-up raising term qsta is a correction term for securing a large amount of intake air necessary for starting the engine 1, and the water temperature correction term qthw is against the increase in friction caused by the oil viscosity at low engine temperature. This is a correction term for causing the engine 1 to rotate stably. The target rotational speed correction term qdlnt is a correction term that is increased or decreased according to the target value for the purpose of bringing the engine rotational speed close to the target value for idle rotational speed control with good responsiveness. . Furthermore, the cranking correction term qcrnk reduces the intake air amount by reducing the ISC correction amount Qcal when the engine speed increases rapidly during cranking after starting the engine, and suppresses the lean air-fuel mixture. It is a correction term for Note that the air-fuel mixture leans with the rapid increase in the engine speed because the time during which the fuel injection from the fuel injection valve 2 can be injected becomes shorter with the rapid increase, and the fuel actually injected from the fuel injection valve 2 This is because the amount of is less than the required amount. In order to suppress such leaning of the air-fuel mixture, the amount of intake air is reduced through the reduction of the ISC correction amount Qcal corresponding to the cranking correction term qcrnk.

[Cold / warm correction term B]
The cold / warm correction term B is a correction term that increases or decreases from the cold time of the engine 1 to the warm time, and includes an alternator correction term qo, an electric load correction term qe, an air conditioner correction term qac, and the like. It is.

  The alternator correction term qo is a correction term that is increased or decreased in order to stably rotate the engine 1 according to the accompanying drive resistance of the engine 1 when power is generated by the alternator of the engine 1 during idle operation. The electric load correction term qe is an engine 1 for obtaining a required power generation amount when it becomes necessary to increase the power generation amount of an alternator that supplies power to the devices with the operation of various electric devices of the automobile. This is a correction term for preventing the engine rotational speed from excessively decreasing due to the driving load (electric load). Further, the air conditioner correction term qac is a correction term that is increased or decreased to stably rotate the engine 1 when the driving resistance of the engine 1 increases with the operation of the air conditioner of the automobile.

[Intake density correction amount H]
The intake air density correction amount H is for compensating for a deviation from an appropriate value of the intake air amount based on a difference in intake air density (intake air density) of the engine 1.

  When the engine 1 is warm, the learned ISC learning value qg becomes a value corresponding to the above-described deviation. By adjusting the cold / warm correction term B based on this ISC learned value qg, the deviation is corrected. Will be compensated. However, when the engine 1 is cold, a larger amount of intake air is required for stable engine operation than when it is warm, and the value corresponding to the above-mentioned deviation is different from that when warm. Since the ISC learning value qg is sometimes not increased or decreased, the ISC learning value qg does not become a value corresponding to the deviation. For this reason, even if the ISC learning value qg that has been learned during the warm period is used for the adjustment of the cold correction term A during the cold period, the above-described deviation cannot be fully compensated. Therefore, for example, when the engine is cold at a high altitude where the intake air density is low, a shortage of the intake air amount becomes remarkable, which may lead to a stall of the internal combustion engine.

  In order to deal with this problem, as described in the “Background Art” column, the technique of Patent Document 1 is applied, and the ISC correction amount Qcal increases as the intake air density decreases regardless of whether it is cold or warm. It is conceivable to correct the intake air density. In this case, the cold correction term A can be adjusted to a value corresponding to the intake air density by the intake air density correction in the cold state to compensate for the deviation, but the intake air density correction is unnecessarily performed in the warm state. As described in the section “Problems to be solved by the invention”, the ISC learning value qg is erroneously learned.

  In view of such a situation, the intake air density correction amount H is corrected only when the engine 1 is cold and only with respect to the cold correction term A. In other words, the intake air density correction amount H is set to a value that increases the cold correction term A as the intake air density decreases to compensate for the deviation from the appropriate value of the intake air amount based on the difference in intake air density when cold. When warm, it is set to “0”. By operating the intake air density correction amount H as described above, the above deviation is accurately compensated by the intake air density correction using the intake air density correction amount H in the cold state, and unnecessary intake density correction is performed in the warm state. And the erroneous learning of the ISC learning value qg accompanying the learning of the ISC learning value qg simultaneously with the correction can be avoided.

  Next, the procedure for calculating the intake air density correction amount H will be described with reference to the flowcharts of FIGS. 2 and 3 showing the intake air density correction amount calculation routine. This intake density correction amount calculation routine is executed through the electronic control unit 20 by, for example, a time interruption every predetermined time.

The intake air density correction amount H is calculated using the following equation (3) based on the cold correction term A and the intake air density correction coefficient K2.
H = (A / K2) -A (3)
H: Intake density correction amount
A: Cold correction term
K2: Intake density correction coefficient Here, the intake density correction coefficient K2 is a value that is increased or decreased around the reference value “1.0” based on the atmospheric pressure. That is, as the atmospheric pressure becomes lower than the standard atmospheric pressure and the intake air density becomes smaller, the intake air density correction coefficient K2 becomes farther from the reference value “1.0”. Conversely, as the atmospheric pressure becomes higher than the standard atmospheric pressure and the intake air density increases, the intake air density correction coefficient increases from the reference value “1.0” toward the increasing side. For this reason, the intake air density correction amount H calculated by the equation (3) in the cold state has a characteristic that it increases as the intake air density decreases and decreases as the intake air density increases. The intake density correction amount H calculated in this way is a value that compensates for a deviation from an appropriate value of the intake air amount based on a difference in intake air density during cold. Then, by adding the intake air density correction amount H to the cold correction term A in the equation (2) in the cold state, the cold correction term A is corrected to the value corresponding to the intake air density.

In the intake air density correction amount calculation routine of FIG. 2 and FIG. 3, the following various processes related to the intake air density correction amount H are executed in order.
[1] Atmospheric pressure estimation processing for estimating atmospheric pressure (S101, S102).

[2] Intake density correction coefficient calculation processing for calculating the intake density correction coefficient K2 based on the estimated atmospheric pressure (S103 to S106).
[3] Intake density correction coefficient guard processing (S107 to S113) for calculating the guard value G of the intake density correction coefficient K2 and guarding the intake density correction coefficient K2 on the intake air amount increase side based on the guard value G.

[4] Intake density correction amount calculation processing (S114) for calculating the intake density correction amount H based on the above equation (3).
[5] Intake density correction prohibition processing (S115, S116) in which the intake density correction is not performed when the calculated intake density correction amount H is a value (less than “0”) that decreases the intake air amount.

Hereinafter, each of the processes [1] to [5] will be described in detail individually.
[1] Atmospheric pressure estimation processing (S101, S102)
In this process, first, it is determined whether or not the opening degree of the throttle valve 12 is large, for example, whether or not the opening degree is close to full opening (S101 in FIG. 2). If the determination is affirmative, atmospheric pressure is calculated and stored (S102).

  More specifically, the actual intake air amount of the engine 1 is obtained based on the detection signal from the air flow meter 13, and the intake air that should be drawn into the engine 1 under the standard atmospheric pressure based on the throttle opening at that time. The amount (reference air amount) is obtained by map calculation or the like. Note that as the throttle opening for obtaining the reference air amount, an actual measurement value obtained based on a detection signal from the throttle position sensor 16 is used. Here, the fact that the actual intake air amount is less than the reference air amount means that the atmospheric pressure is lower than the standard atmospheric pressure and the intake density is small, and the actual intake air amount is larger than the reference air amount. This means that the atmospheric pressure is higher than the standard atmospheric pressure and the intake density is large. In this way, using the fact that the difference between the actual intake air amount and the reference air amount is related to the deviation of the actual atmospheric pressure from the standard atmospheric pressure, the atmospheric pressure is calculated based on the difference. . The calculated atmospheric pressure is stored in a nonvolatile memory of the electronic control unit 20.

  However, the calculation and storage of the atmospheric pressure described above is performed only when the throttle opening is large. This is because the difference between the actual intake air amount and the reference air amount is unlikely to appear as the difference between the actual intake air amount and the reference air amount in the operation region where the throttle opening is small and the intake air amount is small, such as during idle operation. It is because it is difficult to make the atmospheric pressure calculated | required based on this to an exact value. Accordingly, the calculation and storage of the atmospheric pressure is performed only in the operation region where the intake air amount increases and the atmospheric pressure can be accurately calculated, that is, the operation region where the throttle opening is large.

[2] Intake density correction coefficient calculation processing (S103 to S106)
In this process, the atmospheric pressure correction coefficient K1 used for various controls other than the idle rotation speed control is calculated using the atmospheric pressure stored in the nonvolatile memory of the electronic control unit 20 (S103). The atmospheric pressure correction coefficient K1 calculated in this way is “1.0” when the atmospheric pressure is the standard atmospheric pressure, and changes from “1.0” to a smaller value as it becomes lower than the standard atmospheric pressure. go.

  Subsequently, on the condition that the engine 1 is cold (S104: YES), the intake air density correction coefficient K2 is calculated with reference to the map of FIG. 4 based on the atmospheric pressure correction coefficient K1 (S105). The intake air density correction coefficient K2 calculated in this way becomes a value close to “1.0” as compared to the atmospheric pressure correction coefficient K1 used in various controls other than the idle rotation speed control. When the atmospheric pressure (intake density) becomes small and the intake density correction coefficient K2 becomes less than “1.0”, the intake density correction amount H becomes larger than the reference value “0”, and the intake density correction is performed. By adding the amount H to the cold correction term A as shown in the equation (2), the cold correction term A is corrected to the value corresponding to the intake air density.

  On the other hand, when the engine 1 is warm (S104: NO), the intake density correction coefficient K2 is set to "1.0" (S106). As a result, the intake air density correction amount H is set to the reference value “0”, and the intake air density correction by the intake air density correction amount H is not performed.

  By the way, since the atmospheric pressure is calculated and stored only when the throttle opening is large as described above, the stored atmospheric pressure is lower than the actual atmospheric pressure under the following conditions, for example. That happens. That is, atmospheric pressure is calculated and stored when the throttle opening is large while driving from low to high, and when returning from low to high The atmospheric pressure at high altitude remains memorized. It is highly possible that only the fully closed area is used as the opening area of the throttle valve 12 when returning from the highland to the lowland, and the atmospheric pressure is calculated and stored when the throttle opening is large. This is because there is a high possibility that it will not be broken.

  As described above, when the atmospheric pressure of the highland is stored in the lowland, when the engine 1 is stopped once and the engine 1 is cooled, the cold correction term A is used regardless of the lowland. On the other hand, the intake density correction at a high altitude by the intake density correction amount H is erroneously performed. As a result, the intake air amount of the engine 1 becomes too large, and the engine rotational speed may be excessively increased. In order to deal with this, the calculation of the intake air density correction coefficient K2 in step S105 is performed so as to be a value that can suppress an excessive increase in the engine rotation speed under the above-described circumstances. For this reason, regarding the intake air density correction of the cold correction term A by the intake air density correction amount H calculated based on the intake air density correction coefficient K2, the engine rotation when the intake air density correction corresponding to the high altitude is erroneously performed in the low altitude. It is performed in such a manner that an excessive increase in speed is suppressed as much as possible.

[3] Intake density correction coefficient guard processing (S107 to S113)
As described above, this process is performed when the intake air density correction at the high altitude by the intake air density correction amount H is mistakenly performed for the cold correction term A in spite of the low altitude as described above. The intake air density correction coefficient K2 for calculating the intake air density correction amount H is guarded on the intake air amount increase side based on the guard value G so as not to increase excessively.

  In this processing, when the accelerator depression amount is “0 (accelerator off)” (S107: YES in FIG. 3), for example, when in an idle operation state, the automatic transmission connected to the engine 1 is in the neutral position (S108). : YES), the guard value G is calculated based on the engine speed during idling (S109). The guard value G thus calculated shifts to the increasing side (intake air amount decreasing side) as shown in FIG. 5 as the engine speed during idling increases. Note that the calculation of the guard value G under the neutral position is performed under the condition that the engine 1 is not loaded on the automatic transmission side, and the engine 1 side such as the drive position is on the automatic transmission side. This is because an influence on the engine rotation speed is more likely to occur due to the erroneous intake air density correction than in the state where the load is applied.

  After calculating the guard value G as described above, if the guard value G is smaller than the previous value (the value on the intake air amount increase side) (S110: YES), the previous guard value G remains unchanged. The guard value G is set, and updating of the guard value G to the intake air amount increase side is prohibited. In other words, the update of the guard value G is permitted only for the side that reduces the intake air amount. When the intake density correction coefficient K2 becomes smaller than the guard value G (S112: YES), that is, when the intake air amount increase side value is reached, the guard value G is set as a new intake density correction coefficient K2. (S113) Thereby, the intake density correction coefficient K2 is guarded on the intake air amount increase side.

  Therefore, if the engine speed during idling suddenly increases due to the above-described situation or the like, the guard value G becomes a large value (value on the intake air amount reduction side), and the intake density correction coefficient K2 based on the guard value G A sudden increase in engine speed is suppressed through the guard. Here, an execution example of the intake density correction coefficient guard process will be described with reference to the time chart of FIG. In the figure, (a) shows the transition of the engine speed, and (b) shows the transition of the intake density correction coefficient K2.

  When the engine speed is excessively increased as shown by the solid line in FIG. 6A during idling in the cold state, the guard value G calculated based on the engine speed at that time is, for example, FIG. 6B. The value changes from the value indicated by the one-dot chain line L1 to the value indicated by the one-dot chain line L2 on the increase side (intake air amount decrease side). As a result, the intake air density correction coefficient K2 becomes a value on the intake air amount increase side with respect to the guard value G, so that the guard value G (L2) is a new intake air density as shown by the solid line in FIG. The correction coefficient K2 is set, and guarding is performed on the intake air amount increase side of the intake density correction coefficient K2. By the above guard process, the excessive increase in the engine rotational speed described above is suppressed, and the engine rotational speed changes as indicated by a broken line in FIG.

  By the way, as described above, the guard value G is only allowed to be updated to the increase side (intake air amount decrease side) with respect to the change in the engine rotation speed through the processing of steps S110 and S111. If such an update regulation is not performed and the guard value G is also updated to the decreasing side (intake air amount increasing side) with respect to the change in the engine rotation speed, the guard execution / guard cancellation of the intake density correction coefficient K2 is performed. Will cause hunting to be repeated.

  That is, when the engine rotational speed decreases due to the execution of the guard for the intake density correction coefficient K2, if the guard value G is updated to the decrease side (intake air amount increase side) at the same time, the intake density correction coefficient K2 is set to the guard value G. As a result, the value of the intake air amount is reduced, the guard for the intake density correction coefficient K2 is released, and the engine speed increases again. When the guard value G is updated to a value on the intake air amount decrease side with respect to the intake density correction coefficient K2 as the engine rotational speed increases, the intake air density correction coefficient K2 again uses the guard value G and the intake air amount. It is guarded on the side that increases.

  As described above, if the update of the guard value G to the decreasing side (intake air amount increasing side) is permitted, hunting that the guard execution / guard release of the intake density correction coefficient K2 is repeated is caused, but the guard value G Since the update to the intake air amount increase side is prohibited through the processing of steps S110 and S111, the occurrence of the hunting can be avoided.

[4] Intake density correction amount calculation processing (S114)
In this process, as described above, during the idling operation, the intake air density correction amount H is calculated using Equation (3) based on the cold correction term A and the intake air density correction coefficient K2 (S114).

[5] Inhalation density correction prohibition processing (S115, S116)
In this process, whether or not the cold correction term A becomes a value (negative value) for reducing the intake air amount in the idle state (accelerator off), that is, the intake density correction amount H is “0”. It is determined whether it is less than “” (S115 in FIG. 3). If the determination in step S115 is affirmative, the intake air density correction amount H is set to the reference value “0” (S116), whereby the intake air density correction by the intake air density correction amount H for the cold correction term A is not performed. To be done. Here, an execution example of the intake density correction prohibition process will be described with reference to the time chart of FIG. In the figure, (a) shows the transition of the cold correction term A, (b) shows the transition of the intake density correction amount H, and (c) shows the transition of the engine speed.

  In the cold accelerator off state, the cold correction term A may be a negative value (value on the intake air amount reduction side) (timing T1). As a situation where the cold correction term A becomes a negative value in this way, a situation where the cold correction term A is decreased by the cranking correction term qcrnk during the cranking at the cold start of the engine 1 is considered. It is done. When the cold correction term A becomes a negative value, the cold correction term A is subjected to the intake density correction by the intake density correction amount H, and the cold correction term A further reduces the intake air amount. When adjusted to the side, the amount of intake air is excessively reduced. As a result, the engine rotation speed decreases as shown by the solid line in FIG. 7C, and the startability of the engine 1 may be deteriorated.

  However, when the cold correction term A is a negative value, the intake air density correction amount H is set to the reference value “0” as shown by the broken line in FIG. As a result, the intake air density correction by the intake air density correction amount H with respect to the cold correction term A is not performed, and the decrease in the engine speed is suppressed as shown by the broken line in FIG. Accordingly, it is possible to suppress a decrease in the engine rotation speed due to the excessive reduction of the intake air amount as described above, and hence a deterioration in the startability of the engine 1 associated therewith.

According to the embodiment described in detail above, the following effects can be obtained.
(1) When the engine 1 is warm, the learned ISC learning value qg becomes a value corresponding to a deviation from the appropriate value of the intake air amount based on the difference in the intake air density (intake density) of the engine 1. Then, the deviation is compensated by adjusting the ISC correction amount Qcal (cold / warm correction term B) based on the ISC learning value qg. On the other hand, when the engine 1 is cold, the intake air density correction based on the intake air density correction amount H is performed only for the cold correction term A, thereby compensating for the deviation. The intake air density correction amount H is set to a value that increases the cold correction term A as the intake air density decreases to compensate for the deviation from the appropriate value of the intake air amount based on the difference in intake air density when cold. It is set to “0” in the meantime. By operating the intake air density correction amount H in this way, the above-described deviation is accurately compensated by the intake air density correction using the intake air density correction amount H when cold, and unnecessary intake air density due to the intake air density correction amount H during temperature. It is possible to avoid erroneous learning of the ISC learning value qg accompanying the execution of the correction and the learning of the ISC learning value qg simultaneously with the correction.

  (2) During the cold cranking, the cold correction term A may become a negative value (value on the intake air amount reduction side). At this time, if the cold correction term A is subjected to the intake density correction by the intake density correction amount H, and the cold correction term A is further adjusted to the intake air amount reduction side, the intake air amount is excessively reduced. There is a possibility that startability of the engine 1 is deteriorated. However, when the cold correction term A becomes a negative value, the intake density correction amount H is set to the reference value “0”. As a result, the intake air density correction by the intake air density correction amount H with respect to the cold correction term A is not performed, and a decrease in engine rotation speed is suppressed. Accordingly, it is possible to suppress a decrease in the engine rotation speed due to the excessive reduction of the intake air amount as described above, and hence a deterioration in the startability of the engine 1 associated therewith.

  (3) Since the frequency of calculation and storage of the atmospheric pressure is low when traveling from high altitude to low altitude, when the engine 1 is cold after returning to the low altitude, the cold correction term A is incorrect despite the low altitude. Thus, the intake air density correction at high altitude by the intake air density correction amount H may be performed. In this case, the intake air amount of the engine 1 is excessively increased, and there is a possibility that the engine speed is excessively increased during the idling operation. In order to cope with this, the calculation of the intake air density correction coefficient K2 with reference to the map of FIG. 4 is performed so that an excessive increase in the engine speed under the above-described situation can be suppressed as much as possible. Is called. For this reason, regarding the intake air density correction of the cold correction term A by the intake air density correction amount H calculated based on the intake air density correction coefficient K2, the engine when the intake air density correction corresponding to the high altitude is erroneously performed in the low altitude This is performed in such a manner that an excessive increase in rotational speed is suppressed as much as possible. Therefore, even if the cold correction term A is mistakenly corrected for intake air density at high altitude by the intake air density correction amount H, the engine rotational speed increases excessively and affects the operability of the engine 1. Can be suppressed.

  (4) In addition, there may be a case where it is not possible to suppress an excessive increase in the engine speed due to the intake density correction at the high altitude in the low altitude. In this case, the guard value G calculated based on the engine speed increases. Changes to the side (intake air volume reduction side). As a result, since the intake density correction coefficient K2 becomes a value on the intake air amount increase side with respect to the guard value G, the guard value G is set as a new intake density correction coefficient K2, and the intake air with the intake density correction coefficient K2 is set. Guarding on the volume increasing side is performed. By the guard process described above, the excessive increase in the engine rotational speed described above can be suppressed, and the excessive increase in the operability of the engine 1 can be suppressed.

  (5) Regarding the guard value G, only updating to the increasing side (intake air amount decreasing side) is permitted with respect to changes in the engine speed, and updating to the decreasing side (intake air amount increasing side) is prohibited. . If such an update regulation is not performed and the guard value G is also updated to the decreasing side (intake air amount increasing side) with respect to the change in the engine rotation speed, the guard execution / guard cancellation of the intake density correction coefficient K2 is performed. Will cause hunting to be repeated. However, by prohibiting the guard value G from being updated to the intake air amount increase side, the occurrence of the hunting can be avoided.

In addition, the said embodiment can also be changed as follows, for example.
The calculation of the guard value G may be performed based on the difference between the engine speed and the target value during idle operation. In this case, the guard value G becomes a value on the increase side (intake air amount decrease side) as the engine speed becomes higher than the target value.

-The guard value G may be calculated at a position other than the neutral position.
Instead of calculating the intake air density correction coefficient K2 based on the atmospheric pressure correction coefficient K1, it may be calculated directly from the atmospheric pressure.

  The intake air density correction amount H is calculated using only the cold correction term A as a value for correcting the intake air density. However, the intake air density correction amount H is calculated using the cold correction term A and the cold / warm correction term B as values for correcting the intake air density. May be calculated.

  However, the cold / warm correction term B is adjusted based on the ISC learning value qg learned during the warm time during the cold time, so the necessity of the intake air density correction is reduced. Therefore, the intake air density correction amount H is calculated so that the intake air density correction for the cold / warm correction term B is smaller than the intake air density correction for the cold correction term A.

  Specifically, the intake air density correction amount H is calculated based on the equation “H = {(A / K2) −A} + {(B / K3) −B} (4)”. In this equation (4), the term “{(B / K3) −B}” is for correcting the cold / warm correction term B for the intake air density. Further, the intake air density correction coefficient K3 in the same term moves away from “1.0” as the actual intake air density becomes smaller than the intake air density at the standard atmospheric pressure, and the intake air density correction at that time is corrected. The value is closer to “1.0” than the coefficient K2. By calculating the intake air density correction amount H in this way and adding it to the cold correction term A and the cold / warm correction term B in the equation (2), the intake density correction for the cold / warm correction term B is performed. This can be performed smaller than the intake air density correction for the cold correction term A.

  When the engine 1 is cold, the intake air density correction of the ISC correction amount Qcal (cold correction term A and cold / warm correction term B) is performed using the intake air density correction amount H. As described above, the effect according to the above embodiment can be obtained.

  A bypass passage is connected to the intake passage 4 so as to bypass the throttle valve 12, and an idle speed control valve is provided in the passage, and the amount of intake air during idle operation is adjusted by adjusting the opening of the idle speed control valve. You may apply this invention to the engine which adjusts and implements idle rotational speed control.

BRIEF DESCRIPTION OF THE DRAWINGS Schematic which shows the whole engine to which the idle rotational speed control apparatus of this embodiment is applied. The flowchart which shows the calculation procedure of the intake density correction amount H. The flowchart which shows the calculation procedure of the intake density correction amount H. A map used for calculating the intake air density correction coefficient K2. The graph which shows transition of the guard value G with respect to the change of an engine speed. (A) And (b) is a time chart which shows transition of the engine speed at the time of execution of an intake density correction coefficient guard process, and the intake density correction coefficient K2. (A)-(c) is a time chart which shows transition of the cold correction term A, the intake density correction amount H, and the engine rotation speed when the intake density correction prohibition process is executed.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 ... Engine, 2 ... Fuel injection valve, 3 ... Combustion chamber, 4 ... Intake passage, 9 ... Crankshaft, 10 ... Crank position sensor, 11 ... Water temperature sensor, 12 ... Throttle valve, 13 ... Air flow meter, 14 ... Accelerator pedal , 15 ... Accelerator position sensor, 16 ... Throttle position sensor, 20 ... Electronic control unit.

Claims (6)

In an idling engine speed control device for an internal combustion engine that controls an engine speed during idling through adjustment of an intake air amount based on an ISC correction amount,
The ISC correction amount includes a feedback term that increases or decreases to bring the engine speed close to a target value, an ISC learning value that increases or decreases to converge the feedback term within a predetermined range when the internal combustion engine is warm, and a cold state of the engine A cold correction term that sometimes increases and decreases, and a cold and warm correction term that increases and decreases from the cold to the warm of the engine,
An intake air density correction is performed only when the internal combustion engine is cold and only for the cold correction term, so that the cold correction term becomes larger as the intake air density becomes smaller. Idle rotation speed control device. In an idle rotation speed control device for an internal combustion engine that controls an idle rotation speed through adjustment of an intake air amount based on an ISC correction amount,
The ISC correction amount includes a feedback term that increases and decreases to bring the engine speed close to a target value, an ISC learning value that increases and decreases to converge the feedback term within a predetermined range when the internal combustion engine is warm, and a cold temperature of the internal combustion engine A cold correction term that sometimes increases and decreases, and a cold and warm correction term that increases and decreases from the cold to the warm of the engine,
Only when the internal combustion engine is cold, the cold correction term and the cold / warm correction term are corrected for the intake air density so that the smaller the intake air density is, the larger the correction terms are. An intake rotational speed control apparatus for an internal combustion engine, wherein the intake air density correction for the warm correction term is performed smaller than the intake air density correction for the cold correction term. The idle speed control apparatus for an internal combustion engine according to claim 1 or 2, wherein the intake air density correction is not performed when the cold correction term is a value for reducing the intake air amount. The intake air density correction of the cold correction term is performed in a manner that does not cause an excessive increase in engine rotation when the correction corresponding to the intake air density in the high altitude is erroneously performed in the low altitude. An idle rotation speed control device for an internal combustion engine according to claim 1. The intake air density correction of the cold correction term is performed using an intake air density correction coefficient calculated based on the intake air density,
The said intake density correction coefficient is guarded about the side which increases intake air amount based on the guard value set according to the engine speed in an idle state. An idle speed control device for an internal combustion engine as described. The idle rotation speed control device for an internal combustion engine according to claim 5, wherein the update of the guard value based on the engine rotation speed is permitted only to the update of the guard value to the intake air amount reduction side.

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