JP4127707B2 - Internal combustion engine control device - Google Patents

Description

  The present invention relates to an internal combustion engine controller used in a vehicle such as an automobile, and more particularly to a novel technique for estimating atmospheric pressure from a plurality of operating state quantities (such as measured values of intake pipe pressure) of an internal combustion engine. is there.

In general, vehicles such as automobiles have many opportunities to travel on high altitudes (running up and down slopes such as mountain roads), and changes in atmospheric pressure according to travel altitude (altitude) result in changes in the intake pipe pressure of the internal combustion engine. Appearing to hinder the control of the internal combustion engine.
Therefore, an internal combustion engine control device mounted on a vehicle such as an automobile is provided with an atmospheric pressure detection means for measuring the atmospheric pressure under the usage environment of the internal combustion engine, and based on the information obtained by the atmospheric pressure detection means, High altitude compensation processing is performed to prevent the effects of atmospheric pressure changes.

In addition, in order to realize high altitude compensation processing at low cost, it is desirable to use detection information of various sensors that are normally used without using a dedicated pressure sensor (atmospheric pressure sensor) for detecting atmospheric pressure. .
Therefore, in order to calculate the intake air amount of the internal combustion engine, the detection information (intake pipe pressure) of the pressure sensor provided downstream of the throttle valve (intake throttle valve) is used to measure the intake pipe pressure when the throttle valve is fully opened. An internal combustion engine control device that estimates the atmospheric pressure by regarding the value as being substantially equal to the atmospheric pressure has also been proposed.

By the way, when estimating the atmospheric pressure without using the atmospheric pressure sensor, when the atmospheric pressure is estimated using the intake pipe pressure, the intake pipe pressure when the throttle is fully opened is used, so that the atmospheric pressure decreases. Sometimes atmospheric pressure can be estimated relatively accurately.
However, when driving downhill, there is almost no case where the throttle is fully opened, so it is determined that the vehicle is driving downhill by fuel cut control, and the estimated atmospheric pressure is increased in proportion to the time of fuel cut control. Looking for.

  In other words, in an operating state where the throttle opening is fully open, such as when the throttle is fully open (when initializing) or when the accelerator is fully open when learning about full opening / closing of the throttle opening, such as when starting or when the engine is stopped When estimating the atmospheric pressure, it can be said that the accuracy of the estimated atmospheric pressure is high because the intake pressure and the atmospheric pressure are almost equal.

  On the other hand, when the atmospheric pressure is estimated in a state where the throttle is not fully opened, such as when the fuel is being decelerated during downhill slopes, an error occurs between the detected intake pipe pressure and the actual atmospheric pressure. However, the estimated atmospheric pressure cannot be maintained in an unupdated state until the throttle is fully opened, so the estimated atmospheric pressure is updated according to the duration of the fuel cut, the vehicle speed during the fuel cut, and the distance traveled. I am letting.

From the above situation, it can be said that the accuracy of the estimated atmospheric pressure estimated during the deceleration fuel cut is insufficient compared to the estimated atmospheric pressure when the throttle is fully opened.
As a result, in some cases, the estimated atmospheric pressure value estimated during the deceleration fuel cut increases from the actual atmospheric pressure every time it is updated.

Here, the error in the estimated atmospheric pressure value estimated during the deceleration fuel cut will be described with reference to the explanatory diagram of FIG.
In FIG. 7, the vertical axis represents atmospheric pressure [kPa], the horizontal axis represents time [sec], the broken line represents the actual atmospheric pressure, and the one-dot chain line represents the estimated atmospheric pressure.

If the atmospheric pressure estimation process when the throttle is fully opened is performed at time t11, the actual atmospheric pressure and the estimated atmospheric pressure value are substantially equal. Therefore, the first estimated atmospheric pressure value _CAPWOFC detected at time t11 is It can be said that the detection accuracy is relatively high.

However, from time t12 to time t13, the second estimated atmospheric pressure value _CAPFC estimated in a state in which the downhill is continued in the fuel cut state is an open loop control, so that the actual atmospheric pressure is A large error ΔC1 may occur, and it can be said that the detection accuracy is relatively low.

As shown in FIG. 7, in a state where an error ΔC1 occurs in the atmospheric pressure estimated value, the first atmospheric pressure estimated value C _APWOFC at the time when the throttle is fully opened next time (relatively high detection accuracy) is calculated from time t13. When the operation state of the internal combustion engine shifts to the idle state and the idle rotation speed control is performed until the time t14, the air density correction of the idle rotation speed control includes a large error. An atmospheric pressure estimate will be used.

  As described above, when the atmospheric pressure estimation value including an error is used, when the atmospheric pressure estimation is performed at a value lower than the actual altitude, a state of falling idle rotation speed occurs. When the atmospheric pressure is estimated at a value higher than the actual altitude, the idle rotation speed increases.

That is, when an atmospheric pressure estimated value including an estimation error is used for control of an internal combustion engine (for example, when the base air amount used for idle rotation speed control is corrected for air density), the atmospheric pressure estimated value is actual. If the estimated value is larger than the atmospheric pressure, the base air amount is corrected to a small amount when the vehicle shifts from the normal running state to the idle state. There is a problem that the engine becomes unstable and exhaust gas and drivability deteriorate, or the engine is stopped in some cases.
On the other hand, if the estimated atmospheric pressure is estimated to be smaller than the actual atmospheric pressure, the base air amount is corrected to a larger value, so the actual idle speed increases and wastes fuel. Problem occurs.

In view of the above problems, a technique for improving the accuracy of the estimated atmospheric pressure value at the time of deceleration fuel cut and improving the reliability of the estimated atmospheric pressure value is proposed (for example, Patent Document 1). , Patent Document 2 and Patent Document 3).
First, in the atmospheric pressure correction device disclosed in Patent Document 1, the increase rate of the atmospheric pressure estimated value is changed in accordance with the vehicle speed to improve the accuracy of the atmospheric pressure estimated value.

  However, since the vehicle speed fluctuates due to changes in the gear ratio and the like, even if the amount of increase in the estimated atmospheric pressure value is changed based on the vehicle speed, an error occurs between the actual atmospheric pressure and the estimated atmospheric pressure value. Absent. Therefore, in Patent Document 1, no countermeasure is taken when an error occurs between the actual atmospheric pressure and the estimated atmospheric pressure.

Moreover, in the atmospheric pressure estimation method disclosed in Patent Document 2, the accuracy of the atmospheric pressure estimated value is improved by updating the atmospheric pressure estimated value in accordance with the travel distance. No countermeasure is taken when an error occurs between the actual atmospheric pressure and the estimated atmospheric pressure.
Furthermore, the atmospheric pressure estimation device disclosed in Patent Document 3 performs a process of correcting the atmospheric pressure estimated value using data before the previous time (so-called annealing process), but performs an annealing process. Then, the atmospheric pressure estimated value estimated with high accuracy is also subjected to a smoothing process, and the value estimated with high accuracy is wasted.

Japanese Patent Laid-Open No. 7-197841 JP 2003-49694 A JP-A-6-101558

In the conventional internal combustion engine control apparatus, in the case of Patent Document 1 and Patent Document 2, there is a problem that no countermeasure is taken when an error occurs between the actual atmospheric pressure and the estimated atmospheric pressure. .
Moreover, in the case of patent document 3, there existed a subject that the atmospheric pressure estimated value estimated with high precision will be wasted by the annealing process.

  The present invention has been made to solve the above-mentioned problems, and while maintaining and improving the accuracy of the atmospheric pressure estimated value, an error has occurred between the actual atmospheric pressure and the atmospheric pressure estimated value. Even in this case, an object of the present invention is to obtain an internal combustion engine control device that implements measures that do not deteriorate the control reliability of the internal combustion engine.

The internal combustion engine control apparatus according to the present invention is based on the relationship between a plurality of operating state quantities indicating the operating state of the internal combustion engine, and the first atmospheric pressure estimated value with relatively high detection accuracy and the detection accuracy is relatively low. An internal combustion engine control device comprising an atmospheric pressure estimating means for obtaining a second atmospheric pressure estimated value, wherein the atmospheric pressure estimating means obtains a first atmospheric pressure estimated value when the operating state indicates a throttle fully open state. The second atmospheric pressure estimated value is obtained when the operating state indicates a deceleration fuel cut state, and the upper limit value of the second atmospheric pressure estimated value is limited by a predetermined ratio based on the first atmospheric pressure estimated value. is there.

  According to the present invention, the upper limit value of the second atmospheric pressure estimated value during downhill (during deceleration fuel cut) is greater than or equal to a predetermined value based on the first atmospheric pressure estimated value with relatively high detection accuracy. By limiting the pressure so that it is not corrected, the atmospheric pressure estimation error can be suppressed while maintaining high estimation accuracy of the atmospheric pressure estimated value. Can be prevented.

Embodiment 1 FIG.
Hereinafter, the first embodiment of the present invention will be described in detail with reference to the drawings.
FIG. 1 is a block configuration diagram showing an internal combustion engine control apparatus according to Embodiment 1 of the present invention, and shows an overall system configuration of a fuel injection type internal combustion engine used for atmospheric pressure estimation.
An engine main body 1 constituting an internal combustion engine has a piston 3 in a combustion chamber 2 of each cylinder, and the piston 3 is connected to a crankshaft 5 through a connecting rod 4.

The intake port 6 of the engine body 1 is opened and closed by an intake valve 7.
An intake pipe 11 communicates with the intake port 6, and air is taken into the combustion chamber 2 of each cylinder through the intake pipe 11.
The intake pipe 11 includes an air cleaner 8, a throttle valve 9 that controls the amount of intake air, a pressure sensor 10 that detects an intake pipe pressure downstream of the throttle valve 9, and a throttle opening sensor 21 that detects the throttle opening. And a motor 28 for driving the throttle valve 9 is provided.

The engine body 1 is provided with a fuel injection valve 12 that injects fuel into the intake port 6 and an ignition plug 13 that generates a spark spark in the combustion chamber 2.
The exhaust port 14 of the engine body 1 is opened and closed by an exhaust valve 15.
An exhaust pipe 16 communicates with the exhaust port 14, and exhaust gas is discharged through the exhaust pipe 16.
The exhaust pipe 16 is provided with a three-way catalytic converter 17, an air-fuel ratio sensor 25 that detects the air-fuel ratio in the exhaust pipe 16, and an exhaust temperature sensor 26 that detects the exhaust temperature.

Each part of the engine body 1 is provided with a coolant temperature sensor 22 that detects the coolant temperature, a knock sensor 23 that detects knock vibration, and a crank angle sensor 24 that detects the engine speed.
In addition, a vehicle speed sensor 27 that detects the vehicle speed is provided in a vehicle on which the engine body 1 is mounted.
Detection values (a plurality of operation state quantities indicating operation states) of these various sensors 10, 21 to 27 are input to an electronic control unit (hereinafter referred to as “ECU”) 30.

The ECU 30 calculates control amounts for various actuators such as the fuel injection valve 12, the spark plug 13, and the motor 28 based on various operation state quantities, and drives the various actuators 12, 13, and 28.
Further, the ECU 30 includes an atmospheric pressure estimating means, calculates an estimated atmospheric pressure value based on the intake pipe pressure detected by the pressure sensor 10, and estimates the atmospheric pressure during fuel cut during deceleration, the motor 28 And the throttle valve 9 at the time of deceleration is fixed at a predetermined opening degree.

That is, the atmospheric pressure estimation means uses map data stored in advance in a storage device (not shown) in the ECU 30 based on the intake pipe pressure detected by the pressure sensor 10 and the engine speed detected by the crank angle sensor 24. Read out and calculate atmospheric pressure estimate.
The atmospheric pressure estimating means calculates an atmospheric pressure estimated value using the intake pipe pressure calculated when the throttle is fully opened as an atmospheric pressure equivalent value when estimating the atmospheric pressure when the throttle is fully opened such as when the engine is stopped or started.

  Further, as will be described later, the atmospheric pressure estimating means obtains a first atmospheric pressure estimated value having a relatively high detection accuracy when the throttle is fully opened, based on the relationship between a plurality of operating state quantities indicating the operating state of the internal combustion engine. When the fuel is cut during deceleration, a second atmospheric pressure estimated value having a relatively low detection accuracy is obtained, and the upper limit value of the second atmospheric pressure estimated value is limited by a predetermined ratio based on the first atmospheric pressure estimated value. It is like that.

The ECU 30 corrects the amount of fuel injected from the fuel injection valve 12 during fuel control based on the calculated estimated atmospheric pressure, and controls the ISC means for controlling the intake air amount during idle rotation speed control. Then, an air density correction process is performed.
In this case, the ISC means is composed of a throttle valve 9 and a motor 28, and the intake air amount is controlled by driving the throttle valve 9 with the motor 28 and changing the opening of the throttle valve 9.

Next, control processing by the ECU 30 will be described with reference to the flowchart of FIG.
In FIG. 2, first, the operating state is determined from input signals from various sensors (step S100), and it is determined whether the atmospheric pressure estimation condition is satisfied (step S101).

In step S101, the atmospheric pressure estimation condition is not satisfied (i.e., NO) and when it is determined, is set to a predetermined value _{C AP0} as atmospheric pressure estimate _{C AP} and atmospheric pressure estimated upper clip value _{C K} (step S102 ), The processing routine of FIG. 2 is terminated.
Here, the predetermined value _CAP0 is an atmospheric pressure (for example, 101.3 [kPa]) corresponding to a lowland (altitude is 0 m).

On the other hand, if it is determined in step S101 that the atmospheric pressure estimation condition is satisfied (that is, YES), it is subsequently determined whether or not the throttle fully open condition is satisfied (the throttle valve 9 is fully open). (Step S103).
Here, the throttle fully open condition is a condition under which the first atmospheric pressure estimated value _CAPWOFC with relatively high detection accuracy can be detected, and when the engine body 1 is stopped or started (initialization of the throttle opening learning value). ), When the accelerator is fully open, and so on.

If it is determined in step S103 that the throttle fully open condition is satisfied (that is, YES), a first atmospheric pressure estimated value _CAPWOFC with relatively high detection accuracy is calculated (step S104), and atmospheric pressure estimation is performed. as well as set the first atmospheric pressure estimated value _{C APWOFC} as the value _{C AP,} as the atmospheric pressure estimated upper clip value _{C K,} to set the value represented by the following formula (1) (step S105), in FIG. 2 The processing routine ends.

_{C K = C AP0 - (C} AP0 -C APWOFC) × K ··· (1)

The predetermined ratio K in Equation (1) is “½” as an example, but is a value that can be arbitrarily set to limit the atmospheric pressure estimated value.
Therefore, as for the value of the predetermined ratio K, the actual atmospheric pressure data is measured using an actual vehicle, and the value obtained by comparing the measured value of the atmospheric pressure with the estimated atmospheric pressure value is examined. Therefore, it may be determined so as to be an optimum value for each model.

On the other hand, if it is determined in step S103 that the throttle fully open condition is not satisfied (that is, NO), then it is determined whether or not the deceleration fuel cut determination condition is satisfied (deceleration fuel cut state). (Step S106).
If it is determined in step S106 that the deceleration fuel cut determination condition is not satisfied (that is, NO), the previously used atmospheric pressure estimated value _CAP and atmospheric pressure estimated upper limit clip value _CK are retained (step S107). ), The processing routine of FIG. 2 is terminated.

On the other hand, if it is determined in step S106 that the deceleration fuel cut determination condition is satisfied (that is, YES), the second atmospheric pressure estimated value _CAPFC with relatively low detection accuracy is calculated (step S108). sets a second atmospheric pressure estimated value _{C APFC} as the atmospheric pressure estimate _{C AP} (step S109).

Then, by comparing the atmospheric pressure estimated value _{C AP} and the atmospheric pressure estimated upper clip value _{C K,} it determines whether to satisfy the relationship of _{C AP} ≧ _{C K} (step _{S110), C AP <C K} ( That is, if it is determined as NO), the processing routine of FIG. 2 is terminated.
On the other hand, in step _{S110, C AP} ≧ _{C K} (that is, NO), it is determined that sets the atmospheric pressure estimated upper clip value _{C K} as the atmospheric pressure estimate _{C AP} (step S 111), the processing routine of FIG. 2 Exit.

Next, the effect of the update process of the atmospheric pressure estimated value _CAP according to the first embodiment of the present invention will be described more specifically with reference to FIG.
FIG. 3 is a timing chart showing the process of updating the atmospheric pressure estimated value _CAP according to the first embodiment of the present invention, and corresponds to the above-described FIG.
In FIG. 3, the vertical axis represents atmospheric pressure [kPa], the horizontal axis represents time [sec], the broken line represents the actual atmospheric pressure, the one-dot chain line represents the conventional atmospheric pressure estimated value, and the solid line represents the first embodiment of the present invention. It is an atmospheric pressure estimate.

First, when the throttle fully open condition is satisfied at time t1, the first atmospheric pressure estimated value _CAPWOFC is estimated from the intake pipe pressure value when the throttle opening is fully open.
As described above, the first atmospheric pressure estimated value _CAPWOFC has relatively high accuracy and is approximately equal to the actual atmospheric pressure.

At time t1, for example, when altitude 3000m substantial atmospheric pressure (70.1 [kPa]) is detected, the atmospheric pressure estimate upper clip value _{C K,} corrected predetermined value _C AP0 _{- (C} AP0 -C _APWOFC ) × K is set. Therefore, when the predetermined ratio K = 1/2, a value represented by the following equation (2) is set.

_{C K = C AP0 - (C} AP0 -C APWOFC) × K = 101.3- (101.3-70.1) × 1/2 = 85.7 [kPa] ··· (2)

Next, when the deceleration fuel cut condition is satisfied at time t2, a second atmospheric pressure estimated value _CAPFC with relatively low detection accuracy is calculated every predetermined time.
At this time, the update of the atmospheric pressure estimated value _CAPFC is continued over the period in which the fuel cut state is continued (period from time t2 to time t4).

As described above, since the second atmospheric pressure estimated value _CAPFC is open loop control, the accuracy is relatively low, and an error may occur with respect to the actual atmospheric pressure.
Therefore, especially when the deceleration fuel cut state continues due to continuous downhill, according to the conventional device (see the one-dot chain line), errors accumulate and when the deceleration fuel cut state is released at time t4, A considerably large error ΔC1 occurs.

However, according to the present invention (see the solid line), it takes a second atmospheric pressure estimate C _APFC during deceleration fuel cut clips at time t3 has reached the atmospheric pressure estimated upper clip value C _K, more atmospheric pressure estimation Since the value is not updated, it is suppressed to the minimum error ΔC2.

Then, again full throttle condition is satisfied at time t5, the first atmospheric pressure estimate C _APWOFC and atmospheric pressure estimated upper clip value C _K is calculated.
If the operating state of the internal combustion engine shifts to the idle state between time t4 and time t5, the atmospheric pressure estimated value is used for the air density correction of the idle rotation speed control. .

  Therefore, when an atmospheric pressure estimated value (see the one-dot chain line) including a large error ΔC1 as in the conventional device is used, if an estimated value lower than the actual altitude remains, the idle rotational speed drops. (Conversely, when an estimated value higher than the actual altitude remains, an increase in the idle rotation speed) occurs. However, according to the present invention, since the error ΔC2 is suppressed, Compared to the atmospheric pressure estimation, the atmospheric pressure estimation error is improved by a substantial difference ΔC3, and the decrease in idle rotation speed (or the increase in idle rotation speed) is suppressed.

As a result, the first atmospheric pressure estimate _{C APWOFC} and atmospheric pressure estimated upper clip value _{C K} at time t5, for example, a first atmospheric pressure estimate _{C APWOFC} is met 84.5KPa (altitude 1500m equivalent value) If, atmospheric pressure estimated upper clip value _{C K,} a 92.9 [kPa].

Subsequently, when the deceleration fuel cut condition is satisfied at time t6, the second atmospheric pressure estimated value C _APFC with relatively low detection accuracy is calculated as described above.
As described above, the second atmospheric pressure estimated value _CAPFC during the deceleration fuel cut is relatively inaccurate and may cause an error with respect to the actual atmospheric pressure.

  Therefore, when the deceleration fuel cut state continues due to the continuous downhill, according to the conventional device, the error is accumulated without being clipped, and when the deceleration fuel cut state is canceled at time t8, a considerably large error ΔC4. (Refer to the one-dot chain line).

On the other hand, according to the present invention, a second atmospheric pressure estimate C _APFC it takes clips at time t7 reaching the atmospheric pressure estimated upper clip value C _K, since more the atmospheric pressure estimated value is not to be updated , The minimum error is suppressed to ΔC5.
Thereafter, when the throttle fully open condition is satisfied again at time t9, the first estimated atmospheric pressure value C _APWOFC (and the estimated atmospheric pressure upper limit clip value C _K ) is calculated.

  As described above, according to the first embodiment of the present invention, the atmospheric pressure estimation means detects the first atmospheric pressure estimated value with relatively high detection accuracy based on the relationship between the plurality of operating state quantities, and the detection. The second atmospheric pressure estimated value with relatively low accuracy is obtained, and the upper limit value of the second atmospheric pressure estimated value during the downhill (during deceleration fuel cut) is used as the first accurate atmospheric pressure estimated value. The atmospheric pressure estimation error is maintained while maintaining the high estimation accuracy of the atmospheric pressure estimated value by limiting at a predetermined ratio based on the first atmospheric pressure estimated value and limiting so as not to be corrected beyond the predetermined value. Thus, it is possible to prevent the rotation increase, the rotation drop, the engine stop and the like during the idle rotation control.

That is, the air density correction at the time of idling rotation control is prevented from being overcorrected, and the atmospheric pressure estimated value is maintained with high accuracy, and an error occurs between the actual atmospheric pressure and the atmospheric pressure estimated value. Even in such a case, it is possible to realize a measure that does not deteriorate the control reliability of the internal combustion engine.
In addition, if the increase in idle rotation is suppressed, wasteful fuel consumption is suppressed, which leads to improved fuel efficiency.If the decrease in idle rotation is suppressed, exhaust gas and drivability due to unstable idle rotation Deterioration and engine stall can be prevented.

Embodiment 2. FIG.
In the first embodiment, the predetermined ratio K is set to an arbitrary value, but the predetermined ratio K may be fixedly set to “½” as in the above-described equation (2).
In this case, the upper limit value of the second atmospheric pressure estimated value is set to an intermediate value between the first atmospheric pressure estimated value and the lowland equivalent atmospheric pressure corresponding to the lowland.

  As described above, the upper limit value of the second atmospheric pressure estimated value with relatively low detection accuracy is set to an intermediate value (predetermined ratio) between the first atmospheric pressure estimated value with relatively high detection accuracy and the low-equivalent atmospheric pressure. By fixedly setting K = 1/2), the man-hour for setting the optimum value for each vehicle model can be omitted, which can contribute to shortening the development period.

Normally, when the predetermined ratio K is set, the actual atmospheric pressure data is measured using an actual vehicle, and the result of comparing the measured atmospheric pressure value with the estimated atmospheric pressure value is set to an optimum value for each model. The value of the predetermined ratio K is examined and set. In this case, a large number of work steps are required.
However, when the predetermined ratio K is fixed to “1/2”, these operations can be simplified, and the time required for development such as data measurement time and coefficient setting time can be shortened.

Embodiment 3 FIG.
In the first embodiment, the operating state is not considered when setting the predetermined ratio K (the upper limit value of the second atmospheric pressure estimated value with relatively low detection accuracy), but as shown in FIG. The predetermined ratio K may be variably set according to the operating state.
FIG. 4 is a flowchart showing the control processing of the internal combustion engine control apparatus according to Embodiment 3 of the present invention, and steps S100 to S111 are the same processing as described above (see FIG. 2).

In this case, the upper limit value and the predetermined ratio K of the second atmospheric pressure estimated value are variably set according to the operating state of the internal combustion engine.
Hereinafter, the variable setting process of the predetermined ratio K according to the operation state according to the third embodiment of the present invention will be described with reference to FIGS. 4 and 5.

FIG. 5 is an explanatory diagram showing the relationship between the vehicle speed change ΔV and the coefficient Kv with respect to the vehicle speed, and shows the relationship when the deceleration fuel is cut and the brake is not depressed.
In this case, the configuration of the internal combustion engine control device is as shown in FIG. 1, and only a partial function of the ECU 30 is different.

As described above, since the second estimated atmospheric pressure value during the deceleration fuel cut is estimated in the operation state where the throttle is not fully opened, the detection accuracy is relatively low, and when the deceleration fuel cut state continues, The error from the actual atmospheric pressure may be enlarged.
Therefore, in the third embodiment of the present invention, the driving state (vehicle speed, travel distance, etc.) during the deceleration fuel cut is detected and the condition is determined so as to cope with the case where the deceleration fuel cut state continues. When the above-mentioned (predetermined value or predetermined time) is continued, the predetermined ratio K is changed to a coefficient corresponding to the driving state (a coefficient Kv corresponding to the vehicle speed, a coefficient Kd corresponding to the travel distance, etc.). Yes.

In FIG. 4, steps S100 to S109 are the same processing as described above, and thus description thereof is omitted here.
In step S109, after setting the second atmospheric pressure estimate _{C APFC} during deceleration fuel cut as the atmospheric pressure estimate _{C AP,} ECU 30 detects a predetermined operating condition of the internal combustion engine (step S210).

The driving state detected in step S210 is predetermined information that may affect the estimated atmospheric pressure value, such as the vehicle speed and the travel distance, and is not limited to the vehicle speed and the travel distance. A case where the vehicle speed detected by the sensor 27 is applied will be described.
In FIG. 5, when the vehicle speed change ΔV is large, it is considered that the vehicle is in a traveling road state where the slope of the downhill is large (steep slope), and “2/3” is set as the value of the coefficient Kv, for example.
On the contrary, when the change ΔV in the vehicle speed is small, it is considered that the traveling road state is a gentle downhill, and the value of the coefficient Kv is set to “1/3”, for example.

Thus, when the vehicle speed state is detected as the predetermined driving state in step S210, it is subsequently determined whether or not the vehicle speed change ΔV has continued for a predetermined time or more (predetermined value or predetermined time) (step S211).
In step S211, for example, the change ΔV in the predetermined value or more of the vehicle speed does not continue for a predetermined time (that is, NO), it is determined that, compared with the atmospheric pressure estimated value C _AP and the atmospheric pressure estimated upper clip value C _K It progresses to a process (step S110).

On the other hand, in step S211, for example, if it is determined that the vehicle speed change ΔV of a predetermined value or more has continued for a predetermined time (that is, YES), the predetermined ratio K is changed according to the driving state (step S212).
For example, in this case, the predetermined ratio K is changed to the value of the coefficient Kv corresponding to the detected vehicle speed information.

Specifically, the ECU 30 stores in advance a coefficient Kv corresponding to the vehicle speed, a coefficient Kd corresponding to the travel distance, and the like in a storage device in the ECU 30, and the predetermined ratio K is set to each coefficient according to the corresponding driving condition. Change to Kv, Kd (for example, K = Kv or K = Kd).
Therefore, based on FIG. 5, if Kv = 1/2, the predetermined ratio K is also set to “1/2”, and if Kv = 1/3, the predetermined ratio K is also set to “1/3”. The

Next, using the value of a predetermined percentage K was modified in step S212, the atmospheric pressure estimate upper clip value _{C K,} changing in accordance with equation (1) described above (step S213).
Hereinafter, in the same manner as described above, it executes a comparison process between the atmospheric pressure estimated value _{C AP} and the atmospheric pressure estimated upper clipping value _{C K} (step S110), the upper limit clipping of the atmospheric pressure estimated value _{C AP} and (step S111) Then, the processing routine of FIG.

Next, the variable setting process of the predetermined ratio K according to the third embodiment of the present invention will be described more specifically with reference to the timing chart of FIG.
In FIG. 6, the horizontal axis is time [sec], the vertical axis is the predetermined ratio K, the one-dot chain line is the characteristic according to the conventional atmospheric pressure estimation value, the broken line is the characteristic at the actual atmospheric pressure, and the solid line is the implementation of the present invention. The characteristic in the atmospheric pressure estimated value by the form 3 is shown.

As is clear from FIG. 6, the slope of the characteristic (time change rate) at the actual atmospheric pressure (broken line) is smaller than that at the normal time during a gentle slope and larger than that during a steep slope.
Further, the characteristic of the predetermined ratio K increases with the passage of time without being clipped with the characteristic at the conventional atmospheric pressure estimated value (one-dot chain line).
On the other hand, the characteristic at the atmospheric pressure estimated value (solid line) according to the third embodiment of the present invention is clipped according to the value of the predetermined ratio K (for example, 1/3, 1/2, 2/3).

  In FIG. 6, suppose that the predetermined ratio K when the vehicle speed or travel distance continues for a predetermined time or more (predetermined value or predetermined time) is set to a value (= 2/3) larger than the normal value (= 1/2). If it is, the actual atmospheric pressure change degree is large (corresponding to a steep slope), so that the actual atmospheric pressure and the atmospheric pressure are estimated more than when the predetermined ratio K is clipped at the normal value (= 1/2). Correction is performed in a direction in which an error from the value is reduced.

  Further, when the predetermined ratio K is set to a value smaller than the normal value (= 1/3), the degree of change in the actual atmospheric pressure is also small (corresponding to the actual atmospheric pressure during a gentle slope). The correction is made so that the error between the estimated atmospheric pressure value and the actual atmospheric pressure is smaller than when the ratio K is clipped at the normal value (= 1/2).

As described above, according to the third embodiment of the present invention, the upper limit value (predetermined ratio K) for applying the second atmospheric pressure estimated value restriction is variably set according to the operating state, so the deceleration fuel cut The atmospheric pressure estimation accuracy at the time can be improved, and atmospheric pressure estimation closer to the actual situation can be performed.
Further, since the error between the atmospheric pressure estimated value and the actual atmospheric pressure can be corrected in accordance with the operating state, the estimation accuracy of the second atmospheric pressure estimated value at the time of deceleration fuel cut can be improved. it can.

In addition, this invention is not limited to the said Embodiment 1-3, A various change can be added in a design in the range which does not deviate from the mind of the invention described in the claim.
The system configuration shown in FIG. 1 is only an example when the present invention is applied, and it goes without saying that the present invention can be applied to configurations other than the illustrated system.

Further, in the above description, the case where the atmospheric pressure is estimated from the intake pipe pressure value detected during the fuel cut has been described. However, the term “under fuel cut” here refers to the fuel cut during the downhill. Also included is a fuel cut during deceleration.
The atmospheric pressure estimating means in the ECU 30 estimates the atmospheric pressure from the intake pipe pressure value, but is not limited to this, and it is possible to estimate the atmospheric pressure by any method without using the atmospheric pressure sensor. Needless to say, any means can be applied.
Furthermore, since it can be dealt with only by changing the software that causes the ECU 30 to store a program for estimating atmospheric pressure, the configuration is not complicated, and the cost can be kept low, which is economically advantageous.

BRIEF DESCRIPTION OF THE DRAWINGS It is a block diagram which shows roughly the atmospheric pressure correction apparatus by Embodiment 1 of this invention. It is a flowchart which shows the control processing of the atmospheric pressure correction apparatus by Embodiment 1 of this invention. It is a timing chart which shows the operation | movement of the atmospheric pressure estimated value by Embodiment 1 of this invention. It is a flowchart which shows the control processing of the atmospheric pressure correction apparatus by Embodiment 3 of this invention. It is explanatory drawing which shows the relationship between the change according to the vehicle speed in the fuel cut by Embodiment 3 of this invention, and the coefficient according to a vehicle speed with a graph. It is explanatory drawing which shows the variable control of the predetermined ratio by Embodiment 3 of this invention with a graph. It is a timing chart for demonstrating the problem of the atmospheric pressure estimation process by the conventional apparatus.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Engine body, 2 Combustion chamber, 9 Throttle valve, 10 Pressure sensor, 12 Fuel injection valve, 13 Spark plug, 17 Three-way catalytic converter, 28 Motor, 25 Air-fuel ratio sensor, 27 Vehicle speed sensor, 30 ECU, _CAP atmospheric pressure Coefficient according to estimated value, first atmospheric pressure estimated value, _CAPFC second atmospheric pressure estimated value, K predetermined ratio, Kv vehicle speed.

Claims (3)

Based on the relationship between a plurality of operating state quantities indicating the operating state of the internal combustion engine, a first atmospheric pressure estimated value with a relatively high detection accuracy and a second atmospheric pressure estimated value with a relatively low detection accuracy are obtained. An internal combustion engine control device comprising an atmospheric pressure estimation means to be obtained,
The atmospheric pressure estimating means includes
Obtaining the first atmospheric pressure estimate when the operating state indicates a throttle fully open state;
Obtaining the second atmospheric pressure estimate when the operating state indicates a deceleration fuel cut state;
An internal combustion engine control device that limits an upper limit value of the second estimated atmospheric pressure value at a predetermined ratio based on the estimated first atmospheric pressure value. The upper limit value of the second atmospheric pressure estimated value is set to an intermediate value between the first atmospheric pressure estimated value and a lowland equivalent atmospheric pressure corresponding to a lowland,
The internal combustion engine control device according to claim 1, wherein the predetermined ratio is set to ½.   3. The internal combustion engine control device according to claim 1, wherein the upper limit value and the predetermined ratio are variably set according to an operating state of the internal combustion engine.

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