JP2012077726A - Atmospheric pressure estimating device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an atmospheric pressure estimating device which can perform an estimation of the atmospheric pressure according to a detected intake pressure even during a fuel cut operation, and also can perform an accurate estimation by inhibiting a degradation of an estimation accuracy.SOLUTION: Immediately after an ignition switch is turned on, or in a state where a throttle valve opening TH is larger than a predetermined high opening THL, a stop estimated value PAESTP or a high load operation estimated value PAEHL is computed based on the intake pressure PBA, and during the fuel cut operation, a fuel cut operation estimated value PAEFC is computed based on an engine speed NE and the intake pressure PBA. A correction coefficient KFCPAE is computed based on the stop estimated value PAESTP or the high load operation estimated value PAEHL as well as the fuel cut operation estimated value PAEFC, and an estimated atmospheric pressure PAEST is computed based on the computed correction coefficient KFCPAE and the fuel cut operation estimated value PAEFC during the fuel cut operation.

Description

  The present invention relates to an atmospheric pressure estimation device that estimates an atmospheric pressure applied to calculation of a control parameter of an internal combustion engine.

  The atmospheric pressure detected by the atmospheric pressure sensor is usually applied to calculate the control parameters such as the fuel supply amount and ignition timing of the internal combustion engine. However, the number of sensors for calculating the engine control parameter is as small as possible. It is desirable to do.

  Patent Document 1 discloses a method for estimating the atmospheric pressure according to the throttle valve opening, the engine speed, and the intake pressure. According to this atmospheric pressure estimation method, the gradient Kpbpa and the standard intake pressure Pbpa at the standard atmospheric pressure are calculated by searching a map set in advance according to the throttle valve opening and the engine speed, and the gradient Kpbpa and the standard The estimated atmospheric pressure is calculated by applying the detected intake pressure to a linear expression including the intake pressure Pbpa.

JP-A-2-23253

  In the deceleration operation in which the throttle valve is fully closed, a fuel cut operation that temporarily stops the fuel supply to the engine is performed. During fuel cut operation, the intake pressure is lower than that during normal operation, so the above-mentioned conventional method is more susceptible to variations in engine characteristics and the accuracy of estimating atmospheric pressure decreases. There is.

  The present invention has been made paying attention to this point, and even during fuel cut operation, the atmospheric pressure is estimated according to the detected intake pressure, and accurate estimation is performed while suppressing a decrease in estimation accuracy. An object of the present invention is to provide an atmospheric pressure estimation device that can perform the above-described process.

  In order to achieve the above object, according to a first aspect of the present invention, there is provided an atmospheric pressure estimation device for estimating an atmospheric pressure to be applied to calculation of a control parameter of an internal combustion engine, and detecting an opening (TH) of a throttle valve of the engine. Throttle valve opening degree detecting means, speed detecting means for detecting the engine speed (NE), intake pressure detecting means for detecting the intake pressure (PBA) of the engine, and ignition of the engine are enabled. A first estimated value (PAEHL) of the atmospheric pressure is calculated based on the intake pressure (PBA) immediately after the ignition switch is turned on or in a state where the throttle valve opening (TH) is larger than a predetermined opening (THHL). 1 Estimated value calculating means and a second estimated value of atmospheric pressure based on the engine speed (NE) and the intake pressure (PBA) during fuel cut operation for temporarily stopping fuel supply to the engine Second estimated value calculating means for calculating (AEFC), and correction coefficient calculating means for calculating a correction coefficient (KFCPAE) based on the first and second estimated values (PAEHL, PAEFC), during the fuel cut operation Is characterized in that the atmospheric pressure is estimated based on the correction coefficient (KFCPAE) and the second estimated value (PAEFC).

  According to the first aspect of the present invention, the first estimated value of the atmospheric pressure is calculated based on the intake pressure immediately after the ignition switch is turned on or in a state where the throttle valve opening is larger than the predetermined opening, and the engine During the fuel cut operation in which the fuel supply to is temporarily stopped, the second estimated value of the atmospheric pressure is calculated based on the engine speed and the intake pressure. Further, a correction coefficient is calculated based on the first and second estimated values, and atmospheric pressure is estimated based on the calculated correction coefficient and the second estimated value during the fuel cut operation. Since the correction coefficient reflects the influence of variations in engine characteristics, the estimated atmospheric pressure is calculated using the second estimated value and the correction coefficient calculated during the fuel cut operation. Atmospheric pressure estimation can be performed.

It is a figure which shows the structure of the internal combustion engine and its control apparatus concerning one Embodiment of this invention. It is a flowchart of an atmospheric pressure estimation process. It is a flowchart of the process which calculates a correction coefficient (KFCPAE). It is a time chart for demonstrating the effect of the correction | amendment by a correction coefficient (KFCPAE).

Embodiments of the present invention will be described below with reference to the drawings.
FIG. 1 is a diagram showing a configuration of an internal combustion engine and a control device thereof according to an embodiment of the present invention. In FIG. 1, for example, an internal combustion engine (hereinafter simply referred to as “engine”) 1 having four cylinders is an intake pipe. 2 and a throttle valve 3 is arranged in the middle of the intake pipe 2. The throttle valve 3 is connected to a throttle valve opening sensor 4 for detecting the throttle valve opening TH, and the detection signal is supplied to an electronic control unit (hereinafter referred to as “ECU”) 5. An actuator 7 that drives the throttle valve 3 is connected to the throttle valve 3, and the operation of the actuator 7 is controlled by the ECU 5. The intake pipe 2 is provided with an intake air temperature sensor 9 for detecting the intake air temperature TA, and a detection signal thereof is supplied to the ECU 5.

  The fuel injection valve 6 is provided for each cylinder between the engine 1 and the throttle valve 3 and slightly upstream of the intake valve (not shown) of the intake pipe 2, and each injection valve is connected to a fuel pump (not shown). At the same time, it is electrically connected to the ECU 5 and the valve opening time of the fuel injection valve 6 is controlled by a signal from the ECU 5.

The ignition plug 12 of each cylinder of the engine 1 is connected to the ECU 5, and the ECU 5 supplies an ignition signal to the ignition plug 12 to perform ignition timing control.
An intake pressure sensor 8 for detecting the intake pressure PBA is attached downstream of the throttle valve 3. An engine cooling water temperature sensor 10 that detects the engine cooling water temperature TW is attached to the main body of the engine 1. The detection signals of these sensors 8 and 10 are supplied to the ECU 5.

  The ECU 5 is connected to a crank angle position sensor 11 that detects a rotation angle of a crankshaft (not shown) of the engine 1, and a signal corresponding to the rotation angle of the crankshaft is supplied to the ECU 5. The crank angle position sensor 11 is a cylinder discrimination sensor that outputs a pulse (hereinafter referred to as “CYL pulse”) at a predetermined crank angle position of a specific cylinder of the engine 1, and relates to a top dead center (TDC) at the start of the intake stroke of each cylinder. A TDC sensor that outputs a TDC pulse at a crank angle position before a predetermined crank angle (every 180 degrees of crank angle in a four-cylinder engine) and one pulse (hereinafter referred to as “CRK”) with a constant crank angle cycle shorter than the TDC pulse (for example, a cycle of 6 °). The CYL pulse, the TDC pulse, and the CRK pulse are supplied to the ECU 5. These pulses are used for various timing controls such as fuel injection timing and ignition timing, and detection of engine speed (engine speed) NE.

  The ECU 5 includes an accelerator sensor 31 for detecting an accelerator pedal depression amount (hereinafter referred to as “accelerator pedal operation amount”) AP of a vehicle driven by the engine 1, and a traveling speed (vehicle speed) VP of the vehicle driven by the engine 1. A vehicle speed sensor 32 for detecting the above is connected. Detection signals from these sensors are supplied to the ECU 5. Further, an on / off signal of an ignition switch 33 that enables ignition by the spark plug 12 is supplied to the ECU 5.

  The ECU 5 shapes input signal waveforms from various sensors, corrects the voltage level to a predetermined level, converts an analog signal value into a digital signal value, etc., and a central processing unit (hereinafter referred to as “CPU”). ), An arithmetic circuit executed by the CPU, a storage circuit for storing arithmetic results, and the like, and an output circuit for supplying drive signals to the actuator 7, the fuel injection valve 6, and the spark plug 12.

  The CPU of the ECU 5 controls the ignition timing, the opening degree of the throttle valve 3, and the amount of fuel supplied to the engine 1 (opening time of the fuel injection valve 6) according to the detection signal of the sensor.

  Further, the CPU of the ECU 5 executes an atmospheric pressure estimation process for estimating the atmospheric pressure PA, and applies the estimated atmospheric pressure PAEST obtained by the atmospheric pressure estimation process to the control such as the ignition timing control and the fuel amount control.

FIG. 2 is a flowchart of atmospheric pressure estimation processing. This process is executed at predetermined intervals by the CPU of the ECU 5 after the ignition switch 33 is turned on.
In step S11, it is determined whether or not the engine stop flag FESTP is “1”. If the answer is affirmative (YES), that is, before the engine rotation starts immediately after the ignition switch 33 is turned on, the estimated atmospheric pressure PAESTP and estimated atmospheric pressure PAEST when the engine is stopped are detected. The intake pressure PBA is set (step S12), and the initialization completion flag FPAINI is set to “1” (step S13).

  If the answer to step S11 is negative (NO), it is determined whether or not a high load operation flag FHL is “1” (step S14). The high load operation flag FHL is set to “1” when the throttle valve opening TH is larger than a predetermined opening THHL (for example, an opening corresponding to 20% of the fully opened opening) and the traveling state of the vehicle is stable. Is set. If the answer is no (NO), the process immediately proceeds to step S17. On the other hand, when FHL = 1 and the engine 1 is in a predetermined high load operation state, the atmospheric pressure estimated value (hereinafter referred to as “high load operation estimated value”) PAEHL in the high load operation is set to the intake pressure PBA and the engine speed. The number NE is calculated by a known method (for example, the method disclosed in Patent Document 1) (step S15). The calculated high load operation estimated value PAEHL is sequentially stored, and when the number of high load operation estimated values PAEHL calculated from the current operation start time of the engine 1 reaches a predetermined number N1 (for example, 100), the average high load The operation estimated value PAEHLAV (= ΣPAEHL / N1) is calculated, and a high load operation average value calculation completion flag FHLAVEEND indicating that the calculation of the average high load operation estimated value PAEHLAV is completed is set to “1”.

In step S16, the estimated atmospheric pressure PAEST is set to the high load operation estimated value PAEHL calculated in step S15.
In step S17, it is determined whether or not a fuel cut flag FFC is “1”. The fuel cut flag FFC is set to “1” when the fuel cut operation for temporarily stopping the fuel supply to the engine 1 during the deceleration of the vehicle and the traveling state of the vehicle is stable. The If this answer is negative (NO), the processing is immediately terminated.

  On the other hand, when the fuel cut flag FFC is “1”, the atmospheric pressure estimated value (hereinafter referred to as “fuel cut operation estimated value”) PAEFC during the fuel cut operation is known according to the intake pressure PBA and the engine speed NE. Calculation is performed by a method (for example, the method disclosed in Patent Document 1) (step S18). The calculated fuel cut operation estimated value PAEFC is sequentially stored, and the average fuel cut is calculated when the number of fuel cut operation estimated values PAEFC calculated from the current operation start time of the engine 1 reaches a predetermined number N2 (for example, 100). The operation estimated value PAEFCAV (= ΣPAEFC / N2) is calculated, and the fuel cut operation average value calculation completion flag FFCAVEND indicating that the calculation of the average fuel cut operation estimated value PAEFCAV is completed is set to “1”.

In step S19, the correction coefficient KFCPAE calculated in the process of FIG. 3 and the fuel cut operation estimated value PAEFC calculated in step S18 are applied to the following equation (1) to calculate the estimated atmospheric pressure PAEST (step S20). Since the correction coefficient KFCPAE is initialized to “1.0” when the stored value is lost, the estimated atmospheric pressure PAEST is equal to the period until the calculation of the correction coefficient KFCPAE is completed in the process of FIG. The fuel cut operation estimated value PAEFC becomes equal.
PAEST = KFCPAE × PAEFC (1)

  FIG. 3 is a flowchart of a process for calculating the correction coefficient KFCPAE. This process is executed at predetermined intervals by the CPU of the ECU 5 after the ignition switch 33 is turned on.

  In step S31, it is determined whether or not a correction coefficient calculation completion flag FKCEND is “1”. Since the correction coefficient calculation completion flag FKCEND is returned to “0” when the ignition switch 33 is turned off, the answer is initially negative (NO), the process proceeds to step S32, and the fuel cut operation average value calculation completion flag FFCAVEEND is set. It is determined whether or not “1”. Initially, the answer is negative (NO). Therefore, the process is immediately terminated, and when the fuel cut operation average value calculation completion flag FFCAVEEND is set to “1”, the process proceeds to step S33, and the high load operation average value calculation is completed. It is determined whether or not the flag FHLAEND is “1”.

  If the answer to step S33 is negative (NO), it is determined whether or not a vehicle travel flag FDIST is “1” (step S34). The vehicle travel flag FDIST has an initial value of “0”, and is set to “1” when the vehicle travels a predetermined distance DIST (for example, 3000 m) after the start of the current driving. Initially, the answer to step S34 is negative (NO), and the process proceeds to step S35 to determine whether or not the initialization flag FPAINI is “1”.

If the answer to step S35 is negative (NO), the process ends immediately. If the answer to step S33 or S35 is affirmative (YES), the process proceeds to step S36, and the following equation (2) or (3) is used. The current value KFCPAEP of the correction coefficient is calculated. Equation (2) is used to calculate the ratio between the average high-load operation estimated value PAEHLAV and the average fuel cut operation estimated value PAEFCAV, and is applied when the routine immediately proceeds from step S33 to step S36. Equation (3) calculates the ratio between the estimated stop value PAESTP and the estimated average fuel cut operation value PAEFCAV, and is applied when the process proceeds from step S35 to step S36.
KFCPAEP = PAEHLAV / PAEFCAV (2)
KFCPAEP = PAESTP / PAEFCAV (3)

  If the answer to step S34 is affirmative (YES) and the vehicle has traveled more than a predetermined distance DIST after the ignition switch is turned on, the vehicle travel environment is likely to be changing and the reliability of the estimated stop value PAESTP is low. The process ends.

  In step S37, it is determined whether or not the reset flag FKFCRST is “1”. The reset flag FKFCRST is set to “0” when the value of the correction coefficient KFCPAE stored in the memory is lost. If the answer to step S37 is negative (NO), the correction coefficient KFCPAE is set to the current value KFCPAEP (step S38), and the reset flag FKFCRST is returned to “1” (step S39). In step S41, the correction coefficient calculation completion flag FKCEND is set to “1”.

If the answer to step S37 is affirmative (YES), that is, if the correction coefficient KFCPAE is stored in the memory, the correction coefficient KFCPAE is calculated by a smoothing operation (step S40). That is, the current value KFCPAEP and the stored value KFCPAE are applied to the right side of the following formula (4), and the correction coefficient KFCPAE is updated. CFCPAE in Expression (4) is an annealing coefficient set to a value between 0 and 1, and more specifically, for example, set to a value between 0 and 0.1.
KFCPAE = CFCPAE × KFCPAEP
+ (1-CFCPAE) × KFCPAE (4)

  When step S38 or S40 is executed and the correction coefficient KFCPAE is initialized or updated, the correction coefficient calculation completion flag FKCEND is set to “1”, and thereafter, the answer to step S31 becomes affirmative (YES). The process of FIG. 3 is substantially not executed. That is, the correction coefficient KFCPAE is updated only once in one operation period (period from the time when the ignition switch 33 is turned on to the time when it is turned off).

  FIG. 4 is a time chart for explaining the effect of calculating the estimated atmospheric pressure PAEST using the above-described correction coefficient KFCPAE. FIGS. 4A to 4F are respectively a high load operation flag FHL, The fuel cut flag FFC, estimated atmospheric pressure PAEST (without correction), estimated error DPA (without correction), estimated atmospheric pressure PAEST (with correction), and estimated error DPA (with correction) are shown. The estimated error DPA is calculated by subtracting the actual atmospheric pressure PA from the estimated atmospheric pressure PAEST.

  In the example shown in FIGS. 4C and 4D in which correction by the correction coefficient KFCPAE is not performed, the estimation error DPA of the high load operation estimated value PAEHL is almost “0” (time t1), but the fuel cut operation estimation is performed. The value PAEFC is considerably lower than the actual atmospheric pressure PA, and the estimation error DPA increases in the negative direction (time t2). Although the fuel cut operation is performed six times and the fuel cut operation estimated value PAEFC slightly changes, the state where the estimation error DPA is large is not improved. At time t3, the high load operation estimated value PAEHL is calculated again, and the estimated atmospheric pressure PAEST is set to the high load operation estimated value PAEHL. Therefore, the absolute value of the estimated error DPA is decreased.

  In the example shown in FIGS. 4E and 4F in which correction is performed using the correction coefficient KFCPAE, the application of the correction coefficient KFCPAE is started from time t2, and therefore the estimated atmospheric pressure that is updated during the subsequent fuel cut operation. The estimated error DPA of PAEST slightly increases in the positive direction, but it can be confirmed that it is significantly improved compared to the estimated error DPA (absolute value) of the example shown in FIG.

  As described above, in the present embodiment, immediately after the ignition switch 33 is turned on or in a state where the throttle valve opening TH is greater than the predetermined opening THHL, the stop estimated value PAESTP or the high load operation estimated value PAEHL is based on the intake pressure PBA. The calculated fuel cut operation value PAEFC is calculated based on the engine speed NE and the intake pressure PBA during the fuel cut operation. Further, the correction coefficient KFCPAE is calculated by dividing the average value PAEHLAV of the stop estimated value PAESTP or the high load operation estimated value PAEHL by the average value PAEFCAV of the fuel cut operation estimated value PAEFC, and is calculated during the fuel cut operation. The estimated atmospheric pressure PAEST is calculated based on the correction coefficient KFCPAE and the fuel cut operation estimated value PAEFC. Since the correction coefficient KFCPAE reflects the influence of variations in engine characteristics, the estimated atmospheric pressure PAEST is calculated using the fuel cut operation estimated value PAEFC and the correction coefficient KFCPAE. Atmospheric pressure estimation can be performed.

  In the present embodiment, the throttle valve opening sensor 4, the crank angle position sensor 11, and the intake pressure sensor 8 correspond to a throttle valve opening detection means, a rotation speed detection means, and an intake pressure detection means, respectively. 1 estimation value calculation means, 2nd estimation value calculation means, and correction coefficient calculation means are comprised. Specifically, steps S11 to S15 in FIG. 2 correspond to the first estimated value calculating means, steps S17 and S18 correspond to the second estimated value calculating means, and the processing in FIG. 3 corresponds to the correction coefficient calculating means. .

  The present invention is not limited to the above-described embodiment, and various modifications can be made. For example, in the above-described embodiment, the high load operation estimated value PAEHL is calculated by a known method according to the intake pressure PBA and the engine speed NE, but the predetermined opening THHL is set near the fully opened opening, The detected intake pressure PBA when the throttle valve opening TH is larger than the predetermined high opening THHL may be used as the high load operation estimated value PAEHL as it is.

1 Internal combustion engine 3 Throttle valve 4 Throttle valve opening sensor (throttle valve opening detection means)
5 Electronic control unit (first estimated value calculating means, second estimated value calculating means, correction coefficient calculating means)
8 Intake pressure sensor (Intake pressure detection means)
11 Crank angle position sensor (rotational speed detection means)
33 Ignition switch

Claims (1)

In an atmospheric pressure estimation device for estimating an atmospheric pressure applied to calculation of a control parameter of an internal combustion engine,
Throttle valve opening detection means for detecting the opening of the throttle valve of the engine;
A rotational speed detecting means for detecting the rotational speed of the engine;
An intake pressure detecting means for detecting an intake pressure of the engine;
A first estimated value calculation that calculates a first estimated value of atmospheric pressure based on the intake pressure immediately after turning on an ignition switch that enables ignition of the engine or in a state where the throttle valve opening is larger than a predetermined opening. Means,
A second estimated value calculating means for calculating a second estimated value of the atmospheric pressure based on the engine speed and the intake pressure during a fuel cut operation for temporarily stopping fuel supply to the engine;
Correction coefficient calculation means for calculating a correction coefficient based on the first and second estimated values,
During the fuel cut operation, the atmospheric pressure is estimated based on the correction coefficient and the second estimated value.

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