JP6007841B2 - Control device for internal combustion engine - Google Patents

Description

  The present invention relates to an internal combustion engine control apparatus, and more particularly to an internal combustion engine control apparatus suitable as an apparatus for executing various engine controls using detection values of a cylinder pressure sensor.

  In recent years, an internal combustion engine mounted on a vehicle has been operated to automatically stop the internal combustion engine during idling and then start the vehicle for the purpose of reducing fuel consumption and exhaust emissions. Some have an idling stop function for restarting the internal combustion engine.

  For example, Patent Document 1 discloses a start control device for an internal combustion engine having the idling stop function. In this conventional start control device, when restarting the internal combustion engine after automatic stop by idling stop, combustion is generated in the cylinder by performing fuel injection and ignition on the cylinder stopped in the expansion stroke, A starting method (hereinafter referred to as “ignition start”) in which the internal combustion engine is started without using a starter motor by rotationally driving the crankshaft with the combustion pressure is used.

JP 2004-332598 A JP 2009-156108 A JP 2011-153586 A JP 2003-138777 A JP 2011-185136 A JP 2004-360594 A Japanese Patent Laid-Open No. 06-346824 JP-A-11-190250 Japanese Patent Laid-Open No. 02-099743

  By the way, an internal combustion engine provided with an in-cylinder pressure sensor for detecting an in-cylinder pressure is known. According to the internal combustion engine including such an in-cylinder pressure sensor, by acquiring in-cylinder pressure information associated with the crank angle (synchronized with the crank angle) using the in-cylinder pressure sensor, the combustion performed in each cycle is performed. On the other hand, it is possible to calculate various combustion state quantities (for example, calorific value) that are useful for various engine controls (fuel injection control, ignition control, etc.).

  However, when the crank angle is detected using a crank angle sensor having a general configuration, the crank angle cannot be determined unless the crankshaft rotates to some extent immediately after starting (the current crank angle cannot be recognized). ). Therefore, in the case of the ignition start described above, since the internal combustion engine is started by injecting fuel into the cylinders stopped in the expansion stroke, the cycle is synchronized with the crank angle in the cycle from the start to the determination of the crank angle. It becomes impossible to obtain the in-cylinder pressure information. As a result, immediately after start-up, engine control using in-cylinder pressure information from the in-cylinder pressure sensor cannot be performed.

  The present invention has been made to solve the above-described problems, and is an internal combustion engine capable of obtaining in-cylinder pressure data synchronized with a crank angle from the first start cycle in an internal combustion engine that performs ignition start. An object of the present invention is to provide an engine control device.

A first invention is a control device for an internal combustion engine,
A cylinder having a fuel injection valve for directly injecting fuel into the cylinder, an in-cylinder pressure sensor for detecting the in-cylinder pressure, and a crank angle sensor for detecting the crank angle, and being stopped in the expansion stroke A control device for an internal combustion engine that performs an ignition start by executing fuel injection using the fuel injection valve and starting the internal combustion engine by rotationally driving a crankshaft by a combustion pressure accompanying the fuel injection,
First crank angle acquisition means for acquiring a first crank angle that is a crank angle of a cylinder that is stopped in an expansion stroke;
In-cylinder pressure time series that acquires time-series data of the in-cylinder pressure of the start-up cylinder detected by using the in-cylinder pressure sensor when the ignition start is performed with the cylinder stopped in the expansion stroke as the start-up cylinder. Data acquisition means;
Using the time-series data of the in-cylinder pressure, an atmospheric pressure decrease time acquisition means for acquiring an atmospheric pressure decrease time, which is a time when the in-cylinder pressure of the start start cylinder decreases to an atmospheric pressure after combustion in the start start cylinder;
Second crank angle acquisition means for acquiring a second crank angle that is a crank angle of an opening timing of the exhaust valve at the time of starting ignition in the start start cylinder;
Crank angular speed time-series data acquisition means for acquiring time-series data of crank angular speed during an elapsed time from the start time of the ignition start until reaching the atmospheric pressure decrease time point, using the crank angle sensor;
Crank angle time-series data acquisition means for acquiring time-series data of the crank angle during the elapsed time based on the time-series data of the crank angular speed;
The crank angle at the start of the ignition start in the start cylinder is the first crank angle, and the crank angle at the atmospheric pressure drop is the second crank angle. In-cylinder pressure data acquisition means for acquiring in-cylinder pressure data synchronized with the crank angle by associating the time-series data with the time-series data of the crank angle;
It is characterized by providing.

The second invention is the first invention, wherein
The apparatus further comprises elapsed time correction means for correcting the elapsed time by subtracting the elapsed time from a predetermined time required from the time when the exhaust valve opens to the time when the atmospheric pressure decreases.

The third invention is the first invention, wherein
The second crank angle acquisition means adds a predetermined crank angle change amount from the crank angle at the opening timing of the exhaust valve to the crank angle at the time of the decrease in atmospheric pressure to the second crank angle. It is characterized by correcting.

Moreover, 4th invention is set in any one of 1st-3rd invention,
The in-cylinder pressure time-series data acquiring unit corrects the time-series data of the in-cylinder pressure based on a difference between the in-cylinder pressure at the start of the ignition start and the in-cylinder pressure at the time when the atmospheric pressure decreases. .

Moreover, 5th invention is based on any one of 1st-4th invention,
An in-cylinder temperature estimating means for estimating an in-cylinder temperature at the start of the ignition start, based on a difference between the in-cylinder pressure at the start of the ignition start and the in-cylinder pressure at the time of the atmospheric pressure decrease;
An injection amount correction means for correcting a fuel injection amount in a predetermined cycle after the start of the ignition start based on the in-cylinder temperature at the start of the ignition start;
Is further provided.

  According to the first aspect of the invention, the atmospheric pressure drop time after combustion in the starting cylinder at the start of ignition is obtained from the time-series data of the cylinder pressure obtained using the cylinder pressure sensor, By using the opening timing in association with each other, the time-series data of the in-cylinder pressure during the elapsed time from the start of ignition start to the time of the atmospheric pressure decrease is associated with the time-series data of the crank angle, In-cylinder pressure data synchronized with the crank angle can be acquired from the first cycle of the start.

  A certain amount of time is required from when the exhaust valve starts to open until the in-cylinder pressure drops to atmospheric pressure. Therefore, strictly speaking, there is a time difference between the time when the exhaust valve opening timing arrives and the time when the atmospheric pressure drops. According to the second invention, the time difference is eliminated by a method of correcting the elapsed time by subtracting the elapsed time from a predetermined time required from the arrival timing of the exhaust valve opening timing to the atmospheric pressure decrease time. In the state, the point of atmospheric pressure drop and the opening timing of the exhaust valve can be correlated. As a result, in-cylinder pressure data synchronized with the crank angle can be acquired with higher accuracy.

  As described above, strictly speaking, there is a time difference between the time when the exhaust valve opening timing arrives and the time when the atmospheric pressure drops. According to the third aspect of the invention, the second crank angle is corrected by adding a predetermined crank angle change amount from the crank angle at the exhaust valve opening timing to the crank angle at the time when the atmospheric pressure drops to the second crank angle. Thus, it is possible to associate the atmospheric pressure drop time with the opening timing of the exhaust valve in a state where the time difference is eliminated. Even with such a method, the in-cylinder pressure data synchronized with the crank angle can be acquired with higher accuracy.

  According to the fourth aspect of the invention, it is possible to correct the time series data of the in-cylinder pressure so that the influence of temperature drift is eliminated. For this reason, even when a temperature drift effect on the sensor, which is a problem at the start of ignition, occurs, it is possible to accurately calculate the various combustion state quantities and the estimated value of the air-fuel ratio using the detection value of the in-cylinder pressure sensor. become.

  According to the fifth aspect of the present invention, the in-cylinder temperature at the start is estimated using the difference between the in-cylinder pressure at the start of the ignition start and the in-cylinder pressure at the time when the atmospheric pressure drops, and the fuel corresponding to the estimated in-cylinder temperature. The injection amount can be corrected. Thereby, it is possible to suppress the deterioration of combustion at the start-up regardless of the state of the in-cylinder temperature at the start-up.

It is a figure for demonstrating the system configuration | structure of the internal combustion engine in Embodiment 1 of this invention. It is a figure for demonstrating the outline | summary of the process performed in order to acquire the in-cylinder pressure data synchronized with the crank angle from the 1st cycle of ignition start in Embodiment 1 of this invention. It is a figure used in order to explain the acquisition method of in-cylinder pressure data of crank angle synchronization in consideration of the time required for pressure drop. It is a figure used in order to explain the acquisition method of in-cylinder pressure data of crank angle synchronization in consideration of the time required for pressure drop. It is a flowchart of the routine performed in Embodiment 1 of the present invention. It is a figure showing the relationship between an air fuel ratio (A / F) and an air fuel ratio correlation value (KL / (Q / low heating value)). It is a figure for demonstrating the acquisition method of the air quantity KL in the 1st cycle of ignition start. It is a flowchart of the routine performed in Embodiment 1 of the present invention. It is a figure for demonstrating the correction method of the temperature drift influence of the cylinder pressure waveform in Embodiment 2 of this invention. It is a flowchart of the routine performed in Embodiment 2 of this invention. It is a figure for demonstrating the correction method of the fuel injection quantity using the temperature drift amount (delta) of the cylinder pressure waveform in Embodiment 3 of this invention. It is a flowchart of the routine performed in Embodiment 3 of the present invention.

Embodiment 1 FIG.
FIG. 1 is a diagram for explaining a system configuration of an internal combustion engine 10 according to Embodiment 1 of the present invention.
The system shown in FIG. 1 includes an internal combustion engine (for example, a spark ignition internal combustion engine) 10. A piston 12 is provided in the cylinder of the internal combustion engine 10. A combustion chamber 14 is formed on the top side of the piston 12 in the cylinder. An intake passage 16 and an exhaust passage 18 communicate with the combustion chamber 14.

  The intake port of the intake passage 16 is provided with an intake valve 20 that opens and closes the intake port, and the exhaust port of the exhaust passage 18 is provided with an exhaust valve 22 that opens and closes the exhaust port. The intake passage 16 is provided with an electronically controlled throttle valve 24.

  Each cylinder of the internal combustion engine 10 is provided with a fuel injection valve 26 for directly injecting fuel into the combustion chamber 14 (inside the cylinder) and an ignition plug 28 for igniting the air-fuel mixture. Furthermore, an in-cylinder pressure sensor 30 for detecting the in-cylinder pressure is incorporated in each cylinder. The detection value of the in-cylinder pressure sensor 30 is a relative pressure with respect to the atmospheric pressure.

  Furthermore, the system of this embodiment includes an ECU (Electronic Control Unit) 40. In addition to the in-cylinder pressure sensor 30 described above, an input unit of the ECU 40 includes a crank angle sensor 42 for detecting the crank angle and the engine speed (crank angular speed), an air flow meter 44 for measuring the intake air amount, and the like. Various sensors for detecting the operating state of the internal combustion engine 10 are connected. Here, as an example, the crank angle sensor 42 is an electromagnetic pickup (MPU) type sensor. The timing rotor 48 provided on the crankshaft 46 is provided with signal teeth partially missing for detecting the top dead center (in FIG. 1, only some signal teeth not missing are shown). . The crank angle sensor 42 can detect a crank rotation signal for each predetermined crank angle, and can detect an accurate top dead center based on the missing part. Various actuators such as the throttle valve 24, the fuel injection valve 26, and the spark plug 28 described above are connected to the output portion of the ECU 40. The ECU 40 performs predetermined engine control such as fuel injection control and ignition control by driving the various actuators based on the sensor output and a predetermined program.

  The internal combustion engine 10 having the above-described configuration is configured to automatically stop the internal combustion engine 10 at the time of idling for the purpose of reducing fuel consumption and exhaust emission, and then the driver performs an operation to start the vehicle. In this case, the engine has an idling stop function for restarting the internal combustion engine 10. More specifically, in the internal combustion engine 10, when the internal combustion engine 10 is restarted after the automatic stop by the idling stop, fuel is injected into the cylinder stopped in the expansion stroke and ignition is performed in the cylinder. And starting the internal combustion engine 10 without using the starter motor by rotationally driving the crankshaft 46 with this combustion pressure (hereinafter referred to as “ignition start”). Is used.

  The internal combustion engine 10 having the above-described configuration includes an in-cylinder pressure sensor 30. According to the internal combustion engine 10 including such an in-cylinder pressure sensor 30, by using the in-cylinder pressure sensor 30, the in-cylinder pressure information (in-cylinder pressure data) associated with the crank angle (synchronized with the crank angle) is acquired. Various combustion state quantities (for example, calorific value) useful for various engine controls (fuel injection control, ignition control, etc.) can be calculated for the combustion performed in each cycle.

  However, when the crank angle is detected using a crank angle sensor having a general configuration such as the crank angle sensor 42, the crank angle cannot be determined unless the crankshaft 46 is rotated to some extent immediately after the start (current position). Crank angle cannot be recognized). Therefore, in the case of the ignition start, the internal combustion engine 10 is started by injecting and igniting the cylinders that are stopped in the expansion stroke. Therefore, in the cycle from the start to the determination of the crank angle, In-cylinder pressure data synchronized with the angle cannot be obtained. As a result, immediately after starting, engine control using the in-cylinder pressure data from the in-cylinder pressure sensor 30 cannot be performed. Therefore, in the present embodiment, the following processing shown in FIGS. 2 to 5 is executed in order to obtain in-cylinder pressure data synchronized with the crank angle from the first start cycle.

FIG. 2 is a diagram for explaining an overview of processing executed to acquire in-cylinder pressure data synchronized with the crank angle from the first cycle of ignition start in the first embodiment of the present invention.
FIG. 2A shows an in-cylinder pressure waveform of a cylinder in which combustion is first performed at the start of ignition (that is, a cylinder stopped in the expansion stroke). When the internal combustion engine 10 stops, the in-cylinder pressure drops to the atmospheric pressure in about several seconds. At time T0 in FIG. 2, the timing at which ignition start (fuel injection and ignition) is performed with the cylinder stopped in the expansion stroke as the start start cylinder in the state where the in-cylinder pressure is atmospheric pressure (depending on the combustion pressure) The timing at which the crankshaft 46 starts to rotate) is shown.

  First, the first crank angle CA1, which is the crank angle at the ignition start start time T0 (that is, the crank angle of the cylinder stopped in the expansion stroke), is acquired using the crank angle sensor 42 at the time of automatic stop. As shown in FIG. 2 (A), in this embodiment, the cylinder pressure (relative value) is acquired every predetermined time in the first cycle of the start, so that the cylinder pressure in the first cycle of the start of the cylinder is obtained. Series data is acquired.

  Next, using the acquired time-series data of the in-cylinder pressure, an atmospheric pressure decrease time point T1 at which the in-cylinder pressure has decreased to atmospheric pressure (equivalent) after combustion in the start-start cylinder is acquired. After the combustion is performed in the expansion stroke, the in-cylinder pressure is reduced to the atmospheric pressure by opening the exhaust valve 22. Therefore, in the method shown in FIG. 2, as shown in FIG. 2A, the opening timing (EVO) of the exhaust valve 22 has arrived at the time T1 when the in-cylinder pressure decreased to the atmospheric pressure in the time-series data of the in-cylinder pressure. I decided to judge. Then, the crank angle at the opening timing of the exhaust valve 22 is acquired as the second crank angle CA2. Since the crank angle that is the opening timing of the exhaust valve 22 is stored in advance in the ECU 40 as a control value, the second crank angle CA2 can be acquired using the control value.

  Next, an elapsed time (T1-T0) from the ignition start start time T0 to the atmospheric pressure decrease time T1 is calculated. Further, time-series data of the engine speed (crank angular speed) during the elapsed time (T1-T0) is acquired as shown in FIG. More specifically, the MPU-type crank angle sensor 42 cannot detect the crank angle below the specified engine speed due to the sensor characteristics, and is higher than the specified engine speed. Crank angle data can be acquired. Therefore, as shown in FIG. 2 (B), the engine speed equal to or lower than the specified engine speed is the engine speed at a predetermined timing when the data can be acquired and the engine speed at the start start time T0 (that is, zero). ) With linear interpolation. When an MPU type sensor is used like the crank angle sensor 42 of the present embodiment, time series data of the engine speed (crank angular speed) during the elapsed time (T1-T0) is obtained by such a method. Can be acquired. Next, based on the time-series data of the engine speed, the relationship shown in FIG. 2C, that is, the time-series data of the crank angle CA during the elapsed time (T1-T0) is acquired.

Finally, the crank angle at the ignition start start time T0 in the start start cylinder is set to the first crank angle CA1, and the crank angle at the atmospheric pressure decrease time T1 is set to the second crank angle CA2. A process for associating the time-series data of the in-cylinder pressure shown in FIG. 2 with the time-series data of the crank angle shown in FIG. Thereby, crank angle information can be given to the time-series data of in-cylinder pressure, that is, in-cylinder pressure data synchronized with the crank angle can be acquired. According to such a method, in-cylinder pressure information synchronized with the crank angle can be obtained from the first cycle of ignition start. As a result, the first cycle of the ignition starting (i.e., the information of the compression stroke is not the first cycle), using a cylinder pressure Ru can be calculated combustion state quantity of each species. As a result, various engine controls can be performed at an early stage by using the in- cylinder pressure sensor.

  Next, referring to FIG. 3 and FIG. 4, by considering a predetermined time (hereinafter referred to as “required pressure drop time”) required for the in-cylinder pressure to drop to atmospheric pressure after the exhaust valve 22 starts to open. A method will be described in which the time difference between the time point when the second crank angle CA2 is obtained and the atmospheric pressure decrease time point T1 is corrected, and thereby the in-cylinder pressure data synchronized with the crank angle can be obtained more accurately. FIG. 3 and FIG. 4 are diagrams used for explaining a method of acquiring in-cylinder pressure data synchronized with the crank angle in consideration of the pressure drop required time.

  More specifically, the opening timing EVO of the exhaust valve 22 is a timing at which the exhaust valve 22 starts to open. Since the crank angle at this timing can be obtained from the control value of the ECU 40 as described above, it is particularly referred to as “EVOecu” here. It takes a certain amount of time from when the exhaust valve 22 starts to open until the valve lift amount becomes maximum. Therefore, strictly speaking, since the time T_EVOecu when the crank angle EVOecu (control value) arrives and the time T1 when the atmospheric pressure decreases (the time detected using the in-cylinder pressure sensor 30), hereinafter, “T_EVOcps” is used instead of T1. There is a time difference (corresponding to this time required for pressure drop). The method shown in FIG. 2 described above can be said to be a method performed by regarding these time points T_EVOecu and T_EVOcps as being the same. However, in order to more accurately acquire the in-cylinder pressure data synchronized with the crank angle, it is preferable to use the method described below with reference to FIGS. Since the combustion gas is discharged from the combustion chamber 14 to the exhaust passage 18 at a sonic speed, when the valve lift amount of the exhaust valve 22 is maximized, the time required for the in-cylinder pressure to be reduced to the atmospheric pressure is 1/1000 second or less. For this reason, the influence of the said time with respect to the control period (several milliseconds order) of ECU40 can be disregarded. That is, in consideration of the time required for the pressure drop from when the exhaust valve 22 starts to open until the in-cylinder pressure decreases to atmospheric pressure, as described above, from when the exhaust valve 22 starts to open until the valve lift amount becomes maximum. It can be said that time should be taken into consideration.

  In the method shown here, the time (pressure reduction required time Tmap) required from the arrival time T_EVOecu of the opening timing EVO of the exhaust valve 22 to the atmospheric pressure reduction time T_EVOcps is stored in advance in the ECU 40 as a map value. Then, using this pressure drop required time Tmap as a correction value, a value obtained by subtracting the pressure drop required time Tmap from the atmospheric pressure drop time T_EVOcps is acquired as the arrival time T_EVOecu of the exhaust valve 22 opening timing EVO. . Thus, the time difference between T_EVOecu, which is the acquisition time point of the second crank angle CA2, and the atmospheric pressure decrease time point T_EVOcps can be eliminated, so that in-cylinder pressure data synchronized with the crank angle can be acquired more accurately.

  More specifically, the correction using the pressure drop required time Tmap can be performed by the following procedure. That is, as shown in FIG. 3A, the change in the in-cylinder pressure at the predetermined time ΔT (control cycle of the ECU 40) using the time-series data of the in-cylinder pressure after the predetermined time α has elapsed from the maximum in-cylinder pressure Pmax. It is determined every predetermined time ΔT whether or not the amount ΔP exceeds a predetermined threshold. The change amount ΔP of the in-cylinder pressure becomes a negative value as shown in FIG. 3B during the period in which the in-cylinder pressure decreases after the maximum in-cylinder pressure Pmax elapses, and then decreases to the atmospheric pressure. As a result, the value approaches zero (the value becomes larger than before). The threshold value is set to a value that can capture such a change in the change amount ΔP. When the change amount ΔP of the in-cylinder pressure exceeds the threshold value, it is determined that the atmospheric pressure drop time T_EVOcps has arrived. In addition, as described above, the pressure drop required time Tmap is acquired in advance and then mapped to the ECU 40 as a map value (for example, a map defining the pressure drop required time Tmap in relation to the crank angle at the start of ignition start). It is remembered.

  In addition, for correction described later, for example, the angular velocity (ΔCA / ΔT) from the crank stop position (crank angle at the time of automatic stop) to the top dead center (TDC) is also acquired. The period for calculating the change amount ΔP of the in-cylinder pressure may not be the maximum in-cylinder pressure Pmax but the elapsed time β corresponding to the crank angle position at the time of automatic stop. Further, since the elapsed times α, β, and ΔT are affected by the combustion speed, a correction term based on the oil temperature, the water temperature, the intake air temperature, or the maximum in-cylinder pressure Pmax may be provided. Alternatively, as another correction method, the angular velocity (ΔCA / ΔT) may be compared with a previously acquired value, and the pressure drop required time Tmap may be corrected according to the comparison result. By performing these corrections, the pressure drop required time Tmap can be corrected with higher accuracy in consideration of the combustion state in the first cycle of ignition start, the environmental conditions, and the like.

With reference to FIG. 4, the above-described correction method for the pressure drop required time Tmap will be described again.
As described above, the crank angle (here, used as the second crank angle CA2) CA_EVOecu at the opening timing (timing to start opening) of the exhaust valve 22 is known as a control value of the ECU 40. Further, the atmospheric pressure drop time T_EVOcps (T1) can be acquired using time series data of the in-cylinder pressure acquired by using the in-cylinder pressure sensor 30.

  On the other hand, as shown in FIG. 4, the time point T_EVOecu corresponding to the crank angle CA_EVOecu at the opening timing of the exhaust valve 22 is unknown. Therefore, in the above-described method, the arrival time T_EVOecu of the opening timing EVOecu of the exhaust valve 22 is obtained by subtracting the pressure decrease required time Tmap from the atmospheric pressure decrease time T_EVOcps. As a result, as described above, the time difference between T_EVOecu, which is the acquisition time point of the second crank angle CA2, and the atmospheric pressure decrease time point T_EVOcps can be eliminated, so that in-cylinder pressure data synchronized with the crank angle is acquired more accurately. become able to.

  How many seconds after the start of ignition start, the opening timing EVOecu of the exhaust valve 22 changes according to predetermined parameters relating to the combustion state and the state of the internal combustion engine (for example, friction). Therefore, by providing a map that reflects the influence of the above parameters, it is also possible to obtain the time T_EVOecu when the opening timing EVOecu of the exhaust valve 22 arrives. However, with such a method, it is difficult to acquire the time T_EVOecu with sufficient accuracy. On the other hand, in the method of the present embodiment, the atmospheric pressure drop time T_EVOcps is obtained using the measured data of the in-cylinder pressure by the in-cylinder pressure sensor 30, so the arrival time of the opening timing of the exhaust valve 22 is accurately obtained. become able to. Then, by correcting the time required for pressure reduction as described above, and also correcting the combustion state and environmental conditions, the in-cylinder pressure data synchronized with the crank angle can be acquired more accurately.

  Further, as shown in FIG. 4, the crank angle CA_EVOcps at the atmospheric pressure drop time T_EVOcps is also unknown. Therefore, instead of the above-described method, the following method may be used to perform correction in consideration of the above time difference (required pressure drop time). That is, a crank angle change amount CAmap, which is a change amount of the crank angle that changes from when the exhaust valve 22 starts to open until the in-cylinder pressure reaches atmospheric pressure, is obtained in advance, and a map value (for example, start of ignition start) is obtained. A map defining the crank angle change amount CAmap in relation to the crank angle at the time. Then, the crank angle CA_EVOcps at the atmospheric pressure drop time T_EVOcps may be acquired by adding the crank angle change amount CAmap to the known crank angle CA_EVOecu of the opening timing of the exhaust valve 22. Then, the obtained crank angle CA_EVOcps may be used as the second crank angle CA2. This can be said to correspond to the correction taking into account the time difference (required pressure drop time) when calculating the second crank angle CA2 using the crank angle change amount CAmap.

  In the method described above with reference to FIG. 3, the opening timing crank of the exhaust valve 22 is obtained by subtracting the pressure decrease required time Tmap from the atmospheric pressure decreasing time T_EVOcps to obtain the arrival time T_EVOecu of the opening timing EVOecu of the exhaust valve 22. The angle CA_EVOecu and the time point T_EVOecu corresponding to the crank angle can be obtained while eliminating the time difference. On the other hand, the time difference can also be eliminated by obtaining the atmospheric pressure drop time T_EVOcps and the crank angle CA_EVOcps at that time by the method described here.

Next, with reference to FIG. 5, a specific process executed by ECU 40 in the first embodiment of the present invention will be described.
FIG. 5 is a flowchart showing a routine executed by the ECU 40 in the first embodiment in order to acquire in-cylinder pressure data synchronized with the crank angle. Note that this routine is started when the internal combustion engine 10 that is automatically stopped by the idling stop function is restarted by ignition start.

  In the routine shown in FIG. 5, first, the crank angle acquired at the time of the most recent automatic stop is acquired as the first crank angle CA1 at the time of ignition start (in the automatic stop state) (step 100). Next, the output signal of the in-cylinder pressure sensor 30 is AD-converted every predetermined time (control cycle of the ECU 40) to acquire the in-cylinder pressure, whereby a time-synchronized in-cylinder pressure waveform (A) (in-cylinder pressure time-series data) is obtained. Obtained (step 102).

  Next, the cylinder pressure data after the predetermined time α (predetermined time from the maximum in-cylinder pressure Pmax) or the predetermined time β (predetermined time from the start of ignition start) in the in-cylinder pressure waveform (A) is used. A change amount ΔP of the internal pressure is calculated (step 104). Next, a time point at which the change amount ΔP of the in-cylinder pressure becomes larger than a predetermined threshold (that is, an atmospheric pressure drop time point T_EVOcps) is calculated (step 106).

  Next, referring to a predetermined map, a pressure drop required time Tmap corresponding to the first crank angle CA1 at the start of ignition start is acquired (step 108). Next, a value obtained by subtracting the pressure decrease required time Tmap from the atmospheric pressure decrease time T_EVOcps is acquired as the arrival time T_EVOecu of the opening timing EVO of the exhaust valve 22 (step 110).

  Next, using the control value of the ECU 40, the crank angle CA_EVOecu at the opening timing of the exhaust valve 22 is acquired as the second crank angle CA2 (step 112). Next, using the crank angle sensor 42 as the time series data of the engine speed (crank angular speed) during the elapsed time (T_EVOcps-T0) from the start start time T0 to the atmospheric pressure decrease time T_EVOcps, the engine speed per unit time is used. A numerical increase amount (B) is calculated (step 114). As an example, the increase amount (B) of the engine speed is calculated between the engine speed at the atmospheric pressure drop time T_EVOcps and the engine speed (that is, zero) at the ignition start start time T0.

  Next, crank angle data (C) (time series data) with respect to the elapsed time (T_EVOcps−T0) is calculated (step 116). Next, the crank angle at the ignition start start time T0 in the start start cylinder is set to the first crank angle CA1, the crank angle at the atmospheric pressure decrease time T1 is set to the second crank angle CA2, and the in-cylinder pressure waveform (A) And cylinder angle change information (C) are associated with each other, in-cylinder pressure data synchronized with the crank angle is calculated in the first cycle of ignition start (step 118).

Next, absolute pressure correction is performed on the in-cylinder pressure data acquired in step 118 (step 120). Since the detected value (output value) of the in-cylinder pressure sensor 30 is a relative pressure, correction (absolute pressure correction) is performed here to make it an absolute pressure. As such absolute pressure correction, any known method (for example, a method using Poisson's relational expression (PV ^κ = constant)) can be used.

  Next, using the in-cylinder pressure data after absolute pressure correction synchronized with the crank angle, various combustion state quantities (for example, heat generation amount) are calculated (step 122). Next, CPS control (various engine control using an in-cylinder pressure sensor) using the calculated various combustion state quantities is executed (step 124).

Next, a method for estimating the air-fuel ratio at the start of ignition using the crank angle-synchronized in-cylinder pressure data acquired by the above-described method will be described with reference to FIGS.
FIG. 6 is a diagram showing the relationship between the air-fuel ratio (A / F) and the air-fuel ratio correlation value (KL / (Q / low heating value)).

  As shown in FIG. 6, the air-fuel ratio is obtained by dividing the air amount KL by the value obtained by dividing the calorific value Q (which can be calculated based on the in-cylinder pressure measured using the in-cylinder pressure sensor 30) by the lower calorific value of the fuel used. There is a correlation with the value (KL / (Q / low heating value)) obtained by. The calorific value Q calculated using the detection value of the in-cylinder pressure sensor 30 does not consider the effects of cooling loss and unburned loss.

  If the internal combustion engine 10 is in normal operation, the air amount KL can be acquired based on the intake air amount measured using the air flow meter 44. It is important to optimally control the air-fuel ratio in the cylinder not only during normal operation but also to maintain good combustion from the start of restart by ignition start until the engine speed rises. However, since the ignition start is started from a state in which the internal combustion engine 10 is completely stopped, the air amount KL cannot be acquired using the air flow meter 44 immediately after the ignition start. Thus, the method using the air flow meter 44 cannot estimate the air-fuel ratio at the start of ignition. Further, if the in-cylinder pressure data synchronized with the crank angle in the first start cycle cannot be acquired using the special method of the present embodiment described above, the calorific value Q used for estimating the air-fuel ratio cannot be calculated. .

FIG. 7 is a diagram for explaining a method for acquiring the air amount KL in the first cycle of the ignition start.
As described above, at the start of ignition, the cylinder that is stopped in the expansion stroke is selected as the first explosion cylinder. In the cylinder stopped in the expansion stroke, both the intake valve 20 and the exhaust valve 22 are closed. As shown in FIG. 7B, the crank angle (first crank angle CA1) at the time of automatic stop is set in the cylinder. ) Contains the cylinder content integral air volume according to the position. Further, at the time of automatic stop, the in-cylinder pressure drops to atmospheric pressure within a few seconds after the stop, so that the inside of the cylinder during automatic stop is maintained at atmospheric pressure as shown in FIG. For this reason, the amount of air used for combustion in the first cycle of the ignition start is an air amount of the cylinder content integral corresponding to the position of the first crank angle CA1 at the time of automatic stop.

  In order to calculate various combustion state quantities, the ECU 40 stores in-cylinder pressure volume data corresponding to the crank angle shown in FIG. 7C as a map value for each predetermined crank angle. For this reason, if the first crank angle CA1 at the time of automatic stop is known, the in-cylinder volume can be acquired by referring to the map value.

In order to accurately estimate the air-fuel ratio from the first start cycle, it is necessary to estimate the injected fuel amount together with the in-cylinder air amount KL in the first start cycle. The amount of injected fuel can be estimated using, for example, the following equation (1).
Fuel amount = Calorific value Q / Lower calorific value + γ (1)
However, in the above equation (1), γ is a correction term for taking into account the cooling loss and the unburned loss. Here, it is assumed that γ is a value acquired in advance and stored in the ECU 40.

  According to the method of the present embodiment described above, since the in-cylinder pressure data synchronized with the crank angle can be acquired from the first cycle at the start of ignition, the calorific value Q can be calculated from the first cycle. It becomes. Therefore, the amount of fuel injected in the first start cycle can be calculated using the above equation (1). Therefore, the air-fuel ratio in the first start cycle can be estimated by dividing the amount of air used for combustion in the first cycle of ignition start by the fuel amount calculated by the equation (1).

  FIG. 8 is a flowchart showing a routine executed by the ECU 40 in the first embodiment to acquire the air-fuel ratio (A / F) in the first cycle of the ignition start. This routine is started when the internal combustion engine 10 that is automatically stopped is restarted by ignition start.

  In the routine shown in FIG. 8, first, a cylinder stopped in the expansion stroke is specified (step 200). This specification is performed based on the crank stop position (first crank angle CA1) acquired at the time of automatic stop. Next, the first crank angle CA1 at the time of stop is acquired (step 202).

  Next, the in-cylinder volume of the start cylinder for ignition start (cylinder stopped in the expansion stroke) is calculated using a map value corresponding to the crank angle (CA1) at the time of stop stored in the ECU 40. (Step 204). Next, based on the calculated in-cylinder volume, the air amount KL charged in the cylinder of the start cylinder in the first start cycle is acquired (step 206).

  Next, ignition start is executed by performing fuel injection and ignition for the start cylinder of ignition start (step 208). Next, after the crank angle is determined according to the processing of the routine shown in FIG. 5 described above, in-cylinder pressure data synchronized with the crank angle is acquired (step 212). In step 212, as described above, the absolute pressure correction of the in-cylinder pressure is also performed.

  Next, based on the in-cylinder pressure data synchronized with the crank angle, the calorific value Q at the time of combustion in the first start cycle is acquired (step 212). Next, the amount of fuel injected in the first start cycle is calculated according to the above equation (1) (step 214). Next, using the acquired air amount KL and fuel amount, the air-fuel ratio (A / F) at the first start cycle is calculated (step 216). The calculated air-fuel ratio is reflected in various controls (such as fuel injection control) of the internal combustion engine 10 (step 218).

In the first embodiment described above, the ECU 40 executes the process of step 100, so that the “first crank angle acquisition means” in the first invention causes the ECU 40 to execute the process of step 102. Thus, the “in-cylinder pressure time-series data acquisition unit” according to the first aspect of the present invention causes the ECU 40 to execute the processing of the above steps 104 and 106 so that the “atmospheric pressure drop time acquisition unit” according to the first aspect of the present invention is determined by the ECU 40. By executing the process of step 112, the “second crank angle acquisition means” in the first invention causes the ECU 40 to execute the process of step 114, so that “crank angular velocity time-series data” in the first invention is achieved. The acquisition means "is executed before the ECU 40 executes the process of step 116. "Crank angle time series data acquisition means" in the first invention, ECU 40 is "in-cylinder pressure data acquiring means" of the invention by executing the process of step 118 is implemented, respectively.
Further, in the first embodiment described above, the “elapsed time correction means” in the second aspect of the present invention is realized by the ECU 40 executing the processing of steps 108 and 110 described above.

Embodiment 2. FIG.
Next, a second embodiment of the present invention will be described with reference to FIG. 9 and FIG.
The system of the present embodiment can be realized by causing the ECU 40 to execute a routine shown in FIG. 10 described later together with a routine shown in FIG. 5 using the hardware configuration shown in FIG.

FIG. 9 is a diagram for explaining a method for correcting the effect of temperature drift of the in-cylinder pressure waveform in the second embodiment of the present invention.
An offset change (temperature drift) may occur in the output value of the in-cylinder pressure sensor 30 due to thermal deformation (expansion / contraction) of the diaphragm (pressure receiving portion) accompanying a change in the in-cylinder temperature. The influence of the temperature drift on the sensor output becomes large at the start (including the restart). This is because the diaphragm of the in-cylinder pressure sensor 30 is exposed to a large temperature change when combustion is performed in the internal combustion engine 10 in a stopped state.

  FIG. 9 (the same applies to the above-described FIG. 2 and the like) shows the in-cylinder pressure waveform in which the above-described temperature drift occurs in the first cycle of the ignition start. Specifically, as shown in FIG. 9B, the in-cylinder pressure at the timing after the opening timing EVO of the exhaust valve 22, which should be equivalent to the atmospheric pressure, is started by the occurrence of temperature drift. There is a deviation from the in-cylinder pressure before being exposed to a temperature change due to combustion in the first cycle (before starting).

  Therefore, in this embodiment, when the difference between the in-cylinder pressure P (0) at the start of the start and the P (EVO) at the opening timing EVO of the exhaust valve 22 is larger than the predetermined threshold A, the in-cylinder pressure becomes a temperature drift. In this case, using the correction amount corresponding to the magnitude of the difference, as shown in FIG. 9C, the deviation of the in-cylinder pressure caused by the temperature drift is corrected. I made it.

  FIG. 10 is a flowchart showing a routine executed by the ECU 40 in the second embodiment in order to realize the correction of the temperature drift effect on the in-cylinder pressure waveform. This routine is started when the in-cylinder pressure waveform (A) (in-cylinder pressure time-series data) in the first cycle of start is acquired by the processing of step 102 in the routine shown in FIG. .

  In the routine shown in FIG. 10, first, the time-series data of the in-cylinder pressure in the first start cycle is acquired (step 300). Next, using the acquired in-cylinder pressure data, the in-cylinder pressure P (0) at the start of starting is calculated (step 302), and the in-cylinder pressure P (EVO) at the opening timing EVO of the exhaust valve 22 is calculated. (Step 304). As the in-cylinder pressure P (EVO), the value at the time T_EVOcps at which the atmospheric pressure drops is used.

  Next, it is determined whether or not the difference between the in-cylinder pressure P (0) and the in-cylinder pressure P (EVO) is greater than a predetermined threshold A (step 306). The threshold value A in step 306 is a value set in advance as a threshold value for determining whether or not the in-cylinder pressure in the first start cycle is affected by temperature drift.

If the determination in step 306 is satisfied, that is, if it can be determined that the in-cylinder pressure is affected by the temperature drift, the temperature drift correction amount δ is calculated according to the following equation (2) (step 308). .
δ = (P (EVO) −P (0)) / Δt (2)
However, Δt in the above equation (2) corresponds to the elapsed time from the start start time T0 to the atmospheric pressure decrease time T1 (T_EVOcps).

Next, the temperature drift correction of the in-cylinder pressure waveform (A) is performed using the calculated temperature drift correction amount δ (step 310). Assuming that t is the elapsed time from the start of startup, the cylinder pressure after temperature drift correction at a certain time t with respect to the cylinder pressure P acquired in time synchronization is approximated by a linear function (3) It can be calculated according to the formula.
In-cylinder pressure after correction = P (t) + δt (3)

  In the present embodiment, it is assumed that the time series data of the in-cylinder pressure after the correction of the temperature drift influence by the routine shown in FIG. 10 described above is used in the processing after step 104 in the routine shown in FIG.

  According to the processing of the present embodiment described above, when a temperature drift occurs, the differential pressure between the atmospheric pressure (P (0)) and the in-cylinder pressure (P (EVO)) at the opening timing of the exhaust valve 22. The in-cylinder pressure is corrected by using the temperature drift correction amount δ for setting the value to zero. Thereby, the temperature drift influence with respect to the output value of the in-cylinder pressure sensor 30 can be corrected at the start. As a result, even when the influence of temperature drift on the sensor, which is a problem at the start of ignition, occurs, it is possible to accurately calculate the various combustion state quantities and the estimated value of the air-fuel ratio using the detection value of the in-cylinder pressure sensor 30. It becomes like this.

Embodiment 3 FIG.
Next, Embodiment 3 of the present invention will be described with reference to FIG. 11 and FIG.
The system of the present embodiment can be realized by causing the ECU 40 to execute a routine shown in FIG. 12 described later together with a routine shown in FIG. 5 using the hardware configuration shown in FIG.

FIG. 11 is a diagram for explaining a fuel injection amount correction method using the temperature drift amount δ of the in-cylinder pressure waveform in the third embodiment of the present invention.
If the air-fuel ratio in the cycle until the engine speed rises at the start (including restart) is not properly controlled, combustion deteriorates and in some cases misfires may occur. When automatic stop is performed, the in-cylinder temperature changes according to the stop time. More specifically, the longer the stop time, the lower the in-cylinder temperature. In order to prevent the deterioration of combustion at the time of starting, it is necessary to correct the fuel injection amount according to the in-cylinder temperature at the time of starting, and when the correction amount of the fuel injection amount is insufficient, the combustion deteriorates In some cases, however, misfire occurs.

  Therefore, in this embodiment, the in-cylinder temperature at the start (before the start of combustion) is estimated according to the temperature drift amount of the in-cylinder pressure in the in-cylinder pressure data in the first cycle of the start. Then, the fuel injection amount is corrected by an amount corresponding to the estimated in-cylinder temperature at the start.

  Specifically, in this embodiment, the temperature drift correction amount δ calculated in the second embodiment is used as the temperature drift amount. The temperature drift amount δ is affected by the temperature difference of the diaphragm of the in-cylinder pressure sensor 30 before and after combustion. More specifically, the temperature drift amount δ increases as the temperature difference increases, that is, as the in-cylinder temperature before the start of combustion decreases. For this reason, in the present embodiment, the relationship shown in FIG. 11A is used to estimate the in-cylinder temperature before the start of combustion (at the start of starting) as a lower value as the temperature drift amount is larger.

  In addition, in this embodiment, the correction amount of the fuel injection amount is determined according to the estimated value of the in-cylinder temperature before the start of combustion. More specifically, as an example, as shown in FIG. 11 (B), the correction amount of the fuel injection amount is set so as to increase as the in-cylinder temperature before the start of combustion increases.

  Further, in the present embodiment, the combustion state in the first start cycle is determined, and when it is determined that the combustion state is good, the current correction amount of the fuel injection amount is reflected in the learned value. On the other hand, if the combustion state in the first start cycle is not good, the fuel is injected after the next cycle (during the cycle until the engine speed rises to a predetermined value at the current start), and at the next start, etc. The amount was corrected using the correction amount. In addition, since it is possible to acquire various combustion state quantities in the first cycle of starting by the above-described methods of the first and second embodiments, not only the fuel injection quantity but also after the fuel injection depending on the acquired combustion state quantity. You may make it change the timing to ignition.

  FIG. 12 is a flowchart showing a routine executed by the ECU 40 in the third embodiment in order to realize the correction of the fuel injection amount at the start using the temperature drift amount δ of the in-cylinder pressure. This routine is started when the in-cylinder pressure waveform (A) (in-cylinder pressure time-series data) is acquired by the processing of step 102 in the routine shown in FIG.

  In the routine shown in FIG. 12, first, the temperature drift amount δ is calculated by the same processing as in step 308 (step 400). Next, based on the calculated temperature drift amount δ, the in-cylinder temperature at the start (before the start of combustion in the first start cycle) is calculated (step 402). As shown in FIG. 11A, the ECU 40 stores a map that defines the relationship between the temperature drift amount δ and the in-cylinder temperature at the start. In step 402, the ECU 40 refers to such a map. The in-cylinder temperature at the start is calculated.

  Next, a correction amount for the fuel injection amount is calculated based on the calculated in-cylinder temperature at the start (step 404). As shown in FIG. 11B, the ECU 40 stores a map that defines the relationship between the in-cylinder temperature at the start and the correction amount of the fuel injection amount. In step 404, refer to such a map. Thus, the correction amount of the fuel injection amount is calculated.

  Next, it is determined whether or not the combustion state in the first start cycle is good (step 406). The determination of the combustion state can be performed using, for example, various combustion state quantities that can be acquired using the in-cylinder pressure sensor 30 as an index.

  If it is determined in step 406 that the combustion state in the first start cycle is good, the correction amount of the fuel injection amount calculated at the time of the current start is reflected in the learned value (step 408). In this case, the fuel injection amount in the first cycle after the next cycle (during the cycle until the engine speed rises to a predetermined value at the time of the current start) and the next start of the next start is set to the learning value updated this time. And corrected (step 410).

  On the other hand, when it is determined in step 406 that the combustion state in the first start cycle is not good, the fuel injection amount in the cycle after the next cycle at the time of the current start is calculated using the correction amount calculated in step 404. And corrected (step 412).

  According to the processing of the present embodiment described above, it is possible to correct the fuel injection amount according to the in-cylinder temperature at start-up estimated using the temperature drift amount of the output of the in-cylinder pressure sensor 30. Thereby, it is possible to suppress the deterioration of combustion at the start, regardless of the state of the in-cylinder temperature at the start.

  In the third embodiment described above, the “in-cylinder temperature estimating means” according to the fifth aspect of the present invention is realized by the ECU 40 executing the processes of steps 400 and 402. By executing the processing, the “injection amount correcting means” according to the fifth aspect of the present invention is realized.

DESCRIPTION OF SYMBOLS 10 Internal combustion engine 12 Piston 14 Combustion chamber 16 Intake passage 18 Exhaust passage 20 Intake valve 22 Exhaust valve 24 Throttle valve 26 Fuel injection valve 28 Spark plug 30 In-cylinder pressure sensor 40 ECU (Electronic Control Unit)
42 Crank angle sensor 44 Air flow meter 46 Crankshaft 48 Timing rotor

Claims (5)

A cylinder having a fuel injection valve for directly injecting fuel into the cylinder, an in-cylinder pressure sensor for detecting the in-cylinder pressure, and a crank angle sensor for detecting the crank angle, and being stopped in the expansion stroke A control device for an internal combustion engine that performs an ignition start by executing fuel injection using the fuel injection valve and starting the internal combustion engine by rotationally driving a crankshaft by a combustion pressure accompanying the fuel injection,
First crank angle acquisition means for acquiring a first crank angle that is a crank angle of a cylinder that is stopped in an expansion stroke;
In-cylinder pressure time series that acquires time-series data of the in-cylinder pressure of the start-up cylinder detected by using the in-cylinder pressure sensor when the ignition start is performed with the cylinder stopped in the expansion stroke as the start-up cylinder. Data acquisition means;
Using the time-series data of the in-cylinder pressure, an atmospheric pressure decrease time acquisition means for acquiring an atmospheric pressure decrease time, which is a time when the in-cylinder pressure of the start start cylinder decreases to an atmospheric pressure after combustion in the start start cylinder;
Second crank angle acquisition means for acquiring a second crank angle that is a crank angle of an opening timing of the exhaust valve at the time of starting ignition in the start start cylinder;
Crank angular speed time-series data acquisition means for acquiring time-series data of crank angular speed during an elapsed time from the start time of the ignition start until reaching the atmospheric pressure decrease time point, using the crank angle sensor;
Crank angle time-series data acquisition means for acquiring time-series data of the crank angle during the elapsed time based on the time-series data of the crank angular speed;
The crank angle at the start of the ignition start in the start cylinder is the first crank angle, and the crank angle at the atmospheric pressure drop is the second crank angle. In-cylinder pressure data acquisition means for acquiring in-cylinder pressure data synchronized with the crank angle by associating the time-series data with the time-series data of the crank angle;
A control device for an internal combustion engine, comprising:   2. An elapsed time correcting means for correcting the elapsed time by subtracting the elapsed time from a predetermined time required from the arrival timing of the exhaust valve opening timing to the atmospheric pressure decrease time. The control apparatus of the internal combustion engine described in 1.   The second crank angle acquisition means adds a predetermined crank angle change amount from the crank angle at the opening timing of the exhaust valve to the crank angle at the time of the decrease in atmospheric pressure to the second crank angle. The control apparatus for an internal combustion engine according to claim 1, wherein:   The in-cylinder pressure time-series data acquiring unit corrects the time-series data of the in-cylinder pressure based on a difference between the in-cylinder pressure at the start of the ignition start and the in-cylinder pressure at the time when the atmospheric pressure decreases. The control device for an internal combustion engine according to any one of claims 1 to 3. An in-cylinder temperature estimating means for estimating an in-cylinder temperature at the start of the ignition start, based on a difference between the in-cylinder pressure at the start of the ignition start and the in-cylinder pressure at the time of the atmospheric pressure decrease;
An injection amount correction means for correcting a fuel injection amount in a predetermined cycle after the start of the ignition start based on the in-cylinder temperature at the start of the ignition start;
The control device for an internal combustion engine according to claim 1, further comprising:

Images