JP6397745B2 - Electronic control unit - Google Patents

Description

  The present invention relates to an electronic control device for a vehicle, and more particularly to an electronic control device that controls an engine that performs automatic start and automatic restart.

When the air-fuel ratio is calculated using the air flow sensor when the intake air amount is small, the flow rate sensitivity of the air flow sensor is lower and the intake air amount cannot be acquired correctly. As an exhaust improvement method when the amount of intake air entering the intake pipe is small, there is a technique described in Patent Document 1. This publication states that “a pressure sensor attached to an intake manifold is used in a low air flow velocity region, an air flow meter is used in a high air flow velocity region, and an electronic control unit Is determined whether to use a pressure sensor or an air flow meter.
In Patent Document 1, when the intake air amount is small, such as in the vicinity of an idle, the fuel injection amount is set by the intake pipe pressure acquired from the pressure sensor.

JP 2013-234680 A

  When the intake air amount is small, for example, when the engine is started for the first time or restarted from idle stop, the flow rate sensitivity of the air flow sensor falls below and the intake air amount cannot be measured correctly. Therefore, the fuel injection amount calculated from the intake air amount There is a problem that cannot be measured correctly. Here, the required fuel injection amount can be determined in advance to some extent when starting after the engine is completely stopped, but if the engine is restarted before it is completely stopped during idle stop, It is difficult to determine the flow rate due to the influence of the engine state before the stop.

  Here, in the technique described in Patent Document 1, when the intake air amount is small, the fuel injection amount is set based on the intake pipe pressure acquired from the pressure sensor. There is no disclosure about a method of correctly measuring the amount of intake air at the time of restart without using a sensor.

  The present invention has been made in view of such problems, and it is intended to improve exhaust performance even when the flow rate sensitivity of the air flow sensor is lower than when the engine is restarted without using a pressure sensor. Objective.

  In order to solve the above-described problems, an internal combustion engine control apparatus according to the present invention includes an idle air stop function for automatically stopping and restarting an intake air amount detecting means for detecting an intake air amount flowing into an intake pipe. In the electronic control device for controlling an equipped engine, the electronic control device includes an estimation means for estimating an intake air amount flowing into the intake pipe, and the engine rotation is not stopped after the engine is automatically stopped. When the automatic restart is executed in the state, the intake air amount is calculated based on the estimation means.

  According to the present invention, the exhaust performance can be improved even when the flow rate sensitivity of the air flow sensor is lower than when the engine is restarted without using the pressure sensor.

1 is an overall schematic diagram showing an embodiment of a control system for a direct injection type internal combustion engine according to the present invention. It is a block diagram which shows the structure of the engine output control apparatus in embodiment of this invention. It is a figure which shows that there is a difference between the actual intake air amount and the intake air amount acquired by the airflow sensor after the engine automatic restart, which is a problem in the present invention. It is an example flowchart which shows the Example in this invention. It is an example which shows the Example in this invention, and is a figure which shows the conditions (The threshold value of an engine speed at the time of an engine automatic stop) which estimates and performs the intake air amount. It is an example which shows the Example in this invention, and is a figure which shows the conditions (difference between an estimated value and an air flow sensor actual value) which estimates and performs the intake air amount. It is an example which shows the Example in this invention, and is the figure which showed estimating intake air amount with an engine speed and throttle opening.

  The intake air amount is estimated from the throttle opening and the engine speed. When the air flow sensor is in a measurable state, the intake air amount of the air flow sensor is used for calculating the fuel injection amount. The fuel injection amount is calculated from the amount.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

  FIG. 1 is a schematic configuration diagram of the entire control system of a direct injection type internal combustion engine 1 according to an embodiment of the present invention. The intake air taken in from the inlet of the air cleaner 102 passes through a flow rate measurement unit in which an intake air flow meter (air flow sensor) 103 is disposed, and the flow rate is measured. Thereafter, the intake air is distributed to the intake pipe 105 connected to each cylinder (each cylinder) 124 through the electric throttle valve 104 that controls the intake air flow rate. The intake air is distributed to the intake pipe 105 and then introduced into the combustion chamber 106 through an intake valve 119 provided in each cylinder. The combustion chamber 106 is formed by the inner wall surface of the cylinder 124 and the crown surface 125a of the piston 125 that reciprocates within the cylinder 124. The volume of the combustion chamber 106 changes as the piston 125 reciprocates. From the intake air flow meter 103, an output signal representing the intake air flow rate is input to the engine control unit (ECU) 101. A throttle opening sensor 107 for detecting the opening of the electric throttle valve 104 is attached to the electric throttle valve 104, and its output signal is also input to the engine control unit 101.

  The fuel is first pressurized by a low-pressure fuel pump (not shown), then secondarily pressurized to a higher pressure by the high-pressure fuel pump 108, and a fuel injection valve provided in each cylinder via the common rail 117. 109 is injected into the combustion chamber 106. The fuel injected into the combustion chamber 106 generates an air-fuel mixture with intake air, is ignited by the ignition plug 111 by the ignition energy from the ignition coil 110, and burns in the combustion chamber 106.

  Exhaust gas generated by the combustion of the air-fuel mixture is discharged from the combustion chamber 106 to the exhaust pipe 123 through the exhaust valve 122 provided in each cylinder. An air-fuel ratio sensor 127 and a catalyst 126 are provided in the middle of the exhaust pipe 123. The exhaust gas air-fuel ratio sensor output signal detected by the air-fuel ratio sensor 127 is input to the engine control unit 101. Based on this, feedback control is executed from the engine control unit 101 to the fuel injection valve 109 so as to achieve a predetermined air-fuel ratio. As the air-fuel ratio sensor 127, an O2 sensor whose output voltage changes suddenly near the theoretical air-fuel ratio or an A / F sensor that detects the actual air-fuel ratio is adopted.

  The catalyst 126 is composed of a three-way catalyst, and exhaust gas purification is performed. In order for the purifying action of the catalyst 126 to be exerted, it is necessary to reach the activation temperature, and the engine control unit 101 performs control to bring the catalyst into a warm-up state at an early stage. For this purpose, it is necessary to detect the catalyst temperature state. The estimation is based on the integrated intake air amount from the intake air flow meter 103, the water temperature sensor 128 or the oil temperature sensor 129 is substituted, and the direct catalyst temperature sensor (not shown) is used. It is executed by a method such as detection of

  A knock sensor 130 for detecting knocking that occurs during combustion is provided on the side surface of the internal combustion engine 1, and the detection signal is output to the engine control unit 101.

  A crank angle sensor 116 attached to the crankshaft 115 of the internal combustion engine 1 outputs a signal indicating the rotational position of the crankshaft 115 to the engine control unit 101.

  A cam angle sensor 121 attached to the cam shaft 120 of the internal combustion engine 1 outputs a signal indicating the rotational position of the cam shaft to the engine control unit 101. The cam shaft 120 and the cam angle sensor 121 are provided for each of the intake valve 119 and the exhaust valve 122.

  FIG. 2 is a diagram showing various input signals such as sensors for inputting the system configuration of the engine control unit (ECU) 201, and various output signals output from the engine control unit 201 to a control device or the like.

  The input circuit of the engine control unit 201 includes an accelerator opening sensor 210 that detects a depression amount of an accelerator pedal (not shown) of the vehicle, a throttle opening sensor 211 that detects an opening amount of a throttle valve (not shown), and an internal combustion engine 1. An air flow sensor 212 for measuring the amount of intake air sucked into the cylinder, a vehicle speed sensor 213 for detecting the traveling speed of the vehicle, a brake switch 214 for detecting an operation of a foot brake (not shown), ignition of the engine, calculation of injection timing, A cam angle sensor 215 and a crank angle sensor 216 for detecting a cam angle signal and a crank angle signal used for cylinder determination are connected.

  An injector 220 that injects fuel and an igniter 221 that performs ignition are connected to the output circuit.

  The engine control unit 201 includes an intake air amount calculation process 202 that is executed using the intake air amount acquired from the air flow sensor 212, and an engine that executes calculation by the crank angle sensor 216 or the crank angle sensor 216 and the cam angle sensor 215. When the condition for stopping the engine is satisfied, and the vehicle speed acquired from the vehicle speed sensor 213, for example, the vehicle speed is acquired from the vehicle speed sensor 213. An automatic engine stop determination process 214 that is executed when the vehicle speed falls below a certain value, or when the brake switch 214 is turned on and it is determined that the brake is being depressed, and after the automatic engine stop , When a restart judgment is made after automatic engine stop For example, when after an automatic engine stop accelerator opening sensor 210 exceeds a certain value, or some automatic engine restart determination process 206 to be executed when the brake switch 214 is determined to brake becomes OFF is released it is. Further, the automatic engine restart determination process 206 includes an automatic engine restart after the engine is completely stopped after the automatic engine stop, a driver request (change of mind) before the engine is completely stopped, For example, when an accelerator is depressed or a brake is released, automatic engine restart is performed before the engine is completely stopped.

  FIG. 3 shows that when the engine is automatically stopped by the idle stop control, when the automatic restart is determined before the engine rotation is completely stopped, for example, when the brake is off, from the engine speed and the actual intake air amount. It is a figure which shows the request | requirement fuel injection amount calculated from the calculated request | requirement fuel injection amount and the intake air amount acquired from the airflow sensor.

  Here, when the automatic restart is performed, since the intake air amount does not satisfy the detection sensitivity of the air flow sensor, the value of the intake air amount obtained from the air flow sensor is not accurate, and the required fuel injection calculated from the actual intake air amount It shows that the error is large with respect to the quantity.

  FIG. 4 is a control flowchart of an example of claim 1 in the present invention. First, after the automatic stop by the step 1001 idle stop is executed, when there is an engine automatic restart request from the step 1002 idle stop, it is determined in step 1003 whether the engine is still rotating. When the engine is completely stopped, step 1004 performs normal engine start control. Normal engine start control is a state in which the engine is stopped, so that the intake pipe pressure is constant and the injection amount required to move the engine from the stop state is known in advance. This is start control in a state where the required fuel injection amount and ignition timing can be determined to some extent. If it is determined in step 1003 that the engine has not completely stopped, the engine state, for example, the pressure in the intake pipe, is uncertain, and it is difficult to determine the fuel injection amount. In order to inject fuel, it is necessary to obtain the fuel injection amount from the intake air amount. However, when the actual intake air amount is lower than the detection sensitivity of the air flow sensor, for example, in the case of processing that becomes 0 V when the air flow sensor is below a predetermined flow rate, the intake air amount is obtained using the air flow sensor. Since the actual intake air amount and the error increase and the intake air amount cannot be measured correctly, the calculation method is switched in step 1005.

  As the switching means, for example, as shown in FIG. 5, it is assumed that the threshold value N1 of the engine speed is equal to or lower than a predetermined value at the time of automatic restart, or when the engine is automatically stopped by an idle stop in step 1001. In addition, as a condition for returning the calculation method from the method of calculation by estimation to the method of calculation by the airflow sensor, it is assumed that the threshold value N2 of the engine speed becomes a predetermined value or more. The engine speed threshold N2 is, for example, an idle speed.

  As the switching means, for example, as shown in FIG. 6, during automatic restart, the difference ΔTP1 between the required fuel injection amount calculated from the intake air amount acquired from the air flow sensor and the required fuel injection amount calculated by estimation is more than a certain value. When it becomes. In addition, as a condition for returning the calculation method from the method of calculation to the method of calculation with the airflow sensor, the difference between the required fuel injection amount calculated from the intake air amount acquired from the airflow sensor and the required fuel injection amount calculated by estimation Suppose that ΔTP2 falls below a certain level.

  When it is determined that switching is necessary, the calculation is performed using the intake air amount estimated in step 1006 instead of the value obtained from the air flow sensor. As an estimation method, there is a method of obtaining an intake pipe pressure by attaching a pressure sensor, but in the present invention, an intake air amount is obtained by estimation without attaching a pressure sensor. For example, as shown in FIG. 7, the intake air amount is estimated from the throttle opening and the engine speed. When the amount of intake air is lower than the sensitivity of the air flow sensor, for example, when the value of the air flow sensor is 0 V, it is greatly different from the actual value. However, as shown in FIG. 7, the throttle opening obtained from the throttle opening sensor and the engine speed obtained from the crank angle sensor can be detected even in a scene such as when the engine is started. For this reason, when the intake air amount is small, such as when the engine is started, the intake air flow rate that can be estimated from the throttle opening and the engine speed is closer to the actual intake air flow rate than the method of detecting with the air flow sensor.

  When it is determined that switching is not necessary, the value obtained from the airflow sensor for the intake air amount in step 1007 is used.

  Even when the airflow sensor cannot measure, information from other sensors, for example, a pressure sensor is attached and the intake pipe pressure is not acquired to obtain the intake air amount, but the intake air amount obtained by estimation is used. Thus, the intake air amount can be obtained with higher accuracy than the intake air amount obtained from the air flow sensor.

  Finally, engine control is performed based on the amount of intake air in step 1008. The engine control is, for example, fuel injection control or ignition control.

  As described above, the electronic control unit according to the present embodiment includes an estimation unit that estimates the amount of intake air flowing into the intake pipe, and after the engine is automatically stopped by the idle stop, the engine rotation is not stopped. When performing the restart, it is determined whether or not to calculate the intake air amount by the estimation unit, and when it is determined to perform the calculation using the estimation unit, the intake air amount is determined based on the estimation unit. Perform the operation. Therefore, even when restarting from an idle stop, the flow rate sensitivity of the air flow sensor is lower, the intake air amount cannot be measured correctly, and the fuel injection amount calculated from the intake air amount cannot be measured correctly. Performance can be improved. In other words, when restarting the engine before it is completely stopped, it is difficult to determine the fuel injection amount required for starting the engine in advance, it was estimated from the state of other actuators without using the measured value of the airflow sensor with a large measurement error. By using the estimated value of the intake air amount, it is possible to reduce the intake air amount error at the time of a restart request without using another sensor. As a result, fuel can be injected at a correct air-fuel ratio, and exhaust performance can be improved.

DESCRIPTION OF SYMBOLS 101 ... Engine control unit (ECU), 102 ... Air cleaner, 103 ... Intake air flow meter (air flow sensor), 104 ... Electric throttle valve, 105 ... Intake pipe, 106 ... Combustion chamber, 107 ... Throttle opening sensor, 108 ... High pressure fuel pump, 109 ... fuel injection valve, 110 ... ignition coil, 111 ... ignition plug, 115 ... crankshaft, 116 ... crank angle sensor, 117 ... common rail, 119 ... intake valve, 120 ... camshaft, 121 ... cam angle sensor , 122 ... exhaust valve, 123 ... exhaust pipe, 124 ... cylinder, 125 ... piston, 126 ... catalyst, 127 ... air-fuel ratio sensor, 128 ... water temperature sensor, 129 ... oil temperature sensor, 130 ... knock sensor

Claims (7)

In an electronic control device for controlling an engine having an intake air amount detecting means for detecting an air amount flowing into an intake pipe, and an idle stop function for performing automatic stop and automatic restart,
The electronic control unit estimates the intake air amount flowing into the intake pipe, and an actual measurement means for actually measuring the intake air amount flowing into the intake pipe as an intake air amount calculation means for calculating using the intake air amount An estimation means for switching, and a switching determination means for switching between,
An electronic control unit, wherein after the automatic stop of the engine is executed, the calculation of the intake air amount is switched based on the switching determination means when the automatic restart is executed in a state where the engine is not stopped.   The switching determination means switches the intake air amount calculation means from the actual measurement means to the estimation means when the rotational speed of the engine becomes a predetermined value or less. Electronic control device.   The switching determination unit switches the intake air amount calculation unit from the actual measurement unit to the estimation unit when the difference between the intake air amounts obtained by the estimation unit and the actual measurement unit is a predetermined value or more. The electronic control device according to claim 1.   The electronic control device according to claim 1, wherein the switching determination unit switches the intake air amount calculation unit from the actual measurement unit to the estimation unit when the engine is automatically stopped.   The switching determination unit switches the intake air amount calculation unit from the estimation unit to the actual measurement unit when the rotational speed of the engine becomes a predetermined value or more. Electronic control device.   The switching determination unit switches the intake air amount calculation unit from the estimation unit to the actual measurement unit when the difference between the intake air amounts obtained by the estimation unit and the actual measurement unit is a predetermined value or less. The electronic control device according to claim 1. It said estimating means, the electronic control device according to any one of claims 1 to 6, characterized in that for estimating the amount of intake air from the throttle opening and the engine speed.