Vehicle control system

Abstract

The present invention provides a vehicle control device that can suppress the air-fuel ratio from becoming richer than the stoichiometric air-fuel ratio immediately after restarting an internal combustion engine, even when the internal combustion engine is restarted immediately after being stopped. [Solution] The control device is applied to a vehicle that transmits torque output from an internal combustion engine to the drive wheels. The control device includes a processing circuit that controls the internal combustion engine. The processing circuit estimates the intake manifold pressure PM and performs fuel injection control to determine the amount of fuel injected from the fuel injector based on the estimated intake manifold pressure PM. The processing circuit performs automatic stop control and automatic start control. The processing circuit performs a process (step S13) to correct the estimated value of the intake manifold pressure PM to a lower value if the time from the start of the automatic stop control to the start of the automatic start control is short.

Description

【Technical Field】 【0001】 This invention relates to a control device for a vehicle. 【Background Art】 【0002】 In Patent Document 1, in a vehicle in which an intake pipe pressure sensor is provided in a portion downstream of a throttle valve in an intake passage, an apparatus for detecting atmospheric pressure based on a signal output from the intake pipe pressure sensor during engine stoppage is disclosed. Within a predetermined period after the engine stops, the intake pipe pressure is negative relative to atmospheric pressure. Therefore, for a predetermined time after the engine stops, the apparatus does not detect atmospheric pressure based on the signal output from the intake pipe pressure sensor. 【Prior Art Documents】 【Patent Documents】 【0003】 【Patent Document 1】 Japanese Unexamined Patent Application Publication No. 2010 - 090803 【Summary of the Invention】 【Problems to be Solved by the Invention】 【0004】 Immediately after the internal combustion engine stops, the intake pipe pressure is in a negative pressure state. That is, immediately after stopping the internal combustion engine, the amount of air in the cylinder is less compared to when sufficient time has elapsed since stopping the internal combustion engine. 【0005】 When the internal combustion engine is restarted immediately after it is stopped and when the internal combustion engine is started after sufficient time has elapsed since it was stopped, there is almost no difference in the intake air flow rate detected by the air flow meter. Therefore, when the fuel injection amount is determined based on the intake pipe pressure estimated from the intake air flow rate, the following problems occur. 【0006】 When an internal combustion engine is restarted immediately after being stopped, the same amount of fuel is injected as if sufficient time had passed since the engine was stopped, even though the amount of air in the cylinder is low. As a result, when an internal combustion engine is restarted immediately after being stopped, the air-fuel ratio immediately after restarting may become richer than the stoichiometric air-fuel ratio. [Means for solving the problem] 【0007】 The vehicle control device for solving the above problems is a control device applied to a vehicle equipped with an internal combustion engine that transmits torque output from the internal combustion engine to the drive wheels. The control device includes a processing circuit for controlling the internal combustion engine. The processing circuit estimates the intake manifold pressure of the internal combustion engine and performs fuel injection control to determine the amount of fuel injected from the fuel injector based on the estimated intake manifold pressure. The processing circuit performs automatic stop control to stop fuel injection from the fuel injector when an automatic stop request occurs during the operation of the internal combustion engine. The processing circuit performs automatic start control to restart fuel injection from the fuel injector and start the internal combustion engine when a restart request occurs while fuel injection is stopped due to the automatic stop control. The processing circuit performs a process to correct the estimated value of the intake manifold pressure to a lower value the shorter the time between the start of the automatic stop control and the start of the automatic start control. [Effects of the Invention] 【0008】 The above-described control device can prevent the air-fuel ratio from becoming richer than the stoichiometric air-fuel ratio immediately after restarting the internal combustion engine, even if the engine is restarted immediately after being stopped. [Brief explanation of the drawing] 【0009】 [Figure 1] Figure 1 is a schematic diagram showing the configuration of a control device in one embodiment and the internal combustion engine of a vehicle to which the control device is applied. [Figure 2] Figure 2 is a flowchart showing the sequence of processes by which the processing circuit shown in Figure 1 corrects the estimated intake manifold pressure. [Figure 3] Figure 3 is a timing chart showing the operation of the processing circuit shown in Figure 1, where (a) shows the change in the fuel cut flag, (b) shows the change in engine rotational speed, and (c) shows the change in the estimated intake manifold pressure. [Modes for carrying out the invention] 【0010】 An embodiment of the vehicle's control system will be described below with reference to Figures 1 to 3. <Configuration of Vehicle 1 to which the control device 100 is applied> As shown in Figure 1, the control device 100 of this embodiment includes a processing circuit 101 that executes a program and performs various processes, and a storage device 102 in which the program is stored. The processing circuit 101 includes a processor. The storage device 102 is capable of storing various data. The vehicle 1 to which the control device 100 is applied includes an internal combustion engine 10, a transmission 30, a differential 31, and a plurality of drive wheels 32. Torque output from the internal combustion engine 10 is transmitted to the plurality of drive wheels 32 via the transmission 30 and the differential 31. 【0011】 The internal combustion engine 10 comprises a combustion chamber 11 for burning a fuel-air mixture, an intake passage 12 which serves as an air introduction path to the combustion chamber 11, and an exhaust passage 13 which serves as an exhaust discharge path from the combustion chamber 11. The intake passage 12 is provided with a throttle valve 14, which is a valve for adjusting the intake air flow rate GA. The exhaust passage 13 is provided with a catalytic converter 16 which performs oxidation of HC and CO and reduction of NOx in the exhaust gas. Downstream of the exhaust gas from the catalytic converter 16, a filter 33 is provided to collect particulate matter contained in the exhaust gas. The internal combustion engine 10 is equipped with a fuel injection valve 17 which injects fuel into the air used for combustion in the combustion chamber 11 to form a fuel-air mixture. The internal combustion engine 10 is equipped with an ignition device 18 which ignites the fuel-air mixture in the combustion chamber 11 by spark discharge. 【0012】 The processing circuit 101 of the control device 100 controls the internal combustion engine 10. The control device 100 receives detection signals from the airflow meter 23, crank angle sensor 24, accelerator pedal sensor 25, atmospheric pressure sensor 29, and water temperature sensor 34. The airflow meter 23 is a sensor that detects the intake airflow rate GA. The intake airflow rate GA represents the flow rate of air flowing into the combustion chamber 11 through the intake passage 12. The crank angle sensor 24 is a sensor that detects the crank angle. The crank angle represents the rotation angle of the crankshaft 27, which is the output shaft of the internal combustion engine 10. Based on the detection result of the crank angle, the processing circuit 101 determines the engine speed NE of the internal combustion engine 10. The accelerator pedal sensor 25 is a sensor that detects the accelerator pedal opening degree Acc. The accelerator pedal opening degree Acc represents the amount the driver depresses the accelerator pedal 28. The atmospheric pressure sensor 29 is a sensor that detects the atmospheric pressure KPA. The water temperature sensor 34 is a sensor that detects the coolant temperature THW of the internal combustion engine 10. 【0013】 The processing circuit 101 determines the control parameters of the internal combustion engine 10, such as throttle opening TA, fuel injection amount QF, and ignition timing, based on the detection signals from each sensor. Then, the processing circuit 101 controls the internal combustion engine 10 by operating actuators such as the throttle valve 14, fuel injector 17, and ignition device 18, based on the determined control parameters. 【0014】 The processing circuit 101 estimates the intake manifold pressure PM, which is the pressure downstream of the throttle valve 14 in the intake passage 12 of the internal combustion engine 10, based on the detection signals from each sensor. The processing circuit 101 estimates the intake manifold pressure PM based on the throttle opening TA, intake airflow rate GA, atmospheric pressure KPA, and engine rotational speed NE. When the throttle opening TA is small, the processing circuit 101 estimates the intake manifold pressure PM as a lower value than when the throttle opening TA is large. When the atmospheric pressure KPA is low, the processing circuit 101 estimates the intake manifold pressure PM as a lower value than when the atmospheric pressure KPA is high. When the intake airflow rate GA is small, the processing circuit 101 estimates the intake manifold pressure PM as a lower value than when the intake airflow rate GA is large. When the engine rotational speed NE is large, the processing circuit 101 estimates the intake manifold pressure PM as a lower value than when the engine rotational speed NE is small. 【0015】 <Regarding fuel injection control, automatic start control, and automatic stop control> The processing circuit 101 performs fuel injection control to determine the fuel injection amount QF from the fuel injector 17 based on the estimated intake manifold pressure PM. The processing circuit 101 calculates the load factor KL based on the intake manifold pressure PM and the engine rotational speed NE. The load factor KL represents the intake air filling rate of the combustion chamber 11. When the intake manifold pressure PM is high, the processing circuit 101 calculates the load factor KL as a higher value than when the intake manifold pressure PM is low. Based on the load factor KL and the coolant temperature THW, the processing circuit 101 calculates the amount of fuel injection QF necessary to make the air-fuel ratio of the mixture burned in the combustion chamber 11 the stoichiometric air-fuel ratio. When the load factor KL is high, the processing circuit 101 calculates the fuel injection amount QF as a larger value than when the load factor KL is low. In other words, the processing circuit 101 calculates the fuel injection amount QF as a larger value when the estimated intake manifold pressure PM is high than when the estimated intake manifold pressure PM is low. 【0016】 The processing circuit 101 calculates the requested output Pe based on the accelerator pedal opening degree Acc, etc. The requested output Pe represents the output of the internal combustion engine 10 required to generate the driving force of the vehicle 1 requested by the driver through the operation of the accelerator pedal 28. Then, the processing circuit 101 controls the throttle valve 14, the fuel injector 17, and the ignition device 18 according to the requested output Pe. 【0017】 The processing circuit 101 performs automatic stop control. Automatic stop control is a control that stops fuel injection from the fuel injector 17 when an automatic stop request occurs while the internal combustion engine 10 is running. An automatic stop request occurs, for example, when the request output Pe for the internal combustion engine 10 becomes "0". An example of when the request output Pe becomes "0" is when the accelerator pedal opening Acc becomes "0". When an automatic stop request occurs, the processing circuit 101 sets the fuel cut flag to "ON". While the fuel cut flag is set to "ON", the processing circuit 101 stops fuel injection from the fuel injector 17. 【0018】 The processing circuit 101 performs automatic start control. Automatic start control is a control that restarts fuel injection from the fuel injector 17 and operates the internal combustion engine 10 when a restart request occurs while fuel injection is stopped by automatic stop control. A restart request occurs, for example, when the request output Pe for the internal combustion engine 10 increases from a state of "0" to a state greater than "0". An example of the request output Pe increasing from a state of "0" to a state greater than "0" is when the accelerator pedal opening Acc increases from "0" to a state greater than "0" due to the driver's operation of the accelerator pedal 28. A restart request occurs, for example, when the brake pedal is released from a state where the vehicle is stopped with the brake pedal pressed down. When a restart request occurs, the processing circuit 101 resets the fuel cut flag to "OFF". While the fuel cut flag is reset to "OFF", the processing circuit 101 causes the fuel injector 17 to perform fuel injection. When a restart request occurs and cranking is required to restart the internal combustion engine 10, the motor may be used for cranking. 【0019】 <Process for correcting estimated intake pipe pressure PM> When calculating the estimated intake pipe pressure PM, the processing circuit 101 sets an initial value when the crank angle is determined following engine startup, and then starts calculating the estimated value. The initial value is calculated by subtracting a predetermined value from the atmospheric pressure KPA. The initial value may be calculated by subtracting a larger value as the period from the atmospheric pressure KPA until the crank angle is determined becomes longer. 【0020】 When sufficient time has elapsed after stopping the internal combustion engine 10, air flows from the intake passage 12 into the combustion chamber 11, and the actual intake pipe pressure PM becomes approximately equal to the atmospheric pressure KPA. On the other hand, immediately after stopping the internal combustion engine 10, the actual intake pipe pressure PM is lower than the atmospheric pressure KPA compared to when sufficient time has elapsed after stopping the internal combustion engine 10. Therefore, at the time of restart immediately after stopping the internal combustion engine 10, the initial value becomes larger than the actual intake pipe pressure PM, and the estimated value of the intake pipe pressure PM deviates from the actual intake pipe pressure PM. 【0021】 Therefore, when the automatic stop control starts, the processing circuit 101 repeatedly executes a series of processes for correcting the estimated intake pipe pressure PM to a lower value during the operation of the internal combustion engine 10, where the shorter the time from the start of the automatic stop control to the start of the automatic start control. 【0022】 As shown in FIG. 2, when starting this series of processes, in the process of step S10, the processing circuit 101 determines whether the automatic stop control has started. When the automatic stop control has started (step S10: YES), the processing circuit 101 advances the process to step S11. When the automatic stop control has not started (step S10: NO), the processing circuit 101 temporarily ends the series of processes shown in FIG. 2. 【0023】 In the process of step S11, the processing circuit 101 starts measuring the timer from zero. Then, the processing circuit 101 advances the process to step S12. In step S12, the processing circuit 101 determines whether or not automatic start control has started. If automatic start control has started (step S12: YSE), the processing circuit 101 proceeds to step S13. If automatic start control has not started (step S12: NO), the processing circuit 101 continues timer measurement. 【0024】 In step S13, the processing circuit 101 stops measuring with the timer. The time indicated by the timer is the time from when the automatic stop control starts until when the automatic start control starts. Subsequently, based on the time indicated by the timer, the processing circuit 101 corrects the estimated intake manifold pressure PM to a lower value the shorter the time from when the automatic stop control starts until when the automatic start control starts. The amount of correction for the estimated intake manifold pressure PM with respect to the time from when the automatic stop control starts until when the automatic start control starts is determined in advance by testing or simulation. Based on the corrected estimated intake manifold pressure PM, the processing circuit 101 determines the fuel injection amount QF at the time of restart. Subsequently, the processing circuit 101 proceeds to step S14. 【0025】 In step S14, the processing circuit 101 clears the timer. After that, the processing circuit 101 completes the series of processes shown in Figure 2. <Operation of this embodiment> The operation of this embodiment will be explained with reference to the timing chart shown in Figure 3. Figure 3(a) shows the changes in the fuel cut flag. Figure 3(b) shows the changes in the engine rotational speed NE. Figure 3(c) shows the changes in the estimated intake manifold pressure PM. The dashed line L1 in Figure 3(c) represents atmospheric pressure KPA. In Figures 3(a), 3(b), and 3(c), the changes in the fuel cut flag, the changes in engine rotational speed NE, and the changes in the estimated intake manifold pressure PM are shown by solid lines when the elapsed time from the automatic shutdown of the internal combustion engine 10 to its restart is short. In Figures 3(a), 3(b), and 3(c), the changes in the fuel cut flag, the changes in engine rotational speed NE, and the changes in the estimated intake manifold pressure PM are shown by double-dash lines when the internal combustion engine 10 is restarted after a sufficient amount of time has elapsed since the automatic shutdown of the internal combustion engine 10. 【0026】 First, we will explain the case where the internal combustion engine 10 is automatically stopped and then restarted after a sufficient amount of time has elapsed. The time "T1" shown in Figure 3 is the time when the automatic stop request occurred. When the automatic stop request occurs, the processing circuit 101 starts automatic stop control. After starting automatic stop control, the processing circuit 101 sets the fuel cut flag to "ON". As a result, fuel injection from the fuel injector 17 is stopped. With the fuel injection stopped, the engine rotation speed NE decreases. 【0027】 The time "T3" shown in Figure 3 is the time when an automatic start request occurs after a sufficient amount of time has elapsed since the internal combustion engine 10 was automatically stopped. When an automatic start request occurs, the processing circuit 101 starts automatic start control. At time "T3", the processing circuit 101, which started automatic start control, performs cranking with the motor. 【0028】 The time "T4" shown in Figure 3 is the time when the crank angle is determined and the processing circuit 101 resets the fuel cut flag to "OFF" in the automatic start control. This allows the initial value of the estimated intake manifold pressure PM to be calculated and the calculation of the estimated intake manifold pressure PM to begin. In the example shown in Figure 3, the initial value at this time is the first estimated value PM1, which is lower than the atmospheric pressure KPA. Then, fuel injection from the fuel injector 17 begins. The engine rotational speed NE at time "T4" is "NE1". 【0029】 Next, as an example of a case where the elapsed time from the automatic shutdown of the internal combustion engine 10 to its restart is short, we will explain the case where an automatic start request occurs at time "T2" as shown in Figure 3. When an automatic start request occurs at time "T2", the processing circuit 101 starts automatic start control. The engine rotational speed NE at time "T2" is "NE1". The processing circuit 101, which started automatic start control at time "T2", resets the fuel cut flag to "OFF". At this time, the crank angle is known, so the initial value of the estimated intake manifold pressure PM is calculated and the calculation of the estimated intake manifold pressure PM begins. In the example shown in Figure 3, the initial value at this time is the first estimated value PM1, which is lower than the atmospheric pressure KPA. Then, fuel injection from the fuel injector 17 begins. 【0030】 At time "T2", the elapsed time between the automatic shutdown of the internal combustion engine 10 and its restart is short. Therefore, the processing circuit 101 corrects the initial value of the intake manifold pressure PM to a corrected estimated value PM2, which is obtained by decreasing the first estimated value PM1 by the correction value "A". The correction value is set to a larger value the shorter the elapsed time between the automatic shutdown of the internal combustion engine 10 and its restart. Therefore, if the automatic start request occurs before time "T2", the processing circuit 101 will set the estimated value of the intake manifold pressure PM to a value lower than the corrected estimated value PM2. 【0031】 The processing circuit 101 of the control device 100 corrects the estimated intake manifold pressure PM to a lower value when the internal combustion engine 10 is restarted, as the time between the automatic shutdown of the internal combustion engine 10 and its restart is shorter. Therefore, the processing circuit 101 can set the estimated value of the intake manifold pressure PM used to determine the fuel injection amount QF to a value close to the actual intake manifold pressure PM. 【0032】 <Effects of this embodiment> (1) The control device 100 can suppress the air-fuel ratio immediately after restarting the internal combustion engine 10, even if the internal combustion engine 10 is restarted immediately after stopping the internal combustion engine 10, from becoming richer than the stoichiometric air-fuel ratio. [Explanation of Symbols] 【0033】 1...Vehicle, 10...Internal combustion engine, 17...Fuel injector, 32...Drive wheel, 100...Control device, 101...Processing circuit, PM...Intake manifold pressure, QF...Fuel injection volume

Claims

[Claim 1] A control device applied to a vehicle equipped with an internal combustion engine and transmitting torque output from the internal combustion engine to the drive wheels, comprising a processing circuit for controlling the internal combustion engine, The processing circuit described above A fuel injection control system that estimates the intake manifold pressure of the internal combustion engine and determines the amount of fuel injected from the fuel injector based on the estimated intake manifold pressure, Automatic stop control that stops fuel injection from the fuel injection valve when an automatic stop request occurs during the operation of the internal combustion engine, Automatic start control that restarts fuel injection from the fuel injection valve to start the internal combustion engine when a restart request occurs while fuel injection is stopped by the automatic stop control, The shorter the time between the start of the automatic stop control and the start of the automatic start control, the more the process of correcting the estimated intake manifold pressure to a lower value is performed. Vehicle control system.

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