JP2004052656A - Engine start control device for vehicle - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an engine start control device for a vehicle capable of constraining variation in torque of an engine for the vehicle when the vehicle outgoes intermediately after the engine is started. <P>SOLUTION: The engine start control device is provided with an intake quantity sensor 20 which is disposed in an intake passage 18 of the engine and outputs intake quantity signal with delay to actual intake quantity, a correction means 22 which performs predefined first lead correction relative to the intake quantity signal from the intake quantity sensor, and fuel injection control means 16 which controls fuel injection to the engine on the basis of the corrected intake quantity signal. The correction means is characterized in that predefined period after the engine is started performs second lead correction distinct from the predefined first lead correction. <P>COPYRIGHT: (C)2004,JPO

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a vehicle engine start control device, and more particularly, to a vehicle engine start control device provided with a correction unit that performs advance correction on an intake air amount signal.
[0002]
[Prior art]
2. Description of the Related Art There is known a vehicle having a so-called idle stop mechanism for stopping an engine when the vehicle is stopped in order to minimize fuel consumption and exhaust gas emission of the engine. When a vehicle provided with such an idle stop mechanism stops when waiting for a traffic light, the fuel supply to the engine is stopped to stop the engine.
[0003]
Also, there is known a vehicle provided with a so-called hybrid mechanism that uses both electric energy from a battery and power of an engine as running power of the vehicle. When this hybrid mechanism is combined with an idle stop mechanism, when the engine restarts from a stopped state in which the engine has stopped, the vehicle runs on electric energy from the battery until the engine starts, and the engine starts and torque generated by the engine is reduced. A vehicle that switches to running by an engine when it starts to occur has been proposed.
[0004]
[Problems to be solved by the invention]
Here, the intake air amount used in engine control such as determination of the fuel injection amount is detected by an intake air amount sensor such as an air flow sensor disposed in an intake passage to the engine. Since such an intake air amount sensor is mounted around an intake passage through which a change in the inflow air amount is transmitted with a delay, the intake air amount signal from the intake air amount sensor is delayed with respect to the actual intake air amount. For this reason, “advance correction” taking into account the rate of change is performed on the intake air amount signal to correct this delay.
[0005]
However, when the engine is started, the amount of intake air sharply increases, so that the "advance correction" acts excessively, and an "overshoot" occurs in which the corrected intake air amount signal greatly exceeds the actual intake air amount. Then, since the fuel injection amount is determined based on the intake air amount signal greatly exceeding the actual intake air amount due to the “overshoot”, the fuel injection amount becomes too large and the engine speed rapidly increases. At the time of normal engine start, it is rare that the engine starts immediately after the start, and thus such a sudden increase in the engine speed does not cause much problem in practical use.
[0006]
However, such a rapid increase in the engine speed causes a torque shock, and thus such a rapid increase in the engine speed may cause a problem. For example, when the engine restarts from a stopped state in which the engine is stopped as described above, the vehicle runs on electric energy from the battery until the engine is started, and the engine starts when the engine starts and torque starts to be generated by the engine. In a vehicle that switches to running, there is a problem that if the torque on the engine side fluctuates when switching from running by battery to running by engine, a torque shock occurs and the occupant feels discomfort.
[0007]
The present invention has been made in view of such a problem, and an object of the present invention is to provide an engine start control device for a vehicle that can suppress engine torque fluctuation at the time of transmission immediately after starting.
[0008]
[Means for Solving the Problems]
According to the present invention, an intake air amount sensor that is arranged in an intake passage of an engine and outputs an intake air amount signal with a delay with respect to an actual intake air amount, and a predetermined intake air amount signal from the intake air amount sensor. Correction means for performing a first advance correction; and fuel injection control means for controlling fuel injection to the engine based on the corrected intake air amount signal, wherein the correction means has a predetermined period after the engine is started. An engine start control device for a vehicle is provided that performs a second advance correction different from the predetermined first advance correction.
[0009]
According to such a configuration, when the engine is started, in which the intake air amount of the engine is rapidly increased, the advance correction control having contents different from those in other states is performed, so that an appropriate fuel injection amount corresponding to the actual intake air amount is provided. Is set, and stable engine rotation is obtained. As a result, torque shock is avoided.
[0010]
According to a preferred aspect of the present invention, in a predetermined vehicle stop state, the fuel injection control means stops fuel injection to stop an engine, and drives wheels when restarting from the vehicle stop state, and And a motor for cranking and starting the engine.
[0011]
According to such a configuration, even when the engine is started while the wheels are driven by the motor, the torque shock on the engine side is unlikely to occur at the time of starting, so that the torque shock on the engine side is transmitted to the wheels to cause discomfort to the occupant. Is suppressed.
[0012]
According to a preferred aspect of the present invention, at the time of the restart, the motor drives the wheels to cause the vehicle to creep, and the fuel injection control unit controls the engine after the creep running is started. Restart the fuel injection control.
[0013]
According to such a configuration, during the creep running in which the torque shock is easily felt, the torque shock is less likely to occur on the engine side. Therefore, during the creep running, the torque shock on the engine side is transmitted to the wheels, which may cause discomfort to the occupant. Is suppressed.
[0014]
According to another preferred aspect of the present invention, a rotational speed change detecting unit for detecting a rotational speed change of the engine, and a rotational speed change based on the rotational speed change during fuel injection control by a fuel injection control unit based on the second correction. Learning means for changing the content of the second advance correction.
[0015]
According to such a configuration, the content of the second advance correction is changed according to the actual change in the engine speed, so that the second correction of the content that matches the actual situation is performed.
[0016]
According to another preferred embodiment of the present invention, the advance correction is a correction for performing a differentiation process on an output value of the intake air amount sensor.
[0017]
According to another preferred aspect of the present invention, the fuel injection control means starts fuel injection in a state where the wheel and the engine are fastened. According to such a configuration, since torque shock is unlikely to occur on the engine side, transmission of the engine-side torque shock to the wheels to suppress discomfort to the occupant is suppressed.
[0018]
According to another aspect of the present invention, an intake air amount sensor that is arranged in an intake passage of an engine and outputs an intake air amount signal delayed with respect to an actual intake air amount, and an intake air amount signal from the intake air amount sensor. A fuel injection control means for controlling fuel injection to the engine based on the corrected intake air amount signal, wherein the fuel injection control means is provided for a predetermined period after the engine is started. Performs a fuel injection control of a fuel injection amount smaller than a combustion injection amount calculated based on the advance correction.
[0019]
According to such a configuration, the fuel injection amount is reduced during the period after the engine is started in which overshoot is likely to occur, so that the occurrence of torque shock due to overshoot is suppressed.
[0020]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, a first embodiment of the present invention will be described with reference to the drawings. First, a basic mechanism of a hybrid vehicle to which the engine start control device according to the first embodiment of the present invention is applied will be described.
[0021]
FIG. 1 is a block diagram schematically showing a drive mechanism of a hybrid vehicle to which the engine start control device according to the first embodiment of the present invention is applied. When the hybrid vehicle is stopped in a predetermined stop state, the engine is stopped, and when restarting, the vehicle runs on the electric energy from the battery until the engine is started, and the engine starts to start generating torque by the engine. And a hybrid vehicle having an idle stop mechanism for switching to running by an engine.
[0022]
As shown in FIG. 1, a hybrid vehicle 1 according to the present embodiment includes an engine 8 that drives left and right drive wheels 4 and 6 via a CVT automatic transmission 2, and a drive wheel 4 that is connected to the engine 8. , 6 as an auxiliary drive. The motor 10 is driven by the power of the battery 14 via the inverter 12, cranks the engine 8, and further drives the drive wheels 4, 6. At the time of deceleration, the motor 10 is driven by the drive wheels 4, 6 via the engine 8 to regenerate. The power is generated and the battery 14 is stored.
[0023]
In the present embodiment, the engine 8 is of a type that delays the closing timing of a fuel-efficient valve, the motor 10 is an IPM synchronous motor, and the battery 14 is a nickel-metal hydride battery. However, the engine, motor, and battery of the present invention are not limited to these.
[0024]
The vehicle 1 includes an ECU (electronic control unit) 16. The ECU 16 includes a CPU, a ROM, a RAM, an interface circuit, an inverter circuit, and the like. The ECU 16 determines the throttle valve opening, fuel injection to the engine 8, ignition timing, and the like based on the input accelerator opening, engine speed, engine water temperature, intake air temperature, intake air amount, vehicle speed, shift range, and other signals. While controlling, the operation of the CVT 2 such as the output torque and the number of revolutions of the motor 10 is controlled. Further, the ECU 16 controls the operation of the inverter 12 such as storing the electric power generated by the motor 10 in the operation of the engine 8 in the battery 14. Further, the ECU 16 is provided with advance correction means 22 which receives an intake air amount signal from an air flow sensor 20 disposed in the intake passage 18 and performs a predetermined advance correction on this signal. As will be described later, this correction means 22 is configured to perform advance correction of a different content during a predetermined period after starting the engine than in other periods. Then, the ECU 16 determines the fuel injection amount based on the corrected intake air amount signal and the like. The ECU 16 also controls the opening of the throttle valve 24 arranged in the intake passage 18.
[0025]
In the speed change control of the CVT 2, the speed ratio is controlled based on the CVT map stored in the ECU 16 so that the target engine speed corresponding to the accelerator opening and the vehicle speed is obtained. For example, when the accelerator is depressed during steady running, the vehicle speed does not increase immediately, so the target engine speed increases, and the gear ratio decreases correspondingly. Thereafter, if the accelerator opening does not change as the vehicle speed increases, the gear ratio increases.
[0026]
Next, the configuration of the engine 8 will be described with reference to FIG. FIG. 2 is a drawing schematically showing the entire engine system including the engine 8. As shown in FIG. 2, the engine 8 has a cylinder 26, in which a piston 28 is loaded, and a combustion chamber 30 is formed above. An intake port and an exhaust port are formed in the combustion chamber 30. The intake port is opened and closed by an intake valve 32, and the exhaust port is opened and closed by an exhaust valve 34. An ignition plug 36 is attached to an upper portion of the combustion chamber 30.
[0027]
In the intake passage 18 connected to the intake port, an air cleaner 38, an air flow sensor 20, a throttle valve 24, and a surge tank 40 are provided in this order from the upstream side, and an injector 42 for injecting fuel near the intake port is provided. Is provided. Since the airflow sensor 20 is attached to the periphery of the intake passage 18, the intake airflow signal from the airflow sensor 20 is delayed from the actual intake airflow. The intake passage 18 is provided with an ISC passage 44 that bypasses the throttle valve 24. The ISC passage 44 is provided with an ISC valve 46 that adjusts an air flow rate and executes idle speed control. Meanwhile, _{O 2} sensor 50 and the catalytic converter 52 and the like is provided in the exhaust passage 48.
[0028]
Further, the engine 8 is provided with a crank angle sensor 54 for detecting a rotation speed of a crankshaft and a water temperature sensor 56 for detecting a cooling water temperature of the engine. An intake air temperature sensor for detecting an intake air temperature is provided in the air cleaner 38. 58 are provided.
[0029]
Next, the operation of the hybrid vehicle according to the present embodiment will be described. As described above, in the hybrid vehicle of the present embodiment, the engine is stopped in a predetermined stop state, and when restarting from the stopped state in which the engine is stopped, electric power from the battery is used until the engine is started. A hybrid vehicle equipped with an idle stop mechanism that switches to running by the engine when the vehicle starts running and the engine starts to generate torque by the engine. Therefore, for example, when a predetermined condition is satisfied by stopping at a signal or the like, the ECU 16 stops fuel injection from the injector 42 and stops the engine. When the driver releases the foot from the brake pedal and starts the operation of the vehicle again, for example, when the signal changes to green, the ECU 16 drives the driving wheels 4 and 6 with the driving force of the motor 10 to creep the vehicle. Start off. Further, the ECU 16 starts fuel injection control to the engine 8 after a predetermined time has elapsed, and starts the engine 8.
[0030]
Next, the operating states of the engine 8 and the motor 10 in the hybrid vehicle 1 will be described for each operation mode (running state). Note that the target torque Tr is calculated based on the accelerator opening.
[0031]
(During steady driving)
When the target torque Tr is larger than 0 and smaller than the predetermined torque Tr1 (0 <Tr <Tr1), the vehicle speed V is higher than the creep speed V1 (V1 <V), the brake is off, and the engine is running at steady speed in the shift range D. The torque ET = Tr (target torque), and the motor 10 is turned off. In other words, the motor 10 does not operate, and the vehicle travels only with the power of the engine 8.
[0032]
(When accelerating)
When the accelerator is depressed and the target torque Tr is larger than the predetermined torque Tr1 (Tr> Tr1), the brake is off, and the vehicle is accelerating in the shift range D, the target torque Tr = ETac (engine torque during acceleration) + MTac (motor during acceleration). The engine 8 and the motor 10 are operated so as to obtain the torque. That is, the vehicle is in a traveling state in which the vehicle travels with the power of the motor 10 and the engine 8.
[0033]
(At start)
When the target torque Tr is greater than 0 (Tr> 0), the vehicle speed V is equal to or less than the creep speed V1 (V1 ≦ V), the brake is off, and the vehicle is in the shift range D, the target torque Tr = ETac (the engine torque during acceleration). ) + MTac (motor torque during acceleration), the engine and the motor are operated. That is, the vehicle is in a traveling state in which the vehicle travels with the power of the motor 10 and the engine 8.
[0034]
(During creep)
When the target torque Tr is 0 (Tr = 0), the vehicle speed V is 0 or more and the creep speed V1 or less (0 ≦ V ≦ V1), the brake is OFF, and the shift range is D, the engine torque ET = ETc (the creep during the creep). (Engine torque), and the motor 10 is turned off. That is, the motor 10 does not operate, and a running state in which the motor 8 creeps only by the power of the engine 8 is set.
[0035]
However, at the time of creep when starting and restarting the engine after the idle stop, first, the creep is caused only by the torque from the motor 10, and then, when the engine 8 is started and the torque by the engine 8 is generated, the creep occurs. The torque by the motor 10 is reduced by the torque of the engine 8, and control is performed so that the sum of the torque by the motor 10 and the torque by the engine 8 becomes the torque for creep.
[0036]
(During deceleration)
When the target torque Tr is 0 (Tr = 0), and the vehicle speed V is higher than the creep speed V1 (V1 <V), the brake is ON, and the vehicle is decelerating in the shift range D, the engine operates as a fuel cut and the motor operates as a generator. The control of the regeneration mode is performed.
[0037]
(When stopped)
When the target torque Tr is 0 (Tr = 0) and the vehicle speed V is 0 (V = 0), and the vehicle is stopped in the brake ON shift range D or the brake OFF shift range P (N or P), the engine and the motor are stopped. Is stopped. However, when the charged amount of the battery 14 is small, the engine 8 is driven, the motor 10 is operated as a generator, and the battery 14 is charged. At this time, the clutch of the CVT 2 is turned off.
[0038]
Next, the control regarding the torque distribution between the engine 8 and the motor 10 performed by the ECU 16 when the vehicle restarts from the stopped state after the idle stop will be described with reference to FIG.
[0039]
First, in step S1, data such as accelerator opening, engine speed, and vehicle speed are input, and in step S2, a target torque Tr is set. The target torque Tr is set from a predetermined map according to the accelerator opening α and the vehicle speed. Further, in step S3, the above-described operation mode is set. Next, in step S4, it is determined whether or not the vehicle is in the D (drive) range.
[0040]
When YES is determined in the step S4, the process proceeds to a step S5, and it is determined whether or not it is immediately after shifting from the N (neutral) range (or P: parking) to the D range. When YES is determined in step S5, it is at the time of starting, the process proceeds to step S6, the flag F1 is set to 1, and in step S7, it is determined whether or not the engine is ignited. When NO is determined in the step S7, that is, when the engine is not ignited, the process proceeds to a step S8, and the starting motor torque MTs is set to a torque at which the engine speed Ne is rotated at 500 rpm. With this torque, the engine can be cranked and started, and the driving wheels can be driven via the engine to cause the vehicle to creep.
[0041]
Next, in step S9, a value obtained by adding the starting motor torque MTac to the starting motor torque MTs is set as the motor torque MT. The starting motor torque MTac takes a positive value at the time of starting, that is, when the accelerator is depressed, and becomes 0 otherwise. Further, the process proceeds to step S10, where the engine torque ET is set to zero.
[0042]
On the other hand, if YES in step S7, that is, if the engine is running, the process proceeds to step S11, and the starting motor torque MTs is set to MTs (n−1) −α. That is, the motor torque MTs at the time of the previous start is decreased by the predetermined value α. Next, the process proceeds to step S12, in which a value obtained by adding the starting motor torque MTac to the starting motor torque MTs (n) is set as the motor torque MT. The starting motor torque MTac takes a positive value at the time of starting, that is, when the accelerator is depressed, and becomes 0 otherwise.
[0043]
Next, at step S13, the current motor torque MT (n) set at step S12 is replaced with the previous motor torque MT (n-1), and the routine proceeds to step S14, where it is determined whether or not MTs is 0. If NO in step S14, the process proceeds to step S15, in which the starting engine torque ETs is set to MTs (n-1) + α. That is, the engine torque ETs at the time of the previous start is increased by the predetermined value α. Next, the process proceeds to step S16, and it is determined whether or not a creep condition is present. This determination is made based on whether the target torque Tr is 0 (Tr = 0), the vehicle speed V is 0 or more and the creep speed V1 or less (0 ≦ V ≦ V1), the brake is OFF, and all the conditions of the shift range D are satisfied. I do. If YES in step S16, that is, if the vehicle is in the creep state, the process proceeds to step S17, and it is determined whether the current engine torque ETs (n) is larger than the torque ETc required for creep running.
[0044]
When YES is determined in the step S17, since the creep running is possible only by the engine torque, the motor torque MT is set to 0 and the engine torque ET is set to ETc (step S18). On the other hand, if NO in step S17, the engine torque ET is set to the current engine torque ET (n) in step S19, and in step S20, the previous engine torque ET (n-1) is changed to the current engine torque ET (n). n).
[0045]
If NO in step S16, that is, if it is not creep running, the process proceeds to step S22, in which a value obtained by adding a torque ETac according to the acceleration request (accelerator opening) to the engine torque ETs (n) is set as ET. Next, in step S22, the previous engine torque ET (n-1) is replaced with the current engine torque ET (n).
[0046]
When YES is determined in the step S14, the torque required for the motor is 0, that is, only the torque by the engine is sufficient to meet the required torque. Therefore, the flag F1 is set to 0 in a step S23.
[0047]
On the other hand, when the answer to the determination of step S4 is NO, the engine torque ET and the motor torque MT are set to 0 in order to continue the stopped state. If NO in step S5, that is, if it is not immediately after shifting from the N or P range to D, the process proceeds to step S24, and it is determined whether or not it is immediately after the brake is released. This is to cope with a case where the vehicle is stopped by the foot brake while the shift range is maintained at the D range when the vehicle is stopped. When YES is determined in the step S24, the state is the same as YES in the step S5, and the process proceeds to the step S6. When NO is determined in the step S24, the process proceeds to a step S25 to determine whether or not the flag F1 is 1, and when YES, the process proceeds to a step S7.
[0048]
When NO in step S25, and when step S10, step S18, step S20, step S22, or step S26 is completed, the process proceeds to step S27, and according to the set motor torque MT and engine torque ET, and the traveling mode. The clutch signal is output to the motor 10, the engine 8, and the CVT 2.
[0049]
Next, the contents of the engine control during traveling performed by the ECU 16 in the first embodiment will be described with reference to FIG. FIG. 4 is a flowchart illustrating the engine control process performed by the ECU 16.
[0050]
First, in step S30, data such as accelerator opening, engine speed, and vehicle speed are input, and in step S31, a throttle valve opening Tv is set. The throttle valve opening Tv is set from a predetermined map according to the torque ET required for the engine and the engine speed Ne. Further, in step S32, the throttle valve is driven based on the set throttle valve opening Tv.
[0051]
Next, in step S33, it is determined whether or not the motor torque MTs is greater than zero. If NO in step S33, that is, if the vehicle is running only with the power of the engine, the process proceeds to step S34 to determine whether or not the timer T is counting. If NO in step S34, that is, if the timer T is not counting, the process proceeds to step S35, and normal advance correction is performed on the intake air amount signal AFSp from the air flow sensor 20.
[0052]
In this advance correction, the intake air amount signal AFS from the air flow sensor 20 which causes a delay with respect to the actual intake air amount is corrected in accordance with the rate of change, and this delay is corrected, and the appropriate fuel injection amount with respect to the intake air amount is corrected. Is calculated. Specifically, the intake air amount signal AFSp from the air flow sensor 20 is multiplied by a predetermined first correction (K0A × dNe / dt + K1A) s + 1 / (K2A × s + 1). K0A, K1A, and K2A are constants.
[0053]
On the other hand, if YES in step S33 or step S34, for example, at the time of or immediately after the start of the engine running by the motor or assisted by the motor, the process proceeds to step S36, and the state at the time of or immediately after the engine is started Is performed on the intake air amount signal AFSp from the air flow sensor 20.
[0054]
Specifically, a second correction (K0B × dNe / dt + K1B) s + 1 / (K2B × s + 1) different from the first coefficient in step S35 is multiplied by the intake air amount signal AFSp from the air flow sensor. K0B, K1B, and K2B are constants. The second correction is set so that the response is smaller than the first correction.
[0055]
When the throttle valve is opened, such as when the engine is restarted, a normal “advance correction” using the first coefficient is performed, and this correction acts excessively, as shown by the dashed line in FIG. In other words, a so-called “overshoot” occurs in which the corrected output value AFS of the airflow sensor greatly exceeds the actual intake air amount indicated by the dotted line. Therefore, when the fuel injection amount and the like are determined based on the overshoot excessive output value AFS of the air flow sensor and the engine control is performed, the engine rotation becomes unstable, and there is a high possibility that a torque shock will occur.
[0056]
In this embodiment, when the engine is started, immediately after the engine is started, or the like, the advance correction using the second coefficient is performed, so that the raw output value AFSP of the airflow sensor is changed to, for example, as shown by a solid line in FIG. It is corrected so that "overshoot" does not occur. Therefore, during a predetermined period after the engine is started, for example, immediately after the engine is started, the fuel injection amount Q that is actually adapted to the intake air amount is set, the engine rotation is stabilized, and the torque shock is suppressed.
[0057]
Next, upon completion of the process in the step S36, the process proceeds to a step S37 to determine whether or not the engine speed Ne is 500 rpm or more. If NO in step S37, the engine speed has not reached 500 rpm due to cranking by the motor, so the fuel injection amount Q is set to 0 in step S38 and the routine returns. When the charge amount of the battery is small, the control contents may be changed so that fuel injection is executed and the engine is burned even if the engine speed does not reach 500 rpm.
[0058]
When YES is determined in the step S37, or when the process in the step S35 is completed, the process proceeds to a step S39, and based on the data input in the step S30, the correction result in the step S35 or the step S36, the fuel injection amount Q, The fuel injection timing I and the ignition timing θ are set, and in step S40, the fuel injection and ignition control are executed based on these I, Q, and θ, and the engine is operated. When the fuel injection is performed, the motor is driving the wheels via the engine, so that the engine is in a connected state with the wheels.
[0059]
Next, in step S41, it is determined whether or not the engine has just been started. When the determination in step S41 is NO, the process proceeds to step S42, in which it is determined whether or not the timer T is counting. When the determination is NO, the process returns. . When YES is determined in the step S41 or S42, it is determined whether or not the creep operation is being performed in a step S43. This is because the learning control performed next is difficult except during the creep operation.
[0060]
When YES is determined in the step S43, 1 is added to the timer T in a step S44, and it is determined whether or not T is larger than a threshold value T0 in a step S45. When NO is determined in the step S45, the engine speed Ne used for the learning control is stored in a step S46, and the process returns.
[0061]
If YES in step S45, that is, if the advance correction based on the second coefficient has continued for the predetermined period, the process proceeds to step S47, in which the total value of the stored engine speed Ne is divided by the number of samples to obtain the predetermined period (T0). The average value Neav of the engine rotation speed is calculated. Next, in step S48, a difference ΔNe from the average value Neav is calculated for each sample engine speed (NE (1, 2,... N)), and a maximum value ΔNemax and a minimum value ΔNemin of these differences ΔNe are extracted. .
[0062]
Further, the process proceeds to step S49, and it is determined whether or not the maximum value ΔNemax or the minimum value ΔNemin is larger than the difference threshold value ΔNe0. If YES in step S49, it is determined that the correction based on the second coefficient is not appropriate because the engine speed is large, and the constants K0B, K1B, and K2B in the second coefficient are changed in step S50. Learning control is performed. For example, when ΔNemax is larger than the threshold value, the AFS after the second correction is too large, so that K0B and K1B are made small or K2B is made large in order to suppress the differential term in the second coefficient. Such changes are made. On the other hand, when ΔNemin is smaller than the threshold value, conversely, a change is made to increase K0B and K1B or decrease K2B.
[0063]
NO in step S49, or after the process in step S50 is completed, in step S51, the value T of the timer is cleared, and the process returns.
[0064]
Next, an example of the state of the vehicle when the vehicle restarts from the idle stop due to the stop will be described with reference to the time chart of FIG. It is assumed that the vehicle is stopped due to waiting for a traffic light or the like, the engine is stopped by the idle stop mechanism, and the driver is applying a brake.
[0065]
When the vehicle starts moving due to a change in signal, the driver first releases the brake at t1, and the motor 10 starts rotating (cranking) the engine 8 at t2. The motor 10 rotates the engine at a motor torque MTs that causes the engine to rotate at 500 rpm or more. When the vehicle is stopped with the AT range set to N or P without stepping on the foot brake, the range is switched from N or P to D instead of releasing the brake. At the same time, since the clutch of the CVT 2 is engaged at t2, the driving wheels 4 and 6 are also rotated by the rotation of the motor 10, and the vehicle starts creep running with the driving force of the motor 10.
[0066]
As the engine rotates, the intake air amount increases, and the intake signal AFSp from the air flow sensor increases. At this time, when the normal advance correction for multiplying the intake signal AFSp by the first coefficient is performed, as described above with reference to FIG. 5, an overshoot occurs in which the corrected value greatly exceeds the actual intake air amount. However, in the control device of the present embodiment, at the time of starting the engine (immediately after the start), the advance correction using the second coefficient is performed so that such overshoot does not occur, and the corrected AFS value is Thus, the value appropriately reflects the actual intake air amount.
[0067]
When the engine speed reaches 500 rpm in the cranking by the motor 10 (t3), fuel injection and ignition are executed, and the engine is ignited. At the same time, the throttle opening increases. When the engine is ignited, the engine torque ET starts to increase, and the motor torque MTs decreases by this increment, and the torque required for creep running is maintained. When the engine torque MT reaches a torque required for creep running at t4, the motor torque MTs becomes zero.
[0068]
Further, when the accelerator is depressed at t5, the throttle opening Tv further increases, the engine torque ET further increases, and the mode shifts from creep running to acceleration running. At this time, the motor 10 generates the torque MTac to assist the engine 8. When the accelerator depression is completed and the accelerator opening becomes constant, the assist by the motor 10 ends (MTac = 0), and the engine ET also becomes constant.
[0069]
Further, the engine speed during a predetermined period (T0) after t3 is stored, and when the engine speed fluctuates, learning control for changing the advance correction coefficient is executed in response to the fluctuation.
[0070]
According to the present embodiment, the engine is started during the creep running from t2 to t5, but at the time of starting the engine and for a predetermined period thereafter, the output of the airflow sensor corrected to match the actual intake air amount. Since the fuel injection amount is set based on the value AFS, the engine rotation is stabilized, and torque shock is less likely to occur during creep running.
[0071]
Next, a description will be given of an engine start control device according to a second embodiment of the present invention. The basic configuration of the engine start control device of the second embodiment is the same as that of the first embodiment. The difference from the first embodiment lies in the content of engine control during traveling performed by the ECU. Accordingly, an engine control process performed by the engine start control device according to the second embodiment will be described with reference to the flowchart of FIG.
[0072]
In step S60, data such as the accelerator opening, the engine speed, and the vehicle speed are input, and in step S61, the throttle valve opening Tv is set. The throttle valve opening Tv is set from a predetermined map according to the torque ET required for the engine and the engine speed Ne. Further, in step S62, the throttle valve is driven based on the set throttle valve opening Tv.
[0073]
Next, the process proceeds to step S63, in which the advance correction is performed on the intake air amount signal AFSp from the air flow sensor 20. In this advance correction, the intake air amount signal AFS from the air flow sensor 20 which causes a delay with respect to the actual intake air amount is corrected in accordance with the rate of change, and this delay is corrected, and the appropriate fuel injection amount with respect to the intake air amount is corrected. Is calculated. Specifically, the intake air amount signal AFSp from the air flow sensor 20 is multiplied by a predetermined coefficient (K0A × dNe / dt + K1A) s + 1 / (K2A × s + 1). K0A, K1A, and K2A are constants.
[0074]
Next, the process proceeds to step S64, where the fuel injection amount Q, the fuel injection timing I, and the ignition timing θ are set based on the data input in step S60, the correction result in step S63, and the like. Further, in step S65, it is determined whether or not the motor torque MTS is greater than 0, that is, whether or not the vehicle is traveling by the driving force of the motor. When YES is determined in the step S65, the process proceeds to a step S66, and it is determined whether or not the engine speed Ne is equal to or more than 500 rpm. If NO in step S66, since the engine speed has not reached 500 rpm due to cranking by the motor, the fuel injection amount Q is set to 0 in step S67, and the routine returns. When the charge amount of the battery is small, the control contents may be changed so that fuel injection is executed and the engine is burned even if the engine speed does not reach 500 rpm.
[0075]
When YES is determined in the step S66, the process proceeds to a step S68, in which a predetermined value (correction value) ΔQ is divided from the set fuel injection amount Q, and this is set as a new fuel injection amount Q. That is, the fuel injection amount is changed to the fuel injection amount in which the intake air amount signal is reduced by the overshoot (ΔQ) by the delay correction. Next, in step S69, fuel injection and ignition control are executed based on these I, Q, and θ to operate the engine.
[0076]
In the second embodiment having such a configuration, while the motor is operating at the time of restart after idling stop, that is, during the period of switching from running by the motor to running by the engine, the fuel injection amount is Since the set fuel injection amount is reduced by a predetermined amount, even if the fuel injection amount is set to be relatively large due to the overshoot due to the advance correction, a torque shock does not easily occur.
[0077]
The present invention is not limited to the above embodiments, and various changes or modifications can be made within the scope of technical matters described in the claims.
[0078]
For example, when the learning is insufficient, the increase in the engine rotation immediately after the engine is started may be made gentler, or the throttle opening may be made gentler so that the learning control is facilitated. Learning is insufficient when, for example, the content of engine control is changed at a garage or the like to change the condition of the engine.
[0079]
Further, in the first embodiment, when the engine is started or the like, the advance correction is different by multiplying the raw intake signal AFSP from the air flow sensor by a second coefficient different from the first coefficient. A different advance correction may be performed by further correcting the advance correction result multiplied by the first coefficient.
[0080]
【The invention's effect】
As described above, according to the present invention, there is provided an engine start control device for a vehicle that can suppress a fluctuation in engine torque at the time of transmission immediately after starting.
[Brief description of the drawings]
FIG. 1 is a block diagram schematically showing a drive mechanism of a hybrid vehicle to which an engine start control device according to a first embodiment of the present invention is applied.
FIG. 2 is a drawing schematically showing an entire engine system according to the first embodiment of the present invention.
FIG. 3 is a flowchart illustrating a process related to torque distribution between an engine and a motor performed by an ECU according to the first embodiment when the vehicle restarts from a stopped state in which an idle stop is performed.
FIG. 4 is a flowchart illustrating an engine control process performed by an ECU according to the first embodiment.
FIG. 5 is a graph showing the relationship between the advance corrected airflow sensor output value and the actual intake air amount;
FIG. 6 is a time chart illustrating an operation state of the apparatus, a change in a signal, and the like when starting from an idle stop in the first embodiment.
FIG. 7 is a flowchart illustrating an engine control process performed by an ECU according to a second embodiment.
[Explanation of symbols]
1: Hybrid vehicle 2: CVT automatic transmissions 4, 6: Drive wheels 8: Engine 10: Motor 14: Battery

Claims (7)

An intake air amount sensor that is arranged in an intake passage of the engine and outputs an intake air amount signal with a delay with respect to an actual intake amount;
Correction means for performing a predetermined first advance correction on the intake air amount signal from the intake air amount sensor;
Fuel injection control means for controlling fuel injection to the engine based on the corrected intake air amount signal,
The correction means performs a second advance correction different from the predetermined first advance correction during a predetermined period after the engine is started.
An engine start control device for a vehicle. The fuel injection control means, in a predetermined vehicle stop state, stops fuel injection and stops the engine,
A motor that drives wheels when restarting from the vehicle stopped state, and that starts the engine by cranking,
The engine start control device for a vehicle according to claim 1. The motor drives the wheels to creep the vehicle during the restart,
The fuel injection control means restarts the fuel injection control to the engine after the creep running is started,
The engine start control device for a vehicle according to claim 2. Rotation speed change detection means for detecting a rotation speed change of the engine,
Learning means for changing the content of the second advance correction based on the change in the number of revolutions during fuel injection control by the fuel injection control means based on the second correction.
An engine start control device according to any one of claims 1 to 3. The advance correction is a correction for performing a differentiation process on the output value of the intake air amount sensor,
An engine start control device for a vehicle according to any one of claims 1 to 4. The fuel injection control means starts fuel injection in a state where the wheels and the engine are fastened,
An engine start control device for a vehicle according to any one of claims 1 to 5. An intake air amount sensor that is arranged in an intake passage of the engine and outputs an intake air amount signal with a delay with respect to an actual intake amount;
Correction means for performing advance correction on the intake air amount signal from the intake air amount sensor;
Fuel injection control means for controlling fuel injection to the engine based on the corrected intake air amount signal,
The fuel injection control means performs a fuel injection control of a fuel injection amount smaller than a combustion injection amount calculated based on the advance correction for a predetermined period after the engine start,
An engine start control device for a vehicle.

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