JP4165237B2 - Start control device for internal combustion engine - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a start control device for an internal combustion engine, and more particularly to a start control device that can prevent the internal combustion engine from blowing up at the start.
[0002]
[Prior art]
Recently, in order to reduce fuel consumption and exhaust gas when idling, from the viewpoint of environmental conservation or resource saving energy, when the vehicle stops, the internal combustion engine (hereinafter also referred to as “engine”) is automatically stopped. An engine stop / start control device is known that automatically restarts an engine when a start instruction is issued from a stopped state to start the vehicle. This control is also called “idling stop”.
[0003]
In the case of automatically performing the idling stop technology, it has been found that it is effective to control the stop position of the engine in order to minimize the required energy when starting the engine. By minimizing the energy required when starting the engine, the engine starter after idling stop, such as a motor generator (MG), can be downsized, and the battery life can be extended by reducing the electrical energy. There is an advantage.
[0004]
As a problem that may occur at the time of automatic engine start after idling stop, there is an engine blow-up. While the engine is stopped, the surge tank is generally at atmospheric pressure and the negative pressure is usually insufficient. Therefore, if fuel injection is performed when the engine is started, the intake pipe negative pressure is small, so the fuel injection amount increases and the explosion energy increases. As a result, the idling speed temporarily increases until the negative pressure in the intake pipe is secured. This is called “blow-up”. The blow-up causes a reduction in fuel consumption and causes vibration and noise when starting the engine. In particular, in an eco-run car or the like, if the engine blows up every time the engine is automatically started after idling is stopped, the driver often feels uncomfortable.
[0005]
In order to prevent such a blow-up, the engine speed is increased with a motor until the negative pressure in the surge tank is secured during automatic engine start, and fuel injection is performed after the negative pressure is secured. A method of switching to driving by an engine has been proposed (for example, Patent Document 1).
[0006]
[Patent Document 1]
JP 2001-304007 A
[0007]
[Problems to be solved by the invention]
However, as described above, the method of driving the engine by the motor generator until the negative pressure in the surge tank is ensured requires a lot of electric power when the engine is automatically started. Moreover, in order to ensure the electric power, the power generation load resistance at the time of idling increases, which adversely affects fuel consumption. Further, since a large amount of electric power is used, a high voltage, high output motor generator is required, resulting in an increase in cost.
[0008]
The present invention has been made in view of the above points, and provides a start control device for an internal combustion engine that can prevent a blow-up during an automatic engine start without requiring a large amount of electric power. Let it be an issue.
[0009]
[Means for Solving the Problems]
According to one aspect of the present invention, an internal combustion engine start control device includes: an engine start unit that cranks and starts an engine with an electric motor; a rotation number detection unit that detects a rotation number of the engine; Negative pressure state detecting means for detecting that the negative pressure has become normal; and combustion control means for supplying fuel to the engine to execute combustion, wherein the combustion control means is provided by the engine starting means. Combustion starting means for executing combustion in a predetermined cylinder of the engine at the time of starting the engine, and when the rotational speed detected by the rotational speed detecting means after the engine starts becomes equal to or higher than a predetermined target rotational speed Combustion stop means for stopping fuel supply to at least some of the predetermined cylinders, and when the negative pressure state detection means detects that the negative pressure has become normal, the at least one Part And a combustion resuming means resumes the fuel supply to the cylinder.
[0010]
According to the above internal combustion engine start control device, for example, when the engine is automatically started at an idling stop or the like, the engine is first cranked and started by an electric motor, and combustion is performed in a predetermined cylinder. When the engine speed increases due to the execution of combustion and exceeds the predetermined target speed, the fuel supply to at least some of the cylinders that started combustion is stopped to stop the combustion. Since the negative pressure in the engine is insufficient at the start of the engine, the engine speed can rapidly increase after combustion starts and a so-called blow-up can occur, but by stopping combustion in some cylinders, the engine speed can be reduced. It is further lifted to prevent blow-up. After that, when it is detected that the negative pressure of the engine is in a normal state, there is no risk of a sudden increase in engine speed due to insufficient negative pressure, so fuel supply to the stopped engine is resumed and combustion is resumed. . As described above, it is possible to prevent a blow-up at the time of starting the engine.
[0011]
In one aspect of the start control apparatus for an internal combustion engine, the combustion stopping unit stops the fuel supply to the plurality of cylinders, and the combustion resuming unit sequentially restarts the combustion of the plurality of cylinders. When combustion is restarted after stopping combustion in a plurality of cylinders to prevent blow-up, restarting combustion in all of the cylinders at the same time may cause the engine speed to increase suddenly and cause vibration of the vehicle. . Therefore, the vibrations and noises of the vehicle are suppressed by restarting combustion of all the cylinders in order, not all at the same time.
[0012]
In this case, the combustion of the plurality of cylinders can be resumed in order at predetermined time intervals, and the combustion can be resumed in the order in which the engine is unlikely to vibrate. Thereby, it is possible to prevent the driver from feeling uncomfortable due to a sudden increase in the engine speed.
[0013]
One aspect of the start control device for the internal combustion engine further includes means for detecting an input of an acceleration request by a driver, wherein the combustion control means detects the acceleration request before the combustion is stopped by the combustion stop means. If this happens, stop of combustion by the combustion stop means is prohibited. Further, one aspect of the start control device for the internal combustion engine further includes means for detecting an input of an acceleration request by a driver, and the combustion control means detects the acceleration request after the combustion is stopped by the combustion stop means. If it has been done, the combustion is immediately restarted by the combustion restarting means regardless of the detection result by the negative pressure state detecting means.
[0014]
When the driver inputs an acceleration request by turning on the accelerator while the combustion is stopped in some cylinders to prevent the engine from blowing up, it is not necessary to suppress the increase in the rotational speed. It is preferable to accelerate quickly by increasing the number of revolutions. Therefore, if an acceleration request is input before stopping combustion to prevent blow-up, combustion stop is not executed from the beginning. Further, when an acceleration request is input while combustion is stopped to prevent blow-up, combustion is immediately resumed to meet the acceleration request.
[0015]
In one aspect of the start control device for an internal combustion engine, combustion is resumed by the combustion resuming means when the engine speed falls below a predetermined reference speed while combustion is stopped by the combustion stopping means. When combustion is stopped in some cylinders in order to prevent blow-up, engine stall may occur if the engine speed is too low for some reason. Therefore, the engine speed at which engine stall is assumed to occur when the engine speed is lower than that is set as the reference engine speed, and when the engine speed becomes lower than that, combustion is resumed to prevent engine stall.
[0016]
According to one aspect of the start control device for an internal combustion engine, when the engine speed decreases below a predetermined reference speed while the combustion is stopped by the combustion stop means, the engine is driven to rotate by the electric motor. A means for suppressing a decrease in number is further provided. As described above, when the engine speed is too low during combustion stop, combustion is restarted to prevent engine stall. At that time, engine can be driven by an electric motor to reliably prevent engine stall. it can. In this case, it is preferable that the engine is driven by an electric motor so as to maintain the rotational speed of the engine at or above the reference rotational speed.
[0017]
In one aspect of the start control device for an internal combustion engine, the combustion control unit determines a cylinder in which the combustion state after the resumption of combustion by the combustion resuming unit is not in a normal state, and thereafter, the combustion stop unit Prohibit combustion stop of cylinder. If there is a cylinder that does not resume combustion normally even though it has been instructed to resume combustion, the control for stopping and restarting combustion of that cylinder becomes unstable, and thereafter, the combustion is stopped in that cylinder. To stabilize the combustion control. Here, the cylinder in which the combustion state is not in a normal state can be, for example, a cylinder in which the engine speed does not increase even though combustion is resumed.
[0018]
In one aspect of the internal combustion engine start control apparatus, the combustion control means performs an ignition operation even when the fuel supply is stopped. If fuel injection is stopped in a specific cylinder to prevent blow-up, if ignition operation is also stopped, unburned fuel will be discharged to the exhaust side when there is fuel remaining in the cylinder. Problems can arise. Therefore, while combustion is stopped, ignition is continued even if fuel injection is stopped, thereby preventing unburned fuel from being discharged.
[0019]
In one aspect of the start control device for an internal combustion engine, the negative pressure state detection means determines that the negative pressure of the engine has become a normal state when a predetermined time has elapsed after the start of the engine. Usually, since the time required until the negative pressure becomes normal after the engine is started is substantially constant, the negative pressure state can be detected based on the elapsed time after the engine is started.
[0020]
In one aspect of the start control device for an internal combustion engine, the negative pressure state detection means determines that the negative pressure of the engine is in a normal state when an air flow rate in the engine becomes equal to a predetermined air flow rate. To do. When the negative pressure of the engine is ensured, the air flow rate in the engine shows a standard value, so that the negative pressure state can be detected based on the air flow rate in the engine.
[0021]
In one aspect of the start control apparatus for an internal combustion engine, the combustion stop means can increase the number of cylinders that stop the fuel supply as the difference between the detected rotation speed and the target rotation speed is larger. Thereby, fuel injection can be stopped by the number of cylinders according to the degree of blow-up, and blow-up can be effectively suppressed.
[0022]
DETAILED DESCRIPTION OF THE INVENTION
Preferred embodiments of the present invention will be described below with reference to the drawings.
[0023]
[Vehicle configuration]
First, a schematic configuration of a vehicle including a start control device for an internal combustion engine according to the present invention will be described. The start control device for an internal combustion engine according to the present invention targets a so-called eco-run vehicle or a hybrid vehicle to which an idling stop technology is applied. An “eco-run vehicle” is a vehicle that is equipped with an electric motor (motor generator) mainly for the purpose of starting the engine and that automatically restarts the engine by the motor generator after the engine is stopped by idling stop. The “hybrid vehicle” is a power train that uses an engine and a motor generator as power sources. In a hybrid vehicle, it is possible to obtain smooth and responsive power performance by cooperating or selectively using both the engine and the motor generator according to the running state.
[0024]
FIG. 1 shows a system configuration of a vehicle 10 according to the present invention.
[0025]
As shown in FIG. 1, the vehicle 10 includes a DC starter 1, an engine 2, a motor generator 3 that can be driven as a cell motor when the engine 2 is started while generating electric power by driving force output from the engine 2, and a motor A motor control device 4 for controlling the generator 3 and the like, a power supply device 5 that exchanges power with the motor generator 3 and the like via the motor control device 4, and the motor generator 3, the motor control device 4, and the power supply device 5. A power cable 6 to be connected, a power transmission device 7 for transmitting a driving force generated from the engine 2 to the wheels, and a wheel 8 are provided.
[0026]
Next, each configuration will be described with reference to FIG.
[0027]
The DC starter 1 is a direct-current cell motor that starts the engine 2. The DC starter 1 has a shaft. When the ignition switch is turned on, the DC starter 1 receives power supplied from the 12V power supply device and rotates the shaft. When the shaft of the DC starter 1 rotates, the crankshaft of the engine 2 is rotated and the engine 2 is started. Specifically, a pinion gear is attached to the tip of the shaft of the DC starter 1. The pinion gear meshes with a ring gear of a flywheel provided on the crankshaft of the engine 2. Therefore, when the DC starter 1 receives power supply from the 12V power supply by starting the engine 2, the pinion gear meshes with the ring gear of the flywheel and rotates, thereby rotating the flywheel. As a result, the crankshaft to which a predetermined number of cylinders of pistons are connected is rotated, so that the engine 2 can be started by the rotational driving force. Driving the crankshaft to start the engine is called “cranking”.
[0028]
The engine 2 is an internal combustion engine that generates power by causing an air-fuel mixture in a cylinder to explode. The internal combustion engine includes a gasoline engine using gasoline as a fuel, or a diesel engine using light oil as a fuel. The gasoline engine is a four-cycle gasoline engine that generates power by completing one cycle of intake, compression, expansion, and exhaust during two revolutions of the crankshaft, or the aforementioned one cycle during one revolution of the crankshaft. There is a two-cycle gasoline engine that completes. Note that the vehicle 10 in the present embodiment is a four-cycle gasoline engine.
[0029]
FIG. 2 shows an example of a schematic configuration of the engine 2.
[0030]
An intake port 24 formed in the cylinder head 12 is opened and closed by an intake valve 26. Intake air is supplied to the intake port 24 via an intake passage 28. A surge tank 30 is provided in the intake passage 28, and a throttle valve 32 is provided upstream of the surge tank 30. The opening degree of the throttle valve 32 (throttle opening degree TA) is adjusted by an electric motor 34, and the throttle opening degree TA is detected by a throttle opening degree sensor 36.
[0031]
The engine 2 is a so-called port injection type engine, and a fuel injection valve 14 is provided in an intake port 24. An air-fuel mixture is generated by the intake air in the intake port 24 and the fuel injected into the intake port 24 and is introduced into the combustion chamber 20 defined by the cylinder block 16, the piston 18 and the cylinder head 12. A spark plug 22 is disposed on the ceiling portion of the combustion chamber 20 so that the air-fuel mixture introduced from the intake port 24 can be ignited. The fuel injection valve 14 is supplied with high-pressure fuel from a high-pressure fuel pump (not shown) via a delivery pipe 14a. Thus, fuel can be injected from the fuel injection valve 14 into the combustion chamber 20 even at the end of the compression stroke. The fuel pressure in the delivery pipe 14a is detected by a fuel pressure sensor 14b.
[0032]
An exhaust port 38 formed in the cylinder head 12 is opened and closed by an exhaust valve 40. Exhaust gas discharged from the combustion chamber 20 to the exhaust port 38 is discharged to the outside through the exhaust passage 42 and an exhaust purification catalyst (not shown).
[0033]
The reciprocating motion of the piston 18 accompanying the combustion of the air-fuel mixture in the combustion chamber 20 is converted into the rotational motion of the crankshaft 46 via the connecting rod 44. The crankshaft 46 transmits power to the wheels 8 via a torque converter and a transmission (not shown).
[0034]
Apart from such a power transmission system, one end of the crankshaft 46 is connected to a pulley 50 (hereinafter also referred to as “crankshaft pulley”) via an electromagnetic clutch 48. The pulley 50 can transmit power to the other three pulleys 54, 56, and 58 by a belt 52. In this example, the air conditioner compressor 60 can be driven by the pulley 54, and the power steering pump 62 can be driven by the pulley 56. Another pulley 58 (hereinafter also referred to as “MG pulley”) is connected to the motor generator 3. The motor generator 3 has both a function as a generator that generates power by the engine driving force from the MG pulley 58 side and a function as an electric motor that supplies the driving force of the motor generator 3 to the MG pulley 58 side.
[0035]
An ECU 70 (Engine Control Unit) mainly composed of a microcomputer is composed of an input / output device, a storage device, a central processing unit, and the like, and comprehensively controls the system of the vehicle 10. The ECU 70 controls the vehicle 10 to an optimum state based on input information from sensors and the like mounted on the engine 2. Specifically, the ECU 70 controls the fuel pressure from the fuel pressure sensor 14b, the throttle opening TA from the throttle opening sensor 36, the motor generator rotation speed from the rotation speed sensor built in the motor generator 3, the voltage of the power supply device 5 or the charge / discharge. Current amount, ignition switch 72 switch state, vehicle speed sensor 74 to vehicle speed SPD, accelerator opening sensor 76 to accelerator pedal depression amount (accelerator opening ACCP), brake switch 78 to brake pedal depression, engine speed From the sensor 80 to the rotation speed of the crankshaft 46 (engine rotation speed NE), from the air flow meter 82 to the intake air amount GA, from the cooling water temperature sensor 84 to the engine cooling water temperature THW, from the idle switch 86 to whether the accelerator pedal is depressed, to the exhaust passage 42 Establishment Air-fuel ratio sensor 88 air-fuel ratio detection value from Vox that, the rotational position of the cam shaft (not shown) from the cam angle sensor 92, the crank angle from the crank angle sensor 90 are respectively detected.
[0036]
Based on the data obtained in this way, the ECU 70 drives the electric motor 34 to adjust the throttle opening degree TA and adjust the injection timing from the fuel injection valve 14. Further, when the automatic stop condition is satisfied, the fuel injection from the fuel injection valve 14 is stopped, and the operation of the engine 2 is automatically stopped. When the automatic start condition is satisfied, the crankshaft 46 is rotated by the driving force of the motor generator 3 through the pulley 58, the belt 52, the pulley 50, and the electromagnetic clutch 48, and the engine 2 is started. Further, the ECU 70 performs ignition timing control and other necessary control.
[0037]
The motor generator 3 is connected to the crankshaft 46 through the pulley 50, the pulley 58, and the belt 52. When one of the crankshaft pulley 50 connected to the crankshaft 46 or the MG pulley 58 connected to the motor generator 3 is rotationally driven, power is transmitted to the other via the belt 52.
[0038]
The motor generator 3 has a function as a motor (electric motor) that rotates by receiving power supply from a power supply device 5 to be described later, and is three-phase when rotating by receiving a rotational driving force from the wheels 8. It also has a function as a generator (generator) that generates electromotive force at both ends of the coil. When the motor generator 3 functions as an electric motor, the motor generator 3 rotates upon receiving power supply from the power supply device 5, and transmits the rotational driving force to the crankshaft pulley 50 to rotate the crankshaft 46 to rotate the engine 2. Start. On the other hand, when the motor generator 3 functions as a generator, the rotational driving force from the wheels 8 is transmitted to the MG pulley 58 on the motor generator side via the crankshaft 46 and the crankshaft pulley 50 to rotate the motor generator 3. Let When the motor generator 3 rotates, an electromotive force is generated in the motor generator 3, and the electromotive force is converted into a direct current via the motor control device 4 to supply power to the power supply device 5. Thereby, the power supply device 5 is charged.
[0039]
Returning to FIG. 1, the motor angle sensor 3 a is preferably provided at a predetermined position in the motor generator 3 with a Hall element or the like suitably applied to the detection unit. The motor angle sensor 3a can detect the rotation angle of the shaft of the motor generator 3 with a high accuracy of approximately 7.5 ° CA. When the motor generator 3 is rotated by receiving power supplied from the power supply device 5, the motor angle sensor 3a detects the rotation angle of the shaft. Specifically, the motor angle sensor 3a is provided in each of the phases so as to detect the alternating currents of the U, V, and W phases. Each motor angle sensor 3a detects the alternating current of each phase of U, V, and W, converts it into a pulse signal, and outputs it to the motor control device 4 described later.
[0040]
The motor control device 4 is provided in the engine 2 and is connected to the motor generator 3, the power supply device 5, and the power supply cable 6. The motor control device 4 is mainly composed of an inverter, a converter, a control computer, or the like.
[0041]
The inverter converts the high-voltage direct current from the power supply device 5 into a predetermined three-phase alternating current, and supplies power to the motor generator 3. On the contrary, the inverter converts the electromotive force (three-phase alternating current) generated from the motor generator 3 into a direct current suitable for charging the power supply device 5.
[0042]
The converter is a DC / DC converter that converts a predetermined DC voltage to a predetermined DC voltage. That is, the converter steps down the rated voltage (for example, 36V voltage) of the power supply device 5 to a predetermined voltage (for example, 12V voltage) to drive auxiliary equipment or to a 12V power supply device mounted on a vehicle. Charge the battery.
[0043]
The control computer controls the inverter and the converter. That is, the control computer controls the driving torque and power generation amount of the motor generator 3 to an optimal state, and charges the power supply device 5 by controlling the charging amount to the optimal state. Specifically, when the motor generator 3 functions as an electric motor, the control computer controls the driving torque and power generation amount of the motor generator 3 based on the electric power supplied from the power supply device 5. As a result, the motor generator 3 is controlled to an optimum state for functioning as an electric motor. On the other hand, when the motor generator 3 functions as a generator, the control computer supplies a predetermined direct current to the power supply device 5 based on the electromotive force generated from the motor generator 3 to charge the power supply device 5. Do.
[0044]
The power supply device 5 is a secondary battery such as a lead storage battery or a nickel metal hydride battery. The power supply device 5 is installed, for example, at the rear of the vehicle 10 in order to improve the space efficiency of the vehicle 10 and the like. The power supply device 5 can be set to a rated voltage of 36V, for example. Therefore, the power supply device 5 has high input / output characteristics in starting the motor generator 3 or in energy regeneration during vehicle braking. Specifically, the power supply device 5 supplies power to the auxiliary machines, the motor generator 3 and the like. The power supply to the motor generator 3 is mainly performed while the vehicle 10 is stopped. When the vehicle 10 is traveling or braking, an electromotive force generated from the motor generator 3 is converted into a direct current through the motor control device 4 and supplied to the power supply device 5. Thereby, the power supply device 5 can be charged.
[0045]
As described above, the power cable 6 is connected to the motor generator 3 and the motor control device 4, and the motor control device 4 and the power supply device 5, respectively, and plays a role of flowing a direct current or a three-phase alternating current.
[0046]
The power transmission device 7 mainly includes a torque converter, a lockup clutch, a transmission, a power switching mechanism, and the like. When these act organically, the power transmission device 7 transmits or blocks the rotational driving force generated from the engine 2 or the motor generator 3 to the wheels 8 according to the traveling state or the like. The power transmission device 7 transmits the rotational driving force from the wheels 8 to the motor generator 3 conversely during braking or the like.
[0047]
The wheels 8 are an axle, a tire, and the like that transmit the rotational driving force from the power transmission device 7 to the road surface. In the present embodiment, a rear wheel is illustrated as the wheel 8.
[0048]
[Vehicle operation]
Next, the operation of the vehicle 10 having the above configuration will be described. The vehicle 10 performs various operations according to each driving state such as stopping, starting, normal traveling, accelerated traveling, or braking.
[0049]
The vehicle 10 automatically stops idling, that is, the engine 2 when traveling is stopped. At this time, the vehicle 10 is controlled so that the crank angle is stopped at the optimum crank angle stop position inside the engine 2 at the time of idling stop in order to enable a smooth start when the engine 2 is automatically started.
[0050]
During the automatic stop (idling stop) of the vehicle 10, the engine 2 is in a stopped state. In this state, when it is necessary to drive an auxiliary machine such as an air compressor, a water pump, or a power steering pump, the motor generator 3 receives power supply from the power supply device 5 without driving the engine 2. Drive those auxiliary machines. However, since the engine 2 and the motor generator 3 are rotatably connected to each other by a V-belt via respective pulleys, in this state, the rotation driving force is generated by the rotation of the shaft of the motor generator 3. It is transmitted to the engine 2. Therefore, in order to drive only the auxiliary machines, the electromagnetic clutch is operated so that the crankshaft of the engine 2 does not rotate, and the rotational driving force from the motor generator 3 is cut off. Thereby, it is possible to drive only the auxiliary machines without driving the engine 2.
[0051]
When the vehicle 10 is started, that is, in the idling stop state, when the driver removes his / her foot from the brake pedal, the motor generator 3 performs cranking and starts the engine 2. Thereafter, combustion is performed in a specific cylinder (all cylinders or some cylinders) of the engine 2 to increase the rotational speed to near the idling rotational speed. Thereafter, when the driver turns on the accelerator, the engine 2 increases the rotational speed and accelerates.
[0052]
During normal travel, the vehicle 10 travels with the driving force from the engine 2 transmitted to the wheels 8 in the same manner as a general vehicle. When the voltage of power supply device 5 is reduced during normal travel, the driving force from wheels 8 is transmitted to motor generator 3 and motor generator 3 generates power. Thereby, the motor generator 3 functions as a generator, and charges the power supply device 5 in order to supplement the power shortage of the power supply device 5 (hereinafter, this operation state is referred to as “regeneration”). Therefore, the power supply device 5 is always maintained in an appropriate charged state.
[0053]
When the vehicle 10 travels uphill or accelerates, the motor generator 3 is driven using the power of the power supply device 5 in addition to the above-described normal traveling state in order to exhibit appropriate power performance. 3 can be applied to the rotational driving force of the engine 2 (hereinafter, this operating state is referred to as “assist”). As a result, the vehicle 10 has two power sources of the engine 2 and the motor generator 3. Can be used effectively to obtain high power performance.
[0054]
At the time of braking in deceleration or the like, the driving force by the wheels 8 is transmitted to the motor generator 3 via the power transmission device 7 and the engine 2 and regeneration is performed.
[0055]
[Engine start control]
(First embodiment)
Next, engine start control according to the present invention will be described. FIG. 3A shows a change in the engine speed at the time of normal engine start. In FIG. 3A, if the engine is automatically started at time t0 and fuel injection is started, fuel injection and ignition are performed in all or a part of all cylinders (four cylinders in this embodiment) of the engine. The engine speed increases rapidly as shown in the figure. Assuming that the idling speed in the normal state of the engine is referred to as “target idling speed NEt”, the engine speed continues to increase even if it exceeds the target idling speed. This is because, as described above, the inside of the surge tank is almost atmospheric pressure while the engine is stopped, and the fuel injection amount suddenly increases because the negative pressure in the intake pipe is insufficient when starting the engine. .
[0056]
In order to prevent such a blow-up, in the present invention, in order to avoid an excessive increase in the engine speed when the engine speed reaches the target idling speed after the engine is started, fuel is supplied to some cylinders. Perform the cut. When the negative pressure in the intake pipe of the engine is secured, the fuel cut is stopped and the normal fuel injection state is restored. The fuel injection and the fuel cut are executed by the ECU 70 controlling the fuel injection valve 14 of the engine 2.
[0057]
FIG. 3B shows the state of control according to the present invention. In FIG.3 (b), a vertical axis | shaft shows an engine speed and a horizontal axis shows the elapsed time after an engine automatic start. Referring to FIG. 3 (b), the engine is automatically started at time t0. The cranking operation at the time of automatic engine start is performed using the motor generator 3, and then fuel injection and ignition are performed in all cylinders (four cylinders in the present embodiment) or a part of the engine. As a result, the engine speed rapidly increases. After the engine is started, the ECU 70 monitors changes in the engine speed based on the output of the engine speed sensor 80. When it is detected that the engine speed has reached the target idling speed (time t1), it is determined that the engine has been successfully started, and fuel cut is executed in one or more cylinders. However, from the viewpoint of preventing engine stop (engine stall), at least one cylinder continues to inject fuel.
[0058]
The number of cylinders that execute the fuel cut can be determined according to the increase degree of the engine speed. As the number of cylinders that perform fuel cut increases, the effect of suppressing an excessive increase in the engine speed increases, but the vibration of the engine also increases. Therefore, it is preferable to perform fuel cut with the minimum number of cylinders based on the degree of increase in engine speed. Specifically, the relationship between the transition of the engine speed and the number of cylinders for which fuel cut should be performed may be determined and stored in advance. For example, in the case of a four-cylinder engine as in the present embodiment, reference engine speeds NE1 to NE3 (NE1 <NE2 <NE3) are set to engine speeds higher than the target idling engine speed NEt, respectively, and the engine speed is NE1. If the engine speed exceeds NE2, the fuel will be cut by 1 cylinder (total 2 cylinders). If the engine speed exceeds NE3, 1 cylinder (total 3 cylinders) will be cut. ) To cut the fuel.
[0059]
Thus, after the engine speed exceeds the target idling speed NEt, fuel cut is performed with an appropriate number of cylinders to prevent the engine speed from rising excessively and causing a blow-up.
[0060]
When the ECU 70 detects that the negative pressure in the engine surge tank (intake passage) is secured (time t2), the ECU 70 resumes fuel injection in the cylinders that have been fuel cut until then. After the negative pressure in the surge tank is secured, no blow-up occurs, and thereafter fuel injection is performed in all cylinders as usual.
[0061]
The determination of whether or not the negative pressure in the surge tank has been secured can be made by several methods. One method is a method of judging based on the elapsed time after the engine is started. Usually, the time required until the negative pressure in the surge tank is ensured after the start of the engine is almost constant. Therefore, the predetermined time required for ensuring the negative pressure in the surge tank is determined in advance, and the ECU 70 ends the fuel cut for preventing the blow-up and stops the fuel injection when the predetermined time has elapsed. do it.
[0062]
Another method is to make a determination based on the air flow rate in the intake passage. When the negative pressure in the surge tank is secured, the air flow rate in the intake manifold shows a standard value. Therefore, a predetermined air flow rate in a state where a negative pressure is ensured in the surge tank is determined in advance, and the ECU 70 monitors the output of the air flow meter 82 to prevent a blow-up when the predetermined air flow rate is detected. Therefore, the fuel cut may be finished. In addition, you may judge that the negative pressure in a surge tank was ensured by methods other than these.
[0063]
As described above, according to the present embodiment, after the engine is automatically started, when the engine speed exceeds a predetermined target idling speed, the fuel is cut by an appropriate number of cylinders. Can be prevented from rising rapidly. As a result, it is possible to save useless fuel that is consumed by an unnecessary increase in engine speed when the engine is blown up. Further, since it is only necessary to temporarily stop fuel injection in a specific cylinder, it is possible to prevent the blow-up at a low cost without requiring a large amount of power.
[0064]
It should be noted that in a cylinder that performs fuel cut to prevent blow-up, fuel injection is not performed, but it is desirable to continue ignition. This is because even after starting the fuel cut, some fuel may remain in the cylinder and the like, and if it stops until ignition, unburned fuel may flow out to the exhaust side. It is.
[0065]
An example of fuel cut by the engine start process according to the present embodiment will be described with reference to FIGS. 4 (a) and 4 (b). FIG. 4A shows the transition of the engine speed after the engine is started, and is basically the same as FIG. 3B. FIG. 4B shows an example of change in the number of cylinders that perform fuel injection in the case shown in FIG. 4 (a) and 4 (b), when the engine is started at time t0, first, fuel injection is performed in all four cylinders. After that, when the engine speed reaches the target idling speed NEt at time t1, fuel cut is sequentially performed for each cylinder as the engine speed increases. Then, the fuel cut is performed with a total of three cylinders at maximum. Thereafter, when it is detected that the negative pressure in the surge tank is secured at time t2, fuel injection is resumed in all four cylinders.
[0066]
The method of selecting the cylinder that performs the fuel cut for preventing the blow-up may be selected at random, or may be selected according to a predetermined rule. When selecting a plurality of cylinders to perform fuel cut, it is preferable to give priority to a combination in which vibrations and the like are unlikely to occur in engine rotation in consideration of an ignition order.
[0067]
Next, engine start control according to the present embodiment will be described with reference to the flowchart of FIG. First, the ECU 70 determines whether or not an engine start condition is satisfied (step S1). The engine start condition can be, for example, when the driver detects that the brake is turned off in the idling stop state. When the engine start condition is satisfied, the ECU 70 first performs cranking by the motor generator 3, then performs fuel injection and ignition in a predetermined cylinder, and starts the engine (step S2). In this case, fuel injection and ignition may be performed in all cylinders or in some cylinders.
[0068]
Thereafter, the ECU 70 monitors the engine speed NE and detects that the engine speed NE has exceeded the target idling speed NEt (ie, NE> NEt) (step S3; Yes). Fuel cut is performed with an appropriate number of cylinders according to the degree of increase in the rotational speed (step S4). Then, the ECU 70 determines whether or not the negative pressure in the surge tank is secured (step S5). As described above, whether or not the negative pressure is secured can be determined based on the elapsed time from the engine start, the air flow rate in the engine, and the like. Until the negative pressure is secured, the process returns to step S4, and the ECU 70 continues the fuel cut in the specific cylinder. On the other hand, when the negative pressure is secured (step S5; Yes), the ECU 70 ends the fuel cut and restarts fuel injection in all cylinders (step S6). Thus, since the fuel cut is performed in the required number of cylinders until the negative pressure in the surge tank is ensured, the occurrence of the blow-up phenomenon can be prevented.
[0069]
(Second Embodiment)
Next, a second embodiment of the present invention will be described. The second embodiment is basically the same as the first embodiment described above. However, the method for restarting the fuel injection of the cylinder which has been performing the fuel cut for preventing the blow-up is different. In the first embodiment, when the negative pressure in the surge tank is ensured, as shown in FIG. 4B, fuel injection is resumed simultaneously in all the cylinders that have been fuel cut. However, if the number of cylinders that have been subjected to fuel cut is large, restarting fuel injection in all cylinders at the same time may cause the engine speed to increase rapidly, resulting in vibration and noise.
[0070]
Therefore, in this embodiment, the fuel injection is not restarted simultaneously in all the cylinders, but the fuel injection is restarted sequentially at a predetermined number of time intervals, for example, one cylinder or two cylinders. This state is shown in FIG. In this example, when it is detected that the negative pressure in the surge tank is secured at time t2, the fuel injection is resumed at predetermined time intervals one by one in order. As a result, it is possible to prevent the engine speed from rapidly increasing and causing the driver to feel uncomfortable.
[0071]
Further, it is preferable that the order of restarting fuel injection in a plurality of cylinders is restarted in the order in which the engine is unlikely to vibrate in consideration of the ignition order of each cylinder.
[0072]
The processing of the second embodiment is basically the same as that of the first embodiment shown in FIG. However, when the fuel injection is restarted in all the cylinders in step S6, the fuel injection is sequentially restarted in a predetermined order, not all the cylinders that have been performing the fuel cut.
[0073]
(Third embodiment)
Next, a third embodiment of engine start control according to the present invention will be described. The third embodiment relates to processing when an accelerator is turned on by the driver during the engine start control described above. In the engine start control described above, the fuel was cut to prevent the engine from being blown up at the time of automatic engine start such as idling stop, but when the driver turns on the accelerator after the engine is automatically started, There is no problem with the engine speed increasing rapidly, but rather it allows the vehicle to operate quickly in response to the driver's accelerator input. Therefore, when the accelerator is turned on by the driver during the engine start control, the fuel cut for preventing the blow-up is not performed.
[0074]
Specifically, when the accelerator is turned on after the engine start control is started and before the engine speed reaches the target idling speed NEt (between times t0 and t1 in FIG. 3B), the engine speed is thereafter increased. Even when the engine speed exceeds the target idling speed, fuel cut for preventing blow-up is not performed. If the accelerator is turned on during fuel cut for the blow-up prevention process (between times t1 and t2 in FIG. 3B), the normal operation mode is immediately restored and fuel injection is performed in all cylinders. Resume.
[0075]
FIG. 6 shows a flowchart of engine start control according to this embodiment. When the engine start condition is satisfied (step S11; Yes), the ECU 70 performs cranking by the motor generator 3, and subsequently performs fuel injection / ignition in a predetermined cylinder (step S12). As a result, the engine speed rapidly increases. Then, the ECU 70 determines whether the accelerator is turned on until the engine speed NE exceeds the target idling speed NEt (step S13). If the accelerator is turned on, the ECU 70 does not perform the blow-up prevention process. The process ends.
[0076]
On the other hand, when the engine speed NE exceeds the target idling speed NEt without turning on the accelerator (step S14; Yes), the ECU 70 performs the fuel cut for preventing the blow-up as in the previous embodiment. In step S15, it is detected whether or not the accelerator is turned on (step S16). If the accelerator is turned on before the negative pressure in the surge tank is secured (step S16; Yes), the ECU 70 ends the fuel cut for preventing the blow-up and restarts the fuel injection in all cylinders ( Step S18).
[0077]
On the other hand, when it is detected that the negative pressure in the surge tank is secured without detecting the accelerator on (step S17; Yes), the ECU 70 finishes the fuel cut for preventing the blow-up and fuels in all cylinders. The injection is resumed (step S18).
[0078]
As described above, in the present embodiment, after the start of the engine start control, when the driver's accelerator on is detected, the fuel cut for preventing the blow-up is not performed or all the cylinders are terminated. Inject fuel at. Thereby, it becomes possible to respond quickly to the accelerator input by the driver.
[0079]
(Fourth embodiment)
Next, a fourth embodiment of engine start control according to the present invention will be described. In the present embodiment, in order to prevent engine stall when the engine speed drops below a predetermined reference speed (hereinafter referred to as “NE3”) for some reason during the fuel cut for preventing the above-mentioned blow-up. In addition, fuel injection is resumed in all cylinders. Here, the predetermined reference rotational speed NE3 is a rotational speed at which the engine may cause an engine stall, and is normally set to a rotational speed lower than the target idling rotational speed.
[0080]
FIG. 7 shows a flowchart of engine start control according to the present embodiment. When the engine start condition is satisfied (step S21; Yes), the ECU 70 performs cranking by the motor generator 3, and subsequently performs fuel injection / ignition in a predetermined cylinder (step S22). As a result, the engine speed rapidly increases. Next, the ECU 70 detects whether or not the engine speed NE has exceeded the target idling speed NEt (step S23), and if it has exceeded, performs fuel cut in a specific cylinder to prevent the engine from blowing up (step S24). ).
[0081]
Then, the ECU 70 continues the fuel cut until the negative pressure in the surge tank is secured, but determines whether the engine speed has become equal to or lower than the predetermined speed NE3 during that time (step S25), and the predetermined speed When it becomes NE3 or less, fuel injection is restarted in all cylinders to prevent engine stall (step S27). Also, when the negative pressure in the surge tank is secured during the fuel cut for preventing the blow-up (step S26; Yes), the fuel injection is restarted in all the cylinders (step S27).
[0082]
In the above example, if the engine speed drops to a predetermined speed NE3 or less during fuel cut to prevent blow-up, fuel injection is forcibly restarted in all cylinders to prevent engine stall. However, the engine 2 can also be assisted by the motor generator 3 in order to prevent engine stall more reliably. That is, as shown by a broken line in FIG. 7, when it is detected in step S25 that the engine speed has decreased to a predetermined speed NE3 or less, the engine 2 is driven by the motor generator 3 to prevent engine stall ( In step S28, fuel injection can be restarted in all cylinders. This makes it possible to reliably prevent engine stall even when the engine speed is reduced.
[0083]
(Fifth embodiment)
Next, a fifth embodiment of engine start control according to the present invention will be described. In this embodiment, the ECU 70 determines whether or not fuel injection in the cylinder has been correctly restarted based on the change in the engine speed when the fuel injection is restarted in the cylinder after the fuel cut for preventing the blow-up is performed. Determine whether. That is, after instructing the cylinder that has been fuel cut to resume fuel injection, whether or not fuel injection in the cylinder has been resumed according to the instruction is determined by increasing the engine speed. If the fuel injection is not restarted as instructed for some reason, the engine speed cannot be increased by that amount, so the ECU 70 can know that the restart of the fuel injection in the cylinder has failed. If such a cylinder is found, fuel cut in the cylinder is prohibited in the subsequent engine start control.
[0084]
For example, after performing fuel cuts to prevent blow-up in the # 1 and # 3 cylinders of the four cylinders, the engine rotation is performed even though the ECU instructs the # 1 cylinder to resume fuel injection. If the number does not increase, the ECU 70 can determine that the restart of fuel injection has failed in the # 1 cylinder. Therefore, at the next engine start control, the fuel cut for preventing the blow-up is performed in the cylinders other than the # 1 cylinder. Thereby, it is possible to detect a cylinder in which fuel injection is not normal and take necessary measures. If injection in a specific cylinder is not performed in a normal running state, vibrations and noises may occur in the rotation of the engine, so that such a problem can be avoided.
[0085]
【The invention's effect】
As described above, according to the engine start control of the present invention, when the engine speed increases more than necessary, the fuel cut is performed in some cylinders, so that the blow-up at the start of the engine is prevented. be able to. As a result, fuel consumption can be prevented from being lowered, and vibrations at the time of starting the engine due to blowing up can be eliminated.
[Brief description of the drawings]
FIG. 1 shows a system configuration of a vehicle that performs engine stop control according to the present invention.
FIG. 2 is a schematic configuration diagram of an engine according to the present invention.
FIG. 3 is a graph showing changes in engine speed by engine start control of the present invention.
FIG. 4 is a graph showing changes in fuel injection cylinders in engine start control of the present invention.
FIG. 5 shows a flowchart of engine start control according to the first embodiment.
FIG. 6 shows a flowchart of engine start control according to a third embodiment.
FIG. 7 shows a flowchart of engine start control according to a fourth embodiment.
[Explanation of symbols]
1 DC starter
2 Engine
3 Motor generator
4 Motor controller
5 Power supply
6 Power cable
7 Power transmission device
8 wheels
9 ECU
10 Vehicle

Claims (15)

Engine starting means for cranking and starting the engine with an electric motor;
A rotational speed detection means for detecting the rotational speed of the engine;
Negative pressure state detecting means for detecting that the negative pressure in the engine is in a normal state;
Combustion control means for supplying fuel to the engine and executing combustion,
The combustion control means includes
Combustion starting means for executing combustion in a predetermined cylinder of the engine when the engine is started by the engine starting means;
Combustion stop for stopping fuel supply to at least some of the predetermined cylinders when the rotational speed detected by the rotational speed detection means is equal to or higher than a predetermined target rotational speed after starting the engine Means,
An internal combustion engine comprising: combustion resuming means for resuming fuel supply to at least some of the cylinders when the negative pressure state detecting means detects that the negative pressure has become normal. Start control device. 2. The start control device for an internal combustion engine according to claim 1, wherein the combustion stopping unit stops the fuel supply to the plurality of cylinders, and the combustion resuming unit sequentially restarts the combustion of the plurality of cylinders. The start control device for an internal combustion engine according to claim 2, wherein the combustion restarting means restarts the combustion of the plurality of cylinders in order at predetermined time intervals. 3. The start control device for an internal combustion engine according to claim 2, wherein the combustion resuming means restarts the combustion of the plurality of cylinders in an order in which vibration is hardly generated in the engine. Means for detecting an acceleration request input by the driver;
2. The internal combustion engine according to claim 1, wherein the combustion control unit prohibits the combustion stop by the combustion stop unit when the acceleration request is detected before the combustion stop by the combustion stop unit is stopped. 3. Engine start control device. Means for detecting an acceleration request input by the driver;
When the acceleration request is detected after the combustion is stopped by the combustion stop means, the combustion control means immediately restarts the combustion by the combustion restart means regardless of the detection result by the negative pressure state detection means. The start control device for an internal combustion engine according to claim 1. 2. The internal combustion engine according to claim 1, wherein the combustion is restarted by the combustion restarting means when the engine speed is lower than a predetermined reference speed while the combustion stopping means stops the combustion. Start control device. The engine further comprises means for driving the engine by the electric motor to suppress a decrease in the rotational speed when the rotational speed of the engine is lower than a predetermined reference rotational speed while the combustion is stopped by the combustion stop means. The start control device for an internal combustion engine according to claim 7. 9. The start control of the internal combustion engine according to claim 8, wherein the means for suppressing a decrease in the rotational speed maintains the rotational speed of the engine to be equal to or higher than the reference rotational speed by driving the engine with the electric motor. apparatus. The combustion control means determines a cylinder whose combustion state after the restart of combustion by the combustion resumption means is not in a normal state, and thereafter prohibits the combustion stop of the cylinder by the combustion stop means. Item 2. A start control device for an internal combustion engine according to Item 1. The combustion control means determines that the specific cylinder is a cylinder in which the combustion state is not in a normal state when the engine speed does not increase in spite of the restart of the combustion in the specific cylinder. The start control device for an internal combustion engine according to claim 10, wherein the start control device is an internal combustion engine. The start control device for an internal combustion engine according to claim 1, wherein the combustion control means executes an ignition operation even when the fuel supply is stopped. 2. The internal combustion engine start control according to claim 1, wherein the negative pressure state detection means determines that the negative pressure of the engine is in a normal state when a predetermined time has elapsed after the start of the engine. apparatus. 2. The internal combustion engine according to claim 1, wherein the negative pressure state detection means determines that the negative pressure of the engine is in a normal state when an air flow rate in the engine becomes equal to a predetermined air flow rate. Engine start control device. 2. The start control device for an internal combustion engine according to claim 1, wherein the combustion stopping unit increases the number of cylinders that stop the fuel supply as the difference between the detected rotational speed and the target rotational speed is larger. .

Images