JP2008163796A - Control device for internal combustion engine - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a control device for an internal combustion engine capable of shortening engine stop time and surely improving ability of restart in idling stop control of a vehicle provided with a common rail type internal combustion engine. <P>SOLUTION: Crank angle is stopped at predetermined crank angle suitable for restart by increasing delivery flow quantity of a supply pump to adjust engine load in engine stop of idling stop control. Fuel injection is started simultaneously with operation of a starter in restart. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a control technique for a fuel injection device at the time of idling stop of a vehicle equipped with a common rail internal combustion engine.

A so-called common rail type fuel injection device that stores fuel pressurized to a high pressure by a pressurizing pump (hereinafter referred to as a supply pump) in a common rail and injects the fuel into a cylinder at a predetermined time from a fuel injection valve connected to the common rail. There are internal combustion engines (hereinafter referred to as engines) equipped with
The fuel injection valve of the engine for injecting high-pressure fuel is provided with a leak passage for returning excess fuel to the fuel tank. The common rail is provided with a relief valve that opens when the pressure exceeds a predetermined pressure, and the fuel is returned to the fuel tank when the relief valve is opened.

In the common rail type fuel injection device configured as described above, when the engine is stopped, the supply pump is stopped, and the fuel is not pumped, the fuel gradually flows from the common rail and the leak passage of the fuel injection valve to the fuel tank. The fuel pressure in the common rail (hereinafter referred to as common rail pressure) gradually decreases with time.
Here, in recent years, there are vehicles that perform engine stop / restart control (hereinafter referred to as idle stop control) for stopping the engine during idling for the purpose of improving fuel consumption and reducing exhaust gas.

In vehicles that perform such idle stop control, it is desired to shorten the stop time and improve the restartability.
However, in order to secure the fuel injection pressure in the common rail fuel injection device, it is necessary to increase the common rail pressure that is reduced during engine stop every time the engine is restarted. This causes a problem that the restartability is deteriorated. .

Therefore, in an internal combustion engine equipped with a common rail type fuel injection device, a technique has been disclosed in which the load on the fuel pump (supply pump) is maximized at the time of idling stop, thereby shortening the engine stop time and increasing the common rail pressure. (See Patent Document 1).
JP 2004-36459 A

However, with the technique disclosed in Patent Document 1, even if the common rail pressure at the time of restart can be secured, the restartability changes depending on the crank angle at the time of restart, that is, the crank angle at the time of engine stop. There's a problem.
If the crank angle is not suitable for starting, combustion cannot be normally caused even if the common rail pressure is secured, and fuel injection can be performed until a crank angle suitable for starting is obtained by a starter or the like. There is a problem that it cannot be performed, and restartability cannot always be improved.

  The present invention has been made to solve such problems, and the object of the present invention is to reliably shorten the engine stop time and improve the restartability in the idle stop control of a vehicle equipped with a common rail internal combustion engine. An object of the present invention is to provide a control device for an internal combustion engine that can be made to operate.

  In order to achieve the above object, in the control apparatus for an internal combustion engine according to claim 1, a pressure pump driven by the power of the internal combustion engine, a common rail for storing fuel pressurized by the pressure pump, and the common rail A fuel injection valve that injects fuel stored in the cylinder of the internal combustion engine, common rail pressure detection means for detecting fuel pressure in the common rail, crank angle detection means for detecting a crank angle of the internal combustion engine, A fuel injection control means for controlling fuel injection by the fuel injection valve; a discharge flow rate control means for adjusting the discharge flow rate to the common rail of the pressurizing pump; and the internal combustion engine is stopped when a predetermined stop condition is satisfied, Internal combustion engine stop / restart control means for restarting the internal combustion engine when the restart condition is satisfied, and the discharge flow rate control means is configured to satisfy the predetermined stop condition. When the internal combustion engine is stopped by the internal combustion engine stop / restart control means, the discharge flow rate of the pressurizing pump is adjusted to the increase side, and the crank angle of a predetermined cylinder is set to a predetermined level within the expansion stroke from the compression top dead center. It is characterized by stopping at the crank angle.

  In the control device for an internal combustion engine according to claim 2, when the predetermined restart condition is satisfied and the internal combustion engine is restarted after the internal combustion engine is stopped by the internal combustion engine stop / restart control means, the common rail pressure detection means When the detected fuel pressure is equal to or higher than a predetermined pressure, the fuel injection control means starts fuel injection from the predetermined cylinder simultaneously with the restart.

  In the control device for an internal combustion engine according to claim 3, when the predetermined restart condition is satisfied and the internal combustion engine is restarted after the internal combustion engine is stopped by the internal combustion engine stop / restart control means, the common rail pressure detection means When the detected fuel pressure is less than a predetermined pressure, a starting means provided in the internal combustion engine for cranking the internal combustion engine is driven, and the discharge flow rate of the pressure pump is maximized by the discharge flow rate control means. The fuel injection control means starts fuel injection after the fuel pressure detected by the common rail detection means exceeds the predetermined pressure.

  According to the control device for an internal combustion engine of the present invention using the above means, the discharge flow rate of the pressurizing pump is adjusted to the increase side when the engine is stopped in the internal combustion engine stop / restart control (idle stop control). By adjusting the load of the pressurizing pump, the load of the engine that drives the pressurizing pump is adjusted, and the crank angle of a predetermined cylinder is set at a predetermined crank angle within the expansion stroke from the compression top dead center suitable for restart. Stop.

In this way, by increasing the discharge flow rate of the pressure pump when the engine is stopped, the load on the engine can be increased and the engine stop time can be shortened, and the common rail fuel pressure (common rail pressure) can be increased and restarted. The common rail pressure at the time, that is, the fuel injection pressure can be secured.
Furthermore, the starting time is shortened by setting the crank angle of a predetermined cylinder to a predetermined crank angle in the expansion stroke from the compression top dead center suitable for restarting, and starting fuel injection from the predetermined cylinder at the time of restarting. The restartability can be improved by improving fuel consumption, reducing exhaust gas, and reducing vibration.

  According to the control device for an internal combustion engine of claim 3, when the common rail pressure is lower than the predetermined common rail pressure at the time of restart, cranking is performed by the starter and the discharge flow rate of the pressurizing pump is maximized. , And fuel injection is started after the common rail pressure becomes equal to or higher than a predetermined pressure, whereby stable restart can be performed.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.
Referring to FIG. 1, there is shown a schematic configuration diagram of a control device for an internal combustion engine according to the present invention. Hereinafter, a description will be given based on FIG.
The fuel injection device shown in FIG. 1 is provided in a four-cylinder diesel engine (hereinafter simply referred to as an engine) (not shown). A manual transmission is connected to the engine.

A vehicle equipped with the engine is provided with a fuel tank 2, and the fuel tank 2 is connected to a supply pump 10 via a tank fuel passage 4. Note that a fuel filter 6 for removing foreign matter in the fuel from the fuel tank 2 is interposed in the tank flow path 4.
Inside the supply pump 10, a pump body 14 and a feed pump 16 are provided on a drive shaft 12 that is rotated by the power of the engine. The feed pump 16 has a function of sucking up fuel from the fuel tank 2 and supplying it to the pump body 14 by being driven to rotate. The internal fuel passage 18 connecting the feed pump 16 and the pump body 14 is provided with a discharge flow rate control valve 20 (discharge flow rate control means). The discharge flow rate control valve 20 is connected from the feed pump 16 to the pump body 14. It has a function of adjusting the discharge flow rate discharged from the supply pump 10 by discharging excess fuel to the discharge passage 22 and adjusting the amount of fuel supplied to the pump body 14. The pump main body 14 has a function of pressurizing the supplied fuel and sending it to the common rail 30 via the supply fuel passage 24 connected to the supply pump 10.

The common rail 30 is connected to a fuel injection valve 40 provided facing each cylinder of the engine via a common rail fuel path 32. The common rail 30 is provided with a relief valve 34 that opens when a certain pressure is applied, and is connected to the fuel tank 2 from the relief valve 34 through a relief passage 36.
The fuel injection valve 40 is provided with a solenoid valve therein, and fuel injection is performed by opening the solenoid valve. Further, the fuel injection valve 40 is connected to the fuel tank 2 via a leak passage 42, and the extra fuel that has been sent when the fuel is not injected is returned to the fuel tank 2 from the leak passage 42.

The vehicle equipped with the engine includes an input / output device (not shown), a storage device (ROM, RAM, etc.) used for storing control programs and control maps, a central processing unit (CPU), a timer counter, and the like. An ECU (electronic control unit) 50 is provided.
On the input side of the ECU 50, a common rail pressure sensor 52 that detects the fuel pressure in the common rail 30 (hereinafter also referred to as common rail pressure), and a crank angle sensor 54 that outputs a crank angle signal synchronized with the rotation of the engine (crank angle detecting means). A vehicle speed sensor 56 for detecting the vehicle speed, a clutch sensor 58 for detecting the operation state of the clutch of the transmission, a shift position sensor 60 for detecting the shift position of the transmission, and other various switches and sensors are connected.

  Further, various devices such as a discharge flow rate control valve 20, each fuel injection valve 40, and an electric starter 62 for cranking the engine are connected to the output side of the ECU 50. The ECU 50 performs drive control of various devices based on various information detected from these sensors. For example, the ECU 50 performs discharge flow control (discharge flow control means), fuel injection control (fuel injection control means) and idle stop control (internal combustion engine stop / restart control means) of the supply pump 10.

Here, with respect to the idle stop control, the engine stop control is performed when the idle stop flag is turned ON when a preset engine stop condition is satisfied. Similarly, the engine restart control is performed by switching the idle stop flag to OFF when the preset engine restart condition is satisfied.
The engine stop condition is that the vehicle speed detected by the vehicle speed sensor 56 is zero, that the clutch depression operation of the clutch is not detected by the clutch sensor 58, and the shift position detected by the shift position sensor 60 is When the N (neutral) position is set and these conditions are satisfied, the ECU 50 determines that the engine stop condition is satisfied, and switches the idle stop flag to ON.

Further, as engine restart conditions, it is set that the clutch depression operation is detected by the clutch sensor 58 (clutch disengagement state), and that the shift position detected by the shift position sensor 60 is the N position. When these conditions are satisfied, the idle stop flag is switched off.
Hereinafter, engine stop control and restart control in the idle stop control will be described in detail.

  Referring to FIGS. 2 to 4, FIG. 2 shows a flowchart showing an engine stop control routine executed by the ECU 50, and FIG. 3 shows a flowchart showing a restart control routine executed by the ECU 50. FIG. 4 shows a time chart showing each operation state in time series when the engine stop control and the restart control are performed, and will be described below with reference to these drawings.

When the engine stop condition is satisfied and the idle stop flag is turned ON, the ECU 50 first stops fuel injection by the fuel injection valve 40 in step S1, as shown in FIG.
In the subsequent step S2, the engine stop angle control flag for turning the crank angle when the engine is stopped in the predetermined cylinder, that is, the crank angle at the time of restart, to a predetermined crank angle suitable for restart is turned ON. Switch. The predetermined crank angle is set to a predetermined angle at the beginning of the expansion stroke from the compression top dead center, for example, so that combustion can be satisfactorily caused by injecting fuel into the cylinder.

In step S3, each cylinder is discriminated from the crank angle detected by the crank angle sensor 54, and the engine speed is acquired.
In step S4, an optimum cylinder for engine stop angle control is determined based on the cylinder discrimination. The optimum cylinder is set according to the engine speed and the crank angle acquired in step S3. When the discharge flow rate of the supply pump 10 is continuously maximized after the fuel injection is stopped, the predetermined cylinder is set. The cylinder that stops before the corner is determined as the optimum cylinder.

In step S5, the discharge flow rate control valve 20 is controlled to maximize the discharge flow rate of the supply pump 10.
In step S6, it is determined whether or not the crank angle of the cylinder determined in step S4 is a predetermined crank angle. If the determination result is false (No), the process proceeds to step S7.

In step S7, the crank angle and the engine speed are acquired again from the crank angle sensor 54.
In the following step S8, a load required to obtain a predetermined crank angle when the engine stops, that is, when the engine speed becomes zero, is calculated from the crank angle and the engine speed acquired in step S7. The discharge flow rate of the supply pump 10 is adjusted by the discharge flow rate control valve 20 so as to realize the load, and the process returns to step S6. In step S4, since the cylinder that stops before the predetermined crank angle when the discharge flow rate is continuously maximized after the stop of fuel injection is determined as the optimum cylinder, at least the predetermined crank angle is determined. Can be controlled not to exceed.

Then, steps S7 and S8 are repeated until the determination result of step S6 becomes true (Yes). If the determination result of step S6 becomes true (Yes), that is, the engine speed is 0 and the crank angle is a predetermined value. If the crank angle is reached, the process proceeds to step S9.
In step S9, the engine stop angle control flag is switched off, that is, the discharge flow rate of the supply pump 10 is set to 0, and the routine is exited.

As described above, in the engine stop control in the idle stop control, after stopping the fuel injection, when the engine is stopped by increasing the discharge flow rate of the supply pump 10, the crank angle of the predetermined cylinder is set to the predetermined crank at the initial stage of the expansion stroke. Control to stop at the corner.
Then, after the engine is stopped, when a predetermined restart condition is satisfied and the idle stop flag is turned OFF, the ECU 50 executes engine restart control.

  As shown in FIG. 3, the restart control first determines in step S10 whether or not the common rail pressure detected by the common rail pressure sensor 54 is equal to or higher than a predetermined common rail pressure. The predetermined common rail pressure is set to a startable common rail pressure, that is, a fuel injection pressure capable of causing stable combustion. If the determination result is true (Yes), the process proceeds to step S11.

In step S11, cylinder discrimination is performed from the crank angle detected by the crank angle sensor 54, and a cylinder at a crank angle suitable for starting fuel injection is confirmed.
In step S12, the starter 62 is operated, and at the same time, fuel injection is started from the cylinder determined in step S11, and the routine is exited.
On the other hand, if the common rail pressure is less than the predetermined common rail pressure and the determination result is false (No) in step S10, the process proceeds to step S13.

In step S13, the starter 62 is operated to crank the engine.
In step S14, the discharge flow rate control valve 20 controls the supply pump 10 to maximize the discharge flow rate.
In step S15, the common rail pressure is detected again, and it is determined whether or not the common rail pressure is equal to or higher than a predetermined common rail pressure. If the determination result is false (No), the process returns to step S14, and the maximum discharge flow rate of the supply pump 10 is maintained.

If the common rail pressure is equal to or higher than the predetermined common rail pressure and the determination result in step S15 is true (Yes), the process proceeds to step S16.
In step S16, cylinder discrimination is performed from the crank angle detected by the crank angle sensor 54, and a cylinder having a crank angle suitable for starting fuel injection at this time is determined.
In step S17, fuel injection is started from the cylinder determined in step S16, and the routine is exited.

Thus, at the time of restart, if the common rail pressure is equal to or higher than a predetermined common rail pressure that can be started, fuel injection is started together with cranking by the starter.
That is, when the engine stop control is performed, since the discharge flow rate of the supply pump 10 is increased when the engine is stopped, the common rail pressure is high, and the crank angle of a predetermined cylinder is suitable for starting. Since the engine is stopped at a predetermined crank angle at the initial stage of the expansion stroke, early restart is performed by the restart control.

On the other hand, when the common rail pressure is insufficient, cranking is performed by the starter, the discharge flow rate of the supply pump 10 is maximized, the common rail pressure is increased, and fuel injection is started after the common rail pressure becomes sufficiently high.
That is, when the engine stop time is long and the common rail pressure has dropped below a predetermined common rail pressure, fuel injection is started after the common rail pressure is increased by cranking the starter.

Here, the change of each driving | running state when the said engine stop control and restart control are performed concretely is demonstrated.
As shown in FIG. 4, when a predetermined stop condition is satisfied at time t1 and the idle stop flag is turned ON, the fuel injection is stopped and the engine stop angle control flag is turned ON.

In the period from time t1 to t2, first, the discharge flow rate of the supply pump 10 rapidly increases to the maximum discharge flow rate, and the common rail pressure also increases rapidly. Then, after the discharge flow rate becomes maximum, the crank angle is adjusted to a predetermined crank angle.
At time t2 when the crank angle becomes a predetermined crank angle, the engine stop angle control flag is switched to OFF, and the discharge flow rate decreases.

In the engine stop angle control, the common rail pressure is increased to a sufficiently high level by increasing the discharge flow rate.
When a predetermined restart condition is satisfied at time t3, the idle stop flag is switched to OFF. At this time, the common rail pressure is slightly decreased from the time t2 when the engine rotation is stopped, but it is secured to a predetermined common rail pressure sufficient to cause combustion, and the crank angle is an expansion stroke suitable for combustion. Since the engine is stopped at the initial predetermined crank angle, fuel injection can be started simultaneously with the starter 62 being started.

  Thus, in the engine stop control in the idle stop control, the engine load is adjusted by increasing the discharge flow rate of the supply pump 10, and the engine stop is performed by stopping the crank angle of a predetermined cylinder at a predetermined crank angle. In addition to shortening the time, the common rail pressure can be increased to ensure the common rail pressure at the time of restart, that is, the fuel injection pressure.

In addition, by setting the crank angle of a predetermined cylinder to a predetermined crank angle in the initial stage of the expansion stroke suitable for restart, fuel injection is started from the predetermined cylinder at the time of restart, thereby shortening the start time and improving fuel efficiency. It is possible to improve restartability such as improvement of exhaust gas, reduction of exhaust gas, and reduction of vibration.
Further, when the common rail pressure is lower than the predetermined common rail pressure at the time of restart, cranking is performed by the starter 62 and the common rail pressure is increased by maximizing the discharge flow rate of the supply pump 10 so that the common rail pressure is equal to or higher than the predetermined pressure. Then, stable restart can be performed by starting fuel injection.

As described above, according to the control apparatus for an internal combustion engine according to the present invention, the engine stop time of the idle stop control in the common rail internal combustion engine can be shortened, and the restartability can be improved reliably.
Although the description of the embodiment of the control device for an internal combustion engine according to the present invention has been completed, the embodiment is not limited to the above embodiment.

In the above embodiment, the predetermined crank angle is set as the crank angle at the initial stage of the expansion stroke. However, the predetermined crank angle may be any crank angle suitable for combustion, for example, the compression top dead center. I do not care.
In the above embodiment, the predetermined cylinder is determined from the engine rotation speed and the crank angle at the time of engine stop angle control. However, the present invention is not limited to this, and a cylinder that starts fuel injection at the time of restart is set in advance. Alternatively, the discharge flow rate of the supply pump 10 may be controlled so that the cylinder is a predetermined cylinder and the crank angle of the cylinder is a predetermined crank angle.

Further, in the above embodiment, a manual transmission is connected to the engine, but this may be a Jizo excursion. In this case, the shift position is set in the engine stop condition and the restart condition of the idle stop control. A position such as D or the like where the vehicle can travel or N position is set.
Furthermore, the engine stop condition and the restart condition for the idle stop control are not limited to the above-described embodiment, but are set according to the specifications and characteristics of the vehicle.

It is a schematic block diagram of the control apparatus of the internal combustion engine which concerns on this invention. It is a flowchart which shows the engine stop control routine performed by ECU of the control apparatus of the internal combustion engine which concerns on this invention. It is a flowchart which shows the restart control routine performed by ECU of the control apparatus of the internal combustion engine which concerns on this invention. It is the time chart which showed each operation state when performing engine stop control and restart control of the control device of an internal-combustion engine concerning the present invention in time series.

Explanation of symbols

2 Fuel tank 10 Supply pump (pressure pump)
20 Discharge flow control valve (Discharge flow control means)
30 common rail 34 relief valve 36 relief passage 40 fuel injection valve 42 leak passage 50 ECU (discharge flow rate control means, fuel injection control means, internal combustion engine stop / restart control means)
52 Common rail pressure sensor (common rail pressure detection means)
54 Crank angle sensor (crank angle detection means)
62 Starter (starting means)

Claims (3)

A pressure pump driven by the power of the internal combustion engine;
A common rail for storing fuel pressurized by the pressure pump;
A fuel injection valve for injecting fuel stored in the common rail into a cylinder of the internal combustion engine;
Common rail pressure detecting means for detecting fuel pressure in the common rail;
Crank angle detecting means for detecting a crank angle of the internal combustion engine;
Fuel injection control means for controlling fuel injection by the fuel injection valve;
A discharge flow rate control means for adjusting a discharge flow rate to the common rail of the pressure pump;
An internal combustion engine stop / restart control means for stopping the internal combustion engine when a predetermined stop condition is satisfied, and restarting the internal combustion engine when a predetermined restart condition is satisfied,
When the predetermined stop condition is satisfied and the internal combustion engine is stopped by the internal combustion engine stop / restart control means, the discharge flow rate control means adjusts the discharge flow rate of the pressurizing pump to the increase side to control the predetermined cylinder. A control apparatus for an internal combustion engine, wherein a crank angle is stopped at a predetermined crank angle in an expansion stroke from a compression top dead center.   When the predetermined restart condition is satisfied after the internal combustion engine is stopped by the internal combustion engine stop / restart control means and the internal combustion engine is restarted, the fuel pressure detected by the common rail pressure detecting means is equal to or higher than a predetermined pressure. 2. The control device for an internal combustion engine according to claim 1, wherein the fuel injection control means starts fuel injection from the predetermined cylinder simultaneously with the restart.   When the predetermined restart condition is satisfied after the internal combustion engine is stopped by the internal combustion engine stop / restart control means and the internal combustion engine is restarted, the fuel pressure detected by the common rail pressure detecting means is less than the predetermined pressure. In this case, a starting means provided in the internal combustion engine for cranking the internal combustion engine is driven, the discharge flow rate control means maximizes the discharge flow rate of the pressurizing pump, and the fuel injection control means is the common rail detection means. 3. The control device for an internal combustion engine according to claim 1, wherein the fuel injection is started after the fuel pressure detected by the step becomes equal to or higher than the predetermined pressure.

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