JP2009228637A - Control device of engine - Google Patents

Abstract

To provide an engine control device capable of accurately adjusting a position where a piston stops when the engine is stopped, and improving startability of the engine by direct start.
When the engine is stopped, ignition by the spark plug is terminated (S1), and when the crank angle from the ignition end point reaches a predetermined crank angle (S3), the engine speed is detected (S4), When the engine speed is smaller than the first predetermined speed, air is supplied into the expansion stroke cylinder by the air supply means (S6). When the engine speed is higher than the second predetermined speed, the compression stroke is performed. Adjust the piston stop position by supplying air into a combustion chamber (S9).

Description

  The present invention relates to an engine control device, and more particularly to engine stop control.

  Conventionally, it has been common to use a starter motor when starting an engine. However, in recent years, in order to reduce the noise at the time of starting the engine and realize a quick start, the cranking by the starter motor is not performed. There has been proposed a starter that performs a so-called direct start in which fuel is injected and ignited in a combustion chamber of an engine. In particular, in recent years, from the viewpoint of environmental protection and energy saving, there has been proposed a vehicle that temporarily stops the engine when the vehicle is stopped, so-called idle stop, and when the engine stopped at the idle stop is started again. Since the engine can be started quickly without the need for cranking by the starter motor, the direct start is preferable.

In the direct start, a cylinder in an expansion stroke (hereinafter also referred to as an expansion stroke cylinder) is determined when the engine is stopped, and when the engine is restarted according to a vehicle start operation or a driver start operation, the expansion is performed. After the fuel is injected into the stroke cylinder, ignition is performed to burn the injected fuel, and the engine is started by the combustion pressure generated at this time.
And in the said direct start, since the startability of an engine changes with the piston stop position at the time of an engine stop, it is preferable to stop a piston in the predetermined position set beforehand.

For this reason, in an engine that performs direct start, engine stop control may be performed to stop the piston at a predetermined position.
For example, a cylinder that stops in the expansion stroke and the compression stroke is estimated before the engine is stopped, and the cylinder that is estimated to stop in the expansion stroke is in the cylinder by the fuel injection valve when it is in the last compression stroke before the engine is stopped. There is a technique for reducing fluctuations in engine rotational speed by injecting fuel and reducing the compression reaction force by the latent heat of vaporization of the fuel (see Patent Document 1).
JP 2005-163660 A

  However, as in the technique disclosed in Patent Document 1, when the engine is stopped, the position at which the piston stops can be estimated to some extent, but the piston stop position is a residual due to the piston of the cylinder in the compression stroke. Various forces acting on the crankshaft such as the so-called cam reaction force that the air compression pressure, the frictional resistance of each part of the engine, or the urging force of the valve spring acts on the crankshaft via the camshaft contribute, The piston stop position may deviate from the estimated position. Thus, the stop position of the piston in each cylinder when the engine is stopped is not constant, and the stop position of the piston of the expansion stroke cylinder that injects fuel for starting is not constant.

For this reason, there arises a problem that engine start by direct start is not stable.
In the technique disclosed in Patent Document 1, the throttle valve is opened for a predetermined period after fuel cut to ensure scavenging, and the engine speed reduction degree is adjusted by power generation control of the alternator and throttle valve opening control. Thus, the stop position of the piston is stopped at an appropriate position.

However, the influence of alternator power generation control, throttle valve opening control, and the like on the rotation of the engine is insignificant, and there is a problem that the piston cannot always be stopped at a predetermined position.
In addition, in the above-mentioned Patent Document 1, although applied to an in-cylinder injection engine that can inject fuel directly into a combustion chamber, an intake pipe injection type (Multi Point Injection: MPI) that cannot inject fuel directly into the combustion chamber In the case of an engine (hereinafter referred to as an MPI engine), it is necessary to supply fuel in advance to the combustion chamber of the cylinder that is in the expansion stroke when the piston is stopped, during the intake stroke immediately before the stop. Not applicable.

  The present invention has been made to solve such problems. The object of the present invention is to accurately adjust the position where the piston stops when the engine stops, and to start the engine by direct start. An object of the present invention is to provide an engine control device capable of improving the performance.

  In order to achieve the above object, the engine control apparatus according to claim 1 is a control apparatus for an engine having a plurality of cylinders, wherein the fuel injection valve supplies fuel into the combustion chamber of each cylinder, and the fuel injection valve. An ignition plug for igniting the fuel supplied into the combustion chamber, air supply means for supplying air into the combustion chamber independently of opening and closing of the intake valve of the engine, and engine rotation of the engine Engine speed detecting means for detecting the engine speed and engine speed detected by the engine speed detecting means at a predetermined time from when the ignition is stopped by the spark plug when the engine is stopped until the piston stops. Is smaller than the first predetermined rotational speed, air is supplied by the air supply means into the combustion chamber of the cylinder in the expansion stroke at the predetermined time, When the engine speed is greater than the second predetermined speed, which is higher than the first predetermined speed, the air supply means puts into the combustion chamber of the cylinder in the compression stroke at the predetermined time. And piston stop position control means for adjusting the piston stop position of the engine to stop at a predetermined position by supplying air.

According to a second aspect of the present invention, there is provided the engine control device according to the first aspect, further comprising crank angle detecting means for detecting a crank angle of the engine, wherein the predetermined time is determined from the end point of ignition by the spark plug when the engine is stopped. The crank angle detected by the crank angle detecting means is a time when the crank angle becomes a predetermined crank angle.
According to a third aspect of the present invention, in the engine control device according to the first or second aspect, the piston stop position control means closes a throttle valve that controls the intake air amount of the engine from the end of ignition by the spark plug. It is characterized by.

  According to a fourth aspect of the present invention, there is provided the engine control device according to any one of the first to third aspects, wherein the piston stop position control means determines the amount of air supplied by the air supply means at the predetermined time by rotating the engine at the predetermined time. It is characterized by setting according to the number.

  According to the engine control apparatus of the first aspect of the present invention using the above-described means, the ignition by the spark plug is terminated when the engine is stopped, and the engine speed is set at a predetermined time between the ignition end time and the piston stop. When the rotation speed is smaller than the first predetermined rotation speed, air is supplied into the expansion stroke cylinder by the air supply means. When the rotation speed is higher than the second predetermined rotation speed, the air is discharged into the cylinder in the compression stroke. The piston stop position is adjusted by supplying.

  That is, when the engine rotates due to inertia from the end of ignition and the engine speed at a predetermined time before the rotation stops is smaller than the first predetermined speed, the piston stop position is less than the predetermined position. At this time, air is supplied by the air supply valve into the combustion chamber of the cylinder in the expansion stroke. By supplying air to the expansion stroke cylinder in this way, the pressure in the combustion chamber increases, the piston is further pushed down, and the rotation of the engine is accelerated.

  On the other hand, if the engine speed at the predetermined time is larger than the second predetermined speed, it is determined that the piston stop position passes the predetermined position, and at this time, the air supply valve is placed in the combustion chamber of the cylinder in the compression stroke. To supply air. By supplying air to the compression stroke cylinder in this way, the pressure in the combustion chamber increases, and the rise of the piston is suppressed, so that the rotation of the crankshaft is decelerated.

As described above, the rotation of the engine is accelerated or decelerated by supplying air into the combustion chamber of the expansion stroke cylinder or the compression stroke cylinder in accordance with the engine rotation speed at a predetermined time, so that the engine rotation speed is within an appropriate range. Adjustment can be made to stop the piston in place.
And since the piston can be stopped at a predetermined position in this way, the startability of the engine by direct start can be improved.

According to the engine control apparatus of the second aspect, the predetermined timing is set to a timing at which the crank angle from the ignition end point becomes the predetermined crank angle.
Thereby, the predetermined time can be set easily and accurately.
According to the engine control apparatus of the third aspect, the throttle valve for controlling the intake air amount of the engine is closed from the ignition end point.

By closing the throttle valve from the end of ignition in this way, intake into the combustion chamber is hindered, the combustion chamber becomes negative pressure, and the effect of air supply to the combustion chamber by the air supply means increases.
Thereby, adjustment of the piston stop position by air supply can be performed more correctly.
According to the engine control apparatus of the fourth aspect, the amount of air supplied by the air supply means at a predetermined time is set in proportion to the engine speed at this time.

  Thereby, the piston stop position can be accurately adjusted with simple control.

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 an engine control apparatus according to the present invention.
Engine 1 is an intake pipe injection (MPI) four-cycle in-line four-cylinder engine that has four cylinders arranged in series and explodes at equal intervals of 180 ° CA. A longitudinal section of one cylinder is shown. In addition, illustration and description are abbreviate | omitted as what has the same structure also about another cylinder.

As shown in FIG. 1, the engine 1 is configured by mounting a cylinder head 4 on a cylinder block 2.
A piston 8 is fitted into the cylinder 6 formed in the cylinder block 2 so as to be vertically slidable. A combustion chamber 10 is formed by being surrounded by the cylinder 6, the top surface of the piston 8, and the lower surface of the cylinder head 4. Has been.

  The piston 8 is connected to the crankshaft 14 via a connecting rod 12. The engine 1 is also provided with a crank angle sensor 18 (crank angle detection means) that detects the crank angle synchronized with the rotation of the crankshaft 14 by using the rotation of the ring gear 16 provided on the crankshaft 14. Note that the rotation of the crankshaft 14 is the rotation of the engine 1, and the engine speed can be calculated from the crank angle, or the cylinder can be discriminated together with the cam angle (engine speed detection means).

On the other hand, the cylinder head 4 is provided with a spark plug 20 so that the electrode portion faces the combustion chamber 10.
Further, the cylinder head 4 is provided with an air supply valve 22 (air supply means) that faces the discharge port in the combustion chamber 10 and can supply air directly into the combustion chamber 10. The air supply valve 22 is connected to a pressure accumulator 24 that stores compressed air supplied from a compressor (not shown) via an air supply pipe 26, and air is supplied from the pressure accumulator 24.

Further, the cylinder head 4 is formed with an intake port 28 that communicates with the combustion chamber 10 and extends to one side in the width direction of the engine 1, and an injection port faces the intake port 28, and the intake port 28 extends from the injection port to the intake port 28. A fuel injection valve 30 capable of supplying fuel into the combustion chamber 10 is provided.
The cylinder head 4 is formed with an exhaust port 32 that communicates with the combustion chamber 10 and extends to the other side in the width direction of the engine 1.

Further, the cylinder head 4 is provided with an intake valve 34 and an exhaust valve 36 which are driven by an intake cam and an exhaust cam (not shown), and connect and block the combustion chamber 10 and the intake port 28 and the combustion chamber 10 and the exhaust port 32. Is provided.
An intake manifold 38 is connected to one side of the engine 1 so as to communicate with the intake port 28, and the intake manifold 38 is connected to an intake pipe 42 via a surge tank 40.

A throttle valve 44 that is opened and closed by an electric actuator (not shown) is provided in the intake pipe 42.
On the other hand, an exhaust manifold 46 is connected to the other side of the engine 1 so as to communicate with the exhaust port 32, and an exhaust pipe (not shown) is connected to one end of the exhaust manifold 46.

In addition, a vehicle equipped with the engine 1 includes a vehicle speed sensor 48 that detects the traveling speed of the vehicle, a shift position sensor 50 that detects an operation position of a select lever provided in the driver's seat, and a brake operation by the driver. Various sensors such as a brake switch 52 for detecting the above are provided.
Various devices and sensors such as the spark plug 20, the air supply valve 22, the fuel injection valve 30, the throttle valve 44, the crank angle sensor 18, the vehicle speed sensor 48, the shift position sensor 50, and the brake switch 52 are ECU (electronic Control unit) 54 (piston stop position control means) is electrically connected, and the ECU 54 controls the operation of various devices based on information from various sensors.

  For example, the ECU 54 executes idle stop control for temporarily automatically stopping the engine 1 while the vehicle is stopped due to a signal waiting or traffic jam. In the present embodiment, as engine stop conditions, the vehicle speed detected by the vehicle speed sensor 48 is 0 km / h, the brake operation is detected by the brake switch 52, and the shift position detected by the shift position sensor 50 is A driving range such as a D (drive) range or an N (neutral) range is set, and when these conditions are satisfied, the ECU 54 performs stop control of the engine 1.

Further, as engine start conditions in the idle stop control, the release of the brake operation is detected by the brake switch 52, and the shift position detected by the shift position sensor 50 is a travel range such as the D range. If these conditions are satisfied, the ECU 54 performs start control of the engine 1.
In the start control, a so-called direct start is performed in which the cylinder 6 in which fuel is supplied in advance into the combustion chamber 10 during the stop control and the piston 8 is stopped in the expansion stroke is determined and ignited by the spark plug 20 of the cylinder 6. Do. Thereby, combustion is caused in the expansion stroke cylinder, and the engine 1 is started by the combustion pressure generated at this time.

On the other hand, the stop control of the engine 1 in the idle stop control by the ECU 54 will be described in detail below.
Referring to FIGS. 2 to 5, FIG. 2 is a flowchart showing a stop control routine of the engine 1 executed by the ECU 54. FIG. 3 is a time chart in the case of supplying air to the expansion stroke cylinder. 2 shows a time chart when air is supplied to the compression stroke cylinder, and FIG. 5 shows an air supply amount setting map, respectively. Hereinafter, referring to FIGS. I will explain.

The combustion order of the engine 1 is the order of cylinders # 1 → # 3 → # 4 → # 2 as shown in FIG.
When the engine stop condition is satisfied, the ECU 54 starts the engine stop control routine shown in FIG. 2, and performs an idle stop process as step S1. In the idle stop process, fuel injection is stopped and ignition is stopped. Therefore, combustion is not caused from the time when ignition is finished, and the engine 1 starts rotating from here due to inertia.

Further, the cylinder 6 that is in the expansion stroke when the engine is stopped, that is, when the piston is stopped, is estimated from the engine speed and the like at this time. For example, in the present embodiment, it is assumed that the fourth cylinder # 4 is stopped in the expansion stroke.
Next, in step S2, the throttle valve 44 is closed to a predetermined opening degree from the time when ignition is stopped (hereinafter also referred to as the ignition end time). Thus, when the throttle valve 44 is closed, the amount of intake air is limited, so that the inside of the combustion chamber 10 becomes negative pressure.

In step S3, it is determined whether or not the crank angle from the end of ignition has reached a predetermined crank angle, that is, whether or not a predetermined time has been reached. The predetermined crank angle is, for example, a crank angle that is a predetermined stroke before the piston stop time estimated in step S1.
When the determination result is false (No), that is, when the crank angle has not reached the predetermined crank angle, the step S3 is repeated, and when the predetermined crank angle is reached and the determination result is true (Yes) The process proceeds to the next step S4.

In step S4, the engine speed at a predetermined time when the predetermined crank angle is reached is detected. For example, the crank angular speed obtained from the time elapsed from the specified crank angle before the predetermined crank angle to the predetermined crank angle is calculated, and the engine speed at the predetermined time is calculated based on the crank angular speed. .
In the next step S5, it is determined whether or not the engine speed detected in step S4 is smaller than a preset first predetermined speed. If the determination result is true (Yes), the process proceeds to step S6.

  In step S6, as shown in FIG. 3, the cylinder 6 (cylinder # 3 in FIG. 3) in the expansion stroke at a predetermined time is determined, and air is supplied into the combustion chamber 10 of the expansion stroke cylinder by the air supply valve 22. To do. That is, if the engine speed at a predetermined time is smaller than the first predetermined speed, it is determined that the piston stop position is lower than the appropriate engine speed and the piston stop position stops before the predetermined position. Air is supplied into the combustion chamber 10 of the cylinder (# 3) in the stroke. Thus, by supplying air to the expansion stroke cylinder (# 3), the pressure in the combustion chamber 10 increases, the descending piston 8 is further pushed down, and the engine rotation is accelerated.

  In the next step S7, when the cylinder (# 4) estimated to stop in the expansion stroke in step S1 is in the final intake stroke before the piston stops, fuel injection by the fuel injection valve 30 is performed, and the routine Exit. The fuel injected in step S7 is supplied into the combustion chamber 10 through the intake port 28. When the piston is stopped, the fuel is mixed in the combustion chamber 10 of the cylinder (# 4) and stopped in the expansion stroke.

On the other hand, if the determination result in step S5 is false (No), that is, if the engine speed detected in step S4 is greater than or equal to the first predetermined speed, the process proceeds to step S8.
In step S8, it is determined whether or not the engine speed detected in step S4 is greater than a preset second predetermined speed. The second predetermined rotation speed is set to a value larger than the first predetermined rotation speed. If the determination result is true (Yes), the process proceeds to step S9.

  In step S9, as shown in FIG. 4, the cylinder 6 (cylinder # 4 in FIG. 4) in the compression stroke at a predetermined time is determined, and air is supplied into the combustion chamber 10 of the compression stroke cylinder by the air supply valve 22. To do. In other words, when the engine speed at a predetermined time is greater than the second predetermined speed, it is determined that the piston stop position is higher than the appropriate engine speed and the piston stop position passes through the predetermined position. Air is supplied into the combustion chamber 10 of the cylinder (# 4). Thus, by supplying air to the compression stroke cylinder (# 4), the pressure in the combustion chamber 10 increases, the rise of the piston 8 is suppressed, and the engine rotation is decelerated.

In the next step S7, fuel is supplied when the cylinder (# 4) estimated to stop in the expansion stroke as described above is in the last intake stroke before the piston stops, and the routine is exited.
On the other hand, if the determination result in step S8 is false (No), that is, if the engine speed detected in step S4 is equal to or lower than the second predetermined speed, the process proceeds to step S10.

In step S10, it is determined that the engine speed at a predetermined time is within an appropriate range, air is not supplied, the process proceeds to step S7, and the cylinder (# 4) that is estimated to stop in the expansion stroke is in the state before the piston stops. When in the last intake stroke, fuel is supplied and the routine is exited.
Here, the amount of air supplied in steps S6 and S9 is set in proportion to the engine speed detected in step S4, and is set based on the air supply amount setting map shown in FIG. 5 in detail. Is done.

As shown in FIG. 5, when the engine speed is smaller than the first predetermined speed, the air supply amount increases as the engine speed is lower, and is larger than the second predetermined speed. In some cases, the air supply amount is set to increase as the engine speed increases.
As described above, in the engine control apparatus according to the present invention, in the stop control of the engine 1, the engine 1 enters the combustion chamber 10 of the expansion stroke cylinder or the compression stroke cylinder in accordance with the engine speed at a predetermined time after the end of ignition. By supplying air by the air supply valve 22, the rotation of the engine 1 can be accelerated or decelerated, the engine speed can be adjusted to an appropriate range, and the piston 8 can be stopped at a predetermined position.

  In step S3, the throttle valve 44 is closed to increase the effect of the air supply, and the adjustment of the piston stop position by the air supply can be made more accurate. Furthermore, it is possible to easily and accurately perform stop control from the setting of a predetermined time based on the crank angle and the control of setting the air supply amount from the air supply amount setting map proportional to the engine speed.

Since the piston 8 can be stopped at the predetermined position in this way, the startability of the engine 1 by the direct start of the start control can be improved.
Although the description of the embodiment of the engine control apparatus according to the present invention has been completed above, the embodiment is not limited to the above embodiment.
For example, in the above embodiment, the engine 1 is an MPI engine. However, the present invention is not limited to this, and an in-cylinder injection type in which an injection port of a fuel injection valve faces the combustion chamber and fuel can be directly injected into the fuel chamber. You can use an engine. In the in-cylinder injection type engine, it is only necessary to inject fuel into the combustion chamber of the expansion stroke cylinder at the time of start-up. Therefore, in the engine stop control, the fuel is previously supplied to the cylinder that becomes the expansion stroke when the piston is stopped as in step S7. There is no need to spray.

Moreover, in the said embodiment, although idle stop conditions are set based on the detection result from the vehicle speed sensor 48, the shift position sensor 50, and the brake switch 52, the said idle stop conditions are not restricted to this, A configuration in which conditions are set may be used.
In the above embodiment, in the engine stop control, the predetermined timing for detecting the engine speed after the end of ignition is set as the predetermined crank angle. However, the setting of the predetermined timing is not limited to this. You may set based on the time after completion | finish.

  In the above embodiment, in engine stop control, the detection of the engine speed at a predetermined time is based on the crank angular speed obtained from the time elapsed from the specified crank angle before the predetermined crank angle to the predetermined crank angle. Although it is calculated, the detection of the engine speed at the predetermined time is not limited to this.

It is a schematic block diagram of embodiment in the control apparatus of the engine which concerns on this invention. It is a flowchart which shows the engine stop control routine performed in the engine control apparatus which concerns on this invention. It is a time chart in the case of supplying air to an expansion stroke cylinder. It is a time chart in the case of supplying air to a compression stroke cylinder. It is an air supply amount setting map. It is a figure which shows the combustion order of embodiment in the control apparatus of the engine which concerns on this invention.

Explanation of symbols

1 Engine 6 Cylinder 10 Combustion chamber 18 Crank angle sensor (engine speed detection means, crank angle detection means)
DESCRIPTION OF SYMBOLS 20 Spark plug 22 Air supply valve 28 Intake port 30 Fuel injection valve 44 Throttle valve 48 Vehicle speed sensor 50 Shift position sensor 52 Brake switch 54 ECU (piston stop position control means)

Claims (4)

A control device for an engine having a plurality of cylinders,
A fuel injection valve for supplying fuel into the combustion chamber of each cylinder;
A spark plug for igniting the fuel supplied into the combustion chamber by the fuel injection valve;
Air supply means for supplying air into the combustion chamber independently of supply of intake air by opening and closing an intake valve of the engine;
Engine speed detecting means for detecting the engine speed of the engine;
The engine speed detected by the engine speed detecting means is smaller than the first predetermined speed at a predetermined time from the end of ignition by the spark plug accompanying the stop of the engine until the piston stops. In some cases, air is supplied by the air supply means into the combustion chamber of the cylinder in the expansion stroke at the predetermined time, and the engine speed is a second predetermined speed that is greater than the first predetermined speed. If the rotational speed is greater than the rotational speed, air is supplied by the air supply means into the combustion chamber of the cylinder in the compression stroke at the predetermined time so that the piston stop position of the engine is stopped at the predetermined position. Piston stop position control means to be adjusted;
An engine control device comprising: Crank angle detection means for detecting the crank angle of the engine,
2. The predetermined time is a time when a crank angle detected by the crank angle detection means from a time point when ignition by the spark plug accompanying the stop of the engine becomes a predetermined crank angle. Engine control device.   The engine control device according to claim 1 or 2, wherein the piston stop position control means closes a throttle valve that controls an intake air amount of the engine from a point of time when ignition by the spark plug ends.   The said piston stop position control means sets the quantity of the air supplied by the said air supply means at the said predetermined time according to the engine speed in this predetermined time, The any one of Claim 1 thru | or 3 characterized by the above-mentioned. Engine control device.

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