JP2011163319A - Automatic stop-and-restart vehicle - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To sufficiently ensure startability even when a key is turned off during automatic stop while suppressing vibration during automatic stop and restart. <P>SOLUTION: A variable valve lift mechanism is controlled so that during the automatic stop, the valve timing of an intake valve is set to a second control position with an actual compression ratio comparatively reduced, and also when a key switch is turned off during the automatic stop (S10), a vehicle power supply is turned off (S50) after the variable valve lift mechanism is controlled so that the valve timing of the intake valve is set to a first control position with the actual compression ratio increased in comparison with that in the second control position (S70). <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to an engine control technique for an automatic stop / restart vehicle equipped with a variable valve mechanism.

An automatic stop / restart vehicle has been developed that automatically stops the engine when driving is stopped to improve fuel efficiency. The automatic stop / restart vehicle automatically stops the engine when a predetermined stop condition such as a vehicle speed of 0 is satisfied. Further, the engine is automatically restarted when a predetermined start condition such as release of brake operation is satisfied after the engine is automatically stopped.
On the other hand, an engine having a variable valve mechanism that varies the lift amount of the intake valve of the engine has been developed. In an engine equipped with such a variable valve mechanism, at the time of cold start, in order to reduce the starting fuel and improve the exhaust performance, the closing timing of the intake valve is set to the top dead center so that the actual compression ratio becomes as high as possible. Generally it is set near.

However, when the actual compression ratio is set to be high as described above, torque fluctuations increase, which causes a problem that vibration and starter hitting sound increase when the engine is stopped and started. In particular, in an automatic stop / restart vehicle such as that described above, it is desirable to suppress vibrations and the like as much as possible so as not to be detected by the occupant during automatic stop / restart.
Therefore, in an automatic stop / restart vehicle equipped with an engine with a variable valve operating device, during a normal stop or normal start by key switch ON / OFF, the variable valve mechanism is controlled so that the actual compression ratio becomes high during the cold state. Technology has been developed to control the variable valve mechanism so as to suppress the compression ratio, for example, by changing the closing timing of the intake valve at the time of automatic stop and restart in a warm state while ensuring startability of the engine (Patent Document 1).

JP 2002-213261 A

  However, if control is performed so as to suppress the compression ratio at the time of automatic stop and restart as in the above-mentioned Patent Document 1, for example, if key-off occurs during automatic stop, a time elapses until the engine starts and the engine is in a cold state. If this happens, the engine in the cold state will be started with a low compression ratio at the next start. In such a case, the variable valve mechanism may be operated at the time of starting so that the compression ratio becomes high.However, in the cold state, the sliding resistance increases due to a decrease in the oil temperature, and the variable valve mechanism operates. There is a risk that it will be insufficient, and quick start-up becomes difficult.

  The present application has been invented in view of such a problem, and is an automatic stop / restart vehicle that enables quick start even when the engine is in a cold state at the time of subsequent start when key-off occurs during automatic stop. Is to provide.

  In order to achieve the above object, the invention according to claim 1 is directed to a variable valve mechanism that changes at least one of the lift amount and opening / closing timing of an intake valve of an engine, and automatically stops the engine when a predetermined stop condition is satisfied. And a control means for automatically starting the engine when a predetermined start condition is established after the automatic stop, wherein the variable valve mechanism has at least the first valve timing of the intake valve. And the second control position where the actual compression ratio is lower than that of the first control position, and the control means sets the valve timing of the intake valve to the second control position during automatic stop. The variable valve mechanism is controlled so that the valve timing of the intake valve is set to the first control position when the key switch is turned off during automatic stop. Characterized by turning off the vehicle power after controlling the valve mechanism.

The invention according to claim 2 is characterized in that, in claim 1, the first control position is such that the closing timing of the intake valve is a predetermined position near bottom dead center.
According to a third aspect of the present invention, in the first or second aspect, the first control position is such that the closing timing of the intake valve is a predetermined position near the bottom dead center.
According to a fourth aspect of the present invention, in any one of the first to third aspects, the control means controls the variable valve mechanism so that the valve timing of the intake valve is set to the second control position at the time of automatic stop. At the same time, if the key switch is turned off during automatic stop, the engine is started and the variable valve mechanism is controlled so that the valve timing of the intake valve is set to the first control position. Is turned off.

  According to a fifth aspect of the present invention, in any one of the first to third aspects, an actual valve timing detecting means for detecting an actual valve timing of the intake valve is provided, and the control means is provided when the key switch is turned off at the time of automatic stop. If the actual valve timing is detected by the actual valve timing detection means after the control of the variable valve mechanism that sets the valve timing of the intake valve to the first control position, and the actual valve timing is not at the first control position, The actual valve timing is stored, and at the next start, at least one of the fuel injection amount and the ignition timing of the engine is corrected and controlled so that the startability is improved based on the stored actual valve timing.

According to the automatic stop / restart vehicle of claim 1 of the present invention, during the automatic stop, the valve timing of the intake valve is set to the second control position where the actual compression ratio is lower than the first control position. Can be suppressed and vibration can be suppressed.
Further, when the key switch is turned off during the automatic stop, the vehicle power is turned off after the valve timing of the intake valve is set to the first control position having a higher actual compression ratio than the second control position. The engine can be started with the valve timing of the intake valve at the first control position having a relatively high actual compression ratio when starting with the key switch, so even if the engine is in a cold state, the engine can be started. Sex can be secured.

According to the automatic stop / restart vehicle of claim 2 of the present invention, when the key switch is turned off at the time of the automatic stop, the valve closing timing is set to the first control position near the bottom dead center before the vehicle power is turned off. Since the valve timing of the intake valve is set and controlled, the engine can be started at a setting at which the actual compression ratio becomes higher at the next start by the key switch, and sufficient startability can be ensured.
According to the automatic stop / restart vehicle of claim 3 of the present invention, the lift amount of the intake valve at the second control position is smaller than the lift amount of the intake valve at the first control position. When the engine is restarted, the intake air amount is limited so that the engine speed does not increase excessively. When the engine is started in the cold state, the lift amount is increased to increase the intake air amount, thereby ensuring startability. Furthermore, controlling the variable valve mechanism from the second control position to the first control position increases the lift amount, which is a large load on the variable valve mechanism. Sometimes it is possible to suppress an increase in load, and the responsiveness to change is also high, so it does not take time to change from the second control position to the first control position, so the driver feels uncomfortable. Never give.

According to the automatic stop / restart vehicle of claim 4 of the present invention, the engine is started when the variable valve mechanism is controlled so that the valve timing of the intake valve is set to the first control position. The variable valve mechanism can be controlled.
According to the automatic stop / restart vehicle of claim 5 of the present invention, when the variable valve mechanism is controlled so that the key switch is turned off and the valve timing of the intake valve becomes the first control position at the time of automatic stop. When the valve timing is not in the first control position, the engine can be controlled so that the startability is improved at the next start based on the valve timing stored at this time, and the startability is further improved. Can do.

It is a schematic block diagram of the engine control system of the automatic stop / restart vehicle according to the present invention. It is a graph which shows the valve timing of the engine of this embodiment. It is a flowchart which shows the control point of the variable valve lift mechanism and engine at the time of key-off.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.
FIG. 1 is a schematic configuration diagram of an engine control system of an automatic stop / restart vehicle according to the present invention.
The automatic stop / restart vehicle of this embodiment includes a variable valve lift mechanism 2 (variable valve mechanism) in the engine 1.
As shown in FIG. 1, the engine 1 is a so-called SOHC engine in which one camshaft 10 is provided with an intake cam 11 and an exhaust cam 12. The structure of the variable valve lift mechanism 2 is described in, for example, Japanese Patent Application Laid-Open No. 2005-299536. Although the detailed structure is omitted, in addition to the camshaft 10 and the rocker arm 14 that drives the intake valve 13, a center is provided. A rocker arm 15 and a swing cam 16 are provided. When the rocker arm 14 is moved up and down by the rotation of the intake cam 11, the rocker shaft 18 is rotated by the motor 17 to move the fulcrum position of the center rocker arm 15, thereby changing the maximum lift amount of the intake valve 13. On the other hand, from the maximum lift amount to the minimum lift amount, it is possible to uniquely advance the valve closing timing of the intake valve 13 as the lift amount decreases while keeping the valve opening timing substantially constant. The motor 17 is provided with a rotation angle sensor 20 (actual valve timing detection means) for detecting the rotation angle. The rotation angle sensor 20 has a function of indirectly detecting the actual valve timing of the intake valve 13 by detecting the rotation angle.

  The ECU 30 (control means) includes an input / output device, a storage device (ROM, RAM, nonvolatile RAM, etc.), a central processing unit (CPU), and a timer, and performs overall control of the engine 1. In particular, the ECU 30 inputs operation information of the key switch 31, the rotation angle of the motor 17, and other engine operation information such as an idle switch, a brake switch, a vehicle speed, an engine rotation speed, and the motor 17 as a variable valve lift mechanism control function. And the operation of the starter motor 32, the fuel injection valve 33, and the ignition device 34 are controlled as an automatic stop / restart control function.

  Specifically, the ECU 30 has, as an automatic stop / restart control function, predetermined idle stop conditions, for example, the key switch 31, the idle switch and the brake switch are turned on, the vehicle speed is equal to or lower than the predetermined vehicle speed, the engine rotation speed is equal to or lower than the predetermined rotation speed, and the engine 1 When the engine is in a warm state, the fuel injection from the fuel injection valve 33 is stopped and the operation of the engine 1 is automatically stopped. Further, the ECU 30 restarts the engine 1 by operating the starter motor 32 and the ignition device 34 when the brake switch is turned off by a predetermined start condition, for example, by releasing the brake operation, during the automatic stop (idle stop). Let

FIG. 2 is a graph showing the valve timing of the engine 1 of the present embodiment. Specifically, FIG. 2 shows changes in lift amounts of the intake valve 13 and the exhaust valve.
As shown in FIG. 2, in the engine 1 having the variable valve lift mechanism 2, the valve timing of the intake valve 13 (the position where the lift amount and the valve closing timing are set) and the valve closing timing of the intake valve 13 are dead. The first control position that is set near the point (BDC) is included, and before and after the first control position, the second control position that is the minimum lift amount to the third control position that is the maximum lift amount. Can be variably set.

In the first control position, since the closing timing of the intake valve 13 is set near the bottom dead center as described above, the actual compression ratio becomes the highest in a state where the engine speed including the start time is low. In addition, since it becomes larger than the lift amount at the time of idling stop in the temperature state of the engine 1, which will be described later, the intake air amount can be secured.
In the second control position, the closing timing of the intake valve 13 is advanced most, and the actual compression ratio becomes smaller. The second control position is set so that the lift amount becomes as small as possible within the range in which the engine 1 can be started at idling stop, which is possible when the engine 1 is in a warm state, and the intake air amount is limited. Suppresses unnecessary blowing.

In the third control position, the closing timing of the intake valve 13 is retarded from the bottom dead center, the actual compression ratio is smaller than the actual compression ratio in the first control position, and the actual compression in the second control position. Greater than the ratio.
Further, in the present embodiment, the ECU 30 performs control in association with the automatic stop / restart control function and the variable valve lift mechanism control function. Hereinafter, the details will be described with reference to FIG.
FIG. 3 is a flowchart showing a control procedure of the variable valve lift mechanism 2 and the engine 1 at the time of key-off.

The ECU 30 normally controls the variable valve lift mechanism 2 so that the valve timing is at the second control position during automatic stop (idle stop).
Further, the ECU 30 starts the routine shown in FIG. 3 every time the key switch 31 of the engine 1 is turned off.
First, in step S10, it is determined whether or not the engine 1 is currently in an automatic stop state by the automatic stop / restart control function. If it is in the automatic stop state, the process proceeds to step S60. If it is not in the automatic stop state, the process proceeds to step S20.

In step S20, the rotation angle of the motor 17 is input from the rotation angle sensor 20, and the valve timing setting of the intake valve 13 in the current variable valve lift mechanism 2 is the first control position where the actual compression ratio is the highest. It is determined whether or not. If it is the first control position, the process proceeds to step S40. If it is not the first control position, the process proceeds to step S30.
In step S30, the motor 17 is controlled so that the valve timing of the intake valve 13 becomes the first control position. Then, the process proceeds to step S40.

In step S40, the fuel injection from the fuel injection valve 33 is stopped, and the engine 1 is stopped. Then, the process proceeds to step S50.
In step S50, the vehicle power supply is turned off. Then, this routine ends.
In step S60, the rotation angle of the motor 17 is input from the rotation angle sensor 20, and it is determined whether or not the setting of the valve timing of the intake valve 13 in the current variable valve lift mechanism 2 is the first control position. If it is the first control position, the process proceeds to step S80. If it is not the first control position, the process proceeds to step S70.

  In step S70, the motor 17 is controlled so that the valve timing of the intake valve 13 becomes the first control position. At this time, a timer is started as the operation of the motor 17 starts, and the operation time of the motor 17 until reaching the first control position is measured. If the operation time of the motor 17 exceeds the specified time T1 before the valve timing of the intake valve 13 reaches the first control position, the operation of the motor 17 is stopped. The specified time T1 may be set to a time required when the valve timing of the intake valve 13 moves from the second control position to the first control position when the engine 1 is in a warm state. Then, the process proceeds to step S80.

In step S80, it is determined in step S70 whether or not the motor 17 is stopped without the valve timing of the intake valve 13 reaching the first control position within the specified time T1. If the first control position has not been reached within the specified time T1, the process proceeds to step S90. If it has reached the specified time T1, the process proceeds to step S50.
In step S90, the rotation angle of the motor 17 is input from the rotation angle sensor 20, and the valve timing setting state of the intake valve 13 is stored. Then, the process proceeds to step S50.

  As described above, in the present embodiment, the valve timing is set at the second control position having a low actual compression ratio during automatic stop, so the load at the time of starting is reduced, the cranking rotational speed is increased, and the rotation is performed. Variation is suppressed. Therefore, the vibration of the engine 1 is suppressed, the hitting sound of the starter motor 32 is reduced, and the engine 1 can be restarted with little uncomfortable feeling hardly noticed by the occupant.

  When the key-off operation is performed during the automatic stop, the motor 17 is operated so that the valve timing moves from the second control position to the first control position, and the power is turned off. Therefore, at the subsequent normal start by the key switch 31, the valve timing of the intake valve 13 is already set to the first control position, so even if the time after key-off has elapsed and the engine is in a cold state Thus, the starting is performed at the first control position where the actual compression ratio becomes the highest, and the startability can be sufficiently ensured.

  If the key switch 31 is turned off at the time of automatic stop, the engine 1 has already stopped and must be moved relatively large from the second control position to the first control position. It may be difficult to reach the first control position. However, the fact that the engine 1 is in the warm state is set as one of the automatic stop execution conditions, so that the friction is relatively suppressed and the possibility that the first control position cannot be reached is suppressed. . In addition, since there is little deterioration in the variable responsiveness, the vehicle power can be turned off without requiring much variable time after turning off the key switch 31, so that the driver does not feel uncomfortable.

  Further, when the key switch 31 is turned off during the automatic stop and the motor 17 is controlled to operate, even if the first control position is not reached, the valve timing at this time is stored, so the next key The fuel injection amount, the ignition timing, and the like may be corrected and controlled in accordance with the stored valve timing so that the startability is improved when the switch 31 is started. In this way, starting can be performed more reliably.

In this embodiment, the variable valve lift mechanism 2 varies the valve closing timing and the lift amount. However, the present invention is not limited to this, and has a function of varying the actual compression ratio. If there is, it can be applied to various variable valve mechanisms.
In the present embodiment, the variable valve lift mechanism 2 can continuously change the second control position and the third control position. However, the present invention is not limited to this, and at least the key switch It is only necessary to be able to switch between the valve timing set at the start by the valve timing and the valve timing set at the automatic stop.

DESCRIPTION OF SYMBOLS 1 Engine 2 Variable valve lift mechanism 13 Intake valve 20 Rotation angle sensor 30 ECU
31 Key switch

Claims (5)

A variable valve mechanism that varies at least one of the lift amount and opening / closing timing of an intake valve of the engine, and the engine is automatically stopped when a predetermined stop condition is satisfied, and the engine is stopped when a predetermined start condition is satisfied after the automatic stop An automatic stop / restart vehicle comprising: control means for automatically starting the vehicle;
The variable valve mechanism can set the valve timing of the intake valve to at least a first control position and a second control position at which an actual compression ratio is lower than the first control position.
The control means controls the variable valve mechanism so that the valve timing of the intake valve is set to the second control position during the automatic stop, and when the key switch is turned off during the automatic stop. The automatic stop / restart vehicle characterized in that the vehicle power supply is turned off after controlling the variable valve mechanism so that the valve timing of the intake valve is set to the first control position.   2. The automatic stop / restart vehicle according to claim 1, wherein the first control position is a predetermined position near a bottom dead center when the intake valve is closed. 3.   3. The automatic stop / restart vehicle according to claim 1, wherein a lift amount of the intake valve at the second control position is smaller than a lift amount of the intake valve at the first control position. 4.   The control means controls the variable valve mechanism so that the valve timing of the intake valve is set to the second control position during the automatic stop, and when the key switch is turned off during the automatic stop. Is configured to start the engine, control the variable valve mechanism so that the valve timing of the intake valve is set to the first control position, and then stop the engine and turn off the vehicle power supply. The automatic stop / restart vehicle according to any one of claims 1 to 3. An actual valve timing detecting means for detecting an actual valve timing of the intake valve;
The control means is configured to detect the actual valve timing by the actual valve timing detection means after the control of the variable valve mechanism that sets the valve timing of the intake valve to the first control position when a key switch is turned off during the automatic stop. When the timing is detected and the actual valve timing is not in the first control position, the actual valve timing is stored, and the startability is improved based on the stored actual valve timing at the next start. The automatic stop / restart vehicle according to any one of claims 1 to 3, wherein at least one of a fuel injection amount and an ignition timing of the engine is corrected and controlled.

Images