JP2007239584A - STARTING DEVICE AND STARTING METHOD FOR INTERNAL COMBUSTION ENGINE - Google Patents

Abstract

PROBLEM TO BE SOLVED: To start by combustion without using a starter motor after idle stop or the like.
SOLUTION: When starting an engine, fuel is supplied to a cylinder that is stopped in an expansion stroke, and ignition is performed to burn the cylinder, and engine rotation is started by combustion. During a predetermined period of such combustion start, the reaction force of rotation due to combustion is reduced. Specifically, the fastening element that is fastened in the D range is disconnected by the automatic transmission. In addition, the decompression device reduces the compression stroke reaction force of the engine. After the predetermined period, the fastening element is immediately fastened. In preparation for fastening, the fastening line pressure is secured by the line pressure holding mechanism from the time of engine stop.
[Selection] Figure 1

Description

  The present invention relates to a starting device and a starting method for an internal combustion engine that starts a rotation of an engine by combustion by supplying fuel and igniting a cylinder that is stopped in an expansion stroke at the time of starting.

Conventionally, as described in Patent Document 1, as a starting device for an internal combustion engine, a cylinder stopped in an expansion stroke (after the top dead center of the piston and before the exhaust stroke) is determined, and the determined cylinder On the other hand, by supplying fuel and igniting, starting the engine with torque generated by combustion, the engine is started (combustion start or starterless start) without using a starter motor. It has been.
JP-A-2-271073

However, there are various types of friction torque (friction torque in an automatic transmission, friction torque due to engine compression stroke reaction, friction torque due to engine auxiliary load) against the torque generated by combustion. Therefore, there is a problem that it is difficult to secure startability in practice.
In view of such a situation, the present invention has an object of improving startability and startability at the time of combustion start.

  For this reason, in this invention, it is set as the structure which reduces the reaction force of the rotation by combustion for a predetermined period at the time of combustion start.

  According to the present invention, the start probability at the start of combustion can be significantly improved by reducing the reaction force of rotation due to combustion for a predetermined period.

Embodiments of the present invention will be described below with reference to the drawings.
FIG. 1 is a system diagram of an automobile internal combustion engine (engine) showing an embodiment of the present invention.
In the intake passage 2 of the engine 1, an electric throttle valve 3 for controlling the intake air amount is installed. The opening degree of the electric throttle valve 3 is controlled by a step motor or the like that is operated by a signal from an engine control unit (hereinafter referred to as ECU) 20.

The combustion chamber 4 of the engine 1 is provided with a fuel injection valve 5 and a spark plug 6.
The fuel injection valve 5 is energized to open a solenoid by an injection pulse signal output from the ECU 20 in synchronization with engine rotation, and injects fuel adjusted to a predetermined pressure.
The fuel injected into the combustion chamber 4 forms an air-fuel mixture, and is ignited and burned by the spark plug 6 based on the ignition signal from the ECU 20.

Of the intake valve 7 and the exhaust valve 8, at least the intake valve 7 is provided with a variable valve timing mechanism (VTC) 9 that can change the valve timing, and the valve timing is controlled by a signal from the ECU 20. It is possible.
An exhaust purification catalyst 11 is provided in the exhaust passage 10 of the engine 1.
A signal from the crank angle sensor 21 is input to the ECU 20. Here, the crank angle sensor 21 is provided so as to detect the rotation of the crankshaft and the camshaft, and detects the cylinder discrimination (expansion stroke cylinder discrimination) and the crank angle position (expansion stroke cylinder crank angle). In addition, the engine speed Ne can be detected. In addition, the crank angle sensor 21 used here can detect reverse rotation, including swinging back when the engine is stopped, and stores the information when the engine is stopped in the backup memory, so that cylinder discrimination and cranking can be performed from before the start. The angular position can be detected.

Further, the ECU 20 receives signals from an accelerator pedal sensor 22 for detecting the accelerator opening APO, an air flow meter 23 for detecting the intake air amount Qa, and a water temperature sensor 24 for detecting the engine cooling water temperature Tw. A signal from the brake switch 25 that is turned on by a stepping operation is also input.
Based on the engine operating conditions detected from these input signals, the ECU 20 opens the electric throttle valve 3, the fuel injection timing and fuel injection amount of the fuel injection valve 5, the ignition timing of the spark plug 6, and the intake valve 7. The valve timing of (and the exhaust valve 8) is controlled.

The output shaft 12 of the engine 1 is connected to the automatic transmission 30.
FIG. 2 is an internal connection diagram (skeleton diagram) of the automatic transmission. This is an example of a 5-speed AT, and a combination of planetary gears in 3 rows (front, mid, rear) and various fastening elements (clutch C and brake B) It is comprised so that it may become. FIG. 3 is an operation table in the configuration of FIG.

  Returning to FIG. 1, various fastening elements of the automatic transmission 30 are controlled by an automatic transmission control unit (hereinafter referred to as ATCU) 40. The ATCU 40 includes shift positions (P, R, N, D) of a shift selector. A signal from a shift position sensor 41 that detects the vehicle speed and a vehicle speed sensor 42 that detects the vehicle speed VSP are input. The ATCU 40 also receives a signal from a line pressure sensor 43 that detects the line pressure of the automatic transmission 30.

Moreover, ECU20 and ATCU40 are connected by the communication line 44, and can mutually transmit / receive information.
The ATCU 40 sets a gear position (1 to 5 speeds) based on the shift position detected by the shift position sensor 41, and in the travel range (D range) based on the accelerator opening APO and the vehicle speed VSP, Various fastening elements of the automatic transmission 30 are controlled.

  Further, the engine 1 is provided with a starter motor 13 and can be started by cranking by operating the starter motor 13 with the pinion gear 14 meshed with the ring gear 15 on the engine 1 side. . The starter motor 13 can mesh with the ring gear 15 on the engine 1 side when the engine is stopped, and the rotor of the starter motor 13 does not rotate due to the rotation of the engine 1 side (the mechanism that idles even when driven from the engine side). ).

  Further, the automatic transmission 30 is provided with a line pressure holding mechanism 32. The line pressure holding mechanism 32 is a mechanism that holds the line pressure until the start-up by closing the line pressure circuit when the engine is stopped (closing the drain side with a valve). Instead of the line pressure holding mechanism, an electric oil pump that can quickly raise the line pressure at the time of start-up may be used.

Next, idle stop control performed as cooperative control between the ECU 20 and the ATCU 40 and combustion start control at the time of release will be described.
In the idle stop control, the engine is stopped under a predetermined idle stop condition (when the engine is in an idle state and the vehicle is stopped), and the predetermined idle stop release condition (when the driver's intention to start) is detected. Start the engine.

In this embodiment, when starting from such an idle stop, combustion start is performed, and this control will be described with reference to the flowcharts of FIGS.
FIG. 4 is a flowchart of idle stop control.
In S1, it is determined whether an idle stop condition is satisfied during engine operation. The idle stop condition is a state in which the engine is in an idle state (accelerator opening APO = 0), the brake is on, and the vehicle is stopped (vehicle speed VSP = 0).

If the idle stop condition is satisfied, the process proceeds to S2.
In S2, the following processes (1) and (2) are performed in preparation for the combustion start at the time of releasing the idle stop.
(1) A fastening element (hereinafter referred to as a D range clutch element) that is fastened when the automatic transmission is in the D range is disconnected. Specifically, the high & low reverse clutch (H & LR / C), front brake (Fr / B), and low coast brake (LC / B) that are engaged at the first speed of the D range are disconnected (FIGS. 2 and 3). reference).

(2) A variable valve timing mechanism (VTC) is used as a decompression device, and decompression is set. Specifically, the closing timing of the intake valve is delayed until the middle of the compression stroke. This is to reduce the compression stroke reaction force of the engine at the start of combustion.
In S3, an engine stop command is issued. Thereby, fuel injection and ignition are stopped, and the engine is stopped.

In S4, after the engine stop command, the AT line pressure is monitored, and when the line pressure falls below the pressure a necessary for the next start, the process proceeds to S5 to activate the line pressure holding mechanism.
FIG. 5 is a flowchart of the engine stop command post-control executed in parallel with the engine stop command post-control (S4, S5) in FIG.
In S11, it is determined whether or not a predetermined time b has elapsed after the engine stop command. This is to confirm that the engine has stopped.

In S12, the pinion gear of the starter motor jumps into the ring gear on the engine side in preparation for starter assist start. And it progresses to S13 and waits in preparation for engine starting.
FIG. 6 is a flowchart of the combustion start control from the idle stop. FIG. 7 is a timing chart.

In S21, it is determined whether the brake has been turned off as the idle stop release condition, that is, whether the driver's intention to start has been detected. If the brake is OFF (start intention detection), the process proceeds to S22.
In S22, an engine start command is issued to start combustion.
That is, fuel is injected and supplied from the fuel injection valve to the cylinders stopped in the expansion stroke, and the ignition plug is ignited and burned to start the rotation of the engine.

For example, in the case of a six-cylinder engine, when the engine is stopped, one cylinder stops at the ATDC 60 ° during the expansion stroke, and the next cylinder stops at the BTDC 60 ° during the compression stroke due to the balance of moments between the cylinders. Stops at the BDC (BTDC 180 °) at the compression stroke start point.
Therefore, the cylinder stopped at the ATDC 60 ° during the expansion stroke is the # 1 cylinder, the cylinder stopped at the BTDC 60 ° during the compression stroke is the # 2 cylinder, and the cylinder stopped at the BDC at the compression stroke starting point is the # 3 cylinder. Then, first, fuel is injected and supplied to the # 1 cylinder stopped in the expansion stroke, and ignition is performed for combustion to obtain the first torque.

Thereafter, fuel is injected and supplied to the next # 2 cylinder at an appropriate timing, and ignition is performed in the vicinity of TDC to burn, thereby obtaining a second torque. Since this cylinder starts in the middle of the compression stroke, the second stroke can obtain a larger torque than the first stroke.
Thereafter, fuel is injected and supplied to the next # 3 cylinder at an appropriate timing, and ignition is performed in the vicinity of TDC to burn it, thereby obtaining a third torque. Since this cylinder starts from the intake bottom dead center, the amount of intake air is maximized, and a substantially normal torque greater than the second is obtained for the third shot. In other words, during the predetermined period during which the reaction force against the rotation due to combustion is reduced at the start, the cylinder that starts compression from the vicinity of the intake bottom dead center burns (or the cylinder surely burns as described later). It can be considered that it is until the time when it is confirmed that it will be.

  During the combustion start, since the fastening element that is fastened when the automatic transmission is in the D range is disconnected, the friction torque by the automatic transmission can be reduced. In addition, since the decompression is set, the friction torque due to the compression stroke reaction force of the engine can be reduced. In addition, when an engine start command is issued, power generation by the alternator (ALT) is prohibited, and the operation of other auxiliary machines (hydraulic power steering pump, air conditioner, engine oil pump, etc.) is prohibited. The friction torque due to the load can be reduced. Therefore, the reaction force of rotation due to combustion can be reduced, and the start probability of combustion start can be increased.

Further, during the combustion start, the control after S23 is performed based on the expansion stroke TDC counter (cylinder discrimination counter) and the expansion stroke crank angle.
The expansion stroke crank angle counts the crank angle from the TDC of the cylinder in the expansion stroke, and is reset at the TDC of the cylinder that newly reaches the expansion stroke. The expansion stroke TDC counter is counted up with the TDC of the cylinder that newly reaches the expansion stroke, and is initially 0 (indicating the # 1 cylinder), 1 at the TDC of the # 2 cylinder, and 1 at the # 3 cylinder. 2 at TDC.

In S23, it is monitored whether the expansion stroke crank angle has reached a predetermined angle c, and when the crank angle = c, the process proceeds to S24. The predetermined angle c is set to a timing at which the torque becomes maximum by the first ignition.
In S24, the expansion stroke crank angular velocity (ω) at the time of expansion stroke crank angle = c is detected, and it is determined whether or not this is equal to or greater than a predetermined value d. The predetermined value d is set to a value such that the next cylinder can survive the compression top dead center with the first torque.

If the crank angular speed is greater than d, starter assist is not required, so the process proceeds to S25.
In S25, it is monitored whether the expansion stroke TDC counter is equal to 1 (whether the # 2 cylinder has reached TDC).
In S26, it is monitored whether the expansion stroke crank angle has reached a predetermined angle e, and when the crank angle = e, the process proceeds to S27. The predetermined angle e is set to a timing at which the torque becomes maximum at the second ignition.

In S27, the expansion stroke crank angular velocity (ω) at the time of expansion stroke crank angle = e is detected, and it is determined whether or not this is equal to or greater than a predetermined value f. The predetermined value f is set to such a value that the second cylinder can survive the compression top dead center with the second torque.
If the crank angular speed is greater than f, the starter assist is not required, so the process proceeds to S28.
In S28, the jumping into the ring gear on the engine side of the pinion gear of the starter motor is turned off and retracted. This is because starter assist is no longer necessary.

In S29, it is monitored whether or not the expansion stroke TDC counter = 2 has been reached (whether # 3 cylinder has reached TDC).
In S30, it is monitored whether the expansion stroke crank angle has reached a predetermined angle g, and the process proceeds to S31 when the crank angle = g. The predetermined angle g is set to a timing at which the torque is maximized by the third ignition.

In S31, the following processes (1) to (5) are performed. This is because sufficient startability has already been obtained, and preparation for starting (improvement of starting performance) is achieved.
(1) The D-range clutch element is fastened in preparation for starting. Specifically, the high & low reverse clutch (H & LR / C), the front brake (Fr / B), and the low coast brake (LC / B) are engaged in order to achieve the first speed in the D range (FIGS. 2 and 2). 3).

(2) The power generation of the alternator (ALT) is permitted by the timer.
(3) The operation of other auxiliary machines is permitted by the timer. Note that (2) and (3) are permitted by the timer, but may be simultaneously with the D range clutch element engagement. However, if it overlaps with other operations, it may become unstable, and as a precaution, permission is provided by a timer so that it can be set separately.

(4) Release decompression (release by timer). That is, the intake valve closing timing delayed by the variable valve timing mechanism (VTC) is returned to the normal setting (required intake valve closing timing from the relationship between the driver request torque and the engine generated torque). Again, from the viewpoint of shock prevention, etc., it is canceled by a timer.
(5) Stop the line pressure holding mechanism. Specifically, the actual line pressure that rises as the engine rotates is monitored, and the line pressure holding mechanism is stopped when the actual line pressure exceeds a predetermined value h.

If the expansion stroke crank angle velocity (ω) at the time of the expansion stroke crank angle = c is equal to or smaller than the predetermined value d in the determination in S24, or the expansion at the time of the expansion stroke crank angle = e in the determination in S27. If the stroke crank angular velocity (ω) is less than or equal to the predetermined value f, it can be determined that the next cylinder cannot survive the compression top dead center at the start of combustion, and thus the routine proceeds to S32.
In S32, the starter motor is driven to start starter assist.

In S33, as in S31 described above, the processes (1) to (5) are performed to prepare for the start.
According to this embodiment, at the time of starting, when the fuel is supplied to the cylinders that are stopped in the expansion stroke and ignited to be burned and the engine is started to rotate by the combustion, the automatic transmission is set to the travel range (D Range), the reaction force of the rotation due to combustion (piston push-down reaction force) is reduced by separating the fastening element that is fastened in the automatic transmission during the travel range (D range) for a predetermined period, The probability of starting without using a starter motor is improved by increasing the rising speed of rotation at the time of starting. In addition, after the predetermined period has elapsed, by fastening the fastening element, it is possible to ensure start performance, and to achieve both start performance and start performance.

  In the present embodiment, for the predetermined period, from the compression stroke start point (or before it) to the time point when the maximum torque is obtained by combustion in the cylinder that has started rotating (the point of crank angle = g in FIG. 7). However, it is determined that the cylinder can overcome the compression TDC until or before the compression TDC of the cylinder (the point where the expansion stroke TDC counter = 2 in FIG. 7). = Point where ω> f). Alternatively, it may be delayed until the compression TDC of the next cylinder (the point at which the expansion stroke TDC counter = 3 in FIG. 7).

In addition, according to the present embodiment, it is possible to ensure start performance by providing means for securing the line pressure of the automatic transmission in preparation for fastening of the fastening element.
Here, the means for securing the line pressure secures the line pressure from before the engine is started by adopting a line pressure retaining mechanism for retaining the line pressure by closing the line pressure circuit when the engine is stopped. be able to.

The line pressure holding mechanism monitors the line pressure after the engine is stopped and operates when the line pressure falls below the pressure necessary for the next start, thereby ensuring a necessary and sufficient line pressure. .
However, the means for securing the line pressure may be an electric oil pump capable of increasing the line pressure to a pressure required for fastening of the fastening element at the time of starting the engine. The line pressure can be secured.

Further, according to the present embodiment, by providing a decompression device for reducing the compression stroke reaction force of the engine as the reaction force reducing means, the rotation reaction force (piston push-down reaction force) due to combustion is further reduced, and combustion start The starting probability can be further improved.
Further, the decompression device reduces the compression stroke reaction force of the engine by delaying the closing timing of the intake valve, so that a variable valve device such as a variable valve timing mechanism can be used.

Further, according to the present embodiment, the reaction force reducing means is provided with means for limiting power generation by the alternator, thereby further reducing the reaction force of rotation caused by combustion (piston-pressing reaction force) and increasing the start probability of combustion start. Further improvement can be achieved.
Further, according to the present embodiment, the reaction force reducing means is provided with means for limiting the operation of the auxiliary load of the engine, thereby further reducing the rotational reaction force (piston push-down reaction force) due to combustion and starting combustion. The starting probability can be further improved.

Further, according to this embodiment, the crank angular velocity is detected at a predetermined timing of the start by the combustion, and when it is less than the predetermined value, the start fails due to fail-safe control of performing the assist start by the starter motor. It will be possible to avoid it reliably.
Here, the starter motor is engaged with the ring gear on the engine side after the engine is stopped and before starting, thereby enabling quick fail-safe control (assist starting).

Engine system diagram showing an embodiment of the present invention Skeleton diagram of automatic transmission Operating table of fastening elements Idle stop control flowchart Flow chart of control after engine stop command Flow chart of combustion start control from idle stop Timing chart

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Engine 2 Intake passage 3 Electric throttle valve 4 Combustion chamber 5 Fuel injection valve 6 Spark plug 7 Intake valve 8 Exhaust valve 9 Valve timing variable mechanism (VTC)
13 Starter motor 15 Ring gear 20 ECU
21 Crank angle sensor 22 Accelerator opening sensor 25 Brake switch 30 Automatic transmission 32 Line pressure holding mechanism 40 ATCU
41 Shift position sensor 42 Vehicle speed sensor 43 Line pressure sensor 44 Communication line

Claims (13)

In the starter of the internal combustion engine that supplies fuel to the cylinders that are stopped in the expansion stroke at the time of starting and ignites and burns, and starts the rotation of the engine by combustion,
A starting device for an internal combustion engine, characterized in that a reaction force reducing means for reducing a reaction force of rotation due to combustion is provided for a predetermined period at the time of starting.   The reaction force reducing means reduces the reaction force by separating a fastening element that is fastened when the vehicle is in a travel range by an automatic transmission for a predetermined period, and fastens the fastening element after the predetermined period has elapsed. The starter for an internal combustion engine according to claim 1.   The starter for an internal combustion engine according to claim 2, further comprising means for securing a line pressure of the automatic transmission in preparation for fastening of the fastening element.   4. The starter for an internal combustion engine according to claim 3, wherein the means for securing the line pressure is a line pressure holding mechanism that holds the line pressure by closing the line pressure circuit when the engine is stopped. .   5. The internal combustion engine starter according to claim 4, wherein the line pressure holding mechanism monitors the line pressure after the engine is stopped and operates when the line pressure falls below a pressure required for the next start.   The starter for an internal combustion engine according to claim 3, wherein the means for securing the line pressure is an electric oil pump capable of increasing the line pressure to a pressure required for fastening of the fastening element when the engine is started. .   The starter for an internal combustion engine according to any one of claims 1 to 6, wherein the reaction force reducing means includes a decompression device for reducing a compression stroke reaction force of the engine.   8. The internal combustion engine starter according to claim 7, wherein the decompression device reduces the compression stroke reaction force of the engine by delaying the closing timing of the intake valve.   The starter for an internal combustion engine according to any one of claims 1 to 8, further comprising means for limiting power generation by an alternator as the reaction force reducing means.   The starter for an internal combustion engine according to any one of claims 1 to 9, wherein the reaction force reducing means includes means for restricting operation of an auxiliary load of the engine.   11. The internal combustion engine according to claim 1, wherein a crank angular velocity is detected at a predetermined timing of the start by the combustion, and if it is less than a predetermined value, an assist start by a starter motor is performed. Engine starter.   12. The starter for an internal combustion engine according to claim 11, wherein the starter motor meshes with a ring gear on the engine side after the engine is stopped and before starting. At the time of starting, when fuel is supplied to the cylinders that are stopped in the expansion stroke and ignition is performed for combustion, the rotation of the engine is started by combustion,
When the automatic transmission is in the travel range, the fastening element that is fastened when the automatic transmission is in the travel range is separated for a predetermined period, and the fastening element is fastened after the predetermined period has elapsed. A method for starting an internal combustion engine.

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