JP5961005B2 - Engine control device - Google Patents

Description

  The present invention relates to an engine control device that automatically stops / starts an engine when a predetermined condition is satisfied.

  In recent years, for the purpose of reducing exhaust emissions, reducing noise, improving fuel efficiency, etc., when certain conditions to stop the vehicle running, such as when the driver steps on the brake with a red light, the engine is automatically stopped, Thereafter, when a driver performs a start operation (for example, an operation such as switching a foot from a brake to an accelerator) by switching a signal or the like, an increasing number of vehicles include an idle stop system that automatically restarts an engine.

  In a vehicle equipped with such an idle stop system, when an idle stop execution condition is satisfied, a fuel cut is executed in order to stop the engine rotation, but the engine rotation is completely stopped after the fuel cut is started. Until the engine is restarted, engine restart conditions may be satisfied. In this case, in a vehicle that uses an electromagnetic push-in type starter that pushes out the pinion gear and meshes with the ring gear on the engine side, in order to smoothly engage the gear, it must wait until the engine rotation is completely stopped or close to it. The restart is delayed against the driver's intention. Further, even when a constantly meshing starter is used, the starter is driven each time the engine is restarted from the idle stop, and there is a concern about the durability of the starter.

  In order to cope with this, Patent Document 1 discloses that the inertial condition is established without fuel supply when the start condition is satisfied after the engine stop condition is satisfied and the fuel supply is stopped and before the engine rotation is stopped. There is disclosed a technique for determining whether or not it is possible to return from a state in which the engine is rotating by force to a state in which the engine rotates independently by restarting fuel supply, based on the engine speed.

Japanese Patent No. 4029891

  However, in the technique for determining whether or not the self-sustained rotation return is possible based on the engine speed as disclosed in Patent Document 1, a delay occurs until the engine speed is calculated. Actually, there is a possibility that it cannot return to the self-supporting rotation.

  That is, the engine speed is generally calculated from the time between the detection signals of the crank angle sensor, but is often calculated between the top dead centers of each cylinder in order to average the angular velocity change due to combustion, and the engine speed is reduced. As it is, it takes time to calculate the engine speed, and a delay occurs in the determination of the independent rotation return. Also, depending on the fuel injection timing, even if the fuel cut of a certain cylinder is executed, the fuel injected in the previous cycle burns in the other cylinders, so it takes time until the engine speed decreases. In the same manner, there is a delay in the determination of the self-sustained rotation return.

  The present invention has been made in view of the above circumstances, and it is determined whether or not the engine can return to a self-supporting rotation when a start condition is established between the stop of the fuel supply and the stop of the engine rotation. An object of the present invention is to provide an engine control apparatus that can accurately determine without delay.

The engine control device according to the present invention performs fuel cut for each cylinder when a predetermined stop condition is satisfied, stops fuel supply to the engine, and performs fuel cut when a predetermined start condition is satisfied. In the engine control device that stops and restarts the fuel supply, when the stop condition is satisfied, a fuel cut frequency integration unit that integrates the number of executions of the fuel cut, and rotation of the engine from the start of the fuel cut When the start condition is satisfied until the fuel is cut, the fuel cut frequency integrated by the fuel cut frequency integration unit is compared with a predetermined threshold value, and whether or not it is possible to return to the independent rotation by restarting the fuel supply. A self-sustained rotation return determination unit that determines whether or not the self-recovery rotation return determination unit returns to the self-revolution of the engine when the number of fuel cuts is equal to or less than the threshold value. Judges that allows to resume the fuel supply, the return fuel cut number to self rotation is greater than the threshold value is continued the fuel cut is determined impossible to stop the rotation of the engine.

  According to the present invention, when a start condition is established between the time when fuel supply is stopped and the time when engine rotation stops, it is accurately determined without delay whether or not the engine can return to self-sustaining rotation. Can do.

Schematic configuration diagram of engine control system Functional block diagram related to idle stop Explanatory drawing showing the timing of fuel cut and engine speed calculation for each cylinder Explanatory drawing which shows the example of a threshold value setting with respect to the number of fuel cut cylinders Idle stop fuel cut control routine flowchart

Embodiments of the present invention will be described below with reference to the drawings.
In FIG. 1, reference numeral 1 denotes an engine. A transmission 2 is connected to the engine 1 and a starter 3 for cranking and starting the engine 1 is connected to the engine 1. The engine 1 is mounted on a vehicle having an idle stop system (ISS). When the driver steps on the brake and the vehicle stops, the engine 1 is automatically stopped, and then the driver releases the brake and steps on the accelerator. For example, when traveling is restarted, the engine 1 is automatically restarted.

  The starter 3 for starting the engine 1 is a gear type starter using a DC motor in the present embodiment. This gear-type starter 3 can push the motor-side pinion gear to mesh with the engine-side ring gear by operating the magnet switch when the engine rotation is zero or close to zero. Can be started.

  The starter 3 is driven and controlled by an idle stop control unit (ISS-ECU) 10 composed of a microcomputer or the like. An idle stop control unit (ISS-ECU) 10 is a control unit that plays a major role in an idle stop system (ISS) that stops engine rotation when a predetermined condition for idle operation is satisfied. The engine is controlled from an idle stop (engine stop) via the engine control unit (ENG-ECU) 20 for engine control and engine restart from the idle stop by driving the starter 3.

  The idle stop control unit 10 and the engine control unit 20 are connected to a crank angle sensor 4 that detects the crank angle of the engine 1 and other sensors (not shown). For example, a signal is output from the crank angle sensor 4 every 180 ° CA, and the engine speed is calculated from the time interval of the signal every 180 ° CA.

  The idle stop control unit 10 and the engine control unit 20 are connected to an in-vehicle network 100 such as a CAN (Controller Area Network), a transmission control unit (TM-ECU) 30, an air conditioner control unit (AIRCON-ECU) 40, and the like. Are connected to each other so that they can communicate with each other. Based on signals from sensors and control information from other control units, the idle stop control unit 10 determines whether or not a predetermined stop condition (idle stop permission condition) is established in order to perform idle stop. When it is determined that the idle stop permission condition is satisfied, a control command (ISS fuel cut request) for cutting the fuel supply of the engine is transmitted to the engine control unit 20.

  In response to the ISS fuel cut request, the engine control unit 20 stops driving a fuel injection valve (not shown), and shuts off the fuel supply to the engine 1 (fuel cut). The engine control unit 20 monitors the on / off state of the ISS fuel cut request, and performs the fuel cut to stop the engine rotation as long as the ISS fuel cut request is maintained in the on state.

  On the other hand, if the predetermined start condition is satisfied to return from the idle stop before the engine stops rotating (idle stop permission condition is not satisfied) and the ISS fuel cut request is turned off, the engine The control unit 20 determines whether or not it is possible to return the engine independently. That is, when the ISS fuel cut request is changed from ON to OFF, the engine control unit 20 restarts fuel injection from the state where the engine is rotated by inertial force without supplying fuel, thereby causing the combustion of the fuel. It is determined whether or not it is possible to return to a state where the engine rotates independently.

  As a result, when it is determined that the self-revolution of the engine can be restored, the fuel injection is immediately resumed, and the engine is restored to the self-revolution. On the other hand, when it is determined that the self-recovery rotation of the engine is not possible, the engine is quickly stopped by continuing the fuel cut, and the engine can be restarted early by driving the starter 3.

  Judgment as to whether or not the engine can return to self-sustained rotation is made using a value obtained by integrating the number of times of fuel cut across the cylinders after the start of fuel cut. Therefore, as shown in FIG. 2, the engine control unit 20 includes a fuel cut execution / self-sustained rotation return determination unit 21, a fuel cut number integration unit 22, and an engine determination unit 23 as control functions related to idle stop. .

  The engine control unit 20 uses these functional units to perform fuel cut to stop the engine rotation when the ISS fuel cut request from the idle stop control unit 10 is ON, and the driver before the engine rotation stops. If the ISS fuel cut request is turned off, it is determined whether or not the engine can be recovered from the self-sustained rotation. Realizes the function of resuming fuel injection.

  Specifically, the idle stop control unit 10 checks whether or not an idle stop permission condition is satisfied, and when the idle stop permission condition is satisfied, the ISS fuel cut request is turned ON. The idle stop permission conditions are, for example, a condition that the vehicle speed is equal to or less than a set value close to zero, a condition that the brake pedal is depressed (the brake switch is ON), and the idle stop when these conditions are satisfied. The ISS fuel cut request output from the control unit 10 is turned ON.

  Further, after the idle stop permission condition is satisfied and the ISS fuel cut request is turned ON, the idle stop control unit 10 performs an operation to indicate an intention to start by releasing the brake or the like. Turn off the fuel cut request. At this time, if the engine rotation has not stopped yet, the engine control unit 20 determines whether or not the engine can return to the independent rotation. If the engine can return to the independent rotation, the fuel injection is resumed. If the engine rotates independently, and the self-recovery rotation cannot be restored, the fuel cut is continued to stop the engine rotation. When the rotation of the engine stops, the idle stop control unit 10 drives the starter 3 to restart the engine.

  The engine control unit 20 receives the ISS fuel cut request from the idle stop control unit 10 at the fuel cut execution / independent rotation return determination unit 21. The fuel cut execution / self-sustaining rotation return determination unit 21 instructs a fuel injection control unit (not shown) that controls fuel injection to execute fuel cut for each cylinder when the ISS fuel cut request is turned ON. The fuel cut frequency integration unit 22 is instructed to integrate the fuel cut execution frequency.

  When the fuel cut execution unit 22 starts execution of fuel cut according to an instruction from the fuel cut execution / self-sustaining rotation return determination unit 21, the fuel cut number integration unit 22 integrates the number of fuel cuts for each cylinder between the cylinders. The number of cylinders. Further, along with the execution of this fuel cut, the engine determination unit 23 determines whether or not the engine has stopped rotating based on the signal from the crank angle sensor 4. For example, when the signal from the crank angle sensor 4 cannot be detected within the set time, it is determined that the engine is stopped (engine stall).

  Further, the fuel cut execution / self-sustained rotation return determination unit 21 determines whether or not the self-recovery rotation of the engine can be returned when the ISS fuel cut request is turned OFF before the engine stops. In response to this, an instruction is given to resume or continue the fuel cut. Whether or not self-sustained rotation can be restored is determined using the number of fuel cut cylinders instead of the engine speed. By determining the self-sustained rotation return using this fuel cut cylinder number, the influence of the delay until the engine speed decreases after starting the fuel cut and the timing until the engine speed can be calculated is eliminated, It is possible to improve the determination accuracy of the self-sustained rotation return.

  For example, when the engine 1 in the present embodiment is a four-cylinder engine and the fuel cylinder performs fuel injection during the exhaust stroke in the order of # 1 cylinder → # 3 cylinder → # 2 cylinder → # 4 cylinder, engine control The fuel cut and engine speed calculation processing by the unit 20 is performed at the timing shown in FIG. In the example of FIG. 3, fuel injection is stopped from the exhaust stroke of the # 1 cylinder, and fuel injection is restarted from the intake stroke of the # 2 cylinder.

  The engine speed is calculated every 180 ° CA, and during the fuel cut, the # 3, # 2, and # 4 cylinders burn the fuel injected in the exhaust stroke before the fuel cut is started. Therefore, although the engine speed does not decrease immediately, there is no fuel to be combusted in the explosion strokes of the # 1 and # 3 cylinders after the fuel cut is released, so the engine speed is delayed by about 3 strokes. Hold it down. When the fuel cut is cancelled, the engine speed starts to increase due to the fuel combustion of the # 2 and # 4 cylinders. Therefore, if it is attempted to determine whether or not self-sustained rotation can be restored based on the engine speed, not only will there be a delay in the determination, but there will be a divergence from the actual engine state when the engine speed is calculated, and accurate determination will be made. It becomes difficult.

  For this reason, in this embodiment, the number of fuel cuts is counted to grasp the number of cylinders whose fuel supply has been stopped, and the number of fuel cut cylinders (how many fuel cuts have been performed) is small or large. Thus, it is possible to quickly and accurately determine whether or not it is possible to return to the self-supporting rotation. Specifically, the number of fuel cut cylinders is compared with a predetermined threshold value, and when the number of fuel cut cylinders is equal to or less than the threshold value and the number of cylinders in which fuel supply is stopped is small, it is determined that it is possible to return to independent rotation, and the fuel cut cylinder When the number is larger than the threshold value (when the number of cylinders whose fuel supply is stopped is large), it is determined that it is impossible to return to the independent rotation.

  In this case, since the threshold value for determining whether or not self-recovery rotation can be restored differs depending on the engine characteristics, the value obtained in advance by experiment or simulation may be stored in the system as a fixed value for each model. Whether or not is possible depends on "force (torque) to stop engine rotation" and "current rotational energy (rotation speed)", so a threshold value is set using parameters correlated to these. You may make it do. Specifically, a threshold value table is created with at least one of the engine speed at the start of fuel cut and the load torque applied to the engine as an argument, and the threshold value is set by referring to the table. As the load torque, for example, torque as shown in the following (1) to (4) can be used.

(1) Friction torque of the engine body: It can be determined by the oil temperature (or water temperature) and the engine speed.
(2) Alternator consumption torque: It can be determined by the amount of power generation.
(3) Consumption torque of hydraulic power steering can be determined by the operating state (hydraulic pressure, etc.) of the power steering drive pump.
(4) Consumption torque of air conditioner compressor: It can be determined by the operating state (various temperatures, refrigerant pressure, etc.) of the compressor.

  FIG. 4 shows an example of a threshold table using both the engine speed [rpm] and the load torque [Nm] at the start of fuel cut as arguments. In this threshold value table, when the load torque is the same, the higher the engine speed, the larger the threshold for the fuel-cut cylinder number. When the engine speed is the same, the higher the load torque, the greater the fuel-cut cylinder number. It has a characteristic that the threshold value becomes small.

  Next, program processing for realizing the functions of the respective units related to the idle stop control of the engine control unit will be described with reference to the flowchart of FIG.

  The flowchart of FIG. 5 shows an idle stop fuel cut control routine for controlling the stop / restart of fuel injection in response to an ISS fuel cut request transmitted from the idle stop control unit 10.

  In this idle stop fuel cut control routine, first, in the first step S1, it is checked whether or not the ISS fuel cut request is ON. If the ISS fuel cut request is OFF, this routine is exited from step S1, and if the ISS fuel cut request is ON, the process proceeds from step S1 to step S2 to execute the fuel cut and shut off the fuel supply to the engine. .

  Next, in step S3, the number of fuel cut cylinders is integrated, and in step S4, it is checked whether the rotation of the engine has stopped based on the signal from the crank angle sensor 4. If the engine rotation is stopped, the routine is exited from step S4. If the engine rotation is not stopped, the process proceeds from step S4 to step S5 to check whether the ISS fuel cut request is turned off. Note that when the rotation of the engine is stopped, the number of fuel cut cylinders accumulated so far is cleared.

  If the fuel cut request is not turned off, the process returns from step S5 to step S2, and in steps S2 to S5, execution of fuel cut, integration of the number of fuel cut cylinders, engine rotation stop, and fuel cut request are repeated. If the ISS fuel cut request is turned off before the engine stops, the process proceeds from step S5 to step S6 to check whether the number of fuel cut cylinders is equal to or less than a threshold value.

  As a result, if the number of fuel cut cylinders is less than or equal to the threshold value, the routine proceeds from step S6 to step S7, fuel injection is resumed (fuel cut is stopped), and processing such as clearing the number of fuel cut cylinders is performed, and this routine is executed. Exit. Under this condition, by restarting the fuel injection, the engine can be rotated independently without driving the starter 3.

  On the other hand, if the number of fuel cut cylinders exceeds the threshold value in step S6, it is determined that the engine cannot be rotated independently, and the process proceeds from step S6 to step S8, where the fuel cut is performed in order to quickly stop the engine rotation. continue. Then, it is checked in step S9 whether or not the engine has stopped. If the engine has not stopped, the fuel cut is continued in step S8. Exit the routine.

  As described above, in the present embodiment, when the engine stop process is canceled by the driver's start operation during the engine stop process of the idle stop due to the fuel cut, the number of fuel cut cylinders is determined as to whether or not the engine can be returned to the independent rotation. Determine by. As a result, it is possible to accurately determine whether or not the self-sustained rotation can be returned, and moreover, it is possible to determine without delay as compared with the case of determining whether or not the self-sustained rotation can be returned by the engine speed. By improving the determination accuracy of this self-sustained rotation return, it is possible to avoid wasteful driving of the starter, to prevent waste of electric power, and to reduce the number of starter operations during the life cycle, thereby extending the life of the starter.

  In addition, by improving the accuracy of determination of the self-sustained rotation return, when the self-sustained rotation return is impossible, the fuel injection is resumed to extend the time until the engine rotation stops and the starter start delay is prevented. be able to. That is, when the self-sustained rotation recovery is impossible, the engine cut can be stopped early by continuing the fuel cut, and the time until restart by the starter can be shortened.

1 Engine 3 Starter 4 Crank Angle Sensor 10 Idle Stop Control Unit 20 Engine Control Unit 21 Fuel Cut Execution / Independent Rotation Return Determination Unit 22 Fuel Cut Number Integration Unit 23 Engine Determination Unit

Claims (2)

When a predetermined stop condition is satisfied, a fuel cut is executed for each cylinder to stop fuel supply to the engine. When a predetermined start condition is satisfied, the fuel cut is stopped and the fuel supply is restarted. In the engine control device,
When the stop condition is satisfied, a fuel cut frequency integration unit that integrates the number of times the fuel cut is performed;
When the start condition is satisfied from the start of the fuel cut until the engine stops, the fuel cut frequency integrated by the fuel cut frequency integration unit is compared with a predetermined threshold value, and the fuel supply is resumed. A self-sustained rotation return determination unit that determines whether or not it is possible to return to the self-supporting rotation,
The self-sustaining rotation return determination unit
When the number of fuel cuts is less than or equal to the threshold value, it is determined that the engine can be returned to independent rotation, and the fuel supply is resumed. When the number of fuel cuts is greater than the threshold value, return to independent rotation is not possible. The engine control apparatus is characterized in that the fuel cut is continued and the rotation of the engine is stopped . 2. The engine according to claim 1, wherein the self-sustained rotation return determination unit sets the threshold based on at least one of an engine speed at the start of the fuel cut and a load torque applied to the engine. Control device.

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