JP2017219019A - Control device of internal combustion engine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a control device of an internal combustion engine capable of improving startability in starting ignition from a stop state of the internal combustion engine.SOLUTION: In starting an internal combustion engine from a stop state, a control device implements fuel injection and ignition while closing an exhaust valve of an exhaust stroke cylinder in an exhaust stroke in stopping the internal combustion engine, rotates a crank shaft backward, then releases the valve closing state of the exhaust valve of the exhaust stroke cylinder, and implements fuel injection and ignition to a cylinder in an expansion stroke in stopping the internal combustion engine. Here, the control device releases the valve closing state of the exhaust valve of the exhaust stroke cylinder at a timing when the crank shaft is rotated backward to a reference angle when the crank shaft is rotated backward to the reference angle before a top dead center of a cylinder in the expansion stroke by combustion of the exhaust stroke cylinder, and releases the valve closing state of the exhaust valve of the cylinder in the exhaust stroke at a timing when the crank shaft is turned to forward rotation, when the crank shaft is turned to forward rotation before rotated backward to the reference angle.SELECTED DRAWING: Figure 3

Description

  The present invention relates to a control device for an internal combustion engine, and more particularly, to a control device for an internal combustion engine capable of starting ignition from an engine stop state.

  2. Description of the Related Art Conventionally, a technique for starting ignition is known when an engine is temporarily stopped and then automatically restarted. The ignition start is a start method in which fuel is injected and ignited in a specific cylinder of a stopped engine to perform ignition and combustion, and the engine is started using the energy. Patent Document 1 discloses a technique related to such ignition start. More specifically, in this technique, when the engine is restarted, the exhaust valve of the cylinder in the exhaust stroke (exhaust stroke cylinder) is closed when the engine is stopped, and then fuel is supplied to the cylinder and forced ignition is executed. Then, the piston is moved in the reverse direction. As a result, the in-cylinder pressure of the cylinder in the expansion stroke is increased when the engine is stopped, so that the driving force in the normal engine rotation direction can be obtained by performing ignition and combustion in the cylinder in the expansion stroke.

JP 2004-301081 A

  In the technique of Patent Document 1, when the torque generated by the combustion in the exhaust stroke cylinder is large, the piston may move too much in the reverse direction. In this case, the torque generated by the combustion of the exhaust stroke cylinder may cause the piston of the expansion stroke cylinder to move in the opposite direction beyond the top dead center, which may not lead to subsequent combustion of the expansion stroke cylinder.

  The present invention has been made in view of the above-described problems, and an object of the present invention is to provide a control device for an internal combustion engine that can improve startability in ignition starting from a stopped state of the internal combustion engine.

  The present invention relates to a fuel injection device that injects fuel into each cylinder of a plurality of cylinders, an ignition device that ignites each of the plurality of cylinders, and a valve operating device that forcibly stops an exhaust valve in a closed state. And a control device for an internal combustion engine. When the internal combustion engine is started from a stopped state, the control device controls the fuel injection device, the ignition device, and the valve operating device to close the exhaust valve of the cylinder in the exhaust stroke when the internal combustion engine is stopped. After injecting and igniting the cylinder and reversing the crankshaft of the internal combustion engine, the closed state of the exhaust valve of the cylinder in the exhaust stroke is released, and the fuel is injected into the cylinder in the expansion stroke when the internal combustion engine is stopped. Ignition is performed. At this time, when the crankshaft reverses to the reference angle corresponding to the top dead center of the cylinder in the expansion stroke due to the combustion of the cylinder in the exhaust stroke, the control device performs the timing at which the crankshaft reverses to the reference angle. When the exhaust valve closed state of the cylinder in the exhaust stroke is released and the crankshaft rotates in the forward direction before reversing to the reference angle, the cylinder in the exhaust stroke at the timing when the crankshaft is rotated in the forward rotation Release the closed state of the exhaust valve.

  According to the present invention, when the internal combustion engine is started from a stopped state, it is possible to prevent the piston of the cylinder in the expansion stroke from moving in the reverse direction beyond the top dead center due to the combustion of the cylinder in the exhaust stroke. Can do. Thereby, in the ignition start-up from the state in which the internal combustion engine is stopped, it is possible to prevent the occurrence of defective combustion in the cylinders in the expansion stroke, so it is possible to improve the startability.

1 is a diagram illustrating a schematic configuration of a system according to a first embodiment. FIG. 3 is a diagram for explaining ignition start control executed by the system of the first embodiment. 3 is a flowchart showing a control routine executed by the control device in the first embodiment.

  Embodiments of the present invention will be described below with reference to the drawings. However, in the embodiment shown below, when referring to the number of each element, quantity, quantity, range, etc., unless otherwise specified or clearly specified in principle, the reference However, the present invention is not limited to these numbers. Further, the structures, steps, and the like described in the embodiments below are not necessarily essential to the present invention unless otherwise specified or clearly specified in principle.

Embodiment 1 FIG.
Embodiment 1 of the present invention will be described with reference to the drawings.

[Configuration of Embodiment 1]
FIG. 1 is a diagram illustrating a schematic configuration of a system according to the first embodiment. The system shown in FIG. 1 includes an internal combustion engine (hereinafter also simply referred to as an engine). The engine 10 is a four-cylinder engine in which four cylinders are arranged in series. The number of cylinders of the engine applicable to the present invention is not limited to four cylinders, and can be widely applied to other engines having a plurality of cylinders.

  In the present embodiment, the engine 10 shown in FIG. 1 is configured as a spark ignition in-cylinder direct injection engine, and an ignition plug and an in-cylinder injection valve (not shown) are attached to each cylinder. Further, the engine 10 is provided with an electric variable valve operating device 12 that electrically controls opening and closing of the exhaust valve in an extremely low rotation range. As such a configuration of the electric variable valve operating apparatus 12, for example, an electric VVT type apparatus that electrically rotates a camshaft, or an electromagnetically driven valve that individually controls the exhaust valve of each cylinder is used.

  The engine 10 configured as described above is controlled by the control device 30. The control device 30 is an ECU (Electronic Control Unit). The control device 30 has at least an input / output interface, a ROM, a RAM, and a CPU. The input / output interface is provided to take in sensor signals from the engine 10 and various sensors attached to the vehicle and to output an operation signal to an actuator provided in the engine 10. The sensors from which the control device 30 takes in signals include various sensors necessary for controlling the engine 10 in addition to the crank angle sensor 14 capable of detecting the rotation angle and the rotation direction of the crankshaft. The actuator from which the control device 30 outputs an operation signal includes an ignition device (not shown), a fuel injection device, and the like in addition to the electric variable valve operating device 12 described above. Various control programs and maps for controlling the engine 10 are stored in the ROM. The CPU reads and executes the control program from the ROM, and generates an operation signal based on the acquired sensor signal.

[Operation of Embodiment 1]
(Basic operation of the system of the first embodiment)
First, the basic operation of the system according to the first embodiment will be described. The control program executed by the control device 30 includes a control program for idle stop control. In the idling stop control, the operation of the engine 10 is automatically stopped when an automatic stop condition is satisfied during the operation of the engine 10 in order to improve fuel consumption. In the idle stop control, the engine 10 is automatically started when an automatic start condition is satisfied while the engine 10 is stopped by the idle stop control.

  Further, the control program executed by the control device 30 includes a control program for ignition start control for starting ignition from the time of engine stop by the idle stop control described above. The cylinder (expansion stroke cylinder) in the expansion stroke when the engine 10 is stopped is in a state where the intake valve and the exhaust valve are closed when the engine 10 is stopped. Therefore, in the ignition start control, combustion torque is generated by performing fuel injection and ignition to the expansion stroke cylinder while the operation of the engine 10 is stopped.

  However, the combustion torque generated in the expansion stroke cylinder may be insufficient to start the engine 10. That is, when the operation of the engine 10 is stopped, the piston of each cylinder normally stops at a position near the middle between the top dead center and the bottom dead center due to the cylinder balance. In this case, since the in-cylinder pressure of the expansion stroke cylinder is relatively low during the operation stop, there is a possibility that the combustion torque necessary for the ignition start cannot be generated.

  Therefore, in the ignition start control of the system of the first embodiment, in addition to the combustion torque of the expansion stroke cylinder described above, the ignition start is performed using the combustion torque of the cylinder (exhaust stroke cylinder) that is in the exhaust stroke when the engine 10 is stopped. I do.

  In the combustion of the exhaust stroke cylinder in the ignition start control, the electric variable valve operating device 12 is used. More specifically, when the engine 10 is started, the electric variable valve mechanism 12 is first controlled to forcibly close (fully close) the exhaust valve of the exhaust stroke cylinder. As a result, the cylinder of the exhaust stroke cylinder is sealed, so that combustion torque can be generated by performing fuel injection and ignition on the exhaust stroke cylinder.

  When combustion torque is generated in the exhaust stroke cylinder, a force acts in a direction in which the piston of the cylinder is pushed down to reverse the crankshaft. As a result, since the piston position of the expansion stroke cylinder moves toward the compression top dead center (TDC), the in-cylinder pressure of the expansion stroke cylinder is increased. Therefore, by controlling the electric variable valve device 12 to release the closed state of the exhaust valve of the exhaust stroke cylinder and injecting and igniting the fuel in the expansion stroke cylinder, a large combustion torque is generated in the expansion stroke cylinder. It becomes possible.

(Characteristic operation of the system of the first embodiment)
Next, a characteristic operation of the system according to the first embodiment will be described. As described above, in the ignition start control, after fuel injection and ignition are performed on the exhaust stroke cylinder, the electric variable valve apparatus 12 is controlled to release the exhaust valve of the exhaust stroke cylinder. Here, if the timing at which the exhaust valve of the exhaust stroke cylinder is released is delayed, the startability in the ignition start control may be reduced. That is, when combustion is performed in the exhaust stroke cylinder, combustion torque is generated in a direction that reverses the crankshaft. However, when the start-up request is issued before the rotation of the engine 10 completely stops, such as when the piston rises after closing the exhaust valve of the exhaust stroke cylinder and the in-cylinder pressure increases more than necessary, The combustion torque generated in the exhaust stroke cylinder may become larger than necessary. In this case, the combustion torque of the exhaust stroke cylinder may reverse the piston of the expansion stroke cylinder to a position exceeding the top dead center, which may not lead to subsequent combustion of the expansion stroke cylinder.

  Therefore, in the system of the first embodiment, control is performed to prevent the crankshaft from excessively moving in the reverse rotation direction due to the combustion torque of the exhaust stroke cylinder. FIG. 2 is a diagram for explaining ignition start control executed by the system of the first embodiment. As shown to (A) in this figure, after the ignition to the exhaust stroke cylinder, the control device 30 has the crankshaft before the top dead center of the expansion stroke cylinder (in the case of a 4-cylinder engine, the bottom dead center of the exhaust stroke cylinder). When the crank angle corresponding to the front (hereinafter referred to as “reference angle”) is reached, the exhaust valve of the exhaust stroke cylinder is released at the time of arrival and the ignition (fuel) of the exhaust stroke cylinder is released. Injection and ignition). When the exhaust valve of the exhaust stroke cylinder is opened, torque in the direction to reverse the crankshaft is not generated. As a result, it is possible to prevent the crankshaft from exceeding the top dead center of the exhaust stroke cylinder, so that the torque in the forward rotation direction can be reliably generated by the subsequent combustion of the expansion stroke cylinder. The reference angle may be an angle at which the crankshaft turns forward before the top dead center of the expansion stroke cylinder by opening the exhaust valve, but the expansion stroke is closer to the top dead center of the expansion stroke cylinder. The startability can be improved by increasing the in-cylinder pressure of the cylinder.

  On the other hand, as shown in (B) in this figure, when the combustion torque generated in the exhaust stroke cylinder is small and the crankshaft rotates forward before reaching the reference angle, the control device 30 At the timing when the forward rotation is started, the exhaust valve of the exhaust stroke cylinder is released, and the exhaust stroke cylinder is ignited (fuel injection and ignition). According to such control, it is possible to prevent the generation of the compression reaction force in the exhaust stroke cylinder, so that it is possible to reliably start the engine by the forward rotation direction torque generated by the combustion of the expansion stroke cylinder.

[Specific Processing in First Embodiment]
Next, specific processing of ignition start control executed in the system of the first embodiment will be described with reference to FIG. FIG. 3 is a flowchart showing a control routine executed by the control device 30 in the present embodiment. The routine shown in FIG. 3 is executed when the automatic start condition of the engine 10 is satisfied in a state where the engine 10 is stopped by idle stop control or the like.

  In the routine shown in FIG. 3, it is first determined whether or not the exhaust valve of the exhaust stroke cylinder is open (step S2). As a result, when it is determined that the exhaust valve of the exhaust stroke cylinder is already closed by the control such as the reduced-cylinder operation, the process proceeds to step S6 described later. On the other hand, when it is determined in step S2 that the exhaust valve of the exhaust stroke cylinder is open, the process proceeds to the next step, and the electric variable valve device 12 is operated to exhaust the exhaust valve of the exhaust stroke cylinder. Is closed (fully closed) (step S4).

  Next, the fuel injection device and the ignition device are operated to ignite the exhaust stroke cylinder (that is, fuel injection and ignition) (step S6). When the exhaust stroke cylinder is ignited, the crankshaft is reversed by the combustion torque generated in the cylinder. In the routine shown in FIG. 3, it is determined whether or not the current crank angle detected by the crank angle sensor 14 has been reversed to the reference angle (step S8). As a result, if the determination is confirmed, the process proceeds to the next step, and the closing of the exhaust valve of the exhaust stroke cylinder is released (step S10). Next, it is determined whether or not the crankshaft has started normal rotation (step S12). As a result, when the determination is not confirmed, the process of step S12 is repeatedly executed until the determination is satisfied. When the determination is confirmed in step S12, the process proceeds to the next step, and ignition (fuel injection and ignition) is performed on the expansion stroke cylinder (step S14).

  On the other hand, if it is determined in step S8 that the current crank angle is not reversed to the reference angle, the process proceeds to the next step, and it is determined whether or not the crankshaft has started normal rotation. (Step S16). As a result, if the determination is not accepted, the determination in step S8 is executed again. On the other hand, when the determination in step S16 is confirmed, the process proceeds to the next step, and ignition (fuel injection and ignition) is performed on the expansion stroke cylinder (step S18).

  As described above, according to the system of the first embodiment, it is possible to improve the startability in the ignition start after the operation of the engine 10 is stopped.

10 Internal combustion engine
12 Electric variable valve device 14 Crank angle sensor 30 Control device (ECU)

Claims (1)

A fuel injection device that injects fuel into each cylinder of the plurality of cylinders, an ignition device that ignites each of the plurality of cylinders, and a valve operating device that forcibly stops the exhaust valve in a closed state. In a control device for an internal combustion engine having
When the internal combustion engine is started from a stopped state, the control device controls the fuel injection device, the ignition device, and the valve operating device, and exhausts the cylinder in the exhaust stroke when the internal combustion engine is stopped. After closing the valve and injecting and igniting the cylinder with fuel and reversing the crankshaft of the internal combustion engine, the closed state of the exhaust valve of the cylinder in the exhaust stroke is released to stop the internal combustion engine It is configured to inject and ignite a cylinder in the expansion stroke,
When the crankshaft is reversed to the reference angle corresponding to the top dead center of the cylinder in the expansion stroke by the combustion of the cylinder in the exhaust stroke, the crankshaft is reversed to the reference angle. When the exhaust valve closed state of the cylinder in the exhaust stroke is released at the timing, and the crankshaft rotates in the forward direction before reversing to the reference angle, the timing at which the crankshaft turns in the forward rotation The control device for an internal combustion engine, wherein the closed state of the exhaust valve of the cylinder in the exhaust stroke is released.

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