Control method and device for electrically-driven valve timing mechanism of internal combustion engine

Abstract

To quickly make an actual conversion angle VTCr of an electrically-driven variable valve timing mechanism reach a target conversion angle VTCt1 for restarting, when restarting after an idling stop.SOLUTION: An internal combustion engine has an electrically-driven variable valve timing mechanism on the intake side. When an idling stop condition is met (t1), before stopping of power supply, an actual conversion angle VTCr is set to a stop-time conversion angle VTCt2 that is on an advance side by a predetermined amount from the target conversion angle VTCt1 for restarting. When the idling stop release condition is met (t3), the target conversion angle VTCt is set to the target conversion angle VTCt1 for restarting. Since a camshaft is naturally displaced to a retard side due to the alternating torque acting on the camshaft during cranking, the actual conversion angle VTCr quickly reaches the target conversion angle VTCt1 for restarting (t4). Therefore, an appropriate intake volume is obtained and quick restarting is possible.SELECTED DRAWING: Figure 2

Description

[Technical field]

[0001] The present invention relates to control of an electric variable valve timing mechanism that changes the valve timing of an intake valve or an exhaust valve of an internal combustion engine during idling stop. [Background technology]

[0002] Patent Document 1 discloses an electric variable valve timing mechanism that retards the phase of a camshaft within a predetermined angle range with respect to the phase of a crankshaft by an electric actuator. Patent Document 1 also describes that during idling stop, the relative rotation phase angle (so-called conversion angle) between the crankshaft and the camshaft is set to the retard side of the required phase angle, and the variable valve timing mechanism is driven to the advance side by open loop control until the actual phase angle is detected at the start of cranking for restart, thereby transitioning the mechanical contact parts inside the variable valve timing mechanism from a static friction state to a dynamic friction state. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2015-72014 A Summary of the Invention [Problem to be solved by the invention]

[0004] When restarting from an idling stop in which the internal combustion engine has already finished warming up, an intermediate target conversion angle suitable for restarting is required. If the internal combustion engine is stopped with the variable valve timing mechanism set to such a target conversion angle suitable for restarting when the engine is stopped due to an idling stop, the next time the engine is cranked to restart, an alternating torque acts on the camshaft, and as a result, the conversion angle naturally shifts to the retarded side.

[0005] Therefore, even if control of the variable valve timing mechanism is started at the same time as the restart process starts, it takes time to return to the target conversion angle suitable for restart, and during that time, the desired torque is not generated, resulting in a problem that the start time until independent operation is extended. In the technology of Patent Document 1, the conversion angle is controlled to be more retarded than the required phase angle when stopped by idling stop, so that the alternating torque caused by cranking causes it to be further displaced to the retarded side, and as a result, it takes even longer to reach the appropriate conversion angle after cranking starts. [Means for solving the problem]

[0006] A control method for an electric variable valve timing mechanism of an internal combustion engine according to the present invention is provided for an internal combustion engine equipped with an electric variable valve timing mechanism that changes, within a predetermined angle range, the phase of a camshaft that opens and closes an intake valve or an exhaust valve of the internal combustion engine, and the phase of a crankshaft that rotates and drives the camshaft, When the internal combustion engine is stopped due to an idling stop, the electrically operated variable valve timing mechanism is controlled to a stop-time conversion angle that is more advanced than a target conversion angle at the time of restarting, prior to the interruption of power supply.

[0007] In this way, if the stop-time conversion angle is set to be more advanced than the target conversion angle when the engine is stopped due to an idling stop, the alternating torque acting on the camshaft due to cranking at the time of restart displaces the camshaft to the retard side, and as a result, the actual conversion angle is quickly obtained near the target conversion angle at the time of restart. Effect of the Invention

[0008] According to the present invention, an appropriate conversion angle can be obtained immediately when restarting the engine after an idling stop, enabling a quick restart. [Brief description of the drawings]

[0009] [Figure 1] 1 is a configuration explanatory diagram of an internal combustion engine according to the present invention; [Diagram 2]4 is a time chart showing the operation of an embodiment from idling stop to restart. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0010] An embodiment of the present invention will be described in detail below with reference to the drawings. Fig. 1 shows an outline of an internal combustion engine 1 according to an embodiment of the present invention. The internal combustion engine 1 is a drive source for a vehicle, and drives the drive wheels of the vehicle via a transmission (not shown).

[0011] The internal combustion engine 1 of the embodiment is a four-stroke cycle spark ignition internal combustion engine, so-called a gasoline engine. The internal combustion engine 1 is controlled by an engine controller 2. The engine controller 2 receives detection signals from sensors such as a crank angle sensor 11 for detecting the engine speed, an air flow meter 12 for detecting the amount of intake air corresponding to the load, a water temperature sensor 13 for detecting the temperature of cooling water, an accelerator pedal position sensor 14 for detecting the opening (depression amount) of an accelerator pedal operated by a driver, an air-fuel ratio sensor 15 for detecting the exhaust air-fuel ratio, a vehicle speed sensor 16 for detecting the vehicle speed, a cam angle sensor 17 for detecting the angular position of a camshaft described later, and a brake sensor 18 for detecting the depression of a brake pedal, directly or via other controllers. Based on these detection signals, the engine controller 2 optimally controls the amount and injection timing of fuel injection by a fuel injection valve, the ignition timing by a spark plug, the opening of a throttle valve, and the like.

[0012] The internal combustion engine 1 has an intake camshaft 3 that drives the intake valves of each cylinder to open and close, and an exhaust camshaft 4 that drives the exhaust valves to open and close. These camshafts 3, 4 are rotated in synchronization with the crankshaft 5 via a winding transmission mechanism 6 using a cog belt or a chain. The intake camshaft 3 is equipped with an electric variable valve timing mechanism 7 that changes the phase of the intake camshaft 3 and the phase of the crankshaft 5 within a predetermined angle range. The electric variable valve timing mechanism 7 may be of any type, but may include, for example, an outer peripheral ring member 7a that rotates in mesh with the cog belt or chain, and an electric actuator 7b that displaces the ring member 7a and the camshaft 3 at the center relative to each other in the rotational direction. The electric actuator 7b includes, for example, a motor and a reduction mechanism, and is configured to operate in both forward and reverse directions by a control signal output from the engine controller 2 to change the phase of the camshaft 3 relative to the ring member 7a. The rotational position of the intake camshaft 3 is detected by a cam angle sensor 17, and the electric actuator 7b is feedback-controlled to achieve a target conversion angle corresponding to the operating conditions while the internal combustion engine 1 is in operation. Note that the conversion angle is the phase change of the camshaft 3 to the advance side, expressed as a crank angle, with the crankshaft 5 as the reference.

[0013] The internal combustion engine 1 also has an idling stop function that stops combustion and rotation when the engine 1 is temporarily stopped at an intersection, etc. That is, if a predetermined idling stop condition is met, for example, when waiting for a traffic light at an intersection, the engine controller 2 automatically stops the internal combustion engine 1, that is, performs idling stop. If a predetermined idling stop cancellation condition is met during idling stop, the idling stop is cancelled and the internal combustion engine 1 is automatically restarted.

[0014] The idling stop condition is an AND condition of several conditions, such as vehicle speed being 0, accelerator opening being 0, brake switch being on (i.e., brake pedal being depressed), water temperature being equal to or higher than a predetermined temperature, battery charge state being equal to or higher than a predetermined level, and no engine start request being made from the vehicle air conditioning system. In other words, when all of these conditions are met, the idling stop condition is deemed to be established and idling stop is performed. During idling stop, power is not supplied to the electric variable valve timing mechanism 7 in order to reduce power consumption.

[0015] The idling stop cancellation condition is an OR condition of several conditions, such as the accelerator opening being not 0, the brake switch being off, the battery charge state being below a predetermined level, and an engine start request being made from the vehicle air conditioning system. In other words, if any one of these conditions is met, it is determined that the idling stop cancellation condition is met, the idling stop is cancelled, and the internal combustion engine 1 is restarted. The restart is performed by cranking using a starter motor 8 provided in the internal combustion engine 1. The starter motor 8 is driven via a switching module (not shown) based on a control signal from the engine controller 2. Power supply to the electric variable valve timing mechanism 7 is resumed in conjunction with the restart.

[0016] Next, the control of the electric variable valve timing mechanism 7 during idling stop and restart will be described with reference to the time chart of Fig. 2. Fig. 2 shows changes in (a) engine speed, (b) an idling stop flag indicating the presence or absence of an idling stop request (in other words, whether idling stop is possible), and (c) the conversion angle of the electric variable valve timing mechanism 7. Note that in (c), the target conversion angle VTCt and the actual conversion angle VTCr are shown overlapping each other.

[0017] 2, the above-mentioned idling stop condition is satisfied at time t1, the idling stop flag is turned ON, and the idling stop process is started. Then, at time t2, the rotation of the internal combustion engine 1 is completely stopped. Just before time t1, the rotation speed of the internal combustion engine 1 is the idle rotation speed, and the actual conversion angle VTCr of the electric variable valve timing mechanism 7 is controlled according to the target conversion angle VTCt, that is, a predetermined target conversion angle VTCt0 suitable for idling operation after warming up.

[0018] When the idling stop condition is satisfied at time t1, the target conversion angle VTCt of the electric variable valve timing mechanism 7 becomes a predetermined stop-time conversion angle VTCt2. This stop-time conversion angle VTCt2 is set to a value advanced by a predetermined amount from the target conversion angle VTCt1 for restart suitable for restart. In the illustrated example, the target conversion angle VTCt1 for restart is approximately the same as the target conversion angle VTC0 for idle operation before time t1, and the stop-time conversion angle VTCt2 is more advanced than the target conversion angle VTCt0 for idle operation. Therefore, the electric actuator 7b of the electric variable valve timing mechanism 7 operates to the advanced side by feedback control. At this stage, power supply to the electric variable valve timing mechanism 7 continues, and the actual conversion angle VTCr becomes the stop-time conversion angle VTCt2 with a slight delay from time t1. In order to ensure the operation of such electric variable valve timing mechanism 7, the power supply to the electric variable valve timing mechanism 7 is stopped with a delay of a predetermined time (for example, about 1 to 2 seconds) from time t1 when the idling stop condition is established. A timer for stopping the power supply may be counted from time t2 when the internal combustion engine 1 stops rotating. Until the power supply is stopped, the electric variable valve timing mechanism 7 is controlled according to the target conversion angle VTCt, that is, the stop-time conversion angle VTCt2. After the power supply is stopped, the conversion angle of the electric variable valve timing mechanism 7 becomes indefinite, but since the internal combustion engine 1 stops rotating at this stage and no large external force acts, in reality, the actual conversion angle VTCr is basically maintained at the stop-time conversion angle VTCt2 as shown by the dashed line.

[0019] After that, at time t3, when the driver releases the brake pedal, etc., and the idling stop cancellation condition is satisfied, the idling stop flag is turned OFF and the restart process is started. That is, cranking is performed using the starter motor 8, and fuel injection and ignition are restarted. At the same time as the restart process is started, power supply to the electric variable valve timing mechanism 7 is restarted. As a result, the target conversion angle VTCt is set to the target conversion angle VTCt1 for restart.

[0020] On the other hand, at time t3, the actual conversion angle VTCr is the stop conversion angle VTCt2 because the conversion angle at the time of stopping the internal combustion engine 1 is maintained as it is, but since an alternating torque acts on the camshaft 3 by cranking, it naturally displaces to the retard side. Therefore, together with the action of the electric actuator 7b accompanying the resumption of power supply, the actual conversion angle VTCr quickly converges to the target conversion angle VTCt1 for restart. In the illustrated example, the actual conversion angle VTCr reaches the target conversion angle VTCt1 for restart at time t4. In this way, the actual conversion angle VTCr becomes in line with the target conversion angle VTCt1 for restart, so that the intake amount in the cylinder and therefore the actual compression ratio become appropriate, and the engine quickly transitions to independent operation by cranking. In the illustrated example, the engine enters independent operation at time t5, and a so-called fast idle operation in which a relatively high idle speed is maintained is performed.

[0021] In this manner, in the above embodiment, when the internal combustion engine 1 is stopped by idling stop, the electric variable valve timing mechanism 7 is controlled to the stop-time conversion angle VTCt2 that is more advanced than the target conversion angle VTCt1 for restart by a predetermined amount before the power supply is stopped, so that the target conversion angle VTCt1 for restart can be quickly set at the time of restart. This enables a quick restart.

[0022] In a preferred embodiment, the displacement of the camshaft 3 toward the retard side due to the alternating torque during cranking at the time of restart is obtained by an experiment or the like, and the stop-time conversion angle VTCt2 is determined by adding an advance angle amount corresponding to this displacement to the target conversion angle VTCt1 for the time of restart. The advance angle amount is, for example, about several degrees in crank angle. As described above, since the control by the electric actuator 7b is performed in parallel when the power supply is started in association with the start of the restart process, there is no problem even if the advance angle amount does not completely match the actual displacement due to the alternating torque.

[0023] Although one embodiment of the present invention has been described above in detail, the present invention is not limited to the above embodiment and various modifications are possible. For example, in the above embodiment, the intake valve is provided with the electric variable valve timing mechanism 7, but the same control can be applied to a case where an electric variable valve timing mechanism is provided on the exhaust valve side. In addition, the internal combustion engine may be a diesel engine that performs compression ignition. [Explanation of symbols]

[0024] 1. Internal combustion engine 2. Engine controller 3...Intake camshaft 5…Crankshaft 7...Electric variable valve timing mechanism

Claims

1. An internal combustion engine equipped with an electric variable valve timing mechanism that changes, within a predetermined angle range, the phase of a camshaft that opens and closes an intake valve or an exhaust valve of the internal combustion engine and the phase of a crankshaft that rotates the camshaft, When the internal combustion engine is stopped due to an idling stop, before the supply of power is stopped, the electric variable valve timing mechanism is controlled to a stop-time conversion angle that is more advanced than a target conversion angle at the time of restart. A method for controlling an electric variable valve timing mechanism of an internal combustion engine.

2. The camshaft is an intake valve camshaft.

2. A method for controlling an electric variable valve timing mechanism of an internal combustion engine according to claim 1.

3. when an idling stop condition is satisfied, driving of the electric variable valve timing mechanism to the stop-time conversion angle is started, and power supply is stopped with a delay from the satisfaction of the idling stop condition so that power supply is continued at least until the stop-time conversion angle is reached.

2. A method for controlling an electric variable valve timing mechanism of an internal combustion engine according to claim 1.

4. The stop-time conversion angle is set by adding an advance amount corresponding to a displacement toward the retard side due to the alternating torque during cranking at the time of restart to the target conversion angle.

2. A method for controlling an electric variable valve timing mechanism of an internal combustion engine according to claim 1.

5. an electric variable valve timing mechanism that changes, within a predetermined angle range, the phase of a camshaft that opens and closes an intake valve or an exhaust valve of an internal combustion engine and the phase of a crankshaft that rotates and drives the camshaft; A controller for controlling the conversion angle of the electric variable valve timing mechanism; Equipped with The above controller is When the internal combustion engine is stopped due to an idling stop, before the supply of power is stopped, the electric variable valve timing mechanism is controlled to a stop-time conversion angle that is more advanced than a target conversion angle at the time of restart. A control device for an electric variable valve timing mechanism of an internal combustion engine.

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