JP2011220136A - Engine stop control device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce the shock at the time of engine start.SOLUTION: An engine stop control device has a control valve 40 that is provided in a gas circulation system for circulating gas in a crankcase 20 of an engine 10 to an engine intake system and controls the circulation amount of the gas in the crankcase 20 to an engine cylinder 12. The PCV valve 40 is shut prior to the engine stop in an engine stop process and the circulation of the gas in the crankcase 20 to the engine 10 before stopping is stopped, so that the amount of an air supply into the engine cylinder is decreased.

Description

  The present invention relates to an engine stop control device for an engine, which is provided in a gas circulation system for circulating gas in an engine crankcase to an engine intake system and has a control valve for controlling the circulation amount of the gas in the crankcase to an engine cylinder. About.

  Hybrid vehicles equipped with an engine and a motor are widely used, and such a hybrid vehicle has a function of storing and supplying electric power generated by the engine in a battery for supplying electric power to the motor. That is, when the state of charge (SOC) of the battery becomes a predetermined low level, the engine is started, the generator generates power, and the battery is charged with the generated power. When the SOC reaches a predetermined high level, the engine is stopped and charging is terminated. As is well known in the art, hybrid vehicles include a series hybrid vehicle that uses an engine only for power generation and travels with the output of a motor, and a parallel hybrid vehicle that uses the engine output for vehicle travel. Has a function of charging the battery. The generator is used when a motor generator capable of outputting power as a motor is normal.

  Thus, in the hybrid vehicle, the engine is driven in accordance with the SOC of the battery, so that the engine is started and stopped separately from the user's intention. Therefore, there is a demand for reducing the shock at the time of engine start / stop as much as possible. In particular, in a normally used multi-cylinder engine, when the engine is stopped, the compression stroke is included in the middle or is terminated, and if the compression ratio in these cylinders becomes high at the start, the torque for engine rotation increases and shock is applied. (Vibration) occurs. Moreover, the hybrid vehicle does not have a mechanism for shutting off power, such as a normal clutch. For this reason, there is also a problem that when the torque at the time of starting the engine is large, the shock becomes a vehicle shock.

  Patent Document 1 discloses that the air supply system is depressurized when the engine is stopped, and the engine speed is decreased in the depressurized state. Patent Document 2 shows that the compression ratio is reduced and the engine starting torque is reduced when the engine is started.

JP 2004-308570 A JP 2009-036152 A

  As described above, there is a demand for reducing the engine start-up shock in the hybrid vehicle, and there is a problem of more efficiently reducing the shock.

  The present invention relates to an engine stop control device for an engine, which is provided in a gas circulation system for circulating gas in an engine crankcase to an engine intake system and has a control valve for controlling the circulation amount of the gas in the crankcase to an engine cylinder. Before the engine is stopped in the engine stop process, the control valve is closed to stop the circulation of the gas in the crankcase to the engine before the stop, thereby reducing the air supply amount into the engine cylinder. Features.

  In addition, during the engine stop process, it is preferable that the control valve is closed when a decrease in the engine speed is started.

  Moreover, it is preferable that the engine stop control device is mounted on a hybrid vehicle in which both the engine and the motor are mounted and the motor is driven by using the electric power generated by the engine.

  According to the present invention, since the circulation of the gas in the crankcase to the engine is stopped when the engine is stopped, the amount of air supplied into the engine cylinder can be reduced. Therefore, each cylinder is started the next time the engine is started. The compression ratio is small, and the torque at the start of the engine can be reduced to suppress the occurrence of shock.

It is a figure which shows the whole structure. It is a flowchart which shows the procedure of a process.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. FIG. 1 is a diagram showing an overall configuration. The engine 10 has a plurality of cylinders 12, and a piston is inserted into each cylinder 12. Each piston is supported by a crank 16 so as to be movable in the cylinder, and a crankshaft 18 of the crank 16 serves as an engine output shaft. The crank 16 is accommodated in the crankcase 20.

  In addition, an intake pipe 22 is connected to the upper part of each cylinder 12 via an intake valve, and an exhaust pipe 24 is connected via an exhaust valve. Further, the upper part of the crankcase 20 of the engine 10 is covered by a cylinder head cover as a whole including the upper part of the cylinder 12.

  The side of the intake pipe 22 opposite to the cylinder 12 is connected to a surge tank 28, and air that has been purified by external air cleaner 30 is supplied to the surge tank through a throttle valve 32. Note that fuel is injected between the surge tank 28 and the intake valve, and the air-fuel mixture is supplied into the cylinder 12 through the intake valve. A spark plug is provided on the upper portion of the cylinder 12.

  Engine oil is collected at the bottom of the crankcase 20, and the space above the engine oil is a space in the crankcase 20. A piston ring is disposed on the outer periphery of the piston 14 to fill the gap with the cylinder 12, but part of the cylinder gas leaks into the crankcase 20 from the gap of the piston ring. Most of the components of this gas are intake air mixture (about 75-90%), and the rest is exhaust gas. However, since it also causes deterioration of this engine oil and rust inside the engine, it is desired to exhaust it, but carbonization It cannot be exhausted as it contains hydrogen.

  Therefore, a circulation system (PCV hose 44) is connected to the crankcase 20 via a PCV valve 40, which is a control valve, so that the blow gas in the crankcase 20 is circulated to the surge tank 28. In addition, fresh air that has passed through the air cleaner is supplied into the crankcase 20 via the fresh air introduction hose 34.

  In the engine 10, when the piston 14 descends, the intake valve opens and the air-fuel mixture is introduced into the cylinder 12, and the air intake valve closes and the piston 14 ascends to compress the air-fuel mixture in the cylinder 12. Then, the air-fuel mixture compressed by the spark plug is ignited and the air-fuel mixture explodes, and the piston 14 descends by the explosive force, and then the piston 14 rises with the exhaust valve opened, so that the exhaust gas after the explosion is The exhaust gas is exhausted from the cylinder 12 through the exhaust pipe 24.

  The crankcase 20 has a relatively high pressure due to the gas in the compression process entering from the cylinder 12 and the gas in the crankcase 20 is circulated to the surge tank 28. Here, the flow rate of the PCV valve 40 is automatically controlled according to the state of the engine. For example, the flow rate is controlled so that the flow rate is small during idling / deceleration, the flow rate is large during steady running, and the flow rate is small when the engine is fully open (WOT). In a normal case, the PCV valve 40 is configured to automatically control the flow rate as described above according to the degree of negative pressure on the intake pipe 22 side.

  In this embodiment, the PCV valve 40 can be controlled by the control unit 42 and is forcibly closed during the engine stop process. Thereby, the gas circulation from the crankcase 20 is stopped thereafter. During the engine stop process, the throttle valve 32 is closed, and the surge tank 28 and the intake pipe 22 are in a negative pressure (decompression) state. Accordingly, the inside of the cylinder 12 of the engine 10 is similarly in a negative pressure state. Therefore, the compression ratio due to the upper and lower sides of the piston 14 is reduced. For this reason, when the engine is restarted after being stopped, the engine torque at the time of starting becomes small, and the shock at the time of starting is reduced.

  In particular, in the present embodiment, the stop process for reducing the shock at the start time can be performed only by using the PCV valve 40 and controlling the closing thereof.

  In the above example, forcible closing control by a signal from the control unit 42 is added to the normal PCV valve 40. This closing control may be performed so that the PCV valve 40 can be driven by a motor or the like. In addition, a normal PCV valve 40 is used as it is, and as shown by a broken line in FIG. 1, another control valve is attached to the PCVB hose that is a circulation system, and this control valve is controlled by the control unit 42. May be.

  FIG. 2 shows a PCV valve control process in the control unit 42. First, it is determined whether the engine stop process is in progress (S11). As described above, since the engine is stopped when the battery SOC reaches a predetermined value, the control unit 42 can determine whether or not to perform the engine stop process. In a normal case, an engine ECU (electronic control unit) is provided. The engine ECU controls engine stop processing, and the control unit 42 preferably has one function of the engine ECU. If the determination in S11 is NO, the PCV valve only needs to operate normally, so the PCV valve remains open (S12) and the process ends.

  On the other hand, if it is determined in S11, it is determined whether the engine speed is decreasing (S13). Since the engine speed decreases due to the engine stop process, it is determined whether the engine stop process is actually proceeding. If NO in this determination, it is determined that the engine must be driven normally, and the process proceeds to S13.

  On the other hand, if “YES” in the determination of S13, the PCV valve is closed to limit the air supply to the engine (S14), and the process ends. In this way, when the engine stop process is started and the engine speed starts to decrease, the PCV valve is closed and the circulation of the gas in the crankcase is prohibited, so that the gas in each cylinder of the engine is The amount can be reduced. Therefore, when the engine is started next time, the compression ratio in each cylinder is small, and the torque at the time of engine start can be reduced to suppress the occurrence of shock.

  10 Engine, 12 Cylinder, 14 Piston, 16 Crank, 18 Crankshaft, 20 Crankcase, 22 Intake pipe, 24 Exhaust pipe, 28 Surge tank, 30 Air cleaner, 32 Throttle valve, 34 Fresh air introduction hose, 40 PCV valve, 42 Control unit, 44 PCV hose.

Claims (3)

An engine stop control device for an engine having a control valve that is provided in a gas circulation system that circulates gas in an engine crankcase to an engine intake system and that controls a circulation amount of gas in the crankcase to an engine cylinder,
Prior to stopping the engine in the engine stop process, the control valve is closed to stop the circulation of the gas in the crankcase to the engine before the stop, thereby reducing the amount of air supplied into the engine cylinder. Stop control device. The engine stop control device according to claim 1,
An engine stop control device that closes the control valve when engine speed reduction starts during engine stop processing.   The engine stop control device according to claim 1 or 2 is mounted on a hybrid vehicle in which both the engine and the motor are mounted and the motor is driven by using the electric power generated by the engine. An engine stop control device.

Images