JP4737128B2 - Engine start control device and start control method - Google Patents

Description

  The present invention relates to an engine start control device and a start control method.

In a hybrid vehicle equipped with both an internal combustion engine (hereinafter referred to as an engine) and a motor as a vehicle drive source, cranking for starting the engine is performed using the generator as a motor, and a battery that supplies electric power to the generator The charge / discharge performance deteriorates with the passage of time, and the output voltage decreases.
Patent Documents 1 and 2 disclose a technique for determining a deterioration state of a battery from cranking rotation speed or the like.
JP 2006-240541 A Japanese Patent Laid-Open No. 11-178233

  By the way, if the battery is deteriorated, the compression reaction force of air in the cylinder during the compression process acts and the cranking rotation speed does not increase to the required rotation speed during cranking, making it difficult to start the engine. Become. Especially in a cold environment, it may be more difficult to start the engine. Since the hybrid vehicle uses a battery having a high voltage of about 200 V, if this deteriorates and it becomes difficult to start the engine, it is not easy to restart the engine. Further, an increase in internal resistance due to battery wiring deterioration, an increase in friction due to engine oil deterioration, and the like also hinder the engine cranking speed increase.

  The present invention has been made in view of the above problems, and the object of the present invention is to enable the engine to start even in a situation where the cranking speed is difficult to increase due to factors such as battery deterioration. An engine start control device and a start control method are provided.

The engine start control device according to the present invention is configured to stop the fuel supply to the combustion chamber and reduce the actual compression ratio when the cranking rotational speed during cranking does not reach the predetermined rotational speed within a predetermined period. When the cranking rotational speed has increased to a speed at which the engine can be started due to compression ratio reduction means and reduction of the actual compression ratio, fuel is supplied to the combustion chamber to increase the actual compression ratio and perform ignition. According to this configuration, when the cranking rotation at the time of cranking does not increase properly, the crankshaft is easily rotated by reducing the compression pressure in the combustion chamber. When the cranking speed increases and the engine speed is reached, the fuel is supplied, the compression pressure is increased, and ignition is performed.

In the above configuration, the actual compression ratio reducing means delays the timing of closing the intake valve to reduce the actual compression ratio, and the actual compression ratio increasing means advances the timing of closing the intake valve to advance the actual compression ratio. A configuration that increases the compression ratio can be adopted.
According to this configuration, the actual compression ratio can be controlled by the variable valve timing mechanism.

  In the above configuration, the engine may include a variable valve timing mechanism that is electrically driven with respect to the intake valve.

  The engine start control method of the present invention stops the fuel supply to the combustion chamber and reduces the actual compression ratio when the cranking rotation speed during cranking does not reach the predetermined rotation speed within a predetermined period. When the cranking speed increases to a speed at which the engine can be started, fuel is supplied to the combustion chamber and ignition is performed by increasing the actual compression ratio.

  According to the present invention, the engine can be started even in a situation where the cranking rotational speed is unlikely to increase due to deterioration of charge / discharge performance of a battery that supplies electric power to a motor that rotates the crankshaft of the engine. .

DESCRIPTION OF EXEMPLARY EMBODIMENTS Hereinafter, exemplary embodiments of the invention will be described with reference to the accompanying drawings.
FIG. 1 is a schematic configuration diagram of a hybrid vehicle to which a start control device according to the present invention is applied, and FIG. 2 is a diagram showing a configuration of an engine of the hybrid vehicle of FIG.
The hybrid vehicle 20 includes an engine 22, an engine electronic control unit (engine ECU) 24, a motor / generator MG1, a motor / generator MG2, a power distribution and integration mechanism 30, a reduction gear 35, a motor electronic control unit (motor ECU) 40, Inverters 41 and 42, a battery 50, a gear mechanism 60, a hybrid electronic control unit (ECU) 70, and the like are provided.

The engine 22 has a crankshaft 26 connected to a carrier 34 of a power distribution and integration mechanism 30 via a damper 28.
The power distribution and integration mechanism 30 includes a sun gear 31 connected to the rotor of the motor / generator MG1, a ring gear 32 concentrically disposed on the outer periphery of the sun gear 31, and connected to the output side of the reduction gear 35, the sun gear 31 and the ring. A ring gear shaft 32a, which includes a pinion gear 33 that meshes with the gear 32, a carrier 34 that holds the pinion gear 33, and the like and is connected to the ring gear 32, is connected to the output side of the reduction gear 35, and It is connected to the input gear of the mechanism 60.
The rotor of motor / generator MG2 is connected to the input side of the reduction gear.

The rotation of the crankshaft 26 that is the output shaft of the engine 22 is distributed to the drive wheels 63a and 63b via the motor / generator MG1, the gear mechanism 60, and the differential gear 62.
The rotation of the motor / generator MG2 is output to the ring gear shaft 32a via the speed reducer 35 and can be input to the drive wheels 63a and 63b via the gear mechanism 60 and the differential gear 62.

  Inverters 41 and 42 convert the direct current of battery 50 into three-phase alternating current and supply it to motor / generators MG1 and MG2, respectively, and convert the three-phase alternating current generated by motor / generators MG1 and MG2 into direct current. 50 can be supplied.

  Motor ECU 40 drives inverters 41 and 42 based on signals from rotational position detection sensors 43 and 44 provided in motor / generators MG1 and MG2, respectively, and controls rotation of motor / generators MG1 and MG2.

The battery 50 stores electric power generated by the motor / generator MG1, supplies electric power to the motor / generator MG2 when starting, accelerating, and climbing, and stores electric power regenerated by the motor / generator MG2 during deceleration. The battery 50 supplies and charges power at a voltage of about 200 volts.
The battery ECU 52 monitors the state of charge of the battery 50 based on a signal from a temperature sensor 51 provided in the battery 50.
The sub-battery 53 supplies power for driving auxiliary equipment and a VVT 150 described later. The sub-battery 53 has a lower voltage than the battery ECU 52, and is about 12V, for example.

  The hybrid ECU 70 includes hardware such as a CPU 72, a ROM 74, and a RAM 76 and necessary software, and includes an ignition switch 80, a shift position sensor 82 provided on the shift lever 81, an accelerator position sensor 84 provided on the accelerator pedal 83, Driving is performed by receiving signals from the brake pedal sensor 86, the vehicle speed sensor 88, and the like provided in the brake pedal 85, obtaining the output of the engine 22 and the motor torque according to the driving state, and outputting the required value to each ECU. It has functions such as force control. The hybrid ECU 70 constitutes an engine start control device.

  As shown in FIG. 2, the engine 22 generates power by burning a mixture of fuel and air in a combustion chamber 131 formed in a cylinder block and reciprocating a piston 132 in the combustion chamber 131. . The engine 22 of the present embodiment is a vehicular multi-cylinder engine (for example, a four-cylinder engine, only one cylinder is shown), and is a spark ignition internal combustion engine, more specifically a gasoline engine.

  In the cylinder head of the engine 22, an intake valve 128 that opens and closes an intake port and an exhaust valve 129 that opens and closes an exhaust port are provided for each cylinder. Each intake valve 128 and each exhaust valve 130 are opened and closed by a camshaft (not shown). A spark plug 130 for igniting the air-fuel mixture in the combustion chamber 131 is attached to the top of the cylinder head for each cylinder.

  An intake pipe that forms an intake manifold passage is connected to the upstream side of the intake port of each cylinder, and an air cleaner 122 is provided at the upstream end of the intake pipe. An air flow meter 148 for detecting the intake air amount, a temperature sensor 149, and a throttle valve 124 are incorporated in the intake pipe in order from the upstream side. The throttle valve 124 is provided with a throttle motor 136 for driving the throttle valve 124 and a throttle valve position sensor 146.

  An injector (fuel injection valve) 126 for injecting fuel into the intake passage, particularly into the intake port, is provided for each cylinder. The fuel injected from the injector 126 is mixed with intake air to form an air-fuel mixture. The air-fuel mixture is sucked into the combustion chamber 131 when the intake valve 128 is opened, compressed by the piston 132, and ignited and burned by the spark plug 130. It is done.

  An exhaust pipe is connected to the downstream side of the exhaust port of each cylinder, and a purification device 134 made of a three-way catalyst is attached to the exhaust pipe on the downstream side. Further, an air-fuel ratio sensor 135a for detecting the air-fuel ratio of the exhaust gas is provided on the upstream side of the purification device 134, and an oxygen sensor 135b for detecting the oxygen concentration in the exhaust gas is provided on the downstream side.

A variable valve timing mechanism (VVT) 150 is provided on the cylinder head. VVT 150 varies the phase of the camshaft on the intake valve 128 side in accordance with a command from engine ECU 24.
As shown in FIG. 3, the VVT 150 is provided with an electric drive unit 151 including a motor 151A and its drive circuit 151B. In other words, the VVT 150 is an electric variable valve timing mechanism that can change the phase regardless of the state of the engine, and has better responsiveness than the hydraulic drive type.

  As shown in FIG. 2, the engine ECU 24 includes hardware such as a CPU 24a, ROM 24b, and RAM 24c and necessary software, and includes an air-fuel ratio sensor 135a, an oxygen sensor 135b, a crank position sensor 140, a water temperature sensor 142, and a cam position sensor. 144, signals from the throttle valve position sensor 146, air flow meter 148, temperature sensor 149, etc. are input, and control signals are output to the throttle motor 136, the ignition coil 138, the electric drive unit 151 of the VVT 150, and the like.

Here, FIG. 4 is a diagram showing the relationship of the valve timing of the intake / exhaust valve when the intake valve closing timing by the VVT 150 is advanced (at the time of VVT advance), and FIG. 5 is a delay of the intake valve closing timing. It is a figure which shows the relationship of the valve timing of an intake / exhaust valve when it makes it horn (at the time of VVT retardation). FIG. 6 is a graph showing fluctuations in the compression pressure in the cylinder during cranking when the VVT is advanced and when the VVT is retarded.
When the closing timing of the intake valve by the VVT 150 is advanced, the engine 22 is operated in an Otto cycle. Further, when the closing timing of the intake valve by VVT 150 is retarded, engine 22 is operated in the Atkinson cycle.

  As can be seen from FIG. 4 and FIG. 5, if the intake valve closing timing is retarded and the intake valve is kept open during the compression stroke, the actual compression ratio of the engine is reduced, and accordingly Since the compression reaction force acting on the ranking shaft is reduced, the rotation reaction force acting on the cranking shaft at the time of starting is reduced. That is, if the intake valve closing timing is advanced, the compression region becomes relatively long (the actual compression ratio is relatively increased), and if the intake valve closing timing is retarded, the compression region is relatively increased. Shorten (actual compression ratio is relatively reduced). Therefore, as shown in FIG. 6, during cranking, if the closing timing of the intake valve is retarded, the actual compression ratio during the compression process will be greatly reduced and cranking rotational speed will be lower than when the intake valve is advanced. It becomes easy to rise. The state shown in FIG. 5 is a so-called decompressed state.

Next, an example of engine start control by the hybrid ECU 70 will be described with reference to the flowchart of FIG.
First, the hybrid ECU 70 starts cranking (step S1). Specifically, hybrid ECU 70 gives a command to motor ECU 40, and motor ECU 40 controls inverter 41 to convert electric power stored in battery 50 into three-phase alternating current to drive and control motor / generator MG1, The engine 22 is cranked.

Next, the hybrid ECU 70 determines whether or not the predetermined period A has elapsed after starting cranking (step S2). If the predetermined period A has elapsed, it is determined whether the cranking speed (engine speed NE) is equal to or lower than the predetermined speed 400 rpm (step S3).
Here, as shown in FIG. 8, when the battery 50 is normal, when the predetermined cranking period A elapses, the engine speed NE reaches a predetermined speed of about 400 rpm at which the engine can be started. In this case, the closing timing of the intake valve by the VVT 150 is in the advanced state, fuel injection and ignition are performed, and the engine 22 is started.

On the other hand, if the battery 50 is deteriorated, the engine speed NE may not reach the predetermined speed of 400 rpm within the predetermined period A as shown in FIG.
Therefore, when the cranking rotation speed is 400 rpm or less in step S3, the hybrid ECU 70 determines that the battery 50 has deteriorated and reduces the compression pressure (step S4). Specifically, the compression timing is reduced by delaying the closing timing of the intake valve by the VVT 150 to a decompressed state. At this time, since the VVT 150 is driven by the electric drive unit 151, the closing timing of the intake valve can be surely retarded regardless of the driving state of the engine.
At the same time, the fuel injection is cut and the fuel supply to the combustion chamber 131 is stopped. This is to prevent the release of unburned gas.
Regarding the determination of the deterioration of the battery 50, for example, it may be determined that the battery 50 has deteriorated for the first time when a predetermined amount of decompression has been performed, for example, when the speed does not reach 400 rpm. In addition, when it is determined that the battery 50 has deteriorated, it is possible to notify the user by lighting a warning lamp or the like. Accordingly, the user (driver) can be notified that the vehicle is evacuating by decompression, and the vehicle can be evacuated to a repair shop or the like before it becomes impossible to start within the range where the decompression has a sufficient starting capacity.

When the engine 22 is in the decompressed state and cranking is continued, if the battery 50 has sufficient power, the cranking speed (engine speed) increases as shown in FIG. 9, and the engine can be started. The predetermined rotation speed reaches about 400 rpm. In this state, the rotation of the crankshaft is in a state of rotational inertia due to the flywheel.
The hybrid ECU 70 determines whether or not a predetermined rotational speed of 400 rpm at which the engine can be started has been reached (step S5). If the predetermined rotational speed of 400 rpm has been reached, the hybrid ECU 70 increases the compression pressure (step S6). Specifically, as shown in FIG. 9, the closing timing of the intake valve is advanced again by VVT 150, fuel is injected, and the air-fuel mixture is ignited.

  In step S5, if the battery 50 is deteriorated and does not reach the predetermined rotation speed of 400 rpm even in the decompressed state, the user is informed that the engine 22 cannot be started by, for example, lighting a warning lamp (step S7). ).

  As described above, according to the present embodiment, the engine 22 can be started by reducing the compression pressure in the combustion chamber even when the cranking rotational speed is difficult to increase due to deterioration of the battery 50 or the like. become.

  In the above embodiment, the case where the start control device of the present invention is applied to the hybrid vehicle shown in FIG. 1 has been described. However, the present invention is not limited to this, and can be applied to other types of hybrid vehicles. . The present invention can also be applied to a vehicle that performs cranking by a cell motor having only an internal combustion engine as a drive source, not a hybrid vehicle.

  In the above embodiment, the case where the VVT 150 is driven by the electric drive unit 151 has been described, but the VVT 150 may be hydraulically driven.

  In the above embodiment, the case where the compression pressure is changed by delaying the timing of closing the intake valve has been described. However, the present invention is not limited to this, and other means capable of varying the compression pressure can also be adopted. It is.

1 is a schematic configuration diagram of a hybrid vehicle to which a start control device according to the present invention is applied. It is a figure which shows the structure of the engine of the hybrid vehicle of FIG. It is a schematic block diagram of an electric variable valve timing mechanism. It is a figure which shows the relationship of the valve timing of the intake / exhaust valve at the time of VVT advance. It is a figure which shows the relationship of the valve timing of the intake / exhaust valve at the time of VVT retardation. It is a graph which shows the fluctuation | variation of the compression pressure in a cylinder at the time of cranking at the time of VVT advance and the time of VVT retard. It is a flowchart which shows an example of engine starting control by a hybrid. 6 is a graph showing VVT control, fuel injection / ignition timing, and engine speed when the battery is normal. It is a graph which shows the timing of VVT control and fuel injection and ignition at the time of battery deterioration, and an engine speed.

Explanation of symbols

20 ... Hybrid vehicle 22 ... Engine 24 ... Engine ECU
30 ... Power distribution and integration mechanism 35 ... Reduction gear 40 ... Motor ECU
41, 42 ... Inverter 50 ... Battery 53 ... Sub-battery 60 ... Gear mechanism 70 ... ECU for hybrid
MG1, MG2 ... Motor / Generator

Claims (4)

Means for determining whether the cranking rotational speed at the time of cranking for rotating the cranking motor by electric power supplied from the battery has reached a predetermined rotational speed within a predetermined period from the start of cranking ;
An actual compression ratio reducing means for determining that the battery has deteriorated when the predetermined rotational speed is not reached, and stopping the fuel supply to the combustion chamber and reducing the actual compression ratio;
An actual compression ratio increasing means for supplying fuel to the combustion chamber and increasing the actual compression ratio to perform ignition when the cranking rotation speed has increased to a speed at which the engine can be started by reducing the actual compression ratio; ,
An engine start control device comprising: The actual compression ratio reducing means retards the timing of closing the intake valve to reduce the actual compression ratio,
The actual compression ratio increasing means advances the timing for closing the intake valve to increase the actual compression ratio.
The engine start control device according to claim 1.   The engine start control device according to claim 2, wherein the engine includes an electric variable valve timing mechanism for the intake valve. Determining whether the cranking rotational speed at the time of cranking for rotating the cranking motor by the power supplied from the battery has reached a predetermined rotational speed within a predetermined period from the start of cranking ;
When the predetermined number of revolutions is not reached within the predetermined period, it is determined that the battery is deteriorated , the fuel supply to the combustion chamber is stopped, and the actual compression ratio is reduced.
When the cranking rotational speed has increased to a rotational speed at which the engine can be started, fuel is supplied to the combustion chamber and ignition is performed by increasing the actual compression ratio.
An engine start control method.

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