JP3894272B2 - Hybrid car - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a hybrid vehicle.
[0002]
[Prior art]
In a hybrid vehicle that combines a gasoline engine and an electric motor as a power source, the engine is basically stopped at low speed range for motor driving, and at medium and high speed range, the engine is operated and used in combination with the motor. Yes. For example, when accelerating when the engine is stopped and running by the motor, the engine is started to compensate for the torque. By the way, when the engine is stopped, the initial compression overcoming torque (torque required until the cylinder stopped in the compression stroke gets over the compression top dead center) is large. On the other hand, a motor that secures the minimum performance (capacity) necessary for reducing the size, weight, and cost is used. For this reason, in starting and accelerating the engine from the motor running (engine stop), the motor torque at the initial stage of acceleration is accelerated while being distributed for starting the engine and accelerating the vehicle, resulting in poor acceleration.
[0003]
In a hybrid vehicle, as means for assisting the load of the motor at the start of the engine, for example, Japanese Patent Application Laid-Open No. 11-270445 discloses a hybrid vehicle having an engine, a motor generator, and a start motor. A technique is disclosed in which an engine is started by a motor to reduce a load of a motor generator on the engine. In this technology, when the engine temperature is in a starting state equal to or higher than a predetermined temperature corresponding to a warm-up state, only a motor generator (hereinafter referred to as “motor”) is started as a motor. The motor assist load is reduced by activating both the motor and the motor.
[0004]
[Problems to be solved by the invention]
According to the above prior art, the engine load related to the motor is large in the cold state, but the engine load related to the motor temporarily receives the compression reaction force near the compression top dead center of the engine regardless of the engine temperature. Will increase. In particular, when the top dead center is overcome in the first compression stroke at the start when the engine has almost no inertia torque, the increase in the engine load increases, and the engine start work of the motor increases and the driving force of the vehicle decreases. During acceleration, acceleration performance may deteriorate and drivability may deteriorate. Therefore, since the above conventional technology only considers the temperature at the start of the engine, it solves the problem of poor acceleration while distributing the motor torque at the initial stage of acceleration for engine start and vehicle acceleration. Can not do it.
[0005]
Therefore, an object of the present invention is to provide a hybrid vehicle in which drivability is improved by reducing the engine start work of the motor at the initial stage of engine start.
[0006]
[Means for Solving the Problems]
To achieve the above object, the present onset bright, started from a state in which mounting the starter motor to assist only start the engine in a hybrid vehicle having an engine and a motor, said engine by start decision means is stopped In this case, it is determined whether or not the start condition is satisfied. When the start condition is satisfied, the start motor is driven to start the engine together with the motor. When starting from a state in which the engine is stopped, the starter motor gets over the first compression when the crank angle before the top dead center in the first compression stroke is a predetermined angle or on the lower dead center side than the predetermined angle. Torque assistance at the time.
Moreover, startup motor, the torque auxiliary at overcoming compression twice from starting if crank angle is the top dead center side than a predetermined angle in the first compression stroke when starting from a state in which the engine is stopped Do.
As a result, the work of the motor when the engine starts is reduced, and the torque can be distributed to the vehicle acceleration torque, thereby improving the acceleration response.
[0007]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the drawings.
FIG. 1 is a schematic configuration diagram of a hybrid vehicle according to the present invention. As shown in FIG. 1, the hybrid vehicle includes an engine 1 and a traveling motor (main motor) 2, and an output shaft (crankshaft) of the engine 1 is one end of a rotating shaft of the motor 2 via a clutch 3. Can be directly connected to. The other end of the rotating shaft of the motor 2 is connected to, for example, an input shaft of a continuously variable transmission (CVT) 4, and the output shaft of the continuously variable transmission 4 is connected to the rear wheels 7, 7 via a starting clutch 5. Directly connected to the differential (difference) 6.
[0008]
The starter motor motor 8 is attached to the engine 1, and a pinion 9 provided on the rotating shaft of the starter motor motor 8 can mesh with a ring gear 10 attached to the output shaft of the engine 1. The starter motor 8 rotates the rotation shaft of the engine 1 with the pinion 9 meshing with the ring gear 10 only when the engine 1 is started. Therefore, the starter motor 8 is a small motor similar to a normal starter motor.
[0009]
The electronic control unit (hereinafter referred to as “ECU”) 12 includes a start condition determining means for the engine 1 and a control means for controlling the engine 1, the main motor 2, the clutch 3, the start motor 8, etc., and includes a vehicle speed sensor 15, an accelerator pedal. Signals from the sensor 16, the engine rotation sensor 17, the crank angle sensor 18, etc. are input to determine the starting condition of the engine 1, and when the starting condition is satisfied, the clutch 3 is connected and the engine 1 is directly connected to the motor 2. At the same time, the motor 8 is driven and controlled only when the engine 1 is started.
[0010]
The operation will be described below.
First, an outline of control will be described. As shown by the solid line I in FIG. 2, the vehicle stops the engine 1 (engine speed Ne = 0, solid line I) and runs at a constant speed at a vehicle speed Va by the motor 2 (motor speed Nm = a, solid line II). If the accelerator pedal is depressed to accelerate at time t1, the accelerator signal input from the accelerator pedal sensor 16 increases accordingly. The ECU 12 determines that acceleration should be performed by increasing the accelerator pedal signal, increases the torque of the motor 2 (solid line IVa) and connects the clutch 3 to directly connect the motor 2 and the engine 1. At the same time, the starting motor 8 is driven to assist the torque of the motor 2 when the engine 1 is started. That is, the starting motor 8 assists the compression overcoming torque in the first compression stroke when the engine is started. As a result, as shown by the solid line Va, the compression overcoming torque of the engine at the start-up is assisted. The motor 2 is controlled to a predetermined torque after the compression overcoming, the torque gradually decreases (solid line IVb). On the other hand, the torque of the engine 1 increases after starting and is controlled to a predetermined torque (solid line Vb). As a result, the reduction of the engine starting work (torque) at the initial acceleration of the motor 2 is suppressed, and the acceleration of the vehicle, particularly the initial acceleration, is increased (solid line VI). Then, the rotational speeds Ne and Nm of the engine 1 and the motor 2 are increased (solid lines I and II), and the vehicle speed is increased accordingly (solid line III).
[0011]
In FIG. 2, a dotted line Va ′ indicates the compression overcoming torque (load torque) in the first compression stroke of the engine 1, and when starting assistance is not performed by the motor, the torque of the motor 2 is indicated by a dotted line IVb ′. It is necessary to lengthen the rising time, and the overload state of the motor 2 and the power source (battery) becomes longer. When the starting assistance is not performed, the engine speed, motor speed, vehicle speed, and vehicle acceleration are as indicated by dotted lines I ′, II ′, III ′, and VI ′, respectively. Therefore, by performing the starting assistance by the starting motor 8, the vehicle speed V can follow well according to the depression of the accelerator pedal, and drivability (acceleration performance of the vehicle) can be improved.
[0012]
Next, the control procedure will be described in detail with reference to the flowcharts shown in FIGS. The ECU 12 stores information on a cylinder in the compression stroke of the stopped engine 1 (hereinafter referred to as “compression stroke cylinder”) and a stop crank angle of the cylinder in a storage device. This information is calculated based on a crank angle signal detected by the crank angle sensor 18 immediately before the engine is stopped and a compression top dead center (TDC) signal detected by a cam angle sensor (not shown), and the engine is automatically stopped. Of course, it is held in the storage device even during parking when the ignition switch is turned off.
[0013]
In the flowchart of FIG. 3, when starting the engine 1, the ECU 12 determines whether or not the engine 1 is stopped (step S1). When the engine 1 is not stopped, the ECU 12 ends the control, and the engine 1 When the engine is stopped, it is determined whether or not the crank angle (BTDC) before the top dead center when the engine 1 is stopped is smaller than a predetermined angle α (for example, 50 °) (step S2). If it is not smaller in step S3, the process proceeds to step S4. In step S3, the auxiliary stroke of the starter motor 8 is set to two strokes, and the starter motor 8 is set to be driven during two compression passes. This is because when the crank angle before top dead center (BTDC) when the engine is stopped is smaller than a predetermined angle α, the compression stroke cylinder may be misfired. To avoid this, the cylinder in the next compression stroke may be Rotate to compression top dead center and ignite completely. Therefore, in this case, when the engine 1 is started, it is necessary to perform the compression overcoming twice. In step S4, the auxiliary stroke of the starter motor 8 is set as one stroke, and the starter motor 8 is set to be driven only during the first (first) compression ride. This is because, when the crank angle before top dead center (BTDC) when the engine is stopped is not smaller than the predetermined angle α, the compression stroke cylinder can be ignited. Start assistance may be performed during (one time) overcoming the compression.
[0014]
The ECU 12 determines whether or not the engine 1 is being started during traveling after the auxiliary stroke of the starting motor 8 is set to one stroke or two strokes in step S3 or step S4 (step S5). Whether or not the starting condition is during traveling is determined based on a vehicle speed signal from the vehicle speed sensor 15 and a signal from the accelerator pedal sensor 17 (step S5). In other words, the ECU 12 determines that the starting condition is during traveling when the accelerator pedal is depressed during acceleration and an acceleration operation is performed, or when the accelerator pedal is depressed on an uphill. Is set (step S6), and the running flag is reset when the engine 1 is started when the running condition is not met, that is, when the vehicle is stopped (step S7).
[0015]
In the flowchart shown in FIG. 4, the ECU 12 determines whether or not a running start flag is set (step S8). When the running flag is not set, the ECU 12 ends the control. When the running flag is set, the ECU 12 3 is operated to directly connect the engine 1 and the motor (main motor) 2 (step S9), and the engine 1 is started by the motor 2 and the starter motor 8 is driven to assist the start of the engine 1 (step S10). ). The ECU 12 determines whether or not one or two auxiliary strokes by the starting motor 8 have passed (finished) (step S11), and continues the starting assistance by the starting motor 8 when the auxiliary stroke has not passed (step S11). Step S12) When the auxiliary stroke has elapsed, the starting assistance by the starting motor 8 is terminated (step S13). That is, the starting assistance of the engine 1 by the starting motor 8 ends when the crank angle signal is at the top dead center of the first compression stroke cylinder or the top dead center of the next compression stroke cylinder. Next, the ECU 12 determines whether or not the engine speed has exceeded a predetermined value (step S14), and if it has exceeded, determines that the engine 1 has started and resets the running start flag (step S15). When it does not exceed, it is determined that the engine 1 has not started, and the control is repeated.
[0016]
In this way, when starting the engine 1 while the motor 2 is running, the starter motor 8 assists the engine 1 to overcome the initial compression torque, and the engine start-up work of the motor 2 is reduced. It is possible to improve.
[0017]
【The invention's effect】
According to the onset bright, starting condition when starting from a state in which mounting the starter motor to assist only start the engine in a hybrid vehicle having an engine and a motor, said engine by start decision means has stopped It is determined whether or not the condition is satisfied, and when the start condition is satisfied, the engine is started by driving the start motor and starting the engine together with the motor, thereby reducing the engine start work of the motor at the initial start of the engine. In particular, when the engine is stopped and the engine is started from the running by the motor for acceleration, the starting work of the motor can be reduced and the acceleration response of the vehicle can be improved. .
[Brief description of the drawings]
FIG. 1 is a schematic configuration diagram of a hybrid vehicle according to the present invention.
FIG. 2 is a diagram showing a time chart of the hybrid vehicle shown in FIG.
FIG. 3 is a part of a flowchart showing a control procedure of the hybrid vehicle shown in FIG. 1;
FIG. 4 is the remaining part of the flowchart shown in FIG. 3;
[Explanation of symbols]
1 Engine 2 Motor (traveling motor)
3 Clutch 12 Electronic control device (starting condition determination means, control means)

Claims (1)

In a hybrid vehicle equipped with an engine and a motor,
A starting motor for assisting in starting the engine;
Start condition determining means for determining whether a start condition is satisfied when the engine stops rotating;
A compression stroke cylinder detecting means for detecting a cylinder in the compression stroke when the engine stops rotating;
Crank angle detecting means for detecting a crank angle before top dead center in a cylinder in the compression stroke detected by the compression stroke cylinder detecting means;
When the engine start condition is determined by the start condition determining means, the motor is driven to start the engine, and the crank angle detected by the crank angle detecting means is a predetermined angle or a predetermined angle If the crank angle is on the top dead center side from the start until the compression stroke cylinder exceeds the top dead center when the engine is on the bottom dead center side, compression occurs when the engine rotation is stopped from the start. A hybrid vehicle comprising: control means for driving the starter motor to assist start until a cylinder in a compression stroke next to a cylinder in a stroke passes over the top dead center .

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