JP5206004B2 - Engine starter for hybrid vehicle - Google Patents

Description

  The present invention relates to a hybrid vehicle having an engine (internal combustion engine) and a motor (electric motor) as drive sources, and more particularly to a starting device for the engine.

  In a hybrid vehicle that travels by generating a driving force of the vehicle with the output of at least one of the engine and the motor, the engine starts and stops repeatedly, so that the engine is started to the extent that the driver does not notice the engine starting. There is a demand for suppressing vibration.

  The vibration associated with engine start-up includes a driving force transmission system that passes through a rotation speed range where the engine speed increases during cranking and resonance of the driving force transmission system occurs (this is referred to as a “resonance band”). The vibration due to the resonance is remarkable, and this is transmitted to the vehicle body to give unpleasant feeling.

Therefore, in Patent Document 1, when the engine speed at the time of cranking is predicted and entering the resonance band is predicted, the cranking motor is set so that the engine speed does not enter the resonance band during cranking. The torque is controlled so that the resonance band can be passed quickly after the first explosion.
JP 2006-152877 A

  However, with the technology described in Patent Document 1, it is possible to avoid the resonance band during cranking, but if the engine blows up after the first explosion is bad, there is a possibility that the resonance band will remain after the first explosion. There was still room for improvement.

  In view of such a situation, an object of the present invention is to allow a resonance band to pass through reliably and promptly after the initial explosion.

For this reason, in the present invention, it is provided with means for predicting the rise of the engine rotation ,
Result before Symbol predicted, when the engine speed during cranking is determined that can not pass through the resonance band, and means for controlling the torque of the cranking means so that the engine rotational speed during cranking from entering the resonance band and means for Ru increase the amount of intake air provided to the initial combustion, the engine speed after the initial explosion control the assist amount by the motor after the first explosion to pass through the resonance band at a rotation rate of increase above a predetermined value Means .
The means for controlling the assist amount is characterized in that, during a predetermined period immediately after the first explosion, a load is applied by the motor to suppress the engine speed to the resonance band or lower.

  The cranking means (cranking motor) may be a motor that is a driving source of the hybrid vehicle, or may be a dedicated cranking motor (starter) different from the driving motor. .

  According to the present invention, the engine speed is kept below the resonance point during cranking, and after the first explosion, the resonance band can be passed quickly by increasing the intake air amount and the motor assist, and a good engine start Can be realized.

Embodiments of the present invention will be described below with reference to the drawings.
FIG. 1 is a configuration diagram of a hybrid vehicle showing an embodiment of the present invention.
The engine 1 is, for example, a direct-injection spark ignition internal combustion engine, and its output shaft 2 is connected to one end of a shaft of a motor (motor generator) 4 that also serves as a generator via a first clutch 3.

  The other end of the shaft of the motor 4 is connected to the input shaft of the automatic transmission 6 via the second clutch 5. The output shaft of the automatic transmission 6 is connected to a wheel drive shaft 8 via a differential device 7.

Therefore, this hybrid vehicle can travel by generating the driving force of the vehicle with the output of at least one of the engine 1 and the motor 4.
Here, the engine 1 can be used to drive the motor 4 for power generation in addition to generating the driving force of the vehicle by its output.

  The motor 4 is connected to a battery 10 via an inverter 9, and the battery 10 can supply driving power to the motor 4 and charge generated power from the motor 4. The motor 4 can generate electric power by being driven from the engine 1 or the vehicle side as a generator, in addition to generating the driving force of the vehicle alone or in the form of assisting the engine 1.

More specifically, the motor 4 travels mainly when starting and running at low speed. That is, the motor 4 is driven by the electric power from the battery 10.
During normal driving (during steady driving), at least one of the engine 1 and the motor 4 is used to achieve the driving with the best fuel efficiency, and during acceleration, the maximum power is drawn using both to accelerate strongly.

During deceleration and braking, the motor 4 is used as a generator, and the recovered energy is stored in the battery 10.
When the vehicle stops, both the engine 1 and the motor 4 are automatically stopped to eliminate wasteful fuel consumption and power consumption due to idle operation.

The engine 1 will be described in further detail.
An electrically controlled throttle valve 13 is provided in the intake passage 12 to the combustion chamber 11 of the engine 1, and this throttle valve 13 is mainly for securing a control negative pressure, and the amount of intake air to the combustion chamber 11 This control is performed by the intake valve 14, more specifically, by controlling the valve operating angle (and the lift amount) of the intake valve 14 by a variable valve mechanism 15 described later.

  The combustion chamber 11 of the engine 1 is provided with a fuel injection valve 16 that injects and supplies fuel, and an amount of fuel corresponding to the intake air amount detected by the air flow meter is injected at a predetermined injection timing. 11 is formed with a predetermined air-fuel ratio mixture.

  The combustion chamber 11 of the engine 1 is further provided with an ignition plug 17 that ignites the air-fuel mixture, and ignition is performed at a predetermined ignition timing, and the air-fuel mixture burns. The exhaust after combustion is discharged to the exhaust passage 19 through the exhaust valve 18.

Next, the variable valve mechanism 15 of the intake valve 14 of the engine 1 will be described with reference to FIG.
As the variable valve mechanism, the valve operating angle of the intake valve (the opening period from the intake valve opening timing to the valve closing timing), specifically, the valve operating angle that can continuously change the valve operating angle and the lift amount, A variable lift amount mechanism (VEL mechanism; VEL actuator 49) and a variable valve timing mechanism (VTC mechanism; VTC actuator 51) capable of continuously changing the valve timing (center phase of the valve operating angle) of the intake valve. Is provided.

  Specifically, an intake valve 14 (two per cylinder, only the end of the valve stem is shown) is positioned above the valve lifter 40 at the end thereof and is driven to rotate around the shaft in conjunction with a crankshaft (not shown). The cam shaft 41 is extended in the cylinder row direction. A swing cam 42 is swingably mounted on the outer periphery of the cam shaft 41 so as to correspond to the intake valve 14, and the swing cam 42 abuts against and presses the valve lifter 40. The valve 14 is driven to open and close against the spring force of a valve spring (not shown).

  Here, the valve operating angle and the lift amount of the intake valve 14 are continuously variably controlled by changing the posture of the link that mechanically links both the cam shaft 41 and the swing cam 42 between the cam shaft 41 and the swing cam 42. A possible valve operating angle and lift amount variable mechanism (VEL mechanism) is provided.

  The VEL mechanism includes a circular drive cam 43 that is eccentrically provided on the cam shaft 41 and rotates integrally with the cam shaft 41, a ring-shaped link 44 that is fitted on the outer periphery of the drive cam 43 so as to be relatively rotatable, and a cam A control shaft 45 extending substantially in parallel with the shaft 41 in the cylinder row direction, a circular control cam 46 that is eccentrically provided on the control shaft 45 and rotates integrally with the control shaft 45, and an outer periphery of the control cam 46 And a rocker arm 47 having one end rotatably connected to the tip of the ring-shaped link 44, and the other end of the rocker arm 47 and the tip of the swing cam 42 are rotatably connected. The rod-shaped link 48 that mechanically links the two 47 and 42 is provided.

  The cam shaft 41 and the control shaft 45 are rotatably supported on the cylinder head side of the engine via a bearing bracket. One end of the control shaft 45 is connected to an output end of an actuator (VEL actuator) 49 for changing the valve operating angle and lift amount. The VEL actuator 49 causes the control shaft 45 to move around the axis within a predetermined control angle range. While being rotated, it is held at a predetermined rotational phase.

  With such a configuration, when the cam shaft 41 rotates in conjunction with the crankshaft, the ring-shaped link 44 substantially translates via the drive cam 43, and the rocker arm 47 swings around the control cam 46, The swing cam 42 swings through the rod-shaped link 48, and the intake valve 14 is driven to open and close.

  Further, when the control shaft 45 is rotated by the VEL actuator 49, the center position of the control cam 46, which is the rocking center of the rocker arm 47, is changed, and the postures of the links 44, 48, etc. are changed. The swing angle range of 42 changes. As a result, the valve operating angle and the lift amount continuously change while the central phase of the valve operating angle remains substantially constant. More specifically, the valve operating angle and the lift amount are increased by rotating the control shaft 45 in one direction, and the valve operating angle and the lift amount are decreased by rotating in the other direction. Yes.

  Therefore, duty control of the energization amount of the VEL actuator 49 can change the rotation phase of the control shaft 45 and change the valve operating angle and lift amount of the intake valve 14 (see FIG. 3). A valve operating angle and lift amount variable mechanism (VEL mechanism) is configured. The lift amount is uniquely determined with respect to the valve operating angle. When the valve operating angle is controlled from large to small, the lift amount is also controlled from large to small, and the large operating angle / high lift to the small operating angle / low lift are controlled. Can be controlled within the range.

  On the other hand, the camshaft 41 is driven by the rotation of the crankshaft being input to the sprocket 50 by the timing belt, but the rotational phase of the camshaft 41 can be controlled between the sprocket 50 and the camshaft 41 to change the valve timing. A rotary actuator (VTC actuator) 51 is mounted.

  Therefore, duty control of the energization amount of the VTC actuator 51 changes the rotation phase between the crankshaft and the camshaft 41, and the valve timing of the intake valve 14 (the central phase of the valve operating angle; indicated by the dotted line in FIG. 3). Thus, a variable valve timing mechanism (VTC mechanism) is configured.

  Here, as shown in FIG. 3, the valve timing is advanced by the VTC mechanism in accordance with the control of the large operating angle / high lift to the small operating angle / low lift by the VEL mechanism. The valve closing timing is advanced by controlling from a large operating angle / high lift to a small operating angle / low lift while maintaining a constant value.

More specifically, in relation to operating conditions, low operating speed and low load, small operating angle and low lift (valve closing timing advance), high operating speed and high load, large operating angle and high lift (late valve timing delayed). Control).
FIG. 4 is a diagram showing input / output to / from the engine control unit (ECU) 61 and the hybrid control unit (HCU) 62.

The ECU 61 and the HCU 62 are connected to each other via a communication line, and perform cooperative control while sharing information.
Input to the ECU 61 is an accelerator opening sensor 63 for detecting the accelerator opening APO, an engine speed sensor (crank angle sensor) 64 for detecting the engine speed Ne, an air flow meter 65 for detecting the intake air amount Qa, and engine cooling. An engine water temperature sensor 66 for detecting the water temperature Tw, a VEL position sensor 67 for detecting the actual position (actual valve operating angle) of the VEL actuator 49, a VTC position sensor 68 for detecting the actual position (actual valve timing) of the VTC actuator 51, etc. is there.

The output destination of the ECU 61 is the throttle valve 13, the fuel injection valve 16 of each cylinder, the ignition plug 17 of each cylinder, the VEL actuator 49, the VTC actuator 51, and the like.
The control of the VEL actuator 49 and the VTC actuator 51 by the ECU 61 will be described. The ECU 61 calculates the target valve operating angle and the target valve timing according to the operating conditions. Then, the drive amount of the VEL actuator 49 is feedback controlled while detecting the actual valve operating angle according to the target valve operating angle. Further, the drive amount of the VTC actuator 51 is feedback controlled while detecting the actual valve timing according to the target valve timing.

The input to the HCU 62 is a vehicle speed sensor 69 that detects the vehicle speed VSP, a battery voltage sensor 70 that detects the voltage VB of the battery 10, and the like.
The output destination of the HCU 62 is the motor 4, the battery 10, and the like.

Next, engine start time control according to the present invention, which is performed by cooperative control of the ECU 61 and the HCU 62, will be described.
FIG. 5 is a flowchart of the first embodiment of engine start control. This flow is started by an engine start command (starter On signal).

  In S1, cranking of the engine 1 by the motor 4 is started by an engine start command (starter On signal). In this embodiment, the motor 4 that is a drive source of the hybrid vehicle is used as cranking means (cranking motor).

  In S2, an instantaneous drop amount ΔV of the battery voltage at the start of cranking is detected. This is because the state of the battery 10 (remaining battery SOC = drive power amount) is reflected. Specifically, it can be determined that as the battery voltage drop amount ΔV is larger, the state of the battery 10 is worse (the amount of drive power is smaller), and therefore, the rotation increase due to cranking is worsened.

  In S3, the engine coolant temperature Tw is detected. This is because the friction of the engine 1 can be estimated. Specifically, it can be determined that the lower the water temperature Tw is, the greater the friction of the engine 1 is, so that the rotational increase due to cranking is worsened.

  In S4, the degree of increase in engine rotation during cranking and after the first explosion is predicted from the battery voltage drop amount ΔV at the start of cranking and the engine coolant temperature Tw. In other words, the engine speed increase rate during cranking and the reached engine speed and the engine speed increase rate after the first explosion are predicted.

  As the battery voltage drop amount ΔV is larger and the engine coolant temperature Tw is lower, the rate of increase of the engine speed and the reached number of revolutions decrease. Therefore, using these as parameters, the rate of increase of the engine speed and the reached number of revolutions A map defining the above may be created and predicted by referring to this map.

  In S5, based on the prediction in S4, is it possible to pass through the resonance band quickly during cranking (the rate of increase in engine speed during cranking when the reached rotation speed in cranking exceeds the resonance band)? Is greater than or equal to a predetermined value).

In the case of YES, normal cranking can quickly pass through the resonance band, and vibration due to resonance hardly causes a problem. Therefore, the process proceeds to S10 and normal control is performed.
In the case of NO, if normal control is used, the engine speed stays in the resonance band for a long time during cranking, and vibration due to resonance becomes significant. Therefore, control after S6 is performed to avoid this. Switch to.

  In S6, since it is determined that the engine speed cannot pass through the resonance band during cranking, the torque of the motor 4 that is the cranking means is controlled so as not to enter the resonance band during cranking. Reduce.

  At this time, the battery voltage drop amount ΔV corresponding to the driving electric energy and the friction are matched so that the engine rotational speed converges to the target cranking rotational speed determined so as to be close to the resonance band but less than the resonance band. From the engine coolant temperature Tw, the motor torque at the time of cranking is determined and controlled.

  In this way, if cranking is likely to be the resonance point of the engine from the battery state (driving power amount) and the water temperature (friction), the motor output is suppressed and cranking is performed below the resonance point. Therefore, vibration during cranking can be suppressed, and not only drivability but also component reliability can be greatly improved.

  In S7, during cranking, in preparation for the first explosion, the variable valve mechanism (VEL actuator 49) increases the valve operating angle of the intake valve to increase the intake air amount in preparation for the first explosion. The VEL operating angle is increased in advance and the amount of air is increased so that the resonance band can be quickly passed after the first explosion, that is, the rotation can be quickly increased after the first explosion. That is, the VEL operating angle is expanded so that the rate of rotation increase by the sum of the engine generated torque after the first explosion and the motor torque becomes a predetermined value or more.

  In S8, the assist amount by the motor 4 is controlled so as to pass through the resonance band at a rotation increase rate of a predetermined value or more after the first explosion. That is, the motor torque is set so that the total increase in engine torque and motor torque after the first explosion is equal to or greater than a predetermined value, that is, the engine blow-up after the first explosion has a predetermined rotation profile. Determine and assist. At this time, since the state of the battery and the friction of the engine have already been detected, a desired rotation increase rate can be realized based on these. However, the motor assist is not performed when the rotation increase rate equal to or higher than the predetermined value can be realized only by the engine output.

Therefore, after the first explosion, the resonance band can be surely and quickly passed, and stable drivability can be ensured.
FIG. 6 is a time chart of the first embodiment of the engine start-up control.

  Estimate the motor torque during cranking and after the first explosion from the water temperature and the battery voltage (drop amount) at the start of cranking, and the rate of increase in rotation and the number of revolutions reached during cranking, and the increase in rotation after the first explosion. Estimate the rate.

  As a result of the estimation, if it is determined that the engine speed remains in the resonance band (depending on the number of cylinders, for example, 200 to 400 rpm) during cranking, the torque value of the motor is lowered so as not to enter the resonance point. In addition, the conventional control value is a predetermined value, and has been varied depending on the battery state of charge SOC.

By reducing the motor torque control value, cranking can be performed while avoiding the resonance point.
When it is determined that the resonance point is not exceeded, the VEL operating angle is widened and the first explosion is waited. The conventional VEL operating angle is a set opening, and when the rotation after the first explosion is low, the operating angle is widened to recover (shown by dotted lines).

  After the first explosion, torque is applied so that the rotation rise has a predetermined inclination, and the target rotation is increased with a predetermined inclination. Thereby, a resonance band can be passed in a short time, and the deterioration of drivability can be suppressed to the minimum. Conventionally (indicated by dotted lines), when the total torque does not exceed the resonance point, the resonance has continued. In addition, after the first explosion, if the motor torque was insufficient, the rotation rise was poor and continued to resonate.

Next, Example 2 will be described.
FIG. 7 is a flowchart of embodiment 2 of engine start-up control. Only parts different from the first embodiment will be described.

S20 is provided between S7 and S8.
In S20, the increase in rotation is suppressed by the motor load so as not to enter the resonance band immediately after the first explosion. That is, motor assist is started after a predetermined period immediately after the first explosion.

  Several shots immediately after the first explosion are not stable and no torque is generated, so even if there is motor assistance, there is a possibility of staying near the resonance band. As a result, vibration occurs in the resonance band, The drivability may deteriorate.

  For this reason, the number of revolutions after the initial explosion is controlled by the motor so that the rotational speed is equal to or lower than the resonance point for a predetermined time. In other words, while combustion is unstable, the rotation is suppressed below the resonance point by applying a load by the motor to limit the blow-up of the rotation.

  And after combustion is stabilized, it can be blown up by motor assist at a stretch and can pass through the resonance band in a shorter time. Therefore, more stable drivability can be ensured.

FIG. 8 is a time chart of embodiment 2 of engine start-up control.
Even after the first explosion, control is performed so that the increase in rotation can be suppressed by estimating the total torque so as not to enter the resonance point for a predetermined number of explosions or for a predetermined time.

That is, the increase in rotation is suppressed by the motor load so as not to enter the resonance point for a predetermined number of explosions or for a predetermined time even after the first explosion.
Then, when the combustion is stabilized, the motor is released and the assist is released. Thereby, it is possible to pass through the resonance band more quickly.

Next, Example 3 will be described.
FIG. 9 is a flowchart of Embodiment 3 of engine start-up control. Only parts different from the first embodiment will be described.

S30 is provided between S6 and S7.
In S30, the actual rotational speed (actual cranking rotational speed) is detected, and the deviation from the target rotational speed (target cranking rotational speed) is learned. After learning, the motor torque is corrected according to the learning value.

  That is, during cranking, when the deviation between the target cranking speed and the actual cranking speed is learned and the torque of the cranking means (motor 4) is controlled, the control value (basis based on ΔV and Tw) Motor torque) is corrected by the learning value of the deviation. That is, if the actual cranking speed is lower than the target cranking speed, the deviation is learned, and the torque corresponding to the deviation is added to the basic motor torque. Conversely, the actual cranking speed is the target cranking speed. If it is higher than the rotational speed, the deviation is learned, and the deviation torque is subtracted from the basic motor torque.

  The reason for this is that the motor torque is commanded by estimating the remaining battery capacity based on the battery voltage drop at the start of cranking. However, if the torque command value and the actual value deviate, the motor enters the resonance band. Because there is a fear.

Therefore, when the torque command value is detected as an actual value and there is a deviation, the deviation amount is learned, and the command value is calculated (learning correction) in such a manner that the deviation is corrected.
As a result, even if a deviation occurs due to errors in estimation of motor power and friction, individual variation, deterioration over time, etc., this is incorporated, and learning correction prevents jumping into the resonance band due to the deviation. Therefore, a stable start can always be performed regardless of variations and deterioration.

FIG. 10 is a time chart of embodiment 3 of engine start-up control.
Based on the estimated motor torque value 1, the torque value is saved so that the engine rotation during cranking does not enter the resonance band, and the command value is output.

Then, the deviation between the actual generated torque estimated value 2 and the command value is monitored, and the command value is learned so as to match the torque value.
In the above embodiment, the motor 4 which is a drive source of the hybrid vehicle is used as the cranking means of the engine. However, a dedicated cranking motor (starter) may be used. In this case, cranking is performed with the starter, and the motor 4 assists after the first explosion.

  Further, in the above embodiment, as a means for increasing the intake air amount in preparation for the first explosion, a variable valve mechanism that can change the valve operating angle of the intake valve according to the operating conditions is used to prepare for the first explosion. Although the valve operating angle is controlled to the large side, the engine that controls the intake air amount with the throttle valve uses a throttle valve as a means to increase the intake air amount in preparation for the first explosion, and prepares for the first explosion. Thus, the throttle valve opening degree may be controlled to the large side.

  In the above embodiment, the battery voltage drop amount ΔV at the start of cranking is detected as the state of the battery, and there is an advantage that it can be easily implemented, but there is means for detecting the remaining battery charge SOC. If so, you may use it.

The block diagram of the hybrid vehicle which shows one Embodiment of this invention Schematic perspective view of variable valve mechanism Characteristic of valve lift with variable valve mechanism Diagram showing input / output of engine control unit, etc. Flow chart of embodiment 1 of engine start-up control Time chart of embodiment 1 of engine start-up control Flow chart of embodiment 2 of engine start-up control Time chart of embodiment 2 of engine start-up control Flow chart of embodiment 3 of engine start-up control Example 3 of engine start-up control time chart

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Engine 2 Output shaft 3 1st clutch 4 Motor 5 2nd clutch 6 Automatic transmission 7 Differential device 8 Wheel drive shaft 9 Inverter 10 Battery 11 Combustion chamber 12 Intake passage 13 Throttle valve 14 Intake valve 15 Variable valve mechanism 16 Fuel Injection valve 17 Spark plug 18 Exhaust valve 19 Exhaust passage 40 Valve lifter 41 Cam shaft 42 Oscillating cam 43 Drive cam 44 Link 45 Control shaft 47 Rocker arm 48 Link 49 VEL actuator 50 Sprocket 51 VTC actuator 61 Engine control unit (ECU)
62 Hybrid Control Unit (HCU)
63 Accelerator opening sensor 64 Engine speed sensor 65 Air flow meter 66 Engine water temperature sensor 67 VEL position sensor 68 VTC position sensor 69 Vehicle speed sensor 70 Battery voltage sensor

Claims (4)

An engine, a motor also serving as a generator, and a battery capable of supplying driving power to the motor and charging the generated power from the motor, and driving power of the vehicle at the output of at least one of the engine and the motor In a hybrid vehicle that travels by generating
Based on the state of the battery and the engine coolant temperature, a means for predicting an increase in engine rotation during cranking and after the first explosion is provided.
As a result of the prediction, when it is determined that the engine speed cannot pass through the resonance band during cranking, means for controlling the torque of the cranking means so that the engine speed does not enter the resonance band during cranking; Means for increasing the amount of intake air in preparation for the first explosion, and means for controlling the amount of assist by the motor after the first explosion so that the engine speed passes through the resonance band at a rate of increase in rotation that is greater than or equal to a predetermined value after the first explosion. , equipped with a,
The engine starter for a hybrid vehicle, characterized in that the means for controlling the assist amount applies a load by the motor to keep the engine speed below the resonance band during a predetermined period immediately after the first explosion . The engine has a variable valve mechanism that can change the valve operating angle of the intake valve according to operating conditions, and controls the amount of intake air by controlling the valve operating angle,
2. The engine starter for a hybrid vehicle according to claim 1, wherein the means for increasing the amount of intake air in preparation for the initial explosion is means for controlling the valve operating angle to the large side by the variable valve mechanism.   3. The engine starter for a hybrid vehicle according to claim 1, wherein the state of the battery is detected based on a drop amount of the battery voltage at the start of cranking. 4. A means for learning the deviation between the target cranking speed and the actual cranking speed during cranking is provided.
The engine starting device for a hybrid vehicle according to any one of claims 1 to 3 , wherein the means for controlling the torque of the cranking means corrects the control value by the learned value of the deviation. .

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