JP6476742B2 - Control device for hybrid vehicle - Google Patents

Description

  The invention relates to a control apparatus for a hybrid vehicle that automatically stops and restarts an internal combustion engine in accordance with predetermined conditions, and at the time of automatic restart, performs self-sustained start by fuel injection and ignition to a cylinder in an expansion stroke. About.

  For example, Patent Document 1 discloses an internal combustion engine that automatically stops and restarts an internal combustion engine in accordance with a predetermined condition and performs self-sustained start by fuel injection and ignition to a cylinder in an expansion stroke at the time of automatic restart. It is disclosed. That is, at the time of automatic restart, an attempt is made to start the internal combustion engine without performing cranking by the starter motor. And in the thing of patent document 1, in order to reduce the torque required for the drive of an intake / exhaust valve at the time of a self-supporting start, the variable valve mechanism which can change a lift / operation angle is used for the small lift / operation angle at the time of an automatic stop. I try to control it.

  Further, in Patent Document 2, in a hybrid vehicle equipped with a manual transmission, the automatic clutch is released so that the engine rotational speed does not enter a predetermined resonance band (frequency band in which vehicle vibration deteriorates due to resonance) during vehicle deceleration. Thus, a technique for disconnecting an internal combustion engine from a vehicle drive system is disclosed.

JP 2008-223499 A JP 2014-189187 A

  If the lift / operating angle is limited to a small value at the time of stopping as in Patent Document 1, the amount of air existing in the cylinder during the subsequent self-starting is reduced, and the starting torque obtained by the first combustion / explosion is reduced. In other words, in order to ensure a large initial starting torque necessary for the self-sustained start, it is desirable to introduce a sufficient amount of air into the cylinder during the automatic stop prior to the self-sustained start.

  On the other hand, when the internal combustion engine is automatically stopped, the rotation speed of the internal combustion engine always crosses the resonance band between the time when the fuel supply to the internal combustion engine stops and the time when the rotation of the crankshaft completely stops. Vibration is temporarily worsened. At this time, if the amount of air in the cylinder is large, the vibration input due to the compression reaction force is large, so that the vehicle vibration due to resonance is further deteriorated.

A control device for a hybrid vehicle according to the present invention performs automatic stop and automatic restart of an internal combustion engine according to an automatic stop condition and an automatic restart condition, and at the time of automatic restart, fuel injection and ignition to a cylinder in an expansion stroke In hybrid cars that are designed to start independently,
While expanding the throttle valve opening after stopping the fuel supply in the internal stop of the internal combustion engine
When the collector pressure becomes equal to or higher than the predetermined pressure with a delay from the expansion of the throttle valve opening, power generation by the motor / generator connected to the internal combustion engine is started, and until the engine speed passes through the resonance band, the motor it is obtained to carry out the by that power to the generator.

  During the automatic stop, the throttle valve opening is increased after stopping the fuel supply, so that the amount of air flowing into the cylinder becomes large, and the cylinder in the expansion stroke when the crankshaft is completely stopped A lot of air is secured. Therefore, a large initial startup torque can be obtained during the subsequent automatic restart.

  On the other hand, when the throttle valve opening is increased, the amount of air flowing into the cylinder increases and the compression reaction force increases.However, after stopping the fuel supply, the motor / generator generates power at least during the period when it passes the resonance band. By doing so, the torque fluctuation is absorbed and the amplitude of the torque fluctuation is reduced. In addition, the engine speed decreases more rapidly after the fuel supply is stopped, and the time for passing through the resonance band is shortened.

  According to the present invention, at the time of automatic stop of the internal combustion engine, ensuring both a sufficient amount of air in preparation for the next self-sustained start and suppression of vehicle vibration that causes an increase in the in-cylinder air amount are a cause of deterioration. Can be made.

The structure explanatory view of the hybrid car concerning this invention. The flowchart which shows 1st Example of control in the case of an automatic stop. The flowchart which shows 2nd Example of control in the case of an automatic stop. The flowchart which shows 3rd Example of control in the case of an automatic stop. The flowchart which shows 4th Example of control in the case of an automatic stop. The flowchart which shows 5th Example of control in the case of an automatic stop. The time chart which shows the effect | action of 1st Example. The time chart which shows the effect | action of 3rd Example. The time chart which shows the effect | action of 4th Example. The time chart which similarly shows the effect | action of 4th Example.

  Hereinafter, an embodiment of the present invention will be described in detail with reference to the drawings.

  FIG. 1 is an explanatory view of the configuration of an embodiment in which the present invention is applied to an internal combustion engine 1 of a hybrid vehicle. A crankshaft 2 of the internal combustion engine 1 is rotated by a first motor / generator 4 via a first clutch 3. It is connected to one end of the shaft 5. An input shaft 8 of a transmission, for example, a belt-type continuously variable transmission (so-called CVT) 7, is connected to the other end of the rotating shaft 5 of the first motor / generator 4 that mainly functions as a traveling motor. It is connected. The output shaft 9 of the continuously variable transmission 7 is connected to the drive wheels 10 via a final reduction mechanism (not shown). The internal combustion engine 1 is also provided with a second motor / generator 11 that also functions as a starter.

  The internal combustion engine 1 is a four-stroke cycle direct injection spark ignition internal combustion engine, and includes an electronically controlled throttle valve (not shown) for controlling the intake air amount. The internal combustion engine 1 performs automatic stop and automatic restart according to predetermined automatic stop conditions and automatic restart conditions during operation of the vehicle, but remains in the expansion stroke at the time of automatic restart. A so-called self-sustained start is performed by discriminating a cylinder and injecting fuel into the cylinder and igniting with a spark plug.

  In the present invention, in order to facilitate a self-sustained start, the intake air amount is increased at the time of automatic stop prior to automatic restart, and the deterioration of vehicle vibration caused by this is reduced in the second motor / generator 11. It is intended to suppress by using.

  Even in the case of self-starting, in order to prevent a starting failure, the second motor / generator 11 may slightly assist the rotation of the crankshaft in the initial stage of starting.

  The flowchart of FIG. 2 shows a first embodiment of control at the time of automatic stop executed in a hybrid controller (not shown). The routine shown in this flowchart is executed when a predetermined automatic stop condition is satisfied. In step 1, an automatic stop command is output. Thereby, the fuel supply (fuel injection into the cylinder) of the internal combustion engine 1 is stopped. In other words, the fuel cut is executed. In addition, at the timing when the fuel cut is started in this way, the first clutch 3 is already controlled to be in the released state. Substantially simultaneously with the stop of the fuel supply to the internal combustion engine 1, in step 2, the throttle valve opening is started to increase. For example, it may be expanded to full open, or may be expanded to an appropriate intermediate opening according to the engine speed or the like. The expansion of the throttle valve opening increases the amount of air flowing into the cylinder after the fuel cut.

  Next, in step 3, it is repeatedly determined whether the pressure in the intake collector (collector pressure) downstream of the throttle valve of the internal combustion engine 1 has become equal to or higher than a predetermined pressure Pc1. The collector pressure is detected by, for example, an intake pressure sensor provided in the intake collector, but can be estimated from a flow rate passing through the throttle valve.

  When the collector pressure becomes equal to or higher than the predetermined pressure Pc1, the process proceeds to step 4 to start power generation using the second motor / generator 11. Due to the energy absorption accompanying the power generation, the rotational speed of the internal combustion engine 1 quickly decreases, and torque fluctuation due to the compression reaction force in the cylinder is suppressed. The power generation amount at this time is controlled to an appropriate level to such an extent that the torque fluctuation due to the compression reaction force in the cylinder can be at least partially suppressed while the rotational speed of the internal combustion engine 1 does not decrease excessively rapidly. It is desirable to do.

  In the next step 5, it is repeatedly determined whether or not the rotational speed of the internal combustion engine 1 has become equal to or lower than a predetermined rotational speed (power generation end rotational speed Ne2). Then, when the rotation speed becomes equal to or lower than the predetermined power generation end rotational speed Ne2, the process proceeds to step 6 and the power generation by the second motor / generator 11 is ended. The power generation end rotation speed Ne2 is set to a rotation speed lower than the resonance lower limit rotation speed NeL corresponding to the lower limit frequency of the predetermined resonance band of the internal combustion engine 1.

  FIG. 7 is a time chart for explaining the operation of the first embodiment. At time t1, a predetermined automatic stop condition is established, and the fuel cut command is turned ON. That is, the fuel supply is stopped. Accordingly, the rotational speed of the internal combustion engine 1 decreases as shown in the figure. A resonance band is between the resonance upper limit rotation speed NeU and the resonance lower limit rotation speed NeL shown in the figure.

  Substantially simultaneously with the stop of the fuel supply, an expansion command for the throttle valve opening is output, and the throttle valve opening increases to a predetermined opening (for example, fully open). As a result, the collector pressure gradually increases. Then, at time t2 when the collector pressure reaches a predetermined pressure Pc1, power generation by the second motor / generator 11 is started. Since the load of the second motor / generator 11 is applied to the crankshaft of the internal combustion engine 1 by the start of power generation, the rotational speed of the internal combustion engine 1 decreases more rapidly, and resonance between the upper limit rotational speed NeU and the lower limit rotational speed NeL. Pass the belt in a short time. In addition, since the torque fluctuation of the crankshaft due to the compression reaction force is suppressed by the load of the second motor / generator 11, the amplitude of the excitation input while passing through the resonance band is reduced, and from this point also, the vibration of the vehicle is reduced. It is suppressed. The comparative example indicated by the phantom line shows a change in rotational speed when power generation by the second motor / generator 11 is not performed. In this case, torque fluctuation that remains in the resonance band and becomes an excitation input is also present. It will be big.

  At time t3, the rotational speed of the internal combustion engine 1 decreases to a predetermined power generation end rotational speed Ne2, and at this time, power generation by the second motor / generator 11 is completed.

  The predetermined collector pressure Pc1, which is a trigger for starting power generation by the second motor / generator 11, is such that power generation is started at a stage where the rotational speed of the internal combustion engine 1 does not decrease to the resonance upper limit rotational speed NeU. It is desirable to set appropriately.

  Next, FIG. 3 is a flowchart showing a second embodiment of control at the time of automatic stop. In the second embodiment, the process of step 3A is performed instead of the process of step 3 in the first embodiment shown in FIG. 2, and the other steps are the same as those of the first embodiment. There is no particular change.

  That is, in this second embodiment, after stopping the fuel supply to the internal combustion engine 1 (step 1) and starting the expansion of the throttle valve opening (step 2), the expansion of the throttle valve opening is started in step 3A. Thereafter, it is repeatedly determined whether or not the predetermined time T1 has elapsed. When the predetermined time T1 elapses, the process proceeds to step 4 where power generation using the second motor / generator 11 is started. Thereafter, when the rotation speed of the internal combustion engine 1 becomes equal to or lower than a predetermined rotation speed (power generation end rotation speed Ne2), power generation by the second motor / generator 11 is ended (steps 5 and 6).

In the second embodiment, in the time chart shown in FIG. 7, the timing of time t3 is defined by the elapsed time from time t2. The predetermined time T1 is preferably set appropriately so that the collector pressure is sufficiently increased and power generation is started at a stage where the rotational speed of the internal combustion engine 1 does not decrease to the resonance upper limit rotational speed NeU. .
The second embodiment is a reference example not strictly included in the claims.

  Next, FIG. 4 is a flowchart showing a third embodiment of control at the time of automatic stop. In the third embodiment, the process of step 3B is performed instead of the process of step 3 in the first embodiment shown in FIG. 2, and the other steps are the same as those of the first embodiment. There is no particular change.

  That is, in this third embodiment, after stopping the fuel supply to the internal combustion engine 1 (step 1) and starting the expansion of the throttle valve opening (step 2), the rotational speed of the internal combustion engine 1 is increased in step 3B. It is repeatedly determined whether the rotation speed is equal to or lower than a predetermined rotation speed (power generation start rotation speed Ne1). The power generation start rotational speed Ne1 is set to a rotational speed slightly higher than the resonance upper limit rotational speed NeU. When the rotational speed of the internal combustion engine 1 decreases to a predetermined power generation start rotational speed Ne1 or less, the process proceeds from step 3B to step 4 and power generation using the second motor / generator 11 is started. Thereafter, when the rotation speed of the internal combustion engine 1 becomes equal to or lower than a predetermined rotation speed (power generation end rotation speed Ne2), power generation by the second motor / generator 11 is ended (steps 5 and 6).

FIG. 8 is a time chart for explaining the operation of the third embodiment. As in the example of FIG. 7, a predetermined automatic stop condition is established at time t1, the fuel cut command is turned ON, and the throttle valve opening is started to increase substantially simultaneously. The rotation speed of the internal combustion engine 1 decreases as shown in the figure by stopping the fuel supply. At the time t2 when the rotation speed decreases to the predetermined power generation start rotation speed Ne1, power generation by the second motor / generator 11 is performed. Is started. Then, at the time t3 when the rotation speed of the internal combustion engine 1 decreases to the predetermined power generation end rotation speed Ne2, the power generation by the second motor / generator 11 ends.
The third embodiment is a reference example not strictly included in the claims.

  Next, FIG. 5 is a flowchart showing a fourth embodiment of control at the time of automatic stop. The fourth embodiment is based on the premise that the internal combustion engine 1 has a variable valve timing mechanism that can change the closing timing of the intake valve, and replaces the processing of step 3 in the first embodiment shown in FIG. Thus, the process of step 3C is performed. The other steps are not particularly different from those of the first embodiment.

  As the variable valve timing mechanism, for example, a known configuration in which the phase of the camshaft relative to the crankshaft is relatively changed by a rotary hydraulic actuator is used. The valve timing changed by the variable valve timing mechanism is controlled according to the engine operating conditions during engine operation. However, when the internal combustion engine 1 is automatically stopped, the intake valve closing timing is the next automatic restart. Control is performed toward a predetermined target value so as to stop at a crank angle suitable for starting. In a variable valve timing mechanism using hydraulic pressure as a drive source, the valve timing cannot generally be changed while the engine is stopped when the hydraulic pressure is lost.

  In the fourth embodiment, after stopping the fuel supply to the internal combustion engine 1 (step 1) and expanding the throttle valve opening (step 2), the valve timing by the variable valve timing mechanism is stopped in step 3C. It is repeatedly determined whether or not the vicinity of the later target value has been reached. Specifically, threshold values are respectively set at positions of ± α (α is a minute value) around the target value, and it is determined whether or not these threshold values have been reached. When the valve timing reaches a threshold value in the vicinity of the target value, the process proceeds from step 3C to step 4 and power generation using the second motor / generator 11 is started. Thereafter, when the rotation speed of the internal combustion engine 1 becomes equal to or lower than a predetermined rotation speed (power generation end rotation speed Ne2), power generation by the second motor / generator 11 is ended (steps 5 and 6).

  FIG. 9 is a time chart for explaining the operation of the fourth embodiment. In particular, the final valve timing target value CA1 is set in the direction of increasing the intake amount (for example, the direction in which the intake valve closing timing approaches the bottom dead center) with respect to the valve timing when the internal combustion engine 1 is automatically stopped. An example of the case is shown. As in the example of FIG. 7, a predetermined automatic stop condition is established at time t1, the fuel cut command is turned ON, and the throttle valve opening is started to increase substantially simultaneously. As the fuel supply stops, the rotational speed of the internal combustion engine 1 decreases as shown in the figure. Further, the valve timing by the variable valve timing mechanism gradually changes toward the target value CA1 so that the intake valve closing timing that is behind the bottom dead center approaches the bottom dead center. Then, at the time t2 when the valve timing reaches a threshold value CA2 set in the vicinity of the target value CA1, power generation by the second motor / generator 11 is started. Then, at the time t3 when the rotation speed of the internal combustion engine 1 decreases to the predetermined power generation end rotation speed Ne2, the power generation by the second motor / generator 11 ends.

  Therefore, power generation by the second motor / generator 11 is started after the valve timing becomes a characteristic that can sufficiently secure the in-cylinder air amount, and a sufficient amount of in-cylinder air can be secured in preparation for a self-sustained start. it can.

  Next, FIG. 10 is a time chart showing an example in which the operation of the fourth embodiment is different. In particular, the final valve timing target value CA3 is set in the intake amount decreasing direction (for example, the direction in which the intake valve closing timing is away from the bottom dead center) with respect to the valve timing when the internal combustion engine 1 is automatically stopped. An example of the case is shown. As in the example of FIG. 9, a predetermined automatic stop condition is satisfied at time t1, the fuel cut command is turned ON, and expansion of the throttle valve opening is started substantially simultaneously. As the fuel supply stops, the rotational speed of the internal combustion engine 1 decreases as shown in the figure. Further, the valve timing by the variable valve timing mechanism gradually changes toward the target value CA3 so that the intake valve closing timing that is in the vicinity of the bottom dead center is separated from the bottom dead center. Then, at the time t2 when the valve timing reaches a threshold value CA4 set in the vicinity of the target value CA3, power generation by the second motor / generator 11 is started. Then, at the time t3 when the rotation speed of the internal combustion engine 1 decreases to the predetermined power generation end rotation speed Ne2, the power generation by the second motor / generator 11 ends.

  Therefore, in this example, it is possible to suppress pre-ignition caused by excessively retarding the intake valve closing timing at the next automatic restart, or suppress startability deterioration due to excessively large compression reaction force. . On the other hand, at the time of automatic stop, the cylinder air amount can be secured sufficiently large by increasing the throttle valve opening.

The target value CA1 in the example of FIG. 9 and the target value CA3 in the example of FIG. 10 may be different from each other depending on various conditions, or may be the same target value.
The fourth embodiment is a reference example that is not strictly included in the claims.

  Next, FIG. 6 is a flowchart showing a fifth embodiment of control at the time of automatic stop. As in the fourth embodiment, the fifth embodiment is based on the premise that the internal combustion engine 1 includes a variable valve timing mechanism that can change the closing timing of the intake valve. In this case, in addition to the process of step 3 in the first embodiment shown in FIG. 2, the process of step 3C of the fourth embodiment and the process of step 3B of the third embodiment are performed. Other steps are not particularly different from those of the first to fourth embodiments. The determination in step 3C and the determination in step 3B have an OR condition relationship with each other, and these determinations in step 3 have an AND condition relationship.

  That is, in this fifth embodiment, after stopping the fuel supply to the internal combustion engine 1 (step 1) and starting the expansion of the throttle valve opening (step 2), in step 3, the collector pressure of the internal combustion engine 1 is increased. It is repeatedly determined whether the predetermined pressure Pc1 or higher is reached. When the collector pressure becomes equal to or higher than the predetermined pressure Pc1, the process proceeds to step 3C, and it is repeatedly determined whether or not the valve timing by the variable valve timing mechanism has reached the vicinity of the target value after the engine is stopped. Specifically, threshold values are respectively set at positions of ± α (α is a minute value) around the target value, and it is determined whether or not these threshold values have been reached. When the valve timing reaches a threshold value in the vicinity of the target value, the process proceeds from step 3C to step 4 and power generation using the second motor / generator 11 is started.

  On the other hand, if “NO” in the step 3C, further, in a step 3B, it is repeatedly determined whether or not the rotational speed of the internal combustion engine 1 is equal to or lower than a predetermined rotational speed (power generation start rotational speed Ne1). The power generation start rotational speed Ne1 is set to a rotational speed slightly higher than the resonance upper limit rotational speed NeU. When the rotational speed of the internal combustion engine 1 decreases to a predetermined power generation start rotational speed Ne1 or less, the process proceeds from step 3B to step 4 regardless of the valve timing, and power generation using the second motor / generator 11 is started.

  Thereafter, when the rotation speed of the internal combustion engine 1 becomes equal to or lower than a predetermined rotation speed (power generation end rotation speed Ne2), power generation by the second motor / generator 11 is ended (steps 5 and 6).

DESCRIPTION OF SYMBOLS 1 ... Internal combustion engine 3 ... 1st clutch 4 ... 1st motor generator 6 ... 2nd clutch 7 ... Continuously variable transmission 11 ... 2nd motor generator

Claims (4)

In a hybrid vehicle that performs automatic stop and automatic restart of the internal combustion engine according to the automatic stop condition and automatic restart condition, and at the time of automatic restart, the fuel injection to the cylinder in the expansion stroke and the self-sustained start by ignition,
While expanding the throttle valve opening after stopping the fuel supply in the internal stop of the internal combustion engine
When the collector pressure becomes equal to or higher than the predetermined pressure with a delay from the expansion of the throttle valve opening, power generation by the motor / generator connected to the internal combustion engine is started, and until the engine speed passes through the resonance band, the motor power generation carried out that by the generator, the hybrid vehicle control device. 2. The power generation is terminated when the engine rotation speed is reduced to a predetermined power generation end rotation speed set lower than the lower limit rotation speed of the resonance band after the start of the power generation. The hybrid vehicle control device described. Equipped with a variable valve timing mechanism that can change the closing timing of the intake valve,
The power generation is started when the collector pressure is equal to or higher than the predetermined pressure, and the closing timing of the intake valve, which is changed by the variable valve timing mechanism, reaches near the target value after the engine stops. The control device for a hybrid vehicle according to claim 1 or 2. The power generation is started regardless of the closing timing of the intake valve when the collector pressure is equal to or higher than the predetermined pressure and the engine speed is reduced to a predetermined power generation start rotational speed. The hybrid vehicle control device described.

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