JP6117084B2 - Coast stop control device and coast stop control method - Google Patents

Description

  The present invention relates to a coast stop technology.

  Patent Document 1 discloses an engine stop technology (hereinafter referred to as a coast stop) during coasting that improves the fuel efficiency of the vehicle by automatically stopping the engine during vehicle deceleration.

JP 2011-226565 A

  Since the engine is stopped during the coast stop and the oil pump driven by the engine is also stopped, in a vehicle in which the variator (continuously variable transmission) is hydraulically shifted like the vehicle disclosed in Patent Document 1, the coast stop is performed. During this, the variator cannot be shifted.

  For this reason, in order to secure driving force at the time of re-acceleration from the coast stop state and realize good acceleration performance, it is necessary to shift the variator to a predetermined Low gear ratio before stopping the engine.

  However, if the variator is shifted to a predetermined Low gear ratio before the engine is stopped, the engine speed increases during engine shift, the engine brake increases, and the driver feels uncomfortable.

  The present invention has been made in view of such a technical problem, and an object thereof is to reduce the above-mentioned feeling of strangeness at the time of coast stop.

According to an aspect of the present invention, there is provided a variator disposed between an engine and a drive wheel, and a frictional engagement element disposed between the engine and the variator or between the variator and the drive wheel. A coast stop control device that is applied to a vehicle equipped with the engine and stops the engine when the vehicle decelerates, when the accelerator pedal is released and the brake pedal is depressed while fuel is supplied to the engine Low return means for shifting the variator to the Low side after reducing the torque capacity of the frictional engagement element, or for reducing the torque capacity of the frictional engagement element and shifting the variator to the Low side; When the speed change ratio of the variator reaches a predetermined low speed change ratio by the return means, fuel is supplied to the engine. Comprising an engine stopping means for stopping the engine is stopped, and the Low return means, the vehicle speed is lower than a predetermined vehicle speed, the accelerator pedal is released, and the friction in a state in which the brake pedal is depressed A coast stop control device is provided in which the torque capacity of the fastening element is reduced, the variator is shifted to the Low side, and the predetermined vehicle speed is lower as the deceleration of the vehicle is smaller .

  A corresponding coast stop control method is also provided.

  According to these aspects, before the engine is automatically stopped, the variator is shifted to a predetermined Low speed ratio to achieve good acceleration performance at the time of reacceleration, while engine brake increases at the time of variator Low side shift. It is possible to suppress the driver from feeling uncomfortable.

1 is a schematic configuration diagram of a vehicle to which a coast stop control device according to an embodiment of the present invention is applied. It is the flowchart which showed the content of the coast stop control. It is a table for setting a coast stop permission vehicle speed. It is a time chart which showed a mode that a coast stop is performed. It is the time chart which showed a mode that a coast stop is performed at the time of slow deceleration, and an idle stop is performed after that.

  Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings.

  FIG. 1 shows a schematic configuration of a vehicle 1 to which a coast stop control device according to an embodiment of the present invention is applied.

  The vehicle 1 includes an engine 2, an oil pump 3, a torque converter 4, a forward clutch 5, a variator 6, a reduction gear train 7, a differential unit 8, a drive wheel 9, a hydraulic circuit 10, and a controller 20. With.

  The engine 2 is an internal combustion engine that uses gasoline, light oil, or the like as fuel, and the rotational speed EngRev, torque, and the like are controlled based on a command from the controller 20.

  The oil pump 3 is attached to the engine 2 and is driven using a part of the output of the engine 2. The hydraulic pressure generated by the oil pump 3 is supplied to the hydraulic circuit 10.

  The torque converter 4 is a torque converter having a lockup clutch 41. When the lock-up clutch 41 is not engaged, the torque input from the engine 2 is amplified and output by the torque amplification action, and when the lock-up clutch 41 is engaged, the rotation of the engine 2 is transmitted without loss. .

  The forward clutch 5 is a hydraulic multi-plate clutch that is fastened during forward movement, and adjusts the hydraulic capacity PCL supplied from the hydraulic circuit 10 to adjust the torque capacity (also referred to as the maximum value of torque that can be transmitted, also referred to as the transmission capacity). can do. Although only the forward clutch 5 is illustrated in FIG. 1, the vehicle 1 is also provided with a reverse clutch that is engaged when the reverse clutch is engaged, and the rotation of the engine 2 is reversed and input to the variator 6 when the reverse clutch is engaged.

  The variator 6 is a so-called belt continuously variable transmission that includes a pair of pulleys capable of changing the width of a groove and a belt wound around the pulleys. The variator 6 can change the transmission gear ratio (= input rotation speed / output rotation speed) steplessly by changing the groove width of the pulley by the hydraulic pressure supplied from the hydraulic circuit 10.

  The rotation of the engine 2 is shifted by the variator 6 and transmitted to the left and right drive wheels 9 via the reduction gear train 7 and the differential unit 8.

  The hydraulic circuit 10 regulates the hydraulic pressure supplied to the lockup clutch 41, the forward clutch 5, the variator 6 and the like using the hydraulic pressure generated by the oil pump 3 as a source pressure, and supplies the regulated hydraulic pressure to each part. Thereby, the engagement state of the lockup clutch 41 and the forward clutch 5 and the gear ratio of the variator 6 are changed.

  The controller 20 includes a CPU, a RAM, a ROM, an input / output interface, and the like. The controller 20 receives signals from a sensor 21 that detects the accelerator opening APO, a sensor 22 that detects the brake operation, a sensor 23 that detects the vehicle speed VSP, and the like, and the rotational speed EngRev of the engine 2 based on the input signals. Control torque, etc. Further, the controller 20 controls the engaged state of the lockup clutch 41 and the forward clutch 5 and the gear ratio of the variator 6 via the hydraulic circuit 10.

  Further, the controller 20 performs a coast stop that automatically stops the engine 2 when the vehicle 1 is in a deceleration state, and an idle stop that automatically stops the engine 2 when the vehicle 1 is in a stopped state. The fuel consumption of the vehicle 1 is improved.

  In performing the coast stop, the controller 20 performs Low return to shift the variator 6 to the Low side before automatically stopping the engine 2 so that good acceleration performance can be obtained at the time of re-acceleration. In order to prevent the engine brake from increasing, the torque capacity of the forward clutch 5 is reduced, and then low return is performed.

  FIG. 2 is a flowchart showing the contents of the coast stop control performed by the controller 20. The contents of the coast stop control will be described with reference to this.

In S11 to S14, the controller 20 determines whether the coast stop condition is satisfied. Coast stop conditions are as follows:
・ The accelerator pedal is released (APO = OFF).
・ The brake pedal is depressed (BRK = ON)
・ After fuel cut recovery (after FCR)
It is determined that the vehicle speed is satisfied when all vehicle speeds VSP ≦ permitted vehicle speed are satisfied.

  The controller 20 executes fuel cut to stop fuel injection of the engine 2 when the accelerator opening APO becomes 0, and restarts fuel injection when the rotational speed EngRev of the engine 2 decreases to a predetermined fuel cut recovery rotational speed. Perform recovery. In S13, it is determined whether this fuel cut recovery has been performed.

  The permitted vehicle speed in S14 is such that the rotational speed of the pulley is lower than the upper limit rotational speed determined from the component strength limit even if the variator 6 shifts to a predetermined low speed ratio described later, and the deceleration of the vehicle 1 is predetermined. In the case of slow deceleration smaller than the deceleration, the lower the deceleration, the lower the setting. Specifically, the permitted vehicle speed is set with reference to the table shown in FIG.

  The permitted vehicle speed is set according to the deceleration. If the permitted vehicle speed is high when the deceleration of the vehicle 1 is small, the coast stop is executed for a long time, and the hydraulic oil from the hydraulic circuit 10 during the coast stop is set. This is because the amount of leakage increases.

  That is, when the amount of hydraulic oil leakage increases and the amount of oil in the hydraulic circuit 10 becomes smaller than the predetermined amount of oil, the engine 2 is restarted so that the responsiveness at the time of reacceleration / restart is not deteriorated. If the amount of leakage during the stop is large, the time until the engine 2 is restarted is shortened due to a decrease in the amount of oil in the hydraulic circuit 10 at the subsequent idle stop, which gives the driver a feeling of strangeness. In the present embodiment, in order to prevent such a sense of incongruity, in the case of slow deceleration where the deceleration of the vehicle 1 is small, the permitted vehicle speed is decreased so that the coast stop time is shortened. Reduces the amount of hydraulic fluid leakage.

  If the coast stop condition is satisfied, the process proceeds to S15, and if not, the process ends.

  In S15 to S19, a low return is performed to return the gear ratio of the variator 6 to a predetermined low gear ratio before starting the coast stop.

  The predetermined low gear ratio is a gear ratio close to the lowest gear ratio, preferably the lowest when a driver depresses the accelerator during a coast stop and tries to reaccelerate the vehicle 1, so that good acceleration performance can be obtained. It is a gear ratio.

  In this embodiment, even if the fuel injection of the engine 2 is stopped by the coast stop, the rotational speed EngRev of the engine 2 does not immediately become zero, but the oil pump 3 generates hydraulic pressure until it becomes zero, Since the variator 6 can be shifted to the Low side using this hydraulic pressure, the predetermined Low gear ratio is set to the High side accordingly.

  In S15, the controller 20 determines whether or not the speed ratio of the variator 6 is smaller than a predetermined low speed ratio. If the gear ratio of the variator 6 is already larger than the predetermined Low gear ratio, there is no need to perform Low return. Therefore, the process proceeds to S20, and the controller 20 immediately stops the fuel injection of the engine 2 and starts the coast stop. To do. If the gear ratio of the variator 6 is smaller than the predetermined Low gear ratio, the low return of the variator 6 is necessary to realize good acceleration performance at the time of reacceleration, so the process proceeds to S16 and the low return of the variator 6 is performed. .

  In S <b> 16, the controller 20 decreases the hydraulic pressure PCL supplied from the hydraulic circuit 10 to the forward clutch 5, and decreases the torque capacity of the forward clutch 5.

  In S17, the controller 20 determines whether the torque capacity of the forward clutch 5 has decreased to a predetermined torque capacity. The predetermined torque capacity is preferably zero. Whether the torque capacity of the forward clutch 5 has decreased to a predetermined torque capacity can be determined by whether the hydraulic pressure PCL supplied to the forward clutch 5 has decreased to a hydraulic pressure corresponding to the predetermined torque capacity.

  If it is determined that the torque capacity of the forward clutch 5 has decreased to a predetermined torque capacity, the process proceeds to S18. Otherwise, the process returns to S16, and the controller 20 lowers the hydraulic pressure PCL supplied to the forward clutch 5 and further reduces its torque capacity.

  In S18, the controller 20 shifts the variator 6 to the Low side. Normally, when the vehicle is decelerated with the accelerator pedal released, the variator 6 is shifted along the highest line or coast line of the shift map. In this embodiment, however, the speed is increased by leaving the highest line or coast line. Thus, the variator 6 is shifted to the Low side, and the speed ratio of the variator 6 is quickly brought close to the predetermined Low speed ratio.

  In S19, the controller 20 determines whether or not the gear ratio of the variator 6 is greater than a predetermined Low gear ratio. If it is determined that the gear ratio of the variator 6 is greater than the predetermined Low gear ratio, the process proceeds to S20. If the gear ratio of the variator 6 is not greater than the predetermined Low gear ratio, the process returns to S18, and the controller 20 further shifts the variator 6 to the Low side.

  In S20, the controller 20 stops the fuel injection of the engine 2 and starts the coast stop.

  In S21, the controller 20 shifts the variator 6 to the lowest gear ratio by the hydraulic pressure generated by the oil pump 3 until the engine 2 stops rotating.

  FIG. 4 is a time chart showing how the coast stop is performed by the coast stop control. In the drawing, the solid line shows the present embodiment in which the low return is performed with the torque capacity of the forward clutch 5 lowered, and the broken line shows a comparative example in which the low return is performed without reducing the torque capacity of the forward clutch 5.

  According to this, at time t11, the accelerator opening APO becomes 0, and the fuel cut is started. Thereafter, as the vehicle speed VSP decreases, the variator 6 shifts to the Low side.

  At time t12, the brake pedal is depressed (BRK = ON).

  At time t13, the fuel cut is completed in response to the decrease in the rotational speed EngRev of the engine 2 to a predetermined fuel cut recovery rotational speed.

  At time t14, the hydraulic pressure PCL supplied to the forward clutch 5 is lowered, and thereby the torque capacity of the forward clutch 5 is lowered.

  At time t15, the hydraulic pressure PCL supplied to the forward clutch 5 becomes smaller than the hydraulic pressure corresponding to the predetermined torque capacity, and in response to this, the low return of the variator 6 is started. In the present embodiment, the low return is performed at a higher speed away from the highest line or coast line, so that the gear ratio of the variator 6 is quickly changed to the low side. In contrast, in the comparative example in which the torque capacity of the forward clutch 5 is not reduced, the variator 6 is shifted along the highest line or the coast line, so that the gear ratio of the variator 6 continues to gradually change to the low side.

  At time t16, the gear ratio of the variator 6 reaches a predetermined low gear ratio, and the engine 2 is automatically stopped in response to this.

  From time t16 to t17, the variator 6 further shifts to the Low side by the hydraulic pressure generated by the oil pump 3 until the engine 2 stops. Thereby, in this embodiment, the transmission gear ratio of the variator 6 reaches the lowest transmission gear ratio.

  In the comparative example, the variator 6 is shifted along the highest line or coast line, and the engine 2 is automatically stopped when reaching the lowest transmission ratio (time t18). For this reason, the timing at which the engine 2 is automatically stopped is delayed compared to the present embodiment, and the fuel efficiency effect due to the coast stop is reduced accordingly.

  As described above, in this embodiment, the torque capacity of the forward clutch 5 is reduced in a state where the accelerator pedal is released and the brake pedal is depressed, the variator 6 is shifted to the low side, and the transmission ratio of the variator 6 is The engine 2 is stopped when a predetermined Low gear ratio is reached.

  Thereby, before the engine 2 is automatically stopped, the variator 6 is shifted to a predetermined Low gear ratio to achieve a good acceleration performance at the time of re-acceleration, while the engine brake by shifting the variator 6 to the Low side is achieved. The increase can be suppressed, and the increase in engine brake can prevent the driver from feeling uncomfortable (effect corresponding to claim 1).

  Recently, due to the increase in fuel efficiency requirements, it is required to increase the coast stop permission vehicle speed. However, according to this embodiment, even if coast stop is performed from a high vehicle speed, excessive engine braking is applied. Since the driver does not feel uncomfortable, the coast stop permission vehicle speed can be set high, and the fuel efficiency improvement effect by the coast stop can be further enhanced.

  The predetermined torque capacity is preferably zero. Thereby, it is possible to completely suppress an increase in engine brake caused by shifting the variator 6 to the Low side (effect corresponding to claim 2).

  The predetermined Low gear ratio is preferably the lowest Low gear ratio. Thereby, the acceleration performance at the time of reacceleration can be enhanced most (effect corresponding to claim 5).

  If the gear ratio during coast stop is the lowest gear ratio, the driving force at the time of re-acceleration may be larger than the driving force required for re-acceleration. Low vehicle speed / stop, uphill road / downhill road / flat road, etc.) and in order to prevent the driving force from being deficient in any acceleration request, the predetermined Low gear ratio is set to the lowest level. It is preferable to use a gear ratio.

  FIG. 5 is a time chart showing a state in which a coast stop is performed during slow deceleration and then an idle stop is performed. The solid line shows the present embodiment in which the permitted vehicle speed is lowered in response to slow deceleration and small deceleration, and the broken line shows a comparative example in which the permitted vehicle speed is constant regardless of the deceleration.

  In the comparative example, at a time earlier than this embodiment (time t21 <time t31), the vehicle speed VSP becomes lower than the permitted vehicle speed, the torque capacity of the forward clutch 5 starts to decrease, and the gear ratio of the variator 6 starts to return low. Is done. When the speed ratio of the variator 6 reaches a predetermined low speed ratio, the engine 2 is automatically stopped (time t22).

  Therefore, in the comparative example, the time during which the coast stop is executed is longer than that in the present embodiment, and the amount of hydraulic oil leaking from the hydraulic circuit 10 is increased accordingly. For this reason, even if the idle stop is started following the coast stop (time t23), the oil amount in the hydraulic circuit 10 becomes smaller than the predetermined oil amount and the engine 2 is immediately restarted (time t24). The driver feels uncomfortable.

  Whether or not the amount of oil in the hydraulic circuit 10 has become smaller than the predetermined amount of oil is determined based on whether or not a timer that starts counting after the engine 2 automatically stops has reached a predetermined release time.

  On the other hand, in the present embodiment, since the permitted vehicle speed is lowered in response to slow deceleration and small deceleration, the time (t31) when the vehicle speed VSP becomes lower than the permitted vehicle speed is delayed compared to the comparative example. The time when the engine 2 is automatically stopped (time t32) is also delayed. Therefore, the amount of hydraulic oil that leaks from the hydraulic circuit 10 is reduced, and even if the idle stop is started following the coast stop, the engine 2 is restarted immediately due to a decrease in the oil amount in the hydraulic circuit 10. In addition, the driver does not feel uncomfortable (effect corresponding to claim 3).

  The embodiment of the present invention has been described above, but the above embodiment is merely one example of application of the present invention, and the technical scope of the present invention is limited to the specific configuration of the above embodiment. is not.

  For example, in the above embodiment, the forward clutch 5 is provided between the engine 2 and the variator 6, but may be provided between the variator 6 and the drive wheel 9. In the configuration in which the forward clutch 5 is provided between the variator 6 and the drive wheel 9, when the variator 6 is shifted to the Low side, the rotational speed of the engine 2 increases and the engine brake increases, but the torque capacity of the forward clutch 5 increases. Since it is lowered, the increased engine brake does not act on the vehicle 1, and the same effect as the above embodiment is achieved.

  In the above embodiment, the low return of the variator 6 is started after the torque capacity of the forward clutch 5 has decreased to a predetermined torque capacity, but the torque capacity of the forward clutch 5 has started to decrease. Before the torque capacity is reduced to a predetermined torque capacity, for example, the low return of the variator 6 may be started simultaneously with the start of the reduction of the torque capacity of the forward clutch 5.

  Even if the low return of the variator 6 is started at such timing, there is an effect of suppressing an increase in engine brake to some extent, and the timing when the gear ratio of the variator 6 reaches a predetermined low gear ratio, Since the time to automatically stop the engine 2 is advanced, the fuel efficiency improvement effect by the coast stop can be enhanced (effect corresponding to claim 4).

  Moreover, although the said embodiment is a structure which is not equipped with the electric oil pump, you may provide the electric oil pump which can generate | occur | produce oil_pressure | hydraulic even when the engine 2 stops.

  If the electric oil pump generates enough hydraulic pressure to shift the variator 6 when the engine 2 is stopped, the electric oil pump becomes larger, which causes deterioration of mountability and cost increase. The hydraulic oil pump generates a hydraulic pressure to the extent that the forward clutch 5 can be held immediately before the engagement, but the present invention can be applied regardless of the size of the electric oil pump.

  Further, when the electric oil pump is operated during the coast stop, the state of charge of the battery is lowered, and when the idle stop is performed following the coast stop, the state of charge of the battery reaches the lower limit value and the engine 2 is immediately turned on. There is a possibility that the driver will feel uncomfortable after restarting, but the coast stop time is shortened in the case of slow deceleration by setting the permitted vehicle speed for coast stop according to the deceleration as in the above embodiment. Thus, it is possible to suppress a decrease in the state of charge of the battery during the coast stop, and to prevent such a sense of incongruity (effect corresponding to claim 3).

1 Engine 2 Oil Pump 5 Forward Clutch 6 Variator 9 Drive Wheel 10 Hydraulic Circuit 20 Controller

Claims (5)

The present invention is applied to a vehicle including a variator disposed between an engine and a drive wheel, and a friction fastening element disposed between the engine and the variator or between the variator and the drive wheel. A coast stop control device for stopping the engine when decelerating,
When the accelerator pedal is released and the brake pedal is depressed while the fuel is supplied to the engine, the torque capacity of the frictional engagement element is reduced and then the variator is shifted to the Low side, or Low return means for reducing the torque capacity of the frictional engagement element and shifting the variator to the Low side;
Engine stop means for stopping fuel supply to the engine and stopping the engine when the gear ratio of the variator reaches a predetermined Low speed ratio by the Low return means;
Equipped with a,
The Low returning means reduces the torque capacity of the frictional engagement element in a state where the vehicle speed is lower than a predetermined vehicle speed, the accelerator pedal is released, and the brake pedal is depressed, and the variator is shifted to the Low side. Let
The predetermined vehicle speed is lower as the deceleration of the vehicle is smaller.
Coast stop control device characterized by that. The coast stop control device according to claim 1,
The Low returning means reduces the torque capacity of the frictional engagement element to zero in a state where the accelerator pedal is released and the brake pedal is depressed, and shifts the variator to the Low side.
Coast stop control device characterized by that. The coast stop control device according to claim 1 or 2 ,
The Low returning means starts shifting the variator to the Low side while reducing the torque capacity of the friction engagement element.
Coast stop control device characterized by that. The coast stop control device according to any one of claims 1 to 3 ,
The predetermined Low gear ratio is a maximum Low gear ratio.
Coast stop control device characterized by that. The present invention is applied to a vehicle including a variator disposed between an engine and a drive wheel, and a friction fastening element disposed between the engine and the variator or between the variator and the drive wheel. A coast stop control method for stopping the engine when decelerating,
When the accelerator pedal is released and the brake pedal is depressed while the fuel is supplied to the engine, the torque capacity of the frictional engagement element is reduced and then the variator is shifted to the Low side, or Lowering the torque capacity of the frictional engagement element and performing low return to shift the variator to the low side,
When the gear ratio of the variator reaches a predetermined low gear ratio by the low return, the fuel supply to the engine is stopped and the engine is stopped .
In the Low return, the vehicle speed is lower than a predetermined vehicle speed, the accelerator pedal is released, and the brake pedal is depressed, the torque capacity of the frictional engagement element is reduced, and the variator is shifted to the Low side. Let
The predetermined vehicle speed is lower as the deceleration of the vehicle is smaller.
A coast stop control method characterized by the above.

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