JP2012087908A - Automatic transmission control device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an automatic transmission control device capable of preventing the occurrence of a shock when decelerating a vehicle, in the vehicle provided with a cooperating regenerative brake for braking the vehicle by cooperating between a friction brake and a regenerative brake.SOLUTION: This device for controlling an automatic transmission of the vehicle provided with the cooperating regenerative brake for braking the vehicle by cooperating between the friction brake and the regenerative brake, includes: a down-shift determining part (S2) for determining whether to become the starting timing of a down-shift in deceleration; a frictional braking increase determining part (S5) for determining whether braking force of the friction brake can be increased in response to reduction in torque of a motor generator when shifting in an ordinary shift time when becoming the starting timing of the down-shift; and a shift control part (S6) for starting the down-shift so as to shift by taking time longer than usual when determining that the braking force cannot be increased.

Description

  The present invention relates to an apparatus for controlling an automatic transmission.

  A technique for obtaining a braking force required by a driver by coordinating a friction brake and a regenerative brake is known (see Patent Document 1).

Japanese Utility Model Publication No. 63-29301

  In such cooperative regenerative control, the braking force of the friction brake must be increased when the braking force of the regenerative brake decreases despite the constant braking force requested by the driver. At this time, if the timings of the two are shifted, a shock occurs.

  The inventor of the present invention is researching cooperative regenerative control and has found that a shock is likely to occur during vehicle deceleration.

  The present invention has been made paying attention to such conventional problems, and an object of the present invention is in a vehicle provided with a cooperative regenerative brake that brakes the vehicle by coordinating the friction brake and the regenerative brake. Another object of the present invention is to provide an automatic transmission control device capable of preventing a shock from occurring during deceleration of a vehicle.

  The present invention solves the above problems by the following means.

  The present invention is an apparatus for controlling an automatic transmission of a vehicle provided with a cooperative regenerative brake that brakes the vehicle by coordinating a friction brake and a regenerative brake. A downshift determination unit that determines whether or not a downshift start timing is reached during deceleration, and when the downshift start timing is reached, the motor generator torque decreases when a shift is made during a normal shift time. A friction braking increase determination unit that determines whether or not the braking force of the friction brake can be increased. And when it determines with it not being able to raise, it is further provided with the shift control part which starts a downshift so that it may change over time longer than usual.

  According to the present invention, when it is estimated that the braking force of the friction brake cannot be increased in accordance with the decrease in the torque of the motor generator when the shift is started at the normal shift time at the start timing of the downshift. Since the gear shifts over a longer time than usual, the torque of the motor generator slowly decreases. Therefore, it is possible to prevent a deviation between the timing at which braking by the regenerative brake decreases and the timing at which braking by the friction brake increases, and to prevent a shock from occurring during deceleration of the vehicle.

  Embodiments of the present invention and advantages of the present invention will be described in detail below with reference to the accompanying drawings.

FIG. 1 is a diagram showing an example of a powertrain of a hybrid vehicle equipped with an automatic transmission control device according to the present invention. FIG. 2 is a diagram illustrating an example of a shift map. FIG. 3 is a diagram showing the correlation between the rotational speed of the motor generator and the torque, and the correlation between the rotational speed of the input shaft of the automatic transmission and the transmittable torque. FIG. 4 is a diagram showing a control flowchart executed by the controller of the automatic transmission control apparatus according to the present invention. FIG. 5 is a diagram showing another example of a powertrain of a hybrid vehicle equipped with an automatic transmission control device according to the present invention.

  FIG. 1 is a diagram showing an example of a powertrain of a hybrid vehicle equipped with an automatic transmission control device according to the present invention.

  The vehicle 100 is a so-called hybrid vehicle in which the driving wheels 2 are driven by the internal combustion engine 1 and the motor generator 5. The hybrid vehicle 100 is a front engine / rear wheel drive.

  The power train of the hybrid vehicle 100 shown in FIG. 1 includes an internal combustion engine 1, an automatic transmission 3, and a motor generator 5.

  The automatic transmission 3 is arranged in tandem behind the engine 1 in the vehicle front-rear direction as in a normal rear wheel drive vehicle.

  The motor generator 5 is disposed between the engine 1 and the automatic transmission 3. The motor generator 5 is coupled to a shaft 4 that transmits the rotation from the engine 1 (crankshaft 1 a) to the input shaft 3 a of the automatic transmission 3. The motor generator 5 acts as a motor according to the driving state of the vehicle and also acts as a generator (generator).

  A first clutch 6 is interposed between the engine 1 and the motor generator 5, more specifically, between the engine crankshaft 1a and the shaft 4. The first clutch 6 can change the transmission torque capacity continuously or stepwise. As such a clutch, for example, there is a wet multi-plate clutch capable of changing the transmission torque capacity by continuously controlling the clutch hydraulic oil flow rate and the clutch hydraulic pressure with a proportional solenoid. The state where the transmission torque capacity becomes zero is a state where the first clutch 6 is completely disconnected, and the engine 1 and the motor generator 5 are completely disconnected.

  When the first clutch 6 is completely disconnected, the output torque of the engine 1 is not transmitted to the drive wheels 2, but only the output torque of the motor generator 5 is transmitted to the drive wheels 2. A mode in which the vehicle travels in this state is an electric travel (EV) mode. On the other hand, when the first clutch 6 is connected, the output torque of the engine 1 is also transmitted to the drive wheels 2 together with the output torque of the motor generator 5. A mode in which the vehicle travels in this state is a hybrid travel (HEV) mode. In this way, the travel mode is switched by the engagement / disengagement of the first clutch 6. The first clutch 6 is an engine side clutch.

  A second clutch 7 is interposed between the motor generator 5 and the differential gear device 8, more specifically, between the transmission input shaft 3a and the transmission output shaft 3b. In FIG. 1, the second clutch 7 is built in the automatic transmission 3. Such a second clutch 7 may be realized, for example, by utilizing a friction element for selecting a forward shift stage or a friction element for selecting a reverse shift stage existing in the automatic transmission 3. Similarly to the first clutch 6, the second clutch 7 can change the transmission torque capacity continuously or stepwise. As such a clutch, for example, there is a wet multi-plate clutch capable of changing the transmission torque capacity by continuously controlling the clutch hydraulic oil flow rate and the clutch hydraulic pressure with a proportional solenoid. The state where the transmission torque capacity becomes zero is a state where the second clutch 7 is completely disconnected, and the motor generator 5 and the differential gear device 8 are completely disconnected. When the engine is started, slip control is performed by reducing the transmission torque capacity of the second clutch 7. Then, the shock when starting the engine 1 is not easily transmitted to the drive wheels 2. The second clutch 7 is a drive wheel side clutch.

  The automatic transmission 3 is, for example, the same as that described in “Chapter C-9 to C-22” issued by Nissan Motor Co., Ltd., “Skyline New Car (CV35 Car) Manual” in January 2003. The automatic transmission 3 has a built-in oil pump that rotates together with the input shaft 3a. By selectively engaging and releasing a plurality of friction elements (clutch, brake, etc.) by the oil pressure of the oil pump, the friction element The transmission path (shift stage) is determined by the combination of engagement and release. Accordingly, the automatic transmission 3 shifts the rotation from the input shaft 3a at a gear ratio corresponding to the selected shift stage, and outputs it to the output shaft 3b. This output rotation is distributed and transmitted to the left and right drive wheels 2 by the differential gear device 8 and used for traveling of the vehicle. However, the automatic transmission 3 is not limited to the stepped type as described above, and may be a continuously variable transmission. The rotational speed of the input shaft 3a is detected by the sensor 13.

  In the power train of FIG. 1 described above, power from the engine 1 is unnecessary when traveling in the electric travel (EV) mode used at low load / low vehicle speed including when starting from a stopped state. The engine 1 is stopped. Then, the first clutch 6 is released. Further, the second clutch 7 is engaged. Further, the automatic transmission 3 is brought into a power transmission state. In this state, the motor generator 5 is driven. Then, only the output rotation from the motor generator 5 reaches the transmission input shaft 3a. The automatic transmission 3 shifts the rotation input from the input shaft 3a according to the selected shift stage, and outputs it from the transmission output shaft 3b. The rotation output from the transmission output shaft 3b then reaches the drive wheel 2 via the differential gear device 8. In this manner, the vehicle travels electrically (EV mode travel) using only the motor generator 5.

  When traveling in a hybrid travel (HEV) mode used during high speed travel or heavy load travel, the first clutch 6 and the second clutch 7 are both engaged, and the automatic transmission 3 is placed in a power transmission state. In this state, the output rotation from the engine 1 and the output rotation from the motor generator 5 reach the transmission input shaft 3a. The automatic transmission 3 shifts the rotation input from the input shaft 3a according to the selected shift stage, and outputs it from the transmission output shaft 3b. The rotation output from the transmission output shaft 3b then reaches the drive wheel 2 via the differential gear device 8. In this way, the vehicle travels hybridly (HEV mode travel) with the engine 1 and the motor generator 5.

  During such HEV mode traveling, if the engine 1 is operated at the optimum fuel efficiency, energy may be surplus. In such a case, the surplus energy is converted into electric power by operating the motor generator 5 with surplus energy, and the electric power is stored so as to be used for driving the motor of the motor generator 5. By doing in this way, the fuel consumption of the engine 1 improves.

  In such a vehicle, the motor generator 5 brakes the vehicle and regenerates the kinetic energy of the vehicle. The method of braking the vehicle in this way is called regenerative braking. Although the braking force due to the regenerative brake varies depending on the driving state of the vehicle, the regenerative braking alone often does not provide the braking force required by the driver. Therefore, the shortage is compensated with a friction brake. Control for changing the braking force of the friction brake in accordance with the change of the braking force due to the regenerative brake is called cooperative regenerative control. In cooperative regenerative control, a shock is generated when the braking timing by the regenerative brake and the braking timing by the friction brake shift.

  The inventor of the present invention is researching cooperative regenerative control and has found that a shock is likely to occur during vehicle deceleration. The inventors of the present invention have found that such a shock can be prevented by devising the control of the automatic transmission by advancing research day and night. This will be described.

  First, shift control of the automatic transmission will be described.

  FIG. 2 is a diagram illustrating an example of a shift map.

  The horizontal axis is the vehicle speed, and the vertical axis is the accelerator pedal operation amount. A solid line in the figure is a shift line used for upshifting. The wavy line in the figure is a shift line used for downshifting.

  For example, a scene in which the vehicle decelerates when the driver releases his or her foot from the accelerator pedal and depresses the brake pedal will be described. In such a scene, the vehicle is braked with a regenerative brake and a friction brake. Until the vehicle speed falls below the shift reference vehicle speed V4, the automatic transmission 3 maintains the fifth speed. When the vehicle speed falls below the shift reference vehicle speed V4, the automatic transmission 3 is downshifted from the fifth speed to the fourth speed. Until the vehicle speed falls below the shift reference vehicle speed V3, the automatic transmission 3 maintains the fourth speed. When the vehicle speed falls below the shift reference vehicle speed V3, the automatic transmission 3 is downshifted from the fourth speed to the third speed. The automatic transmission 3 is similarly controlled thereafter.

  When the downshift is executed, the rotational speed of the input shaft 3a of the automatic transmission 3 increases. Then, the braking force by the regenerative brake decreases. This will be described with reference to FIG. FIG. 3A is a diagram showing the correlation between the rotational speed of the motor generator and the torque. Each line is a constant output line of the motor generator, and the upper right line has a larger output. To regenerate energy efficiently, it is necessary to operate the motor generator along the upper right line.

  That is, when the rotational speed is about 2000 rpm, the engine can be operated with a torque of 150 Nm, and this torque becomes the braking force of the regenerative brake. When the rotational speed is about 3000 rpm, the engine can be operated with a torque of 100 Nm, and this torque becomes the braking force of the regenerative brake. That is, when energy is regenerated efficiently, the rotational speed of the input shaft 3a of the automatic transmission 3 increases with a downshift, and the braking force by the regenerative brake decreases. Therefore, it is necessary to increase the braking force by the friction brake in accordance with the decrease in the braking force by the regenerative brake.

  If the rotational speed of the input shaft 3a of the automatic transmission 3 increases slowly, the braking force by the friction brake may be increased slowly.

  However, when the rotational speed of the input shaft 3a of the automatic transmission 3 increases rapidly, the braking force by the friction brake must also increase rapidly. If the brake force cannot be increased rapidly, the inventor's research indicates that a shift occurs between the timing when the braking force due to the regenerative brake decreases and the timing when the braking force due to the friction brake increases, causing a shock. Revealed by Therefore, when it is time to start downshifting during deceleration and it is estimated that the torque of the motor generator will drop significantly in a short time due to the increased rotation of the motor generator when downshifting, it is longer than usual. The inventor proposes to downshift over time. In this way, the braking force by the regenerative brake is slowly reduced, and accordingly, the braking force by the friction brake may be increased slowly. Therefore, it is possible to prevent a deviation between the timing at which the braking force due to the regenerative brake decreases and the timing at which the braking force due to the friction brake increases, and it is possible to prevent a shock from occurring during deceleration of the vehicle. .

  Note that the greater the ratio between the gear ratio before downshift and the gear ratio before downshift, the greater the rotational speed of the input shaft of the automatic transmission. Therefore, it is preferable to start the downshift so that the longer the ratio between the speed ratio before the downshift and the speed ratio before the downshift is, the longer it takes. By doing so, it is possible to prevent a shift between the timing at which the braking force due to the regenerative brake decreases and the timing at which the braking force due to the friction brake increases, and a shock is generated during deceleration of the vehicle. It can be prevented from occurring.

  When a constant shift stage is maintained, the rotational speed of the input shaft 3a of the automatic transmission 3 is reduced and the oil pressure of the oil pump is reduced as the vehicle speed is reduced. As described above, the automatic transmission 3 selectively engages or releases a plurality of friction elements (such as clutches and brakes) by the oil pressure of the oil pump. Therefore, when the oil pressure of the oil pump is reduced, the fastening force of the friction element (clutch, brake, etc.) is weakened, and the transmittable torque of the automatic transmission 3 is reduced. That is, as shown in FIG. 3B, when the rotational speed of the input shaft 3a of the automatic transmission 3 decreases, the transmittable torque of the automatic transmission 3 decreases. Since torque exceeding the transmittable torque of the automatic transmission 3 cannot be transmitted, if the transmittable torque of the automatic transmission 3 is small, the regenerative torque of the motor generator is limited by the transmittable torque. If it becomes like this, energy cannot be regenerated efficiently.

  Therefore, the rotational speed required to generate the oil pressure supplied to the automatic transmission 3 is set so that the transmittable torque of the automatic transmission 3 is equal to the maximum regenerative torque of the motor generator. When the rotation speed is about to fall, the downshift is started at a timing earlier than usual. That is, the present inventor proposes to shift the shift line used in the downshift of FIG. 2 to the right (increase the shift reference vehicle speed).

  By doing so, the transmittable torque of the automatic transmission 3 does not fall below the regenerative torque of the motor generator. That is, by doing so, it is possible to prevent the regenerative torque of the motor generator from being limited by the transmittable torque of the automatic transmission 3.

  Below, the specific structure which implement | achieves the above-mentioned technical thought is demonstrated.

  FIG. 4 is a diagram showing a control flowchart executed by the controller of the automatic transmission control apparatus according to the present invention.

  In step S1, the controller determines whether or not the vehicle is decelerating. If the controller is decelerating, the process proceeds to step S2, and if not decelerating, the controller exits the process.

  In step S2, the controller determines whether or not the downshift start timing has come. Specifically, the determination is made based on whether or not the vehicle speed is lower than the shift reference vehicle speed. The controller shifts the process to step S3 when the start timing comes, and shifts the process to step S5 if not.

  In step S3, the controller estimates the shift stage after the downshift, and estimates the rotational speed of the automatic transmission input shaft 3a after the downshift, that is, the rotational speed of the shaft 4 of the motor generator 5.

  In step S4, the controller estimates the amount of torque reduction of the motor generator 5 due to the downshift. Specifically, for example, the estimation is performed based on FIG.

  In step S5, the controller determines whether or not the braking force of the friction brake can be increased in accordance with the decrease in the torque of the motor generator 5 when the automatic transmission is shifted in the normal shift time. Specifically, a reference value (speed) that can increase the braking force of the friction brake is set in advance through experiments or simulations, and the reference value is compared with the rate of decrease in torque of the motor generator 5 for determination. . If the controller cannot rise, the process proceeds to step S6. If the controller can rise, the controller exits the process. The shift time is the time from the start of the shift until the rotation speed of the automatic transmission input shaft 3a converges to the rotation speed after the shift.

  In step S6, the controller starts a downshift so as to shift over a longer time than usual.

  In step S7, the controller determines whether or not the rotational speed of the motor generator 5 has fallen below the reference speed. In addition, the reference speed is obtained by adding a margin to the rotational speed necessary to generate the oil pressure supplied to the automatic transmission 3 so that the transmittable torque of the automatic transmission 3 is equal to the maximum regenerative torque of the motor generator. Rotation speed. By setting this margin larger as the rotational speed of the motor generator 5 decreases faster, it is possible to reliably prevent the transmittable torque of the automatic transmission 3 from falling below the maximum regenerative torque of the motor generator. Further, when the temperature of the oil supplied to the automatic transmission 3 is high, the viscosity of the oil is lowered, so that the transmittable torque of the automatic transmission 3 is also lowered. Therefore, the reference speed may be corrected to be larger so that the higher the oil temperature, the faster the speed change. The oil temperature may be detected by a temperature sensor.

  According to the present embodiment, it is estimated that the braking force of the friction brake cannot be increased in accordance with the decrease in the torque of the motor generator when the shift is started at the normal shift time at the start timing of the downshift. When shifting, I took longer time than usual. As a result, the torque of the motor generator slowly decreases. Therefore, it is possible to prevent a deviation between the timing when the braking force due to the regenerative brake decreases and the timing when the braking force due to the friction brake increases, and it is possible to prevent a shock from occurring during deceleration of the vehicle.

  Note that the greater the ratio between the gear ratio before downshift and the gear ratio before downshift, the greater the rotational speed of the input shaft of the automatic transmission. Therefore, it is preferable to start the downshift so that the longer the ratio between the speed ratio before the downshift and the speed ratio before the downshift is, the longer it takes. By doing so, it is possible to prevent a shift between the timing at which the braking force due to the regenerative brake decreases and the timing at which the braking force due to the friction brake increases, and a shock is generated during deceleration of the vehicle. It can be prevented from occurring.

  In addition, when the downshift start timing is not reached, the downshift is started at a timing earlier than usual when the rotational speed of the motor generator falls below the reference speed.

  In addition, when a certain shift stage is maintained, the oil pressure of the oil pump decreases as the vehicle speed decreases and the rotational speed of the input shaft of the automatic transmission decreases. Etc.) is weakened, and the transmission torque of the automatic transmission is also reduced. Since torque exceeding the transmittable torque of the automatic transmission 3 cannot be transmitted, if the transmittable torque of the automatic transmission 3 is small, the regenerative torque of the motor generator may be limited by the transmittable torque. is there. If it becomes like this, energy cannot be regenerated efficiently.

  Therefore, in the present embodiment, the rotational speed required to generate the oil pressure supplied to the automatic transmission is set so that the transmittable torque of the automatic transmission is equal to the maximum regenerative torque of the motor generator. When the rotation speed is about to fall, the downshift is started earlier than usual. By doing in this way, energy can be regenerated efficiently. Note that the margin is increased as the rotational speed of the motor generator decreases more rapidly. By doing so, it is possible to reliably prevent the transmittable torque of the automatic transmission from falling below the maximum regenerative torque of the motor generator.

  Furthermore, the reference speed is set larger as the temperature of the oil supplied to the automatic transmission is higher. If the temperature of the oil supplied to the automatic transmission is high, the viscosity of the oil decreases, so the transmittable torque of the automatic transmission also decreases. Therefore, in the present embodiment, the reference speed is largely corrected so that the speed is changed earlier as the oil temperature is higher. Even in this way, it is possible to reliably prevent the transmittable torque of the automatic transmission from falling below the maximum regenerative torque of the motor generator.

  The embodiment of the present invention has been described above. However, the above embodiment only shows a part of application examples of the present invention, and the technical scope of the present invention is limited to the specific configuration of the above embodiment. Absent.

  For example, in FIG. 1, the second clutch 7 that releasably couples the motor generator 5 and the drive drive wheel 2 is interposed between the motor generator 5 and the automatic transmission 3 and is built in the automatic transmission 3. However, the present invention is not limited to this structure, and may be provided outside the automatic transmission 3 separately from the automatic transmission 3 as shown in FIG. Further, as shown in FIG. 5B, the automatic transmission 3 and the differential gear device 8 may be interposed. Even in these cases, the same function as described above can be achieved.

  In the above embodiment, a so-called hybrid vehicle in which driving wheels are driven by an internal combustion engine and a motor generator has been described as an example. However, the present invention may be applied to an electric vehicle in which driving wheels are driven by a motor generator.

DESCRIPTION OF SYMBOLS 100 Vehicle 1 Internal combustion engine 1a Crankshaft 2 Drive wheel 3 Automatic transmission 3a Transmission input shaft 3b Transmission output shaft 4 Shaft 5 Motor generator 6 First clutch (engine side clutch)
7 Second clutch (drive wheel side clutch)
Step S2 Downshift determination unit Step S5 Friction braking increase determination unit Step S6 Shift control unit

Claims (6)

A device for controlling an automatic transmission of a vehicle provided with a cooperative regenerative brake that brakes the vehicle by coordinating a friction brake and a regenerative brake,
A downshift determination unit that determines whether or not a downshift start timing has been reached during deceleration;
A friction braking increase determination unit that determines whether or not the braking force of the friction brake can be increased in accordance with a decrease in the torque of the motor generator when the shift is started at a normal shift time when the downshift start timing comes. ,
When it is determined that the vehicle cannot be raised, a shift control unit that starts a downshift so as to shift over a longer time than usual;
An automatic transmission control device comprising: In the automatic transmission control device according to claim 1,
The shift control unit starts a downshift so that a longer time is required as the ratio between the speed ratio before the downshift and the speed ratio before the downshift is larger.
An automatic transmission control device characterized by that. In the automatic transmission control device according to claim 1 or 2,
When it is not the start timing of the downshift, a rotational speed determination unit that determines whether the rotational speed of the motor generator has fallen below the reference speed,
When the speed is lower than the reference speed, a downshift early start unit that starts a downshift at a timing earlier than normal,
An automatic transmission control device comprising: In the automatic transmission control device according to claim 3,
The reference speed is a rotational speed obtained by adding a margin to the rotational speed required to generate the oil pressure supplied to the automatic transmission so that the transmittable torque of the automatic transmission is equal to the maximum regenerative torque of the motor generator. Is,
An automatic transmission control device characterized by that. The automatic transmission control device according to claim 4,
The margin is larger as the rotational speed of the motor generator decreases faster.
An automatic transmission control device characterized by that. In the automatic transmission control device according to any one of claims 3 to 5,
The reference speed is larger as the temperature of oil supplied to the automatic transmission is higher.
An automatic transmission control device characterized by that.

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