Brake force control device

Abstract

A braking force control device (100) that controls a regenerative generator (300) in a vehicle in which a negative force, with a traveling direction of the vehicle set to be positive, is generated by at least one automatic step transmission (200) and the regenerative generator (300), the braking force control device (100) comprising: a prediction unit (101) that predicts a time from a current time until a next start of a gearshift operation occurs in the automatic step transmission (200) based on a speed of the vehicle; an acquisition unit (102) that acquires a state of a battery (400) charged by regenerative power generation of the regenerative generator; and a control unit (103) that stops the regenerative power generation by the regenerative generator (300) before a gearshift of the automatic step transmission (200) is started.when, during regenerative power generation by the regenerative generator (300), it is determined, based on a prediction result by the prediction unit (101) and the state of the battery (400) acquired by the acquisition unit (102), that the regenerative power generation by the regenerative generator (300) can be stopped due to the state of the battery (400) during a gear shift operation of the automatic step transmission (200), wherein the control unit (103) predicts a time from the current time until a next stop of the regenerative power generation by the regenerative generator (300) occurs due to the state of the battery (400) based on a power storage rate or a charge current integration value as the state of the battery (400) acquired by the acquisition unit (102), and the control unit (103) determines,that the regenerative power generation by the regenerative generator (300) can be stopped due to the state of the battery (400) during the gearshift operation of the automatic step-change transmission (200) when the predicted time is not less than the time until the gearshift operation in the automatic step-change transmission (200) is started, which is predicted by the prediction unit (101), and when the predicted time is not greater than a time obtained by adding a predetermined time period of the gearshift operation to the time until the gearshift operation is started.

Description

BACKGROUND OF THE INVENTION1. Field of the InventionThe present invention relates to a braking force control device that is mounted in a vehicle and controls the braking force of the vehicle.2. Description of Related ArtIn vehicles, various technologies have been proposed to improve a comfortable driving feeling and an operation feeling. For example, Japanese Patent Publication No. JP H10-280 990 A discloses a fuel cut control apparatus that supplements a deceleration force by an alternator, an air conditioner, a brake, a gear shift, etc. to obtain an expected deceleration force when fuel cut is prevented to avoid catalyst deterioration at a high catalyst temperature during vehicle deceleration. Japanese Patent Publication No. 2006-297 994 A discloses an in-vehicle control device that distributes a control target determined depending on the operation amount by a user to a drive system and a control system according to respective allocation ratios, while sending the control target to a stabilization system before distribution to make this system execute correction, thereby eliminating a need to synchronize distribution values of the control target to reduce a delay, thus improving responsiveness to an operation. Japanese Patent Publication No. 2012-92 673 A discloses a vehicle power generation control apparatus that limits an amount of power generation at the time of regenerative power generation to a decreasing direction to set a difference between a torque of the generator when the battery is charged and a torque of the generator when the battery is not charged to be within a predetermined difference in torque, thereby reducing an influence on ride comfort due to starting or stopping of the regenerative power generation.JP 2010-125 936 A discloses an apparatus for controlling a power transmission device for a vehicle. When an engine friction torque is applied in addition to the regeneration torque by a second motor in an idle mode, the friction torque is temporarily replaced with the regeneration torque under a braking force cooperation coasting control by a braking force cooperation control means, the regeneration torque being replaced with a braking torque by a wheel brake device. In order to replace any torque, an engine torque (regeneration torque) is also used.US 2016 / 0 264 125 A1 describes a control device for a hybrid vehicle provided with a first charge control device configured to maintain the power of an internal combustion engine at a predetermined value or more and charge an energy storage device with an excess of power with respect to a power request for the internal combustion engine. The control device includes a second charge control device configured to charge the energy storage device with an increase in power caused by an upshift of a gear shifter. The control device further includes a transmission time changing device configured to extend an execution time of the upshift or delay the start time of the upshift to prevent the charging power for the energy storage device from exceeding an input limit value for the energy storage device when the control time of the output reduction request overlaps the control time of the upshift request.US 2015 / 0 375 747 A1 describes a control device for a vehicle and a drive system for a vehicle. A control signal output unit (a drive control unit) performs control to maintain a gear position corresponding to a motor generator during deceleration of a vehicle and regeneration performed by the motor generator.SUMMARY OF THE INVENTIONIn general, when a vehicle enters a coasting state in which neither an accelerator pedal nor a brake pedal is depressed by a user, acceleration in a decelerating direction is generated in the vehicle by an engine, a transmission, a regenerative generator, and the like. At this time, when the transmission is a stepped automatic transmission, gear shift-down occurs according to a decrease in the speed of the vehicle. There is a certain transition period in the shift down operation in the transmission, and when an input torque to the transmission varies due to this transition period, the gear ratio and the output torque become temporarily unstable due to the internal structure of the transmission, which may cause a shift shock such as sudden vibrations in the vehicle.During coasting, torque from the wheel side caused by the inertia force of the vehicle is distributed and input to the generator and the transmission. When the state of regenerative power generation by the generator transitions from the execution state to the stop state, the absolute value of the input torque to the generator is decreased due to a decrease in a regenerative load, thus the absolute value of the input torque to the transmission is increased accordingly. Since the control regarding the gear shift of the transmission and the control regarding the regenerative power generation are executed independently of each other, the regenerative power generation can stop during the shift-down transition period in the idle running state, thus the comfortable running feeling due to a shift shock can be deteriorated.The present invention has been made in view of the above-described problems, and an object of the present invention is to provide a braking force control device that can realize appropriate riding comfort in an idle running state of a vehicle.This object is achieved by a braking force control device according to claim 1. Advantageous further developments are specified in the dependent claims.The present invention can provide a braking force control device capable of realizing appropriate riding comfort in an idle running state of a vehicle.BRIEF DESCRIPTION OF THE DRAWINGFeatures, advantages, and technical and industrial significance of exemplary embodiments of the invention will be described below with reference to the accompanying drawings, in which like numerals denote like elements. The following are shown: FIG. 1 is a diagram showing a configuration of a braking force control device and an associated environment according to first and second embodiments of the present invention; FIG. 2 is a flowchart showing processing according to the first embodiment of the present invention; FIG. 3 is a diagram showing an example of a gear shift map according to the first and second embodiments of the present invention; FIG. 4 is a diagram showing an example of processing according to the first embodiment of the present invention; FIG. 5 is a diagram illustrating an example of processing according to a comparative example; FIG. 6 is a flowchart showing processing according to the second embodiment of the present invention.DETAILED DESCRIPTION OF THE EMBODIMENTSA braking force control device according to the present invention, when it is determined that regenerative power generation by a generator can be stopped during a gear shifting operation of a transmission, stops regenerative power generation by the generator before gear shifting of the transmission is started. Thereby, a shift shock due to stopping the regenerative power generation during the gear shift operation of the transmission is reduced.First EmbodimentThe first embodiment of the present invention will be described in detail below with reference to the drawings. Note that a speed, an acceleration, and the like are represented by values with reference numerals while the vehicle running direction is set in a positive direction.ConfigurationFIG. 1 shows a configuration of a braking force control device 100 and an associated environment mounted in a vehicle according to the present embodiment. The vehicle includes the braking force control device 100, a transmission 200 that is a stepped automatic transmission, a generator 300 that can execute regenerative power generation such as an alternator and a motor, and a battery 400 that charges electric power from the regenerative power generation by the generator 300. The transmission 200 and the generator 300 may generate a braking force while the vehicle is in an idle running state. The braking force may be generated by a device such as an engine (not shown) different from the transmission 200 and the generator 300. The vehicle further includes a transmission control unit that controls gear shifting of the transmission 200, and a charge control unit that performs charge-discharge control on the battery 400 and control regarding regenerative power generation of the generator 300 based on the current, voltage, temperature, power storage rate, etc. of the battery 400. In FIG. 1, these control units are included in the transmission 200, the generator 300, and the battery 400, thus omitting related explanations. Besides these control units, various sensors and devices are mounted in the vehicle.The braking force control device 100 includes a prediction unit 101, an acquisition unit 102, and a control unit 103. The prediction unit 101 predicts a time from a present time until a next start of the gear shift operation occurs in the transmission 200 during the idle running state. The acquisition unit 102 acquires a state of the battery 400. The control unit 103 controls the operations of the prediction unit 101 and the acquisition unit 102, and at the same time when it is determined that the regenerative power generation by the generator 300 can be stopped due to the state of the battery 400 during the gear shifting operation of the transmission 200 based on the prediction result of the prediction unit 101 and the acquisition result of the acquisition unit 102, the control unit 103 stops the regenerative power generation by the generator 300 before the start of the gear shifting of the transmission 200.ProcessingFIG. 2 is a flowchart showing an example of the control of the regenerative power generation executed by the braking force control device 100 while the user is driving the vehicle. This processing is executed in a state in which the regenerative power generation by the generator 300 is possible while the vehicle is running.(Step S 101): The control unit 103 constantly acquires the amount of operation of an accelerator pedal and the amount of operation of the brake pedal operated by the user, which are respectively detected by an accelerator pedal sensor and a brake pedal sensor provided to the vehicle. Based on the acquired accelerator pedal operation amount and the acquired brake pedal operation amount, the control unit 103 detects that the vehicle is in a coasting state by detecting that the user does not operate the accelerator pedal (the operation amount is 0) and the user does not operate the brake pedal (the operation amount is 0). When the control unit 103 detects the idle running state, the processing proceeds to step S 102; when the control unit 103 does not detect the idle running state, the control unit 103 repeats step S 105 and waits for the vehicle to enter the idle running state.(Step S 102): The prediction unit 101 identifies the vehicle speed at which a next start of the gear shift operation occurs in the transmission 200. The identification method will be described below.The prediction unit 101 holds a map representing the characteristics of the gear shift control of the transmission 200 executed by the transmission control unit that controls the transmission 200. FIG. 3 shows an example of the figure. In the map shown in FIG. 3, the gear stage of the transmission 200 is determined based on the speed and the throttle opening of the vehicle. As the speed of the vehicle increases, when the vehicle speed is increased to a speed at a current throttle opening indicated by a gear shift line of each solid line in the map, an upshift is started. Further, when the vehicle speed is decreased, when the vehicle speed is decreased to a speed at a current throttle opening indicated by a gear shift line of each dotted line in the map, a downshift is started. In this step, the vehicle is in the idle running state, so that the throttle opening is 0 and the vehicle speed is decreased. Thus, the prediction unit 101 determines a current gear stage of the transmission 200 and identifies the speed at which the downshift from this gear stage is started at the throttle opening 0, thereby identifying a speed at which a next start of the gear shift operation occurs in the transmission 200. In the example shown in FIG. 3, when the current gear stage is the third gear, the prediction unit 101 identifies a speed V 32 at the throttle opening of 0 indicated by the gear shift line for a downshift from a third gear to a second gear as a speed at which a next start of the gear shift operation occurs in the transmission 200.(Step S 103): The prediction unit 101 identifies a current speed v and a current acceleration a of the vehicle. The speed v may be identified by suitably acquiring the current speed and the acceleration from a speed sensor provided on the vehicle or from another device connected to the in-vehicle network. The acceleration may be identified, for example, by acquiring vehicle speeds v at a plurality of times and calculating the associated time rate of change. Alternatively, the prediction unit 101 may acquire the acceleration from an acceleration sensor provided on the vehicle or another device connected to an in-vehicle network. Note that, instead of executing step S 102 after identifying the speed v in this step, the prediction unit 101 may identify the speed at which a next start of the gear shift operation occurs in the transmission 200 based on the speed v and the map described above.(Step S 104): The prediction unit 101 predicts a time t 1 from the present time until a next start of the gear shift operation occurs in the transmission 200. Assuming that the acceleration a of the vehicle is constant, the prediction unit 101 predicts from the current time until the next start of the gear shift operation occurs in the transmission 200 based on the current speed v and a speed V at which the next start of the gear shift occurs in the transmission 200 and the acceleration a using the following equation (1): (step S 105): When the time t 1 predicted by the prediction unit 101 is less than or equal to a predetermined time, the control unit 103 makes the processing proceed to step S 106, and when the time t 1 is greater than the predetermined time, the control unit 103 makes the processing proceed to step S 101.(Step S 106): The acquisition unit 102 acquires a state of the battery 400 charged by regenerative power generation of the generator 300. The state of the battery 400 is not limited to a specific one as long as it provides a prediction regarding a chargeable amount of the battery 400, which is an amount of power that is currently chargeable, including at least one of a power storage rate (SOC) and a charge current integration value from the time of a charge start time. The acquisition unit 102 may acquire the above state of the battery 400 from various sensors provided to the battery 400 and from a charge control unit that performs charge-discharge control of the battery 400 and regenerative power generation control of the generator 300. Alternatively, the acquisition unit 102 may acquire information as source data used for calculation of the state of the battery 400 from the various sensors, the charge control unit, etc., and may calculate the state based on the acquired information.Based on the state acquired by the acquisition unit 102, the control unit 103 determines whether the rechargeable amount of the battery 400 may be less than a predetermined value. For example, the control unit 103 may determine that the chargeable amount may be decreased when the power storage rate is greater than or equal to a predetermined value, or when the charge current integration value is greater than or equal to the predetermined value. The control unit 103 determines that the rechargeable amount of the battery 400 can be decreased when one or all of the one or more states acquired by the acquisition unit 102 is / are within a predetermined range, then the processing proceeds to step S 107; otherwise, the processing proceeds to step S 101.(Step S 107): In this step, it is predicted that the charge control unit that controls charge-discharge of the battery 400 as well as regenerative power generation of the generator 300 will stop regenerative power generation by the generator 300 in the near future to protect the battery 400. In such a case, it may be determined that the regenerative power generation by the generator 300 may be stopped due to the state of the battery 400 during the gear shifting operation of the transmission 200. The control unit 103 requests the charge control unit to stop the regenerative power generation to stop the regenerative power generation by the generator 300 before the transmission 200 downshifts. This is the end of the processing.When the accelerator pedal sensor and the brake pedal sensor provided on the vehicle detect an operation of the accelerator pedal or an operation of the brake pedal by the user during execution of the processing in steps S 102 to S 107, the processing is stopped, and proceeds to step S 101 by suspending the processing until the idle running state is established. Apart from this processing, conventional control of acceleration, deceleration, gear shifting, and the like corresponding to the detected operation of the accelerator pedal or the detected operation of the brake pedal is executed by another control unit.After the regenerative power generation is stopped by the prescribed processing in step S 107, when the regenerative power generation by the generator 300 becomes possible, since the power storage rate of the battery 400 decreases below a predetermined value or the like, the regenerative power generation is resumed by another control unit provided on the vehicle such as the charge control unit. In this case, the above-described processing is executed again.A description will be provided regarding an example of control based on the above-described processing. FIG. 4 shows that respective horizontal axes represent time, respective vertical axes represent a rotational speed of the engine, an input torque from the wheel side to the transmission 200, and an acceleration of the vehicle, and also shows respective timing charts according to the processing according to this embodiment. In the entire period shown in FIG. 4, the vehicle is in the coasting state, and the acceleration of the vehicle due to the negative driving force is negative.It is assumed that at a time T 1, the predicted time t 1 until a next gear shift is equal to the predetermined time. Until time T 1, the predicted time t 1 until the next gear shift occurs is larger than the predetermined time, thus a loop returning from step S 105 to step S 101 is established in the above-described processing. Alternatively, until time T 1, even if the predicted time t 1 until the next gear shift is less than or equal to the predetermined time, it is not determined that the rechargeable amount of the battery 400 can be decreased, thus establishing a loop returning from step S 106 to step S 101.At time T 1, the predicted time t 1 until the next gear shift is less than or equal to the predetermined time, and the rechargeable amount of the battery 400 can be decreased, so step S 107 is executed to stop the regenerative power generation. The regenerative power generation is stopped and the absolute value of the input torque from the wheel side to the generator 300 thus gradually decreases; accordingly, the absolute value of the input torque to the transmission 200 gradually increases during a period from the time T 1 to a time T 2, and at the same time, the acceleration of the vehicle gradually increases (the deceleration force decreases).At a time T 3 after the time T 2, a next gear shift is started, and the transmission 200 shifts from a third speed to a second speed, for example. A period from time T 3 to time T 4 is a transition period of the gear shift operation. From time T 1 to time T 3, the engine speed gradually decreases, but the speed gradually increases during the transition period. After time T4, when the gear shift operation is finished, the rotational speed again gradually decreases. In FIG. 4, it is assumed that after time T 2, the acceleration of the vehicle does not change before and after the gear shift, and this may actually change.Thus, in the present embodiment, it is possible to prevent the regenerative power generation by the generator 300 from being stopped during the gear shifting operation of the transmission 200. For comparison, FIG. 5 shows, like FIG. 4, that respective horizontal axes represent time, respective vertical axes represent a rotational speed of the engine, an input torque from the wheel side into the transmission 200, and an acceleration of the vehicle, and also shows respective timing charts corresponding to the processing according to the comparative example. In the entire period shown in FIG. 5, the vehicle is in the coasting state, and the acceleration of the vehicle due to the negative driving force is negative.In the example shown in FIG. 5, the regenerative power generation by the generator 300 is stopped to a number T3' within a transition period of the transmission 200 from the time T3 to the time T4. Accordingly, after time T3', a shift shock such that the acceleration of the vehicle abruptly varies occurs for a certain period of time.In the present embodiment, in the idle running state, when it is predicted that the shift-down of the transmission 200 is started within a predetermined time and it is determined that the chargeable amount of the battery 400 can be decreased, the regenerative power generation is stopped before the start of the shift-down, and an impact due to the stopping of the regenerative power generation during the transition period of a shift-down is avoided. Accordingly, preferable riding comfort in the idle running state can be obtained.Second EmbodimentNext, the second embodiment of the present invention will be described with reference to the drawings. Descriptions of the same subject matters as those in the first embodiment will be omitted or simplified. The configuration of each constituent element of the braking force control device 100 according to the present embodiment is the same as that according to the first embodiment. In the present embodiment, specifically, the control unit 103 predicts a time t 2 from a present time until the regenerative power generation of the generator 300 is stopped.ProcessingFIG. 6 is a flowchart showing an example of control of regenerative power generation executed by the braking force control device 100 while the driver is driving the vehicle. This processing is executed in a state in which the regenerative power generation by the generator 300 is possible while the vehicle is turned on and can travel.(Step S 201 to S 204): The processing in each step is the same as that in Steps S 101 to S 104 according to the first embodiment. As in the first embodiment, when an idle running state is detected, the time t 1 is predicted from the present time until a next start of the gear shift operation occurs in the transmission 200.(Step S 205): As in the first embodiment, the acquisition unit 102 acquires the state of the battery 400 charged by regenerative power generation of the generator 300.Based on the state acquired by the acquisition unit 102, the control unit 103 predicts a time t 2 from the present time until the charge control unit that controls the charge-discharge of the battery 400 and the regenerative power generation by the generator 300 stops the regenerative power generation by the generator 300. The control unit 103 may predict the time t 2 by executing a predetermined calculation based on, for example, the power storage rate and the charge current integration value of the battery 400.(Step S 206): The control unit 103 determines whether or not the charge control unit is predicted to stop the regenerative power generation within the transition period from the present time to a next start of the gear shift operation in the transmission 200. When a required period (the transition period) of the gear shift operation is defined as T, the condition that the regenerative power generation by the charge control unit is stopped within the transition period is expressed by the following equation (2):When the equation (2) is modified, the following equation (3) is obtained: 0 ≤ t2 - t1 ≤ the required time period T... Equation (3).When Equation (2) (that is, Equation (3)) is established, the control unit 103 may determine that the regenerative power generation by the generator 300 may be stopped due to the state of the battery 400 during the gear shifting operation of the transmission 200. When it is determined that the regenerative power generation by the charge control unit can be stopped within the transition period, the processing proceeds to step S 207; otherwise, the processing proceeds to step S 201.(Step S 207): The control unit 103 requests the charge control unit to stop the regenerative power generation to stop the regenerative power generation by the generator 300 before the transmission 200 downshifts. This is the end of the processing.When the accelerator pedal sensor and the brake pedal sensor provided on the vehicle detect the operation of the accelerator pedal or the operation of the brake pedal by the user during execution of the processing of steps S202 to S207, the processing is stopped, and proceeds to step S201 by suspending the processing until the idle running state is established. Apart from this processing, conventional control of acceleration of deceleration of gear shifting or the like corresponding to the detected operation of the accelerator pedal or the detected operation of the brake pedal is executed by another control unit.In addition, after the regenerative power generation is stopped by the above-described processing in step S 207, when the regenerative power generation by the generator 300 becomes possible, since the power storage rate of the battery 400 becomes lower than a predetermined value or the like, the regenerative power generation by another control unit is resumed. In this case, the above-described processing is started again.In the present embodiment, as in the first embodiment, as shown in the timing chart of FIG. 4, it is possible to prevent the stopping of the regenerative power generation by the generator 300 from being performed during the gear shifting operation of the transmission 200.Effect: EffectIn the present embodiment, in the idle running state, when it is predicted that the regenerative power generation can be stopped within a period predicted to be a transition period of a downshift of the transmission 200, the regenerative power generation is stopped before the downshift is started. As a result, as in the first embodiment, it is possible to avoid a shift shock and obtain a preferred riding comfort in the idle running state.As described above, the respective embodiments of the present invention have been explained, and the present invention can be implemented by appropriately modifying or combining the features of the above-described embodiments. For example, in the second embodiment, in the case of executing the same processing as that in step S 105 according to the first embodiment between step S 204 and step S 205, and when it is not predicted that the downshift of the transmission 200 will be started within the predetermined time, the stopping of the regenerative power generation more than is required can be suppressed without stopping the regenerative power generation. In each embodiment, as described above, typically, the idle running state established by releasing the accelerator pedal operation and the idle running state established by releasing the brake pedal operation are both detected as the coasting running state and the idle running state, respectively (steps S 101 and S 201); however, only one of the two idle running states may be detected instead.The present invention can be considered not only as the braking force control device but also as a braking force control method, a braking force control program, and a computer-readable non-transitory recording medium storing the same, as well as a braking force control system and a vehicle equipped therewith, all of which are executed by one or more computers included / are in the braking force control device.The present invention is useful for a braking force control device mounted in a vehicle or the like.A braking force control device includes: a prediction unit that predicts a time from a present time to a next start of a gear shift operation in a stepped automatic transmission based on a speed of the vehicle; an acquisition unit that acquires a state of a battery charged by regenerative power generation of a regenerative generator; and a control unit that stops the regenerative power generation by the regenerative generator before the gear shift of the stepped automatic transmission is started, when it is determined during the regenerative power generation by the regenerative generator based on a prediction result by the prediction unit and the state of the battery acquired by the acquisition unit that the regenerative power generation by the regenerative generator can be stopped due to the state of the battery during the gear shift operation of the stepped automatic transmission.

Claims

A braking force control device (100) that controls a regenerative generator (300) in a vehicle in which a negative force, a traveling direction of the vehicle being set to be positive, is generated by at least a stepped automatic transmission (200) and the regenerative generator (300), the braking force control device (100) comprising: a prediction unit (101) that predicts a time from a present time until a next start of a gear shift operation occurs in the stepped automatic transmission (200), based on a speed of the vehicle; an acquisition unit (102) that acquires a state of a battery (400) charged by a regenerative power generation of the regenerative generator; and a control unit (103) that stops the regenerative power generation by the regenerative generator (300) before a gear shift of the stepped automatic transmission (200) is started, when it is determined during the regenerative power generation by the regenerative generator (300) that the regenerative power generation by the regenerative generator (300) can be stopped based on a prediction result by the prediction unit (101) and the state of the battery (400) acquired by the acquisition unit (102), it is determined that the regenerative power generation by the regenerative generator (300) can be stopped based on the state of the battery (400) during a gear shift operation of the automatic step-variable transmission (200), wherein the control unit (103) predicts a time from the present time until a next stop of the regenerative power generation by the regenerative generator (300) occurs based on a power storage rate or a charge current integration value as the state of the battery (400) acquired by the acquisition unit (102), and the control unit (103) determines, that the regenerative power generation by the regenerative generator (300) can be stopped due to the state of the battery (400) during the gear shifting operation of the step-variable automatic transmission (200) when the predicted time is not less than the time until the gear shifting operation is started in the step-variable automatic transmission (200) predicted by the prediction unit (101) and when the predicted time is not more than a time obtained by adding a predetermined time period of the gear shifting operation to the time until the gear shifting operation is started.The braking force control device (100) according to claim 1, wherein the control unit (103) determines that the regenerative power generation by the regenerative generator (300) can be stopped due to the state of the battery (400) during the gear shifting operation of the stepped automatic transmission (200), when the time predicted by the prediction unit (101) is not greater than a predetermined time, and when a power storage rate or a charge current integration value as the state of the battery (400) acquired by the acquisition unit (102) is not less than a predetermined value.The braking force control device (100) according to claim 1 or 2, wherein the prediction unit (101) predicts the time from the present time until a next start of the gear shift operation occurs in the stepped automatic transmission (200), based on the speed and an acceleration of the vehicle and a predetermined speed of the vehicle at which the gear shift operation is started in the stepped automatic transmission (200).

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