JP7654435B2 - Gear shift control device - Google Patents

Description

The present invention relates to a gear shift control device that controls an automatic transmission of a vehicle.

For example, Patent Document 1 describes a vehicle that automatically controls the vehicle speed so that it reaches a predetermined target speed. Patent Document 1 also describes how the gear stage is determined based on the gradient of the driving section ahead, and the gear stage is changed in advance to prevent the vehicle from stalling.

JP 2018-194048 A

For example, an automatic transmission may change gears while driving on a road with a gradient. When changing gears, the clutch of the automatic transmission is temporarily released, which can cause the vehicle to unintentionally stall on an uphill road when the clutch is released, or to unintentionally accelerate on a downhill road. For this reason, if these changes in vehicle speed are not taken into consideration, the automatic transmission cannot change gears appropriately, and the vehicle may not be able to travel stably.

The present invention aims to provide a gear change control device that can appropriately change the shift of an automatic transmission and allow the vehicle to run stably.

The present invention is a shift control device for an automatic transmission mounted on an autonomous vehicle that controls the vehicle speed to a target vehicle speed, and includes an acceleration acquisition unit that acquires running resistance acceleration due to the running resistance of the autonomous vehicle, a vehicle speed estimation unit that estimates a post-shift-change vehicle speed, which is the vehicle speed at the time of completion of the shift change, based on the acquired running resistance acceleration and the shift change time required to shift to a candidate gear stage, and a gear stage selection unit that selects a post-shift-change gear stage based on an appropriate vehicle speed set for the candidate gear stage and the estimated post-shift-change vehicle speed, such that the post-shift-change vehicle speed is within the appropriate vehicle speed for the candidate gear stage and the vehicle speed of the autonomous vehicle does not exceed the target vehicle speed.

In this gear change control device, the post-shift vehicle speed for the gear stage that is a candidate for shifting is estimated based on the running resistance acceleration and the shift change time. Then, using the estimated post-shift vehicle speed, the gear stage after the shift change is selected so that the post-shift vehicle speed is within the appropriate vehicle speed for the candidate gear stage and does not exceed the target vehicle speed. In other words, even if the vehicle speed of the autonomous vehicle changes due to running resistance when the clutch is released during a shift change, a gear stage that corresponds to this change in vehicle speed can be selected. This allows the gear change control device to appropriately change the automatic transmission and drive the vehicle stably.

In the gear shift control device, when there are multiple gears that are candidates for shifting and the vehicle speed after the shift change is within the appropriate vehicle speed, the gear selection unit may select the gear with the smallest gear ratio. In this case, the rotation speed of the drive source of the autonomous vehicle can be lowered, and fuel economy can be improved, for example, when the drive source is an engine, or electricity consumption can be improved, for example, when the drive source is an electric motor.

In the gear shift control device, the acceleration acquisition unit may acquire running resistance acceleration due to running resistance including the gradient of the road surface on which the autonomous vehicle is running. In this case, the gear shift control device can appropriately select the gear stage based on the running resistance that takes into account the gradient of the road surface on which the autonomous vehicle is running.

The present invention allows the automatic transmission to appropriately shift gears, enabling the vehicle to travel stably.

FIG. 1 is a block diagram showing a schematic configuration of an autonomous driving vehicle equipped with a gear shift control device. FIG. 2 is a flowchart showing the flow of a shift change process performed by the gear shift control device.

The following describes an embodiment of the present invention with reference to the drawings.

As shown in FIG. 1, the gear shift control device 1 according to this embodiment is mounted on an autonomous vehicle (autonomous vehicle) V that can switch between autonomous driving and manual driving by a driver. The autonomous vehicle V drives autonomously along a preset driving route. The gear shift control device 1 controls the shift change of the automatic transmission 2 mounted on the autonomous vehicle V.

More specifically, the autonomous vehicle V is equipped with a gear shift control device 1 and an autonomous driving control device 3 that controls the autonomous driving of the autonomous vehicle V. The autonomous driving control device 3 controls the autonomous vehicle V to travel automatically using a well-known method based on information from various sensors, etc. Here, the autonomous driving control device 3 sets a travel route in advance and controls the steering, etc. of the autonomous vehicle V so that the autonomous vehicle V travels along the set travel route. In this case, the autonomous driving control device 3 sets a target vehicle speed in advance and controls the engine and other drive sources and the brakes, etc. to achieve the set target vehicle speed. In other words, the autonomous vehicle V is a vehicle that controls its vehicle speed to achieve the target vehicle speed.

In addition, in this embodiment, the autonomous vehicle V is provided with a gradient sensor 4. The gradient sensor 4 is a sensor for detecting the gradient of the road surface on which the autonomous vehicle V is traveling. As the gradient sensor 4, for example, an IMU (Inertial Measurement Unit) can be used.

In this embodiment, the autonomous driving control device 3 calculates the acceleration due to the running resistance of the autonomous driving vehicle V (hereinafter referred to as "running resistance acceleration"). The running resistance acceleration here refers to the fluctuation in speed caused by running resistance. In other words, the calculation of the running resistance acceleration does not take into account the power of the drive source of the autonomous driving vehicle V, such as an engine.

Here, the autonomous driving control device 3 calculates the running resistance of the autonomous driving vehicle V based on the gradient of the road surface detected by the gradient sensor 4. Furthermore, the autonomous driving control device 3 can calculate the running resistance by taking into account the weight of the autonomous driving vehicle V, the mu of the road surface, rolling resistance, air resistance, and the like, in addition to the gradient. Then, the autonomous driving control device 3 calculates the running resistance acceleration due to the running resistance of the autonomous driving vehicle V based on the calculated running resistance.

The autonomous driving control device 3 may use the calculated running resistance and/or running resistance acceleration to control autonomous driving. The autonomous driving control device 3 also transmits the autonomous driving state of the autonomous driving vehicle V, the calculated running resistance acceleration, and the target speed to the shift control device 1.

Based on the autonomous driving state of the autonomous vehicle V transmitted from the autonomous driving control device 3, the gear change control device 1 controls the shift change of the automatic transmission 2 so that the vehicle travels at the target vehicle speed transmitted from the autonomous driving control device 3. In this embodiment, the gear change control device 1 selects the gear of the automatic transmission 2 and performs the shift change while taking into account the running resistance acceleration transmitted from the autonomous driving control device 3.

More specifically, the gear shift control device 1 includes a gear shift control ECU (Electronic Control Unit) 10. The gear shift control ECU 10 is an electronic control unit having a CPU [Central Processing Unit], a ROM [Read Only Memory], a RAM [Random Access Memory], etc. In the gear shift control ECU 10, various functions are realized, for example, by the CPU executing a program recorded in the ROM or RAM. The gear shift control ECU 10 may be composed of multiple electronic units.

The gear shift control ECU 10 functionally comprises an acceleration acquisition unit 11, a vehicle speed estimation unit 12, a gear selection unit 13, and a shift control unit 14.

The acceleration acquisition unit 11 acquires the running resistance acceleration due to the running resistance of the autonomous vehicle. In this embodiment, the acceleration acquisition unit 11 acquires the running resistance acceleration transmitted from the autonomous driving control device 3 as the running resistance acceleration. As described above, the autonomous driving control device 3 calculates the running resistance of the autonomous driving vehicle V based on the gradient amount of the road surface on which the autonomous driving vehicle V is running detected by the gradient sensor 4, and calculates the running resistance acceleration. In other words, the acceleration acquisition unit 11 acquires the running resistance acceleration due to the running resistance including the gradient amount of the road surface on which the autonomous driving vehicle V is running.

The acceleration acquisition unit 11 may acquire the running resistance acceleration by calculating the running resistance acceleration based on the gradient amount detected by the gradient sensor 4 in a manner similar to the way in which the automatic driving control device 3 calculates the running resistance acceleration.

The vehicle speed estimation unit 12 estimates the post-shift-change vehicle speed, which is the vehicle speed at the time of completion of the shift change, based on the running resistance acceleration acquired by the acceleration acquisition unit 11 and the shift change time required to change to the gear stage that is the candidate for the shift change. The shift change time is the time from the start of the shift change (disengagement of the clutch of the automatic transmission 2) to the end of the shift change (engagement of the clutch of the automatic transmission 2).

Here, the automatic transmission 2 in this embodiment is not limited to shifting one gear at a time from the current gear, but can shift from the current gear to a gear that is two or more gears different. One example of an automatic transmission 2 that performs such shifting is an automatic transmission for a large vehicle that has multiple gears.

The vehicle speed estimation unit 12 prestores, for each gear stage of the automatic transmission 2, the shift change time required to shift to a gear stage that is one stage or two or more stages different, for each gear stage after the shift change. This shift change time differs depending on the mechanism of the automatic transmission 2. For example, the shift change time differs between shifting from the current gear stage to a gear stage that is one stage different from that of shifting from the current gear stage to a gear stage that is two stages different.

The vehicle speed estimation unit 12 estimates the post-shift-change vehicle speed when the current gear stage of the automatic transmission 2 is shifted to each of the candidate gear stages as the post-shift-change vehicle speed. The vehicle speed estimation unit 12 can determine the candidate gear stages by various well-known methods. The vehicle speed estimation unit 12 can determine multiple gear stages as candidate gear stages.

Here, the vehicle speed estimation unit 12 estimates a change in vehicle speed due to running resistance during a shift change based on the running resistance acceleration and the shift change time when shifting to each gear stage that is a shift candidate. Then, the vehicle speed estimation unit 12 estimates a post-shift vehicle speed for each of the gear stages that are shift candidates based on the estimated change in vehicle speed and the current vehicle speed (vehicle speed before the shift change). Specifically, as an example, the vehicle speed estimation unit 12 can estimate the post-shift vehicle speed for each of the gear stages that are shift candidates using the following formula:
Post-shift vehicle speed = current vehicle speed + (driving resistance acceleration x shift change time)

The gear stage selection unit 13 selects a gear stage after the shift change based on the appropriate vehicle speed set for the gear stage of the candidate shift and the post-shift vehicle speed for each of the candidate gear stages estimated by the vehicle speed estimation unit 12. Here, when the autonomous vehicle V is under autonomous driving control, the gear stage selection unit 13 selects a gear stage after the shift change such that the post-shift vehicle speed is within the appropriate vehicle speed for the gear stage of the candidate shift and the vehicle speed of the autonomous vehicle V does not exceed the target vehicle speed for autonomous driving. The gear stage selection unit 13 stores the appropriate vehicle speed set for the gear stage in advance for each gear stage of the automatic transmission 2. A predetermined speed range is set as this appropriate vehicle speed.

For example, suppose the current gear is third, and fourth and fifth gears have been determined as candidate gears for shifting. Also, suppose the post-shift vehicle speed when shifting from the current gear to fourth gear is within the appropriate vehicle speed for fourth gear. Suppose the post-shift vehicle speed when shifting from the current gear to fifth gear is within the appropriate vehicle speed for fifth gear. In this case, both fourth and fifth gears meet the condition that the post-shift vehicle speed is within the appropriate vehicle speed.

For example, suppose that the vehicle speed after the shift change when the gear is shifted to the fourth gear does not exceed the target vehicle speed, and the vehicle speed after the shift change when the gear is shifted to the fifth gear exceeds the target vehicle speed. In this case, the gear selection unit 13 selects the fourth gear, in which the vehicle speed after the shift change does not exceed the target vehicle speed, as the gear after the shift change.

In addition, when there are multiple gears that are candidates for shifting and there are multiple gears that will result in a post-shift vehicle speed within the appropriate vehicle speed, the gear selection unit 13 selects the gear with the smallest gear ratio. Note that, if there is no gear that meets the above-mentioned conditions among the gears that are candidates for shifting, the gear selection unit 13 determines not to perform a shift change and maintains the current selection of the gear.

When the autonomous vehicle V is being manually driven, the gear selection unit 13 can select the gear in the same way as in the case of autonomous driving, except for the above-mentioned condition that "the vehicle speed of the autonomous vehicle V does not exceed the target vehicle speed for autonomous driving."

The shift control unit 14 controls the shift change of the automatic transmission 2 so that the gear stage selected by the gear stage selection unit 13 is achieved.

Next, the flow of the shift change process performed in the gear shift control device 1 will be described using the flowchart in FIG. 2. The process shown in FIG. 2 is executed when the gear shift control device 1 determines that a shift change is necessary. As shown in FIG. 2, the acceleration acquisition unit 11 acquires the running resistance acceleration from the automatic driving control device 3 (S101). The vehicle speed estimation unit 12 estimates the post-shift change vehicle speed for each gear stage that is a candidate for shifting (S102). The gear stage selection unit 13 determines whether there is a gear stage in which the post-shift change vehicle speed is within the appropriate vehicle speed based on the appropriate vehicle speed set for the gear stage that is a candidate for shifting and the estimated post-shift change vehicle speed (S103).

If there is no gear stage where the post-shift change vehicle speed is within the appropriate vehicle speed (S103: NO), the gear change control device 1 performs processing again from S101. If there is a gear stage where the post-shift change vehicle speed is within the appropriate vehicle speed (S103: YES), the gear stage selection unit 13 determines whether the autonomous vehicle V is currently under autonomous driving control (traveling by autonomous driving) (S104).

When automatic driving control is in progress (S104: YES), the gear selection unit 13 determines whether or not there is a gear stage in which the post-shift-change vehicle speed is within the appropriate vehicle speed and in which the post-shift-change vehicle speed does not exceed the target vehicle speed (S105). If there is a gear stage in which the post-shift-change vehicle speed does not exceed the target vehicle speed (S105: YES), the gear selection unit 13 selects the gear stage with the smallest gear ratio (S106). Note that, if there is one gear stage in which the post-shift-change vehicle speed does not exceed the target vehicle speed, the gear selection unit 13 selects this gear stage. The shift control unit 14 controls the shift change of the automatic transmission 2 so that the gear stage selected by the gear selection unit 13 is selected (S107).

When the autonomous vehicle V is being manually driven, the target vehicle speed for autonomous driving is not set. When the autonomous vehicle V is being manually driven, the gear shift control device 1 performs shift change control except for the condition that the target vehicle speed is not exceeded (S105). In other words, when the autonomous vehicle V is not being automatically driven (S104: NO), the gear shift control device 1 selects a gear in the processing of S106 described above, and performs shift change control in the processing of S107. In this way, the gear shift control device 1 can perform shift change control according to the driving state, whether the autonomous vehicle V is being manually driven or automatically driven.

On the other hand, if there is no gear where the post-shift vehicle speed does not exceed the target vehicle speed (S105: NO), the shift control unit 14 does not shift the automatic transmission 2. In other words, the shift control unit 14 maintains the current gear.

As described above, the gear change control device 1 estimates the post-shift vehicle speed for the gear stage that is a candidate for shifting based on the running resistance acceleration and the shift change time. Then, using the estimated post-shift vehicle speed, the gear stage after the shift change is selected so that the post-shift vehicle speed is within the appropriate vehicle speed for the candidate gear stage and does not exceed the target vehicle speed. In other words, even if the vehicle speed of the autonomously driven vehicle V changes due to running resistance when the clutch of the automatic transmission 2 is released during a shift change, a gear stage that corresponds to this change in vehicle speed can be selected. This allows the gear change control device 1 to appropriately change the shift of the automatic transmission 2 and allow the autonomously driven vehicle V to travel stably.

When there are multiple gears that are candidates for shifting and that result in a post-shift vehicle speed within the appropriate vehicle speed, the gear selection unit 13 selects the gear with the smallest gear ratio. In this case, the rotation speed of the drive source of the autonomous vehicle V can be reduced. This allows the gear shift control device 1 to improve fuel efficiency, for example, when the drive source of the autonomous vehicle V is an engine, and electricity efficiency, for example, when the drive source is an electric motor.

The acceleration acquisition unit 11 acquires the running resistance acceleration due to running resistance, including the gradient of the road surface on which the autonomous vehicle V is running, from the autonomous driving control device 3. In this case, the gear change control device 1 can appropriately select the gear stage based on the running resistance that takes into account the gradient of the road surface on which the autonomous vehicle V is running.

Although the embodiment of the present invention has been described above, the present invention is not limited to the above embodiment. For example, the gear shift control device 1 is not limited to controlling the shift change of the automatic transmission 2 mounted on an autonomous vehicle V. For example, instead of the autonomous vehicle V, the gear shift control device 1 may control the shift change of an automatic transmission mounted on a vehicle (autonomous vehicle) equipped with an ACC (Auto Cruise Control) function that controls the vehicle speed to a target vehicle speed.

1... gear shift control device, 2... automatic transmission, 11... acceleration acquisition unit, 12... vehicle speed estimation unit, 13... gear selection unit, V... autonomous vehicle (autonomous driving vehicle).

Claims (3)

A shift control device for an automatic transmission mounted on an autonomous vehicle that controls a vehicle speed to a target vehicle speed,
an acceleration acquisition unit that acquires a running resistance acceleration due to a running resistance of the autonomous vehicle;
a vehicle speed estimation unit that estimates a post-shift-change vehicle speed, which is the vehicle speed at a time point when the shift change is completed, based on the acquired running resistance acceleration and a shift change time required to change to a gear stage that is a candidate for the shift change;
and a gear stage selection unit that selects a post-shift-change gear stage based on an appropriate vehicle speed set for the candidate gear stage and the estimated post-shift-change vehicle speed, such that the post-shift-change vehicle speed is within the appropriate vehicle speed for the candidate gear stage and the vehicle speed of the autonomous vehicle does not exceed the target vehicle speed. The gear shift control device according to claim 1, wherein the gear selection unit selects the gear with the smallest gear ratio when there are multiple gears that are the candidate for the shift and the vehicle speed after the shift change is within the appropriate vehicle speed. The gear shift control device according to claim 1 or 2, wherein the acceleration acquisition unit acquires the running resistance acceleration due to the running resistance including the gradient of the road surface on which the autonomous vehicle is running.

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