Gear shift control device

Abstract

To appropriately change shifts of an automatic transmission, to make a vehicle run stably.SOLUTION: A shift controller 1 comprises: an acceleration acquisition unit 11 that acquires a running resistance acceleration due to a running resistance of a self-driving vehicle V; a vehicle speed estimation unit 12 that estimates a vehicle speed after shift change based on the running resistance acceleration and a shift change time required to shift to a gear stage that is a shift candidate; and a gear stage selection unit 13 that selects a gear stage after the shift change so that the vehicle speed after the shift change is within an appropriate vehicle speed of the gear stage of the shift candidate and the vehicle speed of the self-driving vehicle does not exceed a target vehicle speed, based on the appropriate vehicle speed set for the gear stage of the shift candidate and the vehicle speed after the shift change.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a gear shift control device for controlling an automatic transmission of a vehicle. [Background technology]

[0002] For example, Patent Document 1 describes a vehicle that automatically controls the vehicle speed to a predetermined target speed. Patent Document 1 also describes how to prevent the vehicle from stalling by determining the gear stage based on the gradient of the driving section ahead and changing the gear stage in advance. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2018-194048 A Summary of the Invention [Problem to be solved by the invention]

[0004] 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, and the vehicle may stall unintentionally on an uphill road when the clutch is released, or may accelerate unintentionally on a downhill road. For this reason, if these changes in vehicle speed are not taken into consideration, the automatic transmission may not be able to change gears appropriately, and the vehicle may not be able to run stably.

[0005] SUMMARY OF THE PRESENT DISCLOSURE In view of the above, an object of the present invention is to provide a gear change control device that is capable of appropriately performing shift changes in an automatic transmission and allowing a vehicle to run stably. [Means for solving the problem]

[0006] The present invention is a gear change control device for an automatic transmission mounted on an autonomous vehicle that controls 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 the shift change is completed, based on the acquired running resistance acceleration and the shift change time required when shifting to a candidate gear stage, and a gear stage selection unit that selects a gear stage after the shift change, 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.

[0007] In this gear change control device, a post-shift vehicle speed for a 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, a gear stage after the shift change is selected so that the post-shift vehicle speed is within an 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 according to the 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.

[0008] In the shift control device, when there are multiple candidate gears 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 efficiency can be improved when the drive source is an engine, or electricity efficiency can be improved when the drive source is an electric motor.

[0009] 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 traveling. In this case, the gear shift control device can appropriately select a gear based on the running resistance that takes into account the gradient of the road surface on which the autonomous vehicle is traveling. Effect of the Invention

[0010] According to the present invention, the shift change of the automatic transmission can be appropriately performed, and the vehicle can be driven stably. [Brief description of the drawings]

[0011] [Figure 1] FIG. 1 is a block diagram showing a schematic configuration of an autonomous driving vehicle equipped with a gear change control device. [Diagram 2] FIG. 2 is a flowchart showing the flow of the shift change process performed by the gear change control device. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0012] Hereinafter, an embodiment of the present invention will be described with reference to the drawings.

[0013] As shown in Fig. 1, a gear change control device 1 according to this embodiment is mounted on an autonomous vehicle (autonomous driving vehicle) V that is capable of switching between autonomous driving and manual driving by a driver. The autonomous driving vehicle V drives autonomously along a preset driving route. The gear change control device 1 controls shift changes of an automatic transmission 2 mounted on the autonomous driving vehicle V.

[0014] 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 performs control for automatically driving the autonomous vehicle V by a well-known method based on information from various sensors and the like. Here, the autonomous driving control device 3 sets a driving route in advance and controls the steering of the autonomous vehicle V so that the autonomous vehicle V drives along the set driving route. At that time, the autonomous driving control device 3 sets a target vehicle speed in advance and controls a drive source such as an engine and brakes so as to achieve the set target vehicle speed. In other words, the autonomous vehicle V is a vehicle whose vehicle speed is controlled to achieve the target vehicle speed.

[0015] 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 travels. As the gradient sensor 4, for example, an IMU (Inertial Measurement Unit) can be used.

[0016] In this embodiment, the automatic driving control device 3 calculates the acceleration due to the running resistance of the automatic driving vehicle V (hereinafter referred to as "running resistance acceleration"). The running resistance acceleration here is 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 automatic driving vehicle V, such as an engine.

[0017] Here, 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 detected by the gradient sensor 4. Furthermore, the autonomous driving control device 3 can calculate the running resistance by taking into consideration the weight of the autonomous driving vehicle V, the mu of the road surface, rolling resistance, air resistance, etc., in addition to the gradient amount. 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.

[0018] The automatic driving control device 3 may use the calculated running resistance and / or running resistance acceleration for controlling automatic driving. In addition, the automatic driving control device 3 transmits the automatic driving state of the automatically driving vehicle V, the calculated running resistance acceleration, and the target speed to the gear change control device 1.

[0019] The gear change control device 1 controls the shift change of the automatic transmission 2 so that the vehicle travels at a target vehicle speed transmitted from the automatic driving control device 3, based on the automatic driving state of the automatically driven vehicle V transmitted from the automatic driving control device 3. Furthermore, in this embodiment, the gear change control device 1 selects a gear stage of the automatic transmission 2 and performs a shift change, taking into account the running resistance acceleration transmitted from the automatic driving control device 3.

[0020] 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), and the like. In the gear shift control ECU 10, various functions are realized, for example, by the CPU executing a program recorded in the ROM or the RAM. The gear shift control ECU 10 may be composed of multiple electronic units.

[0021] 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.

[0022] 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.

[0023] In addition, 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, etc., in a manner similar to the way in which the automatic driving control device 3 calculates the running resistance acceleration.

[0024] The vehicle speed estimation unit 12 estimates a 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 a gear stage that is a candidate for 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).

[0025] 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 from the current gear. An example of an automatic transmission 2 that performs such a shift change is an automatic transmission for a large vehicle having multiple gears.

[0026] 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 different by one stage and two or more stages after the shift change. This shift change time differs depending on the mechanism of the automatic transmission 2. For example, the shift change time required for shifting from the current gear stage to a gear stage that is different by one stage differs from the shift change time required for shifting from the current gear stage to a gear stage that is different by two stages.

[0027] The vehicle speed estimation unit 12 estimates the post-shift-change vehicle speed when the vehicle is shifted from the current gear stage of the automatic transmission 2 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 candidate gear stages.

[0028] 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 change candidate. Then, the vehicle speed estimation unit 12 estimates a post-shift vehicle speed for each of the gear stages that are shift change candidates based on the estimated vehicle speed change 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 change candidates using the following formula: Vehicle speed after shift change = current vehicle speed + (driving resistance acceleration x shift change time)

[0029] 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 shift candidate and the post-shift change vehicle speed for each of the gear stages that are the shift candidate estimated by the vehicle speed estimation unit 12. Here, when the autonomously driven 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 change vehicle speed is within the appropriate vehicle speed for the gear stage of the shift candidate and the vehicle speed of the autonomously driven vehicle V does not exceed the target vehicle speed of the 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.

[0030] For example, assume that the current gear is third and that fourth and fifth gears have been determined as candidate gears for shifting. Also assume that the post-shift vehicle speed when the current gear is shifted to the fourth gear is within the appropriate vehicle speed for the fourth gear. Assume that the post-shift vehicle speed when the current gear is shifted to the fifth gear is within the appropriate vehicle speed for the fifth gear. In this case, both the fourth and fifth gears meet the condition that the post-shift vehicle speed is within the appropriate vehicle speed.

[0031] For example, assume that the vehicle speed after the shift change to the fourth gear does not exceed the target vehicle speed, and the vehicle speed after the shift change 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.

[0032] Furthermore, when there are multiple candidate gears for shifting and multiple candidate gears for shifting at which the post-shift vehicle speed is within the appropriate vehicle speed, the gear selection unit 13 selects the gear with the smallest gear ratio. Note that, when there is no candidate gear that meets the above-mentioned conditions among the candidate gears for shifting, the gear selection unit 13 determines not to perform a shift change and maintains the selection of the current gear.

[0033] In addition, when the autonomously driven 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 autonomously driven vehicle V does not exceed the target vehicle speed for autonomous driving."

[0034] The shift control unit 14 controls the shift change of the automatic transmission 2 so as to achieve the gear stage selected by the gear stage selection unit 13.

[0035] Next, the flow of the shift change process performed in the gear shift control device 1 will be described with reference to the flowchart of 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 shift candidate (S102). The gear stage 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 based on the appropriate vehicle speed set for the gear stage that is a shift candidate and the estimated post-shift change vehicle speed (S103).

[0036] 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 the process 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).

[0037] When automatic driving control is in progress (S104: YES), the gear stage 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 stage 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 stage 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 stage selection unit 13 is selected (S107).

[0038] It should be noted that 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 under autonomous driving control (S104: NO), the gear shift control device 1 selects a gear in the process of S106 described above, and performs shift change control in the process 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 autonomously driven.

[0039] 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 perform a shift change of the automatic transmission 2. In other words, the shift control unit 14 maintains the current gear.

[0040] As described above, in the gear change control device 1, 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 automatically driven vehicle V changes due to running resistance when the clutch of the automatic transmission 2 is released during the shift change, the gear stage according to the change in vehicle speed can be selected. As a result, the gear change control device 1 can appropriately perform the shift change of the automatic transmission 2 and allow the automatically driven vehicle V to travel stably.

[0041] When there are multiple gear stages as candidate shift stages at which the post-shift vehicle speed is within the appropriate vehicle speed, the gear stage selection unit 13 selects the gear stage with the smallest gear ratio. In this case, the rotation speed of the drive source of the autonomously driven vehicle V can be reduced. This allows the gear change control device 1 to improve fuel efficiency, for example, when the drive source of the autonomously driven vehicle V is an engine, and improve electricity efficiency, for example, when the drive source is an electric motor.

[0042] The acceleration acquisition unit 11 acquires, from the automatic driving control device 3, running resistance acceleration due to running resistance including the gradient amount of the road surface on which the automatic driving vehicle V is running. In this case, the gear change control device 1 can appropriately select a gear stage based on the running resistance that takes into account the gradient amount of the road surface on which the automatic driving vehicle V is running.

[0043] Although the embodiments of the present invention have been described above, the present invention is not limited to the above-mentioned embodiments. For example, the shift control device 1 is not limited to controlling the shift change of the automatic transmission 2 mounted on the autonomous vehicle V. For example, instead of the autonomous vehicle V, the shift control device 1 may control the shift change of the automatic transmission mounted on a vehicle (autonomous vehicle) equipped with an ACC (Auto Cruise Control) function that controls the vehicle speed so as to reach a target vehicle speed. [Explanation of symbols]

[0044] 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

1. 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.

2. 2. The shift control device according to claim 1, wherein when there are a plurality of gear stages that are the candidate shift stages and when there are a plurality of the candidate shift stages that cause the post-shift change vehicle speed to be within the appropriate vehicle speed, the gear stage selection unit selects a gear stage with the smallest gear ratio.

3. The gear shift control device according to claim 1 , wherein the acceleration acquisition unit acquires the running resistance acceleration due to the running resistance including a gradient amount of a road surface on which the autonomous vehicle is running.

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