Shift control device, shift control method, and shift control computer program

Abstract

A variable speed control device, a variable speed control method, and a computer program for variable speed control. The variable speed control device includes: a timing setting unit (31) that sets an acceleration / deceleration start timing for starting acceleration or deceleration of the vehicle based on at least one of a sensor signal indicating the situation around the vehicle (1), the current position of the vehicle, a map including information related to the road on which the vehicle is traveling, and the operation of the vehicle by the driver; and a control unit (32) that controls the power transmission system (4) such that the gear ratio of the second transmission (15) of the power transmission system having two motors (12, 13) and an engine (11) is reduced before the acceleration / deceleration start timing, and changes the first and second gear ratios of the first transmission (14) that can continuously change the first gear ratio between one motor and the engine and the second gear ratio between the other motor and the engine in a manner that keeps the engine speed constant.

Description

Technical Field

[0001] The present invention relates to a transmission control device, a transmission control method, and a computer program for transmission control that control the shift of a vehicle. Background Art

[0002] As a power transmission system of a vehicle, a so-called hybrid power transmission system including an internal combustion engine such as a motor and an engine is used. In such a hybrid power transmission system, a technique for improving the acceleration responsiveness of the vehicle has been proposed (see Japanese Patent Application Laid-Open No. 2010-183733 and International Publication No. 2020 / 008873).

[0003] The control device for an electric vehicle disclosed in Japanese Patent Application Laid-Open No. 2010-183733 predicts a vehicle deceleration situation based on at least one of a driving environment and information related to vehicle operation. When deceleration is predicted, the gear ratio of the transmission is reduced before the start of vehicle deceleration. Further, during the period from the start of the reduction of the gear ratio to the start of vehicle deceleration, the control device performs rotational speed control of the motor of the drive source to maintain the vehicle speed, and during vehicle deceleration, drives a generator connected to the drive wheels via the transmission to recover regenerative energy.

[0004] In addition, the vehicle control device disclosed in International Publication No. 2020 / 008873 determines the presence or absence of an acceleration limit, and restricts an increase in the gear ratio when it is determined that there is an acceleration limit. Summary of the Invention

[0005] In the above technologies, the rotational speed of the engine increases as the gear position of the transmission is reduced. As a result, power exceeding the power desired by the driver is generated in the power transmission system, which may cause discomfort to the driver. Further, the efficiency of the engine may decrease due to an increase in the rotational speed of the engine, deteriorating fuel economy.

[0006] Therefore, an object of the present invention is to provide a transmission control device that suppresses "discomfort to the driver of the vehicle during acceleration and deceleration".

[0007] According to an embodiment, a shift control device for a power transmission system is provided. The power transmission system is mounted on a vehicle and includes a first transmission and a second transmission. The first transmission can continuously change a first gear ratio and a second gear ratio in such a manner that the ratio of the second gear ratio to the first gear ratio is constant. The first gear ratio is the gear ratio between one of two motors and an engine, and the second gear ratio is the gear ratio between the other of the two motors and the engine. The second transmission can set the gear position between one of the two motors and the drive wheels to any one of a predetermined number of gear positions with different gear ratios. The shift control device has a timing setting unit and a control unit. The timing setting unit sets the acceleration / deceleration start timing for starting the acceleration or deceleration of the vehicle based on at least one of a sensor signal indicating the condition around the vehicle, the current position of the vehicle, a map including information related to the road on which the vehicle is traveling, and the operation of the driver on the vehicle. The control unit controls the power transmission system such that the second transmission downshifts before the acceleration / deceleration start timing, and changes the first gear ratio and the second gear ratio of the first transmission in such a manner as to keep the engine speed constant.

[0008] In this shift control device, preferably, the timing setting unit predicts the time from when a control device for controlling the driving of the vehicle recommends overtaking another vehicle traveling ahead of the vehicle until the driver performs an operation to approve the recommendation, based on the elapsed time from when the overtaking recommendation was made until the approval operation was performed in the past. The timing setting unit sets the timing for starting the acceleration of the vehicle as the acceleration / deceleration start timing based on the predicted time.

[0009] In this case, preferably, the timing setting unit sets the timing after the following time has elapsed from the overtaking recommendation as the acceleration / deceleration start timing. The elapsed time is obtained by adding the predicted time required to confirm that overtaking of the other vehicle can start to the predicted time from when the overtaking recommendation was made until the driver performs the approval operation.

[0010] Alternatively, preferably, the timing setting unit sets the timing for starting the deceleration of the vehicle as the acceleration / deceleration start timing based on at least one of the speed of the vehicle and the radius of curvature of the next curve in the traveling direction of the vehicle, and the distance from the vehicle to the next curve.

[0011] Alternatively, more preferably, the timing setting unit sets the timing for starting the deceleration of the vehicle as the acceleration / deceleration start timing based on at least one of the speed of the vehicle and the allowable driving speed of the vehicle at the deceleration required location where deceleration is required in the traveling direction of the vehicle, and the distance from the vehicle to the deceleration required location.

[0012] According to another embodiment, there is provided a shift control method for a power transmission system mounted on a vehicle, the power transmission system having a first transmission and a second transmission. The first transmission is capable of continuously changing a first gear ratio and a second gear ratio in such a manner that the ratio of the second gear ratio to the first gear ratio is constant. The first gear ratio is the gear ratio between one of two motors and an engine, and the second gear ratio is the gear ratio between the other of the two motors and the engine. The second transmission is capable of setting the gear position between one of the two motors and the drive wheels to any one of a predetermined number of gear positions having different gear ratios from each other. The shift control method includes: setting an acceleration / deceleration start timing for starting acceleration or deceleration of the vehicle based on at least one of a sensor signal indicating the condition around the vehicle, the current position of the vehicle, a map including information related to the road on which the vehicle is traveling, and the operation of the vehicle by the driver; and controlling the power transmission system such that downshifting of the second transmission is performed before the acceleration / deceleration start timing, and the first gear ratio and the second gear ratio of the first transmission are changed in such a manner that the engine speed is kept constant.

[0013] According to yet another embodiment, there is provided a computer program for shift control of a power transmission system mounted on a vehicle, the power transmission system having a first transmission and a second transmission. The first transmission is capable of continuously changing a first gear ratio and a second gear ratio in such a manner that the ratio of the second gear ratio to the first gear ratio is constant. The first gear ratio is the gear ratio between one of two motors and an engine, and the second gear ratio is the gear ratio between the other of the two motors and the engine. The second transmission is capable of setting the gear position between one of the two motors and the drive wheels to any one of a predetermined number of gear positions having different gear ratios from each other. The computer program for shift control includes commands for causing a processor mounted on the vehicle to execute the following processing: setting an acceleration / deceleration start timing for starting acceleration or deceleration of the vehicle based on at least one of a sensor signal indicating the condition around the vehicle, the current position of the vehicle, a map including information related to the road on which the vehicle is traveling, and the operation of the vehicle by the driver; and controlling the power transmission system such that downshifting of the second transmission is performed before the acceleration / deceleration start timing, and the first gear ratio and the second gear ratio of the first transmission are changed in such a manner that the engine speed is kept constant.

[0014] The shift control device of the present disclosure achieves the effect of being able to suppress the situation of "causing discomfort to the driver of the vehicle during acceleration and deceleration". BRIEF DESCRIPTION OF THE DRAWINGS

[0015] Figure 1 is a schematic configuration diagram of a vehicle control system including a shift control device and a power transmission system.

[0016] Figure 2 It is a schematic configuration diagram of a power transmission system.

[0017] Figure 3 It is a hardware configuration diagram of an electronic control device as an embodiment of a shift control device.

[0018] Figure 4 It is a functional block diagram of a processor of an electronic control device related to shift control processing.

[0019] Figure 5 It is an explanatory diagram of the rotational speed of a drive wheel, the rotational speed of an engine, and the "relationship between the rotational speeds of the two motors" of the two motors when the automatic transmission downshifts.

[0020] Figure 6 It is a time chart showing the relationship between the deceleration control of the vehicle of the present embodiment and the comparative example and the execution timing of downshifting.

[0021] Figure 7 It is a time chart showing the relationship between the acceleration control of the vehicle of the present embodiment and the comparative example and the execution timing of downshifting.

[0022] Figure 8 It is a flowchart of the operation of shift control processing. Detailed Embodiment

[0023] Hereinafter, a shift control device, a shift control method executed on the shift control device, and a computer program for shift control will be described with reference to the accompanying drawings. The shift control device controls shifting in a power transmission system having two motors and an engine. The shift control device sets an acceleration / deceleration start timing for starting acceleration or deceleration of the vehicle based on at least one of a sensor signal indicating the surrounding conditions of the vehicle, the current position of the vehicle, a map including information related to the road on which the vehicle is traveling, and the operation of the vehicle by the driver. Further, the shift control device performs a downshift of a second transmission before the acceleration / deceleration start timing, and the second transmission can set the gear ratio between one of the two motors and the drive wheel to any one of a predetermined number of gear ratios with different gear ratios. Moreover, the shift control device controls the power transmission system so as to keep the rotational speed of the engine constant.

[0024] Figure 1 It is a schematic configuration diagram of a vehicle control system including a shift control device and a power transmission system. In addition, Figure 2It is a schematic configuration diagram of a power transmission system. In the present embodiment, a vehicle control system mounted on a vehicle 1 and controlling the vehicle 1 includes a camera (imaging device) 2, a GPS receiver 3, a power transmission system 4, and an electronic control unit (ECU) 5 as an example of a shift control device. The camera 2 and the GPS receiver 3 are communicably connected to the ECU 5 via an in-vehicle network conforming to a specification such as Controller Area Network. In addition, the vehicle control system may further include a ranging sensor (not shown), such as a LiDAR (Light Detection and Ranging) or a radar, that measures the distance from the vehicle 1 to an object existing around the vehicle 1. Further, the vehicle control system may also include a wireless communication terminal (not shown) for wireless communication with devices outside the vehicle 1 and a navigation device (not shown) for setting a planned travel route of the vehicle 1.

[0025] The camera 2 is an example of a sensor that generates a sensor signal representing the surroundings of the vehicle 1, and includes a two-dimensional detector composed of an array of photoelectric conversion elements sensitive to visible light, such as a CCD or a C-MOS, and an imaging optical system that forms an image of an area to be photographed on the two-dimensional detector. The camera 2 is mounted, for example, in the passenger compartment of the vehicle 1 so as to face the front of the vehicle 1. The camera 2 photographs the front area of the vehicle 1 at a predetermined photographing cycle (for example, 1 / 30 second to 1 / 10 second), and generates an image reflected by the front area. The image obtained by the camera 2 is an example of a sensor signal. In addition, a plurality of cameras having different photographing directions or focal lengths may be provided on the vehicle 1.

[0026] Whenever the camera 2 generates an image, it outputs the generated image to the ECU 5 via the in-vehicle network.

[0027] The GPS receiver 3 receives GPS signals from GPS satellites at a predetermined cycle, and measures (locates) the own position of the vehicle 1 based on the received GPS signals. The GPS receiver 3 outputs positioning information representing the positioning result of the own position of the vehicle 1 based on the GPS signals to the ECU 5 via the in-vehicle network at a predetermined cycle. In addition, instead of the GPS receiver, the vehicle 1 may have a receiver that receives positioning signals from satellites of other satellite positioning systems to measure the own position of the vehicle 1.

[0028] The power transmission system 4 has an internal combustion engine type engine 11 and two motors 12, 13 as power sources. Among the two motors 12, 13, the motor 13 also operates as a generator for recovering regenerative energy during deceleration of the vehicle 1. The power transmission system 4 also has a continuously variable transmission 14 and an automatic transmission 15 disposed on the power transmission path between the left and right drive wheels 6 of the vehicle 1 and the engine 11. The continuously variable transmission 14 is an example of a first transmission, and the automatic transmission 15 is an example of a second transmission. In addition, the left and right drive wheels 6 of the vehicle 1 can be the rear wheels of the vehicle 1, but are not limited thereto, and the left and right drive wheels 6 of the vehicle 1 can also be the front wheels of the vehicle 1.

[0029] The continuously variable transmission 14 has a planetary gear mechanism as a differential gear mechanism. This planetary gear mechanism has a planet carrier, a sun gear, a ring gear, and pinions in a manner capable of differential rotation. The planet carrier is connected to the crankshaft of the engine 11. The sun gear is connected to the rotating shaft of the motor 12. In addition, the ring gear is disposed outside the sun gear. And, the pinions are connected to the planet carrier, are disposed between the sun gear and the ring gear, and are arranged to engage with the inside of the sun gear and the ring gear. Moreover, the outer periphery of the ring gear is arranged to engage with the gear on the output side of the speed reducer. In addition, the rotating shaft of the motor 13 is connected to the gear on the input side of the speed reducer. With such a configuration, the continuously variable transmission 14 can continuously and steplessly change the differential rotation speed with respect to the rotation speed of the engine 11, that is, the rotation speeds of the motor 12 and the motor 13. That is, the continuously variable transmission 14 can steplessly change the first gear ratio of the rotation speed of the motor 13 with respect to the rotation speed of the engine 11 and the second gear ratio of the rotation speed of the motor 12 with respect to the rotation speed of the engine 11, respectively. And, the continuously variable transmission 14 keeps the ratio of the second gear ratio to the first gear ratio constant. The output torques from the engine 11, the motor 12, and the motor 13 are output to the automatic transmission 15 by the rotation of the rotating shaft (that is, the output shaft of the continuously variable transmission 14) connected to the gear on the output side of the speed reducer of the continuously variable transmission 14.

[0030] The automatic transmission 15 can be a transmission capable of setting the gear ratio between the motor 13 and the drive wheels 6 to any one of a predetermined number of gear positions with different gear ratios from each other. For example, the automatic transmission 15 is configured as a mechanical transmission. And, the automatic transmission 15 selectively operates a hydraulic friction engaging device (not shown), thereby changes the rotation transmitted via the output shaft of the continuously variable transmission 14 to any one of multiple forward gears and a reverse gear of the first gear, and outputs it via the output shaft of the automatic transmission 15. The torque output by the rotation of the output shaft of the automatic transmission 15 is transmitted to the left and right drive wheels 6 of the vehicle 1 via a differential gear (not shown), respectively.

[0031] The ECU 5 controls various parts of the power transmission system 4. The ECU 5 controls the power transmission system based on the driver's required torque corresponding to the depression amount of an accelerator pedal (not shown) and the speed of the vehicle 1. At this time, the ECU 5 controls the amount of fuel supplied to the engine 11, the electric power supplied to the motors 12 and 13, and the gear shift performed by the automatic transmission 15 in a manner that optimizes the fuel economy of the engine 11.

[0032] Moreover, the ECU 5 is communicably connected to an ECU for driving control (not shown) via an in-vehicle network. And the ECU 5, together with the ECU for driving control, sets an acceleration / deceleration start timing for starting the acceleration or deceleration of the vehicle 1 based on at least one of an image from the camera 2, the current position of the vehicle 1, map information, and the operation of the driver on the vehicle 1. And the ECU 5 reduces the gear ratio of the automatic transmission 15 before the acceleration / deceleration start timing. Moreover, the ECU 5 changes the first gear ratio between the motor 13 and the engine 11 and the second gear ratio between the motor 12 and the engine 11 of the continuously variable transmission 14 in a manner that keeps the rotational speed of the engine 11 constant.

[0033] Figure 3 It is a hardware configuration diagram of the ECU 5 as an embodiment of a transmission control device. As Figure 3 shown, the ECU 5 has a communication interface (communication I / F) 21, a memory 22, and a processor 23. The communication interface 21, the memory 22, and the processor 23 can each be configured as separate circuits, or can be integrally formed as one integrated circuit.

[0034] The communication interface 21 has an interface circuit for connecting the ECU 5 to the in-vehicle network. And the communication interface 21 transfers the received image to the processor 23 whenever it receives an image from the camera 2. Additionally, the communication interface 21 transfers the positioning information to the processor 23 whenever it receives positioning information from the GPS receiver 3. Moreover, the communication interface 21 has an interface for connecting to various parts of the power transmission system 4 and an interface for connecting to various sensors such as a vehicle speed sensor for detecting information indicating the behavior of the vehicle 1. And the communication interface 21 receives sensor signals from various sensors and transfers them to the processor 23, and outputs control signals received from the processor 23 for controlling various parts of the power transmission system 4 to the power transmission system 4.

[0035] The memory 22 is an example of a storage unit. For example, it includes a volatile semiconductor memory and a non-volatile semiconductor memory. Also, the memory 22 stores various data used in the speed change control process executed by the processor 23. For example, the memory 22 stores map information including the positions of the entrances and exits of the exclusive motor vehicle lanes, the speed limits of each road section, the positions and radii of curvature of the curves, and other road-related information. In addition, the memory 22 stores various reference tables and historical record information regarding the elapsed time from when the overtaking advice is given until the driver gives approval. Moreover, the memory 22 stores parameters such as the focal length, shooting direction, and installation position of the camera 2, and various parameters of the recognizer used to determine the structure of the road around the vehicle 1. In addition, the memory 22 stores the positioning information of the vehicle 1 and the images around the vehicle 1. In addition, the memory 22 temporarily stores various data generated during the speed change control process.

[0036] The processor 23 has one or more CPUs (Central Processing Unit) and its peripheral circuits. The processor 23 may also have other arithmetic circuits such as a logical arithmetic unit, a numerical arithmetic unit, or a graphics processing unit. And, the processor 23 executes the speed change control process at a predetermined cycle.

[0037] Figure 4 It is a functional block diagram of the processor 23 related to the speed change control process. The processor 23 has a timing setting unit 31 and a control unit 32. Each of the above parts of the processor 23 is, for example, a functional module implemented by a computer program operating on the processor 23. Or, each of the above parts of the processor 23 may also be a dedicated arithmetic circuit provided in the processor 23.

[0038] The timing setting unit 31 sets the acceleration / deceleration start timing based on at least one of the image from the camera 2, the current position of the vehicle 1, the map including information related to the road on which the vehicle 1 is traveling, and the operation of the driver on the vehicle 1. Moreover, the timing setting unit 31 sets the timing that is a predetermined time earlier than the acceleration / deceleration start timing as the shift timing for reducing the gear of the automatic transmission 15 of the power train 4, that is, for performing a downshift.

[0039] For example, when the vehicle 1 approaches a curve or a location where a temporary stop or deceleration of the vehicle 1 is required, such as near the entrance or exit of the exclusive motor vehicle lane, the timing setting unit 31 sets the acceleration / deceleration start timing of the vehicle 1. In this case, the acceleration / deceleration start timing becomes the timing when the vehicle 1 starts to decelerate.

[0040] For example, when the vehicle 1 is approaching a curve, the timing setting unit 31 refers to the current position of the vehicle 1 represented by the latest positioning information and the map information, and determines the curve closest to the current position of the vehicle 1 in the traveling direction of the vehicle 1 (hereinafter, sometimes referred to as the next curve). Further, the timing setting unit 31 determines the radius of curvature of the next curve by referring to the map information. The maximum speed of the vehicle 1 that can travel on the next curve (hereinafter, sometimes referred to as the allowable traveling speed) is determined based on the radius of curvature of the next curve. That is, the smaller the radius of curvature of the next curve, the lower the allowable traveling speed. Further, the timing setting unit 31 compares the current speed of the vehicle 1 indicated by the measurement value obtained by the ECU 5 from a vehicle speed sensor (not shown) with the allowable traveling speed of the next curve. When the current speed of the vehicle 1 is faster than the allowable traveling speed of the next curve, the timing setting unit 31 determines that deceleration is required at the next curve.

[0041] When it is determined that deceleration is required at the next curve, the timing setting unit 31 calculates the distance to the entrance of the next curve by referring to the current position of the vehicle 1 and the map information. Further, the timing setting unit 31 sets the timing at which the distance to the entrance of the next curve becomes a predetermined distance as the acceleration / deceleration start timing. For example, the timing setting unit 31 sets the distance obtained by multiplying the current speed of the vehicle 1 by the deceleration time until the allowable traveling speed is reached as the predetermined distance. The deceleration time is set in such a manner that the deceleration at which the driver does not feel discomfort when the vehicle 1 decelerates can be set, for example, set to about several seconds. Further, an offset time set based on the radius of curvature of the next curve and the current speed of the vehicle 1 may be added to the deceleration time. The timing setting unit 31 may determine the offset time by referring to a reference table stored in advance in the memory 22 indicating the relationship between the offset time, the radius of curvature of the next curve, and the current speed of the vehicle 1. Regarding the offset time, for example, the smaller the radius of curvature of the next curve, or the faster the current speed of the vehicle 1, the longer it is set.

[0042] Moreover, the timing setting unit 31 determines the deceleration for decelerating the vehicle 1 at the acceleration / deceleration start timing. Further, the smaller the radius of curvature of the next curve, or the faster the current speed of the vehicle 1, the larger the speed reduction amplitude as the difference between the current speed and the allowable traveling speed. Therefore, the timing setting unit 31 determines the deceleration by referring to a reference table indicating the relationship between "deceleration" and "the radius of curvature of the next curve and the current speed". Such a reference table is stored in advance in the memory 22.

[0043] Further, the timing setting unit 31 sets the timing for shifting the automatic transmission 15 to be earlier than the acceleration / deceleration start timing by the time required for shifting the automatic transmission 15 (hereinafter sometimes referred to as the shifting time). That is, the shifting timing is set to the timing when the vehicle 1 reaches a position in front of the entrance of the next curve by a distance obtained by adding "the above-mentioned predetermined distance" and "the distance obtained by multiplying the shifting time by the current vehicle speed of the vehicle 1".

[0044] In addition, the timing setting unit 31 may determine to downshift the automatic transmission 15 only when the determined deceleration is greater than a predetermined threshold. The predetermined threshold is set, for example, to a deceleration "at which the motor 13 can obtain the regenerative torque required for recovering regenerative energy".

[0045] In addition, when the vehicle 1 is under autonomous driving control or adaptive cruise control (ACC) is applied to the vehicle 1, the timing setting unit 31 may use the set vehicle speed of the vehicle 1 instead of the current vehicle speed of the vehicle 1 to calculate the predetermined distance and the acceleration / deceleration start timing. Further, the timing setting unit 31 may estimate the radius of curvature of the next curve based on the image acquired by the ECU 5 from the camera 2. In this case, the timing setting unit 31 inputs the image to an identifier that has been previously learned by detecting lane markings, and detects the lane markings from the image. The timing setting unit 31 can use, for example, a deep neural network (DNN) for semantic segmentation such as U-Net as such an identifier. Then, the timing setting unit 31 projects the lane markings on the image into the actual space using parameters such as the mounting position, shooting direction, and focal length of the camera 2, and obtains the radius of curvature of the projected lane markings as the radius of curvature of the next curve.

[0046] Similarly, when the vehicle 1 approaches a location that requires the vehicle 1 to temporarily stop or decelerate, the timing setting unit 31 only needs to set the acceleration / deceleration start timing. Also in this case, the timing setting unit 31 refers to the current position of the vehicle 1 indicated by the latest positioning information and the map information, and determines the location that requires deceleration closest to the current position of the vehicle 1 in the traveling direction of the vehicle 1 and the distance from the current position of the vehicle 1 to this location. Hereinafter, the location that requires the vehicle 1 to temporarily stop or decelerate is sometimes referred to as the target location. The target location can be, for example, a location immediately before the entrance / exit of an exclusive motor vehicle lane where the speed limit is lower than the road on which the vehicle 1 is currently traveling or a location that requires the vehicle 1 to temporarily stop. Then, the timing setting unit 31 sets the timing when the distance to the target location becomes the predetermined distance as the acceleration / deceleration start timing.

[0047] The timing setting unit 31 sets the speed obtained by multiplying the reduced speed limit at the target location by a predetermined ratio (e.g., 0.7 to 0.9) as the allowable driving speed. In addition, when the target location is a location where the vehicle 1 is required to temporarily stop, the timing setting unit 31 sets the allowable driving speed to 0. Also, the timing setting unit 31 can determine the offset time by referring to a reference table indicating the relationship between the allowable driving speed, the current vehicle speed of the vehicle 1, and the offset time. In addition, the timing setting unit 31 can determine the deceleration by referring to a reference table indicating the relationship between the deceleration, the distance to the target location, and the current vehicle speed of the vehicle 1. Such a reference table is pre-stored in the memory 22. Also, in this case as well, the set vehicle speed can be used instead of the current vehicle speed of the vehicle 1.

[0048] In addition, the timing setting unit 31 also sets the acceleration / deceleration start timing when the vehicle 1 overtakes a preceding vehicle traveling ahead of the own vehicle. In this case, the acceleration / deceleration start timing becomes the timing at which the vehicle 1 starts to accelerate.

[0049] For example, when the vehicle 1 is under autonomous driving control, the timing setting unit 31 sets the acceleration / deceleration start timing based on the time point when the ECU (not shown) for driving control of the vehicle 1 gives an overtaking recommendation to the driver via a user interface (not shown) in the vehicle interior. The ECU for driving control detects a preceding vehicle, for example, from a series of time-series images generated by the camera 2 or a series of sensor signals based on the distance measurement sensor, and measures the distance from the vehicle 1 to the detected preceding vehicle. And the ECU for driving control executes an overtaking recommendation when the distance from the vehicle 1 to the preceding vehicle is below a predetermined distance threshold for a predetermined period or more and the speed of the vehicle 1 is below a predetermined speed threshold. In the case of giving an overtaking recommendation, when the driver operates the operation device of the vehicle 1 to approve (agree to) the overtaking recommendation after this overtaking recommendation, and when it is confirmed to be safe by the ECU for driving control through the surrounding monitoring of the vehicle 1 thereafter, the ECU performs control for overtaking. In addition, the operation device can be, for example, an operation switch (not shown) provided on the steering device. Also, through the control for overtaking, the lane change of the vehicle 1 and the acceleration of the vehicle 1 are implemented. Therefore, the timing setting unit 31 calculates the time obtained by adding the predicted time from the overtaking recommendation to the driver's approval of the overtaking recommendation and the predicted time required for the ECU for driving control to confirm that overtaking of the preceding vehicle can start through the surrounding monitoring of the vehicle 1. And the timing setting unit 31 sets the timing after the calculated time has elapsed from the overtaking recommendation as the acceleration / deceleration start timing. And the timing setting unit 31 sets the timing (timing) that is the shift time earlier than this acceleration / deceleration start timing as the shift timing.

[0050] Regarding the prediction time from when an overtaking suggestion is made until the driver approves the overtaking suggestion, learning is performed based on historical record information of the time required for the driver's past approval operations for overtaking suggestions. For example, a correction value obtained by averaging the difference between the time from when an overtaking suggestion is made until the approval operation for each approved overtaking suggestion and a preset standard response time is added to the standard response time to calculate the prediction time until the overtaking suggestion is approved.

[0051] In addition, the prediction time required for surrounding monitoring of Vehicle 1 (hereinafter sometimes referred to as the prediction monitoring time) is prestored in the memory 22. The prediction monitoring time can also be set according to the conditions around Vehicle 1. For example, it is considered that the more the number of other vehicles traveling around Vehicle 1, the longer the time required to be able to perform a lane change. Therefore, it can also be that the more the number of other vehicles traveling around Vehicle 1, the longer the timing setting unit 31 makes the prediction monitoring time. In this case, the timing setting unit 31 inputs the image of the camera 2 to an identifier that has been previously learned in a manner of detecting other vehicles, thereby detecting other vehicles and counting the number of detected other vehicles. The timing setting unit 31 can use, for example, a DNN having a convolutional neural network type architecture such as Single Shot MultiBox Detector or Faster R-CNN as such an identifier. In addition, when Vehicle 1 has a ranging sensor such as a LiDAR sensor, the timing setting unit 31 can detect other vehicles traveling around Vehicle 1 by inputting the ranging signal obtained by the ranging sensor to the identifier. The ranging sensor is another example of a sensor that generates a sensor signal representing the surroundings of Vehicle 1.

[0052] The timing setting unit 31 sets the acceleration based on the current vehicle speed of Vehicle 1 by further referring to a reference table showing the correspondence between the vehicle speed and the acceleration.

[0053] The timing setting unit 31 notifies the control unit 32 of the information determining the start timing and shift timing of the acceleration and deceleration, and the deceleration or acceleration. The information determining the start timing of the acceleration and deceleration can be, for example, information indicating a position corresponding to the start timing of the acceleration and deceleration (the entrance of the next curve or a position a predetermined distance closer to the target point than the target point), or information indicating the time from the current moment until the start timing of the acceleration and deceleration. Similarly, the information determining the shift timing can be information indicating a position corresponding to the shift timing (a position a distance obtained by multiplying the shift time by the current vehicle speed closer to the position corresponding to the start timing of the acceleration and deceleration), or information indicating the time from the current moment until the shift timing.

[0054] The control unit 32 refers to the elapsed time since the shift timing was set or the position of the vehicle 1, and determines whether the notified shift timing has been reached. When the elapsed time reaches the time until the notified shift timing or the position of the vehicle 1 reaches the position corresponding to the notified shift timing, the control unit 32 controls the automatic transmission 15 of the power transmission system 4 to downshift. At this time, the control unit 32 controls the power transmission system 4 so that the rotational speed of the engine 11 is constant. In addition, there are cases where the rotational speed of the engine 11 fluctuates due to external factors or the like, and the rotational speed of the engine 11 may not always be constant. However, even when the fluctuation of the rotational speed of the engine 11 does not completely disappear, the control of the power transmission system 4 that attempts to keep the rotational speed of the engine 11 constant is included in "controlling the power transmission system 4 so as to keep the rotational speed of the engine 11 constant" in the present embodiment.

[0055] As the gear of the automatic transmission 15 is downshifted, the rotational speed of the motor 13 increases. Therefore, the control unit 32 calculates the second gear ratio of the continuously variable transmission 14 after the downshift based on the increased rotational speed of the motor 13 and the rotational speed of the engine 11 immediately before the downshift is to be performed. Further, the control unit 32 calculates the target rotational speed of the motor 12 for keeping the rotational speed of the engine 11 constant based on the ratio between "the calculated second gear ratio" and "the first gear ratio between the rotational speed of the motor 12 and the rotational speed of the engine 11 immediately before the downshift is to be performed". Then, the control unit 32 controls a power supply circuit (not shown) that supplies power to the motor 12 so that the rotational speed of the motor 12 becomes the target rotational speed.

[0056] Figure 5 It is an explanatory diagram of the relationship between the rotational speed of the drive wheel 6, the rotational speed of the engine 11, and the rotational speeds of the motor 12 (MG1) and the motor 13 (MG2) when the automatic transmission 15 downshifts. In Figure 5 the vertical axis represents the rotational speed. In this example, the relationship between the rotational speed of the engine 11, the rotational speeds of the motor 12 and the motor 13, and the rotational speed of the drive wheel 6 when the gear of the automatic transmission 15 is in the third gear is shown by the line 501.

[0057] Here, the relationship between the rotational speed of the engine 11, the rotational speeds of the motors 12 and 13, and the rotational speed of the drive wheels 6 when the rotational speed of the engine 11 is kept constant and the gear of the automatic transmission 15 is downshifted from the third gear to the second gear is shown by the line 502. Along with the downshift of the automatic transmission 15, the rotational speed of the motor 13 increases. In the continuously variable transmission 14, the first gear ratio between the rotational speed of the engine 11 and the rotational speed of the motor 13 and the second gear ratio between the rotational speed of the engine 11 and the rotational speed of the motor 12 are constant. Therefore, according to the first gear ratio between the rotational speed of the engine 11 and the rotational speed of the motor 13 after the downshift of the automatic transmission 15, the rotational speed of the motor 12 is decreased in such a manner that the first gear ratio and the second gear ratio are constant, thereby keeping the rotational speed of the engine 11 constant.

[0058] Moreover, the control unit 32 determines whether the notified acceleration / deceleration start timing has been reached by referring to the elapsed time since the acceleration / deceleration start timing was set or the position of the vehicle 1. And when the elapsed time reaches a time corresponding to the notified acceleration / deceleration start timing, or the position of the vehicle 1 reaches a position corresponding to the notified acceleration / deceleration start timing, the control unit 32 starts the acceleration or deceleration of the vehicle 1. That is, the control unit 32 sets the target rotational speeds of the motors 12 and 13 in such a manner that the vehicle 1 accelerates or decelerates at the notified acceleration / deceleration rate. And the control unit 32 controls the power supply circuits (not shown) that supply power to the motor 12 and the motor 13 in such a manner that the rotational speeds of the motors 12 and 13 become their respective target rotational speeds. Moreover, during acceleration, the control unit 32 sets the target rotational speed of the engine 11 according to an instruction from the ECU for driving control. And when the vehicle speed of the vehicle 1 reaches the target vehicle speed, the control unit 32 sets the target rotational speeds of the motors 12 and 13 in such a manner that the deceleration or acceleration becomes 0. And the control unit 32 controls the power supply circuits (not shown) that supply power to the motor 12 and the motor 13 in such a manner that the rotational speeds of the motors 12 and 13 become their respective target rotational speeds.

[0059] Figure 6 is a time chart showing the relationship between the deceleration control of the vehicle 1 in the present embodiment and the comparative example and the execution timing of the downshift. In Figure 6In the figure, the horizontal axis represents the elapsed time. Waveform 601 shows the evolution of the gear shift of the automatic transmission 15 of the comparative example, and waveform 611 shows the evolution of the gear shift of the automatic transmission 15 of the present embodiment. In addition, waveform 602 shows the evolution of the deceleration of the vehicle 1 until a certain deceleration is reached during deceleration in the comparative example, and waveform 612 shows the evolution of the deceleration of the vehicle 1 until a certain deceleration is reached during deceleration in the present embodiment. Moreover, waveform 603 shows the evolution of the rotational speed of the motor 13 in the comparative example, and waveform 613 shows the evolution of the rotational speed of the motor 13 in the present embodiment. In addition, waveform 621 shows the evolution of the rotational speed of the engine 11. Furthermore, in Figure 6 the deceleration of the vehicle 1 during deceleration is represented by a negative value.

[0060] In the comparative example, as shown in waveform 601, at time t2 after the start of deceleration of the vehicle 1, the gear shift of the automatic transmission 15 downshifts from the third gear to the second gear. Therefore, as shown in waveform 602, when downshifting is performed after the start of deceleration of the vehicle 1, a relatively large and discontinuous speed change occurs. Therefore, due to the acceleration change in the traveling direction of the vehicle 1 when this discontinuous speed change occurs, the driver sometimes feels discomfort.

[0061] On the other hand, in the present embodiment, as shown in waveform 611, at time t1 before the start of deceleration of the vehicle 1, the gear shift of the automatic transmission 15 downshifts from the third gear to the second gear. Therefore, as shown in waveform 612, the discontinuous speed change caused by downshifting before deceleration of the vehicle 1 is smaller than the discontinuous speed change caused by downshifting during deceleration. Therefore, it can be seen that discomfort of the driver caused by downshifting can be suppressed. Moreover, as shown in waveform 613 and waveform 621, even if the rotational speed of the motor 13 increases due to the execution of downshifting, the rotational speed of the engine 11 remains constant. Therefore, it can be seen that the output power as desired by the driver can be maintained.

[0062] Figure 7 is a time chart showing the relationship between the acceleration control of the vehicle 1 in the present embodiment and the comparative example and the execution timing of downshifting. In Figure 7 the horizontal axis represents the elapsed time. Waveform 701 shows the evolution of the gear shift of the automatic transmission 15 of the comparative example, and waveform 711 shows the evolution of the gear shift of the automatic transmission 15 of the present embodiment. In addition, waveform 702 shows the evolution of the acceleration of the vehicle 1 until a certain acceleration is reached during acceleration in the comparative example, and waveform 712 shows the evolution of the acceleration of the vehicle 1 until a certain acceleration is reached during acceleration in the present embodiment. Moreover, waveform 703 shows the evolution of the rotational speed of the motor 13 in the comparative example, and waveform 713 shows the evolution of the rotational speed of the motor 13 in the present embodiment. In addition, waveform 721 shows the evolution of the rotational speed of the engine 11.

[0063] In the comparative example, as shown by waveform 701, at time t2 after the start of acceleration of vehicle 1, the gear of the automatic transmission 15 is downshifted from the 4th gear to the 3rd gear. Therefore, as shown by waveform 702, when a downshift is performed after the start of acceleration of vehicle 1, a relatively large and discontinuous speed change occurs. Therefore, due to the acceleration change in the traveling direction of vehicle 1 when this discontinuous speed change occurs, the driver sometimes feels discomfort.

[0064] On the other hand, in the present embodiment, as shown by waveform 711, at time t1 before the start of acceleration of vehicle 1, the gear of the automatic transmission 15 is downshifted from the 4th gear to the 3rd gear. Therefore, as shown by waveform 712, the discontinuous speed change caused by the downshift before the acceleration of vehicle 1 is smaller than the discontinuous speed change caused by the downshift during the acceleration. Therefore, it can be understood that the discomfort of the driver caused by the downshift can be suppressed. In addition, by performing the downshift before the acceleration, the situation where the driving force stagnates during the acceleration can be suppressed. Therefore, the ECU 5 can make it difficult for the driver to feel a sense of sluggishness. Moreover, as shown by waveform 713, even if the rotational speed of the motor 13 increases due to the execution of the downshift, the rotational speed of the engine 11 remains constant during the execution of the downshift. Therefore, the difference between the timing at which the rotational speed of the engine 11 increases and the timing at which vehicle 1 starts to accelerate becomes smaller. As a result, the ECU 5 can prevent the driver from feeling a sense of strangeness.

[0065] Figure 8 It is a flowchart of the operation of the shift control process executed by the processor 23. The processor 23 may execute the shift control process according to the following flowchart.

[0066] The timing setting unit 31 of the processor 23 sets the acceleration / deceleration start timing and the shift timing based on at least one of the image from the camera 2, the current position of vehicle 1, the map information, and the operation of the driver on vehicle 1 (step S101).

[0067] The control unit 32 of the processor 23 determines whether the set shift timing has arrived (step S102). When the shift timing has not arrived (step S102 - No), the control unit 32 repeats the process of step S102 after a predetermined time. On the other hand, when the shift timing has arrived (step S102 - Yes), the control unit 32 controls the entire power train 4 so as to keep the rotational speed of the engine 11 constant, and performs a downshift of the automatic transmission 15 (step S103).

[0068] Thereafter, the control unit 32 determines whether the acceleration / deceleration start timing has arrived (step S104). When the acceleration / deceleration start timing has not arrived (step S104 - NO), the control unit 32 repeats the process of step S104 after a predetermined time has elapsed. On the other hand, when the acceleration / deceleration start timing has arrived (step S104 - YES), the control unit 32 starts the acceleration or deceleration of the vehicle 1 (step S105). And when the speed of the vehicle 1 reaches the target speed after acceleration or deceleration, the processor 23 stops the acceleration or deceleration of the vehicle 1 and ends the shift control process.

[0069] As described above, this shift control device predicts the timing at which acceleration or deceleration of the vehicle occurs. And before accelerating or decelerating the vehicle, this shift control device keeps the engine speed constant and downshifts the automatic transmission of the power train. Therefore, compared with downshifting the automatic transmission during acceleration or deceleration, this shift control device can suppress the acceleration change caused by downshifting and can suppress the change in engine output caused by the change in engine speed. As a result, this shift control device can suppress the situation of giving discomfort to the driver during acceleration or deceleration of the vehicle.

[0070] According to the modification example, a processor (not shown) of the electronic control device for driving control may also execute the process of the timing setting unit 31. Or, the electronic control device for driving control and the ECU 5 may be integrally configured as one electronic control device.

[0071] According to another modification example, the power train that is the object of the shift control of the shift control device may also be a power train having one motor and one engine. For example, the power train may sequentially have an engine, a clutch, a motor, a torque converter, and an automatic transmission in the power transmission order starting from the engine. Also in this case, the control unit 32 may downshift the automatic transmission at the shift timing before the predicted acceleration / deceleration start timing. However, in this case, the control unit 32 controls the clutch in such a way that the engine and the automatic transmission are disengaged (cut off, separated) in order to keep the engine speed constant during downshifting. Even in this modification example, the shift control device can obtain the same effects as those of the above-described embodiment.

[0072] In addition, a computer program that realizes the function of the processor 23 of the ECU 5 in the above-described embodiment or modification example may be provided in a form recorded in a computer-readable removable recording medium such as a semiconductor memory, a magnetic recording medium, or an optical recording medium.

[0073] As described above, those skilled in the art can make various changes corresponding to the embodiment within the scope of the present invention.

Claims

1. A variable speed control device, The variable speed control device is a variable speed control device for a power transmission system, The power transmission system is mounted on a vehicle and has a first transmission and a second transmission, The first transmission can continuously change the first speed ratio and the second speed ratio in such a way that the ratio of the second speed ratio to the first speed ratio is constant. The first speed ratio is the speed ratio between one of two motors and the engine, and the second speed ratio is the speed ratio between the other of the two motors and the engine. The second transmission can set the speed ratio between one of the two motors and the drive wheels to any one of a predetermined number of speed ratios. The variable speed control device has a timing setting unit and a control unit, The timing setting unit sets the acceleration / deceleration start timing for starting the acceleration or deceleration of the vehicle based on at least one of a sensor signal indicating the condition around the vehicle, the current position of the vehicle, a map including information related to the road on which the vehicle is traveling, and the operation of the vehicle by the driver of the vehicle. The control unit controls the power transmission system so that downshifting of the second transmission is performed before the acceleration / deceleration start timing, and changes the first speed ratio and the second speed ratio of the first transmission in such a way as to keep the engine speed constant.

2. The variable speed control device according to claim 1, Regarding the time from when a control device for controlling the driving of the vehicle recommends overtaking another vehicle traveling in front of the vehicle until the driver performs an operation to approve the recommendation, the timing setting unit predicts the time based on the elapsed time from the recommendation of overtaking until the operation of approval in the past, and sets the timing for starting the acceleration of the vehicle as the acceleration / deceleration start timing based on the predicted time.

3. The variable speed control device according to claim 2, The timing setting unit sets the timing after the following time has elapsed from the recommendation of overtaking as the acceleration / deceleration start timing. The elapsed time is the time obtained by adding the predicted time required to confirm that overtaking of the other vehicle can start to the predicted time from the recommendation of overtaking until the driver performs an operation of approval.

4. The variable speed control device according to claim 1, The timing setting unit sets the timing for starting the deceleration of the vehicle as the acceleration / deceleration start timing based on at least one of the speed of the vehicle and the radius of curvature of the next curve in the traveling direction of the vehicle, and the distance from the vehicle to the next curve.

5. The variable speed control device according to claim 1, The timing setting unit sets the timing for starting the deceleration of the vehicle as the acceleration / deceleration start timing based on at least one of the speed of the vehicle and the drivable speed of the vehicle at a deceleration required location where deceleration is required in the traveling direction of the vehicle, and the distance from the vehicle to the deceleration required location.

6. A variable speed control method, The variable speed control method is a variable speed control method for a power transmission system, The power transmission system is mounted on a vehicle and includes a first transmission and a second transmission. The first transmission is capable of continuously changing the first gear ratio and the second gear ratio in such a way that the ratio of the second gear ratio to the first gear ratio is constant. The first gear ratio is the gear ratio between one of two motors and the engine, and the second gear ratio is the gear ratio between the other of the two motors and the engine. The second transmission is capable of setting the gear ratio between one of the two motors and the drive wheels to any one of a predetermined number of gear ratios. The gear shift control method includes: Based on at least one of a sensor signal indicating the condition around the vehicle, the current position of the vehicle, a map including information related to the road on which the vehicle is traveling, and the operation of the vehicle by the driver, setting an acceleration / deceleration start timing for starting the acceleration or deceleration of the vehicle; and Controlling the power transmission system such that downshifting of the second transmission is performed before the acceleration / deceleration start timing, and changing the first gear ratio and the second gear ratio of the first transmission in such a way as to keep the engine speed constant.

7. A computer program for gear shift control The computer program for gear shift control is a computer program for gear shift control of a power transmission system. The power transmission system is mounted on a vehicle and includes a first transmission and a second transmission. The first transmission is capable of continuously changing the first gear ratio and the second gear ratio in such a way that the ratio of the second gear ratio to the first gear ratio is constant. The first gear ratio is the gear ratio between one of two motors and the engine, and the second gear ratio is the gear ratio between the other of the two motors and the engine. The second transmission is capable of setting the gear ratio between one of the two motors and the drive wheels to any one of a predetermined number of gear ratios. The computer program for gear shift control causes a processor of the vehicle to perform the following processes: Based on at least one of a sensor signal indicating the condition around the vehicle, the current position of the vehicle, a map including information related to the road on which the vehicle is traveling, and the operation of the vehicle by the driver, setting an acceleration / deceleration start timing for starting the acceleration or deceleration of the vehicle; and Controlling the power transmission system such that downshifting of the second transmission is performed before the acceleration / deceleration start timing, and changing the first gear ratio and the second gear ratio of the first transmission in such a way as to keep the engine speed constant.

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