JP2025047825A - Control device of four-wheel drive vehicle - Google Patents

Abstract

To provide a control device of a four-wheel drive vehicle that enables actual front/rear wheel driving force allocation of the four-wheel drive vehicle to fit to liking of a user, during automatic operation and during running on a predetermined bad road.SOLUTION: A vehicle 10 comprises an allocation selection switch 64b as a selection device which enables a driver who is a user to select front/rear wheel driving force allocation that is allocation of front wheel driving force and rear wheel driving force. A driving device ECU 80 of the vehicle 10 controls actual front/rear wheel driving force allocation of the vehicle 10, in accordance with the front/rear wheel driving force allocation selected by the driver using the allocation selection switch 64b, during automatic operation and during running on a predetermined bad road. This enables the actual front/rear wheel driving force allocation of the vehicle 10 to fit to liking of the driver, during the automatic operation and during running on the predetermined bad road.SELECTED DRAWING: Figure 1

Description

This relates to a control device for a four-wheel drive vehicle equipped with a selection device that allows the user to select the front/rear drive force distribution.

There are known vehicle control devices that have a driver preference mode in which at least some of the driving preference items, such as the distance from the vehicle ahead, the degree of acceleration/deceleration, the degree of lane changing, and the driving lane, are set to desired values by the driver (=user) when control that supports automatic driving, such as auto cruise control, is executed. For example, one such device is described in Patent Document 1.

JP 2023-28560 A

However, Patent Document 1 does not disclose a configuration that allows the driver to select the front/rear drive force distribution in a four-wheel drive vehicle.

The present invention has been made against the background of the above circumstances, and its purpose is to provide a control device for a four-wheel drive vehicle that adjusts the actual front/rear drive force distribution of the four-wheel drive vehicle according to the user's preferences while the vehicle is in automatic driving mode and traveling on a specified rough road.

The gist of the present invention is a control device for a four-wheel drive vehicle equipped with a selection device that allows the user to select the front/rear driving force distribution, which is the distribution of front wheel driving force and rear wheel driving force, and during automatic driving and when traveling on a specified rough road, the actual front/rear driving force distribution is controlled according to the front/rear driving force distribution selected by the user using the selection device.

According to the control device for a four-wheel drive vehicle of the present invention, during the automatic driving and while traveling on a predetermined rough road, the actual front and rear driving force distribution is controlled according to the front and rear driving force distribution selected by the user using the selection device. As a result, during the automatic driving and while traveling on a predetermined rough road, the actual front and rear driving force distribution of the four-wheel drive vehicle is made to correspond to the user's preferences.

1 is a schematic configuration diagram of a vehicle equipped with a drive device ECU according to a first embodiment of the present invention, and is also a functional block diagram showing essential parts of control functions for various controls in the vehicle. 2 is an example of a flowchart illustrating a control operation of a drive device ECU shown in FIG. 1 . FIG. 11 is a schematic configuration diagram of a vehicle including a drive device ECU according to a second embodiment of the present invention, and is also a functional block diagram showing the main parts of control functions for various controls in the vehicle.

Each embodiment of the present invention will be described in detail below with reference to the drawings. Note that in each embodiment, the drawings have been appropriately simplified or modified, and the dimensional ratios and shapes of each part are not necessarily drawn accurately.

FIG. 1 is a schematic diagram of a vehicle 10 equipped with a drive unit ECU 80 according to a first embodiment of the present invention, and is also a functional block diagram showing the main parts of the control functions for various controls in the vehicle 10.

The vehicle 10 includes an engine 12, a pair of front wheels 14, a pair of rear wheels 16, a first power transmission path between the engine 12 and the pair of front wheels 14, and a second power transmission path between the engine 12 and the pair of rear wheels 16. The vehicle 10 also includes a hydraulic control circuit 38, a vehicle state sensor 60, a surrounding recognition sensor 62, a driver operation sensor 64, and an electronic control device 70. The driver operation sensor 64 includes an automatic driving changeover switch 64a and a distribution selection switch 64b. The vehicle 10 corresponds to the "four-wheel drive vehicle" in this invention.

The engine 12 is a power source for driving, and is a well-known internal combustion engine. The engine torque Te [Nm], which is the output torque of the engine 12, is controlled by the electronic control device 70. In this specification, unless otherwise specified, the terms torque, driving force, power, and force (= power) are synonymous. The pair of front wheels 14 are main drive wheels, and are drive wheels both during two-wheel drive driving (= 2WD driving) and four-wheel drive driving (= 4WD driving). The pair of rear wheels 16 are auxiliary drive wheels, and are driven wheels during 2WD driving and drive wheels during 4WD driving. The first power transmission path is provided with an automatic transmission 18, a front wheel differential 20, a pair of front wheel axles 22, etc., in this order from the engine 12 side, and these are well-known configurations. The second power transmission path includes an automatic transmission 18, a transfer 24, which is a front/rear wheel power distribution device that distributes a portion of the power of the engine 12 transmitted to the pair of front wheels 14 to the pair of rear wheels 16, a propeller shaft 28 that transmits the power from the engine 12 distributed by the transfer 24 to the pair of rear wheels 16 during 4WD driving, a rear wheel differential 32, a pair of couplings 36, a pair of rear wheel axles 34, and the like, all of which are well-known components.

Figure 1 shows the transfer 24 in a state during 4WD driving. The power of the engine 12 distributed by the transfer 24 is transmitted to the pair of rear wheels 16 via the propeller shaft 28, the rear wheel differential 32, a pair of couplings 36, and a pair of rear wheel axles 34. The pair of couplings 36 are each a well-known electronically controlled coupling. The pair of couplings 36 each have a controlled transmission torque capacity.

In the vehicle 10, for example, when the transfer 24 is in a state in which it can distribute a portion of the power of the engine 12 to the pair of rear wheels 16 and the transmission torque capacity of the pair of couplings 36 is controlled to a value greater than zero, the driving force is also transmitted to the pair of rear wheels 16 according to the transmission torque capacity of the pair of couplings 36. This realizes 4WD driving. In 4WD driving, the transmission torque capacity of the pair of couplings 36 is controlled to adjust the torque distribution between the pair of front wheels 14 and the pair of rear wheels 16. The torque distribution between the pair of front wheels 14 and the pair of rear wheels 16 is the same as the "front/rear driving force distribution" described below.

The vehicle 10 can select a driving mode alternatively between a manual driving mode and an automatic driving mode. The manual driving mode is a driving method based on the manual operation of the driver, and the automatic driving mode is a driving method not based on the manual operation of the driver. The automatic driving mode is a driving mode in which the vehicle 10 is controlled to travel toward a target position based on a preset target position (= target position information) and a current position (= current position information), etc., without depending on the operation by the driver. Note that "automatic driving" in the present invention refers to a driving line (= course selection) being set without depending on at least the operation by the driver, and the driving force transmitted to the pair of front wheels 14 and the pair of rear wheels 16 with respect to the driving line being controlled. Specifically, in automatic driving, at least steering and acceleration/deceleration are controlled.

The selection between the manual driving mode and the automatic driving mode is performed, for example, based on the driver operating the automatic driving changeover switch 64a located near the driver's seat. When the driver operates the automatic driving changeover switch 64a to the ON side (= automatic driving side), the driving mode is switched from the manual driving mode to the automatic driving mode. When the driver operates the automatic driving changeover switch 64a to the OFF side (= manual driving side), or when the driver operates any of the steering wheel, accelerator pedal, or brake pedal (not shown) during automatic driving, the driving mode is switched from the automatic driving mode to the manual driving mode.

For example, in a rally challenge (= a rally competition for beginners), the vehicle 10 can select and set the front/rear driving force distribution during automatic driving in 4WD driving from among multiple distribution modes. "Front/rear driving force distribution" is the distribution ratio between the front wheel driving force (= the driving force for driving transmitted to the pair of front wheels 14) and the rear wheel driving force (= the driving force for driving transmitted to the pair of rear wheels 16). The selection of the front/rear driving force distribution is performed, for example, based on the driver operating the distribution selection switch 64b provided near the driver's seat. The distribution selection switch 64b corresponds to the "selection device" in this invention. The distribution modes include various modes such as an on-the-rail driving mode in which the front/rear driving force distribution is equalized so that the vehicle runs on the rails on the driving line during automatic driving, a drift driving mode in which the distribution to the rear wheel driving force is increased more than the front wheel driving force so that the vehicle runs in a drifting manner on the driving line during automatic driving, and an intermediate mode in which the front/rear driving force distribution is intermediate between them. These distribution modes are selected to realize driving according to the driver's preference for the driving line during automatic driving. In addition, the on-the-rail driving mode, intermediate mode, and drift driving mode are modes in which the distribution of driving force from the front wheels to the rear wheels is gradually increased in that order. In addition, when the drift driving mode is selected during autonomous driving, the well-known traction control function that controls the pair of front wheels 14 and the pair of rear wheels 16 to prevent slipping during driving is stopped so that drift driving is possible. The driver corresponds to the "user" in this invention, and the "user" may include passengers in addition to the driver.

The electronic control device 70 includes multiple ECUs that function as control devices that control various parts of the vehicle 10. Note that ECU stands for Electronic Control Unit, and is abbreviated to the initial letters of each word.

The electronic control device 70 includes a drive device ECU 80 and an automatic driving ECU 90, which are capable of inputting and outputting data to and from each other. The drive device ECU 80 is an ECU for controlling the drive device, which controls the engine 12, the automatic transmission 18, the transfer 24, and the pair of couplings 36. The drive device ECU 80 corresponds to the "control device" in this invention. The automatic driving ECU 90 is an ECU for executing automatic driving control. Each ECU is configured to include a so-called microcomputer equipped with, for example, a CPU, RAM, ROM, an input/output interface, etc., and the CPU executes various controls of the vehicle 10 by performing signal processing according to a program previously stored in the ROM while utilizing the temporary storage function of the RAM.

The autonomous driving ECU 90 receives various signals based on detection values from various sensors (e.g., a vehicle state sensor 60, a surrounding recognition sensor 62, a driver operation sensor 64, etc.) (e.g., (1) an engine rotation speed Ne [rpm] which is the rotation speed of the engine 12, a throttle valve opening θth [%], a shift state signal Ssftsta which indicates the shift range of the automatic transmission 18, a vehicle speed V [km/h], a GPS (Global Positioning System), etc.) (1) Various information representing the vehicle state, such as the friction coefficient μ of the road surface on which the vehicle 10 is traveling, based on vehicle position information based on GPS signals transmitted by satellites and a car navigation device including information on the road; (2) Various information regarding the surroundings of the vehicle 10, such as the presence or absence of obstacles around the vehicle 10 and other vehicles traveling in front, behind, on the left and right of the vehicle 10; (3) Various information regarding the operation by the driver, such as the steering angle Sste [rad] of the steering wheel, the accelerator opening θacc [%] corresponding to the amount of depression of the accelerator pedal, the brake operation amount Sbrk [%] corresponding to the amount of depression of the brake pedal, the shift position signal POSsh indicating the operation position of the shift lever, the driving mode setting signal Ssw1 input from the automatic driving changeover switch 64a, and the distribution selection signal Ssw2 input from the distribution selection switch 64b. The surrounding recognition sensor 62 is composed of a plurality of sensors, such as an infrared sensor, a camera, and a medium-to-long range radar, and the vehicle state sensor 60 and the driver operation sensor 64 are composed of a plurality of sensors that detect each specification, for example.

In the automatic driving mode, the automatic driving ECU 90 outputs an automatic driving control signal Sauto to the drive unit ECU 80 to realize driving in the automatic driving mode based on various signals based on detection values from the vehicle state sensor 60, the surrounding recognition sensor 62, the driver operation sensor 64, etc. The automatic driving control signal Sauto includes target values for controlling the vehicle state during driving, such as the engine torque Te, the gear ratio of the automatic transmission 18, and the steering angle Sste of the steering wheel. When the vehicle is in automatic driving in 4WD driving and is driving on a specified rough road described below, the automatic driving control signal Sauto includes the distribution mode selected by the driver. In the manual driving mode, the automatic driving ECU 90 does not output the automatic driving control signal Sauto to the drive unit ECU 80.

The drive unit ECU 80 receives various information indicating the vehicle state and various information related to the driver's operation from the vehicle state sensor 60 and the driver operation sensor 64, and also receives an automatic driving control signal Sauto from the automatic driving ECU 90 during the automatic driving mode. The drive unit ECU 80 outputs various command signals (e.g., an engine control signal Se for controlling the engine 12, a shift control signal Sat for controlling the shift of the automatic transmission 18, a transfer control signal Str for alternatively selecting 2WD driving or 4WD driving, torque control signals Sc1, Sc2 for controlling the transmission torque capacity of the pair of couplings 36, etc.) to each device (e.g., the engine 12, the hydraulic control circuit 38, the transfer 24, the pair of couplings 36, etc.) provided in the vehicle 10.

From here, we will explain how the front and rear drive force distribution is controlled when the vehicle is in automatic driving mode in 4WD mode and traveling on a specified rough road.

The drive unit ECU 80 functionally comprises an engine control unit 80a, a gear shift control unit 80b, an automatic driving determination unit 80c, a rough road determination unit 80d, an allocation selection determination unit 80e, an allocation amount calculation unit 80f, an allocation amount determination unit 80g, and a coupling control unit 80h.

In the automatic driving mode, the engine control unit 80a controls the engine 12 and the shift control unit 80b controls the automatic transmission 18 based on the automatic driving control signal Sauto. In the manual driving mode, the engine control unit 80a controls the engine 12 and the shift control unit 80b controls the automatic transmission 18 based on various information representing the vehicle state (e.g., vehicle speed V) and various information related to the driver's operation (e.g., accelerator opening θacc).

The autonomous driving determination unit 80c determines whether the autonomous driving mode is selected, i.e., whether the vehicle is in autonomous driving mode.

The rough road determination unit 80d determines whether the vehicle 10 is traveling on a predetermined rough road such as a low μ road based on the friction coefficient μ of the road surface on which the vehicle 10 is traveling. If the friction coefficient μ of the road surface on which the vehicle 10 is traveling is less than a predetermined coefficient determination value μ_jdg, it is determined that the vehicle 10 is traveling on a predetermined rough road. The predetermined coefficient determination value μ_jdg is a determination value that is determined in advance experimentally or by design, and the behavior of the vehicle 10 differs depending on the distribution mode selected by the driver.

The distribution selection determination unit 80e determines whether or not there is a distribution mode selected by the driver. When it is determined that the vehicle is in automatic driving and traveling on a predetermined bad road, and it is determined that there is a distribution mode selected by the driver, the distribution amount calculation unit 80f calculates the distribution amount X of the front and rear driving force distribution according to the distribution mode selected by the driver. The distribution amount X is the distribution ratio between the front wheel driving force and the rear wheel driving force, and is the same as the front and rear driving force distribution. When the distribution amount calculation unit 80f calculates the distribution amount X, the distribution amount determination unit 80g determines whether or not the distribution amount X is realized as the actual front and rear driving force distribution of the vehicle 10. If the distribution amount determination unit 80g determines that the distribution amount X is realized as the actual front and rear driving force distribution of the vehicle 10, the coupling control unit 80h does not change the front and rear driving force distribution of the vehicle 10. If the distribution amount determination unit 80g determines that the distribution amount X is not realized as the actual front and rear driving force distribution of the vehicle 10, the coupling control unit 80h executes control to change the front and rear driving force distribution of the vehicle 10 to the distribution amount X.

Figure 2 is an example of a flowchart that explains the control operation of the drive unit ECU 80 shown in Figure 1. The flowchart in Figure 2 is executed repeatedly while the vehicle 10 is running in 4WD mode.

First, in step (hereinafter, step will be omitted) S10, it is determined whether or not the vehicle is in automatic driving mode. If the determination in S10 is YES, then in S20 it is determined whether or not the vehicle is traveling on a predetermined bad road. If the determination in S20 is YES, then in S30 it is determined whether or not an allocation mode has been selected by the driver. If the determination in S30 is YES, then in S40, an allocation amount X is calculated according to the allocation mode selected by the driver, and it is determined whether or not the allocation amount X has been realized as the actual front/rear driving force allocation of the vehicle 10. If the determination in S40 is YES, then in S50, the front/rear driving force allocation of the vehicle 10 is not changed. If the determination in S40 is NO, then in S60, control is executed to change the front/rear driving force allocation of the vehicle 10 to the allocation amount X. If the determination in S10 is NO, if the determination in S20 is NO, or if the determination in S30 is NO, in S70 the front and rear drive force distribution of the vehicle 10 is controlled to a standard front and rear drive force distribution determined in advance, rather than the distribution mode selected by the driver. After execution of S50 to S70, the process returns in all cases.

According to this embodiment, during automatic driving and when traveling on a predetermined rough road, the actual front and rear driving force distribution is controlled according to the front and rear driving force distribution selected by the driver using the distribution selection switch 64b. As a result, during automatic driving and when traveling on a predetermined rough road, the actual front and rear driving force distribution of the vehicle 10 is set according to the driver's preferences.

FIG. 3 is a schematic diagram of a vehicle 110 equipped with a drive unit ECU 180 according to a second embodiment of the present invention, and is also a functional block diagram showing the main parts of the control functions for various controls in the vehicle 110. This embodiment differs from the previously described first embodiment in terms of vehicle configuration, and therefore the control functions are different. Therefore, the following description will focus on the parts that differ from the first embodiment, and parts that are substantially the same in function as the first embodiment will be given the same reference numerals and descriptions thereof will be omitted as appropriate.

The vehicle 110 is equipped with a well-known configuration including an engine 12, a power split mechanism 150, a generator Gen, a front wheel motor MGfr, a front wheel differential 20, a pair of front wheel axles 22, a pair of front wheels 14, a rear wheel motor MGre, a rear wheel differential 32, a pair of rear wheel axles 34, and a pair of rear wheels 16, which are connected as shown in FIG. 3. The vehicle 110 is configured so that power can be supplied between the generator Gen, the front wheel motor MGfr, the front wheel inverter INVfr, the rear wheel motor MGre, the rear wheel inverter INVre, the battery 152, and the boost converter 154 as shown in FIG. 3. In this way, the vehicle 110 is a well-known four-wheel drive vehicle in which the front wheel drive force and the rear wheel drive force can be controlled independently, and corresponds to the "four-wheel drive vehicle" in the present invention.

The vehicle 110 is equipped with an electronic control device 170. The electronic control device 170 includes a drive device ECU 180 and an automatic driving ECU 90. The drive device ECU 180 corresponds to the "control device" in the present invention. The drive device ECU 180 is substantially the same as the drive device ECU 80 in the first embodiment, but differs in that the drive device ECU 180 does not include a shift control unit 80b and an electric motor control unit 180h is provided instead of the coupling control unit 80h due to the difference in the vehicle configuration from the first embodiment. From the drive device ECU 180, various command signals (e.g., engine control signal Se, generator control signal Sgen for torque control of the generator Gen, MGfr control signal Smgfr for driving and controlling the front wheel electric motor MGfr, MGre control signal Smgre for driving and controlling the rear wheel electric motor MGre, etc.) are output to each device (e.g., engine 12, front wheel inverter INVfr, rear wheel inverter INVre, etc.) provided in the vehicle 10. If it is determined that the vehicle is in automatic driving and traveling on a predetermined rough road, and if it is determined that an allocation mode selected by the driver exists, and if the allocation amount determination unit 80g determines that the allocation amount X is not realized as the actual front/rear driving force allocation of the vehicle 10, the motor control unit 180h executes control to change the front/rear driving force allocation of the vehicle 10 to the allocation amount X by controlling the output of the generator Gen, the front wheel electric motor MGfr, and the rear wheel electric motor MGre, respectively. If the allocation amount determination unit 80g determines that the allocation amount X is realized as the actual front/rear driving force allocation of the vehicle 10, the motor control unit 180h does not change the front/rear driving force allocation of the vehicle 10.

This embodiment provides the same effects as embodiment 1.

The above are examples of the present invention, and the present invention can be implemented in various forms with various modifications and improvements based on the knowledge of those skilled in the art without departing from the spirit of the invention.

In the above-mentioned first embodiment, the vehicle 10 is a part-time 4WD, but the present invention can also be applied to a full-time 4WD.

10, 110: vehicle (four-wheel drive vehicle), 64b: distribution selection switch (selection device), 80, 180: drive unit ECU (control device)

Claims (1)

A control device for a four-wheel drive vehicle including a selection device that allows a user to select a front/rear drive force distribution, which is a distribution of a front wheel drive force and a rear wheel drive force, comprising:
a control device for a four-wheel drive vehicle, the control device controlling an actual front/rear driving force distribution in accordance with the front/rear driving force distribution selected by the user through the selection device during automatic driving and while traveling on a predetermined rough road.

Images