Vehicle body attitude control system

Abstract

To suppress discomfort imparted to occupants of a vehicle when the traveling vehicle decelerates and stops and when the vehicle in a stationary state starts and accelerates on an uphill road.SOLUTION: A vehicle attitude control device comprises: a braking force control unit 128 configured to impart braking force to front wheels 12F and rear wheels 12R; and a driving force control unit 130 configured to impart driving force at least to the rear wheels 12R. The braking force control unit 128 imparts braking force to the front wheels 12F when the vehicle 10 decelerates and stops and when the vehicle 10 starts and accelerates, and the driving force control unit 130 imparts driving force to the rear wheels 12R when the vehicle decelerates and stops and starts and accelerates.SELECTED DRAWING: Figure 3

Description

Technical Field

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[0001] The present invention relates to a vehicle attitude control device.

Background Art

[0002] When stopping a vehicle traveling on an uphill road, if the brake is depressed to decelerate, a nose dive occurs in which the vehicle body dips forward. Then, when the vehicle comes to a complete stop, it is rocked back by the reaction force and the backward force due to gravity, resulting in pitching. On the other hand, when starting a vehicle stopped on an uphill road, if the accelerator is depressed to accelerate, a squat (tail squat) occurs in which the front part of the vehicle body rises.

[0003] Therefore, a vehicle running control device that provides a feeling similar to that of decelerating and stopping on a flat road even on an uphill road has been disclosed (see, for example, Patent Document 1). When the vehicle running control device of this Patent Document 1 detects a road surface gradient of a predetermined value or more when it is determined that the vehicle is immediately before stopping, it is configured to perform a predetermined torque request in parallel with control of temporarily reducing the braking force and then increasing the pressure.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] However, since the running control device of Patent Document 1 is specialized in suppressing pitching during deceleration and stopping of the vehicle, it cannot control the attitude of the vehicle body when stopping a vehicle traveling on an uphill road and then starting the stopped vehicle.

[0006] The present invention has been made in view of the above circumstances, and aims to provide a vehicle attitude control device that suppresses discomfort caused to the occupants of a vehicle when the vehicle is decelerating and stopping on an uphill road, and when the vehicle is accelerating from a standstill. [Means for solving the problem]

[0007] To achieve the above-mentioned objective, one embodiment of the present invention comprises a braking force control unit that applies braking force to the front and rear wheels, and a driving force control unit that applies driving force to at least the rear wheels, wherein the braking force control unit is On an uphill road When the vehicle is decelerating and coming to a stop, and when the vehicle is accelerating from a standstill, the front wheels only The braking force is applied, and the drive force control unit, On an uphill road During the aforementioned deceleration and stopping, and during the aforementioned acceleration from a standstill, the rear wheels only The aforementioned driving force is applied. Furthermore, the vehicle is further equipped with a gradient detection unit that detects the road surface gradient of the road on which the vehicle is traveling, the braking force control unit applies the braking force corresponding to the detected road surface gradient to the front wheels, and the driving force control unit applies the driving force corresponding to the detected road surface gradient to the rear wheels. Furthermore, the braking force control unit is On the uphill road During the deceleration and stopping process, the braking force applied to the front wheels is characterized by adding the braking force equivalent to the driving force applied to the rear wheels to the braking force used to stop the vehicle. Furthermore, the drive force control unit is On the uphill road During the acceleration phase, the driving force applied to the rear wheels is characterized by adding the driving force equivalent to the braking force applied to the front wheels to the driving force used to start the vehicle. The system further comprises a speed detection unit for detecting the vehicle speed and an acceleration / deceleration detection unit for detecting the vehicle's acceleration / deceleration, wherein the braking force control unit applies the braking force corresponding to the detected vehicle speed or acceleration / deceleration to the front wheels, and the driving force control unit applies the driving force corresponding to the detected vehicle speed or acceleration / deceleration to the rear wheels. Furthermore, the vehicle comprises a brake detection unit for detecting the amount of brake operation performed by the driver of the vehicle, an accelerator detection unit for detecting the amount of accelerator operation performed by the driver, and a requested acceleration / deceleration calculation unit for calculating the requested acceleration / deceleration based on the detected brake operation amount or accelerator operation amount. The braking force control unit applies the braking force corresponding to the calculated requested acceleration / deceleration to the front wheels, and the driving force control unit applies the driving force corresponding to the calculated requested acceleration / deceleration to the rear wheels. Furthermore, the system includes a stopping intent determination unit that determines whether the driver has the intention to stop the vehicle based on the detected vehicle speed, acceleration / deceleration, and brake operation amount, and the braking force control unit is On the uphill road, If the driver has the intention to stop, it is determined that it is time to decelerate and stop, and the front wheels only The braking force is applied, and the drive force control unit, On the uphill road, If the driver has the intention to stop, it is determined that it is time to decelerate and stop, and the rear wheels only The aforementioned driving force is applied. Furthermore, the system includes a starting intention determination unit that determines whether the driver has the intention to start the vehicle based on the detected vehicle speed, acceleration / deceleration, and accelerator pedal operation amount, and the braking force control unit, On the uphill road, If the driver has the intention to start, it is determined that it is time to accelerate and the front wheels only The braking force is applied, and the drive force control unit, On the uphill road, If the driver has the intention to start, it is determined that it is time to accelerate and the rear wheels only The aforementioned driving force is applied. Furthermore, the braking force control unit is characterized by maintaining the braking force applied to the front wheels during the initial acceleration for a predetermined period of time. [Effects of the Invention]

[0008] According to one embodiment of the present invention, the braking force control unit On an uphill road When the vehicle is decelerating to a stop and when the vehicle is accelerating from a standstill, the front wheels onlyThe braking force is applied, and the drive force control unit On an uphill road When decelerating to a stop and accelerating from a standstill, the rear wheels only By applying driving force, it is advantageous in suppressing discomfort to the occupants of a vehicle when decelerating and stopping on an uphill road, and when accelerating from a standstill. In other words, when decelerating and stopping, the rear wheels only By applying driving force, nose dive of the vehicle body can be suppressed, and the front wheels during acceleration from a standstill... only Applying braking force can suppress tail squat of the vehicle, which is advantageous in reducing discomfort for the vehicle's occupants. Furthermore, if the system is configured to detect the road surface gradient of the road on which the vehicle is traveling, and the braking force control unit applies braking force corresponding to the road surface gradient to the front wheels, and the driving force control unit applies driving force corresponding to the road surface gradient to the rear wheels, it will be advantageous in suppressing discomfort to the occupants of the vehicle when the vehicle is decelerating and stopping while traveling on an uphill road, and when the vehicle is accelerating from a standstill. Furthermore, the braking force control unit, On the uphill road When decelerating and stopping, if the braking force applied to the front wheels is the sum of the braking force required to stop the vehicle and a braking force equivalent to the driving force applied to the rear wheels, it is advantageous in preventing the vehicle's deceleration and stopping from being hindered by the driving force applied to the rear wheels. Furthermore, the drive force control unit, On the uphill road If, during acceleration from a standstill, the driving force applied to the rear wheels is calculated by adding a driving force equivalent to the braking force applied to the front wheels to the driving force used to start the vehicle, it is advantageous in suppressing the interference of the vehicle's acceleration from a standstill caused by the braking force applied to the front wheels. Furthermore, if the system detects the vehicle's speed and acceleration / deceleration, and the braking force control unit applies braking force to the front wheels corresponding to the vehicle speed or acceleration / deceleration, and the driving force control unit applies driving force to the rear wheels corresponding to the vehicle speed or acceleration / deceleration, it will be advantageous in applying braking force and driving force according to the vehicle's driving conditions. Further, if a required acceleration / deceleration speed by the driver is calculated based on the braking operation amount or the accelerator operation amount by the driver of the vehicle, the braking force control unit applies a braking force corresponding to the required acceleration / deceleration speed to the front wheels, and the driving force control unit applies a driving force corresponding to the required acceleration / deceleration speed to the rear wheels, it is advantageous in applying the braking force and the driving force in consideration of the required acceleration / deceleration speed based on the operation amount by the driver. Also, On the uphill road, when it is determined that decelerating to a stop when the driver has an intention to stop the vehicle, the braking force control unit applies only a braking force to the front wheels, and the driving force control unit applies only a driving force to the rear wheels, it is advantageous in applying the braking force and the driving force at the time of decelerating to a stop based on the driver's intention. Also, On the uphill road, when it is determined that accelerating at the start when the driver has an intention to start the vehicle, the braking force control unit applies only a braking force to the front wheels, and the driving force control unit applies only a driving force to the rear wheels, it is advantageous in applying the braking force and the driving force at the time of accelerating at the start based on the driver's intention. Further, if the braking force control unit is configured to hold the braking force applied to the front wheels at the time of accelerating at the start for a predetermined time, it is possible to reliably suppress the tail squat of the vehicle body, which is advantageous in suppressing the discomfort given to the passengers of the vehicle.

Brief Description of the Drawings

[0009] [Figure 1] (A) is an explanatory diagram showing the state of a conventional vehicle ascending a slope, and (B) is an explanatory diagram showing the state of the vehicle of the present embodiment ascending a slope. [Figure 2] It is a schematic diagram showing the configuration of the vehicle of the present embodiment. [Figure 3] It is a functional configuration diagram of the vehicle of the present embodiment. [Figure 4] (A) is a diagram showing the speed and acceleration / deceleration of a conventional vehicle, (B) is a diagram showing the speed and acceleration / deceleration of the vehicle of the present embodiment, and (C) is a diagram showing the speed and acceleration / deceleration of the conventional vehicle and the vehicle of the present embodiment. [Figure 5](A) is a diagram showing the braking force of a conventional vehicle, (B) is a diagram showing the braking force of the vehicle according to this embodiment, and (C) is a diagram showing the braking forces of a conventional vehicle and the vehicle according to this embodiment. [Figure 6] (A) is a diagram showing the driving force of a conventional vehicle, (B) is a diagram showing the driving force of the vehicle according to this embodiment, and (C) is a diagram showing the driving forces of a conventional vehicle and the vehicle according to this embodiment. [Figure 7] (A) is a diagram showing the pitching angle of a conventional vehicle, (B) is a diagram showing the pitching angle of the vehicle of this embodiment, and (C) is a diagram showing the pitching angles of a conventional vehicle and the vehicle of this embodiment. [Figure 8] This flowchart shows the flow of the vehicle attitude control process in this embodiment. [Modes for carrying out the invention]

[0010] Hereinafter, embodiments of the present invention will be described with reference to the drawings. The vehicle attitude control device of this embodiment controls the attitude of the vehicle 10 by controlling the braking force and driving force applied to the wheels (front wheels 12F, rear wheels 12R) provided on the vehicle 10. First, with reference to Figure 1, the outline of the attitude control process of the vehicle 10 of this embodiment will be described in comparison with a conventional vehicle 90 that does not perform this process.

[0011] Figure 1 shows the state of a vehicle going uphill from left to right on an uphill road, and both (A) and (B) are from left to right. (a) The vehicle is slowing down and coming to a stop. (b) The state immediately after the vehicle has come to a stop (c) The vehicle is stationary. (d) The state in which the vehicle starts and accelerates. This indicates that.

[0012] First, let's describe the conventional vehicle 90. The conventional vehicle 90 shown in Figure 1(A) is equipped with front wheels 92F and rear wheels 92R. In the conventional vehicle 90, in states (a) and (b), braking force is applied to the front wheels 92F and rear wheels 92R in the opposite direction (X2 direction) to the direction of travel (X1 direction). As a result, in state (a), a nose dive occurs where the vehicle body tilts forward, and in state (b), the vehicle is thrown back by the reaction and the backward force due to gravity, causing a pitching behavior.

[0013] In state (c), braking force is applied to the front wheel 92F and the rear wheel 92R in the X2 direction, bringing the vehicle to a stop. Then, in state (d), driving force is applied only to the rear wheel 92R in the X1 direction. As a result, in state (d), tail squat occurs, causing the front of the vehicle to lift off the ground.

[0014] Next, the vehicle 10 of this embodiment will be described. In the vehicle 10 of this embodiment shown in Figure 1(B), in states (a) and (b), a braking force in the X2 direction is applied to the front wheel 12F, and a driving force in the X1 direction is applied to the rear wheel 12R. When a driving force in the X1 direction is applied to the rear wheel 12R in this way, it is possible to suppress the vehicle body from tilting forward when the vehicle 10 decelerates and stops, and furthermore, since the braking force applied to the front wheel 12F is greater than the driving force applied to the rear wheel 12R, the vehicle 10 decelerates.

[0015] In state (c), braking force is applied to the front wheel 12F and rear wheel 12R in the X2 direction, causing the vehicle to stop. Then, in state (d), braking force is applied to the front wheel 12F in the X2 direction, and driving force is applied to the rear wheel 12R in the X1 direction. When braking force is applied to the front wheel 12F in the X1 direction in this way, the front of the vehicle 10 is prevented from lifting when the vehicle 10 starts to accelerate. Furthermore, since the driving force applied to the rear wheel 12R is greater than the braking force applied to the front wheel 12F, the vehicle 10 starts to move and accelerates.

[0016] Next, with reference to Figure 2, the configuration of the vehicle 10 in this embodiment will be described. As shown in Figure 2, the vehicle 10 is a hybrid vehicle equipped with an engine 14 and a motor 16 as driving forces. Furthermore, the vehicle 10 is a so-called FR vehicle (front-engine, rear-wheel drive vehicle), in which the engine 14 is located at the front of the vehicle body and the rear wheels 12R, which are the drive wheels, are located at the rear of the vehicle body. In this embodiment, a hybrid vehicle is used as an example, but the vehicle may be an electric vehicle equipped only with a motor, or a four-wheel drive vehicle with the front and rear wheels as drive wheels.

[0017] Vehicle 10 is equipped with an engine 14, a motor 16, and other drivetrain components such as a battery 18, a transmission 20, and a differential gear 22. Vehicle 10 is also equipped with control systems such as an ECU 24 (engine control unit), an MCU 26 (motor control unit), a TCU 28 (transmission control unit), and a BCU 30 (brake control unit).

[0018] Engine 14 is an internal combustion engine that uses gasoline as fuel for combustion and is a four-stroke engine that generates rotational power by repeating the intake, compression, expansion, and exhaust cycles. Engine 14 is located in the center of the vehicle in the width direction and outputs rotational power via an output shaft that extends from the front to the rear of the vehicle body. Vehicle 10 is equipped with various devices and mechanisms (not shown) associated with the engine, such as an intake system, exhaust system, and fuel supply system. Furthermore, various known internal combustion engines, such as diesel engines, can be used as engine 14.

[0019] Motor 16 is positioned in series behind engine 14 via a clutch (not shown). Motor 16 is a motor-generator (MG) with a power generation function, such as a permanent magnet synchronous motor. The rotational power of motor 16 is output to transmission 20 via a clutch (not shown). Battery 18 supplies power to motor 16 when the vehicle 10 is running using the driving force of motor 16.

[0020] The transmission 20 is a multi-stage automatic transmission (AT), with an input shaft 32 at one end connected to a motor 16 via a clutch (not shown), and an output shaft 34 at the other end that rotates independently of the input shaft 32. A gear shifting mechanism consisting of multiple gear mechanisms and a transmission clutch is incorporated between the input shaft 32 and the output shaft 34, and by switching the gear shifting mechanism, it is possible to switch between forward and reverse, or to change the rotational speed between the input shaft 32 and the output shaft 34 of the transmission 20, i.e., to switch the gear ratio.

[0021] The output shaft 34 extends in the longitudinal direction of the vehicle 10 and is connected to the differential gear 22 via a coaxially arranged propeller shaft 36. The differential gear 22 is connected to a pair of drive shafts 38 that extend in the vehicle width direction and are connected to the left and right rear wheels 12R (drive wheels). The rotational power output through the propeller shaft 36 is distributed by the differential gear 22 and then transmitted to the left and right rear wheels 12R (drive wheels) via this pair of drive shafts 38. In addition, each wheel 12F, 12R is fitted with a brake 40 to slow its rotation.

[0022] Vehicle 10 is equipped with the aforementioned ECU24, MCU26, TCU28, and BCU30 units to control its movement in response to the driver's input. Each of these units consists of hardware such as a processor, memory, and interface, and software such as a database and control programs.

[0023] The ECU24 is a unit that primarily controls the operation of the engine 14. The MCU26 is a unit that primarily controls the operation of the motor 16. The TCU28 is a unit that primarily controls the operation of the transmission 20. The BCU30 is a unit that primarily controls the operation of the brake 40. The vehicle attitude control device of this embodiment is composed of these units, and various processes described later are performed by the cooperation of these units.

[0024] Next, the vehicle attitude control device will be described with reference to Figure 3. As shown in Figure 3, the vehicle attitude control device 100 includes an accelerator pedal 102, an accelerator sensor 104, a brake pedal 106, a brake sensor 108, a speed sensor 110, an acceleration sensor 112, a gradient sensor 114, and a control unit 120. The control unit 120 is further configured to include a stop intention determination unit 122, a start intention determination unit 124, a requested acceleration / deceleration calculation unit 126, a braking force control unit 128, and a driving force control unit 130.

[0025] The accelerator pedal 102 is an operating component that controls the driving force by being pressed down by the driver with their foot. The vehicle 10 accelerates when the accelerator pedal 102 is pressed down and decelerates when the pedal is released (the foot is taken off). The accelerator sensor 104 is attached to the accelerator pedal 102 and detects the amount of operation (brake operation) of the accelerator pedal 102 by the driver.

[0026] The brake pedal 106 is an operating component that controls the braking force when the driver presses it with their foot. Pressing the brake pedal 106 activates the brakes and decelerates the vehicle. The brake sensor 108 is attached to the brake pedal 106 and detects the amount of brake operation (amount of brake operation) performed by the driver on the brake pedal 106.

[0027] The speed sensor 110 detects the vehicle speed of the vehicle 10, for example, by detecting the rotational speed of wheels 12F and 12R and outputting that rotational speed as a detection signal. The acceleration sensor 112 detects the acceleration and deceleration of the vehicle 10. Acceleration and deceleration refer to both acceleration and deceleration, where acceleration is the increase in velocity per unit time and deceleration is the decrease in velocity per unit time.

[0028] The gradient sensor 114 detects the road surface gradient of the road on which the vehicle 10 is traveling, and is, for example, a gyro sensor or an acceleration sensor. Alternatively, or in conjunction with this, the vehicle's geographical location may be obtained using a positioning device such as GPS, and the gradient may be obtained from map data or the like based on this geographical location.

[0029] The stopping intention determination unit 122 determines whether the driver has the intention to stop the vehicle 10 based on the vehicle speed detected by the speed sensor 110, the acceleration / deceleration detected by the acceleration sensor 112, and the amount of brake operation detected by the brake sensor 108. For example, the stopping intention determination unit 122 predicts the speed after a predetermined time has elapsed (for example, 3 seconds later) from the vehicle speed and deceleration at the time when it is determined from the amount of brake operation that the brake pedal 106 has been pressed. The stopping intention determination unit 122 then determines that the driver has the intention to stop if the predicted speed is less than a predetermined threshold, and determines that the driver does not have the intention to stop if the predicted speed is equal to or greater than the threshold.

[0030] The starting intention determination unit 124 determines whether the driver has the intention to start the vehicle 10 based on the vehicle speed detected by the speed sensor 110, the acceleration / deceleration detected by the acceleration sensor 112, and the accelerator operation amount detected by the accelerator sensor 104. For example, the starting intention determination unit 124 predicts the speed after a predetermined time has elapsed (for example, 3 seconds later) from the vehicle speed and acceleration at the time when it is determined from the accelerator operation amount that the accelerator pedal 102 has been pressed. Then, the starting intention determination unit 124 determines that the driver has the intention to start if the predicted speed is equal to or greater than a predetermined threshold, and determines that the driver does not have the intention to start if the predicted speed is less than the threshold.

[0031] The requested acceleration / deceleration calculation unit 126 calculates the driver's requested acceleration / deceleration, that is, the acceleration / deceleration the driver requests from the vehicle 10, based on the brake operation amount detected by the brake sensor 108 or the accelerator operation amount detected by the accelerator sensor 104. For example, the requested deceleration increases as the brake operation amount increases, and the requested acceleration increases as the accelerator operation amount increases. For example, the requested acceleration / deceleration calculation unit 126 calculates the deceleration and acceleration corresponding to the operation amount by referring to a correspondence table that has been pre-stored associating these operation amounts with deceleration and acceleration.

[0032] The braking force control unit 128 applies braking force to the front wheels 12F and rear wheels 12R of the vehicle 10 using brakes 40 attached to the wheels 12F and 12R. In the vehicle attitude control process of this embodiment, the braking force control unit 128 applies braking force to the front wheels 12F when the vehicle 10 slows down and comes to a stop while in motion, and when the vehicle 10 starts moving and accelerates while stationary.

[0033] Furthermore, the braking force control unit 128 applies a braking force to the front wheels 12F corresponding to the road surface gradient detected by the gradient sensor 114 during deceleration and acceleration. In other words, the greater the gradient of the uphill road, the greater the gravitational force acting on the vehicle 10, so the braking force control unit 128 applies a braking force to the front wheels 12F that takes gravity into account.

[0034] Furthermore, when decelerating and stopping, the braking force control unit 128 applies a braking force to the front wheels 12F that is calculated by adding a braking force equivalent to the driving force applied to the rear wheels 12R by the driving force control unit 130 to the braking force required to stop the vehicle 10. In other words, the braking force control unit 128 adds a braking force to the front wheels 12F that cancels out the driving force, so that the driving force applied to the rear wheels 12R does not hinder the deceleration of the vehicle 10.

[0035] Furthermore, the braking force control unit 128 applies a braking force to the front wheels 12F that corresponds to the vehicle speed detected by the speed sensor 110 or the acceleration / deceleration detected by the acceleration sensor 112 during deceleration, stopping, and acceleration. In other words, the braking force control unit 128 applies a braking force to the front wheels 12F that takes into account the speed and acceleration / deceleration of the vehicle 10.

[0036] Furthermore, the braking force control unit 128 applies a braking force to the front wheels 12F corresponding to the required acceleration calculated by the required acceleration calculation unit 126 during deceleration and acceleration. In other words, the braking force control unit 128 applies a braking force to the front wheels 12F that takes into account the acceleration intended by the driver.

[0037] Furthermore, if the stopping intention determination unit 122 determines that the driver intends to stop, the braking force control unit 128 determines that it is time to decelerate and stop, and applies braking force to the front wheels 12F. Also, if the starting intention determination unit 124 determines that the driver intends to start, the braking force control unit 128 determines that it is time to start and accelerate, and applies braking force to the front wheels 12F.

[0038] Furthermore, the braking force control unit 128 maintains the braking force applied to the front wheels 12F during acceleration for a predetermined time in order to reliably suppress tail squat of the vehicle body.

[0039] The drive force control unit 130 applies driving force to the rear wheels 12R of the vehicle 10 using the engine 14, motor 16, etc., provided in the vehicle 10. In the vehicle attitude control processing of this embodiment, the drive force control unit 130 applies driving force to the rear wheels 12R when the vehicle 10 slows down and comes to a stop while in motion, and when the vehicle 10 starts moving and accelerates while stationary.

[0040] Furthermore, the drive force control unit 130 applies a driving force to the rear wheels 12R corresponding to the road surface gradient detected by the gradient sensor 114 during deceleration, stopping, and acceleration. In other words, the greater the gradient of the uphill road, the greater the gravitational force acting on the vehicle 10, so the drive force control unit 130 applies a driving force to the rear wheels 12R that takes gravity into account.

[0041] Furthermore, during acceleration from a standstill, the drive force control unit 130 applies a drive force to the rear wheels 12R that is calculated by adding a drive force equivalent to the braking force applied to the front wheels 12F by the braking force control unit 128 to the drive force used to start the vehicle 10. In other words, to prevent the acceleration of the vehicle 10 from being hindered by the braking force applied to the front wheels 12F, the drive force control unit 130 adds a drive force to the rear wheels 12R that cancels out the braking force.

[0042] Furthermore, the drive force control unit 130 applies a drive force to the rear wheels 12R that corresponds to the vehicle speed detected by the speed sensor 110 or the acceleration / deceleration detected by the acceleration sensor 112 during deceleration, stopping, and acceleration. In other words, the drive force control unit 130 applies a drive force to the rear wheels 12R that takes into account the speed and acceleration / deceleration of the vehicle 10.

[0043] Furthermore, the drive force control unit 130 applies a drive force to the rear wheels 12R corresponding to the required acceleration calculated by the required acceleration calculation unit 126 during deceleration and acceleration. In other words, the drive force control unit 130 applies a drive force to the rear wheels 12R that takes into account the acceleration intended by the driver.

[0044] Furthermore, if the driver has an intention to stop, the drive force control unit 130 determines that it is time to decelerate and stop, and applies drive force to the rear wheels 12R. Also, if the driver has an intention to start, the drive force control unit 130 determines that it is time to accelerate and applies drive force to the rear wheels 12R.

[0045] Next, referring to Figures 4 to 7, the speed, acceleration / deceleration, braking force, driving force, and pitching angle of vehicle 10, which has undergone the vehicle attitude control processing of this embodiment, will be explained in comparison with a conventional vehicle 90. Vehicles 90 and 10 are climbing an uphill road, and in Figures 4 to 7, the horizontal axis represents time t0 to t11, and the vertical axis represents speed, acceleration / deceleration, braking force, driving force, and pitching angle, respectively, as line graphs.

[0046] First, let's explain the speed and acceleration of vehicle 90 and vehicle 10. As shown in Figures 4(A) to (C), the speed and acceleration of vehicle 90 and vehicle 10 are identical throughout the time intervals t0 to t11. Specifically, both vehicle 90 and vehicle 10 are traveling uphill from time t0 to t1, and are decelerating and coming to a stop from time t1 to t4 (see Figure 1(a)). Then, both vehicle 90 and vehicle 10 are stationary from time t4 to t7 (see Figures 1(b) and (c)), start moving and accelerating from time t7 to t10 (see Figure 1(d)), and are traveling uphill again from time t10 to t11. The speed and acceleration / deceleration for both vehicle 90 and vehicle 10 are as follows: t0~t1 (Uphill driving): Speed ​​v1 / Acceleration 0 t1~t4 (during deceleration and stopping): Speed ​​v1 to 0 / Acceleration / deceleration a1 t4~t7 (while stopped): Speed ​​0 / acceleration / deceleration 0 t7~t10 (during acceleration from a standstill): Speed ​​0 to v1 / acceleration / deceleration -a2 t10~t11 (uphill driving): Speed ​​v1 / acceleration 0

[0047] Next, the braking forces of vehicle 90 and vehicle 10 will be described. As shown in Figure 5(A), the braking force applied to the front wheel 12F of vehicle 90 is as follows. t0~t1: Braking force 0 t1~t7: Braking force b1 t7~t11: Braking force 0 On the other hand, as shown in Figure 5(B), the braking force applied to the front wheel 12F of the vehicle 10 is as follows. Note that the braking force is b1 <b2である。 t0~t1: Braking force 0 t1~t1´: Braking force b1 t1´~t4: Braking force b2 t4~t7´: Braking force b1 t7´~t11: Braking force 0 Referring to Figure 5(C), which shows these superimposed, the braking force of vehicle 10 is greater than the braking force of vehicle 90 at times t1' to t4 during deceleration and stopping, and at times t7 to t7' during acceleration from a standstill.

[0048] Next, the driving force of vehicle 90 and vehicle 10 will be explained. As shown in Figure 6(A), the driving force applied to the rear wheel 12R of vehicle 90 is as follows. Note that the driving force is d2 <d3である。 t0~t1: Driving force d2 t1~t7: Driving force 0 t7~t10: Driving force d3 t10~t11: Driving force d2 On the other hand, as shown in Figure 6(B), the driving force applied to the rear wheel 12R of the vehicle 10 is as follows. Note that the driving force is d1 <d2<d3<d4である。 t0~t1: Driving force d2 t1~t1': Driving force 0 t1'~t4: Driving force d1 t4~t7: Driving force 0 t7~t7': Driving force d4 t7'~t10: Driving force d3 t10~t11: Driving force d2 Referring to Figure 6(C), which shows these superimposed, the driving force of vehicle 10 is greater than the driving force of vehicle 90 at times t1' to t4 during deceleration and stopping, and at times t7 to t7' during acceleration from a standstill.

[0049] As shown in Figures 5 and 6, in the vehicle 10 of this embodiment, a driving force d1 is applied to the rear wheels 12R at times t1' to t4 during deceleration and stopping (t1 to t4) in order to avoid nose dive and pitching behavior due to rebound. Therefore, in order to counteract the applied driving force d1, a braking force b2 is applied to the front wheels 12F, which is the braking force b1 plus a braking force equivalent to the driving force d1 (b2 - b1).

[0050] Furthermore, in the vehicle 10 of this embodiment, a braking force b1 is applied to the front wheels 12F at times t7 to t7' during acceleration from a standstill (t7 to t10) in order to avoid tail squat. Therefore, in order to counteract the applied braking force b1, a braking force d4 is applied to the rear wheels 12R, which is the driving force d3 plus a driving force equivalent to the braking force b1 (d4 - d3).

[0051] Based on the speed, acceleration / deceleration, braking force, and driving force shown in Figures 4 to 6, the pitching angle of vehicle 90 and vehicle 10, i.e., the inclination angle of the vehicles, will now be explained. As shown in Figures 5(A) and 6(A), in the conventional vehicle 90, braking force is applied to the front wheels 12F and rear wheels 12R during deceleration and stopping (t1 to t4). As shown in Figure 7(A), a nose dive N occurs around time t4 (see Figure 1(A)(a)), and a pitching behavior P due to rebound occurs around time t4 (see Figure 1(A)(b)).

[0052] Furthermore, as shown in Figures 5(A) and 6(A), since vehicle 90 only applies driving force to the rear wheels 12R during acceleration from a standstill (t7~t10), tail squat S occurs around time t7, as shown in Figure 7(A) (see (d) in Figure 1(A)).

[0053] On the other hand, as shown in Figures 5(B) and 6(B), in this embodiment, vehicle 10 applies braking force to the front wheels 12F and driving force to the rear wheels 12R during deceleration and stopping (t1 to t4). Therefore, as shown in Figure 7(B), there is no significant change in the pitching angle even around time t4, and no nose dive or pitching behavior occurs (see Figures 1(B)(a) and (b)).

[0054] Furthermore, as shown in Figures 5(B) and 6(B), the vehicle 10 applies braking force to the front wheels 12F and driving force to the rear wheels 12R even during acceleration from a standstill (t7~t10). As shown in Figure 7(B), there is no significant change in the pitching angle even after time t7, and tail squat does not occur (see Figure 1(B)(d)). Therefore, as shown in Figure 7(C), in a conventional vehicle 90, the occupants of the vehicle 90 experience discomfort before and after stopping during deceleration and immediately after starting during acceleration from a standstill. However, in the vehicle 10 of this embodiment, discomfort to the occupants can be suppressed.

[0055] Next, the attitude control process by the vehicle 10 of this embodiment will be described. Figure 8 is a flowchart showing the flow of the attitude control process by the vehicle 10 of this embodiment. In the following, we will describe the case where the vehicle 10 is traveling uphill, then decelerates and stops, and then starts again and accelerates.

[0056] First, when the vehicle 10 is traveling on an uphill road, the braking force control unit 128 and the driving force control unit 130 determine whether the road is an uphill road with a predetermined gradient or greater, based on the road surface gradient of the road detected by the gradient sensor 114 (step S10). If it is a flat road or an uphill road with a gradient less than the predetermined gradient (step S10: NO), the process returns to step S10.

[0057] On the other hand, if the road is an uphill slope with a gradient greater than a predetermined gradient (step S10: YES), the stopping intention determination unit 122 determines whether the driver intends to stop based on the vehicle speed, acceleration / deceleration, and brake operation amount of the vehicle 10 detected by the speed sensor 110, acceleration sensor 112, and brake sensor 108, respectively (step S12). If it is determined that the driver does not intend to stop (step S12: NO), the process returns to step S10 and is repeated.

[0058] On the other hand, if it is determined that the vehicle intends to stop (step S12: YES), the braking force control unit 128 and the driving force control unit 130 perform attitude control processing during deceleration and stopping (step S14). Specifically, the braking force control unit 128 and the driving force control unit 130 apply braking force and driving force to the front wheels 12F and rear wheels 12R, respectively, corresponding to the road gradient, the vehicle speed and acceleration / deceleration of the vehicle 10, and the required acceleration / deceleration calculated by the required acceleration / deceleration calculation unit 126. This suppresses nose dive and pitching behavior due to rebound during deceleration and stopping.

[0059] Next, the braking force control unit 128 and the driving force control unit 130 determine whether the vehicle 10 has stopped based on its speed and acceleration (step S16). If the vehicle 10 has not stopped (step S16: NO), the process returns to step S14 and is repeated until the vehicle comes to a stop.

[0060] On the other hand, if the vehicle 10 is stationary (step S16: YES), the braking force control unit 128 and the driving force control unit 130 perform attitude control processing for when the vehicle is stationary (step S18). That is, the braking force control unit 128 and the driving force control unit 130 maintain the tilt angle (pitching angle) of the vehicle body by not applying driving force and maintaining a state in which braking force is applied to the front wheels 12F and rear wheels 12R.

[0061] Next, the departure intention determination unit 124 determines whether the driver intends to depart based on the vehicle speed, acceleration / deceleration, and accelerator operation amount of the vehicle 10 detected by the speed sensor 110, acceleration sensor 112, and accelerator sensor 104, respectively (step S20). If it is determined that the driver does not intend to depart (step S20: NO), the process returns to step S18.

[0062] On the other hand, if it is determined that the vehicle intends to start moving (step S20: YES), the braking force control unit 128 and the driving force control unit 130 perform attitude control processing during acceleration (step S22). Specifically, the braking force control unit 128 and the driving force control unit 130 apply braking force and driving force to the front wheels 12F and rear wheels 12R, respectively, corresponding to the road gradient, the vehicle speed and acceleration / deceleration of the vehicle 10, and the requested acceleration / deceleration. The braking force applied to the front wheels 12F by the braking force control unit 128 is then maintained for a predetermined time. This suppresses tail squat during acceleration.

[0063] Thus, according to this embodiment, the braking force control unit 128 applies braking force to the front wheels 12F when the vehicle 10 is decelerating and stopping, and when the vehicle 10 is accelerating from a standstill, and the driving force control unit 130 applies driving force to the rear wheels 12R when the vehicle is decelerating and stopping and when the vehicle is accelerating from a standstill. This is advantageous in suppressing discomfort to the occupants of the vehicle 10 when the vehicle 10 is decelerating and stopping while moving on an uphill road, and when the vehicle 10 is accelerating from a standstill. In other words, applying driving force to the rear wheels 12R during deceleration and stopping can suppress nose dive of the vehicle body, and applying braking force to the front wheels 12F during acceleration from a standstill can suppress tail squat of the vehicle body, which is advantageous in reducing discomfort to the occupants of the vehicle 10. Furthermore, the system is configured to detect the road surface gradient of the road on which the vehicle 10 is traveling, and the braking force control unit 128 applies braking force corresponding to the road surface gradient to the front wheels 12F, while the driving force control unit 130 applies driving force corresponding to the road surface gradient to the rear wheels 12R. This configuration is advantageous in suppressing discomfort to the occupants of the vehicle 10 when the vehicle 10 is decelerating and stopping while traveling on an uphill road, and when the vehicle 10 is accelerating from a standstill. Furthermore, the braking force control unit 128 is configured to apply a braking force to the front wheels 12F that is the braking force required to stop the vehicle 10, plus a braking force equivalent to the driving force applied to the rear wheels 12R. This configuration is advantageous in preventing the vehicle 10 from being hindered from decelerating and stopping by the driving force applied to the rear wheels 12R. Furthermore, the drive force control unit 130 is configured to apply a drive force to the rear wheels 12R that is the drive force for starting the vehicle 10 plus a drive force equivalent to the braking force applied to the front wheels 12F, which is advantageous in suppressing the braking force applied to the front wheels 12F from hindering the vehicle 10's acceleration from a standstill. Furthermore, the configuration allows for the detection of the vehicle speed and acceleration / deceleration of the vehicle 10, with the braking force control unit 128 applying braking force corresponding to the vehicle speed or acceleration / deceleration to the front wheels 12F, and the driving force control unit 130 applying driving force corresponding to the vehicle speed or acceleration / deceleration to the rear wheels 12R. This configuration is advantageous in applying braking force and driving force in accordance with the driving conditions of the vehicle 10. Furthermore, the system is configured such that the driver's requested acceleration or deceleration is calculated based on the amount of brake or accelerator operation performed by the driver of the vehicle 10, the braking force control unit 128 applies a braking force corresponding to the requested acceleration or deceleration to the front wheels 12F, and the driving force control unit 130 applies a driving force corresponding to the requested acceleration or deceleration to the rear wheels 12R. This configuration is advantageous in that it takes into account the requested acceleration or deceleration based on the driver's operation to apply braking force and driving force. Furthermore, the system is configured such that when the driver intends to stop the vehicle 10, it is determined to be a deceleration stop, and the braking force control unit 128 applies braking force to the front wheels 12F, and the driving force control unit 130 applies driving force to the rear wheels 12R. This configuration is advantageous in applying braking force and driving force when decelerating and stopping based on the driver's intention. Furthermore, the system is configured such that when the driver intends to start the vehicle 10, it is determined to be a time of acceleration, and the braking force control unit 128 applies braking force to the front wheels 12F, and the driving force control unit 130 applies driving force to the rear wheels 12R. This configuration is advantageous in applying braking force and driving force when accelerating to start based on the driver's intention. Furthermore, since the braking force control unit 128 is configured to hold the braking force applied to the front wheels 12F during acceleration from a standstill for a predetermined time, tail squat of the vehicle body can be reliably suppressed, which is advantageous in reducing discomfort to the occupants of the vehicle 10. [Explanation of Symbols]

[0064] 10 vehicles 12F wheels 12R wheels 14 Engine 16 motors 24 ECU 26 MCU 28 TCU 30 BCU 40 Brake 90 vehicles (conventional) 92F Front wheels (conventional) 92R Rear wheel (conventional) 100 Vehicle attitude control system 102 Accelerator pedal 104 Accelerator sensor 106 Brake pedal 108 Brake Sensor 110 Speed ​​Sensor 112 Accelerometer 114 Gradient Sensor 120 Control Unit 122 Stop intention determination unit 124 Departure Intention Determination Unit 126 Requested acceleration / deceleration calculation section 128 Brake Force Control Unit 130 Drive Force Control Unit

Claims

1. A braking force control unit that applies braking force to the front and rear wheels, It comprises a drive force control unit that applies driving force to at least the rear wheels, The braking force control unit applies the braking force only to the front wheels when the vehicle is decelerating and stopping on an uphill road and when the vehicle is accelerating from a standstill. The drive force control unit applies the drive force only to the rear wheels when decelerating and stopping on an uphill road and when accelerating from a standstill. A vehicle attitude control device characterized by the following features.

2. The vehicle further comprises a gradient detection unit that detects the road surface gradient of the road on which the vehicle is traveling. The braking force control unit applies the braking force corresponding to the detected road surface gradient to the front wheel. The drive force control unit applies the drive force corresponding to the detected road surface gradient to the rear wheels. The vehicle attitude control device according to claim 1.

3. The braking force control unit, when decelerating and stopping on an uphill road, applies to the front wheels a braking force obtained by adding to the braking force for stopping the vehicle a braking force corresponding to the driving force applied to the rear wheels. The vehicle attitude control device according to claim 1.

4. The drive force control unit, during acceleration from a standstill on an uphill road, applies to the rear wheels a drive force obtained by adding the drive force equivalent to the braking force applied to the front wheels to the drive force used to start the vehicle. The vehicle attitude control device according to claim 1.

5. A speed detection unit for detecting the vehicle speed of the aforementioned vehicle, The vehicle further comprises an acceleration / deceleration detection unit for detecting the acceleration and deceleration of the vehicle, The braking force control unit applies the braking force corresponding to the detected vehicle speed or acceleration / deceleration to the front wheel. The drive force control unit applies the drive force corresponding to the detected vehicle speed or acceleration / deceleration to the rear wheels. The vehicle attitude control device according to claim 1.

6. A brake detection unit that detects the amount of brake operation performed by the driver of the vehicle, An accelerator detection unit that detects the amount of accelerator operation by the driver, The system further includes a requested acceleration / deceleration calculation unit that calculates the requested acceleration / deceleration by the driver based on the detected brake operation amount or accelerator operation amount, The braking force control unit applies the braking force corresponding to the calculated required acceleration / deceleration to the front wheel. The drive force control unit applies the drive force corresponding to the calculated required acceleration / deceleration to the rear wheels. The vehicle attitude control device according to claim 5.

7. The system further includes a unit that determines whether the driver has the intention to stop the vehicle based on the detected vehicle speed, acceleration / deceleration, and brake operation amount, The braking force control unit, when on an uphill road, determines that the driver intends to stop, and applies the braking force only to the front wheels, The drive force control unit, when on an uphill road, determines that the driver intends to stop, and applies the drive force only to the rear wheels. The vehicle attitude control device according to claim 6.

8. The system further includes a starting intention determination unit that determines whether the driver has the intention to start the vehicle based on the detected vehicle speed, acceleration / deceleration, and accelerator pedal operation amount. The braking force control unit, when on an uphill road, determines that the driver has the intention to start moving, is in the state of acceleration, and applies the braking force only to the front wheels. The drive force control unit, when on an uphill road, determines that the driver has the intention to start moving, and applies the drive force only to the rear wheels. The vehicle attitude control device according to claim 6.

9. The braking force control unit maintains the braking force applied to the front wheels during acceleration for a predetermined time. The vehicle attitude control device according to claim 1.

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