JPH1149019A - Steering control device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To attain improvement of small sharp turn capability by a simple constitution, relating to a steering control device attaining facilitation of operation by selectively applying brake force relating to each wheel. SOLUTION: A steering control device is provided with a steering sensor 88 detecting a steering direction of a steering wheel, brake device (wheel cylinder 44FL, 44FR, 44RL, 44RR) constituted so as to be able to perform brake action independently relating to each wheel, and a brake force control means, based on a vehicle advancing direction (forward or reverse) detected by a car speed sensor 90 and a steering direction detected by the steering sensor 88, generating brake force in a front side turn internal wheel relating to the advancing direction.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a steering control device, and more particularly to a steering control device which facilitates steering by selectively applying a braking force to each wheel.

[0002]

2. Description of the Related Art In the case of a general four-wheel vehicle, the direction of the vehicle is changed by steering two front wheels and steering the two wheels. However, in a configuration (2WS) in which the two front wheels are simply steered by steering, the minimum turning radius cannot be made sufficiently small, so that it is difficult to perform steering when traveling on a narrow road or entering a garage into a narrow parking lot. . For this reason, various devices for reducing the turning radius of the vehicle have been conventionally developed.

[0003] As a device for reducing the turning radius at the time of steering and improving small turning performance, 4WS (Four Wheel St.
eering System) is known. The 4WS is configured to steer the two rear wheels in addition to the two front wheels. Therefore, when the two front wheels and the two rear wheels are steered in opposite phases in 4WS, when the front wheels are steered at the same angle of cut as in the case of 2WS, the center of turning approaches the body when the rear wheels are steered in opposite phases. Therefore, the minimum turning radius and the difference between the inner and outer wheels are reduced, and the small turning property can be improved. As a result, it is possible to improve the steering performance when traveling on a narrow alley or entering a garage in a narrow parking lot.

[0004]

However, 4WS is 4
Since all the wheels are steered, there is a problem in that an actuator is required to steer each wheel, and it is difficult to control to steer each wheel properly. Also, in order to steer the rear wheels, it is necessary to form a space for enabling steering even at the rear wheel arrangement position of the vehicle body, and the provision of this space reduces the capacity of the trunk room. There were also problems.

The present invention has been made in view of the above points, and provides a steering control device capable of improving a small turning performance with a simple configuration by selectively braking the wheels according to the steering direction. The purpose is to provide.

[0006]

Means for Solving the Problems To solve the above problems, the present invention is characterized in that the following means are taken. In the steering control device according to the first aspect of the present invention, a steering angle detecting unit that detects a steering direction of a steered wheel;
Braking means configured to be capable of independently performing a braking operation on each wheel; driving state detection means for detecting a driving state of the vehicle; a vehicle traveling direction detected by the driving state detection means; A braking force control means for generating a braking force on the front turning inner wheel with respect to the traveling direction based on the steering direction detected by the angle detection means is provided.

According to a second aspect of the present invention, in the steering control device according to the first aspect, the braking force control means includes a speed (V1) of the turning outer wheel and a speed of the turning inner wheel determined by the driving state detecting means. Braking force value determining means for determining a braking force value to be generated for each wheel based on a speed ratio (V2 / V1) which is a ratio to the speed (V2); An optimum speed ratio calculating means for obtaining an optimum speed ratio most suitable in the current steering state based on the steering angle is provided.

The above-mentioned means works as follows. According to the first aspect of the present invention, the steering angle detecting means detects the steering direction of the steered wheel and transmits this information to the braking force control means. The driving state detecting means detects the driving state of the vehicle and transmits a signal indicating the traveling direction of the vehicle, which is one of the driving states, to the braking force control means. Further, the braking means is configured to be capable of independently performing a braking operation on each wheel.

The braking force control means applies a braking force to the front turning inner wheel with respect to the traveling direction based on the vehicle traveling direction detected by the driving state detecting means and the steering direction detected by the steering angle detecting means. generate. For example, when the traveling direction is forward and the steering direction is right, the braking force control unit controls the braking unit that generates a braking force on the front right wheel. As described above, by generating the braking force on the front turning inner wheel in the traveling direction, the outermost turning radius of the vehicle body at the time of turning can be reduced, and thus the small turning property can be improved.

According to the second aspect of the present invention, by providing the braking force value determining means in the braking force control means, the braking force value generated on each wheel can be determined by the speed (V1) of the turning outer wheel and the turning force. It is determined based on the speed ratio (V2 / V1) which is the ratio with the speed (V2) of the inner ring. At this time, the speed ratio (V2 / V1) is set to the optimum speed ratio most suitable for the current steering state by the processing of the optimum speed ratio calculating means.

Therefore, it is possible to generate a braking force of a magnitude most suitable for the current driving state of the vehicle (ie, turning angle, vehicle speed, etc.) on the front turning inner wheel in the traveling direction. Performance and maneuverability can be improved.

[0012]

Next, embodiments of the present invention will be described with reference to the drawings. FIG. 1 is a system configuration diagram of a steering control device according to an embodiment of the present invention, and FIG. 2 is a block diagram of a control system of the steering control device. The steering control device according to the present embodiment also functions as a braking force control device, and is controlled by an electronic control unit 10 (hereinafter, referred to as ECU 10). Hereinafter, a specific configuration of the steering control device will be described.

The steering control device includes a pump 12. The pump 12 has a motor 14 as its power source. The suction port 12a of the pump 12 is connected to the reservoir tank 1
6, and a discharge port 12b of the pump 12 communicates with the accumulator 20. The pump 12 pumps the brake fluid in the reservoir tank 16 from its discharge port 12b so that a predetermined hydraulic pressure is always accumulated in the accumulator 20.

The accumulator 20 communicates with a high pressure port 24a of a regulator 24 and a regulator switching solenoid 26 (hereinafter, referred to as STR 26) through a high pressure passage 22. The regulator 24 is connected to the low pressure passage 2
Low pressure port 2 communicating with reservoir tank 16 through port 8
4b, and a control hydraulic pressure port 24c communicating with the STR 26 via a control hydraulic pressure passage 29. STR26 is
A two-position solenoid valve that selectively connects one of the control hydraulic pressure passage 29 and the high-pressure passage 22 to a conductive state. Under normal conditions, the control hydraulic pressure passage 29 is in a conductive state and the high-pressure passage 22 is in a shut-off state. .

The regulator 24 includes the brake pedal 3
0 is connected and the master cylinder 32 is fixed. The regulator 24 has a hydraulic chamber therein. The hydraulic pressure chamber is always in communication with the control hydraulic pressure port 24c, and is selectively connected to the high pressure port 24a or the low pressure port 2 according to the operation state of the brake pedal 30.
4b.

The regulator 24, the internal pressure of the hydraulic chamber is configured to be adjusted to the hydraulic pressure corresponding to the brake pressing force F _P exerted on the brake pedal 30. Therefore, the control fluid pressure port 24c of the regulator 24, always (referred to this fluid pressure and the regulator pressure P _RE) the hydraulic pressure corresponding to the brake pressing force F _P appears. Brake pressing force F _P exerted on the brake pedal 30 is transmitted mechanically to the master cylinder 32 via the regulator 24. Further, the master cylinder 32, corresponding to the hydraulic pressure in the hydraulic chamber of the regulator 24, i.e., a force corresponding to the regulator pressure P _RE is transmitted (referred this force and a brake assist force F _A). Therefore, when the brake pedal 30 is depressed, the master cylinder 32, the resultant force of the brake pressing force F _P and a brake assist force F _A is transmitted.

The master cylinder 32 has a first hydraulic chamber 32a and a second hydraulic chamber 32b therein. The first hydraulic chamber 32a and the second hydraulic chamber 32b are provided with a brake depression force F
_A master cylinder pressure PM _{/ C} is generated according to the resultant force of _P and the brake assist force FA. The master cylinder pressure P _{M / C} generated in the master cylinder pressure P _{M / C} and the second fluid pressure chamber 32b is generated in the first fluid pressure chamber 32a are both proportioning valve 34 (hereinafter, referred to as P valve 34) Communicating.

A first hydraulic passage 36 and a second hydraulic passage 38 communicate with the P valve 34. The P valve 34 supplies the master cylinder pressure PM _{/ C} directly to the first hydraulic passage 36 and the second hydraulic passage 38 in a region where the master cylinder pressure PM _{/ C} is less than a predetermined value. In a region where the master cylinder pressure P _{M / C} exceeds a predetermined value, the P valve 34 controls the master cylinder pressure P _{M with} respect to the first hydraulic pressure passage 36.
_{M / C} is supplied as it is, and a hydraulic pressure is supplied to the second hydraulic passage 38 by reducing the master cylinder pressure PM _{/ C} at a predetermined ratio.

In a passage connecting the second hydraulic chamber 32b of the master cylinder 32 and the P valve 34, a hydraulic sensor 40 for outputting an electric signal corresponding to the master cylinder pressure PM _{/ C} is provided. The output signal of the oil pressure sensor 40 is
Is supplied to The ECU 10 detects the master cylinder pressure P _{M / C} generated in the master cylinder 32 based on the output signal of the oil pressure sensor 40.

The STR 26 has a third hydraulic passage 4
Two are communicating. The third hydraulic passage 42 is electrically connected to one of the control hydraulic passage 29 and the high-pressure passage 22 according to the state of the STR 26. In this embodiment, the left and right front wheels F
Wheel cylinders 44FL, 44F disposed on L, FR
The brake fluid pressure is supplied to R from the first fluid pressure passage 36 communicating with the P valve 34 or the third fluid pressure passage 42 communicating with the STR 26. Further, the wheel cylinders 44RL, 44RR disposed on the left and right rear wheels RL, RR are connected to the second hydraulic pressure passage 38 communicating with the P valve 34 or the STR 26.
The brake fluid pressure is supplied from a third fluid pressure passage 42 communicating with the brake fluid. These wheel cylinders 44FL, 44FR, 44
The RL and 44RR function as braking means for independently performing a braking operation on each of the wheels FL, FR, RL and RR.

The first hydraulic passage 36 communicates with a first assist solenoid 46 (hereinafter, referred to as SA- ₁ 46) and a second assist solenoid 48 (hereinafter, referred to as SA _- 248). On the other hand, in the third hydraulic passage 42, a right front wheel holding solenoid 50 (hereinafter, referred to as SFRH50), a left front wheel holding solenoid 52 (hereinafter, referred to as SFLH52), and a third assist solenoid 54 (hereinafter, referred to as SA- ₃ 54) are provided. Is called).

A pressure increasing device 55 is provided at an intermediate position of the first hydraulic pressure passage 36. The pressure increasing device 55 is configured to increase the hydraulic pressure of the front wheel cylinders 44FL, 44FR when the supplied hydraulic pressure is reduced in a state where the braking is performed by the hydraulic pressure from the accumulator 20 described later. As a result, a high braking force is secured. Reference numeral 57 denotes a pressure limiter which closes a path with the regulator 24 for an input negative pressure exceeding the assisting force limit of the regulator 24, and
5 is prohibited.

The SFRH 50 is a two-position solenoid valve which normally keeps the valve open. The SFRH 50 communicates with the SA- ₂ 48 and a right front wheel pressure reducing solenoid 58 (hereinafter, referred to as an SFRR 58) via a pressure adjusting hydraulic pressure passage 56. A check valve 60 is arranged between the third hydraulic passage 42 and the pressure adjusting hydraulic passage 56 so as to allow only the flow of the fluid from the pressure adjusting hydraulic passage 56 toward the third passage 42. I have.

The SA- ₂ 48 selectively connects one of the first hydraulic passage 36 and the pressure regulating hydraulic passage 56 to the wheel cylinder 44.
This is a two-position solenoid valve that conducts to the FR. In a normal state (off state), the first hydraulic passage 36 and the wheel cylinder 44FR are in a conducting state. On the other hand, the SFRR 58 is a two-position solenoid on-off valve that connects or disconnects the pressure regulating hydraulic pressure passage 56 and the reservoir tank 16. SFRR58
In the normal state (OFF state), the pressure regulating hydraulic passage 56 and the reservoir tank 16 are shut off.

The SFLH 52 is a two-position solenoid valve which normally keeps the valve open. The SFLH 52 communicates with the SA- ₁ 46 and a left front wheel pressure reducing solenoid 64 (hereinafter, referred to as SFLR 64) via a pressure adjusting hydraulic pressure passage 62. A check valve 66 is arranged between the third hydraulic pressure passage 42 and the pressure adjusting hydraulic pressure passage 62 so as to allow only the flow of the fluid from the pressure adjusting hydraulic pressure passage 62 toward the third passage 42. I have.

The SA _- 146 selectively connects one of the first hydraulic passage 36 and the pressure adjusting hydraulic passage 62 to the wheel cylinder 44.
The solenoid valve is a two-position solenoid valve that conducts to the FL. In a normal state (off state), the first hydraulic passage 36 and the wheel cylinder 44FL are in a conducting state. On the other hand, the SFLR 64 is a two-position solenoid on-off valve that brings the pressure regulating hydraulic pressure passage 62 and the reservoir tank 16 into a conductive state or a closed state. SFLR64
In the normal state (off state), the pressure regulating hydraulic passage 62 and the reservoir tank 16 are shut off.

The second hydraulic passage 38 is provided with the above-mentioned SA- ₃ 54
Is in communication with On the downstream side of the SA- ₃ 54, the right rear wheel RR
Right rear wheel holding solenoid 68 (hereinafter referred to as SRRH 68) provided corresponding to the wheel cylinder 44RR, and a left rear wheel holding solenoid 70 (hereinafter referred to as) corresponding to the wheel cylinder 44RL of the left rear wheel RL. , SRLH7
0) is in communication. The SA- ₃ 54 is connected to the second hydraulic passage 38.
Alternatively, one of the third hydraulic passages 42 is selectively connected to the SRRH6
8 and a two-position solenoid valve communicating with the SRLH 70. In a normal state (off state), the second hydraulic passage 38 and the SRR
H68 and the SRLR 70 are brought into a communication state.

A wheel cylinder 44RR and a right rear wheel pressure reducing solenoid 74 (hereinafter referred to as SRRR 74) communicate with a downstream side of the SRRH 68 via a pressure adjusting hydraulic pressure passage 72. The SRRR 74 is a two-position solenoid valve that connects or disconnects the pressure control hydraulic pressure passage 72 and the reservoir tank 16. The SRRR 74 shuts off the pressure control hydraulic pressure passage 72 and the reservoir tank 16 in a normal state (off state). State. A check valve 76 that allows only the flow of the fluid from the pressure-regulating hydraulic pressure passage 72 toward the SA- ₃ 54 is arranged between the SA- ₃ 54 and the pressure-regulating hydraulic pressure passage 72. I have.

Similarly, downstream of the SRLH 70, a wheel cylinder 44RL and a left rear wheel pressure reducing solenoid 80 (hereinafter, referred to as an SRLR 80) communicate with each other through a pressure adjusting hydraulic pressure passage 78. The SRLR 80 is a two-position electromagnetic open / close valve that connects or disconnects the pressure regulating hydraulic pressure passage 78 and the reservoir tank 16, and shuts off the pressure regulating hydraulic pressure passage 78 and the reservoir tank 16 in a normal state (off state). State. A check valve 82 is arranged between the SA- ₃ 54 and the pressure adjusting hydraulic passage 78 so as to allow only a fluid flow from the pressure adjusting hydraulic pressure passage 78 toward the SA- ₃ 54. I have.

In the system of this embodiment, the left and right front wheels F
Wheel speed sensors 86FL, 86FR, 86RL, 86RR that emit a pulse signal each time each wheel rotates a predetermined rotation angle are provided near L, FR and the left and right rear wheels RL, RR.
(Hereinafter, when these are collectively referred to, they are denoted by reference numeral 86 _** ). The output signal of the wheel speed sensor 86 _** is supplied to the ECU 10. The ECU 10 controls each of the wheels FL, F based on the output signal of the wheel speed sensor 86 _**.
R, RL, RR rotation speed, that is, each wheel FL, F
The wheel speed of R, RL, RR is detected.

The ECU 10 has a steering sensor 88 functioning as a steering angle detecting means for detecting a steering direction of a steered wheel, a speed (SPD) and a traveling direction (forward or backward) of the vehicle which is one of the driving states of the vehicle. A vehicle speed sensor 90 for detecting reverse is connected. The steering sensor 88 detects a rotation direction and a rotation angle of the steering shaft, and includes, for example, a slit plate that rotates integrally with the steering shaft and a photo interrupter disposed with the slit plate interposed therebetween.

The vehicle speed sensor 90 detects the vehicle speed SPD.
For example, it is constituted by a magnet rotated by rotation of a gear of a transmission and a magnetic sensor for detecting a magnetic field of the magnet. The vehicle speed SPD is determined by the wheel speed sensor 8 described above.
It is also possible to calculate based on 6 _** . ECU10
The hydraulic sensor 40, wheel speed sensors 86 _**, based on the output signal of the steering sensor 88 and the vehicle speed sensor 90,, STR 26 described _{above, SA -1 46, SA -2 48} , S
A _- 354, SFRH50, SFLH52, SFRR5
8, SFLR64, SRRH68, SRLH70, SR
A drive signal is supplied to the RR 74 and the SRLR 80 as appropriate.

FIG. 1 shows the steering control device in the normal state shown above, and therefore the STR 26, SA _- 146, S
A- ₂ 48, SA- ₃ 54, SFRH50, SFLH52,
SFRR58, SFLR64, SRRH68, SRLH
70, SRRR74 and SRLR80 are all OFF
It is in a state. Next, the operation of the steering control device according to the present embodiment will be described.

As described above, the steering control device according to the present embodiment also functions as a braking force control device.
First, prior to the operation as the steering control device, the operation as the braking force control device will be described. The steering control device (braking force control device) of the present embodiment is configured such that the brake pedal force F acting on the brake pedal 30 is applied when the vehicle state is stable.
Normal control for generating a braking force according to _P is executed. Normal control, as shown in FIG. 1, STR 26, SA _-1 46,
SA- ₂ 48, SA- ₃ 54, SFRH50, SFLH5
2, SFRR58, SFLR64, SRRH68, SR
This is realized by turning off all the LH70, SRRR74, and SRLR80.

That is, in the state shown in FIG. 1, the wheel cylinders 44FR and 44FL are connected to the first hydraulic passage 36.
And the wheel cylinders 44RR and 44RL
The respective hydraulic passages 38 communicate with each other. In this case, the brake fluid is moved between the master cylinder 32 and the wheel cylinder 4.
4FR, 44FL, 44RL, and 44RR (hereinafter, collectively referred to by reference numeral 44 _** ), and the brake pedal force F is applied to each of the wheels FL, FR, RL, and RR. A braking force corresponding to _P is generated.

In this embodiment, any of the wheels
If the possibility of transition to the locked state is detected,
For executing brake braking control (hereinafter referred to as ABS control)
It is determined that the condition has been satisfied, and then ABS control is started.
You. The ECU 10 has a vehicle speed sensor 86_**Based on the output signal of
And the wheel speed Vw of each wheel_FL,Vw_FR,Vw_RL,Vw _RR
(Hereinafter, these are collectively referred to by the symbol Vw_**Table with
To calculate the wheel speeds Vw_**Based on public
Estimated value of vehicle speed V by known method_SO(Hereafter, the estimated vehicle body
Speed V_SOIs calculated). And the vehicle is in the braking state
, The slip ratio S of each wheel according to the following equation:
Is calculated, and if S exceeds a predetermined value, the wheel
It is determined that there is a possibility of shifting to the locked state.

S = (V _SO −SPDVw _** ) · 100 / V _S0 (1) When the execution condition of the ABS control is satisfied for any of the wheels, the ECU 10 determines that the execution condition of the ABS control is satisfied. _-1 46, SA _-2 48, or SA corresponding to
_-3 . It should be noted that ABS control can be executed independently for the left and right wheels for the front wheels, and ABS control is executed commonly for the left and right wheels for the rear wheels.

When the execution condition of the ABS control is established for the right front wheel and SA _- 146 is turned on, the wheel cylinder 44FR is disconnected from the first hydraulic pressure passage 36 and communicates with the pressure adjusting hydraulic pressure passage 56. . Also, ABS for the front left wheel
When the execution condition of the control is satisfied and the SA- ₂ 48 is turned on, the wheel cylinder 44FL is disconnected from the first hydraulic pressure passage 36 and communicated with the pressure adjusting hydraulic pressure passage 62. Further, when the execution condition of the ABS control is satisfied for any of the left rear wheel and the right rear wheel, and the SA- ₃ 54 is turned on, the SRRH is turned on.
The upstream side of 68 and the SRLH 70 is shut off from the second hydraulic passage 38 and communicates with the third hydraulic passage 42.

In this case, the wheel cylinders 44 _{** of the} wheels for which the ABS control is executed are connected to the respective holding solenoids S
FRH50, SFLH52, SRRH68, or SRL
H70 (hereinafter, these are collectively referred to as holding solenoid S _** H), and respective decompression solenoids S
FRR58, SFLR64, SRRR74, or SRL
R80 (hereinafter, when these are collectively referred to as a pressure reducing solenoid S _** R), and upstream of all the holding solenoids S _** H, via the third hydraulic pressure passage 42 and the STR 26, A regulator pressure _PRE is derived.

In the above situation, the holding solenoid S _** H
Is opened and the pressure reducing solenoid S _** R is closed, so that the corresponding wheel cylinder 44
The wheel cylinder pressure P _{W / C of **} is increased with the regulator pressure _PRE as an upper limit. Hereinafter, this state is referred to as a pressure increase mode. When the holding solenoid S _** H is closed and the pressure reducing solenoid S _** R is closed, the wheel cylinder pressure P _{W / C} of the corresponding wheel cylinder 44 _** increases or decreases. It will be kept without being done. Less than,
This state is called a holding mode.

[0041] Moreover, When the holding solenoid valves S _** H is a closed state, and the pressure reducing solenoids S _** by R is an open state, the corresponding wheel cylinders 44 _** wheel cylinder pressure P _{W / C} is decompressed. Hereinafter, this state is referred to as a decompression mode. The ECU 10 appropriately implements the above-described pressure increasing mode, holding mode, and pressure reducing mode so that the slip ratio S of each wheel during braking falls within an appropriate value, that is, so that each wheel does not shift to the locked state. As described above, the ABS control is executed,
Locking of the wheels is prevented, so that the steering stability of the vehicle is properly maintained.

The system of this embodiment has a function of executing VSC and TRC in addition to the above-described ABS control as control for improving the steering stability of the vehicle. Has no direct relationship, and a description of this function will be omitted. . Subsequently, an operation as a steering control device which is a feature of the present embodiment will be described.

FIG. 3 is a flowchart showing the steering control processing executed by the ECU 10. FIGS. 4 to 11 are diagrams showing the operation state of the steering control device which is executed according to the driving state of the vehicle. In the present embodiment, the wheel cylinder 44 _** is selectively pressurized in accordance with the driving state of the vehicle to generate a braking force, thereby improving the small turning performance during turning. Hereinafter, a specific operation will be described.

The steering control process shown in FIG. 3 is a routine process that is performed every predetermined time. When the steering control process shown in the figure is started, first, in step 10 (in the figure, the step is abbreviated as S), the ECU 10 first determines the wheel speed Vw of each wheel based on the output signal of the vehicle speed sensor 86 _**.
FL, Vw _FR, Vw _RL, Vw _RR are calculated, a steering wheel turning angle ST (hereinafter, referred to as a steering angle ST) from the steering wheel neutral position is calculated based on an output signal of the steering sensor 88, and an output of the vehicle speed sensor 90 is further calculated. The vehicle speed SPD is calculated based on the signal.

In the following step 12, it is determined whether or not the vehicle speed SPD is not zero (SPD ≠ 0) based on the calculation result of step 10. In this determination, it is determined whether the vehicle body is moving or stopped, regardless of whether the vehicle is moving forward or backward. And step 1
When a negative determination is made in step 2, that is, when it is determined that the vehicle body is stopped, there is no need to perform the steering control process, and thus the present routine process is terminated.

On the other hand, if an affirmative determination is made in step 12, that is, if it is determined that the vehicle is moving, the process proceeds to step 14, where the absolute value of the vehicle speed SPD calculated in step 10 is calculated. Whether the value (| SPD |) is smaller than the control-permitted vehicle speed VH (| SPD | ≦ VH)
Is determined. Here, the reason why the absolute value of the vehicle body speed SPD is taken is to determine the magnitude of the vehicle body speed regardless of whether the vehicle body is moving forward or backward.

In the present embodiment, since the purpose is to improve the small turning performance during low-speed running such as parking in a garage or parallel parking, the vehicle body speed SPD is set to the maximum value of the normal speed in parking in a garage or parallel parking. If it is larger than the control permission vehicle body speed VH), the steering control process after step 16 is not performed. Therefore,
When a negative determination is made in step 14, the present routine processing is terminated.

On the other hand, if a positive determination is made in step 14, that is, if the absolute value of the vehicle speed SPD is
If it is determined that it is smaller than H, the process proceeds to step 16
To determine whether the vehicle body is currently moving forward or backward. The determination of forward / reverse can be made based on the output signal of the vehicle speed sensor 90. If it is determined in step 16 that the vehicle is moving forward, the process proceeds to step 18 to determine the current steering state of the steering. The determination of the steering state can be made based on the output signal of the steering sensor 88.

If it is determined in step 18 that the current steering state is neutral, there is no need to perform steering control, and the routine is terminated. If it is determined in step 18 that the current steering state is a right-turning state, the process proceeds to step 2
The control proceeds to 0 to determine whether the absolute value (| ST |) of the steering angle ST is larger than the control start steering wheel turning angle SH (| ST | ≧ SH).
Is determined.

As described above, in the present embodiment, the purpose is to improve the small turnability when the steering wheel such as the garage or the parallel parking is turned greatly.
When the steering angle ST is small (that is, in a straight-ahead state or a state close thereto), there is no need to perform steering control. For this reason, the steering angle ST is the maximum steering angle of the steering during normal running (this is referred to as a control start steering wheel turning angle SH).
, The steering control process is not performed. Therefore, when a negative determination is made in step 20, the present routine processing is terminated.

On the other hand, if an affirmative judgment is made in step 20, that is, if the absolute value (| ST |) of the steering angle ST is larger than the control start steering wheel turning angle SH, the steering is advanced at a low speed and greatly steered. It is operating. That is, if the determination in step 20 is affirmative, the vehicle is required to have a particularly small turnability. Therefore, in this case, the process proceeds to step 22, and the forward right turn control is performed to improve the small turning performance. The forward right-turn control will be described later in detail for the sake of convenience.

If it is determined in step 18 that the current steering state is a left-turning state, the process proceeds to step 24, where the absolute value (| ST |) of the steering angle ST is controlled as in step 20. It is determined whether or not it is greater than the start steering wheel turning angle SH (| ST | ≧ SH). As described above, when the steering angle ST is smaller than the control start steering wheel turning angle SH, there is no need to perform the steering control process. Therefore, if a negative determination is made in step 24, the present routine process is terminated. I have.

On the other hand, if an affirmative determination is made in step 24, that is, if the absolute value (| ST |) of the steering angle ST is larger than the control start steering wheel turning angle SH, the vehicle is steered forward at a low speed and greatly steered. It is operating. Therefore, even when the determination in step 24 is affirmative, the vehicle is required to have a small turnability. Therefore, in this case, the process proceeds to step 22, and the forward left turn control is performed to improve the small turning performance. The forward left turn control will be described later in detail for convenience of description.

On the other hand, if it is determined in step 16 that the vehicle is moving backward, the process proceeds to step 28, in which the current steering state of the steering is determined. Then, if it is determined in step 28 that the current steering state is neutral, there is no need to perform steering control, and this routine processing ends. Step 28
If it is determined that the current steering state is a right-turning state in step, the process proceeds to step 30 to determine whether the absolute value (| ST |) of the steering angle ST is larger than the control start steering wheel turning angle SH (| ST | ≧ SH) is determined.

As described above, when the steering angle ST is small (that is, in a straight traveling state or a state close thereto), there is no need to perform steering control. Therefore, when a negative determination is made in step 30, the present routine processing is terminated. On the other hand, if an affirmative determination is made in step 34, that is, if the absolute value (| ST |) of the steering angle ST is larger than the control start steering wheel turning angle SH, the vehicle is steered forward at a low speed as described above and greatly steered. Is operating. Therefore, even when the determination in step 24 is affirmative, the vehicle is required to have a small turnability.

Accordingly, in this case, the process proceeds to step 32, and reverse right-turn control is performed to improve the small turning performance. The reverse right turn control will be described later in detail for convenience of explanation. If it is determined in step 28 that the current steering state is a left-turn state,
The process proceeds to step 34, where it is determined whether the absolute value (| ST |) of the steering angle ST is greater than the control start steering wheel turning angle SH (| ST | ≧ SH), as in step 30. As described above, when the steering angle ST is smaller than the control start steering wheel turning angle SH, there is no need to perform the steering control process. Therefore, if a negative determination is made in step 34, the present routine process is terminated. I have.

On the other hand, if an affirmative determination is made in step 34, that is, if the absolute value (| ST |) of the steering angle ST is greater than the control start steering wheel turning angle SH, the vehicle is steered forward at a low speed and greatly steered. It is operating. Therefore, even if the result of the determination in step 34 is affirmative, the vehicle is required to have small turnability. Therefore, in this case, the process proceeds to step 36, and reverse left turn control is performed in order to improve small turnability. The backward left turn control will be described later in detail for the sake of convenience.

Subsequently, the forward right turning control performed in step 22 described above, the forward left turning control performed in step 26, the backward right turning control performed in step 32, and the backward left turning performed in step 36. The cutting control will be described. When it is intended to improve the small turning property by the braking force, it is effective to generate the braking force on the front turning inner wheel in the traveling direction. When a braking force is generated on the front turning inner wheel with respect to the traveling direction, the outermost turning radius of the vehicle body during turning can be reduced, so that the small turning property can be improved. Forward right turn control performed in step 22 described above, forward left turn control performed in step 26, reverse right turn control performed in step 32,
In the reverse left turn control performed in step 36, the control process is performed based on this principle. [Forward right-turn control] First, forward right-turn control will be described. FIGS. 4 and 5 are diagrams for explaining the forward right-turn control performed in step 22. FIG. As shown in FIG. 5, when the vehicle 92 makes a forward right turn, the right front wheel FR which is a front turning inner wheel with respect to the traveling direction is required to improve small turning performance.
It is desirable to generate a braking force.

Therefore, in the forward right turn control executed in step 22, brake fluid is supplied to the wheel cylinder 44FR of the right front wheel FR.
Specifically, as shown in FIG. 4, the ECU 10 turns on the STR 26 and the SA- ₂ 48 in the normal state shown in FIG. As a result, the high-pressure brake fluid stored in the accumulator 20 is released from the high-pressure passage 22, ST.
R26, SFRH50, pressure regulating hydraulic passage 56, and SA
_The braking force is generated at the right front wheel FR by being supplied to the wheel cylinder 44FR through _-2 48. Thereby, the small turning property at the time of forward right turning can be improved.

Further, although the braking force is generated on the right front wheel FR by the above-described processing, if an excessive braking force is generated, the stability of the vehicle is reduced. Therefore, when an excessive braking force is generated, the pressure in the wheel cylinder FR is reduced by appropriately turning on the SFRH 50 and the SFRR 58. Then, when the pressure in the wheel cylinder 44FR becomes the optimum pressure at which the small turning property can be improved, the SFRR 58 is turned off again. This allows
The wheel cylinder 44FR maintains the optimum pressure, and can maintain a favorable state of small turning performance.

Here, a method for determining the optimum pressure will be described. In this embodiment, the speed ratio (V2 / V), which is the ratio between the speed of the turning outer wheel (V1) and the speed of the turning inner wheel (V2), is used.
Based on 1), a braking force value to be generated for each wheel is determined. Now, the forward right turning control performed in step 22 will be described as an example.
0 is the speed ratio of the wheel speed Vw _FR of the right front wheel FR is a wheel speed Vw _FL and the turning inner ring of the left front wheel FL is a turning outer wheel (V
w _FR / Vw _FL ), the braking force to be generated on the right front wheel FR is determined.

Further, the ECU 10 determines the vehicle speed SPD detected by the vehicle speed sensor 90 and the steering sensor 88
The most suitable optimum speed ratio in the current steering state is calculated based on the steering angle ST obtained by the above (this process corresponds to the process of the speed ratio calculating means). ECU10
Stores a ternary map indicating the relationship among the speed ratio, the steering angle ST, and the vehicle speed SPD, which is obtained in advance through experiments or the like, in an internal ROM. The optimum speed ratio is calculated by referring to the three-way map.

FIG. 12 shows an example of the ternary map. A specific example of calculating the optimum speed ratio will be described with reference to FIG. Now, it is assumed that the current steering angle ST is θ1 and the vehicle speed SPD is SPD2. Then, the optimum speed ratio is determined to be α from the three-way map in FIG. That is, by performing control so that (Vw _FR / Vw _FL ) = α, it is possible to obtain an optimum small turning property.

As described above, the wheel speed Vw _FL of the left front wheel FL and the wheel speed Vw FR of the right front wheel _FR are always detected by the wheel speed sensors 86FL and 86FR. Therefore, the speed ratio (Vw _FR / Vw _FL ) after the braking force is generated on the right front wheel FR is always calculated, and the speed ratio (Vw _FR / Vw _FL ) becomes the optimum speed ratio α. SFRH
By controlling the driving of the wheel cylinder 50 and the SFRR 58, the pressure of the wheel cylinder 44FR is controlled.

As a result, the current driving state of the vehicle (ie, the turning angle S
(T, vehicle speed SPD), it is possible to generate a braking force of a magnitude most suitable for the vehicle, and it is possible to obtain an optimum small turning property at the time of turning and improve the operability. Note that the same control processing is performed also in the forward left-turn control, the backward right-turn control, and the backward left-turn control, which are described below, to improve the small turning performance and the operability. [Forward left turn control] Next, forward left turn control will be described. 6 and 7 are diagrams for explaining the forward left turn control performed in step 26. FIG. As shown in FIG. 7, when the vehicle 92 makes a forward left turn, it is desirable to generate a braking force on the left front wheel FL, which is a front turning inner wheel with respect to the traveling direction, in order to improve small turnability.

Therefore, in the forward left-turn control executed in step 26, the brake fluid is supplied to the wheel cylinder 44FL of the left front wheel FL.
Specifically, as shown in FIG. 6, the ECU 10 turns on the STR 26 and the SA _- 146 in the normal state shown in FIG. As a result, the high-pressure brake fluid stored in the accumulator 20 is released from the high-pressure passage 22, ST.
R26, SFLH52, pressure adjusting hydraulic passage 62, and SA
_The braking force is generated at the left front wheel FL by being supplied to the wheel cylinder 44FL through -146. Thereby, the small turning property at the time of forward left turning can be improved.

Further, a braking force is generated on the left front wheel FL by the above-described processing. However, if an excessive braking force is generated, the stability of the vehicle is reduced. Therefore, when an excessive braking force is generated, the pressure in the wheel cylinder FL is reduced by appropriately turning on the SFLH 52 and the SFLR 64. Then, when the pressure in the wheel cylinder 44FL reaches the optimum pressure at which the small turning property can be improved, the SFLR 64 is turned off again. This allows
The wheel cylinder 44FL maintains the optimum pressure, and can maintain a state of good small turning performance. [Reverse Right Turn Control] FIGS. 8 and 9 are diagrams for explaining the reverse right turn control performed in step 32. FIG. As shown in FIG. 9, when the vehicle 92 makes a reverse right turn, it is desirable to generate a braking force on the right rear wheel RR, which is the front turning inner wheel in the traveling direction, in order to improve the small turning performance.

Therefore, in the reverse right turn control executed in step 32, the brake fluid is supplied to the wheel cylinder 44RR of the right rear wheel RR.
Specifically, as shown in FIG. 8, in contrast to the normal state shown in FIG. 1, the ECU 10 controls the STR 26, the SA- ₃ 54, and the SR
The LR 70 is turned on. As a result, the high-pressure brake fluid stored in the accumulator 20 is released from the high-pressure passage 22, the STR 26, the SA- ₃ 54, the SRRH 68,
The pressure is supplied to the wheel cylinder 44RR via the pressure adjusting hydraulic pressure passage 72, so that a braking force is generated on the right rear wheel RR. This makes it possible to improve the small turning property at the time of backward right turn.

Further, a braking force is generated on the right rear wheel RR by the above-described processing. If an excessive braking force is generated, the stability of the vehicle is reduced. Therefore, when an excessive braking force is generated, the pressure in the wheel cylinder 44RR is reduced by appropriately turning on the SRRH 68 and the SRRR 74. Then, the pressure within the wheel cylinder 44RR is adjusted to an optimum pressure (hereinafter, referred to as an optimum pressure) that can improve the small turning property.
At this point, the SRRR 74 is turned off again. Thereby, the wheel cylinder 44RR
Keeps the optimum pressure, and can maintain a state with good small turning property. [Reverse left turn control] Next, reverse left turn control will be described. FIGS. 10 and 11 are diagrams for explaining the backward left-turn control performed in step 36. FIG. As shown in FIG. 11, when the vehicle 92 makes a reverse left turn, it is desirable to generate a braking force on the left rear wheel RL, which is the front turning inner wheel in the traveling direction, in order to improve the small turning performance.

Therefore, in the reverse left turn control performed in step 36, brake fluid is supplied to the wheel cylinder 44RL of the left rear wheel RL.
Specifically, as shown in FIG. 10, in contrast to the normal state shown in FIG. 1, the ECU 10 sets the SRT 26, the SA- ₃ 54, and the S
The RRH 68 is turned on. As a result, the high-pressure brake fluid stored in the accumulator 20 becomes
High-pressure passage 22, STR26, SA _- 354, SRLH7
0, the wheel cylinder 44R through the pressure regulating hydraulic passage 78
L, so that a braking force is generated on the left rear wheel RL.
This makes it possible to improve the small turning performance when the vehicle turns left.

Further, a braking force is generated on the left rear wheel RL by the above-described processing. If an excessive braking force is generated, the stability of the vehicle is reduced. Therefore, when an excessive braking force is generated, the pressure in the wheel cylinder RL is reduced by appropriately turning on the SRLH 70 and the SRLR 80. Then, when the pressure in the wheel cylinder 44RL becomes the optimum pressure at which the small turning property can be improved, the SRLR 80 is turned off again. This allows
The wheel cylinder 44RL maintains the optimum pressure, and can maintain a favorable state of small turning performance.

As described above, the steering control device according to the present embodiment uses the system of the braking control device corresponding to the ABS control which has been generally used conventionally.
Only the control operation executed by the ECU 10 achieves the optimum small turning property. Therefore, a new configuration is not particularly required to realize the present embodiment, and cost performance can be improved.

[0073]

According to the present invention as described above, the following various effects can be realized. According to the first aspect of the present invention, by generating a braking force on the front turning inner wheel with respect to the traveling direction, the turning radius of the disaster part of the vehicle body during turning can be reduced, thereby improving the turning ability. it can.

According to the second aspect of the present invention, a braking force having a magnitude most suitable for the current driving state of the vehicle (ie, turning angle, vehicle speed, etc.) is applied to the rear turning inner wheel in the traveling direction. As a result, the operability and the operability at the time of turning can be improved.

[Brief description of the drawings]

FIG. 1 is an overall configuration diagram of a steering control device according to an embodiment of the present invention.

FIG. 2 is a block diagram of a control system of the steering control device according to one embodiment of the present invention.

FIG. 3 is a flowchart illustrating a braking control process performed during a turn.

FIG. 4 is a diagram for explaining an operation when the traveling direction is forward and the steering direction is rightward (forward right turn).

FIG. 5 is a diagram for explaining a vehicle state when the traveling direction is forward and the steering direction is rightward (forward right turn).

FIG. 6 is a diagram for explaining an operation when the traveling direction is forward and the steering direction is leftward (forward left turn).

FIG. 7 is a diagram for explaining a vehicle state when the traveling direction is forward and the steering direction is leftward (forward left turn).

FIG. 8 is a diagram for explaining an operation in the case where the traveling direction is backward and the steering direction is rightward (backward right turn).

FIG. 9 is a diagram for explaining a vehicle state when the traveling direction is backward and the steering direction is rightward (backward right turn).

FIG. 10 is a diagram for explaining an operation when the traveling direction is backward and the steering direction is left.

FIG. 11 is a diagram for explaining a vehicle state when the traveling direction is backward and the steering direction is left.

FIG. 12 is a diagram showing a map used in a braking control process performed during a turn.

[Explanation of symbols]

10 Electronic Control Unit 26 Regulator Switching Solenoid (STR) 30 Brake Pedal 32 Master Cylinder 40 Hydraulic Sensor 46 First Assist Solenoid (SA _-1 ) 48 Second Assist Solenoid (SA _-2 ) 50 Right Front Wheel Holding Solenoid (SFRH) 52 Left Front wheel holding solenoid (SFLH) 54 Third assist solenoid (SA- ₃ ) 58 Right front wheel pressure reducing solenoid (SFRR) 64 Left front wheel holding solenoid (SFLR) 68 Right rear wheel holding solenoid (SRRH) 70 Left rear wheel holding solenoid (SRLH) 74 Right rear wheel pressure reducing solenoid (SRRR) 80 Left rear wheel holding solenoid (SRLR) 86FL, 86FR, 86RL, 86RR Wheel speed sensor 88 Steering sensor 90 Vehicle speed sensor

Continued on the front page (51) Int.Cl. ⁶ Identification code FI B62D 115: 00 137: 00

Claims (2)

[Claims] 1. A steering angle detecting means for detecting a steering direction of a steered wheel; a braking means configured to perform a braking operation independently on each wheel; and a driving state detection for detecting a driving state of a vehicle. Means, based on a vehicle traveling direction detected by the driving state detecting means, and a steering direction detected by the steering angle detecting means, braking force control means for generating a braking force on the front turning inner wheel with respect to the traveling direction. A steering control device, comprising: 2. The steering control device according to claim 1, wherein the braking force control means is a ratio of a speed of the turning outer wheel (V1) and a speed of the turning inner wheel (V2) obtained by the driving state detecting means. Braking force value determining means for determining a braking force value to be generated for each wheel based on a speed ratio (V2 / V1); current steering based on a vehicle speed detected by the driving state detecting means and the steering angle; A steering control device provided with an optimum speed ratio calculating means for obtaining an optimum speed ratio most suitable in a state.