JP4062754B2 - vehicle - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a vehicle .
[0002]
[Prior art and problems to be solved by the invention]
Overspeed during curve travel, the transition from the uphill to downhill, the driver of the operation error or the like in an emergency during steering, when the vehicle undergoes a spin and drift, able to steer the vehicle along the intention of the driver become unable.
[0003]
In order to prevent such unstable vehicle behavior such as drift and spin, a technology for controlling the braking force and driving force of the vehicle has been developed.
[0004]
However, such conventional technology is intended to stabilize the vehicle behavior near the motion limit of the vehicle where the grip force is saturated. In the vicinity of the movement limit, there is no allowance for grip force on the road surface of the tire, so there is a limit in control of vehicle behavior.
[0005]
An object of this invention is to provide the vehicle which can solve the said problem.
[0006]
[Means for Solving the Problems]
The vehicle according to the present invention is characterized by means for outputting a signal for adding a braking force of the vehicle when the front wheel load of the vehicle is less than a set value, and for determining a parameter correlated with the front wheel load, the parameter and the front wheel Means for storing a predetermined relationship with the load; means for determining a front wheel load based on the determined parameter and the stored relationship; and means for storing a predetermined relationship between the parameter and a set value of the front wheel load; A means for obtaining a set value of the front wheel load based on the obtained parameter and the stored relationship, and when the obtained front wheel load is less than the obtained set value, a braking force of the vehicle is added according to the difference. And means for obtaining a parameter correlated with the front wheel load has a torque sensor for detecting steering torque and a vehicle speed sensor for detecting vehicle speed, and the front wheel load The correlated parameters include the steering torque detected by the torque sensor and the vehicle speed detected by the vehicle speed sensor, and the amount of braking force added varies depending on the difference in the front wheel load of the cornering force at a constant tire slip angle. It is to be determined to disappear .
According to this configuration, when the front wheel load becomes less than the set value due to a decrease in the road surface friction coefficient or the like, the vehicle is applied in the normal driving state before the vehicle reaches the motion limit by adding the braking force of the vehicle. Safety can be improved by stabilizing the behavior.
As a parameter correlated with the front wheel load, for example, a friction coefficient between the vehicle and the road surface, a yaw rate of the vehicle, and the like may be obtained together.
The set value can be a value that stabilizes the vehicle behavior if the front wheel load is equal to or greater than the set value.
[0008]
When the obtained front wheel load is less than the obtained set value, it is preferable to provide means for reducing the force required for steering as compared with the case where the obtained front wheel load is greater than or equal to the set value.
Thereby, the attitude control performance of the vehicle by steering of the driver can be assisted, and the attitude control performance can be improved as compared with the case where the vehicle behavior is stabilized only by the control of the braking force .
By reducing the force required for the steering as the front wheel load is smaller, the driver's steering can be assisted to improve the attitude control performance.
[0016]
DETAILED DESCRIPTION OF THE INVENTION
A first embodiment of the present invention will be described with reference to FIGS.
[0017]
A rack and pinion type electric power steering apparatus 1 for a vehicle shown in FIG. 1 includes an input shaft 2 connected to a steering wheel H and an output shaft 4 connected to the input shaft 2 via a torque sensor 3. . The output shaft 4 is connected to a pinion 6 via a universal joint 5, and a wheel 8 is connected to a rack 7 that meshes with the pinion 6. As a result, the steering torque is transmitted to the rack 7 via the steering wheel H, the input shaft 2, the torque sensor 3, the output shaft 4, and the pinion 6, and the movement of the rack 7 steers the vehicle. A steering angle sensor 9 is attached to the input shaft 2. In the present embodiment, the front wheels are steered, but the front and rear wheels may be steered.
[0018]
A bevel gear 12 is fitted to the outer periphery of the output shaft 4, and a bevel gear 15 that meshes with the bevel gear 12 is driven to rotate by an actuator 13.
[0019]
A braking system is provided for braking each wheel 8 of the vehicle. In other words, the master cylinder 17 generates a braking pressure corresponding to the depression force of the brake pedal 16. The braking pressure is amplified by the braking pressure control unit 18 and distributed to the brake devices 19 of the wheels 8, and each brake device 19 applies a braking force to each wheel 8. The braking pressure control unit 18 is connected to the brake system controller 60. A wheel speed detection sensor 52 and a braking force detection sensor 61 for each wheel 8 are connected to the brake system controller 60. The brake system controller 60 amplifies and distributes the braking pressure according to the rotational speed of each wheel 8 detected by the wheel speed sensor 52 and the feedback value from the braking force detection sensor 61 so that the braking pressure can be distributed. Control unit 18 is controlled. The braking pressure control unit 18 can generate a braking pressure by a built-in pump even when the brake pedal 16 is not operated.
[0020]
The torque sensor 3 detects a steering torque transmitted from the input shaft 2 to the output shaft 4. The torque sensor 3 is connected to a steering system controller 50 constituted by a computer. A steering angle sensor 9, an actuator 13, a vehicle speed sensor 51, a friction coefficient sensor 62 for detecting a friction coefficient between the vehicle and the road surface, and a brake system controller 60 are connected to the steering system controller 50.
[0021]
As parameters correlated with the front wheel load, the torque sensor 3 determines the steering torque, the vehicle speed sensor 51 determines the vehicle speed, the wheel speed sensor 52 determines the rotational speed of each wheel 8, and the friction coefficient sensor 62 determines the friction coefficient. The braking force of each wheel 8 detected by the braking force detection sensor 61 is sent to the steering system controller 50 via the brake system controller 60.
[0022]
The steering system controller 50 stores a predetermined relationship between the parameter and the front wheel load. This relationship can be determined by experiment. Based on the stored relationship and the obtained parameter, the steering system controller 50 can obtain the front wheel load.
[0023]
Further, the steering system controller 50 stores a predetermined relationship between the parameter and the set value of the front wheel load. The set value can be a lower limit value that stabilizes the vehicle behavior if the front wheel load is equal to or greater than the set value. This relationship can be determined by experiment. Based on the stored relationship and the obtained parameter, the steering system controller 50 obtains a set value of the front wheel load.
[0024]
The steering system controller 50 outputs a signal for adding the braking force of the vehicle to the brake system controller 60 when the front wheel load of the vehicle is less than the set value, and the front wheel load is equal to or greater than the set value. The force required for steering is made smaller than the case.
[0025]
2 and 3 show the control procedure of the system.
That is, as shown in the main routine of FIG. 2, the steering system controller 50 and the brake system controller 60 read data detected by the sensors (step 1), and then perform stabilization control (step 2). .
[0026]
In the stabilization control, as shown in the subroutine of FIG. 3, it is determined whether or not the front wheel load obtained as described above is equal to or larger than the set value obtained as described above (step 101).
[0027]
When the front wheel load is less than the set value, the steering system controller 50 outputs a signal for adding braking force to the brake system controller 60 according to the difference between the set value and the front wheel load. The brake system controller 60 controls the braking pressure control unit 18 based on the difference between the braking force corresponding to the braking force addition signal output from the steering system controller 50 and the braking force detected by the braking force detection sensor 61. Thus, a braking force corresponding to the difference between the set value and the front wheel load is automatically added (step 102). What is necessary is just to determine the additional amount of the braking force so that vehicle behavior may be stabilized. For example, the solid line, the one-dot chain line, and the two-dot chain line shown in FIG. 4 indicate the relationship between the tire slip angle and the cornering force, respectively. Therefore, the vehicle behavior can be stabilized by determining the additional amount of the braking force so as to eliminate the fluctuation due to the difference in the front wheel load of the cornering force at the constant tire slip angle.
[0028]
Next, the steering system controller 50 sets a steering assist force increase flag so as to reduce the force required for steering in accordance with the difference between the set value and the front wheel load (step 103), and returns to the main routine.
[0029]
If the front wheel load is greater than or equal to the set value in step 101, this is canceled when the braking force is automatically applied (step 104), the steering system controller 50 sets a normal steering assist flag (step 105), and the main routine. Return to. Note that the normal steering assist flag is cleared when the steering assist force increase flag is set, and the steering assist force increase flag is cleared when the normal steering assist flag is set.
[0030]
In the main routine of FIG. 2, the steering system controller 50 outputs a control signal for generating a steering assist force to the actuator 13 (step 3). When the normal steering assist flag is set, the actuator 13 is driven based on the control signal, so that a normal steering assist force is applied according to the detected steering torque and vehicle speed. When the steering assist force increase flag is set, the steering assist force generated by driving the actuator 13 based on the control signal is greater than the normal steering assist force when the normal steering assist flag is set. The larger the difference between the set value and the front wheel load, the larger the value, and the specific value may be determined by experiment so that an appropriate steering feeling can be imparted to the driver. This steering assistance is repeated until the engine stops (step 4).
[0031]
According to the configuration of the first embodiment, when the front wheel load becomes less than the set value due to a decrease in the road surface friction coefficient, the front wheel load can be prevented from being reduced by applying the braking force of the vehicle. Therefore, even if there is an unexpected change in the road surface condition, the vehicle behavior can be stabilized in a normal driving state before reaching the vehicle motion limit, and safety can be improved. Since the braking force of the vehicle can be applied according to the difference between the front wheel load and the set value, the vehicle behavior can be further stabilized and the steering feeling can be further improved. Also, when the front wheel load is less than the set value, the force required for steering is smaller than when it is greater than or equal to the set value, so that the attitude control performance can be improved by assisting the attitude control of the vehicle by the driver's steering, By reducing the force required for the steering so that the front wheel load is smaller than the set value, it is possible to assist the driver's steering and improve the attitude control performance.
[0032]
FIG. 5 shows a flowchart of the second embodiment of the present invention. The difference from the first embodiment is in the stabilization control, and other configurations are the same as those in the first embodiment. In addition, in this 2nd Embodiment, the same part as 1st Embodiment is shown with the same code | symbol, and a different point is demonstrated.
[0033]
That is, in the stabilization control, first, the presence or absence of steering is determined (step 201). The presence or absence of this steering is determined, for example, based on whether or not the steering detected by the rudder angle sensor 9 is greater than or equal to a set value. If there is no steering, return to the main routine.
[0034]
If there is steering, it is determined whether or not the front wheel load is greater than or equal to a set value (step 202). The set value is a value that can be set to an ideal value that allows the vehicle behavior to be stable and smoothly steered if the front wheel load is equal to or greater than the set value, and is larger than the set value in the first embodiment. can do.
[0035]
When the front wheel load is less than the set value, the steering system controller 50 outputs a signal for adding braking force to the brake system controller 60 according to the difference between the set value and the front wheel load. The brake system controller 60 controls the braking pressure control unit 18 based on the difference between the braking force corresponding to the braking force addition signal output from the steering system controller 50 and the braking force detected by the braking force detection sensor 61. Thus, a braking force corresponding to the difference between the set value and the front wheel load is automatically added (step 203).
[0036]
Next, it is determined again whether or not the front wheel load is greater than or equal to the set value (step 204). If the front wheel load is less than the set value, the steering system controller 50 sets a steering assist force increase flag so that the force required for steering can be reduced according to the difference between the set value and the front wheel load (step 205) Returning to the main routine.
[0037]
If the front wheel load is greater than or equal to the set value in step 202 and step 204, this is canceled when the braking force is automatically applied (step 206), and the steering system controller 50 sets the normal steering assist flag (step 207). Return to the main routine. Note that the normal steering assist flag is cleared when the steering assist force increase flag is set, and the steering assist force increase flag is cleared when the normal steering assist flag is set.
[0038]
Further, the steering assist force applied in step 3 of the main routine is increased as the detected braking force value sent to the steering system controller 50 via the brake system controller 60 is decreased, and the force required for steering is decreased. This improves the attitude control performance by assisting the driver's steering.
[0039]
According to the configuration of the second embodiment, at the time of steering, when the front wheel load becomes less than the set value due to overspeed or the like, a reduction in the front wheel load can be prevented by applying the braking force of the vehicle. Therefore, it is possible to stabilize the vehicle behavior in a normal driving state before reaching the motion limit of the vehicle, maintain smooth steering, and improve safety. By increasing the amount of increase in the braking force of the vehicle as the front wheel load is smaller than the set value, it is possible to further stabilize the vehicle behavior and further improve the steering feeling. Also, when the front wheel load is less than the set value, the force required for steering is smaller than when it is greater than or equal to the set value, so that the attitude control performance can be improved by assisting the vehicle attitude control by the driver's steering, By reducing the force required for the steering so that the front wheel load is smaller than the set value, it is possible to assist the driver's steering and improve the attitude control performance.
[0040]
In the first and second embodiments, the parameters correlated with the front wheel load include, for example, the yaw rate of the vehicle in addition to the steering torque, the vehicle speed, the friction coefficient between the vehicle and the road surface, and the wheel rotation speed. You may ask for it .
[0084]
In addition, this invention is not limited to the said embodiment. For example, the steering device is not limited to a rack and pinion type, and may be a ball screw type.
[0085]
【The invention's effect】
According to the present invention, it ensures stable vehicle behavior, safety, and improving the steering feeling can be further provides vehicles capable of improving the collision avoidance performance with the obstacle.
[Brief description of the drawings]
FIG. 1 is a diagram illustrating the configuration of a steering apparatus according to a first embodiment of the present invention. FIG. 2 is a flowchart showing a control procedure of the steering apparatus according to the first embodiment of the present invention. description of flowchart [code indicating the control procedure of the steering device of the second embodiment of FIGS. 5A and 5B present invention showing the relationship between the flow chart Figure 4 tire slip angle and the cornering force of a control procedure of the steering device ]
1 rack and pinion type electric power steering device 3 a torque sensor 8 wheel 9 steering angle sensor 13 the actuator 16 the brake pedal 18 brake pressure control unit 19 brake unit 50 the steering system controller 51 a vehicle speed sensor 52 the wheel speed detecting sensor
6 0 brake system controller 61 braking force sensor 62 friction coefficient sensor

Claims (2)

When the front wheel load of the vehicle is less than the set value, a signal for adding the braking force of the vehicle is output ,
Means for obtaining a parameter correlated with the front wheel load;
Means for storing a predetermined relationship between the parameter and the front wheel load;
Means for determining the front wheel load based on the calculated parameters and the stored relationship;
Means for storing a predetermined relationship between the parameter and a set value of the front wheel load;
Means for obtaining a set value of the front wheel load based on the obtained parameter and the stored relationship;
Means for outputting a signal for adding the braking force of the vehicle according to the difference when the determined front wheel load is less than the determined set value;
The means for obtaining the parameter correlated with the front wheel load has a torque sensor for detecting the steering torque and a vehicle speed sensor for detecting the vehicle speed, and the parameter correlated with the front wheel load is the steering torque detected by the torque sensor. Including a vehicle speed detected by the vehicle speed sensor;
The amount of braking force added is determined so that fluctuation due to the difference in the front wheel load of the cornering force at a constant tire slip angle is eliminated . 2. The vehicle according to claim 1, further comprising means for reducing a force required for steering when the obtained front wheel load is less than the set value when the obtained front wheel load is less than the set value .

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