JP3557016B2 - Vehicle steering system - Google Patents

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a steering device that can prevent a running vehicle from colliding with an obstacle.
[0002]
[Prior art]
In order to prevent the vehicle from colliding with an obstacle such as a guardrail on the side or rear side or another vehicle during a lane change or the like, steering is suppressed based on the possibility of collision between the vehicle and an obstacle. Steering devices have been proposed. For example, when the detection of an obstacle on the rear side of the vehicle cancels the application of the steering assist force, applies a steering suppression force in a direction opposite to the direction to be steered, or maintains the currently traveling lane. There has been proposed an apparatus that controls the steering device to control the steering so that the driver can recognize the presence of an obstacle (see JP-A-5-294250 and JP-A-4-19274).
[0003]
[Problems to be solved by the invention]
However, when such a possibility of collision occurs, even if the current lane is maintained without actually performing a lane change or the like in a direction in which there is a possibility of collision, if the steering suppression is performed, There is a problem that the feeling of play in steering in the direction in which the collision is likely to be lost and the steering feeling is reduced.
[0004]
An object of the present invention is to provide a vehicle steering device that can solve the above-described problems.
[0005]
[Means for Solving the Problems]
The vehicle steering apparatus according to the present invention includes a means for detecting a steering torque, a means for determining whether or not the steering torque is equal to or greater than a set value, and a method for determining whether or not an obstacle detected in the steering direction can collide with the vehicle. And a means for controlling the steering torque when the steering torque is equal to or more than a set value and a possibility of collision occurs, and the set value of the steering torque increases as the vehicle speed increases. It is characterized by being set.
[0006]
According to the configuration of the present invention, if the steering torque required for steering in the direction in which there is a possibility of collision is less than the set value, steering suppression is not performed, so that the sense of play in steering in the direction in which there is a possibility of collision is improved. , And a decrease in steering feeling can be prevented.
Further, as shown in the comparative example of FIG. 10, when the set value Tc of the steering torque is constant with respect to the vehicle speed v, the play range of the steering becomes small at the time of high-speed running, and the steering feeling is sufficiently reduced. Can not be prevented. This is because, when the vehicle speed increases, the self-aligning torque acting on the tires from the road surface increases and the torque required for steering increases even when the steering angle is the same as during low-speed running.
On the other hand, according to the configuration of the present invention, the set value of the steering torque increases as the vehicle speed increases, so that even when the self-aligning torque increases during high-speed traveling, the play range of the steering is prevented from being reduced. However, it is possible to sufficiently prevent the steering feeling from deteriorating.
[0007]
Means for controlling an actuator for generating a steering assist force by a control value corresponding to the detected steering torque; and controlling the steering when the steering torque is equal to or more than a set value and a possibility of collision occurs. Means for changing the control value, wherein the rate of increase of the steering assist force with respect to the steering torque is preferably set so as to decrease as the vehicle speed increases.
[0008]
By applying the present invention to a power steering device, a steering suppression force can be applied by a steering assist force generating actuator. Since the rate of increase of the steering assist force with respect to the steering torque decreases with an increase in the vehicle speed, the running stability is improved at a high speed and the turning performance is improved at a low speed. In this case, since the steering assist force decreases at high speeds, the torque required for steering increases even when the steering angle is the same as during low-speed running.
According to the configuration of the present invention, since the set value of the steering torque increases as the vehicle speed increases, it is possible to prevent the play range of the steering from being reduced even during high-speed running, and to sufficiently reduce the steering feeling. In addition, running stability at high speeds and turning performance at low speeds can be improved.
[0009]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, embodiments of the present invention will be described with reference to the drawings.
[0010]
A rack and pinion type electric power steering device 1 shown in FIG. 1 includes an input shaft 2 connected to a steering wheel H of a vehicle 10 and an output shaft 4 connected to the input shaft 2 via a torque sensor 3. I have. The output shaft 4 is connected to a pinion 6 via a universal joint 5, and a steering 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 vehicle 10 is steered by the movement of the rack 7.
[0011]
As shown in FIG. 2, a torsion bar 11 is inserted into the input shaft 2 and the output shaft 4 and is connected by pins 18 and 19. The input shaft 2 is configured by connecting a first shaft 2a on the steering wheel H side and a second shaft 2b on the torque sensor 3 side with a pin 18. As a result, the input shaft 2 and the output shaft 4 rotate relative to each other in accordance with the steering torque. One end of the input shaft 2 is inserted into a concave portion 4a formed at one end of the output shaft 4, and as shown in FIG. 3, a part of the outer peripheral surface of the input shaft 2 and a part of the inner peripheral surface of the concave portion 4a. Are non-circular portions 2 'and 4' facing each other. When the non-circular portion 2 'on the input shaft 2 side and the non-circular portion 4' on the output shaft 4 abut, the relative rotatable amount of the input shaft 2 and the output shaft 4 is restricted to a certain range, and The breakage of the bar 11 is prevented. A worm wheel 12 is fitted on the outer periphery of the output shaft 4, and a worm gear 15 meshing with the worm wheel 12 is connected to a steering assist force generating motor (actuator) 13 as shown in FIG.
[0012]
As shown in FIG. 2, the torque sensor 3 includes a housing 16 fitted to the input shaft 2 and the output shaft 4 so as to be relatively rotatable. A first detection ring 21 made of a magnetic material is fitted around the outer periphery of the input shaft 2, and a second detection ring 23 made of a magnetic material is fitted around the outer periphery of the output shaft 4 so as to rotate together. One end face of the first detection ring 21 and the other end face of the second detection ring 23 are arranged so as to face each other, and teeth 21a and 23a are respectively provided on the facing end faces of the detection rings 21 and 23 along the circumferential direction. A plurality is provided. The other end of the first detection ring 21 is a small diameter portion 21b having an outer diameter smaller than the one end. The housing 16 holds a first detection coil 33 that covers the space between the detection rings 21 and 23 and a second detection coil 34 that covers the small-diameter portion 21 b of the first detection ring 21. Constitutes the signal processing circuit shown in FIG. That is, the first detection coil 33 is connected to the oscillator 46 via the resistor 45, the second detection coil 34 is connected to the oscillator 46 via the resistor 47, and the detection coils 33 and 34 are connected to the differential amplifier circuit 48. Is done.
[0013]
When the torsion bar 11 is elastically twisted by the transmission of the steering torque from the input shaft 2 to the output shaft 4 and the first detection ring 21 and the second detection ring 23 rotate relatively, each of the detection rings 21 and 23 is rotated. The facing area of the teeth 21a, 23a changes. Since the magnetic resistance between the opposing teeth 21a and 23a changes due to the change in the area, the output of the first detection coil 33 changes according to the change, and the steering torque is detected according to the output. . Thus, the torque sensor 3 can detect the steering torque up to the detection limit at which the non-circular portion 2 'on the input shaft 2 side and the non-circular portion 4' on the output shaft 4 abut. In addition, by setting the outer diameter of the small diameter portion 21b so that the magnetic resistance of the first detection coil 33 and the magnetic resistance of the second detection coil 34 are equal in a state where the steering torque is not acting, The output fluctuation of the first detection coil 33 due to the temperature fluctuation is made equal to the output fluctuation of the second detection coil 34 due to the temperature fluctuation, canceled by the differential amplifier circuit 48, and the temperature fluctuation of the detected value of the transmission torque is compensated. The output of the torque sensor 3 becomes zero at a middle point where steering is not performed, and the absolute value of the output at the detection limit at the time of right steering is equal to the absolute value of the output at the detection limit at the time of left steering. Thus, in the assembling process, the input shaft 2 and the output shaft 4 are connected via the pins 18 and 19 by the torsion bar 11 after the relative positions are determined.
[0014]
As shown in FIG. 1, the torque sensor 3 is connected to a controller 50 mainly constituted by a computer. The motor 13, the vehicle speed detection sensor 51, and a plurality of obstacle detection sensors 53, 54, 55, 56 attached to the vehicle 10 are connected to the controller 50. The obstacle detection sensors 53, 54, 55, and 56 detect, for example, obstacles such as other vehicles and guard rails on the left and right sides and the left and right rear sides of the vehicle 10, and detect laser and ultrasonic waves from the vehicle. A transmitter for emitting a radar wave, a receiver for the radar wave, and an amplifier for the received radar wave, and a distance to an obstacle by the controller 50 based on a time difference between the transmission and reception of the radar wave. Can be configured by those that calculate
[0015]
The controller 50 calculates a control value I corresponding to the drive current of the steering assist force generation motor 13 based on the output of the torque sensor 3 and the vehicle speed, and controls the motor 13 with the calculated control value I.
That is, FIG. 5 shows the relationship between the steering torque and the control value I when performing the steering assist. When the steering torque increases, the control value I, that is, the steering assist force increases, and the rate of increase is small at low speeds and small at high speeds. Become. Thereby, the turning performance at low speed and the running stability at high speed are improved.
The controller 50 calculates the control value I so as to satisfy the relationship shown in FIG. 5 when performing the steering assist, and suppresses the steering by changing the control value I when the possibility of collision occurs.
Note that the relationship between the steering torque and the control value I shown in FIG. 5 is merely an example, and the present invention is not limited to this. For example, not only the vehicle speed but also the steering angle is detected, and the control value I is used as the steering angle. In a large low-speed state, the steering assist force may be increased to improve the turning performance of the vehicle, and in a high-speed state in which the steering angle is small, the steering assist force may be reduced to improve the running stability.
[0016]
A control procedure based on the control program of the controller 50 will be described with reference to a flowchart shown in FIG.
[0017]
First, signals from the torque sensor 3, the vehicle speed detection sensor 51, and the obstacle detection sensors 53, 54, 55, 56 are read, the steering torque and the vehicle speed are obtained, and the distance to the obstacle is calculated (step 1).
[0018]
Next, it is determined whether or not the detected torque T is equal to or greater than a set value Ta (step 2). The set value Ta increases as the vehicle speed increases. In the present embodiment, as shown in FIG. 7, the set value Ta is kept constant below a constant vehicle speed va that does not require steering suppression, and above the constant vehicle speed va, the set value Ta is increased in proportion to the vehicle speed v.
[0019]
If the detected torque T is less than the set value Ta, the control value I of the steering assist motor 13 is calculated as described above (step 3), and the motor 13 is controlled by the control value I to perform steering assist ( Step 4), and return to step 1.
[0020]
When the detected torque T is equal to or greater than the set value Ta, the steering direction is determined based on a signal from the torque sensor 3, and an obstacle detection signal from the sensors 53, 54, 55, and 56 in the steering direction is used to determine whether the vehicle 10 has an obstacle. The possibility of collision with an object is determined (step 5). For example, if an obstacle is detected within a predetermined distance in the steering direction, it is determined that there is a possibility of collision.
[0021]
If there is no possibility of collision, steering assist is performed in steps 3 and 4, and the process returns to step 1.
[0022]
If it is determined in step 5 that there is a possibility of collision, steering suppression is performed (step 6), and the process returns to step 1. The manner of the steering suppression is not particularly limited. For example, the application of the steering assist force is released, or the steering suppression force is applied in a direction opposite to the direction in which the steering is to be performed.
[0023]
According to the above configuration, if the steering torque T required for steering in the direction in which there is a possibility of collision is less than the set value Ta, steering suppression is not performed. , And a decrease in steering feeling can be prevented. Further, since the set value Ta of the steering torque increases as the vehicle speed v increases, even if the self-aligning torque increases during high-speed traveling, the rate of increase of the steering assist force with respect to the steering torque decreases due to the increase in the vehicle speed. By doing so, even when improving running stability at high speeds and turning performance at low speeds, it is possible to prevent the play range of steering from becoming smaller at high speed running and sufficiently reduce the steering feeling. Can be prevented.
[0024]
Note that the present invention is not limited to the above embodiment. For example, as shown in a first modification of FIG. 8, the set value Ta can be increased as a quadratic function of the vehicle speed v. Further, as shown in a second modification of FIG. 9, the set value Ta can be increased stepwise with respect to the vehicle speed v. The means for detecting an obstacle is not particularly limited. For example, the presence or absence of an obstacle approaching the vehicle may be determined based on an image around the vehicle using a CCD camera. Further, the means for detecting the steering direction is not particularly limited, and may be detected by, for example, an operation signal of a blinker.
[0025]
【The invention's effect】
ADVANTAGE OF THE INVENTION According to the steering apparatus of the vehicle of this invention, when the possibility of collision with an obstacle arises, the play feeling of steering can be appropriately secured according to the vehicle speed, and a decrease in steering feeling can be prevented. In addition, by applying the present invention to a power steering device, the driving stability at high speeds and the turning performance at low speeds are improved, the appropriate feeling of steering play is secured, and the deterioration of steering feeling is prevented. it can.
[Brief description of the drawings]
FIG. 1 is a configuration explanatory view of a power steering device according to an embodiment of the present invention; FIG. 2 is a cross-sectional view of a torque sensor according to an embodiment of the present invention; FIG. FIG. 5 is a circuit diagram of a torque sensor according to an embodiment of the present invention. FIG. 5 is a diagram showing a relationship between a control value and a steering torque according to the embodiment of the present invention. FIG. 7 is a diagram illustrating a relationship between a torque set value and a vehicle speed according to the embodiment of the present invention. FIG. 8 is a diagram illustrating a relationship between a torque set value and a vehicle speed according to a first modification of the present invention. FIG. 10 is a diagram showing a relationship between a torque set value and a vehicle speed according to a second modified example of FIG. 10. FIG. 10 is a diagram showing a relationship between a torque set value and a vehicle speed according to a comparative example of the present invention.
1 power steering device 3 torque sensor 13 motor (actuator)
50 Controller 51 Vehicle speed detection sensor 53, 54, 55, 56 Obstacle detection sensor

Claims (2)

Means for detecting steering torque;
Means for determining whether the steering torque is equal to or greater than a set value,
Means for determining whether there is a possibility of collision between the vehicle and an obstacle detected in the steering direction,
Means for performing steering suppression when the steering torque is equal to or more than a set value and a collision possibility occurs,
A vehicle steering system in which the set value of the steering torque is set to increase as the vehicle speed increases. Means for controlling an actuator for generating a steering assist force by a control value corresponding to the detected steering torque;
Means for changing the control value so that the steering torque is equal to or more than a set value, and when the possibility of collision occurs, the steering is suppressed.
2. The vehicle steering system according to claim 1, wherein the rate of increase of the steering assist force with respect to the steering torque is set to decrease as the vehicle speed increases.

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