JP3507215B2 - Power steering device - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a power steering system capable of preventing a running vehicle from colliding with an obstacle.

[0002]

2. Description of the Related Art The power to suppress steering based on the possibility of collision between a vehicle and an obstacle for the purpose of preventing the vehicle from colliding with an obstacle on the side or a rear side when changing lanes. Steering devices have been proposed.

Such steering suppression is detected in the steering direction in a power steering system in which a steering torque is detected by a torque sensor and a steering assist force generating actuator is controlled by a control value according to the detected steering torque. This can be done by providing a means for determining the possibility of collision with an obstacle and changing the control value when the possibility of collision occurs.

[0004]

However, when such a possibility of collision occurs, even if the current lane is maintained without actually changing the lane in the direction of the possibility of collision. , When the steering is suppressed, the feeling of play of steering in the direction in which there is a possibility of collision disappears,
There is a problem that the steering feeling is deteriorated.

Therefore, it is conceivable to suppress the steering when the fluctuation range of the steering torque is less than the set value. However, since the steering is not suppressed until the fluctuation range of the steering torque becomes equal to or more than the set value, there is a problem that the risk avoiding effect is lowered due to the control delay. Further, there is a possibility that steering in a direction in which there is a possibility of collision is maintained due to the control delay. Further, the set value of the variation range of the steering torque needs to be changed according to the vehicle speed, but it is difficult to experimentally obtain it according to an arbitrary traveling situation.

Further, when the steering torque is small, it is possible to secure a feeling of steering play by reducing the degree of steering suppression. However, in this case, there is a problem that it is not possible to cope with a case where the steering is slowly performed in a direction in which there is a possibility of collision with a small steering torque.

It is an object of the present invention to provide a power steering device that can solve the above problems.

[0008]

SUMMARY OF THE INVENTION The present invention comprises means for detecting steering torque in time series, means for controlling an actuator for generating steering assist force by a control value according to the detected steering torque, and steering direction. The present invention is applied to a power steering device including a means for determining whether or not there is a possibility of collision between an obstacle detected in 1. and a vehicle.

According to the present invention, in the power steering device, when a collision possibility occurs, the steering control is performed so that the steering is suppressed according to the time integral value of the difference between the detected steering torque and the steering torque in the steady state. Is provided.

As a result, the time integral value of the difference between the detected steering torque and the steering torque in the steady state is small at the beginning of the possibility of collision, and the increase rate increases with the passage of time. Therefore, if the time is such that steering in the direction in which there is a possibility of collision is performed by play, the steering suppression according to the time integration value is reduced to secure that play and prevent the steering feeling from deteriorating. In addition, when the steering time in the direction in which there is a possibility of collision becomes long, the steering suppression can be increased and the collision with the obstacle can be prevented.

The control value after the change during the steering suppression is a value obtained by subtracting the suppression value proportional to the time integrated value from the control value in the steady state, and the proportional value between the time integrated value and the suppression value. The coefficient is preferably a function of vehicle speed. As a result, the proportional coefficient can be made larger at high speed than at low speed, and delay in steering suppression at high speed can be prevented.

Further, according to the present invention, in the power steering device, the value corresponding to the time integrated value of the value corresponding to the difference between the detected steering torque and the steering torque in the steady state after the occurrence of the collision possibility is previously set. When the set value exceeds the set value, a means for changing the control value is provided so as to suppress the steering according to the set value.

Thus, until the value corresponding to the time integration value reaches the set value, steering is not suppressed even if there is a possibility of collision with an obstacle. Therefore, if the time is such that steering in the direction in which there is a possibility of collision is carried out by play, the value corresponding to the time integral value is made smaller than the set value, and the feeling of play is secured to ensure steering feeling. When the steering time in the direction in which there is a possibility of collision becomes long, the value corresponding to the time integrated value exceeds the set value and steering is suppressed to prevent collision with an obstacle. You can

Further, it is preferable to cancel the steering suppression when the value corresponding to the time integrated value of the difference between the control value in the steady state and the changed control value during the steering suppression exceeds the set value. . As a result, the time integral value of the value corresponding to the steering torque applied from the collision possibility occurrence time to the steering suppression start time can be made equal to the time integration value of the steering suppression torque, so that the vehicle steering angle can collide. The value can be substantially returned to the value at the time when the sexuality occurs, and proper steering control can be performed without excess or deficiency.

Further, it is preferable that a vehicle speed detecting means is provided, and the set value thereof is a function of the vehicle speed. This allows
The set value can be set smaller at high speed than at low speed to prevent delay in steering suppression at high speed.

[0016]

DETAILED DESCRIPTION OF THE INVENTION A first embodiment of the present invention will be described below with reference to the drawings.

The rack and pinion type electric power steering apparatus 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. Is equipped with. 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 movement of the rack 7 steers the vehicle 10.

As shown in FIG. 2, the torsion bar 11 is inserted into the input shaft 2 and the output shaft 4, and the pin 1 is inserted.
It is connected by 8 and 19. The input shaft 2
Is configured by connecting the first shaft 2a on the steering wheel H side and the second shaft 2b on the torque sensor 3 side by a pin 18. As a result, the input shaft 2 and the output shaft 4 relatively rotate in accordance with the steering torque. One end of the input shaft 2 is inserted into a recess 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 recess 4a. Are non-circular portions 2'and 4'opposed to each other. By contacting the non-circular portion 2'on the input shaft 2 side and the non-circular portion 4'on the output shaft 4 side,
The relative rotatable amount of the input shaft 2 and the output shaft 4 is regulated within a certain range, and damage to the torsion bar 11 is prevented. A worm wheel 12 is fitted on the outer circumference of the output shaft 4, and a worm gear 15 that meshes with the worm wheel 12 is provided.
Is connected to a steering assist force generating motor (actuator) 13 as shown in FIG.

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 rotatable relative to each other. A first detection ring 21 made of a magnetic material is fitted on the outer circumference of the input shaft 2, and a second detection ring 23 made of a magnetic material is fitted on the outer circumference of the output shaft 4 so as to rotate together. The one end surface of the first detection ring 21 and the other end surface of the second detection ring 23 are arranged so as to face each other, and each of the detection rings 21, 23
A plurality of teeth 21a and 23a are respectively provided on the facing end surfaces of the above along the circumferential direction. The other end side of the first detection ring 21 is a small diameter portion 21b having an outer diameter smaller than that of the one end side. Each of the detection rings 21 and 23 is attached to the housing 16.
The first detection coil 33 that covers the area facing each other and the second detection coil 34 that covers the small-diameter portion 21b of the first detection ring 21 are held, and each detection coil 33, 34 constitutes the signal processing circuit shown in FIG. . That is, the first detection coil 33 has the resistor 4
Is connected to the oscillator 46 via the second detection coil 34.
Is connected to an oscillator 46 via a resistor 47, and the detection coils 33 and 34 are connected to a differential amplifier circuit 48.

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
When the detection ring 21 and the second detection ring 23 rotate relative to each other, the facing areas of the teeth 21a and 23a of the detection rings 21 and 23 change. Due to the area change, the tooth 21
Since the magnetic resistance between a and 23a facing each other changes, the output of the first detection coil 33 changes according to the change, and the steering torque is detected corresponding to the output. As a result, 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 contact each other. Further, by setting the outer diameter of the small diameter portion 21b so that the magnetic resistance on the side of the first detection coil 33 and the magnetic resistance on the side of the second detection coil 34 become equal in the state where no steering torque is applied, The output variation of the first detection coil 33 due to the temperature variation is made equal to the output variation of the second detection coil 34 due to the temperature variation, and is canceled by the differential amplifier circuit 48, and the temperature variation of the detected value of the transmission torque is compensated. The output of the torque sensor 3 becomes zero at the midpoint where steering is not performed, and the absolute value of the output at the detection limit during right steering and the absolute value of the output at the detection limit during left steering become equal. As described above, in the assembly process, after the relative positions of the input shaft 2 and the output shaft 4 are determined, they are connected by the torsion bar 11 via the pins 18 and 19.

As shown in FIG. 1, the torque sensor 3
Is connected to a controller 50 mainly composed of a computer. The controller 50 includes a motor 13, a vehicle speed detection sensor 51, and a plurality of obstacle detection sensors 53, 54, 55 attached to the vehicle 10.
56 is connected. Those obstacle detection sensors 53, 5
Reference numerals 4, 55, and 56 are for detecting obstacles such as other vehicles or guardrails on the left and right sides and the left and right rear sides of the vehicle 10, and are transmitters that emit radar waves such as lasers and ultrasonic waves from the vehicles. And a receiver for the radar wave and an amplifier for the received radar wave, and the controller 50 calculates the distance to the obstacle based on the time difference from the transmission to the reception of the radar wave. .

In the present embodiment, the controller 50 calculates the control value I corresponding to the drive current of the steering assist force generating motor 13 based on the output of the torque sensor 3 in consideration of the vehicle speed. The motor 13 is controlled by the control value I. That is, FIG. 5 shows the relationship between the steering torque and the control value I when steering assist is performed. The control value I increases as the steering torque increases, and the rate of increase increases at low speeds and decreases at high speeds. As a result, the turning performance at low speed and the running stability at high speed are improved. When the steering assist is performed, the controller 50 calculates the control value I so as to satisfy the relationship shown in FIG. 5, and when the possibility of collision occurs, the control value I is changed to suppress the steering. The relationship between the steering torque and the control value I shown in FIG. 5 is 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 calculated 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 where the steering angle is small, the steering assist force may be decreased to improve the running stability.

The control procedure based on the control program of the controller 50 will be described with reference to the flowchart shown in FIG.

First, the torque sensor 3 and the vehicle speed detection sensor 5
1 and the signals from 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).

Next, the steering direction is judged from the signal from the torque sensor 3, and the sensors 53, 5 in the steering direction are determined.
Based on the obstacle detection signals from 4, 55 and 56, the vehicle 10
And the possibility of collision with the obstacle (step 2). For example, when an obstacle is detected within a predetermined distance in the steering direction, it is determined that there is a possibility of collision.

If there is no possibility of collision, the control value I of the steering assisting motor 13 is calculated as described above (step 3), and the motor 13 is controlled by the control value I to perform steering assisting (step 4). ), And returns to step 1.

When it is determined in step 2 that there is a possibility of collision, a torque difference (TT) between the detected steering torque T at the present time and the steering torque To in the steady state.
o) is calculated (step 5). The steering torque To in the steady state is a steady state in which the steering torque does not temporally change immediately before the steering is suppressed, that is, the steering torque during straight traveling or cornering with a constant curvature, and is zero during straight traveling. Therefore, at the time of cornering with a constant curvature, it becomes a constant value that substantially corresponds to the vehicle speed and the steering angle. For example, the steering torque T detected by the controller 50 is stored at fixed time intervals (for example, 10 millisecond intervals), and the stored values are compared to determine whether or not the steering is in a steady steering state. The latest stored value in the steering state can be used as the steering torque To in the steady state, or the average value of a plurality of stored values in the steady steering state immediately before steering suppression can be used as the steering torque To in the steady state. .

Next, the steering torque T in the steady state
Store o (step 6).

Next, a time integrated value ∫ (T-To) dt of the torque difference (T-To) from the time of occurrence of a collision possibility is obtained by step 5 and step 12 described later.
It is obtained by integrating (o) (step 7).

Next, as shown in FIG. 7, the suppression value ΔI proportional to the time integrated value ∫ (T-To) dt is multiplied by the product M of the proportional coefficient M (v) and the integrated value obtained in step 7. (v) ・ ∫ (T-To) dt
(Step 8). The proportional coefficient M (v) is a function of the vehicle speed and is increased as the vehicle speed increases. The specific value may be experimentally obtained so that a play feeling of steering can be secured when steering is suppressed, and a delay in steering suppression at high speed does not occur.

Next, the control value I of the motor 13 is changed to suppress the steering (step 9). As the control value I after the change for steering suppression, the control value I in the steady state is the control value I calculated in step 8.
Obtain by subtracting from o. The control value Io in the steady state is obtained as a value corresponding to the steering torque To in the steady state in the relationship between the steering torque and the control value I shown in FIG.

Next, the signal from the torque sensor 3 is read to obtain the steering torque T at the present time (step 10),
The current value T of the steering torque is compared with the steering torque To stored in step 6 in the steady state (step 11).

If the value T of the steering torque at present is equal to or less than the steering torque To in the steady state, that is, if the driver does not apply the steering torque against the steering suppression, the process returns to step 1. Current steering torque value T
Exceeds the steering torque To in the steady state, that is, if the driver applies the steering torque against the steering suppression, the torque between the steering torque T detected at that time and the steering torque To in the steady state. Difference (T
-To) is calculated (step 12), and the steering suppression is continued by returning to step 7.

According to the first embodiment, the time integral value ∫ (T-To) dt of the difference between the detected steering torque T and the steering torque To in the steady state is small at the beginning of the possibility of collision, The rate of increase increases over time. Therefore, if the time is such that steering in the direction in which there is a possibility of collision is performed by play, the suppression value ΔI corresponding to the time integration value ∫ (T-To) dt is reduced to secure the play feeling. It is possible to prevent the steering feeling from deteriorating and increase the steering suppression when the steering time in the direction in which there is a possibility of collision becomes long, thereby preventing the collision with the obstacle. Further, the proportional coefficient M (v) between the time integrated value ∫ (T-To) dt and the suppression value ΔI is a function of the vehicle speed, and is made larger at low speed than at low speed, so steering at high speed is performed. It is possible to prevent a delay in restraint and perform proper steering restraint.

8 and 9 relate to the second embodiment of the present invention. The second embodiment is the same as the first embodiment except the control procedure based on the control program of the controller 50, and the differences from the first embodiment will be described below.

The control procedure is the same as that of the first embodiment from step 1 to step 4, as shown in the flowchart of FIG.

When it is determined in step 2 that there is a possibility of collision, a torque difference (T-T) between the detected steering torque T at the present time and the steering torque To in the steady state.
o) is calculated. Further, a current difference (I-Io) between the control value I corresponding to the detected steering torque T at the present time and the control value Io in the steady state corresponding to the steering torque To in the steady state is calculated (step 5). .

Next, the steering torque T in the steady state
o and the control value Io in the steady state are stored (step 6).

Next, a time integrated value ∫ (T-To) dt of the torque difference (T-To) from the time of occurrence of a collision possibility is obtained by step 5 and step 14 described later.
It is calculated by integrating o). Further, the current difference (I-I
o), the time integral value ∫ (I-Io) dt from the time of the possibility of collision
Is calculated by integrating the current difference (I-Io) obtained in step 5 and step 14 described later (step 7).

Next, the time-integrated value of the current difference (I-Io) obtained in step 7 is converted into the current-torque conversion coefficient K.
And the torque difference (T
-To) sum with time integration value F (T) = ∫ (T-To) dt + K
-Calculate ∫ (I-Io) dt (step 8). The sum F
(T) corresponds to a time integral value of a value corresponding to the difference between the detected steering torque and the steering torque in the steady state.

Next, the sum F obtained in step 8
It is determined whether (T) exceeds a preset set value C (v) (step 9). The set value C (v) is a function of the vehicle speed, and is set to be smaller as the vehicle speed becomes higher. A specific value of the set value C (v) makes it possible to secure a feeling of play when steering is suppressed and does not cause a delay in steering suppression at high speed. It can be obtained experimentally.

If the sum F (T) does not exceed the set value C (v), the steering torque, the vehicle speed and the obstacle are detected in the same manner as in step 1 (step 10) and in the same manner as step 2. Determine the possibility of collision with an obstacle (Step 1
1). If there is no possibility of collision, the process returns to step 3. If there is a possibility of collision, the control value I is calculated in the same manner as in step 3 (step 12), steering assist is performed based on the control value I (step 13), and the current torque difference (T-To) and current difference are calculated. (I-Io) is calculated (step 14) and the process returns to step 7.

In step 9, when the sum F (T) exceeds the set value C (v), the initial control value Ic after the change for steering suppression is obtained (step 15), and then the motor 13 The control value I of is changed to suppress the steering (step 16). In the steering suppression, the value corresponding to the time integral value of the difference between the control value Io in the steady state and the changed control value during the steering suppression is the set value C.
It is canceled when (v) is exceeded. FIG. 9 shows the relationship between the steering torque T, the control value I, the steering torque To in the steady state, and the control value Io. That is, F (T) = C (v) = K · t, where the preset steering suppression time is to
The control value Ic at the beginning of the change during steering suppression is determined so as to satisfy o · (Ic−Io) / 2, and the control value is set to the steady state value Io when the steering suppression time to has elapsed. Change I. When the steering suppression is released, the process returns to step 1. When the steering is suppressed, the limiter is used to change the control value I, and the steering suppression time to
The limiter time corresponding to can be set to decrease as the vehicle speed increases.

According to the second embodiment, the value F (T) corresponding to the time integrated value of the value corresponding to the difference between the detected steering torque T and the steering torque To in the steady state is the set value C ( Until v), steering is not suppressed even if there is a possibility of collision with an obstacle. Therefore, if the time is such that steering in the direction in which there is a possibility of collision is performed by play, the value F (T) corresponding to the time integration value is made smaller than the set value C (v), and the sense of play is reduced. When the steering time in the direction in which there is a possibility of collision becomes long, the value F (T) corresponding to the time integral value exceeds the set value C (v) and the steering is suppressed. The
It is possible to prevent a collision with an obstacle. When the value corresponding to the time integral value of the difference between the control value in the steady state and the control value after the change during steering suppression exceeds the set value C (v), the steering suppression is released, and thus the possibility of collision may occur. Since the time integration value of the value corresponding to the steering torque applied from the time of occurrence to the time of starting the steering suppression can be made equal to the time integration value of the steering suppression torque, the steering angle of the vehicle is set to the value at the time of the possibility of collision occurrence. It can be returned almost and proper steering control can be performed without excess or deficiency. Furthermore, the set value C
By making (v) smaller at low speed than at low speed, it is possible to prevent a delay in steering suppression at high speed.

The present invention is not limited to the above embodiment. For example, the obstacle detecting means is not particularly limited, and for example, the presence or absence of the obstacle approaching the vehicle may be determined based on the image of the vehicle surroundings by the CCD camera. Further, the steering direction detecting means is not particularly limited, and may be detected by a winker operation signal, for example. In addition, as the value corresponding to the time integrated value of the value corresponding to the difference between the detected steering torque and the steering torque in the steady state, the second
In the embodiment, the value obtained by multiplying the time integral value of the current difference (I-Io) by the conversion coefficient of the current and the torque and the torque difference (T-
Although the sum F (T) of the time To and the time integrated value is used, the present invention is not limited to this. For example, a value obtained by multiplying the time integrated value of the current difference (I-Io) by the conversion coefficient of the current and the torque K. Alternatively, only the time integration value of the torque difference (T-To) may be used.

[0046]

According to the power steering apparatus of the present invention, even when a collision with an obstacle occurs, a feeling of steering play is secured to prevent a reduction in steering feeling, and
Collision with an obstacle can be prevented by proper steering suppression.

[Brief description of drawings]

FIG. 1 is a structural explanatory view of a power steering device according to an embodiment of the present invention.

FIG. 2 is a sectional view of a torque sensor according to an embodiment of the present invention.

FIG. 3 is a sectional view taken along line III-III of FIG.

FIG. 4 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. 6 is a flowchart showing a control procedure of the power steering device according to the first embodiment of the present invention.

FIG. 7 is a diagram showing a relationship between a time integrated value of a torque difference and a suppression value according to the first embodiment of the present invention.

FIG. 8 is a flowchart showing a control procedure of the power steering device according to the second embodiment of the present invention.

FIG. 9 is a diagram showing a relationship between a steering torque T, a control value I, a steering torque To in a steady state, and a control value Io according to a second embodiment of the present invention.

[Explanation of symbols]

1 Power steering device 3 Torque sensor 10 vehicles 13 motor 50 controller 53, 54, 55, 56 Obstacle detection sensor

─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Tomohisa Kada, 3-5-8 Minamisenba, Chuo-ku, Osaka-shi, Osaka Prefecture Koyo Seiko Co., Ltd. No. 5-8 Koyo Seiko Co., Ltd. (56) Reference JP-A-4-19274 (JP, A) JP-A-7-17423 (JP, A) JP-A-7-196049 (JP, A) (58) Fields investigated (Int.Cl. ⁷ , DB name) B62D 6/00-6/06

Claims (5)

(57) [Claims] 1. A means for detecting a steering torque in a time series, a means for controlling an actuator for generating a steering assist force by a control value according to the detected steering torque, an obstacle detected in a steering direction, and a vehicle. And a control value for controlling the steering so that when the collision possibility occurs, the steering is suppressed according to the time integral value of the difference between the detected steering torque and the steering torque in the steady state. And a means for changing the power steering device. Wherein the control value after the change in time of steering inhibition from the control value in the steady state, is a value obtained by subtracting the suppressed value proportional to the time integral value, between the suppression value and the time integral value The proportional coefficient of is a function of vehicle speed.
The power steering device according to. 3. A means for detecting a steering torque in time series, a means for controlling an actuator for generating a steering assist force by a control value according to the detected steering torque, an obstacle detected in a steering direction, and a vehicle. Means for determining the possibility of collision with the vehicle, and a value corresponding to the time integrated value of the value corresponding to the difference between the detected steering torque and the steering torque in the steady state after the collision has occurred are preset. When it exceeds the set value,
A power steering device comprising: a unit that changes a control value so that steering is suppressed according to the set value. Value corresponding to the time integral value of the difference between the control value after the change in the time control value and steering inhibition in wherein steady state, when exceeding the set value, according to claim 3 for releasing the steering inhibition The power steering device according to. 5. comprising a detecting means of the vehicle speed, the set value is a power steering apparatus according to claim 3 or claim 4 which is a function of vehicle speed.