JP3716529B2 - Steering device - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a steering apparatus having a steering angle transmission ratio variable mechanism set so that a steering angle transmission ratio can be changed according to a traveling state.
[0002]
[Prior art]
It is known that the steering angle transmission ratio, which is the ratio of the steering wheel angle steered by the driver and the turning angle of the wheel, affects the handling performance, straight running stability, and steering feeling of the vehicle. This steering angle transmission ratio is fixed to a certain ratio in a normal commercial vehicle.
[0003]
On the other hand, Japanese Patent Laid-Open No. 7-291141 discloses a steering device that can improve the operability of the driver by setting the transmission ratio to be variable according to the vehicle speed. In this steering device, when the vehicle speed is low, the transmission ratio is increased, and the steering amount of the occupant is reduced to improve the handling performance. Conversely, when the vehicle speed is high, the transmission ratio is decreased and the occupant's steering ratio is reduced. It is possible to reduce the burden of the steering wheel holding force and improve the steering stability.
[0004]
[Problems to be solved by the invention]
In the steering device that can change the steering angle transmission ratio as described above, the movable range of the steering wheel (so-called lock-to-lock) can be within ± 180 °, and the entire range can be obtained without crossing the arms. By enabling the steering operation, the amount of steering operation by the driver can be significantly reduced.
[0005]
However, from the fact that human visual characteristics generally appear narrower toward the periphery centering on the forward gazing point and human movement characteristics that both arms become harder to move as they are twisted from the initial position, the response characteristic to the steering operation is The greater the steering angle, the greater the amount of steering that can be expected. Therefore, even when the vehicle speed is the same, changing the characteristics of the wheel turning angle according to the steering angle of the steering wheel is closer to the driver's expected turning value, and the steering device does not feel strange.
[0006]
However, when the steering angle transmission ratio is simply increased as the turning angle increases, a slight correction operation is required when the steering angle is maintained at a relatively large steering angle, such as in a steady circular turn. Since the responsiveness becomes too sensitive, there is a problem that the steering stability is uncomfortable.
[0007]
The present invention has been made to solve such problems, and the purpose thereof is to ensure that the steering operation amount can be reduced in a steering device having a variable steering angle transmission ratio, It is an object of the present invention to provide a steering device that can easily perform an operation of correcting a trajectory during a turn without causing a sense of incongruity.
[0008]
[Means for Solving the Problems]
In order to solve the above-described problems, in the invention of claim 1, the steering angle transmission ratio variable type steering mechanism in which the steering angle transmission ratio which is the ratio of the steering wheel steering angle and the wheel turning angle can be changed according to the vehicle speed. The steering angle detecting means for detecting the steering angle of the driver, the line-of-sight detection means for detecting the driver's line-of-sight direction, and the steering angle detected by the steering angle detecting means increases as the steering angle increases. The angle transmission ratio is increased, and the steering reaction force transmitted to the driver is increased as the steering angle is increased, and the steering reaction force can be changed according to the depression angle between the line-of-sight direction and the traveling direction of the vehicle. And a steering reaction force generating means set as described above.
[0009]
A second aspect of the present invention is the steering apparatus according to the first aspect, wherein the steering reaction force generating means steers the larger the depression angle between the line-of-sight direction and a predetermined direction determined according to the steering angle and the vehicle speed. The reaction force is set to be small.
[0010]
A third aspect of the present invention is the steering apparatus according to the first aspect, wherein the steering reaction force generating means has a saddle angle formed by the line-of-sight direction and a predetermined direction determined according to a steering angle and a vehicle speed equal to or greater than a specified value. In addition, when steering at a speed equal to or higher than a predetermined speed, the steering reaction force is set to be smaller as the depression angle increases.
[0011]
A fourth aspect of the present invention is the steering apparatus according to any one of the first to third aspects, wherein the line-of-sight direction uses an average value within a specified time.
[0012]
【The invention's effect】
According to the invention of claim 1, since the steering reaction force determined from the vehicle speed and the steering angle is corrected according to the driver's line of sight, the operation of adjusting the steering angle in the direction expected by the driver is facilitated. Steering stability during turning is improved.
[0013]
According to the invention of claim 2, when the difference between the direction the driver wants to travel and the current traveling direction is large, the steering reaction is improved and the current traveling direction is maintained in order to reduce the operation reaction force. When it is desired to do so, the operational reaction force is increased and the steering stability is increased, so that the operability of the driver is improved.
[0014]
According to the invention of claim 3, the depression angle that the magnitude of the depression angle formed between the line-of-sight direction and the predetermined direction determined according to the steering angle and the vehicle speed is large and the angular velocity of the steering is equal to or greater than a specified value. Since it is set as a condition for setting the steering reaction force to be smaller as it becomes larger, the reaction force characteristic can be made closer to the human steering feeling, and the steering reaction force is reduced against the occupant's will. This can prevent the steering from becoming unstable.
[0015]
According to the fourth aspect of the present invention, since the gaze movement for the purpose other than the driving operation such as the instantaneous gaze movement and looking away is ignored, the steering reaction force characteristic does not fluctuate unstably and continuously without a sense of incongruity. Reaction force characteristics.
[0016]
DETAILED DESCRIPTION OF THE INVENTION
FIG. 1 is a configuration diagram showing a first embodiment of a steering apparatus according to the present invention. In this figure, the control device 1 controls the entire steering, and signals are inputted from a steering angle sensor 4, a vehicle speed sensor 5, and a line-of-sight detection device 9, which will be described later, and optimum steering is performed based on the inputted signals. The amount and the steering reaction force are determined, and a control signal is output to the motor drive circuits 2 and 10.
[0017]
The reaction force generation motor 3 is an electric motor connected to the steering column 31 in order to apply a steering reaction force to the driver via the steering wheel 30, and a torque corresponding to the electric power input from the motor drive circuit 2. Is generated.
[0018]
The steering angle sensor 4 is a sensor that detects the steering angle of the driver, and the control device 1 outputs an output value for each specified sampling time to the control device 1. As a result, the control device 1 recognizes the current steering angle. The control device 1 also calculates the steering angular velocity by numerically differentiating this recognition value.
[0019]
The steering torque sensor 5 is a sensor for detecting the steering torque generated in the steering column 31. Like the steering angle sensor 4, the steering torque sensor 5 outputs an output value for each specified sampling time to the control device 1, whereby the control device 1 Recognize the steering angle.
[0020]
A vehicle speed sensor 6 for detecting the traveling speed of the vehicle, a lateral acceleration sensor 7 for detecting lateral acceleration acting on the vehicle, and a yaw angular velocity sensor 8 for detecting the yaw angular velocity of the vehicle are all transmission output shafts (not shown). Is output to the control device 1. The controller 1 recognizes the vehicle speed by converting the output value.
[0021]
The line-of-sight detection device 9 detects the driver's line of sight. FIG. 2 shows an outline of the configuration of the visual line detection device 9. In the figure, the vicinity of the driver 16 is shown from vertically above, and 20, 21, and 22 are a headrest, a seat back, and a seat cushion, respectively.
[0022]
On the other hand, CCD cameras 17 and 18 facing both sides of the front side of the driver 16 are arranged on the front side of the instrument panel (not shown) of the vehicle, and the head image of the driver 13 is recognized. The
[0023]
On the other hand, an infrared irradiation device 19 is disposed on the front side of the driver 16. This infrared irradiation device 19 irradiates the driver's 16 head with a light beam in a stable frequency band. In such a line-of-sight detection device, the image data of the CCD cameras 17 and 18 are subjected to image processing, the face direction and the direction of the line of sight are calculated from the difference between the images of the CCD cameras 17 and 18 and transmitted to the control device 1.
[0024]
A motor drive circuit 10 in FIG. 1 is a circuit that drives a steering motor 11 connected to a pinion gear 12, and drives the steering motor 11 to a command position from the control device 1 at a command speed. When the steering motor 11 is driven, the rotational motion of the pinion gear 12 is converted into a linear motion by the rack 13 and the front wheels are steered via the left and right tie rods 14 and 15.
[0025]
The operation of the steering apparatus having the above configuration will be described with reference to the flowchart of FIG. When the driver 16 rotates the steering wheel 30, the control device 1 starts the steering interruption process of FIG.
[0026]
In step S301, signals from the sensors are processed to calculate the steering angle θ, the vehicle speed V, the lateral acceleration G, the yaw angular velocity r, and the depression angle φ between the driver's 16 line-of-sight direction and the vehicle traveling direction.
[0027]
FIG. 4 shows the calculation of the depression angle φ. First, the traveling direction 23 of the vehicle 25 is calculated. However, in order to improve the calculation speed here, the front-rear direction of the vehicle body is substituted as the traveling direction. On the other hand, the accuracy is improved by using a method of logically calculating from the motion model of the vehicle 25, but in order to realize a steering response without a sense of incongruity, avoid complicated calculations and improve the processing speed. There is a need. Therefore, even in the case of a control device that does not have a very high processing capacity, in order to make it a highly versatile device that can be used, in this embodiment, the front-rear direction of the vehicle is simply used as the traveling direction 23. In addition, what a general driver perceives as the traveling direction of the vehicle is not the actual traveling direction of the center of gravity of the vehicle, but the direction of the vehicle body seen through the front window. There is no sense of incongruity even if the direction of travel is substituted.
[0028]
Next, the line-of-sight direction 24 of the driver 25 is input from the line-of-sight detection device 9, the instantaneous depression angle is calculated from the difference from the vehicle traveling direction 23, and average processing is performed on the instantaneous depression angle to obtain the depression angle φ. FIG. 5 is a characteristic diagram showing the relationship between the instantaneous depression angle and the average depression angle.
[0029]
Average processing includes first-order lag processing with a fixed time constant and moving average processing, but because of the nature of eye movement suddenly switching to various locations, the first-order lag asymptotically approaches a certain target value. The process is unsuitable, and it is better to adopt a moving average that is greatly affected by the frequency.
[0030]
In step S302 in FIG. 3, the reference steering angle transmission ratio GRv corresponding to the vehicle speed Vcar is calculated based on the characteristics shown in FIG. FIG. 6 shows the relationship between the reference rudder angle transmission ratio GRv and the vehicle speed Vcar, and the reference rudder angle transmission ratio GRv decreases as the vehicle speed Vcar increases. As a result, in a high-speed driving state, the driving stability is increased by reducing the width of the front wheel with respect to the driver's steering input, and in the low-speed driving state, the front wheel is cut off with respect to the driver's steering input. By increasing the corners, handling is improved.
[0031]
In step S303, the steering angle transmission ratio GR corresponding to the steering angle θ is calculated from the characteristics shown in FIG. As for the steering angle θ, the neutral position (straight steering position) is 0, and the left and right specified values θmax are within the movable range.
[0032]
FIG. 7 shows the relationship of the steering angle transmission ratio GR to the magnitude of the steering angle θ excluding the rotation direction. As shown in the figure, the steering angle transmission ratio GR at the steering angle 0 is the reference steering angle transmission ratio GRv based on the vehicle speed, and the steering angle transmission ratio GR is set to increase as the steering angle θ increases.
[0033]
In step S304, the reference target steering reaction force RF0 with respect to the speed Vcar and the lateral acceleration G is calculated based on the characteristics shown in FIG. First, the reference reaction force RFv that changes depending on the vehicle speed is calculated from RFv = KRFV × Vcar, and RF ₀ is calculated from the characteristics of FIG.
[0034]
FIG. 8 shows a characteristic in which the reaction force increases as the lateral acceleration increases. Gmax is a limit value of the lateral acceleration, and is a value obtained from a road surface friction coefficient calculated from the lateral acceleration, the yaw angular velocity, and the vehicle speed. According to the characteristics of FIG. 8, the reaction force increases as the turning radius decreases at the same vehicle speed, and as the vehicle speed increases at the same turning radius. The reaction force characteristic without any discomfort.
[0035]
In the conventional steering device, the driver determines how much the vehicle is steered, mainly by how much the steering wheel has been rotated, that is, the steering angle, and feeds back by looking at the deviation from the actual vehicle behavior. In contrast, in the present invention, when the steering angle transmission ratio is varied, the relationship between the behavior of the vehicle and the steering angle changes depending on the vehicle speed and other conditions. It is difficult to control with this judgment. For this reason, the steering reaction force is changed according to the lateral acceleration, and the steering positioning is determined based on the steering reaction force. As a result, the reaction force characteristics considering the vehicle speed and the turning radius are obtained, so that the operability is improved.
[0036]
In step S305, the transmission gear selection position is determined. If reverse, that is, reverse, is selected, the process proceeds to step S307, and otherwise, the process proceeds to step S306.
[0037]
In step S306, a steering reaction force correction coefficient _WRF is calculated from the characteristics shown in FIG. W _RF together with changes as shown in FIG. 9 in accordance with the value of the included angle φ between the traveling direction of the driver's line of sight and the vehicle, is a function having a peak at an included angle .phi.0. The depression angle φ0 is an average line-of-sight direction in steady turning with the steering angle θ and the vehicle speed V fixed and the depression angle in the vehicle traveling direction, and can be experimentally obtained using the steering angle θ and the vehicle speed V as parameters.
[0038]
In step S307, the correction coefficient W _RF is set to 1.
[0039]
In step S308, the correction coefficient W _RF by multiplying the reference target steering reaction force RF0 calculated in step S304 to determine the target steering reaction force RF. W _RF changes as shown in FIG. 9 according to the value of the depression angle φ between the driver's line of sight and the traveling direction of the vehicle, and is a function having a peak at the depression angle φ0.
[0040]
In step S309, the steering angle transmission ratio GR and the steering reaction force RF calculated in steps S303 and S308 are converted into the actual steering angle and the rotational speed of the motor, and command values to the motor drive circuits 10 and 2 are respectively obtained. Calculate and output to these circuits 10 and 2.
[0041]
Next, according to the flowchart described above, a situation is assumed in which cornering at a right angle such as an intersection is performed during low-speed urban driving. First, in the straight running just before the start of cornering, the reference rudder angle transmission ratio GRv is close to 1 and not so high when the speed is about 40 km / h. Further, since the steering angle θ is close to 0, the steering angle transmission ratio remains substantially GRv. The steering reaction force at this time is RFv = KRFV × 40 because the lateral acceleration is almost zero.
[0042]
When braking is performed immediately before cornering and the speed is reduced to 20 km / h, the reference rudder angle transmission ratio GR0 increases rapidly from FIG. 6, and the transmission ratio Rv increases as the steering is increased from FIG. In normal driving, the steering reaction force is set so that there is no need to use a steering angle in a range where the transmission ratio increases rapidly. After that, the reaction force increases as the lateral acceleration increases by turning.
[0043]
In addition, since the depression angle between the line of sight and the direction of the vehicle is large at the beginning of steering, the reaction force correction coefficient is small and the steering is easy to turn at once. Therefore, the depression angle φ decreases, the correction coefficient approaches 1, and a reaction force corresponding to the lateral acceleration occurs.
[0044]
When the turn is completed and the vehicle is turned back, the depression angle φ in the reverse direction is increased, so that the reaction force is reduced for a moment and the steering is easily returned.
[0045]
As described above, since the steering reaction force is corrected not only according to the vehicle speed and steering angle but also according to the driver's line of sight, it is easy to adjust the rudder angle in the direction expected by the driver. Improves.
[0046]
Further, when the difference between the direction in which the driver wants to travel and the current traveling direction is large, the steering reaction force is reduced, so that a quick steering operation is possible and the responsiveness is improved. On the other hand, when it is desired to maintain the current traveling direction, the steering reaction force increases and the steering stability increases, so that the driver's steering force can be reduced and fatigue can be reduced.
[0047]
FIG. 10 is a flowchart of the second embodiment of the present invention. The configuration is the same as that of the first embodiment, and only the operation is different.
[0048]
In FIG. 10, steps S1001 to S1005 are the same as steps S301 to S305 in FIG.
[0049]
In step S1006, line-of-sight flag processing is performed. The line-of-sight flag is a flag that is turned on / off according to the magnitude of | φ−φ0 |, and has a prescribed hysteresis that is turned on when | φ−φ0 | is large as shown in FIG.
[0050]
In step S1007, a steering angular velocity flag is processed. Similar to the line-of-sight flag in step S1006, the steering angular velocity flag is a flag that is turned off according to the magnitude of | dθ / dt |, and is specified to be turned on when | dθ / dt | is large as shown in FIG. Has hysteresis.
[0051]
In step 1008, it is determined whether or not a line-of-sight correction mode flag, which will be described later, is ON. If OFF, the process proceeds to step S1009, and if ON, the process proceeds to step S1010.
[0052]
In step S1009, it is determined whether both the line-of-sight flag and the steering angular velocity flag are in the ON state. If the determination is YES, the line-of-sight correction mode flag is turned on in step S1011 and then the process proceeds to step S1014. The process proceeds to step S1013.
[0053]
In step S1010, it is determined whether both the line-of-sight flag and the steering angular velocity flag are in the OFF state. If the determination is YES, the line-of-sight correction mode flag is turned off in step S1012 and then the process proceeds to step S1013. The process proceeds to step S1014.
[0054]
In step S1013, it sets the correction coefficient W _RF target steering reaction force to 1, and calculates the correction coefficient W _RF based on the characteristics of the step 1014 FIG.
[0055]
Steps S1015 and S1016 are the same as steps S308 and S309 in FIG.
[0056]
Next, when assuming cornering at a right angle in an urban area as exemplified in the first embodiment according to the flowchart of FIG. 10, the visual correction mode flag changes as shown in FIG. That is, at the beginning of cornering, the line of sight and the vehicle direction temporarily increase and the line-of-sight flag is turned on.
[0057]
Thereafter, when the driver immediately starts to steer, the steering angular velocity increases rapidly and the steering angular velocity flag is turned on, so that the line-of-sight correction mode flag is turned on. After a while, when the vehicle starts to turn and coincides with the line of sight of steady circle turning, the line-of-sight flag is turned off, but the steering operation is continued.
[0058]
When the steering angular velocity decreases and the steering angular velocity flag is turned off, the line-of-sight correction mode flag is turned off. During this time, the steering reaction force is corrected by the correction coefficient W _RF , and the reaction force becomes smaller than that during normal steering.
[0059]
When the line-of-sight correction mode flag is off, a steering reaction force corresponding to the lateral acceleration is generated, and the characteristics are easily adjusted.
[0060]
Furthermore, as time elapses and the end of the curve approaches, the driver turns in the opposite direction or releases the holding force, so that the steering angular velocity in the opposite direction increases and the steering wheel returns to the neutral position. . At this time, the steering angular velocity flag is turned on, but the line-of-sight flag is not turned on, so the line-of-sight correction mode flag is not turned on.
[0061]
At the beginning of cornering, because it wants to get the information of the destination, it tries to look as far as possible, so the size of the depression angle φ increases, but at the end of cornering, the depression angle φ The size of is not so large. For this reason, the line-of-sight flag is not turned on.
[0062]
This is because, in the initial stage of cornering, the vehicle direction should be changed as soon as possible. Therefore, it is suitable for the steering feeling that the correction is easier if there is a certain amount of steering reaction force.
[0063]
According to the second embodiment, even if the line-of-sight movement continues for a long time, the line-of-sight correction is not performed unless the turning speed is increased. For this reason, when it is desired to maintain the current rudder angle, if the driver turns away from the traveling direction of the vehicle for some reason, it is possible to prevent the operation reaction force from becoming unexpectedly small and difficult to maintain.
[Brief description of the drawings]
FIG. 1 is an overall configuration diagram of a steering apparatus according to the present invention.
FIG. 2 is a plan view showing line-of-sight detection means.
FIG. 3 is a flowchart for explaining the operation of the first embodiment;
FIG. 4 is a plan view for explaining a depression angle between the traveling direction of the vehicle and the line-of-sight direction.
FIG. 5 is a characteristic diagram showing the relationship between the instantaneous depression angle and the average depression angle.
FIG. 6 is a characteristic diagram showing a relationship between a vehicle speed Vcar and a reference rudder angle transmission ratio GRv.
FIG. 7 is a characteristic diagram showing a relationship between a steering angle θ and a steering angle transmission ratio GR.
FIG. 8 is a characteristic diagram showing a relationship between a lateral acceleration G and a reference target steering reaction force RF0.
FIG. 9 is a characteristic diagram showing the relationship between the traveling direction of the vehicle and the target steering reaction force correction coefficient W _RF .
FIG. 10 is a flowchart for explaining the operation of the second embodiment;
FIG. 11 is a characteristic diagram illustrating the process of step S1006 of FIG.
FIG. 12 is a characteristic diagram for explaining the process of step S1007 of FIG.
FIG. 13 is a timing chart illustrating the operation of the second embodiment.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Control apparatus 2,10 Motor drive circuit 3 Reaction force generation motor 4 Steering angle sensor 5 Steering torque sensor 6 Vehicle speed sensor 7 Lateral acceleration sensor 8 Yaw angular velocity sensor 9 Line of sight detection means 11 Steering motor 12 Pinion gear box 13 Rack gear box 14 , 15 Tie rods 17, 18 CCD camera 19 Infrared irradiation device

Claims (4)

In a steering apparatus having a steering angle transmission ratio variable type steering mechanism in which a steering angle transmission ratio which is a ratio of a steering wheel steering angle and a wheel turning angle can be changed according to a vehicle speed,
Steering angle detection means for detecting the steering angle of the driver;
Gaze detection means for detecting the driver's gaze direction;
The larger the steering angle detected by the steering angle detecting means, the larger the steering angle transmission ratio, and the larger the steering angle, the larger the steering reaction force transmitted to the driver, and the line-of-sight direction. And a steering reaction force generating means set so that the steering reaction force can be changed according to a depression angle between the vehicle and the traveling direction of the vehicle. 2. The steering apparatus according to claim 1, wherein the steering reaction force generation unit decreases the steering reaction force as the depression angle between the line-of-sight direction and a predetermined direction determined according to the steering angle and the vehicle speed increases. A steering device characterized by being set. 2. The steering device according to claim 1, wherein the steering reaction force generation unit has a depression angle formed between the line-of-sight direction and a predetermined direction determined according to a steering angle and a vehicle speed equal to or higher than a predetermined value and equal to or higher than a predetermined speed. A steering apparatus characterized in that, when steering at a speed, the steering reaction force is set to decrease as the depression angle increases. The steering apparatus according to any one of claims 1 to 3, wherein the visual line direction uses an average value within a specified time.

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