JPH05675A - Auxiliary steering gear of vehicle - Google Patents

Abstract

PURPOSE:To prevent a driver from unnecessary shocks in small steering wheel gripping force of the driver by inhibiting the auxiliary steering of front wheels in response to the behavior of a vehicle, external turbulence, etc. CONSTITUTION:A yaw rat sensor 52 detects raw rate as an amount representing the behavior of a vehicle and a side wind sensor 53 detects side wind speed as the external turbulence received by the vehicle. A microcomputer 56 controls the rotation of an electric motor 46 according to the detected yaw rate and side wind speed to effect the auxiliary steering of front wheels FW in addition to the steering by pivoting a steering wheel 20. On the other hand, a gripping force sensor 55 detects a steering wheel 20 gripping force of a driver and the microcomputer 56 limits or inhibits the auxiliary steering when the detected gripping force is small. Also, when the gripping force is large and the front wheels FW are subjected to the auxiliary steering, the microcomputer 56 controls a solenoid valve 31 to reduce a steering reaction to the steering handle 20.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an auxiliary steering system for a vehicle, which assists steering of front wheels in addition to steering by turning a steering wheel.

[0002]

2. Description of the Related Art Conventionally, an apparatus of this kind has been disclosed in, for example, Shokai Sho 6
As disclosed in Japanese Patent Application Laid-Open No. 0-131464, an actuator capable of steering the front wheels is provided in a steering mechanism that steers the front wheels according to the rotation of a steering wheel, and the actuator is drive-controlled according to a vehicle speed and a yaw rate. As a result, in addition to steering by turning the steering wheel, the front wheels are supplementarily steered according to the vehicle speed and the yaw rate, so that the running stability of the vehicle is kept good.

[0003]

However, in the above-mentioned conventional device, regardless of the driver's steering wheel operation,
Since the front wheels are assisted by steering, there are the following problems. When the vehicle is traveling straight at high speed, the driver often puts his / her hand on the steering wheel lightly.In such a state, the actuator is driven to cancel the yaw rate generated by the disturbance. Even if an attempt is made to assist steering, the reaction force that the front wheels receive from the road surface due to this assist steering is transmitted to the steering wheel, and this reaction force causes the steering wheel to rotate in the direction opposite to the direction in which the front wheels are steered by the assist steering. At the same time, the effect of the auxiliary steering is canceled, and at the same time, the driver receives a shock due to the rotation of the steering wheel and performs an unstable steering operation,
The vehicle may wander. Even if the driver grips the steering wheel with sufficient force, if the yaw rate becomes excessive due to sudden strong winds while driving on the mountain road, the front wheels are assisted by steering to cancel the yaw rate. Then, a large reaction force is transmitted to the steering wheel without notice,
The driver may be shocked by this reaction force and perform an unstable steering wheel operation, causing the vehicle to sway.

The present invention has been made to solve the above problem, and its purpose is to assist the front wheels by taking into consideration the gripping force of the driver with respect to the steering wheel, thereby maximizing the effect of the assist steering. It is intended to provide an auxiliary steering device for a vehicle, which is made to exhibit and does not inadvertently give a shock to a driver.

[0005]

In order to achieve the above object, the structural features of the present invention as set forth in claim 1 are incorporated in a steering mechanism for steering the front wheels in accordance with the rotation of the steering wheel. An actuator capable of steering the front wheel, and an auxiliary steering control means for driving and controlling the actuator according to at least one of the behavior of the vehicle and the disturbance to the vehicle to assist the front wheel in addition to the steering by turning the steering wheel. In a vehicle auxiliary steering system including: a gripping force detecting means for detecting a gripping force applied to a steering wheel; and an auxiliary steering of front wheels by the auxiliary steering control means when the gripping force detected by the gripping force detecting means is large. And an auxiliary steering limiting means for limiting or prohibiting the auxiliary steering of the front wheels by the auxiliary steering control means when the detected gripping force is small. Located in.

The structural feature of the invention described in claim 2 is applied to a vehicle in which the steering mechanism is a power steering mechanism having a reaction force imparting mechanism, and the invention according to claim 1 is also applied. The configuration further includes reaction force control means for controlling the reaction force applying mechanism to reduce the reaction force by the mechanism when the gripping force detected by the gripping force detection means is large.

[0007]

In the invention according to claim 1 configured as described above, by the operation of the auxiliary steering limiting means,
When the gripping force detected by the gripping force detection means is large, the auxiliary steering of the front wheels by the auxiliary steering control means is permitted, and when the detected gripping force is small, the auxiliary steering of the front wheels by the auxiliary steering control means is limited or prohibited. Thus, according to the invention of claim 1, even if the driver's gripping force on the steering wheel is small and the front wheel is assisted by the steering, the steering wheel is operated by the reaction force received from the road surface by the front wheel due to the assisted steering. When the auxiliary steering causes the front wheels to be rotated in the direction opposite to the direction in which the front wheels are to be steered, and the effect of the auxiliary steering is canceled, useless auxiliary steering can be avoided. At the same time, the driver does not receive a shock due to the abrupt rotation of the steering wheel and does not operate the steering wheel in an unstable manner, so that the running stability of the vehicle is kept good.

Further, in the invention according to claim 2 configured as described above, when the gripping force detected by the gripping force detection means is large, that is, the front wheels are assisted by the steering according to the behavior of the vehicle and the external force applied to the vehicle. In this case, the reaction force control means and the reaction force applying mechanism control the driver so that the reaction force received from the steering wheel is reduced, and the reaction force to the steering wheel, which tends to increase with the assist steering, is offset. To be done. Thus, according to the invention of claim 2,
In addition to the effect of the invention according to claim 1, even if the front wheels are assisted by the steering wheel irrespective of the steering wheel operation by the driver, the driver is not shocked by an unexpected reaction force to the steering wheel, and is unstable. Because you do not operate the handle easily,
The running stability of the vehicle is kept good.

[0009]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings. FIG. 1 shows an entire front wheel steering system including an auxiliary steering system. The steering system operates a front wheel FW in accordance with hydraulic pressure. A power steering mechanism for steering while assisting and an electric control device for electrically controlling the mechanism are provided.

The power steering mechanism includes a housing 1
Valve rotor 1 mounted so as to be coaxially rotatable within 0
1 and a valve sleeve 12. The valve rotor 11 and the valve sleeve 12 move from the hydraulic pump 13 to the oil passage P1 and the diversion valve 14 due to their relative rotational displacements.
And hydraulic oil supplied via the oil passage P2 to one oil chamber of the power cylinder 15 and the cylinder 1
The hydraulic oil from the other oil chamber of No. 5 is discharged to the reservoir 16 via the oil passage P3. The valve rotor 11 is formed integrally with the input shaft 17, and the input shaft 17 is connected to the steering wheel 20 via the steering shaft 18. Valve sleeve 1
Reference numeral 2 is connected to an intermediate shaft 22 via a pin 21 so as to be integrally rotatable, and a torsion bar 23 is interposed between the input shaft 17 and the intermediate shaft 22. The input shaft 17 and the torsion bar 23 are connected via a pin 24, and the intermediate shaft 22 and the torsion bar 23 are connected via a serration 25.

Further, in the housing 10, the input shaft 17
And a hydraulic reaction chamber 28 accommodating a plunger 27 for urging the arm portion 26 formed integrally with the valve rotor 11 to a reference rotational position with a pressing force corresponding to the supplied hydraulic pressure,
The reaction force chamber 28 is connected to the outlet of the flow dividing valve 14 via the oil passage P4, and is also connected to the oil passage P2 via the oil passage P4 and the oil passage P5 having the fixed orifice 29. . The flow dividing valve 14 divides the hydraulic oil supplied via the oil passage P1 into the oil passage P2 and the oil passage P4, and supplies a constant flow amount of hydraulic oil to the oil passage P4 side even if the operating oil pressure fluctuates. Then, one end of the oil passage P6 is connected to the other outlet of the same branch valve 14. The other end of the oil passage P6 has a solenoid valve 3
1 and the oil passage P7 are connected to the oil passage P3. The solenoid valve 31 is electrically controlled, and the opening degree of the valve 31 is proportional to the amount of electricity.

A support shaft 32 is integrally rotatably connected to the lower end of the intermediate shaft 22 via a spline 33, and an output pinion 34 is rotatably mounted on the coaxial shaft 32. A rack bar 35 meshes with the output pinion 34. The rack bar 35 also serves as a piston rod of the power cylinder 15, and is rotated in the axial direction by the rotation of the output pinion 34 and the power cylinder 15 to steer the front wheels FW.

On the outer periphery of the support shaft 32, the elliptical sun gear 3 is provided.
6 is attached via a spline 37 so as to be integrally rotatable. The elliptical sun gear 36 has an elliptical planetary gear 3
8 meshes with each other, and the gear 38 is rotatably mounted on the outer circumference of a carrier shaft 42 mounted on a carrier 41. The carrier 41 includes the housing 10 and the support shaft 32.
It is rotatably attached to. On the outer periphery of the elliptical planetary gear 38, a circular planetary gear 44 is integrally rotatably mounted via a serration 43.
The gear 44 meshes with the output pinion 34. A wheel 45 is fixed to the carrier 41, and the wheel 45 is meshed with a worm 47 that is rotationally driven by an electric motor 46 composed of a step motor, and the wheel 45 of the support shaft 32 is rotated according to the rotation of the motor 46. It is designed to rotate around. With such a configuration, even if the elliptical sun gear 36 rotates independently by the rotation of the handle 20 and the carrier 41 rotates independently by the rotation of the electric motor 46, the output pinion 34 rotates and the rack bar rotates. The front wheels FW are steered via the motor 35, but regarding the rotation direction of the electric motor 46,
The rotation of 6 in the positive direction (or the negative direction) corresponds to the steering of the front wheel FW in the right direction (or the left direction).

The electric control unit includes a vehicle speed sensor 51, a yaw rate sensor 52, a side wind sensor 53, a steering wheel steering angle sensor 54, a gripping force sensor 55 and a microcomputer 56.
Is equipped with.

The vehicle speed sensor 51 outputs a detection signal indicating the vehicle speed V by detecting the rotation speed of the output shaft of a transmission (not shown). The yaw rate sensor 52 detects the rotational angular velocity of the vehicle body about the vertical axis of the center of gravity as a state quantity of the behavior of the vehicle, and outputs a detection signal representing the rotational angular velocity, that is, the yaw rate Y _R. Crosswind sensor 53 detects the crosswind wind speed experienced by the vehicle as the quantity of state of the disturbance to the vehicle, and outputs a detection signal indicative of the crosswind wind G _R. The steering wheel steering angle sensor 54 detects the rotation angle of the steering shaft 18 as a driving operation amount of the vehicle, and the same rotation angle, that is, the steering wheel steering angle δ.
A detection signal representing _H is output. In this case, the yaw rate Y _R and the steering wheel angle δ _H are positive and represent the right rotation direction, and negative and represent the left rotation direction. Crosswind wind G _R represents a crosswind to the right direction of the vehicle than the positive, representing a crosswind leftward by the negative.

The gripping force sensor 55 is the driver's steering wheel 20.
The gripping force P for the steering wheel 2 is detected and a detection signal indicating the gripping force P is output. As shown in FIGS.
It is housed in a ring-shaped space having a rectangular cross section, which is provided in a urethane intermediate layer 20c interposed between a cored bar 20a and a urethane skin 20b forming 0. The gripping force sensor 55 includes a flexible base 55a extending over the entire circumference of the handle 20.
A conductive band 55c made of phosphor bronze faces the upper surface of 5a with a pair of insulating spacers 55b, 55b provided on both sides of the base 55a, with a slight gap therebetween. Conductive band 55
A resin film 55d is provided on the upper surface of c so as to be opposed to each other with a slight gap, and a large number of protrusions 55e fixed to the upper surface of the conductive band 55c are circumferentially provided between the conductive band 55c and the resin film 55d. Is interposed at a predetermined interval.

On the upper surface of the flexible substrate 55a, fixed contacts 55f1 of a large number of switches 55f having conductive bands 55c as movable contacts are formed by printed wiring below the protrusions 55e. A large number of identical resistors 55g corresponding to the switches 55f are provided on the lower surface of the flexible board 55a. As shown in FIG. 5, the switch 55f and the resistor 55g are connected in series, and the series circuits of the switch 55f and the resistor 55g are connected in parallel to form a resistance ladder circuit. One end of this resistance ladder circuit is grounded,
The other end is the operational amplifier 5 provided on the flexible board 55a.
It is connected to the inverting input of 5h. The same resistance 55i as the resistance 55g provided on the flexible substrate 55a is connected between the inverting input and the output of the operational amplifier 55h, and the power supply voltage V is supplied to the non-inverting input of the amplifier 55h. .

In the gripping force sensor 55 thus constructed, the number of the switches 55f turned on increases as the gripping force P of the steering wheel 20 by the driver increases. In this case, assuming that the values of the resistors 55g and 55i are R and the number of the turned-on switches 55f is n, the operational amplifier 55
The output voltage of h is represented as (n + 1) · V. Therefore, the grip force sensor 55 comes to output a voltage signal proportional to the grip force P of the steering wheel 20 by the driver.

The microcomputer 56 is a CPU, RO
It is composed of M, RAM, interface circuit, etc., and executes a program corresponding to the flowcharts of FIGS. A table is provided in the ROM together with the area for storing the program, and the hydraulic control current I _S (see FIG. 8) that changes according to the vehicle speed V is provided in the table.
(A)), steering angle ratio K ₁ (FIG. 8B), yaw rate correction coefficient K ₂ (FIG. 8C), and crosswind correction coefficient K ₃ (FIG. 8D).
And a gripping force correction coefficient K ₄ (FIG. 8 (E)) and a hydraulic pressure increase coefficient K _S (FIG. 8 (F)) that change according to the gripping force P are stored.

Next, the operation of the embodiment configured as described above will be described. When the handle 20 is rotated, this rotation is transmitted to the elliptical sun gear 36 via the input shaft 17, the torsion bar 23, the intermediate shaft 22, and the support shaft 32, and the gear 3
6 rotates. This rotation is transmitted to the output pinion 34 via the elliptical planetary gear 38 and the circular planetary gear 44, and the rotation of the pinion 34 causes the rack bar 3 to rotate.
Since 5 is displaced in the axial direction, the front wheel FW is steered by the rotation of the handle 20. In addition, at this time, the valve rotor 11 is moved in accordance with the steering torque acting on the torsion bar 23.
The rotary valve composed of the valve sleeve 12 and the valve sleeve 12 is operated.
4 and the hydraulic oil supplied through the oil passage P2 to one oil chamber of the power cylinder 15 and the cylinder 1
Since the hydraulic oil in the other oil chamber of No. 5 is returned to the reservoir 16 via the oil passage P3, the power cylinder 15 hydraulically assists the steering of the front wheel FW. It should be noted that in this embodiment, the action of the elliptical sun gear 36 and the elliptical planetary gear 38 on the rotation transmission path of the handle 20 causes the handle 20 to rotate.
The ratio of the steered angle of the front wheels FW to the unit rotational angle can be changed according to the turning position of the handle 20. However, this point is not directly related to the present invention, and the description thereof will be omitted.

On the other hand, the microcomputer 56 responds to the closing of an ignition switch (not shown), as shown in FIG.
In step 60, the execution of the program is started, and while the front wheel FW is being steered, the circulation process of steps 61 to 79 is continuously executed, and the solenoid valve 31 and the electric motor are driven according to the detection signals from the sensors 51 to 55. The operation of the motor 46 is controlled.

In this circulation processing, in step 61, a detection signal representing the vehicle speed V is read from the vehicle speed sensor 51, and in step 62, the hydraulic control current I _S (FIG. 8 (A) is read from the table based on the vehicle speed V. ) Is read.

Next, in step 63, a detection signal indicating the steering wheel steering angle δ _H is read from the steering wheel steering angle sensor 54, and in step 64, the steering angle ratio K ₁ (see FIG. 8 ( (See B)) is read out, and in step 65, the correction value θ _H is calculated by executing the calculation of the following equation 1 based on the steering wheel steering angle δ _H and the steering angle ratio K ₁ .

[Equation 1] θ _H = K ₁ · δ _H

Next, at step 66, the detection signal representing the yaw rate Y _R is read from the yaw rate sensor 52,
In step 67, the yaw rate correction coefficient K ₂ (see FIG. 8C) is read from the table based on the vehicle speed V, and in step 68, the yaw rate Y _R and the following number based on the yaw rate correction coefficient K ₂ are read. The correction value θ _Y is calculated by executing the calculation of 2.

[Equation 2] θ _Y = K ₂ · Y _R

Next, the detection signal representing the crosswind wind G _R from the side wind sensor 53 in step 69 is read, crosswind correction factor K ₃ from the table based on the vehicle speed V at step 70 (see FIG. 8 (D) ) Is read and step 71
The crosswind wind G _R and the correction value theta _G by executing the calculation of the following Equation 3 based on the crosswind correction factor K ₃ is calculated at.

[Equation 3] θ _G = K ₃ · G _R

Then, in step 72, both the calculated correction values θ _Y and θ _G are added and calculated as shown in the following equation 4, and a new correction value θ _E is calculated.

[Equation 4] θ _E = θ _Y + θ _G

Next, in step 73 of FIG. 7, a detection signal indicating the gripping force P of the steering wheel 20 by the driver is read from the gripping force sensor 55, and in step 74 the gripping force P is read.
Is determined to be equal to or greater than the predetermined value P ₀ . In this case, if the driver is firmly gripping the steering wheel 20 and the detected gripping force P is not less than the predetermined value P ₀ , step 7
4 is determined as “YES”, and in step 75, the hydraulic pressure increase coefficient K _S is calculated from the table based on the gripping force P (FIG. 8).
(See (F)) is read out, and the calculation of the following equation 5 is executed based on the hydraulic pressure control current I _S and the hydraulic pressure increase coefficient K _S in step 76, and according to the vehicle speed V in the process of step 62. The determined hydraulic pressure control current I _S is corrected according to the hydraulic pressure increase coefficient K _S.

[Equation 5] I _S = K _S · I _S

After the processing of step 76, step 77
At, the motor rotation angle θ _M is calculated by executing the calculation of the following Expression 6 based on the correction values θ _H and θ _E. Then, in step 78, the current corresponding to the hydraulic control current I _S determined by the process of step 62 is changed to the solenoid valve 3
The control signal corresponding to the motor rotation angle θ _M calculated by the process of step 77 is supplied to the electric motor 46 in step 79.

[Equation 6] θ _M = θ _H + θ _E

As a result, the electric motor 46 rotates to the rotation position represented by the motor rotation angle θ _M. The rotation of the electric motor 46 is transmitted to the carrier 41 via the worm 47 and the wheel 45, and the carrier 41 revolves around the support shaft 32. In this case, the steering wheel 20 is firmly gripped by the driver, and the support shaft 32 and the elliptical sun gear 36 are rotated only by the rotational operation of the driver. Corresponding to the revolution of the carrier 41, it rotates around the carrier shaft 42, and the output pinion 34 rotates corresponding to this revolution. This allows the output pinion 3
4 rotates according to the rotation amount of the electric motor 46 in addition to the rotation corresponding to the rotation amount of the handle 20 described above,
The front wheels FW are steered at an angle that combines the rotation amount of the handle 20 and the rotation amount of the electric motor 46.

[0030] In this case, the motor rotation angle theta _M is based on the calculation of the number 1～4,6, can be expressed as the following equation 7.

[Equation 7] θ _M = K ₁ · δ _H + K ₂ · Y _R + K ₃ · G _R

The first term K ₁ · δ _H of the equation 7 is for correcting the steering angle of the front wheels FW according to the magnitude of the steering wheel steering angle δ _{H. When} the vehicle speed V is low, FIG. As shown
Since the steering angle ratio K ₁ has a positive value, if the steering wheel 20 is steered to the right (or left) and the steering wheel steering angle δ _H is a positive (or negative) value, the first term K ₁ -Δ _H is a positive (or negative) value. As a result, the front wheel FW is turned to the steering wheel 20.
If the electric motor 46 is steered in the right direction (or left direction) by the rotation of, the electric motor 46 is rotationally controlled in the positive direction (or the negative direction), and this rotational force is generated by the worm 47, the wheel 45, the carrier 41, the elliptical planetary gear. 38, the circular planetary gear 44, and the output pinion 34, the rack bar 3
5, the front wheel FW is steered in the right direction (or left direction) in accordance with the rotation amount of the electric motor 46 from the reference position, that is, in addition to the steering amount by the rotation of the handle 20, The correction steering is performed according to the rotation amount. As a result, when the vehicle is traveling at a low speed, the steering amount of the front wheels FW with respect to the rotation of the steering wheel 20 is large, and the maneuverability of the vehicle is improved.

On the other hand, if the vehicle speed V increases, the steering angle ratio K ₁
Also, as shown in FIG. 8 (B), since it decreases to a negative value, the steering wheel 20 is steered to the right (or left), and the steering wheel steering angle δ _{H has a} positive (or negative) value. If so, the first term K ₁ · δ _H changes from a positive (or negative) value to a negative (or) value. Accordingly, if the front wheels FW are steered to the right (or left) by the rotation of the steering wheel 20, the front wheels FW are steered to the left (or right) by the electric motor 46, that is, the steering wheel, as described above. The steering amount by the rotation of 20 is corrected and steered by the rotation amount of the electric motor 46 to the side closer to the neutral state. As a result, as the vehicle travels at high speed, the front wheel F with respect to the turning amount of the steering wheel 20.
The steering amount of W is reduced, and the running stability of the vehicle is improved.

The second term K ₂ · Y _R of the equation ₇ is for correcting the steering angle of the front wheels FW according to the magnitude of the yaw rate Y _R generated in the vehicle, and the yaw rate correction coefficient K ₂ is As shown in 8 (C), since it is a negative value, if the yaw rate in the right (or left) rotation direction is generated in the vehicle and the detected yaw rate Y _R becomes positive (or negative), the second term K ₂・ Y _R
Becomes a negative (or positive) value, and the front wheels FW are corrected and steered in the left (or right) direction. Also, this yaw rate correction coefficient K
₂ of the absolute value | K ₂ | so becomes larger as the vehicle speed V increases, the absolute value of the vehicle speed V and the yaw rate Y _R |
As Y _R | increases, the absolute value | K ₂ · Y _R | of the second term K ₂ · Y _R also increases, and the corrected steering amount of the left and right front wheels FW also increases. Thus, the front wheel FW is, this second term K ₂ · Y _R, yaw rate Y _R
As the vehicle speed V and the yaw rate Y _R increase in the direction of canceling
The running stability of the vehicle, particularly the running stability of the vehicle at high speeds, is improved.

Further, the third term K ₃ · G _R of the equation ₇ is for correcting the steering angle of the front wheels FW according to the magnitude of the crosswind wind speed G _R with respect to the vehicle, and the crosswind correction coefficient K ₃ is shown in FIG. (D), the so is "0" or a negative value, if the left (or right) side wind is blowing detection crosswind velocity of from G _R positive (or negative) with respect to the vehicle, the The third term K ₃ · G _R becomes “0” or negative (or positive), and the front wheels FW are corrected and steered in the left (or right) direction. The absolute value | K ₃ | of the crosswind correction coefficient K ₃ is “0” when the vehicle speed is low and increases as the vehicle speed V increases, so the absolute value | G of the vehicle speed V and the crosswind wind speed G _R | G _{As R} | increases, the absolute value of the third term K ₃ · G _R | K ₃ · G _R |
Is also increased, and the correction steering amount of the front wheel FW to the left and right is also increased. Therefore, the front wheel FW has the third term K ₃ ·.
With G _R , in the direction to cancel the deflection of the vehicle body due to cross wind,
Since the magnitude of the vehicle speed V and lateral wind wind speed G _R is increased corrected steering according increases, the running stability of the vehicle, in particular the running stability of the vehicle at high speeds is improved.

In addition, as a result of the current corresponding to the hydraulic control current I _S being passed through the solenoid valve 31 in the process of step 78, the opening of the valve 31 increases as the hydraulic control current I _S increases. Is set as follows. On the other hand, the hydraulic oil from the hydraulic pump 24, which has been diverted to the oil passages P4 and P6 by the shunt valve 25, increases as the opening degree of the solenoid valve 31 increases.
Since a large amount of oil flows into the reservoir 16 via 7, the operating oil pressure in the oil passage P4 and the hydraulic reaction force chamber 31 becomes smaller as the opening degree of the valve 31 becomes larger. The reaction force also becomes smaller.

In this case, the hydraulic pressure control current I _S is given by
As is clear from FIGS. 8A and 8F, the vehicle speed V decreases as the vehicle speed V increases, and the gripping force P (≧ P
_{As 0} ) increases, it gradually increases from “1.0”. As a result, when the vehicle is traveling at a low speed, the steering wheel 20 can be swung lightly to improve the turning controllability of the vehicle, and when the vehicle is traveling at a high speed, the steering operation of the steering wheel 20 is heavy and the vehicle can be easily turned. The running stability of is good. Further, by the reaction force control by the gripping force P, when the gripping force P is large, the steering and steering holding reaction force to the steering wheel 20 becomes small. As a result, as described above, the front wheels FW are assisted to be steered independently of the turning of the steering wheel, and the reaction force from the front wheels FW caused by the assisted steering is mitigated, so that the driver is shocked by the assisted steering. Is eliminated, and unstable steering wheel operation is not performed, so that the running stability of the vehicle is improved.

On the other hand, if the driver does not firmly grip the steering wheel 20 and the detected gripping force P is less than the predetermined value P ₀ , it is determined to be “NO” in step 74 and the above-mentioned is determined in step 80. The gripping force correction coefficient K ₄ (FIG. 8 (E)) is read out from the table based on the gripping force P, and step 8
By execution of the following calculation equation 8 based on the correction value theta _E and gripping force correction coefficient K ₄ at 1, correction value theta _E calculated by the processing of the step 72 is corrected in accordance with the grasping force correction coefficient K ₄ .

[Equation 8] θ _E = K ₄ · θ _E Then, as described above, at step 77, this correction value θ
_The motor rotation angle θ _M is calculated by adding _E (= K ₄ · θ _E ) to the correction value θ _H , and the front wheel FW is corrected and steered according to the motor rotation angle θ _M by the processing of step 79. . In this case, the motor rotation angle θ _M is expressed by the above equations 1 to 4,
It is based on the operations of 6 and 8 and can be expressed as the following Expression 9.

[Equation 9] θ _M = K ₁ · δ _H + K ₄ · (K ₂ · Y _R + K ₃ · G _R )

The first term K ₁ · δ _H of the equation 9 is to correct the steering angle of the front wheels FW according to the magnitude of the steering angle δ _H , as in the case described above. As described above, in this case as well, the correction steering based on the first term K ₁ · δ _H improves the maneuverability of the vehicle during low speed traveling and also improves the running stability of the vehicle during high speed traveling. Becomes

Further, the second term K ₄ · (K ₂ · Y _R + K) of the equation 9
₃ · G _R ) corrects the steering angle of the front wheels FW according to the yaw rate Y _R and the lateral wind velocity G _R , as in the case described above, to improve the running stability of the vehicle. However, as shown in FIG. 8 (E), the gripping force correction coefficient K ₄ is “0” when the gripping force P is small, and in this case, the second term K ₄ ·
(K ₂ · Y _R + K ₃ · G _R ) is also “0”, so the same term K ₄ · (K
The correction steering of the front wheels FW by ( ₂・ Y _R + K ₃・ G _R ) is not performed. Thus, a small gripping force relative to the handle of the driver, even if the auxiliary steered in accordance with the front wheel FW on the yaw rate Y _R and crosswind wind speed G _R, the reaction force the front wheels FW receives from the road surface, the auxiliary steering handle 20 As a result, the front wheels FW are turned in the direction opposite to the direction in which the steering is attempted,
When the effect of the auxiliary steering is canceled, useless auxiliary steering can be avoided. At the same time, the driver does not receive a shock due to the abrupt rotation of the steering wheel and does not operate the steering wheel in an unstable manner, so that the running stability of the vehicle is kept good.

On the other hand, when the gripping force P increases to some extent, the gripping force correction coefficient K ₄ gradually increases as the gripping force P increases, and becomes "1.0" when the gripping force P reaches the predetermined value P _0. It is supposed to become. As a result, the front wheel F
W is continuously corrected and steered when the gripping force P is equal to or greater than the predetermined value P ₀ .

Also in this case, the reaction force to the steering wheel 20 is controlled in accordance with the hydraulic pressure control current I _S by the processing of step 78 as in the above case. However, in this case, the hydraulic control current I _S is determined only by the process of step 62 and is set to a smaller value than the above case. This is the yaw rate Y _R and cross wind speed G _R
This is because the auxiliary steering of the front wheels FW by the steering wheel 20 is not performed. In this case, the steering wheel 20 can be easily rotated when the vehicle travels at low speed, and the steering wheel 20 can be rotated when the vehicle travels at high speed. Is only heavy. As a result, the above-mentioned front wheel FW is applied to the yaw rate Y _R and the side wind speed G.
It is possible to obtain a steering feeling similar to that in the case of performing correction steering according to _R.

In the above embodiment, the steering wheel steering angle δ _H is used as an amount representing the driving operation amount of the vehicle, but instead of or in addition to the steering wheel steering angle sensor 54, the steering wheel angular velocity sensor, the steering wheel angle. An acceleration sensor, an accelerator opening sensor, or a brake pedal depression amount sensor is used, and the steering wheel steering angle δ
Instead of or in addition to _H , steering wheel angular velocity, steering wheel angular acceleration, accelerator opening, or brake pedal depression amount may be used. Further, in the above embodiment,
Although the yaw rate Y _R is used as the quantity representing the behavior of the vehicle, a lateral acceleration sensor is used instead of or in addition to the yaw rate sensor 52, and instead of or in addition to the yaw rate Y _R , as the quantity representing the behavior of the vehicle. You may make it utilize the lateral acceleration of a vehicle.

[Brief description of drawings]

FIG. 1 is an overall schematic diagram of a front wheel steering system showing an embodiment of the present invention.

FIG. 2 is a plan view of a handle incorporating a gripping force sensor.

3 is a cross-sectional view of the handle taken along line 3-3 of FIG.

4 is a partially cutaway perspective view of the handle of FIG. 2. FIG.

5 is an equivalent electric circuit diagram of the gripping force sensor of FIG.

FIG. 6 is a flowchart corresponding to a part of a program executed by the microcomputer of FIG.

FIG. 7 is a flowchart corresponding to the rest of the program.

8A to 8F are characteristic graphs of various coefficients stored in the microcomputer of FIG.

[Explanation of symbols]

11 ... Valve rotor, 12 ... Valve sleeve, 13 ... Hydraulic pump, 14 ... Flow dividing valve, 15 ... Power cylinder, 20
... Handle, 27 ... Hydraulic reaction chamber, 31 ... Solenoid valve, 32 ... Support shaft, 34 ... Output pinion, 35 ... Rack bar, 36 ... Elliptical sun gear, 38 ... Elliptical planetary gear, 41 ... Carrier, 42 ... Carrier shaft, 44 … Circular planetary gears, 45… Wheels, 46… Electric motors, 4
7 ... worm, 51 ... vehicle speed sensor, 52 ... yaw rate sensor, 53 ... cross wind sensor, 54 ... steering wheel steering angle sensor,
55 ... Gripping force sensor, 56 ... Microcomputer.

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁵ Identification code Internal reference number FI technical display location B62D 137: 00

Claims (2)

[Claims] 1. An actuator incorporated in a steering mechanism for steering front wheels in response to turning of a steering wheel and capable of steering front wheels, and the actuator according to at least one of behavior of a vehicle and disturbance to a vehicle. In an auxiliary steering system for a vehicle, comprising: an auxiliary steering control means for drivingly controlling and steering the front wheels in addition to steering by turning the steering wheel; a gripping force detecting means for detecting a gripping force applied to the steering wheel; When the gripping force detected by the gripping force detection means is large, the auxiliary steering of the front wheels by the auxiliary steering control means is permitted, and when the detected gripping force is small, the auxiliary steering of the front wheels by the auxiliary steering control means is restricted or prohibited. An auxiliary steering device for a vehicle, which is provided with: 2. The auxiliary steering device for a vehicle according to claim 1, wherein the steering mechanism is applied to a vehicle having a power steering mechanism having a reaction force imparting mechanism, and the gripping force detecting means is further applied. An auxiliary steering device for a vehicle, comprising: reaction force control means for controlling the reaction force applying mechanism to reduce the reaction force by the mechanism when the detected gripping force is large.