JP4100130B2 - Vehicle steering system - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a vehicle steering apparatus configured to apply a driving force of a steering actuator (such as an electric motor and a hydraulic cylinder) to a steering mechanism, such as a power steering apparatus and a steer-by-wire (SBW) system.
[0002]
[Prior art]
2. Description of the Related Art Conventionally, a power steering apparatus configured to assist steering by transmitting a driving force generated by an electric motor or a hydraulic cylinder to a steering mechanism has been used in a vehicle. For example, in an electric power steering device configured to transmit the driving force of an electric motor to a steering mechanism via a gear mechanism or to the steering mechanism by a direct drive method, the electric motor is responsive to the steering torque applied to the steering wheel. The target drive value is set, and the electric motor is controlled based on the target drive value. The steering torque is detected by torsion of a torsion bar interposed in a steering shaft that couples the steering wheel and the steering mechanism.
[0003]
On the other hand, as a new vehicle steering device, the mechanical coupling between the steering wheel and the steering mechanism for steering the steering wheel is eliminated, and the steering wheel operation angle is detected, and the detection result is Based on this, a system (a so-called steer-by-wire (SBW) system) has been proposed (for example, a so-called steer-by-wire (SBW) system) that achieves steering of a steering wheel by applying a torque from a steering actuator to a steering mechanism (for example, Patent Document 1) below.
[0004]
The steering actuator is controlled by a control device including a microcomputer. That is, while the ignition key switch of the vehicle is on, detection signals of the operation angle sensor for detecting the operation angle of the steering wheel and the turning angle sensor for detecting the turning angle of the steering wheel are input to the control device. ing. Based on these input signals, the control device controls the steering actuator so that the turning angle of the steering wheel corresponds to the operation angle of the steering wheel.
[0005]
On the other hand, in order to apply an operational reaction force to the steering wheel, a reaction force actuator is attached to the steering shaft. The control device applies an operation reaction force to the steering wheel by driving and controlling the reaction force actuator according to an operation angle or the like.
[0006]
[Patent Document 1]
JP 2000-198453 A
[Patent Document 2]
JP-A-10-324120
[Patent Document 3]
Japanese Patent Laid-Open No. 11-20427
[0007]
[Problems to be solved by the invention]
The above-described conventional electric power steering apparatus is configured to control the electric motor as the steering actuator in accordance with the steering torque, so that the steering assist that reflects the road surface condition is performed as long as it is reflected in the steering torque. It can be said that However, since the road surface condition is transmitted from the wheels via a mechanical link and reflected in the steering torque, detection is delayed due to the effects of backlash and backlash of the steering mechanism and torsion bar torsion. The response delay cannot be avoided. That is, it cannot be said that the steering actuator can be controlled with good responsiveness to the road surface condition.
[0008]
Similarly, in the steer-by-wire system, it is difficult to control the steering actuator that accurately reflects the road surface condition and the like.
Accordingly, an object of the present invention is to provide a vehicle steering apparatus that can detect a tire load and perform a steering control that accurately reflects a road surface condition based on the tire load.
[0009]
[Means for Solving the Problems and Effects of the Invention]
  In order to achieve the above object, the invention according to claim 1 provides a steering mechanism (4, 6, 7, 24) for turning the steering wheel (5, 29) and a steering force to the steering mechanism. Steering actuators (2, 32), load detection means (SL, SR, SP, SA) for detecting a tire load, which is a load applied to the tire of the vehicle, and the tire load detected by the load detection means Steering control means (14, C) for controlling the steering actuator;Steering direction detecting means (13, 46) for detecting the steering direction of the vehicle;IncludingThe load detecting means includes stress detecting means (SL, SR) for detecting stress applied to the tire, and the stress detecting means applies stress applied to the left side portion and the right side portion of the tire in the traveling direction of the vehicle. The steering control means includes a left-side stress detection means (SL) and a right-side stress detection means (SR) for detecting the steering direction of the vehicle detected by the steering direction detection means, the left-side stress detection means, and the right-side stress, respectively. The steering actuator is controlled based on the stress detected by the detecting means.This is a vehicle steering apparatus. The alphanumeric characters in parentheses indicate corresponding components in the embodiments described later. The same applies hereinafter.
[0010]
  According to this configuration, the steering actuator that applies a steering force to the steering mechanism is in accordance with a load applied to a tire of the vehicle (a tire of a steering wheel or a wheel other than the steering wheel). Since the vehicle is controlled, it is possible to perform the steering control that directly reflects the road surface condition and the tire condition. Thereby, the steering control which reflected the road surface condition correctly is realizable.
The stress detection means includes left stress detection means (SL) and right stress detection means (SR) that detect stresses applied to the left and right sides of the tire in the traveling direction of the vehicle. Since it is possible to detect the amount of deformation of the tire when the vehicle travels while drawing a curved locus (when passing along a curve), it is possible to perform appropriate steering control according to the load condition of the tire. For example, the left stress detection means and the right stress detection means may be installed on the left sidewall portion (52L) and the right sidewall portion (52R) of the tire.
In the present invention, the steering control means controls the steering actuator based on the steering direction of the vehicle detected by the steering direction detection means and the stresses respectively detected by the left stress detection means and the right stress detection means.
More specifically, as described in claim 2, the steering control means includes the left side stress detection means for the vehicle steering direction detected by the steering direction detection means, and the tire outside the steering direction of the vehicle, and It is preferable that the steering actuator is controlled based on the stress detected by the right-side stress detection means.
According to this configuration, it is possible to effectively detect the load applied to the tire by utilizing the fact that a larger deformation occurs in the tire outside the steering direction of the vehicle, and this can be reflected in the steering control.
  In addition, it is preferable that the said load detection means is what detects the load added to a tire inside a tire. As a result, the road surface condition can be detected at a position closest to the road surface, and the detection result can be used for steering control. Therefore, it is possible to realize the steering control that satisfactorily follows the change in the road surface condition.
[0011]
  Further, the load detecting means is a claim.3As described in the above, an air pressure detecting means (SP) for detecting the air pressure of the tire may be included..
[0014]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings.
FIG. 1 is a conceptual diagram for explaining a configuration of a vehicle steering apparatus according to a first embodiment of the present invention. This vehicle steering device eliminates the mechanical coupling between the steering wheel 1 and the steering mechanism, and the operation of the steering actuator 2 driven in accordance with the rotation operation of the steering wheel 1 is performed on the steering shaft supported by the housing 3. 4 is converted to a linear motion in the vehicle width direction, and the steering is achieved by converting the linear motion of the steered shaft 4 into the steered motion of the front left and right wheels 5 for steering. A wire (SBW) system.
[0015]
The steering actuator 2 includes, for example, an electric motor such as a brushless motor. The driving force (rotational force of the output shaft) of the steering actuator 2 is applied to the axial direction (vehicle width direction) of the steered shaft 4 by a motion conversion mechanism (for example, a ball screw mechanism) provided in association with the steered shaft 4. ) Linear motion. This linear motion of the steered shaft 4 is transmitted to the tie rods 6 provided so as to protrude from both ends of the steered shaft 4, and further causes the knuckle arm 7 connected to the king pin P to be rotated via the tie rod 6. Thereby, steering of the wheel 5 supported by the knuckle arm 7 is achieved. The steering shaft 4, the tie rod 6, the knuckle arm 7, and the like constitute a steering mechanism for steering the steering wheel 5.
[0016]
The steering wheel 1 is connected to a rotating shaft 8 that is rotatably supported with respect to the vehicle body. A reaction force actuator 9 for applying an operation reaction force to the steering wheel 1 is attached to the rotating shaft 8. The reaction force actuator 9 includes an electric motor such as a brushless motor having an output shaft integrated with the rotary shaft 8.
An elastic member 10 made of a spiral spring or the like is coupled to the end of the rotating shaft 8 on the opposite side of the steering wheel 1 from the vehicle body. The elastic member 10 returns the steering wheel 1 to the straight-ahead steering position by the elastic force when the reaction force actuator 9 is not applying torque to the steering wheel 1.
[0017]
In order to detect an operation input value of the steering wheel 1, an operation angle sensor 11 for detecting an operation angle of the steering wheel 1 is provided in association with the rotary shaft 8. The rotating shaft 8 is provided with a torque sensor 12 for detecting an operation torque applied to the steering wheel 1. On the other hand, a steering angle sensor 13 for detecting the steering angle (tire angle) of the steering wheel 5 is provided in relation to the steering shaft 4.
[0018]
Further, as will be described later, the left side stress sensor SL and the right side stress sensor SR that detect the stress acting on the left and right sidewall portions of the tire W, and the tire W are disposed inside the tire W attached to the wheel 5. An air pressure sensor SP for detecting air pressure is provided.
The detection signals of the operation angle sensor 11, the torque sensor 12, the turning angle sensor 13, the stress sensors SL and SR, and the air pressure sensor SP are input to a control device 14 including an electronic control unit (ECU) including a microcomputer. It has become so. However, the detection signals of the stress sensors SL and SR and the air pressure sensor SP are received by the control device 14 by wireless communication via the antenna 14a.
[0019]
The control device 14 controls the operation angle detected by the operation angle sensor 11, the turning angle detected by the turning angle sensor 13, the vehicle speed detected by the vehicle speed sensor 15, and the tire stress detected by the stress sensors SL and SR. The steering command value is set based on the tire pressure detected by the air pressure sensor SP, and the steering actuator 2 is controlled via the drive circuit 17 based on the steering command value.
Since there is no mechanical coupling between the steering wheel 1 and the steering mechanism, VGR (Variable Gear) that variably sets the ratio (transmission ratio, gear ratio) between the rotation amount of the steering wheel 1 and the steering amount of the wheel 5 Ratio) function can be realized. That is, for example, the control device 14 sets the gear ratio based on the vehicle speed detected by the vehicle speed sensor 15 and the tire load detected by the stress sensors SL, SR and / or the air pressure sensor SP, and this gear ratio. And a steering command value corresponding to a voltage to be applied to the steering actuator 2 is set based on the operation angle of the steering wheel 1.
[0020]
On the other hand, the control device 14 is detected by an operation angle detected by the operation angle sensor 11, an operation torque detected by the torque sensor 12, a vehicle speed detected by the vehicle speed sensor 15, and a stress sensor SL, SR and / or an air pressure sensor SP. The reaction force actuator 9 is controlled via the drive circuit 18 so that an appropriate reaction force in the direction opposite to the operation direction of the steering wheel 1 is generated based on the tire load.
[0021]
Further, for example, an alarm device 19 provided on an instrument panel of the vehicle is connected to the control device 14. The alarm device 19 may be composed of an alarm sound generator, or may be composed of an alarm display device that performs alarm display (lamp display or message display). The control device 14 generates an alarm from the alarm device 19 when detecting a predetermined abnormality requiring maintenance.
FIG. 2 is a schematic cross-sectional view for explaining the configuration of the tire W of the steering wheel 5. The tire W includes a tread portion 51 that contacts a road surface, and a pair of sidewall portions 52L and 52R coupled to both side portions of the tread portion 51. A right stress sensor SR is disposed on the inner wall surface of the right sidewall portion 52R in the traveling direction of the vehicle, and a left stress sensor is disposed on the inner wall surface of the left sidewall portion 52L in the traveling direction of the vehicle. SL is arranged. An air pressure sensor SP is disposed on the inner wall surface of the tread portion 51. In addition, for example, the stress sensor SA may be embedded in the tread portion 51 as necessary.
[0022]
The right side stress sensor SR and the left side stress sensor SL detect the stress applied to the right side wall part 52R and the left side wall part 52L, respectively. A sensor part such as a strain gauge and a detection signal of this sensor part are wirelessly transmitted. A transponder unit for transmission and a power storage unit that converts the rotational motion of the tire W into electric energy and stores the electric energy, and operates by the electric energy accumulated in the power storage unit. Similarly, the air pressure sensor SP is arranged inside the tire W, a sensor unit for detecting the internal air pressure of the tire W, a transponder unit for wirelessly transmitting a detection signal of the sensor unit, and rotation of the tire W And a power storage unit that converts motion into electrical energy and stores the electrical energy, and is operated by the electrical energy stored in the power storage unit. A signal transmitted from the transponder unit is taken into the control device 14 from the antenna 14a.
[0023]
As the stress sensor and the air pressure sensor as described above, for example, known ones as disclosed in Patent Document 2 and Patent Document 3 can be adopted.
FIG. 3 is an illustrative view for explaining deformation of the tire W during cornering. FIG. 3A shows the cross-sectional shapes of the left and right tires WL and WR when leftward steering is performed on a road surface with a relatively small friction coefficient, and FIG. 3B shows road surface friction. The cross-sectional shapes of the left and right tires WL and WR when leftward steering is performed on a road surface having a relatively large coefficient are shown. 3A and 3B, the cross-sectional shapes of the tires WL and WR are shapes as viewed from the rear in the traveling direction of the vehicle.
[0024]
Of the left and right tires WL, WR, the deformation of the left tire WL on the inside in the steering direction is relatively small, and the deformation of the right tire WR on the outside in the steering direction is large. In both the left and right tires WL and WR, the deformation at the left sidewall portion that is inside the steering direction is small, and the deformation at the right sidewall portion that is outside the steering direction is large. This deformation increases as the road surface friction coefficient increases. Therefore, in this embodiment, the control device 14 identifies a tire located on the outer side in the steering direction based on the output signal of the turning angle sensor 13, and is mounted on the tire (right tire WR in the example of FIG. 3). Refer to the outputs of the left and right stress sensors SL, SR. More specifically, the stress To of the outer side wall part detected by the right side stress sensor SR that detects the stress of the right side wall part 52R on the outer side in the steering direction and the stress of the left side wall part 52L on the inner side in the steering direction are determined. A difference ΔT (= To−Ti) from the stress Ti of the inner sidewall portion detected by the detected left stress sensor SL is obtained. Further, the control device 14 obtains a first-order time differential value (stress change rate, tire load change rate) or a second-order time differential value (stress change acceleration, tire load change acceleration) of the stress difference ΔT between the left and right sidewall portions, The steering actuator 2 and the reaction force actuator 9 are driven and controlled based on the tire load change speed or the tire load change acceleration thus obtained.
[0025]
FIG. 4 is a control characteristic diagram showing an example of a control mode of the reaction force actuator 9 by the control device 14. The control device 14 sets a reaction force actuator drive target value that changes, for example, linearly within a certain range in accordance with, for example, a tire load change speed or a tire load change acceleration in a tire outside the steering direction. A control signal is given to the drive circuit 18 so that the drive target value is achieved. In the characteristic diagram of FIG. 4, a reaction force actuator drive target value that linearly increases with an increase in the tire load change speed or the tire load change acceleration is set for a tire load change speed or a tire load change acceleration that is greater than a certain value. As the vehicle speed detected by the vehicle speed sensor 15 increases, a larger reaction force actuator drive target value is set.
[0026]
As a result, the greater the change speed or change acceleration of the load applied to the tire, the greater the reaction force is transmitted to the driver via the steering wheel 1, and the greater the vehicle speed, the greater reaction force is transmitted to the driver via the steering wheel 1. Will be transmitted to.
FIG. 5 is a conceptual diagram showing how information is exchanged between the driver, the vehicle, and the road surface. For example, a disturbance such as a cross wind is applied to the vehicle from the road surface, and information such as traffic conditions is provided to the vehicle as, for example, ITS (Intelligent Transport Systems) electronic information from the infrastructure arranged in the road traffic network. Furthermore, road surface conditions such as a narrow road, a cant road, a wavy road, and a snowy road are transmitted to the vehicle through the tire.
[0027]
On the other hand, from the vehicle to the driver, the control device 14 (ECU: electronic control unit) controls the reaction force actuator 9 (reaction force control) through the steering wheel 1 together with the road surface information (low frequency information). The tire ground contact surface transient information is transmitted. Further, through the above-described alarm device 19, instability information and warning of the steering system are transmitted to the driver by display or sound.
The reaction force actuator 9 can be controlled based on the torque generated by the steering actuator 2 and the output of the turning angle sensor 13, thereby transmitting road surface information, which is low frequency information, to the driver via the steering wheel. it can. In addition to this control, as described above, the reaction force actuator 9 is controlled in accordance with the tire load change speed or the tire load change acceleration, so that tire ground contact surface transient information is transmitted to the driver via the steering wheel 1. Is done.
[0028]
Steering system instability information transmitted by the alarm device 19 includes tire balance and occurrence of shimmy. These pieces of information may be transmitted to the driver through the control of the reaction force actuator 9, but it is more effective to visually or audibly transmit the driver to the driver using the alarm device 19 to promote maintenance. is there.
The control device 14 further controls the steering actuator 2 according to the output of the operation angle sensor 11 and the like and the tire load detected by the stress sensors SL and SR and the air pressure sensor SP (steering control).
[0029]
On the other hand, in addition to the information transmitted from the alarm device 19 or the steering wheel 1, the driver feels the acceleration G on the vehicle, and also feels the vehicle speed V, yaw rate γ, roll φ, and pitch τ. Based on these pieces of information, the driver operates the steering wheel 1 to perform predictive control, tracking control, and compensation control.
Predictive control is control that the driver predicts the next situation, and tracking control is control that tries to track this target with the vehicle behavior intended by the driver as a target. Is a control for compensating for disturbances such as crosswinds. These controls are based on the driver's knowledge about driving the vehicle, but this knowledge can be stratified into a skill base, a rule base and an intelligent base.
[0030]
Skill-based driving knowledge is knowledge that has been acquired by the body and is knowledge that is unconsciously transferred to action based on information perceived by the five senses. The rule-based driving knowledge is knowledge that is transferred to an action according to a determination result based on a driver's memory (for example, whether or not a certain condition is met), that is, knowledge about a patterned action. Intelligent-based driving knowledge is not knowledge about patterned behavior, but advanced knowledge that is transferred to behavior through conscious, abstract and logical thinking.
[0031]
For example, the road surface information transmitted from the steering wheel 1 to the driver as low-frequency information works on the rule-based knowledge and prompts the driver to drive a pattern. On the other hand, the tire ground contact surface transient information transmitted from the steering wheel 1 to the driver is used for more advanced judgment (whether it is a limit point from which the steering torque can be removed, etc.) by working on the knowledge of the intelligent base. It is done.
[0032]
Thus, according to this embodiment, the reaction force actuator 9 is controlled according to the tire load directly detected by the left and right stress sensors SL, SR and the air pressure sensor SP attached to the tire. It has become. Therefore, since appropriate reaction force control can be performed regardless of the mechanical structure of the steering mechanism, it is possible to reduce or eliminate vehicle adaptation technology that makes reaction force control different for each vehicle type or vehicle. it can. Thereby, the development period of the vehicle steering device can be greatly shortened.
[0033]
In addition, since the load state of the tire W is directly detected by the left and right stress sensors SL, SR and the air pressure sensor SP, and the reaction force control is performed using this, complicated calculation processing is not required. The reaction force actuator 9 can be controlled with high-speed response on the order of 10 milliseconds. Therefore, tire ground contact surface transient information such as a grip limit situation in which the tire W loses the gripping force can be transmitted to the driver via the steering wheel 1.
[0034]
FIG. 6 is a characteristic diagram for explaining the control of the steering actuator 2, and shows an example of setting the basic gear ratio according to the vehicle speed. As described above, in the steer-by-wire system, the gear ratio (steering amount / operation amount) that is the ratio of the steering amount of the wheel 5 to the operation amount of the steering wheel 1 can be arbitrarily set. Utilizing this, vehicle speed-sensitive variable gear ratio control is performed. More specifically, the basic gear ratio is set to a relatively high constant value in the low speed range, and the basic gear ratio is set to decrease linearly with an increase in the vehicle speed in the medium and high speed range. As a result, the driver's steering burden in the low speed range where the steering of the large steering angle is reduced can be reduced, and in the middle and high speed range where the steering of the large steering angle is rarely performed, the steering amount is reduced and the vehicle fluctuates. Etc. can be prevented.
[0035]
FIG. 7 is a characteristic diagram for control for correcting the gear ratio in accordance with the tire load. The gear ratio correction amount for correcting the basic gear ratio in consideration of the tire load, and the tire load change amount ( For example, a relationship with a load change amount of a tire outside the steering direction) is expressed.
The tire load change amount is, for example, a tire load amount (tire air pressure, stress, stress difference between left and right sidewalls, etc.) at the time when the ignition key switch of the vehicle is turned on and the control device 14 starts operating as a reference value. The deviation from this reference value. This reference value is a value that varies depending on changes in tire air pressure and tire wear. The tire load change amount is an amount that dynamically changes according to a road surface state or a traveling state (during straight traveling, curve traveling, etc.) while the vehicle is traveling. However, as the tire load change amount, it is preferable to use a value representing the tire load change amount over a relatively long time, such as a sampling average value, a moving average value, or a low-pass filter processing value for a predetermined time. Thereby, the sensitive control based on the tire load change amount is suppressed.
[0036]
In the example of FIG. 7, the gear ratio correction amount is set so as to increase as the tire load change amount increases. Therefore, if a gear ratio obtained by correcting the basic gear ratio with the gear ratio correction amount (basic gear ratio + gear ratio correction amount) is set, an appropriate gear ratio is set according to the tire load. It can be improved. That is, handling of the steering wheel 1 in a situation where the tire load change amount is large (such as when traveling on a mountain road) is improved.
[0037]
In the example of FIG. 7, the gear ratio correction amount is set so as to decrease as the vehicle speed increases. Therefore, the greater the vehicle speed, the smaller the gear ratio variation according to the tire load. Therefore, it is possible to perform the steering control sensitively reflecting the tire load state in the low speed range, and in the middle and high speed range, the gear ratio. Steering stability can be achieved by reducing the fluctuation of the ratio.
FIG. 8 is a schematic diagram showing a schematic configuration of the vehicle steering apparatus according to the second embodiment of the present invention. The vehicle steering device 21 includes a first steering shaft 23 connected to a steering wheel 22 as an operation member so as to be integrally rotatable, and a steering mechanism provided coaxially with the first steering shaft 23, such as a rack and pinion mechanism. And a planetary gear mechanism 26 as a planetary transmission mechanism constituting a differential transmission mechanism for allowing differential rotation between the first and second steering shafts 23 and 25. Prepare.
[0038]
The steering mechanism 24 includes a steering shaft 27 that extends in the left-right direction of the vehicle, and a knuckle arm 30 that is coupled to both ends of the steering shaft 27 via tie rods 28 and supports steering wheels 29. Prepare. The steered shaft 27 is supported by a housing 31 and is slidable in the axial direction, and a steering actuator 32 made of an electric motor is coaxially incorporated in the middle of the steered shaft 27. The drive rotation of the steering actuator 32 is converted into sliding of the turning shaft 27 by a motion conversion mechanism such as a ball screw mechanism, and the turning of the wheel 29 is achieved by the sliding of the turning shaft 27.
[0039]
A rack 27a is formed in a part of the steered shaft 27, and a pinion 34 provided at an end of the second steering shaft 25 and rotating integrally with the second steering shaft 25 is engaged with the rack 27a. ing. When the steering actuator 32 fails, when the second steering shaft 25 is driven to rotate according to the operation of the steering wheel 22, the rotation of the second steering shaft 25 is caused to slide on the turning shaft 27 by the pinion 34 and the rack 27a. The wheel 29 is steered.
[0040]
The planetary gear mechanism 26 includes a plurality of sun gears 35 that are connected to the end of the first steering shaft 23 so as to be integrally rotatable, and are rotatably held by a carrier 36 that is an output side to mesh with the sun gear 35. Planetary gears 37 and ring gears 38 as ring members having inner teeth 38a meshing with the planetary gears 37 on the inner periphery.
The ring gear 38 forms, for example, a worm wheel by forming external teeth 38b. The external teeth 38b are drivingly connected to a reaction force actuator 40 for applying an operation reaction force to the steering wheel 22 via a drive transmission gear 39 made of, for example, a worm. The reaction force actuator 40 is composed of, for example, an electric motor, and its casing is fixed at an appropriate position on the vehicle body.
[0041]
The steering actuator 32 and the reaction force actuator 40 are controlled by a control device C (ECU: electronic control unit) including a CPU 61, a ROM 62 storing a control program, a RAM 63 used as a work area for arithmetic processing, and the like. ing.
The first steering shaft 23 has a steering angle sensor 44 as a steering angle detection means for detecting a steering angle by the steering wheel 22 and a steering torque detection means for detecting a steering torque input from the steering wheel 22. A torque sensor 45 is provided. Detection signals from the steering angle sensor 44 and the torque sensor 45 are input to the control device C.
[0042]
Further, the turning shaft 27 is provided with a turning angle sensor 46 for detecting the turning angle of the wheel 29 by detecting the axial position of the turning shaft 27. This turning angle sensor A detection signal by 46 is also input to the control device C. Further, a detection signal from a vehicle speed sensor 47 for detecting the vehicle speed is input to the control device C.
Inside the tire of the wheel 29, as in the case of the first embodiment described above, a tire air pressure sensor SP, a left stress sensor SL, and a right stress sensor SR are provided as tire load detection means. The output signals of these sensors are taken into the control device C from the antenna Ca by wireless communication.
[0043]
The control device C outputs a control signal to drive circuits 48 and 49 as drive units for driving the steering actuator 32 and the reaction force actuator 40 based on the input signals from the sensors.
The control device C constantly monitors whether the steering system is operating normally. More specifically, the occurrence of abnormality in at least one of the turning angle sensor 46 and the steering actuator 32 is monitored.
[0044]
If there is no abnormality in the turning system, the control device C causes the reaction force actuator 40 to generate torque for applying to the steering wheel 22 a steering reaction force corresponding to the road surface reaction force.
Further, the control device C sets the voltage command value of the steering actuator 32 in accordance with the operation amount of the steering wheel 22, and gives the control signal corresponding to the voltage command value to the drive circuit 48, so that the steering actuator 32 is controlled. Drive control. Although the steering wheel 22 and the steering mechanism 24 are coupled via the planetary gear mechanism 26, the reaction force actuator 40 does not substantially restrain the rotation of the ring gear 38, and the steering reaction force is applied to the steering wheel 22. In the state of operating only for giving, the steering torque applied to the steering wheel 22 is not substantially transmitted to the steering mechanism 24. In this sense, the configuration shown in FIG. 8 can also be said to be a steer-by-wire (SBW) type vehicle steering device, and the same variable gear as in the first embodiment described above. Ratio control is possible.
[0045]
In this embodiment, the control device C is detected by the stress sensors SL, SR and / or the air pressure sensor SP according to the characteristics as shown in FIG. 4 in the same manner as the control device 14 of the first embodiment described above. The reaction force actuator 40 is controlled based on the applied tire load. As a result, not only low frequency information indicating road surface conditions but also high frequency information such as tire ground contact surface transient information can be transmitted to the driver via the steering wheel 22.
[0046]
Further, the control device C variably sets the basic gear ratio (see FIG. 6) in accordance with the vehicle speed, and the gear in accordance with the tire load change amount and the vehicle speed, similarly to the control device 14 in the first embodiment described above. The steering actuator 32 is controlled based on the gear ratio (= basic gear ratio + gear ratio correction amount) obtained by variably setting the ratio correction amount (see FIG. 7) and correcting the basic gear ratio with the gear ratio correction amount. . Thereby, it is possible to perform the steering control that accurately reflects the road surface condition and the tire load condition.
[0047]
When an abnormality occurs in the steering system, the control device C stops the control of the steering actuator 32 to put the steering actuator 32 in a free rotation state, and restricts the rotation of the ring gear 38 by the reaction force actuator 40, and the steering wheel It is assumed that the steering torque applied to 22 is transmitted to the steering mechanism 24. At this time, the steering assist can be performed by the control of the reaction force actuator 40 and the gear ratio can be variably controlled.
[0048]
Next, referring to FIG. 8 again, a third embodiment of the present invention will be described. In the third embodiment, the actuator 40 is used as a gear ratio changing actuator for variable gear ratio control, and the steering actuator 32 is used as a steering assist actuator for generating a steering assist force to be applied to the steering mechanism 24. Used.
That is, the control device C determines the gear ratio by setting the basic gear ratio according to the characteristics shown in FIG. 6 and correcting the basic gear ratio using the gear ratio correction amount shown in FIG. Based on the obtained gear ratio (= basic gear ratio + gear ratio correction amount), the controller C reacts with the reaction force actuator to mechanically transmit the rotation of the steering wheel 22 to the steering mechanism 24 at the gear ratio. 40 is controlled to rotate the ring gear 38. At the same time, the controller C controls the steering actuator 32 based on the steering torque detected by the torque sensor 45 and the target drive value (target current value or target voltage value) set according to the vehicle speed detected by the vehicle speed sensor 47. Is controlled. This achieves steering assistance.
[0049]
With such a configuration, a power steering device with variable gear ratio control according to the tire load is realized, and good steering characteristics can be realized.
Further, for example, as shown in FIG. 9, the assist characteristic (torque range of -T1 to T1) is such that the basic target drive value of the steering actuator 32 increases as the absolute value of the steering torque T increases and decreases as the vehicle speed increases. Is set according to the dead zone), and the target drive value of the steering actuator 32 may be set by correcting the basic target drive value with the drive correction value (≧ 0) according to the characteristics of FIG. However, the target drive value is
Target drive value = basic target drive value + drive correction value
When steering left,
Target drive value = basic target drive value-drive correction value
Sought by.
[0050]
In the example of FIG. 10, for example, the larger the tire load change speed or the tire load change acceleration (the first-order time differential value or the second-order time differential value of the difference between the stress detection values of the left and right sidewalls) in the tire on the outer side in the steering direction. A correction value is set, and the basic target drive value is greatly corrected. Further, the correction value becomes smaller as the vehicle speed increases.
In this way, since the target drive value with a larger correction is set as the absolute value of the tire load change speed or the tire load change acceleration is larger, appropriate steering assistance according to the road surface condition and the tire load state is performed. It becomes possible. Further, when the vehicle speed is high, stable steering characteristics can be realized by reducing the correction amount according to the tire load.
[0051]
Although three embodiments of the present invention have been described above, the present invention can be implemented in other forms. For example, in an ordinary electric power steering apparatus in which a steering wheel and a steering mechanism are coupled by a steering shaft in which a torsion bar is interposed and a steering assist force is applied to the steering mechanism from an electric motor, FIG. By controlling the electric motor in accordance with the characteristics as shown in FIG. 10, steering assistance according to the road surface condition and the load on the tire is possible.
[0052]
The present invention can also be applied to a power steering device configured to generate hydraulic pressure by a pump driven by an electric motor and transmit a driving force generated by a power cylinder operated by the hydraulic pressure to a steering mechanism. . That is, the steering assist can be performed with good responsiveness to the road surface condition and the like by performing correction according to the tire load on the basic target drive value of the electric motor.
[0053]
In addition, various design changes can be made within the scope of matters described in the claims.
[Brief description of the drawings]
FIG. 1 is a conceptual diagram for explaining a configuration of a vehicle steering apparatus according to a first embodiment of the present invention.
FIG. 2 is a schematic cross-sectional view for explaining the configuration of a tire for a steering wheel.
FIG. 3 is an illustrative view for explaining deformation of a tire during cornering.
FIG. 4 is a control characteristic diagram showing an example of a control mode of a reaction force actuator.
FIG. 5 is a conceptual diagram showing how information is exchanged among a driver, a vehicle, and a road surface.
FIG. 6 is a characteristic diagram for explaining the control of the steering actuator, and shows an example of setting the basic gear ratio according to the vehicle speed.
FIG. 7 is a characteristic diagram for control for correcting a gear ratio in accordance with a tire load.
FIG. 8 is a schematic diagram showing a schematic configuration of a vehicle steering apparatus according to a second embodiment of the present invention.
FIG. 9 is a diagram illustrating a characteristic (assist characteristic) of a basic target drive value of a steering actuator with respect to a steering torque.
FIG. 10 is a diagram showing characteristics of a drive correction value for correcting a basic target drive value according to a tire load.
[Explanation of symbols]
1 Steering wheel
2 Steering actuator
4 Steering shaft
5 wheels
9 Reaction force actuator
11 Operation angle sensor
12 Torque sensor
13 Steering angle sensor
14 Control device
14a antenna
15 Vehicle speed sensor
17 Drive circuit
18 Drive circuit
19 Alarm
21 Vehicle steering system
22 Steering wheel
24 Steering mechanism
26 Planetary gear mechanism
27 Steering shaft
27a rack
29 wheels
32 Steering actuator
34 Pinion
35 sun gear
36 Career
37 planetary gear
38 Ring gear
39 Drive transmission gear
40 Reaction force actuator
44 Steering angle sensor
45 Torque sensor
46 Steering angle sensor
47 Vehicle speed sensor
48 Drive circuit
51 tread
52L Left side wall
52R Right side wall
C controller
Ca antenna
SA stress sensor
SL left side stress sensor
SP Air pressure sensor
SR Right side stress sensor
W tire
WL left tire
WR Right tire

Claims (3)

A steering mechanism for steering the steering wheel;
A steering actuator that applies a steering force to the steering mechanism;
Load detecting means for detecting a tire load which is a load applied to a tire of the vehicle;
Steering control means for controlling the steering actuator in accordance with the tire load detected by the load detection means ;
Look including the steering direction detection means for detecting the steering direction of the vehicle,
The load detection means includes stress detection means for detecting stress applied to the tire,
The stress detecting means includes a left stress detecting means and a right stress detecting means for detecting stress applied to the left side and the right side of the tire in the traveling direction of the vehicle,
The steering control means controls the steering actuator based on the steering direction of the vehicle detected by the steering direction detecting means and the stresses detected by the left stress detecting means and the right stress detecting means, respectively. A vehicle steering apparatus characterized by the above. The steering control means is based on the steering direction of the vehicle detected by the steering direction detection means and the stresses detected by the left stress detection means and the right stress detection means for tires outside the steering direction of the vehicle, respectively. The vehicle steering apparatus according to claim 1 , wherein the steering apparatus controls an actuator. 3. The vehicle steering apparatus according to claim 1, wherein the load detecting means includes air pressure detecting means for detecting a tire air pressure.

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