JP4062020B2 - Vehicle steering system - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a vehicle steering apparatus that steers steered wheels based on an operation of a steering member.
[0002]
[Prior art]
In recent years, a so-called steer-by-wire system (also simply referred to as SBW) in which a mechanical connection between a steering member such as a steering wheel and a steered wheel is released and a part of a steering transmission system is configured by an electrical path. ) Is provided.
In this type of vehicle steering apparatus, a reaction force motor for applying a steering reaction force to the steering member is used in addition to a steering motor for turning the steered wheels.
[0003]
Further, a steering angle sensor for detecting the steering angle of the steering member and a turning angle sensor for detecting the turning angle of the steered wheels are provided, and the steering motor is based on signals from these sensors. Is driven, and the position of a steered shaft such as a rack shaft is controlled.
[0004]
[Problems to be solved by the invention]
In this type of steer-by-wire system, it is important to take a fail-safe measure when an abnormality occurs in a steering system such as a steering actuator or a steering angle sensor.
The present invention has been made in view of the above problems, and an object of the present invention is to provide a vehicle steering apparatus capable of achieving good steering even when a steering system failure occurs in a so-called steer-by-wire system. And
[0005]
[Means for Solving the Problems and Effects of the Invention]
In order to achieve the above object, a first aspect of the present invention provides a steering member, a first element connected to the steering member, a second element connected to a steered wheel, and a third element associating the first and second elements. Including a differential transmission mechanism, a steering actuator for turning the steered wheels, and a reaction force coupled to the third element of the differential transmission mechanism so as to be capable of driving transmission and for providing a steering reaction force to the steering member. An actuator, a steering angle detection means for detecting the steering angle of the steering member, a turning angle detection means for detecting the turning angle of the steered wheels, and a detected steering angle and a rotation detected by the steering angle detection means. Detection detected by the rudder angle detecting means Based on the steered angle, a control unit for driving and controlling the steering actuator, and a turning system abnormality occurrence detecting means for detecting occurrence of an abnormality in the turning angle detecting means or the steering actuator. And The turning system abnormality occurrence detecting means is used when the detected turning angle detected by the turning angle detecting means is constant, even though the detected steering angle detected by the steering angle detecting means is fluctuating. Detecting an abnormality of the turning angle detecting means or the steering actuator, and the control section detects the abnormality of the turning angle detecting means or the steering actuator when the turning system abnormality occurrence detecting means detects the abnormality of the reaction force actuator. the is characterized in that the drive control for the transmission ratio variable differential transmission mechanism.
[0006]
In the present invention, normally, appropriate torque is applied to the steering member via the differential transmission mechanism by generating an appropriate torque in the reaction force actuator. In addition, when an abnormality occurs in the steering system such as the steering actuator or the turning angle detection means, the reaction force actuator is driven and controlled to turn the steered wheels, or the transmission ratio of the differential transmission mechanism is changed. You can do it.
In addition, the detected turning angle detected by the turning angle detecting means is constant even though the detected steering angle detected by the steering angle detecting means fluctuates. In this case, since the abnormality of the turning angle detecting means or the steering actuator is detected, there are the following advantages. That is, it is possible to detect an abnormality in the steering system at low cost based on the signals from the steering angle detection means and the turning angle detection means that are originally provided.
According to a second aspect of the present invention, the differential transmission includes a steering member, a first element linked to the steering member, a second element linked to the steered wheel, and a third element that associates the first and second elements. A mechanism, a steering actuator for turning the steered wheels, a reaction force actuator coupled to the third element of the differential transmission mechanism so as to be capable of driving transmission, and a steering force applied to the steering member, and the steering member Steering angle detection means for detecting the steering angle of the steering wheel, turning angle detection means for detecting the turning angle of the steered wheels, and detected steering angle and turning angle detection means detected by the steering angle detection means based on the detection steering angle detected, and a control unit for driving and controlling the steering actuator and a steering system abnormality detecting means for detecting an abnormality of the steering angle detecting means or the steering actuator, the Steering system abnormality occurred The exit means is a turning angle detection means when the detected turning angle detected by the turning angle detection means is constant even though the detected steering angle detected by the steering angle detection means is fluctuating. Alternatively, an abnormality of the steering actuator is detected, and the control unit detects the abnormality of the turning angle detection means or the steering actuator by the turning system abnormality occurrence detection means, and causes the third element to be detected by the reaction force actuator. It is characterized by being restrained so as not to rotate.
In the present invention, normally, appropriate torque is applied to the steering member via the differential transmission mechanism by generating an appropriate torque in the reaction force actuator. Further, when an abnormality occurs in the steering system such as the steering actuator or the steering angle detection means, the third element of the differential transmission mechanism is restrained to be non-rotatable by the reaction force actuator. Manual steering at the transmission ratio by the remaining two elements can be achieved.
[0007]
The upper Symbol steering system abnormality detecting means in the detected steering angle detected despite fluctuations by the steering angle detection means, detecting the steering angle detected by the steering angle detecting means is constant In some cases, since the abnormality of the turning angle detection means or the steering actuator is detected , there are the following advantages. That is , it is possible to detect an abnormality in the steering system at low cost based on the signals from the steering angle detection means and the turning angle detection means that are originally provided.
[0008]
DETAILED DESCRIPTION OF THE INVENTION
Preferred embodiments of the present invention will be described with reference to the accompanying drawings.
FIG. 1 is a schematic diagram showing a schematic configuration of a vehicle steering apparatus according to an embodiment of the present invention. Referring to FIG. 1, the present steering apparatus 1 is provided with a first steering shaft 3 coupled to a steering member 2 such as a steering wheel so as to be integrally rotatable, and coaxially with the first steering shaft 3. A planetary transmission mechanism constituting a differential transmission mechanism for allowing differential rotation between the second steering shaft 5 connected to the steering mechanism 4 such as a rack and pinion mechanism and the first and second steering shafts 3, 5. As a planetary gear mechanism 6.
[0009]
The steering mechanism 4 includes a steered shaft 7 that extends in the left-right direction of the vehicle, and a knuckle arm 10 that is coupled to both ends of the steered shaft 7 via tie rods 8 and supports the steered wheels 9. The steered shaft 7 is supported by a housing 11 and is slidable in the axial direction. A steering actuator 12 made of an electric motor is coaxially incorporated in the middle of the steered shaft 7. The driving rotation of the steering actuator 12 is converted into sliding of the steered shaft 7 by a motion converting mechanism such as a ball screw mechanism, and the steered wheels 9 are steered by sliding of the steered shaft 7.
[0010]
A rack 7 a is formed on a part of the steered shaft 7, and a pinion 14 provided at an end of the second steering shaft 5 and rotating integrally with the second steering shaft 5 is meshed with the rack 7 a. ing. As will be described later, when the second steering shaft 5 is driven to rotate in response to the operation of the steering member 2 when the steering actuator 12 fails, the rotation of the second steering shaft 5 is rotated by the pinion 14 and the rack 7a. It is converted into sliding of the rudder shaft 7, and the turning of the steered wheels 9 is achieved.
[0011]
The planetary gear mechanism 6 is rotatable by a sun gear 15 as a first element (solar member) on the input side connected to the end of the first steering shaft 3 so as to be integrally rotatable, and a carrier 16 on the output side. A plurality of planet gears 17 as second elements (planet members) that are held and meshed with the sun gear 15, and a ring gear 18 as a ring member having inner teeth 18 a meshed with the planet gears 17 on the inner periphery.
The ring gear 18 forms, for example, a worm wheel by forming external teeth 18b. The external teeth 18b are drivingly connected to a reaction force actuator 20 for applying an operation reaction force to the steering member 2 via a drive transmission gear 19 made of, for example, a worm. The reaction force actuator 20 is composed of, for example, an electric motor, and its casing is fixed at an appropriate position on the vehicle body.
[0012]
The steering actuator 12 and the reaction force actuator 20 are controlled by a control unit C including a CPU 31, a ROM 32 storing a control program and the like, a RAM 33 used as a work area for arithmetic processing, and the like.
The first steering shaft 3 has a steering angle sensor 24 as a steering angle detection means for detecting a steering angle by the steering member 2 and a steering torque detection means for detecting a steering torque input from the steering member 2. A torque sensor 25 is provided. Detection signals from the steering angle sensor 24 and the torque sensor 25 are input to the control unit C.
[0013]
The steered shaft 7 is provided with a steered angle sensor 26 as a steered angle detecting means for detecting the steered angle of the steered wheels 9 in relation to the axial position of the steered shaft 7. A detection signal from the turning angle sensor 26 is also input to the control unit C. Further, a detection signal from a vehicle speed sensor 27 for detecting the vehicle speed is input to the control unit C.
The control unit C outputs a control signal to drive circuits 28 and 29 as drive units for driving the steering actuator 12 and the reaction force actuator 20 based on the input signals from the sensors.
[0014]
FIG. 2 is a flowchart for explaining steering control processing executed by the control unit C. Referring to FIG. 2, control unit C monitors whether the steering system is operating normally (step S1). As an abnormality of the steering system, an abnormality of the steering angle sensor 26 or the steering actuator 12 can be considered, but the probability of the abnormality occurring in the steering actuator 12 is abnormal in the steering angle sensor 26 which is an electrical component. Since it is much lower than the probability, the monitoring in step S1 substantially monitors the occurrence of an abnormality in the turning angle sensor 26.
[0015]
If no abnormality has occurred in the turning angle sensor 26 (steering system) (NO in step S1), the control unit C steers a steering reaction force according to, for example, a road surface reaction force by the reaction force actuator 20. Torque to be applied to the member 2 is generated (step S2).
Further, for example, a ratio (transmission ratio, gear ratio) between the rotation amount of the steering member 2 and the turning amount of the steered wheels 9 is set in accordance with the traveling state of the vehicle, and a VGR (Variable Gear Ratio) function is applied. Is also possible. Based on the set transmission ratio, the operation amount of the steering member 2, and the like, a voltage command value of the steering actuator 12 is set, and a control signal corresponding to the voltage command value is given to the drive circuit 28, so that the steering actuator 12 Is controlled (step S3).
[0016]
As a result, torque for sliding the steered shaft 7 in the direction corresponding to the operation direction of the steering member 2 is output from the steering actuator 12, which is good according to the traveling state of the vehicle and the operation mode of the steering member 2. Steering is achieved. It is not always necessary to set the VGR function.
Thus, if an abnormality occurs in the turning angle sensor 26 (steering system) while driving the steering actuator 12 (YES in step S1), the control unit C sets the detected steering angle of the steering angle sensor 24 to the detected steering angle. Accordingly, a control signal is output to the drive circuit 29 so as to control the position of the steered angle of the steered wheels 9 (angle control), thereby drivingly controlling the reaction force actuator 20 (step S4). At this time, the steering actuator 12 is turned off (a state in which idling is possible).
[0017]
In this way, even when an abnormality occurs in the turning angle sensor 26 and the like, good steering can be achieved using the reaction force actuator 20 as a steering actuator. In step S4, the reaction force actuator 20 can be driven and controlled for VGR. However, feedback control using the detected turning angle of the turning angle sensor 26 cannot be performed.
Details of the abnormality detection of the steering system in step S1 of FIG. 2 will be described based on the flowchart of FIG.
[0018]
It is determined whether or not there is a signal input from the turning angle sensor 26 (step T1). If no signal is input (NO in step T1), it is determined that an abnormality has occurred in the turning system (step S1). T2), the process proceeds to step S4 in the flowchart of FIG. 2, and the turning using the reaction force actuator 20 is performed. Alternatively, manual steering and a VGR operation are executed.
Next, when there is a signal input from the turning angle sensor 26 (YES in step T1), the detected steering angle and the detected turning angle during traveling are determined based on the signals of the steering angle sensor 24 and the turning angle sensor 26. Obtained (step T3).
[0019]
If both the detected detected steering angle and the detected turning angle are fluctuating (NO in step T4), the process proceeds to step S2 in the flowchart of FIG. 2, and normal reaction force control and steering control are performed. The
On the other hand, when the calculated detected steering angle is constant even though the calculated detected steering angle is fluctuating (YES in step T4), the steering system such as the steering angle sensor 26 is used. It is determined that an abnormality has occurred (step T5), the process proceeds to step S4 in the flowchart of FIG. 2, and a steering or VGR operation using the reaction force actuator 20 is performed.
[0020]
The present invention is not limited to the above embodiment. For example, in the above embodiment, when an abnormality occurs in the steering system, the reaction force actuator 20 is used for steering (auxiliary) or for VGR. Although the drive control is performed, as shown in the flowchart of FIG. 4, when an abnormality occurs in the steering system (YES in step U1), the reaction force actuator 20 is stopped and locked (step U4), and the ring gear 18 is rotated. The steering member 2 and the steering mechanism 4 are mechanically coupled to each other via the planetary gear mechanism 6, and good steering by manual steering is performed with the transmission ratio of the remaining two elements of the planetary gear mechanism 6. May be achieved. In the flowchart shown in FIG. 4, steps U2 and U3 are the same as steps S2 and S3, respectively.
[0021]
In addition, various modifications can be made within the scope of the claims of the present invention.
[Brief description of the drawings]
FIG. 1 is a schematic diagram showing a schematic configuration of a vehicle steering apparatus according to an embodiment of the present invention.
2 is a flowchart showing a flow of steering control of the vehicle steering apparatus of FIG. 1; FIG.
FIG. 3 is a flowchart showing details of an abnormality detection step in the flowchart of FIG. 2;
FIG. 4 is a flowchart showing a flow of steering control of a vehicle steering system according to another embodiment of the present invention.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Vehicle steering device 2 Steering member 3 1st steering shaft 4 Steering mechanism 5 2nd steering shaft 6 Planetary gear mechanism (differential transmission mechanism)
7 Steering shaft 7a Rack 9 Steering wheel 12 Steering actuator 14 Pinion 15 Sun gear (first element)
16 Carrier (second element)
17 Planetary gear (second element)
18 Ring gear (third element)
18a Internal teeth 18b External teeth 19 Drive transmission gear 20 Reaction force actuator C Control section (steering system abnormality occurrence detecting means)
24 Steering angle sensor (steering angle detection means)
25 Torque sensor 26 Steering angle sensor (steering angle detection means)
27 Vehicle speed sensors 28, 29 Drive circuit 31 CPU
32 ROM
33 RAM

Claims (2)

A steering member;
A differential transmission mechanism including a first element linked to the steering member, a second element linked to the steered wheel, and a third element for associating the first and second elements;
A steering actuator for turning the steered wheels;
A reaction force actuator coupled to the third element of the differential transmission mechanism so as to be capable of driving transmission, and for applying a steering reaction force to the steering member;
Steering angle detection means for detecting the steering angle of the steering member;
A turning angle detection means for detecting the turning angle of the turning wheel;
A control unit that drives and controls the steering actuator based on the detected steering angle detected by the steering angle detection unit and the detection detected by the steering angle detection unit;
A turning system abnormality occurrence detection means for detecting an abnormality occurrence of the steering angle detection means or the steering actuator,
The turning system abnormality occurrence detecting means is used when the detected turning angle detected by the turning angle detecting means is constant, even though the detected steering angle detected by the steering angle detecting means is fluctuating. , Detecting an abnormality in the turning angle detection means or the steering actuator,
The control unit when the abnormality of the steering angle detecting means or the steering actuator is detected by the steering system abnormality detecting means that drives and controls the reaction force actuator for the transmission ratio variable differential transmission mechanism A vehicle steering apparatus characterized by the above. A steering member;
A differential transmission mechanism including a first element linked to the steering member, a second element linked to the steered wheel, and a third element for associating the first and second elements;
A steering actuator for turning the steered wheels;
A reaction force actuator coupled to the third element of the differential transmission mechanism so as to be capable of driving transmission, and for applying a steering reaction force to the steering member;
Steering angle detection means for detecting the steering angle of the steering member;
A turning angle detection means for detecting the turning angle of the turning wheel;
A control unit that drives and controls the steering actuator based on the detected steering angle detected by the steering angle detection unit and the detected steering angle detected by the steering angle detection unit;
A turning system abnormality occurrence detection means for detecting an abnormality occurrence of the steering angle detection means or the steering actuator,
The turning system abnormality occurrence detecting means is used when the detected turning angle detected by the turning angle detecting means is constant, even though the detected steering angle detected by the steering angle detecting means is fluctuating. , Detecting an abnormality in the turning angle detection means or the steering actuator,
The control unit restrains the third element to be non-rotatable by the reaction force actuator when an abnormality of the turning angle detecting means or the steering actuator is detected by the turning system abnormality occurrence detecting means. Vehicle steering system.

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