JP2018122821A - Electric power steering device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an electric power steering device capable of smooth, silent and high accuracy operation, and contributing to vehicle stability, by using an electric actuator of a simple constitution capable of continuously applying direct moving force to a steering shaft.SOLUTION: An electric power steering device of the present invention is the electric power steering device having a steering input device 10, a steering angle sensor 70 for measuring a steering angle of the steering input device, and a steering control device 30 for outputting a driving signal to an actuator in response to the steering angle measured by the steering angle sensor. The actuator is a linear DC motor 100 for transmitting driving force by reciprocating a rod of the actuator in the axial direction, and the rod is connected to a steering link mechanism for steering a wheel 40.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a vehicle steering apparatus, and more particularly to an electric power steering apparatus.

  2. Description of the Related Art In recent years, steer-by-wire type steering devices in which a steering input device and a steering link mechanism are mechanically separated from each other are known as steering devices that drive a steering link mechanism that steers the wheels of a vehicle.

  In the steer-by-wire type steering device, the left and right front wheels of the vehicle are individually steered using two motors having a hollow structure, similar to that applied to the steering device according to Patent Document 1. Ball screw mechanisms are provided on the left and right front wheels, respectively, and the screw shafts of the ball screw mechanisms are connected to tie rods to form a steering link mechanism and are slid by a slide mechanism that also functions as a detent. . Further, the screw shafts are respectively disposed through the motor, and the nut shaft of the ball screw mechanism is connected to the rotor of the motor. The nut shaft is rotatably supported by a support bearing. As a result, the nut shaft rotates integrally with the rotation of the motor, the steering link mechanism moves in the axial direction, and the left and right front wheels are independently driven and controlled.

  According to the configuration of the steering device according to Patent Document 1, since the motor is disposed substantially concentrically with the screw shaft constituting the steering link mechanism, the space occupancy can be kept compact.

JP 2001-310751 A

  However, when the motion conversion device of the ball screw mechanism is used, high accuracy is required to form screw grooves on the outer peripheral surface of the steering shaft and the inner peripheral surface of the ball nut. Further, it takes time to adjust the screwing state realized through a large number of balls between these screw grooves, and there is a problem that a great number of man-hours are required for processing and assembly.

  Furthermore, there is a risk of both wear due to repeated rolling of the ball along the thread groove, causing problems such as looseness of the threaded portion and dust generation, and maintaining stable motion conversion over a long period of time. There was a problem that was difficult

  The present invention has been made in view of such circumstances, and is smooth and quiet by using an actuator having a simple configuration that is driven according to steering and that can continuously apply a direct moving force to a steering shaft. An object of the present invention is to provide an electric power steering device that can operate with high accuracy and contributes to vehicle stability.

  The electric power steering device of the present invention outputs a drive signal to an actuator in accordance with a steering input device, a steering angle sensor for measuring a steering angle of the steering input device, and a steering angle measured by the steering angle sensor. An electric power steering apparatus comprising: a steering control device; wherein the actuator is a linear DC motor that transmits a driving force by reciprocating a rod of the actuator in an axial direction thereof, and the rod rotates a wheel. It is connected to a steering link mechanism for steering.

  According to this configuration, since the driving force of the linear DC motor can be directly transmitted to the steering link mechanism, a direct moving force can be continuously applied to the steering shaft of the vehicle, and the linear DC motor is used. Therefore, smooth, quiet and highly accurate operation is guaranteed.

  In this invention, the linear direct current motor may be arranged so that the axial direction is perpendicular to the straight direction of the vehicle.

  With this configuration, the movement amount of the rod of the linear DC motor can be efficiently transmitted to the steering link mechanism.

  In this invention, it includes a steered position detecting device for detecting the steered position of the wheel, and when the ignition of the vehicle is turned on, the steering control device outputs a signal for switching the steered position of the wheel in the straight traveling direction. You may make it transmit to a linear direct-current motor.

  With this configuration, it is ensured that the steered position is always moved in the straight direction when the vehicle first starts, and at the same time, the recording of the steering angle of the steering input device in the steering control device is reset once.

  In the present invention, the linear DC motor may be disposed on at least two or more wheels, and the steering control device may individually control the linear DC motor.

With this configuration, it is possible to individually control the turning angle of each wheel according to the running position or the stopped state of the vehicle.

  In the present invention, the electric power steering device may be mounted on a steer-by-wire vehicle in which the steering link mechanism and the steering input device are mechanically separated.

  As described above, according to the present invention, the use of the electric actuator having a simple configuration that is driven in accordance with steering and can continuously apply a direct moving force to the steering shaft enables smooth, quiet and high operation. An electric power steering device that can operate accurately and contributes to vehicle stability can be provided.

It is a figure showing a schematic structure of an electric power steering device concerning one embodiment of the present invention, and a conceptual structure of the control system. It is a single figure of the linear direct current motor used for an electric power steering device. It is a figure showing the state of transmission / reception of the signal between each structure in an electric power steering device. It is a figure which shows the connection state of the linear link motor and the steering link mechanism which steers a wheel. It is a figure explaining operation | movement of the wheel according to the motion of a linear direct current motor. It is a figure explaining the application example to the vehicle in the electric power steering apparatus using a linear direct current motor. It is a figure explaining the other application example to the vehicle in the electric power steering apparatus using a linear direct current motor.

  An embodiment of the present invention will be described with reference to the drawings. As shown in FIG. 1, this electric power steering device includes a steering input device 10 such as a steering wheel, and a steering device mechanically separated from the steering input device 10 and including a steering link mechanism 106 and a linear DC motor 100. 20 and a steering control device 50 that controls the steering device 20 based on an input signal from the steering input device 10. The steered device 20 is provided for each wheel 40 on both sides in the vehicle width direction and constitutes an independent steering system. Each wheel 40 is supported on the chassis via a suspension (not shown).

  A steering angle sensor 70 and a steering torque sensor 80 are provided for a steering input device 10 including a steering wheel, and a steering reaction force motor 90 is connected thereto. The steering angle sensor 70 is a sensor that detects the steering angle of the steering input device 10, and the steering torque sensor 80 is a sensor that detects torque that acts on the steering input device 10. The steering reaction force motor is a motor that applies reaction force torque to the steering input device 10, and monitors the input of the steering torque sensor 80 via torque control means (not shown) to give a predetermined reaction force torque. .

  The steering control device 50 is a means for giving a drive command to the linear DC motor 100 connected to each steering link mechanism 106 according to a predetermined rule in accordance with the detected angle of the steering angle sensor 70. The linear DC motor 100 includes a magnet 103 on a sleeve in which N and S magnetized portions are alternately arranged in the axial direction, and a plurality of coils 102 wound inside the magnet. The actuator is configured such that a moving force in the axial length direction is applied to the shaft by periodic excitation of 102. The steering control device 50 may be provided as a part of an ECU (electronic control unit) 30 that controls the entire vehicle, or may be provided as a single steering control device 50. The ECU 30 includes a computer, a program executed on the computer, and various electronic circuits.

  Since the amount of movement of the rod 104 of the linear DC motor 100 is reflected as much as possible in the turning angle of the steered wheels, the linear DC motor 100 has the axis of the rod 104 perpendicular to the straight direction of the vehicle. It is preferable to arrange so as to be. However, it is possible to obtain a desired turning amount by appropriately controlling the amount of movement of the rod 104 by the steering control device 50 even if it is not a right angle.

  FIG. 2 is a diagram showing a configuration of a linear DC motor 100 as an actuator. Each of a plurality of (two in the drawing) coils 102 fixed to the inside of the actuator housing 101 includes a three-phase coil through which currents having different phases flow, and is located outside such a coil 102. The magnet 103 is configured by alternately arranging N and S magnetized portions having a length corresponding to each coil 102 in the axial length direction.

  The magnet 103 generates a magnetic flux in a direction transverse to the respective coils 102 located inside the magnetized portions N and S in the radial direction. Under such a magnetic flux, each coil 102 has a respective circumferential coil. When an electric current is applied, a thrust for moving the rod 104 in the axial length direction is applied to the magnet 103, and a turning force for turning the steered wheels is applied according to this movement.

  The direction of the moving force applied to the rod 104 is determined according to the direction of the coil current flowing through the coil 102, and the magnitude of the thrust is determined according to the magnitude of the coil current. The turning force can be increased or decreased by the control.

FIG. 3 is a block diagram showing the exchange of signals between the components.
The energization control of the coil 102 is performed by a control signal from the steering control device 50 in FIG. The steering control device 50 is provided with a detection result of a steering angle applied to the steering input device 10 for steering from the steering angle sensor 70, and steering from a traveling state sensor such as the vehicle speed sensor 110 and the yaw rate sensor 120. The detection result of the running state of the vehicle that affects the vehicle is given. The steering control device 50 is given a detection result of the moving position of the rod 104 from a rod position sensor 105 attached to the middle of the actuator housing 101.
Here, the rod position sensor detects the position of the rod in the linear DC motor. However, since the rod 104 is directly connected to the steering link mechanism 106, the rotation of the steered wheels is determined by the detection value of the rod position sensor 105. It is possible to detect the rudder position. Accordingly, the rod position sensor 105 functions as a wheel steering position detection device.
In this embodiment, the rod position sensor 105 is attached to the actuator housing 101 and is described as a sensor for measuring the amount of movement of the rod. For example, the rod position sensor 105 is attached to the knuckle arm 106a and measures the amount of rotation. It is good also as measuring the steered position of a steered wheel.

  The steering control device 50 takes in the detected values of the steering angle and the running state given from the steering angle sensor 70 and the running state sensor at a predetermined sampling period, for example, a control stored in advance according to the taken running state. Referring to the map, the turning force to be applied to the rod 104 is determined according to the captured steering angle, and the coil current to be applied to the coil 102 of the linear DC motor 100 is calculated to obtain this turning force. A control signal corresponding to the calculation result is given to the motor driver 60.

  The motor driver 60 performs a control operation in which the coil current corresponding to the control signal is sequentially energized by shifting the phase of each phase of the coil 102, and thrust generated in response to the energization of the coil current is applied to the rod 104. Steering force is applied. At this time, the movement of the rod 104 occurs as a continuous operation during the energization, and also occurs without any mechanical contact, so that the driver who operates the steering input device 10 feels caught. A smooth steering feeling is given without accompanying.

  The detection value of the rod position sensor 105 given to the steering control device 50 is used as a feedback signal indicating the current position of the rod 104. In this embodiment, an optical or magnetic linear encoder can be used as the rod position sensor 105, and the above-described rod positioning by the energization control is performed with an accuracy corresponding to the resolution of the rod position sensor 105. Thus, the magnet 103 and the coil 102 can be positioned with high accuracy without requiring mechanical accuracy.

  Usually, in order to steer a wheel, a driving force of about 10 KN is required as an output of the linear DC motor 100. Such a linear DC motor 100 has already been marketed as a motor having a corresponding magnetic force. Realization is possible. By using such a linear direct current motor 100 and connecting the rod 104 of the motor to the steering link mechanism 106, it is possible to apply sufficient propulsive force to the wheels to steer the wheels. As a result, the operation amount input to the steering input device 10 can be transmitted to the wheels without going through a motion conversion mechanism such as a rack and pinion type steering device, so that the entire device is simply configured. can do.

  Next, the connection state between the linear DC motor 100 and the steering link mechanism 106 that steers the wheel 40 will be described with reference to FIG. The electric power steering apparatus according to the present embodiment includes a wheel 40, a steering link mechanism 106 for turning the wheel 40, and a linear DC motor 100.

  The steering link mechanism 106 includes a knuckle arm 106a that steers the wheel 40, and a tie rod arm 106b that is connected to the knuckle arm 106a at a joint provided at one end. The tie rod arm 106b is rotatably supported on the end of the rod 104 of the linear DC motor 100 at the other end via a ball joint 106c.

  With this configuration, the steering control device 50 can move the rod 104 in the axial direction of the rod by controlling the linear DC motor 100 according to the operation of the steering input device 10 such as a steering wheel by the driver. And since the said steering link mechanism 106 is connected with the said rod 104, the wheel 40 is steered via the steering link mechanism 106. FIG.

  FIG. 5 is a diagram illustrating a state where the wheels are steered in accordance with the operation of the rod 104 of the linear DC motor 100.

  FIG. 5 b shows the position of the rod 104 of the linear DC motor 100 where the wheel 40 is not steered, that is, the position of the rod 104 when the vehicle travels in the straight direction. Here, the steering control device may control the linear DC motor so as to switch the steered position of the wheel to the straight traveling direction of the vehicle every time the ignition of the vehicle is turned on. In this case, the steering angle detected by the steering angle sensor is also reset so that the steering position of the steering input device 10 at that time is recognized as the neutral position that is the straight traveling direction of the vehicle.

  FIG. 5a shows the movement of the rod through the tie rod arm 106b and the knuckle arm 106a by moving the position of the rod 104 of the linear DC motor 100 leftward from the position of the rod 104 in FIG. A state in which a turning force for turning leftward is transmitted is shown.

  Similarly, in FIG. 5c, when the position of the rod 104 of the linear DC motor 100 is moved from the position of the rod 104 in FIG. It shows a state in which a steering force for turning the steering wheel in the right direction is transmitted.

  In the present embodiment, the example of the left and right steering is shown on the assumption that the position of the knuckle arm 106a, which is the connection point to the wheel side of the tie rod arm 106b, is in the front of the wheel. When the position is located in the rear of the wheel, the reverse of the above movement is performed according to the movement of the rod.

Next, an application example to a vehicle using the present invention will be described with reference to FIGS.
FIG. 6 shows an embodiment of a steering method for improving vehicle stability when the vehicle enters a curve.
In consideration of the grip force of the left and right wheels against the road surface when the vehicle enters the corner from the detection value detected by the running state sensor, a steering angle for each of the left and right wheels may be given to stabilize the vehicle. In the figure, the steering angle of the inner wheel is steered by + α larger than the steering angle of the outer wheel, and the grip force of both the left and right wheels is adjusted to be equal, thereby improving the stability of the vehicle in curve driving. . Depending on the calculated wheel grip force, the steering angle of the outer wheel may be steered larger than the steering angle of the inner wheel.
By arranging the steering device 20 according to the present invention on each wheel and independently controlling each linear DC motor by the steering control device 50, it is possible to easily control the steering angle independent of each wheel. Become.

FIG. 7 shows another application example to a vehicle.
FIG. 7a shows a preferable turning state when the vehicle stops on a steep road surface such as a slope. The steering device 20 according to the present invention is arranged on all the wheels of the vehicle, and the steering control device 50 steers the right front wheel and the left rear wheel in the right direction in the traveling direction of the vehicle (the direction of the arrow), By controlling the linear DC motor 100 so that the front wheel and the right rear wheel are steered in the left direction, such a steered state can be maintained on the gradient road surface.

  FIG. 7b shows a preferable steering state in order to increase the frictional force between the road surface and the wheels when the vehicle is suddenly stopped. The steering device 20 according to the present invention is arranged on all the wheels of the vehicle, and the steering control device steers the right front wheel and the left rear wheel in the left direction, and the left front wheel and the right rear wheel steers in the right direction. Thus, by controlling the linear direct current motor 100, such a steered state can be maintained until the vehicle brakes and stops.

  FIG. 7c shows a preferable turning state when the vehicle is turned sharply, such as a U-turn. The linear DC motor is arranged such that the steering device 20 according to the present invention is arranged on all the wheels of the vehicle, and the steering control device 50 steers the left and right front wheels to the right and the left and right rear wheels to the left. By controlling 100, such a steered state can be maintained until the turning of the vehicle is completed.

  FIG. 7d shows a preferred steering state when changing lanes while the vehicle is traveling at high speed. The steering device 20 according to the present invention is disposed on all the wheels of the vehicle, and the steering control device 50 steers the left and right front wheels and the left and right rear wheels in a direction (right in the figure) in which the lane is to be changed. By controlling the linear direct current motor 100, such a steered state can be maintained until the lane change is completed.

DESCRIPTION OF SYMBOLS 10 Steering input device, 20 Steering device, 30 Electronic control unit, 40 Wheel, 50 Steering control device, 60 Motor driver, 70 Steering angle sensor, 80 Steering torque sensor, 90 Steering reaction force motor, 100 Linear direct current motor, 101 Actuator Housing, 102 coil, 103 magnet, 104 rod, 105 rod position sensor, 106 Steering link mechanism.

Claims (5)

A steering input device;
A steering angle sensor for measuring a steering angle of the steering input device;
An electric power steering apparatus comprising: a steering control device that outputs a drive signal to an actuator according to a steering angle measured by the steering angle sensor.
The actuator is a linear DC motor that transmits a driving force by reciprocating the rod of the actuator in the axial direction,
The rod is connected to a steering link mechanism that steers the wheels;
Electric power steering device.   The electric power steering apparatus according to claim 1, wherein the linear DC motor is disposed such that the axial direction is perpendicular to a straight traveling direction of the vehicle. Including a steered position detecting device for detecting the steered position of the wheel,
2. The electric power steering apparatus according to claim 1, wherein when the ignition of the vehicle is turned on, the steering control device transmits a signal for switching the steered position of the wheel to a straight traveling direction to the linear DC motor.   The electric power steering device according to claim 1, wherein the steering device including the linear DC motor and the steering link mechanism is disposed on at least two wheels, and the steering control device individually controls the linear DC motor.   The electric power steering device is mounted on a steer-by-wire vehicle in which the steering link mechanism, the turning device including the linear DC motor, and the steering input device are mechanically separated. Electric power steering device.

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