JP4957359B2 - Steering device - Google Patents

Description

  The present invention relates to a steering device for a vehicle.

  As a vehicle steering apparatus, a power steering apparatus for reducing a driver's steering load is known. Conventionally, hydraulic power steering devices have been widely used as power steering devices. However, in accordance with the recent trend toward higher efficiency of automobiles, there is an increasing number of cases where a hydraulic power steering apparatus is replaced with an efficient electric power steering apparatus.

  The electric power steering apparatus has a configuration in which a motor current command value for driving a motor for applying a steering assist force is calculated based on a steering torque generated in a steering shaft, and the motor current is controlled based on the motor current command value. Yes.

  On the other hand, in a vehicle steering apparatus equipped with a steering mechanism, a motor that applies steering assist force based on steering torque generated by operation of the steering wheel, in addition to directly operating the steering mechanism by operation of the steering wheel. Some drive and operate the steering mechanism.

  FIG. 10 is a diagram for explaining an example of the configuration of a conventional pinion-rack type steering mechanism 100. The rotation output of the engine 101 is transmitted to the hub of the tire wheel 104 via the transmission 102 and the axle shaft 103, and the tire 105 is driven.

  A steering gear box 105 is disposed substantially parallel to the axle shaft 103. Although not shown, a pinion rack mechanism is disposed therein. The tip of the steering shaft 110 extended from the steering wheel is connected to the pinion of the pinion / rack mechanism, and meshes with the pinion so as to be movable in the vehicle width direction (rack axial direction). 106 is joined. A tie rod end 107, which is an end of the tie rod 106, is connected to one end of a knuckle arm 109 via a ball joint 108, and the other end of the knuckle arm 109 passes through a knuckle 110 that rotatably holds a tire wheel. The wheel 104 is connected.

  When the pinion is rotated by the rotation of the steering shaft 110, the tie rod 106 moves in the vehicle width direction via the rack that meshes with the pinion. The movement of the tie rod 106 in the vehicle width direction is transmitted to the tire wheel 104 via the tie rod end 107, the ball joint 108, the knuckle arm 109, and the knuckle 110, and steers the steered wheel in a desired direction (see Patent Document 1). .

And, in the electric power steering device, in the column assist type electric power steering device, a warwheel provided in the middle of the steering shaft is driven by a motor to apply a steering assist force to the steering shaft 110, The pinion assist type electric power steering apparatus is configured to apply a steering assist force to the steering shaft 110 by driving the pinion with a motor.
JP 2006-273144 A

  In the conventional steering mechanism, if the length of the knuckle arm is increased, the steering operation of the steered wheel can be lightened by the lever principle. Can also be reduced.

  However, since the tie rod end and the knuckle arm are connected at a position approaching the inside of the tire wheel, the tie rod end and the tire wheel are likely to interfere with each other in the vicinity of the maximum turning angle of the tire wheel. For this reason, conventionally, the length of the knuckle arm is set to a predetermined constant length in the design of the steering mechanism. The length of the knuckle arm is increased according to the state of the steering operation, and the steering wheel is rotated. There was no idea to lighten the rudder operation or keep the steering assist power small.

  The present invention provides a steering device in which the length of the knuckle arm is variable according to the state of the steering operation, the steering operation of the steered wheels is lightened, and the steering assist force can be suppressed to be less than that of the conventional one. It is for the purpose.

The present invention solves the above-mentioned problems, and the invention of claim 1 includes a pinion attached to one end of a steering shaft extended from a steering wheel, and slidably held in the vehicle width direction and meshed with the pinion. Racks, tie rods provided at both ends of the rack in the vehicle width direction, tie rod ends connected to tip ends of the tie rods, knuckles that rotatably hold tire wheels, and tie rod ends and knuckles. A steering device comprising a knuckle arm to be connected, wherein the knuckle arm comprises an actuator whose length can be changed, and the steering device has a predetermined value at which the vehicle speed is zero or extremely low and the steering torque is preset. when it is detected that more, actuates the actuator, the vehicle speed and the steering angle Is a steering device characterized by comprising a control device for setting the knuckle arm length set in advance in accordance with the steering torque.

  And the actuator with which the said knuckle arm is provided is a linear motion actuator that can be expanded and contracted in the linear direction and is mounted in the middle of both ends of the knuckle arm.

  Further, when it is detected that the vehicle speed is not zero or extremely low, the control device sets a preset standard knuckle arm length.

  As described above, the steering device according to the present invention includes an actuator capable of changing the length of the knuckle arm, and can be set to a knuckle arm length set in advance according to the vehicle speed and the steering angle or steering torque. Is.

  With this configuration, when the vehicle speed is zero or extremely low and the steering angle is large, or when the vehicle speed is zero or extremely low and the steering torque is large, for example, when the vehicle is put in a garage, In the case of steering, by increasing the length of the knuckle arm, heavy steering operation can be reduced by the lever principle, and in the power steering device, the steering assist force is insufficient in the vicinity of the rack end. Even in an expected case, the driver does not feel the lack of steering assist force.

  Hereinafter, a steering apparatus according to an embodiment of the present invention will be described. FIG. 1 is an overall perspective view showing a configuration of a column assist type rack and pinion type steering device which is an example of a steering device suitable for carrying out the present invention.

  In the column assist type rack and pinion type steering device shown in FIG. 1, the steering assist force of the motor 3 attached to the intermediate portion of the steering column 2 is passed through the upper shaft 4a, the universal joint 4b, the intermediate shaft 4c, and the universal joint 4d. A rack (not shown) disposed in the steering gear box 5 is applied to the lower shaft 4e and moved in the vehicle width direction to steer the steered wheel via the tie rod 6.

  FIG. 2 is a diagram for explaining an example of the configuration of the power transmission device and the steering device of the rack and pinion type steering device shown in FIG. 1, and FIG. 3 shows the configuration of the connecting portion between the tie rod 6 and the tire wheel 14 of FIG. It is a figure explaining.

  The rotational output of the engine 11 is transmitted to the hub of the tire wheel 14 via the transmission 12 and the axle shaft 13 to drive the tire 15. A steering gear box 5 extending in the vehicle width direction is disposed substantially parallel to the axle shaft 13, and a tie rod 6 is joined to an end portion of the rack disposed inside.

  A tie rod end 6 a that is an end portion of the tie rod 6 is connected to one end 24 a of the knuckle arm 24 via a ball joint 23. The other end 24b of the knuckle arm 24 is connected to the tire wheel 14 through a knuckle 25 that rotatably holds the tire wheel.

  A linear motion actuator 30 is disposed between the one end 24a and the other end 24b of the knuckle arm 24 so that the distance between the one end 24a and the other end 24b of the knuckle arm 24 can be changed.

  FIG. 4 is a cross-sectional view illustrating the configuration of the linear motion actuator 30. The linear motion actuator 30 has a motor 32 disposed inside a housing 31, and the motor 32 is fixedly disposed inside the housing 31. And a rotor 32b that is rotatably arranged by a bearing 32c that is fixedly arranged inside the housing 31.

  The shaft of the rotor 32b is extended to the left and right in the axial direction, and a screw shaft 34 and a screw shaft 35 are provided. An external screw 34a formed on the screw shaft 34 and an external screw 35a formed on the screw shaft 35 are If the opposite screws, that is, the outer screw 34a is a right screw, the outer screw 35a is a left screw.

  On the other hand, operating members 36 and 37 are mounted inside the housing 31 by spline coupling or the like so as to be movable in the axial direction and not to rotate around the axis. An inner screw 36 a that is screwed to the outer screw 34 a is formed, and an inner screw 37 a that is screwed to the outer screw 35 a is formed inside the operation member 37.

  A connecting portion 36 d connected to the tie rod end 6 a is formed at the outer end portion of the operating member 36, and a connecting portion 37 d connected to one end of the knuckle arm 24 is formed at the outer end portion of the operating member 37. Has been.

  In the linear actuator 30 having the above-described configuration, when the motor 32 is rotated, the screw shaft 34 and the screw shaft 35 are rotated, and the operating member 36 formed with the inner screw 36a to be screwed with the screw 34a and the screw 35a are screwed. The operating member 37 formed with the inner screw 37a moves in the axial direction (the direction of the arrow a), and the distance between the outer end of the operating member 36 and the outer end of the operating member 37, that is, the total length of the knuckle arm 24, It can be changed longer or shorter.

  Next, the operation of the steering apparatus according to the embodiment of the present invention will be described. The steering device according to the present invention controls the linear actuator 30 based on the vehicle speed V and the steering angle θ, or the vehicle speed V and the steering torque T, and performs a steering assist load reduction process. Therefore, the steering device of the present invention is not shown, but includes a vehicle speed sensor for detecting the vehicle speed V, a steering angle sensor for detecting the steering angle θ, and a torque sensor for detecting the steering torque T, in addition to the control device. Yes.

  Since the electric power steering apparatus is equipped with these sensors in addition to a control apparatus that controls a motor for assisting steering, the control apparatus and sensors can be used for controlling the linear actuator 30. . Hereinafter, the steering assist load reduction process executed by the control device will be described.

  FIG. 5 is a flowchart for explaining a first example of a steering assist load reduction process in the case where the knuckle arm length is changed using the above-described linear actuator 30 and the steering wheel is turned off.

  First, it is determined whether or not the vehicle speed V is stopped or extremely low (step P11). If the vehicle speed V is stopped or extremely low, the magnitude of the steering angle θ of the steering wheel is determined (step P12).

  If it is determined in step P12 that the steering angle θ is a large steering angle greater than or equal to a predetermined value θ1, a numerical table relating to the steering torque and the length of the knuckle arm set in advance according to the steering angle or a predetermined value The desired knuckle arm length corresponding to the corresponding steering torque and steering angle is calculated from the above equation (step P13), and the linear actuator 30 is operated to rotate the motor 32 so as to obtain the desired knuckle arm length ( Step P14).

  If it is determined in step P11 that the vehicle speed V is not stopped or not extremely low, the linear actuator is operated to rotate the motor 32 so that the reference knuckle arm length is reached (step P15).

  FIG. 6 is a diagram for explaining the relationship between the steering angle of the steering wheel and the knuckle arm length. The knuckle arm length L is the reference value L1 until the steering angle θ is set to a predetermined value θ1, and the steering angle θ is predetermined. Above the value θ1, the knuckle arm length L becomes longer as the steering angle θ increases. By increasing the knuckle arm length L according to the increase in the steering angle θ, the steering assist load can be reduced.

  FIG. 7 is a flowchart for explaining a second example of the steering assist load reduction process in the case where the knuckle arm length is changed using the above-described linear actuator 30 and the steering wheel is turned off.

  First, it is determined whether or not the vehicle speed V is stopped or extremely low (step P21). If the vehicle speed V is stopped or extremely low, the magnitude of the steering torque T generated by the steering shaft is determined (step P22).

  If it is determined in step P22 that the steering torque T is greater than a predetermined value T1 (steering torque corresponding to the maximum motor current that can be set by the control device of the electric power steering device), the steering torque T Accordingly, a desired knuckle arm length corresponding to the corresponding steering torque is obtained from a numerical table relating to the knuckle arm length set in advance by experiment or a predetermined arithmetic expression (step P23), and the linear actuator 30 is operated. The motor 32 is rotated so as to have a desired knuckle arm length (step P24).

  If it is determined in step P21 that the vehicle speed V is not stopped or extremely low, the linear actuator is operated to rotate the motor 32 so that the reference knuckle arm length is reached (step P25).

  FIG. 8 is a diagram for explaining the relationship between the motor current I that can be set by the control device of the electric power steering device and the steering torque T. The control device increases the motor current I in response to the increase of the steering torque T. When the motor current I1 exceeding the limit value T1 flows in accordance with the increase of the steering torque, a failure such as burnout of the motor occurs, so that the maximum motor current that can be set is limited.

  Therefore, when the steering torque T1 is generated such that the motor current I1 exceeding the limit value flows, it is possible to cope with a large steering assist load by operating the linear actuator and extending the knuckle arm length.

  FIG. 9 is a diagram for explaining the change of the steering torque T with respect to the steering angle θ according to the present invention.

  In general, the manner in which the steering torque T increases / decreases with respect to the increase / decrease of the steering angle θ draws a loop as shown by a solid line in FIG. 9, and the steering torque T increases rapidly with an increase in the steering angle θ near the rack end. In the vicinity of the rack end, the steering assist force may be insufficient, and the steering wheel operation becomes heavy.

  On the other hand, according to the present invention, in the vicinity of the rack end, the actuator is operated according to the steering angle θ and the knuckle arm length is increased, thereby increasing the steering angle θ as shown by the dotted line A in FIG. On the other hand, an increase in the steering torque T (steering assisting force) required can be suppressed.

  The steering device according to the embodiment of the present invention has been described as an example applied to a column type electric power steering device. However, the steering device according to the embodiment of the present invention is not limited to the column assist type but also used as a pinion assist type. Needless to say, the present invention is not limited to power steering devices and other power steering devices, and can be applied to other steering devices.

  A steering device that operates an actuator according to an increase in steering angle to set a longer knuckle arm, lightens a steering operation near the rack end, and suppresses an increase in required steering assist force. .

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is an overall perspective view showing a configuration of a column assist type rack and pinion type steering device suitable for carrying out the present invention. The figure explaining the structure of the power transmission device and steering device of the rack and pinion type steering device shown in FIG. The figure explaining the structure of the connection part of a tie rod and a tire wheel. Sectional drawing explaining the structure of a linear motion actuator. The flowchart explaining the 1st example of the reduction process of a steering assist load in the case of changing a knuckle arm length using a linear actuator and performing a steering wheel stationary operation. The figure explaining the relationship between the steering angle of a steering wheel, and the knuckle arm length. The flowchart explaining the 2nd example of the reduction process of a steering assistance load in the case of changing a knuckle arm length using a linear motion actuator and steering-off operation of a steering wheel. The figure explaining the relationship between the motor electric current which can be set with the control apparatus of an electric power steering device, and steering torque. The figure explaining the change of the steering torque T with respect to the steering angle (theta) by this invention. The figure explaining the structure of the power transmission device and steering device of the conventional rack and pinion type steering device.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Steering wheel 2 Steering column 3 Motor 4a Upper shaft 4b, 4d Universal joint 4c Intermediate shaft 4e Lower shaft 5 Steering gear box 6 Tie rod 11 Engine 12 Transmission 13 Axle shaft 14 Tire wheel 15 Tire 22 Tie rod end 23 Ball joint 24 Knuckle arm 24a One end of knuckle arm 24b Other end of knuckle arm 25 Knuckle 30 Direct acting actuator 31 Housing 32 Motor 32a Stator 32b Rotor 32c Bearing 34, 35 Screw shaft 34a, 35a Outer screw 36, 37 Actuating member 36a, 37a Inner screw

Claims (3)

A pinion attached to one end of a steering shaft extended from the steering wheel;
A rack that is slidably held in the vehicle width direction and meshes with the pinion;
Tie rods provided at both ends of the rack in the vehicle width direction;
A tie rod end connected to the tip of the tie rod;
A knuckle that rotatably holds the tire wheel;
In a steering apparatus comprising a knuckle arm that connects the tie rod end and a knuckle,
The knuckle arm includes an actuator whose length can be changed,
When it is detected that the vehicle speed is zero or extremely low and the steering torque is equal to or higher than a predetermined value , the steering device activates an actuator to respond to the vehicle speed and the steering angle or the steering torque. And a control device for setting the knuckle arm length set in advance. 2. The steering apparatus according to claim 1, wherein the actuator provided in the knuckle arm is a linear motion actuator mounted in the middle of both ends of the knuckle arm and capable of extending and contracting in a linear direction. The steering device according to claim 1 or 2, wherein the control device sets a standard knuckle arm length set in advance when it is detected that the vehicle speed is not zero or extremely low.

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