JP2013159131A - Rear wheel steering device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a small rear wheel steering device which has a function of restricting the rotation of a steering shaft and a function of locking the steering shaft to a neutral position.SOLUTION: A steering shaft supporting member 37 engages with a flat surface 41 (a first engaged part) of a rear wheel steering shaft 11 to restrict the rotation of the rear wheel steering shaft 11. An ECU 16 turns off an electromagnetic actuator 46 when prescribed conditions (that vehicle speed is a predetermined value or faster, for example) are satisfied. A lock member 44 accommodated in an insertion hole 42 of the steering shaft supporting member 37 engages with a recess 43 (a second engaged part) of the rear wheel steering shaft 11 in the neutral position by the biasing force of a biasing member 45 to lock the rear wheel steering shaft 11 to a neutral position of steering.

Description

  The present invention relates to a rear wheel steering device.

Patent Document 1 proposes a technique for regulating rear wheel steering in a rear wheel steering device by energizing a solenoid and inserting a plunger into a rack shaft hole when the front wheel steering angle exceeds a set steering angle. Has been. In Patent Document 1, a mechanical steering angle switch is provided in a solenoid energization circuit to prevent malfunction of rear wheel steering regulation.
In Patent Document 2, a rear wheel steering device that separates a motor used at the time of small steering angle steering from a motor used at the time of large steering angle steering, and always regulates the stroke of the rod connected to the rear wheel when the small steering angle motor is driven. Proposed. This prevents large steering angle steering from being performed during high-speed small steering angle control.

JP-A-7-165099 JP-A-8-268314

In Patent Literatures 1 and 2, a pinion driven by an electric motor is meshed with a rack shaft as a rear wheel steering shaft, and the rotation of the rack shaft is regulated by the pinion.
On the other hand, when the steered shaft is driven in the axial direction via a ball screw mechanism including a ball nut surrounding the steered shaft without using a pinion, the steered shaft is prevented from rotating with the ball nut. A rotation restricting mechanism that restricts the rotation of the steered shaft while allowing axial movement is required.

When such a rotation restricting mechanism and a lock mechanism for restricting rear wheel steering are arranged separately, the size is increased.
The present invention is to provide a small rear wheel steering device having a function of restricting the rotation of a steered shaft and a function of locking the steered shaft to a neutral position when necessary.

  In order to achieve the above object, the invention of claim 1 is directed to a rear wheel steering device (3) in which the mechanical connection between the steering member (4) and the rear wheel (13) is broken. A steering angle sensor (18) for detecting the steering angle (θh), a steering actuator (14) for driving the steering shaft (11) in the axial direction (X1) via the ball screw mechanism (15), and the steering By engaging the control device (16) for controlling the turning of the turning actuator based on the steering angle detected by the angle sensor and the first engaged portion (41) of the turning shaft, A steering shaft support member (37) that supports the rudder shaft so as not to rotate and is slidable in the axial direction (X1), and an insertion position and a reverse position in an insertion hole (42) provided in the steering shaft support member And the second engaged portion (43 of the steered shaft at the advanced position). The locking member (44) that locks the steered shaft in the neutral position, the urging member (45) that urges the locking member to the advanced position, and the urging member. And an electromagnetic actuator (46) for driving the lock member to the retracted position, and the control device has a function of turning off the electromagnetic actuator when a predetermined condition is satisfied. Providing equipment.

In addition, although the alphanumeric character in a parenthesis represents the corresponding component etc. in embodiment mentioned later, this does not mean that this invention should be limited to those embodiment as a matter of course. The same applies hereinafter.
Further, as in claim 2, a steered housing (10) accommodating the steered shaft and a bush (21) held by the steered housing and supporting the steered shaft so as to be slidable in the axial direction. The first engaged portion of the steered shaft is formed on the outer periphery (11a) of the steered shaft, and is opposed to the circumferential direction (Z1) of the steered shaft (41). And the second engaged portion includes a recess (43) disposed between the pair of flat surfaces in the circumferential direction of the steered shaft when the steered shaft is viewed from the axial direction. You may go out.

  According to a third aspect of the present invention, a support hole (36) that supports the steered shaft support member so as to advance and retreat is formed, a support housing (35) provided integrally with the steered housing, and the support hole A sealing member (38) fixed to the inlet of the motor, and an elastic member (39) received by the sealing member and biasing the steered shaft support member toward the steered shaft, the electromagnetic actuator Includes a main body (47) fixed to the sealing member, a rod (48) protruding from the main body and connected to the lock member, and a solenoid (49) for applying an electromagnetic force to the rod. Also good.

According to a fourth aspect of the present invention, the vehicle includes a traveling state detection sensor (19) for detecting a traveling state of the vehicle and a steering neutral state detection sensor (20) for detecting a steering neutral state, and the predetermined condition includes Further, it may be included that a predetermined traveling state is detected by the traveling state detection sensor and a steering neutral state is detected by the steering neutral state detection sensor.
According to a fifth aspect of the present invention, the traveling state detection sensor includes a vehicle speed sensor (19) that detects a vehicle speed (V), and the vehicle speed detected by the vehicle speed sensor is a predetermined value in the predetermined traveling state. A state of (Va) or more may be included.

  According to the invention of claim 1, since the turning shaft support member engages with the first engaged portion of the turning shaft and restricts the rotation of the turning shaft, the axial position of the turning shaft is reduced. Can be controlled with high accuracy. Further, when a predetermined condition is satisfied (for example, when traveling at high speed or when a failure occurs), the electromagnetic actuator is turned off, and the lock member is engaged with the second engaged portion of the steered shaft by the biasing member. Thus, the steered shaft can be locked at the neutral position. Since the lock member is incorporated in the steered shaft support member, a small rear wheel steering device having a function of restricting the rotation of the steered shaft and a function of locking the steered shaft at the neutral position can be realized. .

According to the invention of claim 2, the recess as the second engaged portion pushed by the lock member is disposed between the pair of flat surfaces as the first engaged portion. Therefore, it is possible to improve the durability of the bush by suppressing the interference between the pair of flat surfaces of the steered shaft and the bush.
According to the invention of claim 3, since the turning shaft support member is urged toward the turning shaft by the elastic member received by the sealing member fixed to the inlet of the support hole of the support housing. The regulation of the rotation of the turning shaft is certain. Further, by moving the rod back and forth from the main body of the electromagnetic actuator fixed to the sealing member that seals the support hole, the lock member can be advanced and retracted with a simple structure to achieve locking and unlocking.

According to the invention of claim 4, the steered shaft can be locked at the neutral position when a predetermined traveling state is detected and a steering neutral state is detected.
According to the invention of claim 5, when the vehicle speed is in a high speed state equal to or higher than a predetermined value, the running stability can be ensured by locking the steered shaft to the neutral position.

It is a mimetic diagram of a four-wheel steering device to which a rear-wheel steering device of one embodiment of the present invention was applied. It is a schematic sectional drawing of a rear-wheel steering apparatus. It is an expanded sectional view of the important section of a rear-wheel steering device, and shows the state where the rear-wheel steering shaft was locked in the neutral position by the lock mechanism built in the steering-shaft support device of the rear-wheel steering device. It is an expanded sectional view of the principal part of a rear-wheel steering apparatus, and has shown the cross section which follows the IV-IV line of FIG. It is a flowchart which shows the flow of control of a rear-wheel steering apparatus.

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 four-wheel steering device including a rear wheel steering device according to an embodiment of the present invention. Referring to FIG. 1, the four-wheel steering device 1 includes a front wheel steering device 2 and a rear wheel steering device 3. The front wheel steering device 2 includes a steering member 4 such as a steering wheel, a pinion shaft 5 that rotates as the steering member 4 rotates, a front wheel turning shaft 6 that includes a rack shaft that meshes with the pinion shaft 5, and a front wheel steering. A pair of tie rods 7 connected to both ends of a rack shaft as the shaft 6 and left and right front wheels 8 connected to each tie rod 7 via a knuckle arm (not shown) are provided. The pinion shaft 5 and the rack shaft as the front wheel turning shaft 6 constitute a rack and pinion mechanism A as a front wheel turning mechanism.

The rear wheel steering device 3 is connected to a steered housing 10 fixed to the vehicle body 9, a rear wheel steered shaft 11 supported by the steered housing 10 so as to be movable in the axial direction X1, and both ends of the rear wheel steered shaft 11. And a pair of left and right rear wheels 13 connected to each tie rod 12 via a knuckle arm (not shown).
The rear wheel steering device 3 constitutes a so-called steer-by-wire system in which the mechanical connection between the steering member 4 and the left and right rear wheels 13 is released. That is, the rear wheel steering device 3 converts the turning actuator 14 that is driven to rotate according to the rotation operation of the steering member 4 and the rotational motion of the steering actuator 14 into a linear motion in the axial direction X1 of the rear wheel steering shaft 11. The ball screw mechanism 15 that performs the control, the ECU 16 (Electronic Control Unit) as a control device that controls the turning of the turning actuator 14, and the movement of the rear wheel turning shaft 11 in the axial direction X1 while restricting the rotation of the rear wheel turning shaft 11 And a steered shaft support device 17 that supports the rear wheel steered shaft 11 so as to allow the

Further, the rear wheel steering device 3 includes a steering angle sensor 18 that detects the steering angle θh of the steering member 4, a vehicle speed sensor 19 that detects the vehicle speed V, and the rear wheel steering shaft 11 according to the position in the axial direction X1. A turning angle sensor 20 that detects the turning angle θw of the wheel 13 is provided. Detection signals from the steering angle sensor 18, the vehicle speed sensor 19, and the turning angle sensor 20 are input to the ECU 16.
The ECU 16 controls the steering actuator 14 based on the steering angle θh detected by the steering angle sensor 18 and the vehicle speed V detected by the vehicle speed sensor 19. Specifically, the target turning angle is set based on the detected steering angle θh and the detected vehicle speed V. Then, based on the deviation between the target turning angle and the turning angle θw detected by the turning angle sensor 20, drive control (steering control) of the turning actuator 14 is performed via a drive circuit (not shown). )

  FIG. 2 is a schematic cross-sectional view of the rear wheel steering device 3. With reference to FIG. 2, the steered housing 10 has a cylindrical shape. The middle part of the rear wheel turning shaft 11 is inserted into the cylindrical turning housing 10, and both ends of the rear wheel turning shaft 11 protrude from both ends of the turning housing 10 so as to be able to advance and retreat. The steered housing 10 has a first end 101 and a second end 102. The ball screw mechanism 15 is disposed relatively close to the first end portion 101, and the steered shaft support device 17 is disposed relatively close to the second end portion 102. A bush 21 is held at the second end 102 of the steered housing 10, and the rear wheel steered shaft 11 is supported by the bush 21 so as to be slidable in the axial direction X1.

Between the inner periphery 10a of the steered housing 10 and the rear wheel steered shaft 11, an electric motor constituting the steered actuator 14 and a ball screw mechanism 15 are disposed.
The ball screw mechanism 15 includes a screw shaft 22 formed on a part of the rear wheel steering shaft 11, and a ball nut 24 that surrounds the screw shaft 22 and is screwed to the screw shaft 22 via a large number of balls 23. ing. The ball 23 is interposed between a helical screw groove 25 (female screw groove) formed on the inner periphery of the ball nut 24 and a spiral screw groove 26 (male screw groove) formed on the outer periphery of the screw shaft 22. doing.

  The electric motor constituting the steered actuator 14 includes a stator 27 fixed to the inner periphery 10 a of the steered housing 10, and a rotor 28 surrounding the rear wheel steered shaft 11 and rotating integrally with the ball nut 24. . The rotor 28 includes a cylindrical rotor core 29 that is coupled to the ball nut 24 so as to be integrally rotatable, and a permanent magnet 30 that is disposed on the outer periphery of the rotor core 29.

  The ball nut 24 and the rotor 28 are arranged side by side in the axial direction X1, for example, and constitute a unit U that can rotate integrally. The pair of end portions of the unit U are supported by the first bearing 31 and the second bearing 32 held on the inner periphery 10a of the steered housing 10 so as to be rotatable and immovable in the axial direction. The first bearing 31 supports the outer periphery of the ball nut 24 in a rotatable manner, and the second bearing 32 supports the outer periphery of the rotor core 29 in a rotatable manner.

  The main feature of this embodiment is that the rear wheel steering device 3 includes the above-described steered shaft support device 17 that supports the rear wheel steered shaft 11 so as not to rotate and to be slidable in the axial direction. The shaft support device 17 includes a lock mechanism 34 that locks the rear wheel turning shaft 11 in the neutral position. As shown in FIG. 3 which is an enlarged view, a lock member 44 described later of the lock mechanism 34 is engaged with a recess 43 as a second engaged portion on the outer periphery of the rear wheel turning shaft 11 in a neutral position. The rear wheel turning shaft 11 can be locked at the neutral position.

  The steered shaft support device 17 includes a cylindrical support housing 35 that is formed integrally with the steered housing 10 and intersects the steered housing 10 at right angles, and a support hole 36 formed in the support housing 35. A steering shaft support member 37 slidably supported in the depth direction Y 1 of 36, a sealing member 38 fixed to the inlet of the support hole 36, and a steering shaft support member 37 received by the sealing member 38. And an elastic member 39 that urges the rear wheel toward the rear wheel turning shaft 11.

  As shown in FIG. 4, which is a cross-sectional view taken along the line IV-IV in FIG. 3, the front end 37 a of the steered shaft support member 37 has a pair of first members inclined in opposite directions with respect to the depth direction Y1. A joint 40 is provided. On the other hand, a pair of flat surfaces 41 as a pair of first engaged portions that are respectively engaged with the pair of first engaging portions 40 are formed on the outer periphery 11 a of the rear wheel turning shaft 11. The pair of flat surfaces 41 are disposed to face the circumferential direction Z1 of the rear wheel turning shaft 11. The pair of flat surfaces 41 (first engaged portions) are inclined in directions opposite to each other with respect to the depth direction Y1.

  The turning shaft support member 37 urged by the elastic member 39 engages the pair of engaging portions 40 with the corresponding flat surfaces 41 (first engaged portions), thereby rear wheel turning shafts. 11 is supported so as to be non-rotatable and slidable in the axial direction X1. The pair of first engaging portions 40 of the steered shaft support member 37 may be provided with a low friction member (not shown) such as a fluorine resin that reduces sliding resistance.

  As shown in FIGS. 3 and 4, the lock mechanism 34 has an advanced position (see FIGS. 3 and 4) and a retracted position (see FIG. 2) in an insertion hole 42 provided in the steered shaft support member 37. A locking member 44 that locks the rear wheel turning shaft 11 in a neutral position by engaging with a recess 43 as a second engaged portion of the rear wheel turning shaft 11 in the advanced position. A biasing member 45 that biases the member 44 to the advanced position and an electromagnetic actuator 46 that drives the lock member 44 to the retracted position against the biasing member 45 are provided.

  When the rear wheel turning shaft 11 is viewed along the axial direction X1 (a direction orthogonal to the plane of the drawing in FIG. 4), the recess 43 serving as the second engaged portion of the rear wheel turning shaft 11 is formed on the rear wheel turning shaft 11. It arrange | positions between a pair of flat surfaces 41 (1st to-be-engaged part) regarding the circumferential direction Z1. When the rear wheel turning shaft 11 is in the neutral position, the concave portion 43 as the second engaged portion is moved to a position facing the lock member 44. A second engagement portion 44a provided at the tip of the lock member 44 engages with a recess 43 serving as a second engaged portion of the rear wheel turning shaft 11 in the neutral position.

The electromagnetic actuator 46 includes a main body 47 fixed to the sealing member 38, a rod 48 that protrudes forward and backward from the main body 47 and is connected to the lock member 44, and a solenoid 49 that is built in the main body 47 and applies an electromagnetic force to the rod 48. And.
As shown in the flowchart of FIG. 5, the ECU 16 has a function of turning off the electromagnetic actuator 46 when a predetermined condition is satisfied. That is, in step S1, the solenoid 49 is turned on (excited) as the system is started, and the lock by the lock mechanism 34 is released.

Next, in step S2, the vehicle speed V detected by the vehicle speed sensor 19 (running state detection sensor) is input, and in step S3, it is determined whether or not the detected vehicle speed V is equal to or higher than a predetermined value Va. If vehicle speed V is less than predetermined value Va (V <Va) (NO in step S3), the process returns to step S1.
On the other hand, when vehicle speed V is equal to or higher than predetermined value Va (YES in step S3), turning angle θw detected by turning angle sensor 20 is input in step S4, and detected in step S5. It is determined whether the steered turning angle θw is zero (θw = 0), that is, whether the rear-wheel steered shaft 11 is in the steering neutral position. When the rear wheel turning shaft 11 is not in the neutral position (NO in step S5), the process returns to step S1.

  On the other hand, when rear wheel turning shaft 11 is in the neutral position (YES in step S5), solenoid 49 is turned off in step S6. As a result, the rod 48 of the electromagnetic actuator 46 is extended by the biasing force of the biasing member 45, and the second engagement portion 44a of the lock member 44 is in the concave portion 43 (second target shaft) of the rear wheel turning shaft 11 in the neutral position. Engage with the engaging portion). As a result, the rear wheel turning shaft 11 is locked at the neutral position.

In step S6, after the solenoid 49 is turned off, the process returns to step S2, and the processing from step S2 is repeated.
According to this embodiment, as shown in FIG. 4, the turning shaft support member 37 is engaged with the first engaged portion (flat surface 41) of the rear wheel turning shaft 11, and the rear wheel turning shaft 11. Since the rotation is restricted, the position of the rear wheel turning shaft 11 in the axial direction X1 can be accurately controlled.

  Further, when a predetermined condition is satisfied (for example, when traveling at high speed), the electromagnetic actuator 46 is turned off, and the urging member 45 causes the lock member 44 to move to the second engaged portion ( By engaging the recess 43), the rear wheel turning shaft 11 can be locked in the neutral position. Since the lock member 44 for locking to the neutral position is incorporated in the steered shaft support member 37, the function of restricting the rotation of the rear wheel steered shaft 11 and the function of locking the rear wheel steered shaft 11 to the neutral position are provided. The small rear wheel steering device 3 can be realized.

  Further, when the rear wheel turning shaft 11 is viewed along the axial direction X1 (corresponding to a direction orthogonal to the paper surface in FIG. 4), the concave portion 43 as the second engaged portion pushed by the lock member 44 is With respect to the circumferential direction Z <b> 1 of the wheel turning shaft 11, it is disposed between a pair of flat surfaces 41 as a first engaged portion. Therefore, the interference between the pair of flat surfaces 41 of the rear wheel turning shaft 11 and the bush 21 can be suppressed, and the durability of the bush 21 can be improved.

  Further, since the turning shaft support member 37 is urged toward the rear wheel turning shaft 11 by the elastic member 39 received by the sealing member 38 fixed to the inlet of the support hole 36 of the support housing 35, The regulation of the rotation of the wheel turning shaft 11 is reliable. Further, by moving the rod 48 forward and backward from the main body 47 of the electromagnetic actuator 46 fixed to the sealing member 38, the lock member 44 can be advanced and retracted with a simple structure to achieve locking and unlocking.

  Further, when a predetermined traveling state is detected by a traveling state detection sensor (for example, a vehicle speed sensor 19) and a steering neutral state is detected by a steering neutral state detection sensor (for example, a turning angle sensor 20), the rear wheel turning shaft 11 is detected. Can be locked in the neutral position. Specifically, when the vehicle speed V detected by the vehicle speed sensor 19 is in a high speed state equal to or higher than the predetermined value Va, the running stability can be ensured by locking the rear wheel turning shaft 11 to the neutral position.

  The present invention is not limited to the above-described embodiment. For example, in any one of claims 1 to 5, the turning actuator is subjected to a predetermined condition for turning off the electromagnetic actuator 46 (solenoid 49). The occurrence of a failure of at least one of the electric motor 14 and the steering angle sensor 18 may be included. That is, when an abnormality has occurred in at least one of the electric motor as the steering actuator 14 and the steering angle sensor 18, after confirming that the rear wheel steering shaft 11 is in the neutral position, the solenoid 49 is turned off, The wheel turning shaft 11 may be locked at the neutral position.

  In addition, various modifications can be made within the scope of the claims of the present invention.

  DESCRIPTION OF SYMBOLS 1 ... Four-wheel steering apparatus, 2 ... Front-wheel steering apparatus, 3 ... Rear-wheel steering apparatus, 4 ... Steering member, 9 ... Vehicle body, 10 ... Steering housing, 10a ... Inner periphery, 11 ... Rear-wheel steering shaft, 11a ... Outer periphery , 12 ... Tie rods, 13 ... Rear wheels, 14 ... Steering actuator, 15 ... Ball screw mechanism, 16 ... ECU (control device), 17 ... Steering shaft support device, 18 ... Steering angle sensor, 19 ... Vehicle speed sensor (running) (State detection sensor), 20 ... steering angle sensor (steering neutral state detection sensor), 21 ... bush, 22 ... screw shaft, 23 ... ball, 24 ... ball nut, 34 ... lock mechanism, 35 ... support housing, 36 ... support Hole: 37 ... Steering shaft support member, 38 ... Sealing member, 39 ... Elastic member, 40 ... First engaging portion, 41 ... Flat surface (first engaged portion), 42 ... Insertion hole, 43 ... Recess (Second engaged portion), 44 ... lock member, 44a ... Second engaging portion, 45 ... urging member, 46 ... electromagnetic actuator, 47 ... main body, 48 ... rod, 49 ... solenoid, X1 ... axial direction, Y1 ... depth direction, Z1 ... circumferential direction

Claims (5)

In the rear wheel steering device in which the mechanical connection between the steering member and the rear wheel is broken,
A steering angle sensor for detecting a steering angle of the steering member;
A steering actuator for driving the steering shaft in the axial direction via a ball screw mechanism;
A control device for controlling the turning of the steering actuator based on the steering angle detected by the steering angle sensor;
A steered shaft support member that supports the steered shaft so as not to rotate and to be slidable in the axial direction by engaging the first engaged portion of the steered shaft;
An insertion hole provided in the steered shaft support member is accommodated so as to be movable between an advanced position and a retracted position. By engaging with a second engaged portion of the steered shaft at the advanced position, the rolling shaft is supported. A locking member that locks the rudder shaft in a neutral position;
A biasing member that biases the lock member to the advanced position;
An electromagnetic actuator that drives the lock member to the retracted position against the biasing member,
The control device is a rear wheel steering device having a function of turning off the electromagnetic actuator when a predetermined condition is satisfied. In Claim 1, a steered housing that houses the steered shaft,
A bush that is held by the steered housing and supports the steered shaft so as to be slidable in the axial direction;
The first engaged portion of the steered shaft is formed on the outer periphery of the steered shaft, and includes a pair of flat surfaces facing the circumferential direction of the steered shaft,
When the steered shaft is viewed from the axial direction, the second engaged portion includes a recess disposed between the pair of flat surfaces in the circumferential direction of the steered shaft. The support housing according to claim 1 or 2, wherein a support hole that supports the steered shaft support member so as to advance and retreat is formed, and is provided integrally with the steered housing;
A sealing member fixed to the inlet of the support hole;
An elastic member received by the sealing member and biasing the steered shaft support member toward the steered shaft;
The electromagnetic actuator includes a main body fixed to the sealing member, a rod protruding from the main body and connected to the lock member, and a solenoid for applying an electromagnetic force to the rod. In Claim 1 to 3, the traveling state detection sensor for detecting the traveling state of the vehicle,
A steering neutral state detection sensor for detecting a steering neutral state,
The rear wheel steering apparatus, wherein the predetermined condition includes detecting a predetermined traveling state by the traveling state detection sensor and detecting a steering neutral state by the steering neutral state detection sensor. In Claim 4, the traveling state detection sensor includes a vehicle speed sensor for detecting a vehicle speed,
The rear wheel steering apparatus, wherein the predetermined traveling state includes a state where the vehicle speed detected by the vehicle speed sensor is equal to or higher than a predetermined value.

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