JP2009126261A - Rear wheel steering device for vehicle - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To suppress deterioration of traveling stability and maneuverability even if an ignition switch is switched from an off state to an on state during travel, in a vehicle provided with a rear wheel steering device. <P>SOLUTION: This rear wheel steering device for the vehicle includes: an actuator 11 provided for steering right and left rear wheels 5 of the vehicle 1; a target operative position setting section 32 setting the target operative position of the actuator according to the traveling condition of the vehicle; a drive signal generating section 33 driving and controlling the actuator based on information on the target operative position output from the target operative position setting section when the ignition switch 13 is switched on; and an operative position sensor 16 detecting the actual operative position of the actuator. When switching the ignition switch from the off state to the on state, a temporary operative position is set between the target operative position and the actual operative position by the target operative position setting section, and the temporary operative position is output as information on the target operative position to the drive signal generation section, thereby preventing a sudden change in a rear wheel steering angle. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a rear wheel steering device that steers left and right rear wheels in accordance with a traveling state of a vehicle.

  As for rear wheel steering of a vehicle, for example, an actuator is provided between the trailing link that defines the steering angle and the vehicle body, and the size between the vehicle body and the trailing link is changed by the expansion and contraction of the actuator. There is a rear wheel steering device in which the turning angles of the left and right rear wheels are individually changed in accordance with the turning state (see Patent Document 1). In this type of rear wheel steering device, it is known to steer the rear wheel by controlling the driving of the actuator based on various parameters related to the running state of the vehicle (for example, the steering angle of the front wheel, the vehicle speed, etc.). ing.

Japanese Patent Laid-Open No. 9-30438

  By the way, the actuator as described above is driven and controlled when the ignition switch is on. Therefore, when the driver or the like unexpectedly operates the key while the vehicle is running to turn the ignition switch off, The drive control is interrupted and the operating position is maintained as it is. After that, if the vehicle running state changes when the ignition switch is turned on again, the target operation set from the actual operating position of the actuator (operating position at the time of control interruption) and the changed traveling state The difference from the position (control target) may become large. In such a case, in the above prior art, when the ignition switch is turned on (when driving control is resumed), the operating position of the actuator (that is, the rear wheel turning angle) is significantly changed. There was an adverse effect on sex and maneuverability.

  The present invention has been devised in view of such problems of the prior art, and even when the ignition switch is switched from the off state to the on state while the vehicle is running, the rear wheel turning angle is abrupt. It is an object of the present invention to provide a rear wheel steering device for a vehicle that prevents a change and suppresses a decrease in running stability and controllability of the vehicle.

  A first invention made to solve the above problem is a rear wheel steering device (7) for steering the left and right rear wheels (5) of the vehicle (1), and is used for the steering of the left and right rear wheels. When the actuator (11) to be operated, the target operating position setting means (32) for setting the target operating position of the actuator according to the traveling state of the vehicle, and the ignition switch (13) are in the on state, the target operating position Drive control means (33) for driving and controlling the actuator based on information on the target operation position output from the setting means, and actual operation position detection means (16) for detecting the actual operation position of the actuator, The target operating position setting means sets a temporary operating position between the target operating position and the actual operating position when the ignition switch is switched from the off state to the on state. And, the provisional working position and configured to output to said drive control means as the information of the target operating position for a predetermined time.

  As a second invention made to solve the above-mentioned problem, the target operation position setting means is configured such that the difference between the target operation position and the actual operation position exceeds a predetermined provisional operation determination threshold. It can be set as the structure which sets a temporary operation position.

  According to a third aspect of the present invention for solving the above-described problem, the target operation position setting means is configured to gradually advance the temporary operation position from the actual operation position side toward the target operation position side. it can.

  According to the first aspect of the present invention, even when the ignition switch is switched from the off state to the on state while the vehicle is running, a sudden change in the rear wheel turning angle is prevented, and the running stability and maneuverability of the vehicle are prevented. Can be suppressed. Further, according to the second aspect of the present invention, it is possible to reduce the processing load of the drive control by executing the drive control of the actuator for preventing a sudden change in the rear wheel turning angle only when necessary. In addition, according to the third aspect of the present invention, the difference between the actual operation position and the target operation position can be gradually eliminated by a simple method, and a sudden change in the rear wheel turning angle can be appropriately prevented.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. In the description, for the wheels and the members arranged with respect to them, that is, tires, suspensions, etc., suffixes (L or R) indicating the left and right are respectively added to the numerals, and for example, the left rear wheel 5L, the right The rear wheel 5R (however, when collectively referred to as the rear wheel 5).

  FIG. 1 is a schematic diagram illustrating a schematic configuration of an automobile to which a rear wheel steering apparatus according to an embodiment is applied. The automobile (vehicle) 1 includes front wheels 3L and 3R to which tires 2L and 2R are mounted, and rear wheels 5L and 5R to which tires 4L and 4R are mounted. These front wheels 3 and rear wheels 5 are suspension arms. And a front wheel suspension 6 and a rear wheel suspension 7 made of springs, dampers and the like, respectively. In addition, the automobile 1 is individually connected to the front wheel steering device 9 that directly steers the left and right front wheels 3L and 3R by steering the steering wheel 8 and the left and right knuckles 10L and 10R in the left and right rear wheel suspensions 7L and 7R. The left and right actuators 11L and 11R that individually change the turning angles of the rear wheels 5L and 5R by being expanded and contracted are installed.

  In addition, the automobile 1 has an ECU (Electronic Control Unit) 12 that performs overall control of various systems, an ignition switch 13 that detects the position of an ignition key (not shown), a vehicle speed sensor 14 that detects the vehicle speed, and the steering angle of the steering wheel 8. Steering angle sensor 15 for detecting and operating position sensors 16L and 16R for detecting operating positions of the actuators 11L and 11R are provided. The ECU 12 and the sensors 13 to 16 connected to the ECU 12 and the actuator 11 constitute a rear wheel steering device 17 (see FIG. 3).

  As shown in FIG. 2, the actuator 11 includes a casing 21 attached to the vehicle body side and a shaft 22 connected to an arm or the like of the rear wheel suspension 7. The shaft 22 reciprocates along the axial center direction (arrow direction) in a state in which the shaft 22 is engaged with the rod 23 provided inside the casing 21, whereby the rear wheel 5 is steered. A magnet 24 is attached to the shaft 22, and the operating position sensor 16 detects the actual operating position of the actuator 11 based on the magnetic flux generated by the magnet 24. Since the displacement amount of the actuator 11 corresponds to the turning angle of the rear wheel 5, the operation position sensor 16 also functions as a sensor for detecting the turning angle of the rear wheel 5. In addition, as such an actuator, for example, a known linear displacement actuator such as a rotary motion / linear motion conversion device that combines an electric motor with a speed reducer and a screw mechanism, or a cylinder device that linearly drives a piston rod with fluid pressure. Can be used.

  The ECU 12 includes a microcomputer, a ROM, a RAM, peripheral circuits, various drivers, and the like (not shown), and is connected to the actuators 11 and sensors 13 to 16 through a predetermined communication line.

  The ignition switch 13 has an OFF position in which an ignition circuit (not shown) is turned off, an accessory position in which an accessory circuit (not shown) is turned on, and an ON position in which the ignition circuit is turned on, corresponding to the rotation position of the ignition key. Is set. Moreover, a well-known detection apparatus can be used for each sensor 14-16.

  FIG. 3 is a functional block diagram of the rear wheel steering apparatus according to the embodiment. In the rear wheel steering device 17, the ECU 12 controls the steering angles of the rear wheels 5L and 5R by changing the operating positions of the actuators 11L and 11R based on the outputs of the sensors 13 to 16, respectively.

  The ECU 12 is connected to each of the sensors 13 to 16 and inputs an input interface 31 thereof, a target operating position setting unit 32 that sets a target operating position of the actuator based on information acquired from the sensor, Based on the set target operating position and information on the detection value (actual operating position) of the operating position sensor 16, the driving signal generating unit 33 that generates a driving signal for controlling the driving of the actuator 11 is connected to the actuator 11. Output interface 34.

  The target operating position setting unit 32 operates in the normal mode when the ignition switch 13 is in a normal on state. In this normal mode, the target operation position setting unit 32 sets the target operation position of the actuator 11 according to the traveling state of the automobile (in this embodiment, based on the detection values of the vehicle speed sensor 14, the steering angle sensor 15, etc.). The target position information is appropriately output to the drive signal generation unit 33. In this case, the target position is set based on, for example, an arithmetic expression using a vehicle speed, a steering angle, or the like related to the running state of the vehicle as a variable, or from a map in which a target operation position corresponding to the vehicle speed, the steering angle, or the like is set in advance. Or search.

  On the other hand, when the ignition switch 13 is switched to the on state after the vehicle is traveling, the target operating position setting unit 32 operates in the provisional mode. In the provisional mode, the target operation position setting unit 32 detects the target operation position (hereinafter referred to as “normal target position”) set in the same manner as in the normal mode at the time of switching to the ON state and the operation position sensor 16. A provisional operation position (hereinafter referred to as “provisional position”) is set between the actual operation position (hereinafter referred to as “actual position”) and information on the provisional position is obtained as information on the target operation position over a predetermined time. To the drive signal generation unit 33.

  FIG. 4 is a flowchart showing a control procedure by the rear wheel steering apparatus according to the embodiment. If the ignition switch 13 is turned off by the operation of the ignition key of the driver or the like while the vehicle is running (ST101: Yes), the drive control of the actuator 11 is interrupted (ST102). Thereafter, when the target operating position setting unit 32 detects that the ignition switch 13 is switched to the ON state again (ST103: Yes), the difference between the normal target position and the current actual position detected by the operating position sensor 16 is detected. An absolute value (corresponding to the turning amount of the rear wheels) is calculated, and it is determined whether or not this difference is greater than or equal to a first determination threshold value X set in advance (ST104). The first determination threshold value X can be set in consideration of the magnitude of the influence of actuator drive control based on the difference between the normal target position and the actual position on the running stability and maneuverability of the vehicle.

  In ST104, when the difference between the normal target position and the actual position is greater than or equal to the first determination threshold value X, the target operation position setting unit 32 sets an initial provisional position between the normal target position and the actual position. The provisional position is output to the drive signal generation unit 33 as information on the target operation position (ST105). After that, the target operating position setting unit 32 drives, as a target operating position, a value obtained by adding an increment Δα to the previous provisional position until a predetermined time Ta (see FIG. 5) that has been set elapses (ST106: Yes). The signals are sequentially output to the signal generator 33 (ST107). Here, as the increment Δα, for example, a constant ratio in the difference between the normal target position and the actual position can be set. If the difference between the normal target position and the actual position is less than or equal to a predetermined value (which does not affect the running stability and maneuverability of the vehicle), the provisional mode is terminated before the specified time T in ST106 elapses. Such a configuration is also possible.

  On the other hand, in ST104, when the difference between the normal target position and the actual position is less than the first determination threshold value X, the difference between the normal target position and the actual position does not affect the running stability and maneuverability of the vehicle. The target operation position setting unit 32 executes the normal mode (ST108). Thus, by executing the provisional mode only when necessary, the processing load of the drive control of the actuator 11 can be reduced.

  FIG. 5 is an example of the actuator drive control result in the rear wheel steering device, and shows the transition between the target operating position and the actual position of the actuator. As shown in the figure, when the ignition switch is turned off at time T0, the drive control of the actuator is interrupted, so that the actual position is maintained until it is switched on again at time T1. Thereafter, when the ignition switch is switched to the on state, the difference Y between the target operating position and the actual position becomes equal to or greater than the first determination threshold value X due to the change in the driving state of the vehicle so far. The unit 32 operates in the provisional mode. As a result, the actual position gradually approaches the target operation position, and follows the target operation position substantially after the time T2.

Schematic diagram of an automobile to which a rear wheel steering device according to an embodiment is applied Schematic diagram of actuator according to embodiment Functional block diagram of a rear wheel steering device according to an embodiment The flowchart which shows the control procedure by the rear-wheel steering apparatus which concerns on embodiment. The figure which shows the relationship between the actual position of the actuator at the time of ignition switch switching which concerns on embodiment, and a target operation position

Explanation of symbols

1 Car 3 Front Wheel 5 Rear Wheel 6 Front Wheel Suspension 7 Rear Wheel Suspension 8 Steering Wheel 11 Actuator 12 ECU
13 Ignition switch 14 Vehicle speed sensor 15 Steering angle sensor 16 Operation position sensor 17 Rear wheel steering device 32 Target operation position setting unit 33 Drive signal generation unit

Claims (3)

A rear wheel steering device that steers left and right rear wheels of a vehicle,
An actuator provided for the steering of the left and right rear wheels;
Target operating position setting means for setting a target operating position of the actuator in accordance with the traveling state of the vehicle;
Drive control means for driving and controlling the actuator based on information on the target operation position output from the target operation position setting means when the ignition switch is in an on state;
An actual operating position detecting means for detecting an actual operating position of the actuator,
The target operation position setting means sets a temporary operation position between the target operation position and the actual operation position when the ignition switch is switched from an off state to an on state, and performs the provisional operation over a predetermined time. A rear wheel steering apparatus for a vehicle, wherein a position is output to the drive control means as information on the target operating position.   The target operation position setting means sets the temporary operation position only when a difference between the target operation position and the actual operation position exceeds a predetermined temporary operation determination threshold value. The rear-wheel steering device of the vehicle described.   The vehicle rear wheel steering according to claim 1 or 2, wherein the target operation position setting means gradually advances the temporary operation position from the actual operation position side toward the target operation position side. apparatus.

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