Rear wheel steering device

Abstract

The present invention provides a rear-wheel steering device capable of realizing well-balanced rear-wheel steering control that can reduce discomfort based on working sound and appropriately exert the response performance of rear-wheel steering. The rear-wheel steering device comprises: a rear-wheel steering mechanism capable of setting the control speed of a rear-wheel steering actuator according to the speed of a vehicle; an acquisition unit for acquiring driving operation input information of the vehicle; a correction unit for correcting the control speed based on the driving operation input information; and a drive control unit for driving the rear-wheel steering actuator based on the correction result of switching between limiting the control speed and not limiting the control speed through the correction unit.

Description

Technical Field

[0001] The invention relates to a rear wheel steering control device. Background Art

[0002] In the past, a vehicle that can perform rear wheel steering by a rear wheel steering device in addition to the front wheel steering by a front wheel steering device has been put into practical use. The rear wheel steering device can steer the rear wheels according to the steering angle of the front wheels through an actuator composed of a motor, a planetary gear, etc., so that the front and rear wheels are steered in the same phase or in opposite phases according to the driving state of the vehicle. In addition to the front wheels, the rear wheels are also steered, which can help stabilize the driving posture and improve the turning performance.

[0003] Patent Document 1: Japanese Patent No. 6945799

[0004] Patent Document 2: Japanese Patent Application Publication No. 2019-214311

[0005] The more the control speed of the actuator of the rear-wheel steering control device is increased, the more the rear-wheel steering control performance is improved, and a higher response performance can be obtained. On the other hand, if the control speed is increased, the working sound becomes louder, which becomes a cause of reduced quietness of the vehicle, often causing discomfort to the passengers. That is, in the rear-wheel steering control device, there is a situation where if the control speed is slowed down in order to focus on reducing the working sound, sufficient response performance cannot be obtained. In addition, if the control speed is increased in order to focus on responsiveness, the quietness becomes insufficient, causing discomfort to the passengers. Summary of the invention

[0006] Therefore, one of the problems to be solved by an embodiment of the present invention is to provide a rear-wheel steering device capable of achieving well-balanced rear-wheel steering control, which can reduce the discomfort caused by the operating sound to the passengers and appropriately exert the responsiveness of the rear-wheel steering.

[0007] A rear-wheel steering device as an example of the present invention comprises: a rear-wheel steering mechanism capable of setting a control speed of a rear-wheel steering actuator according to a vehicle speed; an acquisition unit that acquires driving operation input information of the vehicle; a correction unit that corrects the control speed based on the driving operation input information; and a drive control unit that drives the rear-wheel steering actuator based on a correction result obtained by switching between limiting the control speed or not limiting the control speed through the correction unit.

[0008] According to the above structure, for example, the control speed of the rear-wheel steering actuator can be corrected according to the vehicle's driving operation (driving operation input information), and the switching between limiting the control speed and not limiting the control speed can be performed in a well-balanced manner (separate use). BRIEF DESCRIPTION OF THE DRAWINGS

[0009] Figure 1 It is an illustrative and schematic diagram showing a vehicle including the rear-wheel steering device according to the embodiment.

[0010] Figure 2 This is an illustrative and schematic block diagram showing the structure of the rear-wheel steering device according to the embodiment.

[0011] Figure 3 This is an exemplary and schematic control map showing the relationship between the control speed and the vehicle speed when emphasis is placed on suppression of operating noise and when emphasis is placed on performance in the rear-wheel steering device according to the embodiment.

[0012] Figure 4 The following are illustrative and schematic diagrams showing a procedure for limiting and adjusting a control speed of a rear-wheel steering according to a driver input and calculation of a target rear wheel angle after the limit adjustment in the rear-wheel steering device according to the embodiment.

[0013] Figure 5 This is an illustrative and schematic diagram showing a rear-wheel steering holding function when the vehicle is snaking in the rear-wheel steering device according to the embodiment.

[0014] Description of Reference Numerals

[0015] 10…rear-wheel steering device, 12…vehicle, 14…front-wheel steering mechanism, 16…rear-wheel steering mechanism, 18…front wheel, 20…rear wheel, 22…steering wheel, 24…rear-wheel steering actuator, 26…sensor, 28…rear-wheel steering control unit, 28a…acquisition unit, 28b…control speed setting unit, 28c…correction unit, 28d…drive control unit. DETAILED DESCRIPTION

[0016] The following describes the embodiments and modifications of the present invention with reference to the accompanying drawings. The structures of the embodiments and modifications described below, and the functions and effects brought about by the structures are merely examples, and are not limited to the following descriptions.

[0017] Figure 1 It is an illustrative and schematic diagram showing a vehicle 12 equipped with the rear-wheel steering device 10 according to the embodiment.

[0018] The vehicle 12 includes a four-wheel steering system including a front wheel steering mechanism 14 and a rear wheel steering mechanism 16. The front wheel steering mechanism 14 can steer a pair of left and right front wheels 18. The rear wheel steering mechanism 16 can steer a pair of left and right rear wheels 20.

[0019] The steering rod 14a moves according to the steering angle of the steering wheel 22, so that the front wheels 18 are steered. The rotation of the steering wheel 22 steered by the driver is transmitted to the front wheel steering mechanism 14 via the steering column 22a, and the steering rod 14a moves linearly in the axial direction. This linear movement is transmitted via the tie rod 14b, so that the direction of the front wheels 18 changes in conjunction. In addition, a steering angle sensor is provided on the steering column 22a that rotates integrally with the steering wheel 22.

[0020] The rear-wheel steering mechanism 16 is installed across the wheel-side components and the vehicle-side components of the suspension mechanism supporting the left and right rear wheels 20. The left and right wheel brackets 16b are connected to the cross beam 16a on the vehicle-side in a swingable manner. The left and right wheel brackets 16b are connected to the steering link 16c provided in the cross beam 16a in a swingable manner via the left and right tie rods 16d, respectively. The rear-wheel steering mechanism 16 is driven by the rear-wheel steering actuator 24 included in the rear-wheel steering device 10. Of the first connecting portion 24a and the second connecting portion 24b provided at both ends of the rear-wheel steering actuator 24, the first connecting portion 24a is connected to the first connected portion 16e, which is a part of the cross beam 16a, and the second connecting portion 24b is connected to the second connected portion 16f, which is one end of the steering link 16c. Furthermore, the steering link 16c is swung by the extension and contraction of the rod 24c integrally formed with the second connection portion 24b of the rear-wheel steering actuator 24, thereby steering the rear wheel 20. The rod 24c is linearly moved by, for example, the motor M and the planetary gear G constituting the rear-wheel steering actuator 24, thereby extending and contracting relative to the rear-wheel steering actuator 24. Furthermore, the rear-wheel steering mechanism 16 can steer the rear wheel 20 in the same phase with respect to the front wheel 18 or in the opposite phase with respect to the front wheel 18 according to the driving state of the vehicle 12. In addition, the response speed of the rear-wheel steering mechanism 16 can be controlled by controlling the driving speed of the motor M. The vehicle 12 includes the front-wheel steering mechanism 14 and the rear-wheel steering mechanism 16, so that the driving posture can be stabilized and the turning performance can be improved compared with a vehicle only including the front-wheel steering mechanism 14.

[0021] The rear-wheel steering mechanism 16 constructed as described above can improve the rear-wheel steering performance and obtain a high responsiveness as the control speed of the rear-wheel steering actuator 24 is increased. On the other hand, if the control speed of the rear-wheel steering actuator 24 is increased, the operating sound, such as the gear jumping noise of the planetary gear, becomes louder, which becomes a cause of the reduction of the quietness of the vehicle 12, causing discomfort to the passengers. Generally, when the vehicle 12 is running at a low speed, there is a tendency for the steering amount of the rear wheel 20 to increase, and the operating sound of the rear-wheel steering actuator 24 tends to become noticeable. On the contrary, when running at a high speed, there is a tendency for the steering amount of the rear wheel 20 to decrease, and there is a tendency for the road noise to increase, and the operating sound of the rear-wheel steering actuator 24 is not easy to become noticeable. Therefore, when running at a low speed where it is not easy to generate sounds such as road noise, the control speed of the rear-wheel steering actuator 24 is often limited to suppress the generation of the operating sound, and control is performed with emphasis on quietness. On the other hand, when driving at high speeds where road noise and other sounds are easily generated, even if the working sound of the rear-wheel steering actuator 24 is generated, it will not be easy to become noticeable due to the road noise and other sounds. Therefore, the control speed limit of the rear-wheel steering actuator 24 is often relaxed, and control is performed that emphasizes the response performance of the rear-wheel steering performance.

[0022] However, in the case of uniformly controlling the speed limit in units of vehicle speed as described above, there is a situation in which the performance cannot be satisfied in the operation input process for the driver in the low / medium speed range. For example, when returning to forward driving from a left or right turn at an intersection, the steering wheel 22 is sometimes quickly turned to the neutral position. In this case, although the front wheel steering mechanism 14 directly connected to the steering wheel 22 operates in approximately the same phase as the front wheel 18, the rear wheel steering mechanism 16 is driven by wire steering, so the steering operation of the rear wheel 20 will be delayed. As a result, the steering wheel often deviates from the center within a constant time. In this case, the rear wheel 20 is steered, and the corresponding return torque acts to cause the front wheel 18 to steer by the same amount, trying to move straight, which becomes a so-called crab walk, which may cause deviation.

[0023] In addition, even in the case of fast meandering with the steering wheel 22 turned, there is a delay between the steering angle of the rear wheels 20 (rear wheel angle) and the steering angle of the front wheels 18 (front wheel angle). As a result, there is often a delay in the yaw rate, which may cause an error with respect to the ideal driving path.

[0024] Therefore, the rear-wheel steering device 10 of the present embodiment not only controls the rear-wheel steering mechanism 16 according to the vehicle speed, but also controls the rear-wheel steering mechanism 16 in consideration of the driving operation input information of the vehicle 12. That is, by adding a correction in consideration of the driving operation status of the driver to the control speed of the rear-wheel steering actuator 24, the above-mentioned inconvenience is eliminated.

[0025] Figure 2 1 is an illustrative and schematic block diagram showing the structure of the rear-wheel steering device 10. The rear-wheel steering device 10 includes a rear-wheel steering control unit 28 and a storage unit 30 in addition to the above-mentioned rear-wheel steering mechanism 16. The rear-wheel steering control unit 28 controls the rear-wheel steering mechanism 16 based on the detection results of various sensors 26 mounted on the vehicle 12. In addition, the storage unit 30 stores a mapping table or the like to be referred to when the rear-wheel steering control unit 28 sets the control speed of the rear-wheel steering actuator 24. The mapping table includes, for example, a mapping table that determines the relationship between the control speed of the rear-wheel steering actuator 24 and the vehicle speed, a mapping table that determines the relationship between the control speed of the rear-wheel steering actuator 24 and the steering speed of the steering wheel 22, a mapping table that determines the relationship between the control speed of the rear-wheel steering actuator 24 and the acceleration and deceleration of the vehicle 12, and a mapping table that determines the relationship between the control speed of the rear-wheel steering actuator 24 and the control speed of the steering wheel 22 when returning the steering wheel 22 to the neutral direction. The above-mentioned mapping table can be determined, for example, by preliminary experiments or the like. The above-described map is an example, and the storage unit 30 may store a map indicating correspondence with other driving operation input information.

[0026] Various sensors 26 supply the driving operation input information indicating the driving operation status of the driver to the rear-wheel steering control unit 28. The vehicle speed sensor 26a detects the rotation amount or the rotation speed per unit time, and outputs the vehicle speed, for example, by means of a Hall element provided near the front wheel 18 and the rear wheel 20. The yaw rate sensor 26b detects the yaw rate of the vehicle 12 (the rate of change of the rotation angle in the yaw direction (turning direction)). The acceleration sensor 26c detects the acceleration in the front-to-back direction or the left-to-right direction of the vehicle 12. The steering angle sensor 26d is, for example, a sensor that detects the steering amount of the steering wheel 22, and is constructed using, for example, a Hall element. It is also possible to obtain information related to the steering direction and steering speed of the steering wheel 22 based on the signal output by the steering angle sensor 26d. The accelerator pedal sensor 26e outputs information related to the amount of depression and the depression speed of the accelerator pedal, and can be used to detect sudden acceleration of the vehicle 12. The brake pedal sensor 26f outputs information related to the amount of depression and the depression speed of the brake pedal, and can be used to detect sudden deceleration of the vehicle 12. In addition, Figure 2The sensor 26 shown is just an example, and any sensor may be used as long as it outputs driving operation input information indicating the driving operation status of the driver, and the output results may be sequentially provided to the rear-wheel steering control unit 28 .

[0027] The rear-wheel steering control unit 28 includes an acquisition unit 28a, a control speed setting unit 28b, a correction unit 28c, a drive control unit 28d, and the like.

[0028] The acquisition unit 28a acquires the detection results of the various sensors 26, that is, the driving operation input information of the vehicle 12. For example, the acquisition unit 28a acquires the steering speed information of the front wheel steering of the vehicle 12 from the steering angle sensor 26d as the driving operation input information. In addition, the acquisition unit 28a acquires the acceleration and deceleration information of the vehicle 12 from the acceleration sensor 26c, the accelerator pedal sensor 26e, the brake pedal sensor 26f, etc. as the driving operation input information. In addition, the acquisition unit 28a acquires the steering direction information of the front wheel steering of the vehicle 12 from the steering angle sensor 26d, the yaw rate sensor 26b, etc. as the driving operation input information. In addition, the acquisition unit 28a acquires the reverse operation information indicating that the front wheel steering of the vehicle 12 is reversed at a predetermined speed or more, that is, zigzag driving, from the steering angle sensor 26d, the yaw rate sensor 26b, etc. as the driving operation input information.

[0029] The control speed setting unit 28b can set the basic control speed (basic control speed) of the rear-wheel steering actuator 24 based on the vehicle speed of the vehicle 12 obtained from the vehicle speed sensor 26a and with reference to the mapping table stored in the storage unit 30 that determines the relationship between the control speed of the rear-wheel steering actuator 24 and the vehicle speed.

[0030] The correction unit 28c corrects the basic control speed of the rear wheel steering actuator 24 set by the control speed setting unit 28b according to the vehicle speed based on the travel operation input information obtained by the acquisition unit 28a from the various sensors 26. The correction by the correction unit 28c will be described in detail later.

[0031] Based on the correction result of the correction unit 28c, the drive control unit 28d switches (uses separately) between the working sound suppression priority control that limits the control speed of the rear-wheel steering actuator 24 or the performance priority control that does not limit the control speed, generates a drive command for driving the rear-wheel steering actuator 24, and outputs it to the rear-wheel steering actuator 24.

[0032] In addition, the switching between the working sound suppression priority control and the performance priority control can also be performed in the correction unit 28c, where a switching signal for indicating the switching between the working sound suppression priority control and the performance priority control is generated and supplied to the drive control unit 28d, and the drive control unit 28d performs the switching process based on the switching signal. In addition, in other embodiments, the drive control unit 28d can also obtain the correction result (correction content) from the correction unit 28c, such as the correction information required for the control switching obtained by referring to various control mapping tables stored in the storage unit 30, and generate a switching signal in the drive control unit 28d based on the correction information to switch between the working sound suppression priority control and the performance priority control. In addition, in the following description, an example is shown in which the correction unit 28c generates a switching signal for indicating the switching between the working sound suppression priority control and the performance priority control, and the drive control unit 28d performs the control switching process of the rear wheel steering actuator 24 based on the switching signal.

[0033] The details of the rear-wheel steering control of the rear-wheel steering device 10 constructed as described above are described. For example, the discomfort such as deviation when returning to forward driving from left or right turns at an intersection becomes obvious when the control of the rear wheel 20 is delayed relative to the input of the steering wheel 22. That is, the earlier the steering operation of the steering wheel 22 is, the easier it is to produce. On the other hand, in the scene of rapid steering operation, it can be regarded as a situation in which the driver quickly operates the steering wheel 22, and the behavior of the vehicle 12 also changes rapidly. In such a case, it can be said that even at a low vehicle speed, the working sound of the rear-wheel steering actuator 24 is not easy to be recognized by the driver. That is, it can be regarded as a situation in which the working sound is not easy to be obvious.

[0034] Therefore, the correction unit 28c corrects the control speed (basic control speed) determined by the control speed setting unit 28b based on the vehicle speed based on the driving operation input information (driving operation status of the driver) of the vehicle 12. The correction unit 28c corrects the control speed of the rear wheel steering actuator 24 based on, for example, the steering speed of the steering wheel 22, the acceleration and deceleration of the vehicle 12, and whether the steering direction of the steering wheel 22 is the neutral return direction or the non-neutral direction (cut-in direction), and is implemented by limiting the control speed of the rear wheel steering actuator 24. Priority control of suppressing the working sound or performance priority control without limiting the control speed. In other words, in the case of focusing on performance (the case where the sound is not easy to be noticed), even when the vehicle speed is low, the restriction of the control speed is temporarily relaxed (the generation of the working sound is allowed under the condition that it is not easy to be noticed), thereby taking into account both the improvement of the performance of the vehicle 12 and the countermeasures for the working sound.

[0035] Regarding the correction by the correction unit 28c, a specific example will be described. First, the correction corresponding to the steering speed of the steering wheel 22 will be described. The rear-wheel steering control unit 28 basically controls the rear-wheel steering actuator 24 at the control speed corresponding to the vehicle speed set by the control speed setting unit 28b, but in addition, the control speed limit of the rear-wheel steering actuator 24 is adjusted (corrected) according to the steering speed of the steering wheel 22. That is, when the steering wheel 22 is moved quickly, the correction unit 28c generates a switching signal for switching to a control that gives priority to the behavior of the vehicle 12, and releases the control speed limit of the rear-wheel steering actuator 24. That is, although the generation of the operating sound is allowed, in the scene of the fast movement of the steering wheel 22, the behavior of the vehicle 12 also moves quickly, so the operating sound is not easy to become conspicuous, and therefore the performance priority control that gives priority to the response performance of the vehicle 12 is performed. That is, the response performance of the vehicle 12 can be obtained and the discomfort caused by the operating sound can be reduced. On the other hand, when the steering wheel 22 is slowly operated, the behavior of the vehicle 12 also changes slowly, and the operating sound of the rear-wheel steering actuator 24 when it is in operation tends to become noticeable. Therefore, when the steering wheel 22 is slowly operated, the correction unit 28c generates a switching signal for switching to a control that gives priority to reducing the operating sound, and limits the control speed of the rear-wheel steering actuator 24 according to the operating speed of the steering wheel 22 and the vehicle speed, thereby performing the operating sound suppression priority control. That is, the discomfort caused by the operating sound can be reduced.

[0036] Next, the correction corresponding to acceleration and deceleration will be described when the behavior of the vehicle 12 changes significantly due to the acceleration and deceleration state of the vehicle 12, for example, the operation of the accelerator pedal and the brake pedal. While the vehicle 12 is traveling, the rear-wheel steering control unit 28 basically controls the rear-wheel steering actuator 24 at the control speed corresponding to the vehicle speed set by the control speed setting unit 28b, but in addition, the control speed limit of the rear-wheel steering actuator 24 is adjusted (corrected) according to the acceleration and deceleration of the vehicle 12 (accelerator pedal operation, brake pedal operation). That is, the correction unit 28c generates a switching signal for switching to the control that gives priority to the behavior of the vehicle 12 in the case of sudden acceleration and deceleration, and releases the control speed limit of the rear-wheel steering actuator 24. That is, although the generation of the operating sound is allowed, in the case of sudden acceleration and deceleration, the behavior of the vehicle 12 also changes dramatically, so the operating sound is not easy to become noticeable. Therefore, the performance priority control that gives priority to the response performance of the vehicle 12 is performed. That is, the response performance of the vehicle 12 can be obtained and the discomfort caused by the operating sound can be reduced. On the other hand, when there is no sudden acceleration, the behavior of the vehicle 12 also changes slowly, and the working sound of the rear wheel steering actuator 24 when it is in operation tends to become noticeable. Therefore, when there is no sudden acceleration, the correction unit 28c generates a switching signal for switching to a control that gives priority to reducing the working sound, and limits the control speed of the rear wheel steering actuator 24 according to the vehicle speed, thereby performing the working sound suppression priority control that reduces the working sound. That is, the discomfort caused by the working sound can be reduced.

[0037] Figure 3 : is an exemplary and schematic control map showing the relationship between the control speed and the vehicle speed when the rear-wheel steering device 10 focuses on the suppression of the operating sound and the performance. Figure 3In the figure, the horizontal axis is the vehicle speed. In addition, the vertical axis is the control speed that serves as the benchmark for the rear-wheel steering actuator 24. The mapping table A represented by the dotted line shows that the working sound suppression is emphasized, so when the control is performed below the mapping table A, the working sound is considered to be at a level that does not need to be worried about. On the other hand, the mapping table B represented by the solid line takes into account the performance of the vehicle 12, so it is the control speed of the rear-wheel steering actuator 24 required when trying to fully exert the performance of the vehicle 12. Moreover, the control speed variable area E between the mapping table A and the mapping table B is an area where the performance will be reduced if the working sound suppression is emphasized, and the generation of the working sound will be worrying if the performance is emphasized. Therefore, in the control speed variable area E, by setting (correcting) the control speed according to the driving style of the vehicle 12 (the driving operation input information used for driving) and the vehicle speed, as described above, it is possible to achieve a balance between emphasizing the working sound suppression of the rear-wheel steering actuator 24 and emphasizing the performance of the vehicle 12, and to perform rear-wheel steering control. That is, the above-mentioned operation sound suppression priority control is a control that minimizes the performance reduction and gives priority to the operation sound suppression, and the performance priority control is a control that minimizes the effective reduction of the operation sound suppression and gives priority to the performance.

[0038] Next, the correction when returning the steering wheel 22 to the neutral direction, such as when returning to the forward driving from the left or right turn at the intersection, or when returning to the forward driving state from the turning state when making a U-turn, will be described. Generally, for the steering wheel 22, the steering speed of the steering operation to return to the neutral direction (steering operation to the center position) is faster than the steering operation when cutting in for turning (steering operation to the non-neutral direction). When the steering operation to return to the neutral direction is performed, if the rear wheel steering actuator 24 is limited at the same control speed as the cutting in of the steering wheel 22 based on the vehicle speed, the control speed restriction will be stricter. In this case, the front wheel 18 returns in response to the steering operation of the steering wheel 22, but the rear wheel 20 returns with a delay due to the speed restriction. In this case, the vehicle 12 intends to move straight forward. That is, although the front wheel 18 tries to return to the forward driving position, the rear wheel 20 is cut off, and accordingly the front wheel 18 is cut in the opposite direction, resulting in a state of tilted forward driving. Therefore, the correction unit 28c refers to a dedicated mapping table when returning the steering wheel 22 to the neutral direction. The dedicated mapping table in this case is a mapping table that makes it easier to return the rear wheel 20 to the center when the steering wheel 22 is returned to the neutral direction. That is, when the steering wheel 22 returns to the neutral direction, the correction unit 28c generates a switching signal for switching control so that the behavior of the vehicle 12 is prioritized compared to the case of cutting into the steering wheel 22 (turning to the non-neutral direction), and the control speed restriction of the rear wheel steering actuator 24 is released. That is, performance priority control is performed. For example, the correction control of the control speed is not performed. As a result, the occurrence of deflection (steering wheel deviation from the center) that is easy to occur when returning to forward driving from left or right turns at an intersection can be suppressed. In this case, although the generation of working sound is allowed, when the steering wheel 22 returns to the neutral direction, the behavior of the vehicle 12 changes drastically due to the fast steering speed, so the working sound is not easy to become obvious. Therefore, the response performance of the vehicle 12 can be obtained and the discomfort based on the working sound can be reduced. On the other hand, when the steering wheel 22 is cut in, there is a tendency that the steering speed becomes slower and the behavior change of the vehicle 12 also becomes slower compared to when the steering wheel 22 is returned to the neutral direction. That is, the working sound of the rear wheel steering actuator 24 when it is in operation tends to become noticeable. Therefore, in this case, a switching signal for switching control is generated according to the vehicle speed so as to impose a limit on the control speed of the rear wheel steering actuator 24. That is, the working sound suppression priority control for reducing the working sound is performed. As a result, the discomfort caused by the working sound can be reduced.

[0039] Figure 4 1 is a diagram for collectively explaining the above control, and is an illustrative and schematic diagram showing the order of limiting and adjusting the control speed of the rear wheel steering operation corresponding to the driver's input in the rear wheel steering control device 10 and the calculation of the target rear wheel angle after the limit adjustment. Figure 4The case where the steering speed information of the front wheel steering (steering wheel 22 ) of the vehicle 12 is used as the driving operation input information is shown.

[0040] First, as a first step, the rear wheel steering control unit 28 (correction unit 28c) compares the vehicle speed of the vehicle 12 with the map ( Figure 3 The control speed set by the mapping table A) and the control speed set by the control speed variable mapping table based on the turning angle during driving are used, and the larger control speed is used. For example, when the steering operation of the steering wheel 22 is fast, the control speed of the rear-wheel steering actuator 24 is set to the open side (the side that moves quickly). In addition, in the first step, when the acceleration information of the vehicle 12 is referred to as the driving operation input information, when the acceleration and deceleration are large, the control speed of the rear-wheel steering actuator 24 is set to the open side (the side that moves quickly). In addition, when the driving operation input information indicates that the steering wheel 22 is turned in the neutral direction, the control speed of the rear-wheel steering actuator 24 is set to the side that moves quickly (the open side).

[0041] Next, as a second step, the control speed adopted in the first step is compared with the vehicle speed of the vehicle 12 by a performance-oriented mapping table ( Figure 3 The control speed set based on the mapping table B of the vehicle 12 is compared with the control speed set based on the mapping table B of the vehicle 12, and the smaller value is adopted. In this case, the mapping table B that emphasizes performance becomes the upper limit value, but if the control speed adopted in the first step is below the line of the mapping table B that emphasizes performance, the value obtained by emphasizing the working sound suppression adopted in the first step is adopted. In addition, if the control speed set based on the vehicle speed and through the mapping table B that emphasizes performance is small, then the value is the upper limit value, so the control speed that emphasizes performance is adopted. At this stage, the control speed of the rear-wheel steering actuator 24 is determined based on the current driving operation input information of the vehicle 12. That is, the correction unit 28c determines the control speed of the rear-wheel steering actuator 24 based on the driving operation input information, and generates information (switching signal) for switching between the working sound suppression priority control that limits the control speed and the performance priority control that does not limit the control speed.

[0042] Furthermore, the rear-wheel steering control unit 28 (drive control unit 28d) limits the amount of change (late limit) of the target angle (target rear wheel angle) of the rear wheels 20 that are initially intended to move based on the steering of the steering wheel 22, and calculates the final target rear wheel angle (after limit). That is, the rear-wheel steering actuator 24 is controlled based on the restricted target rear wheel angle. As a result, a well-balanced rear-wheel steering control that can achieve both reduction of the discomfort caused to the driver (passenger) by the operating sound and appropriate performance of the response performance of the rear-wheel steering can be achieved.

[0043] However, regarding the delay of the yaw rate during meandering (a movement in which the front wheel steering of the vehicle 12 is reversed at a predetermined speed or higher), the vehicle 12 is in a state of violently turning left and right during fast meandering. Therefore, it can be said that the premature input of the steering wheel 22 does not have the advantage of enhancing the yaw response in the rear wheels 20. Therefore, when the steering wheel 22 is switched at a fast speed or higher than a constant speed, the current position is maintained until the target angle of the rear wheels 20 matches the actual rear wheel angle. That is, the correction unit 28c sets the control speed limit of the rear wheel steering actuator 24 to the maximum and temporarily stops the rear wheel steering control.

[0044] Here, it is considered that the control speed of the rear wheel 20 is limited by emphasizing the suppression of the operating sound during meandering. Figure 5 As shown in FIG. 1 , in response to the reversal (e.g., left to right) of the front wheel angle SA of the front wheel 18 based on the steering operation of the steering wheel 22 during meandering, a delay occurs on the rear wheel 20 side. For example, the target rear wheel angle SB when there is no restriction on the control speed with respect to the delay of the front wheel angle SA becomes the actual rear wheel angle SC (target rear wheel angle after delay). In this case, the rear wheel 20 maintains the target rear wheel angle SB (e.g., left) when the front wheel 18 is turned left and continues to cut in to the left direction before reaching the target rear wheel angle SB, thereby causing a delay in the yaw rate.

[0045] Therefore, when the steering angle sensor 26d or the like detects meandering (point P in the figure), that is, when a quick turn is detected, the correction unit 28c generates a switching signal in a manner that switches to a control that maximally corrects the control speed limit of the rear wheel steering actuator 24 (for example, control speed = 0), and maintains the current rear wheel angle (after point P1 in the figure). That is, the leftward cutting of the rear wheel 20 is stopped. As a result, an increase in the yaw rate in the direction opposite to the direction of the front wheel 18 can be prevented. In addition, the correction unit 28c can also avoid the generation of operating noise by maximally correcting the control speed limit of the wheel steering actuator 24 (switching to the operating noise suppression priority control).

[0046] Furthermore, when the target rear wheel angle SB and the actual rear wheel angle SC coincide with each other (point P2 in the figure), that is, when the target rear wheel angle SB returns to the position of the actual rear wheel angle SC after the steering wheel 22 is steered in the opposite direction, the correction unit 28c restarts the control of the rear wheel steering actuator 24 in such a manner as to restart the control of the rear wheels 20. As a result, it is possible to prevent the yaw rate in the direction opposite to the direction of the front wheels 18 from increasing.

[0047] In this way, in the configuration in which the control speed of the rear-wheel steering actuator 24 is corrected, when the snaking driving is performed, the deviation from the ideal driving route that may be caused by the delay of the yaw rate can be reduced, and the appropriate response performance of the vehicle 12 can be obtained. In addition, at this time, the control speed of the rear-wheel steering actuator 24 is temporarily 0, so the generation of the operation sound can be avoided. As a result, it can help reduce the discomfort caused by the operation sound.

[0048] As described above, according to the present embodiment, the rear-wheel steering device 10 includes: the rear-wheel steering mechanism 16 capable of setting the control speed of the rear-wheel steering actuator 24 according to the vehicle speed of the vehicle 12; the acquisition unit 28a for acquiring the driving operation input information of the vehicle 12; the correction unit 28c for correcting the control speed based on the driving operation input information; and the drive control unit 28d for driving the rear-wheel steering actuator 24 based on the correction result of the correction by the correction unit 28c switching between limiting the control speed and not limiting the control speed. According to this structure, for example, the control speed of the rear-wheel steering actuator 24 can be corrected according to the driving operation (driving operation input information) of the vehicle 12, and the switching between limiting the control speed and not limiting the control speed can be performed in a well-balanced manner (separate use). Therefore, the control that gives priority to the suppression of the working sound corresponding to the driving operation state and the control that gives priority to the performance can be performed in a well-balanced manner.

[0049] In addition, in the above-mentioned embodiment, the acquisition unit 28a may also acquire the steering speed information of the front wheel steering of the vehicle 12 or the acceleration / deceleration information of the vehicle 12 as the driving operation input information. According to this structure, it is possible to respond to the behavior changes such as sudden steering of the vehicle 12 or the behavior changes such as rapid acceleration and rapid deceleration of the vehicle 12, and it is possible to switch between limiting the control speed and not limiting the control speed in a well-balanced manner (separate use).

[0050] In addition, in the above-mentioned embodiment, the acquisition unit 28a may also acquire the acceleration / deceleration information of the vehicle 12 as the driving operation input information, and the correction unit 28c may also correct the control speed according to the acceleration / deceleration information. According to this structure, the operation sound suppression priority control that limits the control speed and the performance priority control that does not limit the control speed can be switched (used separately) in accordance with the behavior changes such as sudden acceleration and sudden deceleration of the vehicle 12, and the operation sound suppression priority control and the performance priority control that correspond to the driving operation state can be well balanced.

[0051] In addition, in the above-mentioned embodiment, the acquisition unit 28a may also acquire the steering direction information of the front wheel steering of the vehicle 12 as the driving operation input information, and the correction unit 28c may not limit the control speed when the steering direction information indicates the steering operation in the steering neutral direction, and limit the control speed when the steering direction information indicates the steering operation in the steering non-neutral direction. According to this structure, the switching (separate use) of limiting the control speed or not limiting the control speed in accordance with the change in behavior when the vehicle 12 returns from the turning state to the forward state can be performed in a well-balanced manner.

[0052] In the above embodiment, the acquisition unit 28a may acquire the reverse operation information indicating that the reverse operation of the front wheel steering of the vehicle 12 is performed at a predetermined speed or more as the driving operation input information, and the correction unit 28c may also, when the reverse operation information is acquired, set the control speed limit to the maximum before the target turning angle of the rear wheel 20 of the rear wheel steering is consistent with the actual turning angle of the rear wheel 20, and release the maximum control speed limit after the consistency. According to this structure, in the structure that corrects the control speed of the rear wheel steering actuator 24, when the meandering is performed, the deviation from the ideal driving route that may be caused by the delay of the yaw rate can be reduced.

[0053] In addition, the correction unit 28c may also perform setting of the control speed based on the driving operation input information through the first step and the second step. The first step compares the control speed set based on the vehicle speed of the vehicle 12 and through the mapping table that emphasizes the suppression of the working sound, and the control speed set based on the turning angle during driving, and adopts the larger control speed. The second step compares the control speed adopted in the first step with the control speed set based on the vehicle speed of the vehicle 12 and through the mapping table that emphasizes the performance, and adopts the smaller value to determine the control speed of the rear wheel steering actuator 24 based on the current driving operation input information of the vehicle 12. According to this structure, the appropriate control speed of the rear wheel steering actuator 24 can be appropriately determined.

[0054] In addition, Figure 4 In the example shown, the correction unit 28c generates a switching signal indicating the switching between the working sound suppression priority control and the performance priority control, and the drive control unit 28d performs the control switching process of the rear wheel steering actuator 24 based on the switching signal. In other embodiments, the drive control unit 28d may also obtain the correction result (correction content) from the correction unit 28c, for example, obtain the correction information required for the control switching obtained by referring to various control mapping tables stored in the storage unit 30. Moreover, the drive control unit 28d may also generate a control switching signal based on the obtained correction information, and decide whether to perform the control by the working sound suppression priority control or the performance priority control, and the same effect can be obtained.

[0055] In addition, Figure 1 In the embodiment, the rear wheel steering actuator 24 is constituted by the motor M and the planetary gear G, etc., but the structure of the rear wheel steering actuator 24 is not limited to this. For example, a structure combining the motor M and the belt can also be used to obtain the same effect.

[0056] Although the embodiments and variations of the present invention are described above, the embodiments and variations are merely examples and are not intended to limit the scope of the invention. The new embodiments and variations can be implemented in various forms, and various omissions, substitutions, and changes can be made without departing from the scope of the invention. The embodiments and variations are included in the scope and purpose of the invention, and are included in the invention described in the technical solution and its equivalent.

Claims

1. A rear wheel steering control device, characterized in that: have: A rear-wheel steering mechanism capable of setting a control speed of a rear-wheel steering actuator according to the vehicle speed; an acquisition unit that acquires the driving operation input information of the vehicle; a correction unit that corrects the control speed based on the driving operation input information; and The drive control unit drives the rear wheel steering actuator based on a correction result of the correction unit switching between limiting the control speed and not limiting the control speed.

2. The rear wheel steering device according to claim 1, characterized in that: The acquisition unit acquires steering speed information of a front wheel steering operation of the vehicle or acceleration / deceleration information of the vehicle as the driving operation input information.

3. The rear wheel steering device according to claim 1, characterized in that: The acquisition unit acquires steering speed information of a front wheel steering operation of the vehicle as the driving operation input information, The correction unit does not limit the control speed when the steering direction information indicates the steering in the steering neutral direction, and limits the control speed when the steering direction information indicates the steering in the steering non-neutral direction.

4. The rear wheel steering device according to claim 1, characterized in that: The acquisition unit acquires, as the driving operation input information, reverse operation information indicating that a reverse operation of the front wheel steering of the vehicle is performed at a speed greater than or equal to a predetermined speed, The correction unit sets the control speed limit to a maximum value until a target turning angle of the rear wheels based on the rear-wheel steering operation coincides with an actual turning angle of the rear wheels when the reverse operation information is acquired.

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