WO2016194885A1 - Rear wheel turning control apparatus - Google Patents

Abstract

In this rear wheel turning control apparatus which independently controls turning of left and right rear wheels of a vehicle: whether a driving limit value is exceeded or not is reliably detected; reliability of a means for preventing an actuator from driving beyond a driving allowable range is improved; unstable vehicle behavior due to unintended turning and driving of the rear wheels beyond the driving allowable range is avoided; and a system failure due to mechanical interference generated when a driving allowable limit is exceeded is avoided. The apparatus is configured by a pair of electronic control devices (13L), (13R). The electronic control devices (13L), (13R) include driving limit monitoring units (21) and motor control target value calculating units (22) that control actuators (14), (15) of steering devices on the basis of turning instruction values, respectively. The driving limit monitoring units (21) constantly monitor information of driving amounts obtained from rotational angle sensors (26L), (26R) and absolute position sensors (27L), (27R), and perform control for limiting the driving amounts of the rear wheels such that the driving amounts do not exceed the driving allowable range.

Description

Rear wheel steering control device Related applications

This application claims the priority of Japanese Patent Application No. 2015-114460 filed on June 5, 2015, and is incorporated herein by reference in its entirety.

The present invention relates to a rear wheel steering control device applied to a vehicle such as an automobile.

Conventionally, a rear wheel steering device that steers rear wheels in addition to front wheel steering is known for the purpose of achieving stable running performance of a vehicle. The control device for the rear wheel steering device has a built-in microcomputer, and determines the appropriate control amount of the steering angle and toe angle from the detected values of various sensor groups for constantly monitoring the state of the vehicle. The actuator is driven. The steering device is an important function that affects the running performance of the vehicle. When the abnormality occurs, it is desired to reliably detect the abnormality and maintain the safety performance.

As one of the abnormalities, there may be a case where control exceeding the limit value of the rear wheel turning angle determined by mechanical constraints (actuator stroke limit, etc.) occurs unintentionally. In the rear wheel turning, there is a limit value of the turning angle as described above, and the control range should naturally be limited to the range in which the turning is possible.

As an example of measures for monitoring a control limit relating to a vehicle rear wheel steering control device, for example, in Patent Document 1, the limit of the rear wheel steering angle is set based on the relative positional relationship between the wheel and the vehicle body while the vehicle is running. In order to control the size so as not to exceed the limit determination unit that determines the limit, the target value tabulated is compared with the target value of the rear wheel steering angle, and the target value The control limit corresponding to is not exceeded. In Patent Document 2, for example, a hardware limit switch is provided as an allowable limit value detecting means, and a pulse signal for driving the motor is forcibly cut by a maximum turning angle signal.

JP 2010-162929 A Japanese Patent Publication No. 4-53752

In the disclosed technique of Patent Document 1, a target value that does not exceed the control limit is calculated, but after the desired control is executed, that is, after the drive is started, an abnormality occurs in the system and the actuator runs away. In this case, there is a possibility that the rear wheel turning drive exceeding an unintended control limit is executed. Patent Document 1 does not describe a specific countermeasure.

In the disclosed technology of Patent Document 2, a hard limit switch is provided. However, if this hard switch fails, there is a possibility that the allowable limit may be exceeded by an erroneous allowable limit value detection signal. It develops into breakage due to mechanical interference.

An object of the present invention is to reliably detect whether or not a drive limit value is exceeded in a rear wheel steering control device that independently controls the left and right rear wheels of a vehicle, and drives an actuator outside a drive allowable range. To prevent the instability of vehicle behavior due to the steering of the rear wheels outside the unacceptable drive tolerance range, and the mechanical interference caused by exceeding the drive tolerance limit. It is to avoid damage.

Hereinafter, in order to facilitate understanding, the present invention will be described with reference to the reference numerals of the embodiments for convenience.

The rear wheel steering control device according to the present invention is a rear wheel steering control device 13 that controls a rear wheel steering device 12 that can control the steering angle and the toe angle of the rear wheels 10 and 11 of the vehicle 1. Consists of control devices 13L and 13R,
The rear wheel steering device 12 includes a pair of actuators 14 and 15 that independently steer the left and right rear wheels 10 and 11, and the pair of actuators 14 and 15 are motors 25L and 25R serving as driving sources, respectively. And absolute position detectors 27L and 27R capable of detecting the absolute positions of the rotation angle detectors 26L and 26R for detecting the rotation angles of the motors 25L and 25R and the steered output portions 56 of the pair of actuators 14 and 15. And
The pair of electronic control devices 13L and 13R are devices that control the corresponding actuators 14 and 15 according to the steering command value input from the higher-level control means 9, respectively (devices having this control as a basic function). The information on the driving amount obtained from the rotation angle detectors 26L and 26R or the absolute position detectors 27L and 27R is constantly monitored, and the driving amount of the rear wheels 10 and 11 is the limit value of the allowable driving range. A drive limit monitoring unit 21 that performs control to limit the drive limit value so as not to be exceeded is provided.

According to this configuration, the drive limit monitoring unit 21 always monitors the drive amount information obtained from the rotation angle detectors 26L and 26R or the absolute position detectors 27L and 27R. Using the monitored information on the driving amount, control is performed so that the driving amount of the rear wheels 10 and 11 does not exceed the driving limit value that is the limit value of the allowable driving range. In this case, since the rotation angle detectors 26L and 26R and the absolute position detectors 27L and 27R are provided, the detection information value of the normal detector can be used when the detector is abnormal. Further, since the rotation angle detectors 26L and 26R and the absolute position detectors 27L and 27R are detected at different locations, there is less possibility of abnormalities at the same time as compared with the case where the detectors are simply duplicated. Thus, since the control limit value monitoring function is made redundant, the detection reliability is improved.

By these, it is reliably detected whether or not the drive limit value is exceeded, and the reliability of the actuator drive prevention means outside the drive allowable range is enhanced, and by the rear wheel steering drive outside the unintended drive allowable range It is possible to avoid destabilization of vehicle behavior and avoid damage to the system due to mechanical interference that occurs when the drive allowable limit is exceeded.

In the present invention, the drive limit monitoring unit 21 determines that the drive amount of the rear wheels 10 and 11 is the drive when the steering command value output from the host control means 9 exceeds the drive limit value. You may make it have a control function which restrict | limits so that it may not exceed a limit value. The steering command value output from the host control means 9 may exceed the drive limit value due to various factors such as a means for generating a steering command value and an abnormality in the detection system for the generation. Therefore, even when the steering command value exceeds the drive limit value, it is possible to further improve safety by performing control to restrict the drive amount of the rear wheels 10 and 11 in advance so as not to exceed the drive limit value. It leads to.

In the present invention, the control for limiting the drive limit value by the drive limit monitoring unit 21 so as not to exceed the drive limit value may be a control for stopping the driving of the actuators 14 and 15. That is, control for stopping the rear wheel turning may be performed. When the drive limit value is exceeded, stopping the driving of the actuators 14 and 15 and stopping the rear wheel steering can more reliably prevent the actuators 14 and 15 from driving outside the drive limit value. Control is also simple. Since the rear wheel steering is an auxiliary function for improving the vehicle running performance together with the front wheel steering that is the main steering, the normal steering of the vehicle 1 is not hindered and can be stopped even if stopped. This is more reliable in avoiding instability of the vehicle behavior that occurs when the drive limit is exceeded.

In this case, the drive limit monitoring unit 21 has a function of notifying the other electronic control devices 13L and 13R of an abnormality when the monitored drive amount exceeds or exceeds the drive limit value. Then, the pair of electronic control units 13L and 13R stops the driving of the actuators 14 and 15 in response to the notification of the abnormality notified from the drive limit monitoring unit 21 of the counterpart electronic control units 13L and 13R. You may make it have the function to do. In the case of this configuration, when at least one of the left and right rear wheels 10 and 11 tries to perform an operation exceeding the allowable drive range, this is detected and the driving of the actuators 14 and 15 is stopped. For safety reasons, it is more preferable to stop the turning of both the rear wheels 10 and 11 as well as the rear wheels 10 and 11 that perform the operation exceeding the allowable drive range.

The rear wheel steering control device according to the present invention includes a detection system failure determination unit 24 that detects an abnormality in the rotation angle detectors 26L and 26R and the absolute position detectors 27L and 27R, and the drive limit monitoring unit 21 includes: When no abnormality is detected by the detection system failure determination unit 24, the drive amount output by the arbitrarily determined detector of the rotation angle detectors 26L and 26R and the absolute position detectors 27L and 27R is output. Information is monitored, and when an abnormality is detected by the detection system failure determination unit 24, the detector of the rotation angle detectors 26L and 26R and the absolute position detectors 27L and 27R that has not detected an abnormality. The drive amount information output by the may be monitored. Thereby, it is possible to always perform control to limit the drive limit value so as not to exceed the drive limit value by using the drive amount information output by the detector without abnormality, and the redundant function can be effectively exhibited.

Any combination of at least two configurations disclosed in the claims and / or the specification and / or the drawings is included in the present invention. In particular, any combination of two or more of each claim in the claims is included in the invention.

The present invention will be understood more clearly from the following description of preferred embodiments with reference to the accompanying drawings. However, the embodiments and drawings are for illustration and description only and should not be used to define the scope of the present invention. The scope of the invention is defined by the appended claims. In the accompanying drawings, the same reference numerals in a plurality of drawings indicate the same or corresponding parts.

It is a schematic explanatory drawing of the motor vehicle carrying the rear-wheel steering apparatus which applies the rear-wheel steering control apparatus which concerns on one Embodiment of this invention. It is a block diagram which shows the conceptual structure of the rear-wheel steering control apparatus. It is a block diagram of a conceptual structure which shows the details of the drive limit monitoring part etc. in the rear-wheel steering control apparatus. It is a fracture front view showing an example of the rear wheel steering device. It is sectional drawing which expands and shows a part of FIG.

An embodiment of the present invention will be described with reference to the drawings. FIG. 1 is a schematic explanatory diagram of an automobile which is a vehicle equipped with a rear wheel steering device to which a rear wheel steering control device according to this embodiment is applied. The left and right front wheels 2 and 3 of the automobile 1 are steered left and right by transmitting the steering angle of the steering wheel 4 to a front wheel steering device 5 which is a main steering device made of, for example, a rack and pinion. The outputs of the steering angle sensor 6, the vehicle speed sensor 7, and the yaw rate sensor 8 provided with respect to the steering shaft of the steering wheel 4 are input to the electronic control unit 9. The electronic control unit 9 is a main control means that performs overall cooperative control, overall control, and the like of the automobile 1, and is generally abbreviated as ECU or VCU.

The left and right rear wheels 10 and 11 are steered by a rear wheel steering device 12 fixed to a chassis (vehicle body) via knuckle arms Na and Nb corresponding to the tie rods connected to the rear wheel steering device 12. The The rear wheel steering device 12 can steer the left and right rear wheels 10 and 11 independently by a pair of steering motors 25L and 25R. Regarding the turning angles of the rear wheels 10 and 11, the target turning angles determined by the electronic control unit 9 according to the input of the travel information of the automobile 1, such as the steering angle sensor 6, the vehicle speed sensor 7, and the yaw rate sensor 8, are used. The rear wheel steering control device 13 receives the left and right rear wheels 10 and 11 independently of each other by the rear wheel steering control device 13.

The rear wheel turning device 12 is provided with driving means for turning the rear wheels 10 and 11 in the same phase and in the opposite phase with respect to the front wheel turning angle. This drive means is a pair of linear motion actuators composed of, for example, a slide screw or a ball screw, and a nut screwed to these is rotated by each motor 25 (25L, 25R) via a speed reducer, It is converted to the linear motion of the actuator. This linear actuator is composed of a first actuator 14 and a second actuator 15 in order to drive the left and right rear wheels 10 and 11 independently. The first actuator 14 is drive means for turning the left rear wheel 10, and the second actuator 15 is drive means for turning the right rear wheel 11. Specific examples of the first and second actuators 14 and 15 will be described later with reference to FIGS.

FIG. 2 is a block diagram of a conceptual configuration of the rear wheel steering control device 13 that controls the rear wheel steering device 12 (FIG. 1) having the above-described configuration. The rear wheel steering control device 13 includes a pair of electronic control devices 13L and 13R that independently control the first and second actuators 14 and 15 that steer the left and right rear wheels 10 and 11 (FIG. 1), respectively. The electronic control devices 13L and 13R have the same control configuration. As for the motor 25L, the rotation angle detector 26L, and the absolute position detector 27L, which are components of the first actuator 14, the second actuator 15 also has similar components (such as a motor 25R). The electronic control device 13L is connected to the actuator 14, and the electronic control device 13R is connected to the actuator 15.

Therefore, the first actuator 14 and its electronic control device 13L will be described with reference numerals attached to the components, and the second actuator 15 and each component of the electronic control device 13R will not be shown. Thereafter, in order to describe the rear wheel steering control device 13, the electronic control device 13L and the first actuator 14 are used in principle.

The electronic control device 13L of the first actuator 14 includes a microprocessor 16, a command-side input signal input interface unit 17 obtained from the electronic control unit 9 which is a higher-level control means, and a detection side obtained from the first actuator 14. The input interface unit 18 for the input signal, the output interface unit 19, and the motor drive unit 20 are included. The command-side and detection-side input interface units 17 and 18 may be separate electronic elements, or may be bundled in one electronic element.

The target value of the rear wheel turning angle determined by the electronic control unit 9 (the target turning angle) is transmitted to the microprocessor 16 via the input interface unit 17 on the command side, and further described later in the microprocessor 16. It is transmitted to the motor control target value calculation unit 22 via the limit monitoring unit 21.

In the microprocessor 16, in order to execute the control of the steering motor 25L, a motor based on the result calculated by the motor control target value calculation unit 22 (in this embodiment, the number of rotations of the motor 25L calculated from the steering angle). A drive command has a semiconductor switch bridge or the like via a command value control unit 28 and an output interface unit 19, which will be described later, and receives a gate signal command or the like to drive the motor 25L (25R). Is transmitted to the motor drive unit 20 that outputs a signal (referred to as a motor drive signal). The motor control target value calculation unit 22 specifically includes a predetermined conversion function stored in an LUT (Look Up Table) realized by software or hardware, or a software library (Library), and the like. Using equivalent hardware or the like (hereinafter referred to as “embodiment model”), the target turning angle via the drive limit monitoring unit 21, information from the mutual monitoring unit 23 described later, and a detection system failure determination unit 24. In response to the input of the detection result of the above, it is constituted by a hardware circuit or a software function on a processor (not shown) that can calculate and output the motor drive command.

When, for example, a brushless motor is used as the steering motor 25L, the basic control is torque (current), speed, and position control, and the control target of the system of this embodiment is the position (steering angle). A control system (not shown) mounted on the processor 16 is a composite control system that constitutes a speed control system and a position control system above the current control system. Therefore, the motor drive command value is calculated based on a calculation result calculated by a command from the electronic control unit 9 and a target steering angle such as the target steering angle based on a feedback value such as a motor current detection value or a rotation angle detection value. Is controlled to reach

The absolute position detector 27L monitors the absolute position of the first actuator 14, that is, the absolute position of the steering output unit. The steering output unit is, for example, a linearly moving rod 56 connected to the knuckle arms Na and Nb (FIG. 1), and detects the absolute position of the advance / retreat position as the absolute position of the actuator 14. The absolute position is detected when the power is turned on, for example, when the ignition (not shown) of the vehicle is turned on, and the subsequent control is the rotation obtained from the rotation angle detector 26L based on the detected absolute position. Position control is performed at the corner. These control systems are mounted on the microprocessor 16 so as to perform control by, for example, software calculation.

Here, problems in this embodiment and countermeasures will be described. The problem is that a motor 25L serving as a drive source for the actuators 14 and 15 that steer the rear wheels 10 and 11 is input by the steering command value that is the target turning angle from the electronic control unit 9 that is the host control means. When driving the 25R, avoiding instability of vehicle behavior due to unintentional driving of the rear wheels outside the allowable driving range, and mechanical interference caused by exceeding the driving limit It is to avoid damage.

I will explain this measure. In this embodiment, in order to solve this problem, the microprocessor 16 includes a drive limit monitoring unit 21, a mutual monitoring unit 23, a detection system failure determination unit 24, and a command value control unit 28. Explain the role of each.

<About the drive limit monitoring unit 21>
The drive limit monitoring unit 21 immediately detects an unintended drive outside the allowable drive range. The drive limit monitoring unit 21 constantly monitors the drive amount information obtained from the rotation angle detector 26L or the absolute position detector 27L, and the drive limit where the drive amount of the rear wheel 10 is the limit value of the drive allowable range. Control to limit so as not to exceed the value.

FIG. 3 shows a detailed conceptual diagram of the drive limit monitoring unit 21 and the like. Since the drive allowable range is determined by design, the drive limit value that is the limit of the drive allowable range is stored in advance in the limit value storage unit 21a. This value may be variable according to the behavior of the vehicle. The steered command value θin output from the electronic control unit 9 which is the host control means is input to the command value comparison unit 21b and compared with the drive limit value stored in the limit value storage unit 21a. At this time, when the steering command value θin exceeds the drive limit value, it is diagnosed that the command value is abnormal, and control is performed so that the drive amount of the rear wheel 10 does not exceed the drive limit value. The steering execution itself is canceled in advance. For example, the steering command value θin is not input to the motor control target value calculation unit 22 (details of the cancellation process are omitted).

When the steering command value θin does not exceed the drive limit value (that is, the command value within the normal range), the steering command value θin is input to the motor control target value calculation unit 22 and motor control is executed. .

In order to monitor that the driving limit value is exceeded due to unintentional driving (malfunction or the like) that occurs after the motor control is executed, the driving value comparison unit 21c selects from the selection unit 24c of the detection system failure determination unit 24 The absolute position information generated from the rotation angle detection signal R0 of the rotation angle detector 26L or the absolute position information P0 obtained from the absolute position detector 27L and the drive limit value (or the corresponding threshold value) ) Is always compared.

The absolute position information generated from the rotation angle detection signal R0 of the rotation angle detector 26L and the absolute position information P0 obtained from the absolute position detector 27L are compared with the drive limit value based on the result of the detection system failure determination unit 24. One of them is selected for the purpose, but when the detection system is normal, either one may be selected. The role of the detection system failure determination unit 24 will be described later.

Here, the drive value comparison unit 21 compares the current absolute position information P0 with the limit value storage unit 21a, and the absolute position information P0 is larger than the drive limit value stored in the limit value storage unit 21a. In this case, the detection signal ENB is immediately invalidated (that is, the detection signal ENB for limiting the command value output from the command value control unit 28 is output). This detection signal ENB is input to the command value control unit 28. In this way, the drive value comparison unit 21 specifically uses a hardware circuit or a software on a processor (not shown) that can perform the same operation as described above and output the result using the above-described implementation model. It consists of functions.

<Regarding the command value control unit 28>
The command value control unit 28 limits the command value based on the detection signal ENB. Specifically, the command value control unit 28 outputs a command value if the absolute position information from the absolute position information P0 or the like exceeds the drive limit value stored in the limit value storage unit 21a. For example, a command to immediately stop the output of the motor drive signal is output. The command value control unit 28 can be realized by, for example, an analog signal switch, a digital signal switch, or a three-state buffer.

<About the mutual monitoring unit 23>
The mutual monitoring unit 23 shown in FIG. 2 monitors, for example, the abnormal state of the microprocessor 16 or the runaway of the software based on the coincidence / mismatch of the comparison results of the respective control targets. When an abnormality occurs in the control device 13L (13R) (indicating an abnormality on the system side that is different from the “abnormality due to drive limit” which is the focus in this embodiment) (even if the sign is detected before the abnormality occurs) The information is transmitted to the other electronic control unit 13R (13L) via the communication means 30. The mutual monitoring unit 23 may further have a self-diagnosis function of each electronic control device 13L, 13R.

In addition, the mutual monitoring unit 23 also monitors the “abnormality exceeding the drive limit value” detected by the drive limit monitoring unit 21 and the detection system abnormality determined by the detection system failure determination unit 24. If detected, information is transmitted to the other control device via the communication means 30. The other electronic control unit 13R (13L) performs a measure (not shown) such as interrupting the control or stopping the motor driving force according to the type or degree of the abnormal state based on the transmitted information. )). Specifically, the mutual monitoring unit 23 has a storage unit for storing the above information, and uses the comparison function or equivalent hardware to transmit the information to the other control device when the abnormality is detected. It consists of a hardware function that can be transmitted or a software function on a processor (not shown). Further, the mutual monitoring unit 23 is specifically configured by a software function on a hardware circuit or a processor (not shown) that can perform the same operation as described above using the above-described implementation model and output the result. Has been.

<About the detection system failure determination unit 24>
It is necessary to refer to signals of position detection systems (rotation angle detectors 26L and 26R, absolute position detectors 27L and 27R, etc.) in order to prevent unintentional driving outside the drive limit range. If so, correct diagnosis is impossible. Therefore, the abnormality is determined by the detection system failure determination unit 24. Even if an abnormality occurs in at least one absolute position detection system of the rotation angle detection information R0 of the rotation angle detector 26L or the absolute position information P0 of the absolute position detector 27L, it is normal if control is possible for the time being. By using absolute position information (absolute position information P0 or absolute position information generated from the rotation angle detection signal R0 from the rotation angle detector 26L) obtained from the other position detection system, it is outside the unintended drive limit range. It becomes possible to monitor the drive to the. Therefore, the absolute position information to be monitored is duplicated, and the detection reliability can be improved. In the case where no abnormality is detected by the detection system failure determination unit 24, the drive limit monitoring unit 21 is a detector that is arbitrarily selected from the rotation angle detectors 26L and 26R and the absolute position detectors 27L and 27R. Monitors the drive amount information output by the.

An abnormality in the position detection system is performed by the abnormality detection unit 24a shown in FIG. Although various methods can be adopted as a failure diagnosis method by the detection system failure determination unit 24, the absolute position information P0 of the absolute position detector 27L and the rotation angle detection information R0 of the rotation angle detector 26L with respect to the steering command value θin. Is information on the position of a predetermined portion of the rear wheel steering device 12 (see FIG. 1) and the rotational position of the steering motor 25L (see FIG. 1), which is a drive source that changes the position, and therefore has a certain relationship. is there. Therefore, the relationship is examined by a test or simulation and set in a table (not shown) or the like, and the absolute position information P0 of the absolute position detector 27L and the rotation of the rotation angle detector 26L with respect to the turning command value θin. If the relationship of the angle detection information R0 is out of the range set in the table until the allowable value is exceeded, it is determined that the output system exceeding the allowable value is abnormal. As a result, it is possible to detect an abnormality in the rotation angle detector 26L and the absolute position detector 27L. Note that the detection system failure determination unit 24 specifically includes a hardware circuit or a hardware circuit that can perform an operation in the same manner as described above using the above-described realization model or a comparison function or hardware equivalent thereto, and output the result. It is composed of software functions on a processor (not shown).

In the above embodiment, the absolute position detection system has been described as an example of an absolute position detector having an output of only one system. However, in order to further improve system redundancy and detection reliability, the absolute position detector 27L A redundant output in which the absolute position information P0 is reversed in the forward and reverse directions may be provided. Thus, when an abnormality is detected in the output of at least one of the two absolute position information of the absolute pair position detector 27L, the other is normal, so the absolute position signal is used for the purpose of detecting the absolute position when the power is turned on. In the case of limited use, the immediate control can be continued. For this purpose, as another example, two detectors (absolute value detectors, rotation angle detectors) can be mounted and duplicated.

Incidentally, since the rotation angle detection information R0 of the rotation angle detector 26L becomes rotation angle information, it is converted into absolute position information by the position information conversion unit 24b. The conversion method can convert the rotation angle into the absolute position information from the absolute position information obtained from the absolute position detector 27L when the power is turned on, for example, when the ignition (not shown) of the vehicle is turned on. . For example, when a resolver is used for the rotation angle detector 26L, the two-phase pulse signal output from the resolver RD converter (not shown in FIG. 2) is used as position information used for motor position control in the microprocessor 16. This is realized by counting up and down.

With the above functions, whether or not the drive limit value is exceeded is reliably detected, the reliability of the actuator drive prevention means outside the drive allowable range is improved, and the rear wheels are steered outside the unintended drive allowable range. The effect of avoiding destabilization of vehicle behavior due to driving and avoiding damage to the system due to mechanical interference that occurs when the drive allowable limit is exceeded can be satisfactorily realized.

Next, with reference to FIGS. 4 and 5, a specific configuration example of the steering device 12 to be controlled will be described. As shown in FIG. 4, the actuators 14 and 15 have the same mechanical configuration and are substantially symmetrical with respect to the center line XX of the rear wheel steering device 12. 14 is used to explain the structure. In addition, although L is attached to the reference numerals of the respective components of the first actuator 14 and R is added to the reference numerals of the respective components of the second actuator 15, it is necessary to distinguish between them when they are collectively referred to or when the left and right are clearly distinguished. When there is no symbol, R and L are omitted (reference numerals 56 to 89).

The first actuator 14 includes a rod 56 serving as a steering output portion of the actuator 14, a trapezoidal screw 58, a thrust bearing mechanism 59, a radial bearing 60, a speed reducer 64, and a motor 25. In the trapezoidal screw 58, a female screw 56 a formed on the inner diameter portion of the rod 56 and a male screw 57 a formed on one end portion of the shaft 57 are screwed together. The thrust bearing mechanism 59 rotatably supports the shaft 57 and restrains the movement in the thrust direction. The radial bearing 60 rotatably supports the shaft 57 in the radial direction.

The speed reducer 64 has a planetary gear 62 that is rotatably supported by a pin 61 on the side surface of the flange 57b of the shaft 57 as a carrier of the planetary gear mechanism, and an internal gear 63 that meshes with the planetary gear 62. The motor 25 has a hollow motor shaft 65 formed with a sun gear 65 a of the speed reducer 64 at its tip, and a stator 66. The trapezoidal screw 58, the speed reducer 64, and the motor 25 are all arranged on the same axis as the rod 56. A magnet 68 having N and S magnetized alternately is fixed to a part of the hollow motor shaft 65. The hollow motor shaft 65 is supported on the housing 72 by a bearing 89. The shaft 57 is supported on the rod 56 by a sliding bearing 88.

The rod 56 is supported by the sliding bearing 87 at the end of the housing 72 and is restricted in rotation by the rotation prevention mechanism 69, and can only move in the axial direction. The rotation prevention mechanism 69 has a configuration in which a tip 71 a of a columnar stopper 71 supported by a bearing 70 is inserted into a long hole 56 b formed in the rod 56. The bearing 70 is fixed to the housing 72, and when the rod 56 moves in the axial direction, the tip 71a of the stopper 71 moves along the elongated hole 56b, and functions as a rotation limiter and a mechanical limit for the rod 56. Limit the range of movement.

A rotation angle detector 26 for detecting the rotation angle is fixed to the motor 25. The rotation angle detector 26 is, for example, a resolver. A resolver rotor 73a is fixed to one end of the hollow motor shaft 65, and a resolver stator 73b is fixed to a housing 72 facing the rotor 73a. Both ends of the hollow motor shaft 65 are rotatably supported by bearings, and a rod 56 is inserted into the hollow hole 65b of the hollow motor shaft 65. Since the trapezoidal screw 58 is disposed inside the hollow hole 65b, the axial length of the rear wheel steering device 12 can be shortened.

When the motor 25 is rotated, the male screw 57a formed at the end of the shaft 57 is decelerated by the speed reducer 64, and the rod 56 moves to the left and right according to the amount of rotation, and is fixed to the tip of the rod 56. The knuckle arm Na (FIG. 1) is moved through the outer ball joint to adjust the toe angle of the rear wheel 10 (FIG. 1).

The turning angle of the rear wheel 10 (FIG. 1) is grasped by detecting the absolute position of the rod 56 with the absolute position detector 27. The detection information is input to the rear wheel steering control device 13 (FIG. 1). The absolute position detector 27 is, for example, a magnetic detector using an analog output Hall IC 75 and a magnet 76. A magnet 76 is fixed in a holder 77 fixed to the rod 56, and a Hall IC 75 is fixed to the housing 72 facing the magnet 76.

The absolute position detector 27 detects the absolute position of the rod 56 by converting a magnetic flux change applied to the Hall IC 75 into a position output. If a programmable IC is used as the Hall IC 75, the absolute position accuracy can be improved by programming the relationship between the position of the rod 16 and the magnetic flux density in advance.

The thrust bearing mechanism 59 will be described with reference to FIG. 5 in which the vicinity of the center line XX in FIG. 4 is enlarged. A connecting shaft 78L, a thrust bearing 79, a race ring 80, and a spacer 81 are inserted into the inner diameter portion 57c formed on the end surface of the shaft 57, respectively. A flange 78a for receiving a thrust force is formed on the connecting shaft 78L. The thrust bearing 79 is provided with a cage and is provided on both sides of the flange 78a. The bearing ring 80 becomes a rolling surface of the thrust bearing 79.

A ring plate 82 and a pressing plate 83 are disposed on the side surface 57d adjacent to the inner diameter portion 57c, and the pressing plate 83 is pressed against the side surface 57d of the shaft 57 by a bolt 84, so that a preload is applied to the thrust bearing 79. By disposing the thrust bearing mechanism 59 inside the shaft 57, the length in the axial direction can be shortened.

A female thread 78Lb is formed on one end face of the connecting shaft 78L on the first actuator 14 side. A male screw 78Ra is formed at one end of the second actuator 15 side. The female screw 78 </ b> Lb and the male screw 78 </ b> Ra are screwed together through a hole 85 b formed in the central wall 85 a of the housing 85, and the connecting shafts 78 </ b> L and 78 </ b> R are fixed to the housing 85. Note that a radial bearing 86 is inserted between the housing 85 and the cylindrical outer diameter portion 57e of the shaft 57 in order to suppress radial deflection of the shaft 57. As the radial bearing 86, for example, a needle roller bearing with an outer ring is used.

The housings 72 (L) and 72 (R) and the housing 85 are connected to form one housing, in which the first and second actuators 14 and 15 are incorporated. As shown in FIG. 4, when the rod 56L of the first actuator 14 is moved left and right, the left rear wheel 10 (FIG. 1) connected to the rod 56L is steered and the toe angle is adjusted. When the rod 56R of the second actuator 15 is moved, the right rear wheel 11 (FIG. 1) connected to the rod 56R is steered and the toe angle is adjusted. While the rear wheel steering device 12 is fixed to the chassis (vehicle body), the left and right rear wheels 10, 11 (FIG. 1) can be steered independently.

As shown in FIG. 5, the connecting shaft 78 </ b> L of the first actuator 14 and the connecting shaft 78 </ b> R of the second actuator 15 are screwed together via the central wall 85 a of the housing 85. Since the load applied to the shaft 57L (FIG. 4) of the second actuator 15 and the shaft 57R (FIG. 4) of the second actuator 15 is equally applied to the central wall 85a of the housing 85, the balance between the left and right rear wheels 10, 11 (FIG. 1) is achieved. Can be secured. Here, the housings 72L, 72R, and 85 are divided into three parts, but those integrated by screw fastening are referred to as one housing.

As mentioned above, although the suitable form for implementing this invention based on embodiment was demonstrated referring drawings, embodiment disclosed this time is an illustration and restrictive at no points. The scope of the present invention is shown not by the above description but by the claims. Those skilled in the art will readily appreciate various changes and modifications within the obvious scope upon reviewing this specification. Therefore, such changes and modifications should be construed as being within the scope of the invention defined by the claims or within the scope equivalent thereto.

1 ... Automobile (vehicle)
9 ... Electronic control unit (upper control means)
DESCRIPTION OF SYMBOLS 10, 11 ... Rear wheel 12 ... Rear wheel steering device 13 ... Rear wheel steering control device 13L, 13R ... Electronic control device 14, 15 ... Actuator 16 ... Microprocessor 24 ... Detection system failure judgment part 36 ... Drive limit monitoring part 25L, 25R ... motor 26L, 26R ... rotation angle detector 27L, 27R ... absolute position detector 56 ... rod (steering output section)

Claims (5)

1. A rear wheel steering control device for controlling a rear wheel steering device capable of controlling a steering angle and a toe angle of a rear wheel of a vehicle, comprising a pair of electronic control devices,
   The rear wheel steering device includes a pair of actuators that independently steer left and right rear wheels, and each of the pair of actuators includes a motor serving as a drive source and a rotation angle detection that detects a rotation angle of the motor. And an absolute position detector capable of detecting the absolute position of the steering output portion of the pair of actuators,
   Each of the pair of electronic control devices is a device that controls the corresponding actuator according to a steering command value input from a higher-level control unit, and is obtained from the rotation angle detector or the absolute position detector. A rear wheel steering control device having a drive limit monitoring unit that constantly monitors information on a drive amount and performs control to limit the drive amount of the rear wheels so as not to exceed a drive limit value that is a limit value of a drive allowable range.
2. 2. The rear wheel steering control device according to claim 1, wherein the drive limit monitoring unit drives the rear wheel when the steering command value output from the host control unit exceeds the drive limit value. A rear wheel steering control device having a control function for limiting the amount so as not to exceed the drive limit value.
3. The rear wheel steering control device according to claim 1 or 2, wherein the control for limiting the driving limit value so as not to exceed the driving limit value by the driving limit monitoring unit is control for stopping driving of the actuator. Control device.
4. 4. The rear wheel steering control device according to claim 3, wherein when the monitored drive amount exceeds or exceeds the drive limit value, the drive limit monitoring unit causes an abnormality in the other electronic control device. The pair of electronic control units has a function of stopping the driving of the actuator in response to the notification of the abnormality notified from the drive limit monitoring unit of the counterpart electronic control unit. Wheel steering control device.
5. 5. The rear wheel steering control device according to claim 1, further comprising a detection system failure determination unit that detects an abnormality in the rotation angle detector and the absolute position detector, and the drive limit. When no abnormality is detected by the detection system failure determination unit, the monitoring unit monitors information on a driving amount output by an arbitrarily determined one of the rotation angle detector and the absolute position detector. When an abnormality is detected by the detection system failure determination unit, the information on the driving amount output by the detector of which the abnormality is not detected among the rotation angle detector and the absolute position detector is monitored. Rear wheel steering control device.

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