JP2007326499A - Steering device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a steering device accomplishing enhancement of steering accuracy while allowing it to be a multiple system. <P>SOLUTION: The steering device is provided with first and second actuators 5, 6 for giving steering torque, and the first actuator 5 and the second actuator 6 are mechanically connected by a connection means 19 in the play-giving state. Since the first and second actuators 5, 6 are connected with the play, interference of the steering torque of the first actuator and the steering torque of the second actuator 6 is prevented. Further, the second actuator 6 is arranged in a downstream side than the first actuator 5 in a steering force transmission route and the steering torque of the second actuator is made smaller than the steering torque of the first actuator 5. A small steering angle can be controlled by the second actuator 6 at high accuracy and the steering accuracy can be enhanced. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a steering apparatus.

  For example, as a next-generation transportation system, a vehicle (for example, a bus) that is automatically steered on a dedicated road in which a magnetic marker is embedded and steered by a driver on a general road has been proposed. In such a vehicle steering apparatus, two actuators for applying steering torque to the steered wheels are provided, one of the actuators is always used, and the other actuator is on standby.

Conventionally, as a vehicle steering apparatus, a main actuator and a subactuator linked via a link mechanism having play are provided, and the main actuator and the subactuator are always driven by the same control. (For example, refer to Patent Document 1).
JP 2002-37112 A

  However, in the prior art described in Patent Document 1, the main actuator and the sub-actuator are controlled in the same manner and move in the same manner, so there is no merit in improving the steering accuracy. Further, even in the above-described steering apparatus, there is no merit in improving the steering accuracy despite the fact that the other actuator is for fail-safe and is constituted by a multiple system.

  The present invention has been made to solve such a problem, and an object of the present invention is to provide a steering device that improves the steering accuracy while using a multiple system.

  A steering apparatus according to the present invention includes a first actuator that has a steering shaft connected to a steering gear and is provided in a steering force transmission path that transmits a steering force to a steered wheel, and that applies a steering torque to the steering shaft; In the transmission path, the second actuator, which is disposed downstream of the first actuator and applies steering torque to the steering shaft, and the first actuator and the second actuator are mechanically connected with play. And a steering torque by the second actuator is smaller than a steering torque by the first actuator.

  According to such a steering apparatus, the first actuator and the second actuator for applying the steering torque are provided, and the first actuator and the second actuator are mechanically connected with play. Connected by connecting means. Since the first actuator and the second actuator are connected with play, the steering torque by the first actuator and the steering torque by the second actuator are prevented from interfering with each other. In addition, the second actuator is arranged downstream of the first actuator in the steering force transmission path, and the steering torque by the second actuator is made smaller than the steering torque by the first actuator. Thus, the large steering angle can be controlled by the first actuator, the small steering angle can be controlled with high accuracy by the second actuator, and the steering accuracy can be improved.

  Here, it is preferable that the first actuator is feedforward-controlled and the second actuator is feedback-controlled. In order to further improve the steering accuracy, the first actuator having a large steering torque is feedforward controlled, and the second actuator having a small steering torque is feedback-controlled. Thereby, it is possible to accurately control the actual rudder angle to be the target rudder angle by the second actuator.

  Further, it is preferable that a steering handle disposed upstream of the first actuator in the steering force transmission path is provided, and the control angle by the second actuator is within the range of play of the connecting means. As a result, it is possible to perform the steering control without changing the steering angle at the steering wheel, and to reduce the driver's anxiety that the steering wheel moves naturally.

  In addition, the steering force transmission path includes a physical quantity detection unit that is disposed closer to the steered wheels than the connection unit and detects a physical quantity related to steering control. Based on the physical quantity detected by the physical quantity detection unit, steering by the second actuator is performed. It is preferable to control the torque and cancel backlash in the steering force transmission path. By canceling the backlash in the steering gear, the steering angle change of the steering wheel can be eliminated, and the steering angle can be accurately detected. Examples of the “physical quantity detection means for detecting a physical quantity related to steering control” include a steering angle detection means (for example, a steering angle sensor) that detects a steering angle.

  In addition, it is preferable that a traveling state detection unit that detects a traveling state of the vehicle is provided, and the steering torque by the second actuator is controlled based on the traveling state detected by the traveling state detection unit. Thereby, the steering angle change of the steering wheel can be eliminated, and the steered wheels can be steered according to the traveling state.

  Moreover, it is preferable that a driving state detection means detects the pitching state of a vehicle or the skid state of a vehicle as a driving state.

  Further, a reduction ratio variable means capable of changing a reduction ratio of the second actuator is provided, and the reduction ratio variable means increases the reduction ratio of the second actuator when the first actuator is abnormal. Is preferred. As a result, when the first actuator is abnormal, the reduction torque of the second actuator is increased by the reduction ratio variable means to increase the steering torque by the second actuator, and the first actuator is not used. In addition, the steered wheels can be steered at a large angle by the steering torque by the second actuator. In this way, the second actuator can have a fail-safe function. It should be noted that the “actuator abnormality” includes a case where the actuator fails and does not operate normally, and a case where the controller that controls the actuator fails and the actuator does not operate normally.

  The reduction ratio variable means includes elastic energy storage means for storing elastic energy, and releases the elastic energy stored in the elastic energy storage means when the temperature of the second actuator exceeds a predetermined reference. It is preferable to increase the reduction ratio of the second actuator. When the first actuator is abnormal, the steering torque of the second actuator increases, the load of the second actuator increases, and the amount of heat generated by the second actuator increases. It is possible to detect the abnormality of the first actuator. As a result, even if the controller is abnormal and the first actuator becomes abnormal, the first actuator is abnormal when the temperature of the second actuator exceeds a predetermined reference. It can be detected, and the elastic energy stored in the elastic energy storage means is used to change and reduce the reduction ratio of the second actuator. In this manner, the reduction ratio of the second actuator is mechanically increased to increase the steering torque by the second actuator, and the steered wheels are driven by the steering torque by the second actuator without using the first actuator. Can be steered at a large angle, and the second actuator can have a fail-safe function. Here, the “predetermined reference” refers to a temperature at which it can be detected that the first actuator is abnormal.

  The variable reduction ratio means includes clutch means that engages when the steering torque by the second actuator increases, and switches from a power transmission path that does not pass the clutch means to a power transmission path that passes through the clutch means. The reduction ratio of the actuator 2 may be increased. Even if comprised in this way, even if it is a case where abnormality arises in a control part and the 1st actuator becomes abnormal, it can detect that the 1st actuator is abnormal, mechanically The steered wheel can be steered at a large steering angle by the steering torque by the second actuator without using the first actuator by increasing the steering torque by the second actuator. In this way, the second actuator can have a fail-safe function.

  Further, it is preferable to perform control for decelerating the vehicle when the reduction ratio of the second actuator is increased. In order to cope with a response delay due to a reduction in the reduction ratio, the vehicle is decelerated to facilitate steering, and the vehicle travels safely. When the vehicle is decelerated, for example, the target speed is set low.

  According to the steering apparatus of the present invention, the first actuator and the second actuator are provided and a multi-system is provided, and torque interference between the steering torque by the first actuator and the steering torque by the second actuator is prevented and the steering accuracy is improved. Can be improved.

  Hereinafter, as preferred embodiments of a steering apparatus according to the present invention, three embodiments having different configurations of sub-actuators (described in detail later) will be described with reference to the drawings. In the description of the drawings, the same or corresponding elements are denoted by the same reference numerals, and redundant description is omitted.

  First, the steering apparatus of 1st Embodiment is demonstrated, referring FIGS. 1-11. 1 is a schematic side view showing a vehicle equipped with a steering apparatus according to an embodiment of the present invention, FIG. 2 is a schematic plan view of the vehicle shown in FIG. 1, and FIG. 3 is a front axle, a kingpin in FIG. It is an enlarged view which shows an actual steering angle sensor from back side.

  The vehicle 1 shown in FIGS. 1 and 2 is used as, for example, a route bus, and is automatically steered (automatically controlled driving) on a dedicated road in which a magnetic marker is embedded, and steered by a driver (manual driving) on a general road. ). A steering device 2 of the vehicle 1 includes a main actuator (first actuator) that applies a steering torque to a steering force transmission path that transmits a steering force of a steering handle (hereinafter referred to as “handle”) 3 to a steered wheel 4. 5 and a secondary actuator (second actuator) 6. The steering device 2 is provided with a steering electronic control unit (hereinafter referred to as “steering ECU”) 7 for controlling the main actuator 5 and the sub-actuator 6 (see FIG. 6).

  The handle 3 is connected to a power steering gear box (hereinafter referred to as “steering gear”) 9 via a steering shaft 8. The steering gear 9 is a hydraulic power steering mechanism that applies a steering assist torque, and is fixed to the vehicle body frame 10. Further, a pitman arm 11, a drag link 12, and a knuckle arm 13 are connected to the steering gear 9. The rotational motion of the steering shaft 8 is converted into a linear motion by the steering gear 9 and the pitman arm 11, and the drag ring 12 is moved. And transmitted to the knuckle arm 13. The knuckle arm 13 is provided at the right end of the front axle 14.

  As shown in FIGS. 1 to 3, the steered wheels 4 are supported so as to be rotatable in the horizontal direction via king pins 15 installed at both ends of the front axle 14. The left and right steered wheels 4 are linked via a knuckle arm 13 and a tie rod 16. The front axle 14 is connected to the vehicle body frame 10 via a suspension having an air spring 17. The king pin 15 is provided with an actual rudder angle sensor 18 that detects the rotation angle of the king pin 15. The actual steering angle sensor 18 can detect the steering angle (cutting angle) of the steered wheels 4.

  Here, the steering device 1 of the present embodiment includes the main actuator 5 and the sub-actuator 6 as described above, and a rubber coupling (connecting means) 19 is provided between the main actuator 5 and the sub-actuator 6. Is arranged. That is, the steering wheel 3, the main actuator 5, the rubber coupling 19, the auxiliary actuator 6, the steering gear 9, and the steered wheels 4 are connected in this order in the steering force transmission path.

  The main actuator 5 is installed on the handle 3 side (upstream side in the steering transmission path) of the steering shaft 8 and has an electric motor. The output from the electric motor is transmitted to the steering shaft 8 via a speed reduction mechanism. The main actuator 5 is in charge of outputting a larger torque than the sub-actuator 6 and performs large-angle steering with rough accuracy.

  The rubber coupling 19 functions as a damping mechanism that mechanically connects the main actuator 5 and the sub-actuator 6 with play. The rubber coupling 19 prevents torque interference between the steering torque by the main actuator 5 and the steering torque by the sub-actuator 6. As described above, since the damping mechanism that mechanically connects with play is provided, torque interference can be prevented and the main actuator 5 and the subactuator 6 can be driven simultaneously. For example, even when a time shift occurs in the control of the main actuator 5 and the sub-actuator 6, the time shift can be absorbed by the damping mechanism. Thereby, even if the torque by the main actuator 5 and the torque by the subactuator 6 are in the opposite directions, it is possible to avoid an excessive load from acting on the steering shaft 8.

  The sub-actuator 6 is installed on the steering gear 9 side (downstream side in the steering transmission path) of the steering shaft 8 and has an electric motor 22 (see FIG. 6). The output from the electric motor 22 is transmitted to the steering shaft 8 through a speed reduction mechanism. The sub-actuator 6 is in charge of outputting torque smaller than that of the main actuator 5, and performs steering at a minute angle with high accuracy.

  The torque from the main actuator 5 and the subactuator 6 is input to the steering gear 9. A steering angle sensor 24 is provided between the rubber coupling 19 and the sub actuator 6. The steering angle sensor 24 can detect the rotation angle of the steering shaft 8.

  FIG. 4 shows the sub-actuator according to the first embodiment of the present invention, and is a cross-sectional view showing the meshing state of the gears during normal control. The sub-actuator 6 has a reduction ratio variable mechanism that makes the reduction ratio between the electric motor 25 and the steering shaft 8 variable. The motor shaft 26 of the electric motor 25 includes a first gear 27 and a second gear 28. The second gear 28 is disposed closer to the steering shaft 8 than the first gear 27 and is smaller than the first gear 27.

  The motor shaft 26 of the electric motor 25 is configured to be movable in the axial direction. The motor shaft 26 is urged to the opposite side of the steering shaft 8 by a coil spring 29 disposed outside the end portion on the steering shaft 8 side. A magnet switch 30 for moving the motor shaft 26 toward the spring shaft 8 is provided in the vicinity of the other end of the motor shaft 26.

  The sub-actuator 6 has an output shaft 31 extending in parallel with the motor shaft 26. The output shaft 31 includes a third gear 32 and a fourth gear 33. The fourth gear 33 is disposed closer to the steering shaft 8 than the third gear 32 and is larger than the third gear 27. The output shaft 31 is formed with a worm gear 34 that meshes with a worm wheel 35 provided on the steering shaft 8.

  The motor shaft 26 is disposed at a position where the first gear 27 and the third gear 32 are engaged with each other and the second gear 28 and the fourth gear 33 are not engaged during normal control. In this case, torque generated in the electric motor 25 is transmitted from the motor shaft 26 to the first gear 27 and the third gear 32. The first gear 27 and the third gear 32 are transmitted at a constant speed and a constant torque. The torque transmitted to the output shaft 31 is transmitted to the steering shaft 8 via the worm gear 34 and the worm wheel 35.

  FIG. 5 shows the sub-actuator according to the first embodiment, and is a cross-sectional view showing the meshing state of the gears when the main actuator is abnormal. When the main actuator 5 is abnormal, the sub-actuator 6 increases the torque by the electric motor 25 to increase the reduction ratio, thereby rotating the steering shaft 8. Specifically, the sub-actuator 6 operates the magnet switch 30 based on the control signal from the steering ECU 7 to slide the motor shaft 26 toward the steering shaft 8 side. Thus, the motor shaft 26 is disposed at a position where the second gear 28 and the fourth gear 33 are engaged with each other and the first gear 27 and the third gear 32 are not engaged with each other. In this case, torque generated in the electric motor 25 is transmitted from the motor shaft 26 to the second gear 28 and the fourth gear 33. The speed is reduced between the second gear 28 and the fourth gear 33, and the torque is increased and transmitted. The torque transmitted to the output shaft 31 is transmitted to the steering shaft 8 via the worm gear 34 and the worm wheel 35.

  FIG. 6 is a block configuration diagram showing a control configuration of the steering device in FIG. The steering ECU 7 is electrically connected to the main actuator 5, the sub actuator 6, the actual rudder angle sensor 18, the rudder angle sensor 24, and the internal pressure sensor 37, and controls the main actuator 5 and the sub actuator 6. A CPU for processing, a ROM and a RAM serving as a storage unit, an input signal circuit, an output signal circuit, a power supply circuit, and the like are provided. In addition, the steering ECU 7 is electrically connected to the main ECU 36 that controls the entire vehicle 1, and can acquire information on various traveling states of the vehicle 1.

  In the steering ECU 7, during automatic steering, “feed-forward control as basic control”, “feedback control”, “control to avoid the influence of backlash in the steering force transmission path”, “control when the sub-actuator 6 is abnormal” “Control when main actuator 5 is abnormal”. Further, the steering ECU 7 performs “control in a pitching state” and “control in a skid state” during manual operation.

  In addition to the program for operating the CPU, the ROM of the steering ECU 7 stores data relating to the travel path of the vehicle 1, data relating to the target vehicle speed of the vehicle 1, data relating to the target state of the vehicle 1, and the like. Examples of the data relating to the travel path include a road position, a road gradient, and a road shape.

  “Feedforward control as basic control” will be described. During automatic steering, the steering ECU 7 detects a magnetic marker provided on the travel path, detects the current position of the vehicle 1, and performs feed-forward control based on data regarding the travel path and data regarding the target vehicle speed. The steering ECU 7 calculates a target steering angle (control target) of the steered wheels 4 and transmits a control signal to the main actuator 5 and the sub-actuator 6. For example, when the target steering angle is 11.15 degrees, the control signal is transmitted so that the steering angle of the main actuator 5 is 11 degrees and the steering angle of the sub actuator 6 is 0.15 degrees. In this manner, the sub-actuator 6 that outputs torque smaller than that of the main actuator 5 performs fine control that is finer than that of the main actuator 5. In the feedforward control, the calculated target steering angle is temporarily stored in the RAM as data relating to the target state.

  Next, “feedback control” will be described. The steering ECU 7 performs feedback control based on the stored data regarding the target state and the steering angle detected by the actual steering angle sensor 18. The steering ECU 7 calculates a corrected steering angle for the steered wheels 4 and transmits a control signal to the sub-actuator 6. Further, the magnitude of the steering angle controlled by the sub-actuator 6 is within the range of play of the rubber coupling 19.

  FIG. 7 is a graph showing an example of the control in the steering device, and is a graph showing the time change of the target steering angle and the actual steering angle. The vertical axis represents the steering angle, and the horizontal axis represents time. A graph L1 indicated by a solid line indicates an actual steering angle controlled by the steering ECU 7, and a graph L2 indicated by a one-dot chain line indicates a target steering angle calculated by feedforward control in the steering ECU 7. Referring to the graph shown in FIG. 7, after the difference between the target steering angle and the actual steering angle increases in the ranges A and B surrounded by the alternate long and short dash line, the difference between the target steering angle and the actual steering angle decreases. You can see that This is because the sub-actuator 6 is operated based on the corrected steering angle calculated by the feedback control, and the actual steering angle approaches the target steering angle.

  Next, “control to avoid the influence of backlash in the steering force transmission path” will be described. The steering ECU 7 can control the torque by the sub-actuator 6 based on the signal from the actual steering angle sensor 18, and can avoid the influence of backlash in the steering force transmission path. Here, “backlash” includes play between the components such as the backlash in the steering gear 9, the pitman arm 11, the drag link 12, and the knuckle arm 13. For example, when the steered wheel 4 is operated in the right direction and then the steered wheel 4 is operated in the left direction, the steering angle of the steered wheel 4 may not be correctly controlled due to the influence of backlash in the steering force transmission path.

  In order to avoid the influence of this backlash, the steering ECU 7 feeds back the value detected by the actual steering angle sensor 18 when the operation is performed in the right direction (right turn), for example, and when the operation is performed in the left direction (left turn), After rotating by the target steering angle + α in the direction, the rotation by α is returned to the right and the backlash is reduced, and then the detected value by the actual steering angle sensor 18 is fed back. Thereby, the vehicle 1 can be safely steered.

  Next, the control when the sub actuator 6 is abnormal will be described. The steering ECU 7 has an abnormality detection function capable of detecting an abnormality in the main actuator 5 and the sub-actuator 6. FIG. 8 is a flowchart showing an operation procedure of “control processing when the sub-actuator is abnormal” executed by the steering ECU. First, in step S1, it is determined whether or not automatic control operation is being performed. Specifically, it is determined based on a signal from the main ECU 36 whether or not automatic control operation is being performed. When it is determined that the automatic control operation is being performed, the process proceeds to step S2, and when it is not determined that the automatic control operation is being performed, the process is terminated.

  In step S2, it is determined whether or not the sub actuator 6 is in an abnormal state. Specifically, based on the signal from the actual steering angle sensor 18, when the steered wheel 4 is not steered according to the control signal to the sub actuator 6, it is determined that the sub actuator 6 is in an abnormal state. If it is determined that the sub-actuator 6 is in an abnormal state, the process proceeds to step S3. If it is not determined that the sub-actuator 6 is in an abnormal state, the process ends. When the main actuator steering ECU for controlling the main actuator 5 and the sub-actuator steering ECU for controlling the sub-actuator 6 are provided, a signal is transmitted from the main actuator steering ECU to the sub-actuator steering ECU. Thus, when the signal is not returned from the auxiliary actuator steering ECU, it may be determined that the auxiliary actuator 6 is in an abnormal state.

  In step S3, a signal is transmitted to the main ECU 36 to instruct to lower the set value of the target speed of the vehicle 1. Thus, when the sub-actuator 6 is in an abnormal state, the vehicle 1 can be safely steered by decelerating the vehicle 1.

  Next, “control when the main actuator 5 is abnormal” will be described. FIG. 9 is a flowchart showing an operation procedure of “control processing when the main actuator is abnormal” executed by the steering ECU. First, in step S11, it is determined whether or not automatic control operation is being performed. If it is determined that the automatic control operation is being performed, the process proceeds to step S12. If it is not determined that the automatic control operation is being performed, the process is terminated.

  In step S12, it is determined whether or not the main actuator 5 is in an abnormal state. Specifically, based on the signal from the actual steering angle sensor 18, when the steered wheels 4 are not steered according to the control signal to the main actuator 5, it is determined that the main actuator 5 is in an abnormal state. If it is determined that the main actuator 5 is in an abnormal state, the process proceeds to step S13. If it is not determined that the main actuator 5 is in an abnormal state, the process ends. In the case of the configuration including the main actuator steering ECU and the sub actuator steering ECU, a signal is transmitted from the sub actuator steering ECU to the main actuator steering ECU, and the signal is returned from the main actuator steering ECU. If not, it may be determined that the main actuator 5 is in an abnormal state.

  In step S13, the steering ECU 7 transmits a signal to the main ECU 36 to instruct to lower the set value of the target speed of the vehicle 1, and proceeds to step S14. Thus, when the main actuator 5 is in an abnormal state, the vehicle 1 can be safely steered by decelerating the vehicle 1.

  In step S14, the steering ECU 7 transmits a signal to the sub-actuator 6, variably controls the reduction ratio in the sub-actuator 6, and increases the reduction ratio to increase the output torque from the sub-actuator 6. As a result, even if the main actuator 5 is in an abnormal state, fail safe can be performed by steering to a large steering angle by the sub-actuator 6.

  Next, “control in the pitching state” executed during manual operation will be described. The steering ECU 7 has a pitching state detection function capable of detecting the pitching state of the vehicle 1. Here, the “pitching state” refers to a so-called nose down in which the front of the vehicle body is lowered in accordance with a brake operation. In the pitching state, the steered wheel 4 is turned to the right in the vehicle 1, and the steered wheel 4 There is a risk that the handle rotates to the right in conjunction with the movement. Specifically, when the brake operation is performed, the front portion of the vehicle body is lowered, the air spring 17 is contracted, and the vehicle body frame 10 and the front axle 14 approach each other. As a result, the drag link 12 is pushed forward, the knuckle arm 13 rotates to turn the steered wheel to the right, and the pitman arm 11 and the steering shaft 8 are interlocked. As a result, the handle 3 rotates to the right. Resulting in. The rotation of the handle 3 sometimes causes the driver to feel uncomfortable. For example, by detecting the internal pressure of the air spring 17 by the internal pressure sensor 37, it is possible to detect that there is a possibility that pitching may occur.

  FIG. 10 is a flowchart showing an operation procedure of “control processing in the pitching state” executed by the steering ECU. First, in step S21, it is determined whether or not manual operation is being performed. Specifically, it is determined based on a signal from the main ECU 36 whether or not manual operation is being performed. If it is determined that the manual operation is being performed, the process proceeds to step S22. If it is not determined that the manual operation is being performed, the process is terminated.

  In step S22, it is determined whether or not the pitching state is set. Specifically, the steering ECU 7 detects the inclination of the vehicle body based on a signal from each internal pressure sensor 37 that detects the internal pressure of the air suspension of each wheel, and determines whether or not the vehicle is in the pitching state. If it is determined that the pitching state is set, the process proceeds to step S23. If it is not determined that the pitching state is set, the process ends.

  In step S23, the steering ECU 7 transmits a control signal to the sub-actuator 6 to perform torque control, steer the steered wheel 4 to the left, and perform control so that the vehicle 1 goes straight, and the process ends. In this way, when in the pitching state, the sub-actuator 6 can be controlled to prevent the vehicle 1 from moving in the right direction. Further, by setting the size of the steering angle controlled by the sub-actuator 6 to be within the range of play of the rubber coupling 19, it is possible to prevent the handle 3 from rotating and to make the driver feel uneasy that the handle 3 moves naturally. Can be reduced. In step S21, it is determined whether or not manual operation is performed, and in the case of manual operation, the processes in steps S22 and S23 are executed. In the automatic control operation, the processes in steps S22 and S23 are performed. May be executed.

  Next, the “control process in a skid state” will be described. The steering ECU 7 has a side-slip state detection function that can detect the side-slip state of the vehicle 1, and can reduce the side-slip when it is in the side-slip state. FIG. 11 is a flowchart showing an operation procedure of “control processing in a skid state” executed by the steering ECU. First, in step 31, it is determined whether or not manual operation is being performed. If it is determined that the manual operation is being performed, the process proceeds to step S32. If the manual operation is not determined, the process is terminated.

  In step S32, it is determined whether or not the vehicle is skidding. Specifically, the steering ECU 7 determines whether or not the vehicle is in a skid state using the skid prevention determination value in the vehicle behavior stabilization system. If it is determined that the vehicle is in a skid state, the process proceeds to step S33. If it is not determined that the vehicle is in a skid state, the process ends.

  In step S33, the steering ECU 7 transmits a control signal to the sub-actuator 6 to perform torque control, applies reverse torque, performs control so that the vehicle 1 goes straight, and ends the process. In this way, when the skid is in the skidding state, the sub-actuator 6 can be controlled to reduce the skidding state. When torque control is performed by the sub-actuator 6 during this manual operation, the main actuator 5 may generate a holding force so that the handle 3 does not rotate in the reverse direction. As a result, the driver's anxiety that the steering wheel 3 moves naturally can be reduced.

  According to such a steering device 2, the main actuator 5 and the sub-actuator 6 that apply steering torque are provided, and the main actuator 5 and the sub-actuator 6 are mechanically connected in a state having play. Since they are connected by the ring 19, the steering torque by the main actuator 5 and the steering torque by the sub actuator 6 are prevented from interfering with each other. Further, the sub actuator 6 is arranged closer to the steering gear 9 than the main actuator 5 in the steering force transmission path, and the steering torque by the sub actuator 6 is made smaller than the steering torque by the main actuator 5. Thereby, the sub-actuator 6 can control the minute angle with high accuracy, and the steering accuracy can be improved. As a result, the steering accuracy can be improved while the steering device 2 is a multiplex system. Further, the steering device 2 further improves control accuracy by performing feedforward control of the main actuator 5 and feedback control of the subactuator 6.

  Further, the steering device 2 has an abnormality detection function capable of detecting an abnormality of the main actuator 5 and an abnormality of the sub-actuator 6, and therefore detects an abnormality of the main actuator 5 and an abnormality of the sub-actuator 6. Steering control can be performed according to the abnormality 5 and the abnormality of the sub-actuator 6, and automatic operation control can be performed even when an abnormality occurs in either the main actuator 5 or the sub-actuator 6. .

  The sub-actuator 6 has a reduction ratio variable function that makes the reduction ratio variable, and when the main actuator 5 is in an abnormal state, the reduction ratio of the sub-actuator can be increased. As a result, when the main actuator 5 is abnormal, the reduction ratio of the sub-actuator 6 is increased by the reduction ratio variable mechanism, thereby increasing the steering torque by the sub-actuator 6 and without using the main actuator 5. The steered wheel 4 can be steered by the steering torque of 6. In this way, the second actuator can have a fail-safe function.

  Further, the steering device 2 controls the steering torque by the sub-actuator 6 in consideration of play and rattling in the steering force transmission path, and performs control to avoid the influence of the backlash. Therefore, the influence of the backlash is avoided. Can be steered.

  Further, the steering device 2 includes an internal pressure sensor 37 that detects the internal pressure of the air spring 17, detects a pitching state based on the detected internal pressure, and steers the steered wheels 4 leftward when the pitching state is established. Then, control in the pitching state is executed. Thus, by performing the steering corresponding to the traveling state of the vehicle 1, the steering stability can be improved and the driving assistance in the manual driving can be performed. This control in the pitching state is particularly effective during manual operation.

  The steering device 2 is electrically connected to the main ECU 36 that controls the entire vehicle 1, detects a skid state based on a signal from the main ECU 36, and uses the skid prevention determination value when the skid state is present. Then, the control angle is calculated to steer the steered wheels 4, and the control in the skid state is executed. Thus, by performing the steering corresponding to the traveling state of the vehicle 1, the steering stability can be improved and the driving assistance in the manual driving can be performed. This control in the skid state is particularly effective during manual operation.

  Next, a steering apparatus according to a second embodiment of the present invention will be described with reference to FIGS. FIG. 12 shows a sub-actuator according to the second embodiment of the present invention, and is a cross-sectional view showing a meshing state of gears during normal control. The difference between the steering device 42 of the second embodiment and the steering device 2 of the first embodiment is that the auxiliary actuator 6 having a variable reduction ratio mechanism having a magnet switch 30 that operates based on a control signal from the steering ECU 7. Instead, a sub-actuator 46 having a variable reduction ratio mechanism having a temperature switch 43 that operates by detecting heat generation of the electric motor 25 is used.

  The motor shaft 26 of the sub-actuator 46 is configured to be movable in the axial direction. A disc-shaped pressing plate 44 having a diameter larger than the diameter of the motor shaft 26 is installed at the other end of the motor shaft 26. A coil spring (elastic energy storage means) 45 is disposed outside the pressing plate 44, and the motor shaft 26 is urged toward the steering shaft 8 via the pressing plate 44.

  The sub-actuator 46 is provided with a locking claw 47 that restrains the movement of the pressing plate 44 toward the steering shaft 8. During normal control, the motor shaft 26 is restrained from moving the pressing plate 44 by a locking claw 47 so that the first gear 27 and the third gear 32 mesh with each other, and the second gear 28 and the fourth gear 33. Are arranged at positions where they do not mesh.

  The temperature switch 43 is made of bimetal or the like, and is installed on the outer surface of the electric motor 25 housing. The temperature switch 43 detects the temperature of the electric motor 25 and is activated when the temperature of the electric motor 25 becomes equal to or higher than a predetermined reference to move the locking claw 47 and store the elastic energy stored in the coil spring 45. Is opened, and the motor shaft 26 is moved in the axial direction. Here, the “predetermined reference” is a temperature at which an abnormality of the main actuator 5 can be detected. If an abnormality occurs in the main actuator 5, the load on the sub-actuator 46 increases and the temperature of the electric motor 25 rises. Therefore, the temperature of the electric motor 25 is detected to detect an abnormality in the main actuator 5. can do.

  FIG. 13 shows a sub-actuator according to a second embodiment of the present invention, and is a cross-sectional view showing a meshing state of gears when the main actuator is abnormal. When the main actuator 5 is abnormal, the temperature switch 43 is operated, and the restraint of the pressing plate 44 by the locking claw 47 is released. As a result, the coil spring 45 is opened, and the motor shaft 26 moves to the steering shaft 8 side. Thus, the motor shaft 26 is disposed at a position where the second gear 28 and the fourth gear 33 are engaged with each other and the first gear 27 and the third gear 32 are not engaged with each other. In this case, torque generated in the electric motor 25 is transmitted from the motor shaft 26 to the second gear 28 and the fourth gear 33. The speed is reduced between the second gear 28 and the fourth gear 33, and the torque is increased and transmitted. The torque transmitted to the output shaft 31 is transmitted to the steering shaft 8 via the worm gear 34 and the worm wheel 35.

  According to the steering device 42 according to the second embodiment, the same effect as that of the steering device 2 of the first embodiment can be obtained. In addition, the abnormality of the main actuator 5 can be prevented regardless of the signal from the steering ECU 7. The speed reduction ratio can be mechanically changed using the temperature switch 43 and the coil spring 44. Even in this case, the sub-actuator 46 can have a fail-safe function.

  Next, a steering apparatus according to a third embodiment of the present invention will be described with reference to FIGS. FIG. 14 is a sectional view showing a sub-actuator according to the third embodiment of the present invention. The difference between the steering device 52 of the third embodiment and the steering device 2 of the first embodiment is that the auxiliary actuator 6 having a variable reduction ratio mechanism having a magnet switch 30 that operates based on a control signal from the steering ECU 7. Instead, a sub-actuator 56 having a variable reduction ratio mechanism having a multi-plate clutch (clutch means) 53 that engages when the steering torque increases is used.

  The sub-actuator 56 has a reduction ratio variable mechanism that makes the reduction ratio between the electric motor 55 and the steering shaft 8 variable. The motor shaft 54 of the electric motor 55 includes a first gear 57 and a second gear 58 that rotate about the axis. The second gear 58 is disposed closer to the steering shaft 8 than the first gear 57 and is smaller than the first gear 57. The second gear 58 is attached to the motor shaft 54 via a torque limiter (for example, a 2-way clutch) 59.

  The motor shaft 54 includes a dog clutch 60 disposed between the electric motor 55 and the first gear 57, and a multi-plate clutch 53 disposed between the first gear 57 and the second gear 58. I have. A worm gear 34 that meshes with a worm wheel 35 provided on the steering shaft 8 is formed on the motor shaft 54.

  The dog clutch 60 generates a thrust force when the torque generated by the electric motor 55 is larger than that during normal control. The multi-plate clutch 53 is idled during normal control. When the torque generated by the electric motor 55 is larger than that during normal control, the multi-plate clutch 53 generates a pressing force by the thrust force generated by the dog clutch 60 and is coupled. To do.

  The sub-actuator 56 has a transmission shaft 61 extending in parallel with the motor shaft 54. The transmission shaft 61 includes a third gear 62 and a fourth gear 63 that rotate together with the transmission shaft 61. The third gear 62 meshes with the first gear 57, and the fourth gear 63 meshes with the second gear 58.

  Next, the power transmission path in the sub-actuator 56 during normal control will be described. Torque generated by the electric motor 55 is transmitted to the first gear 57 and the third gear 62 via the dog clutch 60. The transmitted torque is reduced to improve the accuracy of steering control by the sub-actuator 56, and the transmission shaft 61 is accelerated. At this time, the multi-plate clutch 53 is idle. The torque transmitted to the transmission shaft 61 is transmitted at a constant speed and a constant torque between the fourth gear 63 and the second gear 58, and is transmitted to the steering shaft 8 via the worm gear 34 and the worm wheel 35.

  When the torque generated by the electric motor 55 increases, the sub-actuator 56 can change the power transmission path in the sub-actuator 56 to increase the reduction ratio compared to that during normal control. Specifically, when the main actuator 5 is abnormal, the load of the electric motor 55 is increased and the torque by the electric motor 55 is increased. Therefore, a thrust force is generated by the dog clutch 60 and the multi-plate clutch 53 is moved. Engage. At this time, the torque limiter 59 is activated, and the second gear 58 is in an idle state with respect to the motor shaft 54. The torque generated by the electric motor 55 is transmitted to the steering shaft 8 via the dock clutch 60, the multi-plate clutch 53, the worm gear 34, and the worm wheel 35, and the torque is increased from the normal control to It can be rotated.

  According to the steering device 52 according to the third embodiment, the same effect as that of the steering device 2 of the first embodiment can be obtained. In addition, the abnormality of the main actuator 5 can be prevented regardless of the signal from the steering ECU 7. The power transmission path C that does not pass through the multi-plate clutch 53 is switched from the power transmission path C that passes through the multi-plate clutch 53 using the multi-plate clutch 53 and the dock clutch 60 to mechanically reduce the reduction ratio. Can be changed. Even in this case, the sub-actuator 56 can be provided with a fail-safe function.

  As mentioned above, although this invention was concretely demonstrated based on the embodiment, this invention is not limited to the said embodiment. In the above-described embodiment, the main actuator 5 and the sub-actuator 6 are configured to have electric motors, but actuators having other configurations may be used, and in short, anything that can apply steering torque to the steering force transmission path. That's fine.

  In the above embodiment, the steering device is applied to a vehicle such as a route bus. However, the steering device may be applied to other vehicles such as a sightseeing bus, a truck, a passenger car, and an industrial vehicle.

  In the above embodiment, the steering device is applied to a vehicle capable of both automatic steering operation and manual driving. However, the steering device is applied to a vehicle capable of only automatic steering operation or manual driving. Also good.

  In the above embodiment, the main actuator 5 is feedforward controlled and the subactuator 6 is feedback controlled. However, the main actuator 5 and the subactuator 6 may be feedforward controlled. 6 may be feedback controlled.

  In the above embodiment, the actual steering angle sensor 18 that detects the steering angle by detecting the rotation angle of the steering shaft 8 is adopted as the physical quantity detection means for detecting the physical quantity related to the steering control. Based on the detected steering angle, the steering torque by the sub-actuator 6 is controlled to cancel backlash in the steering force transmission path. For example, the steering angle sensor 24 is used as a physical quantity detection means, and the steering angle sensor Based on the steering angle detected by 24, the steering torque by the sub-actuator 6 may be controlled. Further, the steering torque by the sub-actuator 6 may be controlled using physical quantity detection means for detecting other physical quantities related to steering control.

  In the above embodiment, the vehicle pitching state and the vehicle skid state are detected as the vehicle running state, and the sub-actuator 6 performs steering control corresponding to the vehicle pitching state and the vehicle skid state. However, for example, as the running state of the vehicle, the vehicle body inclination or the like may be detected, and steering control corresponding to the vehicle body inclination may be executed. A corresponding steering control may be executed.

  In the above embodiment, when the reduction ratio of the sub-actuator 6 is increased, the vehicle 1 is preferably controlled to be decelerated. However, it is not always necessary to perform the control for decelerating the vehicle 1.

1 is a schematic side view showing a vehicle including a steering device according to an embodiment of the present invention. It is a schematic plan view of the vehicle shown in FIG. FIG. 3 is an enlarged view showing a front axle, a king pin, and an actual steering angle sensor in FIG. 2 from the rear side. BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a sectional view showing a sub-actuator according to a first embodiment of the present invention and showing a meshing state of gears during normal control. BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a sectional view showing a sub-actuator according to a first embodiment of the present invention and showing a meshing state of gears when a main actuator is abnormal. It is a block block diagram which shows the control structure of the steering apparatus in FIG. It is a graph which shows an example of the control in a steering device, and shows the time change of a target steering angle and an actual steering angle. It is a flowchart which shows the operation | movement procedure of the "control processing at the time of sub-actuator abnormality" performed by steering ECU. It is a flowchart which shows the operation | movement procedure of the "control process at the time of abnormality of a main actuator" performed by steering ECU. It is a flowchart which shows the operation | movement procedure of the "control process in a pitching state" performed by steering ECU. It is a flowchart which shows the operation | movement procedure of the "control process in a skid state" performed by steering ECU. FIG. 9 is a cross-sectional view illustrating a sub-actuator according to a second embodiment of the present invention and illustrating a meshing state of gears during normal control. FIG. 10 is a cross-sectional view showing a sub-actuator according to a second embodiment of the present invention and showing a meshing state of gears when the main actuator is abnormal. It is sectional drawing which shows the subactuator which concerns on 3rd Embodiment of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Vehicle, 2, 42, 52 ... Steering device, 3 ... Steering wheel, 4 ... Steering wheel, 5 ... Main actuator (first actuator), 6, 46, 56 ... Sub actuator (second actuator), 7 ... Steering ECU, 8 ... Steering shaft, 9 ... Power steering gear box, 18 ... Actual steering angle sensor (physical quantity detection means), 19 ... Rubber coupling (connection means), 24 ... Steering angle sensor, 36 ... Main ECU (travel) State detecting means), 37 ... internal pressure sensor (running state detecting means), 45 ... coil spring (elastic energy storage means), 53 ... multi-plate clutch (clutch means).

Claims (10)

A first actuator having a steering shaft coupled to a steering gear and provided in a steering force transmission path for transmitting a steering force to a steered wheel, and for applying a steering torque to the steering shaft;
A second actuator that is disposed downstream of the first actuator in the steering force transmission path and applies a steering torque to the steering shaft;
Connecting means for mechanically connecting the first actuator and the second actuator with play;
The steering apparatus according to claim 1, wherein a steering torque by the second actuator is smaller than a steering torque by the first actuator.   The steering apparatus according to claim 1, wherein the first actuator is feedforward controlled, and the second actuator is feedback controlled. A steering handle disposed upstream of the first actuator in the steering force transmission path;
The steering apparatus according to claim 1 or 2, wherein a control angle by the second actuator is within a range of play of the connecting means. The steering force transmission path includes a physical quantity detection means that is disposed closer to the steered wheel than the connection means and detects a physical quantity related to steering control,
The steering torque by the second actuator is controlled based on the physical quantity detected by the physical quantity detection means, and backlash in the steering force transmission path is canceled. The steering apparatus as described in. A running state detecting means for detecting the running state of the vehicle;
The steering apparatus according to any one of claims 1 to 4, wherein a steering torque by the second actuator is controlled based on the traveling state detected by the traveling state detecting means.   6. The steering apparatus according to claim 5, wherein the traveling state detection unit detects a pitching state of the vehicle or a skid state of the vehicle as the traveling state. A reduction ratio variable means capable of changing a reduction ratio of the second actuator;
The steering apparatus according to any one of claims 1 to 6, wherein the reduction ratio variable means increases the reduction ratio of the second actuator when the first actuator is abnormal. . The speed reduction ratio variable means includes elastic energy storage means for storing elastic energy,
When the temperature of the second actuator becomes equal to or higher than a predetermined reference, the elastic energy stored in the elastic energy storage means is released to increase the reduction ratio of the second actuator. The steering apparatus according to claim 7. The speed reduction ratio variable means includes a clutch means that engages when a steering torque by the second actuator increases,
8. The steering apparatus according to claim 7, wherein the reduction ratio of the second actuator is increased by switching from a power transmission path not via the clutch means to a power transmission path via the clutch means. The steering apparatus according to any one of claims 7 to 9, wherein when the speed reduction ratio of the second actuator is increased, control for decelerating the vehicle is performed.

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