JP4289183B2 - Vehicle steering device - Google Patents

Description

  The present invention relates to a steering apparatus for a vehicle that mechanically connects a steering wheel and a steering wheel and steers the steering wheel in accordance with a steering operation of the steering wheel.

Conventionally, as shown in Patent Document 1 below, in a vehicle steering apparatus in which a gear ratio variable mechanism is interposed between a steering wheel and a steering wheel, steering torque for detecting steering torque acting on the steering wheel is detected. A sensor is provided, and when the detected steering torque changes above a certain speed or changes above a certain acceleration, a load device provided between the steering handle and the gear ratio variable mechanism is operated to move the wheel to the steering handle. It is known to prevent the steering wheel from vibrating by suppressing the reversely input reaction force.
JP 2003-34255 A

  However, in the above-described conventional device, only the fluctuation of the steering torque due to the reaction force reversely input from the wheel to the steering handle is determined, and steering is performed in addition to the steering of the steered wheel corresponding to the steering operation of the steering handle. The controllability at the time of the correction steering or the steering to the driver is not considered without considering the influence on the steering torque by the correction steering (active steering) of the steering wheel by the correction steering device (that is, the active steering device) for correcting and steering the wheel. It is not possible to reduce the discomfort of the reaction force.

  The present invention has been made to address the above problems, and its purpose is to reduce the controllability during correction steering or the discomfort of the steering reaction force to the driver in consideration of the influence on the steering torque by the correction steering. An object of the present invention is to provide a vehicle steering apparatus.

In order to achieve the above object, a feature of the present invention is that in a steering apparatus for a vehicle in which a steering wheel and a steering wheel are mechanically connected and the steering wheel is steered in response to a steering operation of the steering handle, Between the steering wheel and the steering assist device, the steering assist device capable of assisting the steering of the steered wheel and changing the assist amount of the steered wheel, and the steering handle and the steering assist device. In addition to steering of the steering wheel corresponding to the steering operation of the steering wheel, a correction steering device for correcting and steering the steering wheel, and interposed between the steering handle and the correction steering device to restrict the displacement of the steering wheel A load device for applying a load to the steering wheel, a steering reaction force detection means for detecting a steering reaction force acting on a member on the steering wheel side relative to the load device, and a steering reaction force detection means. In that a steering assist control means for controlling the assist amount of the steering of the steering wheel by the steering assist device in accordance with the detected steering reaction force.

In the present invention having the above-described features , the load device, the correction steering device, and the steering assist device are arranged in this order between the steering wheel and the steering wheel, and the operation of the steering reaction force detection means and the steering assist control means is performed. As a result, the steering wheel is steered according to the steering reaction force acting on the steering wheel side member relative to the load device, so that the steering reaction force reversely input from the steering wheel side to the load device and the steering handle is reduced. Can do. Thereby, even if the correction steering device corrects and steers the steered wheel, the influence on the steering wheel can be reduced, and the load device can be used in a small size, that is, with a small maximum allowable load.

In the aspect of the present invention, the load device may be capable of changing a magnitude of a load applied to the steering wheel. According to this, it becomes possible to change the magnitude of the load by the load device in conjunction with the correction steering control by the correction steering device, and the reaction force reversely input to the steering wheel due to the correction steering can be adjusted. The influence on the steering torque by the correction steering can be reduced, and the uncomfortable feeling of the steering reaction force for the driver can be reduced. For example, by changing the magnitude of the load by the load device according to the steering state of the steering handle between when the correction steering device is activated and when it is not operated, the reverse input to the steering handle due to the correction steering is performed. Adjust the force. More specifically, when the correction steering device is operated, the load by the load device is increased when the steering wheel is in the neutral position, that is, when the steering wheel is not being operated, and the steering wheel is in the neutral position. When the steering wheel is not operated, that is, when the steering wheel is being steered, the load by the load device is reduced. According to this, it is possible to eliminate the fluctuation of the steering torque due to the correction steering that gives the driver a great sense of incongruity when the steering wheel is not being steered, and also to prevent the steering wheel from being steered according to the steering operation of the steering wheel. Don't be.

  For example, the configuration of the present invention further includes a steering operation detecting means for detecting a steering operation of the steering handle, and a load applied to the steering handle when the steering operation of the steering handle is detected by the steering operation detecting means is reduced. And a load control means for controlling the load apparatus so that a load applied to the steering handle is increased when the steering operation is not detected by the steering operation detecting means. Good. In this case, the steering operation detection means includes, for example, a steering wheel angle sensor that is interposed between a steering wheel and the load device and detects a steering angle of the steering wheel, and is detected by the steering wheel angle sensor. It is preferable that the steering operation of the steering wheel is detected using the determined steering angle. Further, the steering operation detecting means includes a steering wheel force sensor that is interposed between the steering wheel and the load device and detects a steering force applied to the steering wheel, and is detected by the steering wheel force sensor. The steering operation of the steering wheel may be detected using the obtained steering force.

  According to these, as described above, the fluctuation of the steering torque due to the correction steering that gives the driver a great sense of incongruity when the steering handle is not being steered can be eliminated, and the steering wheel according to the steering operation of the steering handle can be eliminated. It will not interfere with steering.

  Further, the configuration of the present invention further includes a hand release detecting means for detecting a hand release state of the driver with respect to the steering wheel, and a steering handle when the hand release state is not detected by the hand release detecting means. The load device is controlled so that the applied load becomes small, and the load device is controlled so that the load applied to the steering wheel becomes large when the hand release state is detected by the hand release detecting means. Load control means may be provided. In this case, the hand release detecting means includes, for example, a handle steering force sensor that detects a steering force applied to the steering handle, and the hand release state is detected using the steering force detected by the handle steering force sensor. It may be configured to detect.

  According to this, even when the steering wheel is corrected and steered by the correction steering device in a state where the driver releases his hand from the steering wheel, the reaction force due to the correction steering is not transmitted to the steering handle by the load device. Can do. Therefore, the steering wheel is corrected and steered by the correcting steering device, and the steering handle is not displaced against the driver's will by the corrected steering, and there is a sense of incongruity associated with the displacement of the steering handle when the steering handle is released. It is not given to the driver. Further, when the driver is holding the steering wheel, the steering wheel is steered according to the steering operation of the steering wheel by the driver, and the driver also responds to the reaction force to the steering wheel by the correction steering. Since the steering operation force opposes, correction steering of the steered wheels by the correction steering device is allowed.

  Furthermore, another feature of the present invention resides in that an elastic body that can be elastically deformed is interposed between the steering handle and the load device. In this case, as the elastic body, for example, a torsion bar interposed in a steering shaft can be employed. According to this, even in a state where the displacement of the steering wheel is regulated by the load device, a slight displacement of the steering wheel is allowed, and a good operation feeling can be given to the operation of the driver's steering wheel. The force applied to the load device can be reduced.

a. First Embodiment Hereinafter, a first embodiment of the present invention will be described with reference to the drawings. FIG. 1 is an overall schematic diagram of a vehicle steering apparatus according to a first embodiment. This steering device is mechanically coupled to the steering handle 11 and the left and right front wheels FW1 and FW2 as steering wheels, and is similar to a steering mechanism that steers the left and right front wheels FW1 and FW2 in response to the steering operation of the steering handle 11. And an electric control device for controlling the steering mechanism.

  The steering mechanism includes a steering shaft 12 connected to the steering handle 11 so as to integrally rotate at the upper end thereof, and a pinion gear 13 is connected to the lower end of the shaft 12 so as to integrally rotate. The pinion gear 13 meshes with rack teeth formed on the rack bar 14 to constitute a rack and pinion mechanism. The left and right front wheels FW1, FW2 are steerably connected to both ends of the rack bar 14, and the left and right front wheels FW1, FW2 are moved to the left and right according to the axial displacement of the rack bar 14 as the steering shaft 12 rotates about the axis. Steered. An active steering device 20, a steering assist device 40, and a load device 50 are provided in the steering mechanism. These devices 20, 40, 50 are arranged in the steering mechanism in the order of the load device 50, the active steering device 20, and the steering assist device 40 from the steering handle 11 toward the left and right front wheels FW1, FW2, which are the steering wheels. ing.

  As shown in FIG. 2, the active steering device 20 includes stepped cylindrical housings 21 and 22 that are fixed to the vehicle body (not shown), and the steering shaft 12 is disposed in the housings 21 and 22. In detail, it is connected so as to be able to transmit power through a harmonic drive mechanism described later, but is separated into an upper steering shaft 12a and a lower steering shaft 12b. The upper steering shaft 12 a is supported on the inner peripheral surface of the housing 21 via a ball bearing 23 so as to be rotatable about an axis. The lower steering shaft 12b is supported on the inner peripheral surface of the housing 22 via ball bearings 24 and 25 so as to be rotatable about an axis. A ball bearing 26 is interposed between the upper steering shaft 12a and the lower steering shaft 12b so that the shafts 12a and 12b can rotate relative to each other. The housings 21 and 22 accommodate an electric motor 27 for active steering (that is, for correction steering) and a harmonic drive mechanism.

  The electric motor 27 includes a stator 27a made of a coil fixed on the inner peripheral surface of the housing 21, and a rotor 27b made of a permanent magnet disposed to face the stator 27a. The rotor 27b is fixed on the outer peripheral surface of the large-diameter portion of the stepped cylindrical rotating body 28. Ball bearings 31 and 32 are interposed between the inner peripheral surface of the large-diameter portion of the rotating body 28 and the upper steering shaft 12a, and the rotating body 28 responds to the rotation of the rotor 27b of the electric motor 27 according to the rotation of the upper steering shaft 12a. Relative rotation about the axis.

  As shown in FIGS. 2 and 3, the harmonic drive mechanism includes a wave generator 33, a flex spline 34, and a circular spline 35. The wave generator 33 includes a cam 33a and a ball bearing 33b provided on the outer peripheral surface of the cam 33a. The cam 33 a is a metal rigid body formed in an elliptical shape, and is fixed on the outer peripheral surface of the rotating body 28. The inner ring of the ball bearing 33b is made of a metal rigid body and is fixed to the outer peripheral surface of the cam 33a. The outer ring of the ball bearing 33b is made of a metal elastic body and elastically deforms via the ball. The flex spline 34 is formed in a cup shape with a thin metal elastic body, and is assembled on the outer ring of the ball bearing 33b so as to have an elliptical shape in accordance with the shape of the ball bearing 33b. It is fixed to the steering shaft 12a. External teeth are formed on the outer peripheral surface of the flexspline 34.

  The circular spline 35 is formed of a metal rigid body in an annular shape and is fixed to the lower steering shaft 12b. Inner teeth that mesh with the outer teeth of the flexspline 34 are formed on the inner peripheral surface of the circular spline 35. The number of inner teeth of the circular spline 35 is slightly larger than the number of outer teeth of the flex spline 34 (for example, two more), and the inner teeth of the circular spline 35 are only at the major axis portion of the elliptical flex spline 34. It meshes with the external teeth of the flexspline 34.

  As shown in FIG. 1, the steering assist device 40 includes an electric motor 41 and a screw feed mechanism 42. The electric motor 41 is provided on the outer peripheral surface of the rack bar 14 and drives the screw feed mechanism 42. The screw feed mechanism 42 changes the rotational motion of the electric motor 41 to linear motion, and drives the rack bar 14 in the axial direction.

  The load device 50 applies resistance to rotation around the axis lines of the upper steering shaft 12a and the steering handle 11 to restrict the rotation. As shown in FIG. 4, the load device 50 includes an annular fixed side friction plate 51 and a displacement side friction plate 52. The fixed friction plate 51 is fixed to a housing member 53 that rotatably supports the upper steering shaft 12a, and is made of a high permeability material that is excited when an electromagnetic coil 54 fixed to the housing member 53 is energized. ing. The displacement side friction plate 52 is made of a high magnetic permeability material, and is assembled to an annular fixed plate 55 fixed to the upper steering shaft 12a via a disc spring 56. The disc spring 56 always urges the displacement side friction plate 52 toward the fixed plate 55 on the lower side in the figure.

  With this configuration, when the electromagnetic coil 54 is not energized, the displacement side friction plate 52 is pulled to the fixed plate 55 side by the disc spring 56 and is separated from the fixed side friction plate 51, so that the upper steering shaft 12 a and the steering handle 11 can freely rotate. Is set to the restriction release state shown in FIG. On the other hand, when the electromagnetic coil 54 is energized, the displacement side friction plate 52 is attracted by the electromagnetic coil 54 against the disc spring 56 and comes into contact with the fixed side friction plate 51, and the upper steering shaft 12a and the steering handle 11 are prohibited from rotating. The restricted state shown in FIG.

  The electric control apparatus includes a steering wheel steering angle sensor 61, a steering wheel torque sensor 62, an actual steering angle sensor 63, and a vehicle speed sensor 64. The steering wheel steering angle sensor 61 is provided between the steering wheel 11 and the load device 50, and detects the steering wheel steering angle θh, which is the rotational angle of the steering wheel 11, by measuring the rotational angle of the upper steering shaft 12a. To do. The steering angle θh of the steering wheel represents the reference position of the steering wheel 11 by “0”, the right rotation angle of the steering wheel 11 by a positive value, and the left rotation angle of the steering wheel 11 by a negative value.

  A handle torque sensor 62 is also provided between the steering handle 11 and the load device 50, and is provided at each of the upper and lower ends of the torsion bar (elastic body) 62a constituting a part of the upper steering shaft 12a and the torsion bar 62a. The rotation angle sensors 62b and 62c for detecting the rotation angles θht1 and θht2 around the axial lines at both ends are used to detect torque (hereinafter referred to as handle torque Th) acting on the upper steering shaft 12a and the steering handle 11. The rotation angles θht1 and θht2 detected by both the rotation angle sensors 62b and 62c represent the reference positions of the upper and lower ends of the torsion bar 62a by “0”, respectively, and the positive and lower ends of the torsion bar 62a by positive values. Each represents the right rotation angle, and each negative rotation angle represents the left rotation angle of the steering handle 11 at the upper and lower ends of the torsion bar 62a. Then, the handle torque Th is calculated by the ECU 65 described later in accordance with the difference between the rotation angles θht1 and θht2. Instead of the handle torque sensor 62 that detects the rotation angle, a handle torque sensor that detects the handle torque Th by detecting distortion of the torsion bar 62a or the upper steering shaft 12a may be employed.

  The actual steering angle sensor 63 is provided on the left and right front wheels FW1 and FW2 side of the active steering device 20, and detects the actual steering angle δ of the left and right front wheels FW1 and FW2 by measuring the rotation angle of the lower steering shaft 12b. To do. Instead of the actual steering angle sensor 63, the actual steering angle δ of the left and right front wheels FW1, FW2 may be detected by measuring the amount of displacement of the rack bar 14 in the axial direction. This actual steering angle δ represents the neutral state of the left and right front wheels FW1, FW2 by “0”, represents the right steering angle of the left and right front wheels FW1, FW2 by a positive value, and left steered by the left and right front wheels FW1, FW2 by a negative value. Represents a corner. However, the actual steering angle δ indicates a value converted into the steering wheel steering angle θh. The vehicle speed sensor 64 detects the vehicle speed V.

  An electronic control unit 65 (hereinafter simply referred to as ECU 65) is connected to these sensors 61-64. The ECU 65 has a microcomputer composed of a CPU, a ROM, a RAM, and the like as main components, and repeatedly executes the steering control program shown in FIG. 5 and the load device control program shown in FIG. 6 every predetermined short time.

  An active steering selection switch 66 and drive circuits 67 to 69 are also connected to the ECU 65. The active steering selection switch 66 is selected by the driver, and represents an active steering function selection state in the on state, and represents an active steering function non-selection state in the off state. The drive circuits 67 and 68 flow a drive current to the electric motors 27 and 41 in accordance with instructions from the ECU 54 and control the rotation of the electric motors 27 and 41. The drive circuit 68 has a built-in drive current sensor 68 a that detects the drive current flowing through the electric motor 41 and supplies it to the ECU 65. The drive circuit 69 controls energization of the electromagnetic coil 54 in accordance with an instruction from the ECU 65.

  Next, the operation of the first embodiment configured as described above will be described. When the driver drives the vehicle and rotates the steering handle 11, the upper steering shaft 12 a rotates about the axis by a rotation angle equal to the rotation angle of the steering handle 11. In this state, as will be described in detail later, the load device 50 is set to the restriction release state. The rotation of the upper steering shaft 12a is transmitted to the flex spline 34. The flex spline 34 rotates around the axis integrally with the outer ring of the ball bearing 33b, and the circular spline is engaged by the engagement between the outer teeth and the inner teeth of the circular spline 35. 35 is rotated around the axis. However, since the number of external teeth of the flexspline 34 is slightly smaller than the number of internal teeth of the circular spline 35, the rotational angle of the circular spline 35 is a small amount, but the rotational angle of the flexspline 34 is smaller than the number of teeth. Smaller than. The rotation of the circular spline 35 is transmitted to the lower steering shaft 12b, and the rack bar 14 is displaced in the axial direction via the pinion gear 13. The left and right front wheels FW1 and FW2 are steered left and right by the displacement of the rack bar 14 in the axial direction. Therefore, the left and right front wheels FW1 and FW2 are steered left and right by the turning operation of the steering handle 11.

  On the other hand, the ECU 54 repeatedly executes the steering control program of FIG. 5 every predetermined short time during the operation. The execution of this steering control program is started in step S10, and the ECU 54 inputs detection values from the steering wheel steering angle sensor 61, the steering wheel torque sensor 62, the actual steering angle sensor 63, and the vehicle speed sensor 64 in step S11. In step S12, it is determined whether or not active steering is selected by the active steering selection switch 66. If active steering is selected, “Yes” is determined in step S12, and the process proceeds to step S13.

  In step S13, an active steering angle θa as a corrected steering angle corresponding to the steering wheel steering angle θh is calculated with reference to the active steering angle table stored in the ROM. As shown in FIG. 7, the active steering angle table stores an active steering angle θa that increases as the steering wheel steering angle θh increases. Instead of using this active steering angle table, a function indicating the relationship between the steering wheel steering angle θh and the active steering angle θa is prepared in advance, and the active steering angle θa is calculated using the same function. You may do it.

  Further, instead of or in addition to the active steering angle θa, an active steering angle corresponding to the traveling state of the vehicle may be calculated. For example, as indicated by a broken line in FIG. 1, a yaw rate sensor 71 that detects the actual yaw rate γ of the vehicle is connected to the ECU 65. Then, referring to the target yaw rate table stored in the ROM, the target yaw rate γ * corresponding to the input steering angle θh and the vehicle speed V is calculated. As shown in FIG. 8, the target yaw rate table stores a target yaw rate γ * that increases as the steering wheel steering angle θh increases and increases in absolute value as the vehicle speed V increases. Instead of using the target yaw rate table, a function indicating the relationship between the steering angle θh and the vehicle speed V and the target yaw rate γ * is prepared in advance, and the target yaw rate γ * is calculated using the same function. You may make it calculate. Next, an active steering angle (= k · (γ * −γ)) is calculated so that the actual yaw rate γ detected by the yaw rate sensor 71 becomes equal to the target yaw rate γ *. Here, k is a predetermined coefficient. The calculated active steering angle may be used in place of the above-described active steering angle θa, or may be used in addition to the above-described active steering angle θa.

  Further, instead of the yaw rate sensor 71, as shown by a broken line in FIG. 1, a lateral acceleration sensor 72 for detecting the actual lateral acceleration Gy of the vehicle is connected to the ECU 65, and the actual lateral acceleration detected by the lateral acceleration sensor 72 is connected. An active steering angle (= k · (Gy * −Gy)) is calculated as a corrected steering angle so that Gy becomes equal to the target lateral acceleration Gy *. The calculated active steering angle may be used in place of the above-described active steering angle θa, or may be used in addition to the above-described active steering angle θa. In this case as well, the target lateral acceleration Gy * may be calculated using a table storing data having the characteristics shown in FIG. 8 or using a function.

  On the other hand, if active steering is not selected, “No” is determined in step S12, and the active steering angle θa is set to “0” in step S14.

  After the processing in step S13 or S14, in step S15, active steering control is executed, that is, the left and right front wheels FW1, FW2 are steered by the active steering angle θa. In this active steering control, the drive circuit 67 is controlled so that the electric motor 27 is rotated by a rotation angle corresponding to the active steering angle θa. In other words, the rotation of the electric motor 27 is controlled via the drive circuit 68 so that the actual steering angle δ detected by the actual steering angle sensor 63 is equal to the sum θh + θa of the steering wheel steering angle θh and the active steering angle θa. As described above, there is a slight difference between the rotation angle of the upper steering shaft 12a and the rotation angle of the lower steering shaft 12b only by the rotation of the steering handle 11, but this is the steering in the steering mechanism. At the same time as the gear ratio problem, there is no problem because the actual steering angle δ shows a value converted into the steering wheel steering angle θh.

  When the electric motor 27 is controlled to rotate as described above, the rotation of the rotor 27b and the rotating body 28 causes the cam 33a of the wave generator 33 to rotate around its axis, and the flexspline 34 is elastically deformed and its outer teeth circular. The meshing position of the spline 35 with respect to the internal teeth is moved. Since the number of external teeth of the flexspline 34 is different from the number of internal teeth of the circular spline 35, the rotation angle of the flexspline 34 and the rotation of the circular spline 35 are equal to the angle corresponding to the difference in the number of teeth. There is a difference between the corners. This means that relative rotation has occurred between the flexspline 34 and the circular spline 35. When the driver holds the steering handle 11 and restricts the rotation of the upper steering shaft 12a and the flexspline 34, the circular spline 35 is rotated with respect to the flexspline 34 by the rotation of the cam 33a. become. As a result, the lower steering shaft 12b rotates more than the upper steering shaft 12a by the active steering angle θa.

  Then, the rotation of the lower steering shaft 12 b is also converted into an axial displacement of the rack bar 14 via the pinion gear 13. Therefore, the left and right front wheels FW1 and FW2 are steered by the active steering angle θa in addition to the steering by the turning operation of the steering handle 11. As a result, the left and right front wheels FW1 and FW2 are corrected and steered by the active steering angle θa as the corrected steering angle, so that the steering characteristics of the vehicle can be arbitrarily selected and the steering characteristics can be improved. .

  On the other hand, as described above, when the active steering is not selected and the active steering angle θa is set to “0”, the electric motor 27 is kept at the reference position by the active steering control process of step S15. The rotation is not controlled. Therefore, in this case, the left and right front wheels FW1, FW2 are not substantially actively steered.

  After the process of step S15, the ECU 65 calculates the target assist torque Ta * in step S16. In calculating the target assist torque Ta *, the target assist torque Ta * corresponding to the input steering angle θh and the vehicle speed V is calculated with reference to an assist torque table stored in the ROM. As shown in FIG. 9, the assist torque table stores a target assist torque Ta * that increases as the steering wheel steering angle θh increases and increases as the vehicle speed V decreases. Instead of using the assist torque table, a function indicating the relationship between the steering angle θh, the vehicle speed V, and the target assist torque Ta * is prepared in advance, and the target assist torque Ta is used by using the function. * May be calculated.

  Next, in step S17, it is determined whether or not active steering is selected as in step S12. If active steering is selected, “Yes” is determined in step S12, and the process proceeds to step S18.

  In step S18, a reaction force reduction value Taa for reducing the reaction force to the steering wheel 11 due to the active steering is calculated. In the calculation of the reaction force reduction value Taa, the reaction force reduction value Taa corresponding to the calculated active steering angle θa is calculated with reference to the reaction force reduction value table stored in the ROM. As shown in FIG. 10, the reaction force reduction value table stores a reaction force reduction value Taa that increases as the active steering angle θa increases. Instead of using this reaction force reduction value table, a function indicating the relationship between the active steering angle θa and the reaction force reduction value Taa is prepared in advance, and the reaction force reduction value Taa is utilized using the same function. May be calculated.

  On the other hand, if the active steering is not selected, “No” is determined in step S17, and the reaction force reduction value Taa is set to “0” in step S19.

  After the processing of step S18 or S19, in step S20, the target assist torque Ta * corrected by the reaction force reduction value Taa is obtained by adding the calculated reaction force reduction value Taa to the calculated target assist torque Ta *. (= Ta * + Taa) is calculated. In step S21, the drive of the electric motor 41 is controlled via the drive circuit 68, and in step S22, the execution of the steering control program is temporarily terminated. In this drive control, the ECU 54 inputs the drive current detected by the drive current sensor 68a, and controls the drive circuit 68 so that the electric motor 41 generates the target assist torque Ta *. Under this control, the drive circuit 68 drives the electric motor 41 by flowing a drive current corresponding to the target assist torque Ta * to the electric motor 41.

  With such drive control of the electric motor 41, the electric motor 41 transmits power to the rack bar 14 via the screw feed mechanism 42 and linearly drives the rack bar 14 in the axial direction thereof. As a result, when the driver tries to turn the steering handle 11 to steer the left and right front wheels FW1, FW2, the electric motor 41 assists the driver in turning the steering handle 11, and the driver makes small steering. The left and right front wheels FW1, FW2 can be steered by force. In addition, the correction of the target assist torque Ta * using the reaction force reduction value Taa in step S20 cancels the steering reaction force caused by the active steering, so that the driver can perform the steering of the left and right front wheels FW1, FW2 by the active steering control. I don't feel any reaction.

  On the other hand, when the active steering is not selected as described above and the reaction force reduction value Taa is set to “0”, the target assist torque Ta * is obtained in step S16 by the process of step S20. Since the calculated value is maintained, the reaction force reduction value Taa accompanying active steering is not taken into consideration.

  In parallel with the execution of such a steering control program, the ECU 65 repeatedly executes the load device control program of FIG. 6 every predetermined short time. The execution of the load device control program is started in step S30, and it is determined in step S31 whether active steering is selected by the active steering selection switch 66. If active steering is not selected, “No” is determined in step S31, and after the processing in step S37, the execution of the load device control program is temporarily terminated in step S38. In step S37, the load device 50 is set to the restriction release state described above by stopping energization of the electromagnetic coil 54 of the load device 50. Thus, the left and right front wheels FW1, FW2 are steered in accordance with the turning operation of the steering handle 11. Note that when the active steering is not selected, the left and right front wheels FW1, FW2 are not actively steered.

  On the other hand, if active steering is selected, “Yes” is determined in step S31, and the process proceeds to step S32 and subsequent steps. In step S32, the steering wheel steering angle θh is input from the steering wheel steering angle sensor 61, and the rotation angles θht1 and θht2 are input from the steering wheel torque sensor 62. Next, in step S33, a handle torque Th is calculated by multiplying the difference θht1−θht2 between the input rotational angles θht1 and θht2 by a predetermined coefficient.

  Next, in step S34, it is determined whether the absolute value | θh | of the steering wheel steering angle θh is less than a predetermined small predetermined value θh1, and in step S35, the absolute value | Th | It is determined whether it is less than a predetermined small predetermined value Th1. If the absolute value | θh | of the steering wheel steering angle θh is equal to or larger than the predetermined value θh1 or the absolute value | Th | of the steering wheel torque Th is equal to or larger than the predetermined value Th1, “No” is determined in Step S34 or S35, and Step S37 is performed. As described above, the load device 50 is set to the restriction release state, and the load device control program is once terminated in step S38. Therefore, in this state, the left and right front wheels FW1 and FW2 are steered according to the turning operation of the steering handle 11. Further, since active steering is selected, the left and right front wheels FW1, FW2 are actively steered as described above.

  On the other hand, if the absolute value | θh | of the steering wheel steering angle θh is less than the predetermined value θh1 and the absolute value | Th | of the steering wheel torque Th is less than the predetermined value Th1, both “Yes” are determined in steps S34 and S35. The load device 50 is set to a restricted state by energizing the electromagnetic coil 54 of the load device 50 in step S36, and the load device control program is temporarily terminated in step S38. Thereby, the rotation of the upper steering shaft 12a and the steering handle 11 around the axis is restricted. On the other hand, in this state, since the steering handle 11 and the upper steering shaft 12a are fixed, the left and right front wheels FW1, FW2 are actively steered by the active steering device 20.

  When the absolute value | θh | of the steering wheel steering angle θh is less than the predetermined value θh1 and the absolute value | Th | of the steering wheel torque Th is less than the predetermined value Th1, the steering handle 11 is in the vicinity of the neutral state, that is, the steering handle 11 This corresponds to when the vehicle is not steered. When the steering handle 11 is not being steered, the load device 50 restricts the rotation of the steering handle 11, so that the driver feels a sense of discomfort when the steering handle 11 is not steered. Steering wheel steering torque fluctuations can be eliminated. When the steering handle 11 is steered, the load device 50 is set to the restriction release state as described above. Therefore, the steering of the left and right front wheels FW1, FW2 corresponding to the steering operation of the steering handle 11 is not hindered.

  In the first embodiment, the presence or absence of the steering operation of the steering handle 11 is detected using both the steering angle θh and the steering torque Th. However, although the accuracy is somewhat reduced, the determination process of one of steps S34 and S35 is omitted, and the steering operation of the steering wheel 11 is performed by the determination process of one of the steering wheel steering angle θh and the steering wheel torque Th. It may be determined whether or not there is. Also by this, the same effect as the above is expected.

  Further, the determination processing in steps S34 and S35 of FIG. 6 can be regarded as hand release detecting means for detecting the driver's hand release state with respect to the steering handle 11. In a state where the driver has released his / her hand from the steering handle 11 or his / her hand is in contact with the steering handle 11 but is not sufficiently grasping the steering handle 11 (this also corresponds to a kind of hand release state), The steering handle 11 rotates due to the external force. The absolute value | θh | of the steering angle θh of the steering wheel and the absolute value | Th | of the steering torque Th are extremely small, which corresponds to this hand-off state. Therefore, the determination processing in steps S34 and S35 that can detect this state can be regarded as detection of the hand release state of the steering handle 11 by the driver.

  When the driver's hand release state is not detected (| θh | ≧ θh1 and | Th | ≧ Th1), the load applied to the steering handle 11 is reduced by the processing of step S37, that is, the steering handle. 11 is controlled to be released. Further, when the hand release state of the driver is detected (| θh | <θh1 and | Th | <Th1), the load applied to the steering handle 11 is increased by the processing of step S36, that is, the steering handle. 11 is controlled to be restricted.

  As a result, even when the driver has released his / her hand from the steering wheel 11, even when the left and right front wheels FW 1 and FW 2 are actively steered by the active steering device 20, the reaction force due to active steering is transmitted to the steering handle 11 by the load device 50. Can be prevented. Accordingly, the left and right front wheels FW1 and FW2 are actively steered by the active steering device 20, and the steering handle 11 is not displaced against the intention of the driver by the active steering, and the steering handle 11 in the hand released state of the steering handle 11 is released. The driver is not given the uncomfortable feeling that accompanies the rotation. In the state where the driver is holding the steering handle 11, the left and right front wheels FW1 and FW2 are steered according to the steering operation of the steering handle 11 by the driver, and the reaction force to the steering handle 11 by the active steering is applied. On the other hand, since the steering operation force by the driver opposes, active steering of the left and right front wheels FW1, FW2 by the active steering device 20 is also permitted.

  Further, in the first embodiment, a torsion bar 62 a that is an elastic body that can be elastically deformed is interposed between the steering handle 11 and the load device 50. Therefore, even when the displacement of the steering handle 11 is restricted by the load device 50, a slight displacement of the steering handle 11 is allowed, and a good operating feeling can be given to the driver's operation of the steering handle 11. The force applied to the load device 50 can be relaxed.

  Further, in the first embodiment, the restriction state and the restriction release state of the load device 50 are alternatively switched, but the restriction force (resistance force) against the rotation of the steering handle 11 is continuously changed. You may do it. That is, as the absolute value | θh | of the steering wheel steering angle θh decreases or as the absolute value | Th | of the steering wheel torque Th decreases, the restriction force on the rotation of the steering handle 11 by the load device 50 increases. That's fine. In this case, in order to control the magnitude of the regulation force of the load device 50, the value of the current flowing through the electromagnetic coil 54 may be increased as the regulation force increases.

  Moreover, in the said 1st Embodiment, although the load apparatus 50 was comprised with the electromagnetic clutch apparatus using the electromagnetic coil 54, this load apparatus 50 can also be deform | transformed as follows. FIG. 11 shows a modification of the load device 50 in a longitudinal sectional view. The load device 50 according to this modification includes a cylindrical conductive casing 81 that penetrates the upper steering shaft 12a in a liquid-tight manner and is rotatable about an axis. In the casing 81, a rotor 82 is fixed on the outer periphery of the upper steering shaft 12a. The casing 81 is fixed to a housing member 53 that rotatably supports the upper steering shaft 12a, and an electrorheological fluid 83 is sealed in the casing 81. The electrorheological fluid 83 is obtained by dispersing particles as a dispersion medium in a liquid. As the electric field strength in the electric field increases, the coupling force between the particles increases, and the resistance force against the rotation of the rotor 82 increases. It has an increasing property.

  Therefore, an electric field is not applied to the electrorheological fluid 83 when the rotation of the steering handle 11 and the upper steering shaft 12a by the load device 50 is not restricted. When the rotation of the steering handle 11 and the upper steering shaft 12a is restricted, an electric field is preferably applied to the electrorheological fluid 83 via the casing 81. Further, in order to continuously change the force that regulates the rotation of the steering handle 11 and the upper steering shaft 12a, the strength of the electric field applied to the electrorheological fluid 83 through the casing 81 is changed. That is, in order to increase the force that restricts the rotation of the steering handle 11 and the upper steering shaft 12a, the voltage applied to the casing 81 may be increased.

  Further, a magnetorheological fluid may be used in place of the electrorheological fluid 83, and the magnetorheological fluid may be placed in a magnetic field. Further, as the load device 50, an electric motor may be adopted to restrict the rotation of the upper steering shaft 12a by the driving force of the electric motor, or a powder clutch may be used to restrict the rotation of the upper steering shaft 12a. Good.

  When the load of the load device 50 is continuously changed, the ECU 65 executes the load device control program of FIG. 12 instead of the load device control program of FIG. It is good to control. The load device control program of FIG. 12 is obtained by changing the processing of steps S34 to S36 of the load device control program of FIG. 6 to steps S34 ', S35', and S41 to S43. Since the other parts are the same as those of the load device control program of FIG. 6, the same parts are denoted by the same reference numerals and the description thereof is omitted.

  In steps S34 ′ and S35 ′, it is determined whether the absolute value | θh | of the steering wheel steering angle θh is smaller than a predetermined small predetermined value θh2, as in the case of the load device control program of FIG. Then, it is determined whether the absolute value | Th | of the handle torque Th is less than a predetermined small predetermined value Th2. The absolute value | θh | of the steering wheel steering angle θh is compared with a predetermined value θh2, and the absolute value | Th | of the steering wheel torque Th is compared with a predetermined value Th2. These predetermined values θh2 and Th2 are shown in the above-described figure. 6 is set to a value slightly larger than the predetermined values θh1 and Th1. In step S41, the steering speed θv of the steering wheel 11 is calculated by differentiating the steering angle θh.

  In step S42, a first load control value G1 corresponding to the absolute value | θv | of the calculated steering speed θv is calculated with reference to the first load control value table stored in the ROM. In step S42, the second load control value G2 corresponding to the calculated absolute value | Th | of the handle torque Th is calculated with reference to the second load control value table stored in the ROM. . As shown in FIG. 13A, the first load control value table stores a first load control value G1 that decreases as the absolute value | θv | of the steering speed θv increases. As shown in FIG. 13B, the second load control value table stores a second load control value G2 that decreases as the absolute value | Th | of the handle torque Th increases. In this case, the second load control value G2 is a positive value only within a small range of the absolute value | Th | of the handle torque Th, and is “0” in a range beyond that. Also in this case, instead of using the first and second load control value tables, a function indicating the relationship between the absolute value | θv | of the steering speed θv and the first load control value G1, and the steering torque Th A function indicating the relationship between the absolute value | Th | and the second load control value G2 is prepared in advance, and the first and second load control values G1 and G2 are calculated using these functions. Also good.

  Next, in step S43, the load device 50 is controlled by a control signal having a magnitude proportional to the product G1, G2 of the first and second load control values G1, G2, and the product G1, G2 is supplied to the load device 50. The rotation of the steering handle 11 and the upper steering shaft 12a is regulated by a regulation force (resistance force) having a magnitude proportional to Specifically, when the load device 50 is configured by the electromagnetic clutch shown in FIG. 4, a current having a magnitude proportional to the products G 1 and G 2 is supplied to the electromagnetic coil 54. Further, when the load device 50 is configured using the electrorheological fluid 83 or the magnetorheological fluid as shown in FIG. 11, the voltage (the strength of the electric field) having a magnitude proportional to the products G1 and G2 in the electrorheological fluid 83. Or a magnetic field having a magnitude proportional to the products G1 and G2 is applied to the magnetorheological fluid.

  As a result, according to this modification, when the product G1 · G2 of the steering speed θv and the steering torque Th of the steering handle 11 is large, the steering handle 11 is moved from a large restricted state (restraint state) of the steering handle 11 by the load device 50. It is possible to avoid the situation of sudden switching to the deregulated state. As a result, the driver does not feel discomfort due to a sudden change in the steering reaction force.

b. Second Embodiment Next, a vehicle steering apparatus according to a second embodiment of the present invention will be described. As shown in FIG. 14, this steering device is different from the vehicle steering device according to the first embodiment in that an output torque sensor 73 is provided and the ECU 65 executes the steering control program shown in FIG. Different. The other points are the same as those in the first embodiment, and thus the same parts as those in the first embodiment are denoted by the same reference numerals and the description thereof is omitted.

  The output torque sensor 73 is provided on the left and right front wheels FW1, FW2 side with respect to the load device 50, and is provided between the load device 50 and the active steering device 20 in the second embodiment. The output torque sensor 73 is provided at each of the upper and lower ends of the torsion bar (elastic body) 73a constituting a part of the upper steering shaft 12a, and rotates to detect the rotation angles θot1 and θot2 around the axis at both ends. The angle sensors 73b and 73c are used to detect torque (hereinafter referred to as output torque To) acting on the upper steering shaft 12a located between the load device 50 and the active steering device 20. The rotation angles θot1 and θot2 detected by the both rotation angle sensors 73b and 73c represent the reference positions of the upper and lower ends of the torsion bar 73a by “0”, and the right rotation of the upper and lower ends of the torsion bar 73a by a positive value. Each angle represents a left rotation angle of the steering handle 11 at both upper and lower ends of the torsion bar 73a by a negative value. The output torque sensor 73 may be provided on the left and right front wheels FW1, FW2 side of the active steering device 20. Further, in place of the output torque sensor 73 for detecting the rotation angle, the output torque To is detected by detecting distortion of the torsion bar 62a or the lower steering shaft 12b or detecting distortion of the rack shaft 14. A torque sensor or an axial force sensor may be used.

  Next, the operation of the second embodiment configured as described above will be described. In the second embodiment, the ECU 65 executes the steering control program shown in FIG. Also in the steering control program of FIG. 15, the left and right front wheels FW1, FW2 are subjected to active steering control by the processing of steps S11 to S15 similar to the first embodiment. Further, in step S11, in addition to the steering wheel steering angle θh, the rotation angles θht1, θht2 and the actual steering angle δ, the rotation angles θot1, θot2 from the rotation angle sensors 73b, 73c of the output torque sensor 73 are also input.

  After the active steering control, in step S51, an output torque To is calculated by multiplying the difference θot1-θot2 between the input rotational angles θot1, θot2 by a predetermined coefficient. In step S52, the target assist torque Ta * is calculated. In calculating the target assist torque Ta *, the target assist torque Ta * corresponding to the input output torque To is calculated with reference to the assist torque table stored in the ROM. As shown in FIG. 16, the assist torque table stores a target assist torque Ta * that increases as the output torque To increases. Instead of using the assist torque table, a function indicating the relationship between the output torque To and the target assist torque Ta * is prepared in advance, and the target assist torque Ta * is calculated using the function. You may do it.

  Next, the drive circuit 68 is controlled so that the electric motor 41 generates the target assist torque Ta * by the process of step S21 similar to the first embodiment. As a result, in this case as well, the left and right front wheels FW1, FW2 are assisted steered with an assist force corresponding to the target assist torque Ta * by the rotation of the electric motor 41.

  In the second embodiment, the load device 50, the active steering device 20 and the steering assist device 40 are arranged in this order between the steering handle 11 and the left and right front wheels FW1 and FW2. Since the left and right front wheels FW1 and FW2 are assisted by steering according to the output torque acting on the member on the FW2 side, the steering reaction force reversely input to the load device 50 and the steering handle 11 from the left and right front wheels FW1 and FW2 side is reduced. Can do. Thereby, even if the active steering device 20 actively steers the left and right front wheels FW1 and FW2, the influence on the steering handle 11 can be reduced, and the load device 50 can be made small, that is, a device having a small maximum allowable load can be used. become.

  In the second embodiment, an output torque sensor 73 is added to the left and right front wheels FW1 and FW2 from the load device 50 in addition to the vehicle steering device according to the first embodiment. Since the steering assist of the left and right front wheels FW1, FW2 is controlled by the output torque To detected by the torque sensor 73, the effect of the first embodiment is expected in addition to the effect specific to the second embodiment. it can.

  Further, in the second embodiment, in the state where the active steering is not selected by the active steering selection switch 66, the restriction of the rotation of the steering handle 11 by the load device 50 is released, but the active steering selection switch 66 activates it. In a state where the steering is selected, the load device 50 may be always operated so that the rotation of the steering handle 11 is always restricted. In this case, the processing in steps S32 to S36 in FIG. 6 of the first embodiment is omitted, and in the operation control of the load device 50 in step S36, a somewhat small regulation force (resistance force) is applied to the steering handle 11. The load device 50 is controlled so as to be applied to.

  According to this, during active steering, the driver's steering torque (handle torque) with respect to the steering handle 11 tends to increase due to the restriction of the load device 50, but the output torque To detected by the output torque sensor 73 is used. The steering assist control by the processing of steps S51, S52, and S21 makes it possible to suppress the driver's steering torque to some extent. Further, the continuous control of the load device 50 during the active steering also eliminates the need for the handle torque sensor 62, and the reaction torque including the reaction force due to the active steering of the left and right front wheels FW1, FW2 by the active steering device 20 is the steering torque. The influence on (handle torque) can be reduced.

  Furthermore, the present invention is not limited to the above-described embodiment, and various modifications can be employed within the scope of the present invention.

  For example, in the above embodiment, the rack bar 14 is driven in the axial direction by the electric motor 41 for steering assist. However, instead of this, the lower steering shaft 12b may be rotationally driven by the steering assist electric motor 41 via the speed reduction mechanism.

  Further, the present invention is applied to a steering apparatus for a vehicle that steers the left and right front wheels FW1 and FW2 by a turning operation of the steering handle 11. However, the present invention is also applied to a steering apparatus for a vehicle that steers the left and right front wheels FW1 and FW2 by a linear operation such as a joystick.

1 is an overall schematic diagram of a vehicle steering apparatus according to a first embodiment of the present invention. It is a longitudinal cross-sectional view of the active steering apparatus of FIG. FIG. 3 is a cross-sectional view of the harmonic drive mechanism of FIG. 2. (A) and (B) are the longitudinal cross-sectional views of the load apparatus of FIG. 2 is a flowchart of a steering control program executed by the ECU of FIG. It is a flowchart of the load apparatus control program performed by ECU of FIG. It is a graph which shows the relationship between steering wheel steering angle (theta) h and active steering angle (theta) a. It is a graph which shows the relationship between steering wheel steering angle (theta) h and vehicle speed V, and target yaw rate (gamma) * (or target lateral acceleration Gy *). It is a graph which shows the relationship between steering wheel steering angle (theta) h and vehicle speed V, and target assist torque Ta *. It is a graph which shows the relationship between active steering angle (theta) a and reaction force reduction value Taa. It is a longitudinal cross-sectional view which shows the modification of the load apparatus of FIG. It is a flowchart of the load apparatus control program which shows the modification of the load apparatus control program of FIG. (A) is a graph showing the relationship between the steering speed θv and the first load control value G1, and (B) is a graph showing the relationship between the steering torque and the second load control value G2. It is a whole schematic diagram of the steering device of vehicles concerning a 2nd embodiment of the present invention. It is a flowchart of the steering control program performed by ECU of FIG. It is a graph which shows the relationship between output torque and target assist torque Ta *.

Explanation of symbols

DESCRIPTION OF SYMBOLS 11 ... Steering handle, 12 ... Steering shaft, 12a ... Upper steering shaft, 12b ... Lower steering shaft, 13 ... Pinion gear, 14 ... Rack bar, 20 ... Active steering device, 27 ... Electric motor, 40 ... Steering assist device, 41 ... Electric motor, 50 ... load device, 61 ... steering wheel angle sensor, 62 ... steering wheel torque sensor, 63 ... actual steering angle sensor, 64 ... vehicle speed sensor, 65 ... ECU, 66 ... active steering selection switch, 71 ... yaw rate sensor, 72 ... lateral acceleration sensor, 73 ... output torque sensor.

Claims (8)

In a steering apparatus for a vehicle that mechanically connects a steering wheel and a steering wheel and steers the steering wheel in response to a steering operation of the steering wheel,
A steering assist device that is interposed between the steering wheel and the steered wheel and that can assist the steering of the steered wheel and that can change an assist amount of the steered wheel;
A correction steering device interposed between the steering wheel and the steering assist device for correcting and steering the steering wheel in addition to steering the steering wheel corresponding to the steering operation of the steering wheel;
A load device that is interposed between the steering handle and the correction steering device and applies a load to the steering handle to restrict displacement of the steering handle;
Steering reaction force detection means for detecting a steering reaction force acting on the steering wheel side member relative to the load device;
A vehicle steering apparatus comprising: a steering assist control unit that controls an assist amount of steering of the steered wheels by the steering assist device according to the steering reaction force detected by the steering reaction force detection unit. The vehicle steering device according to claim 1 , wherein the load device is capable of changing a magnitude of a load applied to a steering wheel. The vehicle steering apparatus according to claim 2 , further comprising:
Steering operation detection means for detecting the steering operation of the steering wheel;
When the steering operation of the steering wheel is detected by the steering operation detection means, the load device is controlled so that the load applied to the steering wheel is reduced, and the steering operation of the steering wheel is detected by the steering operation detection means. A vehicle steering apparatus comprising load control means for controlling the load apparatus so that a load applied to the steering wheel becomes large when the steering wheel is not. The steering operation detecting means includes a steering wheel angle sensor that is interposed between a steering wheel and the load device and detects a steering angle of the steering wheel, and uses a steering angle detected by the steering wheel angle sensor. The vehicle steering apparatus according to claim 3 , wherein the steering operation of the steering wheel is detected. The steering operation detection means includes a steering wheel force sensor that is interposed between the steering wheel and the load device and detects a steering force applied to the steering wheel, and the steering detected by the steering wheel force sensor. The vehicle steering apparatus according to claim 3 , wherein the steering operation of the steering wheel is detected using force. The vehicle steering apparatus according to claim 2 , further comprising:
Release detection means for detecting the release state of the driver with respect to the steering wheel;
The load device is controlled so that the load applied to the steering wheel is reduced when the release state of the driver is not detected by the release detection unit, and the release state of the driver is determined by the release detection unit. A vehicle steering system comprising load control means for controlling the load device so that a load applied to the steering wheel is increased when detected. The hand away detecting means, according to claim 6 which has a steering force sensor for detecting a steering force applied to the steering wheel, for detecting the hand release state using the steering force detected by said steering force sensor The vehicle steering device described in 1. In the steering apparatus for a vehicle according to any one of claims 1 to 7, further
A vehicle steering apparatus in which an elastic body that is elastically deformable is interposed between a steering handle and the load device.

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