Reaction force generating device and steering device

A reaction force generating device for a steering device includes a steering shaft connected to a steering member on which a steering operation is to be performed by a driver, a direct drive motor connected to the steering shaft and configured to generate reaction torque, an electromagnetic brake configured to generate friction torque and including a first friction portion configured to integrally rotate with the steering shaft, a second friction portion provided to face the first friction portion and to be non-rotatable, and an electromagnetic unit configured to press the second friction portion against the first friction portion.

FIELD OF THE INVENTION

The present invention relates to a reaction force generating device and a steering device using the reaction force generating device.

BACKGROUND OF THE INVENTION

Various steering systems have been developed in order to reduce the burden on a driver who drives an automobile vehicle.

In recent years, a steering system of a steer-by-wire (SBW) manner is under development in which an operation unit that accepts a steering operation by a driver and a turning unit that turns the wheels are mechanically separated, and the steering unit is electrically controlled according to a steering amount of the operation unit.

The steer-by-wire manner has the advantage of being able to eliminate kickback from a road surface, but it requires a reaction force generating device that generates a reaction force to the steering operation in order to provide the driver with a natural feeling of operation.

For example, Patent Literature 1 describes a vehicle steering device in which a reaction force motor that applies a reaction force in a direction opposite to the direction of an operation for steering is attached to a steering member arranged separately from a steering mechanism of a vehicle, and an induction motor is used as the reaction force motor.

It is preferable to reduce the size of the reaction force generating device while ensuring a reaction force that can counter the input of the driver.

SUMMARY OF THE INVENTION

The invention has been made in view of the above-described problems, and an object thereof is to provide a reaction force generating device whose size can be reduced while ensuring a reaction force that can counter input of a driver, and a steering device using the reaction force generating device.

In order to solve the above problem, a reaction force generating device according to the present invention is a reaction force generating device for a steering device, the reaction force generating device including a steering shaft connected to a steering member on which a steering operation is to be performed by a driver, a direct drive motor connected to the steering shaft, and an electromagnetic brake connected to the steering shaft.

Advantageous Effects of Invention

According to the reaction force generating device and the steering device of the present invention, it is possible to reduce the size while ensuring a reaction force that can counter the input of a driver.

DETAILED DESCRIPTION OF THE INVENTION

First Embodiment

A steering device1according to a first embodiment is described with reference toFIGS.1to4.

FIG.1is a schematic view schematically showing a configuration of a main part of the steering device1. As shown inFIG.1, the steering device1includes a steering unit10, a turning unit20, a steering member200, and a control unit300. The steering device1is used to steer wheels400in response to a steering operation by a driver via the steering member200.

As shown inFIG.1, the steering device1is a steering device of the steer-by-wire manner that does not have a mechanical torque transmission path between the steering member200and the turning unit20, but can electrically control a turning angle of the wheels400in response to a steering operation via the steering member200.

As the steering member200, a steering wheel having a wheel shape is given as an example as shown inFIG.1, but the present embodiment is not limited thereto, and the steering member200may have other shapes or mechanisms as long as a driver can perform a steering operation thereon.

The steering unit10has both a function of receiving a steering operation by a driver via the steering member200and a function of generating a reaction force against the steering operation and transmitting the reaction force to the steering member200. As shown inFIG.1, the steering unit10includes a reaction force generating device100, a steering shaft101, and a torque sensor102.

In the following description, an “upper end” refers to an end portion on a side closer to the steering member200, and a “lower end” refers to an end portion on a side farther from the steering member200.

An upper end of the steering shaft101is connected to the steering member200such that torque can be transmitted. Here, “connected such that torque can be transmitted” means that members are connected with each other such that rotation of one member causes the rotation of the other member, and at least includes, for example, a case where the one member and the other member are integrally formed, a case where the other member is directly or indirectly fixed to the one member, and a case where the one member and the other member are connected so as to be interlocked with each other via a joint member or the like.

In the present embodiment, the upper end of the steering shaft101is fixed to the steering member200, and the steering member200and the steering shaft101rotate integrally.

The steering shaft101and the reaction force generating device100are connected with each other such that torque can be transmitted, and the twist generated in the steering shaft101is detected by the torque sensor102.

More specifically, when a driver performs a steering operation via the steering member200, a twist angle θTcorresponding to the magnitude of torque T of the steering operation is generated in a torsion bar provided in the steering shaft101. The torque sensor102detects the twist angle θTand supplies a torque sensor signal indicating the detection result to the control unit300. The steering unit10may further include a steering angle sensor for detecting a steering angle of the steering member200, and the steering angle sensor may be configured to supply a signal indicating the detected steering angle or steering angular velocity to the control unit300. Further, the steering unit10may include a steering angle sensor instead of the torque sensor102, and the steering angle sensor may be configured to supply a signal indicating the detected steering angle or steering angular velocity to the control unit300.

The reaction force generating device100generates torque according to a torque control signal supplied from the control unit300. A specific configuration of the reaction force generating device100will be described later.

The control unit300controls a turning force generated by a turning force generating unit220and the torque generated by the reaction force generating device100in response to the steering operation by the driver.

More specifically, the control unit300refers to the torque sensor signal supplied from the torque sensor102to generate the torque control signal for controlling the torque generated by the reaction force generating device100and a turning force control signal for controlling the turning force generated by the turning force generating unit220, and supplies the torque control signal and the turning force control signal to the reaction force generating device100and the turning force generating unit220, respectively.

The control unit300may be configured to generate the torque control signal and the turning force control signal by further referring to a signal indicating a steering angle of the steering member200, a vehicle speed signal from a vehicle speed sensor, and the like.

The control unit300controls the reaction force generating device100so that the reaction torque in a direction opposite to the steering torque by the driver which is input via the steering member200is transmitted to the steering shaft101. As a result, the driver can obtain a feeling of operation for the steering operation.

The turning unit20is configured to turn the wheels400in response to the steering operation of the driver received by the steering unit10.

As shown inFIG.1, the turning unit20includes a rack shaft211, tie rods212, knuckle arms213, and the turning force generating unit220.

The turning force generating unit220generates a turning force according to the turning force control signal from the control unit300, and displaces the rack shaft211in an axial direction.

When the rack shaft211is displaced in the axial direction, the wheels400are turned via the tie rods212provided at both ends of the rack shaft211and the knuckle arms213connected to the tie rods212.

A specific configuration of the turning force generating unit220is not limited to this embodiment, and examples thereof include the following configuration examples.

Configuration Example 1

The turning force generating unit220includes a motor, and a conversion mechanism that converts rotational motion of an output shaft of the motor into a linear motion in the axial direction of the rack shaft211. Here, the conversion mechanism can adopt, for example, a so-called ball screw mechanism configured by a nut having an inner peripheral surface on which a spiral groove is formed, which is rotationally driven by the motor, a spiral groove formed on an outer peripheral surface of the rack shaft and having the same pitch as the spiral groove of the nut, and a plurality of rolling balls sandwiched between the spiral groove of the nut and the spiral groove of the rack shaft.

Furthermore, the turning force generating unit220can be configured to include a drive pulley connected to the output shaft of the motor arranged along the rack shaft211such that torque can be transmitted, a driven pulley connected to the nut such that torque can be transmitted, and a suspension member that is suspended between the drive pulley and the driven pulley and transmits torque from the drive pulley to the driven pulley.

Configuration Example 2

The turning force generating unit220may include a hollow motor coaxially arranged with the rack shaft211, and the nut in Configuration Example 1 may be rotationally driven by the hollow motor. According to such a configuration, the drive pulley and the driven pulley in the Configuration Example 1 are not required, so that space can be saved.

Configuration Example 3

Instead of the ball screw mechanism, the turning force generating unit220may be configured to include a second pinion shaft that is rotationally driven by a motor, and a pinion gear that is connected to the second pinion shaft such that torque can be transmitted, and that meshes with the second rack formed on the rack shaft211.

Configuration Example 4

The turning force generating unit220may be provided for each of the left, right, front, and rear wheels400. According to such a configuration, the wheels400can be turned independently.

Next, a configuration example of the reaction force generating device100is described more specifically with reference toFIGS.2and3.FIG.2is a sectional view showing a configuration example of the reaction force generating device100.

FIG.2is a sectional view of the reaction force generating device100when an electromagnetic brake120described later is not in operation, andFIG.3is a sectional view of the reaction force generating device100when the electromagnetic brake120is in operation.

As shown inFIG.2, the reaction force generating device100includes a direct drive motor110, the electromagnetic brake120, a housing130, a rotation angle sensor150, and a second spring172.

The direct drive motor110includes a motor rotor111and a motor core112. The motor rotor111is fixedly connected to the steering shaft101, and the motor rotor111and the steering shaft101rotate integrally. The motor rotor111may be configured to include a plurality of permanent magnets as an example, but the present embodiment is not limited thereto. The motor core112is fixedly connected to the housing130and is an electromagnetic component for applying reaction torque to the motor rotor111. As an example, the motor core112may be configured to include a plurality of electromagnets whose polarity and magnitude of the electric field are controlled by the torque control signal supplied from the control unit300, but the present embodiment is not limited thereto.

The direct drive motor110configured as described above rotates the motor rotor111according to the torque control signal supplied from the control unit300, and the motor rotor111and the steering shaft101are integrally rotated. As a result, the direct drive motor110generates reaction torque in response to the steering operation by the driver.

The rotation angle sensor150detects a rotation angle of the steering shaft101, and supplies a rotation angle signal indicating the detected result to the control unit300. The rotation angle signal may be directly supplied to the electromagnetic brake120.

The electromagnetic brake120includes an electromagnetic unit121, a first friction portion123, a second friction portion122, and a support pin124. The first friction portion123includes a first friction plate support portion123aand a first friction plate123b. The first friction plate support portion123ais fixedly connected to the steering shaft101, and therefore, the first friction plate support portion123aand the steering shaft101rotate integrally. Further, on a side of the first friction plate support portion123afacing the second friction portion122, the first friction plate123bis fixedly provided with respect to the first friction plate support portion123a.

On the other hand, the second friction portion122includes a second friction plate support portion122aand a second friction plate122b. The second friction plate support portion122ais supported by the support pin124so as to be non-rotatable about the axis of the steering shaft101in the axial direction and slidable in the axial direction. More specifically, a through hole is formed in the second friction plate support portion122a, one end of the through hole is fixedly connected to the housing130, and the support pin124extending along the axial direction of the steering shaft101penetrates the through hole. On a side of the second friction plate support portion122afacing the first friction plate123b, the second friction plate122bis fixedly provided with respect to the second friction plate support portion122a.

The electromagnetic unit121is fixed to the housing130so as to be non-rotatable around the axis of the steering shaft101in the axial direction and non-slidable in the axial direction. More specifically, a through hole is formed in the electromagnetic unit121, and the support pin124penetrates through the through hole.

The electromagnetic unit121slides the second friction portion122in the axial direction of the steering shaft101in response to the rotation angle signal detected by the rotation angle sensor150. The electromagnetic unit121slides the second friction portion122toward the first friction portion123, so that the second friction plate122bpresses against the first friction plate123b. Therefore, the first friction plate123band the second friction plate122bcome into contact with each other to generate friction torque. As a result, the reaction torque caused by the electromagnetic brake120is applied to the steering shaft101.

The electromagnetic unit121may be configured to operate in response to a steering angle signal of a steering angle sensor (not shown) of the steering member200instead of the rotation angle signal. Further, it is preferable that the members used for the first friction plate123band the second friction plate122bhave a quiet operation noise when the electromagnetic brake120is in operation, are excellent in release ability of the electromagnetic brake120, and reduce a phenomenon such as being flipped when the electromagnetic brake120is in operation. However, the present embodiment is not limited thereto.

The housing130accommodates the direct drive motor110and the electromagnetic brake120. The direct drive motor110and the electromagnetic brake120are accommodated in the housing130, so that the size of the reaction force generating device100can be reduced.

The second spring172is arranged between the first friction portion123and the second friction portion122. More specifically, one end portion of the second spring172is connected to a surface of the first friction plate support portion123aon a side opposite to the direct drive motor110via a rotatably slidable member173, and the other end portion of the second spring172is connected to a surface of the second friction plate support portion122aopposite to the electromagnetic unit121.

Next, the reaction torque generated in the reaction force generating device100is described with reference toFIG.4.

The line graph shown inFIG.4shows the correspondence between a steering angle of the steering member200and reaction torque to be generated in the reaction force generating device100. In the line graph ofFIG.4, the horizontal axis represents the steering angle of the steering member200, and the vertical axis represents the reaction torque to be generated in the reaction force generating device100. A steering angle θ0indicates an angle of an initial position of the steering member200, and steering angles θ1to θ3indicate angles when the steering member200is steered clockwise or counterclockwise with the steering angle θ0as a starting point. Here, in the present embodiment, a steering angle θ2is a steering angle of the steering member200corresponding to the maximum turning angle of the turning unit20. Further, in the present embodiment, the steering angle θ1may be referred to as a predetermined steering angle, and the steering angle θ2may be referred to as a specified steering angle (first steering angle in Claims). A range from the steering angle θ0to the steering angle θ2indicates a normal turning range in which the turning unit20can be turned corresponding to the steering angle of the steering member200, and a range from the steering angle θ2to the steering angle θ3is an abnormal turning range in which the turning unit20cannot be turned corresponding to the steering angle of the steering member200. A range from reaction torque f0to reaction torque f2indicates a value of normal steering reaction force, which is reaction torque generated by the direct drive motor110, and a range from the reaction torque f0to reaction torque f3indicates a value of normal wall reaction force, which is reaction torque obtained by combining the reaction torque generated by the direct drive motor110and the friction torque generated by the electromagnetic brake120. Further, reaction torque f4indicates a value of the reaction torque that can counter excessive input when the driver performs excessively input on the steering member200.

Here, reaction torque generated in the normal turning range is based on the reaction torque generated by the direct drive motor110, and reaction torque generated in an idling range is based on the reaction torque generated by the direct drive motor110and the friction torque generated by the electromagnetic brake120. As shown inFIG.4, the direct drive motor110increases the reaction torque from f0to f1at a constant rate of increase in a range of steering angle θ0to θ1, and then reduces the rate of increase of the reaction torque to increase the reaction torque from f1to f2in a range of steering angle θ1to θ2. Further, as shown inFIG.4, the electromagnetic brake120sharply increases the value of the reaction torque to f3by generating the friction torque, and then maintains the value of the reaction torque at f3.

The laminated graph shown inFIG.4is a graph showing the reaction torque generated by each mechanism included in the reaction force generating device100. Reaction torque F1indicates the reaction torque generated by the direct drive motor110, and reaction torque F2indicates the friction torque generated by the electromagnetic brake120. As shown inFIG.4, a reaction force ratio of the reaction torque F1to the reaction torque F2changes into a reaction force ratio of reaction torque F1′ to reaction torque F2′ by changing the configuration such as the size of the direct drive motor110and the electromagnetic brake120used in the reaction force generating device100.

In this way, the reaction force generating device100can secure the reaction force that can counter the input of the driver by using the friction torque generated by the electromagnetic brake120in addition to the reaction torque generated by the direct drive motor110.

Second Embodiment

Hereinafter, a reaction force generating device100aaccording to a second embodiment is described with reference toFIGS.5to8.

FIG.5is a sectional view showing a configuration example of the reaction force generating device100a. The reaction force generating device100aaccording to the present embodiment further includes a steering angle regulating mechanism160in the reaction force generating device100according to the first embodiment. In the following description, members the same as those already described are denoted by the same reference numerals, and the description thereof will be omitted.

The steering angle regulating mechanism160includes a rotating substrate161that rotates integrally with the steering shaft101, which is a rotating substrate fixedly connected to the steering shaft101, and at least one guide ball162. The steering angle regulating mechanism160regulates the steering of the steering member200when the steering angle of the steering member200reaches the specified steering angle. The method of regulating the steering of the steering member200by the steering angle regulating mechanism160will be described later.

Here, the housing130according to the present embodiment accommodates the steering angle regulating mechanism160in addition to the direct drive motor110and the electromagnetic brake120. The direct drive motor110, the electromagnetic brake120, and the steering angle regulating mechanism160are accommodated in the housing130, so that the size of the reaction force generating device100can be reduced.

The electromagnetic unit121of the electromagnetic brake120is fixed to the housing130so as to be non-rotatable around the axis of the steering shaft101in the axial direction and non-slidable in the axial direction. More specifically, a through hole is formed in the electromagnetic unit121, and the support pin124penetrates through the through hole. Further, the electromagnetic unit121is fixed to the housing130at a surface intersecting a radial direction of the steering shaft101.

Similar to the first embodiment, the electromagnetic unit121slides the second friction portion122in the axial direction of the steering shaft101in response to the rotation angle signal detected by the rotation angle sensor150. The electromagnetic unit121slides the second friction portion122toward the first friction portion123, so that the second friction plate122bpresses against the first friction plate123b. Therefore, the first friction plate123band the second friction plate122bcome into contact with each other to generate friction torque. As a result, the reaction torque caused by the electromagnetic brake120is applied to the steering shaft101.

Next, a configuration example of the steering angle regulating mechanism160is described more specifically with reference toFIGS.6and7.FIG.6is a top perspective view of the steering angle regulating mechanism160.

As shown inFIG.6, the rotating substrate161included in the steering angle regulating mechanism160is formed with a spiral groove163having two end portions164,165on a surface170facing a surface of the electromagnetic unit121on a side opposite to the second friction portion122. Further, as shown inFIG.6, in the rotating substrate161, at least one or more guide balls162are arranged on the spiral groove163. The guide ball162moves on the spiral groove163in response to the steering of the steering member200.

Next, the movement of the guide ball162in the steering angle regulating mechanism160is described with reference toFIG.7.FIG.7shows the arrangements of the guide ball162on the spiral groove163when the steering member200is steered counterclockwise (steered to the left) to the specified steering angle θ2, when the steering member200is not steered, and when the steering member200is steered clockwise (steered to the right) to the specified steering angle θ2.

As shown inFIG.7, when the guide ball162is arranged in the middle position from θ0to less than θ2, the guide ball162does not come into contact with these two end portions164,165of the spiral groove163, and the steering of the steering member200is not regulated. Further, when the steering member200is steered counterclockwise to the specified steering angle θ2, the guide ball162is arranged at a position indicated by “steered to left” inFIG.7, and the guide ball162comes into contact with the end portion165of the spiral groove163. Further, when the steering member200is steered clockwise to the specified steering angle θ2, the guide ball162is arranged at a position indicated by “steered to right” inFIG.7, and the guide ball162comes into contact with the end portion164of the spiral groove163. In this way, when the steering angle of the steering member200reaches the specified steering angle θ2, the guide ball162comes into contact with the end portions164,165of the spiral groove163. Thereby, the steering of the steering member200can be regulated. The spiral groove163is described using a flat shape inFIG.7, but the present embodiment is not limited thereto, and for example, a groove depth at these two end portions164,165may be deeper than that of positions other than these two end portions164,165in the spiral groove163.

More specifically, deep groove portions164a,165aat which a groove depth is relatively deep are formed at these two end portions164,165of the spiral groove163. The deep groove portions164a,165aare provided from the respective end portions164,165of the spiral groove163over a predetermined length. When the steering angle of the steering member200becomes equal to or more than a predetermined steering angle θ4(second steering angle in Claims), the guide ball162is arranged in the deep groove portions164a,165aand moves in a direction away from the electromagnetic unit121. Here, the steering angle θ4is less than the specified steering angle θ2.

A radial groove125is formed on the surface of the electromagnetic unit121on a side opposite to the second friction portion122, and the guide ball162is arranged at an intersection of the spiral groove163and the radial groove125, so that the guide ball162can be prevented from being displaced in the spiral groove163.

Next, reaction torque generated in the reaction force generating device100ais described with reference toFIG.8.

The laminated graph shown inFIG.8is a graph showing the reaction torque generated by each mechanism included in the reaction force generating device100a. Reaction torque F5and reaction torque F6indicate reaction torque generated by the steering angle regulating mechanism160.

More specifically, in the reaction force generating device100a, when the steering angle of the steering member200is less than the predetermined steering angle, as shown in (a) ofFIG.8, the reaction torque F1generated by the direct drive motor110and the reaction torque F2generated by the electromagnetic brake120are combined to generate reaction torque.

Further, in the reaction force generating device100a, when the steering angle of the steering member200reaches the specified steering angle, as shown in (b) ofFIG.8, in addition to the reaction torque F1and the reaction torque F2, reaction torque F5generated by the steering angle regulating mechanism160is also combined to generate reaction torque. Here, the reaction torque F5indicates the reaction torque generated when the guide ball162comes into contact with the end portions164,165. Here, the reaction torque obtained by combining the reaction torque F1, the reaction torque F2, and the reaction torque F5corresponds to the reaction torque f4that can counter the excessive input to the steering member200. As shown in (b) ofFIG.8, even when the direct drive motor110and the electromagnetic brake120are not in operation, the steering angle regulating mechanism160can generate reaction torque F6corresponding to the reaction torque f4that can counter the excessive input. Here, the reaction torque F6indicates the reaction torque generated when the guide ball162comes into contact with the end portions164,165.

In this way, the reaction force generating device100acan secure the reaction force that can counter the input of the driver by using the reaction torque generated by the steering angle regulating mechanism160in addition to the reaction torque generated by the direct drive motor110and the friction torque generated by the electromagnetic brake120.

Third Embodiment

Hereinafter, a reaction force generating device100baccording to a third embodiment is described with reference toFIGS.9to11.

FIG.9is a sectional view showing a configuration example of the reaction force generating device100b. The reaction force generating device100baccording to the present embodiment includes a steering angle regulating mechanism160binstead of the steering angle regulating mechanism160in the reaction force generating device100aaccording to the second embodiment, and further includes a first spring171. In the following description, members the same as those already described are denoted by the same reference numerals, and the description thereof will be omitted.

The first spring171is arranged between the electromagnetic unit121and the first friction portion123. More specifically, one end portion of the first spring171is connected to a surface of the electromagnetic unit121on a side opposite to the steering angle regulating mechanism160b, and the other end portion of the first spring171is connected to a surface of the first friction plate support portion123aon a side opposite to the direct drive motor110via the rotatably slidable member173.

The first spring171can increase the force for pressing the electromagnetic unit121against the rotating substrate161by the repulsive force generated when the spring contracts, so as to increase ball sliding resistance.

The movement of the guide ball162in the steering angle regulating mechanism160is described with reference toFIG.10.

As shown inFIG.10, in the steering angle regulating mechanism160baccording to the present embodiment, first shallow groove portions168,166at which a groove depth is relatively shallow, and second shallow groove portions169,167at which a groove depth is shallower than that of the first shallow groove portions168,166are formed at these two end portions164,165of the spiral groove163a. The first shallow groove portions168,166are provided from the respective end portions164,165of the spiral groove163over a first predetermined length. Further, the second shallow groove portions169,167are provided from the respective end portions164,165of the spiral groove163over a second predetermined length. Here, the second predetermined length is provided to be shorter than the first predetermined length in the spiral groove163a.

As shown inFIG.10, when the steering angle of the steering member200is less than a predetermined steering angle θ1, the guide ball162is arranged at a position other than these two end portions164,165of the spiral groove163a. Further, when the steering angle of the steering member200becomes equal to or more than the predetermined steering angle θ1(third steering angle in Claims) which is less than the specified steering angle θ2, the guide ball162is arranged in the first shallow groove portions168,166of the spiral groove163a. By arranging the guide ball162in the first shallow groove portions168,166, the guide ball162can press the electromagnetic unit121against the second friction portion122. As a result, the friction torque generated by the electromagnetic brake120increases. Further, when the steering member200is steered counterclockwise to the specified steering angle θ2, the guide ball162is arranged at a position indicated by “steered to left” inFIG.10. As a result, the guide ball162is arranged in the second shallow groove portion169of the spiral groove163aand comes into contact with the end portion165of the spiral groove163a. Further, when the steering member200is steered clockwise to the specified steering angle θ2, the guide ball162is arranged at a position indicated by “steered to right” inFIG.10. As a result, the guide ball162is arranged in the second shallow groove portion167of the spiral groove163aand comes into contact with the end portion164of the spiral groove163a. By arranging the guide ball162in the second shallow groove portions169,167, the guide ball162can press the electromagnetic unit121until the first friction portion123and the second friction portion122are completely in close contact with each other. As a result, the friction torque in the electromagnetic brake120is further increased. Further, the steering of the steering member200is regulated by the guide ball162coming into contact with the end portions164,165of the spiral groove163a.

The depth of the second shallow groove portions169,167of the spiral groove163amay be set such that a contact load between the first friction portion123and the second friction portion122is reduced or the contact therebetween is released when the guide ball162comes into contact with the end portions164,165to generate the reaction torque that can counter the excessive input.

More specifically, as shown inFIG.10, the spiral groove163bmay be set such that the groove depth of the second shallow groove portions169a,167ais deeper than the groove depth of the first shallow groove portions168,166. When the steering angle of the steering member200becomes equal to or more than a predetermined steering angle θ5(fourth steering angle in Claims), the guide ball162is arranged in the second shallow groove portions169a,167aand moves in the direction away from the electromagnetic unit121. As a result, damage to the first friction portion123and the second friction portion122can be prevented. Here, the steering angle θ5is less than the specified steering angle θ2and equal to or greater than the predetermined steering angle θ1.

The specified steering angle of the steering angle of the steering member can be set to an optional angle by setting a length between the end portion164and the end portion165of the spiral groove163a, in other words, the positions of these two end portions164,165of the spiral groove in the steering angle regulating mechanism160b. Therefore, these two end portions164,165of the spiral groove163acan be rephrased as optional angle stoppers.

Next, the reaction torque generated in the reaction force generating device100bis described with reference toFIG.11.

The laminated graph shown inFIG.11is a graph showing reaction torque generated by each mechanism included in the reaction force generating device100b. Reaction torque F3inFIG.11indicates the reaction torque generated by the steering angle regulating mechanism160b, and reaction torque F4inFIG.11indicates the reaction torque generated by the first spring171.

More specifically, in the reaction force generating device100b, when the steering angle of the steering member200is less than the predetermined steering angle, as shown in (a) ofFIG.11, the reaction torque F1generated by the direct drive motor110, the reaction torque F2generated by the electromagnetic brake120, and the reaction torque F4generated by the first spring171are combined to generate reaction torque. Here, the reaction torque F4indicates the reaction torque generated by the repulsive force generated when the spring of the first spring171contracts.

Further, in the reaction force generating device100b, when the steering angle of the steering member200is less than the specified steering angle and is equal to or greater than the predetermined steering angle, as shown in (b) ofFIG.11, in addition to the reaction torque F1, the reaction torque F2, and the reaction torque F4, the reaction torque F3generated by the steering angle regulating mechanism160bis also combined to generate reaction torque. Here, the reaction torque F3indicates the reaction torque generated by the increase in electromagnetic force due to the sliding of the electromagnetic unit121of the steering angle regulating mechanism160band the decrease in the clearance with the second friction plate support portion122a.

Further, in the reaction force generating device100b, when the steering angle of the steering member200reaches the specified steering angle, as shown in (c) ofFIG.11, in addition to the reaction torque F1and the reaction torque F2, the reaction torque F5generated by the steering angle regulating mechanism160bis also combined to generate reaction torque. As shown in (c) ofFIG.11, even when the direct drive motor110and the electromagnetic brake120are not in operation, the steering angle regulating mechanism160bcan generate the reaction torque F6corresponding to the reaction torque f4that can counter the excessive input.

In this way, the reaction force generating device100acan secure the reaction force that can counter the input of the driver by using the reaction torque generated by the first spring171and the second spring172in addition to the reaction torque generated by the direct drive motor110, the friction torque generated by the electromagnetic brake120, and the reaction torque generated by the steering angle regulating mechanism160b.

The present invention is not limited to the embodiments described above, various modifications can be made within the scope of the claims, and embodiments obtained by appropriately combining technical means disclosed in different embodiments are also included in the technical scope of the present invention.

Further, a configuration in which the steering angle θ2is a steering angle of the steering member corresponding to the maximum turning angle of the turning unit20is shown as an example, but the present invention is not limited thereto. For example, when the maximum turning angle of the turning unit20is in a regulated state, the steering angle θ2can be set to an angle before reaching the maximum turning angle. Further, in the present embodiment, the “maximum turning angle” includes not only the maximum turning angle determined by a mechanical structure of the turning unit20but also the maximum turning angle set by the control unit300.

REFERENCE SIGNS LIST