JP4506956B2 - Steer-by-wire system - Google Patents

Description

  The present invention relates to a steer-by-wire system in which a steered wheel and a handle are mechanically separated and the steered wheel is steered by a motor in accordance with a handle operation.

In general, this type of steer-by-wire system is configured to detect the steering position of a steering wheel with a position sensor and drive a motor by a motor drive control circuit based on the detection result to steer the steered wheels. For this reason, when the motor drive control circuit and the position sensor fail, the steered wheels cannot be steered according to the steering wheel operation. On the other hand, a steer-by-wire system in which the motor drive control circuit and the position sensor have triple redundancy has been known (for example, see Patent Document 1).
JP 2003-200840 A (Claim 1, Claim 4, FIG. 1)

  However, in the conventional steer-by-wire system described above, the same configuration is simply provided in triplicate to provide redundancy, and therefore, all the triple configurations may fail due to the same cause. Is low. Further, since the triple redundancy is provided, there arises a problem that the mounting space increases approximately three times.

  The present invention has been made in view of the above circumstances, and even if a circuit for supplying a drive current to a motor or a position sensor for detecting a steering position of a steering wheel fails, the steered wheels can be steered according to the steering wheel operation. An object of the present invention is to provide a steer-by-wire system that can be mounted on a vehicle.

  The steer-by-wire system according to the first aspect of the present invention, which is made to achieve the above object, mechanically separates a steering wheel and a steered wheel provided in a vehicle and uses a brushed DC motor as a drive source for steering the steered wheel. In a steer-by-wire system that drives a brushed DC motor in response to a handle operation to steer a steered wheel, the brushed DC motor slides a brush provided on the stator and a commutator provided on the rotor. The stator is configured to energize the rotor windings, and the stator is configured by rotatably connecting a field holding housing holding a field and a brush holding housing holding a brush. Housing locking means switchable between a fixed state in which the holding housing is locked so as not to rotate and a movable state in which the holding housing is unlocked A clutch means that can be switched between a connected state in which the brush holding housing and the handle are mechanically connected and a mechanically disconnected state in a disconnected state is provided, and the brush holding housing and the field holding housing are normally fixed. The brush holding housing and the handle are disconnected, and a direct current corresponding to the handle operation is supplied to the brushed DC motor to rotate the rotor according to the handle operation. By making the field holding housing movable and connecting the brush holding housing and the handle, the brush holding housing is rotated in conjunction with the handle operation to change the crossing angle between the field flux and the winding flux. The rotor is configured to rotate in response to a handle operation.

  According to a second aspect of the present invention, in the steer-by-wire system according to the first aspect, a winding magnetic flux orthogonal to the field magnetic flux is generated by exciting the winding in the rotatable range of the brush holding housing with respect to the field holding housing. Thus, the magnetic flux orthogonal position where the brush and the commutator contact is included, and the housing locking means is characterized in that it is configured to lock the brush holding housing in the magnetic flux orthogonal position.

According to a third aspect of the present invention, in the steer-by-wire system according to the second aspect of the present invention, a stopper is provided to contact the brush holding housing when the brush holding housing is rotated with respect to the field holding housing and reaches the magnetic flux orthogonal position. Have

  According to a fourth aspect of the present invention, in the steer-by-wire system according to any one of the first to third aspects, a winding magnetic flux parallel to the field magnetic flux is wound in a rotatable range of the brush holding housing with respect to the field holding housing. It is characterized in that a neutral position where the brush and the commutator are in contact with each other is included so as to be generated by excitation.

  The invention according to claim 5 is characterized in that in the steer-by-wire system according to claim 4, biasing means for biasing the brush holding housing toward the neutral position is provided.

  According to a sixth aspect of the present invention, in the steer-by-wire system according to any one of the first to fifth aspects, the winding is composed of a plurality of coils, and the winding magnetic flux is a combination of the magnetic fluxes of the plurality of coils. It has the characteristics.

[Inventions of Claims 1 and 6]
In the steer-by-wire system according to the first aspect, normally, the drive current to the brushed DC motor is controlled in accordance with the handle operation to change the rotation amount and the rotation direction of the rotor. Can steer. In this normal drive system, when a circuit for controlling the drive current to the brushed DC motor (hereinafter referred to as “motor drive control circuit”) or a position sensor for detecting the steering position of the steering wheel has failed (that is, during an abnormality). In this case, the drive current to the brushed DC motor becomes uncontrollable and the steered wheels cannot be steered.

  However, according to the configuration of the present invention, when an abnormality occurs, the brush holding housing rotates with respect to the field holding housing in accordance with the handle operation, and the relative position between the field and the brush is changed to rotate the rotor. The amount and the direction of rotation are changed, so that the steered wheels can be steered according to the steering wheel operation.

  Specifically, when the relative position between the field magnet and the brush changes, the angle formed by the field magnetic flux and the winding magnetic flux also changes. Here, at a position where the winding magnetic flux and the field magnetic flux are parallel to each other, the winding does not receive electromagnetic force due to the field magnetic flux, and the rotor does not rotate. When the brush holding housing rotates from this position and the winding magnetic flux and the field magnetic flux cross each other, the winding receives the electromagnetic force due to the field magnetic flux, and the rotor rotates and the winding magnetic flux and the field magnetic flux The rotor rotational torque changes according to the crossing angle. Thus, according to the steer-by-wire system of the present invention, even if the motor drive control circuit or the position sensor fails, the steered wheels can be steered according to the steering wheel operation. Further, in the present invention, since the drive system of the brushed DC motor is different between the normal time and the abnormal time, it is unlikely that both of these different drive systems become unusable and the reliability is improved. Further, since the position sensor is unnecessary in the driving system at the time of abnormality, it is not necessary to provide the position sensor with redundancy, and the installation space can be reduced (that is, the mountability is excellent).

  The winding magnetic flux may be a combination of magnetic fluxes of a plurality of coils constituting the winding (invention of claim 6).

[Invention of claim 2]
In the steer-by-wire system according to the second aspect, the brush holding housing is fixed at a position perpendicular to the magnetic flux by the housing locking means, and the winding magnetic flux and the field magnetic flux are orthogonal to each other, so the brush holding housing is fixed at another position. Compared to the case, the rotor rotational torque can be increased.

[Invention of claim 3]
In the steer-by-wire system according to claim 3, when the brush holding housing is rotated to the limit, the brush holding housing abuts against the stopper and is positioned at a position perpendicular to the magnetic flux, and the rotor is rotated by high torque to steer the steered wheels. be able to.

[Invention of claim 4]
In the steer-by-wire system according to claim 4, when the brush holding housing is held at the neutral position by the handle operation, the field magnetic flux and the winding magnetic flux become parallel, the rotor stops, and the turning angle of the steered wheels becomes the same angle. It becomes possible to hold.

[Invention of claim 5]
In the steer-by-wire system according to the fifth aspect, unless the external torque is applied to the brush holding housing, the brush holding housing is held in the neutral position by the biasing means, and the rotor can be stopped.

[First Embodiment]
Hereinafter, an embodiment of the present invention will be described with reference to FIGS.
FIG. 1 shows an overall configuration of a steer-by-wire system 10 according to the present invention. In the figure, reference numeral 11 denotes a handle, which is fixed to one end of the steering shaft 12. The steering shaft 12 is rotatably supported on the vehicle body, and a reaction force generator 13 is connected to the other end of the steering shaft 12.

  For example, as shown in FIG. 2, the reaction force generator 13 has a configuration in which a worm gear 19 fixed to the output rotation shaft of the reaction force motor 14 is engaged with a worm wheel 20 fixed to the other end of the steering shaft 12. Yes. Then, the output torque of the reaction force motor 14 is applied to the steering shaft 12 as a reaction force to the steering wheel operation.

  Further, the reaction force generator 13 is provided with a mechanical reaction force generation spring 21 in case the reaction force motor 14 fails. Specifically, the reaction force generation spring 21 has a spiral structure, one end of which is fixed to the front end of the steering shaft 12 and the other end is fixed to one end of the clutch 22. The other end of the clutch 22 is fixed to the body of the vehicle. When the reaction force motor 14 fails, the clutch 22 is connected, and the steering shaft 12 is fixed to the body via the reaction force generating spring 21. Is done.

  A torsion bar 16 is provided in the middle of the steering shaft 12, and position sensors 17, 17 are provided at both ends of the torsion bar 16. Then, the steering angle of the handle 11 is detected by one position sensor 17 and the handle 11 is determined from the torsion angle of the torsion bar 16 and the spring rigidity of the torsion bar 16 based on the difference between the detection results of the position sensors 17 and 17. The actual load torque is detected.

  An interlocking shaft 27 is connected to the steering shaft 12 via bevel gears 23 and 24 and spur gears 25 and 26. The interlocking shaft 27 is connected to one end of a steering force transmission clutch 28 (corresponding to “clutch means” according to the present invention), and a flexible cable 29 is connected to the other end of the steering force transmission clutch 28. The steering force transmission clutch 28 is normally disconnected.

  As shown in FIG. 1, a steering rack 31 is passed between a pair of steered wheels 30, 30 provided in the vehicle, and tie rods 32, 32 connected to both ends of the steerable rack 31 are connected to each rolling wheel. It is connected to the steering wheels 30, 30. The steerable rack 31 is inserted into the cylindrical housing 80, and the cylindrical housing 80 is fixed to the main body of the vehicle. The handle 11 is mechanically separated from the parts connected to the steered wheels 30, 30. In order to steer the steered wheel 30 according to the handle 11, the brushed DC motor 50 according to the present invention is used. Is provided.

  As shown in FIG. 5, the brushed DC motor 50 of this embodiment includes a pair of brushes 55 and 56 in a stator 51. As shown in FIG. 8A, the brushes 55 and 56 are aligned with each other and face each other. Normally, a motor drive control circuit (not shown) provided in the ECU 35 (ECU is an abbreviation of “Electric Control Unit”) is connected to the brushes 55 and 56. When an abnormality occurs, a switch (not shown) is activated, and a battery (not shown) provided in the vehicle is connected to the brushes 55 and 56 instead of the ECU 35.

  As shown in FIG. 8B, the field magnet 54 provided in the stator 51 is formed by, for example, arranging a pair of permanent magnets 73 and 74 so that the field flux B <b> 1 is generated from one permanent magnet 73. It faces the other permanent magnet 74.

  As shown in FIG. 5, the rotor 60 is provided with a commutator 63 (so-called commutator) corresponding to the brushes 55 and 56. For example, four arc-shaped segments 71 are laid on the peripheral surface of the commutator 63 as shown in FIG. Further, the winding 62 provided on the rotor 60 is constituted by, for example, two coils 70 and 70. These coils 70 are arranged so that their winding axes are orthogonal to each other, as conceptually shown in FIG. Furthermore, both terminals of one coil 70 are connected to a pair of segments 71 and 71 arranged opposite to each other, and both terminals of the other coil 70 are connected to the remaining pair of segments 71 and 71 opposed to each other. Has been. Then, according to the rotational position of the rotor 60, the brushes 55 and 56 selectively come into contact with a pair of opposed segments 71 and 71 among the four segments 71. At this time, if a DC voltage is applied between the brushes 55 and 56, the coil 70 in contact with the brushes 55 and 56 is excited, and a winding magnetic flux B <b> 2 by the winding 62 is generated.

  As shown in FIG. 5, the stator housing 51 </ b> H includes a field holding housing 52 that holds a field 54 (permanent magnets 73 and 74) and a brush holding housing 53 that holds brushes 55 and 56. Yes. Further, the brush holding housing 53 is rotatably connected to the field holding housing 52 via a bearing 51B.

  The field holding housing 52 is fixed to a cylindrical housing 80 that covers the steering rack 31 described above. As shown in FIG. 2, a pinion 33 is fixed to the output rotation shaft of the brushed DC motor 50, and the pinion 33 meshes with the steered rack 31. As a result, when the brushed DC motor 50 is driven and the pinion 33 rotates, the steerable rack 31 moves directly, and the steered wheels 30, 30 are steered.

  A linear motion position sensor 37 (see FIG. 1) is attached to a portion of the cylindrical housing 80 away from the brushed DC motor 50. The linear motion position sensor 37 is formed, for example, by connecting a detection shaft that meshes with the steerable rack 31 and rotates in conjunction with an absolute encoder, for example. Thereby, the actual linear motion position of the steerable rack 31 can be detected.

  A fixed wall 65 adjacent to the side of the brush holding housing 53 extends from the field holding housing 52. A stopper 68 is formed on the fixed wall 65, and the rotation range of the brush holding housing 53 relative to the field holding housing 52 is 180 degrees due to interference between the stopper 68 and the protrusion 69 provided in the brush holding housing 53. It is regulated. Both ends in the range in which the brush holding housing 53 can rotate correspond to the “magnetic flux orthogonal position” according to the present invention, and the midpoint in the rotatable range corresponds to the “neutral position” in the present invention.

  The fixed wall 65 is provided with a lock device 66 (corresponding to “housing lock means” according to the present invention) for holding the brush holding housing 53 in a non-rotatable manner. The locking device 66 has a structure in which the locking pin 67 is linearly moved by driving the solenoid. Normally, the solenoid is excited by the ECU 35, and the locking pin 67 is inserted into the locking hole 59 formed in the brush holding housing 53. Then, the brush holding housing 53 is locked at one magnetic flux orthogonal position.

  When the brush holding housing 53 is locked at the magnetic flux orthogonal position, the brushes 55 and 56 come into contact with the segments 71 and 71 of the coil 70 having the winding axis orthogonal to the field magnetic flux B1, as shown in the conceptual diagram of FIG. . As a result, an exciting current in a predetermined direction flows through the coil 70, and a winding magnetic flux B2 orthogonal to the field magnetic flux B1 is generated. Then, the winding 62 receives the electromagnetic force generated by the field magnetic flux B1, and the rotor rotational torque is generated. At this time, the rotation direction and the rotational torque of the rotor 60 are changed by changing the direction and magnitude of the voltage applied between the brushes 55 and 56 by the motor drive control circuit. In FIG. 6, the energized coil 70 and the segment 71 are shown in gray.

  Furthermore, it will be described in detail with reference to FIGS. 8A and 8B as follows. 8A and 8B are cross-sectional views of the brushed DC motor 50 viewed from the same axial direction in a state where the brush holding housing 53 is locked at the magnetic flux orthogonal position. Is shown. In FIG. 8B, only one excited coil 70 is shown. Further, in FIG. 8A and FIG. 8B, one brush 55 is held in a positive electrode and the other brush 56 is held in a negative electrode. Here, when the rotor 60 is rotated counterclockwise by the rotor rotational torque from the state shown in FIG. 8B, the winding magnetic flux B2 is also counterclockwise from the state where the winding magnetic flux B2 is orthogonal to the field magnetic flux B1. Rotate to. When the rotor 60 rotates about 90 degrees in mechanical angle, the segments 71 and 71 with which the brushes 55 and 56 come into contact are switched, and the other coil 70 is excited this time. At this time, the winding magnetic flux B2 generated by the other excited coil 70 is deviated by about 90 degrees from the field magnetic flux B1, and the direction of the winding magnetic flux B2 moves to the side perpendicular to the field magnetic flux B1 as the rotor 60 rotates. I will do it. That is, the winding magnetic flux B2 always changes within a range of about 90 degrees centering on a position orthogonal to the field magnetic flux B1, and the field magnetic flux B1 and the winding magnetic flux B2 are always kept in a state of crossing the rotor. 60 continues to rotate. That is, in a state where the brush holding housing 53 is locked at the magnetic flux orthogonal position by the lock device 66, the brushed DC motor 50 functions as a normal brushed DC motor.

  As shown in FIG. 5, an external force application shaft 57 protrudes from the center of the outer surface of the brush holding housing 53, and one end of the flexible cable 29 is connected to the external force application shaft 57. Thus, when the lock device 66 is released and the steering force transmission clutch 28 is in the connected state, the brush holding housing 53 rotates with respect to the field holding housing 52 in accordance with the operation of the handle 11.

  Further, a neutral point return spring 58 (corresponding to “biasing means” of the present invention) is provided between the brush holding housing 53 and the fixed wall 65. The neutral point return spring 58 is formed by spirally winding a leaf spring material (see FIG. 2). The end of the spiral on the center side is fixed in the vicinity of the center of the brush holding housing 53, while the outer side of the spiral is The end is fixed to the fixed wall 65. The neutral point return spring 58 urges the brush holding housing 53 to a midpoint within a rotatable range. Accordingly, when the lock device 66 is unlocked in the event of an abnormality, the brush holding housing 53 is held in the neutral position unless the external force applying shaft 57 receives torque.

  When the brush holding housing 53 is held at the neutral position, as shown in the conceptual diagram of FIG. 7, the brushes 55 and 56 are attached to the segments 71 and 71 to which the coil 70 having a winding axis parallel to the field magnetic flux B1 is connected. Contact. Then, when an exciting current in a predetermined direction flows through the coil 70, a winding magnetic flux B2 substantially parallel to the field magnetic flux B1 is generated, the winding 62 does not receive electromagnetic force due to the field magnetic flux B1, and the rotor 60 is in the stator 51. Is held in a non-rotatable state. In FIG. 7, the energized coil 70 and the segment 71 are shown in gray. 9A and 9B show a cross-sectional view of the brushed DC motor 50 viewed from the same axial direction in a state where the brush holding housing 53 is held at the neutral position. Has been.

  When the brush holding housing 53 receives an external torque due to the operation of the handle 11, for example, as shown in FIG. 10A, the brush holding housing 53 deviates by θ degrees counterclockwise from the neutral position, so It will be in the state of being placed between. Then, as shown in FIG. 10B, a winding magnetic flux B2 is generated that is directed in a direction intersecting with the field magnetic flux B1 at θ degrees. As a result, the winding 62 receives the electromagnetic force generated by the field magnetic flux B1, and a rotor rotational torque that rotates the rotor 60 in the clockwise direction in FIG. 10B is generated.

  Here, if the scalar value of the field flux B1 is ΦM, the scalar value of the winding flux B2 is ΦI, the crossing angle between the field flux B1 and the winding flux B2 is θ (see FIG. 10B), and the constant is K. The rotor rotational torque T can be obtained by the following equation (1).

    T = K ・ ΦM ・ ΦI ・ SINθ ・ ・ ・ ・ (1)

  Accordingly, the rotor rotational torque T increases as the angle θ at which the brush holding housing 53 deviates from the midpoint position approaches 90 degrees, and when the brush holding housing 53 comes into contact with the stopper 68 and reaches the magnetic flux orthogonal position (see FIG. 11). The rotor rotational torque T is maximized.

  When the brush holding housing 53 receives external torque and rotates in the opposite direction to the above-described case shown in FIGS. 10A and 11A, the above case does not indicate the rotor rotational torque. The direction is reversed.

  The description of the brushed DC motor 50 is as described above. The entire steer-by-wire system 10 is controlled by the ECU 35. The ECU 35 controls the reaction force motor 14, the clutch 22, the steering force transmission clutch 28, the brushed DC motor 50, and the lock device 66 by executing the control program PG1 shown in FIG. Specifically, when the control program PG1 is executed, the ECU 35 takes in the detection results of the sensors such as the position sensor 17, the vehicle speed sensor 36, the linear motion position sensor 37 (see FIG. 1) (S1).

  Next, it is checked whether or not the value of any one of the sensors is an abnormal value (that is, any sensor has failed) (S2). If the values of any of the sensors are normal values (S2: NO), the transmission ratio R between the steering wheel 11 and the steered wheels 30 is determined according to the vehicle speed (S3). Here, if the steering angle of the steering wheel 11 is θ1 and the turning angle of the steered wheels 30 is θ2, the transmission ratio R described above can be obtained from the following equation (2).

    R = θ2 / θ1 (2)

  Then, the ECU 35 acquires a predetermined transmission ratio R from the map 42 shown in FIG. 4 according to the vehicle speed. The map 42 is set so that the transmission ratio R decreases as the vehicle speed increases. That is, when the vehicle speed is relatively low (during low speed traveling), a relatively large transmission ratio R is employed. As a result, the vehicle can be turned by a slight operation of the handle 11, and garage entry or the like is facilitated. On the other hand, when the vehicle speed is relatively high (during high-speed traveling), a relatively small transmission ratio R is adopted, which prevents sudden steering (rapid turning) and enables stable traveling.

  The ECU 35 obtains the target turning angle of the steered wheel 30 from the determined transmission ratio R and the steering angle θ1 of the handle 11, and the brushed DC motor 50 for making the steered angle of the steered wheel 30 coincide with the target turning angle. The target rotation position is determined (S4). Then, a drive current corresponding to the deviation between the actual rotation position of the brushed DC motor 50 calculated from the detection result of the linear motion position sensor 37 and the target rotation position is supplied from the motor drive control circuit to the brushed DC motor 50. (S5). At this time, since the brush holding housing 53 is locked by the locking device 66, the brushed DC motor 50 operates as a normal brushed DC motor as described above.

  Next, the ECU 35 estimates the turning resistance of the steered wheels 30 due to the friction between the steered wheels 30 and the road surface based on the drive current necessary to steer the brushed DC motor 50 (S6). Further, the target steering reaction force of the handle 11 is determined with respect to the estimated turning resistance (S7). At this time, the target steering reaction force is determined to be a relatively large value during high speed traveling, while the target steering reaction force is determined to be a relatively small value during low speed traveling. Then, the steering reaction force actually applied to the steering wheel 11 is detected by the steering angle / torque sensor 15, and the reaction force motor 14 of the reaction force generator 13 is adjusted so that the actual steering reaction force coincides with the target steering reaction force. A drive current is supplied (S8), the control program PG1 is exited, and the control program PG1 is executed again after a predetermined period.

  When the value of the motor drive control circuit or any sensor is an abnormal value (when the sensor has failed) (S2: YES), the lock by the lock device 66 is released (S9). ), The clutch 22 and the steering force transmission clutch 28 are brought into a connected state (S10). Specifically, the lock by the locking device 66 is released, and the brush holding housing 53 of the brushed DC motor 50 is moved to the neutral position by the resilient force of the neutral point return spring 58, and then the steering force transmission clutch 28 is connected. To. Then, processing is performed so that the control program PG1 is exited and the control program PG1 is not re-executed.

  As a result, when an abnormality occurs, a steering reaction force can be applied to the handle 11 by the reaction force generation spring 21 instead of the reaction force motor 14, and the handle 11 can be applied to the external force of the brushed DC motor 50 via the flexible cable 29 or the like. It is connected to the application shaft 57.

  When the handle 11 is held at the same position in this state, the brush holding housing 53 is held at the neutral position, the rotor 60 does not rotate, and the turning angles of the steered wheels 30 and 30 are kept constant. Therefore, for example, if the vehicle is traveling straight, it can continue straight.

  When the handle 11 is cut to one side, the brush holding housing 53 is rotated from the neutral position to one side, the rotor 60 rotates in one direction and the steered wheels 30 are steered, while the handle 11 is turned to the other side. When cut, the brush holding housing 53 rotates in the other direction from the neutral position, the rotor 60 rotates in the other direction, and the steered wheels 30 are steered to the opposite side. At this time, the greater the angle at which the handle 11 is turned, the greater the rotation angle of the brush holding housing 53, and the steered wheels 30 are reliably steered against self-aligning torque. By these, for example, the vehicle traveling straight can be turned to the road shoulder and urgently retreated.

  Thus, according to the steer-by-wire system 10 of the present embodiment, even if the motor drive control circuit or the sensor is lost, the steered wheels 30 can be steered according to the operation of the handle 11. Further, since the driving method of the brushed DC motor 50 is different between the normal time and the abnormal time, it is unlikely that both of these different driving methods become unusable and the reliability is improved. Further, since the position sensor 17 is unnecessary in the driving system at the time of abnormality, it is not necessary to provide the position sensor 17 with redundancy, and the installation space can be reduced (that is, the mountability is excellent).

[Second Embodiment]
This embodiment is shown in FIGS. 12 and 13, and the structure of the rotor 60 ′ in the brushed DC motor is mainly different from the rotor 60 of the first embodiment. Hereinafter, only the configuration different from that of the first embodiment will be described, and the same portions as those of the first embodiment are denoted by the same reference numerals, and redundant description will be omitted.

  As shown in FIG. 12, the rotor 60 ′ in the brushed DC motor of the present embodiment includes a rotor core 72 having three teeth 72 </ b> T. The teeth 72T are arranged with an interval of 120 degrees, and coils 70U, 70V, and 70W are wound around the three teeth 72T. As shown in FIG. 13, the coils 70U, 70V, and 70W are star-connected to form a winding 62.

  Further, for example, as shown in FIG. 13, the commutator 63 provided in the rotor 60 ′ is provided with six segments 71, and the opposed segments 71 are electrically connected. And the terminal of each coil 70U, 70V, 70W is connected to these three pairs of segments.

  FIG. 13 shows a state in which the brush holding housing 53 described in the first embodiment is disposed at a position perpendicular to the magnetic flux. In this state, the three coils 70U, 70V, and 70W are all excited, the magnetic flux B10 generated by the coil 70U is directed perpendicular to the field magnetic flux B1 and away from the center of the rotor 60 (see FIG. 12), and the magnetic flux B11 generated by the coil 70V. Crosses the field magnetic flux B1 at an angle of 30 degrees toward the center of the rotor 60, and the magnetic flux B12 generated by the coil 70W intersects the field magnetic flux B1 at an angle of 120 degrees toward the center of the rotor 60. The winding magnetic flux B2 of the entire winding 62 is composed of magnetic fluxes B10, B11, and B12 generated by the coils 70U, 70V, and 70W, and is in a state orthogonal to the field magnetic flux B1. Thereby, a rotor rotational torque is generated and the rotor 60 rotates.

  Also in this embodiment, by rotating the brush holding housing 53 as in the first embodiment, the direction of the winding magnetic flux B2 of the entire winding 62 is changed, and the brush holding housing 53 is disposed at the neutral position. When this is done, the winding magnetic flux B2 becomes parallel to the field magnetic flux B1, and the rotor rotational torque becomes zero.

[Other Embodiments]
The present invention is not limited to the above-described embodiment. For example, the embodiments described below are also included in the technical scope of the present invention, and various other than the following can be made without departing from the scope of the invention. It can be changed and implemented.

(1) In the first embodiment, the winding 62 is constituted by the two coils 70, but the number of coils constituting the winding may be three or more. Further, although the commutator 63 is composed of the four segments 71, the number of the segments 71 may be more than four. In the first embodiment, since the winding 62 is constituted by the two coils 70, the winding magnetic flux B2 varies in the range of 45 degrees with respect to the field magnetic flux B1 with the brush holding housing 53 fixed. By increasing the number of coils constituting the wire, it is possible to narrow the variation range of the winding magnetic flux with respect to the field magnetic flux.

(2) In the first embodiment, the brush holding housing 53 is biased to the neutral position by the neutral point return spring 58. However, the neutral point return spring 58 may not be provided.

(3) A reduction gear may be provided between the motor 50 and the pinion 33. Specifically, a worm gear may be fixedly provided on the output rotation shaft of the motor 50 and may be engaged with a worm wheel fixed to the pinion 33.

The block diagram of the steer-by-wire system of 1st Embodiment which concerns on this invention Conceptual diagram of steer-by-wire system Flow chart of control program Data map for testing transmission ratio Cross section of brushed DC motor Conceptual diagram of the state where the brush holding housing is arranged at the position perpendicular to the magnetic flux Conceptual diagram of the brush holding housing in the neutral position Sectional view of brushed DC motor with brush holding housing arranged at magnetic flux orthogonal position Sectional view of brushed DC motor with brush holding housing in neutral position Sectional view of brushed DC motor with brush holding housing displaced from neutral position Sectional view of brushed DC motor with brush holding housing rotated to position perpendicular to magnetic flux Sectional drawing of DC motor with brush of 2nd Embodiment Conceptual diagram of DC motor with brush

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Steer-by-wire system 11 Handle 17 Position sensor 22 Clutch 28 Steering force transmission clutch (clutch means)
29 Flexible cable 30 Steering wheel 50 DC motor with brush 51 Stator 52 Field holding housing 53 Brush holding housing 54 Field 55 Brush 58 Neutral point return spring (biasing means)
60, 60 'rotor 62 winding 63 commutator 66 locking device (housing locking means)
67 Locking Pin 68 Stopper 69 Projection 70 Coil 71 Segment

Claims (6)

A steering wheel and a steered wheel provided in the vehicle are mechanically separated from each other, a brushed DC motor is provided as a drive source for steering the steered wheel, and the brushed DC motor is driven according to a handle operation to drive the steered wheel. In steer-by-wire systems that steer
The DC motor with a brush has a structure in which a brush provided on a stator and a commutator provided on a rotor are brought into sliding contact with each other to energize the windings of the rotor,
The stator is formed by rotatably connecting a field holding housing holding a field and a brush holding housing holding the brush,
A housing lock means switchable between a fixed state in which the brush holding housing and the field holding housing are locked so as not to rotate, and a movable state in which the lock is released;
Clutch means switchable between a connected state in which the brush holding housing and the handle are mechanically connected and a disconnected state in which the brush holding housing is mechanically disconnected;
In a normal state, the brush holding housing and the field holding housing are set in the fixed state, the brush holding housing and the handle are set in the non-connected state, and a direct current corresponding to the handle operation is supplied to the DC motor with brush. While the rotor rotates in response to the handle operation,
In an abnormal state, the brush holding housing and the field holding housing are moved to the movable state, the brush holding housing and the handle are connected to each other, and the brush holding housing is rotated in conjunction with the handle operation. A steer-by-wire system configured to rotate the rotor in response to the handle operation by changing an intersection angle between a field magnetic flux and a winding magnetic flux.   In the rotatable range of the brush holding housing with respect to the field holding housing, a magnetic flux orthogonal position where the brush and the commutator are in contact so that a winding magnetic flux orthogonal to the field magnetic flux is generated by excitation of the winding. 2. The steer-by-wire system according to claim 1, wherein the housing locking means is configured to lock the brush holding housing at the magnetic flux orthogonal position. The steer-by-wire system according to claim 2, further comprising a stopper that contacts when the brush holding housing rotates with respect to the field holding housing and reaches the magnetic flux orthogonal position.   In the rotatable range of the brush holding housing with respect to the field holding housing, there is a neutral position where the brush and the commutator are in contact so that a winding magnetic flux parallel to the field magnetic flux is generated by excitation of the winding. The steer-by-wire system according to any one of claims 1 to 3, wherein the steer-by-wire system is included.   The steer-by-wire system according to claim 4, further comprising a biasing unit that biases the brush holding housing toward the neutral position.   The steer-by-wire system according to any one of claims 1 to 5, wherein the winding includes a plurality of coils, and the winding magnetic flux is a combination of magnetic fluxes of the plurality of coils.