JP4899679B2 - Steer-by-wire system - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To improve the reliability and operability of a fail-safe mechanism of a steer-by-wire system having an electric back-up means. <P>SOLUTION: The steering force transmitting mechanism of the steer-by-wire system 100 is composed of a cable 70 formed of a push-pull wire, a cable winding device 71 for winding the cable 70, a cable driving mechanism 72 for driving a gear box 18G' based on the tension of the cable 70, and a cable tension changing means 73 for controlling the tension of the cable 70. The DC voltage to be supplied to a mechanical rectifier 35 (steering motor commutation means) is selected from any one of a low voltage to be supplied from a battery BT0 and a high voltage to be supplied from a battery BT1 by a supply voltage changing means to be composed using a switch SW2. The DC voltage to be supplied to the cable tension changing means 73 also is controlled by the supply voltage changing means. <P>COPYRIGHT: (C)2008,JPO&amp;INPIT

Description

  The present invention relates to a fail-safe mechanism that enables steered wheels to be steered in an emergency evacuation in the event of an abnormality in which a main steered motor control device fails in a steer-by-wire system, and in particular, the reliability of the fail-safe mechanism. The present invention relates to a backup means for improving operability.

An apparatus configuration using a wire for the fail-safe mechanism of the steer-by-wire system is disclosed in Patent Document 1 below. The feature of this prior art is that the back-up means can be configured by using a deformable push-pull wire, so that the degree of freedom of layout in the vehicle interior can be increased, and this structure allows the steering shaft and the steering mechanism to be It is in the point which can increase collision safety by not making it rigidly connect.
However, since this conventional technique requires a large steering force against the self-aligning torque and the road surface resistance of the tire, an emergency evacuation steering operation in the event of an abnormality, that is, when the main steering motor control device fails In this case, the steering load required by the driver increases, and there is a problem in operability.

In the steer-by-wire system, a fail-safe mechanism described in Patent Document 2 below is already known as a fail-safe mechanism that can effectively reduce the steering load on the driver. By adopting this fail-safe mechanism, it is possible to ensure the degree of freedom of layout and collision safety in the vehicle interior, and since the battery is also used in the desired backup means used in the event of an abnormality, the power assist by this battery further Also, the operability of the steering wheel when using the backup means can be significantly improved.
JP 2006-1547 (FIG. 13) JP 2006-21550 A

However, the electrical backup means using the commutation device described in Patent Document 2 has the following problems.
(Problem 1) There is a risk that steering may become impossible due to a battery failure.
(Problem 2) When the driver rotates the steering wheel quickly, the steering motor may step out and become unable to steer.
(Problem 3) Even when the steered wheel is in contact with the curb and can no longer be steered, the steering wheel can be further rotated, so the driver cannot easily recognize the contact state. There is.

  The present invention has been made to solve the above-mentioned problems, and its object is to provide reliability in a fail-safe mechanism of a steer-by-wire system having an electric backup means using the above-described commutation device. And improve operability.

In order to solve the above problems, the following means are effective.
That is, the first means of the present invention is a steer-by-wire system that mechanically separates a steering wheel and a steered wheel provided in a vehicle and drives the steered motor according to the operation of the steering handle to steer the steered wheel. , A steering motor control device that drives and controls the steering motor in normal times, a steering motor commutation means that switches the energization state of the steering motor according to the steering angle of the steering handle, and an abnormality in the steering motor control device sometimes, disconnecting electrically the turning motor controller from turning motor, a connection switching means for electrically connecting to the steering motor to the steering motor commutator instead, the different constant of turning motor controller , is mechanically connected to the steering wheel, a bending deformable cable mechanically transmitting a steering force of a driver of the vehicle steered wheels, when an abnormality of the steering motor controller, Ke for controlling the tension of the cable And Bull tension control unit, to a different constant of turning motor controller, power supply and by energizing the steering motor to the steering motor commutation means, a feeding means for increasing the tension of the cable by feeding cable tension control means When the steering motor control device is abnormal, the power supply voltage is changed to increase or decrease the cable tension by changing the voltage supplied to the cable tension control means according to the steering angle of the steering wheel, the steering speed, or the vehicle speed of the vehicle. And a steer-by-wire system.

In other words, the present invention mainly employs a system in which a mechanical backup means (steering force transmission mechanism) is added to an electrical backup means (steering motor commutation means), that is, a hybrid system related to the backup means. The above-described fail-safe mechanism that is effective when the steering motor control device is abnormal is configured.
For example, a clutch or the like can be used as means for mechanically connecting the steering force transmission mechanism to the steering handle when the steering motor control device is abnormal. Such a connecting means may be an electric means or a hydraulic means .

According to a second means of the present invention, in the first means, the voltage changing means is such that the steering angle is in a neutral position range and the steering speed is higher than a predetermined value when the steering motor control device is abnormal. When the steering angle is not in the neutral range, or when the steering speed is equal to or higher than a predetermined value, a second voltage higher than the first voltage is supplied to the cable tension control means. It is a means.
According to a third means of the present invention, in the first means, the power supply voltage changing means is such that the steering angle is in the neutral position range and the vehicle speed is a predetermined value when the steering motor control device is abnormal. The first voltage is supplied to the cable tension control means when the steering angle is not in the neutral range, or the second voltage higher than the first voltage is supplied to the cable tension control means when the steering angle is not in the neutral range. It is a means.
According to a fourth means of the present invention, in the first or second means, the steering speed of the steering wheel of the reaction force motor that applies a reaction force torque to the steering wheel when the steering motor control device is normal. It is detected by the output generated by the rotation.
According to a fifth means of the present invention, in any one of the first to fourth means, the steered motor commutation means is replaced with a mechanical commutation device having a brush and a commutator. Is to configure.

According to a sixth means of the present invention, in any one of the first to fourth means described above, the rotation angle sensor for detecting the steering angle of the steering wheel and the ON / OFF based on the detected steering angle. The above-described steering motor commutation means is constituted by an electronic commutation device having a semiconductor switch that is controlled to be OFF.

In the present invention , a steering speed detecting means for detecting the steering speed of the steering wheel, and a power supply voltage changing means for changing the power supply voltage from the power supply means according to the steering speed at the time of the abnormality are provided. The power supply voltage may be monotonously increased with respect to the steering speed by the voltage changing means .

However, the object to be fed via the feeding voltage changing means may be the electric backup means (steering motor commutation means), the cable tension control means, or both. May be.
Furthermore, the power source connected to the power supply voltage changing means is not limited to the battery, and for example, a generator that generates electric power based on a steering operation on the steering wheel may be used. Further, a reaction force motor that generates a steering reaction force may be used as such a power generation means. Further, these power sources (battery, power generation means) may be used in any combination. In particular, when a reaction force motor that generates a steering reaction force is used as the power generation means, the power supply based on the generated power can be continuously increased or decreased.
By the above means of the present invention, the above-mentioned problem can be effectively or rationally solved.

The effects obtained by the above-described means of the present invention are as follows.
That is, according to the first means of the present invention, the desired fail-safe mechanism effective when the main steering motor control device is abnormal is mechanical with respect to the electric backup means (steering motor commutation means). Since the backup system (steering force transmission mechanism) is added to the hybrid system, the problems of the individual backup units described above can be solved in a complementary and effective manner by duplicating the backup unit. .

  For example, the steered wheel and the steering wheel are always mechanically reliably connected to each other by the steering force transmission mechanism and the connecting means at the time of the abnormality, so that they operate in synchronism with each other in a mechanically reliable manner. For this reason, fear of said step-out (problem 2), fear of state transmission failure to the driver when contacting the curbstone (problem 3), etc. can be effectively wiped out.

  Furthermore, according to the first means of the present invention, even when the battery fails, or when the commutation device, the steering motor, or the like fails due to disconnection or the like, the steering feeling is somewhat heavy, Necessary steering operation can be effectively continued by the operation of the steering force transmission mechanism. In addition, if there is no such failure, the steering operation is effectively assisted by the electric backup means (steering motor commutation means), and of course, the steering load is effectively reduced.

  For this reason, according to the first means of the present invention, it is possible to effectively ensure the operability and reliability such as followability and responsiveness of the desired fail-safe mechanism at the same time. In addition, according to the first means of the present invention, the backup means constituting the fail-safe mechanism is duplicated, and the load applied to each backup means is effectively reduced. The durability of can also be improved. Further, if each durability of the electric backup means (steering motor commutation means) and the mechanical backup means (steering force transmission mechanism) is improved, of course, the reliability of the fail-safe mechanism according to the present invention is naturally improved. Improves at the same time.

Moreover, according to the 5th or 6th means of this invention, said steering motor commutation means can be comprised concretely and favorably.
In particular, according to the fifth means of the present invention, since the desired commutation device is mechanically configured, the commutation device can be reliably connected even in a high temperature environment or a noise environment with a lot of electromagnetic noise. Can be operated.
On the other hand, according to the sixth means of the present invention, a desired commutation device can be realized using a semiconductor chip, and the arrangement position thereof can be increased. This is very advantageous in terms of downsizing and mountability.

Moreover, according to the 1st-4th means of this invention, the tension | tensile_strength of a cable can be optimized based on the adaptive control according to various steering situations. For example, when it is desired to maintain high responsiveness of the fail-safe mechanism, the cable tension may be increased. Further, the durability of the cable itself can be ensured by reducing the cable tension, which is the load applied to the cable itself. For this reason, according to the 1st-4th means of this invention, the followability and durability (life) of said steering force transmission mechanism can be ensured simultaneously. Further, if the durability of the cable is improved, the reliability of the steering force transmission mechanism is naturally improved.

Further, according to the first to fourth means of the present invention, since the steering state in the OPERATION can be detected, then in accordance with the magnitude of the power and the steering torque required for steering, the fail-safe mechanism It becomes possible to adaptively optimize the response characteristics. That is, for example, when the response performance may be low, the feeding potential can be set to a low value or the tension of the wire can be weakened according to the situation.
For this reason, according to the first to fourth means of the present invention, while ensuring the followability and responsiveness of the failsafe mechanism, the power consumption necessary for turning can be effectively saved. Alternatively, the durability of the cable itself can be ensured.

Hereinafter, the present invention will be described based on specific examples.
However, the embodiments of the present invention are not limited to the following examples.

  FIG. 1 shows a system configuration diagram of a steer-by-wire system 10 according to the first embodiment. The gear box 18G can be driven by a steering force transmission mechanism described below or a brushless DC motor 20 (steering motor). The above-described gear box 18G is attached to the cylindrical housing 18 through which the rack 16 is inserted, and the pinion gear 19 protruding from the gear box 18G is engaged with the rack 16. A pair of tie rods 17, 17 connected to both ends of the rack 16 are connected to the steered wheels 50, 50.

  Hereinafter, the steering force transmission mechanism will be described in detail. The clutch CL attached to the lower side of the gear box 30 controls whether or not the rotational operation of the steering shaft 12 that rotatably supports the steering handle 11 is transmitted to the lower universal joint UJ. The off operation can be controlled by electromagnetic force or hydraulic pressure. Further, the transmission path of the steering force applied by the driver to the steering wheel 11 to each steered wheel 50, 50 is configured by connecting a number of universal joints UJ. That is, based on the on / off operation described above, the gear box 30 and the gear box 18G can be mechanically connected via the clutch CL and the multiple universal joints UJ. The steering force can be transmitted to each steered wheel 50, 50 through these steering force transmission mechanisms. Since the torsional rigidity of the coupling body of the large number of universal joints UJ is configured to be high, play and responsiveness of the steering operation are appropriately secured.

  On the other hand, the driving force of the brushless DC motor 20 can of course be input to the gear box 18G. The rotational position of the brushless DC motor 20 is detected by a position sensor 29 and input to a steered motor control device 60 having a motor drive control circuit 51. A torque sensor 33 is attached to the steering shaft 12, and the steering shaft 12 is connected to the reaction force motor 31 via the gear box 30. The reaction force motor 31 is a brushed DC motor that generates torque for applying a steering reaction force to the driver's steering operation, and is driven and controlled by the turning motor control device 60. The position sensor 32 detects the rotation angle of the rotor of the reaction force motor 31. The steered motor control device 60 also has a control function for the reaction force motor 31, and the rotation angle of the rotor of the reaction force motor 31 detected by the position sensor 32 and the steering torque detected by the torque sensor 33. The drive control of the reaction force motor 31 is executed based on various control parameters such as.

  Based on these configurations, when the steered motor control device 60 is normal, the output line L2 of the motor drive control circuit 51 is connected to the brushless DC motor 20 by the motor power supply switching device 46 (connection switching means), and motor drive control is performed. The brushless DC motor 20 is driven and controlled by the circuit 51, whereby the steered wheels 50 and 50 are steered. In this case, the clutch CL remains in an off state.

  On the other hand, when the steering motor control device 60 is abnormal, the output line L1 of the mechanical rectifier 35 (steering motor commutation means) is connected to the brushless DC motor 20 (steering motor) by the motor power switching device 46. In this case, the steered motor control device 60 is disconnected from the drive control system of each of the motors 20 and 31, and the brushless DC motor 20 is driven and controlled by the mechanical rectifier 35 (the steered motor commutation means of claim 1). The At this time, the clutch CL is controlled to be in an on state, whereby the steering torque applied to the steering shaft 12 by the driver can be transmitted to the steered wheels 50 and 50 through the steering force transmission mechanism. It becomes possible. Therefore, the desired turning operation based on the steering operation via the steering force transmission mechanism is effectively assisted simultaneously by the output torque (auxiliary driving force) from the brushless DC motor 20.

Hereinafter, the configuration of the steering system of the steer-by-wire system 10 will be described in detail with a focus on the mechanical rectifier 35 (steering motor commutation means) constituting the mechanical backup means.
The mechanical rectifier 35 can be configured mechanically as will be described in detail later with reference to FIGS. 3 and 4, for example. Then, a three-phase rectangular wave AC voltage having a phase corresponding to the steering operation with respect to the steering handle 11 is generated from an appropriate DC voltage supplied from the battery BT by the mechanical rectifier 35 and applied to the brushless DC motor 20. can do.

FIG. 2 is a perspective view showing a mechanical configuration of the steering system of the steer-by-wire system 10. A worm wheel 12W located inside the gear box 30 is fixed to the tip of the steering shaft 12, and this worm wheel 12W meshes with a worm gear 31W fixed to the tip of the rotor 31R of the reaction force motor 31. Yes. As a result, the rotor 31R and the steering handle 11 are mechanically interlocked with each other so that they can be rotated mechanically. An appropriate reaction force is applied to the steering handle 11.
The output line L1 (FIG. 1) is composed of three (three-phase) output wirings 40U, 40V, and 40W extending from the mechanical rectifier 35 as described in FIG. .

  FIG. 3 illustrates the logical configuration and electrical connection form of the mechanical rectifier 35 described above. The three-phase output wirings 40U, 40V, and 40W constituting the output line L1 (FIGS. 1 and 2) of the mechanical rectifier 35 are connected to each of the brushless DC motors 20 via the contacts 44 provided in the motor power supply switching device 46. The output wirings 55U, 55V, and 55W constituting the output line L2 of the motor drive control circuit 51 are connected to the phase circuits 24U, 24V, and 24W via the contacts 45 provided in the motor power supply switching device 46, respectively. The brushless DC motor 20 is connected to each phase circuit 24U, 24V, 24W.

  In a normal state, the predetermined power for operation is applied to the motor power supply switching device 46, the contact 44 is in the OFF state, and the contact 45 is in the ON state. Further, when an abnormality occurs in the steering motor control device 60, the application of the operating power is canceled, and the contact 44 is turned on and the contact 45 is turned off.

  The three power supply lines 52 of the motor drive control circuit 51 included in the steered motor control device 60 are each configured by a push-pull connection of a pair of FETs 53 and 54. The rudder motor control device 60 executes well-known ON / OFF control for these six FETs to drive and control the brushless DC motor 20 (steering motor).

  On the other hand, when the steering motor control device 60 is abnormal, the output of the above control signal is suppressed, and the contact 45 is turned off and the contact 44 is turned on. A three-phase rectangular wave AC voltage is generated from the voltage, and a three-phase AC current is supplied to the brushless DC motor 20. That is, in this case, the segments 39U, 39V, and 39W that are in contact with the brushes 41 and 42 in FIGS. 3 and 4 are switched at any time in synchronization with the rotation operation of the rotary input shaft 36J in FIGS. As a result of this switching operation, the phase currents that flow through the phase circuits 24U, 24V, and 24W of the brushless DC motor 20 change appropriately. As a result, the three-phase AC currents that flow through the brushless DC motor 20 The steered wheels 50 and 50 are steered following the steering handle 11.

  FIG. 4 is a cross-sectional view showing the mechanical structure of the mechanical rectifier 35. As shown in FIG. 4, the mechanical rectifier 35 includes a brush holder 36 and a commutator 37 that rotate relative to each other. The commutator 37 is fixed to the vehicle, and a cylindrical cover 43 having a bottom and a columnar base portion 38 are fixed to the commutator 37, respectively. The base part 38 may be formed integrally with the commutator 37. On the outer peripheral surface of the base portion 38, a segment 39U, a segment 39V, and a segment 39W made of metal pieces are arranged in three cycles in this order in the circumferential direction at a regular interval. All of the three segments 39U in total are connected to the output wiring 40U. Of course, the same applies to the other segments.

  Further, a concentric rotation input shaft 36J is fixed to the bottom surface of the cylindrical brush holder 36 with one end. That is, the rotation axis of the brush holder 36 and the rotation axis of the rotation input shaft 36J coincide with each other, and they rotate together with the rotation operation of the rotor 31R in FIG. The bearing 37J rotatably supports the brush holder 36 that rotates smoothly on the rotation shaft around the commutator 37 and the base portion 38 thereof. A pair of power supply brushes 41T and 42T are disposed on the inner surface of the cover 43, and these abut against the thin ring metal rings 41S and 42S fixed to the outer surface of the brush holder 36, respectively. Yes. Accordingly, when the rotation input shaft 36J rotates, the metal ring 41S rotates while maintaining its contact while rubbing against the power supply brush 41T.

On the other hand, inside the brush holder 36, the brushes 41 and 42 fixed in the brush holder 36 are rotated on the outer surface of the base portion 38 of the commutator 37 by rotation of the brush holder 36. 39V, 39W), rotating while maintaining the contact while rubbing against each of these segments. At this time, the metal elastic member 41B constituting the brush 41 has a function of appropriately pressing the metal conductor 41C constituting the brush 41 against each segment (39U, 39V, 39W). The same applies to the elastic member 42B and the metal conductor 42C constituting the brush 42.
With the mechanical configuration of the mechanical rectifier 35 described above, the DC voltage supplied between the pair of power supply brushes 41T and 42T is converted into a three-phase rectangular wave AC voltage having a phase synchronized with the rotation of the rotary input shaft 36J. It can convert and can output from output wiring 40U, 40V, and 40W (output line L1 of FIG. 1, FIG. 2).

  According to the configuration of the first embodiment as described above, the desired fail-safe mechanism to be operated when the main steering motor control device 60 is abnormal is the above-described mechanical backup means (steering force transmission mechanism) and the above-described fail safe mechanism. The electric backup means (steering motor commutation means) can be realized by a compatible configuration, and thus, by duplicating such backup means, each problem of the individual backup means can be complementarily and It can be effectively resolved.

  In addition, a connection body of a large number of universal joints UJ constitutes a mechanical steering force transmission mechanism, but in the event of a collision, the connection body is bent due to the impact. It is also possible to obtain collision safety against Moreover, since the rigidity with respect to the bending deformation of the coupling body can be set low, this characteristic can effectively contribute to increasing the degree of freedom of the arrangement position of the steering handle 11 in the cabin.

FIG. 5 shows a logical configuration diagram of the steer-by-wire system 100 of the second embodiment. The steer-by-wire system 100 corresponds to a modification of the steer-by-wire system 10 of the first embodiment, and the following three points are greatly different.
(Feature 1) A steering force transmission mechanism according to the second embodiment includes a cable 70 made of a push-pull wire, a cable winding device 71 for winding the cable 70, and a cable 70, instead of a connecting body of a large number of universal joints UJ. The cable drive mechanism 72 that drives the gear box 18G ′ based on the tension of the cable and the cable tension changing means 73 that controls the tension of the cable 70 are used.

(Feature 2) The DC potential supplied to the mechanical rectifier 35 (steering motor commutation means) is a low potential supplied from the battery BT0 by the power supply voltage changing means of the present invention configured using the switch SW2. And a high potential supplied from the battery BT1.
(Feature 3) The DC potential supplied to the cable tension changing means 73 (FIG. 6A) is also controlled by the power supply voltage changing means of the present invention.

Hereinafter, these feature points will be described in detail.
The cable 70 is composed of metal wires for right and left pulling, and one end of each wire is connected to a cable winding device 71. For this reason, when the clutch CL is in the on state, a part of one of the wires corresponding to the steering direction is drawn into the cable winding device 71 in synchronization with the rotation of the steering handle 11 and wound up. It is done. By this operation, the cable drive mechanism 72 is rotationally driven based on the tension of the cable, whereby the driver's steering force is transmitted to each steered wheel 50, 50 via the gear box 18G 'or the like.

FIG. 6A illustrates a configuration diagram of the cable tension changing unit 73 described above. As shown in FIG. 5, the cable tension changing means 73 is provided at one place in the middle of each of the metal wires for right pulling and left pulling. One end of the cylindrical iron core 73c is supported to be slidable in the axial direction. Further, the other end is disposed close to the iron pulley 73a.
Since the iron core 73c can be effectively magnetized by the current flowing through the coil 73b wound around the iron core 73c, it is possible to appropriately pull the pulley 73a rightward in the drawing by the magnetic force. Can be variably controlled. The switch 46 ′ provided on the power supply circuit for the coil 73 b is simultaneously turned on when the clutch CL is turned on.

FIG. 6B illustrates a power supply circuit 73B for supplying power to the coil 73b of the cable tension changing unit 73 described above. The power supply circuit 73B is configured by series connection of the switch SW1 and the battery BT, and can be considered as a kind of power supply voltage changing means of the present invention. In other words, the power supply potential to the coil 73b can be changed by the power supply circuit 73B based on the operation of the switch SW1.
When the steering motor control device 60 is abnormal, the reaction force motor 31 shown in FIG. 5 acting as a generator is connected to the bridge BR of the switch SW1, so that when a steering operation is performed at a predetermined rotational speed or higher, A potential difference of a certain level or more occurs between both ends of the resistor R1. Therefore, in that case, the photocoupler FVC is turned on, and subsequently the FET in the figure is turned on, so that power can be supplied from the battery BT to the coil 73b.

Note that a tachometer or the like that rotates in synchronization with the rotation of the steering shaft 12 may be used instead of the reaction force motor 31 applied as the control means of the switch SW1. Such a tacho generator is often mounted on other general steer-by-wire systems as a steering angular velocity sensor.
Further, a power feeding circuit 73B ′ shown in FIG. 6C may be used instead of the power feeding circuit 73B. In this case, the generated power output from the reaction force motor 31 is supplied to the coil 73b as it is through the bridge BR and the variable resistor rr without being converted into an optical signal. The power supply potential to be changed can be continuously changed according to the steering speed. Further, the steering load can be adjusted by appropriately setting the resistance value of the variable resistor rr.

  By using the cable tension changing means 73 as described above, the tension of the cable 70 is maintained high only at the timing when the driver wants to execute the steering operation when the turning motor control device 60 is abnormal. For this reason, the durability of the cable 70 can be ensured, and at the same time, the followability and responsiveness of the steering force transmission mechanism can be well ensured.

Further, similar adaptive control related to the power supply potential can be applied to electrical backup means (that is, mechanical rectifier 35) using the switch SW2 of FIGS. The power supply voltage changing means shown in FIG. 7 described below is also used in Example 4 (FIG. 10) described later.
FIG. 7 illustrates such an application example. FIG. 7 is a detailed circuit diagram of the switch SW2 of the steer-by-wire system 10 of FIG. Here, a reaction force motor 31 composed of a brushed DC motor is used as a steering speed detecting means, and a power supply voltage changing means is constituted by two batteries BT0 and BT1 connected in parallel and a switch SW2.

More specifically, the point p ₂ positive potential output point p ₊ at the same potential of the switch SW2, between the point p ₀ and a point p ₁ at the same potential, a battery BT0 and the battery BT1 is connected in parallel with each other The point p ₀ in the figure is grounded to a predetermined chassis. However, the negative electrode of the battery BT0 and the negative electrode of the battery BT1 are both connected to the point p ₁ (that is, the ground side), and the back electrode is provided between the positive electrode of the battery BT0 and the point p ₂ . A diode D1 is inserted.

On the other hand, between the positive electrode and the point p ₂ of the battery BT1, and a diode D2 for backflow prevention and semiconductor switches FET1 consisting MOSFET is inserted in series. Then, the cathode end of the diode D2 is connected to the point p _2, the drain of the semiconductor switch FET1 is connected to the positive electrode of the battery BT1. In addition, a shunt resistor _RSH is connected between the gate end and the source end of the semiconductor switch FET1. That is, as shown in the figure, the shunt resistor R _SH is connected between a point p ₆ having the same potential as the gate end of the semiconductor switch FET 1 and a point p ₅ having the same potential as the source end of the semiconductor switch FET 1.

The optical switch FVC1 is composed of a commercially available photovoltaic coupler, and the light receiving diode Db on the light receiving side is connected between the points p ₅ and p ₆ . Resistance R _adj1 for adjustment is connected in series to the cathode side of the light emitting side of the light emitting diode Da constituting the optical switch FVC1 to the light emitting diode Da, the other end of the resistor R _adj1 the point p _7, the light emitting the anode end of the diode Da is connected to a point p _8. Between these two points p _7, p _8, the load resistor R _load is connected, between the two points p _7, p _8, further second bridge BR1 in parallel with the load resistor R _load Two output terminals are connected. The bridge BR1 is composed of four diodes arranged one on each of four sides as shown in the figure, and a reaction force motor 31 is connected to two input terminals of the bridge BR1.

If the switch SW2 is configured as described above, the steered motor control device 60 is disconnected from the system, and the output line L1 of the mechanical rectifier 35 is connected to the brushless DC motor 20 (steering motor) by the motor power switching device 46. In the case where the steering motor control device 60 is abnormal (that is, when the steering motor control device 60 is abnormal), the reaction force motor 31 functions as the steering speed detection means of the present invention. That is, in this case, when the rotational speed of the steering handle 11 is larger than a predetermined threshold set by the adjustment resistor _Radj1 , the light emitting diode Da emits light based on the electric power generated by the reaction motor 31, The light receiving diode Db receives the light, and the semiconductor switch FET1 is turned on. As a result, the output potential V1 of the battery BT1 is output to the positive potential output point p ₊ . The diode D1 is an element for preventing current from flowing into the positive electrode side of the battery BT0 at this time.
On the other hand, when the rotation speed of the steering handle 11 is equal to or lower than the above threshold value, the light emitting diode Da does not emit light sufficiently, and the semiconductor switch FET1 is turned off. Therefore, in this case, the output potential V0 (<V1) of the battery BT0 is output to the positive potential output point p ₊ .

According to the above configuration, even when the steering motor control device 60 is abnormal, the power supply voltage corresponding to the steering speed is always supplied via the mechanical rectifier 35 (steering motor commutation means) to the steering motor (brushless). It can be applied to a DC motor 20). Therefore, if the steer-by-wire system 10 according to the second embodiment is used, even when an abnormality occurs in the steering motor control device, excessive power consumption and heat generation in the system are suppressed, and the steering motor with respect to the steering operation is suppressed. Follow-up performance can always be ensured.
Further, by appropriately setting the resistance value of the load resistance R _load , the steering resistance can be generated appropriately.

Note that, for example, the above-described tacho generator (steering angular velocity sensor) or the like may be used instead of the reaction force motor 31 illustrated in FIGS. Since the on-power of the photocoupler is not large, it is possible to share such a steering angular velocity sensor in parallel by both the electric backup means and the mechanical backup means.
In this case, the power generation means (power feeding circuit 73B ′) of FIG. 6C may be inserted in series on the wiring between the connection point P ₀ and the connection point P _{1 of} FIG. Even with such a load required for power generation, a steering resistance can be generated appropriately. It is also possible to adjust the steering load by appropriately setting the resistance value of the variable resistor rr of the power feeding circuit 73B ′.
Note that the battery BT and the battery BT1 in FIG. 1 may be configured by the same battery. These combined configurations may be arbitrary, and many others can be considered.

  FIG. 8 shows an alternative means for the power feeding circuit 73B (FIG. 6B) of the second embodiment. This alternative means 73C is configured by using a switch 30a that switches according to the rotation angle (steering position) of the steering handle 11 instead of the switch SW1 in FIG. 6B.

The switch 30a of FIG. 8 is built in the gear box 30 of FIG. 2, and can take the following two states.
(State 1) A state in which the terminal t1 is connected to the terminal t2.
At this time, the steering position of the steering handle 11 is near the neutral position.
(State 2) A state in which the terminal t1 is connected to the terminal t3.
At this time, the steering position of the steering handle 11 is not near the neutral position.

If such a switch is built in the gear box 30, the feeding potential for the cable tension changing means 73 can be appropriately changed according to the above two states. That is, when the steering position is in the vicinity of the neutral position, it is considered that the vehicle is traveling straight and the necessity of turning is low, so the power supply potential for the cable tension changing means 73 is set to a low potential. If the steering position is not in the vicinity of the neutral position, it is considered that the driver is performing a steering operation and the necessity of turning is high, so the power supply potential for the cable tension changing means 73 is set to a high potential.
For example, such a power supply voltage changing means can also effectively change the power supply state for the cable tension changing means 73 described above.

FIG. 9 illustrates a configuration example (alternative means 73C ′) of the alternative means 73C of FIG. The switch 30a 'is for connecting the two batteries BTa and BTb in the drawing in parallel or in series in accordance with the above two states. That is, in the case of the above state 1, the two batteries BTa and BTb are connected in parallel, and in the case of the above state 2, the two batteries BTa and BTb are connected in series.
Of course, the negative output terminal (−) connected to the negative electrode side of the battery BTb is connected to the switch 46 ′ of the cable tension changing means 73 in FIG. 6A.

FIG. 10 shows another alternative means for the feeding circuit 73B (FIG. 6B) of the second embodiment. This alternative means 73D is configured by combining the switch SW2 of FIG. 7 and the switch 30a of FIG. That is, the terminal t2 of the switch 30a is connected to the positive electrode of the battery BT0, and the terminal t3 of the switch 30a is connected to the positive electrode of the battery BT1. The terminal t1 of the switch 30a is connected to the positive potential output point p ₊ through a backflow preventing diode D3. Of course, this positive potential output point p ₊ is connected to the plus terminal (+) of the cable tension changing means 73 in FIG. 6A.

According to such a configuration, the tension of the cable 70 can be obtained sufficiently and surely even when any of the following conditions is satisfied, so that the mechanical backup means (the steering force transmission mechanism in FIG. 5) can be used. The operability and followability of the steering operation based on this can be improved reliably.
(Condition 1) The steering handle 11 is not in the neutral position.
(Condition 2) The rotational speed of the steering handle 11 is greater than or equal to a predetermined value.

  FIG. 11 shows another alternative to the feeding circuit 73B (FIG. 6B) of the second embodiment. This alternative means 73E is configured by combining a switch that is turned on / off depending on the vehicle speed and the switch 30a of FIG. That is, an input signal (vehicle speed meter voltage) input to the vehicle speed display device 80 is input in parallel to the negative input terminal (−) of the comparator (operational amplifier 81). On the other hand, a threshold voltage (switching reference voltage) for determining whether the vehicle speed is high or low is input to the positive input terminal (+) of the operational amplifier 81.

For this reason, when the vehicle speed is equal to or lower than the predetermined threshold value, the photocoupler FVC is turned on, and then the FET is turned on. In this case, regardless of the steering position of the steering handle 11, the output side The terminal t1 can be maintained at a high potential.
Therefore, if this alternative means 73E is used, the tension of the cable 70 of FIG. 5 can be reliably maintained high regardless of the steering position of the steering handle 11 at the time of extremely low speed or at the time of stationary.
Further, when the vehicle speed is equal to or higher than a predetermined threshold value, the FET is turned off. In this case, the same operation and effect as in the third embodiment can be obtained.

  In each of the above-described embodiments, the above-described mechanical rectifier 35 constitutes the turning motor commutation means that switches the energization state to the turning motor (brushless DC motor 20) according to the steering angle of the steering handle 11. However, such a steering motor commutation means can also be configured electronically using, for example, a small semiconductor chip. In the sixth embodiment, a configuration example of such a steering motor commutation means will be illustrated.

FIG. 12 shows a control block diagram of the electronic commutation device of the sixth embodiment having the semiconductor switch A and the incremental encoder IE. In this semiconductor switch A, the above-described steered motor commutation means for switching the energized state is configured electronically using a semiconductor inverter or the like.
Further, the configuration of the steering system of the sixth embodiment is a modification of the configuration of the steering system of the first embodiment shown in FIG. 1. In the middle of the steering shaft 12, an incremental encoder IE is connected via a gear box GB. Is arranged. Of course, the magnitude of the rotation angle of the incremental encoder IE is proportional to the magnitude of the rotation angle of the steering shaft 12 due to the action of the gear box GB. Further, at the position where the mechanical rectifier 35 is disposed, the tacho generator TG mentioned before is disposed instead.
Based on the above configuration, the operation of the mechanical rectifier 35 (steering motor commutation means of the present invention) in each of the above-described embodiments can be realized alternatively by the incremental encoder IE and the semiconductor switch A. it can.

Hereinafter, the apparatus configuration and operation related to the semiconductor switch A will be described in detail.
The incremental encoder IE outputs +1 every time the rotation angle (mechanical angle) from the reference position of the rotation output shaft of the gear box GB advances by 60 °, and outputs −1 every time it rotates counterclockwise by 60 °. That is, the incremental encoder IE measures the mechanical angle of the rotation output shaft of the gear box GB in units of 1/6 rotation, and outputs 0 while no change in angle of 1 unit or more is observed. The output signal S of the incremental encoder IE is composed of an output string of these detection results (-1, 0, +1).
However, the above 1 unit need not be 60 °, and this angle may be any other angle.

The hex counter circuit CC adds the value (−1, 0, +1) obtained from the incremental encoder IE to the hex counter as needed. As a result, the hex counter circuit CC counts the rotation angle (mechanical angle) with 1/6 rotation of the rotation output shaft of the gear box GB as one unit. Hereinafter, the last digit of the hexadecimal number counted on the hexadecimal counter circuit CC is referred to as phase F.
In the energization pattern table TB1 in FIG. 12, the relationship between the phase F and the control pattern of each transistor in FIG. 12 is defined as shown in Table 1 below.

即ち、図１２の６つのトランジスタは、図３のモータ駆動制御回路５１と略同様の構成を有しており、これらの各トランジスタのベース電圧を、上記の表１にしたがってＯＮ／ＯＦＦ制御することによって、３相矩形波交流電圧を生成することができる。

That is, the six transistors in FIG. 12 have substantially the same configuration as the motor drive control circuit 51 in FIG. 3, and the base voltages of these transistors are ON / OFF controlled according to Table 1 above. Thus, a three-phase rectangular wave AC voltage can be generated.

In accordance with the configuration as described above, the steered motor commutation means of the present invention is configured from the semiconductor switch A having six transistors (semiconductor switches) that are ON / OFF controlled based on the output pulse of the incremental encoder IE. be able to.
According to such a configuration, control is performed based on the output signal S using a semiconductor circuit that is substantially the same as a semiconductor circuit used in an inverter having the simplest known structure that generates a three-phase alternating current. An electronic commutation device having a semiconductor switch (that is, the above-described steering motor commutation means) can be simply and more compactly configured.

[Other variations]
The embodiment of the present invention is not limited to the above-described embodiment, and other modifications as exemplified below may be made. Even with such modifications and applications, the effects of the present invention can be obtained based on the functions of the present invention.
(Modification 1)
For example, in the first embodiment, the steering force transmission mechanism is configured by using a large number of universal joints UJ. However, the number of joint points to be bent and connected by the universal joints may be, for example, about two points. . Even with such a configuration, it is possible to sufficiently ensure the collision safety and the degree of freedom of the indoor layout. Such a steering force transmission mechanism can also be configured using a bellows-structured shaft or the like.

  The present invention relates to a fail-safe mechanism that assists a driver's steering operation in an emergency evacuation when an abnormality occurs in a main steering motor control device in a steer-by-wire system, and in particular, the reliability and operation of the fail-safe mechanism. It is useful for improving the performance.

System configuration diagram of the steer-by-wire system 10 according to the first embodiment. The perspective view which illustrates the device composition of the steering system of steer-by-wire system 10 Circuit diagram of control circuit for three-phase current of brushless DC motor 20 (steering motor) Sectional drawing which illustrates the hardware constitutions of the mechanical commutation apparatus 35 System configuration diagram of the steer-by-wire system 100 according to the second embodiment. Configuration diagram of cable tension changing means 73 Circuit diagram of feeding circuit 73B Circuit diagram of feeding circuit 73B ' Circuit diagram of power supply voltage changing means for controlling power supply voltage Conceptual diagram of alternative means 73C of power feeding circuit 73B (Example 3) The circuit diagram which illustrates the example of composition of alternative means 73C Circuit diagram illustrating configuration example of alternative means 73D (Embodiment 4) Circuit diagram illustrating configuration example of alternative means 73E (Example 5) Circuit diagram of semiconductor switch A (electronic commutation means) of embodiment 6

18G: Gearbox 20: Brushless DC motor (steering motor)
30: Gear box CL: Clutch 71: Cable winding device 72: Cable drive mechanism 73: Cable tension changing means

Claims (6)

In a steer-by-wire system that mechanically separates a steering wheel and a steered wheel provided in a vehicle and drives the steered motor according to an operation of the steering handle to steer the steered wheel.
A steering motor control device for driving and controlling the steering motor in normal times;
A steering motor commutation means for switching an energization state to the steering motor according to a steering angle of the steering handle;
Connection switching for electrically disconnecting the steered motor control device from the steered motor and electrically connecting the steered motor commutation means to the steered motor instead when the steered motor control device is abnormal Means,
A different constant of the turning motor controller, and the steering handle is mechanically connected, a steering force of a driver of the vehicle bending deformable mechanically transmitted to the steering wheel cable,
A cable tension control means for controlling the tension of the cable when the steering motor control device is abnormal;
A different constant of the turning motor controller, and power supply to the steering motor commutation means supplying an electric current to the steering motor, and power supply means for increasing the tension of the cable to power the cable tension control means,
When the steering motor control device is abnormal, the tension of the cable is increased or decreased by changing the voltage supplied to the cable tension control means according to the steering angle of the steering wheel, the steering speed, or the vehicle speed of the vehicle. steer-by-wire system, characterized in that it comprises a supply voltage changing means for. When the steering motor control device is abnormal, the power supply voltage changing means is configured to output a first voltage when the steering angle is in a neutral position range and the steering speed is smaller than a predetermined value. Is not present in the neutral range, or when the steering speed is equal to or higher than a predetermined value, the second voltage higher than the first voltage is supplied to the cable tension control means. The steer-by-wire system according to claim 1. When the steering motor control device is abnormal, the power supply voltage changing means is configured to output a first voltage when the steering angle is in a neutral position range and the vehicle speed is greater than a predetermined value. Is a means for supplying the cable tension control means with a second voltage that is greater than the first voltage when the speed does not exist in the neutral range or when the speed is less than or equal to a predetermined value.
The steer-by-wire system according to claim 1. 2. The steering speed is detected by an output generated by rotation of the steering handle of a reaction force motor that applies reaction torque to the steering handle when the steering motor control device is normal. Or the steer-by-wire system according to claim 2. The steer-by-wire system according to any one of claims 1 to 4, wherein the steered motor commutation means includes a mechanical commutation device having a brush and a commutator. The steering motor commutation means includes an electronic commutation device having a rotation angle sensor that detects a steering angle of the steering handle, and a semiconductor switch that is ON / OFF controlled based on the detected steering angle. The steer-by-wire system according to any one of claims 1 to 4, wherein the steer-by-wire system is configured.

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