JP2007008308A - Steering system - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a steering system capable of steering a steering wheel in accordance with a handle operation even when a motor of a transfer ratio change actuator and a lock mechanism both fails. <P>SOLUTION: An assist power output by a power steering device 40 becomes larger than usual so that a load torque on a control force transmission shaft 12 becomes smaller than an allowable load torque T1 when the a transfer ratio change motor 22 and the lock mechanism 30 are both broken. Therefore, the load torque on a reduction gear 21 of the transfer ratio change actuator 20 becomes smaller than the allowable load torque T1, and the reduction gear 21 does not work due to friction resistance when the reduction gear 21 receives such a small load torque. Accordingly, rotation between an upper part and an lower part of the control force transmission shaft 12 is prevented, and thus, the steering wheel 15 can be steered in accordance with an operation of a handle 11. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention includes a transmission ratio change actuator in the middle of a steering force transmission shaft extending downward from a steering wheel of a vehicle, and by driving the transmission ratio change actuator with a motor, an upper portion and a lower portion of the steering force transmission shaft are provided. It is related with the steering system which can change the transmission ratio of rotation between.

This type of steering system generally includes a lock mechanism for locking the motor in the event of an abnormality (see, for example, Patent Document 1). For example, when the ignition switch is turned on, a rotation command is given to the motor while the motor is locked by the lock mechanism, and it is confirmed whether the lock mechanism locks the motor by the load current of the motor. It was.
Japanese Patent No. 3505992 (paragraphs [0022] to [0024], FIG. 1)

  By the way, in the above-described conventional steering system, for example, when both the motor and the lock mechanism break down during traveling, the steering wheel is rotated freely between the upper part and the lower part of the steering force transmission shaft, and the steered wheels are handled by the steering wheel. There may have been a situation where the vehicle cannot be steered to a position corresponding to the operation.

  The present invention has been made in view of the above circumstances, and provides a steering system capable of turning steered wheels in accordance with steering wheel operations even when both the motor and lock mechanism of the transmission ratio change actuator fail. With the goal.

  In order to achieve the above object, a steering system according to the invention of claim 1 is provided in a steering force transmission shaft extending downward from a steering wheel of a vehicle, and is provided between an upper portion and a lower portion of the steering force transmission shaft. A transmission ratio change actuator capable of changing the rotation transmission ratio of the motor, a power steering device capable of outputting an assist force so as to reduce load torque on the steering wheel and the steering force transmission shaft, a transmission ratio change actuator, and a power steering device And a steering control device that controls the vehicle according to the driving situation of the vehicle, and the transmission ratio change actuator is operated by receiving the output torque from the motor and the motor, and the upper part and the lower part of the steering force transmission shaft. In a steering system provided with a speed reducer that relatively rotates and a lock mechanism for locking the motor, The rudder control device is designed so that when both the motor and the lock mechanism become abnormal and a load torque greater than a predetermined allowable load torque is applied to the steering force transmission shaft, the steering force transmission shaft is placed between the upper portion and the lower portion. Is characterized in that the assist force to be output to the power steering device is made larger than usual so that the load torque applied to the steering force transmission shaft becomes smaller than the allowable load torque.

  According to a second aspect of the present invention, in the steering system according to the first aspect, a non-steering traveling state determining means for determining at a predetermined period during traveling whether or not the steering is in a non-steering traveling state in which the steering wheel is not steered, An energization state switching means for switching the energization state to the drive source of the lock mechanism so as to lock the motor, and a lock confirmation means for detecting a lock abnormality in which the motor is not locked even when the energization state is switched, It is characterized by being provided in the steering control device.

  According to a third aspect of the present invention, in the steering system according to the second aspect, the drive source of the lock mechanism includes a solenoid and a plunger that moves linearly by excitation of the solenoid, and the lock confirmation means includes the self-inductance of the solenoid. Based on the above, it is characterized in that it is configured to detect a lock abnormality.

  According to a fourth aspect of the present invention, in the steering system according to the second aspect, the drive source of the lock mechanism includes a solenoid and a plunger that moves linearly by excitation of the solenoid, and a detection coil is provided on the same axis as the solenoid. The detection coil, solenoid, and plunger constitute a differential transformer, and the lock confirmation means is characterized in that it is configured to detect a lock abnormality based on an induced voltage generated in the detection coil.

  According to a fifth aspect of the present invention, in the steering system according to any one of the first to fourth aspects, when the steering control device is in a neutral position when a lock abnormality occurs while the motor is in a normal state, It is characterized in that the motor is servo-locked.

[Invention of Claim 1]
According to the configuration of the first aspect of the present invention, the power steering device is configured so that the load torque applied to the steering force transmission shaft becomes smaller than the allowable load torque when both the motor provided in the transmission ratio change actuator and the lock mechanism fail. The assist force to be output is greater than normal. As a result, the load torque related to the speed reducer of the transmission ratio change actuator is also smaller than the allowable load torque, and even if the speed reducer receives such a small load torque, the speed reducer does not operate due to frictional resistance. Therefore, rotation between the upper part and the lower part of the steering force transmission shaft is prevented. That is, according to the present invention, even when both the motor and the lock mechanism are out of order, the steered wheels can be steered according to the steering wheel operation, and the vehicle can be moved to an arbitrary position for emergency evacuation. it can.

[Invention of claim 2]
According to the second aspect of the present invention, during running, the energization state to the drive source of the lock mechanism is switched so that the motor is locked, and as a result, it is confirmed whether or not the motor is actually locked. Thereby, lock abnormality can be detected at an early stage. Further, whether or not the motor is locked is confirmed in a non-steering traveling state, so there is no influence on traveling.

[Invention of claim 3]
According to the third aspect of the present invention, the lock mechanism is switched between the locked state and the unlocked state depending on whether the plunger is located on the relatively far side or the relatively closer side of the linear movement stroke. Here, when the plunger is positioned on the side far from the solenoid, the self-inductance of the solenoid increases, whereas when the plunger is positioned on the side close to the solenoid, the self-inductance of the solenoid decreases. Therefore, the position of the plunger can be estimated based on the self-inductance of the solenoid, and it is possible to detect a lock abnormality in which the motor is not locked even when the energization state of the solenoid is switched.

[Invention of claim 4]
According to the fourth aspect of the present invention, since the differential transformer is constituted by the solenoid and the plunger provided in the drive source of the lock mechanism and the detection coil provided on the same axis of the solenoid, the position of the plunger can be accurately detected. Thus, it is possible to accurately detect a locking abnormality in which the motor is not locked even when the energization state of the solenoid is switched.

[Invention of claim 5]
Assuming that the mutual position between the upper and lower parts of the steering force transmission shaft when the handle is in the neutral position is the origin position, the transmission ratio change actuator is used when the handle is turned by performing normal control. And the upper portion and the lower portion of the steering force transmission shaft deviate from the origin position. On the other hand, in the configuration of claim 5, when the lock abnormality occurs while the motor is in a normal state, the motor is servo-locked when the handle is in the neutral position. In addition, the control for an abnormality can be performed in a state where the upper portion and the lower portion of the steering force transmission shaft are held at the origin position. Thereby, when the handle is set to the neutral position, the steered wheels are always arranged at the neutral position, and the operation of the handle becomes easy.

[First Embodiment]
Hereinafter, a first embodiment of the present invention will be described with reference to FIGS.
The vehicle 10 shown in FIG. 1 includes a transmission ratio changing actuator 20 and a power steering device 40. First, the configuration of the transmission ratio changing actuator 20 will be described. The transmission ratio changing actuator 20 is provided in the middle of the steering force transmission shaft 12 extending downward from the handle 11. Specifically, the steering force transmission shaft 12 includes an upper first steering force transmission shaft 12A (corresponding to “an upper portion of the steering force transmission shaft” according to the present invention) and a lower second steering force. The transmission shaft 12B (corresponding to the “lower portion of the steering force transmission shaft” according to the present invention), and the transmission ratio changing actuator 20 is connected between the first and second steering force transmission shafts 12A and 12B. Has been. A universal joint 12J is provided at each intermediate portion of the first and second steering force transmission shafts 12A and 12B.

  As shown in FIG. 2, the transmission ratio changing actuator 20 includes a motor 22 (hereinafter referred to as “transmission ratio changing motor 22”) disposed coaxially above the differential reduction gear 21, and the transmission ratio changing actuator 20 and the transmission ratio. The change motor 22 is housed in a common assy sleeve 23. The reduction gear 21 includes an input portion 21A at the center, and the input portion 21A has a rotor 22R of the transmission ratio changing motor 22 fixed thereto. The speed reducer 21 includes an output portion 21B on the outer surface of the lower end portion, and a disc 12C provided at the upper end portion of the second steering force transmission shaft 12B is fixed to the output portion 21B. When the input portion 21A is rotationally driven by the transmission ratio changing motor 22, the rotation is decelerated and the second steering force transmission shaft 12B is rotated.

  A rotational position detector 24 is provided at a position near the upper end of the transmission ratio changing motor 22. The rotational position detector 24 detects the rotational position of the rotor 22R relative to the stator 22S of the transmission ratio changing motor 22. The rotational position detector 24 includes a magnet 24A that rotates integrally with the rotor 22R, and a Hall element 24B that is fixed to the stator 22S.

  A lock mechanism 30 is provided on the upper surface of the transmission ratio change motor 22, and an upper end portion of the transmission ratio change motor 22 including the lock mechanism 30 is covered with a connection housing 25. The connecting housing 25 includes a top plate portion 25A facing the upper surface of the transmission ratio changing motor 22, a large diameter cylindrical portion 25B extending downward from the top plate portion 25A, and a small diameter cylindrical portion 25C extending upward from the top plate portion 25A. And comprising. The assembly sleeve 23 is fitted and fixed to the lower end of the large-diameter cylindrical portion 25B, while the first steering force transmission shaft 12A is fitted and fixed to the small-diameter cylindrical portion 25C. A handle 11 (see FIG. 1) is fixed to the upper end portion of the first steering force transmission shaft 12A. As a result, when the steering wheel 11 is steered and the rotor 22R of the transmission ratio changing motor 22 rotates, the second steering force transmission shaft 12B rotates relative to the handle 11 and the first steering force transmission shaft 12A. If the rotor 22R does not rotate, the second steering force transmission shaft 12B rotates together with the handle 11 and the first steering force transmission shaft 12A. That is, by rotating the rotor 22R of the transmission ratio changing motor 22, the rotation angle of the second steering force transmission shaft 12B with respect to the steering angle of the handle 11 can be changed.

  A cable case 26 having a donut-shaped accommodation space is assembled to the upper portion of the connection housing 25. A transmission ratio change motor 22, a rotational position detection unit 24, and the like are connected to a steering control device 60 described later via a spiral cable 27 housed in the cable case 26.

  The lock mechanism 30 includes a lock holder 31, a lock arm 32, and a linear drive source 35 described below. An upper end portion of the rotor 22R protrudes from the upper surface of the transmission ratio changing motor 22, and the lock holder 31 is fixed to the upper end portion of the rotor 22R so as to be integrally rotatable. As shown in FIG. 3, the lock holder 31 has a ring shape, and a plurality of concave and convex engaging portions 31A are formed on the peripheral surface thereof.

  The lock arm 32 is pivotally supported by a support column 33 standing upright from the upper surface of the transmission ratio changing motor 22. The column 33 penetrates a position near one end of the lock arm 32, and a locking projection 32 </ b> A is directed toward the lock holder 31 at the tip of the lock arm 32 on the side that extends relatively long from the penetrating portion of the column 33. Is protruding.

  A torsion spring 34 is attached to the lock arm 32. The torsion spring 34 has a coil spring structure, and one end of the spring wire constituting the coil spring is locked to the end face of the support 33 and the other end is locked to the lock arm 32. The lock arm 32 is biased to the locked position by the elastic force of the torsion spring 34. Then, in a state where the lock arm 32 is located at this lock position (the state shown in FIG. 3), the locking projection 32A engages with the concave / convex engaging portion 31A of the lock holder 31, and the rotor 22R is prevented from rotating. .

  The direct drive source 35 is provided on the upper surface of the transmission ratio changing motor 22 and moves the lock arm 32 to the unlock position against the resilient force of the torsion spring 34. The linear drive source 35 is configured to linearly move the plunger 37 by excitation of the solenoid 36. The distal end portion of the plunger 37 is connected to the end portion of the lock arm 32 on the side extending to the outside of the support column 33. When the solenoid 36 is energized, the plunger 37 moves directly so as to be pulled into the back side of the hollow portion of the solenoid 36. As a result, the lock arm 32 rotates counterclockwise in FIG. As a result, the lock arm 32 reaches the lock release position, the engagement between the locking projection 32A and the concave / convex engagement portion 31A is released, and the rotor 22R becomes rotatable. On the other hand, when the excitation of the solenoid 36 is stopped, the plunger 37 can move freely in the solenoid 36, and the plunger 37 is moved to the original position together with the lock arm 32 by the elastic force of the torsion spring 34 ( Return to the locked position.

  This completes the description of the configuration of the transmission ratio changing actuator 20. Next, the configuration of the power steering device 40 will be described. As shown in FIG. 1, the power steering device 40 includes a motor 41 (hereinafter referred to as “assist motor 41”), a steered shaft 42, and a ball screw mechanism 43 that connects between the assist motor 41 and the steered shaft 42. Etc. The steered shaft 42 is passed between the steered wheels 15 and 15 and both ends thereof are connected to the steered wheels 15 and 15 via tie rods (not shown). Further, an intermediate portion of the steered shaft 42 is inserted into a cylindrical case 44, and the cylindrical case 44 is fixed to the main body of the vehicle 10.

  The assist motor 41 is built in an intermediate portion of the cylindrical case 44 in the axial direction. The stator 41S of the assist motor 41 is fitted and fixed to the inner surface of the cylindrical case 44, and the rotor 41R has a cylindrical shape and is loosely fitted inside the stator 41S. And the turning shaft 42 has penetrated the inner side of the rotor 41R. A rotation position sensor 45 for detecting the rotation position of the rotor 41R is provided on one end side of the assist motor 41.

  A ball screw nut 46 is assembled on the inner surface of the rotor 41R. Further, a ball screw portion 47 is formed at an intermediate portion in the axial direction of the steered shaft 42. The ball screw nut 43 and the ball screw portion 47 constitute the ball screw mechanism 43 described above. Thereby, the output torque of the assist motor 41 is converted into the axial force of the steered shaft 42.

  A rack 48 is formed on one end portion side of the steered shaft 42, and a pinion insertion port 50 is open to the side surface on one end side of the cylindrical case 44. A pinion 49 is provided at the lower end of the second steering force transmission shaft 12 </ b> B. The pinion 49 enters the cylindrical case 44 through the pinion insertion port 50 and meshes with the rack 48. As a result, the shaft transmission torque applied to the steering force transmission shaft 12 is converted into the axial force of the steered shaft 42, and the steering force is determined by the resultant force of the axial force and the axial force applied to the steered shaft 42 by the assist motor 41. The shaft 42 moves linearly with respect to the cylindrical case 44, and the steered wheels 15, 15 are steered. That is, the load torque related to the handle 11 and the steering force transmission shaft 12 can be reduced by the output torque of the assist motor 41. And the steering feeling of the steering wheel 11 can be changed by changing the output torque of the assist motor 41 according to the driving situation. This completes the description of the power steering device 40.

  Next, the steering control device 60 according to the present invention will be described below. The steering control device 60 drives and controls the transmission ratio changing actuator 20 and the power steering device 40 according to the driving situation. In order to grasp the driving situation, as shown in FIG. 1, a steering angle sensor 51 and a torque sensor 52 are provided in the middle portion of the first steering force transmission shaft 12A, and in the vicinity of the steered wheels 15, A vehicle speed sensor 53 is provided. The steering angle of the steering wheel 11 is detected by the steering angle sensor 51, and the load torque applied to the steering force transmission shaft 12 is detected by the torque sensor 52. The vehicle speed sensor 53 detects the vehicle speed based on the rotation of the steered wheels 15. The steering control device 60 takes in the detection results of the steering angle sensor 51, the torque sensor 52, and the vehicle speed sensor 53.

  The steering control device 60 includes a CPU 61, a ROM 62, a RAM 63, first and second motor drive circuits 64 and 65, and a solenoid excitation circuit 66. Then, the steering control device 60 performs drive control on the transmission ratio change actuator 20 as follows. That is, the ROM 62 of the steering control device 60 stores a transmission ratio determination map (not shown) that associates the vehicle speed with the transmission ratio as data for controlling the transmission ratio changing actuator 20. Here, the transmission ratio is a ratio (= θ2 / θ1) between the rotation angle θ1 of the first steering force transmission shaft 12A relative to the main body of the vehicle 10 and the rotation angle θ2 of the second steering force transmission shaft 12B.

  The CPU 61 of the steering control device 60 executes a transmission ratio control program (not shown) at a predetermined cycle, and determines the transmission ratio based on the detection result of the vehicle speed sensor 53 and the transmission ratio determination map. Then, the target rotation angle of the second steering force transmission shaft 12B is calculated from the steering angle of the steering wheel 11 detected by the steering angle sensor 51 and the transmission ratio, and the actual rotation angle of the second steering force transmission shaft 12B is calculated. Is caused to flow from the first motor drive circuit 64 to the transmission ratio changing motor 22 in order to match the target rotation angle. Thereby, the reduction gear 21 operates and the rotation angle is changed between the first steering force transmission shaft 12A and the second steering force transmission shaft 12B.

  In the transmission ratio determination map, the transmission ratio is set to decrease as the vehicle speed increases. As a result, in the low speed range, the steered wheels 15, 15 can be turned by a slight steering operation, and the turning performance is improved. On the other hand, in a high speed range, so-called sudden steering is restricted, and stable running is possible.

  In order to drive the transmission ratio changing motor 22 during traveling, when the ignition key of the vehicle 10 is turned on, the solenoid excitation circuit 66 of the steering control device 60 excites the solenoid 36 of the lock mechanism 30 to lock arm 32 is moved to the unlock position. Thereby, the rotor 22R of the transmission ratio changing motor 22 can be rotated. Further, when the ignition key is turned off or when an abnormality occurs in the transmission ratio change motor 22 or various sensors, excitation of the solenoid 36 by the solenoid excitation circuit 66 is stopped, and the rotor 22R of the transmission ratio change motor 22 cannot rotate. Locked to.

  More specifically, as shown in FIG. 4, the solenoid excitation circuit 66 includes a switch element 66S, a shunt resistor 66R, and a voltmeter 66K for detecting the voltage across the shunt resistor 66R, and these switch elements 66S. The shunt resistor 66R is connected in series with the DC power supply 67 together with the solenoid 36. In a normal state, the CPU 61 provided in the steering control device 60 turns on the switch element 66S to excite the solenoid 36, whereby the lock arm 32 is held in the unlocked position. On the other hand, at the time of abnormality and in a state where the ignition switch is turned off, the switch element 66S is turned off and the solenoid 36 is de-energized. As a result, the lock arm 32 is held in the locked position by the resilient force of the torsion spring 34.

  Next, a configuration in which the steering control device 60 drives and controls the power steering device 40 will be described. The ROM 62 of the steering control device 60 stores the load torque Tm applied to the steering force transmission shaft 12 and the assist force F to be output to the power steering device 40 as data for controlling the power steering device 40 as shown in FIG. Are stored in a first assist force determination map MP1. In addition, the ROM 62 includes a first gain determination map (not shown) in which the vehicle speed is associated with the first gain, and a second gain determination map (not shown) in which the steering angle of the steering wheel 11 is associated with the second gain. ), A third gain determination map (not shown) in which the steering angular velocity of the steering wheel 11 is associated with the second gain, and the like are also stored.

  Then, the CPU 61 of the steering control device 60 executes an assist force control program (not shown) at a predetermined period, and obtains an assist force corresponding to the load torque detected by the torque sensor 52 based on the first assist force determination map MP1. To do. Then, based on the first to third gain determination maps, the first to third gains corresponding to the detection results of the steering angle sensor 51 and the vehicle speed sensor 53 are acquired, and the first to third gains are assisted. Multiply the force to calculate the assist force command value. Then, a motor drive current corresponding to the assist force command value is supplied to the assist motor 41. Thereby, the power steering device 40 outputs an assist force according to the driving situation, and the steering resistance of the steering wheel 11 is reduced.

  In the steering control device 60, the CPU 61 executes the abnormality detection program PG1 shown in FIG. 6 at a predetermined period to cope with an abnormal situation. When the abnormality detection program PG1 is executed, it is determined whether or not a predetermined time (for example, 1 second) has elapsed since the lock determination processing in the following steps S14 to S17 in the abnormality detection program PG1 was executed last time. (S10). If a predetermined time (for example, 1 second) has not elapsed (S10: NO), the abnormality detection program PG1 is exited. When a predetermined time (for example, 1 second) has elapsed (S10: YES), detection results of various sensors such as the steering angle sensor 51, the torque sensor 52, the vehicle speed sensor 53, and the like are acquired (S11).

  Next, it is determined whether or not the vehicle is in a no-steering traveling state (S12). Specifically, for example, when all of the following four conditions are satisfied, it is determined that the vehicle is in the non-steering traveling state, and otherwise, it is determined that the vehicle is not in the non-steering traveling state.

Steering angle ≤ 2 [deg]
Steering angular velocity ≦ 0.1 [deg / s]
Steering angular acceleration ≦ 0.1 [deg / s ² ]
30 [km / h] ≦ vehicle speed ≦ 60 [km / h]

  If the vehicle is not in the no-steering traveling state (S12: NO), the abnormality detection program PG1 is exited. On the other hand, when the vehicle is in the non-steering traveling state (S12: YES), in order to confirm whether or not the transmission ratio changing motor 22 can be locked by the lock mechanism 30, the lock mechanism 30 is caused to perform a lock operation. (S13). That is, the energization to the solenoid 36 is stopped. In the present embodiment, the above-described step S12 corresponds to the “non-steering travel state determination unit” according to the present invention, and step S13 corresponds to the “energized state switching unit” according to the present invention. The determination process (S14 to S17) corresponds to the “lock confirmation unit” according to the present invention.

  Next, lock determination processing is performed (S14 to S17). In this lock determination process, it is confirmed whether or not the lock arm 32 is located at the lock position based on the change in the self-inductance of the solenoid 36.

  Here, when the lock mechanism 30 is normally operated and the lock arm 32 is moved to the lock position, the plunger 37 connected to the lock arm 32 moves with respect to the solenoid 36 out of the linearly movable stroke. As a result, the self-inductance of the solenoid 36 increases. On the other hand, when the lock mechanism 30 does not operate normally and the lock arm 32 has moved to the unlock position, the plunger 37 is positioned relatively close to the solenoid 36 and the self-inductance of the solenoid 36 is reduced. descend. Therefore, based on the change in the self-inductance of the solenoid 36, it can be determined whether the lock arm 32 has moved to the lock position or the lock release position. Therefore, in the lock determination process (S14 to S17), in order to check the self-inductance of the solenoid 36, a current that does not operate the plunger 37 is passed through the solenoid 36 (S14).

  Next, the voltage between the terminals of the shunt resistor 66R detected by the voltmeter 66K is acquired via an A / D converter (not shown) (S15), and the solenoid 36 receives the voltage between the terminals and the resistance value of the shunt resistor 66R. The flowing excitation current I is calculated, and the differential value (dI / dt) of the excitation current I is calculated (S16).

  Here, when the self-inductance of the solenoid 36 is L and the voltage applied to the solenoid 36 is E, the following equation (1) is established.

      E = L (dI / dt) (1)

  Therefore, when the applied voltage E to the solenoid 36 is constant, when the self-inductance of the solenoid 36 becomes relatively large (that is, when the lock arm 32 is positioned at the lock position), the differential value of the excitation current I ( dI / dt) is smaller than a predetermined reference value. Therefore, in the abnormality detection program PG1, it is determined whether or not the lock arm 32 is located at the lock position by determining whether or not the differential value (dI / dt) of the excitation current I is smaller than the reference value, that is, the lock is not performed. It is determined whether or not the operation is normal (S17). If the lock is operating normally (S17: YES), the lock determination flag F1 is turned on (S18). Then, energization of the solenoid 36 is resumed, the lock of the transmission ratio changing motor 22 by the lock mechanism 30 is released (S19), and the abnormality detection program PG1 is exited.

  On the other hand, when the lock is not operating normally (S17: NO), the lock determination flag F1 is turned off (S20). At this time, a display indicating that an abnormality has occurred in the lock mechanism 30 is displayed, for example, on the panel of the driver's seat.

  Next, it is determined whether or not the transmission ratio changing motor 22 is operating normally (S21). Specifically, the transmission ratio change motor 22 operates normally based on whether or not the transmission ratio change motor 22 can be energized and whether or not the detected value of the rotational position detector 24 is a normal value. It is determined whether or not. At this time, if the transmission ratio changing motor 22 is operating normally (S21: YES), the transmission ratio changing motor 22 is servo-locked when the handle 11 is positioned at the neutral position (S22). The steering control device 60 performs normal control on the power steering device 40. The servo lock is held while the transmission ratio changing motor 22 is normal.

  Here, when the mutual position between the first steering force transmission shaft 12A and the steering force transmission shaft 12B when the handle 11 is in the neutral position is the origin position, the transmission ratio changing actuator 20 is operated to operate the handle 11. , The first steering force transmission shaft 12A and the second steering force transmission shaft 12B are displaced from the origin position. In this state, when an abnormality occurs in the transmission ratio change motor 22 following the abnormality in the lock mechanism 30 (S17: NO, S21: NO), the first steering force transmission shaft 12A and the second steering force transmission shaft 12B are in contact with each other. Assist force increase control (S24), which will be described later, has to be performed with the gap being shifted from the origin position.

  However, in the abnormality detection program PG1, when the lock mechanism 30 is abnormal and the transmission ratio changing motor 22 is normal (S17: NO, S21: YES), the handle 11 is in the neutral position as described above. Since the transmission ratio changing motor 22 is servo-locked, when the abnormality of the transmission ratio changing motor 22 occurs after the abnormality of the lock mechanism 30 (S17: NO, S21: NO), the first steering force transmission shaft 12A. Assist force increase control (S24), which will be described later, can be performed in a state where the space between the first steering force transmission shaft 12A and the second steering force transmission shaft 12A is held at the origin position. Thereby, when the handle 11 is set to the neutral position, the steered wheels 15 are always arranged at the neutral position, and the operation of the handle 11 is facilitated.

  When the transmission ratio change motor 22 is not operating normally (S21: NO), the reduction gear 21 is not locked by either the lock mechanism 30 or the transmission ratio change motor 22, and therefore the steering force transmission shaft. Thus, the load torque applied to the motor 12 rotates freely between the first steering force transmission shaft 12A and the second steering force transmission shaft 12B. However, since the torque reducer 21 is actuated with a torque cross due to frictional resistance, if the load torque of the steering force transmission shaft 12 is equal to or less than the predetermined allowable load torque T1, the reducer 21 does not operate and the first steering is performed. There is no rotation between the force transmission shaft 12A and the second steering force transmission shaft 12B.

  Therefore, as described above, when both the lock mechanism 30 and the transmission ratio change motor 22 are not normally operated (S17: NO, S21: NO), the steering control device 60 controls the transmission ratio change motor 22. Is stopped (S23), the assist force increase control (S24) is performed, and the assist force to be output to the power steering device 40 is normally set so that the load torque applied to the steering force transmission shaft 12 is smaller than the above-described allowable load torque T1. Increase from time. Specifically, when both the lock mechanism 30 and the transmission ratio change motor 22 are not normally operated (S17: NO, S21: NO), a map used for determining the assist force is shown in FIG. A switch is made from the first assist force determination map MP1 shown in A) to the second assist force determination map MP2 shown in FIG. In the second assist force determination map MP2, the load torque Tm applied to the steering force transmission shaft 12 increases steeply from zero to the maximum value until the load torque Tm changes from zero to the allowable load torque T1. It is set to be.

  The first assist force determination map MP1 described above is a period until the load torque Tm applied to the steering force transmission shaft 12 changes from zero to the allowable load torque T1 as compared with the second assist force determination map MP2. In addition, when the assist force gradually increases from zero and the load torque Tm increases beyond the allowable load torque T1, the assist force is set to increase steeply until reaching the maximum value.

  In the assist force increase control (S24), an assist force corresponding to the load torque detected by the torque sensor 52 is determined based on the second assist force determination map MP2, and the assist force is determined according to the determined assist force. A motor drive current is passed through the assist motor 41. Thereby, the load torque applied to the steering force transmission shaft 12 changes within a range smaller than the allowable load torque T1, and the rotation between the first steering force transmission shaft 12A and the second steering force transmission shaft 12B is reduced. It is prevented.

  As described above, according to the configuration of the present embodiment, even when the transmission ratio change motor 22 and the lock mechanism 30 both fail, the steered wheels 15 and 15 can be steered according to the operation of the handle 11, The vehicle 10 can be moved to an arbitrary position for emergency evacuation.

[Second Embodiment]
This embodiment is shown in FIG. 7, and the configuration of the linear motion drive source 35 of the lock mechanism 30 is mainly different from that of the first embodiment. The linear motion drive source 35 of the present embodiment is provided with a detection coil 36K at one end of the solenoid 36 on the same axis. The detection coil 36K, the solenoid 36, and the plunger 37 constitute a differential transformer. The position of the plunger 37 is detected based on the induced voltage generated in the detection coil 36K when a current is passed through the solenoid 36.

  Accordingly, the position of the plunger 37 can be accurately detected, and based on the position of the plunger 37, it can be accurately detected whether or not the lock mechanism 30 is normally locking the transmission ratio changing motor 22. It becomes possible.

[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 place of the configuration of the first and second embodiments, for example, a limit switch is provided at the upper end of the transmission ratio changing motor 22, and whether or not the lock arm 32 is in the locked position by the limit switch. May be detected to determine whether the lock mechanism 30 is abnormal.

(2) Use car navigation and VICS (Vehicle Information and Communication System) to determine the state of no-steering travel, and make sure that the front of the vehicle's travel path is straight and that there are no obstacles. It may be configured to determine whether or not the non-steering traveling state is continued as a condition.

(3) In addition to the configuration of the first embodiment, when both the lock mechanism 30 and the transmission ratio change motor 22 become abnormal, the engine speed is limited or the shift of the automatic mission is limited. May be.

(4) The power steering device 40 of the first embodiment has a configuration in which the assist motor 41 and the steered shaft 42 are connected by the ball screw mechanism 43. However, between the assist motor 41 and the steered shaft 42, May be connected by a worm gear and a worm wheel.

(5) Although the power steering device 40 of the first embodiment uses the assist motor 41 as a drive source, the power steering device according to the present invention is a hydraulic power steering device that can electrically control the assist force. There may be. Specifically, a power steering device using an electric control pump or an electric pump that can electrically control the discharge amount of the hydraulic pump may be used.

The conceptual diagram of the steering system which concerns on 1st Embodiment of this invention. Cross section of transmission ratio change actuator Top view of the locking mechanism Circuit diagram of solenoid excitation circuit Conceptual diagram of assist force determination map Flow chart of abnormality detection program Plan view of the locking mechanism of the second embodiment

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Vehicle 11 Steering wheel 12 Steering force transmission shaft 15 Steering wheel 20 Transmission ratio change actuator 21 Reducer 22 Transmission ratio change motor 30 Lock mechanism 35 Direct drive source 36 Solenoid 37 Plunger 40 Power steering device 60 Steering control device

Claims (5)

A transmission ratio change actuator provided on a steering force transmission shaft extending downward from a steering wheel of the vehicle, and capable of changing a transmission ratio of rotation between an upper portion and a lower portion of the steering force transmission shaft;
A power steering device capable of outputting an assist force so as to reduce a load torque to the steering wheel and the steering force transmission shaft;
A steering control device that controls the transmission ratio change actuator and the power steering device according to the driving situation of the vehicle;
The transmission ratio change actuator is operated by receiving a motor, an output torque from the motor, and relatively rotating an upper portion and a lower portion of the steering force transmission shaft, and locks the motor. In a steering system provided with a locking mechanism for
In the steering control device, when both the motor and the lock mechanism become abnormal and a load torque higher than a predetermined allowable load torque is applied to the steering force transmission shaft, an upper portion and a lower side of the steering force transmission shaft are applied. The assist force to be output to the power steering device is made larger than usual so that the load torque applied to the steering force transmission shaft becomes smaller than the allowable load torque when the portion can rotate freely. Steering system. A non-steering traveling state determining means for determining whether or not the steering wheel is not steered in a non-steering traveling state at a predetermined period during traveling
Energization state switching means for switching the energization state to the drive source of the lock mechanism so as to lock the motor when the non-steering traveling state;
The steering system according to claim 1, wherein the steering control device includes a lock confirmation unit that detects a lock abnormality in which the motor is not locked even when the energized state is switched.   A drive source of the lock mechanism includes a solenoid and a plunger that moves linearly by excitation of the solenoid, and the lock confirmation unit is configured to detect the lock abnormality based on a self-inductance of the solenoid. The steering system according to claim 2, wherein   The drive source of the lock mechanism includes a solenoid and a plunger that moves linearly by excitation of the solenoid, and a detection coil is provided on the same axis of the solenoid, and a difference between the detection coil, the solenoid, and the plunger is provided. The steering system according to claim 2, wherein a dynamic transformer is configured, and the lock confirmation unit is configured to detect the lock abnormality based on an induced voltage generated in the detection coil. 2. The steering control device according to claim 1, wherein the motor is servo-locked when the handle is in a neutral position when the locking abnormality occurs while the motor is in a normal state. The steering system in any one of thru | or 4.

Images