JP4604642B2 - Vehicle steering system - Google Patents

Description

  The present invention relates to a vehicle steering apparatus.

  Conventionally, by adding the steering angle of the steering wheel based on the motor operation to the steering angle of the steering wheel based on the steering operation, the ratio of the steering angle (tire angle) of the steering wheel to the steering angle (steering angle) of the steering wheel, that is, There is a steering apparatus including a gear ratio variable system that varies a transmission ratio (gear ratio) (for example, see Patent Document 1).

  By the way, in such a gear ratio variable system, feedback control is normally performed so that the steering angle of a steered wheel based on motor drive, that is, the ACT angle follows the control target value (ACT target angle). However, due to its nature, the torque characteristics of the motor are not required to be as smooth as the electric power steering device (EPS). Therefore, in many cases where a brushless motor is used as a drive source, a Hall element that outputs a pulse signal in accordance with the rotation of the motor is used as a rotation angle sensor, and the rotation angle detected based on the pulse signal is adjusted. The rotation of the motor is controlled by switching the energized phase accordingly, that is, by so-called rectangular wave driving.

In this way, by adopting the rectangular wave drive, a simple and inexpensive configuration such as a Hall element can be used for the rotation angle sensor, and the manufacturing cost can be reduced. Further, each phase (U, V, W) On the other hand, a larger motor torque can be obtained than in the case of so-called sine wave drive in which sine wave energization is performed. Further, as shown in FIG. 8, although there is a problem that torque ripple is generated at the time of switching the energized phase due to the low resolution of the rotation angle sensor, humans have a fast cycle (about 30 times per second or more). ), It is difficult to feel the torque ripple. Therefore, the steering feeling is hardly deteriorated by the torque ripple under normal use conditions. In the figure, the waveform α indicates the rotation angle of the motor, and the waveform β indicates the motor torque. And the part shown to the area | region (gamma) is the torque ripple which arises by switching of an electricity supply phase.
JP 2002-240734 A

  However, when the driver performs an extremely slow steering operation (for example, when the steering speed is 4 deg / sec or less), the motor energization phase switching period becomes long, and the torque ripple generated when the driver performs the switching. There is a problem that it becomes easy to feel. As shown in FIG. 9, the magnitude of the torque ripple is proportional to the magnitude of the energization current to the motor (in the figure, the waveform β1 indicates that the current amount is small, and the waveform β2 indicates that the current amount is large. When the road surface reaction force is strong and the load of the motor is large (when the vehicle is almost stopped, for example, 3 km / hour or less), this tendency becomes more remarkable.

  The present invention has been made to solve the above problems, and an object of the present invention is to provide a vehicle steering apparatus that can ensure a good steering feeling regardless of the steering state.

In order to solve the above-mentioned problem, the invention according to claim 1 adds the second rudder angle of the steered wheel based on motor drive to the first rudder angle of the steered wheel based on the steering angle of the steering wheel. A transmission ratio variable device that varies a transmission ratio between the steering wheel and the steering wheel, a rotation angle sensor for detecting a rotation angle of a brushless motor that is a drive source of the transmission ratio variable device, Control means for controlling the operation of the transmission ratio variable device by supplying three-phase driving power to the brushless motor based on the detected rotation angle, and the rotation angle sensor is configured to rotate the brushless motor. The control means is a vehicle steering device that switches the energized phase of the brushless motor according to the rotation angle detected based on the pulse signal. I, comprising a steering speed detection means for detecting a steering speed of the steering wheel, a vehicle speed detecting means for detecting a vehicle speed, said control means, to avoid the occurrence of torque ripple at the time of energization phase switching of the brushless motor Therefore, when the detected steering speed is lower than the predetermined steering speed in the extremely low speed steering state and the detected vehicle speed is lower than the predetermined vehicle speed in the substantially stopped state, The gist is to stop the brushless motor.

According to a second aspect of the present invention, the steering wheel and the steering wheel are obtained by adding the second steering angle of the steering wheel based on motor drive to the first steering angle of the steering wheel based on the steering angle of the steering wheel. A transmission ratio variable device that varies a transmission ratio between the transmission ratio, a rotation angle sensor for detecting a rotation angle of a brushless motor that is a drive source of the transmission ratio variable device, and the rotation angle sensor based on the detected rotation angle. Control means for controlling the operation of the variable transmission ratio device by supplying three-phase driving power to the brushless motor, and the rotation angle sensor outputs a pulse signal corresponding to the rotation of the brushless motor, The control means is a vehicle steering device that switches a current-carrying phase of the brushless motor in accordance with the rotation angle detected based on the pulse signal. Comprising a steering speed detection means for detecting a steering speed of the Le, and a road surface reaction force detection means for detecting a road surface reaction force, the control means, in order to avoid occurrence of a torque ripple at the time of energization phase switching of the brushless motor The detected steering speed is lower than the predetermined steering speed in the extremely low speed steering state , and the detected road surface reaction force is set in advance corresponding to the vehicle speed in the substantially stopped state. The gist is to stop the brushless motor when the reaction force is larger than the reaction force.

According to a third aspect of the present invention, the steering wheel and the steered wheel are obtained by adding the second rudder angle of the steered wheel based on motor drive to the first steered angle of the steered wheel based on the steered angle of the steering wheel. A transmission ratio variable device that varies a transmission ratio between the transmission ratio, a rotation angle sensor for detecting a rotation angle of a brushless motor that is a drive source of the transmission ratio variable device, and the rotation angle sensor based on the detected rotation angle. Control means for controlling the operation of the variable transmission ratio device by supplying three-phase driving power to the brushless motor, and the rotation angle sensor outputs a pulse signal corresponding to the rotation of the brushless motor, The control means is a vehicle steering device that switches a current-carrying phase of the brushless motor in accordance with the rotation angle detected based on the pulse signal. Comprising a steering speed detection means for detecting a steering speed of the Le, the energizing current amount detecting means for detecting the amount of current energizing the brushless motor, the control means, the torque ripple at the time of energization phase switching of the brushless motor The detected steering speed is lower than a predetermined steering speed in the extremely low speed steering state , and the detected current amount is set in advance corresponding to the vehicle speed in the substantially stopped state. The gist is to stop the brushless motor when the amount of current is larger than the predetermined current amount.

  According to each of the above configurations, using a Hall element or the like as a rotation angle sensor, and switching the energized phase according to the rotation angle detected based on the pulse signal, and controlling the rotation by so-called rectangular wave driving, Regardless of the vehicle state such as the steering speed and the vehicle speed, a good steering feeling can be ensured without causing the driver to feel torque ripple. Further, there is no cost increase such as addition of a new sensor.

  According to a fourth aspect of the present invention, when the detected steering speed becomes equal to or higher than a predetermined steering speed after the brushless motor is stopped, the control means sets the second steering angle to the second steering angle. The gist is to control the variable transmission ratio device so as to gradually change the steering angle to a target control value of the steering angle at a rate corresponding to the steering speed.

  According to the above configuration, even when the deviation between the second rudder angle and its control target value is greatly opened by stopping the brushless motor, the second rudder angle rapidly changes when the brushless motor is restarted. It is possible to ensure a good steering feeling.

  ADVANTAGE OF THE INVENTION According to this invention, the steering apparatus for vehicles which can ensure a favorable steering feeling irrespective of a steering state can be provided.

Hereinafter, an embodiment in which the present invention is embodied in a vehicle steering apparatus (steering apparatus) provided with a gear ratio variable system will be described with reference to the drawings.
FIG. 1 is a schematic configuration diagram of a steering apparatus 1 according to the present embodiment. As shown in the figure, a steering shaft 3 to which a steering wheel (steering) 2 is fixed is connected to a rack 5 via a rack and pinion mechanism 4. It is converted into a reciprocating linear motion of the rack 5 by the and pinion mechanism 4. The steering angle of the steered wheels 6, that is, the tire angle is varied by the reciprocating linear motion of the rack 5, whereby the vehicle traveling direction is changed.

  The steering device 1 according to the present embodiment is a so-called rack type electric power steering device (EPS) that uses a motor 7 arranged coaxially with the rack 5 as a drive source. The assist torque generated by the motor 7 is generated by the rack 5. As a result, the assist force is applied to the steering system.

  Further, the steering device 1 of the present embodiment is a transmission ratio variable device that varies the ratio of the steering angle (tire angle) of the steered wheels 6 to the steering angle (steering angle) of the steering wheel 2, that is, the transmission ratio (gear ratio). A variable gear ratio actuator 8 and an ECU 9 as control means for controlling the operation of the variable gear ratio actuator 8 are provided.

  More specifically, the steering shaft 3 includes a first shaft 10 to which the steering 2 is connected and a second shaft 11 to be connected to the rack and pinion mechanism 4. The gear ratio variable actuator 8 includes the first shaft 10 and the first shaft 10. A differential mechanism 12 for connecting the two shafts 11 and a motor 13 for driving the differential mechanism 12 are provided. The gear ratio variable actuator 8 adds the rotation driven by the motor to the rotation of the first shaft 10 accompanying the steering operation and transmits the rotation to the second shaft 11, whereby the steering shaft input to the rack and pinion mechanism 4. The rotation of 3 is increased (or decelerated).

  That is, as shown in FIGS. 2 and 3, the gear ratio variable actuator 8 has the steering angle (ACT angle θta) of the steered wheels based on the motor drive to the steered angle (steer steered angle θts) of the steered wheels 6 based on the steering operation. ) Is added, the gear ratio of the steered wheels 6 with respect to the steering angle θs is varied.

  In this case, “addition” is defined to include not only addition but also subtraction, and so on. In addition, when the “gear ratio of the steered wheels 6 with respect to the steering angle θs” is expressed as an overall gear ratio (steering angle θs / tire angle θt), an overall increase is made by adding an ACT angle θta in the same direction as the steering angle θts. The gear ratio becomes smaller (large tire angle θt, see FIG. 2). Then, the overall gear ratio is increased by adding the ACT angle θta in the reverse direction (small tire angle θt, see FIG. 3).

  Moreover, the motor 13 of this embodiment is a brushless motor, and rotates when three-phase (U, V, W) driving power is supplied from the ECU 9. Then, the ECU 9 controls the operation of the gear ratio variable actuator 8 by controlling the rotation of the motor 13, that is, the ACT angle θta by supplying the driving power (gear ratio variable control).

Next, the electrical configuration and control mode of the steering apparatus according to the present embodiment will be described.
The ECU 9 includes a microcomputer 14 that outputs a motor control signal Sc, and a drive circuit 15 that supplies three-phase drive power to the motor 13 based on the motor control signal Sc. In the present embodiment, the ECU 9 includes a steering sensor 17 as steering speed detection means for detecting the steering angle θs (steering speed ωs) of the steering 2 and a rotation angle sensor 18 for detecting the rotation angle θ of the motor 13. A vehicle speed sensor 19 is connected as vehicle speed detecting means for detecting the vehicle speed. The microcomputer 14 outputs a motor control signal Sc based on various state quantities detected by these sensors.

  More specifically, in the present embodiment, a Hall element that outputs a pulse signal Sp according to the rotation of the motor 13 is employed as the rotation angle sensor 18, and the microcomputer 14 is based on the pulse signal Sp output from the Hall element. The rotation angle θ of the motor 13 is detected. Then, the microcomputer 14 detects the ACT angle θta based on the rotation angle θ. Further, the microcomputer 14 calculates an ACT target angle that is a control target value of the ACT angle θta based on the vehicle speed V, the steering angle θs, and the steering speed ωs. Then, the microcomputer 14 outputs a motor control signal Sc so that the ACT angle θta follows the ACT target angle.

  Specifically, in the present embodiment, rectangular wave driving is adopted in which two of the U, V, and W phases are energized phases (phases to be energized). A motor control signal Sc is output so that the energized phases are sequentially switched according to the rotation angle θ detected based on the output pulse signal Sp. The drive circuit 15 supplies three-phase drive power to the motor 13 based on the motor control signal Sc, whereby the rotation of the motor 13, that is, the ACT angle θta is controlled.

(Gear ratio variable control at extremely low speed steering)
Next, the gear ratio variable control at the time of extremely low speed steering in the steering device of the present embodiment will be described.

  As described above, when the rotation of the motor is controlled by the rectangular wave drive, there is a problem that torque ripple is generated when the energized phase is switched due to the low resolution of the rotation angle sensor 18. This problem becomes prominent when the driver's steering operation is extremely slow, that is, when the driver is surfaced during extremely low speed steering and the vehicle is almost stationary, such as when the road reaction force is strong and the motor load is large. .

In order to avoid such a problem, in this embodiment, as in the example shown in FIG. 4, the ECU 9 detects that the detected steering speed ωs is lower than the predetermined steering speed ω0 and the detected vehicle speed V Is lower than a predetermined vehicle speed V0 , the ACT angle θta is fixed. That is, the motor 13 that is the drive source of the variable gear ratio actuator 8 is stopped in a region where the problem of torque ripple generated when the energized phase of the motor 13 is switched becomes significant.

Specifically, as shown in the flowchart of FIG. 5, when the microcomputer 14 of the ECU 9 detects the vehicle speed V and the steering speed ωs (step 101), the steering speed ωs is lower than the predetermined steering speed ω0, and It is determined whether or not the detected vehicle speed V is lower than a predetermined vehicle speed V0 (step 102). In the present embodiment, the predetermined steering speed ω0 is obtained in advance by experiments, simulations, or the like “a steering speed at which torque ripple is generated at a period (approximately 30 times per second) that is easily perceived by the driver (for example, 4 deg / hr ) "is set, and the predetermined vehicle speed V0 is set to a vehicle speed (for example, 3 Km / sec) at which the vehicle is substantially stopped. When the steering speed ωs is lower than the predetermined steering speed ω0 and the vehicle speed V is lower than the predetermined vehicle speed V0 (step 102: YES), the ACT angle θta is fixed, that is, the gear ratio is variable. A motor control signal Sc is output to stop the motor 13 that is the drive source of the actuator 8 (step 103).

  If it is determined in step 102 that the steering speed ωs is equal to or higher than the predetermined steering speed ω0 or the vehicle speed V is equal to or higher than the predetermined vehicle speed V0 (step 102: NO), the microcomputer 14 sets the ACT angle θta. The normal motor control signal Sc is output without being fixed.

Further, the ECU 9 determines that the detected steering speed ωs after the motor 13 is stopped is a predetermined steering speed ω.
When the vehicle speed V is 0 or higher, or the detected vehicle speed V is equal to or higher than the predetermined vehicle speed V 0 , the gear ratio variable actuator 8 is operated again. In the present embodiment, when the detected steering speed ωs is equal to or higher than the predetermined steering speed ω0 at the time of reactivation after the motor 13 is stopped, the ACT angle θta is a ratio corresponding to the steering speed ωs. To gradually change to the ACT target angle θta * (offset processing). Thus, even when the deviation between the ACT target angle θta * and the ACT angle θta is greatly opened due to the stop of the motor 13, a rapid change in the ACT angle θta is prevented to ensure a good steering feeling. Is possible.

As described above, according to the present embodiment, the following features can be obtained.
(1) When the microcomputer 14 detects the vehicle speed V and the steering speed ωs (step 101), the steering speed ωs is lower than the predetermined steering speed ω0, and the detected vehicle speed V is lower than the predetermined vehicle speed V0. It is determined whether or not (step 102). When the steering speed ωs is lower than the predetermined steering speed ω0 and the vehicle speed V is lower than the predetermined vehicle speed V0 (step 102: YES), the ACT angle θta is fixed, that is, the gear ratio is variable. A motor control signal Sc is output to stop the motor 13 that is the drive source of the actuator 8 (step 103). That is, in a state in which the problem of torque ripple that occurs when the energized phase of the motor 13 is switched becomes prominent, the motor 13 that is the drive source of the gear ratio variable actuator 8 is stopped to prevent generation of torque ripple.

  With such a configuration, a steering speed ωs can be used even in a case where a Hall element or the like is used as a rotation angle sensor and the energized phase is switched according to the rotation angle detected based on the pulse signal, that is, a rectangular wave drive is adopted. Regardless of the vehicle condition such as the vehicle speed V or the vehicle speed V, it is possible to ensure a good steering feeling without causing the driver to feel torque ripple. Further, there is no cost increase such as addition of a new sensor.

  (2) When the detected steering speed ωs becomes equal to or higher than the predetermined steering speed ω0 when the motor 13 is restarted after the motor 13 is stopped, the ECU 9 sets the ACT angle θta to the ACT at a rate corresponding to the steering speed ωs. Gradually change to the target angle θta *.

  With such a configuration, even when the deviation between the ACT target angle θta * and the ACT angle θta is greatly opened due to the stop of the motor 13, a rapid change in the ACT angle θta is prevented and a good steering fee is obtained. A ring can be secured.

In addition, you may change each said embodiment as follows.
In the present embodiment, the embodiment is embodied in the steering device 1 that is an electric power steering device (EPS). However, the hydraulic pump, the power cylinder that applies assist force to the steering system based on the hydraulic pressure, and the power cylinder are supplied. The present invention may be embodied in a variable flow rate hydraulic power steering apparatus including a flow rate control valve capable of changing the flow rate of the pressure oil.

In this embodiment, the ECU 9 fixes the ACT angle θta when the steering speed ωs is lower than the predetermined steering speed ω0 and the vehicle speed V is lower than the predetermined vehicle speed V0 , that is, the gear ratio is variable. The motor 13 that is the drive source of the actuator 8 is stopped. However, the present invention is not limited to this, and stop determination of the motor 13 is performed using parameters other than the vehicle speed V as long as the region in which the problem of torque ripple generated when the energized phase of the motor 13 is switched can be identified. It is good.

  Specifically, for example, when the road surface reaction force detection means includes a torque sensor that can detect the road surface reaction force Fr, the vehicle speed V and the road surface reaction force Fr are detected as shown in the flowchart of FIG. 6 (step 201). Subsequently, it is determined whether or not the steering speed ωs is lower than the predetermined steering speed ω0 and the detected road surface reaction force Fr is greater than the predetermined road surface reaction force Fr0 (step 202). When the steering speed ωs is lower than the predetermined steering speed ω0 and the road surface reaction force Fr is larger than the predetermined road surface reaction force Fr0 (step 202: YES), the ACT angle θta is fixed, that is, the gear The motor 13 that is the drive source of the variable ratio actuator 8 may be stopped (step 203).

  Similarly, as shown in the flowchart of FIG. 7, the vehicle speed V and the current amount I supplied to the motor 13 are detected (step 301), and then the steering speed ωs is lower than the predetermined steering speed ω0, and It is determined whether or not the detected current amount I is larger than a predetermined current amount I0 (step 302). When the steering speed ωs is lower than the predetermined steering speed ω0 and the current amount I is larger than the predetermined current amount I0 (step 302: YES), the ACT angle θta is fixed, that is, the gear ratio is variable. The motor 13 that is a drive source of the actuator 8 may be stopped (step 303).

  In this case, the predetermined road surface reaction force Fr0 may be set to a value when the vehicle is substantially stopped, for example, and the predetermined current amount I0 corresponds to the load applied to the motor 13 in that case. Set it to a value. Further, as an energized current amount detecting means for detecting the current amount I, a current sensor may be provided on the power supply line to the motor 13.

  In the present embodiment, the Hall element is used as the rotation angle sensor 18, but the Hall element is used as a rotation angle sensor that outputs a pulse signal according to the rotation of the motor using a device other than the Hall element. Also good.

Next, technical ideas other than the claims that can be understood from the above embodiments will be described.
(A) The vehicle steering apparatus according to any one of claims 1 to 3, wherein a hall element is used as the rotation angle sensor.

The schematic block diagram of the steering device of this embodiment. Explanatory drawing of gear ratio variable control. Explanatory drawing of gear ratio variable control. Explanatory drawing of the gear ratio variable control at the time of very low speed steering. The flowchart which shows the process sequence of the gear ratio variable control at the time of very low speed steering. The flowchart which shows the process sequence of the gear ratio variable control at the time of very low speed steering of another example. The flowchart which shows the process sequence of the gear ratio variable control at the time of very low speed steering of another example. The wave form diagram which shows the torque ripple which generate | occur | produces at the time of energized phase switching. The wave form diagram which shows the relationship between the electric current amount and the magnitude | size of a torque ripple.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 ... Steering device, 2 ... Steering wheel (steering), 6 ... Steering wheel, 8 ... Variable gear ratio actuator, 9 ... ECU, 13 ... Motor, 14 ... Microcomputer, 15 ... Drive circuit, 17 ... Steering sensor, 18 ... Rotation Angle sensor, 19 ... Vehicle speed sensor, Sp ... Pulse signal, θ ... Rotation angle, ωs, ω0 ... Steering speed, V, V0 ... Vehicle speed, θta ... ACT angle, θta * ... ACT target angle, θts ... Steer turning angle, θt: tire angle, Fr, Fr0: road reaction force, I, I0: current amount.

Claims (4)

The transmission ratio between the steering wheel and the steering wheel is varied by adding the second steering angle of the steering wheel based on the motor drive to the first steering angle of the steering wheel based on the steering angle of the steering wheel. A transmission ratio variable device, a rotation angle sensor for detecting a rotation angle of a brushless motor that is a drive source of the transmission ratio variable device, and three-phase drive power to the brushless motor based on the detected rotation angle The rotation angle sensor outputs a pulse signal corresponding to the rotation of the brushless motor, and the control means is based on the pulse signal. A vehicle steering apparatus that switches an energized phase of the brushless motor according to the detected rotation angle,
Steering speed detecting means for detecting the steering speed of the steering wheel;
Vehicle speed detecting means for detecting the vehicle speed,
The control means is configured such that the detected steering speed is lower than a predetermined steering speed in an extremely low speed steering state and the detected speed is avoided in order to avoid occurrence of torque ripple at the time of switching the energized phase of the brushless motor. When the vehicle speed is lower than a predetermined vehicle speed that is substantially stopped , the brushless motor is stopped. The transmission ratio between the steering wheel and the steering wheel is varied by adding the second steering angle of the steering wheel based on the motor drive to the first steering angle of the steering wheel based on the steering angle of the steering wheel. A transmission ratio variable device, a rotation angle sensor for detecting a rotation angle of a brushless motor that is a drive source of the transmission ratio variable device, and three-phase drive power to the brushless motor based on the detected rotation angle The rotation angle sensor outputs a pulse signal corresponding to the rotation of the brushless motor, and the control means is based on the pulse signal. A vehicle steering apparatus that switches an energized phase of the brushless motor according to the detected rotation angle,
Steering speed detecting means for detecting the steering speed of the steering wheel;
Road surface reaction force detecting means for detecting the road surface reaction force,
The control means is configured such that the detected steering speed is lower than a predetermined steering speed in an extremely low speed steering state and the detected speed is avoided in order to avoid occurrence of torque ripple at the time of switching the energized phase of the brushless motor. A vehicular steering apparatus, wherein the brushless motor is stopped when the road surface reaction force is larger than a predetermined road surface reaction force set in advance corresponding to the vehicle speed in a substantially stopped state . The transmission ratio between the steering wheel and the steering wheel is varied by adding the second steering angle of the steering wheel based on the motor drive to the first steering angle of the steering wheel based on the steering angle of the steering wheel. A transmission ratio variable device, a rotation angle sensor for detecting a rotation angle of a brushless motor that is a drive source of the transmission ratio variable device, and three-phase drive power to the brushless motor based on the detected rotation angle The rotation angle sensor outputs a pulse signal corresponding to the rotation of the brushless motor, and the control means is based on the pulse signal. A vehicle steering apparatus that switches an energized phase of the brushless motor according to the detected rotation angle,
Steering speed detecting means for detecting the steering speed of the steering wheel;
An energizing current amount detecting means for detecting an amount of current energized to the brushless motor,
The control means is configured such that the detected steering speed is lower than a predetermined steering speed in an extremely low speed steering state and the detected speed is avoided in order to avoid occurrence of torque ripple at the time of switching the energized phase of the brushless motor. A vehicle steering apparatus, wherein the brushless motor is stopped when the current amount is larger than a predetermined current amount set in advance corresponding to the vehicle speed in a substantially stopped state . In the vehicle steering device according to any one of claims 1 to 3,
When the detected steering speed is equal to or higher than a predetermined steering speed after the brushless motor is stopped, the control means sets the second steering angle to the control target value of the second steering angle. Controlling the transmission ratio variable device to gradually change at a rate according to the steering speed;
A vehicle steering apparatus characterized by the above.

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