JP2009047542A - Torque detection device and steering unit - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a torque detection device capable of detecting a torque without using an angle of torsion. <P>SOLUTION: A motor 21 for torque detection for imparting an additional torque to an upper side part 2a of a steering shaft 2 is provided. An angle sensor 24 detects a rotation angle θa of the upper side part 2a, and an angle sensor 25 detects a rotation angle θb of a pinion 8. A motor control part 23 for torque detection performs driving control of the motor 21 for torque detection so that a difference between the rotation angles θa, θb becomes zero. A current sensor 26 detects a current Id flowing in the motor 21 for torque detection. A torque calculation part 27 determines a steering torque T working on the steering shaft 2 based on the detected current Id. The determined steering torque T is used when determining a steering auxiliary force generated from a steering auxiliary motor 11. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a torque detection device that detects torque acting on an input shaft, and a steering device that uses the torque detection device.

  In recent vehicles, a power steering device using a hydraulic system or an electric motor is mounted. In order to determine the steering assist force generated by the power steering device, it is necessary to detect the steering torque applied by the driver to the steering wheel (steering wheel) and the steering shaft.

  Conventionally, as a method for detecting the torque acting on the steering shaft, a method of providing a torsion bar between the steering wheel and the rack and pinion mechanism and detecting a torsion angle of the torsion bar caused by the torque has been widely used.

In connection with the present invention, Patent Document 1 discloses that a torque generating device is provided on one output shaft of a differential device having an input shaft and a pair of output shafts so that the rotational speeds of the output shafts are equal. It describes that the torque transmitted from the input shaft to the other output shaft is obtained based on the input current when the generator is controlled.
Japanese Patent Laid-Open No. 7-92041

  However, the method of detecting the torque acting on the steering shaft using the torsion bar has a problem that the torsion bar has a low torsional rigidity, so that the steering system is less rigid and the steering feeling is impaired. In this method, a torsion angle is intentionally generated in order to detect torque, but the presence of the torsion angle causes a steering feeling to be impaired.

  Therefore, an object of the present invention is to provide a torque detection device that detects torque without using a twist angle.

A first invention is a torque detection device for detecting torque acting on an input shaft,
A motor for applying additional torque to the input shaft;
Motor control means for driving and controlling the motor so that the difference between the rotation angle of the input shaft and the amount of movement of the output side member converted to be comparable to the rotation angle becomes zero;
Motor current detection means for detecting current flowing in the motor;
Torque calculating means for obtaining a torque acting on the input shaft based on the current detected by the motor current detecting means.

According to a second invention, in the first invention,
A sensor for detecting a difference between the rotation angle of the input shaft and the rotation angle of the output shaft is further provided.

According to a third invention, in the first invention,
A first sensor for detecting a rotation angle of the input shaft;
And a second sensor for detecting a movement amount of the output side member.

According to a fourth invention, in the third invention,
The second sensor detects a rotation angle of the output side member.

According to a fifth invention, in the third invention,
The second sensor detects a movement amount of the output side member.

  A sixth aspect of the present invention is a steering apparatus that detects torque acting on a steering shaft using the torque detection apparatus according to any one of the first to fifth aspects of the invention.

  According to the first aspect of the invention, the motor is driven and controlled so that the rotation angle of the input shaft corresponds to the amount of movement of the output side member, and the torque is obtained based on the motor current at that time, resulting in the twist angle. Torque can be detected without generating. Also, remove the member provided to generate the torsion angle or increase the torsional rigidity of the member so that the output side member moves with good followability when the input shaft rotates. Can do.

  According to the second aspect of the invention, the difference in rotation angle between the input shaft and the output shaft is detected using a single sensor that detects the difference in rotation angle, and the motor is controlled so that the detected difference becomes zero. As a result, the torque can be detected without generating a twist angle by obtaining the torque based on the motor current.

  According to the third aspect of the invention, the rotation angle of the input shaft and the amount of movement of the output side member are detected using two sensors, and the motor is set so that the rotation angle of the input shaft and the amount of movement of the output side member correspond to each other As a result, the torque can be detected without generating a twist angle.

  According to the fourth aspect of the invention, the rotation angle of the input shaft and the output side member is detected using two angle sensors, and the motor is driven so that the rotation angle of the input shaft corresponds to the rotation angle of the output side member. As a result, the torque can be detected without generating a twist angle by obtaining the torque based on the motor current at the time of control.

  According to the fifth aspect, the movement amount of the input shaft and the output side member is detected using the angle sensor and the displacement sensor, and the motor is driven so that the rotation angle of the input shaft corresponds to the movement amount of the output side member. As a result, the torque can be detected without generating a twist angle by obtaining the torque based on the motor current at the time of control.

  According to the sixth aspect, since the torque acting on the steering shaft can be detected without generating a twist angle as a result, the torsion bar is removed or the torsional rigidity of the torsion bar is increased. The rigidity of the steering system can be improved and the steering feeling can be improved.

  FIG. 1 is a diagram illustrating a configuration of a vehicle steering apparatus including a torque detection device according to an embodiment of the present invention. As shown in FIG. 1, the steering shaft 2 is divided into an upper part 2a and a lower part 2b, and a torsion bar 3 is provided between them. A steering wheel 1 is fixed to the upper end of the upper portion 2a, and the lower end of the lower portion 2b is connected to the rack shaft 5 of the rack and pinion mechanism 4. Both ends of the rack shaft 5 are coupled to the tire 7 via a coupling member 6 composed of a tie rod and a knuckle arm. When the driver rotates the steering wheel 1, the steering shaft 2 rotates, and the rack shaft 5 reciprocates accordingly. As the rack shaft 5 reciprocates, the direction of the tire 7 changes.

  The steering device is provided with an electric power steering device including a steering assist motor 11. The steering assist motor 11 generates a steering assist force in accordance with control from the steering assist motor control unit 13. The steering assist force generated by the steering assist motor 11 is applied to the lower portion 2 b of the steering shaft 2 via the speed reducer 12.

  In order for the steering assist motor 11 to generate a suitable steering assist force, it is necessary to detect the vehicle speed V of the vehicle and the steering torque T applied to the steering wheel 1 and the steering shaft 2 by the driver. For this reason, the steering device is provided with a vehicle speed sensor 14 for detecting the vehicle speed V. The steering torque T is detected by a torque detection device including a torque detection motor 21, a speed reducer 22, a torque detection motor control unit 23, angle sensors 24 and 25, a current sensor 26, and a torque calculation unit 27.

  The torque detection motor 21 generates additional torque in order to detect the steering torque in accordance with control from the torque detection motor control unit 23. Torque generated by the torque detection motor 21 is applied to the upper portion 2 a of the steering shaft 2 via the speed reducer 22.

  The angle sensor 24 detects the rotation angle θa of the upper portion 2 a of the steering shaft 2. Since the steering wheel 1 and the upper part 2a rotate as a unit, it can be said that the angle sensor 24 detects the rotation angle of the steering wheel 1. The angle sensor 25 detects the rotation angle θb of the pinion 8 included in the rack and pinion mechanism 4. Since the pinion 8 and the lower side portion 2b rotate together, it can be said that the angle sensor 25 detects the rotation angle of the lower side portion 2b of the steering shaft 2.

  The rotation angle θa detected by the angle sensor 24 and the rotation angle θb detected by the angle sensor 25 are input to the torque detection motor control unit 23. The torque detection motor control unit 23 obtains the difference between the rotation angle θa and the rotation angle θb, and drives and controls the torque detection motor 21 so that the obtained difference becomes zero (angle difference zero control).

  For example, consider a case where the driver rotates the steering wheel 1 clockwise as viewed from the driver. In this case, torque in this direction acts on the upper part 2a and the lower part 2b of the steering shaft 2, and both the upper part 2a and the lower part 2b rotate in this direction. However, since the torsion bar 3 having torsional elasticity is provided between the upper part 2a and the lower part 2b, the lower part 2b rotates later than the upper part 2a, and the rotation angle θb is the rotation angle θa. Smaller than. The torque detection motor controller 23 applies torque to the upper portion 2a of the steering shaft 2 so that a counterclockwise torque is applied to the upper portion 2a of the steering shaft 2 so that the difference between the rotation angle θa and the rotation angle θb becomes zero. The drive of the detection motor 21 is controlled.

  The current sensor 26 detects the current Id flowing through the torque detection motor 21 at this time (that is, when the torque detection motor 21 is driven and controlled so that the difference between the rotation angle θa and the rotation angle θb becomes zero). The current Id changes according to the steering torque acting on the steering shaft 2, and increases as the steering torque increases.

  The torque calculation unit 27 obtains a steering torque T acting on the upper portion 2a of the steering shaft 2 based on the current Id detected by the current sensor 26. There is a predetermined relationship between the steering torque T and the current Id, and this relationship can be obtained at the time of design or through experiments. Therefore, the current Id can be converted into the steering torque T using the relationship. The torque calculator 27 may obtain the steering torque T by calculation, or may obtain it by drawing a table.

  The steering torque T detected by the torque detector is supplied to the steering assist motor control unit 13 together with the vehicle speed V detected by the vehicle speed sensor 14 and is used when determining the steering assist force generated by the steering assist motor 11. Is done.

  FIG. 2 is a diagram showing a dynamic model of the steering apparatus shown in FIG. In FIG. 2, the sprung dynamic model 31 and the unsprung dynamic model 34 represent the characteristics of the portion above and below the torsion bar 3 of the steering device, respectively. The tire / road surface 35 represents the characteristics of the tire 7 and the road surface. The steering assist motor control 33 represents processing performed by the steering assist motor control unit 13 and the torque calculation unit 27, and the position control loop 32 represents processing performed by the torque detection motor control unit 23.

A difference Δθ between the steering angle θa and the actual steering angle θb is input to the position control loop 32. In the position control loop 32, an additional torque _TTS generated by the torque detection motor 21 to detect the steering torque and a current Id flowing through the torque detection motor 21 at that time are determined based on the angle difference Δθ. Is done. In the tire / road surface 35, the torque that the steering device receives from the ground is determined based on the actual steering angle θb.

In the steering assist motor control 33, the steering torque based on the current Id flowing in the torque detecting motor 21 is determined, the steering assist force T _A to be generated by the steering assist motor 11 based on the steering torque obtained and the vehicle speed V is determined The In the sprung dynamic model 31, the steering angle θa is determined based on the sum of the steering torque T applied to the steering shaft 2 by the driver and the torque T _TS determined by the position control loop 32. In the unsprung dynamic model 34, the actual steering angle θb is determined based on the sum of the steering torque T, the steering assist force T _A determined by the steering assist motor control 33, and the torque received by the steering device from the ground.

  FIG. 3 is a diagram showing details of the position control loop 32. As shown in FIG. 3, in the position control loop 32, triple feedback control is performed with respect to position, velocity, and current. First, the target speed is determined by performing PI control related to the position based on the difference between the target angle and the actual angle. Next, the target current is determined by performing PI control on the speed based on the difference between the target speed and the actual speed. Furthermore, the current to be supplied to the torque detection motor 21 is determined by performing PI control relating to the current based on the difference between the target current and the actual current. The current actually flowing to the torque detection motor 21 is detected as an actual current, the actual speed is calculated by integrating the actual current with time, and the actual angle is calculated by integrating the actual speed with time.

  As described above, according to the torque detection device shown in FIG. 1, the torque detection motor 21 is driven so that the rotation angle θa of the upper portion 2 a of the steering shaft 2 corresponds to the rotation angle θb of the pinion 8. As a result, the steering torque can be detected without generating a torsion angle by obtaining the steering torque based on the current flowing in the torque detection motor 21 at that time. Further, by increasing the torsional rigidity of the torsion bar 3 provided to generate the torsion angle, the output side member such as the pinion 8 can move with good followability when the steering shaft 2 rotates. Even if the torsion bar 3 is removed, the same effect can be obtained.

  Further, according to the steering device shown in FIG. 1, the torque acting on the steering shaft 2 can be detected without using the torsion angle, so that the torsion bar 3 is removed or the torsional rigidity of the torsion bar 3 is increased. As a result, it is possible to improve the steering system and improve the steering system.

  The torque detection device of the present invention replaces the angle sensor 25 that detects the rotation angle θb of the pinion 8 with a displacement sensor that detects the amount of movement of the rack shaft 5, an angle sensor that detects the rotation angle of the tire 7, An angle sensor that detects the rotation angle of the lower side portion 2b of the steering shaft 2 may be provided. Both the rotation angle and the amount of movement detected by these sensors can be converted to be comparable with the rotation angle θa of the upper portion 2a of the steering shaft 2. In addition, the torque detection device of the present invention may include one angle sensor that detects a difference in rotation angle between the upper side portion 2a and the lower side portion 2b of the steering shaft 2.

  In the torque detection device of the present invention, the torque detection motor control unit 23 determines that the difference between the rotation angle θa of the upper portion 2a of the steering shaft 2 and the amount of movement of the output side member converted to be comparable to the rotation angle. What is necessary is just to drive-control the motor 21 for torque detection so that it may become zero. For this reason, the torque detection device of the present invention may include a sensor for detecting the rotation angle of the upper portion 2a and a sensor for detecting the movement amount (rotation angle or movement amount) of the output side member. You may provide the sensor which detects the difference of the rotation angle of the part 2a and the lower part 2b. When two sensors are provided, tire angle information necessary for advanced vehicle control can be acquired.

  Moreover, although the torque detection apparatus shown in FIG. 1 is provided with the torsion bar 3, the torque detection apparatus of the present invention may not include the torsion bar 3. By removing the torsion bar, the steering system can be further improved in rigidity and the steering feeling can be further improved. In the torque detection device shown in FIG. 1, the torque detection motor 21 is connected to the upper portion 2a of the steering shaft 2 via the speed reducer 22, but is directly connected to the upper portion 2a. Also good.

  The torque detection device of the present invention can also be applied to a steer-by-wire system in which the steering wheel 1 and the steering wheel are mechanically separated (see FIG. 4). The steering apparatus shown in FIG. 4 includes a steering actuator 9 and a steering actuator control unit 15 instead of the steering assist motor 11 and the steering assist motor control unit 13. The displacement sensor 28 detects the amount of movement of the steering actuator 9. Also in the steering apparatus shown in FIG. 4, the steering torque T can be detected without using the torsion angle, similarly to the steering apparatus shown in FIG.

It is a figure which shows the structure of the steering apparatus of the vehicle provided with the torque detection apparatus which concerns on embodiment of this invention. It is a figure which shows the dynamic model of the steering apparatus shown in FIG. It is a figure which shows the detail of the position control loop shown in FIG. It is a figure which shows the other structure of the steering apparatus of the vehicle provided with the torque detection apparatus which concerns on embodiment of this invention.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 ... Steering wheel, 2 ... Steering shaft, 3 ... Torsion bar, 4 ... Rack pinion mechanism, 5 ... Rack shaft, 6 ... Connecting member, 7 ... Tire, 8 ... Pinion, 9 ... Steering actuator, 11 ... Steering assist motor , 12, 22 ... reducer, 13 ... steering assist motor control unit, 14 ... vehicle speed sensor, 15 ... steering actuator control unit, 21 ... torque detection motor, 23 ... torque detection motor control unit, 24, 25 ... angle Sensor 26 ... Current sensor 27 ... Torque calculator 28 ... Displacement sensor

Claims (6)

A torque detection device for detecting torque acting on an input shaft,
A motor for applying additional torque to the input shaft;
Motor control means for driving and controlling the motor so that the difference between the rotation angle of the input shaft and the amount of movement of the output side member converted to be comparable to the rotation angle becomes zero;
Motor current detecting means for detecting current flowing in the motor;
A torque detection device comprising: a torque calculation means for obtaining a torque acting on the input shaft based on the current detected by the motor current detection means.   The torque detection device according to claim 1, further comprising a sensor that detects a difference between a rotation angle of the input shaft and a rotation angle of the output shaft. A first sensor for detecting a rotation angle of the input shaft;
The torque detection device according to claim 1, further comprising a second sensor that detects a movement amount of the output side member.   The torque detection device according to claim 3, wherein the second sensor detects a rotation angle of the output side member.   The torque detection apparatus according to claim 3, wherein the second sensor detects a movement amount of the output side member.   A steering device that detects torque acting on a steering shaft using the torque detection device according to any one of claims 1 to 5.

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