JP2013018354A - Steering unit with variable steering angle ratio - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a steering unit with a variable steering angle ratio which provides preferable steering feeling with excellent responsiveness and rigidity feeling.SOLUTION: A steering angle ratio variable mechanism 15 connects an input shaft which is connected to a steering member via a torsion bar, to an output shaft which is connected to a steering mechanism. A steering angle ratio is varied by adding a second steering angle θtm which is based on the drive of a VGR (Variable Gear-Ratio Steering) motor 21 to a steering angle which is base on the operation of the steering member. A control target value δtm* is calculated by a VGR control part 16, by superimposing a compensation component θtmh* which is calculated based on a torsion angle δof the torsion bar detected by a torsion angle sensor, to a base component θtmk* calculated based on a steering angle θs or a vehicle speed V.

Description

  The present invention relates to a steering angle ratio variable steering apparatus.

In Patent Document 1, a steering angle ratio variable mechanism that varies a ratio of a steering angle of a steered wheel to a steering angle of a steering member (steering wheel) (steering angle ratio), and an electric motor that adds assist torque to the steered wheel. Has been proposed.
In a steering apparatus including a steering assist mechanism including this type of steering apparatus, a part of the steering transmission shaft is divided into two parts, and the divided shafts are connected by a torsion bar so as to be relatively rotatable. The steering torque is detected based on the torsion angle of the torsion bar, and the assist force by the electric motor is controlled based on the detected steering torque.

JP 2006-175981 A

However, when the steering member is steered, a phase delay occurs in the steered wheels with respect to the phase of the steering member by an amount corresponding to the twist of the torsion bar. For this reason, the driver may feel that the responsiveness to the steering operation is not sufficient, or the steering rigidity may be low, and a good steering feeling may not be obtained.
If the torsional rigidity of the torsion bar is increased in consideration of the steering feeling, it is necessary to detect a small torsion angle of the torsion bar for torque detection. However, in that case, the detection accuracy of torque detection is deteriorated due to the SN ratio, and as a result, the assist performance is affected, so that the steering feeling may be deteriorated.

  SUMMARY OF THE INVENTION An object of the present invention is to provide a steering angle ratio variable steering apparatus that can obtain a good steering feeling with good responsiveness and rigidity.

In order to achieve the object, the invention according to claim 1 is connected to an input shaft (3b) connected to a rotating steering member (2) via a torsion bar (17), and a steering mechanism (A). The output shaft (3c), the input shaft and the output shaft are connected, and a steering angle ratio variable motor (21) is included. The steering angle is set to the first steering angle (θts) based on the operation of the steering member. By adding a second steering angle (θtm) based on the drive of the variable ratio motor, a steering angle ratio (R) which is a ratio between the steering angle (θs) of the steering member and the steering angle (θt) of the steered wheels A variable steering angle ratio mechanism, a torsion angle sensor (18) for detecting a torsion angle (δ) of the torsion bar, and a control device (16) for controlling the operation of the variable steering angle ratio mechanism. , the control device, the basic component based on the running state of the vehicle (δtmk ^*), the helix angle sensor By superimposing a more detected based on the twist angle compensation component (δtmh ^*), providing the control target value of the second steering angle steering ratio calculating a (? Tm ^*) variable steering device (1).

In addition, although the alphanumeric character in a parenthesis represents the corresponding component etc. in embodiment mentioned later, this does not mean that this invention should be limited to those embodiment as a matter of course. The same applies hereinafter.
The control device may set the compensation component equal to the torsion angle detected by the torsion angle sensor.

  According to the first aspect of the present invention, by executing compensation control based on the twist angle detected by the twist angle sensor, the control target value (target angle) of the second steering angle based on the drive of the steering angle ratio variable motor is determined. The phase can be advanced. As a result, it is possible to suppress a delay in the phase of the output shaft (that is, the phase of the steered wheels) due to the twist of the torsion bar. Therefore, it is possible to give the driver a good steering feeling with good responsiveness and rigidity.

  According to the second aspect of the present invention, the control target value of the second steering angle is calculated by making the compensation component superimposed on the basic component equal to the detected torsion angle of the torsion bar. Therefore, the effect of eliminating the phase delay of the steered wheels due to the twist of the torsion bar can be enhanced. As a result, a better steering feeling can be given to the driver.

It is a mimetic diagram showing a schematic structure of a steering angle ratio variable steering device of one embodiment of the present invention. It is action | operation explanatory drawing of the steering angle ratio variable mechanism of the steering angle ratio variable apparatus of FIG. 1, and has shown the case where a 1st steering angle and a 2nd steering angle are the same direction. It is an operation explanatory view of a rudder angle ratio variable mechanism of Drawing 1, and shows the case where the 2nd rudder angle is a reverse direction to the 1st rudder angle. FIG. 2 is a control block diagram of the steering angle ratio variable steering device of FIG. 1.

  FIG. 1 is a schematic configuration diagram of an electric power steering apparatus according to an embodiment of the present invention. Referring to FIG. 1, a steering angle ratio variable steering apparatus 1 includes a steering shaft 3 connected to a steering member 2 such as a steering wheel, and an intermediate shaft 5 connected to the steering shaft 3 via a universal joint 4. As a steered shaft that extends in the left-right direction of the automobile, has a pinion shaft 7 connected to the intermediate shaft 5 via a universal joint 6 and a rack 8a that meshes with a pinion 8a provided near the end of the pinion shaft 7. Rack shaft 8. The pinion shaft 7 and the rack shaft 8 constitute a steering mechanism A composed of a rack and pinion mechanism.

The rack shaft 8 is supported by a housing (not shown) fixed to the vehicle body so as to be capable of linear reciprocation. Both ends of the rack shaft 8 protrude to both sides of the housing, and tie rods 9 are coupled to the ends. Each tie rod 9 is connected to a corresponding steered wheel 10 via a corresponding knuckle arm (not shown).
When the steering member 2 is operated and the steering shaft 3 is rotated, this rotation is converted into a linear motion of the rack shaft 8 along the left-right direction of the automobile by the pinion 7a and the rack 8a. Thereby, the vehicle traveling direction is changed by changing the rudder angle of the steered wheels 10, that is, the steered angle.

The steering angle ratio variable steering apparatus 1 includes, for example, a so-called column assist type electric motor that includes a steering assist mechanism 11 that applies a steering assist force to the steering system and an EPS control unit 12 that controls the operation of the steering assist mechanism 11. It is configured as a power steering device.
The steering assist mechanism 11 includes an EPS (Electronic Power Steering) motor 13 as a steering assist motor as a drive source, and a speed reduction mechanism 14 that transmits the power of the EPS motor 13 to an output shaft 3c described later of the steering shaft 3. Yes. The speed reduction mechanism 14 includes a drive gear 14a such as a worm that is driven by the EPS motor 13, and a driven gear 14b such as a worm wheel that meshes with the drive gear 14a and is connected to the output shaft 3c so as to be integrally rotatable. I have.

Further, the steering angle ratio variable steering device 1 is configured to vary the transmission ratio (steering angle ratio) between the steering angle (steering angle) of the steering member 2 and the steering angle (steering angle) of the steered wheels 10. A variable mechanism 15 and a VGR control unit 16 as a control device for controlling the operation of the steering angle ratio variable mechanism 15 are provided.
The steering shaft 3 is connected to the steering member 2 via the first shaft 3a and the first shaft 3a and the torsion bar 17 so as to be relatively rotatable on the same axis so as to form a second shaft. An input shaft 3b of the variable mechanism 15 and an output shaft 3c of the steering angle ratio variable mechanism 15 connected to the intermediate shaft 5 via the universal joint 6 and constituting a third shaft are provided.

  A torque sensor 18 is provided for detecting the steering torque T based on the amount of relative rotational displacement (corresponding to the torsion angle δ of the torsion bar 17) between the first shaft 3a and the input shaft 3b (second shaft) via the torsion bar 17. . The torque sensor 18 and the vehicle speed sensor 19 are connected to the EPS control unit 12. The torque sensor 18 also functions as a twist angle detection sensor that detects the twist angle δ of the torsion bar 17.

The EPS control unit 12 controls the driving of the EPS motor 13 based on the steering torque T detected by the torque sensor 18 and the vehicle speed V detected by the vehicle speed sensor 19. The output rotation of the EPS motor 13 is decelerated through the speed reduction mechanism 14 and transmitted to the pinion shaft 7 through the output shaft 3b, and converted into a linear motion of the rack shaft 8, thereby assisting steering.
The steering angle ratio variable mechanism 15 includes a differential mechanism 20 that connects the input shaft 3b and the output shaft 3c, and a VGR (Variable Gear-Ratio Steering) motor 21 as a steering angle ratio variable motor that drives the differential mechanism 20. I have.

The differential mechanism 20 includes, for example, an input element 20a that is, for example, a sangi that rotates with the input shaft 3b, an output element 20b that is, for example, a ring gear that rotates with the output shaft 3c, and the input element 20a and the output element 20b. For example, an intermediate element 20c which is a carrier capable of revolving together with, for example, a planetary gear which supports the planetary gear is provided.
The steering angle ratio variable mechanism 15 is input to the steering mechanism A by adding the rotation due to the drive of the VGR motor 21 to the rotation of the input shaft 3b accompanying the rotation operation of the steering member 2 and transmitting it to the output shaft 3c. The rotation of the steering member 2 can be increased (or decelerated).

  That is, as shown in FIGS. 2 and 3, the rudder angle ratio variable mechanism 15 has the first steered angle θts which is the steered angle of the steered wheel 10 based on the steering operation, to the steered wheel 10 based on the drive of the VGR motor 21. By adding the second steering angle θtm (so-called act angle), which is the steering angle, the transmission ratio between the steering member 2 and the steered wheels 10, that is, the ratio of the steering angle θs to the steered angle θt (steering angle ratio). R: R = θs / θt) is varied.

  In this case, “addition” is defined to include not only addition but also subtraction, and so on. Further, when the “ratio between the steering angle θs and the steering angle θt” is expressed by the overall steering angle ratio R (steering angle θs / steering angle θt), as shown in FIG. 2, the first steering angle θts. The steering angle ratio R in the overall is reduced by adding the second steering angle θtm in the same direction. On the other hand, as shown in FIG. 3, the overall steering angle ratio R is increased by adding the second steering angle θtm in the opposite direction to the first steering angle θts.

  In the present embodiment, a brushless motor is adopted as the VGR motor 21 that is a drive source of the rudder angle ratio variable mechanism 15, and the VGR motor 21 is a three-phase (U, U) supplied from the VGR control unit 16. Rotate based on the driving power of V, W). The VGR control unit 16 is configured to control the operation of the steering angle ratio variable mechanism 15, that is, the second steering angle θtm by controlling the rotation of the VGR motor 21 through the supply of the driving power (the rudder angle θtm). Angle ratio variable control).

  Next, an electrical configuration related to variable steering angle ratio of the steering angle ratio variable steering apparatus 1 will be described. As shown in FIG. 1, the VGR control unit 16 includes a steering angle θs detected by the steering angle sensor 22, a vehicle speed V detected by the vehicle speed sensor 19, and a torsion bar 17 detected by the torque sensor 18. The torsion angle δ and the actual rotation angle θtmr of the VGR motor 21 detected by the rotation angle sensor 23 are input. Then, the VGR control unit 16 controls the operation of the steering angle ratio variable mechanism 15 based on the steering angle θs, the vehicle speed V, the torsion angle δ, and the actual rotation angle θtmr to the VGR motor 21 that is a driving source thereof. By performing power supply, the steering angle ratio variable control as described above is executed.

More specifically, as shown in FIG. 4, the VGR control unit 16 includes a microcomputer 24 that outputs a motor control signal and a drive circuit 25 that supplies drive power to the VGR motor 21 based on the motor control signal. It is configured as an electronic control unit ECU (Electronic Control Unit).
Each control block shown below is realized by a computer program executed by the microcomputer 24. Then, the microcomputer 24 detects each state quantity at a predetermined sampling period, and generates a motor control signal by executing each arithmetic processing shown in the following control blocks every predetermined period.

The microcomputer 24 includes a basic component calculation unit 26, a compensation component calculation unit 27, and a motor control signal calculation unit 28. A steering angle θs and a vehicle speed V are input to the basic component calculation unit 26. The basic component calculation unit 26 calculates a basic component θtmk ^* of a control target value for varying the steering angle ratio according to the vehicle speed V using a characteristic map (not shown). Typically, the steering angle ratio is reduced during low-speed traveling, and the steering angle ratio is increased during high-speed traveling.

Further, the compensation component calculation unit 27 inputs a signal from the torque sensor 18 that also functions as a torsion angle sensor, and calculates a compensation component θtmh ^* of the control target value. The compensation component θtmh ^* is set equal to the torsion angle δ detected by the torsion angle sensor (torque sensor 18), for example (θtmh ^* = δ).
Shitatmh ^* is calculated by the base component Shitatmk ^* and compensation component computing section 27 computed by the basic component calculation unit 26 is inputted to the adder 29 are added by the adder 29. Then, based on the value obtained by superimposing the compensation component θtmh ^* corresponding to the torsion angle on the basic component θtmk ^* , the microcomputer 24 controls the control target value θtm ^* (target angle) of the second steering angle θtm based on the motor drive. It is the structure which calculates.

The control target value θtm ^* calculated in this way is the motor control signal together with the actual rotation angle θtmr detected by the rotation angle sensor 23 provided in the VGR motor 21 of the steering angle ratio variable mechanism 15 that is the control target. Input to the calculation unit 28. The motor control signal calculation unit 28 performs feedback control so that the actual rotation angle θtmr follows the control target value θtm ^* . That is, the motor control signal calculation unit 28 generates a motor control signal by executing the position control calculation.

Then, the microcomputer 24 outputs the motor control signal to the drive circuit 25, and the drive circuit 25 executes the supply of drive power based on the motor control signal, whereby the rotation of the VGR motor 21, that is, the steering angle ratio variable. The operation of the mechanism 15 is controlled.
According to the present embodiment, the steering angle ratio (R) is varied by adding the second steering angle θtm based on the drive of the VGR motor 21 to the first steering angle θts based on the operation of the steering member 2.

On the other hand, the input angle input to the input shaft 3 b of the steering angle ratio variable mechanism 15 is smaller than the operation angle (steering angle θs) of the steering member 2 by the torsion angle δ of the torsion bar 17. Yes (the phase is delayed). Therefore, the first steering angle θts based on the operation of the steering member 2 is decreased (the phase is delayed) by the torsion angle δ.
On the other hand, the compensation component based on the twist angle δ detected by the twist angle sensor (the torque sensor 18 in the present embodiment) is added to the basic component θtmk ^* based on the running state of the vehicle (steering angle θs, vehicle speed V, etc.). A control target value θtm ^* for the second steering angle θtm is set by superimposing θtmh ^* . That is, by executing compensation control based on the twist angle δ, the phase of the control target value θtm ^* (target angle) of the second steering angle θtm based on the drive of the VGR motor 21 can be advanced. As a result, a delay in the phase of the output shaft 3c (that is, the phase of the steered wheels 10) due to the twist of the torsion bar 17 can be suppressed. Therefore, it is possible to give the driver a good steering feeling with good responsiveness and rigidity.

Further, a torsion bar 17 having a low torsional rigidity (spring constant) can be used, and as a result, the detection accuracy of the steering torque T by the torque sensor 18 can be increased. Therefore, it is possible to perform steering assist control with high accuracy by the EPS control unit 12, and it is possible to contribute to the realization of a good steering feeling from this point.
Further, the compensation component θtmh ^* superimposed on the base component θtmk ^* is made equal to the detected torsion angle δ of the torsion bar 17, and the control target value θtm ^* of the second steering angle θtm is calculated, whereby the torsion bar 17 The effect of eliminating the phase delay of the steered wheels 10 caused by twisting can be enhanced. As a result, a better steering feeling can be given to the driver.

The present invention is not limited to the above-described embodiment. For example, in the VGR control unit 16, the basic component calculation unit 26 is abolished, and a vehicle integrated ECU that is an upper ECU of the VGR control unit 16 and the EPS control unit 12. The basic component θtmk ^* of the control target value may be input from a vehicle (not shown) through an in-vehicle network such as CAN (Controller Area Network).
In the above embodiment, the torque sensor 18 is used as a torsion angle sensor. However, a torsion angle sensor may be provided separately from the torque sensor 18.

  In addition, the present invention can be variously modified within the scope of the claims.

DESCRIPTION OF SYMBOLS 1 ... Steering angle ratio variable steering device, 2 ... Steering member, 3 ... Steering shaft, 3a ... 1st axis, 3b ... Input shaft (2nd axis), 3c ... Output shaft (3rd axis), 10 ... Steering wheel, DESCRIPTION OF SYMBOLS 11 ... Steering assistance mechanism, 12 ... EPS control part, 13 ... EPS motor, 15 ... Steering angle ratio variable mechanism, 16 ... VGR control part (control apparatus), 17 ... Torsion bar, 18 ... Torque sensor (torsion angle sensor), DESCRIPTION OF SYMBOLS 19 ... Vehicle speed sensor, 20 ... Differential mechanism, 21 ... VGR motor (steering angle ratio variable motor), 22 ... Steering angle sensor, 23 ... Rotation angle sensor, 26 ... Base component calculation part, 27 ... Compensation component calculation part, 28 Motor control signal calculation unit A A Steering mechanism θs Steering angle θt Steering angle R Steering angle ratio δ Torsion angle V Vehicle speed θts First steering angle θtm Second Rudder angle, θtm ^* … Control target value, θtmk ^* … Basic component, θtmh ^* … Compensation component, θtmr… Actual rotation angle

Claims (2)

An input shaft connected via a torsion bar to a steering member to be rotated;
An output shaft coupled to the steering mechanism;
Connecting the input shaft and the output shaft, including a rudder angle ratio variable motor, and adding a second rudder angle based on driving of the rudder angle ratio variable motor to a first rudder angle based on an operation of the steering member; A steering angle ratio variable mechanism that varies a steering angle ratio that is a ratio of a steering angle of the steering member and a turning angle of the steered wheels;
A twist angle sensor for detecting a twist angle of the torsion bar;
A control device for controlling the operation of the rudder angle ratio variable mechanism,
The control device calculates a control target value of the second steering angle by superimposing a compensation component based on a torsion angle detected by the torsion angle sensor on a basic component based on a running state of a vehicle. Variable steering device.   2. The steering angle ratio variable steering device according to claim 1, wherein the control device sets the compensation component equal to the torsion angle detected by the torsion angle sensor.

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