JP2007269219A - Vehicular steering device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a vehicular steering device capable of consistently continuing the steering angle control even when an abnormality occurs in a steering sensor. <P>SOLUTION: A microcomputer 31 has an abnormality detection unit 40 for detecting an abnormality of a steering sensor. When an abnormality of the steering sensor is detected by the abnormality detection unit 40, the output of the motor control signal, i.e., the variable control of the transmission ratio is continued by using the pinion angle θp detected by a torque sensor in place of the steering angle θs. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a vehicle steering apparatus.

In recent years, a vehicle steering apparatus has a transmission ratio that varies a transmission ratio between a steering angle and a steering angle by adding a second steering angle based on a motor drive to a first steering angle based on a steering operation. There are some equipped with a rudder angle control function for automatically controlling the rudder wheel steering angle, such as a variable function or an automatic steering function for automatically maneuvering on behalf of the driver. In many cases, such steering angle control is performed based on the steering angle detected by the steering sensor (see, for example, Patent Document 1).
JP 2005-170129 A

  However, in the above conventional configuration, if an abnormality occurs in the steering sensor, the steering angle control must be stopped. For this reason, for example, in the transmission ratio variable control described above, the steering angle corresponding to the addition by the motor drive is fixed by stopping the control, and a problem such as a deviation between the steering neutral position and the neutral position of the steered wheels may occur. In this respect, there was still room for improvement.

  The present invention has been made to solve the above-described problems, and an object of the present invention is to provide a vehicle steering apparatus capable of stably continuing steering angle control even when an abnormality occurs in a steering sensor. It is in.

  In order to solve the above-mentioned problem, the invention according to claim 1 is a driving means that is provided in the middle of a steering transmission system that connects a steering wheel and a steered wheel and that can change the steered angle of the steered wheel by motor driving. And a control means for controlling the drive means, the control means being a vehicle steering device for controlling the operation of the drive means based on a steering angle detected by a steering sensor, wherein the steering sensor An abnormality detection means for detecting an abnormality and a detection means capable of detecting the steering angle or a state quantity of the steering transmission system that defines the steering angle, and the control means detects an abnormality of the steering sensor. In this case, the gist is to control the operation of the driving means based on the value detected by the detecting means.

  That is, the steering angle is reflected on the turning angle via the steering transmission system. Therefore, it is possible to estimate the steering angle from the steering angle or the state quantity of the steering transmission system that defines the steering angle. By using this estimated steering angle, correct steering due to an abnormality in the steering sensor can be performed. Even if the angle cannot be detected, the steering angle control can be stably continued.

  According to a second aspect of the present invention, the driving means adds the second steering angle of the steered wheel based on motor drive to the first steered angle of the steered wheel based on a steering operation, thereby adding the steering angle and the steering angle. The gist is that it is a transmission ratio variable device that varies the transmission ratio between the turning angle.

  In other words, in the vehicle steering apparatus provided with such a transmission ratio variable device, the turning angle is the sum of the first steering angle based on the steering operation and the second steering angle based on the motor drive. Therefore, the steering angle can be estimated from the turning angle (or the state quantity of the steering transmission system that defines the turning angle) and the motor control amount. Then, by continuing the transmission ratio variable control using the estimated steering angle, it is possible to avoid the problem that a deviation occurs between the steering neutral position and the neutral position of the steered wheels due to the fixation of the second steering angle when the control is stopped. Thus, good steering characteristics can be maintained.

  The invention according to claim 3 is provided with an electric power steering device that is provided in the middle of the steering transmission system and applies an assist force for assisting a steering operation to the steering transmission system by driving a motor. The gist of the invention is a torque sensor for detecting a steering torque or a motor rotation angle sensor provided in the electric power steering apparatus.

  According to the above configuration, the fail-safe control at the time of abnormality of the steering sensor as described above can be performed without adding any new equipment as long as it has a widely used electric power steering device.

  According to the present invention, it is possible to provide a vehicle steering apparatus capable of stably continuing steering angle control even when an abnormality occurs in a steering sensor.

Hereinafter, an embodiment in which the present invention is embodied in a vehicle steering apparatus having a variable transmission ratio function will be described with reference to the drawings.
FIG. 1 is a schematic configuration diagram of a vehicle steering apparatus 1 according to the present embodiment. As shown in the figure, the steering shaft 3 to which the steering wheel 2 is fixed is connected to a rack 5 via a rack and pinion mechanism 4, and the rotation of the steering shaft 3 accompanying the steering operation is performed by the rack and pinion mechanism 4. Is converted into a reciprocating linear motion of the rack 5. Then, by changing the rudder angle of the steered wheels 6, that is, the steered angle, by the reciprocating linear movement of the rack 5, the traveling direction of the vehicle is changed. That is, in the present embodiment, a steering transmission system that connects the steering wheel 2 and the steered wheels 6 is configured by the steering shaft 3, the rack and pinion mechanism 4, and the rack 5 (and tie rods, knuckle arms and the like not described in detail). Yes.

  The vehicle steering apparatus 1 of the present embodiment includes a gear ratio variable actuator 7 serving as a transmission ratio variable apparatus that varies the transmission ratio (gear ratio) of the steered wheels 6 with respect to the steering angle (steering angle) of the steering 2, and the gear ratio. And an IFSECU 8 for controlling the operation of the variable actuator 7.

  More specifically, the steering shaft 3 includes a first shaft 9 to which the steering 2 is connected and a second shaft 10 to be connected to the rack and pinion mechanism 4. The variable gear ratio actuator 7 includes the first shaft 9 and the first shaft 9. A differential mechanism 11 that couples the two shafts 10 and a motor 12 that drives the differential mechanism 11 are provided. As shown in FIG. 2, the gear ratio variable actuator 7 adds the rotation (ACT rotation angle θvg) based on the motor drive to the rotation (steering angle θs) of the first shaft 9 that accompanies the steering operation. By transmitting to the shaft 10, the rotation (that is, the pinion angle θp that defines the turning angle) of the second shaft 10 input to the rack and pinion mechanism 4 is increased (or decelerated).

  That is, as shown in FIGS. 3 (a) and 3 (b), the gear ratio variable actuator 7 has a steered angle of steered wheels (steered steered angle θts) based on a steering operation (steered steered angle θts). By adding ACT angle θta), the ratio of the turning angle θt of the steered wheels 6 to the steering angle θs, that is, the transmission ratio (gear ratio) is varied. The IFSECU 8 serving as the control means controls the gear ratio variable actuator 7 through the supply of driving power to the motor 12, thereby controlling the transmission ratio (gear ratio) between the steering angle θs and the turning angle θt ( Variable transmission ratio control).

  In this case, “addition” is defined to include not only addition but also subtraction, and so on. Further, when the “gear ratio of the steering angle θt to the steering angle θs” is expressed as an overall gear ratio (steering angle θs / steering angle θt), the ACT angle θta in the same direction as the steering angle θts should be added. Thus, the overall gear ratio becomes small (the turning angle θt is large, see FIG. 3A). Then, the overall gear ratio is increased by adding the ACT angle θta in the opposite direction (small turning angle θt, see FIG. 3B). In this embodiment, the steer turning angle θts constitutes the first rudder angle, and the ACT angle θta constitutes the second rudder angle.

  As shown in FIG. 1, the vehicle steering apparatus 1 includes an EPS actuator 17 that constitutes an electric power steering apparatus that can apply an assist force for assisting a steering operation to the steering transmission system, and the EPS actuator 17. EPSECU 18 for controlling the operation.

  The EPS actuator 17 of the present embodiment is a so-called rack-type EPS actuator in which a motor 22 as a driving source is provided on the rack 5, and assist torque generated by the motor 22 is via a ball screw mechanism (not shown). To the rack 5. The EPS ECU 18 controls the assist force applied to the steering system by controlling the assist torque generated by the motor 22 (power assist control).

  In the present embodiment, the IFSECU 8 that controls the gear ratio variable actuator 7 and the EPSECU 18 that controls the EPS actuator 17 are connected via an in-vehicle network (CAN: Controller Area Network) 23. Are connected to a plurality of sensors for detecting the vehicle state quantity. Specifically, a steering sensor 24, a torque sensor 25, and a vehicle speed sensor 26 are connected to the in-vehicle network 23, and the steering angle θs, the steering torque τ, and the vehicle speed V detected by each of these sensors The data is input to the IFSECU 8 and the EPSECU 18 via the network 23. Then, the IFSECU 8 and EPSECU 18 perform the transmission ratio variable control and the power assist control in an integrated manner by performing mutual communication via the in-vehicle network 23.

  In this embodiment, the torque sensor 25 employs a known twin resolver type torque sensor capable of detecting the rotation angle, and the torque sensor 25 is a second shaft in the vicinity of the rack and pinion mechanism 4. 10 is provided. And in the fail safe control mentioned later, it is the structure using the pinion angle | corner (theta) p which the torque sensor 25 as this detection means detects.

Next, the aspect of transmission ratio variable control in the vehicle steering apparatus of the present embodiment will be described.
FIG. 4 is a control block diagram showing an aspect of transmission ratio variable control in the present embodiment. Each control block shown below is realized by a computer program executed by the microcomputer 31 provided in the IFSECU 8.

  As shown in the figure, the IFSECU 8 includes a microcomputer 31 that outputs a motor control signal, and a drive circuit 32 that supplies drive power to the motor 12 of the gear ratio variable actuator 7 based on the motor control signal.

  The microcomputer 31 includes a target ACT rotation angle calculation unit 33. The target ACT rotation angle calculation unit 33 controls the control target of the gear ratio variable actuator 7 based on the vehicle speed V and the steering angle θs detected by the steering sensor 24. A target ACT rotation angle θvg * which is a quantity is calculated. The microcomputer 31 generates a motor control signal by performing a feedback control calculation so that the actual ACT rotation angle θvg follows the target ACT rotation angle θvg * calculated by the target ACT rotation angle calculation unit 33.

  More specifically, the target ACT rotation angle calculation unit 33 includes a target gear ratio calculation unit 34 and a modified steering angle ratio calculation unit 35, and the target gear ratio calculation unit 34 is based on the vehicle speed V. Rg is calculated, and the corrected rudder angle ratio calculation unit 35 calculates the corrected rudder angle ratio α based on the calculated target gear ratio Rg. The corrected rudder angle ratio α is a value indicating the ratio of the added amount by the motor drive when the steering angle θs is “1”. The corrected steering angle ratio α calculated by the corrected steering angle ratio calculation unit 35 is input to the multiplier 36 together with the steering angle θs. Then, the target ACT rotation angle calculation unit 33 generates the target ACT rotation angle θvg * by multiplying the steering angle θs by the corrected steering angle ratio α in the multiplier 36.

  Further, the microcomputer 31 receives an ACT rotation angle θvg calculated based on the motor rotation angle θm detected by the rotation angle sensor 37 provided in the motor 12, and the target ACT rotation angle calculation unit 33. The target ACT rotation angle θvg * calculated in is input to the F / B control calculation unit 38 together with the ACT rotation angle θvg. The F / B control calculation unit 38 calculates a current command ε that is a target value of power supply to the motor 12 by feedback calculation based on a deviation between the target ACT rotation angle θvg * and the target ACT rotation angle θvg *, and outputs a motor control signal. Output to the output unit 39. The motor control signal output unit 39 outputs a motor control signal generated based on the current command ε to the drive circuit 32, and the drive power based on the motor control signal is supplied to the motor 12, whereby the motor 12 That is, the operation of the gear ratio variable actuator 7 is controlled.

(Fail-safe control)
Next, an aspect of fail-safe control when the steering sensor is abnormal in the vehicle steering device of the present embodiment will be described.

  As shown in FIG. 4, the microcomputer 31 includes an abnormality detection unit 40 that detects an abnormality of the steering sensor 24. In the present embodiment, the steering angle θs is input to the abnormality detection unit 40, and the abnormality detection unit 40 can detect when the input steering angle θs changes discontinuously. When the value becomes no value, it is determined that an abnormality has occurred in the steering sensor 24. When the abnormality detection unit 40 detects an abnormality in the steering sensor 24, the microcomputer 31 uses the pinion angle θp detected by the torque sensor 25 in place of the steering angle θs, thereby generating a motor control signal. The output, that is, transmission ratio variable control is continued.

  More specifically, in the present embodiment, in the target ACT rotation angle calculation unit 33, the steering angle θs is input to the multiplier 36 via the switching unit 41, and the abnormality detection unit 40 is included in the switching unit 41. The abnormality detection signal output from is input. Further, the pinion angle θp is input to the target ACT rotation angle calculation unit 33 together with the steering angle θs and the vehicle speed V. The pinion angle θp input to the target ACT rotation angle calculator 33 is input to the subtractor 42 together with the ACT rotation angle θvg calculated based on the motor rotation angle θm, and the subtractor 42 converts the ACT rotation angle from the pinion angle θp. The estimated steering angle θs ′ calculated by subtracting θvg is input to the switching unit 41 together with the steering angle θs. The switching unit 41 outputs the steering angle θs detected by the steering sensor 24 to the multiplier 36 when no abnormality detection signal is input from the abnormality detection unit 40, and the abnormality detection signal is input. In this case, the estimated steering angle θs ′ calculated based on the pinion angle θp is output instead of the steering angle θs.

  That is, as shown in FIG. 2, the pinion angle θp is a value obtained by adding the rotation based on the motor drive, that is, the ACT rotation angle θvg to the rotation of the first shaft 9 accompanying the steering operation, that is, the steering angle θs (θp = Θs + θvg). Therefore, even when an abnormality occurs in the steering sensor, the current steering angle θs can be estimated by reducing the ACT rotation angle θvg from the pinion angle θp (θs ′ = θp−θvg). In the vehicle steering apparatus 1 according to the present embodiment, when an abnormality occurs in the steering sensor 24, the transmission ratio variable control is continued by using the estimated steering angle θs ′ instead of the steering angle θs.

Next, a processing procedure of target ACT rotation angle calculation in the target ACT rotation angle calculation unit 33 will be described.
As shown in the flowchart of FIG. 5, when the target ACT rotation angle calculation unit 33 acquires the sensor values (θs, V, θp, θvg) output from each sensor (step 101), the target gear ratio calculation (step 101) is performed. 102) and a correction rudder angle ratio calculation (step 103). Next, the target ACT rotation angle calculation unit 33 determines whether there is an input of an abnormality detection signal from the abnormality detection unit 40 (step 104). If no abnormality detection signal is input (step 104: NO), the target ACT rotation angle θvg * is calculated based on the steering angle θs detected by the steering sensor 24 (θvg * = θs × α, step 105) When an abnormality detection signal is input (step 104: YES), the target ACT rotation angle θvg * is calculated based on the pinion angle θp and the ACT rotation angle θvg detected by the torque sensor 25 (θvg * = (Θp−θvg) × α, step 106). Then, the target ACT rotation angle θvg * calculated in step 105 or step 106 is output to the F / B control calculation unit 38 (step 107).

As described above, according to the present embodiment, the following operations and effects can be obtained.
(1) The microcomputer 31 includes an abnormality detection unit 40 that detects an abnormality of the steering sensor 24. When the abnormality detection unit 40 detects an abnormality in the steering sensor 24, the microcomputer 31 uses the pinion angle θp as the state quantity of the steering transmission system that defines the turning angle θt, thereby providing a motor control signal. Output, that is, transmission ratio variable control is continued.

  According to the above configuration, the transmission ratio variable control can be continued even when the correct steering angle θs cannot be detected due to the abnormality of the steering sensor 24. As a result, it is possible to avoid the problem that the steering neutral position and the neutral position of the steered wheels 6 are shifted due to the fixation of the ACT angle θta that accompanies the control stop, and maintain good steering characteristics.

  (2) The pinion angle θp is detected using the torque sensor 25 for detecting the steering torque τ used for power assist control. By adopting such a configuration, if a widely used electric power steering device is provided, the above-described fail-safe control when the steering sensor is abnormal can be performed without adding any new equipment. Can do.

In addition, you may change this embodiment as follows.
In this embodiment, when an abnormality occurs in the steering sensor 24, the target ACT rotation angle calculation unit 33 calculates the target ACT rotation angle θvg * based on the pinion angle θp and the ACT rotation angle θvg detected by the torque sensor 25. The calculation is performed (θvg * = (θp−θvg) × α). However, the present invention is not limited to this, and the target ACT rotation angle θvg * may be set based on the pinion angle θp and the corrected steering angle ratio α (see FIG. 5, θvg * = θp / (1 + α) × α). With such a configuration, the calculation of the target ACT rotation angle θvg * is performed based on the state quantity (pinion angle θp and corrected steering angle ratio α) that does not go through the feedback loop. You can continue. Note that when the target ACT rotation angle θvg * includes other control components such as a so-called differential steer control amount, it is desirable to adopt the configuration of the present embodiment.

  In the present embodiment, the target ACT rotation angle θvg * is calculated using the pinion angle θp that is the rotation angle of the second shaft 10 as the state quantity of the steering transmission system that defines the turning angle θt. However, the present invention is not limited to this. For example, the amount of movement of the rack 5 may be used or the actual turning angle θt may be used as long as it is a state quantity of the steering transmission system that defines the turning angle θt. That is, all the movements of the steering transmission system that couples the steering wheel 2 and the steered wheels 6 are reflected in the steered angle θt, and therefore it is possible to estimate the steered angle θs using any of them. Therefore, the pinion angle θp may be detected by using a device other than the torque sensor 25, and if an electric power steering device is further provided, a motor rotation angle (this is detected by a motor rotation angle sensor provided in the motor. For example, the amount of movement of the rack 5 on the basis of (1) may be detected, and the target ACT rotation angle θvg * may be calculated using this.

  -In this embodiment, although the abnormality detection part 40 as an abnormality detection means which detects abnormality of the steering sensor 24 was provided in the microcomputer 31, it is good also as a structure provided in addition to the microcomputer 31 (IFSECU8).

  In the present embodiment, the present invention is embodied in a vehicle steering apparatus having a transmission ratio variable function. However, the present invention is not limited to this, and any other configuration such as an automatic steering function may be used as long as it has a steering angle control function based on the steering angle θs. That is, it is not always necessary to include a transmission ratio variable device. For example, the transmission ratio variable device may be embodied as one that controls a turning angle using an electric power steering device (EPS actuator) or the like as a driving unit.

The schematic block diagram of the steering apparatus for vehicles. Action | operation explanatory drawing of a transmission ratio variable apparatus. (A) (b) Action explanatory drawing of transmission ratio variable control. The control block diagram which shows the aspect of transmission ratio variable control. The flowchart which shows the process sequence of target ACT rotation angle calculation.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 ... Vehicle steering device, 2 ... Steering, 3 ... Steering shaft, 4 ... Rack & pinion mechanism, 5 ... Rack, 6 ... Steered wheel, 7 ... Gear ratio variable actuator, 8 ... IFSECU, 9 ... 1st shaft, 10 2nd shaft, 12 ... motor, 17 ... EPS actuator, 22 ... motor, 24 ... steering sensor, 25 ... torque sensor, 31 ... microcomputer, 33 ... target ACT rotation angle calculation unit, 40 ... abnormality detection unit, 41 ... switching V, vehicle speed, θs, steering angle, θp, pinion angle, θvg, ACT rotation angle, θvg *, target ACT rotation angle, θt, steering angle, Rg, target gear ratio, α, corrected steering angle ratio.

Claims (3)

A driving means provided in the middle of a steering transmission system for connecting the steering wheel and the steered wheels and capable of changing a steered angle of the steered wheels by motor driving; and a control means for controlling the drive means, the control means comprising: A vehicle steering device for controlling the operation of the drive means based on a steering angle detected by a steering sensor,
An abnormality detection means for detecting an abnormality of the steering sensor;
Detecting means capable of detecting the steering angle or a state quantity of the steering transmission system defining the steering angle;
The control means controls the operation of the drive means based on a value detected by the detection means when an abnormality of the steering sensor is detected;
A vehicle steering apparatus characterized by the above. The vehicle steering apparatus according to claim 1,
The drive means adds a second steering angle of the steered wheel based on motor drive to a first steered angle of the steered wheel based on a steering operation, thereby transferring a transmission ratio between the steering angle and the steered angle. A vehicle steering apparatus characterized by being a transmission ratio variable device that varies the speed. In the vehicle steering device according to claim 1 or 2,
An electric power steering device that is provided in the middle of the steering transmission system and applies an assist force for assisting a steering operation to the steering transmission system by motor drive;
The vehicle steering apparatus according to claim 1, wherein the detection means is a torque sensor for detecting a steering torque or a motor rotation angle sensor provided in the electric power steering apparatus.

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