JP3595979B2 - Variable steering angle ratio steering device - Google Patents

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
According to the present invention, a variable steering angle ratio (hereinafter, referred to as a "steering angle ratio") of a steered wheel to a suitable steering angle of a steering wheel (hereinafter referred to as "steering angle ratio") can be automatically set in accordance with a driving operation situation of a vehicle by a driver. The present invention relates to a steering angle ratio steering device.
[0002]
[Prior art]
2. Description of the Related Art Conventionally, as a vehicular steering device that assists a driver in driving, a vehicular steering device that automatically sets a steering angle ratio according to a surrounding environment of a vehicle is known. However, in this vehicle steering device, the steering angle ratio cannot be set according to the driver's intention.
[0003]
The present applicant has disclosed a variable steering angle ratio steering apparatus for a vehicle in Japanese Patent Application Laid-Open No. H11-78944. The variable steering angle ratio steering device for a vehicle includes a variable steering angle ratio device capable of changing the amount of rotation of a steered wheel with respect to a steering wheel, and a control device for controlling the variable steering angle ratio device. Further, the variable steering angle ratio device includes an electric motor for varying the steering angle ratio.
[0004]
Then, the steering amount of the steered wheels with respect to the steering wheel is changed according to the vehicle speed and the like, and the steering angle ratio is automatically set according to the driver's intention. For example, when the vehicle runs lightly on a mountain road with continuous curves, the steering angle ratio is increased. Conversely, when traveling on a highway or the like at a substantially constant speed, the steering angle ratio is set to be small, and a steering angle ratio suitable for each case is set.
[0005]
Further, the conventional variable steering angle ratio steering device includes an electric motor for changing a steering angle ratio. By displacing the output shaft with this electric motor, the steering angle ratio of the variable steering angle ratio device is changed. Further, the conventional variable steering angle ratio steering device includes a steering angle ratio sensor that detects a displacement amount of an output shaft, and detects whether the steering angle ratio is appropriate by using the steering angle ratio sensor. ing.
[0006]
[Problems to be solved by the invention]
However, in the conventional variable steering angle ratio steering apparatus, if a failure occurs in the steering angle ratio sensor, it is not possible to detect that the steering angle ratio is appropriately changed. If the steering angle ratio is not properly changed, the driver may feel uncomfortable in driving. Further, in the variable steering angle ratio steering device, a stopper is provided on a rack shaft or the like in order to regulate the steering angle of the steered wheels, but if the steering angle ratio is not properly detected, this stopper is damaged. I was worried.
[0007]
In order to detect the failure of the steering angle ratio sensor, it is conceivable that two steering angle ratio sensors are provided and the failure detection is performed mutually. However, if two steering angle ratio sensors are provided, the space for the two steering angle ratio sensors is required, and it is disadvantageous in terms of cost.
[0008]
Therefore, an object of the present invention is to solve the problem of the steering angle ratio sensor by using a simple device when the steering angle ratio sensor for detecting the steering angle ratio of the variable steering angle ratio device occurs in the variable steering angle ratio steering device. The purpose is to enable detection.
[0009]
[Means for Solving the Problems]
The present invention that has solved the above-described problems provides a steering system from a steering wheel to a steered wheel with a variable steering angle ratio device capable of changing a ratio of a steering angle of the steered wheel to the steering wheel. In a variable steering angle ratio steering device provided with a control device for controlling,
The variable steering angle ratio device includes an electric motor for changing a steering angle ratio of the steered wheels with respect to the steering wheel, a steering angle ratio changing member that is driven and displaced by the electric motor, and a steering angle ratio changing member. A steering angle ratio sensor that detects a displacement amount as a ratio of a steering angle of the steered wheels to the steering wheel,
The control device is configured to control a current signal output from the electric motor.Detecting the rotation speed of the electric motor by the current ripple signal detected from the, the estimated displacement amount of the steering angle ratio changing member obtained by this rotation speed,Output from the steering angle ratio sensorIt is characterized in that it is determined whether or not the steering angle ratio sensor has failed by comparing the actual displacement amount of the steering angle ratio changing member with the actual displacement amount.
[0010]
According to the first aspect of the present invention, it is detected whether or not the steering angle ratio sensor has failed based on the current signal from the electric motor current. For this reason, it is not necessary to separately provide a steering angle ratio sensor to mutually perform failure detection, and the failure of the steering angle ratio sensor can be detected by a simple device.
[0012]
In the invention according to claim 1,The rotation speed of the motor is detected based on the current ripple generated in the motor by the current ripple signal, and the estimated displacement amount of the steering angle ratio changing member is obtained from the rotation speed of the motor. Then, the estimated displacement amount of the steering angle ratio changing member obtained from the rotation speed of the electric motor is compared with the actual displacement amount of the steering angle ratio changing member detected by the steering angle ratio sensor, and whether or not these are the same. Thus, the failure of the steering angle ratio sensor is detected. For this reason, a failure of the steering angle ratio sensor can be detected with high accuracy.
[0013]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, embodiments of the present invention will be specifically described with reference to the drawings.
First, the overall configuration of the variable steering angle ratio steering device according to the present invention will be described.
FIG. 1 is an overall configuration diagram of a variable steering angle ratio steering device according to the present invention. The variable steering angle ratio steering device 1 is based on a steering system S from the steering wheel 2 to the steered wheels 9, a variable steering angle ratio device 10 provided in the steering system S, and a vehicle speed signal Va from a vehicle speed sensor VS. A control device 40 for controlling the variable steering angle ratio device 10 is provided.
[0014]
In the steering system S, a steering shaft 3 provided integrally with a steering wheel 2 is connected to an input shaft of a variable steering angle ratio device 10 via a connecting shaft 4 having universal joints 4a and 4b. The variable steering angle ratio device 10 uses a device capable of continuously varying the input / output angle ratio β / α of the rotation angle β of the output shaft to the rotation angle α of the input shaft. Further, the steering system S engages the pinion 5 provided on the output shaft of the variable steering angle ratio device 10 with the rack teeth 6a of the rack shaft 6 to convert the rotational motion of the output shaft into the linear motion of the rack shaft 6. Convert. Then, the steering system S converts the linear motion of the rack shaft 6 into steering motion of the steered wheels 9, 9 via the tie rods 7, 7 and the knuckle arm 8. That is, when the rotation angle β of the output shaft changes, the steering system S changes the stroke L of the rack shaft 6 to steer the steered wheels 9 and 9. Note that the steering angle ratio of the variable steering angle ratio steering device 1 includes an input / output angle ratio β / α (variable) of a rotation angle β of the output shaft to a rotation angle α of the input shaft, and a gear ratio of the pinion 5 and the rack teeth 6a ( Fixed) and varies with the input / output angle ratio β / α.
[0015]
Next, the structure of a specific example of the variable steering angle ratio device 10 according to the present embodiment will be described with reference to FIGS.
As shown in FIG. 2, the input shaft 11 is rotatably supported by an upper casing 13a via a ball bearing 12.(Rudder angle ratio changing member)It is rotatably supported at an eccentric position of 14 via a ball bearing 15. At the end of the input shaft 11 protruding into the lower casing 13b, a coupling 16 for transmitting a rotational force to the output shaft 17 is integrally formed. The input shaft 11 is connected to the connection shaft 4 (see FIG. 1), and is configured to rotate through the connection shaft 4 when the driver steers the steering wheel 2.
[0016]
The output shaft 17 is rotatably supported by the lower casing 13b via a pair of ball bearings 18a, 18b. A pinion 5 meshed with the rack teeth 6a of the rack shaft 6 is integrally formed below the output shaft 17. An end of the output shaft 17 protrudes into the lower casing 13b, and an intermediate shaft 19 protrudes from the end of the output shaft 17 at a position eccentric from the center of the output shaft 17. The intermediate shaft 19 and the coupling 16 formed integrally with the input shaft 11 are connected to each other via a slider 21 having a flat needle bearing 20 interposed therebetween and a tapered roller bearing 22. Further, a seal member 35 having a flexible tubular portion is provided between the input shaft 11 and the upper casing 13a. The seal member 35 maintains airtightness in the variable steering angle ratio device 10.
[0017]
As shown in FIG. 3, a groove 23 having a trapezoidal cross section is formed on the lower surface of the coupling 16 so that the lower part is expanded and opened. A slider 21 having a pair of flat needle bearings 20 interposed therein is engaged with the groove 23 so as to slide on mutually opposing inclined surfaces of the groove 23. An intermediate shaft 19 is engaged with the center of the lower surface of the slider 21 via a tapered roller bearing 22 so as to be relatively rotatable.
[0018]
As shown in FIG. 2, an adjusting screw 24 that is in contact with an outer race of a ball bearing 18 b that supports a lower end of the output shaft 17 is screwed to the lower casing 13 b. By properly tightening the adjusting screw 24, the pinion 5 is pressed in the axial direction, and an appropriate preload is applied between the input shaft 11 and the output shaft 17 via the coupling 16. In this way, it is possible to improve the coupling rigidity by removing the play of the coupling 16.
[0019]
As shown in FIG. 4, a fan-shaped partial worm wheel 25 is provided on a part of the outer peripheral portion of the support member 14. A worm 28 driven by a DC motor 27 as an electric motor is engaged with the partial worm wheel 25 via a worm reduction mechanism 26. In addition, a rotational motion can be given to the support member 14 over a predetermined angle range by the rotational driving force of the DC motor 27. To this DC motor 27, a current ripple detecting means 50 (see FIG. 7) for detecting a current ripple of the DC motor 27 is connected.
[0020]
The worm 28 is supported by the upper casing 13a via a backlash removing member 29 using an eccentric cam. The hexagonal wrench is engaged with the hexagonal hole 30 formed at the end of the backlash removing member 29, and the hexagonal wrench is rotated with respect to the upper casing 13a, so that the axis of the wrench is moved. The engagement with the partial worm wheel 25 is changed. The worm 28 and the worm reduction mechanism 26 are connected via an Oldham coupling 31 in order to allow the axis of the worm 28 to move.
[0021]
Further, a displacement sensor 33, which is a steering angle ratio sensor of the present invention, including a differential transformer and the like engaged with a pin 32 protruding from the upper surface of the support member 14, is attached to the upper casing 13a. This displacement sensor 33 isActual displacementHas been detected. Then, the displacement sensor 33 detects the detectedActual displacementThat is, the input shaft 11 supported by the support member 14Corresponding to the amount of eccentricity with respect to the output shaft 17The eccentricity signal (corresponding to the “steering angle ratio signal” of the present invention) 33 a is output to the control device 40. In the present embodiment, the variable steering angle ratio steering device 1 includes:Input shaft 11The steering angle ratio characteristic changes according to the amount of eccentricity, and the steering angle ratio continuously changes to an optimal value according to the steering angle of the steering wheel based on the steering angle ratio characteristic. That is, in the present embodiment,Input shaft 11The steering angle ratio changes according to the amount of eccentricity. Therefore, in the present embodiment, the steering angle ratio is not directly detected but corresponds to the actual steering angle ratio.Input shaft 11The actual eccentric amount is detected by the displacement sensor 33.
[0022]
The control device 40 detects the target eccentricity (corresponding to the target steering angle ratio) determined based on the vehicle speed signal Va from the vehicle speed sensor VS and the displacement sensor 33.Input shaft 11The rotational drive of the DC motor 27 is controlled by feedback control so as to match the actual eccentric amount (corresponding to the actual steering angle ratio) (see FIG. 7). The control device 40 will be described later in detail.
[0023]
The vehicle speed sensor VS is provided in a speedometer (not shown) and detects the speed of the vehicle. Then, the vehicle speed sensor VS transmits to the control device 40 a vehicle speed signal Va of an analog electric signal corresponding to the detected vehicle speed. The vehicle speed sensor VS may be a dedicated sensor of the variable steering angle ratio steering device 1 or a sensor shared with another system.
[0024]
Next, the operation principle of the variable steering angle ratio device will be described.
FIG. 5 is an explanatory diagram showing the operation principle of the variable steering angle ratio device, and FIG. 6 is an input / output angle characteristic diagram showing the steering angle ratio characteristics of the variable steering angle ratio device.
[0025]
As shown in FIG. 5, the rotation center of the input shaft 11 is A, the rotation center of the output shaft 17 is B, and the action point of the intermediate shaft 19 is C. Further, the dimension between BC is b, the amount of eccentricity between the input shaft 11 and the output shaft 17 (dimension between AB) is a, the rotation angle of the input shaft 11 (steering wheel steering angle) is α, and the rotation angle of the output shaft 17 is α. (Pinion rotation angle) is β. At this time,
b · sin β = (b · cos β−a) tan α
Because
α = tan^-1(B · sin β / (b · cos β-a))
Is represented by
[0026]
When the driver rotates the input shaft 11 by operating the steering wheel 2, the intermediate shaft 19 cranks around the axis of the output shaft 17 due to the engagement of the coupling 16 of the input shaft 11 with the slider 21. . For example, as shown in FIG. 5, when the rotation angle α1 of the input shaft 11 is 90 degrees, the rotation angle β1 of the output shaft 17 becomes as shown in FIG.
[0027]
Here, when the support member 14 is rotated, the axis of the input shaft 11 changes within the range indicated by reference numerals A0 to A2 in FIGS. 3 and 4 due to the eccentric cam action of the support member 14. When the amount of eccentricity a between the input and output shafts is appropriately determined by changing the axis of the input shaft 11 and the axes of the input shaft 11 and the output shaft 17 are eccentric to each other, the input shaft 11 and the output shaft 17 The rotation angles do not match. In addition, the angle change of the output shaft 17 when the input shaft 11 is rotated by equal angles gradually increases (see the solid lines a1 and a2 in FIG. 6).
[0028]
When the eccentricity a of the axis between the input shaft 11 and the output shaft 17 is continuously changed in the range of a2 to a0 (a2> a1> a0 = 0), the output shaft with respect to the rotation angle of the input shaft 11 is changed. 17, the ratio β / α of the rotation angle, that is, the practical steering angle ratio can be continuously changed. Now, if the amount of eccentricity a between the input and output axes is increased, the rate of change of the output angle β with respect to the input angle α gradually increases, and if the amount of eccentricity a between the input and output axes is set to 0, the dashed line (a0) in FIG. ), The input angle α and the output angle β are equal.
[0029]
If this change in the steering angle ratio is controlled to be, for example, the a0 side in the low-speed running range and the a2 side in the high-speed running range, the rack stroke with respect to the steering angle α of the steering wheel in the low-speed running range is smaller than that of the conventional steering device. , The sensitivity can be further increased (quick). Further, in the high-speed running range, the rack stroke with respect to the steering angle α of the steering wheel is set smaller than that of the conventional steering device, so that a more insensitive (dull) characteristic can be realized. Therefore, the relationship between the practical steering wheel angle and the traveling speed can be made flat characteristics.
[0030]
Subsequently, the control device 40 will be described with reference to FIG.
The control device 40 includes a target eccentricity determination unit 41, a deviation calculation unit 42, a PID control unit 43, a PWM control signal generation unit 44, a gate drive circuit unit 45, a motor drive circuit 46, and a displacement sensor failure detection unit 47.
[0031]
The target eccentricity determining unit 41 includes storage means such as a ROM, and stores data (conversion table) corresponding to the vehicle speed signal Va and the target eccentricity set in advance based on experimental values or design values. Then, the target eccentricity determining unit 41 reads the corresponding target eccentricity using the vehicle speed signal Va as an address, and outputs the target eccentricity signal 41a to the deviation calculating unit 42. Here, the target eccentric amount is associated with the vehicle speed signal Va at a low speed where the road surface reaction force is large, and a large value at a high speed in order to secure stability during traveling. Corresponding. The vehicle speed signal Va input to the target eccentricity determination unit 41 is obtained by converting the vehicle speed signal Va input from the vehicle speed sensor VS via an FV converter (not shown) from an analog signal to a digital signal.
[0032]
The deviation calculator 42 is configured to calculate the target eccentricity signal 41a and the displacement sensor 33.Amount of eccentricity of the input shaft 11 obtained based on the eccentricity amount signal 33a (corresponding to the actual steering angle ratio)And outputs a deviation signal 42a. The PID control unit 43 subjects the deviation signal 42a to processing such as proportionality, integration, and differentiation, and generates a drive control signal 43a indicating the direction and current value of the current supplied to the DC motor 27 in order to reduce the deviation to zero. Generate and output.
[0033]
The PWM signal generation section 44 outputs a PWM (pulse width modulation) signal 44a for performing the PWM operation of the DC motor 27 to the gate drive circuit section 45 based on the drive control signal 43a. The gate drive circuit unit 45 outputs to the motor drive circuit 46 a motor drive signal 45a for driving the gate of each FET of the motor drive circuit 46 based on the PWM signal 44a to switch the FETs. The motor drive circuit 46 is configured by a bridge circuit including four FET switching elements, is connected to the battery power supply BAT, and supplies a current to the DC motor 27 to drive the DC motor 27.
[0034]
The displacement sensor failure detection unit 47 is calculated based on the eccentricity amount signal 33a output from the displacement sensor 33.Actual displacement of the support member 14And the supporting member 14 determined based on the current ripple signal 50a output from the current ripple detecting means 50.And the estimated displacement of(Not shown). AndActual displacement of the support member 14And support member 14And the estimated displacement ofAnd when a predetermined condition described later is satisfied, a prohibition signal 47a for prohibiting the output of the motor drive signal 45a output from the gate drive circuit unit 45 is output.
[0035]
The current ripple detecting means 50 connected to the DC motor 27 has a current sensor 51, a first filter 53, a second filter 54, and a comparator 55, as shown in FIG. The current sensor 51 is disposed in the DC motor 27 and detects a current ripple in the DC motor 27. The current ripple detected by the current sensor 51 is supplied to the first filter 53 and the second filter 54. The first filter 53 and the second filter 54 are filters having different frequency cutoff characteristics. By passing through the first filter 53, for example, a waveform H1 shown in FIG. 9 can be obtained, and by passing through the second filter 54, for example, a waveform H2 shown in FIG. 9 can be obtained. The waveforms obtained by passing through the first filter 53 and the second filter 54 are output to a comparator 55, and the comparator 55 compares the respective waveforms H1 and H2. As a result, a pulse wave having a waveform H3 shown in FIG. 9 can be obtained. The peak of the waveform H3, which is the pulse wave, is the current ripple. The waveform H3 obtained by the comparator 55 is output as a current ripple signal 50a to the displacement sensor failure detection unit 47 in the control device 40.
[0036]
Subsequently, control of the variable steering angle ratio device 10 in the variable steering angle ratio steering device 1 according to the present embodiment will be described with reference to FIGS. 7 and 8.
The control device 40 sets the target steering angle ratio of the variable steering angle ratio device 10 based on the vehicle speed signal Va from the vehicle speed sensor VS.
[0037]
The target eccentricity determining unit 41 of the control device 40 reads out the corresponding target eccentricity using the vehicle speed signal Va from the vehicle speed sensor VS as an address, and sets the target eccentricity signal 41a. From the target eccentricity determining unit 41, a target eccentricity signal 41a is output to the deviation calculating unit 42. Also,Actual displacement of the support member 14Is detected by the displacement sensor 33, and the displacement sensor 33 outputs an eccentricity amount signal 33 a to the deviation calculator 42.
[0038]
The deviation calculator 42 is configured to calculate the target eccentricity signal 41a and the displacement sensor 33.Output fromA deviation from the eccentricity amount signal (corresponding to the actual steering angle ratio) 33a is obtained, and a deviation signal 42a is output to the PID control unit 43. The PID control unit 43 subjects the deviation signal 42a to processing such as proportionality, integration, and differentiation, and generates a drive control signal 43a indicating the direction and current value of the current supplied to the DC motor 27 to reduce the deviation to zero. It is generated and output to the PWM signal generator 44. The PWM signal generation unit 44 generates a PWM (pulse width modulation) signal 44a for performing the PWM operation of the DC motor 27 based on the drive control signal 43a, and outputs the PWM signal 44a to the gate drive circuit unit 45.
[0039]
The gate drive circuit unit 45 generates a motor drive signal 45 a for switching driving the gate of each FET of the motor drive circuit 46 based on the PWM signal 44 a output from the PWM signal generation unit 44. At this time, when the prohibition signal 47a is not output from the displacement sensor failure detection unit 47, the motor drive signal 45a is output to the motor drive circuit 46. On the other hand, when the prohibition signal 47a is output from the displacement sensor failure detection unit 47, the output of the motor drive signal 45a is stopped.
[0040]
The drive of the DC motor 27 in the variable steering angle ratio device 10 supplied with the current from the motor drive circuit 46 is controlled according to the direction and magnitude of the current. Here, when the DC motor 27 is driven, the support member 14 rotates, and the displacement sensor 33 (FIG. 4) provided on a pin 32 protruding from the upper surface of the support member 14 causes the support member 14 to rotate.Actual displacement(Corresponding to the actual steering angle ratio) is detected. Then, the displacement sensor 33Actual displacementIs output to the deviation calculation unit 42 and the displacement sensor failure detection unit 47 in the control device 40 as the eccentricity amount signal 33a. As described above, the deviation calculator 42 calculates the deviation between the target eccentricity signal 41a and the eccentricity signal 33a, and performs so-called feedback control.
[0041]
The displacement sensor failure detection unit 47 obtains a deviation between the output eccentricity signal 33a and a unit time as its detection time, for example, the eccentricity signal 33a output 500 ms before.Actual displacement of the support member 14Is calculated.
[0042]
On the other hand, in addition to the eccentricity amount signal 33a, a current ripple signal 50a from the current ripple detecting means 50 is output to the displacement sensor failure detecting section 47. The displacement sensor failure detection unit 47 measures the number of current ripples based on the current ripple signal 50a output from the current ripple detection unit 50, and determines the number of current ripples based on the number of current ripples.Estimated displacement ofSeeking.
[0043]
From the number of current ripples,Estimated displacement ofWill be described. First, a current ripple signal 50a is generated by the current ripple detecting means 50 in order to count the number of current ripples. The current ripple signal 50a is generated as follows. As shown in FIG. 8, the value of the current flowing through the DC motor 27 is detected by the current sensor 51. The current value detected by the current sensor 51 is output to the first filter 53 and the second filter 54 having different frequency cutoff characteristics. In the first filter 53 and the second filter 54, the current values output from the operational amplifiers are passed, respectively, so as to be shaped like, for example, waveforms H1 and H2 shown in FIG. The first filter 53 and the second filter 54 output the shaped waveforms H1 and H2 to the comparator 55. In the comparator 55, these waveforms H1 and H2 are compared and shaped to obtain, for example, a pulse waveform H3 shown in FIG. The peak portion of the waveform H3 is a portion where a current ripple is generated. Then, it outputs the waveform H3 as a current ripple signal 50a to the displacement sensor failure detection unit 47 in the control device 40.
[0044]
The DC motor 27 in the variable steering angle ratio device 10 has, for example, two brushes 27A, 27A and eight commutators 27B, 27B,... As schematically shown in FIG. In the DC motor 27, as shown in FIG. 10A, no current ripple occurs when the brush 27A is completely in contact with the single commutator 27B. On the other hand, as shown in FIG. 10B, when the brush 27A separates from the commutator 27B and starts to contact the next commutator 27B, the armature resistance changes and a current ripple occurs. Therefore, when the DC motor 27 makes one rotation, the same number of current ripples as the number of commutators, eight times in the present embodiment, are generated.
[0045]
Therefore, the displacement sensor failure detection unit 47 counts the number of peaks in the waveform H3 of the current ripple signal 50a per unit time as the above-described detection time, for example, 500 ms, in other words, the number of current ripples. By counting the number of peaks (current ripples) of the waveform H3 per 500 ms and dividing by 8 which is the number of commutators 27B, 27B,..., The rotation speed of the DC motor 27 is calculated.
[0046]
From the rotation speed of the DC motor 27 thus obtained,Estimated displacement of support member 14Ask for. Now, when the DC motor 27 rotates, the support member 14 rotates via the worm 28 and the partial worm wheel 25, and the pin 32 is eccentric. For this reason, the displacement sensor failure detection unit 47 determines the rotational speed of the DC motor 27 determined by the number of teeth of the worm 28 and the partial worm wheel 25 and the like.Estimated displacement of support member 14Is provided. Then, by referring to a table (not shown), the rotation speed of the DC motor 27 calculated from the current ripple signal 50a is referred to.Estimated displacement of support member 14Is required.
[0047]
In the displacement sensor failure detection unit 47, the displacement is obtained from the eccentricity amount signal 33a output from the displacement sensor 33.Actual displacement of the support member 14And the support member 14 obtained from the current ripple signal 50a output from the current ripple detection means 50And the estimated displacement ofAre compared by comparing means (not shown). as a result,The actual displacement amount and the estimated displacement amount of the support member 14If the values match, the displacement sensor 33 has not failed and is working normally. Therefore, the motor drive signal 45a is output from the gate drive circuit unit 45 to the motor drive circuit 46 as usual without outputting the inhibition signal 47a from the displacement sensor failure detection unit 47. In addition,The actual displacement amount and the estimated displacement amount of the support member 14In the case where the two match, the difference includes a deviation within an appropriately set error range, in addition to the case where the two completely match.
[0048]
On the other hand, it was detected by the displacement sensor 33Actual displacement of the support member 14And detected by the current ripple detecting means 50Estimated displacement of the support member 14 andAre different from each other, and if the eccentricity amount signal 33a from the displacement sensor 33 does not change while the pulse waveform H3 is input as the current ripple signal 50a from the current ripple detecting means 50, the displacement sensor It is detected that 33 has failed. When the displacement sensor 33 breaks down, the driver feels uncomfortable in driving. Further, since the feedback control is performed, the support member 14 is inadvertently rotated in one direction, and there is a concern that a stopper (not shown) may be damaged. Therefore, when the displacement sensor failure detection unit 47 detects a failure of the displacement sensor 33, the prohibition signal 47a is output to the gate drive circuit unit 45, and the output of the motor drive signal 45a from the gate drive circuit unit 45 is output. Stop. By stopping the output of the motor drive signal 45a from the gate drive circuit unit 45 and stopping the drive of the DC motor 27, the variable steering angle ratio device 10 is stopped. For this reason, the uncomfortable feeling felt by the driver can be reduced, and the breakage of the stopper can be prevented.
[0049]
The preferred embodiment of the present invention has been described above, but the present invention is not limited to the above embodiment. For example, the current ripple of a DC motor varies depending on various conditions such as load current, power supply voltage, and motor speed. For this reason, in order to improve the detectability and reliability of the speed, when detecting the rotation speed of the DC motor, a mode such as a motor drive voltage may be added to the speed determination condition.
[0050]
When detecting the current of the DC motor, a plurality of pulse averaging processes may be performed to calculate the rotational speed of the DC motor with high reliability. Further, in order to surely prevent the breakage of the stopper, taking into account the time from when the displacement sensor breaks down to when it hits the stopper, for example, a 50% allowance is set for the detection time. In other words, the detection time can be set to 250 ms.
Further, when a failure of the displacement sensor is detected, a warning light may be provided on an instrument panel (not shown), for example, and the warning light may be turned on to prompt repair.
[0051]
【The invention's effect】
As described above, according to the present invention, when a failure occurs in the steering angle ratio sensor that detects the steering angle ratio of the variable steering angle ratio device in the variable steering angle ratio steering device,With high detection accuracyA failure of the steering angle ratio sensor can be detected.
[Brief description of the drawings]
FIG. 1 is an overall configuration diagram of a variable steering angle ratio steering device according to the present embodiment.
FIG. 2 is a front sectional view of the variable steering angle ratio device according to the embodiment.
FIG. 3 is an exploded perspective view of a shaft portion of the variable steering angle ratio device according to the present embodiment.
FIG. 4 is a sectional view taken along line AA of FIG. 2;
FIG. 5 is an explanatory diagram illustrating an operation principle of the variable steering angle ratio steering device according to the present embodiment.
FIG. 6 is an input / output angle characteristic diagram showing a steering angle ratio characteristic of the variable steering angle ratio steering device according to the present embodiment.
FIG. 7 is a block diagram of a control device of the variable steering angle ratio steering device according to the present embodiment.
FIG. 8 is a block diagram of a current ripple detecting unit according to the present embodiment.
FIG. 9 shows an example of a current ripple generated by a DC motor and a current obtained by shaping the current ripple.
It is a graph.
10A and 10B are schematic diagrams of a DC motor. FIG. 10A shows a state in which one brush is in contact with one commutator, and FIG. 10B is a state in which two commutators are in contact with one brush. Shows the status of
[Explanation of symbols]
1 Variable steering angle ratio steering device
2 Steering wheel (handle)
9 Steering wheels
10 Variable steering angle ratio device
27 DC motor (motor)
33 displacement sensor (steering angle ratio sensor)
33a Eccentricity signal (steering angle ratio signal)
40 control device
47 Displacement sensor failure detector
50 Current ripple detection means
50a Current ripple signal (current signal)

Claims (1)

A variable steering system in which a variable steering angle ratio device capable of changing the ratio of the steering angle of the steered wheel to the steering wheel is provided in a steering system from the steering wheel to the steered wheels, and a control device that controls the variable steering angle ratio device is provided. In the steering angle ratio steering device,
The variable steering angle ratio device includes an electric motor for changing a ratio of a steering angle of the steered wheels to the steering wheel, a steering angle ratio changing member that is driven by the electric motor to be displaced, and a steering angle ratio changing member. A steering angle ratio sensor that detects a displacement amount as a ratio of a steering angle of the steered wheels to the steering wheel,
The control device detects a rotation speed of the electric motor by a current ripple signal detected from a current signal output from the electric motor , and estimates an amount of displacement of the steering angle ratio changing member obtained from the rotation speed, and A variable steering angle ratio steering device, which determines whether or not the steering angle ratio sensor has failed by comparing the actual displacement amount of the steering angle ratio changing member output from the angle ratio sensor. .

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