JP3681557B2 - Vehicle steering device - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention provides a variable steering angle ratio mechanism that can change a steering angle ratio (steering wheel angle / steering angle of a steering wheel) in accordance with the vehicle speed, and an auxiliary steering force that acts on the steering system in accordance with the steering torque. BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a vehicle steering apparatus including an electric power steering apparatus that reduces steering force, and more particularly to a vehicle steering apparatus that changes an auxiliary steering force and notifies a driver when an abnormality occurs in a variable steering angle ratio mechanism. .
[0002]
[Prior art]
As disclosed in Japanese Patent Application Laid-Open No. 62-46772, a conventional automobile steering device includes a transmission ratio variable means for changing a wheel steering angle with respect to a steering angle of a steering wheel, and an operating state for detecting an operating state of the automobile. The apparatus includes a detection means and a controller that controls the transmission ratio variable means in response to a signal from the driving state detection means. A power steering mechanism that generates a steering assist force is provided and the steering speed of the steering wheel is determined. A response device that changes the response force to steering the steering wheel is provided.
[0003]
The power steering mechanism of the automobile steering device disclosed in Japanese Patent Application Laid-Open No. 62-46772 is constituted by a hydraulic power steering mechanism.
[0004]
In the automobile steering device disclosed in Japanese Patent Application Laid-Open No. Sho 62-46772, when the steering wheel is steered and the wheel is steered, the power steering mechanism is operated in accordance with the steering of the steering wheel, and the steering force is assisted while the wheel is moved. The controller which is steered and receives the signal from the driving state detecting means controls the transmission ratio variable means and variably controls the transmission ratio of the wheel steering angle to the steering angle.
[0005]
In the automobile steering device disclosed in Japanese Patent Application Laid-Open No. 62-46772, the response force to the steering by the response device is variably controlled according to the steering speed of the steering wheel, and the steering speed of the steering wheel is increased with the variable control of the response force. As the response force increases, the steering speed is substantially reduced even when the steering wheel is quickly steered, and a sufficient flow of pressure oil to the hydraulic power steering mechanism is ensured. This effectively avoids the wheel turning delay.
[0006]
[Problems to be solved by the invention]
The steering system for an automobile disclosed in Japanese Patent Application Laid-Open No. 62-46772 is provided with a response device, which effectively avoids a wheel turning delay due to insufficient pressure oil flow, but there is an abnormality in the transmission ratio variable means. If the actual transmission ratio (actual steering angle ratio) does not match the target transmission ratio (target steering angle ratio), the wheel steering angle may be too large or too small in response to steering. There is a problem that steering feeling is lowered.
[0007]
Also, when an abnormality occurs in the transmission ratio variable means, the driver will recognize the deviation of the transmission ratio (steering angle ratio) from the change in the vehicle behavior, but for the beginner to recognize the change in the vehicle behavior accurately. In many cases, it is difficult to detect a shift in transmission ratio (steering angle ratio).
[0008]
The present invention has been made to solve such problems, and an object of the present invention is to provide a vehicle steering apparatus capable of transmitting an abnormality of a variable steering angle ratio mechanism to a driver as a change in auxiliary steering force.
[0009]
[Means for Solving the Problems]
In order to solve the above problems, a vehicle steering apparatus according to the present invention comprises a control means. However, even if the set time elapses after operating the handle When the actual steering angle ratio of the variable steering angle ratio mechanism does not match the target steering angle ratio Based on a timer means for outputting a timer signal representing an abnormality to the timer signal representing an abnormality supplied from the timer means, When the variable rudder angle ratio mechanism is abnormal To Steering force change means for changing the steering assist force obtained from the rudder torque signal When It is provided with.
[0010]
In the vehicle steering apparatus according to the present invention, the control means is provided with the steering force changing means for changing the steering assist force obtained from the steering torque signal when the variable steering angle ratio mechanism is abnormal. If the rudder angle ratio does not match the target rudder angle ratio, it is determined that the variable rudder angle ratio mechanism is abnormal, and the steering assist force is changed based on the deviation between the target rudder angle ratio and the actual rudder angle ratio to steer the driver. It can be perceived as a reaction force change.
[0011]
Further, the steering force changing means according to the present invention comprises period changing means for changing a duty ratio of a PWM signal for driving the motor with PWM (Pulse Width Modulation) at a constant period, and changes the steering assist force. To do.
[0012]
Since the steering force changing means according to the present invention includes the period changing means for changing the duty ratio of the PWM signal for driving the motor by PWM (Pulse Width Modulation) at a constant period, the abnormality of the variable steering angle ratio mechanism is vibrated. The driver can perceive the change in the steering reaction force.
[0013]
DETAILED DESCRIPTION OF THE INVENTION
Embodiments of the present invention will be described below with reference to the accompanying drawings.
The present invention provides a variable steering angle ratio mechanism that varies a steering angle ratio (C = β / α), which is a ratio of a steering angle (α) of a steering wheel and a steering angle (β) of a wheel, and a steering assist to the steering system. And an electric power steering device that reduces the steering force of the driver by applying a force. When the variable steering angle ratio mechanism is abnormal, the auxiliary steering force of the electric power steering device is changed to correct the steering error of the variable steering angle ratio mechanism. The change in force is transmitted to the driver, and appropriate steering is executed.
[0014]
FIG. 1 is a basic configuration diagram of a vehicle steering apparatus according to an embodiment of the present invention.
In FIG. 1, a vehicle steering device 1 includes a variable steering angle ratio mechanism 2 and an electric power steering device 3.
The vehicle steering apparatus 1 includes a handle 4, a steering shaft 5, a universal joint 6, an input shaft 7 and an output shaft (pinion) 8 of the variable steering ratio mechanism 2, a rack shaft 9 that engages with the pinion of the output shaft 8, and steering A wheel 10 is provided.
[0015]
Further, the vehicle steering apparatus 1 constitutes a sensor system of the variable steering ratio mechanism 2 and includes a vehicle speed sensor 11 that detects the vehicle speed Y of the vehicle and a steering angle ratio sensor 12 that detects the actual steering angle ratio CJ.
Further, the vehicle steering apparatus 1 includes a steering torque sensor 13 that constitutes a sensor system of the electric power steering apparatus 3.
The vehicle speed sensor 11 also constitutes a sensor system of the electric power steering device 3.
[0016]
The vehicle steering apparatus 1 includes a steering angle ratio control means 14 that is a control system of the variable steering ratio mechanism 2 and a control means 15 that is a control system of the electric power steering apparatus 3.
The vehicle steering apparatus 1 includes a steering angle ratio electric motor M2 that is a drive system of the variable steering ratio mechanism 2 and an electric motor M1 that is a drive system of the electric power steering apparatus 3.
[0017]
When the driver operates the handle 4, a rotation angle (twist) according to the steering angle is transmitted to the input shaft 7 of the variable steering ratio mechanism 2 via the steering shaft 5 and the universal joint 6.
[0018]
The outer periphery of the input shaft 7 is provided with a movable housing (not shown) that rotates at the center (O) while decentering the center (A) of the input shaft 7, and this movable housing is connected to the steering angle ratio motor M2. It is rotated by a worm gear (not shown).
The displacement amount of the movable housing rotated by the worm gear is detected by the steering angle ratio sensor 12, and an electric signal corresponding to this displacement amount is supplied to the steering angle ratio control means 14 as the actual steering angle ratio signal CJ of the variable steering angle ratio mechanism 2. Supply.
Further, an electric signal corresponding to the vehicle speed detected by the vehicle speed sensor 11 is supplied as a vehicle speed signal V to the steering angle ratio control means 14.
[0019]
The steering angle ratio control means 14 generates a target steering angle ratio signal (CS) corresponding to the vehicle speed signal V supplied from the vehicle speed sensor 11, and the target steering angle ratio signal (CS) and the actual steering angle ratio signal CJ The motor voltage VM2 is controlled on the basis of the deviation (CS-CJ), the steering angle ratio motor M2 is PWM driven, the movable housing is rotated via the worm gear, the actual steering angle ratio signal CJ and the target steering angle ratio signal Control (CS) to be equal.
[0020]
The target rudder angle ratio signal (CS) defines a target ratio of the steered angle (β) of the steered wheels 10 with respect to the steering angle (α) of the steering wheel 4. For example, the target rudder angle ratio signal When the steering angle (α) is set to 60 degrees in a state where (CS) is set to 0.5, the turning angle (β) is a target value that is set to 30 degrees.
[0021]
The actual steering angle ratio signal (CJ) is a value that is actually embodied by the variable steering ratio mechanism 2 when the target steering angle ratio signal (CS) is set by the vehicle speed signal V. This is the ratio of the actual turning angle (β) when the steering wheel 10 is steered by converting the rotational motion of the pinion of the output shaft 8 to the linear motion of the rack shaft 9 with respect to the actual steering angle (α).
[0022]
The principle of the variable steering ratio mechanism 2 will be described with reference to FIG.
FIG. 2 is an explanatory view of the operating principle of the variable steering ratio mechanism according to the present invention.
In FIG. 2, point A is the rotation center of the input shaft 7, and as already described, by driving the steering angle ratio motor M2 based on the target steering angle ratio signal (CS) corresponding to the vehicle speed signal V, The movable housing can be rotated and moved in the X1 direction or the X2 direction.
[0023]
Point B is the center of rotation of the output shaft 8 and point C is eccentric from the point B by a certain distance. If the relationship between point C and point B is compared to a stone mill, point C is the action point and point B is the millstone. Become the center.
Since the rotation of point A is transmitted to point C, if the distance from point B to point A is a and the distance from point B to point C is b, the relationship between steering angle α and pinion rotation angle γ is expressed.
The turning angle β = K * γ (K: constant).
[0024]
[Expression 1]
b * sinγ = (b * cosγ−a) * tanα
[0025]
FIG. 2 shows the case in which the handle 4 is rotated in the clockwise direction (right steering), but the same relationship exists in the case of the counterclockwise direction (left steering).
The specific configuration of the variable rudder angle ratio mechanism 2 is known from Japanese Patent Application Laid-Open No. 7-257406, and will not be described in detail.
[0026]
FIG. 3 is a characteristic diagram of the rotation angle γ of the steering angle α-pinion of the variable steering ratio mechanism according to the present invention.
In FIG. 3, the rotation angle γ of the pinion with respect to the steering angle α is, for example, the ratio of the rotation angle γ of the pinion to the steering angle α at a distance a = aO (= 0) from the point B to the point A when the vehicle speed V is low. Is 1.
[0027]
When the vehicle speed is in the middle vehicle speed range, the ratio of the pinion rotation angle γ to the steering angle α (steering angle ratio) is a value smaller than 1 at a distance a = a1 from the point B to the point A.
[0028]
Further, in the high vehicle speed region, the ratio of the pinion rotation angle γ to the steering angle α (the turning angle ratio) is a value smaller than 1 at a distance a = a 2 from the point B to the point A.
[0029]
Thus, the variable steering ratio mechanism 2 sets the pinion rotation angle γ (as a result, the turning angle β) with respect to the steering angle α to be smaller as the vehicle speed changes from a low vehicle speed to a high vehicle speed. As a result, stable steering characteristics can be obtained at high vehicle speeds.
[0030]
The variable steering ratio mechanism 2 sets the rotation angle γ of the pinion with respect to the steering angle α with the vehicle speed as a parameter in a one-to-one relationship, but in some cases, the steering force when the driver steers the handle 4 increases. There is.
In order to reduce the steering force of the driver, the electric power steering device 3 is required.
[0031]
Returning to FIG. 1, the electric power steering device 3 detects the steering torque of the handle 4 by the steering torque sensor 13, and supplies the steering torque signal T converted into an electric signal to the control means 15.
Further, the vehicle speed sensor 11 detects the vehicle speed of the vehicle and supplies the vehicle speed signal V converted into an electric signal to the control means 15.
[0032]
The control means 15 generates a target torque signal (IT) based on the steering torque signal T using the vehicle speed signal V as a parameter, and PWM-drives the motor M1 with the motor voltage VM1 corresponding to the target torque signal (IT).
[0033]
By applying an auxiliary steering force to the rack shaft with the motor torque of the motor M1, the steering force of the driver is reduced.
[0034]
When an abnormality occurs in the variable steering ratio mechanism 2 for any reason, the deviation Δ (= CS−CJ) between the target steering angle ratio signal (CS) and the actual steering angle ratio signal CJ does not become zero. Then, the deviation Δ is taken into the control means 15 of the electric power steering device 3, and the duty ratio of the motor voltage VM1 (PWM) for driving the electric motor M1 is changed by the control means 15 and variable to the driver by changing the steering assist force. An abnormality of the steering ratio mechanism 2 is transmitted by a change in the steering reaction force.
[0035]
FIG. 4 is a block diagram of a main part of an embodiment of a vehicle steering apparatus according to the present invention.
In FIG. 4, the vehicle steering apparatus 1 includes a variable steering angle ratio mechanism 2 and an electric power steering apparatus 3.
[0036]
First, the variable steering angle ratio mechanism 2 will be described.
The variable steering angle ratio mechanism 2 includes a vehicle speed sensor 11, a steering angle ratio sensor 12, a steering angle ratio control means 14, and a steering angle ratio motor M2.
The vehicle speed sensor 11 is constituted by a vehicle speedometer or the like, converts the vehicle speed into an electrical signal, and supplies the converted signal to the steering angle ratio control means 14 as the vehicle speed signal V.
[0037]
The steering angle ratio sensor 12 is composed of a displacement sensor or the like, detects the displacement amount TM of the variable housing that rotates with the rotation of the worm gear of the variable steering angle ratio mechanism 2 by the steering angle ratio motor M2, and determines the displacement amount. It converts into an electric signal, and supplies it to the deviation calculating means 22 of the steering angle ratio control means 14 as the actual steering angle ratio signal CJ.
[0038]
The steering angle ratio control means 14 is composed of various calculation means, processing means, memory, analog circuit, etc. based on a microprocessor, and includes target steering angle ratio setting means 21, deviation calculation means 22, steering angle ratio drive control means 23, A steering angle ratio motor driving means 24 is provided.
[0039]
The target rudder angle ratio setting means 21 is constituted by a memory such as a ROM, and stores a vehicle speed signal V-target rudder angle ratio CS data shown in FIG. 14 determined in advance based on a design value or an experimental value, and a vehicle speed sensor. When the vehicle speed signal V is supplied from 11, the corresponding target steering angle ratio CS data is read, and the target steering angle ratio signal CS is supplied to the deviation calculating means 22.
[0040]
The target steering angle ratio signal CS represents the ratio (βS / α) of the target steering angle βS of the steered wheel 10 to the steering angle α of the steering wheel 4 shown in FIG. 1, and as shown in FIG. It sets so that it may decrease as V becomes large.
Further, the actual steering angle ratio signal CJ is driven by the variable steering angle ratio mechanism 2 by the target steering angle ratio signal CS, and the ratio of the actual turning angle βJ of the steered wheel 10 to the steering angle α of the steering wheel 4 (βJ / α ).
[0041]
The deviation calculation means 22 has a subtraction function, and a deviation ΔC (= between the target steering angle ratio signal CS supplied from the target steering angle ratio setting means 21 and the actual steering angle ratio signal CJ supplied from the steering angle ratio sensor 12. CS−CJ) is calculated, and the deviation signal ΔC is supplied to the steering angle ratio drive control means 23 and the control means 15 (time measuring means 28 and steering force changing means 29) of the electric power steering apparatus 3.
[0042]
The steering angle ratio drive control means 23 includes a PID (proportional / integral / differential) controller, a control signal generating means for generating a hybrid signal of a PWM signal, an on signal, and an off signal, and is supplied from the deviation calculating means 22. A drive control signal V02 is supplied to the steering angle ratio motor drive means 24 based on the deviation signal ΔC.
[0043]
The steering angle ratio motor driving means 24 is composed of four FETs (field effect transistors) or IGBTs (insulated gate / bipolar transistors) having a relatively small power capacity, and is supplied from the steering angle ratio drive control means 23. On the basis of the drive control signal V02, a PWM (pulse width modulation) motor voltage VM2 is generated to drive the steering angle ratio motor M2 in PWM, and the steering angle ratio motor M2 is rotated forward or reverse.
[0044]
The steering angle ratio control means 14 forms a negative feedback (NFB) control by supplying the actual steering angle ratio signal CJ from the steering angle ratio sensor 12 to the deviation calculating means 22.
[0045]
By this negative feedback (NFB) control, the variable steering angle ratio mechanism 2 allows the deviation ΔC (= CS−CJ) between the target steering angle ratio signal CS and the actual steering angle ratio signal CJ to be zero in a short time. The actual steering angle ratio signal CJ coincides with the target steering angle ratio signal CS (CJ = CS).
For example, when the steering angle ratio is set to 0.5, when the handle 4 shown in FIG. 1 is rotated 30 degrees (steering angle 30 °), the steered wheel 10 also follows 30 degrees (steering angle 30 °). ) It will rotate.
[0046]
Next, the electric power steering device 3 will be described.
The electric power steering device 3 includes a vehicle speed sensor 11, a steering torque sensor 13, a control means 15, and an electric motor M1.
The steering torque sensor 13 is constituted by a displacement sensor using a differential transformer or the like, converts the steering torque applied to the handle 4 shown in FIG. 1 into an electric signal, and supplies the steering torque signal T to the control means 15.
Further, the vehicle speed sensor 11 supplies a vehicle speed signal V to the control means 15.
[0047]
The motor torque detection means 45 generates a corresponding motor torque signal IMT from the motor current IM flowing in the motor M1, and supplies the motor torque signal IMT to the control means 15.
[0048]
The control means 15 comprises various calculation means based on a microprocessor, processing means, memory, analog circuit, etc., and includes target torque signal setting means 25, deviation calculation means 46, drive control means 26, electric motor drive means 27, timekeeping. Means 28 and steering force changing means 29 are provided.
[0049]
The target torque signal setting means 25 is constituted by a memory such as a ROM, and stores steering torque signal T-target torque signal IT data using the vehicle speed signal V shown in FIG. 13 as a parameter determined in advance based on design values and experimental values. When the steering torque signal T is supplied from the steering torque sensor 13 and the vehicle speed signal V is supplied from the vehicle speed sensor 11, the corresponding target torque signal IT data is read and the target torque signal IT is supplied to the deviation calculating means 46.
[0050]
The deviation calculating means 46 has a subtraction function, and calculates a deviation ΔI (= IT−IMT) between the target torque signal IT supplied from the target torque signal setting means 25 and the motor torque signal IMT supplied from the motor torque detecting means 45. The deviation signal ΔI is calculated and supplied to the drive control means 26.
[0051]
The drive control means 26 comprises a PID (proportional / integral / differential) controller, a motor control signal generating means for generating a hybrid signal of a PWM signal, an ON signal, and an OFF signal, and the deviation signal ΔI is supplied from the deviation calculating means 46. Then, PID (proportional / integral / differential) control is performed on the deviation signal ΔI, and a motor control signal VO1 which is a mixed signal of a PWM signal, an on signal and an off signal is supplied to the motor driving means 27.
[0052]
The drive control means 26 includes a PWM signal generation means for generating a PWM signal in the motor control signal generation means, and changes the duty of the PWM signal based on the duty ratio coefficient KD supplied from the steering force change means 29. The changed duty PWM signal is supplied to the motor drive means 27 as the motor control signal VO1.
[0053]
FIG. 5 is a block diagram showing the principal part of one embodiment of the drive control means according to the present invention.
In FIG. 5, the drive control means 26 includes a PID controller 31 and an electric motor control signal generation means 32.
When the deviation signal ΔI is supplied from the deviation calculating means 46, the PID controller 31 performs PID (proportional / integral / derivative) control on the deviation signal ΔI and provides the PID control signal IH to the motor control signal generating means 32.
[0054]
The motor control signal generating means 32 includes an on / off signal generating means 33 and a PWM signal generating means 34.
The on / off signal generating means 33 generates an on signal VON (for example, H level) and an off signal VOF (for example, L level) based on the PID control signal IH supplied from the PID controller 31, and the motor control signal VO1. Is supplied to the motor drive means 27.
[0055]
The PWM signal generation unit 34 includes a duty ratio setting unit, a multiplication unit, and the like.
The duty ratio setting means determines a duty ratio (DH) corresponding to the PID control signal IH supplied from the PID controller 31, and supplies the determined duty ratio (DH) to the multiplication means.
The multiplying means determines a duty ratio (DHO) obtained by multiplying the duty ratio coefficient KD supplied from the steering force changing means 29 and the duty ratio (DH) (KD * DH), and outputs the PWM signal VPWM of the duty ratio (DHO). The electric motor control signal VO1 is supplied to the electric motor driving means 27.
[0056]
The motor driving means 27 is composed of four FETs (field effect transistors) or IGBTs (insulated gate / bipolar transistors) having a large power capacity, and is based on a drive control signal V01 supplied from the drive control means 26. A motor voltage VM1 of PWM (pulse width modulation) is generated to drive the motor M1 in PWM, and the motor M1 is rotated forward or backward.
[0057]
The time measuring means 28 is constituted by a timer means, and starts measuring time using a deviation signal ΔC (= CS−CJ) supplied from the deviation calculating means 22 of the steering angle ratio control means 14 as a trigger, and the deviation signal ΔC is preset. When continuing beyond the set time TK, for example, an H level timer signal TO is supplied to the steering force changing means 29.
The time counting means 28 supplies the L level timer signal TO to the steering force changing means 29 when the duration of the deviation signal ΔC is equal to or shorter than the set time TK.
[0058]
In the set time TK, the deviation ΔC between the target steering angle ratio signal CS and the actual steering angle ratio signal CJ becomes 0 after the steering wheel 4 shown in FIG. 1 is operated when the variable steering angle ratio mechanism 2 is normal. Set the time slightly longer than the previous time.
[0059]
The deviation signal ΔC (= CS−CJ) is always 0 after the set time TK has elapsed when the variable steering angle ratio mechanism 2 is normal.
On the other hand, the deviation signal ΔC (= CS−CJ) is positive (ΔC> 0) because the deviation ΔC from the actual steering angle ratio signal CJ does not become zero when an abnormality occurs in the variable steering angle ratio mechanism 2. Or it becomes a finite value of minus (ΔC <0), and the state of this finite value continues beyond the set time TK.
[0060]
The steering force changing means 29 includes an absolute value converting means, a signal generating means, a coefficient generating means, etc., and is supplied from the timer signal TO supplied from the time measuring means 28 and the deviation calculating means 22 of the steering angle ratio control means 14. Based on the absolute value | ΔC | of the deviation signal ΔC (= CS−CJ), which is the deviation ΔC between the target steering angle ratio signal CS and the actual steering angle ratio signal CJ, the duty ratio coefficient KD (= 1) of the constant 1; A duty ratio coefficient KD (= KD1) that changes at a constant period, a duty ratio coefficient KD (= KD2) that exceeds a constant 1, or a duty ratio coefficient KD (= KD3) that is less than a constant 1 is driven by a drive control means 26 (PWM signal generating means) 34 multiplication means).
[0061]
When the H level timer signal TO is supplied, the steering force changing means 29 takes in a finite value deviation signal ΔC (= CS−CJ), and a duty ratio coefficient corresponding to the absolute value | ΔC | of the deviation signal ΔC. KD1, KD2, and KD3 are supplied to the drive control means 26 (multiplication means of the PWM signal generation means 34).
Further, when the L level timer signal TO is supplied, the steering force changing means 29 supplies the constant 1 duty ratio coefficient KD to the drive control means 26 (multiplication means of the PWM signal generating means 34).
[0062]
FIG. 6 is a block diagram of a main part of one embodiment of the steering force changing means according to the present invention.
In FIG. 6, the steering force changing means 29 includes a period changing means 35 and a coefficient generating means 36.
[0063]
The period changing unit 35 includes an absolute value converting unit and a voltage (V) -frequency (f) converting unit, and the deviation signal ΔC (= CS−CJ) having a plus (+) or minus (−) polarity is an absolute value. | ΔC | is converted into a signal having a frequency fO corresponding to the absolute value | ΔC | (voltage value), and the frequency signal fO is provided to the coefficient generating means 36.
[0064]
The coefficient generating means 36 includes level shift means and coefficient output means, and has a constant period (TX = TX =) with a constant 1 as a reference for the frequency signal fO supplied from the period changing means 35. A duty ratio coefficient KD1 that changes (eg, sine wave) at 1 / f0 is output.
[0065]
FIG. 7 is a characteristic diagram of the steering force changing means according to the present invention.
(A) shows the absolute value of deviation | ΔC | −frequency fO characteristic diagram, and (b) shows the time t characteristic diagram of the duty ratio coefficient KD1.
(A) In the figure, the frequency fO shows a characteristic proportional to the absolute value | ΔC | of the deviation, and a signal of the frequency fOA is generated at the deviation ΔCO.
[0066]
(B) In the figure, as an example, the duty ratio coefficient KD1 forms a sine wave signal having a peak value 1 with a constant 1 as the center.
[0067]
FIG. 8 is a waveform diagram of the PWM signal changed by the duty ratio coefficient KD1 of the steering force changing means shown in FIG.
In FIG. 8, the PWM signal VPWMO (solid line display) based on the duty ratio (DH) determined by the duty ratio setting means of the PWM signal generating means 34 is changed with a duty ratio coefficient KD1 at a constant cycle, and PWM Signal VPWM (shown in broken lines).
[0068]
The PWM signal VPWM (indicated by a broken line) is obtained when the levels of the duty ratio coefficient KD1 shown in FIG. 7B are 1.2, 1.5, 1.2, 1, 0.8, and 0.5, respectively. Represent.
Since the PWM signal VPWM (shown by a broken line) changes at a constant cycle, the driver senses an abnormality in the variable steering angle ratio mechanism 2 because the steering force changes periodically and the steering reaction force changes vibrationally. be able to.
[0069]
In the present embodiment, the duty ratio coefficient KD1 is a sine wave, but it may be a periodic function waveform such as a saw-tooth wave or a triangular wave.
Further, the frequency fO may be a constant value regardless of the absolute value | ΔC | of the deviation.
Furthermore, the peak value of the duty ratio coefficient KD1 may be increased as the absolute value of deviation | ΔC | increases.
[0070]
In the vehicle steering apparatus 1 according to the present invention, the control means 15 is provided with the steering force changing means 29 for changing the steering assist force obtained from the steering torque signal T when the variable steering angle ratio mechanism 2 is abnormal. If the actual steering angle ratio of the angle ratio mechanism 2 does not match the target steering angle ratio, it is determined that the variable steering angle ratio mechanism 2 is abnormal, and the steering assist force is based on the deviation between the target steering angle ratio and the actual steering angle ratio. And the driver can perceive it as a change in the steering reaction force.
[0071]
Further, since the steering force changing means 29 according to the present invention includes the period changing means 29 for changing the duty ratio of the PWM signal VPWM for driving the electric motor M1 with PWM (Pulse Width Modulation) at a constant period, the variable steering angle ratio An abnormality in the mechanism 2 can be detected by the driver as a change in the steering reaction force that vibrates.
[0072]
Furthermore, the control means 15 according to the present invention comprises a time measuring means 28, and if the actual steering angle ratio CJ does not coincide with the target steering angle ratio CS even after the set time TK has elapsed after the handle 4 is operated, the steering is performed. Since the auxiliary force is changed, the steering auxiliary force can be changed after reliably determining the abnormality of the variable steering angle ratio mechanism 2.
[0073]
FIG. 9 is a block diagram of the main part of another embodiment of the steering force changing means according to the present invention.
In FIG. 9, the steering force changing unit 37 includes a comparing unit 38 and a duty increasing unit 39.
The comparison means 38 includes an absolute value conversion means, a comparator and the like, and converts the deviation signal ΔC into an absolute value | ΔC | when the timer signal TO supplied from the time measuring means 28 is at the H level, and this absolute value | ΔC | And the reference value CK are compared. If the absolute value | ΔC | exceeds the reference value CK (| ΔC |> CK), the H level comparison signal HO1 is supplied to the duty increasing means 39.
[0074]
The comparison means 38 supplies the L level comparison signal HO1 to the duty increase means 39 when the timer signal TO is at the L level or when the absolute value | ΔC | is equal to or smaller than the reference value CK (| ΔC | ≦ CK). To do.
The reference value CK may be set to 0 value (CK = 0).
[0075]
The duty increasing means 39 includes a duty ratio increasing coefficient generating means, and when the comparison signal HO1 of H level is supplied from the comparing means 38, a duty ratio coefficient KD2 (> 1) obtained by increasing the constant 1 by a fixed value. Output.
Further, when the L level comparison signal HO1 is supplied from the comparison means 38, the duty increasing means 39 outputs a duty ratio coefficient KD2 (= 1) of a constant 1.
[0076]
FIG. 10 is a characteristic diagram of the duty ratio coefficient KD2 of the steering force changing means shown in FIG. 9 and a waveform diagram of the PWM signal changed with the duty ratio coefficient KD2.
(A) shows a comparison signal HO1-duty ratio coefficient KD2 characteristic diagram, and (b) shows a waveform diagram of a PWM signal changed by the duty ratio coefficient KD2.
[0077]
(A) In the figure, the duty ratio coefficient KD2 is, for example, a duty ratio coefficient KD2 of 1.5 when the comparison signal HO1 is at the H level, and a duty ratio coefficient of 1 when the comparison signal HO1 is at the L level. Output KD2.
[0078]
(B) In the figure, the PWM signal VPWMO (solid line display) is changed to the PWM signal VPWM (broken line display) by changing the duty ratio by the duty ratio coefficient KD2.
When the absolute value | ΔC | of the deviation signal ΔC exceeds the reference value CK and the duty ratio coefficient KD2 is changed to 1.5, the duty ratio of the PWM signal VPWM (shown by a broken line) is 1 of the PWM signal VPWMO (shown by a solid line). As a result of increasing the auxiliary steering force by a factor of .5, the driver can recognize the abnormality of the variable steering angle ratio mechanism 2 because the steering force of the steering wheel is suddenly reduced and the steering reaction force is suddenly reduced. .
[0079]
As described above, the steering force changing means 37 according to the present invention includes the duty increasing means 39 for increasing the duty ratio of the PWM signal for PWM driving the electric motor 8 by a certain value, so that the abnormality of the variable steering angle ratio mechanism 2 is steered. The reaction force can be reduced to allow the driver to sense.
[0080]
FIG. 11 is a block diagram of the main part of another embodiment of the steering force changing means according to the present invention.
In FIG. 11, the steering force change means 40 includes a comparison means 41 and a duty reduction means 42.
The comparison means 41 comprises an absolute value conversion means, a comparator, etc., and converts the deviation signal ΔC into an absolute value | ΔC | when the timer signal TO from the time measuring means 28 is at the H level, and this absolute value | ΔC | If the absolute value | ΔC | exceeds the reference value CK (| ΔC |> CK), the H level comparison signal HO2 is supplied to the duty reduction means 42.
[0081]
The comparison means 41 supplies the L level comparison signal HO2 to the duty reduction means 42 when the timer signal TO is at the L level or when the absolute value | ΔC | is equal to or smaller than the reference value CK (| ΔC | ≦ CK). To do.
The reference value CK may be set to 0 value (CK = 0).
[0082]
The duty reduction means 42 includes a duty ratio reduction coefficient generation means, and when the comparison signal HO2 is supplied from the comparison means 41, a duty ratio coefficient KD3 (<1) obtained by reducing the constant 1 by a fixed value. Output.
Further, when the L level comparison signal HO2 is supplied from the comparison means 41, the duty reduction means 42 outputs a constant 1 duty ratio coefficient KD3 (= 1).
[0083]
12 is a characteristic diagram of the duty ratio coefficient KD3 of the steering force changing means shown in FIG. 11 and a waveform diagram of the PWM signal changed with the duty ratio coefficient KD3.
(A) shows a comparison signal HO2-duty ratio coefficient KD3 characteristic diagram, and (b) shows a waveform diagram of a PWM signal changed by the duty ratio coefficient KD3.
[0084]
(A) In the figure, the duty ratio coefficient KD3 outputs, for example, a duty ratio coefficient KD3 of 0.5 when the comparison signal HO2 is at the H level, and a duty ratio coefficient of 1 when the comparison signal HO2 is at the L level. Output KD3.
[0085]
(B) In the figure, the PWM signal VPWMO (solid line display) is changed to the PWM signal VPWM (broken line display) by changing the duty ratio by the duty ratio coefficient KD3.
When the absolute value | ΔC | of the deviation signal ΔC exceeds the reference value CK and the duty ratio coefficient KD3 is changed to 0.5, the duty ratio of the PWM signal VPWM (dashed line display) is 0 of the PWM signal VPWMO (solid line display). As a result that the auxiliary steering force is reduced by a factor of .5, the driver can recognize an abnormality in the variable steering angle ratio mechanism 2 because the steering force suddenly increases and the steering reaction force increases suddenly.
[0086]
As described above, the steering force changing means 40 according to the present invention includes the duty reducing means 42 for reducing the duty ratio of the PWM signal for PWM driving the electric motor 8 by a certain value. The steering reaction force can be increased so that the driver can sense it.
[0087]
【The invention's effect】
As described above, in the vehicle steering apparatus according to the present invention, the control means includes the steering force changing means for changing the steering assist force when the variable steering angle ratio mechanism is abnormal, and the actual steering of the variable steering angle ratio mechanism is provided. If the angle ratio does not match the target rudder angle ratio, it is determined that the variable rudder angle ratio mechanism is abnormal, and the steering assist force can be changed so that the driver can sense the change in the steering reaction force. An abnormality in the ratio mechanism can be reliably transmitted to the driver as a change in the steering reaction force.
[0088]
Further, the steering force changing means according to the present invention changes the duty ratio of the PWM signal for driving the motor with PWM (Pulse Width Modulation) at a constant cycle, so that the abnormality of the variable steering angle ratio mechanism is regarded as a change in the steering reaction force. Can be surely communicated to the driver.
[0089]
Therefore, it is possible to provide a vehicle steering apparatus that can accurately notify the driver of the abnormality of the variable steering angle ratio mechanism by changing the steering reaction force.
[Brief description of the drawings]
FIG. 1 is a basic configuration diagram of an embodiment of a vehicle steering device according to the present invention;
FIG. 2 is a diagram for explaining the operating principle of the variable steering ratio mechanism according to the present invention.
FIG. 3 is a characteristic diagram of the rotation angle γ of the steering angle α-pinion of the variable steering ratio mechanism according to the present invention.
FIG. 4 is a block diagram of a main part of an embodiment of a steering apparatus for a vehicle according to the present invention.
FIG. 5 is a block diagram of a main part of an embodiment of drive control means according to the present invention.
FIG. 6 is a block diagram of a main part of an embodiment of a steering force changing means according to the present invention.
FIG. 7 is a characteristic diagram of steering force changing means according to the present invention.
8 is a waveform diagram of a PWM signal changed by a duty ratio coefficient KD1 of the steering force changing means shown in FIG.
FIG. 9 is a block diagram of the main part of another embodiment of the steering force changing means according to the present invention.
10 is a characteristic diagram of the duty ratio coefficient KD2 of the steering force changing means shown in FIG. 9 and a waveform diagram of the PWM signal changed with the duty ratio coefficient KD2.
FIG. 11 is a block diagram of the main part of another embodiment of the steering force changing means according to the present invention.
12 is a characteristic diagram of the duty ratio coefficient KD3 of the steering force changing means shown in FIG. 11 and a waveform diagram of the PWM signal changed with the duty ratio coefficient KD3.
FIG. 13 is a characteristic diagram of steering torque signal T-target torque signal IT data.
FIG. 14 is a characteristic diagram of vehicle speed signal V-target rudder angle ratio CS data.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 ... Vehicle steering device, 2 ... Variable steering angle ratio mechanism, 3 ... Electric power steering device, 4 ... Handle, 7 ... Input shaft, 8 ... Output shaft (pinion), 9 ... Rack shaft, 10 ... Steering wheel, DESCRIPTION OF SYMBOLS 11 ... Vehicle speed sensor, 12 ... Steering angle ratio sensor, 13 ... Steering torque sensor, 14 ... Steering angle ratio control means, 15 ... Control means, 21 ... Target steering angle ratio setting means, 22, 46 ... Deviation calculation means, 23 ... Steering angle ratio drive control means, 24 ... steering angle ratio motor driving means, 25 ... target torque signal setting means, 26 ... drive control means, 27 ... motor driving means, 28 ... time measuring means, 29, 37, 40 ... steering force Changing means 31 ... PID controller 32 ... Motor control signal generating means 33 ... On / off signal generating means 34 ... PWM signal generating means 35 ... Period changing means 36 ... Coefficient generating means 38, 41 ... Comparison means 3 ... duty increasing means, 42 ... duty reducing means, 45 ... motor torque signal detecting means.

Claims (2)

A steering angle ratio motor that determines a target steering angle ratio based on a vehicle speed signal from a vehicle speed sensor and matches an actual steering angle ratio from a steering angle ratio sensor that detects an actual steering angle ratio with the target steering angle ratio. A target steering signal is generated based on a steering torque signal from a steering torque sensor and a variable steering angle ratio mechanism having a steering angle ratio control means for controlling the driving of the steering, and auxiliary steering is performed on the steering system based on the target torque signal. In a vehicle steering apparatus comprising: an electric power steering apparatus provided with a control means for controlling driving of an electric motor that exerts a force;
The control means is a time measuring means for outputting a timer signal indicating an abnormality when the actual steering angle ratio of the variable steering angle ratio mechanism does not coincide with the target steering angle ratio even after a set time has elapsed since the steering wheel operation , based on the timer signal representing an anomaly supplied from the timer, and further comprising a steering force changing means for changing the steering assist force obtained by steering the steering torque signal when abnormality of the variable steering ratio mechanism A vehicle steering device.   2. The steering force changing means includes period changing means for changing a duty ratio of a PWM signal for driving the electric motor by PWM (Pulse Width Modulation) at a constant period, and changes the steering assist force. The vehicle steering apparatus as described.

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